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8d7071af89
linux/mm/memory.c
Linus Torvalds 8d7071af89 mm: always expand the stack with the mmap write lock held 
This finishes the job of always holding the mmap write lock when
extending the user stack vma, and removes the 'write_locked' argument
from the vm helper functions again.

For some cases, we just avoid expanding the stack at all: drivers and
page pinning really shouldn't be extending any stacks.  Let's see if any
strange users really wanted that.

It's worth noting that architectures that weren't converted to the new
lock_mm_and_find_vma() helper function are left using the legacy
"expand_stack()" function, but it has been changed to drop the mmap_lock
and take it for writing while expanding the vma.  This makes it fairly
straightforward to convert the remaining architectures.

As a result of dropping and re-taking the lock, the calling conventions
for this function have also changed, since the old vma may no longer be
valid.  So it will now return the new vma if successful, and NULL - and
the lock dropped - if the area could not be extended.

Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de> # ia64
Tested-by: Frank Scheiner <frank.scheiner@web.de> # ia64
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2023-06-27 09:41:30 -07:00

6081 lines
165 KiB
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// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/mm/memory.c
*
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*/
/*
* demand-loading started 01.12.91 - seems it is high on the list of
* things wanted, and it should be easy to implement. - Linus
*/
/*
* Ok, demand-loading was easy, shared pages a little bit tricker. Shared
* pages started 02.12.91, seems to work. - Linus.
*
* Tested sharing by executing about 30 /bin/sh: under the old kernel it
* would have taken more than the 6M I have free, but it worked well as
* far as I could see.
*
* Also corrected some "invalidate()"s - I wasn't doing enough of them.
*/
/*
* Real VM (paging to/from disk) started 18.12.91. Much more work and
* thought has to go into this. Oh, well..
* 19.12.91 - works, somewhat. Sometimes I get faults, don't know why.
* Found it. Everything seems to work now.
* 20.12.91 - Ok, making the swap-device changeable like the root.
*/
/*
* 05.04.94 - Multi-page memory management added for v1.1.
* Idea by Alex Bligh (alex@cconcepts.co.uk)
*
* 16.07.99 - Support of BIGMEM added by Gerhard Wichert, Siemens AG
* (Gerhard.Wichert@pdb.siemens.de)
*
* Aug/Sep 2004 Changed to four level page tables (Andi Kleen)
*/
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/sched/numa_balancing.h>
#include <linux/sched/task.h>
#include <linux/hugetlb.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/memremap.h>
#include <linux/kmsan.h>
#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/export.h>
#include <linux/delayacct.h>
#include <linux/init.h>
#include <linux/pfn_t.h>
#include <linux/writeback.h>
#include <linux/memcontrol.h>
#include <linux/mmu_notifier.h>
#include <linux/swapops.h>
#include <linux/elf.h>
#include <linux/gfp.h>
#include <linux/migrate.h>
#include <linux/string.h>
#include <linux/memory-tiers.h>
#include <linux/debugfs.h>
#include <linux/userfaultfd_k.h>
#include <linux/dax.h>
#include <linux/oom.h>
#include <linux/numa.h>
#include <linux/perf_event.h>
#include <linux/ptrace.h>
#include <linux/vmalloc.h>
#include <linux/sched/sysctl.h>
#include <trace/events/kmem.h>
#include <asm/io.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include "pgalloc-track.h"
#include "internal.h"
#include "swap.h"
#if defined(LAST_CPUPID_NOT_IN_PAGE_FLAGS) && !defined(CONFIG_COMPILE_TEST)
#warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid.
#endif
#ifndef CONFIG_NUMA
unsigned long max_mapnr;
EXPORT_SYMBOL(max_mapnr);
struct page *mem_map;
EXPORT_SYMBOL(mem_map);
#endif
static vm_fault_t do_fault(struct vm_fault *vmf);
static vm_fault_t do_anonymous_page(struct vm_fault *vmf);
static bool vmf_pte_changed(struct vm_fault *vmf);
/*
* Return true if the original pte was a uffd-wp pte marker (so the pte was
* wr-protected).
*/
static bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf)
{
if (!(vmf->flags & FAULT_FLAG_ORIG_PTE_VALID))
return false;
return pte_marker_uffd_wp(vmf->orig_pte);
}
/*
* A number of key systems in x86 including ioremap() rely on the assumption
* that high_memory defines the upper bound on direct map memory, then end
* of ZONE_NORMAL. Under CONFIG_DISCONTIG this means that max_low_pfn and
* highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
* and ZONE_HIGHMEM.
*/
void *high_memory;
EXPORT_SYMBOL(high_memory);
/*
* Randomize the address space (stacks, mmaps, brk, etc.).
*
* ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
* as ancient (libc5 based) binaries can segfault. )
*/
int randomize_va_space __read_mostly =
#ifdef CONFIG_COMPAT_BRK
1;
#else
2;
#endif
#ifndef arch_wants_old_prefaulted_pte
static inline bool arch_wants_old_prefaulted_pte(void)
{
/*
* Transitioning a PTE from 'old' to 'young' can be expensive on
* some architectures, even if it's performed in hardware. By
* default, "false" means prefaulted entries will be 'young'.
*/
return false;
}
#endif
static int __init disable_randmaps(char *s)
{
randomize_va_space = 0;
return 1;
}
__setup("norandmaps", disable_randmaps);
unsigned long zero_pfn __read_mostly;
EXPORT_SYMBOL(zero_pfn);
unsigned long highest_memmap_pfn __read_mostly;
/*
* CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
*/
static int __init init_zero_pfn(void)
{
zero_pfn = page_to_pfn(ZERO_PAGE(0));
return 0;
}
early_initcall(init_zero_pfn);
void mm_trace_rss_stat(struct mm_struct *mm, int member)
{
trace_rss_stat(mm, member);
}
/*
* Note: this doesn't free the actual pages themselves. That
* has been handled earlier when unmapping all the memory regions.
*/
static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
unsigned long addr)
{
pgtable_t token = pmd_pgtable(*pmd);
pmd_clear(pmd);
pte_free_tlb(tlb, token, addr);
mm_dec_nr_ptes(tlb->mm);
}
static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
pmd_t *pmd;
unsigned long next;
unsigned long start;
start = addr;
pmd = pmd_offset(pud, addr);
do {
next = pmd_addr_end(addr, end);
if (pmd_none_or_clear_bad(pmd))
continue;
free_pte_range(tlb, pmd, addr);
} while (pmd++, addr = next, addr != end);
start &= PUD_MASK;
if (start < floor)
return;
if (ceiling) {
ceiling &= PUD_MASK;
if (!ceiling)
return;
}
if (end - 1 > ceiling - 1)
return;
pmd = pmd_offset(pud, start);
pud_clear(pud);
pmd_free_tlb(tlb, pmd, start);
mm_dec_nr_pmds(tlb->mm);
}
static inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
pud_t *pud;
unsigned long next;
unsigned long start;
start = addr;
pud = pud_offset(p4d, addr);
do {
next = pud_addr_end(addr, end);
if (pud_none_or_clear_bad(pud))
continue;
free_pmd_range(tlb, pud, addr, next, floor, ceiling);
} while (pud++, addr = next, addr != end);
start &= P4D_MASK;
if (start < floor)
return;
if (ceiling) {
ceiling &= P4D_MASK;
if (!ceiling)
return;
}
if (end - 1 > ceiling - 1)
return;
pud = pud_offset(p4d, start);
p4d_clear(p4d);
pud_free_tlb(tlb, pud, start);
mm_dec_nr_puds(tlb->mm);
}
static inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
p4d_t *p4d;
unsigned long next;
unsigned long start;
start = addr;
p4d = p4d_offset(pgd, addr);
do {
next = p4d_addr_end(addr, end);
if (p4d_none_or_clear_bad(p4d))
continue;
free_pud_range(tlb, p4d, addr, next, floor, ceiling);
} while (p4d++, addr = next, addr != end);
start &= PGDIR_MASK;
if (start < floor)
return;
if (ceiling) {
ceiling &= PGDIR_MASK;
if (!ceiling)
return;
}
if (end - 1 > ceiling - 1)
return;
p4d = p4d_offset(pgd, start);
pgd_clear(pgd);
p4d_free_tlb(tlb, p4d, start);
}
/*
* This function frees user-level page tables of a process.
*/
void free_pgd_range(struct mmu_gather *tlb,
unsigned long addr, unsigned long end,
unsigned long floor, unsigned long ceiling)
{
pgd_t *pgd;
unsigned long next;
/*
* The next few lines have given us lots of grief...
*
* Why are we testing PMD* at this top level? Because often
* there will be no work to do at all, and we'd prefer not to
* go all the way down to the bottom just to discover that.
*
* Why all these "- 1"s? Because 0 represents both the bottom
* of the address space and the top of it (using -1 for the
* top wouldn't help much: the masks would do the wrong thing).
* The rule is that addr 0 and floor 0 refer to the bottom of
* the address space, but end 0 and ceiling 0 refer to the top
* Comparisons need to use "end - 1" and "ceiling - 1" (though
* that end 0 case should be mythical).
*
* Wherever addr is brought up or ceiling brought down, we must
* be careful to reject "the opposite 0" before it confuses the
* subsequent tests. But what about where end is brought down
* by PMD_SIZE below? no, end can't go down to 0 there.
*
* Whereas we round start (addr) and ceiling down, by different
* masks at different levels, in order to test whether a table
* now has no other vmas using it, so can be freed, we don't
* bother to round floor or end up - the tests don't need that.
*/
addr &= PMD_MASK;
if (addr < floor) {
addr += PMD_SIZE;
if (!addr)
return;
}
if (ceiling) {
ceiling &= PMD_MASK;
if (!ceiling)
return;
}
if (end - 1 > ceiling - 1)
end -= PMD_SIZE;
if (addr > end - 1)
return;
/*
* We add page table cache pages with PAGE_SIZE,
* (see pte_free_tlb()), flush the tlb if we need
*/
tlb_change_page_size(tlb, PAGE_SIZE);
pgd = pgd_offset(tlb->mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
free_p4d_range(tlb, pgd, addr, next, floor, ceiling);
} while (pgd++, addr = next, addr != end);
}
void free_pgtables(struct mmu_gather *tlb, struct maple_tree *mt,
struct vm_area_struct *vma, unsigned long floor,
unsigned long ceiling, bool mm_wr_locked)
{
MA_STATE(mas, mt, vma->vm_end, vma->vm_end);
do {
unsigned long addr = vma->vm_start;
struct vm_area_struct *next;
/*
* Note: USER_PGTABLES_CEILING may be passed as ceiling and may
* be 0. This will underflow and is okay.
*/
next = mas_find(&mas, ceiling - 1);
/*
* Hide vma from rmap and truncate_pagecache before freeing
* pgtables
*/
if (mm_wr_locked)
vma_start_write(vma);
unlink_anon_vmas(vma);
unlink_file_vma(vma);
if (is_vm_hugetlb_page(vma)) {
hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
floor, next ? next->vm_start : ceiling);
} else {
/*
* Optimization: gather nearby vmas into one call down
*/
while (next && next->vm_start <= vma->vm_end + PMD_SIZE
&& !is_vm_hugetlb_page(next)) {
vma = next;
next = mas_find(&mas, ceiling - 1);
if (mm_wr_locked)
vma_start_write(vma);
unlink_anon_vmas(vma);
unlink_file_vma(vma);
}
free_pgd_range(tlb, addr, vma->vm_end,
floor, next ? next->vm_start : ceiling);
}
vma = next;
} while (vma);
}
void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte)
{
spinlock_t *ptl = pmd_lock(mm, pmd);
if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
mm_inc_nr_ptes(mm);
/*
* Ensure all pte setup (eg. pte page lock and page clearing) are
* visible before the pte is made visible to other CPUs by being
* put into page tables.
*
* The other side of the story is the pointer chasing in the page
* table walking code (when walking the page table without locking;
* ie. most of the time). Fortunately, these data accesses consist
* of a chain of data-dependent loads, meaning most CPUs (alpha
* being the notable exception) will already guarantee loads are
* seen in-order. See the alpha page table accessors for the
* smp_rmb() barriers in page table walking code.
*/
smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
pmd_populate(mm, pmd, *pte);
*pte = NULL;
}
spin_unlock(ptl);
}
int __pte_alloc(struct mm_struct *mm, pmd_t *pmd)
{
pgtable_t new = pte_alloc_one(mm);
if (!new)
return -ENOMEM;
pmd_install(mm, pmd, &new);
if (new)
pte_free(mm, new);
return 0;
}
int __pte_alloc_kernel(pmd_t *pmd)
{
pte_t *new = pte_alloc_one_kernel(&init_mm);
if (!new)
return -ENOMEM;
spin_lock(&init_mm.page_table_lock);
if (likely(pmd_none(*pmd))) { /* Has another populated it ? */
smp_wmb(); /* See comment in pmd_install() */
pmd_populate_kernel(&init_mm, pmd, new);
new = NULL;
}
spin_unlock(&init_mm.page_table_lock);
if (new)
pte_free_kernel(&init_mm, new);
return 0;
}
static inline void init_rss_vec(int *rss)
{
memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
}
static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
{
int i;
if (current->mm == mm)
sync_mm_rss(mm);
for (i = 0; i < NR_MM_COUNTERS; i++)
if (rss[i])
add_mm_counter(mm, i, rss[i]);
}
/*
* This function is called to print an error when a bad pte
* is found. For example, we might have a PFN-mapped pte in
* a region that doesn't allow it.
*
* The calling function must still handle the error.
*/
static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
pte_t pte, struct page *page)
{
pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
p4d_t *p4d = p4d_offset(pgd, addr);
pud_t *pud = pud_offset(p4d, addr);
pmd_t *pmd = pmd_offset(pud, addr);
struct address_space *mapping;
pgoff_t index;
static unsigned long resume;
static unsigned long nr_shown;
static unsigned long nr_unshown;
/*
* Allow a burst of 60 reports, then keep quiet for that minute;
* or allow a steady drip of one report per second.
*/
if (nr_shown == 60) {
if (time_before(jiffies, resume)) {
nr_unshown++;
return;
}
if (nr_unshown) {
pr_alert("BUG: Bad page map: %lu messages suppressed\n",
nr_unshown);
nr_unshown = 0;
}
nr_shown = 0;
}
if (nr_shown++ == 0)
resume = jiffies + 60 * HZ;
mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
index = linear_page_index(vma, addr);
pr_alert("BUG: Bad page map in process %s pte:%08llx pmd:%08llx\n",
current->comm,
(long long)pte_val(pte), (long long)pmd_val(*pmd));
if (page)
dump_page(page, "bad pte");
pr_alert("addr:%px vm_flags:%08lx anon_vma:%px mapping:%px index:%lx\n",
(void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
pr_alert("file:%pD fault:%ps mmap:%ps read_folio:%ps\n",
vma->vm_file,
vma->vm_ops ? vma->vm_ops->fault : NULL,
vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
mapping ? mapping->a_ops->read_folio : NULL);
dump_stack();
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}
/*
* vm_normal_page -- This function gets the "struct page" associated with a pte.
*
* "Special" mappings do not wish to be associated with a "struct page" (either
* it doesn't exist, or it exists but they don't want to touch it). In this
* case, NULL is returned here. "Normal" mappings do have a struct page.
*
* There are 2 broad cases. Firstly, an architecture may define a pte_special()
* pte bit, in which case this function is trivial. Secondly, an architecture
* may not have a spare pte bit, which requires a more complicated scheme,
* described below.
*
* A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
* special mapping (even if there are underlying and valid "struct pages").
* COWed pages of a VM_PFNMAP are always normal.
*
* The way we recognize COWed pages within VM_PFNMAP mappings is through the
* rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
* set, and the vm_pgoff will point to the first PFN mapped: thus every special
* mapping will always honor the rule
*
* pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
*
* And for normal mappings this is false.
*
* This restricts such mappings to be a linear translation from virtual address
* to pfn. To get around this restriction, we allow arbitrary mappings so long
* as the vma is not a COW mapping; in that case, we know that all ptes are
* special (because none can have been COWed).
*
*
* In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
*
* VM_MIXEDMAP mappings can likewise contain memory with or without "struct
* page" backing, however the difference is that _all_ pages with a struct
* page (that is, those where pfn_valid is true) are refcounted and considered
* normal pages by the VM. The disadvantage is that pages are refcounted
* (which can be slower and simply not an option for some PFNMAP users). The
* advantage is that we don't have to follow the strict linearity rule of
* PFNMAP mappings in order to support COWable mappings.
*
*/
struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
pte_t pte)
{
unsigned long pfn = pte_pfn(pte);
if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
if (likely(!pte_special(pte)))
goto check_pfn;
if (vma->vm_ops && vma->vm_ops->find_special_page)
return vma->vm_ops->find_special_page(vma, addr);
if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
return NULL;
if (is_zero_pfn(pfn))
return NULL;
if (pte_devmap(pte))
/*
* NOTE: New users of ZONE_DEVICE will not set pte_devmap()
* and will have refcounts incremented on their struct pages
* when they are inserted into PTEs, thus they are safe to
* return here. Legacy ZONE_DEVICE pages that set pte_devmap()
* do not have refcounts. Example of legacy ZONE_DEVICE is
* MEMORY_DEVICE_FS_DAX type in pmem or virtio_fs drivers.
*/
return NULL;
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
/* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */
if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
if (vma->vm_flags & VM_MIXEDMAP) {
if (!pfn_valid(pfn))
return NULL;
goto out;
} else {
unsigned long off;
off = (addr - vma->vm_start) >> PAGE_SHIFT;
if (pfn == vma->vm_pgoff + off)
return NULL;
if (!is_cow_mapping(vma->vm_flags))
return NULL;
}
}
if (is_zero_pfn(pfn))
return NULL;
check_pfn:
if (unlikely(pfn > highest_memmap_pfn)) {
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
/*
* NOTE! We still have PageReserved() pages in the page tables.
* eg. VDSO mappings can cause them to exist.
*/
out:
return pfn_to_page(pfn);
}
struct folio *vm_normal_folio(struct vm_area_struct *vma, unsigned long addr,
pte_t pte)
{
struct page *page = vm_normal_page(vma, addr, pte);
if (page)
return page_folio(page);
return NULL;
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t pmd)
{
unsigned long pfn = pmd_pfn(pmd);
/*
* There is no pmd_special() but there may be special pmds, e.g.
* in a direct-access (dax) mapping, so let's just replicate the
* !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
*/
if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
if (vma->vm_flags & VM_MIXEDMAP) {
if (!pfn_valid(pfn))
return NULL;
goto out;
} else {
unsigned long off;
off = (addr - vma->vm_start) >> PAGE_SHIFT;
if (pfn == vma->vm_pgoff + off)
return NULL;
if (!is_cow_mapping(vma->vm_flags))
return NULL;
}
}
if (pmd_devmap(pmd))
return NULL;
if (is_huge_zero_pmd(pmd))
return NULL;
if (unlikely(pfn > highest_memmap_pfn))
return NULL;
/*
* NOTE! We still have PageReserved() pages in the page tables.
* eg. VDSO mappings can cause them to exist.
*/
out:
return pfn_to_page(pfn);
}
#endif
static void restore_exclusive_pte(struct vm_area_struct *vma,
struct page *page, unsigned long address,
pte_t *ptep)
{
pte_t pte;
swp_entry_t entry;
pte = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
if (pte_swp_soft_dirty(*ptep))
pte = pte_mksoft_dirty(pte);
entry = pte_to_swp_entry(*ptep);
if (pte_swp_uffd_wp(*ptep))
pte = pte_mkuffd_wp(pte);
else if (is_writable_device_exclusive_entry(entry))
pte = maybe_mkwrite(pte_mkdirty(pte), vma);
VM_BUG_ON(pte_write(pte) && !(PageAnon(page) && PageAnonExclusive(page)));
/*
* No need to take a page reference as one was already
* created when the swap entry was made.
*/
if (PageAnon(page))
page_add_anon_rmap(page, vma, address, RMAP_NONE);
else
/*
* Currently device exclusive access only supports anonymous
* memory so the entry shouldn't point to a filebacked page.
*/
WARN_ON_ONCE(1);
set_pte_at(vma->vm_mm, address, ptep, pte);
/*
* No need to invalidate - it was non-present before. However
* secondary CPUs may have mappings that need invalidating.
*/
update_mmu_cache(vma, address, ptep);
}
/*
* Tries to restore an exclusive pte if the page lock can be acquired without
* sleeping.
*/
static int
try_restore_exclusive_pte(pte_t *src_pte, struct vm_area_struct *vma,
unsigned long addr)
{
swp_entry_t entry = pte_to_swp_entry(*src_pte);
struct page *page = pfn_swap_entry_to_page(entry);
if (trylock_page(page)) {
restore_exclusive_pte(vma, page, addr, src_pte);
unlock_page(page);
return 0;
}
return -EBUSY;
}
/*
* copy one vm_area from one task to the other. Assumes the page tables
* already present in the new task to be cleared in the whole range
* covered by this vma.
*/
static unsigned long
copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *dst_vma,
struct vm_area_struct *src_vma, unsigned long addr, int *rss)
{
unsigned long vm_flags = dst_vma->vm_flags;
pte_t pte = *src_pte;
struct page *page;
swp_entry_t entry = pte_to_swp_entry(pte);
if (likely(!non_swap_entry(entry))) {
if (swap_duplicate(entry) < 0)
return -EIO;
/* make sure dst_mm is on swapoff's mmlist. */
if (unlikely(list_empty(&dst_mm->mmlist))) {
spin_lock(&mmlist_lock);
if (list_empty(&dst_mm->mmlist))
list_add(&dst_mm->mmlist,
&src_mm->mmlist);
spin_unlock(&mmlist_lock);
}
/* Mark the swap entry as shared. */
if (pte_swp_exclusive(*src_pte)) {
pte = pte_swp_clear_exclusive(*src_pte);
set_pte_at(src_mm, addr, src_pte, pte);
}
rss[MM_SWAPENTS]++;
} else if (is_migration_entry(entry)) {
page = pfn_swap_entry_to_page(entry);
rss[mm_counter(page)]++;
if (!is_readable_migration_entry(entry) &&
is_cow_mapping(vm_flags)) {
/*
* COW mappings require pages in both parent and child
* to be set to read. A previously exclusive entry is
* now shared.
*/
entry = make_readable_migration_entry(
swp_offset(entry));
pte = swp_entry_to_pte(entry);
if (pte_swp_soft_dirty(*src_pte))
pte = pte_swp_mksoft_dirty(pte);
if (pte_swp_uffd_wp(*src_pte))
pte = pte_swp_mkuffd_wp(pte);
set_pte_at(src_mm, addr, src_pte, pte);
}
} else if (is_device_private_entry(entry)) {
page = pfn_swap_entry_to_page(entry);
/*
* Update rss count even for unaddressable pages, as
* they should treated just like normal pages in this
* respect.
*
* We will likely want to have some new rss counters
* for unaddressable pages, at some point. But for now
* keep things as they are.
*/
get_page(page);
rss[mm_counter(page)]++;
/* Cannot fail as these pages cannot get pinned. */
BUG_ON(page_try_dup_anon_rmap(page, false, src_vma));
/*
* We do not preserve soft-dirty information, because so
* far, checkpoint/restore is the only feature that
* requires that. And checkpoint/restore does not work
* when a device driver is involved (you cannot easily
* save and restore device driver state).
*/
if (is_writable_device_private_entry(entry) &&
is_cow_mapping(vm_flags)) {
entry = make_readable_device_private_entry(
swp_offset(entry));
pte = swp_entry_to_pte(entry);
if (pte_swp_uffd_wp(*src_pte))
pte = pte_swp_mkuffd_wp(pte);
set_pte_at(src_mm, addr, src_pte, pte);
}
} else if (is_device_exclusive_entry(entry)) {
/*
* Make device exclusive entries present by restoring the
* original entry then copying as for a present pte. Device
* exclusive entries currently only support private writable
* (ie. COW) mappings.
*/
VM_BUG_ON(!is_cow_mapping(src_vma->vm_flags));
if (try_restore_exclusive_pte(src_pte, src_vma, addr))
return -EBUSY;
return -ENOENT;
} else if (is_pte_marker_entry(entry)) {
if (is_swapin_error_entry(entry) || userfaultfd_wp(dst_vma))
set_pte_at(dst_mm, addr, dst_pte, pte);
return 0;
}
if (!userfaultfd_wp(dst_vma))
pte = pte_swp_clear_uffd_wp(pte);
set_pte_at(dst_mm, addr, dst_pte, pte);
return 0;
}
/*
* Copy a present and normal page.
*
* NOTE! The usual case is that this isn't required;
* instead, the caller can just increase the page refcount
* and re-use the pte the traditional way.
*
* And if we need a pre-allocated page but don't yet have
* one, return a negative error to let the preallocation
* code know so that it can do so outside the page table
* lock.
*/
static inline int
copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss,
struct folio **prealloc, struct page *page)
{
struct folio *new_folio;
pte_t pte;
new_folio = *prealloc;
if (!new_folio)
return -EAGAIN;
/*
* We have a prealloc page, all good! Take it
* over and copy the page & arm it.
*/
*prealloc = NULL;
copy_user_highpage(&new_folio->page, page, addr, src_vma);
__folio_mark_uptodate(new_folio);
folio_add_new_anon_rmap(new_folio, dst_vma, addr);
folio_add_lru_vma(new_folio, dst_vma);
rss[MM_ANONPAGES]++;
/* All done, just insert the new page copy in the child */
pte = mk_pte(&new_folio->page, dst_vma->vm_page_prot);
pte = maybe_mkwrite(pte_mkdirty(pte), dst_vma);
if (userfaultfd_pte_wp(dst_vma, *src_pte))
/* Uffd-wp needs to be delivered to dest pte as well */
pte = pte_mkuffd_wp(pte);
set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte);
return 0;
}
/*
* Copy one pte. Returns 0 if succeeded, or -EAGAIN if one preallocated page
* is required to copy this pte.
*/
static inline int
copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss,
struct folio **prealloc)
{
struct mm_struct *src_mm = src_vma->vm_mm;
unsigned long vm_flags = src_vma->vm_flags;
pte_t pte = *src_pte;
struct page *page;
struct folio *folio;
page = vm_normal_page(src_vma, addr, pte);
if (page)
folio = page_folio(page);
if (page && folio_test_anon(folio)) {
/*
* If this page may have been pinned by the parent process,
* copy the page immediately for the child so that we'll always
* guarantee the pinned page won't be randomly replaced in the
* future.
*/
folio_get(folio);
if (unlikely(page_try_dup_anon_rmap(page, false, src_vma))) {
/* Page may be pinned, we have to copy. */
folio_put(folio);
return copy_present_page(dst_vma, src_vma, dst_pte, src_pte,
addr, rss, prealloc, page);
}
rss[MM_ANONPAGES]++;
} else if (page) {
folio_get(folio);
page_dup_file_rmap(page, false);
rss[mm_counter_file(page)]++;
}
/*
* If it's a COW mapping, write protect it both
* in the parent and the child
*/
if (is_cow_mapping(vm_flags) && pte_write(pte)) {
ptep_set_wrprotect(src_mm, addr, src_pte);
pte = pte_wrprotect(pte);
}
VM_BUG_ON(page && folio_test_anon(folio) && PageAnonExclusive(page));
/*
* If it's a shared mapping, mark it clean in
* the child
*/
if (vm_flags & VM_SHARED)
pte = pte_mkclean(pte);
pte = pte_mkold(pte);
if (!userfaultfd_wp(dst_vma))
pte = pte_clear_uffd_wp(pte);
set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte);
return 0;
}
static inline struct folio *page_copy_prealloc(struct mm_struct *src_mm,
struct vm_area_struct *vma, unsigned long addr)
{
struct folio *new_folio;
new_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, addr, false);
if (!new_folio)
return NULL;
if (mem_cgroup_charge(new_folio, src_mm, GFP_KERNEL)) {
folio_put(new_folio);
return NULL;
}
folio_throttle_swaprate(new_folio, GFP_KERNEL);
return new_folio;
}
static int
copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
unsigned long end)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
struct mm_struct *src_mm = src_vma->vm_mm;
pte_t *orig_src_pte, *orig_dst_pte;
pte_t *src_pte, *dst_pte;
spinlock_t *src_ptl, *dst_ptl;
int progress, ret = 0;
int rss[NR_MM_COUNTERS];
swp_entry_t entry = (swp_entry_t){0};
struct folio *prealloc = NULL;
again:
progress = 0;
init_rss_vec(rss);
dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
if (!dst_pte) {
ret = -ENOMEM;
goto out;
}
src_pte = pte_offset_map(src_pmd, addr);
src_ptl = pte_lockptr(src_mm, src_pmd);
spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
orig_src_pte = src_pte;
orig_dst_pte = dst_pte;
arch_enter_lazy_mmu_mode();
do {
/*
* We are holding two locks at this point - either of them
* could generate latencies in another task on another CPU.
*/
if (progress >= 32) {
progress = 0;
if (need_resched() ||
spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
break;
}
if (pte_none(*src_pte)) {
progress++;
continue;
}
if (unlikely(!pte_present(*src_pte))) {
ret = copy_nonpresent_pte(dst_mm, src_mm,
dst_pte, src_pte,
dst_vma, src_vma,
addr, rss);
if (ret == -EIO) {
entry = pte_to_swp_entry(*src_pte);
break;
} else if (ret == -EBUSY) {
break;
} else if (!ret) {
progress += 8;
continue;
}
/*
* Device exclusive entry restored, continue by copying
* the now present pte.
*/
WARN_ON_ONCE(ret != -ENOENT);
}
/* copy_present_pte() will clear `*prealloc' if consumed */
ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte,
addr, rss, &prealloc);
/*
* If we need a pre-allocated page for this pte, drop the
* locks, allocate, and try again.
*/
if (unlikely(ret == -EAGAIN))
break;
if (unlikely(prealloc)) {
/*
* pre-alloc page cannot be reused by next time so as
* to strictly follow mempolicy (e.g., alloc_page_vma()
* will allocate page according to address). This
* could only happen if one pinned pte changed.
*/
folio_put(prealloc);
prealloc = NULL;
}
progress += 8;
} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
arch_leave_lazy_mmu_mode();
spin_unlock(src_ptl);
pte_unmap(orig_src_pte);
add_mm_rss_vec(dst_mm, rss);
pte_unmap_unlock(orig_dst_pte, dst_ptl);
cond_resched();
if (ret == -EIO) {
VM_WARN_ON_ONCE(!entry.val);
if (add_swap_count_continuation(entry, GFP_KERNEL) < 0) {
ret = -ENOMEM;
goto out;
}
entry.val = 0;
} else if (ret == -EBUSY) {
goto out;
} else if (ret == -EAGAIN) {
prealloc = page_copy_prealloc(src_mm, src_vma, addr);
if (!prealloc)
return -ENOMEM;
} else if (ret) {
VM_WARN_ON_ONCE(1);
}
/* We've captured and resolved the error. Reset, try again. */
ret = 0;
if (addr != end)
goto again;
out:
if (unlikely(prealloc))
folio_put(prealloc);
return ret;
}
static inline int
copy_pmd_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
unsigned long end)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
struct mm_struct *src_mm = src_vma->vm_mm;
pmd_t *src_pmd, *dst_pmd;
unsigned long next;
dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
if (!dst_pmd)
return -ENOMEM;
src_pmd = pmd_offset(src_pud, addr);
do {
next = pmd_addr_end(addr, end);
if (is_swap_pmd(*src_pmd) || pmd_trans_huge(*src_pmd)
|| pmd_devmap(*src_pmd)) {
int err;
VM_BUG_ON_VMA(next-addr != HPAGE_PMD_SIZE, src_vma);
err = copy_huge_pmd(dst_mm, src_mm, dst_pmd, src_pmd,
addr, dst_vma, src_vma);
if (err == -ENOMEM)
return -ENOMEM;
if (!err)
continue;
/* fall through */
}
if (pmd_none_or_clear_bad(src_pmd))
continue;
if (copy_pte_range(dst_vma, src_vma, dst_pmd, src_pmd,
addr, next))
return -ENOMEM;
} while (dst_pmd++, src_pmd++, addr = next, addr != end);
return 0;
}
static inline int
copy_pud_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
p4d_t *dst_p4d, p4d_t *src_p4d, unsigned long addr,
unsigned long end)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
struct mm_struct *src_mm = src_vma->vm_mm;
pud_t *src_pud, *dst_pud;
unsigned long next;
dst_pud = pud_alloc(dst_mm, dst_p4d, addr);
if (!dst_pud)
return -ENOMEM;
src_pud = pud_offset(src_p4d, addr);
do {
next = pud_addr_end(addr, end);
if (pud_trans_huge(*src_pud) || pud_devmap(*src_pud)) {
int err;
VM_BUG_ON_VMA(next-addr != HPAGE_PUD_SIZE, src_vma);
err = copy_huge_pud(dst_mm, src_mm,
dst_pud, src_pud, addr, src_vma);
if (err == -ENOMEM)
return -ENOMEM;
if (!err)
continue;
/* fall through */
}
if (pud_none_or_clear_bad(src_pud))
continue;
if (copy_pmd_range(dst_vma, src_vma, dst_pud, src_pud,
addr, next))
return -ENOMEM;
} while (dst_pud++, src_pud++, addr = next, addr != end);
return 0;
}
static inline int
copy_p4d_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
pgd_t *dst_pgd, pgd_t *src_pgd, unsigned long addr,
unsigned long end)
{
struct mm_struct *dst_mm = dst_vma->vm_mm;
p4d_t *src_p4d, *dst_p4d;
unsigned long next;
dst_p4d = p4d_alloc(dst_mm, dst_pgd, addr);
if (!dst_p4d)
return -ENOMEM;
src_p4d = p4d_offset(src_pgd, addr);
do {
next = p4d_addr_end(addr, end);
if (p4d_none_or_clear_bad(src_p4d))
continue;
if (copy_pud_range(dst_vma, src_vma, dst_p4d, src_p4d,
addr, next))
return -ENOMEM;
} while (dst_p4d++, src_p4d++, addr = next, addr != end);
return 0;
}
/*
* Return true if the vma needs to copy the pgtable during this fork(). Return
* false when we can speed up fork() by allowing lazy page faults later until
* when the child accesses the memory range.
*/
static bool
vma_needs_copy(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
{
/*
* Always copy pgtables when dst_vma has uffd-wp enabled even if it's
* file-backed (e.g. shmem). Because when uffd-wp is enabled, pgtable
* contains uffd-wp protection information, that's something we can't
* retrieve from page cache, and skip copying will lose those info.
*/
if (userfaultfd_wp(dst_vma))
return true;
if (src_vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
return true;
if (src_vma->anon_vma)
return true;
/*
* Don't copy ptes where a page fault will fill them correctly. Fork
* becomes much lighter when there are big shared or private readonly
* mappings. The tradeoff is that copy_page_range is more efficient
* than faulting.
*/
return false;
}
int
copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
{
pgd_t *src_pgd, *dst_pgd;
unsigned long next;
unsigned long addr = src_vma->vm_start;
unsigned long end = src_vma->vm_end;
struct mm_struct *dst_mm = dst_vma->vm_mm;
struct mm_struct *src_mm = src_vma->vm_mm;
struct mmu_notifier_range range;
bool is_cow;
int ret;
if (!vma_needs_copy(dst_vma, src_vma))
return 0;
if (is_vm_hugetlb_page(src_vma))
return copy_hugetlb_page_range(dst_mm, src_mm, dst_vma, src_vma);
if (unlikely(src_vma->vm_flags & VM_PFNMAP)) {
/*
* We do not free on error cases below as remove_vma
* gets called on error from higher level routine
*/
ret = track_pfn_copy(src_vma);
if (ret)
return ret;
}
/*
* We need to invalidate the secondary MMU mappings only when
* there could be a permission downgrade on the ptes of the
* parent mm. And a permission downgrade will only happen if
* is_cow_mapping() returns true.
*/
is_cow = is_cow_mapping(src_vma->vm_flags);
if (is_cow) {
mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE,
0, src_mm, addr, end);
mmu_notifier_invalidate_range_start(&range);
/*
* Disabling preemption is not needed for the write side, as
* the read side doesn't spin, but goes to the mmap_lock.
*
* Use the raw variant of the seqcount_t write API to avoid
* lockdep complaining about preemptibility.
*/
mmap_assert_write_locked(src_mm);
raw_write_seqcount_begin(&src_mm->write_protect_seq);
}
ret = 0;
dst_pgd = pgd_offset(dst_mm, addr);
src_pgd = pgd_offset(src_mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(src_pgd))
continue;
if (unlikely(copy_p4d_range(dst_vma, src_vma, dst_pgd, src_pgd,
addr, next))) {
untrack_pfn_clear(dst_vma);
ret = -ENOMEM;
break;
}
} while (dst_pgd++, src_pgd++, addr = next, addr != end);
if (is_cow) {
raw_write_seqcount_end(&src_mm->write_protect_seq);
mmu_notifier_invalidate_range_end(&range);
}
return ret;
}
/* Whether we should zap all COWed (private) pages too */
static inline bool should_zap_cows(struct zap_details *details)
{
/* By default, zap all pages */
if (!details)
return true;
/* Or, we zap COWed pages only if the caller wants to */
return details->even_cows;
}
/* Decides whether we should zap this page with the page pointer specified */
static inline bool should_zap_page(struct zap_details *details, struct page *page)
{
/* If we can make a decision without *page.. */
if (should_zap_cows(details))
return true;
/* E.g. the caller passes NULL for the case of a zero page */
if (!page)
return true;
/* Otherwise we should only zap non-anon pages */
return !PageAnon(page);
}
static inline bool zap_drop_file_uffd_wp(struct zap_details *details)
{
if (!details)
return false;
return details->zap_flags & ZAP_FLAG_DROP_MARKER;
}
/*
* This function makes sure that we'll replace the none pte with an uffd-wp
* swap special pte marker when necessary. Must be with the pgtable lock held.
*/
static inline void
zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
unsigned long addr, pte_t *pte,
struct zap_details *details, pte_t pteval)
{
/* Zap on anonymous always means dropping everything */
if (vma_is_anonymous(vma))
return;
if (zap_drop_file_uffd_wp(details))
return;
pte_install_uffd_wp_if_needed(vma, addr, pte, pteval);
}
static unsigned long zap_pte_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
struct mm_struct *mm = tlb->mm;
int force_flush = 0;
int rss[NR_MM_COUNTERS];
spinlock_t *ptl;
pte_t *start_pte;
pte_t *pte;
swp_entry_t entry;
tlb_change_page_size(tlb, PAGE_SIZE);
again:
init_rss_vec(rss);
start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
pte = start_pte;
flush_tlb_batched_pending(mm);
arch_enter_lazy_mmu_mode();
do {
pte_t ptent = *pte;
struct page *page;
if (pte_none(ptent))
continue;
if (need_resched())
break;
if (pte_present(ptent)) {
unsigned int delay_rmap;
page = vm_normal_page(vma, addr, ptent);
if (unlikely(!should_zap_page(details, page)))
continue;
ptent = ptep_get_and_clear_full(mm, addr, pte,
tlb->fullmm);
tlb_remove_tlb_entry(tlb, pte, addr);
zap_install_uffd_wp_if_needed(vma, addr, pte, details,
ptent);
if (unlikely(!page))
continue;
delay_rmap = 0;
if (!PageAnon(page)) {
if (pte_dirty(ptent)) {
set_page_dirty(page);
if (tlb_delay_rmap(tlb)) {
delay_rmap = 1;
force_flush = 1;
}
}
if (pte_young(ptent) && likely(vma_has_recency(vma)))
mark_page_accessed(page);
}
rss[mm_counter(page)]--;
if (!delay_rmap) {
page_remove_rmap(page, vma, false);
if (unlikely(page_mapcount(page) < 0))
print_bad_pte(vma, addr, ptent, page);
}
if (unlikely(__tlb_remove_page(tlb, page, delay_rmap))) {
force_flush = 1;
addr += PAGE_SIZE;
break;
}
continue;
}
entry = pte_to_swp_entry(ptent);
if (is_device_private_entry(entry) ||
is_device_exclusive_entry(entry)) {
page = pfn_swap_entry_to_page(entry);
if (unlikely(!should_zap_page(details, page)))
continue;
/*
* Both device private/exclusive mappings should only
* work with anonymous page so far, so we don't need to
* consider uffd-wp bit when zap. For more information,
* see zap_install_uffd_wp_if_needed().
*/
WARN_ON_ONCE(!vma_is_anonymous(vma));
rss[mm_counter(page)]--;
if (is_device_private_entry(entry))
page_remove_rmap(page, vma, false);
put_page(page);
} else if (!non_swap_entry(entry)) {
/* Genuine swap entry, hence a private anon page */
if (!should_zap_cows(details))
continue;
rss[MM_SWAPENTS]--;
if (unlikely(!free_swap_and_cache(entry)))
print_bad_pte(vma, addr, ptent, NULL);
} else if (is_migration_entry(entry)) {
page = pfn_swap_entry_to_page(entry);
if (!should_zap_page(details, page))
continue;
rss[mm_counter(page)]--;
} else if (pte_marker_entry_uffd_wp(entry)) {
/*
* For anon: always drop the marker; for file: only
* drop the marker if explicitly requested.
*/
if (!vma_is_anonymous(vma) &&
!zap_drop_file_uffd_wp(details))
continue;
} else if (is_hwpoison_entry(entry) ||
is_swapin_error_entry(entry)) {
if (!should_zap_cows(details))
continue;
} else {
/* We should have covered all the swap entry types */
WARN_ON_ONCE(1);
}
pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
} while (pte++, addr += PAGE_SIZE, addr != end);
add_mm_rss_vec(mm, rss);
arch_leave_lazy_mmu_mode();
/* Do the actual TLB flush before dropping ptl */
if (force_flush) {
tlb_flush_mmu_tlbonly(tlb);
tlb_flush_rmaps(tlb, vma);
}
pte_unmap_unlock(start_pte, ptl);
/*
* If we forced a TLB flush (either due to running out of
* batch buffers or because we needed to flush dirty TLB
* entries before releasing the ptl), free the batched
* memory too. Restart if we didn't do everything.
*/
if (force_flush) {
force_flush = 0;
tlb_flush_mmu(tlb);
}
if (addr != end) {
cond_resched();
goto again;
}
return addr;
}
static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, pud_t *pud,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
pmd_t *pmd;
unsigned long next;
pmd = pmd_offset(pud, addr);
do {
next = pmd_addr_end(addr, end);
if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
if (next - addr != HPAGE_PMD_SIZE)
__split_huge_pmd(vma, pmd, addr, false, NULL);
else if (zap_huge_pmd(tlb, vma, pmd, addr))
goto next;
/* fall through */
} else if (details && details->single_folio &&
folio_test_pmd_mappable(details->single_folio) &&
next - addr == HPAGE_PMD_SIZE && pmd_none(*pmd)) {
spinlock_t *ptl = pmd_lock(tlb->mm, pmd);
/*
* Take and drop THP pmd lock so that we cannot return
* prematurely, while zap_huge_pmd() has cleared *pmd,
* but not yet decremented compound_mapcount().
*/
spin_unlock(ptl);
}
/*
* Here there can be other concurrent MADV_DONTNEED or
* trans huge page faults running, and if the pmd is
* none or trans huge it can change under us. This is
* because MADV_DONTNEED holds the mmap_lock in read
* mode.
*/
if (pmd_none_or_trans_huge_or_clear_bad(pmd))
goto next;
next = zap_pte_range(tlb, vma, pmd, addr, next, details);
next:
cond_resched();
} while (pmd++, addr = next, addr != end);
return addr;
}
static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, p4d_t *p4d,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
pud_t *pud;
unsigned long next;
pud = pud_offset(p4d, addr);
do {
next = pud_addr_end(addr, end);
if (pud_trans_huge(*pud) || pud_devmap(*pud)) {
if (next - addr != HPAGE_PUD_SIZE) {
mmap_assert_locked(tlb->mm);
split_huge_pud(vma, pud, addr);
} else if (zap_huge_pud(tlb, vma, pud, addr))
goto next;
/* fall through */
}
if (pud_none_or_clear_bad(pud))
continue;
next = zap_pmd_range(tlb, vma, pud, addr, next, details);
next:
cond_resched();
} while (pud++, addr = next, addr != end);
return addr;
}
static inline unsigned long zap_p4d_range(struct mmu_gather *tlb,
struct vm_area_struct *vma, pgd_t *pgd,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
p4d_t *p4d;
unsigned long next;
p4d = p4d_offset(pgd, addr);
do {
next = p4d_addr_end(addr, end);
if (p4d_none_or_clear_bad(p4d))
continue;
next = zap_pud_range(tlb, vma, p4d, addr, next, details);
} while (p4d++, addr = next, addr != end);
return addr;
}
void unmap_page_range(struct mmu_gather *tlb,
struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
struct zap_details *details)
{
pgd_t *pgd;
unsigned long next;
BUG_ON(addr >= end);
tlb_start_vma(tlb, vma);
pgd = pgd_offset(vma->vm_mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none_or_clear_bad(pgd))
continue;
next = zap_p4d_range(tlb, vma, pgd, addr, next, details);
} while (pgd++, addr = next, addr != end);
tlb_end_vma(tlb, vma);
}
static void unmap_single_vma(struct mmu_gather *tlb,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr,
struct zap_details *details, bool mm_wr_locked)
{
unsigned long start = max(vma->vm_start, start_addr);
unsigned long end;
if (start >= vma->vm_end)
return;
end = min(vma->vm_end, end_addr);
if (end <= vma->vm_start)
return;
if (vma->vm_file)
uprobe_munmap(vma, start, end);
if (unlikely(vma->vm_flags & VM_PFNMAP))
untrack_pfn(vma, 0, 0, mm_wr_locked);
if (start != end) {
if (unlikely(is_vm_hugetlb_page(vma))) {
/*
* It is undesirable to test vma->vm_file as it
* should be non-null for valid hugetlb area.
* However, vm_file will be NULL in the error
* cleanup path of mmap_region. When
* hugetlbfs ->mmap method fails,
* mmap_region() nullifies vma->vm_file
* before calling this function to clean up.
* Since no pte has actually been setup, it is
* safe to do nothing in this case.
*/
if (vma->vm_file) {
zap_flags_t zap_flags = details ?
details->zap_flags : 0;
__unmap_hugepage_range_final(tlb, vma, start, end,
NULL, zap_flags);
}
} else
unmap_page_range(tlb, vma, start, end, details);
}
}
/**
* unmap_vmas - unmap a range of memory covered by a list of vma's
* @tlb: address of the caller's struct mmu_gather
* @mt: the maple tree
* @vma: the starting vma
* @start_addr: virtual address at which to start unmapping
* @end_addr: virtual address at which to end unmapping
*
* Unmap all pages in the vma list.
*
* Only addresses between `start' and `end' will be unmapped.
*
* The VMA list must be sorted in ascending virtual address order.
*
* unmap_vmas() assumes that the caller will flush the whole unmapped address
* range after unmap_vmas() returns. So the only responsibility here is to
* ensure that any thus-far unmapped pages are flushed before unmap_vmas()
* drops the lock and schedules.
*/
void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
struct vm_area_struct *vma, unsigned long start_addr,
unsigned long end_addr, bool mm_wr_locked)
{
struct mmu_notifier_range range;
struct zap_details details = {
.zap_flags = ZAP_FLAG_DROP_MARKER | ZAP_FLAG_UNMAP,
/* Careful - we need to zap private pages too! */
.even_cows = true,
};
MA_STATE(mas, mt, vma->vm_end, vma->vm_end);
mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm,
start_addr, end_addr);
mmu_notifier_invalidate_range_start(&range);
do {
unmap_single_vma(tlb, vma, start_addr, end_addr, &details,
mm_wr_locked);
} while ((vma = mas_find(&mas, end_addr - 1)) != NULL);
mmu_notifier_invalidate_range_end(&range);
}
/**
* zap_page_range_single - remove user pages in a given range
* @vma: vm_area_struct holding the applicable pages
* @address: starting address of pages to zap
* @size: number of bytes to zap
* @details: details of shared cache invalidation
*
* The range must fit into one VMA.
*/
void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
unsigned long size, struct zap_details *details)
{
const unsigned long end = address + size;
struct mmu_notifier_range range;
struct mmu_gather tlb;
lru_add_drain();
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
address, end);
if (is_vm_hugetlb_page(vma))
adjust_range_if_pmd_sharing_possible(vma, &range.start,
&range.end);
tlb_gather_mmu(&tlb, vma->vm_mm);
update_hiwater_rss(vma->vm_mm);
mmu_notifier_invalidate_range_start(&range);
/*
* unmap 'address-end' not 'range.start-range.end' as range
* could have been expanded for hugetlb pmd sharing.
*/
unmap_single_vma(&tlb, vma, address, end, details, false);
mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}
/**
* zap_vma_ptes - remove ptes mapping the vma
* @vma: vm_area_struct holding ptes to be zapped
* @address: starting address of pages to zap
* @size: number of bytes to zap
*
* This function only unmaps ptes assigned to VM_PFNMAP vmas.
*
* The entire address range must be fully contained within the vma.
*
*/
void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
unsigned long size)
{
if (!range_in_vma(vma, address, address + size) ||
!(vma->vm_flags & VM_PFNMAP))
return;
zap_page_range_single(vma, address, size, NULL);
}
EXPORT_SYMBOL_GPL(zap_vma_ptes);
static pmd_t *walk_to_pmd(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pgd = pgd_offset(mm, addr);
p4d = p4d_alloc(mm, pgd, addr);
if (!p4d)
return NULL;
pud = pud_alloc(mm, p4d, addr);
if (!pud)
return NULL;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
return NULL;
VM_BUG_ON(pmd_trans_huge(*pmd));
return pmd;
}
pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
spinlock_t **ptl)
{
pmd_t *pmd = walk_to_pmd(mm, addr);
if (!pmd)
return NULL;
return pte_alloc_map_lock(mm, pmd, addr, ptl);
}
static int validate_page_before_insert(struct page *page)
{
if (PageAnon(page) || PageSlab(page) || page_has_type(page))
return -EINVAL;
flush_dcache_page(page);
return 0;
}
static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte,
unsigned long addr, struct page *page, pgprot_t prot)
{
if (!pte_none(*pte))
return -EBUSY;
/* Ok, finally just insert the thing.. */
get_page(page);
inc_mm_counter(vma->vm_mm, mm_counter_file(page));
page_add_file_rmap(page, vma, false);
set_pte_at(vma->vm_mm, addr, pte, mk_pte(page, prot));
return 0;
}
/*
* This is the old fallback for page remapping.
*
* For historical reasons, it only allows reserved pages. Only
* old drivers should use this, and they needed to mark their
* pages reserved for the old functions anyway.
*/
static int insert_page(struct vm_area_struct *vma, unsigned long addr,
struct page *page, pgprot_t prot)
{
int retval;
pte_t *pte;
spinlock_t *ptl;
retval = validate_page_before_insert(page);
if (retval)
goto out;
retval = -ENOMEM;
pte = get_locked_pte(vma->vm_mm, addr, &ptl);
if (!pte)
goto out;
retval = insert_page_into_pte_locked(vma, pte, addr, page, prot);
pte_unmap_unlock(pte, ptl);
out:
return retval;
}
#ifdef pte_index
static int insert_page_in_batch_locked(struct vm_area_struct *vma, pte_t *pte,
unsigned long addr, struct page *page, pgprot_t prot)
{
int err;
if (!page_count(page))
return -EINVAL;
err = validate_page_before_insert(page);
if (err)
return err;
return insert_page_into_pte_locked(vma, pte, addr, page, prot);
}
/* insert_pages() amortizes the cost of spinlock operations
* when inserting pages in a loop. Arch *must* define pte_index.
*/
static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
struct page **pages, unsigned long *num, pgprot_t prot)
{
pmd_t *pmd = NULL;
pte_t *start_pte, *pte;
spinlock_t *pte_lock;
struct mm_struct *const mm = vma->vm_mm;
unsigned long curr_page_idx = 0;
unsigned long remaining_pages_total = *num;
unsigned long pages_to_write_in_pmd;
int ret;
more:
ret = -EFAULT;
pmd = walk_to_pmd(mm, addr);
if (!pmd)
goto out;
pages_to_write_in_pmd = min_t(unsigned long,
remaining_pages_total, PTRS_PER_PTE - pte_index(addr));
/* Allocate the PTE if necessary; takes PMD lock once only. */
ret = -ENOMEM;
if (pte_alloc(mm, pmd))
goto out;
while (pages_to_write_in_pmd) {
int pte_idx = 0;
const int batch_size = min_t(int, pages_to_write_in_pmd, 8);
start_pte = pte_offset_map_lock(mm, pmd, addr, &pte_lock);
for (pte = start_pte; pte_idx < batch_size; ++pte, ++pte_idx) {
int err = insert_page_in_batch_locked(vma, pte,
addr, pages[curr_page_idx], prot);
if (unlikely(err)) {
pte_unmap_unlock(start_pte, pte_lock);
ret = err;
remaining_pages_total -= pte_idx;
goto out;
}
addr += PAGE_SIZE;
++curr_page_idx;
}
pte_unmap_unlock(start_pte, pte_lock);
pages_to_write_in_pmd -= batch_size;
remaining_pages_total -= batch_size;
}
if (remaining_pages_total)
goto more;
ret = 0;
out:
*num = remaining_pages_total;
return ret;
}
#endif /* ifdef pte_index */
/**
* vm_insert_pages - insert multiple pages into user vma, batching the pmd lock.
* @vma: user vma to map to
* @addr: target start user address of these pages
* @pages: source kernel pages
* @num: in: number of pages to map. out: number of pages that were *not*
* mapped. (0 means all pages were successfully mapped).
*
* Preferred over vm_insert_page() when inserting multiple pages.
*
* In case of error, we may have mapped a subset of the provided
* pages. It is the caller's responsibility to account for this case.
*
* The same restrictions apply as in vm_insert_page().
*/
int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
struct page **pages, unsigned long *num)
{
#ifdef pte_index
const unsigned long end_addr = addr + (*num * PAGE_SIZE) - 1;
if (addr < vma->vm_start || end_addr >= vma->vm_end)
return -EFAULT;
if (!(vma->vm_flags & VM_MIXEDMAP)) {
BUG_ON(mmap_read_trylock(vma->vm_mm));
BUG_ON(vma->vm_flags & VM_PFNMAP);
vm_flags_set(vma, VM_MIXEDMAP);
}
/* Defer page refcount checking till we're about to map that page. */
return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
#else
unsigned long idx = 0, pgcount = *num;
int err = -EINVAL;
for (; idx < pgcount; ++idx) {
err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);
if (err)
break;
}
*num = pgcount - idx;
return err;
#endif /* ifdef pte_index */
}
EXPORT_SYMBOL(vm_insert_pages);
/**
* vm_insert_page - insert single page into user vma
* @vma: user vma to map to
* @addr: target user address of this page
* @page: source kernel page
*
* This allows drivers to insert individual pages they've allocated
* into a user vma.
*
* The page has to be a nice clean _individual_ kernel allocation.
* If you allocate a compound page, you need to have marked it as
* such (__GFP_COMP), or manually just split the page up yourself
* (see split_page()).
*
* NOTE! Traditionally this was done with "remap_pfn_range()" which
* took an arbitrary page protection parameter. This doesn't allow
* that. Your vma protection will have to be set up correctly, which
* means that if you want a shared writable mapping, you'd better
* ask for a shared writable mapping!
*
* The page does not need to be reserved.
*
* Usually this function is called from f_op->mmap() handler
* under mm->mmap_lock write-lock, so it can change vma->vm_flags.
* Caller must set VM_MIXEDMAP on vma if it wants to call this
* function from other places, for example from page-fault handler.
*
* Return: %0 on success, negative error code otherwise.
*/
int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
struct page *page)
{
if (addr < vma->vm_start || addr >= vma->vm_end)
return -EFAULT;
if (!page_count(page))
return -EINVAL;
if (!(vma->vm_flags & VM_MIXEDMAP)) {
BUG_ON(mmap_read_trylock(vma->vm_mm));
BUG_ON(vma->vm_flags & VM_PFNMAP);
vm_flags_set(vma, VM_MIXEDMAP);
}
return insert_page(vma, addr, page, vma->vm_page_prot);
}
EXPORT_SYMBOL(vm_insert_page);
/*
* __vm_map_pages - maps range of kernel pages into user vma
* @vma: user vma to map to
* @pages: pointer to array of source kernel pages
* @num: number of pages in page array
* @offset: user's requested vm_pgoff
*
* This allows drivers to map range of kernel pages into a user vma.
*
* Return: 0 on success and error code otherwise.
*/
static int __vm_map_pages(struct vm_area_struct *vma, struct page **pages,
unsigned long num, unsigned long offset)
{
unsigned long count = vma_pages(vma);
unsigned long uaddr = vma->vm_start;
int ret, i;
/* Fail if the user requested offset is beyond the end of the object */
if (offset >= num)
return -ENXIO;
/* Fail if the user requested size exceeds available object size */
if (count > num - offset)
return -ENXIO;
for (i = 0; i < count; i++) {
ret = vm_insert_page(vma, uaddr, pages[offset + i]);
if (ret < 0)
return ret;
uaddr += PAGE_SIZE;
}
return 0;
}
/**
* vm_map_pages - maps range of kernel pages starts with non zero offset
* @vma: user vma to map to
* @pages: pointer to array of source kernel pages
* @num: number of pages in page array
*
* Maps an object consisting of @num pages, catering for the user's
* requested vm_pgoff
*
* If we fail to insert any page into the vma, the function will return
* immediately leaving any previously inserted pages present. Callers
* from the mmap handler may immediately return the error as their caller
* will destroy the vma, removing any successfully inserted pages. Other
* callers should make their own arrangements for calling unmap_region().
*
* Context: Process context. Called by mmap handlers.
* Return: 0 on success and error code otherwise.
*/
int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
unsigned long num)
{
return __vm_map_pages(vma, pages, num, vma->vm_pgoff);
}
EXPORT_SYMBOL(vm_map_pages);
/**
* vm_map_pages_zero - map range of kernel pages starts with zero offset
* @vma: user vma to map to
* @pages: pointer to array of source kernel pages
* @num: number of pages in page array
*
* Similar to vm_map_pages(), except that it explicitly sets the offset
* to 0. This function is intended for the drivers that did not consider
* vm_pgoff.
*
* Context: Process context. Called by mmap handlers.
* Return: 0 on success and error code otherwise.
*/
int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
unsigned long num)
{
return __vm_map_pages(vma, pages, num, 0);
}
EXPORT_SYMBOL(vm_map_pages_zero);
static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
pfn_t pfn, pgprot_t prot, bool mkwrite)
{
struct mm_struct *mm = vma->vm_mm;
pte_t *pte, entry;
spinlock_t *ptl;
pte = get_locked_pte(mm, addr, &ptl);
if (!pte)
return VM_FAULT_OOM;
if (!pte_none(*pte)) {
if (mkwrite) {
/*
* For read faults on private mappings the PFN passed
* in may not match the PFN we have mapped if the
* mapped PFN is a writeable COW page. In the mkwrite
* case we are creating a writable PTE for a shared
* mapping and we expect the PFNs to match. If they
* don't match, we are likely racing with block
* allocation and mapping invalidation so just skip the
* update.
*/
if (pte_pfn(*pte) != pfn_t_to_pfn(pfn)) {
WARN_ON_ONCE(!is_zero_pfn(pte_pfn(*pte)));
goto out_unlock;
}
entry = pte_mkyoung(*pte);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
if (ptep_set_access_flags(vma, addr, pte, entry, 1))
update_mmu_cache(vma, addr, pte);
}
goto out_unlock;
}
/* Ok, finally just insert the thing.. */
if (pfn_t_devmap(pfn))
entry = pte_mkdevmap(pfn_t_pte(pfn, prot));
else
entry = pte_mkspecial(pfn_t_pte(pfn, prot));
if (mkwrite) {
entry = pte_mkyoung(entry);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
}
set_pte_at(mm, addr, pte, entry);
update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
out_unlock:
pte_unmap_unlock(pte, ptl);
return VM_FAULT_NOPAGE;
}
/**
* vmf_insert_pfn_prot - insert single pfn into user vma with specified pgprot
* @vma: user vma to map to
* @addr: target user address of this page
* @pfn: source kernel pfn
* @pgprot: pgprot flags for the inserted page
*
* This is exactly like vmf_insert_pfn(), except that it allows drivers
* to override pgprot on a per-page basis.
*
* This only makes sense for IO mappings, and it makes no sense for
* COW mappings. In general, using multiple vmas is preferable;
* vmf_insert_pfn_prot should only be used if using multiple VMAs is
* impractical.
*
* pgprot typically only differs from @vma->vm_page_prot when drivers set
* caching- and encryption bits different than those of @vma->vm_page_prot,
* because the caching- or encryption mode may not be known at mmap() time.
*
* This is ok as long as @vma->vm_page_prot is not used by the core vm
* to set caching and encryption bits for those vmas (except for COW pages).
* This is ensured by core vm only modifying these page table entries using
* functions that don't touch caching- or encryption bits, using pte_modify()
* if needed. (See for example mprotect()).
*
* Also when new page-table entries are created, this is only done using the
* fault() callback, and never using the value of vma->vm_page_prot,
* except for page-table entries that point to anonymous pages as the result
* of COW.
*
* Context: Process context. May allocate using %GFP_KERNEL.
* Return: vm_fault_t value.
*/
vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn, pgprot_t pgprot)
{
/*
* Technically, architectures with pte_special can avoid all these
* restrictions (same for remap_pfn_range). However we would like
* consistency in testing and feature parity among all, so we should
* try to keep these invariants in place for everybody.
*/
BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
(VM_PFNMAP|VM_MIXEDMAP));
BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));
if (addr < vma->vm_start || addr >= vma->vm_end)
return VM_FAULT_SIGBUS;
if (!pfn_modify_allowed(pfn, pgprot))
return VM_FAULT_SIGBUS;
track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
return insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
false);
}
EXPORT_SYMBOL(vmf_insert_pfn_prot);
/**
* vmf_insert_pfn - insert single pfn into user vma
* @vma: user vma to map to
* @addr: target user address of this page
* @pfn: source kernel pfn
*
* Similar to vm_insert_page, this allows drivers to insert individual pages
* they've allocated into a user vma. Same comments apply.
*
* This function should only be called from a vm_ops->fault handler, and
* in that case the handler should return the result of this function.
*
* vma cannot be a COW mapping.
*
* As this is called only for pages that do not currently exist, we
* do not need to flush old virtual caches or the TLB.
*
* Context: Process context. May allocate using %GFP_KERNEL.
* Return: vm_fault_t value.
*/
vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn)
{
return vmf_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
}
EXPORT_SYMBOL(vmf_insert_pfn);
static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
{
/* these checks mirror the abort conditions in vm_normal_page */
if (vma->vm_flags & VM_MIXEDMAP)
return true;
if (pfn_t_devmap(pfn))
return true;
if (pfn_t_special(pfn))
return true;
if (is_zero_pfn(pfn_t_to_pfn(pfn)))
return true;
return false;
}
static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
unsigned long addr, pfn_t pfn, bool mkwrite)
{
pgprot_t pgprot = vma->vm_page_prot;
int err;
BUG_ON(!vm_mixed_ok(vma, pfn));
if (addr < vma->vm_start || addr >= vma->vm_end)
return VM_FAULT_SIGBUS;
track_pfn_insert(vma, &pgprot, pfn);
if (!pfn_modify_allowed(pfn_t_to_pfn(pfn), pgprot))
return VM_FAULT_SIGBUS;
/*
* If we don't have pte special, then we have to use the pfn_valid()
* based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
* refcount the page if pfn_valid is true (hence insert_page rather
* than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP
* without pte special, it would there be refcounted as a normal page.
*/
if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) &&
!pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
struct page *page;
/*
* At this point we are committed to insert_page()
* regardless of whether the caller specified flags that
* result in pfn_t_has_page() == false.
*/
page = pfn_to_page(pfn_t_to_pfn(pfn));
err = insert_page(vma, addr, page, pgprot);
} else {
return insert_pfn(vma, addr, pfn, pgprot, mkwrite);
}
if (err == -ENOMEM)
return VM_FAULT_OOM;
if (err < 0 && err != -EBUSY)
return VM_FAULT_SIGBUS;
return VM_FAULT_NOPAGE;
}
vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
pfn_t pfn)
{
return __vm_insert_mixed(vma, addr, pfn, false);
}
EXPORT_SYMBOL(vmf_insert_mixed);
/*
* If the insertion of PTE failed because someone else already added a
* different entry in the mean time, we treat that as success as we assume
* the same entry was actually inserted.
*/
vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
unsigned long addr, pfn_t pfn)
{
return __vm_insert_mixed(vma, addr, pfn, true);
}
EXPORT_SYMBOL(vmf_insert_mixed_mkwrite);
/*
* maps a range of physical memory into the requested pages. the old
* mappings are removed. any references to nonexistent pages results
* in null mappings (currently treated as "copy-on-access")
*/
static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
unsigned long addr, unsigned long end,
unsigned long pfn, pgprot_t prot)
{
pte_t *pte, *mapped_pte;
spinlock_t *ptl;
int err = 0;
mapped_pte = pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
if (!pte)
return -ENOMEM;
arch_enter_lazy_mmu_mode();
do {
BUG_ON(!pte_none(*pte));
if (!pfn_modify_allowed(pfn, prot)) {
err = -EACCES;
break;
}
set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
pfn++;
} while (pte++, addr += PAGE_SIZE, addr != end);
arch_leave_lazy_mmu_mode();
pte_unmap_unlock(mapped_pte, ptl);
return err;
}
static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
unsigned long addr, unsigned long end,
unsigned long pfn, pgprot_t prot)
{
pmd_t *pmd;
unsigned long next;
int err;
pfn -= addr >> PAGE_SHIFT;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
return -ENOMEM;
VM_BUG_ON(pmd_trans_huge(*pmd));
do {
next = pmd_addr_end(addr, end);
err = remap_pte_range(mm, pmd, addr, next,
pfn + (addr >> PAGE_SHIFT), prot);
if (err)
return err;
} while (pmd++, addr = next, addr != end);
return 0;
}
static inline int remap_pud_range(struct mm_struct *mm, p4d_t *p4d,
unsigned long addr, unsigned long end,
unsigned long pfn, pgprot_t prot)
{
pud_t *pud;
unsigned long next;
int err;
pfn -= addr >> PAGE_SHIFT;
pud = pud_alloc(mm, p4d, addr);
if (!pud)
return -ENOMEM;
do {
next = pud_addr_end(addr, end);
err = remap_pmd_range(mm, pud, addr, next,
pfn + (addr >> PAGE_SHIFT), prot);
if (err)
return err;
} while (pud++, addr = next, addr != end);
return 0;
}
static inline int remap_p4d_range(struct mm_struct *mm, pgd_t *pgd,
unsigned long addr, unsigned long end,
unsigned long pfn, pgprot_t prot)
{
p4d_t *p4d;
unsigned long next;
int err;
pfn -= addr >> PAGE_SHIFT;
p4d = p4d_alloc(mm, pgd, addr);
if (!p4d)
return -ENOMEM;
do {
next = p4d_addr_end(addr, end);
err = remap_pud_range(mm, p4d, addr, next,
pfn + (addr >> PAGE_SHIFT), prot);
if (err)
return err;
} while (p4d++, addr = next, addr != end);
return 0;
}
/*
* Variant of remap_pfn_range that does not call track_pfn_remap. The caller
* must have pre-validated the caching bits of the pgprot_t.
*/
int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn, unsigned long size, pgprot_t prot)
{
pgd_t *pgd;
unsigned long next;
unsigned long end = addr + PAGE_ALIGN(size);
struct mm_struct *mm = vma->vm_mm;
int err;
if (WARN_ON_ONCE(!PAGE_ALIGNED(addr)))
return -EINVAL;
/*
* Physically remapped pages are special. Tell the
* rest of the world about it:
* VM_IO tells people not to look at these pages
* (accesses can have side effects).
* VM_PFNMAP tells the core MM that the base pages are just
* raw PFN mappings, and do not have a "struct page" associated
* with them.
* VM_DONTEXPAND
* Disable vma merging and expanding with mremap().
* VM_DONTDUMP
* Omit vma from core dump, even when VM_IO turned off.
*
* There's a horrible special case to handle copy-on-write
* behaviour that some programs depend on. We mark the "original"
* un-COW'ed pages by matching them up with "vma->vm_pgoff".
* See vm_normal_page() for details.
*/
if (is_cow_mapping(vma->vm_flags)) {
if (addr != vma->vm_start || end != vma->vm_end)
return -EINVAL;
vma->vm_pgoff = pfn;
}
vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
BUG_ON(addr >= end);
pfn -= addr >> PAGE_SHIFT;
pgd = pgd_offset(mm, addr);
flush_cache_range(vma, addr, end);
do {
next = pgd_addr_end(addr, end);
err = remap_p4d_range(mm, pgd, addr, next,
pfn + (addr >> PAGE_SHIFT), prot);
if (err)
return err;
} while (pgd++, addr = next, addr != end);
return 0;
}
/**
* remap_pfn_range - remap kernel memory to userspace
* @vma: user vma to map to
* @addr: target page aligned user address to start at
* @pfn: page frame number of kernel physical memory address
* @size: size of mapping area
* @prot: page protection flags for this mapping
*
* Note: this is only safe if the mm semaphore is held when called.
*
* Return: %0 on success, negative error code otherwise.
*/
int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn, unsigned long size, pgprot_t prot)
{
int err;
err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
if (err)
return -EINVAL;
err = remap_pfn_range_notrack(vma, addr, pfn, size, prot);
if (err)
untrack_pfn(vma, pfn, PAGE_ALIGN(size), true);
return err;
}
EXPORT_SYMBOL(remap_pfn_range);
/**
* vm_iomap_memory - remap memory to userspace
* @vma: user vma to map to
* @start: start of the physical memory to be mapped
* @len: size of area
*
* This is a simplified io_remap_pfn_range() for common driver use. The
* driver just needs to give us the physical memory range to be mapped,
* we'll figure out the rest from the vma information.
*
* NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
* whatever write-combining details or similar.
*
* Return: %0 on success, negative error code otherwise.
*/
int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
{
unsigned long vm_len, pfn, pages;
/* Check that the physical memory area passed in looks valid */
if (start + len < start)
return -EINVAL;
/*
* You *really* shouldn't map things that aren't page-aligned,
* but we've historically allowed it because IO memory might
* just have smaller alignment.
*/
len += start & ~PAGE_MASK;
pfn = start >> PAGE_SHIFT;
pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
if (pfn + pages < pfn)
return -EINVAL;
/* We start the mapping 'vm_pgoff' pages into the area */
if (vma->vm_pgoff > pages)
return -EINVAL;
pfn += vma->vm_pgoff;
pages -= vma->vm_pgoff;
/* Can we fit all of the mapping? */
vm_len = vma->vm_end - vma->vm_start;
if (vm_len >> PAGE_SHIFT > pages)
return -EINVAL;
/* Ok, let it rip */
return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
}
EXPORT_SYMBOL(vm_iomap_memory);
static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
unsigned long addr, unsigned long end,
pte_fn_t fn, void *data, bool create,
pgtbl_mod_mask *mask)
{
pte_t *pte, *mapped_pte;
int err = 0;
spinlock_t *ptl;
if (create) {
mapped_pte = pte = (mm == &init_mm) ?
pte_alloc_kernel_track(pmd, addr, mask) :
pte_alloc_map_lock(mm, pmd, addr, &ptl);
if (!pte)
return -ENOMEM;
} else {
mapped_pte = pte = (mm == &init_mm) ?
pte_offset_kernel(pmd, addr) :
pte_offset_map_lock(mm, pmd, addr, &ptl);
}
BUG_ON(pmd_huge(*pmd));
arch_enter_lazy_mmu_mode();
if (fn) {
do {
if (create || !pte_none(*pte)) {
err = fn(pte++, addr, data);
if (err)
break;
}
} while (addr += PAGE_SIZE, addr != end);
}
*mask |= PGTBL_PTE_MODIFIED;
arch_leave_lazy_mmu_mode();
if (mm != &init_mm)
pte_unmap_unlock(mapped_pte, ptl);
return err;
}
static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
unsigned long addr, unsigned long end,
pte_fn_t fn, void *data, bool create,
pgtbl_mod_mask *mask)
{
pmd_t *pmd;
unsigned long next;
int err = 0;
BUG_ON(pud_huge(*pud));
if (create) {
pmd = pmd_alloc_track(mm, pud, addr, mask);
if (!pmd)
return -ENOMEM;
} else {
pmd = pmd_offset(pud, addr);
}
do {
next = pmd_addr_end(addr, end);
if (pmd_none(*pmd) && !create)
continue;
if (WARN_ON_ONCE(pmd_leaf(*pmd)))
return -EINVAL;
if (!pmd_none(*pmd) && WARN_ON_ONCE(pmd_bad(*pmd))) {
if (!create)
continue;
pmd_clear_bad(pmd);
}
err = apply_to_pte_range(mm, pmd, addr, next,
fn, data, create, mask);
if (err)
break;
} while (pmd++, addr = next, addr != end);
return err;
}
static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d,
unsigned long addr, unsigned long end,
pte_fn_t fn, void *data, bool create,
pgtbl_mod_mask *mask)
{
pud_t *pud;
unsigned long next;
int err = 0;
if (create) {
pud = pud_alloc_track(mm, p4d, addr, mask);
if (!pud)
return -ENOMEM;
} else {
pud = pud_offset(p4d, addr);
}
do {
next = pud_addr_end(addr, end);
if (pud_none(*pud) && !create)
continue;
if (WARN_ON_ONCE(pud_leaf(*pud)))
return -EINVAL;
if (!pud_none(*pud) && WARN_ON_ONCE(pud_bad(*pud))) {
if (!create)
continue;
pud_clear_bad(pud);
}
err = apply_to_pmd_range(mm, pud, addr, next,
fn, data, create, mask);
if (err)
break;
} while (pud++, addr = next, addr != end);
return err;
}
static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
unsigned long addr, unsigned long end,
pte_fn_t fn, void *data, bool create,
pgtbl_mod_mask *mask)
{
p4d_t *p4d;
unsigned long next;
int err = 0;
if (create) {
p4d = p4d_alloc_track(mm, pgd, addr, mask);
if (!p4d)
return -ENOMEM;
} else {
p4d = p4d_offset(pgd, addr);
}
do {
next = p4d_addr_end(addr, end);
if (p4d_none(*p4d) && !create)
continue;
if (WARN_ON_ONCE(p4d_leaf(*p4d)))
return -EINVAL;
if (!p4d_none(*p4d) && WARN_ON_ONCE(p4d_bad(*p4d))) {
if (!create)
continue;
p4d_clear_bad(p4d);
}
err = apply_to_pud_range(mm, p4d, addr, next,
fn, data, create, mask);
if (err)
break;
} while (p4d++, addr = next, addr != end);
return err;
}
static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
unsigned long size, pte_fn_t fn,
void *data, bool create)
{
pgd_t *pgd;
unsigned long start = addr, next;
unsigned long end = addr + size;
pgtbl_mod_mask mask = 0;
int err = 0;
if (WARN_ON(addr >= end))
return -EINVAL;
pgd = pgd_offset(mm, addr);
do {
next = pgd_addr_end(addr, end);
if (pgd_none(*pgd) && !create)
continue;
if (WARN_ON_ONCE(pgd_leaf(*pgd)))
return -EINVAL;
if (!pgd_none(*pgd) && WARN_ON_ONCE(pgd_bad(*pgd))) {
if (!create)
continue;
pgd_clear_bad(pgd);
}
err = apply_to_p4d_range(mm, pgd, addr, next,
fn, data, create, &mask);
if (err)
break;
} while (pgd++, addr = next, addr != end);
if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
arch_sync_kernel_mappings(start, start + size);
return err;
}
/*
* Scan a region of virtual memory, filling in page tables as necessary
* and calling a provided function on each leaf page table.
*/
int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
unsigned long size, pte_fn_t fn, void *data)
{
return __apply_to_page_range(mm, addr, size, fn, data, true);
}
EXPORT_SYMBOL_GPL(apply_to_page_range);
/*
* Scan a region of virtual memory, calling a provided function on
* each leaf page table where it exists.
*
* Unlike apply_to_page_range, this does _not_ fill in page tables
* where they are absent.
*/
int apply_to_existing_page_range(struct mm_struct *mm, unsigned long addr,
unsigned long size, pte_fn_t fn, void *data)
{
return __apply_to_page_range(mm, addr, size, fn, data, false);
}
EXPORT_SYMBOL_GPL(apply_to_existing_page_range);
/*
* handle_pte_fault chooses page fault handler according to an entry which was
* read non-atomically. Before making any commitment, on those architectures
* or configurations (e.g. i386 with PAE) which might give a mix of unmatched
* parts, do_swap_page must check under lock before unmapping the pte and
* proceeding (but do_wp_page is only called after already making such a check;
* and do_anonymous_page can safely check later on).
*/
static inline int pte_unmap_same(struct vm_fault *vmf)
{
int same = 1;
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION)
if (sizeof(pte_t) > sizeof(unsigned long)) {
spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
spin_lock(ptl);
same = pte_same(*vmf->pte, vmf->orig_pte);
spin_unlock(ptl);
}
#endif
pte_unmap(vmf->pte);
vmf->pte = NULL;
return same;
}
/*
* Return:
* 0: copied succeeded
* -EHWPOISON: copy failed due to hwpoison in source page
* -EAGAIN: copied failed (some other reason)
*/
static inline int __wp_page_copy_user(struct page *dst, struct page *src,
struct vm_fault *vmf)
{
int ret;
void *kaddr;
void __user *uaddr;
bool locked = false;
struct vm_area_struct *vma = vmf->vma;
struct mm_struct *mm = vma->vm_mm;
unsigned long addr = vmf->address;
if (likely(src)) {
if (copy_mc_user_highpage(dst, src, addr, vma)) {
memory_failure_queue(page_to_pfn(src), 0);
return -EHWPOISON;
}
return 0;
}
/*
* If the source page was a PFN mapping, we don't have
* a "struct page" for it. We do a best-effort copy by
* just copying from the original user address. If that
* fails, we just zero-fill it. Live with it.
*/
kaddr = kmap_atomic(dst);
uaddr = (void __user *)(addr & PAGE_MASK);
/*
* On architectures with software "accessed" bits, we would
* take a double page fault, so mark it accessed here.
*/
if (!arch_has_hw_pte_young() && !pte_young(vmf->orig_pte)) {
pte_t entry;
vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);
locked = true;
if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) {
/*
* Other thread has already handled the fault
* and update local tlb only
*/
update_mmu_tlb(vma, addr, vmf->pte);
ret = -EAGAIN;
goto pte_unlock;
}
entry = pte_mkyoung(vmf->orig_pte);
if (ptep_set_access_flags(vma, addr, vmf->pte, entry, 0))
update_mmu_cache(vma, addr, vmf->pte);
}
/*
* This really shouldn't fail, because the page is there
* in the page tables. But it might just be unreadable,
* in which case we just give up and fill the result with
* zeroes.
*/
if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) {
if (locked)
goto warn;
/* Re-validate under PTL if the page is still mapped */
vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);
locked = true;
if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) {
/* The PTE changed under us, update local tlb */
update_mmu_tlb(vma, addr, vmf->pte);
ret = -EAGAIN;
goto pte_unlock;
}
/*
* The same page can be mapped back since last copy attempt.
* Try to copy again under PTL.
*/
if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) {
/*
* Give a warn in case there can be some obscure
* use-case
*/
warn:
WARN_ON_ONCE(1);
clear_page(kaddr);
}
}
ret = 0;
pte_unlock:
if (locked)
pte_unmap_unlock(vmf->pte, vmf->ptl);
kunmap_atomic(kaddr);
flush_dcache_page(dst);
return ret;
}
static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma)
{
struct file *vm_file = vma->vm_file;
if (vm_file)
return mapping_gfp_mask(vm_file->f_mapping) | __GFP_FS | __GFP_IO;
/*
* Special mappings (e.g. VDSO) do not have any file so fake
* a default GFP_KERNEL for them.
*/
return GFP_KERNEL;
}
/*
* Notify the address space that the page is about to become writable so that
* it can prohibit this or wait for the page to get into an appropriate state.
*
* We do this without the lock held, so that it can sleep if it needs to.
*/
static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
{
vm_fault_t ret;
struct page *page = vmf->page;
unsigned int old_flags = vmf->flags;
vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
if (vmf->vma->vm_file &&
IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host))
return VM_FAULT_SIGBUS;
ret = vmf->vma->vm_ops->page_mkwrite(vmf);
/* Restore original flags so that caller is not surprised */
vmf->flags = old_flags;
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
return ret;
if (unlikely(!(ret & VM_FAULT_LOCKED))) {
lock_page(page);
if (!page->mapping) {
unlock_page(page);
return 0; /* retry */
}
ret |= VM_FAULT_LOCKED;
} else
VM_BUG_ON_PAGE(!PageLocked(page), page);
return ret;
}
/*
* Handle dirtying of a page in shared file mapping on a write fault.
*
* The function expects the page to be locked and unlocks it.
*/
static vm_fault_t fault_dirty_shared_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct address_space *mapping;
struct page *page = vmf->page;
bool dirtied;
bool page_mkwrite = vma->vm_ops && vma->vm_ops->page_mkwrite;
dirtied = set_page_dirty(page);
VM_BUG_ON_PAGE(PageAnon(page), page);
/*
* Take a local copy of the address_space - page.mapping may be zeroed
* by truncate after unlock_page(). The address_space itself remains
* pinned by vma->vm_file's reference. We rely on unlock_page()'s
* release semantics to prevent the compiler from undoing this copying.
*/
mapping = page_rmapping(page);
unlock_page(page);
if (!page_mkwrite)
file_update_time(vma->vm_file);
/*
* Throttle page dirtying rate down to writeback speed.
*
* mapping may be NULL here because some device drivers do not
* set page.mapping but still dirty their pages
*
* Drop the mmap_lock before waiting on IO, if we can. The file
* is pinning the mapping, as per above.
*/
if ((dirtied || page_mkwrite) && mapping) {
struct file *fpin;
fpin = maybe_unlock_mmap_for_io(vmf, NULL);
balance_dirty_pages_ratelimited(mapping);
if (fpin) {
fput(fpin);
return VM_FAULT_COMPLETED;
}
}
return 0;
}
/*
* Handle write page faults for pages that can be reused in the current vma
*
* This can happen either due to the mapping being with the VM_SHARED flag,
* or due to us being the last reference standing to the page. In either
* case, all we need to do here is to mark the page as writable and update
* any related book-keeping.
*/
static inline void wp_page_reuse(struct vm_fault *vmf)
__releases(vmf->ptl)
{
struct vm_area_struct *vma = vmf->vma;
struct page *page = vmf->page;
pte_t entry;
VM_BUG_ON(!(vmf->flags & FAULT_FLAG_WRITE));
VM_BUG_ON(page && PageAnon(page) && !PageAnonExclusive(page));
/*
* Clear the pages cpupid information as the existing
* information potentially belongs to a now completely
* unrelated process.
*/
if (page)
page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1);
flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
entry = pte_mkyoung(vmf->orig_pte);
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
update_mmu_cache(vma, vmf->address, vmf->pte);
pte_unmap_unlock(vmf->pte, vmf->ptl);
count_vm_event(PGREUSE);
}
/*
* Handle the case of a page which we actually need to copy to a new page,
* either due to COW or unsharing.
*
* Called with mmap_lock locked and the old page referenced, but
* without the ptl held.
*
* High level logic flow:
*
* - Allocate a page, copy the content of the old page to the new one.
* - Handle book keeping and accounting - cgroups, mmu-notifiers, etc.
* - Take the PTL. If the pte changed, bail out and release the allocated page
* - If the pte is still the way we remember it, update the page table and all
* relevant references. This includes dropping the reference the page-table
* held to the old page, as well as updating the rmap.
* - In any case, unlock the PTL and drop the reference we took to the old page.
*/
static vm_fault_t wp_page_copy(struct vm_fault *vmf)
{
const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
struct vm_area_struct *vma = vmf->vma;
struct mm_struct *mm = vma->vm_mm;
struct folio *old_folio = NULL;
struct folio *new_folio = NULL;
pte_t entry;
int page_copied = 0;
struct mmu_notifier_range range;
int ret;
delayacct_wpcopy_start();
if (vmf->page)
old_folio = page_folio(vmf->page);
if (unlikely(anon_vma_prepare(vma)))
goto oom;
if (is_zero_pfn(pte_pfn(vmf->orig_pte))) {
new_folio = vma_alloc_zeroed_movable_folio(vma, vmf->address);
if (!new_folio)
goto oom;
} else {
new_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma,
vmf->address, false);
if (!new_folio)
goto oom;
ret = __wp_page_copy_user(&new_folio->page, vmf->page, vmf);
if (ret) {
/*
* COW failed, if the fault was solved by other,
* it's fine. If not, userspace would re-fault on
* the same address and we will handle the fault
* from the second attempt.
* The -EHWPOISON case will not be retried.
*/
folio_put(new_folio);
if (old_folio)
folio_put(old_folio);
delayacct_wpcopy_end();
return ret == -EHWPOISON ? VM_FAULT_HWPOISON : 0;
}
kmsan_copy_page_meta(&new_folio->page, vmf->page);
}
if (mem_cgroup_charge(new_folio, mm, GFP_KERNEL))
goto oom_free_new;
folio_throttle_swaprate(new_folio, GFP_KERNEL);
__folio_mark_uptodate(new_folio);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm,
vmf->address & PAGE_MASK,
(vmf->address & PAGE_MASK) + PAGE_SIZE);
mmu_notifier_invalidate_range_start(&range);
/*
* Re-check the pte - we dropped the lock
*/
vmf->pte = pte_offset_map_lock(mm, vmf->pmd, vmf->address, &vmf->ptl);
if (likely(pte_same(*vmf->pte, vmf->orig_pte))) {
if (old_folio) {
if (!folio_test_anon(old_folio)) {
dec_mm_counter(mm, mm_counter_file(&old_folio->page));
inc_mm_counter(mm, MM_ANONPAGES);
}
} else {
inc_mm_counter(mm, MM_ANONPAGES);
}
flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
entry = mk_pte(&new_folio->page, vma->vm_page_prot);
entry = pte_sw_mkyoung(entry);
if (unlikely(unshare)) {
if (pte_soft_dirty(vmf->orig_pte))
entry = pte_mksoft_dirty(entry);
if (pte_uffd_wp(vmf->orig_pte))
entry = pte_mkuffd_wp(entry);
} else {
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
}
/*
* Clear the pte entry and flush it first, before updating the
* pte with the new entry, to keep TLBs on different CPUs in
* sync. This code used to set the new PTE then flush TLBs, but
* that left a window where the new PTE could be loaded into
* some TLBs while the old PTE remains in others.
*/
ptep_clear_flush_notify(vma, vmf->address, vmf->pte);
folio_add_new_anon_rmap(new_folio, vma, vmf->address);
folio_add_lru_vma(new_folio, vma);
/*
* We call the notify macro here because, when using secondary
* mmu page tables (such as kvm shadow page tables), we want the
* new page to be mapped directly into the secondary page table.
*/
BUG_ON(unshare && pte_write(entry));
set_pte_at_notify(mm, vmf->address, vmf->pte, entry);
update_mmu_cache(vma, vmf->address, vmf->pte);
if (old_folio) {
/*
* Only after switching the pte to the new page may
* we remove the mapcount here. Otherwise another
* process may come and find the rmap count decremented
* before the pte is switched to the new page, and
* "reuse" the old page writing into it while our pte
* here still points into it and can be read by other
* threads.
*
* The critical issue is to order this
* page_remove_rmap with the ptp_clear_flush above.
* Those stores are ordered by (if nothing else,)
* the barrier present in the atomic_add_negative
* in page_remove_rmap.
*
* Then the TLB flush in ptep_clear_flush ensures that
* no process can access the old page before the
* decremented mapcount is visible. And the old page
* cannot be reused until after the decremented
* mapcount is visible. So transitively, TLBs to
* old page will be flushed before it can be reused.
*/
page_remove_rmap(vmf->page, vma, false);
}
/* Free the old page.. */
new_folio = old_folio;
page_copied = 1;
} else {
update_mmu_tlb(vma, vmf->address, vmf->pte);
}
if (new_folio)
folio_put(new_folio);
pte_unmap_unlock(vmf->pte, vmf->ptl);
/*
* No need to double call mmu_notifier->invalidate_range() callback as
* the above ptep_clear_flush_notify() did already call it.
*/
mmu_notifier_invalidate_range_only_end(&range);
if (old_folio) {
if (page_copied)
free_swap_cache(&old_folio->page);
folio_put(old_folio);
}
delayacct_wpcopy_end();
return 0;
oom_free_new:
folio_put(new_folio);
oom:
if (old_folio)
folio_put(old_folio);
delayacct_wpcopy_end();
return VM_FAULT_OOM;
}
/**
* finish_mkwrite_fault - finish page fault for a shared mapping, making PTE
* writeable once the page is prepared
*
* @vmf: structure describing the fault
*
* This function handles all that is needed to finish a write page fault in a
* shared mapping due to PTE being read-only once the mapped page is prepared.
* It handles locking of PTE and modifying it.
*
* The function expects the page to be locked or other protection against
* concurrent faults / writeback (such as DAX radix tree locks).
*
* Return: %0 on success, %VM_FAULT_NOPAGE when PTE got changed before
* we acquired PTE lock.
*/
vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf)
{
WARN_ON_ONCE(!(vmf->vma->vm_flags & VM_SHARED));
vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, vmf->address,
&vmf->ptl);
/*
* We might have raced with another page fault while we released the
* pte_offset_map_lock.
*/
if (!pte_same(*vmf->pte, vmf->orig_pte)) {
update_mmu_tlb(vmf->vma, vmf->address, vmf->pte);
pte_unmap_unlock(vmf->pte, vmf->ptl);
return VM_FAULT_NOPAGE;
}
wp_page_reuse(vmf);
return 0;
}
/*
* Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED
* mapping
*/
static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
vm_fault_t ret;
pte_unmap_unlock(vmf->pte, vmf->ptl);
vmf->flags |= FAULT_FLAG_MKWRITE;
ret = vma->vm_ops->pfn_mkwrite(vmf);
if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))
return ret;
return finish_mkwrite_fault(vmf);
}
wp_page_reuse(vmf);
return 0;
}
static vm_fault_t wp_page_shared(struct vm_fault *vmf)
__releases(vmf->ptl)
{
struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret = 0;
get_page(vmf->page);
if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
vm_fault_t tmp;
pte_unmap_unlock(vmf->pte, vmf->ptl);
tmp = do_page_mkwrite(vmf);
if (unlikely(!tmp || (tmp &
(VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
put_page(vmf->page);
return tmp;
}
tmp = finish_mkwrite_fault(vmf);
if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
unlock_page(vmf->page);
put_page(vmf->page);
return tmp;
}
} else {
wp_page_reuse(vmf);
lock_page(vmf->page);
}
ret |= fault_dirty_shared_page(vmf);
put_page(vmf->page);
return ret;
}
/*
* This routine handles present pages, when
* * users try to write to a shared page (FAULT_FLAG_WRITE)
* * GUP wants to take a R/O pin on a possibly shared anonymous page
* (FAULT_FLAG_UNSHARE)
*
* It is done by copying the page to a new address and decrementing the
* shared-page counter for the old page.
*
* Note that this routine assumes that the protection checks have been
* done by the caller (the low-level page fault routine in most cases).
* Thus, with FAULT_FLAG_WRITE, we can safely just mark it writable once we've
* done any necessary COW.
*
* In case of FAULT_FLAG_WRITE, we also mark the page dirty at this point even
* though the page will change only once the write actually happens. This
* avoids a few races, and potentially makes it more efficient.
*
* We enter with non-exclusive mmap_lock (to exclude vma changes,
* but allow concurrent faults), with pte both mapped and locked.
* We return with mmap_lock still held, but pte unmapped and unlocked.
*/
static vm_fault_t do_wp_page(struct vm_fault *vmf)
__releases(vmf->ptl)
{
const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
struct vm_area_struct *vma = vmf->vma;
struct folio *folio = NULL;
if (likely(!unshare)) {
if (userfaultfd_pte_wp(vma, *vmf->pte)) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
return handle_userfault(vmf, VM_UFFD_WP);
}
/*
* Userfaultfd write-protect can defer flushes. Ensure the TLB
* is flushed in this case before copying.
*/
if (unlikely(userfaultfd_wp(vmf->vma) &&
mm_tlb_flush_pending(vmf->vma->vm_mm)))
flush_tlb_page(vmf->vma, vmf->address);
}
vmf->page = vm_normal_page(vma, vmf->address, vmf->orig_pte);
/*
* Shared mapping: we are guaranteed to have VM_WRITE and
* FAULT_FLAG_WRITE set at this point.
*/
if (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) {
/*
* VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a
* VM_PFNMAP VMA.
*
* We should not cow pages in a shared writeable mapping.
* Just mark the pages writable and/or call ops->pfn_mkwrite.
*/
if (!vmf->page)
return wp_pfn_shared(vmf);
return wp_page_shared(vmf);
}
if (vmf->page)
folio = page_folio(vmf->page);
/*
* Private mapping: create an exclusive anonymous page copy if reuse
* is impossible. We might miss VM_WRITE for FOLL_FORCE handling.
*/
if (folio && folio_test_anon(folio)) {
/*
* If the page is exclusive to this process we must reuse the
* page without further checks.
*/
if (PageAnonExclusive(vmf->page))
goto reuse;
/*
* We have to verify under folio lock: these early checks are
* just an optimization to avoid locking the folio and freeing
* the swapcache if there is little hope that we can reuse.
*
* KSM doesn't necessarily raise the folio refcount.
*/
if (folio_test_ksm(folio) || folio_ref_count(folio) > 3)
goto copy;
if (!folio_test_lru(folio))
/*
* Note: We cannot easily detect+handle references from
* remote LRU pagevecs or references to LRU folios.
*/
lru_add_drain();
if (folio_ref_count(folio) > 1 + folio_test_swapcache(folio))
goto copy;
if (!folio_trylock(folio))
goto copy;
if (folio_test_swapcache(folio))
folio_free_swap(folio);
if (folio_test_ksm(folio) || folio_ref_count(folio) != 1) {
folio_unlock(folio);
goto copy;
}
/*
* Ok, we've got the only folio reference from our mapping
* and the folio is locked, it's dark out, and we're wearing
* sunglasses. Hit it.
*/
page_move_anon_rmap(vmf->page, vma);
folio_unlock(folio);
reuse:
if (unlikely(unshare)) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
return 0;
}
wp_page_reuse(vmf);
return 0;
}
copy:
/*
* Ok, we need to copy. Oh, well..
*/
if (folio)
folio_get(folio);
pte_unmap_unlock(vmf->pte, vmf->ptl);
#ifdef CONFIG_KSM
if (folio && folio_test_ksm(folio))
count_vm_event(COW_KSM);
#endif
return wp_page_copy(vmf);
}
static void unmap_mapping_range_vma(struct vm_area_struct *vma,
unsigned long start_addr, unsigned long end_addr,
struct zap_details *details)
{
zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
}
static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
pgoff_t first_index,
pgoff_t last_index,
struct zap_details *details)
{
struct vm_area_struct *vma;
pgoff_t vba, vea, zba, zea;
vma_interval_tree_foreach(vma, root, first_index, last_index) {
vba = vma->vm_pgoff;
vea = vba + vma_pages(vma) - 1;
zba = max(first_index, vba);
zea = min(last_index, vea);
unmap_mapping_range_vma(vma,
((zba - vba) << PAGE_SHIFT) + vma->vm_start,
((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
details);
}
}
/**
* unmap_mapping_folio() - Unmap single folio from processes.
* @folio: The locked folio to be unmapped.
*
* Unmap this folio from any userspace process which still has it mmaped.
* Typically, for efficiency, the range of nearby pages has already been
* unmapped by unmap_mapping_pages() or unmap_mapping_range(). But once
* truncation or invalidation holds the lock on a folio, it may find that
* the page has been remapped again: and then uses unmap_mapping_folio()
* to unmap it finally.
*/
void unmap_mapping_folio(struct folio *folio)
{
struct address_space *mapping = folio->mapping;
struct zap_details details = { };
pgoff_t first_index;
pgoff_t last_index;
VM_BUG_ON(!folio_test_locked(folio));
first_index = folio->index;
last_index = folio->index + folio_nr_pages(folio) - 1;
details.even_cows = false;
details.single_folio = folio;
details.zap_flags = ZAP_FLAG_DROP_MARKER;
i_mmap_lock_read(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
unmap_mapping_range_tree(&mapping->i_mmap, first_index,
last_index, &details);
i_mmap_unlock_read(mapping);
}
/**
* unmap_mapping_pages() - Unmap pages from processes.
* @mapping: The address space containing pages to be unmapped.
* @start: Index of first page to be unmapped.
* @nr: Number of pages to be unmapped. 0 to unmap to end of file.
* @even_cows: Whether to unmap even private COWed pages.
*
* Unmap the pages in this address space from any userspace process which
* has them mmaped. Generally, you want to remove COWed pages as well when
* a file is being truncated, but not when invalidating pages from the page
* cache.
*/
void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
pgoff_t nr, bool even_cows)
{
struct zap_details details = { };
pgoff_t first_index = start;
pgoff_t last_index = start + nr - 1;
details.even_cows = even_cows;
if (last_index < first_index)
last_index = ULONG_MAX;
i_mmap_lock_read(mapping);
if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
unmap_mapping_range_tree(&mapping->i_mmap, first_index,
last_index, &details);
i_mmap_unlock_read(mapping);
}
EXPORT_SYMBOL_GPL(unmap_mapping_pages);
/**
* unmap_mapping_range - unmap the portion of all mmaps in the specified
* address_space corresponding to the specified byte range in the underlying
* file.
*
* @mapping: the address space containing mmaps to be unmapped.
* @holebegin: byte in first page to unmap, relative to the start of
* the underlying file. This will be rounded down to a PAGE_SIZE
* boundary. Note that this is different from truncate_pagecache(), which
* must keep the partial page. In contrast, we must get rid of
* partial pages.
* @holelen: size of prospective hole in bytes. This will be rounded
* up to a PAGE_SIZE boundary. A holelen of zero truncates to the
* end of the file.
* @even_cows: 1 when truncating a file, unmap even private COWed pages;
* but 0 when invalidating pagecache, don't throw away private data.
*/
void unmap_mapping_range(struct address_space *mapping,
loff_t const holebegin, loff_t const holelen, int even_cows)
{
pgoff_t hba = holebegin >> PAGE_SHIFT;
pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
/* Check for overflow. */
if (sizeof(holelen) > sizeof(hlen)) {
long long holeend =
(holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (holeend & ~(long long)ULONG_MAX)
hlen = ULONG_MAX - hba + 1;
}
unmap_mapping_pages(mapping, hba, hlen, even_cows);
}
EXPORT_SYMBOL(unmap_mapping_range);
/*
* Restore a potential device exclusive pte to a working pte entry
*/
static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf)
{
struct folio *folio = page_folio(vmf->page);
struct vm_area_struct *vma = vmf->vma;
struct mmu_notifier_range range;
/*
* We need a reference to lock the folio because we don't hold
* the PTL so a racing thread can remove the device-exclusive
* entry and unmap it. If the folio is free the entry must
* have been removed already. If it happens to have already
* been re-allocated after being freed all we do is lock and
* unlock it.
*/
if (!folio_try_get(folio))
return 0;
if (!folio_lock_or_retry(folio, vma->vm_mm, vmf->flags)) {
folio_put(folio);
return VM_FAULT_RETRY;
}
mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0,
vma->vm_mm, vmf->address & PAGE_MASK,
(vmf->address & PAGE_MASK) + PAGE_SIZE, NULL);
mmu_notifier_invalidate_range_start(&range);
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
&vmf->ptl);
if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
restore_exclusive_pte(vma, vmf->page, vmf->address, vmf->pte);
pte_unmap_unlock(vmf->pte, vmf->ptl);
folio_unlock(folio);
folio_put(folio);
mmu_notifier_invalidate_range_end(&range);
return 0;
}
static inline bool should_try_to_free_swap(struct folio *folio,
struct vm_area_struct *vma,
unsigned int fault_flags)
{
if (!folio_test_swapcache(folio))
return false;
if (mem_cgroup_swap_full(folio) || (vma->vm_flags & VM_LOCKED) ||
folio_test_mlocked(folio))
return true;
/*
* If we want to map a page that's in the swapcache writable, we
* have to detect via the refcount if we're really the exclusive
* user. Try freeing the swapcache to get rid of the swapcache
* reference only in case it's likely that we'll be the exlusive user.
*/
return (fault_flags & FAULT_FLAG_WRITE) && !folio_test_ksm(folio) &&
folio_ref_count(folio) == 2;
}
static vm_fault_t pte_marker_clear(struct vm_fault *vmf)
{
vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd,
vmf->address, &vmf->ptl);
/*
* Be careful so that we will only recover a special uffd-wp pte into a
* none pte. Otherwise it means the pte could have changed, so retry.
*
* This should also cover the case where e.g. the pte changed
* quickly from a PTE_MARKER_UFFD_WP into PTE_MARKER_SWAPIN_ERROR.
* So is_pte_marker() check is not enough to safely drop the pte.
*/
if (pte_same(vmf->orig_pte, *vmf->pte))
pte_clear(vmf->vma->vm_mm, vmf->address, vmf->pte);
pte_unmap_unlock(vmf->pte, vmf->ptl);
return 0;
}
static vm_fault_t do_pte_missing(struct vm_fault *vmf)
{
if (vma_is_anonymous(vmf->vma))
return do_anonymous_page(vmf);
else
return do_fault(vmf);
}
/*
* This is actually a page-missing access, but with uffd-wp special pte
* installed. It means this pte was wr-protected before being unmapped.
*/
static vm_fault_t pte_marker_handle_uffd_wp(struct vm_fault *vmf)
{
/*
* Just in case there're leftover special ptes even after the region
* got unregistered - we can simply clear them.
*/
if (unlikely(!userfaultfd_wp(vmf->vma)))
return pte_marker_clear(vmf);
return do_pte_missing(vmf);
}
static vm_fault_t handle_pte_marker(struct vm_fault *vmf)
{
swp_entry_t entry = pte_to_swp_entry(vmf->orig_pte);
unsigned long marker = pte_marker_get(entry);
/*
* PTE markers should never be empty. If anything weird happened,
* the best thing to do is to kill the process along with its mm.
*/
if (WARN_ON_ONCE(!marker))
return VM_FAULT_SIGBUS;
/* Higher priority than uffd-wp when data corrupted */
if (marker & PTE_MARKER_SWAPIN_ERROR)
return VM_FAULT_SIGBUS;
if (pte_marker_entry_uffd_wp(entry))
return pte_marker_handle_uffd_wp(vmf);
/* This is an unknown pte marker */
return VM_FAULT_SIGBUS;
}
/*
* We enter with non-exclusive mmap_lock (to exclude vma changes,
* but allow concurrent faults), and pte mapped but not yet locked.
* We return with pte unmapped and unlocked.
*
* We return with the mmap_lock locked or unlocked in the same cases
* as does filemap_fault().
*/
vm_fault_t do_swap_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct folio *swapcache, *folio = NULL;
struct page *page;
struct swap_info_struct *si = NULL;
rmap_t rmap_flags = RMAP_NONE;
bool exclusive = false;
swp_entry_t entry;
pte_t pte;
int locked;
vm_fault_t ret = 0;
void *shadow = NULL;
if (!pte_unmap_same(vmf))
goto out;
if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
ret = VM_FAULT_RETRY;
goto out;
}
entry = pte_to_swp_entry(vmf->orig_pte);
if (unlikely(non_swap_entry(entry))) {
if (is_migration_entry(entry)) {
migration_entry_wait(vma->vm_mm, vmf->pmd,
vmf->address);
} else if (is_device_exclusive_entry(entry)) {
vmf->page = pfn_swap_entry_to_page(entry);
ret = remove_device_exclusive_entry(vmf);
} else if (is_device_private_entry(entry)) {
vmf->page = pfn_swap_entry_to_page(entry);
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
vmf->address, &vmf->ptl);
if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
spin_unlock(vmf->ptl);
goto out;
}
/*
* Get a page reference while we know the page can't be
* freed.
*/
get_page(vmf->page);
pte_unmap_unlock(vmf->pte, vmf->ptl);
ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
put_page(vmf->page);
} else if (is_hwpoison_entry(entry)) {
ret = VM_FAULT_HWPOISON;
} else if (is_pte_marker_entry(entry)) {
ret = handle_pte_marker(vmf);
} else {
print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL);
ret = VM_FAULT_SIGBUS;
}
goto out;
}
/* Prevent swapoff from happening to us. */
si = get_swap_device(entry);
if (unlikely(!si))
goto out;
folio = swap_cache_get_folio(entry, vma, vmf->address);
if (folio)
page = folio_file_page(folio, swp_offset(entry));
swapcache = folio;
if (!folio) {
if (data_race(si->flags & SWP_SYNCHRONOUS_IO) &&
__swap_count(entry) == 1) {
/* skip swapcache */
folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0,
vma, vmf->address, false);
page = &folio->page;
if (folio) {
__folio_set_locked(folio);
__folio_set_swapbacked(folio);
if (mem_cgroup_swapin_charge_folio(folio,
vma->vm_mm, GFP_KERNEL,
entry)) {
ret = VM_FAULT_OOM;
goto out_page;
}
mem_cgroup_swapin_uncharge_swap(entry);
shadow = get_shadow_from_swap_cache(entry);
if (shadow)
workingset_refault(folio, shadow);
folio_add_lru(folio);
/* To provide entry to swap_readpage() */
folio_set_swap_entry(folio, entry);
swap_readpage(page, true, NULL);
folio->private = NULL;
}
} else {
page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
vmf);
if (page)
folio = page_folio(page);
swapcache = folio;
}
if (!folio) {
/*
* Back out if somebody else faulted in this pte
* while we released the pte lock.
*/
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
vmf->address, &vmf->ptl);
if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
ret = VM_FAULT_OOM;
goto unlock;
}
/* Had to read the page from swap area: Major fault */
ret = VM_FAULT_MAJOR;
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
} else if (PageHWPoison(page)) {
/*
* hwpoisoned dirty swapcache pages are kept for killing
* owner processes (which may be unknown at hwpoison time)
*/
ret = VM_FAULT_HWPOISON;
goto out_release;
}
locked = folio_lock_or_retry(folio, vma->vm_mm, vmf->flags);
if (!locked) {
ret |= VM_FAULT_RETRY;
goto out_release;
}
if (swapcache) {
/*
* Make sure folio_free_swap() or swapoff did not release the
* swapcache from under us. The page pin, and pte_same test
* below, are not enough to exclude that. Even if it is still
* swapcache, we need to check that the page's swap has not
* changed.
*/
if (unlikely(!folio_test_swapcache(folio) ||
page_private(page) != entry.val))
goto out_page;
/*
* KSM sometimes has to copy on read faults, for example, if
* page->index of !PageKSM() pages would be nonlinear inside the
* anon VMA -- PageKSM() is lost on actual swapout.
*/
page = ksm_might_need_to_copy(page, vma, vmf->address);
if (unlikely(!page)) {
ret = VM_FAULT_OOM;
goto out_page;
} else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
ret = VM_FAULT_HWPOISON;
goto out_page;
}
folio = page_folio(page);
/*
* If we want to map a page that's in the swapcache writable, we
* have to detect via the refcount if we're really the exclusive
* owner. Try removing the extra reference from the local LRU
* pagevecs if required.
*/
if ((vmf->flags & FAULT_FLAG_WRITE) && folio == swapcache &&
!folio_test_ksm(folio) && !folio_test_lru(folio))
lru_add_drain();
}
folio_throttle_swaprate(folio, GFP_KERNEL);
/*
* Back out if somebody else already faulted in this pte.
*/
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
&vmf->ptl);
if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte)))
goto out_nomap;
if (unlikely(!folio_test_uptodate(folio))) {
ret = VM_FAULT_SIGBUS;
goto out_nomap;
}
/*
* PG_anon_exclusive reuses PG_mappedtodisk for anon pages. A swap pte
* must never point at an anonymous page in the swapcache that is
* PG_anon_exclusive. Sanity check that this holds and especially, that
* no filesystem set PG_mappedtodisk on a page in the swapcache. Sanity
* check after taking the PT lock and making sure that nobody
* concurrently faulted in this page and set PG_anon_exclusive.
*/
BUG_ON(!folio_test_anon(folio) && folio_test_mappedtodisk(folio));
BUG_ON(folio_test_anon(folio) && PageAnonExclusive(page));
/*
* Check under PT lock (to protect against concurrent fork() sharing
* the swap entry concurrently) for certainly exclusive pages.
*/
if (!folio_test_ksm(folio)) {
exclusive = pte_swp_exclusive(vmf->orig_pte);
if (folio != swapcache) {
/*
* We have a fresh page that is not exposed to the
* swapcache -> certainly exclusive.
*/
exclusive = true;
} else if (exclusive && folio_test_writeback(folio) &&
data_race(si->flags & SWP_STABLE_WRITES)) {
/*
* This is tricky: not all swap backends support
* concurrent page modifications while under writeback.
*
* So if we stumble over such a page in the swapcache
* we must not set the page exclusive, otherwise we can
* map it writable without further checks and modify it
* while still under writeback.
*
* For these problematic swap backends, simply drop the
* exclusive marker: this is perfectly fine as we start
* writeback only if we fully unmapped the page and
* there are no unexpected references on the page after
* unmapping succeeded. After fully unmapped, no
* further GUP references (FOLL_GET and FOLL_PIN) can
* appear, so dropping the exclusive marker and mapping
* it only R/O is fine.
*/
exclusive = false;
}
}
/*
* Remove the swap entry and conditionally try to free up the swapcache.
* We're already holding a reference on the page but haven't mapped it
* yet.
*/
swap_free(entry);
if (should_try_to_free_swap(folio, vma, vmf->flags))
folio_free_swap(folio);
inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
dec_mm_counter(vma->vm_mm, MM_SWAPENTS);
pte = mk_pte(page, vma->vm_page_prot);
/*
* Same logic as in do_wp_page(); however, optimize for pages that are
* certainly not shared either because we just allocated them without
* exposing them to the swapcache or because the swap entry indicates
* exclusivity.
*/
if (!folio_test_ksm(folio) &&
(exclusive || folio_ref_count(folio) == 1)) {
if (vmf->flags & FAULT_FLAG_WRITE) {
pte = maybe_mkwrite(pte_mkdirty(pte), vma);
vmf->flags &= ~FAULT_FLAG_WRITE;
}
rmap_flags |= RMAP_EXCLUSIVE;
}
flush_icache_page(vma, page);
if (pte_swp_soft_dirty(vmf->orig_pte))
pte = pte_mksoft_dirty(pte);
if (pte_swp_uffd_wp(vmf->orig_pte))
pte = pte_mkuffd_wp(pte);
vmf->orig_pte = pte;
/* ksm created a completely new copy */
if (unlikely(folio != swapcache && swapcache)) {
page_add_new_anon_rmap(page, vma, vmf->address);
folio_add_lru_vma(folio, vma);
} else {
page_add_anon_rmap(page, vma, vmf->address, rmap_flags);
}
VM_BUG_ON(!folio_test_anon(folio) ||
(pte_write(pte) && !PageAnonExclusive(page)));
set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
arch_do_swap_page(vma->vm_mm, vma, vmf->address, pte, vmf->orig_pte);
folio_unlock(folio);
if (folio != swapcache && swapcache) {
/*
* Hold the lock to avoid the swap entry to be reused
* until we take the PT lock for the pte_same() check
* (to avoid false positives from pte_same). For
* further safety release the lock after the swap_free
* so that the swap count won't change under a
* parallel locked swapcache.
*/
folio_unlock(swapcache);
folio_put(swapcache);
}
if (vmf->flags & FAULT_FLAG_WRITE) {
ret |= do_wp_page(vmf);
if (ret & VM_FAULT_ERROR)
ret &= VM_FAULT_ERROR;
goto out;
}
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, vmf->address, vmf->pte);
unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
out:
if (si)
put_swap_device(si);
return ret;
out_nomap:
pte_unmap_unlock(vmf->pte, vmf->ptl);
out_page:
folio_unlock(folio);
out_release:
folio_put(folio);
if (folio != swapcache && swapcache) {
folio_unlock(swapcache);
folio_put(swapcache);
}
if (si)
put_swap_device(si);
return ret;
}
/*
* We enter with non-exclusive mmap_lock (to exclude vma changes,
* but allow concurrent faults), and pte mapped but not yet locked.
* We return with mmap_lock still held, but pte unmapped and unlocked.
*/
static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
{
bool uffd_wp = vmf_orig_pte_uffd_wp(vmf);
struct vm_area_struct *vma = vmf->vma;
struct folio *folio;
vm_fault_t ret = 0;
pte_t entry;
/* File mapping without ->vm_ops ? */
if (vma->vm_flags & VM_SHARED)
return VM_FAULT_SIGBUS;
/*
* Use pte_alloc() instead of pte_alloc_map(). We can't run
* pte_offset_map() on pmds where a huge pmd might be created
* from a different thread.
*
* pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
* parallel threads are excluded by other means.
*
* Here we only have mmap_read_lock(mm).
*/
if (pte_alloc(vma->vm_mm, vmf->pmd))
return VM_FAULT_OOM;
/* See comment in handle_pte_fault() */
if (unlikely(pmd_trans_unstable(vmf->pmd)))
return 0;
/* Use the zero-page for reads */
if (!(vmf->flags & FAULT_FLAG_WRITE) &&
!mm_forbids_zeropage(vma->vm_mm)) {
entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address),
vma->vm_page_prot));
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
vmf->address, &vmf->ptl);
if (vmf_pte_changed(vmf)) {
update_mmu_tlb(vma, vmf->address, vmf->pte);
goto unlock;
}
ret = check_stable_address_space(vma->vm_mm);
if (ret)
goto unlock;
/* Deliver the page fault to userland, check inside PT lock */
if (userfaultfd_missing(vma)) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
return handle_userfault(vmf, VM_UFFD_MISSING);
}
goto setpte;
}
/* Allocate our own private page. */
if (unlikely(anon_vma_prepare(vma)))
goto oom;
folio = vma_alloc_zeroed_movable_folio(vma, vmf->address);
if (!folio)
goto oom;
if (mem_cgroup_charge(folio, vma->vm_mm, GFP_KERNEL))
goto oom_free_page;
folio_throttle_swaprate(folio, GFP_KERNEL);
/*
* The memory barrier inside __folio_mark_uptodate makes sure that
* preceding stores to the page contents become visible before
* the set_pte_at() write.
*/
__folio_mark_uptodate(folio);
entry = mk_pte(&folio->page, vma->vm_page_prot);
entry = pte_sw_mkyoung(entry);
if (vma->vm_flags & VM_WRITE)
entry = pte_mkwrite(pte_mkdirty(entry));
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
&vmf->ptl);
if (vmf_pte_changed(vmf)) {
update_mmu_tlb(vma, vmf->address, vmf->pte);
goto release;
}
ret = check_stable_address_space(vma->vm_mm);
if (ret)
goto release;
/* Deliver the page fault to userland, check inside PT lock */
if (userfaultfd_missing(vma)) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
folio_put(folio);
return handle_userfault(vmf, VM_UFFD_MISSING);
}
inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
folio_add_new_anon_rmap(folio, vma, vmf->address);
folio_add_lru_vma(folio, vma);
setpte:
if (uffd_wp)
entry = pte_mkuffd_wp(entry);
set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, vmf->address, vmf->pte);
unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
return ret;
release:
folio_put(folio);
goto unlock;
oom_free_page:
folio_put(folio);
oom:
return VM_FAULT_OOM;
}
/*
* The mmap_lock must have been held on entry, and may have been
* released depending on flags and vma->vm_ops->fault() return value.
* See filemap_fault() and __lock_page_retry().
*/
static vm_fault_t __do_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret;
/*
* Preallocate pte before we take page_lock because this might lead to
* deadlocks for memcg reclaim which waits for pages under writeback:
* lock_page(A)
* SetPageWriteback(A)
* unlock_page(A)
* lock_page(B)
* lock_page(B)
* pte_alloc_one
* shrink_page_list
* wait_on_page_writeback(A)
* SetPageWriteback(B)
* unlock_page(B)
* # flush A, B to clear the writeback
*/
if (pmd_none(*vmf->pmd) && !vmf->prealloc_pte) {
vmf->prealloc_pte = pte_alloc_one(vma->vm_mm);
if (!vmf->prealloc_pte)
return VM_FAULT_OOM;
}
ret = vma->vm_ops->fault(vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
VM_FAULT_DONE_COW)))
return ret;
if (unlikely(PageHWPoison(vmf->page))) {
struct page *page = vmf->page;
vm_fault_t poisonret = VM_FAULT_HWPOISON;
if (ret & VM_FAULT_LOCKED) {
if (page_mapped(page))
unmap_mapping_pages(page_mapping(page),
page->index, 1, false);
/* Retry if a clean page was removed from the cache. */
if (invalidate_inode_page(page))
poisonret = VM_FAULT_NOPAGE;
unlock_page(page);
}
put_page(page);
vmf->page = NULL;
return poisonret;
}
if (unlikely(!(ret & VM_FAULT_LOCKED)))
lock_page(vmf->page);
else
VM_BUG_ON_PAGE(!PageLocked(vmf->page), vmf->page);
return ret;
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void deposit_prealloc_pte(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, vmf->prealloc_pte);
/*
* We are going to consume the prealloc table,
* count that as nr_ptes.
*/
mm_inc_nr_ptes(vma->vm_mm);
vmf->prealloc_pte = NULL;
}
vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
{
struct vm_area_struct *vma = vmf->vma;
bool write = vmf->flags & FAULT_FLAG_WRITE;
unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
pmd_t entry;
int i;
vm_fault_t ret = VM_FAULT_FALLBACK;
if (!transhuge_vma_suitable(vma, haddr))
return ret;
page = compound_head(page);
if (compound_order(page) != HPAGE_PMD_ORDER)
return ret;
/*
* Just backoff if any subpage of a THP is corrupted otherwise
* the corrupted page may mapped by PMD silently to escape the
* check. This kind of THP just can be PTE mapped. Access to
* the corrupted subpage should trigger SIGBUS as expected.
*/
if (unlikely(PageHasHWPoisoned(page)))
return ret;
/*
* Archs like ppc64 need additional space to store information
* related to pte entry. Use the preallocated table for that.
*/
if (arch_needs_pgtable_deposit() && !vmf->prealloc_pte) {
vmf->prealloc_pte = pte_alloc_one(vma->vm_mm);
if (!vmf->prealloc_pte)
return VM_FAULT_OOM;
}
vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
if (unlikely(!pmd_none(*vmf->pmd)))
goto out;
for (i = 0; i < HPAGE_PMD_NR; i++)
flush_icache_page(vma, page + i);
entry = mk_huge_pmd(page, vma->vm_page_prot);
if (write)
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
add_mm_counter(vma->vm_mm, mm_counter_file(page), HPAGE_PMD_NR);
page_add_file_rmap(page, vma, true);
/*
* deposit and withdraw with pmd lock held
*/
if (arch_needs_pgtable_deposit())
deposit_prealloc_pte(vmf);
set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
update_mmu_cache_pmd(vma, haddr, vmf->pmd);
/* fault is handled */
ret = 0;
count_vm_event(THP_FILE_MAPPED);
out:
spin_unlock(vmf->ptl);
return ret;
}
#else
vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
{
return VM_FAULT_FALLBACK;
}
#endif
void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
{
struct vm_area_struct *vma = vmf->vma;
bool uffd_wp = vmf_orig_pte_uffd_wp(vmf);
bool write = vmf->flags & FAULT_FLAG_WRITE;
bool prefault = vmf->address != addr;
pte_t entry;
flush_icache_page(vma, page);
entry = mk_pte(page, vma->vm_page_prot);
if (prefault && arch_wants_old_prefaulted_pte())
entry = pte_mkold(entry);
else
entry = pte_sw_mkyoung(entry);
if (write)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
if (unlikely(uffd_wp))
entry = pte_mkuffd_wp(entry);
/* copy-on-write page */
if (write && !(vma->vm_flags & VM_SHARED)) {
inc_mm_counter(vma->vm_mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, addr);
lru_cache_add_inactive_or_unevictable(page, vma);
} else {
inc_mm_counter(vma->vm_mm, mm_counter_file(page));
page_add_file_rmap(page, vma, false);
}
set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
}
static bool vmf_pte_changed(struct vm_fault *vmf)
{
if (vmf->flags & FAULT_FLAG_ORIG_PTE_VALID)
return !pte_same(*vmf->pte, vmf->orig_pte);
return !pte_none(*vmf->pte);
}
/**
* finish_fault - finish page fault once we have prepared the page to fault
*
* @vmf: structure describing the fault
*
* This function handles all that is needed to finish a page fault once the
* page to fault in is prepared. It handles locking of PTEs, inserts PTE for
* given page, adds reverse page mapping, handles memcg charges and LRU
* addition.
*
* The function expects the page to be locked and on success it consumes a
* reference of a page being mapped (for the PTE which maps it).
*
* Return: %0 on success, %VM_FAULT_ code in case of error.
*/
vm_fault_t finish_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct page *page;
vm_fault_t ret;
/* Did we COW the page? */
if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED))
page = vmf->cow_page;
else
page = vmf->page;
/*
* check even for read faults because we might have lost our CoWed
* page
*/
if (!(vma->vm_flags & VM_SHARED)) {
ret = check_stable_address_space(vma->vm_mm);
if (ret)
return ret;
}
if (pmd_none(*vmf->pmd)) {
if (PageTransCompound(page)) {
ret = do_set_pmd(vmf, page);
if (ret != VM_FAULT_FALLBACK)
return ret;
}
if (vmf->prealloc_pte)
pmd_install(vma->vm_mm, vmf->pmd, &vmf->prealloc_pte);
else if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd)))
return VM_FAULT_OOM;
}
/*
* See comment in handle_pte_fault() for how this scenario happens, we
* need to return NOPAGE so that we drop this page.
*/
if (pmd_devmap_trans_unstable(vmf->pmd))
return VM_FAULT_NOPAGE;
vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
vmf->address, &vmf->ptl);
/* Re-check under ptl */
if (likely(!vmf_pte_changed(vmf))) {
do_set_pte(vmf, page, vmf->address);
/* no need to invalidate: a not-present page won't be cached */
update_mmu_cache(vma, vmf->address, vmf->pte);
ret = 0;
} else {
update_mmu_tlb(vma, vmf->address, vmf->pte);
ret = VM_FAULT_NOPAGE;
}
pte_unmap_unlock(vmf->pte, vmf->ptl);
return ret;
}
static unsigned long fault_around_pages __read_mostly =
65536 >> PAGE_SHIFT;
#ifdef CONFIG_DEBUG_FS
static int fault_around_bytes_get(void *data, u64 *val)
{
*val = fault_around_pages << PAGE_SHIFT;
return 0;
}
/*
* fault_around_bytes must be rounded down to the nearest page order as it's
* what do_fault_around() expects to see.
*/
static int fault_around_bytes_set(void *data, u64 val)
{
if (val / PAGE_SIZE > PTRS_PER_PTE)
return -EINVAL;
/*
* The minimum value is 1 page, however this results in no fault-around
* at all. See should_fault_around().
*/
fault_around_pages = max(rounddown_pow_of_two(val) >> PAGE_SHIFT, 1UL);
return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fault_around_bytes_fops,
fault_around_bytes_get, fault_around_bytes_set, "%llu\n");
static int __init fault_around_debugfs(void)
{
debugfs_create_file_unsafe("fault_around_bytes", 0644, NULL, NULL,
&fault_around_bytes_fops);
return 0;
}
late_initcall(fault_around_debugfs);
#endif
/*
* do_fault_around() tries to map few pages around the fault address. The hope
* is that the pages will be needed soon and this will lower the number of
* faults to handle.
*
* It uses vm_ops->map_pages() to map the pages, which skips the page if it's
* not ready to be mapped: not up-to-date, locked, etc.
*
* This function doesn't cross VMA or page table boundaries, in order to call
* map_pages() and acquire a PTE lock only once.
*
* fault_around_pages defines how many pages we'll try to map.
* do_fault_around() expects it to be set to a power of two less than or equal
* to PTRS_PER_PTE.
*
* The virtual address of the area that we map is naturally aligned to
* fault_around_pages * PAGE_SIZE rounded down to the machine page size
* (and therefore to page order). This way it's easier to guarantee
* that we don't cross page table boundaries.
*/
static vm_fault_t do_fault_around(struct vm_fault *vmf)
{
pgoff_t nr_pages = READ_ONCE(fault_around_pages);
pgoff_t pte_off = pte_index(vmf->address);
/* The page offset of vmf->address within the VMA. */
pgoff_t vma_off = vmf->pgoff - vmf->vma->vm_pgoff;
pgoff_t from_pte, to_pte;
vm_fault_t ret;
/* The PTE offset of the start address, clamped to the VMA. */
from_pte = max(ALIGN_DOWN(pte_off, nr_pages),
pte_off - min(pte_off, vma_off));
/* The PTE offset of the end address, clamped to the VMA and PTE. */
to_pte = min3(from_pte + nr_pages, (pgoff_t)PTRS_PER_PTE,
pte_off + vma_pages(vmf->vma) - vma_off) - 1;
if (pmd_none(*vmf->pmd)) {
vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm);
if (!vmf->prealloc_pte)
return VM_FAULT_OOM;
}
rcu_read_lock();
ret = vmf->vma->vm_ops->map_pages(vmf,
vmf->pgoff + from_pte - pte_off,
vmf->pgoff + to_pte - pte_off);
rcu_read_unlock();
return ret;
}
/* Return true if we should do read fault-around, false otherwise */
static inline bool should_fault_around(struct vm_fault *vmf)
{
/* No ->map_pages? No way to fault around... */
if (!vmf->vma->vm_ops->map_pages)
return false;
if (uffd_disable_fault_around(vmf->vma))
return false;
/* A single page implies no faulting 'around' at all. */
return fault_around_pages > 1;
}
static vm_fault_t do_read_fault(struct vm_fault *vmf)
{
vm_fault_t ret = 0;
/*
* Let's call ->map_pages() first and use ->fault() as fallback
* if page by the offset is not ready to be mapped (cold cache or
* something).
*/
if (should_fault_around(vmf)) {
ret = do_fault_around(vmf);
if (ret)
return ret;
}
ret = __do_fault(vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
return ret;
ret |= finish_fault(vmf);
unlock_page(vmf->page);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
put_page(vmf->page);
return ret;
}
static vm_fault_t do_cow_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret;
if (unlikely(anon_vma_prepare(vma)))
return VM_FAULT_OOM;
vmf->cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address);
if (!vmf->cow_page)
return VM_FAULT_OOM;
if (mem_cgroup_charge(page_folio(vmf->cow_page), vma->vm_mm,
GFP_KERNEL)) {
put_page(vmf->cow_page);
return VM_FAULT_OOM;
}
folio_throttle_swaprate(page_folio(vmf->cow_page), GFP_KERNEL);
ret = __do_fault(vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
goto uncharge_out;
if (ret & VM_FAULT_DONE_COW)
return ret;
copy_user_highpage(vmf->cow_page, vmf->page, vmf->address, vma);
__SetPageUptodate(vmf->cow_page);
ret |= finish_fault(vmf);
unlock_page(vmf->page);
put_page(vmf->page);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
goto uncharge_out;
return ret;
uncharge_out:
put_page(vmf->cow_page);
return ret;
}
static vm_fault_t do_shared_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
vm_fault_t ret, tmp;
ret = __do_fault(vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
return ret;
/*
* Check if the backing address space wants to know that the page is
* about to become writable
*/
if (vma->vm_ops->page_mkwrite) {
unlock_page(vmf->page);
tmp = do_page_mkwrite(vmf);
if (unlikely(!tmp ||
(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
put_page(vmf->page);
return tmp;
}
}
ret |= finish_fault(vmf);
if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
VM_FAULT_RETRY))) {
unlock_page(vmf->page);
put_page(vmf->page);
return ret;
}
ret |= fault_dirty_shared_page(vmf);
return ret;
}
/*
* We enter with non-exclusive mmap_lock (to exclude vma changes,
* but allow concurrent faults).
* The mmap_lock may have been released depending on flags and our
* return value. See filemap_fault() and __folio_lock_or_retry().
* If mmap_lock is released, vma may become invalid (for example
* by other thread calling munmap()).
*/
static vm_fault_t do_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct mm_struct *vm_mm = vma->vm_mm;
vm_fault_t ret;
/*
* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND
*/
if (!vma->vm_ops->fault) {
/*
* If we find a migration pmd entry or a none pmd entry, which
* should never happen, return SIGBUS
*/
if (unlikely(!pmd_present(*vmf->pmd)))
ret = VM_FAULT_SIGBUS;
else {
vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm,
vmf->pmd,
vmf->address,
&vmf->ptl);
/*
* Make sure this is not a temporary clearing of pte
* by holding ptl and checking again. A R/M/W update
* of pte involves: take ptl, clearing the pte so that
* we don't have concurrent modification by hardware
* followed by an update.
*/
if (unlikely(pte_none(*vmf->pte)))
ret = VM_FAULT_SIGBUS;
else
ret = VM_FAULT_NOPAGE;
pte_unmap_unlock(vmf->pte, vmf->ptl);
}
} else if (!(vmf->flags & FAULT_FLAG_WRITE))
ret = do_read_fault(vmf);
else if (!(vma->vm_flags & VM_SHARED))
ret = do_cow_fault(vmf);
else
ret = do_shared_fault(vmf);
/* preallocated pagetable is unused: free it */
if (vmf->prealloc_pte) {
pte_free(vm_mm, vmf->prealloc_pte);
vmf->prealloc_pte = NULL;
}
return ret;
}
int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
unsigned long addr, int page_nid, int *flags)
{
get_page(page);
/* Record the current PID acceesing VMA */
vma_set_access_pid_bit(vma);
count_vm_numa_event(NUMA_HINT_FAULTS);
if (page_nid == numa_node_id()) {
count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
*flags |= TNF_FAULT_LOCAL;
}
return mpol_misplaced(page, vma, addr);
}
static vm_fault_t do_numa_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct page *page = NULL;
int page_nid = NUMA_NO_NODE;
bool writable = false;
int last_cpupid;
int target_nid;
pte_t pte, old_pte;
int flags = 0;
/*
* The "pte" at this point cannot be used safely without
* validation through pte_unmap_same(). It's of NUMA type but
* the pfn may be screwed if the read is non atomic.
*/
vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd);
spin_lock(vmf->ptl);
if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
goto out;
}
/* Get the normal PTE */
old_pte = ptep_get(vmf->pte);
pte = pte_modify(old_pte, vma->vm_page_prot);
/*
* Detect now whether the PTE could be writable; this information
* is only valid while holding the PT lock.
*/
writable = pte_write(pte);
if (!writable && vma_wants_manual_pte_write_upgrade(vma) &&
can_change_pte_writable(vma, vmf->address, pte))
writable = true;
page = vm_normal_page(vma, vmf->address, pte);
if (!page || is_zone_device_page(page))
goto out_map;
/* TODO: handle PTE-mapped THP */
if (PageCompound(page))
goto out_map;
/*
* Avoid grouping on RO pages in general. RO pages shouldn't hurt as
* much anyway since they can be in shared cache state. This misses
* the case where a mapping is writable but the process never writes
* to it but pte_write gets cleared during protection updates and
* pte_dirty has unpredictable behaviour between PTE scan updates,
* background writeback, dirty balancing and application behaviour.
*/
if (!writable)
flags |= TNF_NO_GROUP;
/*
* Flag if the page is shared between multiple address spaces. This
* is later used when determining whether to group tasks together
*/
if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
flags |= TNF_SHARED;
page_nid = page_to_nid(page);
/*
* For memory tiering mode, cpupid of slow memory page is used
* to record page access time. So use default value.
*/
if ((sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) &&
!node_is_toptier(page_nid))
last_cpupid = (-1 & LAST_CPUPID_MASK);
else
last_cpupid = page_cpupid_last(page);
target_nid = numa_migrate_prep(page, vma, vmf->address, page_nid,
&flags);
if (target_nid == NUMA_NO_NODE) {
put_page(page);
goto out_map;
}
pte_unmap_unlock(vmf->pte, vmf->ptl);
writable = false;
/* Migrate to the requested node */
if (migrate_misplaced_page(page, vma, target_nid)) {
page_nid = target_nid;
flags |= TNF_MIGRATED;
} else {
flags |= TNF_MIGRATE_FAIL;
vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
spin_lock(vmf->ptl);
if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
pte_unmap_unlock(vmf->pte, vmf->ptl);
goto out;
}
goto out_map;
}
out:
if (page_nid != NUMA_NO_NODE)
task_numa_fault(last_cpupid, page_nid, 1, flags);
return 0;
out_map:
/*
* Make it present again, depending on how arch implements
* non-accessible ptes, some can allow access by kernel mode.
*/
old_pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte);
pte = pte_modify(old_pte, vma->vm_page_prot);
pte = pte_mkyoung(pte);
if (writable)
pte = pte_mkwrite(pte);
ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
update_mmu_cache(vma, vmf->address, vmf->pte);
pte_unmap_unlock(vmf->pte, vmf->ptl);
goto out;
}
static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
{
if (vma_is_anonymous(vmf->vma))
return do_huge_pmd_anonymous_page(vmf);
if (vmf->vma->vm_ops->huge_fault)
return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
return VM_FAULT_FALLBACK;
}
/* `inline' is required to avoid gcc 4.1.2 build error */
static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
{
const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
vm_fault_t ret;
if (vma_is_anonymous(vmf->vma)) {
if (likely(!unshare) &&
userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd))
return handle_userfault(vmf, VM_UFFD_WP);
return do_huge_pmd_wp_page(vmf);
}
if (vmf->vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) {
if (vmf->vma->vm_ops->huge_fault) {
ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
}
}
/* COW or write-notify handled on pte level: split pmd. */
__split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL);
return VM_FAULT_FALLBACK;
}
static vm_fault_t create_huge_pud(struct vm_fault *vmf)
{
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
/* No support for anonymous transparent PUD pages yet */
if (vma_is_anonymous(vmf->vma))
return VM_FAULT_FALLBACK;
if (vmf->vma->vm_ops->huge_fault)
return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
return VM_FAULT_FALLBACK;
}
static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
{
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \
defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
vm_fault_t ret;
/* No support for anonymous transparent PUD pages yet */
if (vma_is_anonymous(vmf->vma))
goto split;
if (vmf->vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) {
if (vmf->vma->vm_ops->huge_fault) {
ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
}
}
split:
/* COW or write-notify not handled on PUD level: split pud.*/
__split_huge_pud(vmf->vma, vmf->pud, vmf->address);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE && CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
return VM_FAULT_FALLBACK;
}
/*
* These routines also need to handle stuff like marking pages dirty
* and/or accessed for architectures that don't do it in hardware (most
* RISC architectures). The early dirtying is also good on the i386.
*
* There is also a hook called "update_mmu_cache()" that architectures
* with external mmu caches can use to update those (ie the Sparc or
* PowerPC hashed page tables that act as extended TLBs).
*
* We enter with non-exclusive mmap_lock (to exclude vma changes, but allow
* concurrent faults).
*
* The mmap_lock may have been released depending on flags and our return value.
* See filemap_fault() and __folio_lock_or_retry().
*/
static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
{
pte_t entry;
if (unlikely(pmd_none(*vmf->pmd))) {
/*
* Leave __pte_alloc() until later: because vm_ops->fault may
* want to allocate huge page, and if we expose page table
* for an instant, it will be difficult to retract from
* concurrent faults and from rmap lookups.
*/
vmf->pte = NULL;
vmf->flags &= ~FAULT_FLAG_ORIG_PTE_VALID;
} else {
/*
* If a huge pmd materialized under us just retry later. Use
* pmd_trans_unstable() via pmd_devmap_trans_unstable() instead
* of pmd_trans_huge() to ensure the pmd didn't become
* pmd_trans_huge under us and then back to pmd_none, as a
* result of MADV_DONTNEED running immediately after a huge pmd
* fault in a different thread of this mm, in turn leading to a
* misleading pmd_trans_huge() retval. All we have to ensure is
* that it is a regular pmd that we can walk with
* pte_offset_map() and we can do that through an atomic read
* in C, which is what pmd_trans_unstable() provides.
*/
if (pmd_devmap_trans_unstable(vmf->pmd))
return 0;
/*
* A regular pmd is established and it can't morph into a huge
* pmd from under us anymore at this point because we hold the
* mmap_lock read mode and khugepaged takes it in write mode.
* So now it's safe to run pte_offset_map().
*/
vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
vmf->orig_pte = *vmf->pte;
vmf->flags |= FAULT_FLAG_ORIG_PTE_VALID;
/*
* some architectures can have larger ptes than wordsize,
* e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and
* CONFIG_32BIT=y, so READ_ONCE cannot guarantee atomic
* accesses. The code below just needs a consistent view
* for the ifs and we later double check anyway with the
* ptl lock held. So here a barrier will do.
*/
barrier();
if (pte_none(vmf->orig_pte)) {
pte_unmap(vmf->pte);
vmf->pte = NULL;
}
}
if (!vmf->pte)
return do_pte_missing(vmf);
if (!pte_present(vmf->orig_pte))
return do_swap_page(vmf);
if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
return do_numa_page(vmf);
vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
spin_lock(vmf->ptl);
entry = vmf->orig_pte;
if (unlikely(!pte_same(*vmf->pte, entry))) {
update_mmu_tlb(vmf->vma, vmf->address, vmf->pte);
goto unlock;
}
if (vmf->flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) {
if (!pte_write(entry))
return do_wp_page(vmf);
else if (likely(vmf->flags & FAULT_FLAG_WRITE))
entry = pte_mkdirty(entry);
}
entry = pte_mkyoung(entry);
if (ptep_set_access_flags(vmf->vma, vmf->address, vmf->pte, entry,
vmf->flags & FAULT_FLAG_WRITE)) {
update_mmu_cache(vmf->vma, vmf->address, vmf->pte);
} else {
/* Skip spurious TLB flush for retried page fault */
if (vmf->flags & FAULT_FLAG_TRIED)
goto unlock;
/*
* This is needed only for protection faults but the arch code
* is not yet telling us if this is a protection fault or not.
* This still avoids useless tlb flushes for .text page faults
* with threads.
*/
if (vmf->flags & FAULT_FLAG_WRITE)
flush_tlb_fix_spurious_fault(vmf->vma, vmf->address,
vmf->pte);
}
unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
return 0;
}
/*
* By the time we get here, we already hold the mm semaphore
*
* The mmap_lock may have been released depending on flags and our
* return value. See filemap_fault() and __folio_lock_or_retry().
*/
static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
unsigned long address, unsigned int flags)
{
struct vm_fault vmf = {
.vma = vma,
.address = address & PAGE_MASK,
.real_address = address,
.flags = flags,
.pgoff = linear_page_index(vma, address),
.gfp_mask = __get_fault_gfp_mask(vma),
};
struct mm_struct *mm = vma->vm_mm;
unsigned long vm_flags = vma->vm_flags;
pgd_t *pgd;
p4d_t *p4d;
vm_fault_t ret;
pgd = pgd_offset(mm, address);
p4d = p4d_alloc(mm, pgd, address);
if (!p4d)
return VM_FAULT_OOM;
vmf.pud = pud_alloc(mm, p4d, address);
if (!vmf.pud)
return VM_FAULT_OOM;
retry_pud:
if (pud_none(*vmf.pud) &&
hugepage_vma_check(vma, vm_flags, false, true, true)) {
ret = create_huge_pud(&vmf);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
} else {
pud_t orig_pud = *vmf.pud;
barrier();
if (pud_trans_huge(orig_pud) || pud_devmap(orig_pud)) {
/*
* TODO once we support anonymous PUDs: NUMA case and
* FAULT_FLAG_UNSHARE handling.
*/
if ((flags & FAULT_FLAG_WRITE) && !pud_write(orig_pud)) {
ret = wp_huge_pud(&vmf, orig_pud);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
} else {
huge_pud_set_accessed(&vmf, orig_pud);
return 0;
}
}
}
vmf.pmd = pmd_alloc(mm, vmf.pud, address);
if (!vmf.pmd)
return VM_FAULT_OOM;
/* Huge pud page fault raced with pmd_alloc? */
if (pud_trans_unstable(vmf.pud))
goto retry_pud;
if (pmd_none(*vmf.pmd) &&
hugepage_vma_check(vma, vm_flags, false, true, true)) {
ret = create_huge_pmd(&vmf);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
} else {
vmf.orig_pmd = *vmf.pmd;
barrier();
if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
VM_BUG_ON(thp_migration_supported() &&
!is_pmd_migration_entry(vmf.orig_pmd));
if (is_pmd_migration_entry(vmf.orig_pmd))
pmd_migration_entry_wait(mm, vmf.pmd);
return 0;
}
if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) {
if (pmd_protnone(vmf.orig_pmd) && vma_is_accessible(vma))
return do_huge_pmd_numa_page(&vmf);
if ((flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) &&
!pmd_write(vmf.orig_pmd)) {
ret = wp_huge_pmd(&vmf);
if (!(ret & VM_FAULT_FALLBACK))
return ret;
} else {
huge_pmd_set_accessed(&vmf);
return 0;
}
}
}
return handle_pte_fault(&vmf);
}
/**
* mm_account_fault - Do page fault accounting
*
* @regs: the pt_regs struct pointer. When set to NULL, will skip accounting
* of perf event counters, but we'll still do the per-task accounting to
* the task who triggered this page fault.
* @address: the faulted address.
* @flags: the fault flags.
* @ret: the fault retcode.
*
* This will take care of most of the page fault accounting. Meanwhile, it
* will also include the PERF_COUNT_SW_PAGE_FAULTS_[MAJ|MIN] perf counter
* updates. However, note that the handling of PERF_COUNT_SW_PAGE_FAULTS should
* still be in per-arch page fault handlers at the entry of page fault.
*/
static inline void mm_account_fault(struct mm_struct *mm, struct pt_regs *regs,
unsigned long address, unsigned int flags,
vm_fault_t ret)
{
bool major;
/* Incomplete faults will be accounted upon completion. */
if (ret & VM_FAULT_RETRY)
return;
/*
* To preserve the behavior of older kernels, PGFAULT counters record
* both successful and failed faults, as opposed to perf counters,
* which ignore failed cases.
*/
count_vm_event(PGFAULT);
count_memcg_event_mm(mm, PGFAULT);
/*
* Do not account for unsuccessful faults (e.g. when the address wasn't
* valid). That includes arch_vma_access_permitted() failing before
* reaching here. So this is not a "this many hardware page faults"
* counter. We should use the hw profiling for that.
*/
if (ret & VM_FAULT_ERROR)
return;
/*
* We define the fault as a major fault when the final successful fault
* is VM_FAULT_MAJOR, or if it retried (which implies that we couldn't
* handle it immediately previously).
*/
major = (ret & VM_FAULT_MAJOR) || (flags & FAULT_FLAG_TRIED);
if (major)
current->maj_flt++;
else
current->min_flt++;
/*
* If the fault is done for GUP, regs will be NULL. We only do the
* accounting for the per thread fault counters who triggered the
* fault, and we skip the perf event updates.
*/
if (!regs)
return;
if (major)
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
else
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
}
#ifdef CONFIG_LRU_GEN
static void lru_gen_enter_fault(struct vm_area_struct *vma)
{
/* the LRU algorithm only applies to accesses with recency */
current->in_lru_fault = vma_has_recency(vma);
}
static void lru_gen_exit_fault(void)
{
current->in_lru_fault = false;
}
#else
static void lru_gen_enter_fault(struct vm_area_struct *vma)
{
}
static void lru_gen_exit_fault(void)
{
}
#endif /* CONFIG_LRU_GEN */
static vm_fault_t sanitize_fault_flags(struct vm_area_struct *vma,
unsigned int *flags)
{
if (unlikely(*flags & FAULT_FLAG_UNSHARE)) {
if (WARN_ON_ONCE(*flags & FAULT_FLAG_WRITE))
return VM_FAULT_SIGSEGV;
/*
* FAULT_FLAG_UNSHARE only applies to COW mappings. Let's
* just treat it like an ordinary read-fault otherwise.
*/
if (!is_cow_mapping(vma->vm_flags))
*flags &= ~FAULT_FLAG_UNSHARE;
} else if (*flags & FAULT_FLAG_WRITE) {
/* Write faults on read-only mappings are impossible ... */
if (WARN_ON_ONCE(!(vma->vm_flags & VM_MAYWRITE)))
return VM_FAULT_SIGSEGV;
/* ... and FOLL_FORCE only applies to COW mappings. */
if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE) &&
!is_cow_mapping(vma->vm_flags)))
return VM_FAULT_SIGSEGV;
}
return 0;
}
/*
* By the time we get here, we already hold the mm semaphore
*
* The mmap_lock may have been released depending on flags and our
* return value. See filemap_fault() and __folio_lock_or_retry().
*/
vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
unsigned int flags, struct pt_regs *regs)
{
/* If the fault handler drops the mmap_lock, vma may be freed */
struct mm_struct *mm = vma->vm_mm;
vm_fault_t ret;
__set_current_state(TASK_RUNNING);
ret = sanitize_fault_flags(vma, &flags);
if (ret)
goto out;
if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
flags & FAULT_FLAG_INSTRUCTION,
flags & FAULT_FLAG_REMOTE)) {
ret = VM_FAULT_SIGSEGV;
goto out;
}
/*
* Enable the memcg OOM handling for faults triggered in user
* space. Kernel faults are handled more gracefully.
*/
if (flags & FAULT_FLAG_USER)
mem_cgroup_enter_user_fault();
lru_gen_enter_fault(vma);
if (unlikely(is_vm_hugetlb_page(vma)))
ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
else
ret = __handle_mm_fault(vma, address, flags);
lru_gen_exit_fault();
if (flags & FAULT_FLAG_USER) {
mem_cgroup_exit_user_fault();
/*
* The task may have entered a memcg OOM situation but
* if the allocation error was handled gracefully (no
* VM_FAULT_OOM), there is no need to kill anything.
* Just clean up the OOM state peacefully.
*/
if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM))
mem_cgroup_oom_synchronize(false);
}
out:
mm_account_fault(mm, regs, address, flags, ret);
return ret;
}
EXPORT_SYMBOL_GPL(handle_mm_fault);
#ifdef CONFIG_LOCK_MM_AND_FIND_VMA
#include <linux/extable.h>
static inline bool get_mmap_lock_carefully(struct mm_struct *mm, struct pt_regs *regs)
{
/* Even if this succeeds, make it clear we *might* have slept */
if (likely(mmap_read_trylock(mm))) {
might_sleep();
return true;
}
if (regs && !user_mode(regs)) {
unsigned long ip = instruction_pointer(regs);
if (!search_exception_tables(ip))
return false;
}
return !mmap_read_lock_killable(mm);
}
static inline bool mmap_upgrade_trylock(struct mm_struct *mm)
{
/*
* We don't have this operation yet.
*
* It should be easy enough to do: it's basically a
* atomic_long_try_cmpxchg_acquire()
* from RWSEM_READER_BIAS -> RWSEM_WRITER_LOCKED, but
* it also needs the proper lockdep magic etc.
*/
return false;
}
static inline bool upgrade_mmap_lock_carefully(struct mm_struct *mm, struct pt_regs *regs)
{
mmap_read_unlock(mm);
if (regs && !user_mode(regs)) {
unsigned long ip = instruction_pointer(regs);
if (!search_exception_tables(ip))
return false;
}
return !mmap_write_lock_killable(mm);
}
/*
* Helper for page fault handling.
*
* This is kind of equivalend to "mmap_read_lock()" followed
* by "find_extend_vma()", except it's a lot more careful about
* the locking (and will drop the lock on failure).
*
* For example, if we have a kernel bug that causes a page
* fault, we don't want to just use mmap_read_lock() to get
* the mm lock, because that would deadlock if the bug were
* to happen while we're holding the mm lock for writing.
*
* So this checks the exception tables on kernel faults in
* order to only do this all for instructions that are actually
* expected to fault.
*
* We can also actually take the mm lock for writing if we
* need to extend the vma, which helps the VM layer a lot.
*/
struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
unsigned long addr, struct pt_regs *regs)
{
struct vm_area_struct *vma;
if (!get_mmap_lock_carefully(mm, regs))
return NULL;
vma = find_vma(mm, addr);
if (likely(vma && (vma->vm_start <= addr)))
return vma;
/*
* Well, dang. We might still be successful, but only
* if we can extend a vma to do so.
*/
if (!vma || !(vma->vm_flags & VM_GROWSDOWN)) {
mmap_read_unlock(mm);
return NULL;
}
/*
* We can try to upgrade the mmap lock atomically,
* in which case we can continue to use the vma
* we already looked up.
*
* Otherwise we'll have to drop the mmap lock and
* re-take it, and also look up the vma again,
* re-checking it.
*/
if (!mmap_upgrade_trylock(mm)) {
if (!upgrade_mmap_lock_carefully(mm, regs))
return NULL;
vma = find_vma(mm, addr);
if (!vma)
goto fail;
if (vma->vm_start <= addr)
goto success;
if (!(vma->vm_flags & VM_GROWSDOWN))
goto fail;
}
if (expand_stack_locked(vma, addr))
goto fail;
success:
mmap_write_downgrade(mm);
return vma;
fail:
mmap_write_unlock(mm);
return NULL;
}
#endif
#ifdef CONFIG_PER_VMA_LOCK
/*
* Lookup and lock a VMA under RCU protection. Returned VMA is guaranteed to be
* stable and not isolated. If the VMA is not found or is being modified the
* function returns NULL.
*/
struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
unsigned long address)
{
MA_STATE(mas, &mm->mm_mt, address, address);
struct vm_area_struct *vma;
rcu_read_lock();
retry:
vma = mas_walk(&mas);
if (!vma)
goto inval;
/* Only anonymous vmas are supported for now */
if (!vma_is_anonymous(vma))
goto inval;
/* find_mergeable_anon_vma uses adjacent vmas which are not locked */
if (!vma->anon_vma)
goto inval;
if (!vma_start_read(vma))
goto inval;
/*
* Due to the possibility of userfault handler dropping mmap_lock, avoid
* it for now and fall back to page fault handling under mmap_lock.
*/
if (userfaultfd_armed(vma)) {
vma_end_read(vma);
goto inval;
}
/* Check since vm_start/vm_end might change before we lock the VMA */
if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
vma_end_read(vma);
goto inval;
}
/* Check if the VMA got isolated after we found it */
if (vma->detached) {
vma_end_read(vma);
count_vm_vma_lock_event(VMA_LOCK_MISS);
/* The area was replaced with another one */
goto retry;
}
rcu_read_unlock();
return vma;
inval:
rcu_read_unlock();
count_vm_vma_lock_event(VMA_LOCK_ABORT);
return NULL;
}
#endif /* CONFIG_PER_VMA_LOCK */
#ifndef __PAGETABLE_P4D_FOLDED
/*
* Allocate p4d page table.
* We've already handled the fast-path in-line.
*/
int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
{
p4d_t *new = p4d_alloc_one(mm, address);
if (!new)
return -ENOMEM;
spin_lock(&mm->page_table_lock);
if (pgd_present(*pgd)) { /* Another has populated it */
p4d_free(mm, new);
} else {
smp_wmb(); /* See comment in pmd_install() */
pgd_populate(mm, pgd, new);
}
spin_unlock(&mm->page_table_lock);
return 0;
}
#endif /* __PAGETABLE_P4D_FOLDED */
#ifndef __PAGETABLE_PUD_FOLDED
/*
* Allocate page upper directory.
* We've already handled the fast-path in-line.
*/
int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address)
{
pud_t *new = pud_alloc_one(mm, address);
if (!new)
return -ENOMEM;
spin_lock(&mm->page_table_lock);
if (!p4d_present(*p4d)) {
mm_inc_nr_puds(mm);
smp_wmb(); /* See comment in pmd_install() */
p4d_populate(mm, p4d, new);
} else /* Another has populated it */
pud_free(mm, new);
spin_unlock(&mm->page_table_lock);
return 0;
}
#endif /* __PAGETABLE_PUD_FOLDED */
#ifndef __PAGETABLE_PMD_FOLDED
/*
* Allocate page middle directory.
* We've already handled the fast-path in-line.
*/
int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
{
spinlock_t *ptl;
pmd_t *new = pmd_alloc_one(mm, address);
if (!new)
return -ENOMEM;
ptl = pud_lock(mm, pud);
if (!pud_present(*pud)) {
mm_inc_nr_pmds(mm);
smp_wmb(); /* See comment in pmd_install() */
pud_populate(mm, pud, new);
} else { /* Another has populated it */
pmd_free(mm, new);
}
spin_unlock(ptl);
return 0;
}
#endif /* __PAGETABLE_PMD_FOLDED */
/**
* follow_pte - look up PTE at a user virtual address
* @mm: the mm_struct of the target address space
* @address: user virtual address
* @ptepp: location to store found PTE
* @ptlp: location to store the lock for the PTE
*
* On a successful return, the pointer to the PTE is stored in @ptepp;
* the corresponding lock is taken and its location is stored in @ptlp.
* The contents of the PTE are only stable until @ptlp is released;
* any further use, if any, must be protected against invalidation
* with MMU notifiers.
*
* Only IO mappings and raw PFN mappings are allowed. The mmap semaphore
* should be taken for read.
*
* KVM uses this function. While it is arguably less bad than ``follow_pfn``,
* it is not a good general-purpose API.
*
* Return: zero on success, -ve otherwise.
*/
int follow_pte(struct mm_struct *mm, unsigned long address,
pte_t **ptepp, spinlock_t **ptlp)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *ptep;
pgd = pgd_offset(mm, address);
if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
goto out;
p4d = p4d_offset(pgd, address);
if (p4d_none(*p4d) || unlikely(p4d_bad(*p4d)))
goto out;
pud = pud_offset(p4d, address);
if (pud_none(*pud) || unlikely(pud_bad(*pud)))
goto out;
pmd = pmd_offset(pud, address);
VM_BUG_ON(pmd_trans_huge(*pmd));
if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
goto out;
ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
if (!pte_present(*ptep))
goto unlock;
*ptepp = ptep;
return 0;
unlock:
pte_unmap_unlock(ptep, *ptlp);
out:
return -EINVAL;
}
EXPORT_SYMBOL_GPL(follow_pte);
/**
* follow_pfn - look up PFN at a user virtual address
* @vma: memory mapping
* @address: user virtual address
* @pfn: location to store found PFN
*
* Only IO mappings and raw PFN mappings are allowed.
*
* This function does not allow the caller to read the permissions
* of the PTE. Do not use it.
*
* Return: zero and the pfn at @pfn on success, -ve otherwise.
*/
int follow_pfn(struct vm_area_struct *vma, unsigned long address,
unsigned long *pfn)
{
int ret = -EINVAL;
spinlock_t *ptl;
pte_t *ptep;
if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
return ret;
ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
if (ret)
return ret;
*pfn = pte_pfn(*ptep);
pte_unmap_unlock(ptep, ptl);
return 0;
}
EXPORT_SYMBOL(follow_pfn);
#ifdef CONFIG_HAVE_IOREMAP_PROT
int follow_phys(struct vm_area_struct *vma,
unsigned long address, unsigned int flags,
unsigned long *prot, resource_size_t *phys)
{
int ret = -EINVAL;
pte_t *ptep, pte;
spinlock_t *ptl;
if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
goto out;
if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
goto out;
pte = *ptep;
if ((flags & FOLL_WRITE) && !pte_write(pte))
goto unlock;
*prot = pgprot_val(pte_pgprot(pte));
*phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
ret = 0;
unlock:
pte_unmap_unlock(ptep, ptl);
out:
return ret;
}
/**
* generic_access_phys - generic implementation for iomem mmap access
* @vma: the vma to access
* @addr: userspace address, not relative offset within @vma
* @buf: buffer to read/write
* @len: length of transfer
* @write: set to FOLL_WRITE when writing, otherwise reading
*
* This is a generic implementation for &vm_operations_struct.access for an
* iomem mapping. This callback is used by access_process_vm() when the @vma is
* not page based.
*/
int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
void *buf, int len, int write)
{
resource_size_t phys_addr;
unsigned long prot = 0;
void __iomem *maddr;
pte_t *ptep, pte;
spinlock_t *ptl;
int offset = offset_in_page(addr);
int ret = -EINVAL;
if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
return -EINVAL;
retry:
if (follow_pte(vma->vm_mm, addr, &ptep, &ptl))
return -EINVAL;
pte = *ptep;
pte_unmap_unlock(ptep, ptl);
prot = pgprot_val(pte_pgprot(pte));
phys_addr = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;
if ((write & FOLL_WRITE) && !pte_write(pte))
return -EINVAL;
maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot);
if (!maddr)
return -ENOMEM;
if (follow_pte(vma->vm_mm, addr, &ptep, &ptl))
goto out_unmap;
if (!pte_same(pte, *ptep)) {
pte_unmap_unlock(ptep, ptl);
iounmap(maddr);
goto retry;
}
if (write)
memcpy_toio(maddr + offset, buf, len);
else
memcpy_fromio(buf, maddr + offset, len);
ret = len;
pte_unmap_unlock(ptep, ptl);
out_unmap:
iounmap(maddr);
return ret;
}
EXPORT_SYMBOL_GPL(generic_access_phys);
#endif
/*
* Access another process' address space as given in mm.
*/
int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
int len, unsigned int gup_flags)
{
struct vm_area_struct *vma;
void *old_buf = buf;
int write = gup_flags & FOLL_WRITE;
if (mmap_read_lock_killable(mm))
return 0;
/* We might need to expand the stack to access it */
vma = vma_lookup(mm, addr);
if (!vma) {
vma = expand_stack(mm, addr);
if (!vma)
return 0;
}
/* ignore errors, just check how much was successfully transferred */
while (len) {
int bytes, ret, offset;
void *maddr;
struct page *page = NULL;
ret = get_user_pages_remote(mm, addr, 1,
gup_flags, &page, &vma, NULL);
if (ret <= 0) {
#ifndef CONFIG_HAVE_IOREMAP_PROT
break;
#else
/*
* Check if this is a VM_IO | VM_PFNMAP VMA, which
* we can access using slightly different code.
*/
vma = vma_lookup(mm, addr);
if (!vma)
break;
if (vma->vm_ops && vma->vm_ops->access)
ret = vma->vm_ops->access(vma, addr, buf,
len, write);
if (ret <= 0)
break;
bytes = ret;
#endif
} else {
bytes = len;
offset = addr & (PAGE_SIZE-1);
if (bytes > PAGE_SIZE-offset)
bytes = PAGE_SIZE-offset;
maddr = kmap(page);
if (write) {
copy_to_user_page(vma, page, addr,
maddr + offset, buf, bytes);
set_page_dirty_lock(page);
} else {
copy_from_user_page(vma, page, addr,
buf, maddr + offset, bytes);
}
kunmap(page);
put_page(page);
}
len -= bytes;
buf += bytes;
addr += bytes;
}
mmap_read_unlock(mm);
return buf - old_buf;
}
/**
* access_remote_vm - access another process' address space
* @mm: the mm_struct of the target address space
* @addr: start address to access
* @buf: source or destination buffer
* @len: number of bytes to transfer
* @gup_flags: flags modifying lookup behaviour
*
* The caller must hold a reference on @mm.
*
* Return: number of bytes copied from source to destination.
*/
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
void *buf, int len, unsigned int gup_flags)
{
return __access_remote_vm(mm, addr, buf, len, gup_flags);
}
/*
* Access another process' address space.
* Source/target buffer must be kernel space,
* Do not walk the page table directly, use get_user_pages
*/
int access_process_vm(struct task_struct *tsk, unsigned long addr,
void *buf, int len, unsigned int gup_flags)
{
struct mm_struct *mm;
int ret;
mm = get_task_mm(tsk);
if (!mm)
return 0;
ret = __access_remote_vm(mm, addr, buf, len, gup_flags);
mmput(mm);
return ret;
}
EXPORT_SYMBOL_GPL(access_process_vm);
/*
* Print the name of a VMA.
*/
void print_vma_addr(char *prefix, unsigned long ip)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
/*
* we might be running from an atomic context so we cannot sleep
*/
if (!mmap_read_trylock(mm))
return;
vma = find_vma(mm, ip);
if (vma && vma->vm_file) {
struct file *f = vma->vm_file;
char *buf = (char *)__get_free_page(GFP_NOWAIT);
if (buf) {
char *p;
p = file_path(f, buf, PAGE_SIZE);
if (IS_ERR(p))
p = "?";
printk("%s%s[%lx+%lx]", prefix, kbasename(p),
vma->vm_start,
vma->vm_end - vma->vm_start);
free_page((unsigned long)buf);
}
}
mmap_read_unlock(mm);
}
#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
void __might_fault(const char *file, int line)
{
if (pagefault_disabled())
return;
__might_sleep(file, line);
#if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
if (current->mm)
might_lock_read(&current->mm->mmap_lock);
#endif
}
EXPORT_SYMBOL(__might_fault);
#endif
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
/*
* Process all subpages of the specified huge page with the specified
* operation. The target subpage will be processed last to keep its
* cache lines hot.
*/
static inline int process_huge_page(
unsigned long addr_hint, unsigned int pages_per_huge_page,
int (*process_subpage)(unsigned long addr, int idx, void *arg),
void *arg)
{
int i, n, base, l, ret;
unsigned long addr = addr_hint &
~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);
/* Process target subpage last to keep its cache lines hot */
might_sleep();
n = (addr_hint - addr) / PAGE_SIZE;
if (2 * n <= pages_per_huge_page) {
/* If target subpage in first half of huge page */
base = 0;
l = n;
/* Process subpages at the end of huge page */
for (i = pages_per_huge_page - 1; i >= 2 * n; i--) {
cond_resched();
ret = process_subpage(addr + i * PAGE_SIZE, i, arg);
if (ret)
return ret;
}
} else {
/* If target subpage in second half of huge page */
base = pages_per_huge_page - 2 * (pages_per_huge_page - n);
l = pages_per_huge_page - n;
/* Process subpages at the begin of huge page */
for (i = 0; i < base; i++) {
cond_resched();
ret = process_subpage(addr + i * PAGE_SIZE, i, arg);
if (ret)
return ret;
}
}
/*
* Process remaining subpages in left-right-left-right pattern
* towards the target subpage
*/
for (i = 0; i < l; i++) {
int left_idx = base + i;
int right_idx = base + 2 * l - 1 - i;
cond_resched();
ret = process_subpage(addr + left_idx * PAGE_SIZE, left_idx, arg);
if (ret)
return ret;
cond_resched();
ret = process_subpage(addr + right_idx * PAGE_SIZE, right_idx, arg);
if (ret)
return ret;
}
return 0;
}
static void clear_gigantic_page(struct page *page,
unsigned long addr,
unsigned int pages_per_huge_page)
{
int i;
struct page *p;
might_sleep();
for (i = 0; i < pages_per_huge_page; i++) {
p = nth_page(page, i);
cond_resched();
clear_user_highpage(p, addr + i * PAGE_SIZE);
}
}
static int clear_subpage(unsigned long addr, int idx, void *arg)
{
struct page *page = arg;
clear_user_highpage(page + idx, addr);
return 0;
}
void clear_huge_page(struct page *page,
unsigned long addr_hint, unsigned int pages_per_huge_page)
{
unsigned long addr = addr_hint &
~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);
if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
clear_gigantic_page(page, addr, pages_per_huge_page);
return;
}
process_huge_page(addr_hint, pages_per_huge_page, clear_subpage, page);
}
static int copy_user_gigantic_page(struct folio *dst, struct folio *src,
unsigned long addr,
struct vm_area_struct *vma,
unsigned int pages_per_huge_page)
{
int i;
struct page *dst_page;
struct page *src_page;
for (i = 0; i < pages_per_huge_page; i++) {
dst_page = folio_page(dst, i);
src_page = folio_page(src, i);
cond_resched();
if (copy_mc_user_highpage(dst_page, src_page,
addr + i*PAGE_SIZE, vma)) {
memory_failure_queue(page_to_pfn(src_page), 0);
return -EHWPOISON;
}
}
return 0;
}
struct copy_subpage_arg {
struct page *dst;
struct page *src;
struct vm_area_struct *vma;
};
static int copy_subpage(unsigned long addr, int idx, void *arg)
{
struct copy_subpage_arg *copy_arg = arg;
if (copy_mc_user_highpage(copy_arg->dst + idx, copy_arg->src + idx,
addr, copy_arg->vma)) {
memory_failure_queue(page_to_pfn(copy_arg->src + idx), 0);
return -EHWPOISON;
}
return 0;
}
int copy_user_large_folio(struct folio *dst, struct folio *src,
unsigned long addr_hint, struct vm_area_struct *vma)
{
unsigned int pages_per_huge_page = folio_nr_pages(dst);
unsigned long addr = addr_hint &
~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);
struct copy_subpage_arg arg = {
.dst = &dst->page,
.src = &src->page,
.vma = vma,
};
if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES))
return copy_user_gigantic_page(dst, src, addr, vma,
pages_per_huge_page);
return process_huge_page(addr_hint, pages_per_huge_page, copy_subpage, &arg);
}
long copy_folio_from_user(struct folio *dst_folio,
const void __user *usr_src,
bool allow_pagefault)
{
void *kaddr;
unsigned long i, rc = 0;
unsigned int nr_pages = folio_nr_pages(dst_folio);
unsigned long ret_val = nr_pages * PAGE_SIZE;
struct page *subpage;
for (i = 0; i < nr_pages; i++) {
subpage = folio_page(dst_folio, i);
kaddr = kmap_local_page(subpage);
if (!allow_pagefault)
pagefault_disable();
rc = copy_from_user(kaddr, usr_src + i * PAGE_SIZE, PAGE_SIZE);
if (!allow_pagefault)
pagefault_enable();
kunmap_local(kaddr);
ret_val -= (PAGE_SIZE - rc);
if (rc)
break;
flush_dcache_page(subpage);
cond_resched();
}
return ret_val;
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
#if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS
static struct kmem_cache *page_ptl_cachep;
void __init ptlock_cache_init(void)
{
page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
SLAB_PANIC, NULL);
}
bool ptlock_alloc(struct page *page)
{
spinlock_t *ptl;
ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
if (!ptl)
return false;
page->ptl = ptl;
return true;
}
void ptlock_free(struct page *page)
{
kmem_cache_free(page_ptl_cachep, page->ptl);
}
#endif
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