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powerpc: Add set_memory_{p/np}() and remove set_memory_attr()

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set_memory_attr() was implemented by commit 4d1755b6a7 ("powerpc/mm:
implement set_memory_attr()") because the set_memory_xx() couldn't
be used at that time to modify memory "on the fly" as explained it
the commit.

But set_memory_attr() uses set_pte_at() which leads to warnings when
CONFIG_DEBUG_VM is selected, because set_pte_at() is unexpected for
updating existing page table entries.

The check could be bypassed by using __set_pte_at() instead,
as it was the case before commit c988cfd38e ("powerpc/32:
use set_memory_attr()") but since commit 9f7853d760 ("powerpc/mm:
Fix set_memory_*() against concurrent accesses") it is now possible
to use set_memory_xx() functions to update page table entries
"on the fly" because the update is now atomic.

For DEBUG_PAGEALLOC we need to clear and set back _PAGE_PRESENT.
Add set_memory_np() and set_memory_p() for that.

Replace all uses of set_memory_attr() by the relevant set_memory_xx()
and remove set_memory_attr().

Fixes: c988cfd38e ("powerpc/32: use set_memory_attr()")
Cc: stable@vger.kernel.org
Reported-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Maxime Bizon <mbizon@freebox.fr>
Reviewed-by: Russell Currey <ruscur@russell.cc>
Depends-on: 9f7853d760 ("powerpc/mm: Fix set_memory_*() against concurrent accesses")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/cda2b44b55c96f9ac69fa92e68c01084ec9495c5.1640344012.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-12-24 11:07:40 +00:00 committed by Michael Ellerman
parent a4c182ecf3
commit f222ab83df
3 changed files with 28 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
arch/powerpc/include/asm/set_memory.h
View File

@ -6,6 +6,8 @@
#define SET_MEMORY_RW 1
#define SET_MEMORY_NX 2
#define SET_MEMORY_X 3
#define SET_MEMORY_NP 4 /* Set memory non present */
#define SET_MEMORY_P 5 /* Set memory present */
int change_memory_attr(unsigned long addr, int numpages, long action);
@ -29,6 +31,14 @@ static inline int set_memory_x(unsigned long addr, int numpages)
return change_memory_attr(addr, numpages, SET_MEMORY_X);
}
int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot);
static inline int set_memory_np(unsigned long addr, int numpages)
{
return change_memory_attr(addr, numpages, SET_MEMORY_NP);
}
static inline int set_memory_p(unsigned long addr, int numpages)
{
return change_memory_attr(addr, numpages, SET_MEMORY_P);
}
#endif

39
arch/powerpc/mm/pageattr.c
View File

@ -46,6 +46,12 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
case SET_MEMORY_X:
pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_ROX);
break;
case SET_MEMORY_NP:
pte_update(&init_mm, addr, ptep, _PAGE_PRESENT, 0, 0);
break;
case SET_MEMORY_P:
pte_update(&init_mm, addr, ptep, 0, _PAGE_PRESENT, 0);
break;
default:
WARN_ON_ONCE(1);
break;
@ -90,36 +96,3 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
return apply_to_existing_page_range(&init_mm, start, size,
change_page_attr, (void *)action);
}
/*
* Set the attributes of a page:
*
* This function is used by PPC32 at the end of init to set final kernel memory
* protection. It includes changing the maping of the page it is executing from
* and data pages it is using.
*/
static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
{
pgprot_t prot = __pgprot((unsigned long)data);
spin_lock(&init_mm.page_table_lock);
set_pte_at(&init_mm, addr, ptep, pte_modify(*ptep, prot));
flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
spin_unlock(&init_mm.page_table_lock);
return 0;
}
int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
{
unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
unsigned long sz = numpages * PAGE_SIZE;
if (numpages <= 0)
return 0;
return apply_to_existing_page_range(&init_mm, start, sz, set_page_attr,
(void *)pgprot_val(prot));
}

24
arch/powerpc/mm/pgtable_32.c
View File

@ -135,10 +135,12 @@ void mark_initmem_nx(void)
unsigned long numpages = PFN_UP((unsigned long)_einittext) -
PFN_DOWN((unsigned long)_sinittext);
if (v_block_mapped((unsigned long)_sinittext))
if (v_block_mapped((unsigned long)_sinittext)) {
mmu_mark_initmem_nx();
else
set_memory_attr((unsigned long)_sinittext, numpages, PAGE_KERNEL);
} else {
set_memory_nx((unsigned long)_sinittext, numpages);
set_memory_rw((unsigned long)_sinittext, numpages);
}
}
#ifdef CONFIG_STRICT_KERNEL_RWX
@ -152,18 +154,14 @@ void mark_rodata_ro(void)
return;
}
numpages = PFN_UP((unsigned long)_etext) -
PFN_DOWN((unsigned long)_stext);
set_memory_attr((unsigned long)_stext, numpages, PAGE_KERNEL_ROX);
/*
* mark .rodata as read only. Use __init_begin rather than __end_rodata
* to cover NOTES and EXCEPTION_TABLE.
* mark .text and .rodata as read only. Use __init_begin rather than
* __end_rodata to cover NOTES and EXCEPTION_TABLE.
*/
numpages = PFN_UP((unsigned long)__init_begin) -
PFN_DOWN((unsigned long)__start_rodata);
PFN_DOWN((unsigned long)_stext);
set_memory_attr((unsigned long)__start_rodata, numpages, PAGE_KERNEL_RO);
set_memory_ro((unsigned long)_stext, numpages);
// mark_initmem_nx() should have already run by now
ptdump_check_wx();
@ -179,8 +177,8 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
return;
if (enable)
set_memory_attr(addr, numpages, PAGE_KERNEL);
set_memory_p(addr, numpages);
else
set_memory_attr(addr, numpages, __pgprot(0));
set_memory_np(addr, numpages);
}
#endif /* CONFIG_DEBUG_PAGEALLOC */