linux/kernel/fork.c
Laurent Vivier ed75e8d580 [PATCH] UML Support - Ptrace: adds the host SYSEMU support, for UML and general usage
Jeff Dike <jdike@addtoit.com>,
      Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>,
      Bodo Stroesser <bstroesser@fujitsu-siemens.com>

Adds a new ptrace(2) mode, called PTRACE_SYSEMU, resembling PTRACE_SYSCALL
except that the kernel does not execute the requested syscall; this is useful
to improve performance for virtual environments, like UML, which want to run
the syscall on their own.

In fact, using PTRACE_SYSCALL means stopping child execution twice, on entry
and on exit, and each time you also have two context switches; with SYSEMU you
avoid the 2nd stop and so save two context switches per syscall.

Also, some architectures don't have support in the host for changing the
syscall number via ptrace(), which is currently needed to skip syscall
execution (UML turns any syscall into getpid() to avoid it being executed on
the host).  Fixing that is hard, while SYSEMU is easier to implement.

* This version of the patch includes some suggestions of Jeff Dike to avoid
  adding any instructions to the syscall fast path, plus some other little
  changes, by myself, to make it work even when the syscall is executed with
  SYSENTER (but I'm unsure about them). It has been widely tested for quite a
  lot of time.

* Various fixed were included to handle the various switches between
  various states, i.e. when for instance a syscall entry is traced with one of
  PT_SYSCALL / _SYSEMU / _SINGLESTEP and another one is used on exit.
  Basically, this is done by remembering which one of them was used even after
  the call to ptrace_notify().

* We're combining TIF_SYSCALL_EMU with TIF_SYSCALL_TRACE or TIF_SINGLESTEP
  to make do_syscall_trace() notice that the current syscall was started with
  SYSEMU on entry, so that no notification ought to be done in the exit path;
  this is a bit of a hack, so this problem is solved in another way in next
  patches.

* Also, the effects of the patch:
"Ptrace - i386: fix Syscall Audit interaction with singlestep"
are cancelled; they are restored back in the last patch of this series.

Detailed descriptions of the patches doing this kind of processing follow (but
I've already summed everything up).

* Fix behaviour when changing interception kind #1.

  In do_syscall_trace(), we check the status of the TIF_SYSCALL_EMU flag
  only after doing the debugger notification; but the debugger might have
  changed the status of this flag because he continued execution with
  PTRACE_SYSCALL, so this is wrong.  This patch fixes it by saving the flag
  status before calling ptrace_notify().

* Fix behaviour when changing interception kind #2:
  avoid intercepting syscall on return when using SYSCALL again.

  A guest process switching from using PTRACE_SYSEMU to PTRACE_SYSCALL
  crashes.

  The problem is in arch/i386/kernel/entry.S.  The current SYSEMU patch
  inhibits the syscall-handler to be called, but does not prevent
  do_syscall_trace() to be called after this for syscall completion
  interception.

  The appended patch fixes this.  It reuses the flag TIF_SYSCALL_EMU to
  remember "we come from PTRACE_SYSEMU and now are in PTRACE_SYSCALL", since
  the flag is unused in the depicted situation.

* Fix behaviour when changing interception kind #3:
  avoid intercepting syscall on return when using SINGLESTEP.

  When testing 2.6.9 and the skas3.v6 patch, with my latest patch and had
  problems with singlestepping on UML in SKAS with SYSEMU.  It looped
  receiving SIGTRAPs without moving forward.  EIP of the traced process was
  the same for all SIGTRAPs.

What's missing is to handle switching from PTRACE_SYSCALL_EMU to
PTRACE_SINGLESTEP in a way very similar to what is done for the change from
PTRACE_SYSCALL_EMU to PTRACE_SYSCALL_TRACE.

I.e., after calling ptrace(PTRACE_SYSEMU), on the return path, the debugger is
notified and then wake ups the process; the syscall is executed (or skipped,
when do_syscall_trace() returns 0, i.e.  when using PTRACE_SYSEMU), and
do_syscall_trace() is called again.  Since we are on the return path of a
SYSEMU'd syscall, if the wake up is performed through ptrace(PTRACE_SYSCALL),
we must still avoid notifying the parent of the syscall exit.  Now, this
behaviour is extended even to resuming with PTRACE_SINGLESTEP.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-05 00:06:20 -07:00

1291 lines
32 KiB
C

/*
* linux/kernel/fork.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* 'fork.c' contains the help-routines for the 'fork' system call
* (see also entry.S and others).
* Fork is rather simple, once you get the hang of it, but the memory
* management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
*/
#include <linux/config.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/unistd.h>
#include <linux/smp_lock.h>
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/completion.h>
#include <linux/namespace.h>
#include <linux/personality.h>
#include <linux/mempolicy.h>
#include <linux/sem.h>
#include <linux/file.h>
#include <linux/key.h>
#include <linux/binfmts.h>
#include <linux/mman.h>
#include <linux/fs.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/security.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/jiffies.h>
#include <linux/futex.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
#include <linux/audit.h>
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/acct.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
/*
* Protected counters by write_lock_irq(&tasklist_lock)
*/
unsigned long total_forks; /* Handle normal Linux uptimes. */
int nr_threads; /* The idle threads do not count.. */
int max_threads; /* tunable limit on nr_threads */
DEFINE_PER_CPU(unsigned long, process_counts) = 0;
__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
EXPORT_SYMBOL(tasklist_lock);
int nr_processes(void)
{
int cpu;
int total = 0;
for_each_online_cpu(cpu)
total += per_cpu(process_counts, cpu);
return total;
}
#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
static kmem_cache_t *task_struct_cachep;
#endif
/* SLAB cache for signal_struct structures (tsk->signal) */
kmem_cache_t *signal_cachep;
/* SLAB cache for sighand_struct structures (tsk->sighand) */
kmem_cache_t *sighand_cachep;
/* SLAB cache for files_struct structures (tsk->files) */
kmem_cache_t *files_cachep;
/* SLAB cache for fs_struct structures (tsk->fs) */
kmem_cache_t *fs_cachep;
/* SLAB cache for vm_area_struct structures */
kmem_cache_t *vm_area_cachep;
/* SLAB cache for mm_struct structures (tsk->mm) */
static kmem_cache_t *mm_cachep;
void free_task(struct task_struct *tsk)
{
free_thread_info(tsk->thread_info);
free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);
void __put_task_struct(struct task_struct *tsk)
{
WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
WARN_ON(atomic_read(&tsk->usage));
WARN_ON(tsk == current);
if (unlikely(tsk->audit_context))
audit_free(tsk);
security_task_free(tsk);
free_uid(tsk->user);
put_group_info(tsk->group_info);
if (!profile_handoff_task(tsk))
free_task(tsk);
}
void __init fork_init(unsigned long mempages)
{
#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
#ifndef ARCH_MIN_TASKALIGN
#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
#endif
/* create a slab on which task_structs can be allocated */
task_struct_cachep =
kmem_cache_create("task_struct", sizeof(struct task_struct),
ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
#endif
/*
* The default maximum number of threads is set to a safe
* value: the thread structures can take up at most half
* of memory.
*/
max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
/*
* we need to allow at least 20 threads to boot a system
*/
if(max_threads < 20)
max_threads = 20;
init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
init_task.signal->rlim[RLIMIT_SIGPENDING] =
init_task.signal->rlim[RLIMIT_NPROC];
}
static struct task_struct *dup_task_struct(struct task_struct *orig)
{
struct task_struct *tsk;
struct thread_info *ti;
prepare_to_copy(orig);
tsk = alloc_task_struct();
if (!tsk)
return NULL;
ti = alloc_thread_info(tsk);
if (!ti) {
free_task_struct(tsk);
return NULL;
}
*ti = *orig->thread_info;
*tsk = *orig;
tsk->thread_info = ti;
ti->task = tsk;
/* One for us, one for whoever does the "release_task()" (usually parent) */
atomic_set(&tsk->usage,2);
return tsk;
}
#ifdef CONFIG_MMU
static inline int dup_mmap(struct mm_struct * mm, struct mm_struct * oldmm)
{
struct vm_area_struct * mpnt, *tmp, **pprev;
struct rb_node **rb_link, *rb_parent;
int retval;
unsigned long charge;
struct mempolicy *pol;
down_write(&oldmm->mmap_sem);
flush_cache_mm(current->mm);
mm->locked_vm = 0;
mm->mmap = NULL;
mm->mmap_cache = NULL;
mm->free_area_cache = oldmm->mmap_base;
mm->cached_hole_size = ~0UL;
mm->map_count = 0;
set_mm_counter(mm, rss, 0);
set_mm_counter(mm, anon_rss, 0);
cpus_clear(mm->cpu_vm_mask);
mm->mm_rb = RB_ROOT;
rb_link = &mm->mm_rb.rb_node;
rb_parent = NULL;
pprev = &mm->mmap;
for (mpnt = current->mm->mmap ; mpnt ; mpnt = mpnt->vm_next) {
struct file *file;
if (mpnt->vm_flags & VM_DONTCOPY) {
long pages = vma_pages(mpnt);
mm->total_vm -= pages;
__vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
-pages);
continue;
}
charge = 0;
if (mpnt->vm_flags & VM_ACCOUNT) {
unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
if (security_vm_enough_memory(len))
goto fail_nomem;
charge = len;
}
tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
if (!tmp)
goto fail_nomem;
*tmp = *mpnt;
pol = mpol_copy(vma_policy(mpnt));
retval = PTR_ERR(pol);
if (IS_ERR(pol))
goto fail_nomem_policy;
vma_set_policy(tmp, pol);
tmp->vm_flags &= ~VM_LOCKED;
tmp->vm_mm = mm;
tmp->vm_next = NULL;
anon_vma_link(tmp);
file = tmp->vm_file;
if (file) {
struct inode *inode = file->f_dentry->d_inode;
get_file(file);
if (tmp->vm_flags & VM_DENYWRITE)
atomic_dec(&inode->i_writecount);
/* insert tmp into the share list, just after mpnt */
spin_lock(&file->f_mapping->i_mmap_lock);
tmp->vm_truncate_count = mpnt->vm_truncate_count;
flush_dcache_mmap_lock(file->f_mapping);
vma_prio_tree_add(tmp, mpnt);
flush_dcache_mmap_unlock(file->f_mapping);
spin_unlock(&file->f_mapping->i_mmap_lock);
}
/*
* Link in the new vma and copy the page table entries:
* link in first so that swapoff can see swap entries.
* Note that, exceptionally, here the vma is inserted
* without holding mm->mmap_sem.
*/
spin_lock(&mm->page_table_lock);
*pprev = tmp;
pprev = &tmp->vm_next;
__vma_link_rb(mm, tmp, rb_link, rb_parent);
rb_link = &tmp->vm_rb.rb_right;
rb_parent = &tmp->vm_rb;
mm->map_count++;
retval = copy_page_range(mm, current->mm, tmp);
spin_unlock(&mm->page_table_lock);
if (tmp->vm_ops && tmp->vm_ops->open)
tmp->vm_ops->open(tmp);
if (retval)
goto out;
}
retval = 0;
out:
flush_tlb_mm(current->mm);
up_write(&oldmm->mmap_sem);
return retval;
fail_nomem_policy:
kmem_cache_free(vm_area_cachep, tmp);
fail_nomem:
retval = -ENOMEM;
vm_unacct_memory(charge);
goto out;
}
static inline int mm_alloc_pgd(struct mm_struct * mm)
{
mm->pgd = pgd_alloc(mm);
if (unlikely(!mm->pgd))
return -ENOMEM;
return 0;
}
static inline void mm_free_pgd(struct mm_struct * mm)
{
pgd_free(mm->pgd);
}
#else
#define dup_mmap(mm, oldmm) (0)
#define mm_alloc_pgd(mm) (0)
#define mm_free_pgd(mm)
#endif /* CONFIG_MMU */
__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
#define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
#include <linux/init_task.h>
static struct mm_struct * mm_init(struct mm_struct * mm)
{
atomic_set(&mm->mm_users, 1);
atomic_set(&mm->mm_count, 1);
init_rwsem(&mm->mmap_sem);
INIT_LIST_HEAD(&mm->mmlist);
mm->core_waiters = 0;
mm->nr_ptes = 0;
spin_lock_init(&mm->page_table_lock);
rwlock_init(&mm->ioctx_list_lock);
mm->ioctx_list = NULL;
mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm);
mm->free_area_cache = TASK_UNMAPPED_BASE;
mm->cached_hole_size = ~0UL;
if (likely(!mm_alloc_pgd(mm))) {
mm->def_flags = 0;
return mm;
}
free_mm(mm);
return NULL;
}
/*
* Allocate and initialize an mm_struct.
*/
struct mm_struct * mm_alloc(void)
{
struct mm_struct * mm;
mm = allocate_mm();
if (mm) {
memset(mm, 0, sizeof(*mm));
mm = mm_init(mm);
}
return mm;
}
/*
* Called when the last reference to the mm
* is dropped: either by a lazy thread or by
* mmput. Free the page directory and the mm.
*/
void fastcall __mmdrop(struct mm_struct *mm)
{
BUG_ON(mm == &init_mm);
mm_free_pgd(mm);
destroy_context(mm);
free_mm(mm);
}
/*
* Decrement the use count and release all resources for an mm.
*/
void mmput(struct mm_struct *mm)
{
if (atomic_dec_and_test(&mm->mm_users)) {
exit_aio(mm);
exit_mmap(mm);
if (!list_empty(&mm->mmlist)) {
spin_lock(&mmlist_lock);
list_del(&mm->mmlist);
spin_unlock(&mmlist_lock);
}
put_swap_token(mm);
mmdrop(mm);
}
}
EXPORT_SYMBOL_GPL(mmput);
/**
* get_task_mm - acquire a reference to the task's mm
*
* Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
* this kernel workthread has transiently adopted a user mm with use_mm,
* to do its AIO) is not set and if so returns a reference to it, after
* bumping up the use count. User must release the mm via mmput()
* after use. Typically used by /proc and ptrace.
*/
struct mm_struct *get_task_mm(struct task_struct *task)
{
struct mm_struct *mm;
task_lock(task);
mm = task->mm;
if (mm) {
if (task->flags & PF_BORROWED_MM)
mm = NULL;
else
atomic_inc(&mm->mm_users);
}
task_unlock(task);
return mm;
}
EXPORT_SYMBOL_GPL(get_task_mm);
/* Please note the differences between mmput and mm_release.
* mmput is called whenever we stop holding onto a mm_struct,
* error success whatever.
*
* mm_release is called after a mm_struct has been removed
* from the current process.
*
* This difference is important for error handling, when we
* only half set up a mm_struct for a new process and need to restore
* the old one. Because we mmput the new mm_struct before
* restoring the old one. . .
* Eric Biederman 10 January 1998
*/
void mm_release(struct task_struct *tsk, struct mm_struct *mm)
{
struct completion *vfork_done = tsk->vfork_done;
/* Get rid of any cached register state */
deactivate_mm(tsk, mm);
/* notify parent sleeping on vfork() */
if (vfork_done) {
tsk->vfork_done = NULL;
complete(vfork_done);
}
if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
u32 __user * tidptr = tsk->clear_child_tid;
tsk->clear_child_tid = NULL;
/*
* We don't check the error code - if userspace has
* not set up a proper pointer then tough luck.
*/
put_user(0, tidptr);
sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
}
}
static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
{
struct mm_struct * mm, *oldmm;
int retval;
tsk->min_flt = tsk->maj_flt = 0;
tsk->nvcsw = tsk->nivcsw = 0;
tsk->mm = NULL;
tsk->active_mm = NULL;
/*
* Are we cloning a kernel thread?
*
* We need to steal a active VM for that..
*/
oldmm = current->mm;
if (!oldmm)
return 0;
if (clone_flags & CLONE_VM) {
atomic_inc(&oldmm->mm_users);
mm = oldmm;
/*
* There are cases where the PTL is held to ensure no
* new threads start up in user mode using an mm, which
* allows optimizing out ipis; the tlb_gather_mmu code
* is an example.
*/
spin_unlock_wait(&oldmm->page_table_lock);
goto good_mm;
}
retval = -ENOMEM;
mm = allocate_mm();
if (!mm)
goto fail_nomem;
/* Copy the current MM stuff.. */
memcpy(mm, oldmm, sizeof(*mm));
if (!mm_init(mm))
goto fail_nomem;
if (init_new_context(tsk,mm))
goto fail_nocontext;
retval = dup_mmap(mm, oldmm);
if (retval)
goto free_pt;
mm->hiwater_rss = get_mm_counter(mm,rss);
mm->hiwater_vm = mm->total_vm;
good_mm:
tsk->mm = mm;
tsk->active_mm = mm;
return 0;
free_pt:
mmput(mm);
fail_nomem:
return retval;
fail_nocontext:
/*
* If init_new_context() failed, we cannot use mmput() to free the mm
* because it calls destroy_context()
*/
mm_free_pgd(mm);
free_mm(mm);
return retval;
}
static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
{
struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
/* We don't need to lock fs - think why ;-) */
if (fs) {
atomic_set(&fs->count, 1);
rwlock_init(&fs->lock);
fs->umask = old->umask;
read_lock(&old->lock);
fs->rootmnt = mntget(old->rootmnt);
fs->root = dget(old->root);
fs->pwdmnt = mntget(old->pwdmnt);
fs->pwd = dget(old->pwd);
if (old->altroot) {
fs->altrootmnt = mntget(old->altrootmnt);
fs->altroot = dget(old->altroot);
} else {
fs->altrootmnt = NULL;
fs->altroot = NULL;
}
read_unlock(&old->lock);
}
return fs;
}
struct fs_struct *copy_fs_struct(struct fs_struct *old)
{
return __copy_fs_struct(old);
}
EXPORT_SYMBOL_GPL(copy_fs_struct);
static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
{
if (clone_flags & CLONE_FS) {
atomic_inc(&current->fs->count);
return 0;
}
tsk->fs = __copy_fs_struct(current->fs);
if (!tsk->fs)
return -ENOMEM;
return 0;
}
static int count_open_files(struct files_struct *files, int size)
{
int i;
/* Find the last open fd */
for (i = size/(8*sizeof(long)); i > 0; ) {
if (files->open_fds->fds_bits[--i])
break;
}
i = (i+1) * 8 * sizeof(long);
return i;
}
static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
{
struct files_struct *oldf, *newf;
struct file **old_fds, **new_fds;
int open_files, size, i, error = 0, expand;
/*
* A background process may not have any files ...
*/
oldf = current->files;
if (!oldf)
goto out;
if (clone_flags & CLONE_FILES) {
atomic_inc(&oldf->count);
goto out;
}
/*
* Note: we may be using current for both targets (See exec.c)
* This works because we cache current->files (old) as oldf. Don't
* break this.
*/
tsk->files = NULL;
error = -ENOMEM;
newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
if (!newf)
goto out;
atomic_set(&newf->count, 1);
spin_lock_init(&newf->file_lock);
newf->next_fd = 0;
newf->max_fds = NR_OPEN_DEFAULT;
newf->max_fdset = __FD_SETSIZE;
newf->close_on_exec = &newf->close_on_exec_init;
newf->open_fds = &newf->open_fds_init;
newf->fd = &newf->fd_array[0];
spin_lock(&oldf->file_lock);
open_files = count_open_files(oldf, oldf->max_fdset);
expand = 0;
/*
* Check whether we need to allocate a larger fd array or fd set.
* Note: we're not a clone task, so the open count won't change.
*/
if (open_files > newf->max_fdset) {
newf->max_fdset = 0;
expand = 1;
}
if (open_files > newf->max_fds) {
newf->max_fds = 0;
expand = 1;
}
/* if the old fdset gets grown now, we'll only copy up to "size" fds */
if (expand) {
spin_unlock(&oldf->file_lock);
spin_lock(&newf->file_lock);
error = expand_files(newf, open_files-1);
spin_unlock(&newf->file_lock);
if (error < 0)
goto out_release;
spin_lock(&oldf->file_lock);
}
old_fds = oldf->fd;
new_fds = newf->fd;
memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8);
memcpy(newf->close_on_exec->fds_bits, oldf->close_on_exec->fds_bits, open_files/8);
for (i = open_files; i != 0; i--) {
struct file *f = *old_fds++;
if (f) {
get_file(f);
} else {
/*
* The fd may be claimed in the fd bitmap but not yet
* instantiated in the files array if a sibling thread
* is partway through open(). So make sure that this
* fd is available to the new process.
*/
FD_CLR(open_files - i, newf->open_fds);
}
*new_fds++ = f;
}
spin_unlock(&oldf->file_lock);
/* compute the remainder to be cleared */
size = (newf->max_fds - open_files) * sizeof(struct file *);
/* This is long word aligned thus could use a optimized version */
memset(new_fds, 0, size);
if (newf->max_fdset > open_files) {
int left = (newf->max_fdset-open_files)/8;
int start = open_files / (8 * sizeof(unsigned long));
memset(&newf->open_fds->fds_bits[start], 0, left);
memset(&newf->close_on_exec->fds_bits[start], 0, left);
}
tsk->files = newf;
error = 0;
out:
return error;
out_release:
free_fdset (newf->close_on_exec, newf->max_fdset);
free_fdset (newf->open_fds, newf->max_fdset);
free_fd_array(newf->fd, newf->max_fds);
kmem_cache_free(files_cachep, newf);
goto out;
}
/*
* Helper to unshare the files of the current task.
* We don't want to expose copy_files internals to
* the exec layer of the kernel.
*/
int unshare_files(void)
{
struct files_struct *files = current->files;
int rc;
if(!files)
BUG();
/* This can race but the race causes us to copy when we don't
need to and drop the copy */
if(atomic_read(&files->count) == 1)
{
atomic_inc(&files->count);
return 0;
}
rc = copy_files(0, current);
if(rc)
current->files = files;
return rc;
}
EXPORT_SYMBOL(unshare_files);
static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
{
struct sighand_struct *sig;
if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
atomic_inc(&current->sighand->count);
return 0;
}
sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
tsk->sighand = sig;
if (!sig)
return -ENOMEM;
spin_lock_init(&sig->siglock);
atomic_set(&sig->count, 1);
memcpy(sig->action, current->sighand->action, sizeof(sig->action));
return 0;
}
static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
{
struct signal_struct *sig;
int ret;
if (clone_flags & CLONE_THREAD) {
atomic_inc(&current->signal->count);
atomic_inc(&current->signal->live);
return 0;
}
sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
tsk->signal = sig;
if (!sig)
return -ENOMEM;
ret = copy_thread_group_keys(tsk);
if (ret < 0) {
kmem_cache_free(signal_cachep, sig);
return ret;
}
atomic_set(&sig->count, 1);
atomic_set(&sig->live, 1);
init_waitqueue_head(&sig->wait_chldexit);
sig->flags = 0;
sig->group_exit_code = 0;
sig->group_exit_task = NULL;
sig->group_stop_count = 0;
sig->curr_target = NULL;
init_sigpending(&sig->shared_pending);
INIT_LIST_HEAD(&sig->posix_timers);
sig->it_real_value = sig->it_real_incr = 0;
sig->real_timer.function = it_real_fn;
sig->real_timer.data = (unsigned long) tsk;
init_timer(&sig->real_timer);
sig->it_virt_expires = cputime_zero;
sig->it_virt_incr = cputime_zero;
sig->it_prof_expires = cputime_zero;
sig->it_prof_incr = cputime_zero;
sig->tty = current->signal->tty;
sig->pgrp = process_group(current);
sig->session = current->signal->session;
sig->leader = 0; /* session leadership doesn't inherit */
sig->tty_old_pgrp = 0;
sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
sig->sched_time = 0;
INIT_LIST_HEAD(&sig->cpu_timers[0]);
INIT_LIST_HEAD(&sig->cpu_timers[1]);
INIT_LIST_HEAD(&sig->cpu_timers[2]);
task_lock(current->group_leader);
memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
task_unlock(current->group_leader);
if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
/*
* New sole thread in the process gets an expiry time
* of the whole CPU time limit.
*/
tsk->it_prof_expires =
secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
}
return 0;
}
static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
{
unsigned long new_flags = p->flags;
new_flags &= ~PF_SUPERPRIV;
new_flags |= PF_FORKNOEXEC;
if (!(clone_flags & CLONE_PTRACE))
p->ptrace = 0;
p->flags = new_flags;
}
asmlinkage long sys_set_tid_address(int __user *tidptr)
{
current->clear_child_tid = tidptr;
return current->pid;
}
/*
* This creates a new process as a copy of the old one,
* but does not actually start it yet.
*
* It copies the registers, and all the appropriate
* parts of the process environment (as per the clone
* flags). The actual kick-off is left to the caller.
*/
static task_t *copy_process(unsigned long clone_flags,
unsigned long stack_start,
struct pt_regs *regs,
unsigned long stack_size,
int __user *parent_tidptr,
int __user *child_tidptr,
int pid)
{
int retval;
struct task_struct *p = NULL;
if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
return ERR_PTR(-EINVAL);
/*
* Thread groups must share signals as well, and detached threads
* can only be started up within the thread group.
*/
if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
return ERR_PTR(-EINVAL);
/*
* Shared signal handlers imply shared VM. By way of the above,
* thread groups also imply shared VM. Blocking this case allows
* for various simplifications in other code.
*/
if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
return ERR_PTR(-EINVAL);
retval = security_task_create(clone_flags);
if (retval)
goto fork_out;
retval = -ENOMEM;
p = dup_task_struct(current);
if (!p)
goto fork_out;
retval = -EAGAIN;
if (atomic_read(&p->user->processes) >=
p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
p->user != &root_user)
goto bad_fork_free;
}
atomic_inc(&p->user->__count);
atomic_inc(&p->user->processes);
get_group_info(p->group_info);
/*
* If multiple threads are within copy_process(), then this check
* triggers too late. This doesn't hurt, the check is only there
* to stop root fork bombs.
*/
if (nr_threads >= max_threads)
goto bad_fork_cleanup_count;
if (!try_module_get(p->thread_info->exec_domain->module))
goto bad_fork_cleanup_count;
if (p->binfmt && !try_module_get(p->binfmt->module))
goto bad_fork_cleanup_put_domain;
p->did_exec = 0;
copy_flags(clone_flags, p);
p->pid = pid;
retval = -EFAULT;
if (clone_flags & CLONE_PARENT_SETTID)
if (put_user(p->pid, parent_tidptr))
goto bad_fork_cleanup;
p->proc_dentry = NULL;
INIT_LIST_HEAD(&p->children);
INIT_LIST_HEAD(&p->sibling);
p->vfork_done = NULL;
spin_lock_init(&p->alloc_lock);
spin_lock_init(&p->proc_lock);
clear_tsk_thread_flag(p, TIF_SIGPENDING);
init_sigpending(&p->pending);
p->utime = cputime_zero;
p->stime = cputime_zero;
p->sched_time = 0;
p->rchar = 0; /* I/O counter: bytes read */
p->wchar = 0; /* I/O counter: bytes written */
p->syscr = 0; /* I/O counter: read syscalls */
p->syscw = 0; /* I/O counter: write syscalls */
acct_clear_integrals(p);
p->it_virt_expires = cputime_zero;
p->it_prof_expires = cputime_zero;
p->it_sched_expires = 0;
INIT_LIST_HEAD(&p->cpu_timers[0]);
INIT_LIST_HEAD(&p->cpu_timers[1]);
INIT_LIST_HEAD(&p->cpu_timers[2]);
p->lock_depth = -1; /* -1 = no lock */
do_posix_clock_monotonic_gettime(&p->start_time);
p->security = NULL;
p->io_context = NULL;
p->io_wait = NULL;
p->audit_context = NULL;
#ifdef CONFIG_NUMA
p->mempolicy = mpol_copy(p->mempolicy);
if (IS_ERR(p->mempolicy)) {
retval = PTR_ERR(p->mempolicy);
p->mempolicy = NULL;
goto bad_fork_cleanup;
}
#endif
p->tgid = p->pid;
if (clone_flags & CLONE_THREAD)
p->tgid = current->tgid;
if ((retval = security_task_alloc(p)))
goto bad_fork_cleanup_policy;
if ((retval = audit_alloc(p)))
goto bad_fork_cleanup_security;
/* copy all the process information */
if ((retval = copy_semundo(clone_flags, p)))
goto bad_fork_cleanup_audit;
if ((retval = copy_files(clone_flags, p)))
goto bad_fork_cleanup_semundo;
if ((retval = copy_fs(clone_flags, p)))
goto bad_fork_cleanup_files;
if ((retval = copy_sighand(clone_flags, p)))
goto bad_fork_cleanup_fs;
if ((retval = copy_signal(clone_flags, p)))
goto bad_fork_cleanup_sighand;
if ((retval = copy_mm(clone_flags, p)))
goto bad_fork_cleanup_signal;
if ((retval = copy_keys(clone_flags, p)))
goto bad_fork_cleanup_mm;
if ((retval = copy_namespace(clone_flags, p)))
goto bad_fork_cleanup_keys;
retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
if (retval)
goto bad_fork_cleanup_namespace;
p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
/*
* Clear TID on mm_release()?
*/
p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
/*
* Syscall tracing should be turned off in the child regardless
* of CLONE_PTRACE.
*/
clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
#ifdef TIF_SYSCALL_EMU
clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
/* Our parent execution domain becomes current domain
These must match for thread signalling to apply */
p->parent_exec_id = p->self_exec_id;
/* ok, now we should be set up.. */
p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
p->pdeath_signal = 0;
p->exit_state = 0;
/*
* Ok, make it visible to the rest of the system.
* We dont wake it up yet.
*/
p->group_leader = p;
INIT_LIST_HEAD(&p->ptrace_children);
INIT_LIST_HEAD(&p->ptrace_list);
/* Perform scheduler related setup. Assign this task to a CPU. */
sched_fork(p, clone_flags);
/* Need tasklist lock for parent etc handling! */
write_lock_irq(&tasklist_lock);
/*
* The task hasn't been attached yet, so its cpus_allowed mask will
* not be changed, nor will its assigned CPU.
*
* The cpus_allowed mask of the parent may have changed after it was
* copied first time - so re-copy it here, then check the child's CPU
* to ensure it is on a valid CPU (and if not, just force it back to
* parent's CPU). This avoids alot of nasty races.
*/
p->cpus_allowed = current->cpus_allowed;
if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed)))
set_task_cpu(p, smp_processor_id());
/*
* Check for pending SIGKILL! The new thread should not be allowed
* to slip out of an OOM kill. (or normal SIGKILL.)
*/
if (sigismember(&current->pending.signal, SIGKILL)) {
write_unlock_irq(&tasklist_lock);
retval = -EINTR;
goto bad_fork_cleanup_namespace;
}
/* CLONE_PARENT re-uses the old parent */
if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
p->real_parent = current->real_parent;
else
p->real_parent = current;
p->parent = p->real_parent;
if (clone_flags & CLONE_THREAD) {
spin_lock(&current->sighand->siglock);
/*
* Important: if an exit-all has been started then
* do not create this new thread - the whole thread
* group is supposed to exit anyway.
*/
if (current->signal->flags & SIGNAL_GROUP_EXIT) {
spin_unlock(&current->sighand->siglock);
write_unlock_irq(&tasklist_lock);
retval = -EAGAIN;
goto bad_fork_cleanup_namespace;
}
p->group_leader = current->group_leader;
if (current->signal->group_stop_count > 0) {
/*
* There is an all-stop in progress for the group.
* We ourselves will stop as soon as we check signals.
* Make the new thread part of that group stop too.
*/
current->signal->group_stop_count++;
set_tsk_thread_flag(p, TIF_SIGPENDING);
}
if (!cputime_eq(current->signal->it_virt_expires,
cputime_zero) ||
!cputime_eq(current->signal->it_prof_expires,
cputime_zero) ||
current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
!list_empty(&current->signal->cpu_timers[0]) ||
!list_empty(&current->signal->cpu_timers[1]) ||
!list_empty(&current->signal->cpu_timers[2])) {
/*
* Have child wake up on its first tick to check
* for process CPU timers.
*/
p->it_prof_expires = jiffies_to_cputime(1);
}
spin_unlock(&current->sighand->siglock);
}
/*
* inherit ioprio
*/
p->ioprio = current->ioprio;
SET_LINKS(p);
if (unlikely(p->ptrace & PT_PTRACED))
__ptrace_link(p, current->parent);
cpuset_fork(p);
attach_pid(p, PIDTYPE_PID, p->pid);
attach_pid(p, PIDTYPE_TGID, p->tgid);
if (thread_group_leader(p)) {
attach_pid(p, PIDTYPE_PGID, process_group(p));
attach_pid(p, PIDTYPE_SID, p->signal->session);
if (p->pid)
__get_cpu_var(process_counts)++;
}
nr_threads++;
total_forks++;
write_unlock_irq(&tasklist_lock);
retval = 0;
fork_out:
if (retval)
return ERR_PTR(retval);
return p;
bad_fork_cleanup_namespace:
exit_namespace(p);
bad_fork_cleanup_keys:
exit_keys(p);
bad_fork_cleanup_mm:
if (p->mm)
mmput(p->mm);
bad_fork_cleanup_signal:
exit_signal(p);
bad_fork_cleanup_sighand:
exit_sighand(p);
bad_fork_cleanup_fs:
exit_fs(p); /* blocking */
bad_fork_cleanup_files:
exit_files(p); /* blocking */
bad_fork_cleanup_semundo:
exit_sem(p);
bad_fork_cleanup_audit:
audit_free(p);
bad_fork_cleanup_security:
security_task_free(p);
bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
mpol_free(p->mempolicy);
#endif
bad_fork_cleanup:
if (p->binfmt)
module_put(p->binfmt->module);
bad_fork_cleanup_put_domain:
module_put(p->thread_info->exec_domain->module);
bad_fork_cleanup_count:
put_group_info(p->group_info);
atomic_dec(&p->user->processes);
free_uid(p->user);
bad_fork_free:
free_task(p);
goto fork_out;
}
struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
{
memset(regs, 0, sizeof(struct pt_regs));
return regs;
}
task_t * __devinit fork_idle(int cpu)
{
task_t *task;
struct pt_regs regs;
task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
if (!task)
return ERR_PTR(-ENOMEM);
init_idle(task, cpu);
unhash_process(task);
return task;
}
static inline int fork_traceflag (unsigned clone_flags)
{
if (clone_flags & CLONE_UNTRACED)
return 0;
else if (clone_flags & CLONE_VFORK) {
if (current->ptrace & PT_TRACE_VFORK)
return PTRACE_EVENT_VFORK;
} else if ((clone_flags & CSIGNAL) != SIGCHLD) {
if (current->ptrace & PT_TRACE_CLONE)
return PTRACE_EVENT_CLONE;
} else if (current->ptrace & PT_TRACE_FORK)
return PTRACE_EVENT_FORK;
return 0;
}
/*
* Ok, this is the main fork-routine.
*
* It copies the process, and if successful kick-starts
* it and waits for it to finish using the VM if required.
*/
long do_fork(unsigned long clone_flags,
unsigned long stack_start,
struct pt_regs *regs,
unsigned long stack_size,
int __user *parent_tidptr,
int __user *child_tidptr)
{
struct task_struct *p;
int trace = 0;
long pid = alloc_pidmap();
if (pid < 0)
return -EAGAIN;
if (unlikely(current->ptrace)) {
trace = fork_traceflag (clone_flags);
if (trace)
clone_flags |= CLONE_PTRACE;
}
p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
/*
* Do this prior waking up the new thread - the thread pointer
* might get invalid after that point, if the thread exits quickly.
*/
if (!IS_ERR(p)) {
struct completion vfork;
if (clone_flags & CLONE_VFORK) {
p->vfork_done = &vfork;
init_completion(&vfork);
}
if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
/*
* We'll start up with an immediate SIGSTOP.
*/
sigaddset(&p->pending.signal, SIGSTOP);
set_tsk_thread_flag(p, TIF_SIGPENDING);
}
if (!(clone_flags & CLONE_STOPPED))
wake_up_new_task(p, clone_flags);
else
p->state = TASK_STOPPED;
if (unlikely (trace)) {
current->ptrace_message = pid;
ptrace_notify ((trace << 8) | SIGTRAP);
}
if (clone_flags & CLONE_VFORK) {
wait_for_completion(&vfork);
if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
}
} else {
free_pidmap(pid);
pid = PTR_ERR(p);
}
return pid;
}
void __init proc_caches_init(void)
{
sighand_cachep = kmem_cache_create("sighand_cache",
sizeof(struct sighand_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
signal_cachep = kmem_cache_create("signal_cache",
sizeof(struct signal_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
files_cachep = kmem_cache_create("files_cache",
sizeof(struct files_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
fs_cachep = kmem_cache_create("fs_cache",
sizeof(struct fs_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
vm_area_cachep = kmem_cache_create("vm_area_struct",
sizeof(struct vm_area_struct), 0,
SLAB_PANIC, NULL, NULL);
mm_cachep = kmem_cache_create("mm_struct",
sizeof(struct mm_struct), 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
}