4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
14 #include <linux/config.h>
15 #include <linux/slab.h>
16 #include <linux/init.h>
17 #include <linux/unistd.h>
18 #include <linux/smp_lock.h>
19 #include <linux/module.h>
20 #include <linux/vmalloc.h>
21 #include <linux/completion.h>
22 #include <linux/namespace.h>
23 #include <linux/personality.h>
24 #include <linux/mempolicy.h>
25 #include <linux/sem.h>
26 #include <linux/file.h>
27 #include <linux/key.h>
28 #include <linux/binfmts.h>
29 #include <linux/mman.h>
31 #include <linux/cpu.h>
32 #include <linux/cpuset.h>
33 #include <linux/security.h>
34 #include <linux/swap.h>
35 #include <linux/syscalls.h>
36 #include <linux/jiffies.h>
37 #include <linux/futex.h>
38 #include <linux/rcupdate.h>
39 #include <linux/ptrace.h>
40 #include <linux/mount.h>
41 #include <linux/audit.h>
42 #include <linux/profile.h>
43 #include <linux/rmap.h>
44 #include <linux/acct.h>
45 #include <linux/cn_proc.h>
47 #include <asm/pgtable.h>
48 #include <asm/pgalloc.h>
49 #include <asm/uaccess.h>
50 #include <asm/mmu_context.h>
51 #include <asm/cacheflush.h>
52 #include <asm/tlbflush.h>
55 * Protected counters by write_lock_irq(&tasklist_lock)
57 unsigned long total_forks
; /* Handle normal Linux uptimes. */
58 int nr_threads
; /* The idle threads do not count.. */
60 int max_threads
; /* tunable limit on nr_threads */
62 DEFINE_PER_CPU(unsigned long, process_counts
) = 0;
64 __cacheline_aligned
DEFINE_RWLOCK(tasklist_lock
); /* outer */
66 EXPORT_SYMBOL(tasklist_lock
);
68 int nr_processes(void)
73 for_each_online_cpu(cpu
)
74 total
+= per_cpu(process_counts
, cpu
);
79 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
80 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
81 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
82 static kmem_cache_t
*task_struct_cachep
;
85 /* SLAB cache for signal_struct structures (tsk->signal) */
86 kmem_cache_t
*signal_cachep
;
88 /* SLAB cache for sighand_struct structures (tsk->sighand) */
89 kmem_cache_t
*sighand_cachep
;
91 /* SLAB cache for files_struct structures (tsk->files) */
92 kmem_cache_t
*files_cachep
;
94 /* SLAB cache for fs_struct structures (tsk->fs) */
95 kmem_cache_t
*fs_cachep
;
97 /* SLAB cache for vm_area_struct structures */
98 kmem_cache_t
*vm_area_cachep
;
100 /* SLAB cache for mm_struct structures (tsk->mm) */
101 static kmem_cache_t
*mm_cachep
;
103 void free_task(struct task_struct
*tsk
)
105 free_thread_info(tsk
->thread_info
);
106 free_task_struct(tsk
);
108 EXPORT_SYMBOL(free_task
);
110 void __put_task_struct(struct task_struct
*tsk
)
112 WARN_ON(!(tsk
->exit_state
& (EXIT_DEAD
| EXIT_ZOMBIE
)));
113 WARN_ON(atomic_read(&tsk
->usage
));
114 WARN_ON(tsk
== current
);
116 if (unlikely(tsk
->audit_context
))
118 security_task_free(tsk
);
120 put_group_info(tsk
->group_info
);
122 if (!profile_handoff_task(tsk
))
126 void __init
fork_init(unsigned long mempages
)
128 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
129 #ifndef ARCH_MIN_TASKALIGN
130 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
132 /* create a slab on which task_structs can be allocated */
134 kmem_cache_create("task_struct", sizeof(struct task_struct
),
135 ARCH_MIN_TASKALIGN
, SLAB_PANIC
, NULL
, NULL
);
139 * The default maximum number of threads is set to a safe
140 * value: the thread structures can take up at most half
143 max_threads
= mempages
/ (8 * THREAD_SIZE
/ PAGE_SIZE
);
146 * we need to allow at least 20 threads to boot a system
151 init_task
.signal
->rlim
[RLIMIT_NPROC
].rlim_cur
= max_threads
/2;
152 init_task
.signal
->rlim
[RLIMIT_NPROC
].rlim_max
= max_threads
/2;
153 init_task
.signal
->rlim
[RLIMIT_SIGPENDING
] =
154 init_task
.signal
->rlim
[RLIMIT_NPROC
];
157 static struct task_struct
*dup_task_struct(struct task_struct
*orig
)
159 struct task_struct
*tsk
;
160 struct thread_info
*ti
;
162 prepare_to_copy(orig
);
164 tsk
= alloc_task_struct();
168 ti
= alloc_thread_info(tsk
);
170 free_task_struct(tsk
);
174 *ti
= *orig
->thread_info
;
176 tsk
->thread_info
= ti
;
179 /* One for us, one for whoever does the "release_task()" (usually parent) */
180 atomic_set(&tsk
->usage
,2);
181 atomic_set(&tsk
->fs_excl
, 0);
186 static inline int dup_mmap(struct mm_struct
*mm
, struct mm_struct
*oldmm
)
188 struct vm_area_struct
*mpnt
, *tmp
, **pprev
;
189 struct rb_node
**rb_link
, *rb_parent
;
191 unsigned long charge
;
192 struct mempolicy
*pol
;
194 down_write(&oldmm
->mmap_sem
);
195 flush_cache_mm(oldmm
);
196 down_write(&mm
->mmap_sem
);
200 mm
->mmap_cache
= NULL
;
201 mm
->free_area_cache
= oldmm
->mmap_base
;
202 mm
->cached_hole_size
= ~0UL;
204 cpus_clear(mm
->cpu_vm_mask
);
206 rb_link
= &mm
->mm_rb
.rb_node
;
210 for (mpnt
= oldmm
->mmap
; mpnt
; mpnt
= mpnt
->vm_next
) {
213 if (mpnt
->vm_flags
& VM_DONTCOPY
) {
214 long pages
= vma_pages(mpnt
);
215 mm
->total_vm
-= pages
;
216 vm_stat_account(mm
, mpnt
->vm_flags
, mpnt
->vm_file
,
221 if (mpnt
->vm_flags
& VM_ACCOUNT
) {
222 unsigned int len
= (mpnt
->vm_end
- mpnt
->vm_start
) >> PAGE_SHIFT
;
223 if (security_vm_enough_memory(len
))
227 tmp
= kmem_cache_alloc(vm_area_cachep
, SLAB_KERNEL
);
231 pol
= mpol_copy(vma_policy(mpnt
));
232 retval
= PTR_ERR(pol
);
234 goto fail_nomem_policy
;
235 vma_set_policy(tmp
, pol
);
236 tmp
->vm_flags
&= ~VM_LOCKED
;
242 struct inode
*inode
= file
->f_dentry
->d_inode
;
244 if (tmp
->vm_flags
& VM_DENYWRITE
)
245 atomic_dec(&inode
->i_writecount
);
247 /* insert tmp into the share list, just after mpnt */
248 spin_lock(&file
->f_mapping
->i_mmap_lock
);
249 tmp
->vm_truncate_count
= mpnt
->vm_truncate_count
;
250 flush_dcache_mmap_lock(file
->f_mapping
);
251 vma_prio_tree_add(tmp
, mpnt
);
252 flush_dcache_mmap_unlock(file
->f_mapping
);
253 spin_unlock(&file
->f_mapping
->i_mmap_lock
);
257 * Link in the new vma and copy the page table entries.
260 pprev
= &tmp
->vm_next
;
262 __vma_link_rb(mm
, tmp
, rb_link
, rb_parent
);
263 rb_link
= &tmp
->vm_rb
.rb_right
;
264 rb_parent
= &tmp
->vm_rb
;
267 retval
= copy_page_range(mm
, oldmm
, tmp
);
269 if (tmp
->vm_ops
&& tmp
->vm_ops
->open
)
270 tmp
->vm_ops
->open(tmp
);
277 up_write(&mm
->mmap_sem
);
279 up_write(&oldmm
->mmap_sem
);
282 kmem_cache_free(vm_area_cachep
, tmp
);
285 vm_unacct_memory(charge
);
289 static inline int mm_alloc_pgd(struct mm_struct
* mm
)
291 mm
->pgd
= pgd_alloc(mm
);
292 if (unlikely(!mm
->pgd
))
297 static inline void mm_free_pgd(struct mm_struct
* mm
)
302 #define dup_mmap(mm, oldmm) (0)
303 #define mm_alloc_pgd(mm) (0)
304 #define mm_free_pgd(mm)
305 #endif /* CONFIG_MMU */
307 __cacheline_aligned_in_smp
DEFINE_SPINLOCK(mmlist_lock
);
309 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
310 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
312 #include <linux/init_task.h>
314 static struct mm_struct
* mm_init(struct mm_struct
* mm
)
316 atomic_set(&mm
->mm_users
, 1);
317 atomic_set(&mm
->mm_count
, 1);
318 init_rwsem(&mm
->mmap_sem
);
319 INIT_LIST_HEAD(&mm
->mmlist
);
320 mm
->core_waiters
= 0;
322 set_mm_counter(mm
, file_rss
, 0);
323 set_mm_counter(mm
, anon_rss
, 0);
324 spin_lock_init(&mm
->page_table_lock
);
325 rwlock_init(&mm
->ioctx_list_lock
);
326 mm
->ioctx_list
= NULL
;
327 mm
->default_kioctx
= (struct kioctx
)INIT_KIOCTX(mm
->default_kioctx
, *mm
);
328 mm
->free_area_cache
= TASK_UNMAPPED_BASE
;
329 mm
->cached_hole_size
= ~0UL;
331 if (likely(!mm_alloc_pgd(mm
))) {
340 * Allocate and initialize an mm_struct.
342 struct mm_struct
* mm_alloc(void)
344 struct mm_struct
* mm
;
348 memset(mm
, 0, sizeof(*mm
));
355 * Called when the last reference to the mm
356 * is dropped: either by a lazy thread or by
357 * mmput. Free the page directory and the mm.
359 void fastcall
__mmdrop(struct mm_struct
*mm
)
361 BUG_ON(mm
== &init_mm
);
368 * Decrement the use count and release all resources for an mm.
370 void mmput(struct mm_struct
*mm
)
372 if (atomic_dec_and_test(&mm
->mm_users
)) {
375 if (!list_empty(&mm
->mmlist
)) {
376 spin_lock(&mmlist_lock
);
377 list_del(&mm
->mmlist
);
378 spin_unlock(&mmlist_lock
);
384 EXPORT_SYMBOL_GPL(mmput
);
387 * get_task_mm - acquire a reference to the task's mm
389 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
390 * this kernel workthread has transiently adopted a user mm with use_mm,
391 * to do its AIO) is not set and if so returns a reference to it, after
392 * bumping up the use count. User must release the mm via mmput()
393 * after use. Typically used by /proc and ptrace.
395 struct mm_struct
*get_task_mm(struct task_struct
*task
)
397 struct mm_struct
*mm
;
402 if (task
->flags
& PF_BORROWED_MM
)
405 atomic_inc(&mm
->mm_users
);
410 EXPORT_SYMBOL_GPL(get_task_mm
);
412 /* Please note the differences between mmput and mm_release.
413 * mmput is called whenever we stop holding onto a mm_struct,
414 * error success whatever.
416 * mm_release is called after a mm_struct has been removed
417 * from the current process.
419 * This difference is important for error handling, when we
420 * only half set up a mm_struct for a new process and need to restore
421 * the old one. Because we mmput the new mm_struct before
422 * restoring the old one. . .
423 * Eric Biederman 10 January 1998
425 void mm_release(struct task_struct
*tsk
, struct mm_struct
*mm
)
427 struct completion
*vfork_done
= tsk
->vfork_done
;
429 /* Get rid of any cached register state */
430 deactivate_mm(tsk
, mm
);
432 /* notify parent sleeping on vfork() */
434 tsk
->vfork_done
= NULL
;
435 complete(vfork_done
);
437 if (tsk
->clear_child_tid
&& atomic_read(&mm
->mm_users
) > 1) {
438 u32 __user
* tidptr
= tsk
->clear_child_tid
;
439 tsk
->clear_child_tid
= NULL
;
442 * We don't check the error code - if userspace has
443 * not set up a proper pointer then tough luck.
446 sys_futex(tidptr
, FUTEX_WAKE
, 1, NULL
, NULL
, 0);
450 static int copy_mm(unsigned long clone_flags
, struct task_struct
* tsk
)
452 struct mm_struct
* mm
, *oldmm
;
455 tsk
->min_flt
= tsk
->maj_flt
= 0;
456 tsk
->nvcsw
= tsk
->nivcsw
= 0;
459 tsk
->active_mm
= NULL
;
462 * Are we cloning a kernel thread?
464 * We need to steal a active VM for that..
470 if (clone_flags
& CLONE_VM
) {
471 atomic_inc(&oldmm
->mm_users
);
481 /* Copy the current MM stuff.. */
482 memcpy(mm
, oldmm
, sizeof(*mm
));
486 if (init_new_context(tsk
,mm
))
489 retval
= dup_mmap(mm
, oldmm
);
493 mm
->hiwater_rss
= get_mm_rss(mm
);
494 mm
->hiwater_vm
= mm
->total_vm
;
508 * If init_new_context() failed, we cannot use mmput() to free the mm
509 * because it calls destroy_context()
516 static inline struct fs_struct
*__copy_fs_struct(struct fs_struct
*old
)
518 struct fs_struct
*fs
= kmem_cache_alloc(fs_cachep
, GFP_KERNEL
);
519 /* We don't need to lock fs - think why ;-) */
521 atomic_set(&fs
->count
, 1);
522 rwlock_init(&fs
->lock
);
523 fs
->umask
= old
->umask
;
524 read_lock(&old
->lock
);
525 fs
->rootmnt
= mntget(old
->rootmnt
);
526 fs
->root
= dget(old
->root
);
527 fs
->pwdmnt
= mntget(old
->pwdmnt
);
528 fs
->pwd
= dget(old
->pwd
);
530 fs
->altrootmnt
= mntget(old
->altrootmnt
);
531 fs
->altroot
= dget(old
->altroot
);
533 fs
->altrootmnt
= NULL
;
536 read_unlock(&old
->lock
);
541 struct fs_struct
*copy_fs_struct(struct fs_struct
*old
)
543 return __copy_fs_struct(old
);
546 EXPORT_SYMBOL_GPL(copy_fs_struct
);
548 static inline int copy_fs(unsigned long clone_flags
, struct task_struct
* tsk
)
550 if (clone_flags
& CLONE_FS
) {
551 atomic_inc(¤t
->fs
->count
);
554 tsk
->fs
= __copy_fs_struct(current
->fs
);
560 static int count_open_files(struct fdtable
*fdt
)
562 int size
= fdt
->max_fdset
;
565 /* Find the last open fd */
566 for (i
= size
/(8*sizeof(long)); i
> 0; ) {
567 if (fdt
->open_fds
->fds_bits
[--i
])
570 i
= (i
+1) * 8 * sizeof(long);
574 static struct files_struct
*alloc_files(void)
576 struct files_struct
*newf
;
579 newf
= kmem_cache_alloc(files_cachep
, SLAB_KERNEL
);
583 atomic_set(&newf
->count
, 1);
585 spin_lock_init(&newf
->file_lock
);
588 fdt
->max_fds
= NR_OPEN_DEFAULT
;
589 fdt
->max_fdset
= __FD_SETSIZE
;
590 fdt
->close_on_exec
= &newf
->close_on_exec_init
;
591 fdt
->open_fds
= &newf
->open_fds_init
;
592 fdt
->fd
= &newf
->fd_array
[0];
593 INIT_RCU_HEAD(&fdt
->rcu
);
594 fdt
->free_files
= NULL
;
596 rcu_assign_pointer(newf
->fdt
, fdt
);
601 static int copy_files(unsigned long clone_flags
, struct task_struct
* tsk
)
603 struct files_struct
*oldf
, *newf
;
604 struct file
**old_fds
, **new_fds
;
605 int open_files
, size
, i
, error
= 0, expand
;
606 struct fdtable
*old_fdt
, *new_fdt
;
609 * A background process may not have any files ...
611 oldf
= current
->files
;
615 if (clone_flags
& CLONE_FILES
) {
616 atomic_inc(&oldf
->count
);
621 * Note: we may be using current for both targets (See exec.c)
622 * This works because we cache current->files (old) as oldf. Don't
627 newf
= alloc_files();
631 spin_lock(&oldf
->file_lock
);
632 old_fdt
= files_fdtable(oldf
);
633 new_fdt
= files_fdtable(newf
);
634 size
= old_fdt
->max_fdset
;
635 open_files
= count_open_files(old_fdt
);
639 * Check whether we need to allocate a larger fd array or fd set.
640 * Note: we're not a clone task, so the open count won't change.
642 if (open_files
> new_fdt
->max_fdset
) {
643 new_fdt
->max_fdset
= 0;
646 if (open_files
> new_fdt
->max_fds
) {
647 new_fdt
->max_fds
= 0;
651 /* if the old fdset gets grown now, we'll only copy up to "size" fds */
653 spin_unlock(&oldf
->file_lock
);
654 spin_lock(&newf
->file_lock
);
655 error
= expand_files(newf
, open_files
-1);
656 spin_unlock(&newf
->file_lock
);
659 new_fdt
= files_fdtable(newf
);
661 * Reacquire the oldf lock and a pointer to its fd table
662 * who knows it may have a new bigger fd table. We need
663 * the latest pointer.
665 spin_lock(&oldf
->file_lock
);
666 old_fdt
= files_fdtable(oldf
);
669 old_fds
= old_fdt
->fd
;
670 new_fds
= new_fdt
->fd
;
672 memcpy(new_fdt
->open_fds
->fds_bits
, old_fdt
->open_fds
->fds_bits
, open_files
/8);
673 memcpy(new_fdt
->close_on_exec
->fds_bits
, old_fdt
->close_on_exec
->fds_bits
, open_files
/8);
675 for (i
= open_files
; i
!= 0; i
--) {
676 struct file
*f
= *old_fds
++;
681 * The fd may be claimed in the fd bitmap but not yet
682 * instantiated in the files array if a sibling thread
683 * is partway through open(). So make sure that this
684 * fd is available to the new process.
686 FD_CLR(open_files
- i
, new_fdt
->open_fds
);
688 rcu_assign_pointer(*new_fds
++, f
);
690 spin_unlock(&oldf
->file_lock
);
692 /* compute the remainder to be cleared */
693 size
= (new_fdt
->max_fds
- open_files
) * sizeof(struct file
*);
695 /* This is long word aligned thus could use a optimized version */
696 memset(new_fds
, 0, size
);
698 if (new_fdt
->max_fdset
> open_files
) {
699 int left
= (new_fdt
->max_fdset
-open_files
)/8;
700 int start
= open_files
/ (8 * sizeof(unsigned long));
702 memset(&new_fdt
->open_fds
->fds_bits
[start
], 0, left
);
703 memset(&new_fdt
->close_on_exec
->fds_bits
[start
], 0, left
);
712 free_fdset (new_fdt
->close_on_exec
, new_fdt
->max_fdset
);
713 free_fdset (new_fdt
->open_fds
, new_fdt
->max_fdset
);
714 free_fd_array(new_fdt
->fd
, new_fdt
->max_fds
);
715 kmem_cache_free(files_cachep
, newf
);
720 * Helper to unshare the files of the current task.
721 * We don't want to expose copy_files internals to
722 * the exec layer of the kernel.
725 int unshare_files(void)
727 struct files_struct
*files
= current
->files
;
733 /* This can race but the race causes us to copy when we don't
734 need to and drop the copy */
735 if(atomic_read(&files
->count
) == 1)
737 atomic_inc(&files
->count
);
740 rc
= copy_files(0, current
);
742 current
->files
= files
;
746 EXPORT_SYMBOL(unshare_files
);
748 static inline int copy_sighand(unsigned long clone_flags
, struct task_struct
* tsk
)
750 struct sighand_struct
*sig
;
752 if (clone_flags
& (CLONE_SIGHAND
| CLONE_THREAD
)) {
753 atomic_inc(¤t
->sighand
->count
);
756 sig
= kmem_cache_alloc(sighand_cachep
, GFP_KERNEL
);
760 spin_lock_init(&sig
->siglock
);
761 atomic_set(&sig
->count
, 1);
762 memcpy(sig
->action
, current
->sighand
->action
, sizeof(sig
->action
));
766 static inline int copy_signal(unsigned long clone_flags
, struct task_struct
* tsk
)
768 struct signal_struct
*sig
;
771 if (clone_flags
& CLONE_THREAD
) {
772 atomic_inc(¤t
->signal
->count
);
773 atomic_inc(¤t
->signal
->live
);
776 sig
= kmem_cache_alloc(signal_cachep
, GFP_KERNEL
);
781 ret
= copy_thread_group_keys(tsk
);
783 kmem_cache_free(signal_cachep
, sig
);
787 atomic_set(&sig
->count
, 1);
788 atomic_set(&sig
->live
, 1);
789 init_waitqueue_head(&sig
->wait_chldexit
);
791 sig
->group_exit_code
= 0;
792 sig
->group_exit_task
= NULL
;
793 sig
->group_stop_count
= 0;
794 sig
->curr_target
= NULL
;
795 init_sigpending(&sig
->shared_pending
);
796 INIT_LIST_HEAD(&sig
->posix_timers
);
798 sig
->it_real_value
= sig
->it_real_incr
= 0;
799 sig
->real_timer
.function
= it_real_fn
;
800 sig
->real_timer
.data
= (unsigned long) tsk
;
801 init_timer(&sig
->real_timer
);
803 sig
->it_virt_expires
= cputime_zero
;
804 sig
->it_virt_incr
= cputime_zero
;
805 sig
->it_prof_expires
= cputime_zero
;
806 sig
->it_prof_incr
= cputime_zero
;
808 sig
->tty
= current
->signal
->tty
;
809 sig
->pgrp
= process_group(current
);
810 sig
->session
= current
->signal
->session
;
811 sig
->leader
= 0; /* session leadership doesn't inherit */
812 sig
->tty_old_pgrp
= 0;
814 sig
->utime
= sig
->stime
= sig
->cutime
= sig
->cstime
= cputime_zero
;
815 sig
->nvcsw
= sig
->nivcsw
= sig
->cnvcsw
= sig
->cnivcsw
= 0;
816 sig
->min_flt
= sig
->maj_flt
= sig
->cmin_flt
= sig
->cmaj_flt
= 0;
818 INIT_LIST_HEAD(&sig
->cpu_timers
[0]);
819 INIT_LIST_HEAD(&sig
->cpu_timers
[1]);
820 INIT_LIST_HEAD(&sig
->cpu_timers
[2]);
822 task_lock(current
->group_leader
);
823 memcpy(sig
->rlim
, current
->signal
->rlim
, sizeof sig
->rlim
);
824 task_unlock(current
->group_leader
);
826 if (sig
->rlim
[RLIMIT_CPU
].rlim_cur
!= RLIM_INFINITY
) {
828 * New sole thread in the process gets an expiry time
829 * of the whole CPU time limit.
831 tsk
->it_prof_expires
=
832 secs_to_cputime(sig
->rlim
[RLIMIT_CPU
].rlim_cur
);
838 static inline void copy_flags(unsigned long clone_flags
, struct task_struct
*p
)
840 unsigned long new_flags
= p
->flags
;
842 new_flags
&= ~(PF_SUPERPRIV
| PF_NOFREEZE
);
843 new_flags
|= PF_FORKNOEXEC
;
844 if (!(clone_flags
& CLONE_PTRACE
))
846 p
->flags
= new_flags
;
849 asmlinkage
long sys_set_tid_address(int __user
*tidptr
)
851 current
->clear_child_tid
= tidptr
;
857 * This creates a new process as a copy of the old one,
858 * but does not actually start it yet.
860 * It copies the registers, and all the appropriate
861 * parts of the process environment (as per the clone
862 * flags). The actual kick-off is left to the caller.
864 static task_t
*copy_process(unsigned long clone_flags
,
865 unsigned long stack_start
,
866 struct pt_regs
*regs
,
867 unsigned long stack_size
,
868 int __user
*parent_tidptr
,
869 int __user
*child_tidptr
,
873 struct task_struct
*p
= NULL
;
875 if ((clone_flags
& (CLONE_NEWNS
|CLONE_FS
)) == (CLONE_NEWNS
|CLONE_FS
))
876 return ERR_PTR(-EINVAL
);
879 * Thread groups must share signals as well, and detached threads
880 * can only be started up within the thread group.
882 if ((clone_flags
& CLONE_THREAD
) && !(clone_flags
& CLONE_SIGHAND
))
883 return ERR_PTR(-EINVAL
);
886 * Shared signal handlers imply shared VM. By way of the above,
887 * thread groups also imply shared VM. Blocking this case allows
888 * for various simplifications in other code.
890 if ((clone_flags
& CLONE_SIGHAND
) && !(clone_flags
& CLONE_VM
))
891 return ERR_PTR(-EINVAL
);
893 retval
= security_task_create(clone_flags
);
898 p
= dup_task_struct(current
);
903 if (atomic_read(&p
->user
->processes
) >=
904 p
->signal
->rlim
[RLIMIT_NPROC
].rlim_cur
) {
905 if (!capable(CAP_SYS_ADMIN
) && !capable(CAP_SYS_RESOURCE
) &&
906 p
->user
!= &root_user
)
910 atomic_inc(&p
->user
->__count
);
911 atomic_inc(&p
->user
->processes
);
912 get_group_info(p
->group_info
);
915 * If multiple threads are within copy_process(), then this check
916 * triggers too late. This doesn't hurt, the check is only there
917 * to stop root fork bombs.
919 if (nr_threads
>= max_threads
)
920 goto bad_fork_cleanup_count
;
922 if (!try_module_get(p
->thread_info
->exec_domain
->module
))
923 goto bad_fork_cleanup_count
;
925 if (p
->binfmt
&& !try_module_get(p
->binfmt
->module
))
926 goto bad_fork_cleanup_put_domain
;
929 copy_flags(clone_flags
, p
);
932 if (clone_flags
& CLONE_PARENT_SETTID
)
933 if (put_user(p
->pid
, parent_tidptr
))
934 goto bad_fork_cleanup
;
936 p
->proc_dentry
= NULL
;
938 INIT_LIST_HEAD(&p
->children
);
939 INIT_LIST_HEAD(&p
->sibling
);
940 p
->vfork_done
= NULL
;
941 spin_lock_init(&p
->alloc_lock
);
942 spin_lock_init(&p
->proc_lock
);
944 clear_tsk_thread_flag(p
, TIF_SIGPENDING
);
945 init_sigpending(&p
->pending
);
947 p
->utime
= cputime_zero
;
948 p
->stime
= cputime_zero
;
950 p
->rchar
= 0; /* I/O counter: bytes read */
951 p
->wchar
= 0; /* I/O counter: bytes written */
952 p
->syscr
= 0; /* I/O counter: read syscalls */
953 p
->syscw
= 0; /* I/O counter: write syscalls */
954 acct_clear_integrals(p
);
956 p
->it_virt_expires
= cputime_zero
;
957 p
->it_prof_expires
= cputime_zero
;
958 p
->it_sched_expires
= 0;
959 INIT_LIST_HEAD(&p
->cpu_timers
[0]);
960 INIT_LIST_HEAD(&p
->cpu_timers
[1]);
961 INIT_LIST_HEAD(&p
->cpu_timers
[2]);
963 p
->lock_depth
= -1; /* -1 = no lock */
964 do_posix_clock_monotonic_gettime(&p
->start_time
);
966 p
->io_context
= NULL
;
968 p
->audit_context
= NULL
;
970 p
->mempolicy
= mpol_copy(p
->mempolicy
);
971 if (IS_ERR(p
->mempolicy
)) {
972 retval
= PTR_ERR(p
->mempolicy
);
974 goto bad_fork_cleanup
;
979 if (clone_flags
& CLONE_THREAD
)
980 p
->tgid
= current
->tgid
;
982 if ((retval
= security_task_alloc(p
)))
983 goto bad_fork_cleanup_policy
;
984 if ((retval
= audit_alloc(p
)))
985 goto bad_fork_cleanup_security
;
986 /* copy all the process information */
987 if ((retval
= copy_semundo(clone_flags
, p
)))
988 goto bad_fork_cleanup_audit
;
989 if ((retval
= copy_files(clone_flags
, p
)))
990 goto bad_fork_cleanup_semundo
;
991 if ((retval
= copy_fs(clone_flags
, p
)))
992 goto bad_fork_cleanup_files
;
993 if ((retval
= copy_sighand(clone_flags
, p
)))
994 goto bad_fork_cleanup_fs
;
995 if ((retval
= copy_signal(clone_flags
, p
)))
996 goto bad_fork_cleanup_sighand
;
997 if ((retval
= copy_mm(clone_flags
, p
)))
998 goto bad_fork_cleanup_signal
;
999 if ((retval
= copy_keys(clone_flags
, p
)))
1000 goto bad_fork_cleanup_mm
;
1001 if ((retval
= copy_namespace(clone_flags
, p
)))
1002 goto bad_fork_cleanup_keys
;
1003 retval
= copy_thread(0, clone_flags
, stack_start
, stack_size
, p
, regs
);
1005 goto bad_fork_cleanup_namespace
;
1007 p
->set_child_tid
= (clone_flags
& CLONE_CHILD_SETTID
) ? child_tidptr
: NULL
;
1009 * Clear TID on mm_release()?
1011 p
->clear_child_tid
= (clone_flags
& CLONE_CHILD_CLEARTID
) ? child_tidptr
: NULL
;
1014 * Syscall tracing should be turned off in the child regardless
1017 clear_tsk_thread_flag(p
, TIF_SYSCALL_TRACE
);
1018 #ifdef TIF_SYSCALL_EMU
1019 clear_tsk_thread_flag(p
, TIF_SYSCALL_EMU
);
1022 /* Our parent execution domain becomes current domain
1023 These must match for thread signalling to apply */
1025 p
->parent_exec_id
= p
->self_exec_id
;
1027 /* ok, now we should be set up.. */
1028 p
->exit_signal
= (clone_flags
& CLONE_THREAD
) ? -1 : (clone_flags
& CSIGNAL
);
1029 p
->pdeath_signal
= 0;
1033 * Ok, make it visible to the rest of the system.
1034 * We dont wake it up yet.
1036 p
->group_leader
= p
;
1037 INIT_LIST_HEAD(&p
->ptrace_children
);
1038 INIT_LIST_HEAD(&p
->ptrace_list
);
1040 /* Perform scheduler related setup. Assign this task to a CPU. */
1041 sched_fork(p
, clone_flags
);
1043 /* Need tasklist lock for parent etc handling! */
1044 write_lock_irq(&tasklist_lock
);
1047 * The task hasn't been attached yet, so its cpus_allowed mask will
1048 * not be changed, nor will its assigned CPU.
1050 * The cpus_allowed mask of the parent may have changed after it was
1051 * copied first time - so re-copy it here, then check the child's CPU
1052 * to ensure it is on a valid CPU (and if not, just force it back to
1053 * parent's CPU). This avoids alot of nasty races.
1055 p
->cpus_allowed
= current
->cpus_allowed
;
1056 if (unlikely(!cpu_isset(task_cpu(p
), p
->cpus_allowed
) ||
1057 !cpu_online(task_cpu(p
))))
1058 set_task_cpu(p
, smp_processor_id());
1061 * Check for pending SIGKILL! The new thread should not be allowed
1062 * to slip out of an OOM kill. (or normal SIGKILL.)
1064 if (sigismember(¤t
->pending
.signal
, SIGKILL
)) {
1065 write_unlock_irq(&tasklist_lock
);
1067 goto bad_fork_cleanup_namespace
;
1070 /* CLONE_PARENT re-uses the old parent */
1071 if (clone_flags
& (CLONE_PARENT
|CLONE_THREAD
))
1072 p
->real_parent
= current
->real_parent
;
1074 p
->real_parent
= current
;
1075 p
->parent
= p
->real_parent
;
1077 if (clone_flags
& CLONE_THREAD
) {
1078 spin_lock(¤t
->sighand
->siglock
);
1080 * Important: if an exit-all has been started then
1081 * do not create this new thread - the whole thread
1082 * group is supposed to exit anyway.
1084 if (current
->signal
->flags
& SIGNAL_GROUP_EXIT
) {
1085 spin_unlock(¤t
->sighand
->siglock
);
1086 write_unlock_irq(&tasklist_lock
);
1088 goto bad_fork_cleanup_namespace
;
1090 p
->group_leader
= current
->group_leader
;
1092 if (current
->signal
->group_stop_count
> 0) {
1094 * There is an all-stop in progress for the group.
1095 * We ourselves will stop as soon as we check signals.
1096 * Make the new thread part of that group stop too.
1098 current
->signal
->group_stop_count
++;
1099 set_tsk_thread_flag(p
, TIF_SIGPENDING
);
1102 if (!cputime_eq(current
->signal
->it_virt_expires
,
1104 !cputime_eq(current
->signal
->it_prof_expires
,
1106 current
->signal
->rlim
[RLIMIT_CPU
].rlim_cur
!= RLIM_INFINITY
||
1107 !list_empty(¤t
->signal
->cpu_timers
[0]) ||
1108 !list_empty(¤t
->signal
->cpu_timers
[1]) ||
1109 !list_empty(¤t
->signal
->cpu_timers
[2])) {
1111 * Have child wake up on its first tick to check
1112 * for process CPU timers.
1114 p
->it_prof_expires
= jiffies_to_cputime(1);
1117 spin_unlock(¤t
->sighand
->siglock
);
1123 p
->ioprio
= current
->ioprio
;
1126 if (unlikely(p
->ptrace
& PT_PTRACED
))
1127 __ptrace_link(p
, current
->parent
);
1131 attach_pid(p
, PIDTYPE_PID
, p
->pid
);
1132 attach_pid(p
, PIDTYPE_TGID
, p
->tgid
);
1133 if (thread_group_leader(p
)) {
1134 attach_pid(p
, PIDTYPE_PGID
, process_group(p
));
1135 attach_pid(p
, PIDTYPE_SID
, p
->signal
->session
);
1137 __get_cpu_var(process_counts
)++;
1140 proc_fork_connector(p
);
1141 if (!current
->signal
->tty
&& p
->signal
->tty
)
1142 p
->signal
->tty
= NULL
;
1146 write_unlock_irq(&tasklist_lock
);
1151 return ERR_PTR(retval
);
1154 bad_fork_cleanup_namespace
:
1156 bad_fork_cleanup_keys
:
1158 bad_fork_cleanup_mm
:
1161 bad_fork_cleanup_signal
:
1163 bad_fork_cleanup_sighand
:
1165 bad_fork_cleanup_fs
:
1166 exit_fs(p
); /* blocking */
1167 bad_fork_cleanup_files
:
1168 exit_files(p
); /* blocking */
1169 bad_fork_cleanup_semundo
:
1171 bad_fork_cleanup_audit
:
1173 bad_fork_cleanup_security
:
1174 security_task_free(p
);
1175 bad_fork_cleanup_policy
:
1177 mpol_free(p
->mempolicy
);
1181 module_put(p
->binfmt
->module
);
1182 bad_fork_cleanup_put_domain
:
1183 module_put(p
->thread_info
->exec_domain
->module
);
1184 bad_fork_cleanup_count
:
1185 put_group_info(p
->group_info
);
1186 atomic_dec(&p
->user
->processes
);
1193 struct pt_regs
* __devinit
__attribute__((weak
)) idle_regs(struct pt_regs
*regs
)
1195 memset(regs
, 0, sizeof(struct pt_regs
));
1199 task_t
* __devinit
fork_idle(int cpu
)
1202 struct pt_regs regs
;
1204 task
= copy_process(CLONE_VM
, 0, idle_regs(®s
), 0, NULL
, NULL
, 0);
1206 return ERR_PTR(-ENOMEM
);
1207 init_idle(task
, cpu
);
1208 unhash_process(task
);
1212 static inline int fork_traceflag (unsigned clone_flags
)
1214 if (clone_flags
& CLONE_UNTRACED
)
1216 else if (clone_flags
& CLONE_VFORK
) {
1217 if (current
->ptrace
& PT_TRACE_VFORK
)
1218 return PTRACE_EVENT_VFORK
;
1219 } else if ((clone_flags
& CSIGNAL
) != SIGCHLD
) {
1220 if (current
->ptrace
& PT_TRACE_CLONE
)
1221 return PTRACE_EVENT_CLONE
;
1222 } else if (current
->ptrace
& PT_TRACE_FORK
)
1223 return PTRACE_EVENT_FORK
;
1229 * Ok, this is the main fork-routine.
1231 * It copies the process, and if successful kick-starts
1232 * it and waits for it to finish using the VM if required.
1234 long do_fork(unsigned long clone_flags
,
1235 unsigned long stack_start
,
1236 struct pt_regs
*regs
,
1237 unsigned long stack_size
,
1238 int __user
*parent_tidptr
,
1239 int __user
*child_tidptr
)
1241 struct task_struct
*p
;
1243 long pid
= alloc_pidmap();
1247 if (unlikely(current
->ptrace
)) {
1248 trace
= fork_traceflag (clone_flags
);
1250 clone_flags
|= CLONE_PTRACE
;
1253 p
= copy_process(clone_flags
, stack_start
, regs
, stack_size
, parent_tidptr
, child_tidptr
, pid
);
1255 * Do this prior waking up the new thread - the thread pointer
1256 * might get invalid after that point, if the thread exits quickly.
1259 struct completion vfork
;
1261 if (clone_flags
& CLONE_VFORK
) {
1262 p
->vfork_done
= &vfork
;
1263 init_completion(&vfork
);
1266 if ((p
->ptrace
& PT_PTRACED
) || (clone_flags
& CLONE_STOPPED
)) {
1268 * We'll start up with an immediate SIGSTOP.
1270 sigaddset(&p
->pending
.signal
, SIGSTOP
);
1271 set_tsk_thread_flag(p
, TIF_SIGPENDING
);
1274 if (!(clone_flags
& CLONE_STOPPED
))
1275 wake_up_new_task(p
, clone_flags
);
1277 p
->state
= TASK_STOPPED
;
1279 if (unlikely (trace
)) {
1280 current
->ptrace_message
= pid
;
1281 ptrace_notify ((trace
<< 8) | SIGTRAP
);
1284 if (clone_flags
& CLONE_VFORK
) {
1285 wait_for_completion(&vfork
);
1286 if (unlikely (current
->ptrace
& PT_TRACE_VFORK_DONE
))
1287 ptrace_notify ((PTRACE_EVENT_VFORK_DONE
<< 8) | SIGTRAP
);
1296 void __init
proc_caches_init(void)
1298 sighand_cachep
= kmem_cache_create("sighand_cache",
1299 sizeof(struct sighand_struct
), 0,
1300 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
, NULL
);
1301 signal_cachep
= kmem_cache_create("signal_cache",
1302 sizeof(struct signal_struct
), 0,
1303 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
, NULL
);
1304 files_cachep
= kmem_cache_create("files_cache",
1305 sizeof(struct files_struct
), 0,
1306 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
, NULL
);
1307 fs_cachep
= kmem_cache_create("fs_cache",
1308 sizeof(struct fs_struct
), 0,
1309 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
, NULL
);
1310 vm_area_cachep
= kmem_cache_create("vm_area_struct",
1311 sizeof(struct vm_area_struct
), 0,
1312 SLAB_PANIC
, NULL
, NULL
);
1313 mm_cachep
= kmem_cache_create("mm_struct",
1314 sizeof(struct mm_struct
), 0,
1315 SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
, NULL
);