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/capability.h>
32 #include <linux/cpu.h>
33 #include <linux/cpuset.h>
34 #include <linux/security.h>
35 #include <linux/swap.h>
36 #include <linux/syscalls.h>
37 #include <linux/jiffies.h>
38 #include <linux/futex.h>
39 #include <linux/rcupdate.h>
40 #include <linux/ptrace.h>
41 #include <linux/mount.h>
42 #include <linux/audit.h>
43 #include <linux/profile.h>
44 #include <linux/rmap.h>
45 #include <linux/acct.h>
46 #include <linux/cn_proc.h>
48 #include <asm/pgtable.h>
49 #include <asm/pgalloc.h>
50 #include <asm/uaccess.h>
51 #include <asm/mmu_context.h>
52 #include <asm/cacheflush.h>
53 #include <asm/tlbflush.h>
56 * Protected counters by write_lock_irq(&tasklist_lock)
58 unsigned long total_forks; /* Handle normal Linux uptimes. */
59 int nr_threads; /* The idle threads do not count.. */
61 int max_threads; /* tunable limit on nr_threads */
63 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
65 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
67 EXPORT_SYMBOL(tasklist_lock);
69 int nr_processes(void)
74 for_each_online_cpu(cpu)
75 total += per_cpu(process_counts, cpu);
80 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
81 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
82 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
83 static kmem_cache_t *task_struct_cachep;
86 /* SLAB cache for signal_struct structures (tsk->signal) */
87 kmem_cache_t *signal_cachep;
89 /* SLAB cache for sighand_struct structures (tsk->sighand) */
90 kmem_cache_t *sighand_cachep;
92 /* SLAB cache for files_struct structures (tsk->files) */
93 kmem_cache_t *files_cachep;
95 /* SLAB cache for fs_struct structures (tsk->fs) */
96 kmem_cache_t *fs_cachep;
98 /* SLAB cache for vm_area_struct structures */
99 kmem_cache_t *vm_area_cachep;
101 /* SLAB cache for mm_struct structures (tsk->mm) */
102 static kmem_cache_t *mm_cachep;
104 void free_task(struct task_struct *tsk)
106 free_thread_info(tsk->thread_info);
107 free_task_struct(tsk);
109 EXPORT_SYMBOL(free_task);
111 void __put_task_struct(struct task_struct *tsk)
113 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
114 WARN_ON(atomic_read(&tsk->usage));
115 WARN_ON(tsk == current);
117 if (unlikely(tsk->audit_context))
119 security_task_free(tsk);
121 put_group_info(tsk->group_info);
123 if (!profile_handoff_task(tsk))
127 void __init fork_init(unsigned long mempages)
129 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
130 #ifndef ARCH_MIN_TASKALIGN
131 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
133 /* create a slab on which task_structs can be allocated */
135 kmem_cache_create("task_struct", sizeof(struct task_struct),
136 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
140 * The default maximum number of threads is set to a safe
141 * value: the thread structures can take up at most half
144 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
147 * we need to allow at least 20 threads to boot a system
152 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
153 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
154 init_task.signal->rlim[RLIMIT_SIGPENDING] =
155 init_task.signal->rlim[RLIMIT_NPROC];
158 static struct task_struct *dup_task_struct(struct task_struct *orig)
160 struct task_struct *tsk;
161 struct thread_info *ti;
163 prepare_to_copy(orig);
165 tsk = alloc_task_struct();
169 ti = alloc_thread_info(tsk);
171 free_task_struct(tsk);
176 tsk->thread_info = ti;
177 setup_thread_stack(tsk, orig);
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, mpnt);
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->free_area_cache = TASK_UNMAPPED_BASE;
328 mm->cached_hole_size = ~0UL;
330 if (likely(!mm_alloc_pgd(mm))) {
339 * Allocate and initialize an mm_struct.
341 struct mm_struct * mm_alloc(void)
343 struct mm_struct * mm;
347 memset(mm, 0, sizeof(*mm));
354 * Called when the last reference to the mm
355 * is dropped: either by a lazy thread or by
356 * mmput. Free the page directory and the mm.
358 void fastcall __mmdrop(struct mm_struct *mm)
360 BUG_ON(mm == &init_mm);
367 * Decrement the use count and release all resources for an mm.
369 void mmput(struct mm_struct *mm)
371 if (atomic_dec_and_test(&mm->mm_users)) {
374 if (!list_empty(&mm->mmlist)) {
375 spin_lock(&mmlist_lock);
376 list_del(&mm->mmlist);
377 spin_unlock(&mmlist_lock);
383 EXPORT_SYMBOL_GPL(mmput);
386 * get_task_mm - acquire a reference to the task's mm
388 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
389 * this kernel workthread has transiently adopted a user mm with use_mm,
390 * to do its AIO) is not set and if so returns a reference to it, after
391 * bumping up the use count. User must release the mm via mmput()
392 * after use. Typically used by /proc and ptrace.
394 struct mm_struct *get_task_mm(struct task_struct *task)
396 struct mm_struct *mm;
401 if (task->flags & PF_BORROWED_MM)
404 atomic_inc(&mm->mm_users);
409 EXPORT_SYMBOL_GPL(get_task_mm);
411 /* Please note the differences between mmput and mm_release.
412 * mmput is called whenever we stop holding onto a mm_struct,
413 * error success whatever.
415 * mm_release is called after a mm_struct has been removed
416 * from the current process.
418 * This difference is important for error handling, when we
419 * only half set up a mm_struct for a new process and need to restore
420 * the old one. Because we mmput the new mm_struct before
421 * restoring the old one. . .
422 * Eric Biederman 10 January 1998
424 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
426 struct completion *vfork_done = tsk->vfork_done;
428 /* Get rid of any cached register state */
429 deactivate_mm(tsk, mm);
431 /* notify parent sleeping on vfork() */
433 tsk->vfork_done = NULL;
434 complete(vfork_done);
436 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
437 u32 __user * tidptr = tsk->clear_child_tid;
438 tsk->clear_child_tid = NULL;
441 * We don't check the error code - if userspace has
442 * not set up a proper pointer then tough luck.
445 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
450 * Allocate a new mm structure and copy contents from the
451 * mm structure of the passed in task structure.
453 static struct mm_struct *dup_mm(struct task_struct *tsk)
455 struct mm_struct *mm, *oldmm = current->mm;
465 memcpy(mm, oldmm, sizeof(*mm));
470 if (init_new_context(tsk, mm))
473 err = dup_mmap(mm, oldmm);
477 mm->hiwater_rss = get_mm_rss(mm);
478 mm->hiwater_vm = mm->total_vm;
490 * If init_new_context() failed, we cannot use mmput() to free the mm
491 * because it calls destroy_context()
498 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
500 struct mm_struct * mm, *oldmm;
503 tsk->min_flt = tsk->maj_flt = 0;
504 tsk->nvcsw = tsk->nivcsw = 0;
507 tsk->active_mm = NULL;
510 * Are we cloning a kernel thread?
512 * We need to steal a active VM for that..
518 if (clone_flags & CLONE_VM) {
519 atomic_inc(&oldmm->mm_users);
538 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
540 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
541 /* We don't need to lock fs - think why ;-) */
543 atomic_set(&fs->count, 1);
544 rwlock_init(&fs->lock);
545 fs->umask = old->umask;
546 read_lock(&old->lock);
547 fs->rootmnt = mntget(old->rootmnt);
548 fs->root = dget(old->root);
549 fs->pwdmnt = mntget(old->pwdmnt);
550 fs->pwd = dget(old->pwd);
552 fs->altrootmnt = mntget(old->altrootmnt);
553 fs->altroot = dget(old->altroot);
555 fs->altrootmnt = NULL;
558 read_unlock(&old->lock);
563 struct fs_struct *copy_fs_struct(struct fs_struct *old)
565 return __copy_fs_struct(old);
568 EXPORT_SYMBOL_GPL(copy_fs_struct);
570 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
572 if (clone_flags & CLONE_FS) {
573 atomic_inc(¤t->fs->count);
576 tsk->fs = __copy_fs_struct(current->fs);
582 static int count_open_files(struct fdtable *fdt)
584 int size = fdt->max_fdset;
587 /* Find the last open fd */
588 for (i = size/(8*sizeof(long)); i > 0; ) {
589 if (fdt->open_fds->fds_bits[--i])
592 i = (i+1) * 8 * sizeof(long);
596 static struct files_struct *alloc_files(void)
598 struct files_struct *newf;
601 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
605 atomic_set(&newf->count, 1);
607 spin_lock_init(&newf->file_lock);
610 fdt->max_fds = NR_OPEN_DEFAULT;
611 fdt->max_fdset = __FD_SETSIZE;
612 fdt->close_on_exec = &newf->close_on_exec_init;
613 fdt->open_fds = &newf->open_fds_init;
614 fdt->fd = &newf->fd_array[0];
615 INIT_RCU_HEAD(&fdt->rcu);
616 fdt->free_files = NULL;
618 rcu_assign_pointer(newf->fdt, fdt);
624 * Allocate a new files structure and copy contents from the
625 * passed in files structure.
627 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
629 struct files_struct *newf;
630 struct file **old_fds, **new_fds;
631 int open_files, size, i, expand;
632 struct fdtable *old_fdt, *new_fdt;
634 newf = alloc_files();
638 spin_lock(&oldf->file_lock);
639 old_fdt = files_fdtable(oldf);
640 new_fdt = files_fdtable(newf);
641 size = old_fdt->max_fdset;
642 open_files = count_open_files(old_fdt);
646 * Check whether we need to allocate a larger fd array or fd set.
647 * Note: we're not a clone task, so the open count won't change.
649 if (open_files > new_fdt->max_fdset) {
650 new_fdt->max_fdset = 0;
653 if (open_files > new_fdt->max_fds) {
654 new_fdt->max_fds = 0;
658 /* if the old fdset gets grown now, we'll only copy up to "size" fds */
660 spin_unlock(&oldf->file_lock);
661 spin_lock(&newf->file_lock);
662 *errorp = expand_files(newf, open_files-1);
663 spin_unlock(&newf->file_lock);
666 new_fdt = files_fdtable(newf);
668 * Reacquire the oldf lock and a pointer to its fd table
669 * who knows it may have a new bigger fd table. We need
670 * the latest pointer.
672 spin_lock(&oldf->file_lock);
673 old_fdt = files_fdtable(oldf);
676 old_fds = old_fdt->fd;
677 new_fds = new_fdt->fd;
679 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
680 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
682 for (i = open_files; i != 0; i--) {
683 struct file *f = *old_fds++;
688 * The fd may be claimed in the fd bitmap but not yet
689 * instantiated in the files array if a sibling thread
690 * is partway through open(). So make sure that this
691 * fd is available to the new process.
693 FD_CLR(open_files - i, new_fdt->open_fds);
695 rcu_assign_pointer(*new_fds++, f);
697 spin_unlock(&oldf->file_lock);
699 /* compute the remainder to be cleared */
700 size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
702 /* This is long word aligned thus could use a optimized version */
703 memset(new_fds, 0, size);
705 if (new_fdt->max_fdset > open_files) {
706 int left = (new_fdt->max_fdset-open_files)/8;
707 int start = open_files / (8 * sizeof(unsigned long));
709 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
710 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
717 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
718 free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
719 free_fd_array(new_fdt->fd, new_fdt->max_fds);
720 kmem_cache_free(files_cachep, newf);
724 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
726 struct files_struct *oldf, *newf;
730 * A background process may not have any files ...
732 oldf = current->files;
736 if (clone_flags & CLONE_FILES) {
737 atomic_inc(&oldf->count);
742 * Note: we may be using current for both targets (See exec.c)
743 * This works because we cache current->files (old) as oldf. Don't
748 newf = dup_fd(oldf, &error);
759 * Helper to unshare the files of the current task.
760 * We don't want to expose copy_files internals to
761 * the exec layer of the kernel.
764 int unshare_files(void)
766 struct files_struct *files = current->files;
772 /* This can race but the race causes us to copy when we don't
773 need to and drop the copy */
774 if(atomic_read(&files->count) == 1)
776 atomic_inc(&files->count);
779 rc = copy_files(0, current);
781 current->files = files;
785 EXPORT_SYMBOL(unshare_files);
787 void sighand_free_cb(struct rcu_head *rhp)
789 struct sighand_struct *sp;
791 sp = container_of(rhp, struct sighand_struct, rcu);
792 kmem_cache_free(sighand_cachep, sp);
795 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
797 struct sighand_struct *sig;
799 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
800 atomic_inc(¤t->sighand->count);
803 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
804 rcu_assign_pointer(tsk->sighand, sig);
807 spin_lock_init(&sig->siglock);
808 atomic_set(&sig->count, 1);
809 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
813 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
815 struct signal_struct *sig;
818 if (clone_flags & CLONE_THREAD) {
819 atomic_inc(¤t->signal->count);
820 atomic_inc(¤t->signal->live);
823 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
828 ret = copy_thread_group_keys(tsk);
830 kmem_cache_free(signal_cachep, sig);
834 atomic_set(&sig->count, 1);
835 atomic_set(&sig->live, 1);
836 init_waitqueue_head(&sig->wait_chldexit);
838 sig->group_exit_code = 0;
839 sig->group_exit_task = NULL;
840 sig->group_stop_count = 0;
841 sig->curr_target = NULL;
842 init_sigpending(&sig->shared_pending);
843 INIT_LIST_HEAD(&sig->posix_timers);
845 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
846 sig->it_real_incr.tv64 = 0;
847 sig->real_timer.function = it_real_fn;
848 sig->real_timer.data = tsk;
850 sig->it_virt_expires = cputime_zero;
851 sig->it_virt_incr = cputime_zero;
852 sig->it_prof_expires = cputime_zero;
853 sig->it_prof_incr = cputime_zero;
855 sig->leader = 0; /* session leadership doesn't inherit */
856 sig->tty_old_pgrp = 0;
858 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
859 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
860 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
862 INIT_LIST_HEAD(&sig->cpu_timers[0]);
863 INIT_LIST_HEAD(&sig->cpu_timers[1]);
864 INIT_LIST_HEAD(&sig->cpu_timers[2]);
866 task_lock(current->group_leader);
867 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
868 task_unlock(current->group_leader);
870 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
872 * New sole thread in the process gets an expiry time
873 * of the whole CPU time limit.
875 tsk->it_prof_expires =
876 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
882 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
884 unsigned long new_flags = p->flags;
886 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
887 new_flags |= PF_FORKNOEXEC;
888 if (!(clone_flags & CLONE_PTRACE))
890 p->flags = new_flags;
893 asmlinkage long sys_set_tid_address(int __user *tidptr)
895 current->clear_child_tid = tidptr;
901 * This creates a new process as a copy of the old one,
902 * but does not actually start it yet.
904 * It copies the registers, and all the appropriate
905 * parts of the process environment (as per the clone
906 * flags). The actual kick-off is left to the caller.
908 static task_t *copy_process(unsigned long clone_flags,
909 unsigned long stack_start,
910 struct pt_regs *regs,
911 unsigned long stack_size,
912 int __user *parent_tidptr,
913 int __user *child_tidptr,
917 struct task_struct *p = NULL;
919 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
920 return ERR_PTR(-EINVAL);
923 * Thread groups must share signals as well, and detached threads
924 * can only be started up within the thread group.
926 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
927 return ERR_PTR(-EINVAL);
930 * Shared signal handlers imply shared VM. By way of the above,
931 * thread groups also imply shared VM. Blocking this case allows
932 * for various simplifications in other code.
934 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
935 return ERR_PTR(-EINVAL);
937 retval = security_task_create(clone_flags);
942 p = dup_task_struct(current);
947 if (atomic_read(&p->user->processes) >=
948 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
949 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
950 p->user != &root_user)
954 atomic_inc(&p->user->__count);
955 atomic_inc(&p->user->processes);
956 get_group_info(p->group_info);
959 * If multiple threads are within copy_process(), then this check
960 * triggers too late. This doesn't hurt, the check is only there
961 * to stop root fork bombs.
963 if (nr_threads >= max_threads)
964 goto bad_fork_cleanup_count;
966 if (!try_module_get(task_thread_info(p)->exec_domain->module))
967 goto bad_fork_cleanup_count;
969 if (p->binfmt && !try_module_get(p->binfmt->module))
970 goto bad_fork_cleanup_put_domain;
973 copy_flags(clone_flags, p);
976 if (clone_flags & CLONE_PARENT_SETTID)
977 if (put_user(p->pid, parent_tidptr))
978 goto bad_fork_cleanup;
980 p->proc_dentry = NULL;
982 INIT_LIST_HEAD(&p->children);
983 INIT_LIST_HEAD(&p->sibling);
984 p->vfork_done = NULL;
985 spin_lock_init(&p->alloc_lock);
986 spin_lock_init(&p->proc_lock);
988 clear_tsk_thread_flag(p, TIF_SIGPENDING);
989 init_sigpending(&p->pending);
991 p->utime = cputime_zero;
992 p->stime = cputime_zero;
994 p->rchar = 0; /* I/O counter: bytes read */
995 p->wchar = 0; /* I/O counter: bytes written */
996 p->syscr = 0; /* I/O counter: read syscalls */
997 p->syscw = 0; /* I/O counter: write syscalls */
998 acct_clear_integrals(p);
1000 p->it_virt_expires = cputime_zero;
1001 p->it_prof_expires = cputime_zero;
1002 p->it_sched_expires = 0;
1003 INIT_LIST_HEAD(&p->cpu_timers[0]);
1004 INIT_LIST_HEAD(&p->cpu_timers[1]);
1005 INIT_LIST_HEAD(&p->cpu_timers[2]);
1007 p->lock_depth = -1; /* -1 = no lock */
1008 do_posix_clock_monotonic_gettime(&p->start_time);
1010 p->io_context = NULL;
1012 p->audit_context = NULL;
1015 p->mempolicy = mpol_copy(p->mempolicy);
1016 if (IS_ERR(p->mempolicy)) {
1017 retval = PTR_ERR(p->mempolicy);
1018 p->mempolicy = NULL;
1019 goto bad_fork_cleanup_cpuset;
1023 #ifdef CONFIG_DEBUG_MUTEXES
1024 p->blocked_on = NULL; /* not blocked yet */
1028 if (clone_flags & CLONE_THREAD)
1029 p->tgid = current->tgid;
1031 if ((retval = security_task_alloc(p)))
1032 goto bad_fork_cleanup_policy;
1033 if ((retval = audit_alloc(p)))
1034 goto bad_fork_cleanup_security;
1035 /* copy all the process information */
1036 if ((retval = copy_semundo(clone_flags, p)))
1037 goto bad_fork_cleanup_audit;
1038 if ((retval = copy_files(clone_flags, p)))
1039 goto bad_fork_cleanup_semundo;
1040 if ((retval = copy_fs(clone_flags, p)))
1041 goto bad_fork_cleanup_files;
1042 if ((retval = copy_sighand(clone_flags, p)))
1043 goto bad_fork_cleanup_fs;
1044 if ((retval = copy_signal(clone_flags, p)))
1045 goto bad_fork_cleanup_sighand;
1046 if ((retval = copy_mm(clone_flags, p)))
1047 goto bad_fork_cleanup_signal;
1048 if ((retval = copy_keys(clone_flags, p)))
1049 goto bad_fork_cleanup_mm;
1050 if ((retval = copy_namespace(clone_flags, p)))
1051 goto bad_fork_cleanup_keys;
1052 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1054 goto bad_fork_cleanup_namespace;
1056 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1058 * Clear TID on mm_release()?
1060 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1063 * Syscall tracing should be turned off in the child regardless
1066 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1067 #ifdef TIF_SYSCALL_EMU
1068 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1071 /* Our parent execution domain becomes current domain
1072 These must match for thread signalling to apply */
1074 p->parent_exec_id = p->self_exec_id;
1076 /* ok, now we should be set up.. */
1077 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1078 p->pdeath_signal = 0;
1082 * Ok, make it visible to the rest of the system.
1083 * We dont wake it up yet.
1085 p->group_leader = p;
1086 INIT_LIST_HEAD(&p->ptrace_children);
1087 INIT_LIST_HEAD(&p->ptrace_list);
1089 /* Perform scheduler related setup. Assign this task to a CPU. */
1090 sched_fork(p, clone_flags);
1092 /* Need tasklist lock for parent etc handling! */
1093 write_lock_irq(&tasklist_lock);
1096 * The task hasn't been attached yet, so its cpus_allowed mask will
1097 * not be changed, nor will its assigned CPU.
1099 * The cpus_allowed mask of the parent may have changed after it was
1100 * copied first time - so re-copy it here, then check the child's CPU
1101 * to ensure it is on a valid CPU (and if not, just force it back to
1102 * parent's CPU). This avoids alot of nasty races.
1104 p->cpus_allowed = current->cpus_allowed;
1105 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1106 !cpu_online(task_cpu(p))))
1107 set_task_cpu(p, smp_processor_id());
1110 * Check for pending SIGKILL! The new thread should not be allowed
1111 * to slip out of an OOM kill. (or normal SIGKILL.)
1113 if (sigismember(¤t->pending.signal, SIGKILL)) {
1114 write_unlock_irq(&tasklist_lock);
1116 goto bad_fork_cleanup_namespace;
1119 /* CLONE_PARENT re-uses the old parent */
1120 if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1121 p->real_parent = current->real_parent;
1123 p->real_parent = current;
1124 p->parent = p->real_parent;
1126 spin_lock(¤t->sighand->siglock);
1127 if (clone_flags & CLONE_THREAD) {
1129 * Important: if an exit-all has been started then
1130 * do not create this new thread - the whole thread
1131 * group is supposed to exit anyway.
1133 if (current->signal->flags & SIGNAL_GROUP_EXIT) {
1134 spin_unlock(¤t->sighand->siglock);
1135 write_unlock_irq(&tasklist_lock);
1137 goto bad_fork_cleanup_namespace;
1139 p->group_leader = current->group_leader;
1141 if (current->signal->group_stop_count > 0) {
1143 * There is an all-stop in progress for the group.
1144 * We ourselves will stop as soon as we check signals.
1145 * Make the new thread part of that group stop too.
1147 current->signal->group_stop_count++;
1148 set_tsk_thread_flag(p, TIF_SIGPENDING);
1151 if (!cputime_eq(current->signal->it_virt_expires,
1153 !cputime_eq(current->signal->it_prof_expires,
1155 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1156 !list_empty(¤t->signal->cpu_timers[0]) ||
1157 !list_empty(¤t->signal->cpu_timers[1]) ||
1158 !list_empty(¤t->signal->cpu_timers[2])) {
1160 * Have child wake up on its first tick to check
1161 * for process CPU timers.
1163 p->it_prof_expires = jiffies_to_cputime(1);
1170 p->ioprio = current->ioprio;
1173 if (unlikely(p->ptrace & PT_PTRACED))
1174 __ptrace_link(p, current->parent);
1176 if (thread_group_leader(p)) {
1177 p->signal->tty = current->signal->tty;
1178 p->signal->pgrp = process_group(current);
1179 p->signal->session = current->signal->session;
1180 attach_pid(p, PIDTYPE_PGID, process_group(p));
1181 attach_pid(p, PIDTYPE_SID, p->signal->session);
1183 __get_cpu_var(process_counts)++;
1185 attach_pid(p, PIDTYPE_TGID, p->tgid);
1186 attach_pid(p, PIDTYPE_PID, p->pid);
1190 spin_unlock(¤t->sighand->siglock);
1191 write_unlock_irq(&tasklist_lock);
1192 proc_fork_connector(p);
1195 bad_fork_cleanup_namespace:
1197 bad_fork_cleanup_keys:
1199 bad_fork_cleanup_mm:
1202 bad_fork_cleanup_signal:
1204 bad_fork_cleanup_sighand:
1206 bad_fork_cleanup_fs:
1207 exit_fs(p); /* blocking */
1208 bad_fork_cleanup_files:
1209 exit_files(p); /* blocking */
1210 bad_fork_cleanup_semundo:
1212 bad_fork_cleanup_audit:
1214 bad_fork_cleanup_security:
1215 security_task_free(p);
1216 bad_fork_cleanup_policy:
1218 mpol_free(p->mempolicy);
1219 bad_fork_cleanup_cpuset:
1224 module_put(p->binfmt->module);
1225 bad_fork_cleanup_put_domain:
1226 module_put(task_thread_info(p)->exec_domain->module);
1227 bad_fork_cleanup_count:
1228 put_group_info(p->group_info);
1229 atomic_dec(&p->user->processes);
1234 return ERR_PTR(retval);
1237 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1239 memset(regs, 0, sizeof(struct pt_regs));
1243 task_t * __devinit fork_idle(int cpu)
1246 struct pt_regs regs;
1248 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0);
1250 return ERR_PTR(-ENOMEM);
1251 init_idle(task, cpu);
1252 unhash_process(task);
1256 static inline int fork_traceflag (unsigned clone_flags)
1258 if (clone_flags & CLONE_UNTRACED)
1260 else if (clone_flags & CLONE_VFORK) {
1261 if (current->ptrace & PT_TRACE_VFORK)
1262 return PTRACE_EVENT_VFORK;
1263 } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1264 if (current->ptrace & PT_TRACE_CLONE)
1265 return PTRACE_EVENT_CLONE;
1266 } else if (current->ptrace & PT_TRACE_FORK)
1267 return PTRACE_EVENT_FORK;
1273 * Ok, this is the main fork-routine.
1275 * It copies the process, and if successful kick-starts
1276 * it and waits for it to finish using the VM if required.
1278 long do_fork(unsigned long clone_flags,
1279 unsigned long stack_start,
1280 struct pt_regs *regs,
1281 unsigned long stack_size,
1282 int __user *parent_tidptr,
1283 int __user *child_tidptr)
1285 struct task_struct *p;
1287 long pid = alloc_pidmap();
1291 if (unlikely(current->ptrace)) {
1292 trace = fork_traceflag (clone_flags);
1294 clone_flags |= CLONE_PTRACE;
1297 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
1299 * Do this prior waking up the new thread - the thread pointer
1300 * might get invalid after that point, if the thread exits quickly.
1303 struct completion vfork;
1305 if (clone_flags & CLONE_VFORK) {
1306 p->vfork_done = &vfork;
1307 init_completion(&vfork);
1310 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1312 * We'll start up with an immediate SIGSTOP.
1314 sigaddset(&p->pending.signal, SIGSTOP);
1315 set_tsk_thread_flag(p, TIF_SIGPENDING);
1318 if (!(clone_flags & CLONE_STOPPED))
1319 wake_up_new_task(p, clone_flags);
1321 p->state = TASK_STOPPED;
1323 if (unlikely (trace)) {
1324 current->ptrace_message = pid;
1325 ptrace_notify ((trace << 8) | SIGTRAP);
1328 if (clone_flags & CLONE_VFORK) {
1329 wait_for_completion(&vfork);
1330 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
1331 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1340 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1341 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1344 void __init proc_caches_init(void)
1346 sighand_cachep = kmem_cache_create("sighand_cache",
1347 sizeof(struct sighand_struct), 0,
1348 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1349 signal_cachep = kmem_cache_create("signal_cache",
1350 sizeof(struct signal_struct), 0,
1351 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1352 files_cachep = kmem_cache_create("files_cache",
1353 sizeof(struct files_struct), 0,
1354 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1355 fs_cachep = kmem_cache_create("fs_cache",
1356 sizeof(struct fs_struct), 0,
1357 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1358 vm_area_cachep = kmem_cache_create("vm_area_struct",
1359 sizeof(struct vm_area_struct), 0,
1360 SLAB_PANIC, NULL, NULL);
1361 mm_cachep = kmem_cache_create("mm_struct",
1362 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1363 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1368 * Check constraints on flags passed to the unshare system call and
1369 * force unsharing of additional process context as appropriate.
1371 static inline void check_unshare_flags(unsigned long *flags_ptr)
1374 * If unsharing a thread from a thread group, must also
1377 if (*flags_ptr & CLONE_THREAD)
1378 *flags_ptr |= CLONE_VM;
1381 * If unsharing vm, must also unshare signal handlers.
1383 if (*flags_ptr & CLONE_VM)
1384 *flags_ptr |= CLONE_SIGHAND;
1387 * If unsharing signal handlers and the task was created
1388 * using CLONE_THREAD, then must unshare the thread
1390 if ((*flags_ptr & CLONE_SIGHAND) &&
1391 (atomic_read(¤t->signal->count) > 1))
1392 *flags_ptr |= CLONE_THREAD;
1395 * If unsharing namespace, must also unshare filesystem information.
1397 if (*flags_ptr & CLONE_NEWNS)
1398 *flags_ptr |= CLONE_FS;
1402 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1404 static int unshare_thread(unsigned long unshare_flags)
1406 if (unshare_flags & CLONE_THREAD)
1413 * Unshare the filesystem structure if it is being shared
1415 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1417 struct fs_struct *fs = current->fs;
1419 if ((unshare_flags & CLONE_FS) &&
1420 (fs && atomic_read(&fs->count) > 1)) {
1421 *new_fsp = __copy_fs_struct(current->fs);
1430 * Unshare the namespace structure if it is being shared
1432 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1434 struct namespace *ns = current->namespace;
1436 if ((unshare_flags & CLONE_NEWNS) &&
1437 (ns && atomic_read(&ns->count) > 1)) {
1438 if (!capable(CAP_SYS_ADMIN))
1441 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1450 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1453 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1455 struct sighand_struct *sigh = current->sighand;
1457 if ((unshare_flags & CLONE_SIGHAND) &&
1458 (sigh && atomic_read(&sigh->count) > 1))
1465 * Unshare vm if it is being shared
1467 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1469 struct mm_struct *mm = current->mm;
1471 if ((unshare_flags & CLONE_VM) &&
1472 (mm && atomic_read(&mm->mm_users) > 1)) {
1473 *new_mmp = dup_mm(current);
1482 * Unshare file descriptor table if it is being shared
1484 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1486 struct files_struct *fd = current->files;
1489 if ((unshare_flags & CLONE_FILES) &&
1490 (fd && atomic_read(&fd->count) > 1)) {
1491 *new_fdp = dup_fd(fd, &error);
1500 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1503 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1505 if (unshare_flags & CLONE_SYSVSEM)
1512 * unshare allows a process to 'unshare' part of the process
1513 * context which was originally shared using clone. copy_*
1514 * functions used by do_fork() cannot be used here directly
1515 * because they modify an inactive task_struct that is being
1516 * constructed. Here we are modifying the current, active,
1519 asmlinkage long sys_unshare(unsigned long unshare_flags)
1522 struct fs_struct *fs, *new_fs = NULL;
1523 struct namespace *ns, *new_ns = NULL;
1524 struct sighand_struct *sigh, *new_sigh = NULL;
1525 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1526 struct files_struct *fd, *new_fd = NULL;
1527 struct sem_undo_list *new_ulist = NULL;
1529 check_unshare_flags(&unshare_flags);
1531 if ((err = unshare_thread(unshare_flags)))
1532 goto bad_unshare_out;
1533 if ((err = unshare_fs(unshare_flags, &new_fs)))
1534 goto bad_unshare_cleanup_thread;
1535 if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1536 goto bad_unshare_cleanup_fs;
1537 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1538 goto bad_unshare_cleanup_ns;
1539 if ((err = unshare_vm(unshare_flags, &new_mm)))
1540 goto bad_unshare_cleanup_sigh;
1541 if ((err = unshare_fd(unshare_flags, &new_fd)))
1542 goto bad_unshare_cleanup_vm;
1543 if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1544 goto bad_unshare_cleanup_fd;
1546 if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1552 current->fs = new_fs;
1557 ns = current->namespace;
1558 current->namespace = new_ns;
1563 sigh = current->sighand;
1564 current->sighand = new_sigh;
1570 active_mm = current->active_mm;
1571 current->mm = new_mm;
1572 current->active_mm = new_mm;
1573 activate_mm(active_mm, new_mm);
1578 fd = current->files;
1579 current->files = new_fd;
1583 task_unlock(current);
1586 bad_unshare_cleanup_fd:
1588 put_files_struct(new_fd);
1590 bad_unshare_cleanup_vm:
1594 bad_unshare_cleanup_sigh:
1596 if (atomic_dec_and_test(&new_sigh->count))
1597 kmem_cache_free(sighand_cachep, new_sigh);
1599 bad_unshare_cleanup_ns:
1601 put_namespace(new_ns);
1603 bad_unshare_cleanup_fs:
1605 put_fs_struct(new_fs);
1607 bad_unshare_cleanup_thread: