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_cb(struct rcu_head *rhp)
113 struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
115 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
116 WARN_ON(atomic_read(&tsk->usage));
117 WARN_ON(tsk == current);
119 if (unlikely(tsk->audit_context))
121 security_task_free(tsk);
123 put_group_info(tsk->group_info);
125 if (!profile_handoff_task(tsk))
129 void __init fork_init(unsigned long mempages)
131 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
132 #ifndef ARCH_MIN_TASKALIGN
133 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
135 /* create a slab on which task_structs can be allocated */
137 kmem_cache_create("task_struct", sizeof(struct task_struct),
138 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
142 * The default maximum number of threads is set to a safe
143 * value: the thread structures can take up at most half
146 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
149 * we need to allow at least 20 threads to boot a system
154 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
155 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
156 init_task.signal->rlim[RLIMIT_SIGPENDING] =
157 init_task.signal->rlim[RLIMIT_NPROC];
160 static struct task_struct *dup_task_struct(struct task_struct *orig)
162 struct task_struct *tsk;
163 struct thread_info *ti;
165 prepare_to_copy(orig);
167 tsk = alloc_task_struct();
171 ti = alloc_thread_info(tsk);
173 free_task_struct(tsk);
178 tsk->thread_info = ti;
179 setup_thread_stack(tsk, orig);
181 /* One for us, one for whoever does the "release_task()" (usually parent) */
182 atomic_set(&tsk->usage,2);
183 atomic_set(&tsk->fs_excl, 0);
189 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
191 struct vm_area_struct *mpnt, *tmp, **pprev;
192 struct rb_node **rb_link, *rb_parent;
194 unsigned long charge;
195 struct mempolicy *pol;
197 down_write(&oldmm->mmap_sem);
198 flush_cache_mm(oldmm);
199 down_write(&mm->mmap_sem);
203 mm->mmap_cache = NULL;
204 mm->free_area_cache = oldmm->mmap_base;
205 mm->cached_hole_size = ~0UL;
207 cpus_clear(mm->cpu_vm_mask);
209 rb_link = &mm->mm_rb.rb_node;
213 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
216 if (mpnt->vm_flags & VM_DONTCOPY) {
217 long pages = vma_pages(mpnt);
218 mm->total_vm -= pages;
219 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
224 if (mpnt->vm_flags & VM_ACCOUNT) {
225 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
226 if (security_vm_enough_memory(len))
230 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
234 pol = mpol_copy(vma_policy(mpnt));
235 retval = PTR_ERR(pol);
237 goto fail_nomem_policy;
238 vma_set_policy(tmp, pol);
239 tmp->vm_flags &= ~VM_LOCKED;
245 struct inode *inode = file->f_dentry->d_inode;
247 if (tmp->vm_flags & VM_DENYWRITE)
248 atomic_dec(&inode->i_writecount);
250 /* insert tmp into the share list, just after mpnt */
251 spin_lock(&file->f_mapping->i_mmap_lock);
252 tmp->vm_truncate_count = mpnt->vm_truncate_count;
253 flush_dcache_mmap_lock(file->f_mapping);
254 vma_prio_tree_add(tmp, mpnt);
255 flush_dcache_mmap_unlock(file->f_mapping);
256 spin_unlock(&file->f_mapping->i_mmap_lock);
260 * Link in the new vma and copy the page table entries.
263 pprev = &tmp->vm_next;
265 __vma_link_rb(mm, tmp, rb_link, rb_parent);
266 rb_link = &tmp->vm_rb.rb_right;
267 rb_parent = &tmp->vm_rb;
270 retval = copy_page_range(mm, oldmm, mpnt);
272 if (tmp->vm_ops && tmp->vm_ops->open)
273 tmp->vm_ops->open(tmp);
280 up_write(&mm->mmap_sem);
282 up_write(&oldmm->mmap_sem);
285 kmem_cache_free(vm_area_cachep, tmp);
288 vm_unacct_memory(charge);
292 static inline int mm_alloc_pgd(struct mm_struct * mm)
294 mm->pgd = pgd_alloc(mm);
295 if (unlikely(!mm->pgd))
300 static inline void mm_free_pgd(struct mm_struct * mm)
305 #define dup_mmap(mm, oldmm) (0)
306 #define mm_alloc_pgd(mm) (0)
307 #define mm_free_pgd(mm)
308 #endif /* CONFIG_MMU */
310 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
312 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
313 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
315 #include <linux/init_task.h>
317 static struct mm_struct * mm_init(struct mm_struct * mm)
319 atomic_set(&mm->mm_users, 1);
320 atomic_set(&mm->mm_count, 1);
321 init_rwsem(&mm->mmap_sem);
322 INIT_LIST_HEAD(&mm->mmlist);
323 mm->core_waiters = 0;
325 set_mm_counter(mm, file_rss, 0);
326 set_mm_counter(mm, anon_rss, 0);
327 spin_lock_init(&mm->page_table_lock);
328 rwlock_init(&mm->ioctx_list_lock);
329 mm->ioctx_list = NULL;
330 mm->free_area_cache = TASK_UNMAPPED_BASE;
331 mm->cached_hole_size = ~0UL;
333 if (likely(!mm_alloc_pgd(mm))) {
342 * Allocate and initialize an mm_struct.
344 struct mm_struct * mm_alloc(void)
346 struct mm_struct * mm;
350 memset(mm, 0, sizeof(*mm));
357 * Called when the last reference to the mm
358 * is dropped: either by a lazy thread or by
359 * mmput. Free the page directory and the mm.
361 void fastcall __mmdrop(struct mm_struct *mm)
363 BUG_ON(mm == &init_mm);
370 * Decrement the use count and release all resources for an mm.
372 void mmput(struct mm_struct *mm)
374 if (atomic_dec_and_test(&mm->mm_users)) {
377 if (!list_empty(&mm->mmlist)) {
378 spin_lock(&mmlist_lock);
379 list_del(&mm->mmlist);
380 spin_unlock(&mmlist_lock);
386 EXPORT_SYMBOL_GPL(mmput);
389 * get_task_mm - acquire a reference to the task's mm
391 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
392 * this kernel workthread has transiently adopted a user mm with use_mm,
393 * to do its AIO) is not set and if so returns a reference to it, after
394 * bumping up the use count. User must release the mm via mmput()
395 * after use. Typically used by /proc and ptrace.
397 struct mm_struct *get_task_mm(struct task_struct *task)
399 struct mm_struct *mm;
404 if (task->flags & PF_BORROWED_MM)
407 atomic_inc(&mm->mm_users);
412 EXPORT_SYMBOL_GPL(get_task_mm);
414 /* Please note the differences between mmput and mm_release.
415 * mmput is called whenever we stop holding onto a mm_struct,
416 * error success whatever.
418 * mm_release is called after a mm_struct has been removed
419 * from the current process.
421 * This difference is important for error handling, when we
422 * only half set up a mm_struct for a new process and need to restore
423 * the old one. Because we mmput the new mm_struct before
424 * restoring the old one. . .
425 * Eric Biederman 10 January 1998
427 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
429 struct completion *vfork_done = tsk->vfork_done;
431 /* Get rid of any cached register state */
432 deactivate_mm(tsk, mm);
434 /* notify parent sleeping on vfork() */
436 tsk->vfork_done = NULL;
437 complete(vfork_done);
439 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
440 u32 __user * tidptr = tsk->clear_child_tid;
441 tsk->clear_child_tid = NULL;
444 * We don't check the error code - if userspace has
445 * not set up a proper pointer then tough luck.
448 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
453 * Allocate a new mm structure and copy contents from the
454 * mm structure of the passed in task structure.
456 static struct mm_struct *dup_mm(struct task_struct *tsk)
458 struct mm_struct *mm, *oldmm = current->mm;
468 memcpy(mm, oldmm, sizeof(*mm));
473 if (init_new_context(tsk, mm))
476 err = dup_mmap(mm, oldmm);
480 mm->hiwater_rss = get_mm_rss(mm);
481 mm->hiwater_vm = mm->total_vm;
493 * If init_new_context() failed, we cannot use mmput() to free the mm
494 * because it calls destroy_context()
501 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
503 struct mm_struct * mm, *oldmm;
506 tsk->min_flt = tsk->maj_flt = 0;
507 tsk->nvcsw = tsk->nivcsw = 0;
510 tsk->active_mm = NULL;
513 * Are we cloning a kernel thread?
515 * We need to steal a active VM for that..
521 if (clone_flags & CLONE_VM) {
522 atomic_inc(&oldmm->mm_users);
541 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
543 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
544 /* We don't need to lock fs - think why ;-) */
546 atomic_set(&fs->count, 1);
547 rwlock_init(&fs->lock);
548 fs->umask = old->umask;
549 read_lock(&old->lock);
550 fs->rootmnt = mntget(old->rootmnt);
551 fs->root = dget(old->root);
552 fs->pwdmnt = mntget(old->pwdmnt);
553 fs->pwd = dget(old->pwd);
555 fs->altrootmnt = mntget(old->altrootmnt);
556 fs->altroot = dget(old->altroot);
558 fs->altrootmnt = NULL;
561 read_unlock(&old->lock);
566 struct fs_struct *copy_fs_struct(struct fs_struct *old)
568 return __copy_fs_struct(old);
571 EXPORT_SYMBOL_GPL(copy_fs_struct);
573 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
575 if (clone_flags & CLONE_FS) {
576 atomic_inc(¤t->fs->count);
579 tsk->fs = __copy_fs_struct(current->fs);
585 static int count_open_files(struct fdtable *fdt)
587 int size = fdt->max_fdset;
590 /* Find the last open fd */
591 for (i = size/(8*sizeof(long)); i > 0; ) {
592 if (fdt->open_fds->fds_bits[--i])
595 i = (i+1) * 8 * sizeof(long);
599 static struct files_struct *alloc_files(void)
601 struct files_struct *newf;
604 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
608 atomic_set(&newf->count, 1);
610 spin_lock_init(&newf->file_lock);
613 fdt->max_fds = NR_OPEN_DEFAULT;
614 fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
615 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
616 fdt->open_fds = (fd_set *)&newf->open_fds_init;
617 fdt->fd = &newf->fd_array[0];
618 INIT_RCU_HEAD(&fdt->rcu);
619 fdt->free_files = NULL;
621 rcu_assign_pointer(newf->fdt, fdt);
627 * Allocate a new files structure and copy contents from the
628 * passed in files structure.
630 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
632 struct files_struct *newf;
633 struct file **old_fds, **new_fds;
634 int open_files, size, i, expand;
635 struct fdtable *old_fdt, *new_fdt;
637 newf = alloc_files();
641 spin_lock(&oldf->file_lock);
642 old_fdt = files_fdtable(oldf);
643 new_fdt = files_fdtable(newf);
644 size = old_fdt->max_fdset;
645 open_files = count_open_files(old_fdt);
649 * Check whether we need to allocate a larger fd array or fd set.
650 * Note: we're not a clone task, so the open count won't change.
652 if (open_files > new_fdt->max_fdset) {
653 new_fdt->max_fdset = 0;
656 if (open_files > new_fdt->max_fds) {
657 new_fdt->max_fds = 0;
661 /* if the old fdset gets grown now, we'll only copy up to "size" fds */
663 spin_unlock(&oldf->file_lock);
664 spin_lock(&newf->file_lock);
665 *errorp = expand_files(newf, open_files-1);
666 spin_unlock(&newf->file_lock);
669 new_fdt = files_fdtable(newf);
671 * Reacquire the oldf lock and a pointer to its fd table
672 * who knows it may have a new bigger fd table. We need
673 * the latest pointer.
675 spin_lock(&oldf->file_lock);
676 old_fdt = files_fdtable(oldf);
679 old_fds = old_fdt->fd;
680 new_fds = new_fdt->fd;
682 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
683 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
685 for (i = open_files; i != 0; i--) {
686 struct file *f = *old_fds++;
691 * The fd may be claimed in the fd bitmap but not yet
692 * instantiated in the files array if a sibling thread
693 * is partway through open(). So make sure that this
694 * fd is available to the new process.
696 FD_CLR(open_files - i, new_fdt->open_fds);
698 rcu_assign_pointer(*new_fds++, f);
700 spin_unlock(&oldf->file_lock);
702 /* compute the remainder to be cleared */
703 size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
705 /* This is long word aligned thus could use a optimized version */
706 memset(new_fds, 0, size);
708 if (new_fdt->max_fdset > open_files) {
709 int left = (new_fdt->max_fdset-open_files)/8;
710 int start = open_files / (8 * sizeof(unsigned long));
712 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
713 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
720 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
721 free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
722 free_fd_array(new_fdt->fd, new_fdt->max_fds);
723 kmem_cache_free(files_cachep, newf);
727 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
729 struct files_struct *oldf, *newf;
733 * A background process may not have any files ...
735 oldf = current->files;
739 if (clone_flags & CLONE_FILES) {
740 atomic_inc(&oldf->count);
745 * Note: we may be using current for both targets (See exec.c)
746 * This works because we cache current->files (old) as oldf. Don't
751 newf = dup_fd(oldf, &error);
762 * Helper to unshare the files of the current task.
763 * We don't want to expose copy_files internals to
764 * the exec layer of the kernel.
767 int unshare_files(void)
769 struct files_struct *files = current->files;
774 /* This can race but the race causes us to copy when we don't
775 need to and drop the copy */
776 if(atomic_read(&files->count) == 1)
778 atomic_inc(&files->count);
781 rc = copy_files(0, current);
783 current->files = files;
787 EXPORT_SYMBOL(unshare_files);
789 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
791 struct sighand_struct *sig;
793 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
794 atomic_inc(¤t->sighand->count);
797 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
798 rcu_assign_pointer(tsk->sighand, sig);
801 atomic_set(&sig->count, 1);
802 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
806 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
808 struct signal_struct *sig;
811 if (clone_flags & CLONE_THREAD) {
812 atomic_inc(¤t->signal->count);
813 atomic_inc(¤t->signal->live);
816 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
821 ret = copy_thread_group_keys(tsk);
823 kmem_cache_free(signal_cachep, sig);
827 atomic_set(&sig->count, 1);
828 atomic_set(&sig->live, 1);
829 init_waitqueue_head(&sig->wait_chldexit);
831 sig->group_exit_code = 0;
832 sig->group_exit_task = NULL;
833 sig->group_stop_count = 0;
834 sig->curr_target = NULL;
835 init_sigpending(&sig->shared_pending);
836 INIT_LIST_HEAD(&sig->posix_timers);
838 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
839 sig->it_real_incr.tv64 = 0;
840 sig->real_timer.function = it_real_fn;
843 sig->it_virt_expires = cputime_zero;
844 sig->it_virt_incr = cputime_zero;
845 sig->it_prof_expires = cputime_zero;
846 sig->it_prof_incr = cputime_zero;
848 sig->leader = 0; /* session leadership doesn't inherit */
849 sig->tty_old_pgrp = 0;
851 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
852 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
853 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
855 INIT_LIST_HEAD(&sig->cpu_timers[0]);
856 INIT_LIST_HEAD(&sig->cpu_timers[1]);
857 INIT_LIST_HEAD(&sig->cpu_timers[2]);
859 task_lock(current->group_leader);
860 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
861 task_unlock(current->group_leader);
863 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
865 * New sole thread in the process gets an expiry time
866 * of the whole CPU time limit.
868 tsk->it_prof_expires =
869 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
875 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
877 unsigned long new_flags = p->flags;
879 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
880 new_flags |= PF_FORKNOEXEC;
881 if (!(clone_flags & CLONE_PTRACE))
883 p->flags = new_flags;
886 asmlinkage long sys_set_tid_address(int __user *tidptr)
888 current->clear_child_tid = tidptr;
894 * This creates a new process as a copy of the old one,
895 * but does not actually start it yet.
897 * It copies the registers, and all the appropriate
898 * parts of the process environment (as per the clone
899 * flags). The actual kick-off is left to the caller.
901 static task_t *copy_process(unsigned long clone_flags,
902 unsigned long stack_start,
903 struct pt_regs *regs,
904 unsigned long stack_size,
905 int __user *parent_tidptr,
906 int __user *child_tidptr,
910 struct task_struct *p = NULL;
912 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
913 return ERR_PTR(-EINVAL);
916 * Thread groups must share signals as well, and detached threads
917 * can only be started up within the thread group.
919 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
920 return ERR_PTR(-EINVAL);
923 * Shared signal handlers imply shared VM. By way of the above,
924 * thread groups also imply shared VM. Blocking this case allows
925 * for various simplifications in other code.
927 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
928 return ERR_PTR(-EINVAL);
930 retval = security_task_create(clone_flags);
935 p = dup_task_struct(current);
940 if (atomic_read(&p->user->processes) >=
941 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
942 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
943 p->user != &root_user)
947 atomic_inc(&p->user->__count);
948 atomic_inc(&p->user->processes);
949 get_group_info(p->group_info);
952 * If multiple threads are within copy_process(), then this check
953 * triggers too late. This doesn't hurt, the check is only there
954 * to stop root fork bombs.
956 if (nr_threads >= max_threads)
957 goto bad_fork_cleanup_count;
959 if (!try_module_get(task_thread_info(p)->exec_domain->module))
960 goto bad_fork_cleanup_count;
962 if (p->binfmt && !try_module_get(p->binfmt->module))
963 goto bad_fork_cleanup_put_domain;
966 copy_flags(clone_flags, p);
969 if (clone_flags & CLONE_PARENT_SETTID)
970 if (put_user(p->pid, parent_tidptr))
971 goto bad_fork_cleanup;
973 p->proc_dentry = NULL;
975 INIT_LIST_HEAD(&p->children);
976 INIT_LIST_HEAD(&p->sibling);
977 p->vfork_done = NULL;
978 spin_lock_init(&p->alloc_lock);
979 spin_lock_init(&p->proc_lock);
981 clear_tsk_thread_flag(p, TIF_SIGPENDING);
982 init_sigpending(&p->pending);
984 p->utime = cputime_zero;
985 p->stime = cputime_zero;
987 p->rchar = 0; /* I/O counter: bytes read */
988 p->wchar = 0; /* I/O counter: bytes written */
989 p->syscr = 0; /* I/O counter: read syscalls */
990 p->syscw = 0; /* I/O counter: write syscalls */
991 acct_clear_integrals(p);
993 p->it_virt_expires = cputime_zero;
994 p->it_prof_expires = cputime_zero;
995 p->it_sched_expires = 0;
996 INIT_LIST_HEAD(&p->cpu_timers[0]);
997 INIT_LIST_HEAD(&p->cpu_timers[1]);
998 INIT_LIST_HEAD(&p->cpu_timers[2]);
1000 p->lock_depth = -1; /* -1 = no lock */
1001 do_posix_clock_monotonic_gettime(&p->start_time);
1003 p->io_context = NULL;
1005 p->audit_context = NULL;
1008 p->mempolicy = mpol_copy(p->mempolicy);
1009 if (IS_ERR(p->mempolicy)) {
1010 retval = PTR_ERR(p->mempolicy);
1011 p->mempolicy = NULL;
1012 goto bad_fork_cleanup_cpuset;
1014 mpol_fix_fork_child_flag(p);
1017 #ifdef CONFIG_DEBUG_MUTEXES
1018 p->blocked_on = NULL; /* not blocked yet */
1022 if (clone_flags & CLONE_THREAD)
1023 p->tgid = current->tgid;
1025 if ((retval = security_task_alloc(p)))
1026 goto bad_fork_cleanup_policy;
1027 if ((retval = audit_alloc(p)))
1028 goto bad_fork_cleanup_security;
1029 /* copy all the process information */
1030 if ((retval = copy_semundo(clone_flags, p)))
1031 goto bad_fork_cleanup_audit;
1032 if ((retval = copy_files(clone_flags, p)))
1033 goto bad_fork_cleanup_semundo;
1034 if ((retval = copy_fs(clone_flags, p)))
1035 goto bad_fork_cleanup_files;
1036 if ((retval = copy_sighand(clone_flags, p)))
1037 goto bad_fork_cleanup_fs;
1038 if ((retval = copy_signal(clone_flags, p)))
1039 goto bad_fork_cleanup_sighand;
1040 if ((retval = copy_mm(clone_flags, p)))
1041 goto bad_fork_cleanup_signal;
1042 if ((retval = copy_keys(clone_flags, p)))
1043 goto bad_fork_cleanup_mm;
1044 if ((retval = copy_namespace(clone_flags, p)))
1045 goto bad_fork_cleanup_keys;
1046 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1048 goto bad_fork_cleanup_namespace;
1050 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1052 * Clear TID on mm_release()?
1054 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1055 p->robust_list = NULL;
1056 #ifdef CONFIG_COMPAT
1057 p->compat_robust_list = NULL;
1060 * sigaltstack should be cleared when sharing the same VM
1062 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1063 p->sas_ss_sp = p->sas_ss_size = 0;
1066 * Syscall tracing should be turned off in the child regardless
1069 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1070 #ifdef TIF_SYSCALL_EMU
1071 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1074 /* Our parent execution domain becomes current domain
1075 These must match for thread signalling to apply */
1077 p->parent_exec_id = p->self_exec_id;
1079 /* ok, now we should be set up.. */
1080 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1081 p->pdeath_signal = 0;
1085 * Ok, make it visible to the rest of the system.
1086 * We dont wake it up yet.
1088 p->group_leader = p;
1089 INIT_LIST_HEAD(&p->ptrace_children);
1090 INIT_LIST_HEAD(&p->ptrace_list);
1092 /* Perform scheduler related setup. Assign this task to a CPU. */
1093 sched_fork(p, clone_flags);
1095 /* Need tasklist lock for parent etc handling! */
1096 write_lock_irq(&tasklist_lock);
1099 * The task hasn't been attached yet, so its cpus_allowed mask will
1100 * not be changed, nor will its assigned CPU.
1102 * The cpus_allowed mask of the parent may have changed after it was
1103 * copied first time - so re-copy it here, then check the child's CPU
1104 * to ensure it is on a valid CPU (and if not, just force it back to
1105 * parent's CPU). This avoids alot of nasty races.
1107 p->cpus_allowed = current->cpus_allowed;
1108 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1109 !cpu_online(task_cpu(p))))
1110 set_task_cpu(p, smp_processor_id());
1113 * Check for pending SIGKILL! The new thread should not be allowed
1114 * to slip out of an OOM kill. (or normal SIGKILL.)
1116 if (sigismember(¤t->pending.signal, SIGKILL)) {
1117 write_unlock_irq(&tasklist_lock);
1119 goto bad_fork_cleanup_namespace;
1122 /* CLONE_PARENT re-uses the old parent */
1123 if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1124 p->real_parent = current->real_parent;
1126 p->real_parent = current;
1127 p->parent = p->real_parent;
1129 spin_lock(¤t->sighand->siglock);
1130 if (clone_flags & CLONE_THREAD) {
1132 * Important: if an exit-all has been started then
1133 * do not create this new thread - the whole thread
1134 * group is supposed to exit anyway.
1136 if (current->signal->flags & SIGNAL_GROUP_EXIT) {
1137 spin_unlock(¤t->sighand->siglock);
1138 write_unlock_irq(&tasklist_lock);
1140 goto bad_fork_cleanup_namespace;
1142 p->group_leader = current->group_leader;
1144 if (current->signal->group_stop_count > 0) {
1146 * There is an all-stop in progress for the group.
1147 * We ourselves will stop as soon as we check signals.
1148 * Make the new thread part of that group stop too.
1150 current->signal->group_stop_count++;
1151 set_tsk_thread_flag(p, TIF_SIGPENDING);
1154 if (!cputime_eq(current->signal->it_virt_expires,
1156 !cputime_eq(current->signal->it_prof_expires,
1158 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1159 !list_empty(¤t->signal->cpu_timers[0]) ||
1160 !list_empty(¤t->signal->cpu_timers[1]) ||
1161 !list_empty(¤t->signal->cpu_timers[2])) {
1163 * Have child wake up on its first tick to check
1164 * for process CPU timers.
1166 p->it_prof_expires = jiffies_to_cputime(1);
1173 p->ioprio = current->ioprio;
1175 if (likely(p->pid)) {
1177 if (unlikely(p->ptrace & PT_PTRACED))
1178 __ptrace_link(p, current->parent);
1180 if (thread_group_leader(p)) {
1181 p->signal->tty = current->signal->tty;
1182 p->signal->pgrp = process_group(current);
1183 p->signal->session = current->signal->session;
1184 attach_pid(p, PIDTYPE_PGID, process_group(p));
1185 attach_pid(p, PIDTYPE_SID, p->signal->session);
1187 list_add_tail(&p->tasks, &init_task.tasks);
1188 __get_cpu_var(process_counts)++;
1190 attach_pid(p, PIDTYPE_TGID, p->tgid);
1191 attach_pid(p, PIDTYPE_PID, p->pid);
1196 spin_unlock(¤t->sighand->siglock);
1197 write_unlock_irq(&tasklist_lock);
1198 proc_fork_connector(p);
1201 bad_fork_cleanup_namespace:
1203 bad_fork_cleanup_keys:
1205 bad_fork_cleanup_mm:
1208 bad_fork_cleanup_signal:
1210 bad_fork_cleanup_sighand:
1212 bad_fork_cleanup_fs:
1213 exit_fs(p); /* blocking */
1214 bad_fork_cleanup_files:
1215 exit_files(p); /* blocking */
1216 bad_fork_cleanup_semundo:
1218 bad_fork_cleanup_audit:
1220 bad_fork_cleanup_security:
1221 security_task_free(p);
1222 bad_fork_cleanup_policy:
1224 mpol_free(p->mempolicy);
1225 bad_fork_cleanup_cpuset:
1230 module_put(p->binfmt->module);
1231 bad_fork_cleanup_put_domain:
1232 module_put(task_thread_info(p)->exec_domain->module);
1233 bad_fork_cleanup_count:
1234 put_group_info(p->group_info);
1235 atomic_dec(&p->user->processes);
1240 return ERR_PTR(retval);
1243 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1245 memset(regs, 0, sizeof(struct pt_regs));
1249 task_t * __devinit fork_idle(int cpu)
1252 struct pt_regs regs;
1254 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0);
1256 return ERR_PTR(-ENOMEM);
1257 init_idle(task, cpu);
1262 static inline int fork_traceflag (unsigned clone_flags)
1264 if (clone_flags & CLONE_UNTRACED)
1266 else if (clone_flags & CLONE_VFORK) {
1267 if (current->ptrace & PT_TRACE_VFORK)
1268 return PTRACE_EVENT_VFORK;
1269 } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1270 if (current->ptrace & PT_TRACE_CLONE)
1271 return PTRACE_EVENT_CLONE;
1272 } else if (current->ptrace & PT_TRACE_FORK)
1273 return PTRACE_EVENT_FORK;
1279 * Ok, this is the main fork-routine.
1281 * It copies the process, and if successful kick-starts
1282 * it and waits for it to finish using the VM if required.
1284 long do_fork(unsigned long clone_flags,
1285 unsigned long stack_start,
1286 struct pt_regs *regs,
1287 unsigned long stack_size,
1288 int __user *parent_tidptr,
1289 int __user *child_tidptr)
1291 struct task_struct *p;
1293 long pid = alloc_pidmap();
1297 if (unlikely(current->ptrace)) {
1298 trace = fork_traceflag (clone_flags);
1300 clone_flags |= CLONE_PTRACE;
1303 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
1305 * Do this prior waking up the new thread - the thread pointer
1306 * might get invalid after that point, if the thread exits quickly.
1309 struct completion vfork;
1311 if (clone_flags & CLONE_VFORK) {
1312 p->vfork_done = &vfork;
1313 init_completion(&vfork);
1316 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1318 * We'll start up with an immediate SIGSTOP.
1320 sigaddset(&p->pending.signal, SIGSTOP);
1321 set_tsk_thread_flag(p, TIF_SIGPENDING);
1324 if (!(clone_flags & CLONE_STOPPED))
1325 wake_up_new_task(p, clone_flags);
1327 p->state = TASK_STOPPED;
1329 if (unlikely (trace)) {
1330 current->ptrace_message = pid;
1331 ptrace_notify ((trace << 8) | SIGTRAP);
1334 if (clone_flags & CLONE_VFORK) {
1335 wait_for_completion(&vfork);
1336 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
1337 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1346 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1347 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1350 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1352 struct sighand_struct *sighand = data;
1354 if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1355 SLAB_CTOR_CONSTRUCTOR)
1356 spin_lock_init(&sighand->siglock);
1359 void __init proc_caches_init(void)
1361 sighand_cachep = kmem_cache_create("sighand_cache",
1362 sizeof(struct sighand_struct), 0,
1363 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1364 sighand_ctor, NULL);
1365 signal_cachep = kmem_cache_create("signal_cache",
1366 sizeof(struct signal_struct), 0,
1367 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1368 files_cachep = kmem_cache_create("files_cache",
1369 sizeof(struct files_struct), 0,
1370 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1371 fs_cachep = kmem_cache_create("fs_cache",
1372 sizeof(struct fs_struct), 0,
1373 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1374 vm_area_cachep = kmem_cache_create("vm_area_struct",
1375 sizeof(struct vm_area_struct), 0,
1376 SLAB_PANIC, NULL, NULL);
1377 mm_cachep = kmem_cache_create("mm_struct",
1378 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1379 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1384 * Check constraints on flags passed to the unshare system call and
1385 * force unsharing of additional process context as appropriate.
1387 static inline void check_unshare_flags(unsigned long *flags_ptr)
1390 * If unsharing a thread from a thread group, must also
1393 if (*flags_ptr & CLONE_THREAD)
1394 *flags_ptr |= CLONE_VM;
1397 * If unsharing vm, must also unshare signal handlers.
1399 if (*flags_ptr & CLONE_VM)
1400 *flags_ptr |= CLONE_SIGHAND;
1403 * If unsharing signal handlers and the task was created
1404 * using CLONE_THREAD, then must unshare the thread
1406 if ((*flags_ptr & CLONE_SIGHAND) &&
1407 (atomic_read(¤t->signal->count) > 1))
1408 *flags_ptr |= CLONE_THREAD;
1411 * If unsharing namespace, must also unshare filesystem information.
1413 if (*flags_ptr & CLONE_NEWNS)
1414 *flags_ptr |= CLONE_FS;
1418 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1420 static int unshare_thread(unsigned long unshare_flags)
1422 if (unshare_flags & CLONE_THREAD)
1429 * Unshare the filesystem structure if it is being shared
1431 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1433 struct fs_struct *fs = current->fs;
1435 if ((unshare_flags & CLONE_FS) &&
1436 (fs && atomic_read(&fs->count) > 1)) {
1437 *new_fsp = __copy_fs_struct(current->fs);
1446 * Unshare the namespace structure if it is being shared
1448 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1450 struct namespace *ns = current->namespace;
1452 if ((unshare_flags & CLONE_NEWNS) &&
1453 (ns && atomic_read(&ns->count) > 1)) {
1454 if (!capable(CAP_SYS_ADMIN))
1457 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1466 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1469 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1471 struct sighand_struct *sigh = current->sighand;
1473 if ((unshare_flags & CLONE_SIGHAND) &&
1474 (sigh && atomic_read(&sigh->count) > 1))
1481 * Unshare vm if it is being shared
1483 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1485 struct mm_struct *mm = current->mm;
1487 if ((unshare_flags & CLONE_VM) &&
1488 (mm && atomic_read(&mm->mm_users) > 1)) {
1496 * Unshare file descriptor table if it is being shared
1498 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1500 struct files_struct *fd = current->files;
1503 if ((unshare_flags & CLONE_FILES) &&
1504 (fd && atomic_read(&fd->count) > 1)) {
1505 *new_fdp = dup_fd(fd, &error);
1514 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1517 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1519 if (unshare_flags & CLONE_SYSVSEM)
1526 * unshare allows a process to 'unshare' part of the process
1527 * context which was originally shared using clone. copy_*
1528 * functions used by do_fork() cannot be used here directly
1529 * because they modify an inactive task_struct that is being
1530 * constructed. Here we are modifying the current, active,
1533 asmlinkage long sys_unshare(unsigned long unshare_flags)
1536 struct fs_struct *fs, *new_fs = NULL;
1537 struct namespace *ns, *new_ns = NULL;
1538 struct sighand_struct *sigh, *new_sigh = NULL;
1539 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1540 struct files_struct *fd, *new_fd = NULL;
1541 struct sem_undo_list *new_ulist = NULL;
1543 check_unshare_flags(&unshare_flags);
1545 /* Return -EINVAL for all unsupported flags */
1547 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1548 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
1549 goto bad_unshare_out;
1551 if ((err = unshare_thread(unshare_flags)))
1552 goto bad_unshare_out;
1553 if ((err = unshare_fs(unshare_flags, &new_fs)))
1554 goto bad_unshare_cleanup_thread;
1555 if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1556 goto bad_unshare_cleanup_fs;
1557 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1558 goto bad_unshare_cleanup_ns;
1559 if ((err = unshare_vm(unshare_flags, &new_mm)))
1560 goto bad_unshare_cleanup_sigh;
1561 if ((err = unshare_fd(unshare_flags, &new_fd)))
1562 goto bad_unshare_cleanup_vm;
1563 if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1564 goto bad_unshare_cleanup_fd;
1566 if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1572 current->fs = new_fs;
1577 ns = current->namespace;
1578 current->namespace = new_ns;
1583 sigh = current->sighand;
1584 rcu_assign_pointer(current->sighand, new_sigh);
1590 active_mm = current->active_mm;
1591 current->mm = new_mm;
1592 current->active_mm = new_mm;
1593 activate_mm(active_mm, new_mm);
1598 fd = current->files;
1599 current->files = new_fd;
1603 task_unlock(current);
1606 bad_unshare_cleanup_fd:
1608 put_files_struct(new_fd);
1610 bad_unshare_cleanup_vm:
1614 bad_unshare_cleanup_sigh:
1616 if (atomic_dec_and_test(&new_sigh->count))
1617 kmem_cache_free(sighand_cachep, new_sigh);
1619 bad_unshare_cleanup_ns:
1621 put_namespace(new_ns);
1623 bad_unshare_cleanup_fs:
1625 put_fs_struct(new_fs);
1627 bad_unshare_cleanup_thread: