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/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/smp_lock.h>
18 #include <linux/module.h>
19 #include <linux/vmalloc.h>
20 #include <linux/completion.h>
21 #include <linux/namespace.h>
22 #include <linux/personality.h>
23 #include <linux/mempolicy.h>
24 #include <linux/sem.h>
25 #include <linux/file.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
30 #include <linux/capability.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/tracehook.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>
46 #include <linux/delayacct.h>
47 #include <linux/taskstats_kern.h>
48 #include <linux/vs_base.h>
49 #include <linux/vs_context.h>
50 #include <linux/vs_network.h>
51 #include <linux/vs_limit.h>
52 #include <linux/vs_memory.h>
54 #include <asm/pgtable.h>
55 #include <asm/pgalloc.h>
56 #include <asm/uaccess.h>
57 #include <asm/mmu_context.h>
58 #include <asm/cacheflush.h>
59 #include <asm/tlbflush.h>
62 * Protected counters by write_lock_irq(&tasklist_lock)
64 unsigned long total_forks; /* Handle normal Linux uptimes. */
65 int nr_threads; /* The idle threads do not count.. */
67 int max_threads; /* tunable limit on nr_threads */
69 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
71 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
73 int nr_processes(void)
78 for_each_online_cpu(cpu)
79 total += per_cpu(process_counts, cpu);
84 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
85 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
86 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
87 static kmem_cache_t *task_struct_cachep;
90 /* SLAB cache for signal_struct structures (tsk->signal) */
91 static kmem_cache_t *signal_cachep;
93 /* SLAB cache for sighand_struct structures (tsk->sighand) */
94 kmem_cache_t *sighand_cachep;
96 /* SLAB cache for files_struct structures (tsk->files) */
97 kmem_cache_t *files_cachep;
99 /* SLAB cache for fs_struct structures (tsk->fs) */
100 kmem_cache_t *fs_cachep;
102 /* SLAB cache for vm_area_struct structures */
103 kmem_cache_t *vm_area_cachep;
105 /* SLAB cache for mm_struct structures (tsk->mm) */
106 static kmem_cache_t *mm_cachep;
108 void free_task(struct task_struct *tsk)
110 free_thread_info(tsk->thread_info);
111 rt_mutex_debug_task_free(tsk);
112 clr_vx_info(&tsk->vx_info);
113 clr_nx_info(&tsk->nx_info);
114 free_task_struct(tsk);
116 EXPORT_SYMBOL(free_task);
118 void __put_task_struct(struct task_struct *tsk)
120 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
121 WARN_ON(atomic_read(&tsk->usage));
122 WARN_ON(tsk == current);
124 security_task_free(tsk);
126 put_group_info(tsk->group_info);
127 delayacct_tsk_free(tsk);
129 if (!profile_handoff_task(tsk))
133 void __init fork_init(unsigned long mempages)
135 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
136 #ifndef ARCH_MIN_TASKALIGN
137 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
139 /* create a slab on which task_structs can be allocated */
141 kmem_cache_create("task_struct", sizeof(struct task_struct),
142 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
146 * The default maximum number of threads is set to a safe
147 * value: the thread structures can take up at most half
150 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
153 * we need to allow at least 20 threads to boot a system
158 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
159 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
160 init_task.signal->rlim[RLIMIT_SIGPENDING] =
161 init_task.signal->rlim[RLIMIT_NPROC];
164 static struct task_struct *dup_task_struct(struct task_struct *orig)
166 struct task_struct *tsk;
167 struct thread_info *ti;
169 prepare_to_copy(orig);
171 tsk = alloc_task_struct();
175 ti = alloc_thread_info(tsk);
177 free_task_struct(tsk);
182 tsk->thread_info = ti;
183 setup_thread_stack(tsk, orig);
185 /* One for us, one for whoever does the "release_task()" (usually parent) */
186 atomic_set(&tsk->usage,2);
187 atomic_set(&tsk->fs_excl, 0);
189 tsk->splice_pipe = NULL;
194 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
196 struct vm_area_struct *mpnt, *tmp, **pprev;
197 struct rb_node **rb_link, *rb_parent;
199 unsigned long charge;
200 struct mempolicy *pol;
202 down_write(&oldmm->mmap_sem);
203 flush_cache_mm(oldmm);
205 * Not linked in yet - no deadlock potential:
207 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
211 mm->mmap_cache = NULL;
212 mm->free_area_cache = oldmm->mmap_base;
213 mm->cached_hole_size = ~0UL;
215 __set_mm_counter(mm, file_rss, 0);
216 __set_mm_counter(mm, anon_rss, 0);
217 cpus_clear(mm->cpu_vm_mask);
219 rb_link = &mm->mm_rb.rb_node;
223 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
226 if (mpnt->vm_flags & VM_DONTCOPY) {
227 long pages = vma_pages(mpnt);
228 vx_vmpages_sub(mm, pages);
229 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
234 if (mpnt->vm_flags & VM_ACCOUNT) {
235 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
236 if (security_vm_enough_memory(len))
240 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
244 pol = mpol_copy(vma_policy(mpnt));
245 retval = PTR_ERR(pol);
247 goto fail_nomem_policy;
248 vma_set_policy(tmp, pol);
249 tmp->vm_flags &= ~VM_LOCKED;
255 struct inode *inode = file->f_dentry->d_inode;
257 if (tmp->vm_flags & VM_DENYWRITE)
258 atomic_dec(&inode->i_writecount);
260 /* insert tmp into the share list, just after mpnt */
261 spin_lock(&file->f_mapping->i_mmap_lock);
262 tmp->vm_truncate_count = mpnt->vm_truncate_count;
263 flush_dcache_mmap_lock(file->f_mapping);
264 vma_prio_tree_add(tmp, mpnt);
265 flush_dcache_mmap_unlock(file->f_mapping);
266 spin_unlock(&file->f_mapping->i_mmap_lock);
270 * Link in the new vma and copy the page table entries.
273 pprev = &tmp->vm_next;
275 __vma_link_rb(mm, tmp, rb_link, rb_parent);
276 rb_link = &tmp->vm_rb.rb_right;
277 rb_parent = &tmp->vm_rb;
280 retval = copy_page_range(mm, oldmm, mpnt);
282 if (tmp->vm_ops && tmp->vm_ops->open)
283 tmp->vm_ops->open(tmp);
289 arch_dup_mmap(mm, oldmm);
293 up_write(&mm->mmap_sem);
295 up_write(&oldmm->mmap_sem);
298 kmem_cache_free(vm_area_cachep, tmp);
301 vm_unacct_memory(charge);
305 static inline int mm_alloc_pgd(struct mm_struct * mm)
307 mm->pgd = pgd_alloc(mm);
308 if (unlikely(!mm->pgd))
313 static inline void mm_free_pgd(struct mm_struct * mm)
318 #define dup_mmap(mm, oldmm) (0)
319 #define mm_alloc_pgd(mm) (0)
320 #define mm_free_pgd(mm)
321 #endif /* CONFIG_MMU */
323 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
325 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
326 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
328 #include <linux/init_task.h>
330 static struct mm_struct * mm_init(struct mm_struct * mm)
332 atomic_set(&mm->mm_users, 1);
333 atomic_set(&mm->mm_count, 1);
334 init_rwsem(&mm->mmap_sem);
335 INIT_LIST_HEAD(&mm->mmlist);
336 mm->core_waiters = 0;
338 spin_lock_init(&mm->page_table_lock);
339 rwlock_init(&mm->ioctx_list_lock);
340 mm->ioctx_list = NULL;
341 mm->free_area_cache = TASK_UNMAPPED_BASE;
342 mm->cached_hole_size = ~0UL;
344 if (likely(!mm_alloc_pgd(mm))) {
346 set_vx_info(&mm->mm_vx_info, current->vx_info);
354 * Allocate and initialize an mm_struct.
356 struct mm_struct * mm_alloc(void)
358 struct mm_struct * mm;
362 memset(mm, 0, sizeof(*mm));
369 * Called when the last reference to the mm
370 * is dropped: either by a lazy thread or by
371 * mmput. Free the page directory and the mm.
373 void fastcall __mmdrop(struct mm_struct *mm)
375 BUG_ON(mm == &init_mm);
378 clr_vx_info(&mm->mm_vx_info);
383 * Decrement the use count and release all resources for an mm.
385 void mmput(struct mm_struct *mm)
389 if (atomic_dec_and_test(&mm->mm_users)) {
392 if (!list_empty(&mm->mmlist)) {
393 spin_lock(&mmlist_lock);
394 list_del(&mm->mmlist);
395 spin_unlock(&mmlist_lock);
401 EXPORT_SYMBOL_GPL(mmput);
404 * get_task_mm - acquire a reference to the task's mm
406 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
407 * this kernel workthread has transiently adopted a user mm with use_mm,
408 * to do its AIO) is not set and if so returns a reference to it, after
409 * bumping up the use count. User must release the mm via mmput()
410 * after use. Typically used by /proc and ptrace.
412 struct mm_struct *get_task_mm(struct task_struct *task)
414 struct mm_struct *mm;
419 if (task->flags & PF_BORROWED_MM)
422 atomic_inc(&mm->mm_users);
427 EXPORT_SYMBOL_GPL(get_task_mm);
429 /* Please note the differences between mmput and mm_release.
430 * mmput is called whenever we stop holding onto a mm_struct,
431 * error success whatever.
433 * mm_release is called after a mm_struct has been removed
434 * from the current process.
436 * This difference is important for error handling, when we
437 * only half set up a mm_struct for a new process and need to restore
438 * the old one. Because we mmput the new mm_struct before
439 * restoring the old one. . .
440 * Eric Biederman 10 January 1998
442 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
444 struct completion *vfork_done = tsk->vfork_done;
446 /* Get rid of any cached register state */
447 deactivate_mm(tsk, mm);
449 /* notify parent sleeping on vfork() */
451 tsk->vfork_done = NULL;
452 complete(vfork_done);
454 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
455 u32 __user * tidptr = tsk->clear_child_tid;
456 tsk->clear_child_tid = NULL;
459 * We don't check the error code - if userspace has
460 * not set up a proper pointer then tough luck.
463 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
468 * Allocate a new mm structure and copy contents from the
469 * mm structure of the passed in task structure.
471 static struct mm_struct *dup_mm(struct task_struct *tsk)
473 struct mm_struct *mm, *oldmm = current->mm;
483 memcpy(mm, oldmm, sizeof(*mm));
484 mm->mm_vx_info = NULL;
489 if (init_new_context(tsk, mm))
492 err = dup_mmap(mm, oldmm);
496 mm->hiwater_rss = get_mm_rss(mm);
497 mm->hiwater_vm = mm->total_vm;
509 * If init_new_context() failed, we cannot use mmput() to free the mm
510 * because it calls destroy_context()
512 clr_vx_info(&mm->mm_vx_info);
518 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
520 struct mm_struct * mm, *oldmm;
523 tsk->min_flt = tsk->maj_flt = 0;
524 tsk->nvcsw = tsk->nivcsw = 0;
527 tsk->active_mm = NULL;
530 * Are we cloning a kernel thread?
532 * We need to steal a active VM for that..
538 if (clone_flags & CLONE_VM) {
539 atomic_inc(&oldmm->mm_users);
558 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
560 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
561 /* We don't need to lock fs - think why ;-) */
563 atomic_set(&fs->count, 1);
564 rwlock_init(&fs->lock);
565 fs->umask = old->umask;
566 read_lock(&old->lock);
567 fs->rootmnt = mntget(old->rootmnt);
568 fs->root = dget(old->root);
569 fs->pwdmnt = mntget(old->pwdmnt);
570 fs->pwd = dget(old->pwd);
572 fs->altrootmnt = mntget(old->altrootmnt);
573 fs->altroot = dget(old->altroot);
575 fs->altrootmnt = NULL;
578 read_unlock(&old->lock);
583 struct fs_struct *copy_fs_struct(struct fs_struct *old)
585 return __copy_fs_struct(old);
588 EXPORT_SYMBOL_GPL(copy_fs_struct);
590 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
592 if (clone_flags & CLONE_FS) {
593 atomic_inc(¤t->fs->count);
596 tsk->fs = __copy_fs_struct(current->fs);
602 static int count_open_files(struct fdtable *fdt)
604 int size = fdt->max_fdset;
607 /* Find the last open fd */
608 for (i = size/(8*sizeof(long)); i > 0; ) {
609 if (fdt->open_fds->fds_bits[--i])
612 i = (i+1) * 8 * sizeof(long);
616 static struct files_struct *alloc_files(void)
618 struct files_struct *newf;
621 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
625 atomic_set(&newf->count, 1);
627 spin_lock_init(&newf->file_lock);
630 fdt->max_fds = NR_OPEN_DEFAULT;
631 fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
632 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
633 fdt->open_fds = (fd_set *)&newf->open_fds_init;
634 fdt->fd = &newf->fd_array[0];
635 INIT_RCU_HEAD(&fdt->rcu);
636 fdt->free_files = NULL;
638 rcu_assign_pointer(newf->fdt, fdt);
644 * Allocate a new files structure and copy contents from the
645 * passed in files structure.
646 * errorp will be valid only when the returned files_struct is NULL.
648 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
650 struct files_struct *newf;
651 struct file **old_fds, **new_fds;
652 int open_files, size, i, expand;
653 struct fdtable *old_fdt, *new_fdt;
656 newf = alloc_files();
660 spin_lock(&oldf->file_lock);
661 old_fdt = files_fdtable(oldf);
662 new_fdt = files_fdtable(newf);
663 size = old_fdt->max_fdset;
664 open_files = count_open_files(old_fdt);
668 * Check whether we need to allocate a larger fd array or fd set.
669 * Note: we're not a clone task, so the open count won't change.
671 if (open_files > new_fdt->max_fdset) {
672 new_fdt->max_fdset = 0;
675 if (open_files > new_fdt->max_fds) {
676 new_fdt->max_fds = 0;
680 /* if the old fdset gets grown now, we'll only copy up to "size" fds */
682 spin_unlock(&oldf->file_lock);
683 spin_lock(&newf->file_lock);
684 *errorp = expand_files(newf, open_files-1);
685 spin_unlock(&newf->file_lock);
688 new_fdt = files_fdtable(newf);
690 * Reacquire the oldf lock and a pointer to its fd table
691 * who knows it may have a new bigger fd table. We need
692 * the latest pointer.
694 spin_lock(&oldf->file_lock);
695 old_fdt = files_fdtable(oldf);
698 old_fds = old_fdt->fd;
699 new_fds = new_fdt->fd;
701 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
702 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
704 for (i = open_files; i != 0; i--) {
705 struct file *f = *old_fds++;
708 /* FIXME: sum it first for check and performance */
709 vx_openfd_inc(open_files - i);
712 * The fd may be claimed in the fd bitmap but not yet
713 * instantiated in the files array if a sibling thread
714 * is partway through open(). So make sure that this
715 * fd is available to the new process.
717 FD_CLR(open_files - i, new_fdt->open_fds);
719 rcu_assign_pointer(*new_fds++, f);
721 spin_unlock(&oldf->file_lock);
723 /* compute the remainder to be cleared */
724 size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
726 /* This is long word aligned thus could use a optimized version */
727 memset(new_fds, 0, size);
729 if (new_fdt->max_fdset > open_files) {
730 int left = (new_fdt->max_fdset-open_files)/8;
731 int start = open_files / (8 * sizeof(unsigned long));
733 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
734 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
741 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
742 free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
743 free_fd_array(new_fdt->fd, new_fdt->max_fds);
744 kmem_cache_free(files_cachep, newf);
748 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
750 struct files_struct *oldf, *newf;
754 * A background process may not have any files ...
756 oldf = current->files;
760 if (clone_flags & CLONE_FILES) {
761 atomic_inc(&oldf->count);
766 * Note: we may be using current for both targets (See exec.c)
767 * This works because we cache current->files (old) as oldf. Don't
771 newf = dup_fd(oldf, &error);
782 * Helper to unshare the files of the current task.
783 * We don't want to expose copy_files internals to
784 * the exec layer of the kernel.
787 int unshare_files(void)
789 struct files_struct *files = current->files;
794 /* This can race but the race causes us to copy when we don't
795 need to and drop the copy */
796 if(atomic_read(&files->count) == 1)
798 atomic_inc(&files->count);
801 rc = copy_files(0, current);
803 current->files = files;
807 EXPORT_SYMBOL(unshare_files);
809 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
811 struct sighand_struct *sig;
813 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
814 atomic_inc(¤t->sighand->count);
817 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
818 rcu_assign_pointer(tsk->sighand, sig);
821 atomic_set(&sig->count, 1);
822 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
826 void __cleanup_sighand(struct sighand_struct *sighand)
828 if (atomic_dec_and_test(&sighand->count))
829 kmem_cache_free(sighand_cachep, sighand);
832 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
834 struct signal_struct *sig;
837 if (clone_flags & CLONE_THREAD) {
838 atomic_inc(¤t->signal->count);
839 atomic_inc(¤t->signal->live);
840 taskstats_tgid_alloc(current->signal);
843 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
848 ret = copy_thread_group_keys(tsk);
850 kmem_cache_free(signal_cachep, sig);
854 atomic_set(&sig->count, 1);
855 atomic_set(&sig->live, 1);
856 init_waitqueue_head(&sig->wait_chldexit);
858 sig->group_exit_code = 0;
859 sig->group_exit_task = NULL;
860 sig->group_stop_count = 0;
861 sig->curr_target = NULL;
862 init_sigpending(&sig->shared_pending);
863 INIT_LIST_HEAD(&sig->posix_timers);
865 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
866 sig->it_real_incr.tv64 = 0;
867 sig->real_timer.function = it_real_fn;
870 sig->it_virt_expires = cputime_zero;
871 sig->it_virt_incr = cputime_zero;
872 sig->it_prof_expires = cputime_zero;
873 sig->it_prof_incr = cputime_zero;
875 sig->leader = 0; /* session leadership doesn't inherit */
876 sig->tty_old_pgrp = 0;
878 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
879 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
880 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
882 INIT_LIST_HEAD(&sig->cpu_timers[0]);
883 INIT_LIST_HEAD(&sig->cpu_timers[1]);
884 INIT_LIST_HEAD(&sig->cpu_timers[2]);
885 taskstats_tgid_init(sig);
887 task_lock(current->group_leader);
888 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
889 task_unlock(current->group_leader);
891 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
893 * New sole thread in the process gets an expiry time
894 * of the whole CPU time limit.
896 tsk->it_prof_expires =
897 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
899 acct_init_pacct(&sig->pacct);
904 void __cleanup_signal(struct signal_struct *sig)
906 exit_thread_group_keys(sig);
907 taskstats_tgid_free(sig);
908 kmem_cache_free(signal_cachep, sig);
911 static inline void cleanup_signal(struct task_struct *tsk)
913 struct signal_struct *sig = tsk->signal;
915 atomic_dec(&sig->live);
917 if (atomic_dec_and_test(&sig->count))
918 __cleanup_signal(sig);
921 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
923 unsigned long new_flags = p->flags;
925 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
926 new_flags |= PF_FORKNOEXEC;
927 new_flags |= PF_STARTING;
928 p->flags = new_flags;
931 asmlinkage long sys_set_tid_address(int __user *tidptr)
933 current->clear_child_tid = tidptr;
938 static inline void rt_mutex_init_task(struct task_struct *p)
940 #ifdef CONFIG_RT_MUTEXES
941 spin_lock_init(&p->pi_lock);
942 plist_head_init(&p->pi_waiters, &p->pi_lock);
943 p->pi_blocked_on = NULL;
948 * This creates a new process as a copy of the old one,
949 * but does not actually start it yet.
951 * It copies the registers, and all the appropriate
952 * parts of the process environment (as per the clone
953 * flags). The actual kick-off is left to the caller.
955 static struct task_struct *copy_process(unsigned long clone_flags,
956 unsigned long stack_start,
957 struct pt_regs *regs,
958 unsigned long stack_size,
959 int __user *parent_tidptr,
960 int __user *child_tidptr,
964 struct task_struct *p = NULL;
968 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
969 return ERR_PTR(-EINVAL);
972 * Thread groups must share signals as well, and detached threads
973 * can only be started up within the thread group.
975 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
976 return ERR_PTR(-EINVAL);
979 * Shared signal handlers imply shared VM. By way of the above,
980 * thread groups also imply shared VM. Blocking this case allows
981 * for various simplifications in other code.
983 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
984 return ERR_PTR(-EINVAL);
986 retval = security_task_create(clone_flags);
991 p = dup_task_struct(current);
995 rt_mutex_init_task(p);
999 #ifdef CONFIG_TRACE_IRQFLAGS
1000 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1001 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1003 init_vx_info(&p->vx_info, current->vx_info);
1004 init_nx_info(&p->nx_info, current->nx_info);
1006 /* check vserver memory */
1007 if (p->mm && !(clone_flags & CLONE_VM)) {
1008 if (vx_vmpages_avail(p->mm, p->mm->total_vm))
1009 vx_pages_add(p->vx_info, RLIMIT_AS, p->mm->total_vm);
1013 if (p->mm && vx_flags(VXF_FORK_RSS, 0)) {
1014 if (!vx_rsspages_avail(p->mm, get_mm_counter(p->mm, file_rss)))
1015 goto bad_fork_cleanup_vm;
1019 if (!vx_nproc_avail(1))
1020 goto bad_fork_cleanup_vm;
1022 if (atomic_read(&p->user->processes) >=
1023 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1024 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1025 p->user != &root_user)
1026 goto bad_fork_cleanup_vm;
1029 atomic_inc(&p->user->__count);
1030 atomic_inc(&p->user->processes);
1031 get_group_info(p->group_info);
1034 * If multiple threads are within copy_process(), then this check
1035 * triggers too late. This doesn't hurt, the check is only there
1036 * to stop root fork bombs.
1038 if (nr_threads >= max_threads)
1039 goto bad_fork_cleanup_count;
1041 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1042 goto bad_fork_cleanup_count;
1044 if (p->binfmt && !try_module_get(p->binfmt->module))
1045 goto bad_fork_cleanup_put_domain;
1048 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1049 copy_flags(clone_flags, p);
1052 if (clone_flags & CLONE_PARENT_SETTID)
1053 if (put_user(p->pid, parent_tidptr))
1054 goto bad_fork_cleanup_delays_binfmt;
1056 INIT_LIST_HEAD(&p->children);
1057 INIT_LIST_HEAD(&p->sibling);
1058 p->vfork_done = NULL;
1059 spin_lock_init(&p->alloc_lock);
1060 #ifdef CONFIG_PTRACE
1061 INIT_LIST_HEAD(&p->ptracees);
1064 clear_tsk_thread_flag(p, TIF_SIGPENDING);
1065 init_sigpending(&p->pending);
1067 p->utime = cputime_zero;
1068 p->stime = cputime_zero;
1070 p->rchar = 0; /* I/O counter: bytes read */
1071 p->wchar = 0; /* I/O counter: bytes written */
1072 p->syscr = 0; /* I/O counter: read syscalls */
1073 p->syscw = 0; /* I/O counter: write syscalls */
1074 acct_clear_integrals(p);
1076 p->it_virt_expires = cputime_zero;
1077 p->it_prof_expires = cputime_zero;
1078 p->it_sched_expires = 0;
1079 INIT_LIST_HEAD(&p->cpu_timers[0]);
1080 INIT_LIST_HEAD(&p->cpu_timers[1]);
1081 INIT_LIST_HEAD(&p->cpu_timers[2]);
1083 p->lock_depth = -1; /* -1 = no lock */
1084 do_posix_clock_monotonic_gettime(&p->start_time);
1086 p->io_context = NULL;
1088 p->audit_context = NULL;
1091 p->mempolicy = mpol_copy(p->mempolicy);
1092 if (IS_ERR(p->mempolicy)) {
1093 retval = PTR_ERR(p->mempolicy);
1094 p->mempolicy = NULL;
1095 goto bad_fork_cleanup_cpuset;
1097 mpol_fix_fork_child_flag(p);
1099 #ifdef CONFIG_TRACE_IRQFLAGS
1101 p->hardirqs_enabled = 0;
1102 p->hardirq_enable_ip = 0;
1103 p->hardirq_enable_event = 0;
1104 p->hardirq_disable_ip = _THIS_IP_;
1105 p->hardirq_disable_event = 0;
1106 p->softirqs_enabled = 1;
1107 p->softirq_enable_ip = _THIS_IP_;
1108 p->softirq_enable_event = 0;
1109 p->softirq_disable_ip = 0;
1110 p->softirq_disable_event = 0;
1111 p->hardirq_context = 0;
1112 p->softirq_context = 0;
1114 #ifdef CONFIG_LOCKDEP
1115 p->lockdep_depth = 0; /* no locks held yet */
1116 p->curr_chain_key = 0;
1117 p->lockdep_recursion = 0;
1120 #ifdef CONFIG_DEBUG_MUTEXES
1121 p->blocked_on = NULL; /* not blocked yet */
1125 if (clone_flags & CLONE_THREAD)
1126 p->tgid = current->tgid;
1128 if ((retval = security_task_alloc(p)))
1129 goto bad_fork_cleanup_policy;
1130 if ((retval = audit_alloc(p)))
1131 goto bad_fork_cleanup_security;
1132 /* copy all the process information */
1133 if ((retval = copy_semundo(clone_flags, p)))
1134 goto bad_fork_cleanup_audit;
1135 if ((retval = copy_files(clone_flags, p)))
1136 goto bad_fork_cleanup_semundo;
1137 if ((retval = copy_fs(clone_flags, p)))
1138 goto bad_fork_cleanup_files;
1139 if ((retval = copy_sighand(clone_flags, p)))
1140 goto bad_fork_cleanup_fs;
1141 if ((retval = copy_signal(clone_flags, p)))
1142 goto bad_fork_cleanup_sighand;
1143 if ((retval = copy_mm(clone_flags, p)))
1144 goto bad_fork_cleanup_signal;
1145 if ((retval = copy_keys(clone_flags, p)))
1146 goto bad_fork_cleanup_mm;
1147 if ((retval = copy_namespace(clone_flags, p)))
1148 goto bad_fork_cleanup_keys;
1149 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1151 goto bad_fork_cleanup_namespace;
1153 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1155 * Clear TID on mm_release()?
1157 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1158 p->robust_list = NULL;
1159 #ifdef CONFIG_COMPAT
1160 p->compat_robust_list = NULL;
1162 INIT_LIST_HEAD(&p->pi_state_list);
1163 p->pi_state_cache = NULL;
1166 * sigaltstack should be cleared when sharing the same VM
1168 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1169 p->sas_ss_sp = p->sas_ss_size = 0;
1172 * Syscall tracing should be turned off in the child regardless
1175 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1176 #ifdef TIF_SYSCALL_EMU
1177 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1180 /* Our parent execution domain becomes current domain
1181 These must match for thread signalling to apply */
1183 p->parent_exec_id = p->self_exec_id;
1185 /* ok, now we should be set up.. */
1186 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1187 p->pdeath_signal = 0;
1191 * Ok, make it visible to the rest of the system.
1192 * We dont wake it up yet.
1194 p->group_leader = p;
1195 INIT_LIST_HEAD(&p->thread_group);
1197 /* Perform scheduler related setup. Assign this task to a CPU. */
1198 sched_fork(p, clone_flags);
1200 /* Need tasklist lock for parent etc handling! */
1201 write_lock_irq(&tasklist_lock);
1204 * The task hasn't been attached yet, so its cpus_allowed mask will
1205 * not be changed, nor will its assigned CPU.
1207 * The cpus_allowed mask of the parent may have changed after it was
1208 * copied first time - so re-copy it here, then check the child's CPU
1209 * to ensure it is on a valid CPU (and if not, just force it back to
1210 * parent's CPU). This avoids alot of nasty races.
1212 p->cpus_allowed = current->cpus_allowed;
1213 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1214 !cpu_online(task_cpu(p))))
1215 set_task_cpu(p, smp_processor_id());
1217 /* CLONE_PARENT re-uses the old parent */
1218 if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1219 p->parent = current->parent;
1221 p->parent = current;
1223 spin_lock(¤t->sighand->siglock);
1226 * Process group and session signals need to be delivered to just the
1227 * parent before the fork or both the parent and the child after the
1228 * fork. Restart if a signal comes in before we add the new process to
1229 * it's process group.
1230 * A fatal signal pending means that current will exit, so the new
1231 * thread can't slip out of an OOM kill (or normal SIGKILL).
1233 recalc_sigpending();
1234 if (signal_pending(current)) {
1235 spin_unlock(¤t->sighand->siglock);
1236 write_unlock_irq(&tasklist_lock);
1237 retval = -ERESTARTNOINTR;
1238 goto bad_fork_cleanup_namespace;
1241 if (clone_flags & CLONE_THREAD) {
1242 p->group_leader = current->group_leader;
1243 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1245 if (!cputime_eq(current->signal->it_virt_expires,
1247 !cputime_eq(current->signal->it_prof_expires,
1249 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1250 !list_empty(¤t->signal->cpu_timers[0]) ||
1251 !list_empty(¤t->signal->cpu_timers[1]) ||
1252 !list_empty(¤t->signal->cpu_timers[2])) {
1254 * Have child wake up on its first tick to check
1255 * for process CPU timers.
1257 p->it_prof_expires = jiffies_to_cputime(1);
1264 p->ioprio = current->ioprio;
1266 if (likely(p->pid)) {
1268 tracehook_init_task(p);
1270 if (thread_group_leader(p)) {
1271 p->signal->tty = current->signal->tty;
1272 p->signal->pgrp = process_group(current);
1273 p->signal->session = current->signal->session;
1274 attach_pid(p, PIDTYPE_PGID, process_group(p));
1275 attach_pid(p, PIDTYPE_SID, p->signal->session);
1277 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1278 __get_cpu_var(process_counts)++;
1280 attach_pid(p, PIDTYPE_PID, p->pid);
1285 spin_unlock(¤t->sighand->siglock);
1287 /* p is copy of current */
1290 claim_vx_info(vxi, p);
1291 atomic_inc(&vxi->cvirt.nr_threads);
1292 atomic_inc(&vxi->cvirt.total_forks);
1297 claim_nx_info(nxi, p);
1298 write_unlock_irq(&tasklist_lock);
1299 proc_fork_connector(p);
1302 bad_fork_cleanup_namespace:
1304 bad_fork_cleanup_keys:
1306 bad_fork_cleanup_mm:
1309 bad_fork_cleanup_signal:
1311 bad_fork_cleanup_sighand:
1312 __cleanup_sighand(p->sighand);
1313 bad_fork_cleanup_fs:
1314 exit_fs(p); /* blocking */
1315 bad_fork_cleanup_files:
1316 exit_files(p); /* blocking */
1317 bad_fork_cleanup_semundo:
1319 bad_fork_cleanup_audit:
1321 bad_fork_cleanup_security:
1322 security_task_free(p);
1323 bad_fork_cleanup_policy:
1325 mpol_free(p->mempolicy);
1326 bad_fork_cleanup_cpuset:
1329 bad_fork_cleanup_delays_binfmt:
1330 delayacct_tsk_free(p);
1332 module_put(p->binfmt->module);
1333 bad_fork_cleanup_put_domain:
1334 module_put(task_thread_info(p)->exec_domain->module);
1335 bad_fork_cleanup_count:
1336 put_group_info(p->group_info);
1337 atomic_dec(&p->user->processes);
1339 bad_fork_cleanup_vm:
1340 if (p->mm && !(clone_flags & CLONE_VM))
1341 vx_pages_sub(p->vx_info, RLIMIT_AS, p->mm->total_vm);
1345 return ERR_PTR(retval);
1348 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1350 memset(regs, 0, sizeof(struct pt_regs));
1354 struct task_struct * __devinit fork_idle(int cpu)
1356 struct task_struct *task;
1357 struct pt_regs regs;
1359 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0);
1361 return ERR_PTR(-ENOMEM);
1362 init_idle(task, cpu);
1368 * Ok, this is the main fork-routine.
1370 * It copies the process, and if successful kick-starts
1371 * it and waits for it to finish using the VM if required.
1373 long do_fork(unsigned long clone_flags,
1374 unsigned long stack_start,
1375 struct pt_regs *regs,
1376 unsigned long stack_size,
1377 int __user *parent_tidptr,
1378 int __user *child_tidptr)
1380 struct task_struct *p;
1381 struct pid *pid = alloc_pid();
1388 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1390 * Do this prior waking up the new thread - the thread pointer
1391 * might get invalid after that point, if the thread exits quickly.
1394 struct completion vfork;
1396 if (clone_flags & CLONE_VFORK) {
1397 p->vfork_done = &vfork;
1398 init_completion(&vfork);
1401 tracehook_report_clone(clone_flags, p);
1403 p->flags &= ~PF_STARTING;
1405 if (clone_flags & CLONE_STOPPED) {
1407 * We'll start up with an immediate SIGSTOP.
1409 sigaddset(&p->pending.signal, SIGSTOP);
1410 set_tsk_thread_flag(p, TIF_SIGPENDING);
1411 p->state = TASK_STOPPED;
1414 wake_up_new_task(p, clone_flags);
1416 tracehook_report_clone_complete(clone_flags, nr, p);
1418 if (clone_flags & CLONE_VFORK) {
1419 wait_for_completion(&vfork);
1420 tracehook_report_vfork_done(p, nr);
1429 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1430 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1433 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1435 struct sighand_struct *sighand = data;
1437 if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1438 SLAB_CTOR_CONSTRUCTOR)
1439 spin_lock_init(&sighand->siglock);
1442 void __init proc_caches_init(void)
1444 sighand_cachep = kmem_cache_create("sighand_cache",
1445 sizeof(struct sighand_struct), 0,
1446 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1447 sighand_ctor, NULL);
1448 signal_cachep = kmem_cache_create("signal_cache",
1449 sizeof(struct signal_struct), 0,
1450 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1451 files_cachep = kmem_cache_create("files_cache",
1452 sizeof(struct files_struct), 0,
1453 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1454 fs_cachep = kmem_cache_create("fs_cache",
1455 sizeof(struct fs_struct), 0,
1456 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1457 vm_area_cachep = kmem_cache_create("vm_area_struct",
1458 sizeof(struct vm_area_struct), 0,
1459 SLAB_PANIC, NULL, NULL);
1460 mm_cachep = kmem_cache_create("mm_struct",
1461 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1462 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1467 * Check constraints on flags passed to the unshare system call and
1468 * force unsharing of additional process context as appropriate.
1470 static inline void check_unshare_flags(unsigned long *flags_ptr)
1473 * If unsharing a thread from a thread group, must also
1476 if (*flags_ptr & CLONE_THREAD)
1477 *flags_ptr |= CLONE_VM;
1480 * If unsharing vm, must also unshare signal handlers.
1482 if (*flags_ptr & CLONE_VM)
1483 *flags_ptr |= CLONE_SIGHAND;
1486 * If unsharing signal handlers and the task was created
1487 * using CLONE_THREAD, then must unshare the thread
1489 if ((*flags_ptr & CLONE_SIGHAND) &&
1490 (atomic_read(¤t->signal->count) > 1))
1491 *flags_ptr |= CLONE_THREAD;
1494 * If unsharing namespace, must also unshare filesystem information.
1496 if (*flags_ptr & CLONE_NEWNS)
1497 *flags_ptr |= CLONE_FS;
1501 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1503 static int unshare_thread(unsigned long unshare_flags)
1505 if (unshare_flags & CLONE_THREAD)
1512 * Unshare the filesystem structure if it is being shared
1514 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1516 struct fs_struct *fs = current->fs;
1518 if ((unshare_flags & CLONE_FS) &&
1519 (fs && atomic_read(&fs->count) > 1)) {
1520 *new_fsp = __copy_fs_struct(current->fs);
1529 * Unshare the namespace structure if it is being shared
1531 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1533 struct namespace *ns = current->namespace;
1535 if ((unshare_flags & CLONE_NEWNS) &&
1536 (ns && atomic_read(&ns->count) > 1)) {
1537 if (!capable(CAP_SYS_ADMIN))
1540 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1549 * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1552 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1554 struct sighand_struct *sigh = current->sighand;
1556 if ((unshare_flags & CLONE_SIGHAND) &&
1557 (sigh && atomic_read(&sigh->count) > 1))
1564 * Unshare vm if it is being shared
1566 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1568 struct mm_struct *mm = current->mm;
1570 if ((unshare_flags & CLONE_VM) &&
1571 (mm && atomic_read(&mm->mm_users) > 1)) {
1579 * Unshare file descriptor table if it is being shared
1581 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1583 struct files_struct *fd = current->files;
1586 if ((unshare_flags & CLONE_FILES) &&
1587 (fd && atomic_read(&fd->count) > 1)) {
1588 *new_fdp = dup_fd(fd, &error);
1597 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1600 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1602 if (unshare_flags & CLONE_SYSVSEM)
1609 * unshare allows a process to 'unshare' part of the process
1610 * context which was originally shared using clone. copy_*
1611 * functions used by do_fork() cannot be used here directly
1612 * because they modify an inactive task_struct that is being
1613 * constructed. Here we are modifying the current, active,
1616 asmlinkage long sys_unshare(unsigned long unshare_flags)
1619 struct fs_struct *fs, *new_fs = NULL;
1620 struct namespace *ns, *new_ns = NULL;
1621 struct sighand_struct *sigh, *new_sigh = NULL;
1622 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1623 struct files_struct *fd, *new_fd = NULL;
1624 struct sem_undo_list *new_ulist = NULL;
1626 check_unshare_flags(&unshare_flags);
1628 /* Return -EINVAL for all unsupported flags */
1630 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1631 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
1632 goto bad_unshare_out;
1634 if ((err = unshare_thread(unshare_flags)))
1635 goto bad_unshare_out;
1636 if ((err = unshare_fs(unshare_flags, &new_fs)))
1637 goto bad_unshare_cleanup_thread;
1638 if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1639 goto bad_unshare_cleanup_fs;
1640 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1641 goto bad_unshare_cleanup_ns;
1642 if ((err = unshare_vm(unshare_flags, &new_mm)))
1643 goto bad_unshare_cleanup_sigh;
1644 if ((err = unshare_fd(unshare_flags, &new_fd)))
1645 goto bad_unshare_cleanup_vm;
1646 if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1647 goto bad_unshare_cleanup_fd;
1649 if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1655 current->fs = new_fs;
1660 ns = current->namespace;
1661 current->namespace = new_ns;
1666 sigh = current->sighand;
1667 rcu_assign_pointer(current->sighand, new_sigh);
1673 active_mm = current->active_mm;
1674 current->mm = new_mm;
1675 current->active_mm = new_mm;
1676 activate_mm(active_mm, new_mm);
1681 fd = current->files;
1682 current->files = new_fd;
1686 task_unlock(current);
1689 bad_unshare_cleanup_fd:
1691 put_files_struct(new_fd);
1693 bad_unshare_cleanup_vm:
1697 bad_unshare_cleanup_sigh:
1699 if (atomic_dec_and_test(&new_sigh->count))
1700 kmem_cache_free(sighand_cachep, new_sigh);
1702 bad_unshare_cleanup_ns:
1704 put_namespace(new_ns);
1706 bad_unshare_cleanup_fs:
1708 put_fs_struct(new_fs);
1710 bad_unshare_cleanup_thread: