On Tue, Nov 06, 2007 at 02:33:53AM -0800, akpm@linux-foundation.org wrote:
[mmotm.git] / kernel / fork.c
blobe631d1599d43f3545811ccc41f234b476a71dcf2
1 /*
2 * linux/kernel/fork.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
7 /*
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/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/personality.h>
21 #include <linux/mempolicy.h>
22 #include <linux/sem.h>
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/iocontext.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
29 #include <linux/mmu_notifier.h>
30 #include <linux/fs.h>
31 #include <linux/nsproxy.h>
32 #include <linux/capability.h>
33 #include <linux/cpu.h>
34 #include <linux/cgroup.h>
35 #include <linux/security.h>
36 #include <linux/hugetlb.h>
37 #include <linux/swap.h>
38 #include <linux/syscalls.h>
39 #include <linux/jiffies.h>
40 #include <linux/tracehook.h>
41 #include <linux/futex.h>
42 #include <linux/compat.h>
43 #include <linux/task_io_accounting_ops.h>
44 #include <linux/rcupdate.h>
45 #include <linux/ptrace.h>
46 #include <linux/mount.h>
47 #include <linux/audit.h>
48 #include <linux/memcontrol.h>
49 #include <linux/ftrace.h>
50 #include <linux/profile.h>
51 #include <linux/rmap.h>
52 #include <linux/ksm.h>
53 #include <linux/acct.h>
54 #include <linux/tsacct_kern.h>
55 #include <linux/cn_proc.h>
56 #include <linux/freezer.h>
57 #include <linux/delayacct.h>
58 #include <linux/taskstats_kern.h>
59 #include <linux/random.h>
60 #include <linux/tty.h>
61 #include <linux/proc_fs.h>
62 #include <linux/blkdev.h>
63 #include <linux/fs_struct.h>
64 #include <linux/magic.h>
65 #include <linux/perf_event.h>
66 #include <linux/posix-timers.h>
68 #include <asm/pgtable.h>
69 #include <asm/pgalloc.h>
70 #include <asm/uaccess.h>
71 #include <asm/mmu_context.h>
72 #include <asm/cacheflush.h>
73 #include <asm/tlbflush.h>
75 #include <trace/events/sched.h>
78 * Protected counters by write_lock_irq(&tasklist_lock)
80 unsigned long total_forks; /* Handle normal Linux uptimes. */
81 int nr_threads; /* The idle threads do not count.. */
83 int max_threads; /* tunable limit on nr_threads */
85 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
87 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
89 int nr_processes(void)
91 int cpu;
92 int total = 0;
94 for_each_online_cpu(cpu)
95 total += per_cpu(process_counts, cpu);
97 return total;
100 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
101 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
102 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
103 static struct kmem_cache *task_struct_cachep;
104 #endif
106 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
107 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
109 #ifdef CONFIG_DEBUG_STACK_USAGE
110 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
111 #else
112 gfp_t mask = GFP_KERNEL;
113 #endif
114 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
117 static inline void free_thread_info(struct thread_info *ti)
119 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
121 #endif
123 /* SLAB cache for signal_struct structures (tsk->signal) */
124 static struct kmem_cache *signal_cachep;
126 /* SLAB cache for sighand_struct structures (tsk->sighand) */
127 struct kmem_cache *sighand_cachep;
129 /* SLAB cache for files_struct structures (tsk->files) */
130 struct kmem_cache *files_cachep;
132 /* SLAB cache for fs_struct structures (tsk->fs) */
133 struct kmem_cache *fs_cachep;
135 /* SLAB cache for vm_area_struct structures */
136 struct kmem_cache *vm_area_cachep;
138 /* SLAB cache for mm_struct structures (tsk->mm) */
139 static struct kmem_cache *mm_cachep;
141 static void account_kernel_stack(struct thread_info *ti, int account)
143 struct zone *zone = page_zone(virt_to_page(ti));
145 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
148 void free_task(struct task_struct *tsk)
150 prop_local_destroy_single(&tsk->dirties);
151 account_kernel_stack(tsk->stack, -1);
152 free_thread_info(tsk->stack);
153 rt_mutex_debug_task_free(tsk);
154 ftrace_graph_exit_task(tsk);
155 free_task_struct(tsk);
157 EXPORT_SYMBOL(free_task);
159 void __put_task_struct(struct task_struct *tsk)
161 WARN_ON(!tsk->exit_state);
162 WARN_ON(atomic_read(&tsk->usage));
163 WARN_ON(tsk == current);
165 exit_creds(tsk);
166 delayacct_tsk_free(tsk);
168 if (!profile_handoff_task(tsk))
169 free_task(tsk);
173 * macro override instead of weak attribute alias, to workaround
174 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
176 #ifndef arch_task_cache_init
177 #define arch_task_cache_init()
178 #endif
180 void __init fork_init(unsigned long mempages)
182 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
183 #ifndef ARCH_MIN_TASKALIGN
184 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
185 #endif
186 /* create a slab on which task_structs can be allocated */
187 task_struct_cachep =
188 kmem_cache_create("task_struct", sizeof(struct task_struct),
189 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
190 #endif
192 /* do the arch specific task caches init */
193 arch_task_cache_init();
196 * The default maximum number of threads is set to a safe
197 * value: the thread structures can take up at most half
198 * of memory.
200 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
203 * we need to allow at least 20 threads to boot a system
205 if(max_threads < 20)
206 max_threads = 20;
208 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
209 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
210 init_task.signal->rlim[RLIMIT_SIGPENDING] =
211 init_task.signal->rlim[RLIMIT_NPROC];
214 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
215 struct task_struct *src)
217 *dst = *src;
218 return 0;
221 static struct task_struct *dup_task_struct(struct task_struct *orig)
223 struct task_struct *tsk;
224 struct thread_info *ti;
225 unsigned long *stackend;
227 int err;
229 prepare_to_copy(orig);
231 tsk = alloc_task_struct();
232 if (!tsk)
233 return NULL;
235 ti = alloc_thread_info(tsk);
236 if (!ti) {
237 free_task_struct(tsk);
238 return NULL;
241 err = arch_dup_task_struct(tsk, orig);
242 if (err)
243 goto out;
245 tsk->stack = ti;
247 err = prop_local_init_single(&tsk->dirties);
248 if (err)
249 goto out;
251 setup_thread_stack(tsk, orig);
252 stackend = end_of_stack(tsk);
253 *stackend = STACK_END_MAGIC; /* for overflow detection */
255 #ifdef CONFIG_CC_STACKPROTECTOR
256 tsk->stack_canary = get_random_int();
257 #endif
259 /* One for us, one for whoever does the "release_task()" (usually parent) */
260 atomic_set(&tsk->usage,2);
261 atomic_set(&tsk->fs_excl, 0);
262 #ifdef CONFIG_BLK_DEV_IO_TRACE
263 tsk->btrace_seq = 0;
264 #endif
265 tsk->splice_pipe = NULL;
267 account_kernel_stack(ti, 1);
269 return tsk;
271 out:
272 free_thread_info(ti);
273 free_task_struct(tsk);
274 return NULL;
277 #ifdef CONFIG_MMU
278 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
280 struct vm_area_struct *mpnt, *tmp, **pprev;
281 struct rb_node **rb_link, *rb_parent;
282 int retval;
283 unsigned long charge;
284 struct mempolicy *pol;
286 down_write(&oldmm->mmap_sem);
287 flush_cache_dup_mm(oldmm);
289 * Not linked in yet - no deadlock potential:
291 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
293 mm->locked_vm = 0;
294 mm->mmap = NULL;
295 mm->mmap_cache = NULL;
296 mm->free_area_cache = oldmm->mmap_base;
297 mm->cached_hole_size = ~0UL;
298 mm->map_count = 0;
299 cpumask_clear(mm_cpumask(mm));
300 mm->mm_rb = RB_ROOT;
301 rb_link = &mm->mm_rb.rb_node;
302 rb_parent = NULL;
303 pprev = &mm->mmap;
304 retval = ksm_fork(mm, oldmm);
305 if (retval)
306 goto out;
308 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
309 struct file *file;
311 if (mpnt->vm_flags & VM_DONTCOPY) {
312 long pages = vma_pages(mpnt);
313 mm->total_vm -= pages;
314 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
315 -pages);
316 continue;
318 charge = 0;
319 if (mpnt->vm_flags & VM_ACCOUNT) {
320 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
321 if (security_vm_enough_memory(len))
322 goto fail_nomem;
323 charge = len;
325 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
326 if (!tmp)
327 goto fail_nomem;
328 *tmp = *mpnt;
329 pol = mpol_dup(vma_policy(mpnt));
330 retval = PTR_ERR(pol);
331 if (IS_ERR(pol))
332 goto fail_nomem_policy;
333 vma_set_policy(tmp, pol);
334 tmp->vm_flags &= ~VM_LOCKED;
335 tmp->vm_mm = mm;
336 tmp->vm_next = NULL;
337 anon_vma_link(tmp);
338 file = tmp->vm_file;
339 if (file) {
340 struct inode *inode = file->f_path.dentry->d_inode;
341 struct address_space *mapping = file->f_mapping;
343 get_file(file);
344 if (tmp->vm_flags & VM_DENYWRITE)
345 atomic_dec(&inode->i_writecount);
346 spin_lock(&mapping->i_mmap_lock);
347 if (tmp->vm_flags & VM_SHARED)
348 mapping->i_mmap_writable++;
349 tmp->vm_truncate_count = mpnt->vm_truncate_count;
350 flush_dcache_mmap_lock(mapping);
351 /* insert tmp into the share list, just after mpnt */
352 vma_prio_tree_add(tmp, mpnt);
353 flush_dcache_mmap_unlock(mapping);
354 spin_unlock(&mapping->i_mmap_lock);
358 * Clear hugetlb-related page reserves for children. This only
359 * affects MAP_PRIVATE mappings. Faults generated by the child
360 * are not guaranteed to succeed, even if read-only
362 if (is_vm_hugetlb_page(tmp))
363 reset_vma_resv_huge_pages(tmp);
366 * Link in the new vma and copy the page table entries.
368 *pprev = tmp;
369 pprev = &tmp->vm_next;
371 __vma_link_rb(mm, tmp, rb_link, rb_parent);
372 rb_link = &tmp->vm_rb.rb_right;
373 rb_parent = &tmp->vm_rb;
375 mm->map_count++;
376 retval = copy_page_range(mm, oldmm, mpnt);
378 if (tmp->vm_ops && tmp->vm_ops->open)
379 tmp->vm_ops->open(tmp);
381 if (retval)
382 goto out;
384 /* a new mm has just been created */
385 arch_dup_mmap(oldmm, mm);
386 retval = 0;
387 out:
388 up_write(&mm->mmap_sem);
389 flush_tlb_mm(oldmm);
390 up_write(&oldmm->mmap_sem);
391 return retval;
392 fail_nomem_policy:
393 kmem_cache_free(vm_area_cachep, tmp);
394 fail_nomem:
395 retval = -ENOMEM;
396 vm_unacct_memory(charge);
397 goto out;
400 static inline int mm_alloc_pgd(struct mm_struct * mm)
402 mm->pgd = pgd_alloc(mm);
403 if (unlikely(!mm->pgd))
404 return -ENOMEM;
405 return 0;
408 static inline void mm_free_pgd(struct mm_struct * mm)
410 pgd_free(mm, mm->pgd);
412 #else
413 #define dup_mmap(mm, oldmm) (0)
414 #define mm_alloc_pgd(mm) (0)
415 #define mm_free_pgd(mm)
416 #endif /* CONFIG_MMU */
418 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
420 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
421 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
423 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
425 static int __init coredump_filter_setup(char *s)
427 default_dump_filter =
428 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
429 MMF_DUMP_FILTER_MASK;
430 return 1;
433 __setup("coredump_filter=", coredump_filter_setup);
435 #include <linux/init_task.h>
437 static void mm_init_aio(struct mm_struct *mm)
439 #ifdef CONFIG_AIO
440 spin_lock_init(&mm->ioctx_lock);
441 INIT_HLIST_HEAD(&mm->ioctx_list);
442 #endif
445 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
447 atomic_set(&mm->mm_users, 1);
448 atomic_set(&mm->mm_count, 1);
449 init_rwsem(&mm->mmap_sem);
450 INIT_LIST_HEAD(&mm->mmlist);
451 mm->flags = (current->mm) ?
452 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
453 mm->core_state = NULL;
454 mm->nr_ptes = 0;
455 set_mm_counter(mm, file_rss, 0);
456 set_mm_counter(mm, anon_rss, 0);
457 spin_lock_init(&mm->page_table_lock);
458 mm->free_area_cache = TASK_UNMAPPED_BASE;
459 mm->cached_hole_size = ~0UL;
460 mm_init_aio(mm);
461 mm_init_owner(mm, p);
463 if (likely(!mm_alloc_pgd(mm))) {
464 mm->def_flags = 0;
465 mmu_notifier_mm_init(mm);
466 return mm;
469 free_mm(mm);
470 return NULL;
474 * Allocate and initialize an mm_struct.
476 struct mm_struct * mm_alloc(void)
478 struct mm_struct * mm;
480 mm = allocate_mm();
481 if (mm) {
482 memset(mm, 0, sizeof(*mm));
483 mm = mm_init(mm, current);
485 return mm;
489 * Called when the last reference to the mm
490 * is dropped: either by a lazy thread or by
491 * mmput. Free the page directory and the mm.
493 void __mmdrop(struct mm_struct *mm)
495 BUG_ON(mm == &init_mm);
496 mm_free_pgd(mm);
497 destroy_context(mm);
498 mmu_notifier_mm_destroy(mm);
499 free_mm(mm);
501 EXPORT_SYMBOL_GPL(__mmdrop);
504 * Decrement the use count and release all resources for an mm.
506 void mmput(struct mm_struct *mm)
508 might_sleep();
510 if (atomic_dec_and_test(&mm->mm_users)) {
511 exit_aio(mm);
512 ksm_exit(mm);
513 exit_mmap(mm);
514 set_mm_exe_file(mm, NULL);
515 if (!list_empty(&mm->mmlist)) {
516 spin_lock(&mmlist_lock);
517 list_del(&mm->mmlist);
518 spin_unlock(&mmlist_lock);
520 put_swap_token(mm);
521 if (mm->binfmt)
522 module_put(mm->binfmt->module);
523 mmdrop(mm);
526 EXPORT_SYMBOL_GPL(mmput);
529 * get_task_mm - acquire a reference to the task's mm
531 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
532 * this kernel workthread has transiently adopted a user mm with use_mm,
533 * to do its AIO) is not set and if so returns a reference to it, after
534 * bumping up the use count. User must release the mm via mmput()
535 * after use. Typically used by /proc and ptrace.
537 struct mm_struct *get_task_mm(struct task_struct *task)
539 struct mm_struct *mm;
541 task_lock(task);
542 mm = task->mm;
543 if (mm) {
544 if (task->flags & PF_KTHREAD)
545 mm = NULL;
546 else
547 atomic_inc(&mm->mm_users);
549 task_unlock(task);
550 return mm;
552 EXPORT_SYMBOL_GPL(get_task_mm);
554 /* Please note the differences between mmput and mm_release.
555 * mmput is called whenever we stop holding onto a mm_struct,
556 * error success whatever.
558 * mm_release is called after a mm_struct has been removed
559 * from the current process.
561 * This difference is important for error handling, when we
562 * only half set up a mm_struct for a new process and need to restore
563 * the old one. Because we mmput the new mm_struct before
564 * restoring the old one. . .
565 * Eric Biederman 10 January 1998
567 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
569 struct completion *vfork_done = tsk->vfork_done;
571 /* Get rid of any futexes when releasing the mm */
572 #ifdef CONFIG_FUTEX
573 if (unlikely(tsk->robust_list)) {
574 exit_robust_list(tsk);
575 tsk->robust_list = NULL;
577 #ifdef CONFIG_COMPAT
578 if (unlikely(tsk->compat_robust_list)) {
579 compat_exit_robust_list(tsk);
580 tsk->compat_robust_list = NULL;
582 #endif
583 if (unlikely(!list_empty(&tsk->pi_state_list)))
584 exit_pi_state_list(tsk);
585 #endif
587 /* Get rid of any cached register state */
588 deactivate_mm(tsk, mm);
590 /* notify parent sleeping on vfork() */
591 if (vfork_done) {
592 tsk->vfork_done = NULL;
593 complete(vfork_done);
597 * If we're exiting normally, clear a user-space tid field if
598 * requested. We leave this alone when dying by signal, to leave
599 * the value intact in a core dump, and to save the unnecessary
600 * trouble otherwise. Userland only wants this done for a sys_exit.
602 if (tsk->clear_child_tid) {
603 if (!(tsk->flags & PF_SIGNALED) &&
604 atomic_read(&mm->mm_users) > 1) {
606 * We don't check the error code - if userspace has
607 * not set up a proper pointer then tough luck.
609 put_user(0, tsk->clear_child_tid);
610 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
611 1, NULL, NULL, 0);
613 tsk->clear_child_tid = NULL;
618 * Allocate a new mm structure and copy contents from the
619 * mm structure of the passed in task structure.
621 struct mm_struct *dup_mm(struct task_struct *tsk)
623 struct mm_struct *mm, *oldmm = current->mm;
624 int err;
626 if (!oldmm)
627 return NULL;
629 mm = allocate_mm();
630 if (!mm)
631 goto fail_nomem;
633 memcpy(mm, oldmm, sizeof(*mm));
635 /* Initializing for Swap token stuff */
636 mm->token_priority = 0;
637 mm->last_interval = 0;
639 if (!mm_init(mm, tsk))
640 goto fail_nomem;
642 if (init_new_context(tsk, mm))
643 goto fail_nocontext;
645 dup_mm_exe_file(oldmm, mm);
647 err = dup_mmap(mm, oldmm);
648 if (err)
649 goto free_pt;
651 mm->hiwater_rss = get_mm_rss(mm);
652 mm->hiwater_vm = mm->total_vm;
654 if (mm->binfmt && !try_module_get(mm->binfmt->module))
655 goto free_pt;
657 return mm;
659 free_pt:
660 /* don't put binfmt in mmput, we haven't got module yet */
661 mm->binfmt = NULL;
662 mmput(mm);
664 fail_nomem:
665 return NULL;
667 fail_nocontext:
669 * If init_new_context() failed, we cannot use mmput() to free the mm
670 * because it calls destroy_context()
672 mm_free_pgd(mm);
673 free_mm(mm);
674 return NULL;
677 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
679 struct mm_struct * mm, *oldmm;
680 int retval;
682 tsk->min_flt = tsk->maj_flt = 0;
683 tsk->nvcsw = tsk->nivcsw = 0;
684 #ifdef CONFIG_DETECT_HUNG_TASK
685 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
686 #endif
688 tsk->mm = NULL;
689 tsk->active_mm = NULL;
692 * Are we cloning a kernel thread?
694 * We need to steal a active VM for that..
696 oldmm = current->mm;
697 if (!oldmm)
698 return 0;
700 if (clone_flags & CLONE_VM) {
701 atomic_inc(&oldmm->mm_users);
702 mm = oldmm;
703 goto good_mm;
706 retval = -ENOMEM;
707 mm = dup_mm(tsk);
708 if (!mm)
709 goto fail_nomem;
711 good_mm:
712 /* Initializing for Swap token stuff */
713 mm->token_priority = 0;
714 mm->last_interval = 0;
716 tsk->mm = mm;
717 tsk->active_mm = mm;
718 return 0;
720 fail_nomem:
721 return retval;
724 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
726 struct fs_struct *fs = current->fs;
727 if (clone_flags & CLONE_FS) {
728 /* tsk->fs is already what we want */
729 write_lock(&fs->lock);
730 if (fs->in_exec) {
731 write_unlock(&fs->lock);
732 return -EAGAIN;
734 fs->users++;
735 write_unlock(&fs->lock);
736 return 0;
738 tsk->fs = copy_fs_struct(fs);
739 if (!tsk->fs)
740 return -ENOMEM;
741 return 0;
744 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
746 struct files_struct *oldf, *newf;
747 int error = 0;
750 * A background process may not have any files ...
752 oldf = current->files;
753 if (!oldf)
754 goto out;
756 if (clone_flags & CLONE_FILES) {
757 atomic_inc(&oldf->count);
758 goto out;
761 newf = dup_fd(oldf, &error);
762 if (!newf)
763 goto out;
765 tsk->files = newf;
766 error = 0;
767 out:
768 return error;
771 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
773 #ifdef CONFIG_BLOCK
774 struct io_context *ioc = current->io_context;
776 if (!ioc)
777 return 0;
779 * Share io context with parent, if CLONE_IO is set
781 if (clone_flags & CLONE_IO) {
782 tsk->io_context = ioc_task_link(ioc);
783 if (unlikely(!tsk->io_context))
784 return -ENOMEM;
785 } else if (ioprio_valid(ioc->ioprio)) {
786 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
787 if (unlikely(!tsk->io_context))
788 return -ENOMEM;
790 tsk->io_context->ioprio = ioc->ioprio;
792 #endif
793 return 0;
796 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
798 struct sighand_struct *sig;
800 if (clone_flags & CLONE_SIGHAND) {
801 atomic_inc(&current->sighand->count);
802 return 0;
804 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
805 rcu_assign_pointer(tsk->sighand, sig);
806 if (!sig)
807 return -ENOMEM;
808 atomic_set(&sig->count, 1);
809 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
810 return 0;
813 void __cleanup_sighand(struct sighand_struct *sighand)
815 if (atomic_dec_and_test(&sighand->count))
816 kmem_cache_free(sighand_cachep, sighand);
821 * Initialize POSIX timer handling for a thread group.
823 static void posix_cpu_timers_init_group(struct signal_struct *sig)
825 /* Thread group counters. */
826 thread_group_cputime_init(sig);
828 /* Expiration times and increments. */
829 sig->it[CPUCLOCK_PROF].expires = cputime_zero;
830 sig->it[CPUCLOCK_PROF].incr = cputime_zero;
831 sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
832 sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
834 /* Cached expiration times. */
835 sig->cputime_expires.prof_exp = cputime_zero;
836 sig->cputime_expires.virt_exp = cputime_zero;
837 sig->cputime_expires.sched_exp = 0;
839 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
840 sig->cputime_expires.prof_exp =
841 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
842 sig->cputimer.running = 1;
845 /* The timer lists. */
846 INIT_LIST_HEAD(&sig->cpu_timers[0]);
847 INIT_LIST_HEAD(&sig->cpu_timers[1]);
848 INIT_LIST_HEAD(&sig->cpu_timers[2]);
851 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
853 struct signal_struct *sig;
855 if (clone_flags & CLONE_THREAD)
856 return 0;
858 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
859 tsk->signal = sig;
860 if (!sig)
861 return -ENOMEM;
863 atomic_set(&sig->count, 1);
864 atomic_set(&sig->live, 1);
865 init_waitqueue_head(&sig->wait_chldexit);
866 sig->flags = 0;
867 if (clone_flags & CLONE_NEWPID)
868 sig->flags |= SIGNAL_UNKILLABLE;
869 sig->group_exit_code = 0;
870 sig->group_exit_task = NULL;
871 sig->group_stop_count = 0;
872 sig->curr_target = tsk;
873 init_sigpending(&sig->shared_pending);
874 INIT_LIST_HEAD(&sig->posix_timers);
876 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
877 sig->it_real_incr.tv64 = 0;
878 sig->real_timer.function = it_real_fn;
880 sig->leader = 0; /* session leadership doesn't inherit */
881 sig->tty_old_pgrp = NULL;
882 sig->tty = NULL;
884 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
885 sig->gtime = cputime_zero;
886 sig->cgtime = cputime_zero;
887 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
888 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
889 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
890 sig->maxrss = sig->cmaxrss = 0;
891 task_io_accounting_init(&sig->ioac);
892 sig->sum_sched_runtime = 0;
893 taskstats_tgid_init(sig);
895 task_lock(current->group_leader);
896 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
897 task_unlock(current->group_leader);
899 posix_cpu_timers_init_group(sig);
901 acct_init_pacct(&sig->pacct);
903 tty_audit_fork(sig);
905 sig->oom_adj = current->signal->oom_adj;
907 return 0;
910 void __cleanup_signal(struct signal_struct *sig)
912 thread_group_cputime_free(sig);
913 tty_kref_put(sig->tty);
914 kmem_cache_free(signal_cachep, sig);
917 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
919 unsigned long new_flags = p->flags;
921 new_flags &= ~PF_SUPERPRIV;
922 new_flags |= PF_FORKNOEXEC;
923 new_flags |= PF_STARTING;
924 p->flags = new_flags;
925 clear_freeze_flag(p);
928 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
930 current->clear_child_tid = tidptr;
932 return task_pid_vnr(current);
935 static void rt_mutex_init_task(struct task_struct *p)
937 spin_lock_init(&p->pi_lock);
938 #ifdef CONFIG_RT_MUTEXES
939 plist_head_init(&p->pi_waiters, &p->pi_lock);
940 p->pi_blocked_on = NULL;
941 #endif
944 #ifdef CONFIG_MM_OWNER
945 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
947 mm->owner = p;
949 #endif /* CONFIG_MM_OWNER */
952 * Initialize POSIX timer handling for a single task.
954 static void posix_cpu_timers_init(struct task_struct *tsk)
956 tsk->cputime_expires.prof_exp = cputime_zero;
957 tsk->cputime_expires.virt_exp = cputime_zero;
958 tsk->cputime_expires.sched_exp = 0;
959 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
960 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
961 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
965 * This creates a new process as a copy of the old one,
966 * but does not actually start it yet.
968 * It copies the registers, and all the appropriate
969 * parts of the process environment (as per the clone
970 * flags). The actual kick-off is left to the caller.
972 static struct task_struct *copy_process(unsigned long clone_flags,
973 unsigned long stack_start,
974 struct pt_regs *regs,
975 unsigned long stack_size,
976 int __user *child_tidptr,
977 struct pid *pid,
978 int trace)
980 int retval;
981 struct task_struct *p;
982 int cgroup_callbacks_done = 0;
984 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
985 return ERR_PTR(-EINVAL);
988 * Thread groups must share signals as well, and detached threads
989 * can only be started up within the thread group.
991 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
992 return ERR_PTR(-EINVAL);
995 * Shared signal handlers imply shared VM. By way of the above,
996 * thread groups also imply shared VM. Blocking this case allows
997 * for various simplifications in other code.
999 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1000 return ERR_PTR(-EINVAL);
1003 * Siblings of global init remain as zombies on exit since they are
1004 * not reaped by their parent (swapper). To solve this and to avoid
1005 * multi-rooted process trees, prevent global and container-inits
1006 * from creating siblings.
1008 if ((clone_flags & CLONE_PARENT) &&
1009 current->signal->flags & SIGNAL_UNKILLABLE)
1010 return ERR_PTR(-EINVAL);
1012 retval = security_task_create(clone_flags);
1013 if (retval)
1014 goto fork_out;
1016 retval = -ENOMEM;
1017 p = dup_task_struct(current);
1018 if (!p)
1019 goto fork_out;
1021 ftrace_graph_init_task(p);
1023 rt_mutex_init_task(p);
1025 #ifdef CONFIG_PROVE_LOCKING
1026 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1027 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1028 #endif
1029 retval = -EAGAIN;
1030 if (atomic_read(&p->real_cred->user->processes) >=
1031 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1032 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1033 p->real_cred->user != INIT_USER)
1034 goto bad_fork_free;
1037 retval = copy_creds(p, clone_flags);
1038 if (retval < 0)
1039 goto bad_fork_free;
1042 * If multiple threads are within copy_process(), then this check
1043 * triggers too late. This doesn't hurt, the check is only there
1044 * to stop root fork bombs.
1046 retval = -EAGAIN;
1047 if (nr_threads >= max_threads)
1048 goto bad_fork_cleanup_count;
1050 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1051 goto bad_fork_cleanup_count;
1053 p->did_exec = 0;
1054 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1055 copy_flags(clone_flags, p);
1056 INIT_LIST_HEAD(&p->children);
1057 INIT_LIST_HEAD(&p->sibling);
1058 rcu_copy_process(p);
1059 p->vfork_done = NULL;
1060 spin_lock_init(&p->alloc_lock);
1062 init_sigpending(&p->pending);
1064 p->utime = cputime_zero;
1065 p->stime = cputime_zero;
1066 p->gtime = cputime_zero;
1067 p->utimescaled = cputime_zero;
1068 p->stimescaled = cputime_zero;
1069 p->prev_utime = cputime_zero;
1070 p->prev_stime = cputime_zero;
1072 p->default_timer_slack_ns = current->timer_slack_ns;
1074 task_io_accounting_init(&p->ioac);
1075 acct_clear_integrals(p);
1077 posix_cpu_timers_init(p);
1079 p->lock_depth = -1; /* -1 = no lock */
1080 do_posix_clock_monotonic_gettime(&p->start_time);
1081 p->real_start_time = p->start_time;
1082 monotonic_to_bootbased(&p->real_start_time);
1083 p->io_context = NULL;
1084 p->audit_context = NULL;
1085 cgroup_fork(p);
1086 #ifdef CONFIG_NUMA
1087 p->mempolicy = mpol_dup(p->mempolicy);
1088 if (IS_ERR(p->mempolicy)) {
1089 retval = PTR_ERR(p->mempolicy);
1090 p->mempolicy = NULL;
1091 goto bad_fork_cleanup_cgroup;
1093 mpol_fix_fork_child_flag(p);
1094 #endif
1095 #ifdef CONFIG_TRACE_IRQFLAGS
1096 p->irq_events = 0;
1097 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1098 p->hardirqs_enabled = 1;
1099 #else
1100 p->hardirqs_enabled = 0;
1101 #endif
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;
1113 #endif
1114 #ifdef CONFIG_LOCKDEP
1115 p->lockdep_depth = 0; /* no locks held yet */
1116 p->curr_chain_key = 0;
1117 p->lockdep_recursion = 0;
1118 #endif
1120 #ifdef CONFIG_DEBUG_MUTEXES
1121 p->blocked_on = NULL; /* not blocked yet */
1122 #endif
1123 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1124 p->memcg_batch.do_batch = 0;
1125 p->memcg_batch.memcg = NULL;
1126 #endif
1128 p->bts = NULL;
1130 p->stack_start = stack_start;
1132 /* Perform scheduler related setup. Assign this task to a CPU. */
1133 sched_fork(p, clone_flags);
1135 retval = perf_event_init_task(p);
1136 if (retval)
1137 goto bad_fork_cleanup_policy;
1139 if ((retval = audit_alloc(p)))
1140 goto bad_fork_cleanup_policy;
1141 /* copy all the process information */
1142 if ((retval = copy_semundo(clone_flags, p)))
1143 goto bad_fork_cleanup_audit;
1144 if ((retval = copy_files(clone_flags, p)))
1145 goto bad_fork_cleanup_semundo;
1146 if ((retval = copy_fs(clone_flags, p)))
1147 goto bad_fork_cleanup_files;
1148 if ((retval = copy_sighand(clone_flags, p)))
1149 goto bad_fork_cleanup_fs;
1150 if ((retval = copy_signal(clone_flags, p)))
1151 goto bad_fork_cleanup_sighand;
1152 if ((retval = copy_mm(clone_flags, p)))
1153 goto bad_fork_cleanup_signal;
1154 if ((retval = copy_namespaces(clone_flags, p)))
1155 goto bad_fork_cleanup_mm;
1156 if ((retval = copy_io(clone_flags, p)))
1157 goto bad_fork_cleanup_namespaces;
1158 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1159 if (retval)
1160 goto bad_fork_cleanup_io;
1162 if (pid != &init_struct_pid) {
1163 retval = -ENOMEM;
1164 pid = alloc_pid(p->nsproxy->pid_ns);
1165 if (!pid)
1166 goto bad_fork_cleanup_io;
1168 if (clone_flags & CLONE_NEWPID) {
1169 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1170 if (retval < 0)
1171 goto bad_fork_free_pid;
1175 p->pid = pid_nr(pid);
1176 p->tgid = p->pid;
1177 if (clone_flags & CLONE_THREAD)
1178 p->tgid = current->tgid;
1180 if (current->nsproxy != p->nsproxy) {
1181 retval = ns_cgroup_clone(p, pid);
1182 if (retval)
1183 goto bad_fork_free_pid;
1186 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1188 * Clear TID on mm_release()?
1190 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1191 #ifdef CONFIG_FUTEX
1192 p->robust_list = NULL;
1193 #ifdef CONFIG_COMPAT
1194 p->compat_robust_list = NULL;
1195 #endif
1196 INIT_LIST_HEAD(&p->pi_state_list);
1197 p->pi_state_cache = NULL;
1198 #endif
1200 * sigaltstack should be cleared when sharing the same VM
1202 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1203 p->sas_ss_sp = p->sas_ss_size = 0;
1206 * Syscall tracing should be turned off in the child regardless
1207 * of CLONE_PTRACE.
1209 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1210 #ifdef TIF_SYSCALL_EMU
1211 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1212 #endif
1213 clear_all_latency_tracing(p);
1215 /* ok, now we should be set up.. */
1216 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1217 p->pdeath_signal = 0;
1218 p->exit_state = 0;
1221 * Ok, make it visible to the rest of the system.
1222 * We dont wake it up yet.
1224 p->group_leader = p;
1225 INIT_LIST_HEAD(&p->thread_group);
1227 /* Now that the task is set up, run cgroup callbacks if
1228 * necessary. We need to run them before the task is visible
1229 * on the tasklist. */
1230 cgroup_fork_callbacks(p);
1231 cgroup_callbacks_done = 1;
1233 /* Need tasklist lock for parent etc handling! */
1234 write_lock_irq(&tasklist_lock);
1237 * The task hasn't been attached yet, so its cpus_allowed mask will
1238 * not be changed, nor will its assigned CPU.
1240 * The cpus_allowed mask of the parent may have changed after it was
1241 * copied first time - so re-copy it here, then check the child's CPU
1242 * to ensure it is on a valid CPU (and if not, just force it back to
1243 * parent's CPU). This avoids alot of nasty races.
1245 p->cpus_allowed = current->cpus_allowed;
1246 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1247 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1248 !cpu_online(task_cpu(p))))
1249 set_task_cpu(p, smp_processor_id());
1251 /* CLONE_PARENT re-uses the old parent */
1252 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1253 p->real_parent = current->real_parent;
1254 p->parent_exec_id = current->parent_exec_id;
1255 } else {
1256 p->real_parent = current;
1257 p->parent_exec_id = current->self_exec_id;
1260 spin_lock(&current->sighand->siglock);
1263 * Process group and session signals need to be delivered to just the
1264 * parent before the fork or both the parent and the child after the
1265 * fork. Restart if a signal comes in before we add the new process to
1266 * it's process group.
1267 * A fatal signal pending means that current will exit, so the new
1268 * thread can't slip out of an OOM kill (or normal SIGKILL).
1270 recalc_sigpending();
1271 if (signal_pending(current)) {
1272 spin_unlock(&current->sighand->siglock);
1273 write_unlock_irq(&tasklist_lock);
1274 retval = -ERESTARTNOINTR;
1275 goto bad_fork_free_pid;
1278 if (clone_flags & CLONE_THREAD) {
1279 atomic_inc(&current->signal->count);
1280 atomic_inc(&current->signal->live);
1281 p->group_leader = current->group_leader;
1282 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1285 if (likely(p->pid)) {
1286 tracehook_finish_clone(p, clone_flags, trace);
1288 if (thread_group_leader(p)) {
1289 if (clone_flags & CLONE_NEWPID)
1290 p->nsproxy->pid_ns->child_reaper = p;
1292 p->signal->leader_pid = pid;
1293 tty_kref_put(p->signal->tty);
1294 p->signal->tty = tty_kref_get(current->signal->tty);
1295 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1296 attach_pid(p, PIDTYPE_SID, task_session(current));
1297 list_add_tail(&p->sibling, &p->real_parent->children);
1298 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1299 __get_cpu_var(process_counts)++;
1301 attach_pid(p, PIDTYPE_PID, pid);
1302 nr_threads++;
1305 total_forks++;
1306 spin_unlock(&current->sighand->siglock);
1307 write_unlock_irq(&tasklist_lock);
1308 proc_fork_connector(p);
1309 cgroup_post_fork(p);
1310 perf_event_fork(p);
1311 return p;
1313 bad_fork_free_pid:
1314 if (pid != &init_struct_pid)
1315 free_pid(pid);
1316 bad_fork_cleanup_io:
1317 put_io_context(p->io_context);
1318 bad_fork_cleanup_namespaces:
1319 exit_task_namespaces(p);
1320 bad_fork_cleanup_mm:
1321 if (p->mm)
1322 mmput(p->mm);
1323 bad_fork_cleanup_signal:
1324 if (!(clone_flags & CLONE_THREAD))
1325 __cleanup_signal(p->signal);
1326 bad_fork_cleanup_sighand:
1327 __cleanup_sighand(p->sighand);
1328 bad_fork_cleanup_fs:
1329 exit_fs(p); /* blocking */
1330 bad_fork_cleanup_files:
1331 exit_files(p); /* blocking */
1332 bad_fork_cleanup_semundo:
1333 exit_sem(p);
1334 bad_fork_cleanup_audit:
1335 audit_free(p);
1336 bad_fork_cleanup_policy:
1337 perf_event_free_task(p);
1338 #ifdef CONFIG_NUMA
1339 mpol_put(p->mempolicy);
1340 bad_fork_cleanup_cgroup:
1341 #endif
1342 cgroup_exit(p, cgroup_callbacks_done);
1343 delayacct_tsk_free(p);
1344 module_put(task_thread_info(p)->exec_domain->module);
1345 bad_fork_cleanup_count:
1346 atomic_dec(&p->cred->user->processes);
1347 exit_creds(p);
1348 bad_fork_free:
1349 free_task(p);
1350 fork_out:
1351 return ERR_PTR(retval);
1354 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1356 memset(regs, 0, sizeof(struct pt_regs));
1357 return regs;
1360 struct task_struct * __cpuinit fork_idle(int cpu)
1362 struct task_struct *task;
1363 struct pt_regs regs;
1365 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1366 &init_struct_pid, 0);
1367 if (!IS_ERR(task))
1368 init_idle(task, cpu);
1370 return task;
1374 * Ok, this is the main fork-routine.
1376 * It copies the process, and if successful kick-starts
1377 * it and waits for it to finish using the VM if required.
1379 long do_fork(unsigned long clone_flags,
1380 unsigned long stack_start,
1381 struct pt_regs *regs,
1382 unsigned long stack_size,
1383 int __user *parent_tidptr,
1384 int __user *child_tidptr)
1386 struct task_struct *p;
1387 int trace = 0;
1388 long nr;
1391 * Do some preliminary argument and permissions checking before we
1392 * actually start allocating stuff
1394 if (clone_flags & CLONE_NEWUSER) {
1395 if (clone_flags & CLONE_THREAD)
1396 return -EINVAL;
1397 /* hopefully this check will go away when userns support is
1398 * complete
1400 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1401 !capable(CAP_SETGID))
1402 return -EPERM;
1406 * We hope to recycle these flags after 2.6.26
1408 if (unlikely(clone_flags & CLONE_STOPPED)) {
1409 static int __read_mostly count = 100;
1411 if (count > 0 && printk_ratelimit()) {
1412 char comm[TASK_COMM_LEN];
1414 count--;
1415 printk(KERN_INFO "fork(): process `%s' used deprecated "
1416 "clone flags 0x%lx\n",
1417 get_task_comm(comm, current),
1418 clone_flags & CLONE_STOPPED);
1423 * When called from kernel_thread, don't do user tracing stuff.
1425 if (likely(user_mode(regs)))
1426 trace = tracehook_prepare_clone(clone_flags);
1428 p = copy_process(clone_flags, stack_start, regs, stack_size,
1429 child_tidptr, NULL, trace);
1431 * Do this prior waking up the new thread - the thread pointer
1432 * might get invalid after that point, if the thread exits quickly.
1434 if (!IS_ERR(p)) {
1435 struct completion vfork;
1437 trace_sched_process_fork(current, p);
1439 nr = task_pid_vnr(p);
1441 if (clone_flags & CLONE_PARENT_SETTID)
1442 put_user(nr, parent_tidptr);
1444 if (clone_flags & CLONE_VFORK) {
1445 p->vfork_done = &vfork;
1446 init_completion(&vfork);
1449 audit_finish_fork(p);
1450 tracehook_report_clone(regs, clone_flags, nr, p);
1453 * We set PF_STARTING at creation in case tracing wants to
1454 * use this to distinguish a fully live task from one that
1455 * hasn't gotten to tracehook_report_clone() yet. Now we
1456 * clear it and set the child going.
1458 p->flags &= ~PF_STARTING;
1460 if (unlikely(clone_flags & CLONE_STOPPED)) {
1462 * We'll start up with an immediate SIGSTOP.
1464 sigaddset(&p->pending.signal, SIGSTOP);
1465 set_tsk_thread_flag(p, TIF_SIGPENDING);
1466 __set_task_state(p, TASK_STOPPED);
1467 } else {
1468 wake_up_new_task(p, clone_flags);
1471 tracehook_report_clone_complete(trace, regs,
1472 clone_flags, nr, p);
1474 if (clone_flags & CLONE_VFORK) {
1475 freezer_do_not_count();
1476 wait_for_completion(&vfork);
1477 freezer_count();
1478 tracehook_report_vfork_done(p, nr);
1480 } else {
1481 nr = PTR_ERR(p);
1483 return nr;
1486 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1487 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1488 #endif
1490 static void sighand_ctor(void *data)
1492 struct sighand_struct *sighand = data;
1494 spin_lock_init(&sighand->siglock);
1495 init_waitqueue_head(&sighand->signalfd_wqh);
1498 void __init proc_caches_init(void)
1500 sighand_cachep = kmem_cache_create("sighand_cache",
1501 sizeof(struct sighand_struct), 0,
1502 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1503 SLAB_NOTRACK, sighand_ctor);
1504 signal_cachep = kmem_cache_create("signal_cache",
1505 sizeof(struct signal_struct), 0,
1506 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1507 files_cachep = kmem_cache_create("files_cache",
1508 sizeof(struct files_struct), 0,
1509 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1510 fs_cachep = kmem_cache_create("fs_cache",
1511 sizeof(struct fs_struct), 0,
1512 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1513 mm_cachep = kmem_cache_create("mm_struct",
1514 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1515 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1516 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1517 mmap_init();
1521 * Check constraints on flags passed to the unshare system call and
1522 * force unsharing of additional process context as appropriate.
1524 static void check_unshare_flags(unsigned long *flags_ptr)
1527 * If unsharing a thread from a thread group, must also
1528 * unshare vm.
1530 if (*flags_ptr & CLONE_THREAD)
1531 *flags_ptr |= CLONE_VM;
1534 * If unsharing vm, must also unshare signal handlers.
1536 if (*flags_ptr & CLONE_VM)
1537 *flags_ptr |= CLONE_SIGHAND;
1540 * If unsharing signal handlers and the task was created
1541 * using CLONE_THREAD, then must unshare the thread
1543 if ((*flags_ptr & CLONE_SIGHAND) &&
1544 (atomic_read(&current->signal->count) > 1))
1545 *flags_ptr |= CLONE_THREAD;
1548 * If unsharing namespace, must also unshare filesystem information.
1550 if (*flags_ptr & CLONE_NEWNS)
1551 *flags_ptr |= CLONE_FS;
1555 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1557 static int unshare_thread(unsigned long unshare_flags)
1559 if (unshare_flags & CLONE_THREAD)
1560 return -EINVAL;
1562 return 0;
1566 * Unshare the filesystem structure if it is being shared
1568 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1570 struct fs_struct *fs = current->fs;
1572 if (!(unshare_flags & CLONE_FS) || !fs)
1573 return 0;
1575 /* don't need lock here; in the worst case we'll do useless copy */
1576 if (fs->users == 1)
1577 return 0;
1579 *new_fsp = copy_fs_struct(fs);
1580 if (!*new_fsp)
1581 return -ENOMEM;
1583 return 0;
1587 * Unsharing of sighand is not supported yet
1589 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1591 struct sighand_struct *sigh = current->sighand;
1593 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1594 return -EINVAL;
1595 else
1596 return 0;
1600 * Unshare vm if it is being shared
1602 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1604 struct mm_struct *mm = current->mm;
1606 if ((unshare_flags & CLONE_VM) &&
1607 (mm && atomic_read(&mm->mm_users) > 1)) {
1608 return -EINVAL;
1611 return 0;
1615 * Unshare file descriptor table if it is being shared
1617 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1619 struct files_struct *fd = current->files;
1620 int error = 0;
1622 if ((unshare_flags & CLONE_FILES) &&
1623 (fd && atomic_read(&fd->count) > 1)) {
1624 *new_fdp = dup_fd(fd, &error);
1625 if (!*new_fdp)
1626 return error;
1629 return 0;
1633 * unshare allows a process to 'unshare' part of the process
1634 * context which was originally shared using clone. copy_*
1635 * functions used by do_fork() cannot be used here directly
1636 * because they modify an inactive task_struct that is being
1637 * constructed. Here we are modifying the current, active,
1638 * task_struct.
1640 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1642 int err = 0;
1643 struct fs_struct *fs, *new_fs = NULL;
1644 struct sighand_struct *new_sigh = NULL;
1645 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1646 struct files_struct *fd, *new_fd = NULL;
1647 struct nsproxy *new_nsproxy = NULL;
1648 int do_sysvsem = 0;
1650 check_unshare_flags(&unshare_flags);
1652 /* Return -EINVAL for all unsupported flags */
1653 err = -EINVAL;
1654 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1655 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1656 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1657 goto bad_unshare_out;
1660 * CLONE_NEWIPC must also detach from the undolist: after switching
1661 * to a new ipc namespace, the semaphore arrays from the old
1662 * namespace are unreachable.
1664 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1665 do_sysvsem = 1;
1666 if ((err = unshare_thread(unshare_flags)))
1667 goto bad_unshare_out;
1668 if ((err = unshare_fs(unshare_flags, &new_fs)))
1669 goto bad_unshare_cleanup_thread;
1670 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1671 goto bad_unshare_cleanup_fs;
1672 if ((err = unshare_vm(unshare_flags, &new_mm)))
1673 goto bad_unshare_cleanup_sigh;
1674 if ((err = unshare_fd(unshare_flags, &new_fd)))
1675 goto bad_unshare_cleanup_vm;
1676 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1677 new_fs)))
1678 goto bad_unshare_cleanup_fd;
1680 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1681 if (do_sysvsem) {
1683 * CLONE_SYSVSEM is equivalent to sys_exit().
1685 exit_sem(current);
1688 if (new_nsproxy) {
1689 switch_task_namespaces(current, new_nsproxy);
1690 new_nsproxy = NULL;
1693 task_lock(current);
1695 if (new_fs) {
1696 fs = current->fs;
1697 write_lock(&fs->lock);
1698 current->fs = new_fs;
1699 if (--fs->users)
1700 new_fs = NULL;
1701 else
1702 new_fs = fs;
1703 write_unlock(&fs->lock);
1706 if (new_mm) {
1707 mm = current->mm;
1708 active_mm = current->active_mm;
1709 current->mm = new_mm;
1710 current->active_mm = new_mm;
1711 activate_mm(active_mm, new_mm);
1712 new_mm = mm;
1715 if (new_fd) {
1716 fd = current->files;
1717 current->files = new_fd;
1718 new_fd = fd;
1721 task_unlock(current);
1724 if (new_nsproxy)
1725 put_nsproxy(new_nsproxy);
1727 bad_unshare_cleanup_fd:
1728 if (new_fd)
1729 put_files_struct(new_fd);
1731 bad_unshare_cleanup_vm:
1732 if (new_mm)
1733 mmput(new_mm);
1735 bad_unshare_cleanup_sigh:
1736 if (new_sigh)
1737 if (atomic_dec_and_test(&new_sigh->count))
1738 kmem_cache_free(sighand_cachep, new_sigh);
1740 bad_unshare_cleanup_fs:
1741 if (new_fs)
1742 free_fs_struct(new_fs);
1744 bad_unshare_cleanup_thread:
1745 bad_unshare_out:
1746 return err;
1750 * Helper to unshare the files of the current task.
1751 * We don't want to expose copy_files internals to
1752 * the exec layer of the kernel.
1755 int unshare_files(struct files_struct **displaced)
1757 struct task_struct *task = current;
1758 struct files_struct *copy = NULL;
1759 int error;
1761 error = unshare_fd(CLONE_FILES, &copy);
1762 if (error || !copy) {
1763 *displaced = NULL;
1764 return error;
1766 *displaced = task->files;
1767 task_lock(task);
1768 task->files = copy;
1769 task_unlock(task);
1770 return 0;