hugetlb: reserve huge pages for reliable MAP_PRIVATE hugetlbfs mappings until fork()
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / fork.c
blob552c8d8e77ad5e3fb43f606081c57023bb25e4c6
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/mnt_namespace.h>
21 #include <linux/personality.h>
22 #include <linux/mempolicy.h>
23 #include <linux/sem.h>
24 #include <linux/file.h>
25 #include <linux/fdtable.h>
26 #include <linux/iocontext.h>
27 #include <linux/key.h>
28 #include <linux/binfmts.h>
29 #include <linux/mman.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/futex.h>
41 #include <linux/task_io_accounting_ops.h>
42 #include <linux/rcupdate.h>
43 #include <linux/ptrace.h>
44 #include <linux/mount.h>
45 #include <linux/audit.h>
46 #include <linux/memcontrol.h>
47 #include <linux/profile.h>
48 #include <linux/rmap.h>
49 #include <linux/acct.h>
50 #include <linux/tsacct_kern.h>
51 #include <linux/cn_proc.h>
52 #include <linux/freezer.h>
53 #include <linux/delayacct.h>
54 #include <linux/taskstats_kern.h>
55 #include <linux/random.h>
56 #include <linux/tty.h>
57 #include <linux/proc_fs.h>
58 #include <linux/blkdev.h>
60 #include <asm/pgtable.h>
61 #include <asm/pgalloc.h>
62 #include <asm/uaccess.h>
63 #include <asm/mmu_context.h>
64 #include <asm/cacheflush.h>
65 #include <asm/tlbflush.h>
68 * Protected counters by write_lock_irq(&tasklist_lock)
70 unsigned long total_forks; /* Handle normal Linux uptimes. */
71 int nr_threads; /* The idle threads do not count.. */
73 int max_threads; /* tunable limit on nr_threads */
75 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
77 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
79 int nr_processes(void)
81 int cpu;
82 int total = 0;
84 for_each_online_cpu(cpu)
85 total += per_cpu(process_counts, cpu);
87 return total;
90 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
91 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
92 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
93 static struct kmem_cache *task_struct_cachep;
94 #endif
96 /* SLAB cache for signal_struct structures (tsk->signal) */
97 static struct kmem_cache *signal_cachep;
99 /* SLAB cache for sighand_struct structures (tsk->sighand) */
100 struct kmem_cache *sighand_cachep;
102 /* SLAB cache for files_struct structures (tsk->files) */
103 struct kmem_cache *files_cachep;
105 /* SLAB cache for fs_struct structures (tsk->fs) */
106 struct kmem_cache *fs_cachep;
108 /* SLAB cache for vm_area_struct structures */
109 struct kmem_cache *vm_area_cachep;
111 /* SLAB cache for mm_struct structures (tsk->mm) */
112 static struct kmem_cache *mm_cachep;
114 void free_task(struct task_struct *tsk)
116 prop_local_destroy_single(&tsk->dirties);
117 free_thread_info(tsk->stack);
118 rt_mutex_debug_task_free(tsk);
119 free_task_struct(tsk);
121 EXPORT_SYMBOL(free_task);
123 void __put_task_struct(struct task_struct *tsk)
125 WARN_ON(!tsk->exit_state);
126 WARN_ON(atomic_read(&tsk->usage));
127 WARN_ON(tsk == current);
129 security_task_free(tsk);
130 free_uid(tsk->user);
131 put_group_info(tsk->group_info);
132 delayacct_tsk_free(tsk);
134 if (!profile_handoff_task(tsk))
135 free_task(tsk);
139 * macro override instead of weak attribute alias, to workaround
140 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
142 #ifndef arch_task_cache_init
143 #define arch_task_cache_init()
144 #endif
146 void __init fork_init(unsigned long mempages)
148 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
149 #ifndef ARCH_MIN_TASKALIGN
150 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
151 #endif
152 /* create a slab on which task_structs can be allocated */
153 task_struct_cachep =
154 kmem_cache_create("task_struct", sizeof(struct task_struct),
155 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
156 #endif
158 /* do the arch specific task caches init */
159 arch_task_cache_init();
162 * The default maximum number of threads is set to a safe
163 * value: the thread structures can take up at most half
164 * of memory.
166 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
169 * we need to allow at least 20 threads to boot a system
171 if(max_threads < 20)
172 max_threads = 20;
174 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
175 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
176 init_task.signal->rlim[RLIMIT_SIGPENDING] =
177 init_task.signal->rlim[RLIMIT_NPROC];
180 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
181 struct task_struct *src)
183 *dst = *src;
184 return 0;
187 static struct task_struct *dup_task_struct(struct task_struct *orig)
189 struct task_struct *tsk;
190 struct thread_info *ti;
191 int err;
193 prepare_to_copy(orig);
195 tsk = alloc_task_struct();
196 if (!tsk)
197 return NULL;
199 ti = alloc_thread_info(tsk);
200 if (!ti) {
201 free_task_struct(tsk);
202 return NULL;
205 err = arch_dup_task_struct(tsk, orig);
206 if (err)
207 goto out;
209 tsk->stack = ti;
211 err = prop_local_init_single(&tsk->dirties);
212 if (err)
213 goto out;
215 setup_thread_stack(tsk, orig);
217 #ifdef CONFIG_CC_STACKPROTECTOR
218 tsk->stack_canary = get_random_int();
219 #endif
221 /* One for us, one for whoever does the "release_task()" (usually parent) */
222 atomic_set(&tsk->usage,2);
223 atomic_set(&tsk->fs_excl, 0);
224 #ifdef CONFIG_BLK_DEV_IO_TRACE
225 tsk->btrace_seq = 0;
226 #endif
227 tsk->splice_pipe = NULL;
228 return tsk;
230 out:
231 free_thread_info(ti);
232 free_task_struct(tsk);
233 return NULL;
236 #ifdef CONFIG_MMU
237 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
239 struct vm_area_struct *mpnt, *tmp, **pprev;
240 struct rb_node **rb_link, *rb_parent;
241 int retval;
242 unsigned long charge;
243 struct mempolicy *pol;
245 down_write(&oldmm->mmap_sem);
246 flush_cache_dup_mm(oldmm);
248 * Not linked in yet - no deadlock potential:
250 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
252 mm->locked_vm = 0;
253 mm->mmap = NULL;
254 mm->mmap_cache = NULL;
255 mm->free_area_cache = oldmm->mmap_base;
256 mm->cached_hole_size = ~0UL;
257 mm->map_count = 0;
258 cpus_clear(mm->cpu_vm_mask);
259 mm->mm_rb = RB_ROOT;
260 rb_link = &mm->mm_rb.rb_node;
261 rb_parent = NULL;
262 pprev = &mm->mmap;
264 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
265 struct file *file;
267 if (mpnt->vm_flags & VM_DONTCOPY) {
268 long pages = vma_pages(mpnt);
269 mm->total_vm -= pages;
270 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
271 -pages);
272 continue;
274 charge = 0;
275 if (mpnt->vm_flags & VM_ACCOUNT) {
276 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
277 if (security_vm_enough_memory(len))
278 goto fail_nomem;
279 charge = len;
281 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
282 if (!tmp)
283 goto fail_nomem;
284 *tmp = *mpnt;
285 pol = mpol_dup(vma_policy(mpnt));
286 retval = PTR_ERR(pol);
287 if (IS_ERR(pol))
288 goto fail_nomem_policy;
289 vma_set_policy(tmp, pol);
290 tmp->vm_flags &= ~VM_LOCKED;
291 tmp->vm_mm = mm;
292 tmp->vm_next = NULL;
293 anon_vma_link(tmp);
294 file = tmp->vm_file;
295 if (file) {
296 struct inode *inode = file->f_path.dentry->d_inode;
297 get_file(file);
298 if (tmp->vm_flags & VM_DENYWRITE)
299 atomic_dec(&inode->i_writecount);
301 /* insert tmp into the share list, just after mpnt */
302 spin_lock(&file->f_mapping->i_mmap_lock);
303 tmp->vm_truncate_count = mpnt->vm_truncate_count;
304 flush_dcache_mmap_lock(file->f_mapping);
305 vma_prio_tree_add(tmp, mpnt);
306 flush_dcache_mmap_unlock(file->f_mapping);
307 spin_unlock(&file->f_mapping->i_mmap_lock);
311 * Clear hugetlb-related page reserves for children. This only
312 * affects MAP_PRIVATE mappings. Faults generated by the child
313 * are not guaranteed to succeed, even if read-only
315 if (is_vm_hugetlb_page(tmp))
316 reset_vma_resv_huge_pages(tmp);
319 * Link in the new vma and copy the page table entries.
321 *pprev = tmp;
322 pprev = &tmp->vm_next;
324 __vma_link_rb(mm, tmp, rb_link, rb_parent);
325 rb_link = &tmp->vm_rb.rb_right;
326 rb_parent = &tmp->vm_rb;
328 mm->map_count++;
329 retval = copy_page_range(mm, oldmm, mpnt);
331 if (tmp->vm_ops && tmp->vm_ops->open)
332 tmp->vm_ops->open(tmp);
334 if (retval)
335 goto out;
337 /* a new mm has just been created */
338 arch_dup_mmap(oldmm, mm);
339 retval = 0;
340 out:
341 up_write(&mm->mmap_sem);
342 flush_tlb_mm(oldmm);
343 up_write(&oldmm->mmap_sem);
344 return retval;
345 fail_nomem_policy:
346 kmem_cache_free(vm_area_cachep, tmp);
347 fail_nomem:
348 retval = -ENOMEM;
349 vm_unacct_memory(charge);
350 goto out;
353 static inline int mm_alloc_pgd(struct mm_struct * mm)
355 mm->pgd = pgd_alloc(mm);
356 if (unlikely(!mm->pgd))
357 return -ENOMEM;
358 return 0;
361 static inline void mm_free_pgd(struct mm_struct * mm)
363 pgd_free(mm, mm->pgd);
365 #else
366 #define dup_mmap(mm, oldmm) (0)
367 #define mm_alloc_pgd(mm) (0)
368 #define mm_free_pgd(mm)
369 #endif /* CONFIG_MMU */
371 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
373 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
374 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
376 #include <linux/init_task.h>
378 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
380 atomic_set(&mm->mm_users, 1);
381 atomic_set(&mm->mm_count, 1);
382 init_rwsem(&mm->mmap_sem);
383 INIT_LIST_HEAD(&mm->mmlist);
384 mm->flags = (current->mm) ? current->mm->flags
385 : MMF_DUMP_FILTER_DEFAULT;
386 mm->core_waiters = 0;
387 mm->nr_ptes = 0;
388 set_mm_counter(mm, file_rss, 0);
389 set_mm_counter(mm, anon_rss, 0);
390 spin_lock_init(&mm->page_table_lock);
391 rwlock_init(&mm->ioctx_list_lock);
392 mm->ioctx_list = NULL;
393 mm->free_area_cache = TASK_UNMAPPED_BASE;
394 mm->cached_hole_size = ~0UL;
395 mm_init_owner(mm, p);
397 if (likely(!mm_alloc_pgd(mm))) {
398 mm->def_flags = 0;
399 return mm;
402 free_mm(mm);
403 return NULL;
407 * Allocate and initialize an mm_struct.
409 struct mm_struct * mm_alloc(void)
411 struct mm_struct * mm;
413 mm = allocate_mm();
414 if (mm) {
415 memset(mm, 0, sizeof(*mm));
416 mm = mm_init(mm, current);
418 return mm;
422 * Called when the last reference to the mm
423 * is dropped: either by a lazy thread or by
424 * mmput. Free the page directory and the mm.
426 void __mmdrop(struct mm_struct *mm)
428 BUG_ON(mm == &init_mm);
429 mm_free_pgd(mm);
430 destroy_context(mm);
431 free_mm(mm);
433 EXPORT_SYMBOL_GPL(__mmdrop);
436 * Decrement the use count and release all resources for an mm.
438 void mmput(struct mm_struct *mm)
440 might_sleep();
442 if (atomic_dec_and_test(&mm->mm_users)) {
443 exit_aio(mm);
444 exit_mmap(mm);
445 set_mm_exe_file(mm, NULL);
446 if (!list_empty(&mm->mmlist)) {
447 spin_lock(&mmlist_lock);
448 list_del(&mm->mmlist);
449 spin_unlock(&mmlist_lock);
451 put_swap_token(mm);
452 mmdrop(mm);
455 EXPORT_SYMBOL_GPL(mmput);
458 * get_task_mm - acquire a reference to the task's mm
460 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning
461 * this kernel workthread has transiently adopted a user mm with use_mm,
462 * to do its AIO) is not set and if so returns a reference to it, after
463 * bumping up the use count. User must release the mm via mmput()
464 * after use. Typically used by /proc and ptrace.
466 struct mm_struct *get_task_mm(struct task_struct *task)
468 struct mm_struct *mm;
470 task_lock(task);
471 mm = task->mm;
472 if (mm) {
473 if (task->flags & PF_BORROWED_MM)
474 mm = NULL;
475 else
476 atomic_inc(&mm->mm_users);
478 task_unlock(task);
479 return mm;
481 EXPORT_SYMBOL_GPL(get_task_mm);
483 /* Please note the differences between mmput and mm_release.
484 * mmput is called whenever we stop holding onto a mm_struct,
485 * error success whatever.
487 * mm_release is called after a mm_struct has been removed
488 * from the current process.
490 * This difference is important for error handling, when we
491 * only half set up a mm_struct for a new process and need to restore
492 * the old one. Because we mmput the new mm_struct before
493 * restoring the old one. . .
494 * Eric Biederman 10 January 1998
496 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
498 struct completion *vfork_done = tsk->vfork_done;
500 /* Get rid of any cached register state */
501 deactivate_mm(tsk, mm);
503 /* notify parent sleeping on vfork() */
504 if (vfork_done) {
505 tsk->vfork_done = NULL;
506 complete(vfork_done);
510 * If we're exiting normally, clear a user-space tid field if
511 * requested. We leave this alone when dying by signal, to leave
512 * the value intact in a core dump, and to save the unnecessary
513 * trouble otherwise. Userland only wants this done for a sys_exit.
515 if (tsk->clear_child_tid
516 && !(tsk->flags & PF_SIGNALED)
517 && atomic_read(&mm->mm_users) > 1) {
518 u32 __user * tidptr = tsk->clear_child_tid;
519 tsk->clear_child_tid = NULL;
522 * We don't check the error code - if userspace has
523 * not set up a proper pointer then tough luck.
525 put_user(0, tidptr);
526 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
531 * Allocate a new mm structure and copy contents from the
532 * mm structure of the passed in task structure.
534 struct mm_struct *dup_mm(struct task_struct *tsk)
536 struct mm_struct *mm, *oldmm = current->mm;
537 int err;
539 if (!oldmm)
540 return NULL;
542 mm = allocate_mm();
543 if (!mm)
544 goto fail_nomem;
546 memcpy(mm, oldmm, sizeof(*mm));
548 /* Initializing for Swap token stuff */
549 mm->token_priority = 0;
550 mm->last_interval = 0;
552 if (!mm_init(mm, tsk))
553 goto fail_nomem;
555 if (init_new_context(tsk, mm))
556 goto fail_nocontext;
558 dup_mm_exe_file(oldmm, mm);
560 err = dup_mmap(mm, oldmm);
561 if (err)
562 goto free_pt;
564 mm->hiwater_rss = get_mm_rss(mm);
565 mm->hiwater_vm = mm->total_vm;
567 return mm;
569 free_pt:
570 mmput(mm);
572 fail_nomem:
573 return NULL;
575 fail_nocontext:
577 * If init_new_context() failed, we cannot use mmput() to free the mm
578 * because it calls destroy_context()
580 mm_free_pgd(mm);
581 free_mm(mm);
582 return NULL;
585 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
587 struct mm_struct * mm, *oldmm;
588 int retval;
590 tsk->min_flt = tsk->maj_flt = 0;
591 tsk->nvcsw = tsk->nivcsw = 0;
593 tsk->mm = NULL;
594 tsk->active_mm = NULL;
597 * Are we cloning a kernel thread?
599 * We need to steal a active VM for that..
601 oldmm = current->mm;
602 if (!oldmm)
603 return 0;
605 if (clone_flags & CLONE_VM) {
606 atomic_inc(&oldmm->mm_users);
607 mm = oldmm;
608 goto good_mm;
611 retval = -ENOMEM;
612 mm = dup_mm(tsk);
613 if (!mm)
614 goto fail_nomem;
616 good_mm:
617 /* Initializing for Swap token stuff */
618 mm->token_priority = 0;
619 mm->last_interval = 0;
621 tsk->mm = mm;
622 tsk->active_mm = mm;
623 return 0;
625 fail_nomem:
626 return retval;
629 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
631 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
632 /* We don't need to lock fs - think why ;-) */
633 if (fs) {
634 atomic_set(&fs->count, 1);
635 rwlock_init(&fs->lock);
636 fs->umask = old->umask;
637 read_lock(&old->lock);
638 fs->root = old->root;
639 path_get(&old->root);
640 fs->pwd = old->pwd;
641 path_get(&old->pwd);
642 if (old->altroot.dentry) {
643 fs->altroot = old->altroot;
644 path_get(&old->altroot);
645 } else {
646 fs->altroot.mnt = NULL;
647 fs->altroot.dentry = NULL;
649 read_unlock(&old->lock);
651 return fs;
654 struct fs_struct *copy_fs_struct(struct fs_struct *old)
656 return __copy_fs_struct(old);
659 EXPORT_SYMBOL_GPL(copy_fs_struct);
661 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
663 if (clone_flags & CLONE_FS) {
664 atomic_inc(&current->fs->count);
665 return 0;
667 tsk->fs = __copy_fs_struct(current->fs);
668 if (!tsk->fs)
669 return -ENOMEM;
670 return 0;
673 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
675 struct files_struct *oldf, *newf;
676 int error = 0;
679 * A background process may not have any files ...
681 oldf = current->files;
682 if (!oldf)
683 goto out;
685 if (clone_flags & CLONE_FILES) {
686 atomic_inc(&oldf->count);
687 goto out;
690 newf = dup_fd(oldf, &error);
691 if (!newf)
692 goto out;
694 tsk->files = newf;
695 error = 0;
696 out:
697 return error;
700 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
702 #ifdef CONFIG_BLOCK
703 struct io_context *ioc = current->io_context;
705 if (!ioc)
706 return 0;
708 * Share io context with parent, if CLONE_IO is set
710 if (clone_flags & CLONE_IO) {
711 tsk->io_context = ioc_task_link(ioc);
712 if (unlikely(!tsk->io_context))
713 return -ENOMEM;
714 } else if (ioprio_valid(ioc->ioprio)) {
715 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
716 if (unlikely(!tsk->io_context))
717 return -ENOMEM;
719 tsk->io_context->ioprio = ioc->ioprio;
721 #endif
722 return 0;
725 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
727 struct sighand_struct *sig;
729 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
730 atomic_inc(&current->sighand->count);
731 return 0;
733 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
734 rcu_assign_pointer(tsk->sighand, sig);
735 if (!sig)
736 return -ENOMEM;
737 atomic_set(&sig->count, 1);
738 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
739 return 0;
742 void __cleanup_sighand(struct sighand_struct *sighand)
744 if (atomic_dec_and_test(&sighand->count))
745 kmem_cache_free(sighand_cachep, sighand);
748 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
750 struct signal_struct *sig;
751 int ret;
753 if (clone_flags & CLONE_THREAD) {
754 atomic_inc(&current->signal->count);
755 atomic_inc(&current->signal->live);
756 return 0;
758 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
759 tsk->signal = sig;
760 if (!sig)
761 return -ENOMEM;
763 ret = copy_thread_group_keys(tsk);
764 if (ret < 0) {
765 kmem_cache_free(signal_cachep, sig);
766 return ret;
769 atomic_set(&sig->count, 1);
770 atomic_set(&sig->live, 1);
771 init_waitqueue_head(&sig->wait_chldexit);
772 sig->flags = 0;
773 sig->group_exit_code = 0;
774 sig->group_exit_task = NULL;
775 sig->group_stop_count = 0;
776 sig->curr_target = tsk;
777 init_sigpending(&sig->shared_pending);
778 INIT_LIST_HEAD(&sig->posix_timers);
780 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
781 sig->it_real_incr.tv64 = 0;
782 sig->real_timer.function = it_real_fn;
784 sig->it_virt_expires = cputime_zero;
785 sig->it_virt_incr = cputime_zero;
786 sig->it_prof_expires = cputime_zero;
787 sig->it_prof_incr = cputime_zero;
789 sig->leader = 0; /* session leadership doesn't inherit */
790 sig->tty_old_pgrp = NULL;
792 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
793 sig->gtime = cputime_zero;
794 sig->cgtime = cputime_zero;
795 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
796 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
797 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
798 sig->sum_sched_runtime = 0;
799 INIT_LIST_HEAD(&sig->cpu_timers[0]);
800 INIT_LIST_HEAD(&sig->cpu_timers[1]);
801 INIT_LIST_HEAD(&sig->cpu_timers[2]);
802 taskstats_tgid_init(sig);
804 task_lock(current->group_leader);
805 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
806 task_unlock(current->group_leader);
808 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
810 * New sole thread in the process gets an expiry time
811 * of the whole CPU time limit.
813 tsk->it_prof_expires =
814 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
816 acct_init_pacct(&sig->pacct);
818 tty_audit_fork(sig);
820 return 0;
823 void __cleanup_signal(struct signal_struct *sig)
825 exit_thread_group_keys(sig);
826 kmem_cache_free(signal_cachep, sig);
829 static void cleanup_signal(struct task_struct *tsk)
831 struct signal_struct *sig = tsk->signal;
833 atomic_dec(&sig->live);
835 if (atomic_dec_and_test(&sig->count))
836 __cleanup_signal(sig);
839 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
841 unsigned long new_flags = p->flags;
843 new_flags &= ~PF_SUPERPRIV;
844 new_flags |= PF_FORKNOEXEC;
845 if (!(clone_flags & CLONE_PTRACE))
846 p->ptrace = 0;
847 p->flags = new_flags;
848 clear_freeze_flag(p);
851 asmlinkage long sys_set_tid_address(int __user *tidptr)
853 current->clear_child_tid = tidptr;
855 return task_pid_vnr(current);
858 static void rt_mutex_init_task(struct task_struct *p)
860 spin_lock_init(&p->pi_lock);
861 #ifdef CONFIG_RT_MUTEXES
862 plist_head_init(&p->pi_waiters, &p->pi_lock);
863 p->pi_blocked_on = NULL;
864 #endif
867 #ifdef CONFIG_MM_OWNER
868 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
870 mm->owner = p;
872 #endif /* CONFIG_MM_OWNER */
875 * This creates a new process as a copy of the old one,
876 * but does not actually start it yet.
878 * It copies the registers, and all the appropriate
879 * parts of the process environment (as per the clone
880 * flags). The actual kick-off is left to the caller.
882 static struct task_struct *copy_process(unsigned long clone_flags,
883 unsigned long stack_start,
884 struct pt_regs *regs,
885 unsigned long stack_size,
886 int __user *child_tidptr,
887 struct pid *pid)
889 int retval;
890 struct task_struct *p;
891 int cgroup_callbacks_done = 0;
893 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
894 return ERR_PTR(-EINVAL);
897 * Thread groups must share signals as well, and detached threads
898 * can only be started up within the thread group.
900 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
901 return ERR_PTR(-EINVAL);
904 * Shared signal handlers imply shared VM. By way of the above,
905 * thread groups also imply shared VM. Blocking this case allows
906 * for various simplifications in other code.
908 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
909 return ERR_PTR(-EINVAL);
911 retval = security_task_create(clone_flags);
912 if (retval)
913 goto fork_out;
915 retval = -ENOMEM;
916 p = dup_task_struct(current);
917 if (!p)
918 goto fork_out;
920 rt_mutex_init_task(p);
922 #ifdef CONFIG_PROVE_LOCKING
923 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
924 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
925 #endif
926 retval = -EAGAIN;
927 if (atomic_read(&p->user->processes) >=
928 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
929 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
930 p->user != current->nsproxy->user_ns->root_user)
931 goto bad_fork_free;
934 atomic_inc(&p->user->__count);
935 atomic_inc(&p->user->processes);
936 get_group_info(p->group_info);
939 * If multiple threads are within copy_process(), then this check
940 * triggers too late. This doesn't hurt, the check is only there
941 * to stop root fork bombs.
943 if (nr_threads >= max_threads)
944 goto bad_fork_cleanup_count;
946 if (!try_module_get(task_thread_info(p)->exec_domain->module))
947 goto bad_fork_cleanup_count;
949 if (p->binfmt && !try_module_get(p->binfmt->module))
950 goto bad_fork_cleanup_put_domain;
952 p->did_exec = 0;
953 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
954 copy_flags(clone_flags, p);
955 INIT_LIST_HEAD(&p->children);
956 INIT_LIST_HEAD(&p->sibling);
957 #ifdef CONFIG_PREEMPT_RCU
958 p->rcu_read_lock_nesting = 0;
959 p->rcu_flipctr_idx = 0;
960 #endif /* #ifdef CONFIG_PREEMPT_RCU */
961 p->vfork_done = NULL;
962 spin_lock_init(&p->alloc_lock);
964 clear_tsk_thread_flag(p, TIF_SIGPENDING);
965 init_sigpending(&p->pending);
967 p->utime = cputime_zero;
968 p->stime = cputime_zero;
969 p->gtime = cputime_zero;
970 p->utimescaled = cputime_zero;
971 p->stimescaled = cputime_zero;
972 p->prev_utime = cputime_zero;
973 p->prev_stime = cputime_zero;
975 #ifdef CONFIG_DETECT_SOFTLOCKUP
976 p->last_switch_count = 0;
977 p->last_switch_timestamp = 0;
978 #endif
980 #ifdef CONFIG_TASK_XACCT
981 p->rchar = 0; /* I/O counter: bytes read */
982 p->wchar = 0; /* I/O counter: bytes written */
983 p->syscr = 0; /* I/O counter: read syscalls */
984 p->syscw = 0; /* I/O counter: write syscalls */
985 #endif
986 task_io_accounting_init(p);
987 acct_clear_integrals(p);
989 p->it_virt_expires = cputime_zero;
990 p->it_prof_expires = cputime_zero;
991 p->it_sched_expires = 0;
992 INIT_LIST_HEAD(&p->cpu_timers[0]);
993 INIT_LIST_HEAD(&p->cpu_timers[1]);
994 INIT_LIST_HEAD(&p->cpu_timers[2]);
996 p->lock_depth = -1; /* -1 = no lock */
997 do_posix_clock_monotonic_gettime(&p->start_time);
998 p->real_start_time = p->start_time;
999 monotonic_to_bootbased(&p->real_start_time);
1000 #ifdef CONFIG_SECURITY
1001 p->security = NULL;
1002 #endif
1003 p->cap_bset = current->cap_bset;
1004 p->io_context = NULL;
1005 p->audit_context = NULL;
1006 cgroup_fork(p);
1007 #ifdef CONFIG_NUMA
1008 p->mempolicy = mpol_dup(p->mempolicy);
1009 if (IS_ERR(p->mempolicy)) {
1010 retval = PTR_ERR(p->mempolicy);
1011 p->mempolicy = NULL;
1012 goto bad_fork_cleanup_cgroup;
1014 mpol_fix_fork_child_flag(p);
1015 #endif
1016 #ifdef CONFIG_TRACE_IRQFLAGS
1017 p->irq_events = 0;
1018 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1019 p->hardirqs_enabled = 1;
1020 #else
1021 p->hardirqs_enabled = 0;
1022 #endif
1023 p->hardirq_enable_ip = 0;
1024 p->hardirq_enable_event = 0;
1025 p->hardirq_disable_ip = _THIS_IP_;
1026 p->hardirq_disable_event = 0;
1027 p->softirqs_enabled = 1;
1028 p->softirq_enable_ip = _THIS_IP_;
1029 p->softirq_enable_event = 0;
1030 p->softirq_disable_ip = 0;
1031 p->softirq_disable_event = 0;
1032 p->hardirq_context = 0;
1033 p->softirq_context = 0;
1034 #endif
1035 #ifdef CONFIG_LOCKDEP
1036 p->lockdep_depth = 0; /* no locks held yet */
1037 p->curr_chain_key = 0;
1038 p->lockdep_recursion = 0;
1039 #endif
1041 #ifdef CONFIG_DEBUG_MUTEXES
1042 p->blocked_on = NULL; /* not blocked yet */
1043 #endif
1045 /* Perform scheduler related setup. Assign this task to a CPU. */
1046 sched_fork(p, clone_flags);
1048 if ((retval = security_task_alloc(p)))
1049 goto bad_fork_cleanup_policy;
1050 if ((retval = audit_alloc(p)))
1051 goto bad_fork_cleanup_security;
1052 /* copy all the process information */
1053 if ((retval = copy_semundo(clone_flags, p)))
1054 goto bad_fork_cleanup_audit;
1055 if ((retval = copy_files(clone_flags, p)))
1056 goto bad_fork_cleanup_semundo;
1057 if ((retval = copy_fs(clone_flags, p)))
1058 goto bad_fork_cleanup_files;
1059 if ((retval = copy_sighand(clone_flags, p)))
1060 goto bad_fork_cleanup_fs;
1061 if ((retval = copy_signal(clone_flags, p)))
1062 goto bad_fork_cleanup_sighand;
1063 if ((retval = copy_mm(clone_flags, p)))
1064 goto bad_fork_cleanup_signal;
1065 if ((retval = copy_keys(clone_flags, p)))
1066 goto bad_fork_cleanup_mm;
1067 if ((retval = copy_namespaces(clone_flags, p)))
1068 goto bad_fork_cleanup_keys;
1069 if ((retval = copy_io(clone_flags, p)))
1070 goto bad_fork_cleanup_namespaces;
1071 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1072 if (retval)
1073 goto bad_fork_cleanup_io;
1075 if (pid != &init_struct_pid) {
1076 retval = -ENOMEM;
1077 pid = alloc_pid(task_active_pid_ns(p));
1078 if (!pid)
1079 goto bad_fork_cleanup_io;
1081 if (clone_flags & CLONE_NEWPID) {
1082 retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1083 if (retval < 0)
1084 goto bad_fork_free_pid;
1088 p->pid = pid_nr(pid);
1089 p->tgid = p->pid;
1090 if (clone_flags & CLONE_THREAD)
1091 p->tgid = current->tgid;
1093 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1095 * Clear TID on mm_release()?
1097 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1098 #ifdef CONFIG_FUTEX
1099 p->robust_list = NULL;
1100 #ifdef CONFIG_COMPAT
1101 p->compat_robust_list = NULL;
1102 #endif
1103 INIT_LIST_HEAD(&p->pi_state_list);
1104 p->pi_state_cache = NULL;
1105 #endif
1107 * sigaltstack should be cleared when sharing the same VM
1109 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1110 p->sas_ss_sp = p->sas_ss_size = 0;
1113 * Syscall tracing should be turned off in the child regardless
1114 * of CLONE_PTRACE.
1116 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1117 #ifdef TIF_SYSCALL_EMU
1118 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1119 #endif
1120 clear_all_latency_tracing(p);
1122 /* Our parent execution domain becomes current domain
1123 These must match for thread signalling to apply */
1124 p->parent_exec_id = p->self_exec_id;
1126 /* ok, now we should be set up.. */
1127 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1128 p->pdeath_signal = 0;
1129 p->exit_state = 0;
1132 * Ok, make it visible to the rest of the system.
1133 * We dont wake it up yet.
1135 p->group_leader = p;
1136 INIT_LIST_HEAD(&p->thread_group);
1137 INIT_LIST_HEAD(&p->ptrace_entry);
1138 INIT_LIST_HEAD(&p->ptraced);
1140 /* Now that the task is set up, run cgroup callbacks if
1141 * necessary. We need to run them before the task is visible
1142 * on the tasklist. */
1143 cgroup_fork_callbacks(p);
1144 cgroup_callbacks_done = 1;
1146 /* Need tasklist lock for parent etc handling! */
1147 write_lock_irq(&tasklist_lock);
1150 * The task hasn't been attached yet, so its cpus_allowed mask will
1151 * not be changed, nor will its assigned CPU.
1153 * The cpus_allowed mask of the parent may have changed after it was
1154 * copied first time - so re-copy it here, then check the child's CPU
1155 * to ensure it is on a valid CPU (and if not, just force it back to
1156 * parent's CPU). This avoids alot of nasty races.
1158 p->cpus_allowed = current->cpus_allowed;
1159 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1160 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1161 !cpu_online(task_cpu(p))))
1162 set_task_cpu(p, smp_processor_id());
1164 /* CLONE_PARENT re-uses the old parent */
1165 if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1166 p->real_parent = current->real_parent;
1167 else
1168 p->real_parent = current;
1169 p->parent = p->real_parent;
1171 spin_lock(&current->sighand->siglock);
1174 * Process group and session signals need to be delivered to just the
1175 * parent before the fork or both the parent and the child after the
1176 * fork. Restart if a signal comes in before we add the new process to
1177 * it's process group.
1178 * A fatal signal pending means that current will exit, so the new
1179 * thread can't slip out of an OOM kill (or normal SIGKILL).
1181 recalc_sigpending();
1182 if (signal_pending(current)) {
1183 spin_unlock(&current->sighand->siglock);
1184 write_unlock_irq(&tasklist_lock);
1185 retval = -ERESTARTNOINTR;
1186 goto bad_fork_free_pid;
1189 if (clone_flags & CLONE_THREAD) {
1190 p->group_leader = current->group_leader;
1191 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1193 if (!cputime_eq(current->signal->it_virt_expires,
1194 cputime_zero) ||
1195 !cputime_eq(current->signal->it_prof_expires,
1196 cputime_zero) ||
1197 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1198 !list_empty(&current->signal->cpu_timers[0]) ||
1199 !list_empty(&current->signal->cpu_timers[1]) ||
1200 !list_empty(&current->signal->cpu_timers[2])) {
1202 * Have child wake up on its first tick to check
1203 * for process CPU timers.
1205 p->it_prof_expires = jiffies_to_cputime(1);
1209 if (likely(p->pid)) {
1210 list_add_tail(&p->sibling, &p->real_parent->children);
1211 if (unlikely(p->ptrace & PT_PTRACED))
1212 __ptrace_link(p, current->parent);
1214 if (thread_group_leader(p)) {
1215 if (clone_flags & CLONE_NEWPID)
1216 p->nsproxy->pid_ns->child_reaper = p;
1218 p->signal->leader_pid = pid;
1219 p->signal->tty = current->signal->tty;
1220 set_task_pgrp(p, task_pgrp_nr(current));
1221 set_task_session(p, task_session_nr(current));
1222 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1223 attach_pid(p, PIDTYPE_SID, task_session(current));
1224 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1225 __get_cpu_var(process_counts)++;
1227 attach_pid(p, PIDTYPE_PID, pid);
1228 nr_threads++;
1231 total_forks++;
1232 spin_unlock(&current->sighand->siglock);
1233 write_unlock_irq(&tasklist_lock);
1234 proc_fork_connector(p);
1235 cgroup_post_fork(p);
1236 return p;
1238 bad_fork_free_pid:
1239 if (pid != &init_struct_pid)
1240 free_pid(pid);
1241 bad_fork_cleanup_io:
1242 put_io_context(p->io_context);
1243 bad_fork_cleanup_namespaces:
1244 exit_task_namespaces(p);
1245 bad_fork_cleanup_keys:
1246 exit_keys(p);
1247 bad_fork_cleanup_mm:
1248 if (p->mm)
1249 mmput(p->mm);
1250 bad_fork_cleanup_signal:
1251 cleanup_signal(p);
1252 bad_fork_cleanup_sighand:
1253 __cleanup_sighand(p->sighand);
1254 bad_fork_cleanup_fs:
1255 exit_fs(p); /* blocking */
1256 bad_fork_cleanup_files:
1257 exit_files(p); /* blocking */
1258 bad_fork_cleanup_semundo:
1259 exit_sem(p);
1260 bad_fork_cleanup_audit:
1261 audit_free(p);
1262 bad_fork_cleanup_security:
1263 security_task_free(p);
1264 bad_fork_cleanup_policy:
1265 #ifdef CONFIG_NUMA
1266 mpol_put(p->mempolicy);
1267 bad_fork_cleanup_cgroup:
1268 #endif
1269 cgroup_exit(p, cgroup_callbacks_done);
1270 delayacct_tsk_free(p);
1271 if (p->binfmt)
1272 module_put(p->binfmt->module);
1273 bad_fork_cleanup_put_domain:
1274 module_put(task_thread_info(p)->exec_domain->module);
1275 bad_fork_cleanup_count:
1276 put_group_info(p->group_info);
1277 atomic_dec(&p->user->processes);
1278 free_uid(p->user);
1279 bad_fork_free:
1280 free_task(p);
1281 fork_out:
1282 return ERR_PTR(retval);
1285 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1287 memset(regs, 0, sizeof(struct pt_regs));
1288 return regs;
1291 struct task_struct * __cpuinit fork_idle(int cpu)
1293 struct task_struct *task;
1294 struct pt_regs regs;
1296 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1297 &init_struct_pid);
1298 if (!IS_ERR(task))
1299 init_idle(task, cpu);
1301 return task;
1304 static int fork_traceflag(unsigned clone_flags)
1306 if (clone_flags & CLONE_UNTRACED)
1307 return 0;
1308 else if (clone_flags & CLONE_VFORK) {
1309 if (current->ptrace & PT_TRACE_VFORK)
1310 return PTRACE_EVENT_VFORK;
1311 } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1312 if (current->ptrace & PT_TRACE_CLONE)
1313 return PTRACE_EVENT_CLONE;
1314 } else if (current->ptrace & PT_TRACE_FORK)
1315 return PTRACE_EVENT_FORK;
1317 return 0;
1321 * Ok, this is the main fork-routine.
1323 * It copies the process, and if successful kick-starts
1324 * it and waits for it to finish using the VM if required.
1326 long do_fork(unsigned long clone_flags,
1327 unsigned long stack_start,
1328 struct pt_regs *regs,
1329 unsigned long stack_size,
1330 int __user *parent_tidptr,
1331 int __user *child_tidptr)
1333 struct task_struct *p;
1334 int trace = 0;
1335 long nr;
1338 * We hope to recycle these flags after 2.6.26
1340 if (unlikely(clone_flags & CLONE_STOPPED)) {
1341 static int __read_mostly count = 100;
1343 if (count > 0 && printk_ratelimit()) {
1344 char comm[TASK_COMM_LEN];
1346 count--;
1347 printk(KERN_INFO "fork(): process `%s' used deprecated "
1348 "clone flags 0x%lx\n",
1349 get_task_comm(comm, current),
1350 clone_flags & CLONE_STOPPED);
1354 if (unlikely(current->ptrace)) {
1355 trace = fork_traceflag (clone_flags);
1356 if (trace)
1357 clone_flags |= CLONE_PTRACE;
1360 p = copy_process(clone_flags, stack_start, regs, stack_size,
1361 child_tidptr, NULL);
1363 * Do this prior waking up the new thread - the thread pointer
1364 * might get invalid after that point, if the thread exits quickly.
1366 if (!IS_ERR(p)) {
1367 struct completion vfork;
1369 nr = task_pid_vnr(p);
1371 if (clone_flags & CLONE_PARENT_SETTID)
1372 put_user(nr, parent_tidptr);
1374 if (clone_flags & CLONE_VFORK) {
1375 p->vfork_done = &vfork;
1376 init_completion(&vfork);
1379 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1381 * We'll start up with an immediate SIGSTOP.
1383 sigaddset(&p->pending.signal, SIGSTOP);
1384 set_tsk_thread_flag(p, TIF_SIGPENDING);
1387 if (!(clone_flags & CLONE_STOPPED))
1388 wake_up_new_task(p, clone_flags);
1389 else
1390 __set_task_state(p, TASK_STOPPED);
1392 if (unlikely (trace)) {
1393 current->ptrace_message = nr;
1394 ptrace_notify ((trace << 8) | SIGTRAP);
1397 if (clone_flags & CLONE_VFORK) {
1398 freezer_do_not_count();
1399 wait_for_completion(&vfork);
1400 freezer_count();
1401 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1402 current->ptrace_message = nr;
1403 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1406 } else {
1407 nr = PTR_ERR(p);
1409 return nr;
1412 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1413 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1414 #endif
1416 static void sighand_ctor(struct kmem_cache *cachep, void *data)
1418 struct sighand_struct *sighand = data;
1420 spin_lock_init(&sighand->siglock);
1421 init_waitqueue_head(&sighand->signalfd_wqh);
1424 void __init proc_caches_init(void)
1426 sighand_cachep = kmem_cache_create("sighand_cache",
1427 sizeof(struct sighand_struct), 0,
1428 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1429 sighand_ctor);
1430 signal_cachep = kmem_cache_create("signal_cache",
1431 sizeof(struct signal_struct), 0,
1432 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1433 files_cachep = kmem_cache_create("files_cache",
1434 sizeof(struct files_struct), 0,
1435 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1436 fs_cachep = kmem_cache_create("fs_cache",
1437 sizeof(struct fs_struct), 0,
1438 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1439 vm_area_cachep = kmem_cache_create("vm_area_struct",
1440 sizeof(struct vm_area_struct), 0,
1441 SLAB_PANIC, NULL);
1442 mm_cachep = kmem_cache_create("mm_struct",
1443 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1444 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1448 * Check constraints on flags passed to the unshare system call and
1449 * force unsharing of additional process context as appropriate.
1451 static void check_unshare_flags(unsigned long *flags_ptr)
1454 * If unsharing a thread from a thread group, must also
1455 * unshare vm.
1457 if (*flags_ptr & CLONE_THREAD)
1458 *flags_ptr |= CLONE_VM;
1461 * If unsharing vm, must also unshare signal handlers.
1463 if (*flags_ptr & CLONE_VM)
1464 *flags_ptr |= CLONE_SIGHAND;
1467 * If unsharing signal handlers and the task was created
1468 * using CLONE_THREAD, then must unshare the thread
1470 if ((*flags_ptr & CLONE_SIGHAND) &&
1471 (atomic_read(&current->signal->count) > 1))
1472 *flags_ptr |= CLONE_THREAD;
1475 * If unsharing namespace, must also unshare filesystem information.
1477 if (*flags_ptr & CLONE_NEWNS)
1478 *flags_ptr |= CLONE_FS;
1482 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1484 static int unshare_thread(unsigned long unshare_flags)
1486 if (unshare_flags & CLONE_THREAD)
1487 return -EINVAL;
1489 return 0;
1493 * Unshare the filesystem structure if it is being shared
1495 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1497 struct fs_struct *fs = current->fs;
1499 if ((unshare_flags & CLONE_FS) &&
1500 (fs && atomic_read(&fs->count) > 1)) {
1501 *new_fsp = __copy_fs_struct(current->fs);
1502 if (!*new_fsp)
1503 return -ENOMEM;
1506 return 0;
1510 * Unsharing of sighand is not supported yet
1512 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1514 struct sighand_struct *sigh = current->sighand;
1516 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1517 return -EINVAL;
1518 else
1519 return 0;
1523 * Unshare vm if it is being shared
1525 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1527 struct mm_struct *mm = current->mm;
1529 if ((unshare_flags & CLONE_VM) &&
1530 (mm && atomic_read(&mm->mm_users) > 1)) {
1531 return -EINVAL;
1534 return 0;
1538 * Unshare file descriptor table if it is being shared
1540 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1542 struct files_struct *fd = current->files;
1543 int error = 0;
1545 if ((unshare_flags & CLONE_FILES) &&
1546 (fd && atomic_read(&fd->count) > 1)) {
1547 *new_fdp = dup_fd(fd, &error);
1548 if (!*new_fdp)
1549 return error;
1552 return 0;
1556 * unshare allows a process to 'unshare' part of the process
1557 * context which was originally shared using clone. copy_*
1558 * functions used by do_fork() cannot be used here directly
1559 * because they modify an inactive task_struct that is being
1560 * constructed. Here we are modifying the current, active,
1561 * task_struct.
1563 asmlinkage long sys_unshare(unsigned long unshare_flags)
1565 int err = 0;
1566 struct fs_struct *fs, *new_fs = NULL;
1567 struct sighand_struct *new_sigh = NULL;
1568 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1569 struct files_struct *fd, *new_fd = NULL;
1570 struct nsproxy *new_nsproxy = NULL;
1571 int do_sysvsem = 0;
1573 check_unshare_flags(&unshare_flags);
1575 /* Return -EINVAL for all unsupported flags */
1576 err = -EINVAL;
1577 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1578 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1579 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1580 CLONE_NEWNET))
1581 goto bad_unshare_out;
1584 * CLONE_NEWIPC must also detach from the undolist: after switching
1585 * to a new ipc namespace, the semaphore arrays from the old
1586 * namespace are unreachable.
1588 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1589 do_sysvsem = 1;
1590 if ((err = unshare_thread(unshare_flags)))
1591 goto bad_unshare_out;
1592 if ((err = unshare_fs(unshare_flags, &new_fs)))
1593 goto bad_unshare_cleanup_thread;
1594 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1595 goto bad_unshare_cleanup_fs;
1596 if ((err = unshare_vm(unshare_flags, &new_mm)))
1597 goto bad_unshare_cleanup_sigh;
1598 if ((err = unshare_fd(unshare_flags, &new_fd)))
1599 goto bad_unshare_cleanup_vm;
1600 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1601 new_fs)))
1602 goto bad_unshare_cleanup_fd;
1604 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1605 if (do_sysvsem) {
1607 * CLONE_SYSVSEM is equivalent to sys_exit().
1609 exit_sem(current);
1612 if (new_nsproxy) {
1613 switch_task_namespaces(current, new_nsproxy);
1614 new_nsproxy = NULL;
1617 task_lock(current);
1619 if (new_fs) {
1620 fs = current->fs;
1621 current->fs = new_fs;
1622 new_fs = fs;
1625 if (new_mm) {
1626 mm = current->mm;
1627 active_mm = current->active_mm;
1628 current->mm = new_mm;
1629 current->active_mm = new_mm;
1630 activate_mm(active_mm, new_mm);
1631 new_mm = mm;
1634 if (new_fd) {
1635 fd = current->files;
1636 current->files = new_fd;
1637 new_fd = fd;
1640 task_unlock(current);
1643 if (new_nsproxy)
1644 put_nsproxy(new_nsproxy);
1646 bad_unshare_cleanup_fd:
1647 if (new_fd)
1648 put_files_struct(new_fd);
1650 bad_unshare_cleanup_vm:
1651 if (new_mm)
1652 mmput(new_mm);
1654 bad_unshare_cleanup_sigh:
1655 if (new_sigh)
1656 if (atomic_dec_and_test(&new_sigh->count))
1657 kmem_cache_free(sighand_cachep, new_sigh);
1659 bad_unshare_cleanup_fs:
1660 if (new_fs)
1661 put_fs_struct(new_fs);
1663 bad_unshare_cleanup_thread:
1664 bad_unshare_out:
1665 return err;
1669 * Helper to unshare the files of the current task.
1670 * We don't want to expose copy_files internals to
1671 * the exec layer of the kernel.
1674 int unshare_files(struct files_struct **displaced)
1676 struct task_struct *task = current;
1677 struct files_struct *copy = NULL;
1678 int error;
1680 error = unshare_fd(CLONE_FILES, &copy);
1681 if (error || !copy) {
1682 *displaced = NULL;
1683 return error;
1685 *displaced = task->files;
1686 task_lock(task);
1687 task->files = copy;
1688 task_unlock(task);
1689 return 0;