sysfs: Fail bin file mmap if vma close is implemented.
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / fork.c
blobc445f8cc408d777dd7a94aec3fa78c07e1d98b98
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>
67 #include <linux/user-return-notifier.h>
69 #include <asm/pgtable.h>
70 #include <asm/pgalloc.h>
71 #include <asm/uaccess.h>
72 #include <asm/mmu_context.h>
73 #include <asm/cacheflush.h>
74 #include <asm/tlbflush.h>
76 #include <trace/events/sched.h>
79 * Protected counters by write_lock_irq(&tasklist_lock)
81 unsigned long total_forks; /* Handle normal Linux uptimes. */
82 int nr_threads; /* The idle threads do not count.. */
84 int max_threads; /* tunable limit on nr_threads */
86 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
90 #ifdef CONFIG_PROVE_RCU
91 int lockdep_tasklist_lock_is_held(void)
93 return lockdep_is_held(&tasklist_lock);
95 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
96 #endif /* #ifdef CONFIG_PROVE_RCU */
98 int nr_processes(void)
100 int cpu;
101 int total = 0;
103 for_each_possible_cpu(cpu)
104 total += per_cpu(process_counts, cpu);
106 return total;
109 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
110 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
111 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
112 static struct kmem_cache *task_struct_cachep;
113 #endif
115 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
116 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
118 #ifdef CONFIG_DEBUG_STACK_USAGE
119 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
120 #else
121 gfp_t mask = GFP_KERNEL;
122 #endif
123 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
126 static inline void free_thread_info(struct thread_info *ti)
128 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
130 #endif
132 /* SLAB cache for signal_struct structures (tsk->signal) */
133 static struct kmem_cache *signal_cachep;
135 /* SLAB cache for sighand_struct structures (tsk->sighand) */
136 struct kmem_cache *sighand_cachep;
138 /* SLAB cache for files_struct structures (tsk->files) */
139 struct kmem_cache *files_cachep;
141 /* SLAB cache for fs_struct structures (tsk->fs) */
142 struct kmem_cache *fs_cachep;
144 /* SLAB cache for vm_area_struct structures */
145 struct kmem_cache *vm_area_cachep;
147 /* SLAB cache for mm_struct structures (tsk->mm) */
148 static struct kmem_cache *mm_cachep;
150 static void account_kernel_stack(struct thread_info *ti, int account)
152 struct zone *zone = page_zone(virt_to_page(ti));
154 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
157 void free_task(struct task_struct *tsk)
159 prop_local_destroy_single(&tsk->dirties);
160 account_kernel_stack(tsk->stack, -1);
161 free_thread_info(tsk->stack);
162 rt_mutex_debug_task_free(tsk);
163 ftrace_graph_exit_task(tsk);
164 free_task_struct(tsk);
166 EXPORT_SYMBOL(free_task);
168 static inline void free_signal_struct(struct signal_struct *sig)
170 taskstats_tgid_free(sig);
171 kmem_cache_free(signal_cachep, sig);
174 static inline void put_signal_struct(struct signal_struct *sig)
176 if (atomic_dec_and_test(&sig->sigcnt))
177 free_signal_struct(sig);
180 void __put_task_struct(struct task_struct *tsk)
182 WARN_ON(!tsk->exit_state);
183 WARN_ON(atomic_read(&tsk->usage));
184 WARN_ON(tsk == current);
186 exit_creds(tsk);
187 delayacct_tsk_free(tsk);
188 put_signal_struct(tsk->signal);
190 if (!profile_handoff_task(tsk))
191 free_task(tsk);
195 * macro override instead of weak attribute alias, to workaround
196 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
198 #ifndef arch_task_cache_init
199 #define arch_task_cache_init()
200 #endif
202 void __init fork_init(unsigned long mempages)
204 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
205 #ifndef ARCH_MIN_TASKALIGN
206 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
207 #endif
208 /* create a slab on which task_structs can be allocated */
209 task_struct_cachep =
210 kmem_cache_create("task_struct", sizeof(struct task_struct),
211 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
212 #endif
214 /* do the arch specific task caches init */
215 arch_task_cache_init();
218 * The default maximum number of threads is set to a safe
219 * value: the thread structures can take up at most half
220 * of memory.
222 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
225 * we need to allow at least 20 threads to boot a system
227 if(max_threads < 20)
228 max_threads = 20;
230 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
231 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
232 init_task.signal->rlim[RLIMIT_SIGPENDING] =
233 init_task.signal->rlim[RLIMIT_NPROC];
236 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
237 struct task_struct *src)
239 *dst = *src;
240 return 0;
243 static struct task_struct *dup_task_struct(struct task_struct *orig)
245 struct task_struct *tsk;
246 struct thread_info *ti;
247 unsigned long *stackend;
249 int err;
251 prepare_to_copy(orig);
253 tsk = alloc_task_struct();
254 if (!tsk)
255 return NULL;
257 ti = alloc_thread_info(tsk);
258 if (!ti) {
259 free_task_struct(tsk);
260 return NULL;
263 err = arch_dup_task_struct(tsk, orig);
264 if (err)
265 goto out;
267 tsk->stack = ti;
269 err = prop_local_init_single(&tsk->dirties);
270 if (err)
271 goto out;
273 setup_thread_stack(tsk, orig);
274 clear_user_return_notifier(tsk);
275 stackend = end_of_stack(tsk);
276 *stackend = STACK_END_MAGIC; /* for overflow detection */
278 #ifdef CONFIG_CC_STACKPROTECTOR
279 tsk->stack_canary = get_random_int();
280 #endif
282 /* One for us, one for whoever does the "release_task()" (usually parent) */
283 atomic_set(&tsk->usage,2);
284 atomic_set(&tsk->fs_excl, 0);
285 #ifdef CONFIG_BLK_DEV_IO_TRACE
286 tsk->btrace_seq = 0;
287 #endif
288 tsk->splice_pipe = NULL;
290 account_kernel_stack(ti, 1);
292 return tsk;
294 out:
295 free_thread_info(ti);
296 free_task_struct(tsk);
297 return NULL;
300 #ifdef CONFIG_MMU
301 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
303 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
304 struct rb_node **rb_link, *rb_parent;
305 int retval;
306 unsigned long charge;
307 struct mempolicy *pol;
309 down_write(&oldmm->mmap_sem);
310 flush_cache_dup_mm(oldmm);
312 * Not linked in yet - no deadlock potential:
314 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
316 mm->locked_vm = 0;
317 mm->mmap = NULL;
318 mm->mmap_cache = NULL;
319 mm->free_area_cache = oldmm->mmap_base;
320 mm->cached_hole_size = ~0UL;
321 mm->map_count = 0;
322 cpumask_clear(mm_cpumask(mm));
323 mm->mm_rb = RB_ROOT;
324 rb_link = &mm->mm_rb.rb_node;
325 rb_parent = NULL;
326 pprev = &mm->mmap;
327 retval = ksm_fork(mm, oldmm);
328 if (retval)
329 goto out;
331 prev = NULL;
332 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
333 struct file *file;
335 if (mpnt->vm_flags & VM_DONTCOPY) {
336 long pages = vma_pages(mpnt);
337 mm->total_vm -= pages;
338 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
339 -pages);
340 continue;
342 charge = 0;
343 if (mpnt->vm_flags & VM_ACCOUNT) {
344 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
345 if (security_vm_enough_memory(len))
346 goto fail_nomem;
347 charge = len;
349 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
350 if (!tmp)
351 goto fail_nomem;
352 *tmp = *mpnt;
353 INIT_LIST_HEAD(&tmp->anon_vma_chain);
354 pol = mpol_dup(vma_policy(mpnt));
355 retval = PTR_ERR(pol);
356 if (IS_ERR(pol))
357 goto fail_nomem_policy;
358 vma_set_policy(tmp, pol);
359 tmp->vm_mm = mm;
360 if (anon_vma_fork(tmp, mpnt))
361 goto fail_nomem_anon_vma_fork;
362 tmp->vm_flags &= ~VM_LOCKED;
363 tmp->vm_next = tmp->vm_prev = NULL;
364 file = tmp->vm_file;
365 if (file) {
366 struct inode *inode = file->f_path.dentry->d_inode;
367 struct address_space *mapping = file->f_mapping;
369 get_file(file);
370 if (tmp->vm_flags & VM_DENYWRITE)
371 atomic_dec(&inode->i_writecount);
372 spin_lock(&mapping->i_mmap_lock);
373 if (tmp->vm_flags & VM_SHARED)
374 mapping->i_mmap_writable++;
375 tmp->vm_truncate_count = mpnt->vm_truncate_count;
376 flush_dcache_mmap_lock(mapping);
377 /* insert tmp into the share list, just after mpnt */
378 vma_prio_tree_add(tmp, mpnt);
379 flush_dcache_mmap_unlock(mapping);
380 spin_unlock(&mapping->i_mmap_lock);
384 * Clear hugetlb-related page reserves for children. This only
385 * affects MAP_PRIVATE mappings. Faults generated by the child
386 * are not guaranteed to succeed, even if read-only
388 if (is_vm_hugetlb_page(tmp))
389 reset_vma_resv_huge_pages(tmp);
392 * Link in the new vma and copy the page table entries.
394 *pprev = tmp;
395 pprev = &tmp->vm_next;
396 tmp->vm_prev = prev;
397 prev = tmp;
399 __vma_link_rb(mm, tmp, rb_link, rb_parent);
400 rb_link = &tmp->vm_rb.rb_right;
401 rb_parent = &tmp->vm_rb;
403 mm->map_count++;
404 retval = copy_page_range(mm, oldmm, mpnt);
406 if (tmp->vm_ops && tmp->vm_ops->open)
407 tmp->vm_ops->open(tmp);
409 if (retval)
410 goto out;
412 /* a new mm has just been created */
413 arch_dup_mmap(oldmm, mm);
414 retval = 0;
415 out:
416 up_write(&mm->mmap_sem);
417 flush_tlb_mm(oldmm);
418 up_write(&oldmm->mmap_sem);
419 return retval;
420 fail_nomem_anon_vma_fork:
421 mpol_put(pol);
422 fail_nomem_policy:
423 kmem_cache_free(vm_area_cachep, tmp);
424 fail_nomem:
425 retval = -ENOMEM;
426 vm_unacct_memory(charge);
427 goto out;
430 static inline int mm_alloc_pgd(struct mm_struct * mm)
432 mm->pgd = pgd_alloc(mm);
433 if (unlikely(!mm->pgd))
434 return -ENOMEM;
435 return 0;
438 static inline void mm_free_pgd(struct mm_struct * mm)
440 pgd_free(mm, mm->pgd);
442 #else
443 #define dup_mmap(mm, oldmm) (0)
444 #define mm_alloc_pgd(mm) (0)
445 #define mm_free_pgd(mm)
446 #endif /* CONFIG_MMU */
448 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
450 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
451 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
453 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
455 static int __init coredump_filter_setup(char *s)
457 default_dump_filter =
458 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
459 MMF_DUMP_FILTER_MASK;
460 return 1;
463 __setup("coredump_filter=", coredump_filter_setup);
465 #include <linux/init_task.h>
467 static void mm_init_aio(struct mm_struct *mm)
469 #ifdef CONFIG_AIO
470 spin_lock_init(&mm->ioctx_lock);
471 INIT_HLIST_HEAD(&mm->ioctx_list);
472 #endif
475 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
477 atomic_set(&mm->mm_users, 1);
478 atomic_set(&mm->mm_count, 1);
479 init_rwsem(&mm->mmap_sem);
480 INIT_LIST_HEAD(&mm->mmlist);
481 mm->flags = (current->mm) ?
482 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
483 mm->core_state = NULL;
484 mm->nr_ptes = 0;
485 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
486 spin_lock_init(&mm->page_table_lock);
487 mm->free_area_cache = TASK_UNMAPPED_BASE;
488 mm->cached_hole_size = ~0UL;
489 mm_init_aio(mm);
490 mm_init_owner(mm, p);
492 if (likely(!mm_alloc_pgd(mm))) {
493 mm->def_flags = 0;
494 mmu_notifier_mm_init(mm);
495 return mm;
498 free_mm(mm);
499 return NULL;
503 * Allocate and initialize an mm_struct.
505 struct mm_struct * mm_alloc(void)
507 struct mm_struct * mm;
509 mm = allocate_mm();
510 if (mm) {
511 memset(mm, 0, sizeof(*mm));
512 mm = mm_init(mm, current);
514 return mm;
518 * Called when the last reference to the mm
519 * is dropped: either by a lazy thread or by
520 * mmput. Free the page directory and the mm.
522 void __mmdrop(struct mm_struct *mm)
524 BUG_ON(mm == &init_mm);
525 mm_free_pgd(mm);
526 destroy_context(mm);
527 mmu_notifier_mm_destroy(mm);
528 free_mm(mm);
530 EXPORT_SYMBOL_GPL(__mmdrop);
533 * Decrement the use count and release all resources for an mm.
535 void mmput(struct mm_struct *mm)
537 might_sleep();
539 if (atomic_dec_and_test(&mm->mm_users)) {
540 exit_aio(mm);
541 ksm_exit(mm);
542 exit_mmap(mm);
543 set_mm_exe_file(mm, NULL);
544 if (!list_empty(&mm->mmlist)) {
545 spin_lock(&mmlist_lock);
546 list_del(&mm->mmlist);
547 spin_unlock(&mmlist_lock);
549 put_swap_token(mm);
550 if (mm->binfmt)
551 module_put(mm->binfmt->module);
552 mmdrop(mm);
555 EXPORT_SYMBOL_GPL(mmput);
558 * get_task_mm - acquire a reference to the task's mm
560 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
561 * this kernel workthread has transiently adopted a user mm with use_mm,
562 * to do its AIO) is not set and if so returns a reference to it, after
563 * bumping up the use count. User must release the mm via mmput()
564 * after use. Typically used by /proc and ptrace.
566 struct mm_struct *get_task_mm(struct task_struct *task)
568 struct mm_struct *mm;
570 task_lock(task);
571 mm = task->mm;
572 if (mm) {
573 if (task->flags & PF_KTHREAD)
574 mm = NULL;
575 else
576 atomic_inc(&mm->mm_users);
578 task_unlock(task);
579 return mm;
581 EXPORT_SYMBOL_GPL(get_task_mm);
583 /* Please note the differences between mmput and mm_release.
584 * mmput is called whenever we stop holding onto a mm_struct,
585 * error success whatever.
587 * mm_release is called after a mm_struct has been removed
588 * from the current process.
590 * This difference is important for error handling, when we
591 * only half set up a mm_struct for a new process and need to restore
592 * the old one. Because we mmput the new mm_struct before
593 * restoring the old one. . .
594 * Eric Biederman 10 January 1998
596 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
598 struct completion *vfork_done = tsk->vfork_done;
600 /* Get rid of any futexes when releasing the mm */
601 #ifdef CONFIG_FUTEX
602 if (unlikely(tsk->robust_list)) {
603 exit_robust_list(tsk);
604 tsk->robust_list = NULL;
606 #ifdef CONFIG_COMPAT
607 if (unlikely(tsk->compat_robust_list)) {
608 compat_exit_robust_list(tsk);
609 tsk->compat_robust_list = NULL;
611 #endif
612 if (unlikely(!list_empty(&tsk->pi_state_list)))
613 exit_pi_state_list(tsk);
614 #endif
616 /* Get rid of any cached register state */
617 deactivate_mm(tsk, mm);
619 /* notify parent sleeping on vfork() */
620 if (vfork_done) {
621 tsk->vfork_done = NULL;
622 complete(vfork_done);
626 * If we're exiting normally, clear a user-space tid field if
627 * requested. We leave this alone when dying by signal, to leave
628 * the value intact in a core dump, and to save the unnecessary
629 * trouble otherwise. Userland only wants this done for a sys_exit.
631 if (tsk->clear_child_tid) {
632 if (!(tsk->flags & PF_SIGNALED) &&
633 atomic_read(&mm->mm_users) > 1) {
635 * We don't check the error code - if userspace has
636 * not set up a proper pointer then tough luck.
638 put_user(0, tsk->clear_child_tid);
639 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
640 1, NULL, NULL, 0);
642 tsk->clear_child_tid = NULL;
647 * Allocate a new mm structure and copy contents from the
648 * mm structure of the passed in task structure.
650 struct mm_struct *dup_mm(struct task_struct *tsk)
652 struct mm_struct *mm, *oldmm = current->mm;
653 int err;
655 if (!oldmm)
656 return NULL;
658 mm = allocate_mm();
659 if (!mm)
660 goto fail_nomem;
662 memcpy(mm, oldmm, sizeof(*mm));
664 /* Initializing for Swap token stuff */
665 mm->token_priority = 0;
666 mm->last_interval = 0;
668 if (!mm_init(mm, tsk))
669 goto fail_nomem;
671 if (init_new_context(tsk, mm))
672 goto fail_nocontext;
674 dup_mm_exe_file(oldmm, mm);
676 err = dup_mmap(mm, oldmm);
677 if (err)
678 goto free_pt;
680 mm->hiwater_rss = get_mm_rss(mm);
681 mm->hiwater_vm = mm->total_vm;
683 if (mm->binfmt && !try_module_get(mm->binfmt->module))
684 goto free_pt;
686 return mm;
688 free_pt:
689 /* don't put binfmt in mmput, we haven't got module yet */
690 mm->binfmt = NULL;
691 mmput(mm);
693 fail_nomem:
694 return NULL;
696 fail_nocontext:
698 * If init_new_context() failed, we cannot use mmput() to free the mm
699 * because it calls destroy_context()
701 mm_free_pgd(mm);
702 free_mm(mm);
703 return NULL;
706 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
708 struct mm_struct * mm, *oldmm;
709 int retval;
711 tsk->min_flt = tsk->maj_flt = 0;
712 tsk->nvcsw = tsk->nivcsw = 0;
713 #ifdef CONFIG_DETECT_HUNG_TASK
714 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
715 #endif
717 tsk->mm = NULL;
718 tsk->active_mm = NULL;
721 * Are we cloning a kernel thread?
723 * We need to steal a active VM for that..
725 oldmm = current->mm;
726 if (!oldmm)
727 return 0;
729 if (clone_flags & CLONE_VM) {
730 atomic_inc(&oldmm->mm_users);
731 mm = oldmm;
732 goto good_mm;
735 retval = -ENOMEM;
736 mm = dup_mm(tsk);
737 if (!mm)
738 goto fail_nomem;
740 good_mm:
741 /* Initializing for Swap token stuff */
742 mm->token_priority = 0;
743 mm->last_interval = 0;
745 tsk->mm = mm;
746 tsk->active_mm = mm;
747 return 0;
749 fail_nomem:
750 return retval;
753 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
755 struct fs_struct *fs = current->fs;
756 if (clone_flags & CLONE_FS) {
757 /* tsk->fs is already what we want */
758 spin_lock(&fs->lock);
759 if (fs->in_exec) {
760 spin_unlock(&fs->lock);
761 return -EAGAIN;
763 fs->users++;
764 spin_unlock(&fs->lock);
765 return 0;
767 tsk->fs = copy_fs_struct(fs);
768 if (!tsk->fs)
769 return -ENOMEM;
770 return 0;
773 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
775 struct files_struct *oldf, *newf;
776 int error = 0;
779 * A background process may not have any files ...
781 oldf = current->files;
782 if (!oldf)
783 goto out;
785 if (clone_flags & CLONE_FILES) {
786 atomic_inc(&oldf->count);
787 goto out;
790 newf = dup_fd(oldf, &error);
791 if (!newf)
792 goto out;
794 tsk->files = newf;
795 error = 0;
796 out:
797 return error;
800 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
802 #ifdef CONFIG_BLOCK
803 struct io_context *ioc = current->io_context;
805 if (!ioc)
806 return 0;
808 * Share io context with parent, if CLONE_IO is set
810 if (clone_flags & CLONE_IO) {
811 tsk->io_context = ioc_task_link(ioc);
812 if (unlikely(!tsk->io_context))
813 return -ENOMEM;
814 } else if (ioprio_valid(ioc->ioprio)) {
815 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
816 if (unlikely(!tsk->io_context))
817 return -ENOMEM;
819 tsk->io_context->ioprio = ioc->ioprio;
821 #endif
822 return 0;
825 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
827 struct sighand_struct *sig;
829 if (clone_flags & CLONE_SIGHAND) {
830 atomic_inc(&current->sighand->count);
831 return 0;
833 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
834 rcu_assign_pointer(tsk->sighand, sig);
835 if (!sig)
836 return -ENOMEM;
837 atomic_set(&sig->count, 1);
838 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
839 return 0;
842 void __cleanup_sighand(struct sighand_struct *sighand)
844 if (atomic_dec_and_test(&sighand->count))
845 kmem_cache_free(sighand_cachep, sighand);
850 * Initialize POSIX timer handling for a thread group.
852 static void posix_cpu_timers_init_group(struct signal_struct *sig)
854 unsigned long cpu_limit;
856 /* Thread group counters. */
857 thread_group_cputime_init(sig);
859 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
860 if (cpu_limit != RLIM_INFINITY) {
861 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
862 sig->cputimer.running = 1;
865 /* The timer lists. */
866 INIT_LIST_HEAD(&sig->cpu_timers[0]);
867 INIT_LIST_HEAD(&sig->cpu_timers[1]);
868 INIT_LIST_HEAD(&sig->cpu_timers[2]);
871 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
873 struct signal_struct *sig;
875 if (clone_flags & CLONE_THREAD)
876 return 0;
878 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
879 tsk->signal = sig;
880 if (!sig)
881 return -ENOMEM;
883 sig->nr_threads = 1;
884 atomic_set(&sig->live, 1);
885 atomic_set(&sig->sigcnt, 1);
886 init_waitqueue_head(&sig->wait_chldexit);
887 if (clone_flags & CLONE_NEWPID)
888 sig->flags |= SIGNAL_UNKILLABLE;
889 sig->curr_target = tsk;
890 init_sigpending(&sig->shared_pending);
891 INIT_LIST_HEAD(&sig->posix_timers);
893 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
894 sig->real_timer.function = it_real_fn;
896 task_lock(current->group_leader);
897 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
898 task_unlock(current->group_leader);
900 posix_cpu_timers_init_group(sig);
902 tty_audit_fork(sig);
904 sig->oom_adj = current->signal->oom_adj;
905 sig->oom_score_adj = current->signal->oom_score_adj;
907 return 0;
910 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
912 unsigned long new_flags = p->flags;
914 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
915 new_flags |= PF_FORKNOEXEC;
916 new_flags |= PF_STARTING;
917 p->flags = new_flags;
918 clear_freeze_flag(p);
921 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
923 current->clear_child_tid = tidptr;
925 return task_pid_vnr(current);
928 static void rt_mutex_init_task(struct task_struct *p)
930 raw_spin_lock_init(&p->pi_lock);
931 #ifdef CONFIG_RT_MUTEXES
932 plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
933 p->pi_blocked_on = NULL;
934 #endif
937 #ifdef CONFIG_MM_OWNER
938 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
940 mm->owner = p;
942 #endif /* CONFIG_MM_OWNER */
945 * Initialize POSIX timer handling for a single task.
947 static void posix_cpu_timers_init(struct task_struct *tsk)
949 tsk->cputime_expires.prof_exp = cputime_zero;
950 tsk->cputime_expires.virt_exp = cputime_zero;
951 tsk->cputime_expires.sched_exp = 0;
952 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
953 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
954 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
958 * This creates a new process as a copy of the old one,
959 * but does not actually start it yet.
961 * It copies the registers, and all the appropriate
962 * parts of the process environment (as per the clone
963 * flags). The actual kick-off is left to the caller.
965 static struct task_struct *copy_process(unsigned long clone_flags,
966 unsigned long stack_start,
967 struct pt_regs *regs,
968 unsigned long stack_size,
969 int __user *child_tidptr,
970 struct pid *pid,
971 int trace)
973 int retval;
974 struct task_struct *p;
975 int cgroup_callbacks_done = 0;
977 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
978 return ERR_PTR(-EINVAL);
981 * Thread groups must share signals as well, and detached threads
982 * can only be started up within the thread group.
984 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
985 return ERR_PTR(-EINVAL);
988 * Shared signal handlers imply shared VM. By way of the above,
989 * thread groups also imply shared VM. Blocking this case allows
990 * for various simplifications in other code.
992 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
993 return ERR_PTR(-EINVAL);
996 * Siblings of global init remain as zombies on exit since they are
997 * not reaped by their parent (swapper). To solve this and to avoid
998 * multi-rooted process trees, prevent global and container-inits
999 * from creating siblings.
1001 if ((clone_flags & CLONE_PARENT) &&
1002 current->signal->flags & SIGNAL_UNKILLABLE)
1003 return ERR_PTR(-EINVAL);
1005 retval = security_task_create(clone_flags);
1006 if (retval)
1007 goto fork_out;
1009 retval = -ENOMEM;
1010 p = dup_task_struct(current);
1011 if (!p)
1012 goto fork_out;
1014 ftrace_graph_init_task(p);
1016 rt_mutex_init_task(p);
1018 #ifdef CONFIG_PROVE_LOCKING
1019 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1020 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1021 #endif
1022 retval = -EAGAIN;
1023 if (atomic_read(&p->real_cred->user->processes) >=
1024 task_rlimit(p, RLIMIT_NPROC)) {
1025 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1026 p->real_cred->user != INIT_USER)
1027 goto bad_fork_free;
1030 retval = copy_creds(p, clone_flags);
1031 if (retval < 0)
1032 goto bad_fork_free;
1035 * If multiple threads are within copy_process(), then this check
1036 * triggers too late. This doesn't hurt, the check is only there
1037 * to stop root fork bombs.
1039 retval = -EAGAIN;
1040 if (nr_threads >= max_threads)
1041 goto bad_fork_cleanup_count;
1043 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1044 goto bad_fork_cleanup_count;
1046 p->did_exec = 0;
1047 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1048 copy_flags(clone_flags, p);
1049 INIT_LIST_HEAD(&p->children);
1050 INIT_LIST_HEAD(&p->sibling);
1051 rcu_copy_process(p);
1052 p->vfork_done = NULL;
1053 spin_lock_init(&p->alloc_lock);
1055 init_sigpending(&p->pending);
1057 p->utime = cputime_zero;
1058 p->stime = cputime_zero;
1059 p->gtime = cputime_zero;
1060 p->utimescaled = cputime_zero;
1061 p->stimescaled = cputime_zero;
1062 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1063 p->prev_utime = cputime_zero;
1064 p->prev_stime = cputime_zero;
1065 #endif
1066 #if defined(SPLIT_RSS_COUNTING)
1067 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1068 #endif
1070 p->default_timer_slack_ns = current->timer_slack_ns;
1072 task_io_accounting_init(&p->ioac);
1073 acct_clear_integrals(p);
1075 posix_cpu_timers_init(p);
1077 p->lock_depth = -1; /* -1 = no lock */
1078 do_posix_clock_monotonic_gettime(&p->start_time);
1079 p->real_start_time = p->start_time;
1080 monotonic_to_bootbased(&p->real_start_time);
1081 p->io_context = NULL;
1082 p->audit_context = NULL;
1083 cgroup_fork(p);
1084 #ifdef CONFIG_NUMA
1085 p->mempolicy = mpol_dup(p->mempolicy);
1086 if (IS_ERR(p->mempolicy)) {
1087 retval = PTR_ERR(p->mempolicy);
1088 p->mempolicy = NULL;
1089 goto bad_fork_cleanup_cgroup;
1091 mpol_fix_fork_child_flag(p);
1092 #endif
1093 #ifdef CONFIG_TRACE_IRQFLAGS
1094 p->irq_events = 0;
1095 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1096 p->hardirqs_enabled = 1;
1097 #else
1098 p->hardirqs_enabled = 0;
1099 #endif
1100 p->hardirq_enable_ip = 0;
1101 p->hardirq_enable_event = 0;
1102 p->hardirq_disable_ip = _THIS_IP_;
1103 p->hardirq_disable_event = 0;
1104 p->softirqs_enabled = 1;
1105 p->softirq_enable_ip = _THIS_IP_;
1106 p->softirq_enable_event = 0;
1107 p->softirq_disable_ip = 0;
1108 p->softirq_disable_event = 0;
1109 p->hardirq_context = 0;
1110 p->softirq_context = 0;
1111 #endif
1112 #ifdef CONFIG_LOCKDEP
1113 p->lockdep_depth = 0; /* no locks held yet */
1114 p->curr_chain_key = 0;
1115 p->lockdep_recursion = 0;
1116 #endif
1118 #ifdef CONFIG_DEBUG_MUTEXES
1119 p->blocked_on = NULL; /* not blocked yet */
1120 #endif
1121 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1122 p->memcg_batch.do_batch = 0;
1123 p->memcg_batch.memcg = NULL;
1124 #endif
1126 /* Perform scheduler related setup. Assign this task to a CPU. */
1127 sched_fork(p, clone_flags);
1129 retval = perf_event_init_task(p);
1130 if (retval)
1131 goto bad_fork_cleanup_policy;
1133 if ((retval = audit_alloc(p)))
1134 goto bad_fork_cleanup_policy;
1135 /* copy all the process information */
1136 if ((retval = copy_semundo(clone_flags, p)))
1137 goto bad_fork_cleanup_audit;
1138 if ((retval = copy_files(clone_flags, p)))
1139 goto bad_fork_cleanup_semundo;
1140 if ((retval = copy_fs(clone_flags, p)))
1141 goto bad_fork_cleanup_files;
1142 if ((retval = copy_sighand(clone_flags, p)))
1143 goto bad_fork_cleanup_fs;
1144 if ((retval = copy_signal(clone_flags, p)))
1145 goto bad_fork_cleanup_sighand;
1146 if ((retval = copy_mm(clone_flags, p)))
1147 goto bad_fork_cleanup_signal;
1148 if ((retval = copy_namespaces(clone_flags, p)))
1149 goto bad_fork_cleanup_mm;
1150 if ((retval = copy_io(clone_flags, p)))
1151 goto bad_fork_cleanup_namespaces;
1152 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1153 if (retval)
1154 goto bad_fork_cleanup_io;
1156 if (pid != &init_struct_pid) {
1157 retval = -ENOMEM;
1158 pid = alloc_pid(p->nsproxy->pid_ns);
1159 if (!pid)
1160 goto bad_fork_cleanup_io;
1162 if (clone_flags & CLONE_NEWPID) {
1163 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1164 if (retval < 0)
1165 goto bad_fork_free_pid;
1169 p->pid = pid_nr(pid);
1170 p->tgid = p->pid;
1171 if (clone_flags & CLONE_THREAD)
1172 p->tgid = current->tgid;
1174 if (current->nsproxy != p->nsproxy) {
1175 retval = ns_cgroup_clone(p, pid);
1176 if (retval)
1177 goto bad_fork_free_pid;
1180 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1182 * Clear TID on mm_release()?
1184 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1185 #ifdef CONFIG_FUTEX
1186 p->robust_list = NULL;
1187 #ifdef CONFIG_COMPAT
1188 p->compat_robust_list = NULL;
1189 #endif
1190 INIT_LIST_HEAD(&p->pi_state_list);
1191 p->pi_state_cache = NULL;
1192 #endif
1194 * sigaltstack should be cleared when sharing the same VM
1196 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1197 p->sas_ss_sp = p->sas_ss_size = 0;
1200 * Syscall tracing and stepping should be turned off in the
1201 * child regardless of CLONE_PTRACE.
1203 user_disable_single_step(p);
1204 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1205 #ifdef TIF_SYSCALL_EMU
1206 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1207 #endif
1208 clear_all_latency_tracing(p);
1210 /* ok, now we should be set up.. */
1211 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1212 p->pdeath_signal = 0;
1213 p->exit_state = 0;
1216 * Ok, make it visible to the rest of the system.
1217 * We dont wake it up yet.
1219 p->group_leader = p;
1220 INIT_LIST_HEAD(&p->thread_group);
1222 /* Now that the task is set up, run cgroup callbacks if
1223 * necessary. We need to run them before the task is visible
1224 * on the tasklist. */
1225 cgroup_fork_callbacks(p);
1226 cgroup_callbacks_done = 1;
1228 /* Need tasklist lock for parent etc handling! */
1229 write_lock_irq(&tasklist_lock);
1231 /* CLONE_PARENT re-uses the old parent */
1232 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1233 p->real_parent = current->real_parent;
1234 p->parent_exec_id = current->parent_exec_id;
1235 } else {
1236 p->real_parent = current;
1237 p->parent_exec_id = current->self_exec_id;
1240 spin_lock(&current->sighand->siglock);
1243 * Process group and session signals need to be delivered to just the
1244 * parent before the fork or both the parent and the child after the
1245 * fork. Restart if a signal comes in before we add the new process to
1246 * it's process group.
1247 * A fatal signal pending means that current will exit, so the new
1248 * thread can't slip out of an OOM kill (or normal SIGKILL).
1250 recalc_sigpending();
1251 if (signal_pending(current)) {
1252 spin_unlock(&current->sighand->siglock);
1253 write_unlock_irq(&tasklist_lock);
1254 retval = -ERESTARTNOINTR;
1255 goto bad_fork_free_pid;
1258 if (clone_flags & CLONE_THREAD) {
1259 current->signal->nr_threads++;
1260 atomic_inc(&current->signal->live);
1261 atomic_inc(&current->signal->sigcnt);
1262 p->group_leader = current->group_leader;
1263 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1266 if (likely(p->pid)) {
1267 tracehook_finish_clone(p, clone_flags, trace);
1269 if (thread_group_leader(p)) {
1270 if (clone_flags & CLONE_NEWPID)
1271 p->nsproxy->pid_ns->child_reaper = p;
1273 p->signal->leader_pid = pid;
1274 p->signal->tty = tty_kref_get(current->signal->tty);
1275 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1276 attach_pid(p, PIDTYPE_SID, task_session(current));
1277 list_add_tail(&p->sibling, &p->real_parent->children);
1278 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1279 __get_cpu_var(process_counts)++;
1281 attach_pid(p, PIDTYPE_PID, pid);
1282 nr_threads++;
1285 total_forks++;
1286 spin_unlock(&current->sighand->siglock);
1287 write_unlock_irq(&tasklist_lock);
1288 proc_fork_connector(p);
1289 cgroup_post_fork(p);
1290 perf_event_fork(p);
1291 return p;
1293 bad_fork_free_pid:
1294 if (pid != &init_struct_pid)
1295 free_pid(pid);
1296 bad_fork_cleanup_io:
1297 if (p->io_context)
1298 exit_io_context(p);
1299 bad_fork_cleanup_namespaces:
1300 exit_task_namespaces(p);
1301 bad_fork_cleanup_mm:
1302 if (p->mm)
1303 mmput(p->mm);
1304 bad_fork_cleanup_signal:
1305 if (!(clone_flags & CLONE_THREAD))
1306 free_signal_struct(p->signal);
1307 bad_fork_cleanup_sighand:
1308 __cleanup_sighand(p->sighand);
1309 bad_fork_cleanup_fs:
1310 exit_fs(p); /* blocking */
1311 bad_fork_cleanup_files:
1312 exit_files(p); /* blocking */
1313 bad_fork_cleanup_semundo:
1314 exit_sem(p);
1315 bad_fork_cleanup_audit:
1316 audit_free(p);
1317 bad_fork_cleanup_policy:
1318 perf_event_free_task(p);
1319 #ifdef CONFIG_NUMA
1320 mpol_put(p->mempolicy);
1321 bad_fork_cleanup_cgroup:
1322 #endif
1323 cgroup_exit(p, cgroup_callbacks_done);
1324 delayacct_tsk_free(p);
1325 module_put(task_thread_info(p)->exec_domain->module);
1326 bad_fork_cleanup_count:
1327 atomic_dec(&p->cred->user->processes);
1328 exit_creds(p);
1329 bad_fork_free:
1330 free_task(p);
1331 fork_out:
1332 return ERR_PTR(retval);
1335 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1337 memset(regs, 0, sizeof(struct pt_regs));
1338 return regs;
1341 static inline void init_idle_pids(struct pid_link *links)
1343 enum pid_type type;
1345 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1346 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1347 links[type].pid = &init_struct_pid;
1351 struct task_struct * __cpuinit fork_idle(int cpu)
1353 struct task_struct *task;
1354 struct pt_regs regs;
1356 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1357 &init_struct_pid, 0);
1358 if (!IS_ERR(task)) {
1359 init_idle_pids(task->pids);
1360 init_idle(task, cpu);
1363 return task;
1367 * Ok, this is the main fork-routine.
1369 * It copies the process, and if successful kick-starts
1370 * it and waits for it to finish using the VM if required.
1372 long do_fork(unsigned long clone_flags,
1373 unsigned long stack_start,
1374 struct pt_regs *regs,
1375 unsigned long stack_size,
1376 int __user *parent_tidptr,
1377 int __user *child_tidptr)
1379 struct task_struct *p;
1380 int trace = 0;
1381 long nr;
1384 * Do some preliminary argument and permissions checking before we
1385 * actually start allocating stuff
1387 if (clone_flags & CLONE_NEWUSER) {
1388 if (clone_flags & CLONE_THREAD)
1389 return -EINVAL;
1390 /* hopefully this check will go away when userns support is
1391 * complete
1393 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1394 !capable(CAP_SETGID))
1395 return -EPERM;
1399 * We hope to recycle these flags after 2.6.26
1401 if (unlikely(clone_flags & CLONE_STOPPED)) {
1402 static int __read_mostly count = 100;
1404 if (count > 0 && printk_ratelimit()) {
1405 char comm[TASK_COMM_LEN];
1407 count--;
1408 printk(KERN_INFO "fork(): process `%s' used deprecated "
1409 "clone flags 0x%lx\n",
1410 get_task_comm(comm, current),
1411 clone_flags & CLONE_STOPPED);
1416 * When called from kernel_thread, don't do user tracing stuff.
1418 if (likely(user_mode(regs)))
1419 trace = tracehook_prepare_clone(clone_flags);
1421 p = copy_process(clone_flags, stack_start, regs, stack_size,
1422 child_tidptr, NULL, trace);
1424 * Do this prior waking up the new thread - the thread pointer
1425 * might get invalid after that point, if the thread exits quickly.
1427 if (!IS_ERR(p)) {
1428 struct completion vfork;
1430 trace_sched_process_fork(current, p);
1432 nr = task_pid_vnr(p);
1434 if (clone_flags & CLONE_PARENT_SETTID)
1435 put_user(nr, parent_tidptr);
1437 if (clone_flags & CLONE_VFORK) {
1438 p->vfork_done = &vfork;
1439 init_completion(&vfork);
1442 audit_finish_fork(p);
1443 tracehook_report_clone(regs, clone_flags, nr, p);
1446 * We set PF_STARTING at creation in case tracing wants to
1447 * use this to distinguish a fully live task from one that
1448 * hasn't gotten to tracehook_report_clone() yet. Now we
1449 * clear it and set the child going.
1451 p->flags &= ~PF_STARTING;
1453 if (unlikely(clone_flags & CLONE_STOPPED)) {
1455 * We'll start up with an immediate SIGSTOP.
1457 sigaddset(&p->pending.signal, SIGSTOP);
1458 set_tsk_thread_flag(p, TIF_SIGPENDING);
1459 __set_task_state(p, TASK_STOPPED);
1460 } else {
1461 wake_up_new_task(p, clone_flags);
1464 tracehook_report_clone_complete(trace, regs,
1465 clone_flags, nr, p);
1467 if (clone_flags & CLONE_VFORK) {
1468 freezer_do_not_count();
1469 wait_for_completion(&vfork);
1470 freezer_count();
1471 tracehook_report_vfork_done(p, nr);
1473 } else {
1474 nr = PTR_ERR(p);
1476 return nr;
1479 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1480 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1481 #endif
1483 static void sighand_ctor(void *data)
1485 struct sighand_struct *sighand = data;
1487 spin_lock_init(&sighand->siglock);
1488 init_waitqueue_head(&sighand->signalfd_wqh);
1491 void __init proc_caches_init(void)
1493 sighand_cachep = kmem_cache_create("sighand_cache",
1494 sizeof(struct sighand_struct), 0,
1495 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1496 SLAB_NOTRACK, sighand_ctor);
1497 signal_cachep = kmem_cache_create("signal_cache",
1498 sizeof(struct signal_struct), 0,
1499 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1500 files_cachep = kmem_cache_create("files_cache",
1501 sizeof(struct files_struct), 0,
1502 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1503 fs_cachep = kmem_cache_create("fs_cache",
1504 sizeof(struct fs_struct), 0,
1505 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1506 mm_cachep = kmem_cache_create("mm_struct",
1507 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1508 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1509 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1510 mmap_init();
1514 * Check constraints on flags passed to the unshare system call and
1515 * force unsharing of additional process context as appropriate.
1517 static void check_unshare_flags(unsigned long *flags_ptr)
1520 * If unsharing a thread from a thread group, must also
1521 * unshare vm.
1523 if (*flags_ptr & CLONE_THREAD)
1524 *flags_ptr |= CLONE_VM;
1527 * If unsharing vm, must also unshare signal handlers.
1529 if (*flags_ptr & CLONE_VM)
1530 *flags_ptr |= CLONE_SIGHAND;
1533 * If unsharing namespace, must also unshare filesystem information.
1535 if (*flags_ptr & CLONE_NEWNS)
1536 *flags_ptr |= CLONE_FS;
1540 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1542 static int unshare_thread(unsigned long unshare_flags)
1544 if (unshare_flags & CLONE_THREAD)
1545 return -EINVAL;
1547 return 0;
1551 * Unshare the filesystem structure if it is being shared
1553 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1555 struct fs_struct *fs = current->fs;
1557 if (!(unshare_flags & CLONE_FS) || !fs)
1558 return 0;
1560 /* don't need lock here; in the worst case we'll do useless copy */
1561 if (fs->users == 1)
1562 return 0;
1564 *new_fsp = copy_fs_struct(fs);
1565 if (!*new_fsp)
1566 return -ENOMEM;
1568 return 0;
1572 * Unsharing of sighand is not supported yet
1574 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1576 struct sighand_struct *sigh = current->sighand;
1578 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1579 return -EINVAL;
1580 else
1581 return 0;
1585 * Unshare vm if it is being shared
1587 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1589 struct mm_struct *mm = current->mm;
1591 if ((unshare_flags & CLONE_VM) &&
1592 (mm && atomic_read(&mm->mm_users) > 1)) {
1593 return -EINVAL;
1596 return 0;
1600 * Unshare file descriptor table if it is being shared
1602 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1604 struct files_struct *fd = current->files;
1605 int error = 0;
1607 if ((unshare_flags & CLONE_FILES) &&
1608 (fd && atomic_read(&fd->count) > 1)) {
1609 *new_fdp = dup_fd(fd, &error);
1610 if (!*new_fdp)
1611 return error;
1614 return 0;
1618 * unshare allows a process to 'unshare' part of the process
1619 * context which was originally shared using clone. copy_*
1620 * functions used by do_fork() cannot be used here directly
1621 * because they modify an inactive task_struct that is being
1622 * constructed. Here we are modifying the current, active,
1623 * task_struct.
1625 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1627 int err = 0;
1628 struct fs_struct *fs, *new_fs = NULL;
1629 struct sighand_struct *new_sigh = NULL;
1630 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1631 struct files_struct *fd, *new_fd = NULL;
1632 struct nsproxy *new_nsproxy = NULL;
1633 int do_sysvsem = 0;
1635 check_unshare_flags(&unshare_flags);
1637 /* Return -EINVAL for all unsupported flags */
1638 err = -EINVAL;
1639 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1640 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1641 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1642 goto bad_unshare_out;
1645 * CLONE_NEWIPC must also detach from the undolist: after switching
1646 * to a new ipc namespace, the semaphore arrays from the old
1647 * namespace are unreachable.
1649 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1650 do_sysvsem = 1;
1651 if ((err = unshare_thread(unshare_flags)))
1652 goto bad_unshare_out;
1653 if ((err = unshare_fs(unshare_flags, &new_fs)))
1654 goto bad_unshare_cleanup_thread;
1655 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1656 goto bad_unshare_cleanup_fs;
1657 if ((err = unshare_vm(unshare_flags, &new_mm)))
1658 goto bad_unshare_cleanup_sigh;
1659 if ((err = unshare_fd(unshare_flags, &new_fd)))
1660 goto bad_unshare_cleanup_vm;
1661 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1662 new_fs)))
1663 goto bad_unshare_cleanup_fd;
1665 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1666 if (do_sysvsem) {
1668 * CLONE_SYSVSEM is equivalent to sys_exit().
1670 exit_sem(current);
1673 if (new_nsproxy) {
1674 switch_task_namespaces(current, new_nsproxy);
1675 new_nsproxy = NULL;
1678 task_lock(current);
1680 if (new_fs) {
1681 fs = current->fs;
1682 spin_lock(&fs->lock);
1683 current->fs = new_fs;
1684 if (--fs->users)
1685 new_fs = NULL;
1686 else
1687 new_fs = fs;
1688 spin_unlock(&fs->lock);
1691 if (new_mm) {
1692 mm = current->mm;
1693 active_mm = current->active_mm;
1694 current->mm = new_mm;
1695 current->active_mm = new_mm;
1696 activate_mm(active_mm, new_mm);
1697 new_mm = mm;
1700 if (new_fd) {
1701 fd = current->files;
1702 current->files = new_fd;
1703 new_fd = fd;
1706 task_unlock(current);
1709 if (new_nsproxy)
1710 put_nsproxy(new_nsproxy);
1712 bad_unshare_cleanup_fd:
1713 if (new_fd)
1714 put_files_struct(new_fd);
1716 bad_unshare_cleanup_vm:
1717 if (new_mm)
1718 mmput(new_mm);
1720 bad_unshare_cleanup_sigh:
1721 if (new_sigh)
1722 if (atomic_dec_and_test(&new_sigh->count))
1723 kmem_cache_free(sighand_cachep, new_sigh);
1725 bad_unshare_cleanup_fs:
1726 if (new_fs)
1727 free_fs_struct(new_fs);
1729 bad_unshare_cleanup_thread:
1730 bad_unshare_out:
1731 return err;
1735 * Helper to unshare the files of the current task.
1736 * We don't want to expose copy_files internals to
1737 * the exec layer of the kernel.
1740 int unshare_files(struct files_struct **displaced)
1742 struct task_struct *task = current;
1743 struct files_struct *copy = NULL;
1744 int error;
1746 error = unshare_fd(CLONE_FILES, &copy);
1747 if (error || !copy) {
1748 *displaced = NULL;
1749 return error;
1751 *displaced = task->files;
1752 task_lock(task);
1753 task->files = copy;
1754 task_unlock(task);
1755 return 0;