ACPI: thinkpad-acpi: clean up hotkey_notify()
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / fork.c
blob8f753e529469baaf99736484af7d38e61ebd7291
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/mmu_notifier.h>
31 #include <linux/fs.h>
32 #include <linux/nsproxy.h>
33 #include <linux/capability.h>
34 #include <linux/cpu.h>
35 #include <linux/cgroup.h>
36 #include <linux/security.h>
37 #include <linux/hugetlb.h>
38 #include <linux/swap.h>
39 #include <linux/syscalls.h>
40 #include <linux/jiffies.h>
41 #include <linux/tracehook.h>
42 #include <linux/futex.h>
43 #include <linux/compat.h>
44 #include <linux/task_io_accounting_ops.h>
45 #include <linux/rcupdate.h>
46 #include <linux/ptrace.h>
47 #include <linux/mount.h>
48 #include <linux/audit.h>
49 #include <linux/memcontrol.h>
50 #include <linux/profile.h>
51 #include <linux/rmap.h>
52 #include <linux/acct.h>
53 #include <linux/tsacct_kern.h>
54 #include <linux/cn_proc.h>
55 #include <linux/freezer.h>
56 #include <linux/delayacct.h>
57 #include <linux/taskstats_kern.h>
58 #include <linux/random.h>
59 #include <linux/tty.h>
60 #include <linux/proc_fs.h>
61 #include <linux/blkdev.h>
62 #include <trace/sched.h>
64 #include <asm/pgtable.h>
65 #include <asm/pgalloc.h>
66 #include <asm/uaccess.h>
67 #include <asm/mmu_context.h>
68 #include <asm/cacheflush.h>
69 #include <asm/tlbflush.h>
72 * Protected counters by write_lock_irq(&tasklist_lock)
74 unsigned long total_forks; /* Handle normal Linux uptimes. */
75 int nr_threads; /* The idle threads do not count.. */
77 int max_threads; /* tunable limit on nr_threads */
79 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
81 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
83 int nr_processes(void)
85 int cpu;
86 int total = 0;
88 for_each_online_cpu(cpu)
89 total += per_cpu(process_counts, cpu);
91 return total;
94 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
95 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
96 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
97 static struct kmem_cache *task_struct_cachep;
98 #endif
100 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
101 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
103 #ifdef CONFIG_DEBUG_STACK_USAGE
104 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
105 #else
106 gfp_t mask = GFP_KERNEL;
107 #endif
108 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
111 static inline void free_thread_info(struct thread_info *ti)
113 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
115 #endif
117 /* SLAB cache for signal_struct structures (tsk->signal) */
118 static struct kmem_cache *signal_cachep;
120 /* SLAB cache for sighand_struct structures (tsk->sighand) */
121 struct kmem_cache *sighand_cachep;
123 /* SLAB cache for files_struct structures (tsk->files) */
124 struct kmem_cache *files_cachep;
126 /* SLAB cache for fs_struct structures (tsk->fs) */
127 struct kmem_cache *fs_cachep;
129 /* SLAB cache for vm_area_struct structures */
130 struct kmem_cache *vm_area_cachep;
132 /* SLAB cache for mm_struct structures (tsk->mm) */
133 static struct kmem_cache *mm_cachep;
135 void free_task(struct task_struct *tsk)
137 prop_local_destroy_single(&tsk->dirties);
138 free_thread_info(tsk->stack);
139 rt_mutex_debug_task_free(tsk);
140 free_task_struct(tsk);
142 EXPORT_SYMBOL(free_task);
144 void __put_task_struct(struct task_struct *tsk)
146 WARN_ON(!tsk->exit_state);
147 WARN_ON(atomic_read(&tsk->usage));
148 WARN_ON(tsk == current);
150 security_task_free(tsk);
151 free_uid(tsk->user);
152 put_group_info(tsk->group_info);
153 delayacct_tsk_free(tsk);
155 if (!profile_handoff_task(tsk))
156 free_task(tsk);
160 * macro override instead of weak attribute alias, to workaround
161 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
163 #ifndef arch_task_cache_init
164 #define arch_task_cache_init()
165 #endif
167 void __init fork_init(unsigned long mempages)
169 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
170 #ifndef ARCH_MIN_TASKALIGN
171 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
172 #endif
173 /* create a slab on which task_structs can be allocated */
174 task_struct_cachep =
175 kmem_cache_create("task_struct", sizeof(struct task_struct),
176 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
177 #endif
179 /* do the arch specific task caches init */
180 arch_task_cache_init();
183 * The default maximum number of threads is set to a safe
184 * value: the thread structures can take up at most half
185 * of memory.
187 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
190 * we need to allow at least 20 threads to boot a system
192 if(max_threads < 20)
193 max_threads = 20;
195 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
196 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
197 init_task.signal->rlim[RLIMIT_SIGPENDING] =
198 init_task.signal->rlim[RLIMIT_NPROC];
201 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
202 struct task_struct *src)
204 *dst = *src;
205 return 0;
208 static struct task_struct *dup_task_struct(struct task_struct *orig)
210 struct task_struct *tsk;
211 struct thread_info *ti;
212 int err;
214 prepare_to_copy(orig);
216 tsk = alloc_task_struct();
217 if (!tsk)
218 return NULL;
220 ti = alloc_thread_info(tsk);
221 if (!ti) {
222 free_task_struct(tsk);
223 return NULL;
226 err = arch_dup_task_struct(tsk, orig);
227 if (err)
228 goto out;
230 tsk->stack = ti;
232 err = prop_local_init_single(&tsk->dirties);
233 if (err)
234 goto out;
236 setup_thread_stack(tsk, orig);
238 #ifdef CONFIG_CC_STACKPROTECTOR
239 tsk->stack_canary = get_random_int();
240 #endif
242 /* One for us, one for whoever does the "release_task()" (usually parent) */
243 atomic_set(&tsk->usage,2);
244 atomic_set(&tsk->fs_excl, 0);
245 #ifdef CONFIG_BLK_DEV_IO_TRACE
246 tsk->btrace_seq = 0;
247 #endif
248 tsk->splice_pipe = NULL;
249 return tsk;
251 out:
252 free_thread_info(ti);
253 free_task_struct(tsk);
254 return NULL;
257 #ifdef CONFIG_MMU
258 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
260 struct vm_area_struct *mpnt, *tmp, **pprev;
261 struct rb_node **rb_link, *rb_parent;
262 int retval;
263 unsigned long charge;
264 struct mempolicy *pol;
266 down_write(&oldmm->mmap_sem);
267 flush_cache_dup_mm(oldmm);
269 * Not linked in yet - no deadlock potential:
271 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
273 mm->locked_vm = 0;
274 mm->mmap = NULL;
275 mm->mmap_cache = NULL;
276 mm->free_area_cache = oldmm->mmap_base;
277 mm->cached_hole_size = ~0UL;
278 mm->map_count = 0;
279 cpus_clear(mm->cpu_vm_mask);
280 mm->mm_rb = RB_ROOT;
281 rb_link = &mm->mm_rb.rb_node;
282 rb_parent = NULL;
283 pprev = &mm->mmap;
285 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
286 struct file *file;
288 if (mpnt->vm_flags & VM_DONTCOPY) {
289 long pages = vma_pages(mpnt);
290 mm->total_vm -= pages;
291 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
292 -pages);
293 continue;
295 charge = 0;
296 if (mpnt->vm_flags & VM_ACCOUNT) {
297 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
298 if (security_vm_enough_memory(len))
299 goto fail_nomem;
300 charge = len;
302 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
303 if (!tmp)
304 goto fail_nomem;
305 *tmp = *mpnt;
306 pol = mpol_dup(vma_policy(mpnt));
307 retval = PTR_ERR(pol);
308 if (IS_ERR(pol))
309 goto fail_nomem_policy;
310 vma_set_policy(tmp, pol);
311 tmp->vm_flags &= ~VM_LOCKED;
312 tmp->vm_mm = mm;
313 tmp->vm_next = NULL;
314 anon_vma_link(tmp);
315 file = tmp->vm_file;
316 if (file) {
317 struct inode *inode = file->f_path.dentry->d_inode;
318 struct address_space *mapping = file->f_mapping;
320 get_file(file);
321 if (tmp->vm_flags & VM_DENYWRITE)
322 atomic_dec(&inode->i_writecount);
323 spin_lock(&mapping->i_mmap_lock);
324 if (tmp->vm_flags & VM_SHARED)
325 mapping->i_mmap_writable++;
326 tmp->vm_truncate_count = mpnt->vm_truncate_count;
327 flush_dcache_mmap_lock(mapping);
328 /* insert tmp into the share list, just after mpnt */
329 vma_prio_tree_add(tmp, mpnt);
330 flush_dcache_mmap_unlock(mapping);
331 spin_unlock(&mapping->i_mmap_lock);
335 * Clear hugetlb-related page reserves for children. This only
336 * affects MAP_PRIVATE mappings. Faults generated by the child
337 * are not guaranteed to succeed, even if read-only
339 if (is_vm_hugetlb_page(tmp))
340 reset_vma_resv_huge_pages(tmp);
343 * Link in the new vma and copy the page table entries.
345 *pprev = tmp;
346 pprev = &tmp->vm_next;
348 __vma_link_rb(mm, tmp, rb_link, rb_parent);
349 rb_link = &tmp->vm_rb.rb_right;
350 rb_parent = &tmp->vm_rb;
352 mm->map_count++;
353 retval = copy_page_range(mm, oldmm, mpnt);
355 if (tmp->vm_ops && tmp->vm_ops->open)
356 tmp->vm_ops->open(tmp);
358 if (retval)
359 goto out;
361 /* a new mm has just been created */
362 arch_dup_mmap(oldmm, mm);
363 retval = 0;
364 out:
365 up_write(&mm->mmap_sem);
366 flush_tlb_mm(oldmm);
367 up_write(&oldmm->mmap_sem);
368 return retval;
369 fail_nomem_policy:
370 kmem_cache_free(vm_area_cachep, tmp);
371 fail_nomem:
372 retval = -ENOMEM;
373 vm_unacct_memory(charge);
374 goto out;
377 static inline int mm_alloc_pgd(struct mm_struct * mm)
379 mm->pgd = pgd_alloc(mm);
380 if (unlikely(!mm->pgd))
381 return -ENOMEM;
382 return 0;
385 static inline void mm_free_pgd(struct mm_struct * mm)
387 pgd_free(mm, mm->pgd);
389 #else
390 #define dup_mmap(mm, oldmm) (0)
391 #define mm_alloc_pgd(mm) (0)
392 #define mm_free_pgd(mm)
393 #endif /* CONFIG_MMU */
395 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
397 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
398 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
400 #include <linux/init_task.h>
402 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
404 atomic_set(&mm->mm_users, 1);
405 atomic_set(&mm->mm_count, 1);
406 init_rwsem(&mm->mmap_sem);
407 INIT_LIST_HEAD(&mm->mmlist);
408 mm->flags = (current->mm) ? current->mm->flags
409 : MMF_DUMP_FILTER_DEFAULT;
410 mm->core_state = NULL;
411 mm->nr_ptes = 0;
412 set_mm_counter(mm, file_rss, 0);
413 set_mm_counter(mm, anon_rss, 0);
414 spin_lock_init(&mm->page_table_lock);
415 rwlock_init(&mm->ioctx_list_lock);
416 mm->ioctx_list = NULL;
417 mm->free_area_cache = TASK_UNMAPPED_BASE;
418 mm->cached_hole_size = ~0UL;
419 mm_init_owner(mm, p);
421 if (likely(!mm_alloc_pgd(mm))) {
422 mm->def_flags = 0;
423 mmu_notifier_mm_init(mm);
424 return mm;
427 free_mm(mm);
428 return NULL;
432 * Allocate and initialize an mm_struct.
434 struct mm_struct * mm_alloc(void)
436 struct mm_struct * mm;
438 mm = allocate_mm();
439 if (mm) {
440 memset(mm, 0, sizeof(*mm));
441 mm = mm_init(mm, current);
443 return mm;
447 * Called when the last reference to the mm
448 * is dropped: either by a lazy thread or by
449 * mmput. Free the page directory and the mm.
451 void __mmdrop(struct mm_struct *mm)
453 BUG_ON(mm == &init_mm);
454 mm_free_pgd(mm);
455 destroy_context(mm);
456 mmu_notifier_mm_destroy(mm);
457 free_mm(mm);
459 EXPORT_SYMBOL_GPL(__mmdrop);
462 * Decrement the use count and release all resources for an mm.
464 void mmput(struct mm_struct *mm)
466 might_sleep();
468 if (atomic_dec_and_test(&mm->mm_users)) {
469 exit_aio(mm);
470 exit_mmap(mm);
471 set_mm_exe_file(mm, NULL);
472 if (!list_empty(&mm->mmlist)) {
473 spin_lock(&mmlist_lock);
474 list_del(&mm->mmlist);
475 spin_unlock(&mmlist_lock);
477 put_swap_token(mm);
478 mmdrop(mm);
481 EXPORT_SYMBOL_GPL(mmput);
484 * get_task_mm - acquire a reference to the task's mm
486 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
487 * this kernel workthread has transiently adopted a user mm with use_mm,
488 * to do its AIO) is not set and if so returns a reference to it, after
489 * bumping up the use count. User must release the mm via mmput()
490 * after use. Typically used by /proc and ptrace.
492 struct mm_struct *get_task_mm(struct task_struct *task)
494 struct mm_struct *mm;
496 task_lock(task);
497 mm = task->mm;
498 if (mm) {
499 if (task->flags & PF_KTHREAD)
500 mm = NULL;
501 else
502 atomic_inc(&mm->mm_users);
504 task_unlock(task);
505 return mm;
507 EXPORT_SYMBOL_GPL(get_task_mm);
509 /* Please note the differences between mmput and mm_release.
510 * mmput is called whenever we stop holding onto a mm_struct,
511 * error success whatever.
513 * mm_release is called after a mm_struct has been removed
514 * from the current process.
516 * This difference is important for error handling, when we
517 * only half set up a mm_struct for a new process and need to restore
518 * the old one. Because we mmput the new mm_struct before
519 * restoring the old one. . .
520 * Eric Biederman 10 January 1998
522 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
524 struct completion *vfork_done = tsk->vfork_done;
526 /* Get rid of any futexes when releasing the mm */
527 #ifdef CONFIG_FUTEX
528 if (unlikely(tsk->robust_list))
529 exit_robust_list(tsk);
530 #ifdef CONFIG_COMPAT
531 if (unlikely(tsk->compat_robust_list))
532 compat_exit_robust_list(tsk);
533 #endif
534 #endif
536 /* Get rid of any cached register state */
537 deactivate_mm(tsk, mm);
539 /* notify parent sleeping on vfork() */
540 if (vfork_done) {
541 tsk->vfork_done = NULL;
542 complete(vfork_done);
546 * If we're exiting normally, clear a user-space tid field if
547 * requested. We leave this alone when dying by signal, to leave
548 * the value intact in a core dump, and to save the unnecessary
549 * trouble otherwise. Userland only wants this done for a sys_exit.
551 if (tsk->clear_child_tid
552 && !(tsk->flags & PF_SIGNALED)
553 && atomic_read(&mm->mm_users) > 1) {
554 u32 __user * tidptr = tsk->clear_child_tid;
555 tsk->clear_child_tid = NULL;
558 * We don't check the error code - if userspace has
559 * not set up a proper pointer then tough luck.
561 put_user(0, tidptr);
562 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
567 * Allocate a new mm structure and copy contents from the
568 * mm structure of the passed in task structure.
570 struct mm_struct *dup_mm(struct task_struct *tsk)
572 struct mm_struct *mm, *oldmm = current->mm;
573 int err;
575 if (!oldmm)
576 return NULL;
578 mm = allocate_mm();
579 if (!mm)
580 goto fail_nomem;
582 memcpy(mm, oldmm, sizeof(*mm));
584 /* Initializing for Swap token stuff */
585 mm->token_priority = 0;
586 mm->last_interval = 0;
588 if (!mm_init(mm, tsk))
589 goto fail_nomem;
591 if (init_new_context(tsk, mm))
592 goto fail_nocontext;
594 dup_mm_exe_file(oldmm, mm);
596 err = dup_mmap(mm, oldmm);
597 if (err)
598 goto free_pt;
600 mm->hiwater_rss = get_mm_rss(mm);
601 mm->hiwater_vm = mm->total_vm;
603 return mm;
605 free_pt:
606 mmput(mm);
608 fail_nomem:
609 return NULL;
611 fail_nocontext:
613 * If init_new_context() failed, we cannot use mmput() to free the mm
614 * because it calls destroy_context()
616 mm_free_pgd(mm);
617 free_mm(mm);
618 return NULL;
621 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
623 struct mm_struct * mm, *oldmm;
624 int retval;
626 tsk->min_flt = tsk->maj_flt = 0;
627 tsk->nvcsw = tsk->nivcsw = 0;
629 tsk->mm = NULL;
630 tsk->active_mm = NULL;
633 * Are we cloning a kernel thread?
635 * We need to steal a active VM for that..
637 oldmm = current->mm;
638 if (!oldmm)
639 return 0;
641 if (clone_flags & CLONE_VM) {
642 atomic_inc(&oldmm->mm_users);
643 mm = oldmm;
644 goto good_mm;
647 retval = -ENOMEM;
648 mm = dup_mm(tsk);
649 if (!mm)
650 goto fail_nomem;
652 good_mm:
653 /* Initializing for Swap token stuff */
654 mm->token_priority = 0;
655 mm->last_interval = 0;
657 tsk->mm = mm;
658 tsk->active_mm = mm;
659 return 0;
661 fail_nomem:
662 return retval;
665 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
667 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
668 /* We don't need to lock fs - think why ;-) */
669 if (fs) {
670 atomic_set(&fs->count, 1);
671 rwlock_init(&fs->lock);
672 fs->umask = old->umask;
673 read_lock(&old->lock);
674 fs->root = old->root;
675 path_get(&old->root);
676 fs->pwd = old->pwd;
677 path_get(&old->pwd);
678 read_unlock(&old->lock);
680 return fs;
683 struct fs_struct *copy_fs_struct(struct fs_struct *old)
685 return __copy_fs_struct(old);
688 EXPORT_SYMBOL_GPL(copy_fs_struct);
690 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
692 if (clone_flags & CLONE_FS) {
693 atomic_inc(&current->fs->count);
694 return 0;
696 tsk->fs = __copy_fs_struct(current->fs);
697 if (!tsk->fs)
698 return -ENOMEM;
699 return 0;
702 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
704 struct files_struct *oldf, *newf;
705 int error = 0;
708 * A background process may not have any files ...
710 oldf = current->files;
711 if (!oldf)
712 goto out;
714 if (clone_flags & CLONE_FILES) {
715 atomic_inc(&oldf->count);
716 goto out;
719 newf = dup_fd(oldf, &error);
720 if (!newf)
721 goto out;
723 tsk->files = newf;
724 error = 0;
725 out:
726 return error;
729 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
731 #ifdef CONFIG_BLOCK
732 struct io_context *ioc = current->io_context;
734 if (!ioc)
735 return 0;
737 * Share io context with parent, if CLONE_IO is set
739 if (clone_flags & CLONE_IO) {
740 tsk->io_context = ioc_task_link(ioc);
741 if (unlikely(!tsk->io_context))
742 return -ENOMEM;
743 } else if (ioprio_valid(ioc->ioprio)) {
744 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
745 if (unlikely(!tsk->io_context))
746 return -ENOMEM;
748 tsk->io_context->ioprio = ioc->ioprio;
750 #endif
751 return 0;
754 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
756 struct sighand_struct *sig;
758 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
759 atomic_inc(&current->sighand->count);
760 return 0;
762 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
763 rcu_assign_pointer(tsk->sighand, sig);
764 if (!sig)
765 return -ENOMEM;
766 atomic_set(&sig->count, 1);
767 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
768 return 0;
771 void __cleanup_sighand(struct sighand_struct *sighand)
773 if (atomic_dec_and_test(&sighand->count))
774 kmem_cache_free(sighand_cachep, sighand);
779 * Initialize POSIX timer handling for a thread group.
781 static void posix_cpu_timers_init_group(struct signal_struct *sig)
783 /* Thread group counters. */
784 thread_group_cputime_init(sig);
786 /* Expiration times and increments. */
787 sig->it_virt_expires = cputime_zero;
788 sig->it_virt_incr = cputime_zero;
789 sig->it_prof_expires = cputime_zero;
790 sig->it_prof_incr = cputime_zero;
792 /* Cached expiration times. */
793 sig->cputime_expires.prof_exp = cputime_zero;
794 sig->cputime_expires.virt_exp = cputime_zero;
795 sig->cputime_expires.sched_exp = 0;
797 /* The timer lists. */
798 INIT_LIST_HEAD(&sig->cpu_timers[0]);
799 INIT_LIST_HEAD(&sig->cpu_timers[1]);
800 INIT_LIST_HEAD(&sig->cpu_timers[2]);
803 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
805 struct signal_struct *sig;
806 int ret;
808 if (clone_flags & CLONE_THREAD) {
809 ret = thread_group_cputime_clone_thread(current);
810 if (likely(!ret)) {
811 atomic_inc(&current->signal->count);
812 atomic_inc(&current->signal->live);
814 return ret;
816 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
817 tsk->signal = sig;
818 if (!sig)
819 return -ENOMEM;
821 ret = copy_thread_group_keys(tsk);
822 if (ret < 0) {
823 kmem_cache_free(signal_cachep, sig);
824 return ret;
827 atomic_set(&sig->count, 1);
828 atomic_set(&sig->live, 1);
829 init_waitqueue_head(&sig->wait_chldexit);
830 sig->flags = 0;
831 sig->group_exit_code = 0;
832 sig->group_exit_task = NULL;
833 sig->group_stop_count = 0;
834 sig->curr_target = tsk;
835 init_sigpending(&sig->shared_pending);
836 INIT_LIST_HEAD(&sig->posix_timers);
838 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
839 sig->it_real_incr.tv64 = 0;
840 sig->real_timer.function = it_real_fn;
842 sig->leader = 0; /* session leadership doesn't inherit */
843 sig->tty_old_pgrp = NULL;
844 sig->tty = NULL;
846 sig->cutime = sig->cstime = cputime_zero;
847 sig->gtime = cputime_zero;
848 sig->cgtime = cputime_zero;
849 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
850 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
851 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
852 task_io_accounting_init(&sig->ioac);
853 taskstats_tgid_init(sig);
855 task_lock(current->group_leader);
856 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
857 task_unlock(current->group_leader);
859 posix_cpu_timers_init_group(sig);
861 acct_init_pacct(&sig->pacct);
863 tty_audit_fork(sig);
865 return 0;
868 void __cleanup_signal(struct signal_struct *sig)
870 thread_group_cputime_free(sig);
871 exit_thread_group_keys(sig);
872 tty_kref_put(sig->tty);
873 kmem_cache_free(signal_cachep, sig);
876 static void cleanup_signal(struct task_struct *tsk)
878 struct signal_struct *sig = tsk->signal;
880 atomic_dec(&sig->live);
882 if (atomic_dec_and_test(&sig->count))
883 __cleanup_signal(sig);
886 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
888 unsigned long new_flags = p->flags;
890 new_flags &= ~PF_SUPERPRIV;
891 new_flags |= PF_FORKNOEXEC;
892 new_flags |= PF_STARTING;
893 p->flags = new_flags;
894 clear_freeze_flag(p);
897 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
899 current->clear_child_tid = tidptr;
901 return task_pid_vnr(current);
904 static void rt_mutex_init_task(struct task_struct *p)
906 spin_lock_init(&p->pi_lock);
907 #ifdef CONFIG_RT_MUTEXES
908 plist_head_init(&p->pi_waiters, &p->pi_lock);
909 p->pi_blocked_on = NULL;
910 #endif
913 #ifdef CONFIG_MM_OWNER
914 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
916 mm->owner = p;
918 #endif /* CONFIG_MM_OWNER */
921 * Initialize POSIX timer handling for a single task.
923 static void posix_cpu_timers_init(struct task_struct *tsk)
925 tsk->cputime_expires.prof_exp = cputime_zero;
926 tsk->cputime_expires.virt_exp = cputime_zero;
927 tsk->cputime_expires.sched_exp = 0;
928 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
929 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
930 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
934 * This creates a new process as a copy of the old one,
935 * but does not actually start it yet.
937 * It copies the registers, and all the appropriate
938 * parts of the process environment (as per the clone
939 * flags). The actual kick-off is left to the caller.
941 static struct task_struct *copy_process(unsigned long clone_flags,
942 unsigned long stack_start,
943 struct pt_regs *regs,
944 unsigned long stack_size,
945 int __user *child_tidptr,
946 struct pid *pid,
947 int trace)
949 int retval;
950 struct task_struct *p;
951 int cgroup_callbacks_done = 0;
953 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
954 return ERR_PTR(-EINVAL);
957 * Thread groups must share signals as well, and detached threads
958 * can only be started up within the thread group.
960 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
961 return ERR_PTR(-EINVAL);
964 * Shared signal handlers imply shared VM. By way of the above,
965 * thread groups also imply shared VM. Blocking this case allows
966 * for various simplifications in other code.
968 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
969 return ERR_PTR(-EINVAL);
971 retval = security_task_create(clone_flags);
972 if (retval)
973 goto fork_out;
975 retval = -ENOMEM;
976 p = dup_task_struct(current);
977 if (!p)
978 goto fork_out;
980 rt_mutex_init_task(p);
982 #ifdef CONFIG_PROVE_LOCKING
983 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
984 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
985 #endif
986 retval = -EAGAIN;
987 if (atomic_read(&p->user->processes) >=
988 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
989 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
990 p->user != current->nsproxy->user_ns->root_user)
991 goto bad_fork_free;
994 atomic_inc(&p->user->__count);
995 atomic_inc(&p->user->processes);
996 get_group_info(p->group_info);
999 * If multiple threads are within copy_process(), then this check
1000 * triggers too late. This doesn't hurt, the check is only there
1001 * to stop root fork bombs.
1003 if (nr_threads >= max_threads)
1004 goto bad_fork_cleanup_count;
1006 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1007 goto bad_fork_cleanup_count;
1009 if (p->binfmt && !try_module_get(p->binfmt->module))
1010 goto bad_fork_cleanup_put_domain;
1012 p->did_exec = 0;
1013 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1014 copy_flags(clone_flags, p);
1015 INIT_LIST_HEAD(&p->children);
1016 INIT_LIST_HEAD(&p->sibling);
1017 #ifdef CONFIG_PREEMPT_RCU
1018 p->rcu_read_lock_nesting = 0;
1019 p->rcu_flipctr_idx = 0;
1020 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1021 p->vfork_done = NULL;
1022 spin_lock_init(&p->alloc_lock);
1024 clear_tsk_thread_flag(p, TIF_SIGPENDING);
1025 init_sigpending(&p->pending);
1027 p->utime = cputime_zero;
1028 p->stime = cputime_zero;
1029 p->gtime = cputime_zero;
1030 p->utimescaled = cputime_zero;
1031 p->stimescaled = cputime_zero;
1032 p->prev_utime = cputime_zero;
1033 p->prev_stime = cputime_zero;
1035 p->default_timer_slack_ns = current->timer_slack_ns;
1037 #ifdef CONFIG_DETECT_SOFTLOCKUP
1038 p->last_switch_count = 0;
1039 p->last_switch_timestamp = 0;
1040 #endif
1042 task_io_accounting_init(&p->ioac);
1043 acct_clear_integrals(p);
1045 posix_cpu_timers_init(p);
1047 p->lock_depth = -1; /* -1 = no lock */
1048 do_posix_clock_monotonic_gettime(&p->start_time);
1049 p->real_start_time = p->start_time;
1050 monotonic_to_bootbased(&p->real_start_time);
1051 #ifdef CONFIG_SECURITY
1052 p->security = NULL;
1053 #endif
1054 p->cap_bset = current->cap_bset;
1055 p->io_context = NULL;
1056 p->audit_context = NULL;
1057 cgroup_fork(p);
1058 #ifdef CONFIG_NUMA
1059 p->mempolicy = mpol_dup(p->mempolicy);
1060 if (IS_ERR(p->mempolicy)) {
1061 retval = PTR_ERR(p->mempolicy);
1062 p->mempolicy = NULL;
1063 goto bad_fork_cleanup_cgroup;
1065 mpol_fix_fork_child_flag(p);
1066 #endif
1067 #ifdef CONFIG_TRACE_IRQFLAGS
1068 p->irq_events = 0;
1069 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1070 p->hardirqs_enabled = 1;
1071 #else
1072 p->hardirqs_enabled = 0;
1073 #endif
1074 p->hardirq_enable_ip = 0;
1075 p->hardirq_enable_event = 0;
1076 p->hardirq_disable_ip = _THIS_IP_;
1077 p->hardirq_disable_event = 0;
1078 p->softirqs_enabled = 1;
1079 p->softirq_enable_ip = _THIS_IP_;
1080 p->softirq_enable_event = 0;
1081 p->softirq_disable_ip = 0;
1082 p->softirq_disable_event = 0;
1083 p->hardirq_context = 0;
1084 p->softirq_context = 0;
1085 #endif
1086 #ifdef CONFIG_LOCKDEP
1087 p->lockdep_depth = 0; /* no locks held yet */
1088 p->curr_chain_key = 0;
1089 p->lockdep_recursion = 0;
1090 #endif
1092 #ifdef CONFIG_DEBUG_MUTEXES
1093 p->blocked_on = NULL; /* not blocked yet */
1094 #endif
1096 /* Perform scheduler related setup. Assign this task to a CPU. */
1097 sched_fork(p, clone_flags);
1099 if ((retval = security_task_alloc(p)))
1100 goto bad_fork_cleanup_policy;
1101 if ((retval = audit_alloc(p)))
1102 goto bad_fork_cleanup_security;
1103 /* copy all the process information */
1104 if ((retval = copy_semundo(clone_flags, p)))
1105 goto bad_fork_cleanup_audit;
1106 if ((retval = copy_files(clone_flags, p)))
1107 goto bad_fork_cleanup_semundo;
1108 if ((retval = copy_fs(clone_flags, p)))
1109 goto bad_fork_cleanup_files;
1110 if ((retval = copy_sighand(clone_flags, p)))
1111 goto bad_fork_cleanup_fs;
1112 if ((retval = copy_signal(clone_flags, p)))
1113 goto bad_fork_cleanup_sighand;
1114 if ((retval = copy_mm(clone_flags, p)))
1115 goto bad_fork_cleanup_signal;
1116 if ((retval = copy_keys(clone_flags, p)))
1117 goto bad_fork_cleanup_mm;
1118 if ((retval = copy_namespaces(clone_flags, p)))
1119 goto bad_fork_cleanup_keys;
1120 if ((retval = copy_io(clone_flags, p)))
1121 goto bad_fork_cleanup_namespaces;
1122 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1123 if (retval)
1124 goto bad_fork_cleanup_io;
1126 if (pid != &init_struct_pid) {
1127 retval = -ENOMEM;
1128 pid = alloc_pid(task_active_pid_ns(p));
1129 if (!pid)
1130 goto bad_fork_cleanup_io;
1132 if (clone_flags & CLONE_NEWPID) {
1133 retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1134 if (retval < 0)
1135 goto bad_fork_free_pid;
1139 p->pid = pid_nr(pid);
1140 p->tgid = p->pid;
1141 if (clone_flags & CLONE_THREAD)
1142 p->tgid = current->tgid;
1144 if (current->nsproxy != p->nsproxy) {
1145 retval = ns_cgroup_clone(p, pid);
1146 if (retval)
1147 goto bad_fork_free_pid;
1150 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1152 * Clear TID on mm_release()?
1154 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1155 #ifdef CONFIG_FUTEX
1156 p->robust_list = NULL;
1157 #ifdef CONFIG_COMPAT
1158 p->compat_robust_list = NULL;
1159 #endif
1160 INIT_LIST_HEAD(&p->pi_state_list);
1161 p->pi_state_cache = NULL;
1162 #endif
1164 * sigaltstack should be cleared when sharing the same VM
1166 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1167 p->sas_ss_sp = p->sas_ss_size = 0;
1170 * Syscall tracing should be turned off in the child regardless
1171 * of CLONE_PTRACE.
1173 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1174 #ifdef TIF_SYSCALL_EMU
1175 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1176 #endif
1177 clear_all_latency_tracing(p);
1179 /* ok, now we should be set up.. */
1180 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1181 p->pdeath_signal = 0;
1182 p->exit_state = 0;
1185 * Ok, make it visible to the rest of the system.
1186 * We dont wake it up yet.
1188 p->group_leader = p;
1189 INIT_LIST_HEAD(&p->thread_group);
1191 /* Now that the task is set up, run cgroup callbacks if
1192 * necessary. We need to run them before the task is visible
1193 * on the tasklist. */
1194 cgroup_fork_callbacks(p);
1195 cgroup_callbacks_done = 1;
1197 /* Need tasklist lock for parent etc handling! */
1198 write_lock_irq(&tasklist_lock);
1201 * The task hasn't been attached yet, so its cpus_allowed mask will
1202 * not be changed, nor will its assigned CPU.
1204 * The cpus_allowed mask of the parent may have changed after it was
1205 * copied first time - so re-copy it here, then check the child's CPU
1206 * to ensure it is on a valid CPU (and if not, just force it back to
1207 * parent's CPU). This avoids alot of nasty races.
1209 p->cpus_allowed = current->cpus_allowed;
1210 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1211 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1212 !cpu_online(task_cpu(p))))
1213 set_task_cpu(p, smp_processor_id());
1215 /* CLONE_PARENT re-uses the old parent */
1216 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1217 p->real_parent = current->real_parent;
1218 p->parent_exec_id = current->parent_exec_id;
1219 } else {
1220 p->real_parent = current;
1221 p->parent_exec_id = current->self_exec_id;
1224 spin_lock(&current->sighand->siglock);
1227 * Process group and session signals need to be delivered to just the
1228 * parent before the fork or both the parent and the child after the
1229 * fork. Restart if a signal comes in before we add the new process to
1230 * it's process group.
1231 * A fatal signal pending means that current will exit, so the new
1232 * thread can't slip out of an OOM kill (or normal SIGKILL).
1234 recalc_sigpending();
1235 if (signal_pending(current)) {
1236 spin_unlock(&current->sighand->siglock);
1237 write_unlock_irq(&tasklist_lock);
1238 retval = -ERESTARTNOINTR;
1239 goto bad_fork_free_pid;
1242 if (clone_flags & CLONE_THREAD) {
1243 p->group_leader = current->group_leader;
1244 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1247 if (likely(p->pid)) {
1248 list_add_tail(&p->sibling, &p->real_parent->children);
1249 tracehook_finish_clone(p, clone_flags, trace);
1251 if (thread_group_leader(p)) {
1252 if (clone_flags & CLONE_NEWPID)
1253 p->nsproxy->pid_ns->child_reaper = p;
1255 p->signal->leader_pid = pid;
1256 tty_kref_put(p->signal->tty);
1257 p->signal->tty = tty_kref_get(current->signal->tty);
1258 set_task_pgrp(p, task_pgrp_nr(current));
1259 set_task_session(p, task_session_nr(current));
1260 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1261 attach_pid(p, PIDTYPE_SID, task_session(current));
1262 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1263 __get_cpu_var(process_counts)++;
1265 attach_pid(p, PIDTYPE_PID, pid);
1266 nr_threads++;
1269 total_forks++;
1270 spin_unlock(&current->sighand->siglock);
1271 write_unlock_irq(&tasklist_lock);
1272 proc_fork_connector(p);
1273 cgroup_post_fork(p);
1274 return p;
1276 bad_fork_free_pid:
1277 if (pid != &init_struct_pid)
1278 free_pid(pid);
1279 bad_fork_cleanup_io:
1280 put_io_context(p->io_context);
1281 bad_fork_cleanup_namespaces:
1282 exit_task_namespaces(p);
1283 bad_fork_cleanup_keys:
1284 exit_keys(p);
1285 bad_fork_cleanup_mm:
1286 if (p->mm)
1287 mmput(p->mm);
1288 bad_fork_cleanup_signal:
1289 cleanup_signal(p);
1290 bad_fork_cleanup_sighand:
1291 __cleanup_sighand(p->sighand);
1292 bad_fork_cleanup_fs:
1293 exit_fs(p); /* blocking */
1294 bad_fork_cleanup_files:
1295 exit_files(p); /* blocking */
1296 bad_fork_cleanup_semundo:
1297 exit_sem(p);
1298 bad_fork_cleanup_audit:
1299 audit_free(p);
1300 bad_fork_cleanup_security:
1301 security_task_free(p);
1302 bad_fork_cleanup_policy:
1303 #ifdef CONFIG_NUMA
1304 mpol_put(p->mempolicy);
1305 bad_fork_cleanup_cgroup:
1306 #endif
1307 cgroup_exit(p, cgroup_callbacks_done);
1308 delayacct_tsk_free(p);
1309 if (p->binfmt)
1310 module_put(p->binfmt->module);
1311 bad_fork_cleanup_put_domain:
1312 module_put(task_thread_info(p)->exec_domain->module);
1313 bad_fork_cleanup_count:
1314 put_group_info(p->group_info);
1315 atomic_dec(&p->user->processes);
1316 free_uid(p->user);
1317 bad_fork_free:
1318 free_task(p);
1319 fork_out:
1320 return ERR_PTR(retval);
1323 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1325 memset(regs, 0, sizeof(struct pt_regs));
1326 return regs;
1329 struct task_struct * __cpuinit fork_idle(int cpu)
1331 struct task_struct *task;
1332 struct pt_regs regs;
1334 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1335 &init_struct_pid, 0);
1336 if (!IS_ERR(task))
1337 init_idle(task, cpu);
1339 return task;
1343 * Ok, this is the main fork-routine.
1345 * It copies the process, and if successful kick-starts
1346 * it and waits for it to finish using the VM if required.
1348 long do_fork(unsigned long clone_flags,
1349 unsigned long stack_start,
1350 struct pt_regs *regs,
1351 unsigned long stack_size,
1352 int __user *parent_tidptr,
1353 int __user *child_tidptr)
1355 struct task_struct *p;
1356 int trace = 0;
1357 long nr;
1360 * We hope to recycle these flags after 2.6.26
1362 if (unlikely(clone_flags & CLONE_STOPPED)) {
1363 static int __read_mostly count = 100;
1365 if (count > 0 && printk_ratelimit()) {
1366 char comm[TASK_COMM_LEN];
1368 count--;
1369 printk(KERN_INFO "fork(): process `%s' used deprecated "
1370 "clone flags 0x%lx\n",
1371 get_task_comm(comm, current),
1372 clone_flags & CLONE_STOPPED);
1377 * When called from kernel_thread, don't do user tracing stuff.
1379 if (likely(user_mode(regs)))
1380 trace = tracehook_prepare_clone(clone_flags);
1382 p = copy_process(clone_flags, stack_start, regs, stack_size,
1383 child_tidptr, NULL, trace);
1385 * Do this prior waking up the new thread - the thread pointer
1386 * might get invalid after that point, if the thread exits quickly.
1388 if (!IS_ERR(p)) {
1389 struct completion vfork;
1391 trace_sched_process_fork(current, p);
1393 nr = task_pid_vnr(p);
1395 if (clone_flags & CLONE_PARENT_SETTID)
1396 put_user(nr, parent_tidptr);
1398 if (clone_flags & CLONE_VFORK) {
1399 p->vfork_done = &vfork;
1400 init_completion(&vfork);
1403 audit_finish_fork(p);
1404 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1407 * We set PF_STARTING at creation in case tracing wants to
1408 * use this to distinguish a fully live task from one that
1409 * hasn't gotten to tracehook_report_clone() yet. Now we
1410 * clear it and set the child going.
1412 p->flags &= ~PF_STARTING;
1414 if (unlikely(clone_flags & CLONE_STOPPED)) {
1416 * We'll start up with an immediate SIGSTOP.
1418 sigaddset(&p->pending.signal, SIGSTOP);
1419 set_tsk_thread_flag(p, TIF_SIGPENDING);
1420 __set_task_state(p, TASK_STOPPED);
1421 } else {
1422 wake_up_new_task(p, clone_flags);
1425 tracehook_report_clone_complete(trace, regs,
1426 clone_flags, nr, p);
1428 if (clone_flags & CLONE_VFORK) {
1429 freezer_do_not_count();
1430 wait_for_completion(&vfork);
1431 freezer_count();
1432 tracehook_report_vfork_done(p, nr);
1434 } else {
1435 nr = PTR_ERR(p);
1437 return nr;
1440 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1441 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1442 #endif
1444 static void sighand_ctor(void *data)
1446 struct sighand_struct *sighand = data;
1448 spin_lock_init(&sighand->siglock);
1449 init_waitqueue_head(&sighand->signalfd_wqh);
1452 void __init proc_caches_init(void)
1454 sighand_cachep = kmem_cache_create("sighand_cache",
1455 sizeof(struct sighand_struct), 0,
1456 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1457 sighand_ctor);
1458 signal_cachep = kmem_cache_create("signal_cache",
1459 sizeof(struct signal_struct), 0,
1460 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1461 files_cachep = kmem_cache_create("files_cache",
1462 sizeof(struct files_struct), 0,
1463 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1464 fs_cachep = kmem_cache_create("fs_cache",
1465 sizeof(struct fs_struct), 0,
1466 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1467 vm_area_cachep = kmem_cache_create("vm_area_struct",
1468 sizeof(struct vm_area_struct), 0,
1469 SLAB_PANIC, NULL);
1470 mm_cachep = kmem_cache_create("mm_struct",
1471 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1472 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1476 * Check constraints on flags passed to the unshare system call and
1477 * force unsharing of additional process context as appropriate.
1479 static void check_unshare_flags(unsigned long *flags_ptr)
1482 * If unsharing a thread from a thread group, must also
1483 * unshare vm.
1485 if (*flags_ptr & CLONE_THREAD)
1486 *flags_ptr |= CLONE_VM;
1489 * If unsharing vm, must also unshare signal handlers.
1491 if (*flags_ptr & CLONE_VM)
1492 *flags_ptr |= CLONE_SIGHAND;
1495 * If unsharing signal handlers and the task was created
1496 * using CLONE_THREAD, then must unshare the thread
1498 if ((*flags_ptr & CLONE_SIGHAND) &&
1499 (atomic_read(&current->signal->count) > 1))
1500 *flags_ptr |= CLONE_THREAD;
1503 * If unsharing namespace, must also unshare filesystem information.
1505 if (*flags_ptr & CLONE_NEWNS)
1506 *flags_ptr |= CLONE_FS;
1510 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1512 static int unshare_thread(unsigned long unshare_flags)
1514 if (unshare_flags & CLONE_THREAD)
1515 return -EINVAL;
1517 return 0;
1521 * Unshare the filesystem structure if it is being shared
1523 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1525 struct fs_struct *fs = current->fs;
1527 if ((unshare_flags & CLONE_FS) &&
1528 (fs && atomic_read(&fs->count) > 1)) {
1529 *new_fsp = __copy_fs_struct(current->fs);
1530 if (!*new_fsp)
1531 return -ENOMEM;
1534 return 0;
1538 * Unsharing of sighand is not supported yet
1540 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1542 struct sighand_struct *sigh = current->sighand;
1544 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1545 return -EINVAL;
1546 else
1547 return 0;
1551 * Unshare vm if it is being shared
1553 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1555 struct mm_struct *mm = current->mm;
1557 if ((unshare_flags & CLONE_VM) &&
1558 (mm && atomic_read(&mm->mm_users) > 1)) {
1559 return -EINVAL;
1562 return 0;
1566 * Unshare file descriptor table if it is being shared
1568 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1570 struct files_struct *fd = current->files;
1571 int error = 0;
1573 if ((unshare_flags & CLONE_FILES) &&
1574 (fd && atomic_read(&fd->count) > 1)) {
1575 *new_fdp = dup_fd(fd, &error);
1576 if (!*new_fdp)
1577 return error;
1580 return 0;
1584 * unshare allows a process to 'unshare' part of the process
1585 * context which was originally shared using clone. copy_*
1586 * functions used by do_fork() cannot be used here directly
1587 * because they modify an inactive task_struct that is being
1588 * constructed. Here we are modifying the current, active,
1589 * task_struct.
1591 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1593 int err = 0;
1594 struct fs_struct *fs, *new_fs = NULL;
1595 struct sighand_struct *new_sigh = NULL;
1596 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1597 struct files_struct *fd, *new_fd = NULL;
1598 struct nsproxy *new_nsproxy = NULL;
1599 int do_sysvsem = 0;
1601 check_unshare_flags(&unshare_flags);
1603 /* Return -EINVAL for all unsupported flags */
1604 err = -EINVAL;
1605 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1606 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1607 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1608 CLONE_NEWNET))
1609 goto bad_unshare_out;
1612 * CLONE_NEWIPC must also detach from the undolist: after switching
1613 * to a new ipc namespace, the semaphore arrays from the old
1614 * namespace are unreachable.
1616 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1617 do_sysvsem = 1;
1618 if ((err = unshare_thread(unshare_flags)))
1619 goto bad_unshare_out;
1620 if ((err = unshare_fs(unshare_flags, &new_fs)))
1621 goto bad_unshare_cleanup_thread;
1622 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1623 goto bad_unshare_cleanup_fs;
1624 if ((err = unshare_vm(unshare_flags, &new_mm)))
1625 goto bad_unshare_cleanup_sigh;
1626 if ((err = unshare_fd(unshare_flags, &new_fd)))
1627 goto bad_unshare_cleanup_vm;
1628 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1629 new_fs)))
1630 goto bad_unshare_cleanup_fd;
1632 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1633 if (do_sysvsem) {
1635 * CLONE_SYSVSEM is equivalent to sys_exit().
1637 exit_sem(current);
1640 if (new_nsproxy) {
1641 switch_task_namespaces(current, new_nsproxy);
1642 new_nsproxy = NULL;
1645 task_lock(current);
1647 if (new_fs) {
1648 fs = current->fs;
1649 current->fs = new_fs;
1650 new_fs = fs;
1653 if (new_mm) {
1654 mm = current->mm;
1655 active_mm = current->active_mm;
1656 current->mm = new_mm;
1657 current->active_mm = new_mm;
1658 activate_mm(active_mm, new_mm);
1659 new_mm = mm;
1662 if (new_fd) {
1663 fd = current->files;
1664 current->files = new_fd;
1665 new_fd = fd;
1668 task_unlock(current);
1671 if (new_nsproxy)
1672 put_nsproxy(new_nsproxy);
1674 bad_unshare_cleanup_fd:
1675 if (new_fd)
1676 put_files_struct(new_fd);
1678 bad_unshare_cleanup_vm:
1679 if (new_mm)
1680 mmput(new_mm);
1682 bad_unshare_cleanup_sigh:
1683 if (new_sigh)
1684 if (atomic_dec_and_test(&new_sigh->count))
1685 kmem_cache_free(sighand_cachep, new_sigh);
1687 bad_unshare_cleanup_fs:
1688 if (new_fs)
1689 put_fs_struct(new_fs);
1691 bad_unshare_cleanup_thread:
1692 bad_unshare_out:
1693 return err;
1697 * Helper to unshare the files of the current task.
1698 * We don't want to expose copy_files internals to
1699 * the exec layer of the kernel.
1702 int unshare_files(struct files_struct **displaced)
1704 struct task_struct *task = current;
1705 struct files_struct *copy = NULL;
1706 int error;
1708 error = unshare_fd(CLONE_FILES, &copy);
1709 if (error || !copy) {
1710 *displaced = NULL;
1711 return error;
1713 *displaced = task->files;
1714 task_lock(task);
1715 task->files = copy;
1716 task_unlock(task);
1717 return 0;