SCSI: scsi_dh: check queuedata pointer before proceeding further
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / fork.c
blob4bde56fabe98cd9869ce16549474ffc365de4a89
1 /*
2 * linux/kernel/fork.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
7 /*
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/personality.h>
21 #include <linux/mempolicy.h>
22 #include <linux/sem.h>
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/iocontext.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
29 #include <linux/mmu_notifier.h>
30 #include <linux/fs.h>
31 #include <linux/nsproxy.h>
32 #include <linux/capability.h>
33 #include <linux/cpu.h>
34 #include <linux/cgroup.h>
35 #include <linux/security.h>
36 #include <linux/hugetlb.h>
37 #include <linux/swap.h>
38 #include <linux/syscalls.h>
39 #include <linux/jiffies.h>
40 #include <linux/tracehook.h>
41 #include <linux/futex.h>
42 #include <linux/compat.h>
43 #include <linux/task_io_accounting_ops.h>
44 #include <linux/rcupdate.h>
45 #include <linux/ptrace.h>
46 #include <linux/mount.h>
47 #include <linux/audit.h>
48 #include <linux/memcontrol.h>
49 #include <linux/ftrace.h>
50 #include <linux/profile.h>
51 #include <linux/rmap.h>
52 #include <linux/ksm.h>
53 #include <linux/acct.h>
54 #include <linux/tsacct_kern.h>
55 #include <linux/cn_proc.h>
56 #include <linux/freezer.h>
57 #include <linux/delayacct.h>
58 #include <linux/taskstats_kern.h>
59 #include <linux/random.h>
60 #include <linux/tty.h>
61 #include <linux/proc_fs.h>
62 #include <linux/blkdev.h>
63 #include <linux/fs_struct.h>
64 #include <linux/magic.h>
65 #include <linux/perf_event.h>
66 #include <linux/posix-timers.h>
68 #include <asm/pgtable.h>
69 #include <asm/pgalloc.h>
70 #include <asm/uaccess.h>
71 #include <asm/mmu_context.h>
72 #include <asm/cacheflush.h>
73 #include <asm/tlbflush.h>
75 #include <trace/events/sched.h>
78 * Protected counters by write_lock_irq(&tasklist_lock)
80 unsigned long total_forks; /* Handle normal Linux uptimes. */
81 int nr_threads; /* The idle threads do not count.. */
83 int max_threads; /* tunable limit on nr_threads */
85 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
87 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
89 int nr_processes(void)
91 int cpu;
92 int total = 0;
94 for_each_possible_cpu(cpu)
95 total += per_cpu(process_counts, cpu);
97 return total;
100 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
101 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
102 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
103 static struct kmem_cache *task_struct_cachep;
104 #endif
106 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
107 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
109 #ifdef CONFIG_DEBUG_STACK_USAGE
110 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
111 #else
112 gfp_t mask = GFP_KERNEL;
113 #endif
114 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
117 static inline void free_thread_info(struct thread_info *ti)
119 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
121 #endif
123 /* SLAB cache for signal_struct structures (tsk->signal) */
124 static struct kmem_cache *signal_cachep;
126 /* SLAB cache for sighand_struct structures (tsk->sighand) */
127 struct kmem_cache *sighand_cachep;
129 /* SLAB cache for files_struct structures (tsk->files) */
130 struct kmem_cache *files_cachep;
132 /* SLAB cache for fs_struct structures (tsk->fs) */
133 struct kmem_cache *fs_cachep;
135 /* SLAB cache for vm_area_struct structures */
136 struct kmem_cache *vm_area_cachep;
138 /* SLAB cache for mm_struct structures (tsk->mm) */
139 static struct kmem_cache *mm_cachep;
141 static void account_kernel_stack(struct thread_info *ti, int account)
143 struct zone *zone = page_zone(virt_to_page(ti));
145 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
148 void free_task(struct task_struct *tsk)
150 prop_local_destroy_single(&tsk->dirties);
151 account_kernel_stack(tsk->stack, -1);
152 free_thread_info(tsk->stack);
153 rt_mutex_debug_task_free(tsk);
154 ftrace_graph_exit_task(tsk);
155 free_task_struct(tsk);
157 EXPORT_SYMBOL(free_task);
159 void __put_task_struct(struct task_struct *tsk)
161 WARN_ON(!tsk->exit_state);
162 WARN_ON(atomic_read(&tsk->usage));
163 WARN_ON(tsk == current);
165 exit_creds(tsk);
166 delayacct_tsk_free(tsk);
168 if (!profile_handoff_task(tsk))
169 free_task(tsk);
173 * macro override instead of weak attribute alias, to workaround
174 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
176 #ifndef arch_task_cache_init
177 #define arch_task_cache_init()
178 #endif
180 void __init fork_init(unsigned long mempages)
182 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
183 #ifndef ARCH_MIN_TASKALIGN
184 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
185 #endif
186 /* create a slab on which task_structs can be allocated */
187 task_struct_cachep =
188 kmem_cache_create("task_struct", sizeof(struct task_struct),
189 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
190 #endif
192 /* do the arch specific task caches init */
193 arch_task_cache_init();
196 * The default maximum number of threads is set to a safe
197 * value: the thread structures can take up at most half
198 * of memory.
200 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
203 * we need to allow at least 20 threads to boot a system
205 if(max_threads < 20)
206 max_threads = 20;
208 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
209 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
210 init_task.signal->rlim[RLIMIT_SIGPENDING] =
211 init_task.signal->rlim[RLIMIT_NPROC];
214 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
215 struct task_struct *src)
217 *dst = *src;
218 return 0;
221 static struct task_struct *dup_task_struct(struct task_struct *orig)
223 struct task_struct *tsk;
224 struct thread_info *ti;
225 unsigned long *stackend;
227 int err;
229 prepare_to_copy(orig);
231 tsk = alloc_task_struct();
232 if (!tsk)
233 return NULL;
235 ti = alloc_thread_info(tsk);
236 if (!ti) {
237 free_task_struct(tsk);
238 return NULL;
241 err = arch_dup_task_struct(tsk, orig);
242 if (err)
243 goto out;
245 tsk->stack = ti;
247 err = prop_local_init_single(&tsk->dirties);
248 if (err)
249 goto out;
251 setup_thread_stack(tsk, orig);
252 stackend = end_of_stack(tsk);
253 *stackend = STACK_END_MAGIC; /* for overflow detection */
255 #ifdef CONFIG_CC_STACKPROTECTOR
256 tsk->stack_canary = get_random_int();
257 #endif
259 /* One for us, one for whoever does the "release_task()" (usually parent) */
260 atomic_set(&tsk->usage,2);
261 atomic_set(&tsk->fs_excl, 0);
262 #ifdef CONFIG_BLK_DEV_IO_TRACE
263 tsk->btrace_seq = 0;
264 #endif
265 tsk->splice_pipe = NULL;
267 account_kernel_stack(ti, 1);
269 return tsk;
271 out:
272 free_thread_info(ti);
273 free_task_struct(tsk);
274 return NULL;
277 #ifdef CONFIG_MMU
278 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
280 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
281 struct rb_node **rb_link, *rb_parent;
282 int retval;
283 unsigned long charge;
284 struct mempolicy *pol;
286 down_write(&oldmm->mmap_sem);
287 flush_cache_dup_mm(oldmm);
289 * Not linked in yet - no deadlock potential:
291 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
293 mm->locked_vm = 0;
294 mm->mmap = NULL;
295 mm->mmap_cache = NULL;
296 mm->free_area_cache = oldmm->mmap_base;
297 mm->cached_hole_size = ~0UL;
298 mm->map_count = 0;
299 cpumask_clear(mm_cpumask(mm));
300 mm->mm_rb = RB_ROOT;
301 rb_link = &mm->mm_rb.rb_node;
302 rb_parent = NULL;
303 pprev = &mm->mmap;
304 retval = ksm_fork(mm, oldmm);
305 if (retval)
306 goto out;
308 prev = NULL;
309 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
310 struct file *file;
312 if (mpnt->vm_flags & VM_DONTCOPY) {
313 long pages = vma_pages(mpnt);
314 mm->total_vm -= pages;
315 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
316 -pages);
317 continue;
319 charge = 0;
320 if (mpnt->vm_flags & VM_ACCOUNT) {
321 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
322 if (security_vm_enough_memory(len))
323 goto fail_nomem;
324 charge = len;
326 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
327 if (!tmp)
328 goto fail_nomem;
329 *tmp = *mpnt;
330 pol = mpol_dup(vma_policy(mpnt));
331 retval = PTR_ERR(pol);
332 if (IS_ERR(pol))
333 goto fail_nomem_policy;
334 vma_set_policy(tmp, pol);
335 tmp->vm_flags &= ~VM_LOCKED;
336 tmp->vm_mm = mm;
337 tmp->vm_next = tmp->vm_prev = NULL;
338 anon_vma_link(tmp);
339 file = tmp->vm_file;
340 if (file) {
341 struct inode *inode = file->f_path.dentry->d_inode;
342 struct address_space *mapping = file->f_mapping;
344 get_file(file);
345 if (tmp->vm_flags & VM_DENYWRITE)
346 atomic_dec(&inode->i_writecount);
347 spin_lock(&mapping->i_mmap_lock);
348 if (tmp->vm_flags & VM_SHARED)
349 mapping->i_mmap_writable++;
350 tmp->vm_truncate_count = mpnt->vm_truncate_count;
351 flush_dcache_mmap_lock(mapping);
352 /* insert tmp into the share list, just after mpnt */
353 vma_prio_tree_add(tmp, mpnt);
354 flush_dcache_mmap_unlock(mapping);
355 spin_unlock(&mapping->i_mmap_lock);
359 * Clear hugetlb-related page reserves for children. This only
360 * affects MAP_PRIVATE mappings. Faults generated by the child
361 * are not guaranteed to succeed, even if read-only
363 if (is_vm_hugetlb_page(tmp))
364 reset_vma_resv_huge_pages(tmp);
367 * Link in the new vma and copy the page table entries.
369 *pprev = tmp;
370 pprev = &tmp->vm_next;
371 tmp->vm_prev = prev;
372 prev = tmp;
374 __vma_link_rb(mm, tmp, rb_link, rb_parent);
375 rb_link = &tmp->vm_rb.rb_right;
376 rb_parent = &tmp->vm_rb;
378 mm->map_count++;
379 retval = copy_page_range(mm, oldmm, mpnt);
381 if (tmp->vm_ops && tmp->vm_ops->open)
382 tmp->vm_ops->open(tmp);
384 if (retval)
385 goto out;
387 /* a new mm has just been created */
388 arch_dup_mmap(oldmm, mm);
389 retval = 0;
390 out:
391 up_write(&mm->mmap_sem);
392 flush_tlb_mm(oldmm);
393 up_write(&oldmm->mmap_sem);
394 return retval;
395 fail_nomem_policy:
396 kmem_cache_free(vm_area_cachep, tmp);
397 fail_nomem:
398 retval = -ENOMEM;
399 vm_unacct_memory(charge);
400 goto out;
403 static inline int mm_alloc_pgd(struct mm_struct * mm)
405 mm->pgd = pgd_alloc(mm);
406 if (unlikely(!mm->pgd))
407 return -ENOMEM;
408 return 0;
411 static inline void mm_free_pgd(struct mm_struct * mm)
413 pgd_free(mm, mm->pgd);
415 #else
416 #define dup_mmap(mm, oldmm) (0)
417 #define mm_alloc_pgd(mm) (0)
418 #define mm_free_pgd(mm)
419 #endif /* CONFIG_MMU */
421 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
423 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
424 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
426 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
428 static int __init coredump_filter_setup(char *s)
430 default_dump_filter =
431 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
432 MMF_DUMP_FILTER_MASK;
433 return 1;
436 __setup("coredump_filter=", coredump_filter_setup);
438 #include <linux/init_task.h>
440 static void mm_init_aio(struct mm_struct *mm)
442 #ifdef CONFIG_AIO
443 spin_lock_init(&mm->ioctx_lock);
444 INIT_HLIST_HEAD(&mm->ioctx_list);
445 #endif
448 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
450 atomic_set(&mm->mm_users, 1);
451 atomic_set(&mm->mm_count, 1);
452 init_rwsem(&mm->mmap_sem);
453 INIT_LIST_HEAD(&mm->mmlist);
454 mm->flags = (current->mm) ?
455 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
456 mm->core_state = NULL;
457 mm->nr_ptes = 0;
458 set_mm_counter(mm, file_rss, 0);
459 set_mm_counter(mm, anon_rss, 0);
460 spin_lock_init(&mm->page_table_lock);
461 mm->free_area_cache = TASK_UNMAPPED_BASE;
462 mm->cached_hole_size = ~0UL;
463 mm_init_aio(mm);
464 mm_init_owner(mm, p);
466 if (likely(!mm_alloc_pgd(mm))) {
467 mm->def_flags = 0;
468 mmu_notifier_mm_init(mm);
469 return mm;
472 free_mm(mm);
473 return NULL;
477 * Allocate and initialize an mm_struct.
479 struct mm_struct * mm_alloc(void)
481 struct mm_struct * mm;
483 mm = allocate_mm();
484 if (mm) {
485 memset(mm, 0, sizeof(*mm));
486 mm = mm_init(mm, current);
488 return mm;
492 * Called when the last reference to the mm
493 * is dropped: either by a lazy thread or by
494 * mmput. Free the page directory and the mm.
496 void __mmdrop(struct mm_struct *mm)
498 BUG_ON(mm == &init_mm);
499 mm_free_pgd(mm);
500 destroy_context(mm);
501 mmu_notifier_mm_destroy(mm);
502 free_mm(mm);
504 EXPORT_SYMBOL_GPL(__mmdrop);
507 * Decrement the use count and release all resources for an mm.
509 void mmput(struct mm_struct *mm)
511 might_sleep();
513 if (atomic_dec_and_test(&mm->mm_users)) {
514 exit_aio(mm);
515 ksm_exit(mm);
516 exit_mmap(mm);
517 set_mm_exe_file(mm, NULL);
518 if (!list_empty(&mm->mmlist)) {
519 spin_lock(&mmlist_lock);
520 list_del(&mm->mmlist);
521 spin_unlock(&mmlist_lock);
523 put_swap_token(mm);
524 if (mm->binfmt)
525 module_put(mm->binfmt->module);
526 mmdrop(mm);
529 EXPORT_SYMBOL_GPL(mmput);
532 * get_task_mm - acquire a reference to the task's mm
534 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
535 * this kernel workthread has transiently adopted a user mm with use_mm,
536 * to do its AIO) is not set and if so returns a reference to it, after
537 * bumping up the use count. User must release the mm via mmput()
538 * after use. Typically used by /proc and ptrace.
540 struct mm_struct *get_task_mm(struct task_struct *task)
542 struct mm_struct *mm;
544 task_lock(task);
545 mm = task->mm;
546 if (mm) {
547 if (task->flags & PF_KTHREAD)
548 mm = NULL;
549 else
550 atomic_inc(&mm->mm_users);
552 task_unlock(task);
553 return mm;
555 EXPORT_SYMBOL_GPL(get_task_mm);
557 /* Please note the differences between mmput and mm_release.
558 * mmput is called whenever we stop holding onto a mm_struct,
559 * error success whatever.
561 * mm_release is called after a mm_struct has been removed
562 * from the current process.
564 * This difference is important for error handling, when we
565 * only half set up a mm_struct for a new process and need to restore
566 * the old one. Because we mmput the new mm_struct before
567 * restoring the old one. . .
568 * Eric Biederman 10 January 1998
570 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
572 struct completion *vfork_done = tsk->vfork_done;
574 /* Get rid of any futexes when releasing the mm */
575 #ifdef CONFIG_FUTEX
576 if (unlikely(tsk->robust_list)) {
577 exit_robust_list(tsk);
578 tsk->robust_list = NULL;
580 #ifdef CONFIG_COMPAT
581 if (unlikely(tsk->compat_robust_list)) {
582 compat_exit_robust_list(tsk);
583 tsk->compat_robust_list = NULL;
585 #endif
586 if (unlikely(!list_empty(&tsk->pi_state_list)))
587 exit_pi_state_list(tsk);
588 #endif
590 /* Get rid of any cached register state */
591 deactivate_mm(tsk, mm);
593 /* notify parent sleeping on vfork() */
594 if (vfork_done) {
595 tsk->vfork_done = NULL;
596 complete(vfork_done);
600 * If we're exiting normally, clear a user-space tid field if
601 * requested. We leave this alone when dying by signal, to leave
602 * the value intact in a core dump, and to save the unnecessary
603 * trouble otherwise. Userland only wants this done for a sys_exit.
605 if (tsk->clear_child_tid) {
606 if (!(tsk->flags & PF_SIGNALED) &&
607 atomic_read(&mm->mm_users) > 1) {
609 * We don't check the error code - if userspace has
610 * not set up a proper pointer then tough luck.
612 put_user(0, tsk->clear_child_tid);
613 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
614 1, NULL, NULL, 0);
616 tsk->clear_child_tid = NULL;
621 * Allocate a new mm structure and copy contents from the
622 * mm structure of the passed in task structure.
624 struct mm_struct *dup_mm(struct task_struct *tsk)
626 struct mm_struct *mm, *oldmm = current->mm;
627 int err;
629 if (!oldmm)
630 return NULL;
632 mm = allocate_mm();
633 if (!mm)
634 goto fail_nomem;
636 memcpy(mm, oldmm, sizeof(*mm));
638 /* Initializing for Swap token stuff */
639 mm->token_priority = 0;
640 mm->last_interval = 0;
642 if (!mm_init(mm, tsk))
643 goto fail_nomem;
645 if (init_new_context(tsk, mm))
646 goto fail_nocontext;
648 dup_mm_exe_file(oldmm, mm);
650 err = dup_mmap(mm, oldmm);
651 if (err)
652 goto free_pt;
654 mm->hiwater_rss = get_mm_rss(mm);
655 mm->hiwater_vm = mm->total_vm;
657 if (mm->binfmt && !try_module_get(mm->binfmt->module))
658 goto free_pt;
660 return mm;
662 free_pt:
663 /* don't put binfmt in mmput, we haven't got module yet */
664 mm->binfmt = NULL;
665 mmput(mm);
667 fail_nomem:
668 return NULL;
670 fail_nocontext:
672 * If init_new_context() failed, we cannot use mmput() to free the mm
673 * because it calls destroy_context()
675 mm_free_pgd(mm);
676 free_mm(mm);
677 return NULL;
680 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
682 struct mm_struct * mm, *oldmm;
683 int retval;
685 tsk->min_flt = tsk->maj_flt = 0;
686 tsk->nvcsw = tsk->nivcsw = 0;
687 #ifdef CONFIG_DETECT_HUNG_TASK
688 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
689 #endif
691 tsk->mm = NULL;
692 tsk->active_mm = NULL;
695 * Are we cloning a kernel thread?
697 * We need to steal a active VM for that..
699 oldmm = current->mm;
700 if (!oldmm)
701 return 0;
703 if (clone_flags & CLONE_VM) {
704 atomic_inc(&oldmm->mm_users);
705 mm = oldmm;
706 goto good_mm;
709 retval = -ENOMEM;
710 mm = dup_mm(tsk);
711 if (!mm)
712 goto fail_nomem;
714 good_mm:
715 /* Initializing for Swap token stuff */
716 mm->token_priority = 0;
717 mm->last_interval = 0;
719 tsk->mm = mm;
720 tsk->active_mm = mm;
721 return 0;
723 fail_nomem:
724 return retval;
727 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
729 struct fs_struct *fs = current->fs;
730 if (clone_flags & CLONE_FS) {
731 /* tsk->fs is already what we want */
732 write_lock(&fs->lock);
733 if (fs->in_exec) {
734 write_unlock(&fs->lock);
735 return -EAGAIN;
737 fs->users++;
738 write_unlock(&fs->lock);
739 return 0;
741 tsk->fs = copy_fs_struct(fs);
742 if (!tsk->fs)
743 return -ENOMEM;
744 return 0;
747 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
749 struct files_struct *oldf, *newf;
750 int error = 0;
753 * A background process may not have any files ...
755 oldf = current->files;
756 if (!oldf)
757 goto out;
759 if (clone_flags & CLONE_FILES) {
760 atomic_inc(&oldf->count);
761 goto out;
764 newf = dup_fd(oldf, &error);
765 if (!newf)
766 goto out;
768 tsk->files = newf;
769 error = 0;
770 out:
771 return error;
774 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
776 #ifdef CONFIG_BLOCK
777 struct io_context *ioc = current->io_context;
779 if (!ioc)
780 return 0;
782 * Share io context with parent, if CLONE_IO is set
784 if (clone_flags & CLONE_IO) {
785 tsk->io_context = ioc_task_link(ioc);
786 if (unlikely(!tsk->io_context))
787 return -ENOMEM;
788 } else if (ioprio_valid(ioc->ioprio)) {
789 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
790 if (unlikely(!tsk->io_context))
791 return -ENOMEM;
793 tsk->io_context->ioprio = ioc->ioprio;
795 #endif
796 return 0;
799 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
801 struct sighand_struct *sig;
803 if (clone_flags & CLONE_SIGHAND) {
804 atomic_inc(&current->sighand->count);
805 return 0;
807 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
808 rcu_assign_pointer(tsk->sighand, sig);
809 if (!sig)
810 return -ENOMEM;
811 atomic_set(&sig->count, 1);
812 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
813 return 0;
816 void __cleanup_sighand(struct sighand_struct *sighand)
818 if (atomic_dec_and_test(&sighand->count))
819 kmem_cache_free(sighand_cachep, sighand);
824 * Initialize POSIX timer handling for a thread group.
826 static void posix_cpu_timers_init_group(struct signal_struct *sig)
828 /* Thread group counters. */
829 thread_group_cputime_init(sig);
831 /* Expiration times and increments. */
832 sig->it[CPUCLOCK_PROF].expires = cputime_zero;
833 sig->it[CPUCLOCK_PROF].incr = cputime_zero;
834 sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
835 sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
837 /* Cached expiration times. */
838 sig->cputime_expires.prof_exp = cputime_zero;
839 sig->cputime_expires.virt_exp = cputime_zero;
840 sig->cputime_expires.sched_exp = 0;
842 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
843 sig->cputime_expires.prof_exp =
844 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
845 sig->cputimer.running = 1;
848 /* The timer lists. */
849 INIT_LIST_HEAD(&sig->cpu_timers[0]);
850 INIT_LIST_HEAD(&sig->cpu_timers[1]);
851 INIT_LIST_HEAD(&sig->cpu_timers[2]);
854 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
856 struct signal_struct *sig;
858 if (clone_flags & CLONE_THREAD)
859 return 0;
861 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
862 tsk->signal = sig;
863 if (!sig)
864 return -ENOMEM;
866 atomic_set(&sig->count, 1);
867 atomic_set(&sig->live, 1);
868 init_waitqueue_head(&sig->wait_chldexit);
869 sig->flags = 0;
870 if (clone_flags & CLONE_NEWPID)
871 sig->flags |= SIGNAL_UNKILLABLE;
872 sig->group_exit_code = 0;
873 sig->group_exit_task = NULL;
874 sig->group_stop_count = 0;
875 sig->curr_target = tsk;
876 init_sigpending(&sig->shared_pending);
877 INIT_LIST_HEAD(&sig->posix_timers);
879 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
880 sig->it_real_incr.tv64 = 0;
881 sig->real_timer.function = it_real_fn;
883 sig->leader = 0; /* session leadership doesn't inherit */
884 sig->tty_old_pgrp = NULL;
885 sig->tty = NULL;
887 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
888 sig->gtime = cputime_zero;
889 sig->cgtime = cputime_zero;
890 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
891 sig->prev_utime = sig->prev_stime = cputime_zero;
892 #endif
893 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
894 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
895 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
896 sig->maxrss = sig->cmaxrss = 0;
897 task_io_accounting_init(&sig->ioac);
898 sig->sum_sched_runtime = 0;
899 taskstats_tgid_init(sig);
901 task_lock(current->group_leader);
902 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
903 task_unlock(current->group_leader);
905 posix_cpu_timers_init_group(sig);
907 acct_init_pacct(&sig->pacct);
909 tty_audit_fork(sig);
911 sig->oom_adj = current->signal->oom_adj;
913 return 0;
916 void __cleanup_signal(struct signal_struct *sig)
918 thread_group_cputime_free(sig);
919 tty_kref_put(sig->tty);
920 kmem_cache_free(signal_cachep, sig);
923 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
925 unsigned long new_flags = p->flags;
927 new_flags &= ~PF_SUPERPRIV;
928 new_flags |= PF_FORKNOEXEC;
929 new_flags |= PF_STARTING;
930 p->flags = new_flags;
931 clear_freeze_flag(p);
934 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
936 current->clear_child_tid = tidptr;
938 return task_pid_vnr(current);
941 static void rt_mutex_init_task(struct task_struct *p)
943 spin_lock_init(&p->pi_lock);
944 #ifdef CONFIG_RT_MUTEXES
945 plist_head_init(&p->pi_waiters, &p->pi_lock);
946 p->pi_blocked_on = NULL;
947 #endif
950 #ifdef CONFIG_MM_OWNER
951 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
953 mm->owner = p;
955 #endif /* CONFIG_MM_OWNER */
958 * Initialize POSIX timer handling for a single task.
960 static void posix_cpu_timers_init(struct task_struct *tsk)
962 tsk->cputime_expires.prof_exp = cputime_zero;
963 tsk->cputime_expires.virt_exp = cputime_zero;
964 tsk->cputime_expires.sched_exp = 0;
965 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
966 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
967 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
971 * This creates a new process as a copy of the old one,
972 * but does not actually start it yet.
974 * It copies the registers, and all the appropriate
975 * parts of the process environment (as per the clone
976 * flags). The actual kick-off is left to the caller.
978 static struct task_struct *copy_process(unsigned long clone_flags,
979 unsigned long stack_start,
980 struct pt_regs *regs,
981 unsigned long stack_size,
982 int __user *child_tidptr,
983 struct pid *pid,
984 int trace)
986 int retval;
987 struct task_struct *p;
988 int cgroup_callbacks_done = 0;
990 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
991 return ERR_PTR(-EINVAL);
994 * Thread groups must share signals as well, and detached threads
995 * can only be started up within the thread group.
997 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
998 return ERR_PTR(-EINVAL);
1001 * Shared signal handlers imply shared VM. By way of the above,
1002 * thread groups also imply shared VM. Blocking this case allows
1003 * for various simplifications in other code.
1005 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1006 return ERR_PTR(-EINVAL);
1009 * Siblings of global init remain as zombies on exit since they are
1010 * not reaped by their parent (swapper). To solve this and to avoid
1011 * multi-rooted process trees, prevent global and container-inits
1012 * from creating siblings.
1014 if ((clone_flags & CLONE_PARENT) &&
1015 current->signal->flags & SIGNAL_UNKILLABLE)
1016 return ERR_PTR(-EINVAL);
1018 retval = security_task_create(clone_flags);
1019 if (retval)
1020 goto fork_out;
1022 retval = -ENOMEM;
1023 p = dup_task_struct(current);
1024 if (!p)
1025 goto fork_out;
1027 ftrace_graph_init_task(p);
1029 rt_mutex_init_task(p);
1031 #ifdef CONFIG_PROVE_LOCKING
1032 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1033 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1034 #endif
1035 retval = -EAGAIN;
1036 if (atomic_read(&p->real_cred->user->processes) >=
1037 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1038 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1039 p->real_cred->user != INIT_USER)
1040 goto bad_fork_free;
1043 retval = copy_creds(p, clone_flags);
1044 if (retval < 0)
1045 goto bad_fork_free;
1048 * If multiple threads are within copy_process(), then this check
1049 * triggers too late. This doesn't hurt, the check is only there
1050 * to stop root fork bombs.
1052 retval = -EAGAIN;
1053 if (nr_threads >= max_threads)
1054 goto bad_fork_cleanup_count;
1056 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1057 goto bad_fork_cleanup_count;
1059 p->did_exec = 0;
1060 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1061 copy_flags(clone_flags, p);
1062 INIT_LIST_HEAD(&p->children);
1063 INIT_LIST_HEAD(&p->sibling);
1064 rcu_copy_process(p);
1065 p->vfork_done = NULL;
1066 spin_lock_init(&p->alloc_lock);
1068 init_sigpending(&p->pending);
1070 p->utime = cputime_zero;
1071 p->stime = cputime_zero;
1072 p->gtime = cputime_zero;
1073 p->utimescaled = cputime_zero;
1074 p->stimescaled = cputime_zero;
1075 p->prev_utime = cputime_zero;
1076 p->prev_stime = cputime_zero;
1078 p->default_timer_slack_ns = current->timer_slack_ns;
1080 task_io_accounting_init(&p->ioac);
1081 acct_clear_integrals(p);
1083 posix_cpu_timers_init(p);
1085 p->lock_depth = -1; /* -1 = no lock */
1086 do_posix_clock_monotonic_gettime(&p->start_time);
1087 p->real_start_time = p->start_time;
1088 monotonic_to_bootbased(&p->real_start_time);
1089 p->io_context = NULL;
1090 p->audit_context = NULL;
1091 cgroup_fork(p);
1092 #ifdef CONFIG_NUMA
1093 p->mempolicy = mpol_dup(p->mempolicy);
1094 if (IS_ERR(p->mempolicy)) {
1095 retval = PTR_ERR(p->mempolicy);
1096 p->mempolicy = NULL;
1097 goto bad_fork_cleanup_cgroup;
1099 mpol_fix_fork_child_flag(p);
1100 #endif
1101 #ifdef CONFIG_TRACE_IRQFLAGS
1102 p->irq_events = 0;
1103 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1104 p->hardirqs_enabled = 1;
1105 #else
1106 p->hardirqs_enabled = 0;
1107 #endif
1108 p->hardirq_enable_ip = 0;
1109 p->hardirq_enable_event = 0;
1110 p->hardirq_disable_ip = _THIS_IP_;
1111 p->hardirq_disable_event = 0;
1112 p->softirqs_enabled = 1;
1113 p->softirq_enable_ip = _THIS_IP_;
1114 p->softirq_enable_event = 0;
1115 p->softirq_disable_ip = 0;
1116 p->softirq_disable_event = 0;
1117 p->hardirq_context = 0;
1118 p->softirq_context = 0;
1119 #endif
1120 #ifdef CONFIG_LOCKDEP
1121 p->lockdep_depth = 0; /* no locks held yet */
1122 p->curr_chain_key = 0;
1123 p->lockdep_recursion = 0;
1124 #endif
1126 #ifdef CONFIG_DEBUG_MUTEXES
1127 p->blocked_on = NULL; /* not blocked yet */
1128 #endif
1130 p->bts = NULL;
1132 /* Perform scheduler related setup. Assign this task to a CPU. */
1133 sched_fork(p, clone_flags);
1135 retval = perf_event_init_task(p);
1136 if (retval)
1137 goto bad_fork_cleanup_policy;
1139 if ((retval = audit_alloc(p)))
1140 goto bad_fork_cleanup_policy;
1141 /* copy all the process information */
1142 if ((retval = copy_semundo(clone_flags, p)))
1143 goto bad_fork_cleanup_audit;
1144 if ((retval = copy_files(clone_flags, p)))
1145 goto bad_fork_cleanup_semundo;
1146 if ((retval = copy_fs(clone_flags, p)))
1147 goto bad_fork_cleanup_files;
1148 if ((retval = copy_sighand(clone_flags, p)))
1149 goto bad_fork_cleanup_fs;
1150 if ((retval = copy_signal(clone_flags, p)))
1151 goto bad_fork_cleanup_sighand;
1152 if ((retval = copy_mm(clone_flags, p)))
1153 goto bad_fork_cleanup_signal;
1154 if ((retval = copy_namespaces(clone_flags, p)))
1155 goto bad_fork_cleanup_mm;
1156 if ((retval = copy_io(clone_flags, p)))
1157 goto bad_fork_cleanup_namespaces;
1158 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1159 if (retval)
1160 goto bad_fork_cleanup_io;
1162 if (pid != &init_struct_pid) {
1163 retval = -ENOMEM;
1164 pid = alloc_pid(p->nsproxy->pid_ns);
1165 if (!pid)
1166 goto bad_fork_cleanup_io;
1168 if (clone_flags & CLONE_NEWPID) {
1169 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1170 if (retval < 0)
1171 goto bad_fork_free_pid;
1175 p->pid = pid_nr(pid);
1176 p->tgid = p->pid;
1177 if (clone_flags & CLONE_THREAD)
1178 p->tgid = current->tgid;
1180 if (current->nsproxy != p->nsproxy) {
1181 retval = ns_cgroup_clone(p, pid);
1182 if (retval)
1183 goto bad_fork_free_pid;
1186 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1188 * Clear TID on mm_release()?
1190 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1191 #ifdef CONFIG_FUTEX
1192 p->robust_list = NULL;
1193 #ifdef CONFIG_COMPAT
1194 p->compat_robust_list = NULL;
1195 #endif
1196 INIT_LIST_HEAD(&p->pi_state_list);
1197 p->pi_state_cache = NULL;
1198 #endif
1200 * sigaltstack should be cleared when sharing the same VM
1202 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1203 p->sas_ss_sp = p->sas_ss_size = 0;
1206 * Syscall tracing should be turned off in the child regardless
1207 * of CLONE_PTRACE.
1209 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1210 #ifdef TIF_SYSCALL_EMU
1211 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1212 #endif
1213 clear_all_latency_tracing(p);
1215 /* ok, now we should be set up.. */
1216 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1217 p->pdeath_signal = 0;
1218 p->exit_state = 0;
1221 * Ok, make it visible to the rest of the system.
1222 * We dont wake it up yet.
1224 p->group_leader = p;
1225 INIT_LIST_HEAD(&p->thread_group);
1227 /* Now that the task is set up, run cgroup callbacks if
1228 * necessary. We need to run them before the task is visible
1229 * on the tasklist. */
1230 cgroup_fork_callbacks(p);
1231 cgroup_callbacks_done = 1;
1233 /* Need tasklist lock for parent etc handling! */
1234 write_lock_irq(&tasklist_lock);
1236 /* CLONE_PARENT re-uses the old parent */
1237 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1238 p->real_parent = current->real_parent;
1239 p->parent_exec_id = current->parent_exec_id;
1240 } else {
1241 p->real_parent = current;
1242 p->parent_exec_id = current->self_exec_id;
1245 spin_lock(&current->sighand->siglock);
1248 * Process group and session signals need to be delivered to just the
1249 * parent before the fork or both the parent and the child after the
1250 * fork. Restart if a signal comes in before we add the new process to
1251 * it's process group.
1252 * A fatal signal pending means that current will exit, so the new
1253 * thread can't slip out of an OOM kill (or normal SIGKILL).
1255 recalc_sigpending();
1256 if (signal_pending(current)) {
1257 spin_unlock(&current->sighand->siglock);
1258 write_unlock_irq(&tasklist_lock);
1259 retval = -ERESTARTNOINTR;
1260 goto bad_fork_free_pid;
1263 if (clone_flags & CLONE_THREAD) {
1264 atomic_inc(&current->signal->count);
1265 atomic_inc(&current->signal->live);
1266 p->group_leader = current->group_leader;
1267 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1270 if (likely(p->pid)) {
1271 list_add_tail(&p->sibling, &p->real_parent->children);
1272 tracehook_finish_clone(p, clone_flags, trace);
1274 if (thread_group_leader(p)) {
1275 if (clone_flags & CLONE_NEWPID)
1276 p->nsproxy->pid_ns->child_reaper = p;
1278 p->signal->leader_pid = pid;
1279 tty_kref_put(p->signal->tty);
1280 p->signal->tty = tty_kref_get(current->signal->tty);
1281 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1282 attach_pid(p, PIDTYPE_SID, task_session(current));
1283 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1284 __get_cpu_var(process_counts)++;
1286 attach_pid(p, PIDTYPE_PID, pid);
1287 nr_threads++;
1290 total_forks++;
1291 spin_unlock(&current->sighand->siglock);
1292 write_unlock_irq(&tasklist_lock);
1293 proc_fork_connector(p);
1294 cgroup_post_fork(p);
1295 perf_event_fork(p);
1296 return p;
1298 bad_fork_free_pid:
1299 if (pid != &init_struct_pid)
1300 free_pid(pid);
1301 bad_fork_cleanup_io:
1302 put_io_context(p->io_context);
1303 bad_fork_cleanup_namespaces:
1304 exit_task_namespaces(p);
1305 bad_fork_cleanup_mm:
1306 if (p->mm)
1307 mmput(p->mm);
1308 bad_fork_cleanup_signal:
1309 if (!(clone_flags & CLONE_THREAD))
1310 __cleanup_signal(p->signal);
1311 bad_fork_cleanup_sighand:
1312 __cleanup_sighand(p->sighand);
1313 bad_fork_cleanup_fs:
1314 exit_fs(p); /* blocking */
1315 bad_fork_cleanup_files:
1316 exit_files(p); /* blocking */
1317 bad_fork_cleanup_semundo:
1318 exit_sem(p);
1319 bad_fork_cleanup_audit:
1320 audit_free(p);
1321 bad_fork_cleanup_policy:
1322 perf_event_free_task(p);
1323 #ifdef CONFIG_NUMA
1324 mpol_put(p->mempolicy);
1325 bad_fork_cleanup_cgroup:
1326 #endif
1327 cgroup_exit(p, cgroup_callbacks_done);
1328 delayacct_tsk_free(p);
1329 module_put(task_thread_info(p)->exec_domain->module);
1330 bad_fork_cleanup_count:
1331 atomic_dec(&p->cred->user->processes);
1332 exit_creds(p);
1333 bad_fork_free:
1334 free_task(p);
1335 fork_out:
1336 return ERR_PTR(retval);
1339 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1341 memset(regs, 0, sizeof(struct pt_regs));
1342 return regs;
1345 struct task_struct * __cpuinit fork_idle(int cpu)
1347 struct task_struct *task;
1348 struct pt_regs regs;
1350 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1351 &init_struct_pid, 0);
1352 if (!IS_ERR(task))
1353 init_idle(task, cpu);
1355 return task;
1359 * Ok, this is the main fork-routine.
1361 * It copies the process, and if successful kick-starts
1362 * it and waits for it to finish using the VM if required.
1364 long do_fork(unsigned long clone_flags,
1365 unsigned long stack_start,
1366 struct pt_regs *regs,
1367 unsigned long stack_size,
1368 int __user *parent_tidptr,
1369 int __user *child_tidptr)
1371 struct task_struct *p;
1372 int trace = 0;
1373 long nr;
1376 * Do some preliminary argument and permissions checking before we
1377 * actually start allocating stuff
1379 if (clone_flags & CLONE_NEWUSER) {
1380 if (clone_flags & CLONE_THREAD)
1381 return -EINVAL;
1382 /* hopefully this check will go away when userns support is
1383 * complete
1385 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1386 !capable(CAP_SETGID))
1387 return -EPERM;
1391 * We hope to recycle these flags after 2.6.26
1393 if (unlikely(clone_flags & CLONE_STOPPED)) {
1394 static int __read_mostly count = 100;
1396 if (count > 0 && printk_ratelimit()) {
1397 char comm[TASK_COMM_LEN];
1399 count--;
1400 printk(KERN_INFO "fork(): process `%s' used deprecated "
1401 "clone flags 0x%lx\n",
1402 get_task_comm(comm, current),
1403 clone_flags & CLONE_STOPPED);
1408 * When called from kernel_thread, don't do user tracing stuff.
1410 if (likely(user_mode(regs)))
1411 trace = tracehook_prepare_clone(clone_flags);
1413 p = copy_process(clone_flags, stack_start, regs, stack_size,
1414 child_tidptr, NULL, trace);
1416 * Do this prior waking up the new thread - the thread pointer
1417 * might get invalid after that point, if the thread exits quickly.
1419 if (!IS_ERR(p)) {
1420 struct completion vfork;
1422 trace_sched_process_fork(current, p);
1424 nr = task_pid_vnr(p);
1426 if (clone_flags & CLONE_PARENT_SETTID)
1427 put_user(nr, parent_tidptr);
1429 if (clone_flags & CLONE_VFORK) {
1430 p->vfork_done = &vfork;
1431 init_completion(&vfork);
1434 audit_finish_fork(p);
1435 tracehook_report_clone(regs, clone_flags, nr, p);
1438 * We set PF_STARTING at creation in case tracing wants to
1439 * use this to distinguish a fully live task from one that
1440 * hasn't gotten to tracehook_report_clone() yet. Now we
1441 * clear it and set the child going.
1443 p->flags &= ~PF_STARTING;
1445 if (unlikely(clone_flags & CLONE_STOPPED)) {
1447 * We'll start up with an immediate SIGSTOP.
1449 sigaddset(&p->pending.signal, SIGSTOP);
1450 set_tsk_thread_flag(p, TIF_SIGPENDING);
1451 __set_task_state(p, TASK_STOPPED);
1452 } else {
1453 wake_up_new_task(p, clone_flags);
1456 tracehook_report_clone_complete(trace, regs,
1457 clone_flags, nr, p);
1459 if (clone_flags & CLONE_VFORK) {
1460 freezer_do_not_count();
1461 wait_for_completion(&vfork);
1462 freezer_count();
1463 tracehook_report_vfork_done(p, nr);
1465 } else {
1466 nr = PTR_ERR(p);
1468 return nr;
1471 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1472 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1473 #endif
1475 static void sighand_ctor(void *data)
1477 struct sighand_struct *sighand = data;
1479 spin_lock_init(&sighand->siglock);
1480 init_waitqueue_head(&sighand->signalfd_wqh);
1483 void __init proc_caches_init(void)
1485 sighand_cachep = kmem_cache_create("sighand_cache",
1486 sizeof(struct sighand_struct), 0,
1487 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1488 SLAB_NOTRACK, sighand_ctor);
1489 signal_cachep = kmem_cache_create("signal_cache",
1490 sizeof(struct signal_struct), 0,
1491 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1492 files_cachep = kmem_cache_create("files_cache",
1493 sizeof(struct files_struct), 0,
1494 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1495 fs_cachep = kmem_cache_create("fs_cache",
1496 sizeof(struct fs_struct), 0,
1497 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1498 mm_cachep = kmem_cache_create("mm_struct",
1499 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1500 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1501 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1502 mmap_init();
1506 * Check constraints on flags passed to the unshare system call and
1507 * force unsharing of additional process context as appropriate.
1509 static void check_unshare_flags(unsigned long *flags_ptr)
1512 * If unsharing a thread from a thread group, must also
1513 * unshare vm.
1515 if (*flags_ptr & CLONE_THREAD)
1516 *flags_ptr |= CLONE_VM;
1519 * If unsharing vm, must also unshare signal handlers.
1521 if (*flags_ptr & CLONE_VM)
1522 *flags_ptr |= CLONE_SIGHAND;
1525 * If unsharing signal handlers and the task was created
1526 * using CLONE_THREAD, then must unshare the thread
1528 if ((*flags_ptr & CLONE_SIGHAND) &&
1529 (atomic_read(&current->signal->count) > 1))
1530 *flags_ptr |= CLONE_THREAD;
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 write_lock(&fs->lock);
1683 current->fs = new_fs;
1684 if (--fs->users)
1685 new_fs = NULL;
1686 else
1687 new_fs = fs;
1688 write_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;