Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc
[linux-2.6/linux-2.6-stable.git] / kernel / fork.c
blob8e6b6f4fb272ba498a4acdbcb6a29c8f7e6c87dd
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/futex.h>
41 #include <linux/compat.h>
42 #include <linux/kthread.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/blkdev.h>
62 #include <linux/fs_struct.h>
63 #include <linux/magic.h>
64 #include <linux/perf_event.h>
65 #include <linux/posix-timers.h>
66 #include <linux/user-return-notifier.h>
67 #include <linux/oom.h>
68 #include <linux/khugepaged.h>
70 #include <asm/pgtable.h>
71 #include <asm/pgalloc.h>
72 #include <asm/uaccess.h>
73 #include <asm/mmu_context.h>
74 #include <asm/cacheflush.h>
75 #include <asm/tlbflush.h>
77 #include <trace/events/sched.h>
80 * Protected counters by write_lock_irq(&tasklist_lock)
82 unsigned long total_forks; /* Handle normal Linux uptimes. */
83 int nr_threads; /* The idle threads do not count.. */
85 int max_threads; /* tunable limit on nr_threads */
87 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
89 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
91 #ifdef CONFIG_PROVE_RCU
92 int lockdep_tasklist_lock_is_held(void)
94 return lockdep_is_held(&tasklist_lock);
96 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
97 #endif /* #ifdef CONFIG_PROVE_RCU */
99 int nr_processes(void)
101 int cpu;
102 int total = 0;
104 for_each_possible_cpu(cpu)
105 total += per_cpu(process_counts, cpu);
107 return total;
110 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
111 # define alloc_task_struct_node(node) \
112 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
113 # define free_task_struct(tsk) \
114 kmem_cache_free(task_struct_cachep, (tsk))
115 static struct kmem_cache *task_struct_cachep;
116 #endif
118 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
119 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
120 int node)
122 #ifdef CONFIG_DEBUG_STACK_USAGE
123 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
124 #else
125 gfp_t mask = GFP_KERNEL;
126 #endif
127 struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
129 return page ? page_address(page) : NULL;
132 static inline void free_thread_info(struct thread_info *ti)
134 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
136 #endif
138 /* SLAB cache for signal_struct structures (tsk->signal) */
139 static struct kmem_cache *signal_cachep;
141 /* SLAB cache for sighand_struct structures (tsk->sighand) */
142 struct kmem_cache *sighand_cachep;
144 /* SLAB cache for files_struct structures (tsk->files) */
145 struct kmem_cache *files_cachep;
147 /* SLAB cache for fs_struct structures (tsk->fs) */
148 struct kmem_cache *fs_cachep;
150 /* SLAB cache for vm_area_struct structures */
151 struct kmem_cache *vm_area_cachep;
153 /* SLAB cache for mm_struct structures (tsk->mm) */
154 static struct kmem_cache *mm_cachep;
156 static void account_kernel_stack(struct thread_info *ti, int account)
158 struct zone *zone = page_zone(virt_to_page(ti));
160 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
163 void free_task(struct task_struct *tsk)
165 prop_local_destroy_single(&tsk->dirties);
166 account_kernel_stack(tsk->stack, -1);
167 free_thread_info(tsk->stack);
168 rt_mutex_debug_task_free(tsk);
169 ftrace_graph_exit_task(tsk);
170 free_task_struct(tsk);
172 EXPORT_SYMBOL(free_task);
174 static inline void free_signal_struct(struct signal_struct *sig)
176 taskstats_tgid_free(sig);
177 sched_autogroup_exit(sig);
178 kmem_cache_free(signal_cachep, sig);
181 static inline void put_signal_struct(struct signal_struct *sig)
183 if (atomic_dec_and_test(&sig->sigcnt))
184 free_signal_struct(sig);
187 void __put_task_struct(struct task_struct *tsk)
189 WARN_ON(!tsk->exit_state);
190 WARN_ON(atomic_read(&tsk->usage));
191 WARN_ON(tsk == current);
193 exit_creds(tsk);
194 delayacct_tsk_free(tsk);
195 put_signal_struct(tsk->signal);
197 if (!profile_handoff_task(tsk))
198 free_task(tsk);
200 EXPORT_SYMBOL_GPL(__put_task_struct);
203 * macro override instead of weak attribute alias, to workaround
204 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
206 #ifndef arch_task_cache_init
207 #define arch_task_cache_init()
208 #endif
210 void __init fork_init(unsigned long mempages)
212 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
213 #ifndef ARCH_MIN_TASKALIGN
214 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
215 #endif
216 /* create a slab on which task_structs can be allocated */
217 task_struct_cachep =
218 kmem_cache_create("task_struct", sizeof(struct task_struct),
219 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
220 #endif
222 /* do the arch specific task caches init */
223 arch_task_cache_init();
226 * The default maximum number of threads is set to a safe
227 * value: the thread structures can take up at most half
228 * of memory.
230 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
233 * we need to allow at least 20 threads to boot a system
235 if (max_threads < 20)
236 max_threads = 20;
238 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
239 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
240 init_task.signal->rlim[RLIMIT_SIGPENDING] =
241 init_task.signal->rlim[RLIMIT_NPROC];
244 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
245 struct task_struct *src)
247 *dst = *src;
248 return 0;
251 static struct task_struct *dup_task_struct(struct task_struct *orig)
253 struct task_struct *tsk;
254 struct thread_info *ti;
255 unsigned long *stackend;
256 int node = tsk_fork_get_node(orig);
257 int err;
259 prepare_to_copy(orig);
261 tsk = alloc_task_struct_node(node);
262 if (!tsk)
263 return NULL;
265 ti = alloc_thread_info_node(tsk, node);
266 if (!ti) {
267 free_task_struct(tsk);
268 return NULL;
271 err = arch_dup_task_struct(tsk, orig);
272 if (err)
273 goto out;
275 tsk->stack = ti;
277 err = prop_local_init_single(&tsk->dirties);
278 if (err)
279 goto out;
281 setup_thread_stack(tsk, orig);
282 clear_user_return_notifier(tsk);
283 clear_tsk_need_resched(tsk);
284 stackend = end_of_stack(tsk);
285 *stackend = STACK_END_MAGIC; /* for overflow detection */
287 #ifdef CONFIG_CC_STACKPROTECTOR
288 tsk->stack_canary = get_random_int();
289 #endif
292 * One for us, one for whoever does the "release_task()" (usually
293 * parent)
295 atomic_set(&tsk->usage, 2);
296 #ifdef CONFIG_BLK_DEV_IO_TRACE
297 tsk->btrace_seq = 0;
298 #endif
299 tsk->splice_pipe = NULL;
301 account_kernel_stack(ti, 1);
303 return tsk;
305 out:
306 free_thread_info(ti);
307 free_task_struct(tsk);
308 return NULL;
311 #ifdef CONFIG_MMU
312 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
314 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
315 struct rb_node **rb_link, *rb_parent;
316 int retval;
317 unsigned long charge;
318 struct mempolicy *pol;
320 down_write(&oldmm->mmap_sem);
321 flush_cache_dup_mm(oldmm);
323 * Not linked in yet - no deadlock potential:
325 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
327 mm->locked_vm = 0;
328 mm->mmap = NULL;
329 mm->mmap_cache = NULL;
330 mm->free_area_cache = oldmm->mmap_base;
331 mm->cached_hole_size = ~0UL;
332 mm->map_count = 0;
333 cpumask_clear(mm_cpumask(mm));
334 mm->mm_rb = RB_ROOT;
335 rb_link = &mm->mm_rb.rb_node;
336 rb_parent = NULL;
337 pprev = &mm->mmap;
338 retval = ksm_fork(mm, oldmm);
339 if (retval)
340 goto out;
341 retval = khugepaged_fork(mm, oldmm);
342 if (retval)
343 goto out;
345 prev = NULL;
346 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
347 struct file *file;
349 if (mpnt->vm_flags & VM_DONTCOPY) {
350 long pages = vma_pages(mpnt);
351 mm->total_vm -= pages;
352 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
353 -pages);
354 continue;
356 charge = 0;
357 if (mpnt->vm_flags & VM_ACCOUNT) {
358 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
359 if (security_vm_enough_memory(len))
360 goto fail_nomem;
361 charge = len;
363 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
364 if (!tmp)
365 goto fail_nomem;
366 *tmp = *mpnt;
367 INIT_LIST_HEAD(&tmp->anon_vma_chain);
368 pol = mpol_dup(vma_policy(mpnt));
369 retval = PTR_ERR(pol);
370 if (IS_ERR(pol))
371 goto fail_nomem_policy;
372 vma_set_policy(tmp, pol);
373 tmp->vm_mm = mm;
374 if (anon_vma_fork(tmp, mpnt))
375 goto fail_nomem_anon_vma_fork;
376 tmp->vm_flags &= ~VM_LOCKED;
377 tmp->vm_next = tmp->vm_prev = NULL;
378 file = tmp->vm_file;
379 if (file) {
380 struct inode *inode = file->f_path.dentry->d_inode;
381 struct address_space *mapping = file->f_mapping;
383 get_file(file);
384 if (tmp->vm_flags & VM_DENYWRITE)
385 atomic_dec(&inode->i_writecount);
386 mutex_lock(&mapping->i_mmap_mutex);
387 if (tmp->vm_flags & VM_SHARED)
388 mapping->i_mmap_writable++;
389 flush_dcache_mmap_lock(mapping);
390 /* insert tmp into the share list, just after mpnt */
391 vma_prio_tree_add(tmp, mpnt);
392 flush_dcache_mmap_unlock(mapping);
393 mutex_unlock(&mapping->i_mmap_mutex);
397 * Clear hugetlb-related page reserves for children. This only
398 * affects MAP_PRIVATE mappings. Faults generated by the child
399 * are not guaranteed to succeed, even if read-only
401 if (is_vm_hugetlb_page(tmp))
402 reset_vma_resv_huge_pages(tmp);
405 * Link in the new vma and copy the page table entries.
407 *pprev = tmp;
408 pprev = &tmp->vm_next;
409 tmp->vm_prev = prev;
410 prev = tmp;
412 __vma_link_rb(mm, tmp, rb_link, rb_parent);
413 rb_link = &tmp->vm_rb.rb_right;
414 rb_parent = &tmp->vm_rb;
416 mm->map_count++;
417 retval = copy_page_range(mm, oldmm, mpnt);
419 if (tmp->vm_ops && tmp->vm_ops->open)
420 tmp->vm_ops->open(tmp);
422 if (retval)
423 goto out;
425 /* a new mm has just been created */
426 arch_dup_mmap(oldmm, mm);
427 retval = 0;
428 out:
429 up_write(&mm->mmap_sem);
430 flush_tlb_mm(oldmm);
431 up_write(&oldmm->mmap_sem);
432 return retval;
433 fail_nomem_anon_vma_fork:
434 mpol_put(pol);
435 fail_nomem_policy:
436 kmem_cache_free(vm_area_cachep, tmp);
437 fail_nomem:
438 retval = -ENOMEM;
439 vm_unacct_memory(charge);
440 goto out;
443 static inline int mm_alloc_pgd(struct mm_struct *mm)
445 mm->pgd = pgd_alloc(mm);
446 if (unlikely(!mm->pgd))
447 return -ENOMEM;
448 return 0;
451 static inline void mm_free_pgd(struct mm_struct *mm)
453 pgd_free(mm, mm->pgd);
455 #else
456 #define dup_mmap(mm, oldmm) (0)
457 #define mm_alloc_pgd(mm) (0)
458 #define mm_free_pgd(mm)
459 #endif /* CONFIG_MMU */
461 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
463 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
464 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
466 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
468 static int __init coredump_filter_setup(char *s)
470 default_dump_filter =
471 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
472 MMF_DUMP_FILTER_MASK;
473 return 1;
476 __setup("coredump_filter=", coredump_filter_setup);
478 #include <linux/init_task.h>
480 static void mm_init_aio(struct mm_struct *mm)
482 #ifdef CONFIG_AIO
483 spin_lock_init(&mm->ioctx_lock);
484 INIT_HLIST_HEAD(&mm->ioctx_list);
485 #endif
488 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
490 atomic_set(&mm->mm_users, 1);
491 atomic_set(&mm->mm_count, 1);
492 init_rwsem(&mm->mmap_sem);
493 INIT_LIST_HEAD(&mm->mmlist);
494 mm->flags = (current->mm) ?
495 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
496 mm->core_state = NULL;
497 mm->nr_ptes = 0;
498 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
499 spin_lock_init(&mm->page_table_lock);
500 mm->free_area_cache = TASK_UNMAPPED_BASE;
501 mm->cached_hole_size = ~0UL;
502 mm_init_aio(mm);
503 mm_init_owner(mm, p);
504 atomic_set(&mm->oom_disable_count, 0);
506 if (likely(!mm_alloc_pgd(mm))) {
507 mm->def_flags = 0;
508 mmu_notifier_mm_init(mm);
509 return mm;
512 free_mm(mm);
513 return NULL;
517 * Allocate and initialize an mm_struct.
519 struct mm_struct *mm_alloc(void)
521 struct mm_struct *mm;
523 mm = allocate_mm();
524 if (!mm)
525 return NULL;
527 memset(mm, 0, sizeof(*mm));
528 mm_init_cpumask(mm);
529 return mm_init(mm, current);
533 * Called when the last reference to the mm
534 * is dropped: either by a lazy thread or by
535 * mmput. Free the page directory and the mm.
537 void __mmdrop(struct mm_struct *mm)
539 BUG_ON(mm == &init_mm);
540 mm_free_pgd(mm);
541 destroy_context(mm);
542 mmu_notifier_mm_destroy(mm);
543 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
544 VM_BUG_ON(mm->pmd_huge_pte);
545 #endif
546 free_mm(mm);
548 EXPORT_SYMBOL_GPL(__mmdrop);
551 * Decrement the use count and release all resources for an mm.
553 void mmput(struct mm_struct *mm)
555 might_sleep();
557 if (atomic_dec_and_test(&mm->mm_users)) {
558 exit_aio(mm);
559 ksm_exit(mm);
560 khugepaged_exit(mm); /* must run before exit_mmap */
561 exit_mmap(mm);
562 set_mm_exe_file(mm, NULL);
563 if (!list_empty(&mm->mmlist)) {
564 spin_lock(&mmlist_lock);
565 list_del(&mm->mmlist);
566 spin_unlock(&mmlist_lock);
568 put_swap_token(mm);
569 if (mm->binfmt)
570 module_put(mm->binfmt->module);
571 mmdrop(mm);
574 EXPORT_SYMBOL_GPL(mmput);
577 * We added or removed a vma mapping the executable. The vmas are only mapped
578 * during exec and are not mapped with the mmap system call.
579 * Callers must hold down_write() on the mm's mmap_sem for these
581 void added_exe_file_vma(struct mm_struct *mm)
583 mm->num_exe_file_vmas++;
586 void removed_exe_file_vma(struct mm_struct *mm)
588 mm->num_exe_file_vmas--;
589 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
590 fput(mm->exe_file);
591 mm->exe_file = NULL;
596 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
598 if (new_exe_file)
599 get_file(new_exe_file);
600 if (mm->exe_file)
601 fput(mm->exe_file);
602 mm->exe_file = new_exe_file;
603 mm->num_exe_file_vmas = 0;
606 struct file *get_mm_exe_file(struct mm_struct *mm)
608 struct file *exe_file;
610 /* We need mmap_sem to protect against races with removal of
611 * VM_EXECUTABLE vmas */
612 down_read(&mm->mmap_sem);
613 exe_file = mm->exe_file;
614 if (exe_file)
615 get_file(exe_file);
616 up_read(&mm->mmap_sem);
617 return exe_file;
620 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
622 /* It's safe to write the exe_file pointer without exe_file_lock because
623 * this is called during fork when the task is not yet in /proc */
624 newmm->exe_file = get_mm_exe_file(oldmm);
628 * get_task_mm - acquire a reference to the task's mm
630 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
631 * this kernel workthread has transiently adopted a user mm with use_mm,
632 * to do its AIO) is not set and if so returns a reference to it, after
633 * bumping up the use count. User must release the mm via mmput()
634 * after use. Typically used by /proc and ptrace.
636 struct mm_struct *get_task_mm(struct task_struct *task)
638 struct mm_struct *mm;
640 task_lock(task);
641 mm = task->mm;
642 if (mm) {
643 if (task->flags & PF_KTHREAD)
644 mm = NULL;
645 else
646 atomic_inc(&mm->mm_users);
648 task_unlock(task);
649 return mm;
651 EXPORT_SYMBOL_GPL(get_task_mm);
653 /* Please note the differences between mmput and mm_release.
654 * mmput is called whenever we stop holding onto a mm_struct,
655 * error success whatever.
657 * mm_release is called after a mm_struct has been removed
658 * from the current process.
660 * This difference is important for error handling, when we
661 * only half set up a mm_struct for a new process and need to restore
662 * the old one. Because we mmput the new mm_struct before
663 * restoring the old one. . .
664 * Eric Biederman 10 January 1998
666 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
668 struct completion *vfork_done = tsk->vfork_done;
670 /* Get rid of any futexes when releasing the mm */
671 #ifdef CONFIG_FUTEX
672 if (unlikely(tsk->robust_list)) {
673 exit_robust_list(tsk);
674 tsk->robust_list = NULL;
676 #ifdef CONFIG_COMPAT
677 if (unlikely(tsk->compat_robust_list)) {
678 compat_exit_robust_list(tsk);
679 tsk->compat_robust_list = NULL;
681 #endif
682 if (unlikely(!list_empty(&tsk->pi_state_list)))
683 exit_pi_state_list(tsk);
684 #endif
686 /* Get rid of any cached register state */
687 deactivate_mm(tsk, mm);
689 /* notify parent sleeping on vfork() */
690 if (vfork_done) {
691 tsk->vfork_done = NULL;
692 complete(vfork_done);
696 * If we're exiting normally, clear a user-space tid field if
697 * requested. We leave this alone when dying by signal, to leave
698 * the value intact in a core dump, and to save the unnecessary
699 * trouble otherwise. Userland only wants this done for a sys_exit.
701 if (tsk->clear_child_tid) {
702 if (!(tsk->flags & PF_SIGNALED) &&
703 atomic_read(&mm->mm_users) > 1) {
705 * We don't check the error code - if userspace has
706 * not set up a proper pointer then tough luck.
708 put_user(0, tsk->clear_child_tid);
709 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
710 1, NULL, NULL, 0);
712 tsk->clear_child_tid = NULL;
717 * Allocate a new mm structure and copy contents from the
718 * mm structure of the passed in task structure.
720 struct mm_struct *dup_mm(struct task_struct *tsk)
722 struct mm_struct *mm, *oldmm = current->mm;
723 int err;
725 if (!oldmm)
726 return NULL;
728 mm = allocate_mm();
729 if (!mm)
730 goto fail_nomem;
732 memcpy(mm, oldmm, sizeof(*mm));
733 mm_init_cpumask(mm);
735 /* Initializing for Swap token stuff */
736 mm->token_priority = 0;
737 mm->last_interval = 0;
739 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
740 mm->pmd_huge_pte = NULL;
741 #endif
743 if (!mm_init(mm, tsk))
744 goto fail_nomem;
746 if (init_new_context(tsk, mm))
747 goto fail_nocontext;
749 dup_mm_exe_file(oldmm, mm);
751 err = dup_mmap(mm, oldmm);
752 if (err)
753 goto free_pt;
755 mm->hiwater_rss = get_mm_rss(mm);
756 mm->hiwater_vm = mm->total_vm;
758 if (mm->binfmt && !try_module_get(mm->binfmt->module))
759 goto free_pt;
761 return mm;
763 free_pt:
764 /* don't put binfmt in mmput, we haven't got module yet */
765 mm->binfmt = NULL;
766 mmput(mm);
768 fail_nomem:
769 return NULL;
771 fail_nocontext:
773 * If init_new_context() failed, we cannot use mmput() to free the mm
774 * because it calls destroy_context()
776 mm_free_pgd(mm);
777 free_mm(mm);
778 return NULL;
781 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
783 struct mm_struct *mm, *oldmm;
784 int retval;
786 tsk->min_flt = tsk->maj_flt = 0;
787 tsk->nvcsw = tsk->nivcsw = 0;
788 #ifdef CONFIG_DETECT_HUNG_TASK
789 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
790 #endif
792 tsk->mm = NULL;
793 tsk->active_mm = NULL;
796 * Are we cloning a kernel thread?
798 * We need to steal a active VM for that..
800 oldmm = current->mm;
801 if (!oldmm)
802 return 0;
804 if (clone_flags & CLONE_VM) {
805 atomic_inc(&oldmm->mm_users);
806 mm = oldmm;
807 goto good_mm;
810 retval = -ENOMEM;
811 mm = dup_mm(tsk);
812 if (!mm)
813 goto fail_nomem;
815 good_mm:
816 /* Initializing for Swap token stuff */
817 mm->token_priority = 0;
818 mm->last_interval = 0;
819 if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
820 atomic_inc(&mm->oom_disable_count);
822 tsk->mm = mm;
823 tsk->active_mm = mm;
824 return 0;
826 fail_nomem:
827 return retval;
830 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
832 struct fs_struct *fs = current->fs;
833 if (clone_flags & CLONE_FS) {
834 /* tsk->fs is already what we want */
835 spin_lock(&fs->lock);
836 if (fs->in_exec) {
837 spin_unlock(&fs->lock);
838 return -EAGAIN;
840 fs->users++;
841 spin_unlock(&fs->lock);
842 return 0;
844 tsk->fs = copy_fs_struct(fs);
845 if (!tsk->fs)
846 return -ENOMEM;
847 return 0;
850 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
852 struct files_struct *oldf, *newf;
853 int error = 0;
856 * A background process may not have any files ...
858 oldf = current->files;
859 if (!oldf)
860 goto out;
862 if (clone_flags & CLONE_FILES) {
863 atomic_inc(&oldf->count);
864 goto out;
867 newf = dup_fd(oldf, &error);
868 if (!newf)
869 goto out;
871 tsk->files = newf;
872 error = 0;
873 out:
874 return error;
877 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
879 #ifdef CONFIG_BLOCK
880 struct io_context *ioc = current->io_context;
882 if (!ioc)
883 return 0;
885 * Share io context with parent, if CLONE_IO is set
887 if (clone_flags & CLONE_IO) {
888 tsk->io_context = ioc_task_link(ioc);
889 if (unlikely(!tsk->io_context))
890 return -ENOMEM;
891 } else if (ioprio_valid(ioc->ioprio)) {
892 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
893 if (unlikely(!tsk->io_context))
894 return -ENOMEM;
896 tsk->io_context->ioprio = ioc->ioprio;
898 #endif
899 return 0;
902 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
904 struct sighand_struct *sig;
906 if (clone_flags & CLONE_SIGHAND) {
907 atomic_inc(&current->sighand->count);
908 return 0;
910 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
911 rcu_assign_pointer(tsk->sighand, sig);
912 if (!sig)
913 return -ENOMEM;
914 atomic_set(&sig->count, 1);
915 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
916 return 0;
919 void __cleanup_sighand(struct sighand_struct *sighand)
921 if (atomic_dec_and_test(&sighand->count))
922 kmem_cache_free(sighand_cachep, sighand);
927 * Initialize POSIX timer handling for a thread group.
929 static void posix_cpu_timers_init_group(struct signal_struct *sig)
931 unsigned long cpu_limit;
933 /* Thread group counters. */
934 thread_group_cputime_init(sig);
936 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
937 if (cpu_limit != RLIM_INFINITY) {
938 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
939 sig->cputimer.running = 1;
942 /* The timer lists. */
943 INIT_LIST_HEAD(&sig->cpu_timers[0]);
944 INIT_LIST_HEAD(&sig->cpu_timers[1]);
945 INIT_LIST_HEAD(&sig->cpu_timers[2]);
948 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
950 struct signal_struct *sig;
952 if (clone_flags & CLONE_THREAD)
953 return 0;
955 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
956 tsk->signal = sig;
957 if (!sig)
958 return -ENOMEM;
960 sig->nr_threads = 1;
961 atomic_set(&sig->live, 1);
962 atomic_set(&sig->sigcnt, 1);
963 init_waitqueue_head(&sig->wait_chldexit);
964 if (clone_flags & CLONE_NEWPID)
965 sig->flags |= SIGNAL_UNKILLABLE;
966 sig->curr_target = tsk;
967 init_sigpending(&sig->shared_pending);
968 INIT_LIST_HEAD(&sig->posix_timers);
970 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
971 sig->real_timer.function = it_real_fn;
973 task_lock(current->group_leader);
974 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
975 task_unlock(current->group_leader);
977 posix_cpu_timers_init_group(sig);
979 tty_audit_fork(sig);
980 sched_autogroup_fork(sig);
982 #ifdef CONFIG_CGROUPS
983 init_rwsem(&sig->threadgroup_fork_lock);
984 #endif
986 sig->oom_adj = current->signal->oom_adj;
987 sig->oom_score_adj = current->signal->oom_score_adj;
988 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
990 mutex_init(&sig->cred_guard_mutex);
992 return 0;
995 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
997 unsigned long new_flags = p->flags;
999 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1000 new_flags |= PF_FORKNOEXEC;
1001 new_flags |= PF_STARTING;
1002 p->flags = new_flags;
1003 clear_freeze_flag(p);
1006 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1008 current->clear_child_tid = tidptr;
1010 return task_pid_vnr(current);
1013 static void rt_mutex_init_task(struct task_struct *p)
1015 raw_spin_lock_init(&p->pi_lock);
1016 #ifdef CONFIG_RT_MUTEXES
1017 plist_head_init(&p->pi_waiters);
1018 p->pi_blocked_on = NULL;
1019 #endif
1022 #ifdef CONFIG_MM_OWNER
1023 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1025 mm->owner = p;
1027 #endif /* CONFIG_MM_OWNER */
1030 * Initialize POSIX timer handling for a single task.
1032 static void posix_cpu_timers_init(struct task_struct *tsk)
1034 tsk->cputime_expires.prof_exp = cputime_zero;
1035 tsk->cputime_expires.virt_exp = cputime_zero;
1036 tsk->cputime_expires.sched_exp = 0;
1037 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1038 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1039 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1043 * This creates a new process as a copy of the old one,
1044 * but does not actually start it yet.
1046 * It copies the registers, and all the appropriate
1047 * parts of the process environment (as per the clone
1048 * flags). The actual kick-off is left to the caller.
1050 static struct task_struct *copy_process(unsigned long clone_flags,
1051 unsigned long stack_start,
1052 struct pt_regs *regs,
1053 unsigned long stack_size,
1054 int __user *child_tidptr,
1055 struct pid *pid,
1056 int trace)
1058 int retval;
1059 struct task_struct *p;
1060 int cgroup_callbacks_done = 0;
1062 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1063 return ERR_PTR(-EINVAL);
1066 * Thread groups must share signals as well, and detached threads
1067 * can only be started up within the thread group.
1069 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1070 return ERR_PTR(-EINVAL);
1073 * Shared signal handlers imply shared VM. By way of the above,
1074 * thread groups also imply shared VM. Blocking this case allows
1075 * for various simplifications in other code.
1077 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1078 return ERR_PTR(-EINVAL);
1081 * Siblings of global init remain as zombies on exit since they are
1082 * not reaped by their parent (swapper). To solve this and to avoid
1083 * multi-rooted process trees, prevent global and container-inits
1084 * from creating siblings.
1086 if ((clone_flags & CLONE_PARENT) &&
1087 current->signal->flags & SIGNAL_UNKILLABLE)
1088 return ERR_PTR(-EINVAL);
1090 retval = security_task_create(clone_flags);
1091 if (retval)
1092 goto fork_out;
1094 retval = -ENOMEM;
1095 p = dup_task_struct(current);
1096 if (!p)
1097 goto fork_out;
1099 ftrace_graph_init_task(p);
1101 rt_mutex_init_task(p);
1103 #ifdef CONFIG_PROVE_LOCKING
1104 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1105 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1106 #endif
1107 retval = -EAGAIN;
1108 if (atomic_read(&p->real_cred->user->processes) >=
1109 task_rlimit(p, RLIMIT_NPROC)) {
1110 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1111 p->real_cred->user != INIT_USER)
1112 goto bad_fork_free;
1114 current->flags &= ~PF_NPROC_EXCEEDED;
1116 retval = copy_creds(p, clone_flags);
1117 if (retval < 0)
1118 goto bad_fork_free;
1121 * If multiple threads are within copy_process(), then this check
1122 * triggers too late. This doesn't hurt, the check is only there
1123 * to stop root fork bombs.
1125 retval = -EAGAIN;
1126 if (nr_threads >= max_threads)
1127 goto bad_fork_cleanup_count;
1129 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1130 goto bad_fork_cleanup_count;
1132 p->did_exec = 0;
1133 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1134 copy_flags(clone_flags, p);
1135 INIT_LIST_HEAD(&p->children);
1136 INIT_LIST_HEAD(&p->sibling);
1137 rcu_copy_process(p);
1138 p->vfork_done = NULL;
1139 spin_lock_init(&p->alloc_lock);
1141 init_sigpending(&p->pending);
1143 p->utime = cputime_zero;
1144 p->stime = cputime_zero;
1145 p->gtime = cputime_zero;
1146 p->utimescaled = cputime_zero;
1147 p->stimescaled = cputime_zero;
1148 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1149 p->prev_utime = cputime_zero;
1150 p->prev_stime = cputime_zero;
1151 #endif
1152 #if defined(SPLIT_RSS_COUNTING)
1153 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1154 #endif
1156 p->default_timer_slack_ns = current->timer_slack_ns;
1158 task_io_accounting_init(&p->ioac);
1159 acct_clear_integrals(p);
1161 posix_cpu_timers_init(p);
1163 do_posix_clock_monotonic_gettime(&p->start_time);
1164 p->real_start_time = p->start_time;
1165 monotonic_to_bootbased(&p->real_start_time);
1166 p->io_context = NULL;
1167 p->audit_context = NULL;
1168 if (clone_flags & CLONE_THREAD)
1169 threadgroup_fork_read_lock(current);
1170 cgroup_fork(p);
1171 #ifdef CONFIG_NUMA
1172 p->mempolicy = mpol_dup(p->mempolicy);
1173 if (IS_ERR(p->mempolicy)) {
1174 retval = PTR_ERR(p->mempolicy);
1175 p->mempolicy = NULL;
1176 goto bad_fork_cleanup_cgroup;
1178 mpol_fix_fork_child_flag(p);
1179 #endif
1180 #ifdef CONFIG_CPUSETS
1181 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1182 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1183 #endif
1184 #ifdef CONFIG_TRACE_IRQFLAGS
1185 p->irq_events = 0;
1186 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1187 p->hardirqs_enabled = 1;
1188 #else
1189 p->hardirqs_enabled = 0;
1190 #endif
1191 p->hardirq_enable_ip = 0;
1192 p->hardirq_enable_event = 0;
1193 p->hardirq_disable_ip = _THIS_IP_;
1194 p->hardirq_disable_event = 0;
1195 p->softirqs_enabled = 1;
1196 p->softirq_enable_ip = _THIS_IP_;
1197 p->softirq_enable_event = 0;
1198 p->softirq_disable_ip = 0;
1199 p->softirq_disable_event = 0;
1200 p->hardirq_context = 0;
1201 p->softirq_context = 0;
1202 #endif
1203 #ifdef CONFIG_LOCKDEP
1204 p->lockdep_depth = 0; /* no locks held yet */
1205 p->curr_chain_key = 0;
1206 p->lockdep_recursion = 0;
1207 #endif
1209 #ifdef CONFIG_DEBUG_MUTEXES
1210 p->blocked_on = NULL; /* not blocked yet */
1211 #endif
1212 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1213 p->memcg_batch.do_batch = 0;
1214 p->memcg_batch.memcg = NULL;
1215 #endif
1217 /* Perform scheduler related setup. Assign this task to a CPU. */
1218 sched_fork(p);
1220 retval = perf_event_init_task(p);
1221 if (retval)
1222 goto bad_fork_cleanup_policy;
1223 retval = audit_alloc(p);
1224 if (retval)
1225 goto bad_fork_cleanup_policy;
1226 /* copy all the process information */
1227 retval = copy_semundo(clone_flags, p);
1228 if (retval)
1229 goto bad_fork_cleanup_audit;
1230 retval = copy_files(clone_flags, p);
1231 if (retval)
1232 goto bad_fork_cleanup_semundo;
1233 retval = copy_fs(clone_flags, p);
1234 if (retval)
1235 goto bad_fork_cleanup_files;
1236 retval = copy_sighand(clone_flags, p);
1237 if (retval)
1238 goto bad_fork_cleanup_fs;
1239 retval = copy_signal(clone_flags, p);
1240 if (retval)
1241 goto bad_fork_cleanup_sighand;
1242 retval = copy_mm(clone_flags, p);
1243 if (retval)
1244 goto bad_fork_cleanup_signal;
1245 retval = copy_namespaces(clone_flags, p);
1246 if (retval)
1247 goto bad_fork_cleanup_mm;
1248 retval = copy_io(clone_flags, p);
1249 if (retval)
1250 goto bad_fork_cleanup_namespaces;
1251 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1252 if (retval)
1253 goto bad_fork_cleanup_io;
1255 if (pid != &init_struct_pid) {
1256 retval = -ENOMEM;
1257 pid = alloc_pid(p->nsproxy->pid_ns);
1258 if (!pid)
1259 goto bad_fork_cleanup_io;
1262 p->pid = pid_nr(pid);
1263 p->tgid = p->pid;
1264 if (clone_flags & CLONE_THREAD)
1265 p->tgid = current->tgid;
1267 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1269 * Clear TID on mm_release()?
1271 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1272 #ifdef CONFIG_BLOCK
1273 p->plug = NULL;
1274 #endif
1275 #ifdef CONFIG_FUTEX
1276 p->robust_list = NULL;
1277 #ifdef CONFIG_COMPAT
1278 p->compat_robust_list = NULL;
1279 #endif
1280 INIT_LIST_HEAD(&p->pi_state_list);
1281 p->pi_state_cache = NULL;
1282 #endif
1284 * sigaltstack should be cleared when sharing the same VM
1286 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1287 p->sas_ss_sp = p->sas_ss_size = 0;
1290 * Syscall tracing and stepping should be turned off in the
1291 * child regardless of CLONE_PTRACE.
1293 user_disable_single_step(p);
1294 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1295 #ifdef TIF_SYSCALL_EMU
1296 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1297 #endif
1298 clear_all_latency_tracing(p);
1300 /* ok, now we should be set up.. */
1301 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1302 p->pdeath_signal = 0;
1303 p->exit_state = 0;
1306 * Ok, make it visible to the rest of the system.
1307 * We dont wake it up yet.
1309 p->group_leader = p;
1310 INIT_LIST_HEAD(&p->thread_group);
1312 /* Now that the task is set up, run cgroup callbacks if
1313 * necessary. We need to run them before the task is visible
1314 * on the tasklist. */
1315 cgroup_fork_callbacks(p);
1316 cgroup_callbacks_done = 1;
1318 /* Need tasklist lock for parent etc handling! */
1319 write_lock_irq(&tasklist_lock);
1321 /* CLONE_PARENT re-uses the old parent */
1322 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1323 p->real_parent = current->real_parent;
1324 p->parent_exec_id = current->parent_exec_id;
1325 } else {
1326 p->real_parent = current;
1327 p->parent_exec_id = current->self_exec_id;
1330 spin_lock(&current->sighand->siglock);
1333 * Process group and session signals need to be delivered to just the
1334 * parent before the fork or both the parent and the child after the
1335 * fork. Restart if a signal comes in before we add the new process to
1336 * it's process group.
1337 * A fatal signal pending means that current will exit, so the new
1338 * thread can't slip out of an OOM kill (or normal SIGKILL).
1340 recalc_sigpending();
1341 if (signal_pending(current)) {
1342 spin_unlock(&current->sighand->siglock);
1343 write_unlock_irq(&tasklist_lock);
1344 retval = -ERESTARTNOINTR;
1345 goto bad_fork_free_pid;
1348 if (clone_flags & CLONE_THREAD) {
1349 current->signal->nr_threads++;
1350 atomic_inc(&current->signal->live);
1351 atomic_inc(&current->signal->sigcnt);
1352 p->group_leader = current->group_leader;
1353 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1356 if (likely(p->pid)) {
1357 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1359 if (thread_group_leader(p)) {
1360 if (is_child_reaper(pid))
1361 p->nsproxy->pid_ns->child_reaper = p;
1363 p->signal->leader_pid = pid;
1364 p->signal->tty = tty_kref_get(current->signal->tty);
1365 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1366 attach_pid(p, PIDTYPE_SID, task_session(current));
1367 list_add_tail(&p->sibling, &p->real_parent->children);
1368 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1369 __this_cpu_inc(process_counts);
1371 attach_pid(p, PIDTYPE_PID, pid);
1372 nr_threads++;
1375 total_forks++;
1376 spin_unlock(&current->sighand->siglock);
1377 write_unlock_irq(&tasklist_lock);
1378 proc_fork_connector(p);
1379 cgroup_post_fork(p);
1380 if (clone_flags & CLONE_THREAD)
1381 threadgroup_fork_read_unlock(current);
1382 perf_event_fork(p);
1383 return p;
1385 bad_fork_free_pid:
1386 if (pid != &init_struct_pid)
1387 free_pid(pid);
1388 bad_fork_cleanup_io:
1389 if (p->io_context)
1390 exit_io_context(p);
1391 bad_fork_cleanup_namespaces:
1392 exit_task_namespaces(p);
1393 bad_fork_cleanup_mm:
1394 if (p->mm) {
1395 task_lock(p);
1396 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1397 atomic_dec(&p->mm->oom_disable_count);
1398 task_unlock(p);
1399 mmput(p->mm);
1401 bad_fork_cleanup_signal:
1402 if (!(clone_flags & CLONE_THREAD))
1403 free_signal_struct(p->signal);
1404 bad_fork_cleanup_sighand:
1405 __cleanup_sighand(p->sighand);
1406 bad_fork_cleanup_fs:
1407 exit_fs(p); /* blocking */
1408 bad_fork_cleanup_files:
1409 exit_files(p); /* blocking */
1410 bad_fork_cleanup_semundo:
1411 exit_sem(p);
1412 bad_fork_cleanup_audit:
1413 audit_free(p);
1414 bad_fork_cleanup_policy:
1415 perf_event_free_task(p);
1416 #ifdef CONFIG_NUMA
1417 mpol_put(p->mempolicy);
1418 bad_fork_cleanup_cgroup:
1419 #endif
1420 if (clone_flags & CLONE_THREAD)
1421 threadgroup_fork_read_unlock(current);
1422 cgroup_exit(p, cgroup_callbacks_done);
1423 delayacct_tsk_free(p);
1424 module_put(task_thread_info(p)->exec_domain->module);
1425 bad_fork_cleanup_count:
1426 atomic_dec(&p->cred->user->processes);
1427 exit_creds(p);
1428 bad_fork_free:
1429 free_task(p);
1430 fork_out:
1431 return ERR_PTR(retval);
1434 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1436 memset(regs, 0, sizeof(struct pt_regs));
1437 return regs;
1440 static inline void init_idle_pids(struct pid_link *links)
1442 enum pid_type type;
1444 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1445 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1446 links[type].pid = &init_struct_pid;
1450 struct task_struct * __cpuinit fork_idle(int cpu)
1452 struct task_struct *task;
1453 struct pt_regs regs;
1455 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1456 &init_struct_pid, 0);
1457 if (!IS_ERR(task)) {
1458 init_idle_pids(task->pids);
1459 init_idle(task, cpu);
1462 return task;
1466 * Ok, this is the main fork-routine.
1468 * It copies the process, and if successful kick-starts
1469 * it and waits for it to finish using the VM if required.
1471 long do_fork(unsigned long clone_flags,
1472 unsigned long stack_start,
1473 struct pt_regs *regs,
1474 unsigned long stack_size,
1475 int __user *parent_tidptr,
1476 int __user *child_tidptr)
1478 struct task_struct *p;
1479 int trace = 0;
1480 long nr;
1483 * Do some preliminary argument and permissions checking before we
1484 * actually start allocating stuff
1486 if (clone_flags & CLONE_NEWUSER) {
1487 if (clone_flags & CLONE_THREAD)
1488 return -EINVAL;
1489 /* hopefully this check will go away when userns support is
1490 * complete
1492 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1493 !capable(CAP_SETGID))
1494 return -EPERM;
1498 * Determine whether and which event to report to ptracer. When
1499 * called from kernel_thread or CLONE_UNTRACED is explicitly
1500 * requested, no event is reported; otherwise, report if the event
1501 * for the type of forking is enabled.
1503 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1504 if (clone_flags & CLONE_VFORK)
1505 trace = PTRACE_EVENT_VFORK;
1506 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1507 trace = PTRACE_EVENT_CLONE;
1508 else
1509 trace = PTRACE_EVENT_FORK;
1511 if (likely(!ptrace_event_enabled(current, trace)))
1512 trace = 0;
1515 p = copy_process(clone_flags, stack_start, regs, stack_size,
1516 child_tidptr, NULL, trace);
1518 * Do this prior waking up the new thread - the thread pointer
1519 * might get invalid after that point, if the thread exits quickly.
1521 if (!IS_ERR(p)) {
1522 struct completion vfork;
1524 trace_sched_process_fork(current, p);
1526 nr = task_pid_vnr(p);
1528 if (clone_flags & CLONE_PARENT_SETTID)
1529 put_user(nr, parent_tidptr);
1531 if (clone_flags & CLONE_VFORK) {
1532 p->vfork_done = &vfork;
1533 init_completion(&vfork);
1536 audit_finish_fork(p);
1539 * We set PF_STARTING at creation in case tracing wants to
1540 * use this to distinguish a fully live task from one that
1541 * hasn't finished SIGSTOP raising yet. Now we clear it
1542 * and set the child going.
1544 p->flags &= ~PF_STARTING;
1546 wake_up_new_task(p);
1548 /* forking complete and child started to run, tell ptracer */
1549 if (unlikely(trace))
1550 ptrace_event(trace, nr);
1552 if (clone_flags & CLONE_VFORK) {
1553 freezer_do_not_count();
1554 wait_for_completion(&vfork);
1555 freezer_count();
1556 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1558 } else {
1559 nr = PTR_ERR(p);
1561 return nr;
1564 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1565 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1566 #endif
1568 static void sighand_ctor(void *data)
1570 struct sighand_struct *sighand = data;
1572 spin_lock_init(&sighand->siglock);
1573 init_waitqueue_head(&sighand->signalfd_wqh);
1576 void __init proc_caches_init(void)
1578 sighand_cachep = kmem_cache_create("sighand_cache",
1579 sizeof(struct sighand_struct), 0,
1580 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1581 SLAB_NOTRACK, sighand_ctor);
1582 signal_cachep = kmem_cache_create("signal_cache",
1583 sizeof(struct signal_struct), 0,
1584 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1585 files_cachep = kmem_cache_create("files_cache",
1586 sizeof(struct files_struct), 0,
1587 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1588 fs_cachep = kmem_cache_create("fs_cache",
1589 sizeof(struct fs_struct), 0,
1590 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1592 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1593 * whole struct cpumask for the OFFSTACK case. We could change
1594 * this to *only* allocate as much of it as required by the
1595 * maximum number of CPU's we can ever have. The cpumask_allocation
1596 * is at the end of the structure, exactly for that reason.
1598 mm_cachep = kmem_cache_create("mm_struct",
1599 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1600 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1601 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1602 mmap_init();
1603 nsproxy_cache_init();
1607 * Check constraints on flags passed to the unshare system call.
1609 static int check_unshare_flags(unsigned long unshare_flags)
1611 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1612 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1613 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1614 return -EINVAL;
1616 * Not implemented, but pretend it works if there is nothing to
1617 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1618 * needs to unshare vm.
1620 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1621 /* FIXME: get_task_mm() increments ->mm_users */
1622 if (atomic_read(&current->mm->mm_users) > 1)
1623 return -EINVAL;
1626 return 0;
1630 * Unshare the filesystem structure if it is being shared
1632 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1634 struct fs_struct *fs = current->fs;
1636 if (!(unshare_flags & CLONE_FS) || !fs)
1637 return 0;
1639 /* don't need lock here; in the worst case we'll do useless copy */
1640 if (fs->users == 1)
1641 return 0;
1643 *new_fsp = copy_fs_struct(fs);
1644 if (!*new_fsp)
1645 return -ENOMEM;
1647 return 0;
1651 * Unshare file descriptor table if it is being shared
1653 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1655 struct files_struct *fd = current->files;
1656 int error = 0;
1658 if ((unshare_flags & CLONE_FILES) &&
1659 (fd && atomic_read(&fd->count) > 1)) {
1660 *new_fdp = dup_fd(fd, &error);
1661 if (!*new_fdp)
1662 return error;
1665 return 0;
1669 * unshare allows a process to 'unshare' part of the process
1670 * context which was originally shared using clone. copy_*
1671 * functions used by do_fork() cannot be used here directly
1672 * because they modify an inactive task_struct that is being
1673 * constructed. Here we are modifying the current, active,
1674 * task_struct.
1676 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1678 struct fs_struct *fs, *new_fs = NULL;
1679 struct files_struct *fd, *new_fd = NULL;
1680 struct nsproxy *new_nsproxy = NULL;
1681 int do_sysvsem = 0;
1682 int err;
1684 err = check_unshare_flags(unshare_flags);
1685 if (err)
1686 goto bad_unshare_out;
1689 * If unsharing namespace, must also unshare filesystem information.
1691 if (unshare_flags & CLONE_NEWNS)
1692 unshare_flags |= CLONE_FS;
1694 * CLONE_NEWIPC must also detach from the undolist: after switching
1695 * to a new ipc namespace, the semaphore arrays from the old
1696 * namespace are unreachable.
1698 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1699 do_sysvsem = 1;
1700 err = unshare_fs(unshare_flags, &new_fs);
1701 if (err)
1702 goto bad_unshare_out;
1703 err = unshare_fd(unshare_flags, &new_fd);
1704 if (err)
1705 goto bad_unshare_cleanup_fs;
1706 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1707 if (err)
1708 goto bad_unshare_cleanup_fd;
1710 if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1711 if (do_sysvsem) {
1713 * CLONE_SYSVSEM is equivalent to sys_exit().
1715 exit_sem(current);
1718 if (new_nsproxy) {
1719 switch_task_namespaces(current, new_nsproxy);
1720 new_nsproxy = NULL;
1723 task_lock(current);
1725 if (new_fs) {
1726 fs = current->fs;
1727 spin_lock(&fs->lock);
1728 current->fs = new_fs;
1729 if (--fs->users)
1730 new_fs = NULL;
1731 else
1732 new_fs = fs;
1733 spin_unlock(&fs->lock);
1736 if (new_fd) {
1737 fd = current->files;
1738 current->files = new_fd;
1739 new_fd = fd;
1742 task_unlock(current);
1745 if (new_nsproxy)
1746 put_nsproxy(new_nsproxy);
1748 bad_unshare_cleanup_fd:
1749 if (new_fd)
1750 put_files_struct(new_fd);
1752 bad_unshare_cleanup_fs:
1753 if (new_fs)
1754 free_fs_struct(new_fs);
1756 bad_unshare_out:
1757 return err;
1761 * Helper to unshare the files of the current task.
1762 * We don't want to expose copy_files internals to
1763 * the exec layer of the kernel.
1766 int unshare_files(struct files_struct **displaced)
1768 struct task_struct *task = current;
1769 struct files_struct *copy = NULL;
1770 int error;
1772 error = unshare_fd(CLONE_FILES, &copy);
1773 if (error || !copy) {
1774 *displaced = NULL;
1775 return error;
1777 *displaced = task->files;
1778 task_lock(task);
1779 task->files = copy;
1780 task_unlock(task);
1781 return 0;