projects/linux·blob v2.6.37 · refs

1772 lines · 42.1 KiB

1/*
2 * linux/kernel/fork.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
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()'
12 */
13
14#include <linux/slab.h>
15#include <linux/init.h>
16#include <linux/unistd.h>
17#include <linux/module.h>
18#include <linux/vmalloc.h>
19#include <linux/completion.h>
20#include <linux/personality.h>
21#include <linux/mempolicy.h>
22#include <linux/sem.h>
23#include <linux/file.h>
24#include <linux/fdtable.h>
25#include <linux/iocontext.h>
26#include <linux/key.h>
27#include <linux/binfmts.h>
28#include <linux/mman.h>
29#include <linux/mmu_notifier.h>
30#include <linux/fs.h>
31#include <linux/nsproxy.h>
32#include <linux/capability.h>
33#include <linux/cpu.h>
34#include <linux/cgroup.h>
35#include <linux/security.h>
36#include <linux/hugetlb.h>
37#include <linux/swap.h>
38#include <linux/syscalls.h>
39#include <linux/jiffies.h>
40#include <linux/tracehook.h>
41#include <linux/futex.h>
42#include <linux/compat.h>
43#include <linux/task_io_accounting_ops.h>
44#include <linux/rcupdate.h>
45#include <linux/ptrace.h>
46#include <linux/mount.h>
47#include <linux/audit.h>
48#include <linux/memcontrol.h>
49#include <linux/ftrace.h>
50#include <linux/profile.h>
51#include <linux/rmap.h>
52#include <linux/ksm.h>
53#include <linux/acct.h>
54#include <linux/tsacct_kern.h>
55#include <linux/cn_proc.h>
56#include <linux/freezer.h>
57#include <linux/delayacct.h>
58#include <linux/taskstats_kern.h>
59#include <linux/random.h>
60#include <linux/tty.h>
61#include <linux/proc_fs.h>
62#include <linux/blkdev.h>
63#include <linux/fs_struct.h>
64#include <linux/magic.h>
65#include <linux/perf_event.h>
66#include <linux/posix-timers.h>
67#include <linux/user-return-notifier.h>
68#include <linux/oom.h>
69
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>
76
77#include <trace/events/sched.h>
78
79/*
80 * Protected counters by write_lock_irq(&tasklist_lock)
81 */
82unsigned long total_forks; /* Handle normal Linux uptimes. */
83int nr_threads; /* The idle threads do not count.. */
84
85int max_threads; /* tunable limit on nr_threads */
86
87DEFINE_PER_CPU(unsigned long, process_counts) = 0;
88
89__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
90
91#ifdef CONFIG_PROVE_RCU
92int lockdep_tasklist_lock_is_held(void)
93{
94 return lockdep_is_held(&tasklist_lock);
95}
96EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
97#endif /* #ifdef CONFIG_PROVE_RCU */
98
99int nr_processes(void)
100{
101 int cpu;
102 int total = 0;
103
104 for_each_possible_cpu(cpu)
105 total += per_cpu(process_counts, cpu);
106
107 return total;
108}
109
110#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
111# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
112# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
113static struct kmem_cache *task_struct_cachep;
114#endif
115
116#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
117static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
118{
119#ifdef CONFIG_DEBUG_STACK_USAGE
120 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
121#else
122 gfp_t mask = GFP_KERNEL;
123#endif
124 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
125}
126
127static inline void free_thread_info(struct thread_info *ti)
128{
129 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
130}
131#endif
132
133/* SLAB cache for signal_struct structures (tsk->signal) */
134static struct kmem_cache *signal_cachep;
135
136/* SLAB cache for sighand_struct structures (tsk->sighand) */
137struct kmem_cache *sighand_cachep;
138
139/* SLAB cache for files_struct structures (tsk->files) */
140struct kmem_cache *files_cachep;
141
142/* SLAB cache for fs_struct structures (tsk->fs) */
143struct kmem_cache *fs_cachep;
144
145/* SLAB cache for vm_area_struct structures */
146struct kmem_cache *vm_area_cachep;
147
148/* SLAB cache for mm_struct structures (tsk->mm) */
149static struct kmem_cache *mm_cachep;
150
151static void account_kernel_stack(struct thread_info *ti, int account)
152{
153 struct zone *zone = page_zone(virt_to_page(ti));
154
155 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
156}
157
158void free_task(struct task_struct *tsk)
159{
160 prop_local_destroy_single(&tsk->dirties);
161 account_kernel_stack(tsk->stack, -1);
162 free_thread_info(tsk->stack);
163 rt_mutex_debug_task_free(tsk);
164 ftrace_graph_exit_task(tsk);
165 free_task_struct(tsk);
166}
167EXPORT_SYMBOL(free_task);
168
169static inline void free_signal_struct(struct signal_struct *sig)
170{
171 taskstats_tgid_free(sig);
172 kmem_cache_free(signal_cachep, sig);
173}
174
175static inline void put_signal_struct(struct signal_struct *sig)
176{
177 if (atomic_dec_and_test(&sig->sigcnt))
178 free_signal_struct(sig);
179}
180
181void __put_task_struct(struct task_struct *tsk)
182{
183 WARN_ON(!tsk->exit_state);
184 WARN_ON(atomic_read(&tsk->usage));
185 WARN_ON(tsk == current);
186
187 exit_creds(tsk);
188 delayacct_tsk_free(tsk);
189 put_signal_struct(tsk->signal);
190
191 if (!profile_handoff_task(tsk))
192 free_task(tsk);
193}
194
195/*
196 * macro override instead of weak attribute alias, to workaround
197 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
198 */
199#ifndef arch_task_cache_init
200#define arch_task_cache_init()
201#endif
202
203void __init fork_init(unsigned long mempages)
204{
205#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
206#ifndef ARCH_MIN_TASKALIGN
207#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
208#endif
209 /* create a slab on which task_structs can be allocated */
210 task_struct_cachep =
211 kmem_cache_create("task_struct", sizeof(struct task_struct),
212 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
213#endif
214
215 /* do the arch specific task caches init */
216 arch_task_cache_init();
217
218 /*
219 * The default maximum number of threads is set to a safe
220 * value: the thread structures can take up at most half
221 * of memory.
222 */
223 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
224
225 /*
226 * we need to allow at least 20 threads to boot a system
227 */
228 if(max_threads < 20)
229 max_threads = 20;
230
231 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
232 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
233 init_task.signal->rlim[RLIMIT_SIGPENDING] =
234 init_task.signal->rlim[RLIMIT_NPROC];
235}
236
237int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
238 struct task_struct *src)
239{
240 *dst = *src;
241 return 0;
242}
243
244static struct task_struct *dup_task_struct(struct task_struct *orig)
245{
246 struct task_struct *tsk;
247 struct thread_info *ti;
248 unsigned long *stackend;
249
250 int err;
251
252 prepare_to_copy(orig);
253
254 tsk = alloc_task_struct();
255 if (!tsk)
256 return NULL;
257
258 ti = alloc_thread_info(tsk);
259 if (!ti) {
260 free_task_struct(tsk);
261 return NULL;
262 }
263
264 err = arch_dup_task_struct(tsk, orig);
265 if (err)
266 goto out;
267
268 tsk->stack = ti;
269
270 err = prop_local_init_single(&tsk->dirties);
271 if (err)
272 goto out;
273
274 setup_thread_stack(tsk, orig);
275 clear_user_return_notifier(tsk);
276 clear_tsk_need_resched(tsk);
277 stackend = end_of_stack(tsk);
278 *stackend = STACK_END_MAGIC; /* for overflow detection */
279
280#ifdef CONFIG_CC_STACKPROTECTOR
281 tsk->stack_canary = get_random_int();
282#endif
283
284 /* One for us, one for whoever does the "release_task()" (usually parent) */
285 atomic_set(&tsk->usage,2);
286 atomic_set(&tsk->fs_excl, 0);
287#ifdef CONFIG_BLK_DEV_IO_TRACE
288 tsk->btrace_seq = 0;
289#endif
290 tsk->splice_pipe = NULL;
291
292 account_kernel_stack(ti, 1);
293
294 return tsk;
295
296out:
297 free_thread_info(ti);
298 free_task_struct(tsk);
299 return NULL;
300}
301
302#ifdef CONFIG_MMU
303static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
304{
305 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
306 struct rb_node **rb_link, *rb_parent;
307 int retval;
308 unsigned long charge;
309 struct mempolicy *pol;
310
311 down_write(&oldmm->mmap_sem);
312 flush_cache_dup_mm(oldmm);
313 /*
314 * Not linked in yet - no deadlock potential:
315 */
316 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
317
318 mm->locked_vm = 0;
319 mm->mmap = NULL;
320 mm->mmap_cache = NULL;
321 mm->free_area_cache = oldmm->mmap_base;
322 mm->cached_hole_size = ~0UL;
323 mm->map_count = 0;
324 cpumask_clear(mm_cpumask(mm));
325 mm->mm_rb = RB_ROOT;
326 rb_link = &mm->mm_rb.rb_node;
327 rb_parent = NULL;
328 pprev = &mm->mmap;
329 retval = ksm_fork(mm, oldmm);
330 if (retval)
331 goto out;
332
333 prev = NULL;
334 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
335 struct file *file;
336
337 if (mpnt->vm_flags & VM_DONTCOPY) {
338 long pages = vma_pages(mpnt);
339 mm->total_vm -= pages;
340 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
341 -pages);
342 continue;
343 }
344 charge = 0;
345 if (mpnt->vm_flags & VM_ACCOUNT) {
346 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
347 if (security_vm_enough_memory(len))
348 goto fail_nomem;
349 charge = len;
350 }
351 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
352 if (!tmp)
353 goto fail_nomem;
354 *tmp = *mpnt;
355 INIT_LIST_HEAD(&tmp->anon_vma_chain);
356 pol = mpol_dup(vma_policy(mpnt));
357 retval = PTR_ERR(pol);
358 if (IS_ERR(pol))
359 goto fail_nomem_policy;
360 vma_set_policy(tmp, pol);
361 tmp->vm_mm = mm;
362 if (anon_vma_fork(tmp, mpnt))
363 goto fail_nomem_anon_vma_fork;
364 tmp->vm_flags &= ~VM_LOCKED;
365 tmp->vm_next = tmp->vm_prev = NULL;
366 file = tmp->vm_file;
367 if (file) {
368 struct inode *inode = file->f_path.dentry->d_inode;
369 struct address_space *mapping = file->f_mapping;
370
371 get_file(file);
372 if (tmp->vm_flags & VM_DENYWRITE)
373 atomic_dec(&inode->i_writecount);
374 spin_lock(&mapping->i_mmap_lock);
375 if (tmp->vm_flags & VM_SHARED)
376 mapping->i_mmap_writable++;
377 tmp->vm_truncate_count = mpnt->vm_truncate_count;
378 flush_dcache_mmap_lock(mapping);
379 /* insert tmp into the share list, just after mpnt */
380 vma_prio_tree_add(tmp, mpnt);
381 flush_dcache_mmap_unlock(mapping);
382 spin_unlock(&mapping->i_mmap_lock);
383 }
384
385 /*
386 * Clear hugetlb-related page reserves for children. This only
387 * affects MAP_PRIVATE mappings. Faults generated by the child
388 * are not guaranteed to succeed, even if read-only
389 */
390 if (is_vm_hugetlb_page(tmp))
391 reset_vma_resv_huge_pages(tmp);
392
393 /*
394 * Link in the new vma and copy the page table entries.
395 */
396 *pprev = tmp;
397 pprev = &tmp->vm_next;
398 tmp->vm_prev = prev;
399 prev = tmp;
400
401 __vma_link_rb(mm, tmp, rb_link, rb_parent);
402 rb_link = &tmp->vm_rb.rb_right;
403 rb_parent = &tmp->vm_rb;
404
405 mm->map_count++;
406 retval = copy_page_range(mm, oldmm, mpnt);
407
408 if (tmp->vm_ops && tmp->vm_ops->open)
409 tmp->vm_ops->open(tmp);
410
411 if (retval)
412 goto out;
413 }
414 /* a new mm has just been created */
415 arch_dup_mmap(oldmm, mm);
416 retval = 0;
417out:
418 up_write(&mm->mmap_sem);
419 flush_tlb_mm(oldmm);
420 up_write(&oldmm->mmap_sem);
421 return retval;
422fail_nomem_anon_vma_fork:
423 mpol_put(pol);
424fail_nomem_policy:
425 kmem_cache_free(vm_area_cachep, tmp);
426fail_nomem:
427 retval = -ENOMEM;
428 vm_unacct_memory(charge);
429 goto out;
430}
431
432static inline int mm_alloc_pgd(struct mm_struct * mm)
433{
434 mm->pgd = pgd_alloc(mm);
435 if (unlikely(!mm->pgd))
436 return -ENOMEM;
437 return 0;
438}
439
440static inline void mm_free_pgd(struct mm_struct * mm)
441{
442 pgd_free(mm, mm->pgd);
443}
444#else
445#define dup_mmap(mm, oldmm) (0)
446#define mm_alloc_pgd(mm) (0)
447#define mm_free_pgd(mm)
448#endif /* CONFIG_MMU */
449
450__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
451
452#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
453#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
454
455static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
456
457static int __init coredump_filter_setup(char *s)
458{
459 default_dump_filter =
460 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
461 MMF_DUMP_FILTER_MASK;
462 return 1;
463}
464
465__setup("coredump_filter=", coredump_filter_setup);
466
467#include <linux/init_task.h>
468
469static void mm_init_aio(struct mm_struct *mm)
470{
471#ifdef CONFIG_AIO
472 spin_lock_init(&mm->ioctx_lock);
473 INIT_HLIST_HEAD(&mm->ioctx_list);
474#endif
475}
476
477static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
478{
479 atomic_set(&mm->mm_users, 1);
480 atomic_set(&mm->mm_count, 1);
481 init_rwsem(&mm->mmap_sem);
482 INIT_LIST_HEAD(&mm->mmlist);
483 mm->flags = (current->mm) ?
484 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
485 mm->core_state = NULL;
486 mm->nr_ptes = 0;
487 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
488 spin_lock_init(&mm->page_table_lock);
489 mm->free_area_cache = TASK_UNMAPPED_BASE;
490 mm->cached_hole_size = ~0UL;
491 mm_init_aio(mm);
492 mm_init_owner(mm, p);
493 atomic_set(&mm->oom_disable_count, 0);
494
495 if (likely(!mm_alloc_pgd(mm))) {
496 mm->def_flags = 0;
497 mmu_notifier_mm_init(mm);
498 return mm;
499 }
500
501 free_mm(mm);
502 return NULL;
503}
504
505/*
506 * Allocate and initialize an mm_struct.
507 */
508struct mm_struct * mm_alloc(void)
509{
510 struct mm_struct * mm;
511
512 mm = allocate_mm();
513 if (mm) {
514 memset(mm, 0, sizeof(*mm));
515 mm = mm_init(mm, current);
516 }
517 return mm;
518}
519
520/*
521 * Called when the last reference to the mm
522 * is dropped: either by a lazy thread or by
523 * mmput. Free the page directory and the mm.
524 */
525void __mmdrop(struct mm_struct *mm)
526{
527 BUG_ON(mm == &init_mm);
528 mm_free_pgd(mm);
529 destroy_context(mm);
530 mmu_notifier_mm_destroy(mm);
531 free_mm(mm);
532}
533EXPORT_SYMBOL_GPL(__mmdrop);
534
535/*
536 * Decrement the use count and release all resources for an mm.
537 */
538void mmput(struct mm_struct *mm)
539{
540 might_sleep();
541
542 if (atomic_dec_and_test(&mm->mm_users)) {
543 exit_aio(mm);
544 ksm_exit(mm);
545 exit_mmap(mm);
546 set_mm_exe_file(mm, NULL);
547 if (!list_empty(&mm->mmlist)) {
548 spin_lock(&mmlist_lock);
549 list_del(&mm->mmlist);
550 spin_unlock(&mmlist_lock);
551 }
552 put_swap_token(mm);
553 if (mm->binfmt)
554 module_put(mm->binfmt->module);
555 mmdrop(mm);
556 }
557}
558EXPORT_SYMBOL_GPL(mmput);
559
560/**
561 * get_task_mm - acquire a reference to the task's mm
562 *
563 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
564 * this kernel workthread has transiently adopted a user mm with use_mm,
565 * to do its AIO) is not set and if so returns a reference to it, after
566 * bumping up the use count. User must release the mm via mmput()
567 * after use. Typically used by /proc and ptrace.
568 */
569struct mm_struct *get_task_mm(struct task_struct *task)
570{
571 struct mm_struct *mm;
572
573 task_lock(task);
574 mm = task->mm;
575 if (mm) {
576 if (task->flags & PF_KTHREAD)
577 mm = NULL;
578 else
579 atomic_inc(&mm->mm_users);
580 }
581 task_unlock(task);
582 return mm;
583}
584EXPORT_SYMBOL_GPL(get_task_mm);
585
586/* Please note the differences between mmput and mm_release.
587 * mmput is called whenever we stop holding onto a mm_struct,
588 * error success whatever.
589 *
590 * mm_release is called after a mm_struct has been removed
591 * from the current process.
592 *
593 * This difference is important for error handling, when we
594 * only half set up a mm_struct for a new process and need to restore
595 * the old one. Because we mmput the new mm_struct before
596 * restoring the old one. . .
597 * Eric Biederman 10 January 1998
598 */
599void mm_release(struct task_struct *tsk, struct mm_struct *mm)
600{
601 struct completion *vfork_done = tsk->vfork_done;
602
603 /* Get rid of any futexes when releasing the mm */
604#ifdef CONFIG_FUTEX
605 if (unlikely(tsk->robust_list)) {
606 exit_robust_list(tsk);
607 tsk->robust_list = NULL;
608 }
609#ifdef CONFIG_COMPAT
610 if (unlikely(tsk->compat_robust_list)) {
611 compat_exit_robust_list(tsk);
612 tsk->compat_robust_list = NULL;
613 }
614#endif
615 if (unlikely(!list_empty(&tsk->pi_state_list)))
616 exit_pi_state_list(tsk);
617#endif
618
619 /* Get rid of any cached register state */
620 deactivate_mm(tsk, mm);
621
622 /* notify parent sleeping on vfork() */
623 if (vfork_done) {
624 tsk->vfork_done = NULL;
625 complete(vfork_done);
626 }
627
628 /*
629 * If we're exiting normally, clear a user-space tid field if
630 * requested. We leave this alone when dying by signal, to leave
631 * the value intact in a core dump, and to save the unnecessary
632 * trouble otherwise. Userland only wants this done for a sys_exit.
633 */
634 if (tsk->clear_child_tid) {
635 if (!(tsk->flags & PF_SIGNALED) &&
636 atomic_read(&mm->mm_users) > 1) {
637 /*
638 * We don't check the error code - if userspace has
639 * not set up a proper pointer then tough luck.
640 */
641 put_user(0, tsk->clear_child_tid);
642 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
643 1, NULL, NULL, 0);
644 }
645 tsk->clear_child_tid = NULL;
646 }
647}
648
649/*
650 * Allocate a new mm structure and copy contents from the
651 * mm structure of the passed in task structure.
652 */
653struct mm_struct *dup_mm(struct task_struct *tsk)
654{
655 struct mm_struct *mm, *oldmm = current->mm;
656 int err;
657
658 if (!oldmm)
659 return NULL;
660
661 mm = allocate_mm();
662 if (!mm)
663 goto fail_nomem;
664
665 memcpy(mm, oldmm, sizeof(*mm));
666
667 /* Initializing for Swap token stuff */
668 mm->token_priority = 0;
669 mm->last_interval = 0;
670
671 if (!mm_init(mm, tsk))
672 goto fail_nomem;
673
674 if (init_new_context(tsk, mm))
675 goto fail_nocontext;
676
677 dup_mm_exe_file(oldmm, mm);
678
679 err = dup_mmap(mm, oldmm);
680 if (err)
681 goto free_pt;
682
683 mm->hiwater_rss = get_mm_rss(mm);
684 mm->hiwater_vm = mm->total_vm;
685
686 if (mm->binfmt && !try_module_get(mm->binfmt->module))
687 goto free_pt;
688
689 return mm;
690
691free_pt:
692 /* don't put binfmt in mmput, we haven't got module yet */
693 mm->binfmt = NULL;
694 mmput(mm);
695
696fail_nomem:
697 return NULL;
698
699fail_nocontext:
700 /*
701 * If init_new_context() failed, we cannot use mmput() to free the mm
702 * because it calls destroy_context()
703 */
704 mm_free_pgd(mm);
705 free_mm(mm);
706 return NULL;
707}
708
709static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
710{
711 struct mm_struct * mm, *oldmm;
712 int retval;
713
714 tsk->min_flt = tsk->maj_flt = 0;
715 tsk->nvcsw = tsk->nivcsw = 0;
716#ifdef CONFIG_DETECT_HUNG_TASK
717 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
718#endif
719
720 tsk->mm = NULL;
721 tsk->active_mm = NULL;
722
723 /*
724 * Are we cloning a kernel thread?
725 *
726 * We need to steal a active VM for that..
727 */
728 oldmm = current->mm;
729 if (!oldmm)
730 return 0;
731
732 if (clone_flags & CLONE_VM) {
733 atomic_inc(&oldmm->mm_users);
734 mm = oldmm;
735 goto good_mm;
736 }
737
738 retval = -ENOMEM;
739 mm = dup_mm(tsk);
740 if (!mm)
741 goto fail_nomem;
742
743good_mm:
744 /* Initializing for Swap token stuff */
745 mm->token_priority = 0;
746 mm->last_interval = 0;
747 if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
748 atomic_inc(&mm->oom_disable_count);
749
750 tsk->mm = mm;
751 tsk->active_mm = mm;
752 return 0;
753
754fail_nomem:
755 return retval;
756}
757
758static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
759{
760 struct fs_struct *fs = current->fs;
761 if (clone_flags & CLONE_FS) {
762 /* tsk->fs is already what we want */
763 spin_lock(&fs->lock);
764 if (fs->in_exec) {
765 spin_unlock(&fs->lock);
766 return -EAGAIN;
767 }
768 fs->users++;
769 spin_unlock(&fs->lock);
770 return 0;
771 }
772 tsk->fs = copy_fs_struct(fs);
773 if (!tsk->fs)
774 return -ENOMEM;
775 return 0;
776}
777
778static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
779{
780 struct files_struct *oldf, *newf;
781 int error = 0;
782
783 /*
784 * A background process may not have any files ...
785 */
786 oldf = current->files;
787 if (!oldf)
788 goto out;
789
790 if (clone_flags & CLONE_FILES) {
791 atomic_inc(&oldf->count);
792 goto out;
793 }
794
795 newf = dup_fd(oldf, &error);
796 if (!newf)
797 goto out;
798
799 tsk->files = newf;
800 error = 0;
801out:
802 return error;
803}
804
805static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
806{
807#ifdef CONFIG_BLOCK
808 struct io_context *ioc = current->io_context;
809
810 if (!ioc)
811 return 0;
812 /*
813 * Share io context with parent, if CLONE_IO is set
814 */
815 if (clone_flags & CLONE_IO) {
816 tsk->io_context = ioc_task_link(ioc);
817 if (unlikely(!tsk->io_context))
818 return -ENOMEM;
819 } else if (ioprio_valid(ioc->ioprio)) {
820 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
821 if (unlikely(!tsk->io_context))
822 return -ENOMEM;
823
824 tsk->io_context->ioprio = ioc->ioprio;
825 }
826#endif
827 return 0;
828}
829
830static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
831{
832 struct sighand_struct *sig;
833
834 if (clone_flags & CLONE_SIGHAND) {
835 atomic_inc(&current->sighand->count);
836 return 0;
837 }
838 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
839 rcu_assign_pointer(tsk->sighand, sig);
840 if (!sig)
841 return -ENOMEM;
842 atomic_set(&sig->count, 1);
843 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
844 return 0;
845}
846
847void __cleanup_sighand(struct sighand_struct *sighand)
848{
849 if (atomic_dec_and_test(&sighand->count))
850 kmem_cache_free(sighand_cachep, sighand);
851}
852
853
854/*
855 * Initialize POSIX timer handling for a thread group.
856 */
857static void posix_cpu_timers_init_group(struct signal_struct *sig)
858{
859 unsigned long cpu_limit;
860
861 /* Thread group counters. */
862 thread_group_cputime_init(sig);
863
864 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
865 if (cpu_limit != RLIM_INFINITY) {
866 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
867 sig->cputimer.running = 1;
868 }
869
870 /* The timer lists. */
871 INIT_LIST_HEAD(&sig->cpu_timers[0]);
872 INIT_LIST_HEAD(&sig->cpu_timers[1]);
873 INIT_LIST_HEAD(&sig->cpu_timers[2]);
874}
875
876static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
877{
878 struct signal_struct *sig;
879
880 if (clone_flags & CLONE_THREAD)
881 return 0;
882
883 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
884 tsk->signal = sig;
885 if (!sig)
886 return -ENOMEM;
887
888 sig->nr_threads = 1;
889 atomic_set(&sig->live, 1);
890 atomic_set(&sig->sigcnt, 1);
891 init_waitqueue_head(&sig->wait_chldexit);
892 if (clone_flags & CLONE_NEWPID)
893 sig->flags |= SIGNAL_UNKILLABLE;
894 sig->curr_target = tsk;
895 init_sigpending(&sig->shared_pending);
896 INIT_LIST_HEAD(&sig->posix_timers);
897
898 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
899 sig->real_timer.function = it_real_fn;
900
901 task_lock(current->group_leader);
902 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
903 task_unlock(current->group_leader);
904
905 posix_cpu_timers_init_group(sig);
906
907 tty_audit_fork(sig);
908
909 sig->oom_adj = current->signal->oom_adj;
910 sig->oom_score_adj = current->signal->oom_score_adj;
911
912 mutex_init(&sig->cred_guard_mutex);
913
914 return 0;
915}
916
917static void copy_flags(unsigned long clone_flags, struct task_struct *p)
918{
919 unsigned long new_flags = p->flags;
920
921 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
922 new_flags |= PF_FORKNOEXEC;
923 new_flags |= PF_STARTING;
924 p->flags = new_flags;
925 clear_freeze_flag(p);
926}
927
928SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
929{
930 current->clear_child_tid = tidptr;
931
932 return task_pid_vnr(current);
933}
934
935static void rt_mutex_init_task(struct task_struct *p)
936{
937 raw_spin_lock_init(&p->pi_lock);
938#ifdef CONFIG_RT_MUTEXES
939 plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
940 p->pi_blocked_on = NULL;
941#endif
942}
943
944#ifdef CONFIG_MM_OWNER
945void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
946{
947 mm->owner = p;
948}
949#endif /* CONFIG_MM_OWNER */
950
951/*
952 * Initialize POSIX timer handling for a single task.
953 */
954static void posix_cpu_timers_init(struct task_struct *tsk)
955{
956 tsk->cputime_expires.prof_exp = cputime_zero;
957 tsk->cputime_expires.virt_exp = cputime_zero;
958 tsk->cputime_expires.sched_exp = 0;
959 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
960 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
961 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
962}
963
964/*
965 * This creates a new process as a copy of the old one,
966 * but does not actually start it yet.
967 *
968 * It copies the registers, and all the appropriate
969 * parts of the process environment (as per the clone
970 * flags). The actual kick-off is left to the caller.
971 */
972static struct task_struct *copy_process(unsigned long clone_flags,
973 unsigned long stack_start,
974 struct pt_regs *regs,
975 unsigned long stack_size,
976 int __user *child_tidptr,
977 struct pid *pid,
978 int trace)
979{
980 int retval;
981 struct task_struct *p;
982 int cgroup_callbacks_done = 0;
983
984 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
985 return ERR_PTR(-EINVAL);
986
987 /*
988 * Thread groups must share signals as well, and detached threads
989 * can only be started up within the thread group.
990 */
991 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
992 return ERR_PTR(-EINVAL);
993
994 /*
995 * Shared signal handlers imply shared VM. By way of the above,
996 * thread groups also imply shared VM. Blocking this case allows
997 * for various simplifications in other code.
998 */
999 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1000 return ERR_PTR(-EINVAL);
1001
1002 /*
1003 * Siblings of global init remain as zombies on exit since they are
1004 * not reaped by their parent (swapper). To solve this and to avoid
1005 * multi-rooted process trees, prevent global and container-inits
1006 * from creating siblings.
1007 */
1008 if ((clone_flags & CLONE_PARENT) &&
1009 current->signal->flags & SIGNAL_UNKILLABLE)
1010 return ERR_PTR(-EINVAL);
1011
1012 retval = security_task_create(clone_flags);
1013 if (retval)
1014 goto fork_out;
1015
1016 retval = -ENOMEM;
1017 p = dup_task_struct(current);
1018 if (!p)
1019 goto fork_out;
1020
1021 ftrace_graph_init_task(p);
1022
1023 rt_mutex_init_task(p);
1024
1025#ifdef CONFIG_PROVE_LOCKING
1026 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1027 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1028#endif
1029 retval = -EAGAIN;
1030 if (atomic_read(&p->real_cred->user->processes) >=
1031 task_rlimit(p, RLIMIT_NPROC)) {
1032 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1033 p->real_cred->user != INIT_USER)
1034 goto bad_fork_free;
1035 }
1036
1037 retval = copy_creds(p, clone_flags);
1038 if (retval < 0)
1039 goto bad_fork_free;
1040
1041 /*
1042 * If multiple threads are within copy_process(), then this check
1043 * triggers too late. This doesn't hurt, the check is only there
1044 * to stop root fork bombs.
1045 */
1046 retval = -EAGAIN;
1047 if (nr_threads >= max_threads)
1048 goto bad_fork_cleanup_count;
1049
1050 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1051 goto bad_fork_cleanup_count;
1052
1053 p->did_exec = 0;
1054 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1055 copy_flags(clone_flags, p);
1056 INIT_LIST_HEAD(&p->children);
1057 INIT_LIST_HEAD(&p->sibling);
1058 rcu_copy_process(p);
1059 p->vfork_done = NULL;
1060 spin_lock_init(&p->alloc_lock);
1061
1062 init_sigpending(&p->pending);
1063
1064 p->utime = cputime_zero;
1065 p->stime = cputime_zero;
1066 p->gtime = cputime_zero;
1067 p->utimescaled = cputime_zero;
1068 p->stimescaled = cputime_zero;
1069#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1070 p->prev_utime = cputime_zero;
1071 p->prev_stime = cputime_zero;
1072#endif
1073#if defined(SPLIT_RSS_COUNTING)
1074 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1075#endif
1076
1077 p->default_timer_slack_ns = current->timer_slack_ns;
1078
1079 task_io_accounting_init(&p->ioac);
1080 acct_clear_integrals(p);
1081
1082 posix_cpu_timers_init(p);
1083
1084 p->lock_depth = -1; /* -1 = no lock */
1085 do_posix_clock_monotonic_gettime(&p->start_time);
1086 p->real_start_time = p->start_time;
1087 monotonic_to_bootbased(&p->real_start_time);
1088 p->io_context = NULL;
1089 p->audit_context = NULL;
1090 cgroup_fork(p);
1091#ifdef CONFIG_NUMA
1092 p->mempolicy = mpol_dup(p->mempolicy);
1093 if (IS_ERR(p->mempolicy)) {
1094 retval = PTR_ERR(p->mempolicy);
1095 p->mempolicy = NULL;
1096 goto bad_fork_cleanup_cgroup;
1097 }
1098 mpol_fix_fork_child_flag(p);
1099#endif
1100#ifdef CONFIG_TRACE_IRQFLAGS
1101 p->irq_events = 0;
1102#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1103 p->hardirqs_enabled = 1;
1104#else
1105 p->hardirqs_enabled = 0;
1106#endif
1107 p->hardirq_enable_ip = 0;
1108 p->hardirq_enable_event = 0;
1109 p->hardirq_disable_ip = _THIS_IP_;
1110 p->hardirq_disable_event = 0;
1111 p->softirqs_enabled = 1;
1112 p->softirq_enable_ip = _THIS_IP_;
1113 p->softirq_enable_event = 0;
1114 p->softirq_disable_ip = 0;
1115 p->softirq_disable_event = 0;
1116 p->hardirq_context = 0;
1117 p->softirq_context = 0;
1118#endif
1119#ifdef CONFIG_LOCKDEP
1120 p->lockdep_depth = 0; /* no locks held yet */
1121 p->curr_chain_key = 0;
1122 p->lockdep_recursion = 0;
1123#endif
1124
1125#ifdef CONFIG_DEBUG_MUTEXES
1126 p->blocked_on = NULL; /* not blocked yet */
1127#endif
1128#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1129 p->memcg_batch.do_batch = 0;
1130 p->memcg_batch.memcg = NULL;
1131#endif
1132
1133 /* Perform scheduler related setup. Assign this task to a CPU. */
1134 sched_fork(p, clone_flags);
1135
1136 retval = perf_event_init_task(p);
1137 if (retval)
1138 goto bad_fork_cleanup_policy;
1139
1140 if ((retval = audit_alloc(p)))
1141 goto bad_fork_cleanup_policy;
1142 /* copy all the process information */
1143 if ((retval = copy_semundo(clone_flags, p)))
1144 goto bad_fork_cleanup_audit;
1145 if ((retval = copy_files(clone_flags, p)))
1146 goto bad_fork_cleanup_semundo;
1147 if ((retval = copy_fs(clone_flags, p)))
1148 goto bad_fork_cleanup_files;
1149 if ((retval = copy_sighand(clone_flags, p)))
1150 goto bad_fork_cleanup_fs;
1151 if ((retval = copy_signal(clone_flags, p)))
1152 goto bad_fork_cleanup_sighand;
1153 if ((retval = copy_mm(clone_flags, p)))
1154 goto bad_fork_cleanup_signal;
1155 if ((retval = copy_namespaces(clone_flags, p)))
1156 goto bad_fork_cleanup_mm;
1157 if ((retval = copy_io(clone_flags, p)))
1158 goto bad_fork_cleanup_namespaces;
1159 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1160 if (retval)
1161 goto bad_fork_cleanup_io;
1162
1163 if (pid != &init_struct_pid) {
1164 retval = -ENOMEM;
1165 pid = alloc_pid(p->nsproxy->pid_ns);
1166 if (!pid)
1167 goto bad_fork_cleanup_io;
1168
1169 if (clone_flags & CLONE_NEWPID) {
1170 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1171 if (retval < 0)
1172 goto bad_fork_free_pid;
1173 }
1174 }
1175
1176 p->pid = pid_nr(pid);
1177 p->tgid = p->pid;
1178 if (clone_flags & CLONE_THREAD)
1179 p->tgid = current->tgid;
1180
1181 if (current->nsproxy != p->nsproxy) {
1182 retval = ns_cgroup_clone(p, pid);
1183 if (retval)
1184 goto bad_fork_free_pid;
1185 }
1186
1187 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1188 /*
1189 * Clear TID on mm_release()?
1190 */
1191 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1192#ifdef CONFIG_FUTEX
1193 p->robust_list = NULL;
1194#ifdef CONFIG_COMPAT
1195 p->compat_robust_list = NULL;
1196#endif
1197 INIT_LIST_HEAD(&p->pi_state_list);
1198 p->pi_state_cache = NULL;
1199#endif
1200 /*
1201 * sigaltstack should be cleared when sharing the same VM
1202 */
1203 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1204 p->sas_ss_sp = p->sas_ss_size = 0;
1205
1206 /*
1207 * Syscall tracing and stepping should be turned off in the
1208 * child regardless of CLONE_PTRACE.
1209 */
1210 user_disable_single_step(p);
1211 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1212#ifdef TIF_SYSCALL_EMU
1213 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1214#endif
1215 clear_all_latency_tracing(p);
1216
1217 /* ok, now we should be set up.. */
1218 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1219 p->pdeath_signal = 0;
1220 p->exit_state = 0;
1221
1222 /*
1223 * Ok, make it visible to the rest of the system.
1224 * We dont wake it up yet.
1225 */
1226 p->group_leader = p;
1227 INIT_LIST_HEAD(&p->thread_group);
1228
1229 /* Now that the task is set up, run cgroup callbacks if
1230 * necessary. We need to run them before the task is visible
1231 * on the tasklist. */
1232 cgroup_fork_callbacks(p);
1233 cgroup_callbacks_done = 1;
1234
1235 /* Need tasklist lock for parent etc handling! */
1236 write_lock_irq(&tasklist_lock);
1237
1238 /* CLONE_PARENT re-uses the old parent */
1239 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1240 p->real_parent = current->real_parent;
1241 p->parent_exec_id = current->parent_exec_id;
1242 } else {
1243 p->real_parent = current;
1244 p->parent_exec_id = current->self_exec_id;
1245 }
1246
1247 spin_lock(&current->sighand->siglock);
1248
1249 /*
1250 * Process group and session signals need to be delivered to just the
1251 * parent before the fork or both the parent and the child after the
1252 * fork. Restart if a signal comes in before we add the new process to
1253 * it's process group.
1254 * A fatal signal pending means that current will exit, so the new
1255 * thread can't slip out of an OOM kill (or normal SIGKILL).
1256 */
1257 recalc_sigpending();
1258 if (signal_pending(current)) {
1259 spin_unlock(&current->sighand->siglock);
1260 write_unlock_irq(&tasklist_lock);
1261 retval = -ERESTARTNOINTR;
1262 goto bad_fork_free_pid;
1263 }
1264
1265 if (clone_flags & CLONE_THREAD) {
1266 current->signal->nr_threads++;
1267 atomic_inc(&current->signal->live);
1268 atomic_inc(&current->signal->sigcnt);
1269 p->group_leader = current->group_leader;
1270 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1271 }
1272
1273 if (likely(p->pid)) {
1274 tracehook_finish_clone(p, clone_flags, trace);
1275
1276 if (thread_group_leader(p)) {
1277 if (clone_flags & CLONE_NEWPID)
1278 p->nsproxy->pid_ns->child_reaper = p;
1279
1280 p->signal->leader_pid = pid;
1281 p->signal->tty = tty_kref_get(current->signal->tty);
1282 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1283 attach_pid(p, PIDTYPE_SID, task_session(current));
1284 list_add_tail(&p->sibling, &p->real_parent->children);
1285 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1286 __get_cpu_var(process_counts)++;
1287 }
1288 attach_pid(p, PIDTYPE_PID, pid);
1289 nr_threads++;
1290 }
1291
1292 total_forks++;
1293 spin_unlock(&current->sighand->siglock);
1294 write_unlock_irq(&tasklist_lock);
1295 proc_fork_connector(p);
1296 cgroup_post_fork(p);
1297 perf_event_fork(p);
1298 return p;
1299
1300bad_fork_free_pid:
1301 if (pid != &init_struct_pid)
1302 free_pid(pid);
1303bad_fork_cleanup_io:
1304 if (p->io_context)
1305 exit_io_context(p);
1306bad_fork_cleanup_namespaces:
1307 exit_task_namespaces(p);
1308bad_fork_cleanup_mm:
1309 if (p->mm) {
1310 task_lock(p);
1311 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1312 atomic_dec(&p->mm->oom_disable_count);
1313 task_unlock(p);
1314 mmput(p->mm);
1315 }
1316bad_fork_cleanup_signal:
1317 if (!(clone_flags & CLONE_THREAD))
1318 free_signal_struct(p->signal);
1319bad_fork_cleanup_sighand:
1320 __cleanup_sighand(p->sighand);
1321bad_fork_cleanup_fs:
1322 exit_fs(p); /* blocking */
1323bad_fork_cleanup_files:
1324 exit_files(p); /* blocking */
1325bad_fork_cleanup_semundo:
1326 exit_sem(p);
1327bad_fork_cleanup_audit:
1328 audit_free(p);
1329bad_fork_cleanup_policy:
1330 perf_event_free_task(p);
1331#ifdef CONFIG_NUMA
1332 mpol_put(p->mempolicy);
1333bad_fork_cleanup_cgroup:
1334#endif
1335 cgroup_exit(p, cgroup_callbacks_done);
1336 delayacct_tsk_free(p);
1337 module_put(task_thread_info(p)->exec_domain->module);
1338bad_fork_cleanup_count:
1339 atomic_dec(&p->cred->user->processes);
1340 exit_creds(p);
1341bad_fork_free:
1342 free_task(p);
1343fork_out:
1344 return ERR_PTR(retval);
1345}
1346
1347noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1348{
1349 memset(regs, 0, sizeof(struct pt_regs));
1350 return regs;
1351}
1352
1353static inline void init_idle_pids(struct pid_link *links)
1354{
1355 enum pid_type type;
1356
1357 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1358 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1359 links[type].pid = &init_struct_pid;
1360 }
1361}
1362
1363struct task_struct * __cpuinit fork_idle(int cpu)
1364{
1365 struct task_struct *task;
1366 struct pt_regs regs;
1367
1368 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1369 &init_struct_pid, 0);
1370 if (!IS_ERR(task)) {
1371 init_idle_pids(task->pids);
1372 init_idle(task, cpu);
1373 }
1374
1375 return task;
1376}
1377
1378/*
1379 * Ok, this is the main fork-routine.
1380 *
1381 * It copies the process, and if successful kick-starts
1382 * it and waits for it to finish using the VM if required.
1383 */
1384long do_fork(unsigned long clone_flags,
1385 unsigned long stack_start,
1386 struct pt_regs *regs,
1387 unsigned long stack_size,
1388 int __user *parent_tidptr,
1389 int __user *child_tidptr)
1390{
1391 struct task_struct *p;
1392 int trace = 0;
1393 long nr;
1394
1395 /*
1396 * Do some preliminary argument and permissions checking before we
1397 * actually start allocating stuff
1398 */
1399 if (clone_flags & CLONE_NEWUSER) {
1400 if (clone_flags & CLONE_THREAD)
1401 return -EINVAL;
1402 /* hopefully this check will go away when userns support is
1403 * complete
1404 */
1405 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1406 !capable(CAP_SETGID))
1407 return -EPERM;
1408 }
1409
1410 /*
1411 * We hope to recycle these flags after 2.6.26
1412 */
1413 if (unlikely(clone_flags & CLONE_STOPPED)) {
1414 static int __read_mostly count = 100;
1415
1416 if (count > 0 && printk_ratelimit()) {
1417 char comm[TASK_COMM_LEN];
1418
1419 count--;
1420 printk(KERN_INFO "fork(): process `%s' used deprecated "
1421 "clone flags 0x%lx\n",
1422 get_task_comm(comm, current),
1423 clone_flags & CLONE_STOPPED);
1424 }
1425 }
1426
1427 /*
1428 * When called from kernel_thread, don't do user tracing stuff.
1429 */
1430 if (likely(user_mode(regs)))
1431 trace = tracehook_prepare_clone(clone_flags);
1432
1433 p = copy_process(clone_flags, stack_start, regs, stack_size,
1434 child_tidptr, NULL, trace);
1435 /*
1436 * Do this prior waking up the new thread - the thread pointer
1437 * might get invalid after that point, if the thread exits quickly.
1438 */
1439 if (!IS_ERR(p)) {
1440 struct completion vfork;
1441
1442 trace_sched_process_fork(current, p);
1443
1444 nr = task_pid_vnr(p);
1445
1446 if (clone_flags & CLONE_PARENT_SETTID)
1447 put_user(nr, parent_tidptr);
1448
1449 if (clone_flags & CLONE_VFORK) {
1450 p->vfork_done = &vfork;
1451 init_completion(&vfork);
1452 }
1453
1454 audit_finish_fork(p);
1455 tracehook_report_clone(regs, clone_flags, nr, p);
1456
1457 /*
1458 * We set PF_STARTING at creation in case tracing wants to
1459 * use this to distinguish a fully live task from one that
1460 * hasn't gotten to tracehook_report_clone() yet. Now we
1461 * clear it and set the child going.
1462 */
1463 p->flags &= ~PF_STARTING;
1464
1465 if (unlikely(clone_flags & CLONE_STOPPED)) {
1466 /*
1467 * We'll start up with an immediate SIGSTOP.
1468 */
1469 sigaddset(&p->pending.signal, SIGSTOP);
1470 set_tsk_thread_flag(p, TIF_SIGPENDING);
1471 __set_task_state(p, TASK_STOPPED);
1472 } else {
1473 wake_up_new_task(p, clone_flags);
1474 }
1475
1476 tracehook_report_clone_complete(trace, regs,
1477 clone_flags, nr, p);
1478
1479 if (clone_flags & CLONE_VFORK) {
1480 freezer_do_not_count();
1481 wait_for_completion(&vfork);
1482 freezer_count();
1483 tracehook_report_vfork_done(p, nr);
1484 }
1485 } else {
1486 nr = PTR_ERR(p);
1487 }
1488 return nr;
1489}
1490
1491#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1492#define ARCH_MIN_MMSTRUCT_ALIGN 0
1493#endif
1494
1495static void sighand_ctor(void *data)
1496{
1497 struct sighand_struct *sighand = data;
1498
1499 spin_lock_init(&sighand->siglock);
1500 init_waitqueue_head(&sighand->signalfd_wqh);
1501}
1502
1503void __init proc_caches_init(void)
1504{
1505 sighand_cachep = kmem_cache_create("sighand_cache",
1506 sizeof(struct sighand_struct), 0,
1507 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1508 SLAB_NOTRACK, sighand_ctor);
1509 signal_cachep = kmem_cache_create("signal_cache",
1510 sizeof(struct signal_struct), 0,
1511 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1512 files_cachep = kmem_cache_create("files_cache",
1513 sizeof(struct files_struct), 0,
1514 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1515 fs_cachep = kmem_cache_create("fs_cache",
1516 sizeof(struct fs_struct), 0,
1517 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1518 mm_cachep = kmem_cache_create("mm_struct",
1519 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1520 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1521 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1522 mmap_init();
1523}
1524
1525/*
1526 * Check constraints on flags passed to the unshare system call and
1527 * force unsharing of additional process context as appropriate.
1528 */
1529static void check_unshare_flags(unsigned long *flags_ptr)
1530{
1531 /*
1532 * If unsharing a thread from a thread group, must also
1533 * unshare vm.
1534 */
1535 if (*flags_ptr & CLONE_THREAD)
1536 *flags_ptr |= CLONE_VM;
1537
1538 /*
1539 * If unsharing vm, must also unshare signal handlers.
1540 */
1541 if (*flags_ptr & CLONE_VM)
1542 *flags_ptr |= CLONE_SIGHAND;
1543
1544 /*
1545 * If unsharing namespace, must also unshare filesystem information.
1546 */
1547 if (*flags_ptr & CLONE_NEWNS)
1548 *flags_ptr |= CLONE_FS;
1549}
1550
1551/*
1552 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1553 */
1554static int unshare_thread(unsigned long unshare_flags)
1555{
1556 if (unshare_flags & CLONE_THREAD)
1557 return -EINVAL;
1558
1559 return 0;
1560}
1561
1562/*
1563 * Unshare the filesystem structure if it is being shared
1564 */
1565static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1566{
1567 struct fs_struct *fs = current->fs;
1568
1569 if (!(unshare_flags & CLONE_FS) || !fs)
1570 return 0;
1571
1572 /* don't need lock here; in the worst case we'll do useless copy */
1573 if (fs->users == 1)
1574 return 0;
1575
1576 *new_fsp = copy_fs_struct(fs);
1577 if (!*new_fsp)
1578 return -ENOMEM;
1579
1580 return 0;
1581}
1582
1583/*
1584 * Unsharing of sighand is not supported yet
1585 */
1586static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1587{
1588 struct sighand_struct *sigh = current->sighand;
1589
1590 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1591 return -EINVAL;
1592 else
1593 return 0;
1594}
1595
1596/*
1597 * Unshare vm if it is being shared
1598 */
1599static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1600{
1601 struct mm_struct *mm = current->mm;
1602
1603 if ((unshare_flags & CLONE_VM) &&
1604 (mm && atomic_read(&mm->mm_users) > 1)) {
1605 return -EINVAL;
1606 }
1607
1608 return 0;
1609}
1610
1611/*
1612 * Unshare file descriptor table if it is being shared
1613 */
1614static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1615{
1616 struct files_struct *fd = current->files;
1617 int error = 0;
1618
1619 if ((unshare_flags & CLONE_FILES) &&
1620 (fd && atomic_read(&fd->count) > 1)) {
1621 *new_fdp = dup_fd(fd, &error);
1622 if (!*new_fdp)
1623 return error;
1624 }
1625
1626 return 0;
1627}
1628
1629/*
1630 * unshare allows a process to 'unshare' part of the process
1631 * context which was originally shared using clone. copy_*
1632 * functions used by do_fork() cannot be used here directly
1633 * because they modify an inactive task_struct that is being
1634 * constructed. Here we are modifying the current, active,
1635 * task_struct.
1636 */
1637SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1638{
1639 int err = 0;
1640 struct fs_struct *fs, *new_fs = NULL;
1641 struct sighand_struct *new_sigh = NULL;
1642 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1643 struct files_struct *fd, *new_fd = NULL;
1644 struct nsproxy *new_nsproxy = NULL;
1645 int do_sysvsem = 0;
1646
1647 check_unshare_flags(&unshare_flags);
1648
1649 /* Return -EINVAL for all unsupported flags */
1650 err = -EINVAL;
1651 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1652 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1653 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1654 goto bad_unshare_out;
1655
1656 /*
1657 * CLONE_NEWIPC must also detach from the undolist: after switching
1658 * to a new ipc namespace, the semaphore arrays from the old
1659 * namespace are unreachable.
1660 */
1661 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1662 do_sysvsem = 1;
1663 if ((err = unshare_thread(unshare_flags)))
1664 goto bad_unshare_out;
1665 if ((err = unshare_fs(unshare_flags, &new_fs)))
1666 goto bad_unshare_cleanup_thread;
1667 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1668 goto bad_unshare_cleanup_fs;
1669 if ((err = unshare_vm(unshare_flags, &new_mm)))
1670 goto bad_unshare_cleanup_sigh;
1671 if ((err = unshare_fd(unshare_flags, &new_fd)))
1672 goto bad_unshare_cleanup_vm;
1673 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1674 new_fs)))
1675 goto bad_unshare_cleanup_fd;
1676
1677 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1678 if (do_sysvsem) {
1679 /*
1680 * CLONE_SYSVSEM is equivalent to sys_exit().
1681 */
1682 exit_sem(current);
1683 }
1684
1685 if (new_nsproxy) {
1686 switch_task_namespaces(current, new_nsproxy);
1687 new_nsproxy = NULL;
1688 }
1689
1690 task_lock(current);
1691
1692 if (new_fs) {
1693 fs = current->fs;
1694 spin_lock(&fs->lock);
1695 current->fs = new_fs;
1696 if (--fs->users)
1697 new_fs = NULL;
1698 else
1699 new_fs = fs;
1700 spin_unlock(&fs->lock);
1701 }
1702
1703 if (new_mm) {
1704 mm = current->mm;
1705 active_mm = current->active_mm;
1706 current->mm = new_mm;
1707 current->active_mm = new_mm;
1708 if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
1709 atomic_dec(&mm->oom_disable_count);
1710 atomic_inc(&new_mm->oom_disable_count);
1711 }
1712 activate_mm(active_mm, new_mm);
1713 new_mm = mm;
1714 }
1715
1716 if (new_fd) {
1717 fd = current->files;
1718 current->files = new_fd;
1719 new_fd = fd;
1720 }
1721
1722 task_unlock(current);
1723 }
1724
1725 if (new_nsproxy)
1726 put_nsproxy(new_nsproxy);
1727
1728bad_unshare_cleanup_fd:
1729 if (new_fd)
1730 put_files_struct(new_fd);
1731
1732bad_unshare_cleanup_vm:
1733 if (new_mm)
1734 mmput(new_mm);
1735
1736bad_unshare_cleanup_sigh:
1737 if (new_sigh)
1738 if (atomic_dec_and_test(&new_sigh->count))
1739 kmem_cache_free(sighand_cachep, new_sigh);
1740
1741bad_unshare_cleanup_fs:
1742 if (new_fs)
1743 free_fs_struct(new_fs);
1744
1745bad_unshare_cleanup_thread:
1746bad_unshare_out:
1747 return err;
1748}
1749
1750/*
1751 * Helper to unshare the files of the current task.
1752 * We don't want to expose copy_files internals to
1753 * the exec layer of the kernel.
1754 */
1755
1756int unshare_files(struct files_struct **displaced)
1757{
1758 struct task_struct *task = current;
1759 struct files_struct *copy = NULL;
1760 int error;
1761
1762 error = unshare_fd(CLONE_FILES, &copy);
1763 if (error || !copy) {
1764 *displaced = NULL;
1765 return error;
1766 }
1767 *displaced = task->files;
1768 task_lock(task);
1769 task->files = copy;
1770 task_unlock(task);
1771 return 0;
1772}