projects/linux·blob v2.6.38-rc4 · refs

1761 lines · 41.9 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#include <linux/khugepaged.h>
70
71#include <asm/pgtable.h>
72#include <asm/pgalloc.h>
73#include <asm/uaccess.h>
74#include <asm/mmu_context.h>
75#include <asm/cacheflush.h>
76#include <asm/tlbflush.h>
77
78#include <trace/events/sched.h>
79
80/*
81 * Protected counters by write_lock_irq(&tasklist_lock)
82 */
83unsigned long total_forks; /* Handle normal Linux uptimes. */
84int nr_threads; /* The idle threads do not count.. */
85
86int max_threads; /* tunable limit on nr_threads */
87
88DEFINE_PER_CPU(unsigned long, process_counts) = 0;
89
90__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
91
92#ifdef CONFIG_PROVE_RCU
93int lockdep_tasklist_lock_is_held(void)
94{
95 return lockdep_is_held(&tasklist_lock);
96}
97EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
98#endif /* #ifdef CONFIG_PROVE_RCU */
99
100int nr_processes(void)
101{
102 int cpu;
103 int total = 0;
104
105 for_each_possible_cpu(cpu)
106 total += per_cpu(process_counts, cpu);
107
108 return total;
109}
110
111#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
112# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
113# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
114static struct kmem_cache *task_struct_cachep;
115#endif
116
117#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
118static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
119{
120#ifdef CONFIG_DEBUG_STACK_USAGE
121 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
122#else
123 gfp_t mask = GFP_KERNEL;
124#endif
125 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
126}
127
128static inline void free_thread_info(struct thread_info *ti)
129{
130 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
131}
132#endif
133
134/* SLAB cache for signal_struct structures (tsk->signal) */
135static struct kmem_cache *signal_cachep;
136
137/* SLAB cache for sighand_struct structures (tsk->sighand) */
138struct kmem_cache *sighand_cachep;
139
140/* SLAB cache for files_struct structures (tsk->files) */
141struct kmem_cache *files_cachep;
142
143/* SLAB cache for fs_struct structures (tsk->fs) */
144struct kmem_cache *fs_cachep;
145
146/* SLAB cache for vm_area_struct structures */
147struct kmem_cache *vm_area_cachep;
148
149/* SLAB cache for mm_struct structures (tsk->mm) */
150static struct kmem_cache *mm_cachep;
151
152static void account_kernel_stack(struct thread_info *ti, int account)
153{
154 struct zone *zone = page_zone(virt_to_page(ti));
155
156 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
157}
158
159void free_task(struct task_struct *tsk)
160{
161 prop_local_destroy_single(&tsk->dirties);
162 account_kernel_stack(tsk->stack, -1);
163 free_thread_info(tsk->stack);
164 rt_mutex_debug_task_free(tsk);
165 ftrace_graph_exit_task(tsk);
166 free_task_struct(tsk);
167}
168EXPORT_SYMBOL(free_task);
169
170static inline void free_signal_struct(struct signal_struct *sig)
171{
172 taskstats_tgid_free(sig);
173 sched_autogroup_exit(sig);
174 kmem_cache_free(signal_cachep, sig);
175}
176
177static inline void put_signal_struct(struct signal_struct *sig)
178{
179 if (atomic_dec_and_test(&sig->sigcnt))
180 free_signal_struct(sig);
181}
182
183void __put_task_struct(struct task_struct *tsk)
184{
185 WARN_ON(!tsk->exit_state);
186 WARN_ON(atomic_read(&tsk->usage));
187 WARN_ON(tsk == current);
188
189 exit_creds(tsk);
190 delayacct_tsk_free(tsk);
191 put_signal_struct(tsk->signal);
192
193 if (!profile_handoff_task(tsk))
194 free_task(tsk);
195}
196
197/*
198 * macro override instead of weak attribute alias, to workaround
199 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
200 */
201#ifndef arch_task_cache_init
202#define arch_task_cache_init()
203#endif
204
205void __init fork_init(unsigned long mempages)
206{
207#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
208#ifndef ARCH_MIN_TASKALIGN
209#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
210#endif
211 /* create a slab on which task_structs can be allocated */
212 task_struct_cachep =
213 kmem_cache_create("task_struct", sizeof(struct task_struct),
214 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
215#endif
216
217 /* do the arch specific task caches init */
218 arch_task_cache_init();
219
220 /*
221 * The default maximum number of threads is set to a safe
222 * value: the thread structures can take up at most half
223 * of memory.
224 */
225 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
226
227 /*
228 * we need to allow at least 20 threads to boot a system
229 */
230 if(max_threads < 20)
231 max_threads = 20;
232
233 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
234 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
235 init_task.signal->rlim[RLIMIT_SIGPENDING] =
236 init_task.signal->rlim[RLIMIT_NPROC];
237}
238
239int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
240 struct task_struct *src)
241{
242 *dst = *src;
243 return 0;
244}
245
246static struct task_struct *dup_task_struct(struct task_struct *orig)
247{
248 struct task_struct *tsk;
249 struct thread_info *ti;
250 unsigned long *stackend;
251
252 int err;
253
254 prepare_to_copy(orig);
255
256 tsk = alloc_task_struct();
257 if (!tsk)
258 return NULL;
259
260 ti = alloc_thread_info(tsk);
261 if (!ti) {
262 free_task_struct(tsk);
263 return NULL;
264 }
265
266 err = arch_dup_task_struct(tsk, orig);
267 if (err)
268 goto out;
269
270 tsk->stack = ti;
271
272 err = prop_local_init_single(&tsk->dirties);
273 if (err)
274 goto out;
275
276 setup_thread_stack(tsk, orig);
277 clear_user_return_notifier(tsk);
278 clear_tsk_need_resched(tsk);
279 stackend = end_of_stack(tsk);
280 *stackend = STACK_END_MAGIC; /* for overflow detection */
281
282#ifdef CONFIG_CC_STACKPROTECTOR
283 tsk->stack_canary = get_random_int();
284#endif
285
286 /* One for us, one for whoever does the "release_task()" (usually parent) */
287 atomic_set(&tsk->usage,2);
288 atomic_set(&tsk->fs_excl, 0);
289#ifdef CONFIG_BLK_DEV_IO_TRACE
290 tsk->btrace_seq = 0;
291#endif
292 tsk->splice_pipe = NULL;
293
294 account_kernel_stack(ti, 1);
295
296 return tsk;
297
298out:
299 free_thread_info(ti);
300 free_task_struct(tsk);
301 return NULL;
302}
303
304#ifdef CONFIG_MMU
305static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
306{
307 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
308 struct rb_node **rb_link, *rb_parent;
309 int retval;
310 unsigned long charge;
311 struct mempolicy *pol;
312
313 down_write(&oldmm->mmap_sem);
314 flush_cache_dup_mm(oldmm);
315 /*
316 * Not linked in yet - no deadlock potential:
317 */
318 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
319
320 mm->locked_vm = 0;
321 mm->mmap = NULL;
322 mm->mmap_cache = NULL;
323 mm->free_area_cache = oldmm->mmap_base;
324 mm->cached_hole_size = ~0UL;
325 mm->map_count = 0;
326 cpumask_clear(mm_cpumask(mm));
327 mm->mm_rb = RB_ROOT;
328 rb_link = &mm->mm_rb.rb_node;
329 rb_parent = NULL;
330 pprev = &mm->mmap;
331 retval = ksm_fork(mm, oldmm);
332 if (retval)
333 goto out;
334 retval = khugepaged_fork(mm, oldmm);
335 if (retval)
336 goto out;
337
338 prev = NULL;
339 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
340 struct file *file;
341
342 if (mpnt->vm_flags & VM_DONTCOPY) {
343 long pages = vma_pages(mpnt);
344 mm->total_vm -= pages;
345 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
346 -pages);
347 continue;
348 }
349 charge = 0;
350 if (mpnt->vm_flags & VM_ACCOUNT) {
351 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
352 if (security_vm_enough_memory(len))
353 goto fail_nomem;
354 charge = len;
355 }
356 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
357 if (!tmp)
358 goto fail_nomem;
359 *tmp = *mpnt;
360 INIT_LIST_HEAD(&tmp->anon_vma_chain);
361 pol = mpol_dup(vma_policy(mpnt));
362 retval = PTR_ERR(pol);
363 if (IS_ERR(pol))
364 goto fail_nomem_policy;
365 vma_set_policy(tmp, pol);
366 tmp->vm_mm = mm;
367 if (anon_vma_fork(tmp, mpnt))
368 goto fail_nomem_anon_vma_fork;
369 tmp->vm_flags &= ~VM_LOCKED;
370 tmp->vm_next = tmp->vm_prev = NULL;
371 file = tmp->vm_file;
372 if (file) {
373 struct inode *inode = file->f_path.dentry->d_inode;
374 struct address_space *mapping = file->f_mapping;
375
376 get_file(file);
377 if (tmp->vm_flags & VM_DENYWRITE)
378 atomic_dec(&inode->i_writecount);
379 spin_lock(&mapping->i_mmap_lock);
380 if (tmp->vm_flags & VM_SHARED)
381 mapping->i_mmap_writable++;
382 tmp->vm_truncate_count = mpnt->vm_truncate_count;
383 flush_dcache_mmap_lock(mapping);
384 /* insert tmp into the share list, just after mpnt */
385 vma_prio_tree_add(tmp, mpnt);
386 flush_dcache_mmap_unlock(mapping);
387 spin_unlock(&mapping->i_mmap_lock);
388 }
389
390 /*
391 * Clear hugetlb-related page reserves for children. This only
392 * affects MAP_PRIVATE mappings. Faults generated by the child
393 * are not guaranteed to succeed, even if read-only
394 */
395 if (is_vm_hugetlb_page(tmp))
396 reset_vma_resv_huge_pages(tmp);
397
398 /*
399 * Link in the new vma and copy the page table entries.
400 */
401 *pprev = tmp;
402 pprev = &tmp->vm_next;
403 tmp->vm_prev = prev;
404 prev = tmp;
405
406 __vma_link_rb(mm, tmp, rb_link, rb_parent);
407 rb_link = &tmp->vm_rb.rb_right;
408 rb_parent = &tmp->vm_rb;
409
410 mm->map_count++;
411 retval = copy_page_range(mm, oldmm, mpnt);
412
413 if (tmp->vm_ops && tmp->vm_ops->open)
414 tmp->vm_ops->open(tmp);
415
416 if (retval)
417 goto out;
418 }
419 /* a new mm has just been created */
420 arch_dup_mmap(oldmm, mm);
421 retval = 0;
422out:
423 up_write(&mm->mmap_sem);
424 flush_tlb_mm(oldmm);
425 up_write(&oldmm->mmap_sem);
426 return retval;
427fail_nomem_anon_vma_fork:
428 mpol_put(pol);
429fail_nomem_policy:
430 kmem_cache_free(vm_area_cachep, tmp);
431fail_nomem:
432 retval = -ENOMEM;
433 vm_unacct_memory(charge);
434 goto out;
435}
436
437static inline int mm_alloc_pgd(struct mm_struct * mm)
438{
439 mm->pgd = pgd_alloc(mm);
440 if (unlikely(!mm->pgd))
441 return -ENOMEM;
442 return 0;
443}
444
445static inline void mm_free_pgd(struct mm_struct * mm)
446{
447 pgd_free(mm, mm->pgd);
448}
449#else
450#define dup_mmap(mm, oldmm) (0)
451#define mm_alloc_pgd(mm) (0)
452#define mm_free_pgd(mm)
453#endif /* CONFIG_MMU */
454
455__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
456
457#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
458#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
459
460static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
461
462static int __init coredump_filter_setup(char *s)
463{
464 default_dump_filter =
465 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
466 MMF_DUMP_FILTER_MASK;
467 return 1;
468}
469
470__setup("coredump_filter=", coredump_filter_setup);
471
472#include <linux/init_task.h>
473
474static void mm_init_aio(struct mm_struct *mm)
475{
476#ifdef CONFIG_AIO
477 spin_lock_init(&mm->ioctx_lock);
478 INIT_HLIST_HEAD(&mm->ioctx_list);
479#endif
480}
481
482static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
483{
484 atomic_set(&mm->mm_users, 1);
485 atomic_set(&mm->mm_count, 1);
486 init_rwsem(&mm->mmap_sem);
487 INIT_LIST_HEAD(&mm->mmlist);
488 mm->flags = (current->mm) ?
489 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
490 mm->core_state = NULL;
491 mm->nr_ptes = 0;
492 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
493 spin_lock_init(&mm->page_table_lock);
494 mm->free_area_cache = TASK_UNMAPPED_BASE;
495 mm->cached_hole_size = ~0UL;
496 mm_init_aio(mm);
497 mm_init_owner(mm, p);
498 atomic_set(&mm->oom_disable_count, 0);
499
500 if (likely(!mm_alloc_pgd(mm))) {
501 mm->def_flags = 0;
502 mmu_notifier_mm_init(mm);
503 return mm;
504 }
505
506 free_mm(mm);
507 return NULL;
508}
509
510/*
511 * Allocate and initialize an mm_struct.
512 */
513struct mm_struct * mm_alloc(void)
514{
515 struct mm_struct * mm;
516
517 mm = allocate_mm();
518 if (mm) {
519 memset(mm, 0, sizeof(*mm));
520 mm = mm_init(mm, current);
521 }
522 return mm;
523}
524
525/*
526 * Called when the last reference to the mm
527 * is dropped: either by a lazy thread or by
528 * mmput. Free the page directory and the mm.
529 */
530void __mmdrop(struct mm_struct *mm)
531{
532 BUG_ON(mm == &init_mm);
533 mm_free_pgd(mm);
534 destroy_context(mm);
535 mmu_notifier_mm_destroy(mm);
536#ifdef CONFIG_TRANSPARENT_HUGEPAGE
537 VM_BUG_ON(mm->pmd_huge_pte);
538#endif
539 free_mm(mm);
540}
541EXPORT_SYMBOL_GPL(__mmdrop);
542
543/*
544 * Decrement the use count and release all resources for an mm.
545 */
546void mmput(struct mm_struct *mm)
547{
548 might_sleep();
549
550 if (atomic_dec_and_test(&mm->mm_users)) {
551 exit_aio(mm);
552 ksm_exit(mm);
553 khugepaged_exit(mm); /* must run before exit_mmap */
554 exit_mmap(mm);
555 set_mm_exe_file(mm, NULL);
556 if (!list_empty(&mm->mmlist)) {
557 spin_lock(&mmlist_lock);
558 list_del(&mm->mmlist);
559 spin_unlock(&mmlist_lock);
560 }
561 put_swap_token(mm);
562 if (mm->binfmt)
563 module_put(mm->binfmt->module);
564 mmdrop(mm);
565 }
566}
567EXPORT_SYMBOL_GPL(mmput);
568
569/**
570 * get_task_mm - acquire a reference to the task's mm
571 *
572 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
573 * this kernel workthread has transiently adopted a user mm with use_mm,
574 * to do its AIO) is not set and if so returns a reference to it, after
575 * bumping up the use count. User must release the mm via mmput()
576 * after use. Typically used by /proc and ptrace.
577 */
578struct mm_struct *get_task_mm(struct task_struct *task)
579{
580 struct mm_struct *mm;
581
582 task_lock(task);
583 mm = task->mm;
584 if (mm) {
585 if (task->flags & PF_KTHREAD)
586 mm = NULL;
587 else
588 atomic_inc(&mm->mm_users);
589 }
590 task_unlock(task);
591 return mm;
592}
593EXPORT_SYMBOL_GPL(get_task_mm);
594
595/* Please note the differences between mmput and mm_release.
596 * mmput is called whenever we stop holding onto a mm_struct,
597 * error success whatever.
598 *
599 * mm_release is called after a mm_struct has been removed
600 * from the current process.
601 *
602 * This difference is important for error handling, when we
603 * only half set up a mm_struct for a new process and need to restore
604 * the old one. Because we mmput the new mm_struct before
605 * restoring the old one. . .
606 * Eric Biederman 10 January 1998
607 */
608void mm_release(struct task_struct *tsk, struct mm_struct *mm)
609{
610 struct completion *vfork_done = tsk->vfork_done;
611
612 /* Get rid of any futexes when releasing the mm */
613#ifdef CONFIG_FUTEX
614 if (unlikely(tsk->robust_list)) {
615 exit_robust_list(tsk);
616 tsk->robust_list = NULL;
617 }
618#ifdef CONFIG_COMPAT
619 if (unlikely(tsk->compat_robust_list)) {
620 compat_exit_robust_list(tsk);
621 tsk->compat_robust_list = NULL;
622 }
623#endif
624 if (unlikely(!list_empty(&tsk->pi_state_list)))
625 exit_pi_state_list(tsk);
626#endif
627
628 /* Get rid of any cached register state */
629 deactivate_mm(tsk, mm);
630
631 /* notify parent sleeping on vfork() */
632 if (vfork_done) {
633 tsk->vfork_done = NULL;
634 complete(vfork_done);
635 }
636
637 /*
638 * If we're exiting normally, clear a user-space tid field if
639 * requested. We leave this alone when dying by signal, to leave
640 * the value intact in a core dump, and to save the unnecessary
641 * trouble otherwise. Userland only wants this done for a sys_exit.
642 */
643 if (tsk->clear_child_tid) {
644 if (!(tsk->flags & PF_SIGNALED) &&
645 atomic_read(&mm->mm_users) > 1) {
646 /*
647 * We don't check the error code - if userspace has
648 * not set up a proper pointer then tough luck.
649 */
650 put_user(0, tsk->clear_child_tid);
651 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
652 1, NULL, NULL, 0);
653 }
654 tsk->clear_child_tid = NULL;
655 }
656}
657
658/*
659 * Allocate a new mm structure and copy contents from the
660 * mm structure of the passed in task structure.
661 */
662struct mm_struct *dup_mm(struct task_struct *tsk)
663{
664 struct mm_struct *mm, *oldmm = current->mm;
665 int err;
666
667 if (!oldmm)
668 return NULL;
669
670 mm = allocate_mm();
671 if (!mm)
672 goto fail_nomem;
673
674 memcpy(mm, oldmm, sizeof(*mm));
675
676 /* Initializing for Swap token stuff */
677 mm->token_priority = 0;
678 mm->last_interval = 0;
679
680#ifdef CONFIG_TRANSPARENT_HUGEPAGE
681 mm->pmd_huge_pte = NULL;
682#endif
683
684 if (!mm_init(mm, tsk))
685 goto fail_nomem;
686
687 if (init_new_context(tsk, mm))
688 goto fail_nocontext;
689
690 dup_mm_exe_file(oldmm, mm);
691
692 err = dup_mmap(mm, oldmm);
693 if (err)
694 goto free_pt;
695
696 mm->hiwater_rss = get_mm_rss(mm);
697 mm->hiwater_vm = mm->total_vm;
698
699 if (mm->binfmt && !try_module_get(mm->binfmt->module))
700 goto free_pt;
701
702 return mm;
703
704free_pt:
705 /* don't put binfmt in mmput, we haven't got module yet */
706 mm->binfmt = NULL;
707 mmput(mm);
708
709fail_nomem:
710 return NULL;
711
712fail_nocontext:
713 /*
714 * If init_new_context() failed, we cannot use mmput() to free the mm
715 * because it calls destroy_context()
716 */
717 mm_free_pgd(mm);
718 free_mm(mm);
719 return NULL;
720}
721
722static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
723{
724 struct mm_struct * mm, *oldmm;
725 int retval;
726
727 tsk->min_flt = tsk->maj_flt = 0;
728 tsk->nvcsw = tsk->nivcsw = 0;
729#ifdef CONFIG_DETECT_HUNG_TASK
730 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
731#endif
732
733 tsk->mm = NULL;
734 tsk->active_mm = NULL;
735
736 /*
737 * Are we cloning a kernel thread?
738 *
739 * We need to steal a active VM for that..
740 */
741 oldmm = current->mm;
742 if (!oldmm)
743 return 0;
744
745 if (clone_flags & CLONE_VM) {
746 atomic_inc(&oldmm->mm_users);
747 mm = oldmm;
748 goto good_mm;
749 }
750
751 retval = -ENOMEM;
752 mm = dup_mm(tsk);
753 if (!mm)
754 goto fail_nomem;
755
756good_mm:
757 /* Initializing for Swap token stuff */
758 mm->token_priority = 0;
759 mm->last_interval = 0;
760 if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
761 atomic_inc(&mm->oom_disable_count);
762
763 tsk->mm = mm;
764 tsk->active_mm = mm;
765 return 0;
766
767fail_nomem:
768 return retval;
769}
770
771static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
772{
773 struct fs_struct *fs = current->fs;
774 if (clone_flags & CLONE_FS) {
775 /* tsk->fs is already what we want */
776 spin_lock(&fs->lock);
777 if (fs->in_exec) {
778 spin_unlock(&fs->lock);
779 return -EAGAIN;
780 }
781 fs->users++;
782 spin_unlock(&fs->lock);
783 return 0;
784 }
785 tsk->fs = copy_fs_struct(fs);
786 if (!tsk->fs)
787 return -ENOMEM;
788 return 0;
789}
790
791static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
792{
793 struct files_struct *oldf, *newf;
794 int error = 0;
795
796 /*
797 * A background process may not have any files ...
798 */
799 oldf = current->files;
800 if (!oldf)
801 goto out;
802
803 if (clone_flags & CLONE_FILES) {
804 atomic_inc(&oldf->count);
805 goto out;
806 }
807
808 newf = dup_fd(oldf, &error);
809 if (!newf)
810 goto out;
811
812 tsk->files = newf;
813 error = 0;
814out:
815 return error;
816}
817
818static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
819{
820#ifdef CONFIG_BLOCK
821 struct io_context *ioc = current->io_context;
822
823 if (!ioc)
824 return 0;
825 /*
826 * Share io context with parent, if CLONE_IO is set
827 */
828 if (clone_flags & CLONE_IO) {
829 tsk->io_context = ioc_task_link(ioc);
830 if (unlikely(!tsk->io_context))
831 return -ENOMEM;
832 } else if (ioprio_valid(ioc->ioprio)) {
833 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
834 if (unlikely(!tsk->io_context))
835 return -ENOMEM;
836
837 tsk->io_context->ioprio = ioc->ioprio;
838 }
839#endif
840 return 0;
841}
842
843static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
844{
845 struct sighand_struct *sig;
846
847 if (clone_flags & CLONE_SIGHAND) {
848 atomic_inc(&current->sighand->count);
849 return 0;
850 }
851 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
852 rcu_assign_pointer(tsk->sighand, sig);
853 if (!sig)
854 return -ENOMEM;
855 atomic_set(&sig->count, 1);
856 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
857 return 0;
858}
859
860void __cleanup_sighand(struct sighand_struct *sighand)
861{
862 if (atomic_dec_and_test(&sighand->count))
863 kmem_cache_free(sighand_cachep, sighand);
864}
865
866
867/*
868 * Initialize POSIX timer handling for a thread group.
869 */
870static void posix_cpu_timers_init_group(struct signal_struct *sig)
871{
872 unsigned long cpu_limit;
873
874 /* Thread group counters. */
875 thread_group_cputime_init(sig);
876
877 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
878 if (cpu_limit != RLIM_INFINITY) {
879 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
880 sig->cputimer.running = 1;
881 }
882
883 /* The timer lists. */
884 INIT_LIST_HEAD(&sig->cpu_timers[0]);
885 INIT_LIST_HEAD(&sig->cpu_timers[1]);
886 INIT_LIST_HEAD(&sig->cpu_timers[2]);
887}
888
889static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
890{
891 struct signal_struct *sig;
892
893 if (clone_flags & CLONE_THREAD)
894 return 0;
895
896 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
897 tsk->signal = sig;
898 if (!sig)
899 return -ENOMEM;
900
901 sig->nr_threads = 1;
902 atomic_set(&sig->live, 1);
903 atomic_set(&sig->sigcnt, 1);
904 init_waitqueue_head(&sig->wait_chldexit);
905 if (clone_flags & CLONE_NEWPID)
906 sig->flags |= SIGNAL_UNKILLABLE;
907 sig->curr_target = tsk;
908 init_sigpending(&sig->shared_pending);
909 INIT_LIST_HEAD(&sig->posix_timers);
910
911 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
912 sig->real_timer.function = it_real_fn;
913
914 task_lock(current->group_leader);
915 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
916 task_unlock(current->group_leader);
917
918 posix_cpu_timers_init_group(sig);
919
920 tty_audit_fork(sig);
921 sched_autogroup_fork(sig);
922
923 sig->oom_adj = current->signal->oom_adj;
924 sig->oom_score_adj = current->signal->oom_score_adj;
925 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
926
927 mutex_init(&sig->cred_guard_mutex);
928
929 return 0;
930}
931
932static void copy_flags(unsigned long clone_flags, struct task_struct *p)
933{
934 unsigned long new_flags = p->flags;
935
936 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
937 new_flags |= PF_FORKNOEXEC;
938 new_flags |= PF_STARTING;
939 p->flags = new_flags;
940 clear_freeze_flag(p);
941}
942
943SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
944{
945 current->clear_child_tid = tidptr;
946
947 return task_pid_vnr(current);
948}
949
950static void rt_mutex_init_task(struct task_struct *p)
951{
952 raw_spin_lock_init(&p->pi_lock);
953#ifdef CONFIG_RT_MUTEXES
954 plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
955 p->pi_blocked_on = NULL;
956#endif
957}
958
959#ifdef CONFIG_MM_OWNER
960void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
961{
962 mm->owner = p;
963}
964#endif /* CONFIG_MM_OWNER */
965
966/*
967 * Initialize POSIX timer handling for a single task.
968 */
969static void posix_cpu_timers_init(struct task_struct *tsk)
970{
971 tsk->cputime_expires.prof_exp = cputime_zero;
972 tsk->cputime_expires.virt_exp = cputime_zero;
973 tsk->cputime_expires.sched_exp = 0;
974 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
975 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
976 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
977}
978
979/*
980 * This creates a new process as a copy of the old one,
981 * but does not actually start it yet.
982 *
983 * It copies the registers, and all the appropriate
984 * parts of the process environment (as per the clone
985 * flags). The actual kick-off is left to the caller.
986 */
987static struct task_struct *copy_process(unsigned long clone_flags,
988 unsigned long stack_start,
989 struct pt_regs *regs,
990 unsigned long stack_size,
991 int __user *child_tidptr,
992 struct pid *pid,
993 int trace)
994{
995 int retval;
996 struct task_struct *p;
997 int cgroup_callbacks_done = 0;
998
999 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1000 return ERR_PTR(-EINVAL);
1001
1002 /*
1003 * Thread groups must share signals as well, and detached threads
1004 * can only be started up within the thread group.
1005 */
1006 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1007 return ERR_PTR(-EINVAL);
1008
1009 /*
1010 * Shared signal handlers imply shared VM. By way of the above,
1011 * thread groups also imply shared VM. Blocking this case allows
1012 * for various simplifications in other code.
1013 */
1014 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1015 return ERR_PTR(-EINVAL);
1016
1017 /*
1018 * Siblings of global init remain as zombies on exit since they are
1019 * not reaped by their parent (swapper). To solve this and to avoid
1020 * multi-rooted process trees, prevent global and container-inits
1021 * from creating siblings.
1022 */
1023 if ((clone_flags & CLONE_PARENT) &&
1024 current->signal->flags & SIGNAL_UNKILLABLE)
1025 return ERR_PTR(-EINVAL);
1026
1027 retval = security_task_create(clone_flags);
1028 if (retval)
1029 goto fork_out;
1030
1031 retval = -ENOMEM;
1032 p = dup_task_struct(current);
1033 if (!p)
1034 goto fork_out;
1035
1036 ftrace_graph_init_task(p);
1037
1038 rt_mutex_init_task(p);
1039
1040#ifdef CONFIG_PROVE_LOCKING
1041 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1042 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1043#endif
1044 retval = -EAGAIN;
1045 if (atomic_read(&p->real_cred->user->processes) >=
1046 task_rlimit(p, RLIMIT_NPROC)) {
1047 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1048 p->real_cred->user != INIT_USER)
1049 goto bad_fork_free;
1050 }
1051
1052 retval = copy_creds(p, clone_flags);
1053 if (retval < 0)
1054 goto bad_fork_free;
1055
1056 /*
1057 * If multiple threads are within copy_process(), then this check
1058 * triggers too late. This doesn't hurt, the check is only there
1059 * to stop root fork bombs.
1060 */
1061 retval = -EAGAIN;
1062 if (nr_threads >= max_threads)
1063 goto bad_fork_cleanup_count;
1064
1065 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1066 goto bad_fork_cleanup_count;
1067
1068 p->did_exec = 0;
1069 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1070 copy_flags(clone_flags, p);
1071 INIT_LIST_HEAD(&p->children);
1072 INIT_LIST_HEAD(&p->sibling);
1073 rcu_copy_process(p);
1074 p->vfork_done = NULL;
1075 spin_lock_init(&p->alloc_lock);
1076
1077 init_sigpending(&p->pending);
1078
1079 p->utime = cputime_zero;
1080 p->stime = cputime_zero;
1081 p->gtime = cputime_zero;
1082 p->utimescaled = cputime_zero;
1083 p->stimescaled = cputime_zero;
1084#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1085 p->prev_utime = cputime_zero;
1086 p->prev_stime = cputime_zero;
1087#endif
1088#if defined(SPLIT_RSS_COUNTING)
1089 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1090#endif
1091
1092 p->default_timer_slack_ns = current->timer_slack_ns;
1093
1094 task_io_accounting_init(&p->ioac);
1095 acct_clear_integrals(p);
1096
1097 posix_cpu_timers_init(p);
1098
1099 p->lock_depth = -1; /* -1 = no lock */
1100 do_posix_clock_monotonic_gettime(&p->start_time);
1101 p->real_start_time = p->start_time;
1102 monotonic_to_bootbased(&p->real_start_time);
1103 p->io_context = NULL;
1104 p->audit_context = NULL;
1105 cgroup_fork(p);
1106#ifdef CONFIG_NUMA
1107 p->mempolicy = mpol_dup(p->mempolicy);
1108 if (IS_ERR(p->mempolicy)) {
1109 retval = PTR_ERR(p->mempolicy);
1110 p->mempolicy = NULL;
1111 goto bad_fork_cleanup_cgroup;
1112 }
1113 mpol_fix_fork_child_flag(p);
1114#endif
1115#ifdef CONFIG_TRACE_IRQFLAGS
1116 p->irq_events = 0;
1117#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1118 p->hardirqs_enabled = 1;
1119#else
1120 p->hardirqs_enabled = 0;
1121#endif
1122 p->hardirq_enable_ip = 0;
1123 p->hardirq_enable_event = 0;
1124 p->hardirq_disable_ip = _THIS_IP_;
1125 p->hardirq_disable_event = 0;
1126 p->softirqs_enabled = 1;
1127 p->softirq_enable_ip = _THIS_IP_;
1128 p->softirq_enable_event = 0;
1129 p->softirq_disable_ip = 0;
1130 p->softirq_disable_event = 0;
1131 p->hardirq_context = 0;
1132 p->softirq_context = 0;
1133#endif
1134#ifdef CONFIG_LOCKDEP
1135 p->lockdep_depth = 0; /* no locks held yet */
1136 p->curr_chain_key = 0;
1137 p->lockdep_recursion = 0;
1138#endif
1139
1140#ifdef CONFIG_DEBUG_MUTEXES
1141 p->blocked_on = NULL; /* not blocked yet */
1142#endif
1143#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1144 p->memcg_batch.do_batch = 0;
1145 p->memcg_batch.memcg = NULL;
1146#endif
1147
1148 /* Perform scheduler related setup. Assign this task to a CPU. */
1149 sched_fork(p, clone_flags);
1150
1151 retval = perf_event_init_task(p);
1152 if (retval)
1153 goto bad_fork_cleanup_policy;
1154
1155 if ((retval = audit_alloc(p)))
1156 goto bad_fork_cleanup_policy;
1157 /* copy all the process information */
1158 if ((retval = copy_semundo(clone_flags, p)))
1159 goto bad_fork_cleanup_audit;
1160 if ((retval = copy_files(clone_flags, p)))
1161 goto bad_fork_cleanup_semundo;
1162 if ((retval = copy_fs(clone_flags, p)))
1163 goto bad_fork_cleanup_files;
1164 if ((retval = copy_sighand(clone_flags, p)))
1165 goto bad_fork_cleanup_fs;
1166 if ((retval = copy_signal(clone_flags, p)))
1167 goto bad_fork_cleanup_sighand;
1168 if ((retval = copy_mm(clone_flags, p)))
1169 goto bad_fork_cleanup_signal;
1170 if ((retval = copy_namespaces(clone_flags, p)))
1171 goto bad_fork_cleanup_mm;
1172 if ((retval = copy_io(clone_flags, p)))
1173 goto bad_fork_cleanup_namespaces;
1174 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1175 if (retval)
1176 goto bad_fork_cleanup_io;
1177
1178 if (pid != &init_struct_pid) {
1179 retval = -ENOMEM;
1180 pid = alloc_pid(p->nsproxy->pid_ns);
1181 if (!pid)
1182 goto bad_fork_cleanup_io;
1183
1184 if (clone_flags & CLONE_NEWPID) {
1185 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1186 if (retval < 0)
1187 goto bad_fork_free_pid;
1188 }
1189 }
1190
1191 p->pid = pid_nr(pid);
1192 p->tgid = p->pid;
1193 if (clone_flags & CLONE_THREAD)
1194 p->tgid = current->tgid;
1195
1196 if (current->nsproxy != p->nsproxy) {
1197 retval = ns_cgroup_clone(p, pid);
1198 if (retval)
1199 goto bad_fork_free_pid;
1200 }
1201
1202 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1203 /*
1204 * Clear TID on mm_release()?
1205 */
1206 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1207#ifdef CONFIG_FUTEX
1208 p->robust_list = NULL;
1209#ifdef CONFIG_COMPAT
1210 p->compat_robust_list = NULL;
1211#endif
1212 INIT_LIST_HEAD(&p->pi_state_list);
1213 p->pi_state_cache = NULL;
1214#endif
1215 /*
1216 * sigaltstack should be cleared when sharing the same VM
1217 */
1218 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1219 p->sas_ss_sp = p->sas_ss_size = 0;
1220
1221 /*
1222 * Syscall tracing and stepping should be turned off in the
1223 * child regardless of CLONE_PTRACE.
1224 */
1225 user_disable_single_step(p);
1226 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1227#ifdef TIF_SYSCALL_EMU
1228 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1229#endif
1230 clear_all_latency_tracing(p);
1231
1232 /* ok, now we should be set up.. */
1233 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1234 p->pdeath_signal = 0;
1235 p->exit_state = 0;
1236
1237 /*
1238 * Ok, make it visible to the rest of the system.
1239 * We dont wake it up yet.
1240 */
1241 p->group_leader = p;
1242 INIT_LIST_HEAD(&p->thread_group);
1243
1244 /* Now that the task is set up, run cgroup callbacks if
1245 * necessary. We need to run them before the task is visible
1246 * on the tasklist. */
1247 cgroup_fork_callbacks(p);
1248 cgroup_callbacks_done = 1;
1249
1250 /* Need tasklist lock for parent etc handling! */
1251 write_lock_irq(&tasklist_lock);
1252
1253 /* CLONE_PARENT re-uses the old parent */
1254 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1255 p->real_parent = current->real_parent;
1256 p->parent_exec_id = current->parent_exec_id;
1257 } else {
1258 p->real_parent = current;
1259 p->parent_exec_id = current->self_exec_id;
1260 }
1261
1262 spin_lock(&current->sighand->siglock);
1263
1264 /*
1265 * Process group and session signals need to be delivered to just the
1266 * parent before the fork or both the parent and the child after the
1267 * fork. Restart if a signal comes in before we add the new process to
1268 * it's process group.
1269 * A fatal signal pending means that current will exit, so the new
1270 * thread can't slip out of an OOM kill (or normal SIGKILL).
1271 */
1272 recalc_sigpending();
1273 if (signal_pending(current)) {
1274 spin_unlock(&current->sighand->siglock);
1275 write_unlock_irq(&tasklist_lock);
1276 retval = -ERESTARTNOINTR;
1277 goto bad_fork_free_pid;
1278 }
1279
1280 if (clone_flags & CLONE_THREAD) {
1281 current->signal->nr_threads++;
1282 atomic_inc(&current->signal->live);
1283 atomic_inc(&current->signal->sigcnt);
1284 p->group_leader = current->group_leader;
1285 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1286 }
1287
1288 if (likely(p->pid)) {
1289 tracehook_finish_clone(p, clone_flags, trace);
1290
1291 if (thread_group_leader(p)) {
1292 if (clone_flags & CLONE_NEWPID)
1293 p->nsproxy->pid_ns->child_reaper = p;
1294
1295 p->signal->leader_pid = pid;
1296 p->signal->tty = tty_kref_get(current->signal->tty);
1297 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1298 attach_pid(p, PIDTYPE_SID, task_session(current));
1299 list_add_tail(&p->sibling, &p->real_parent->children);
1300 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1301 __this_cpu_inc(process_counts);
1302 }
1303 attach_pid(p, PIDTYPE_PID, pid);
1304 nr_threads++;
1305 }
1306
1307 total_forks++;
1308 spin_unlock(&current->sighand->siglock);
1309 write_unlock_irq(&tasklist_lock);
1310 proc_fork_connector(p);
1311 cgroup_post_fork(p);
1312 perf_event_fork(p);
1313 return p;
1314
1315bad_fork_free_pid:
1316 if (pid != &init_struct_pid)
1317 free_pid(pid);
1318bad_fork_cleanup_io:
1319 if (p->io_context)
1320 exit_io_context(p);
1321bad_fork_cleanup_namespaces:
1322 exit_task_namespaces(p);
1323bad_fork_cleanup_mm:
1324 if (p->mm) {
1325 task_lock(p);
1326 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1327 atomic_dec(&p->mm->oom_disable_count);
1328 task_unlock(p);
1329 mmput(p->mm);
1330 }
1331bad_fork_cleanup_signal:
1332 if (!(clone_flags & CLONE_THREAD))
1333 free_signal_struct(p->signal);
1334bad_fork_cleanup_sighand:
1335 __cleanup_sighand(p->sighand);
1336bad_fork_cleanup_fs:
1337 exit_fs(p); /* blocking */
1338bad_fork_cleanup_files:
1339 exit_files(p); /* blocking */
1340bad_fork_cleanup_semundo:
1341 exit_sem(p);
1342bad_fork_cleanup_audit:
1343 audit_free(p);
1344bad_fork_cleanup_policy:
1345 perf_event_free_task(p);
1346#ifdef CONFIG_NUMA
1347 mpol_put(p->mempolicy);
1348bad_fork_cleanup_cgroup:
1349#endif
1350 cgroup_exit(p, cgroup_callbacks_done);
1351 delayacct_tsk_free(p);
1352 module_put(task_thread_info(p)->exec_domain->module);
1353bad_fork_cleanup_count:
1354 atomic_dec(&p->cred->user->processes);
1355 exit_creds(p);
1356bad_fork_free:
1357 free_task(p);
1358fork_out:
1359 return ERR_PTR(retval);
1360}
1361
1362noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1363{
1364 memset(regs, 0, sizeof(struct pt_regs));
1365 return regs;
1366}
1367
1368static inline void init_idle_pids(struct pid_link *links)
1369{
1370 enum pid_type type;
1371
1372 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1373 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1374 links[type].pid = &init_struct_pid;
1375 }
1376}
1377
1378struct task_struct * __cpuinit fork_idle(int cpu)
1379{
1380 struct task_struct *task;
1381 struct pt_regs regs;
1382
1383 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1384 &init_struct_pid, 0);
1385 if (!IS_ERR(task)) {
1386 init_idle_pids(task->pids);
1387 init_idle(task, cpu);
1388 }
1389
1390 return task;
1391}
1392
1393/*
1394 * Ok, this is the main fork-routine.
1395 *
1396 * It copies the process, and if successful kick-starts
1397 * it and waits for it to finish using the VM if required.
1398 */
1399long do_fork(unsigned long clone_flags,
1400 unsigned long stack_start,
1401 struct pt_regs *regs,
1402 unsigned long stack_size,
1403 int __user *parent_tidptr,
1404 int __user *child_tidptr)
1405{
1406 struct task_struct *p;
1407 int trace = 0;
1408 long nr;
1409
1410 /*
1411 * Do some preliminary argument and permissions checking before we
1412 * actually start allocating stuff
1413 */
1414 if (clone_flags & CLONE_NEWUSER) {
1415 if (clone_flags & CLONE_THREAD)
1416 return -EINVAL;
1417 /* hopefully this check will go away when userns support is
1418 * complete
1419 */
1420 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1421 !capable(CAP_SETGID))
1422 return -EPERM;
1423 }
1424
1425 /*
1426 * When called from kernel_thread, don't do user tracing stuff.
1427 */
1428 if (likely(user_mode(regs)))
1429 trace = tracehook_prepare_clone(clone_flags);
1430
1431 p = copy_process(clone_flags, stack_start, regs, stack_size,
1432 child_tidptr, NULL, trace);
1433 /*
1434 * Do this prior waking up the new thread - the thread pointer
1435 * might get invalid after that point, if the thread exits quickly.
1436 */
1437 if (!IS_ERR(p)) {
1438 struct completion vfork;
1439
1440 trace_sched_process_fork(current, p);
1441
1442 nr = task_pid_vnr(p);
1443
1444 if (clone_flags & CLONE_PARENT_SETTID)
1445 put_user(nr, parent_tidptr);
1446
1447 if (clone_flags & CLONE_VFORK) {
1448 p->vfork_done = &vfork;
1449 init_completion(&vfork);
1450 }
1451
1452 audit_finish_fork(p);
1453 tracehook_report_clone(regs, clone_flags, nr, p);
1454
1455 /*
1456 * We set PF_STARTING at creation in case tracing wants to
1457 * use this to distinguish a fully live task from one that
1458 * hasn't gotten to tracehook_report_clone() yet. Now we
1459 * clear it and set the child going.
1460 */
1461 p->flags &= ~PF_STARTING;
1462
1463 wake_up_new_task(p, clone_flags);
1464
1465 tracehook_report_clone_complete(trace, regs,
1466 clone_flags, nr, p);
1467
1468 if (clone_flags & CLONE_VFORK) {
1469 freezer_do_not_count();
1470 wait_for_completion(&vfork);
1471 freezer_count();
1472 tracehook_report_vfork_done(p, nr);
1473 }
1474 } else {
1475 nr = PTR_ERR(p);
1476 }
1477 return nr;
1478}
1479
1480#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1481#define ARCH_MIN_MMSTRUCT_ALIGN 0
1482#endif
1483
1484static void sighand_ctor(void *data)
1485{
1486 struct sighand_struct *sighand = data;
1487
1488 spin_lock_init(&sighand->siglock);
1489 init_waitqueue_head(&sighand->signalfd_wqh);
1490}
1491
1492void __init proc_caches_init(void)
1493{
1494 sighand_cachep = kmem_cache_create("sighand_cache",
1495 sizeof(struct sighand_struct), 0,
1496 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1497 SLAB_NOTRACK, sighand_ctor);
1498 signal_cachep = kmem_cache_create("signal_cache",
1499 sizeof(struct signal_struct), 0,
1500 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1501 files_cachep = kmem_cache_create("files_cache",
1502 sizeof(struct files_struct), 0,
1503 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1504 fs_cachep = kmem_cache_create("fs_cache",
1505 sizeof(struct fs_struct), 0,
1506 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1507 mm_cachep = kmem_cache_create("mm_struct",
1508 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1509 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1510 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1511 mmap_init();
1512}
1513
1514/*
1515 * Check constraints on flags passed to the unshare system call and
1516 * force unsharing of additional process context as appropriate.
1517 */
1518static void check_unshare_flags(unsigned long *flags_ptr)
1519{
1520 /*
1521 * If unsharing a thread from a thread group, must also
1522 * unshare vm.
1523 */
1524 if (*flags_ptr & CLONE_THREAD)
1525 *flags_ptr |= CLONE_VM;
1526
1527 /*
1528 * If unsharing vm, must also unshare signal handlers.
1529 */
1530 if (*flags_ptr & CLONE_VM)
1531 *flags_ptr |= CLONE_SIGHAND;
1532
1533 /*
1534 * If unsharing namespace, must also unshare filesystem information.
1535 */
1536 if (*flags_ptr & CLONE_NEWNS)
1537 *flags_ptr |= CLONE_FS;
1538}
1539
1540/*
1541 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1542 */
1543static int unshare_thread(unsigned long unshare_flags)
1544{
1545 if (unshare_flags & CLONE_THREAD)
1546 return -EINVAL;
1547
1548 return 0;
1549}
1550
1551/*
1552 * Unshare the filesystem structure if it is being shared
1553 */
1554static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1555{
1556 struct fs_struct *fs = current->fs;
1557
1558 if (!(unshare_flags & CLONE_FS) || !fs)
1559 return 0;
1560
1561 /* don't need lock here; in the worst case we'll do useless copy */
1562 if (fs->users == 1)
1563 return 0;
1564
1565 *new_fsp = copy_fs_struct(fs);
1566 if (!*new_fsp)
1567 return -ENOMEM;
1568
1569 return 0;
1570}
1571
1572/*
1573 * Unsharing of sighand is not supported yet
1574 */
1575static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1576{
1577 struct sighand_struct *sigh = current->sighand;
1578
1579 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1580 return -EINVAL;
1581 else
1582 return 0;
1583}
1584
1585/*
1586 * Unshare vm if it is being shared
1587 */
1588static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1589{
1590 struct mm_struct *mm = current->mm;
1591
1592 if ((unshare_flags & CLONE_VM) &&
1593 (mm && atomic_read(&mm->mm_users) > 1)) {
1594 return -EINVAL;
1595 }
1596
1597 return 0;
1598}
1599
1600/*
1601 * Unshare file descriptor table if it is being shared
1602 */
1603static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1604{
1605 struct files_struct *fd = current->files;
1606 int error = 0;
1607
1608 if ((unshare_flags & CLONE_FILES) &&
1609 (fd && atomic_read(&fd->count) > 1)) {
1610 *new_fdp = dup_fd(fd, &error);
1611 if (!*new_fdp)
1612 return error;
1613 }
1614
1615 return 0;
1616}
1617
1618/*
1619 * unshare allows a process to 'unshare' part of the process
1620 * context which was originally shared using clone. copy_*
1621 * functions used by do_fork() cannot be used here directly
1622 * because they modify an inactive task_struct that is being
1623 * constructed. Here we are modifying the current, active,
1624 * task_struct.
1625 */
1626SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1627{
1628 int err = 0;
1629 struct fs_struct *fs, *new_fs = NULL;
1630 struct sighand_struct *new_sigh = NULL;
1631 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1632 struct files_struct *fd, *new_fd = NULL;
1633 struct nsproxy *new_nsproxy = NULL;
1634 int do_sysvsem = 0;
1635
1636 check_unshare_flags(&unshare_flags);
1637
1638 /* Return -EINVAL for all unsupported flags */
1639 err = -EINVAL;
1640 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1641 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1642 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1643 goto bad_unshare_out;
1644
1645 /*
1646 * CLONE_NEWIPC must also detach from the undolist: after switching
1647 * to a new ipc namespace, the semaphore arrays from the old
1648 * namespace are unreachable.
1649 */
1650 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1651 do_sysvsem = 1;
1652 if ((err = unshare_thread(unshare_flags)))
1653 goto bad_unshare_out;
1654 if ((err = unshare_fs(unshare_flags, &new_fs)))
1655 goto bad_unshare_cleanup_thread;
1656 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1657 goto bad_unshare_cleanup_fs;
1658 if ((err = unshare_vm(unshare_flags, &new_mm)))
1659 goto bad_unshare_cleanup_sigh;
1660 if ((err = unshare_fd(unshare_flags, &new_fd)))
1661 goto bad_unshare_cleanup_vm;
1662 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1663 new_fs)))
1664 goto bad_unshare_cleanup_fd;
1665
1666 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1667 if (do_sysvsem) {
1668 /*
1669 * CLONE_SYSVSEM is equivalent to sys_exit().
1670 */
1671 exit_sem(current);
1672 }
1673
1674 if (new_nsproxy) {
1675 switch_task_namespaces(current, new_nsproxy);
1676 new_nsproxy = NULL;
1677 }
1678
1679 task_lock(current);
1680
1681 if (new_fs) {
1682 fs = current->fs;
1683 spin_lock(&fs->lock);
1684 current->fs = new_fs;
1685 if (--fs->users)
1686 new_fs = NULL;
1687 else
1688 new_fs = fs;
1689 spin_unlock(&fs->lock);
1690 }
1691
1692 if (new_mm) {
1693 mm = current->mm;
1694 active_mm = current->active_mm;
1695 current->mm = new_mm;
1696 current->active_mm = new_mm;
1697 if (current->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
1698 atomic_dec(&mm->oom_disable_count);
1699 atomic_inc(&new_mm->oom_disable_count);
1700 }
1701 activate_mm(active_mm, new_mm);
1702 new_mm = mm;
1703 }
1704
1705 if (new_fd) {
1706 fd = current->files;
1707 current->files = new_fd;
1708 new_fd = fd;
1709 }
1710
1711 task_unlock(current);
1712 }
1713
1714 if (new_nsproxy)
1715 put_nsproxy(new_nsproxy);
1716
1717bad_unshare_cleanup_fd:
1718 if (new_fd)
1719 put_files_struct(new_fd);
1720
1721bad_unshare_cleanup_vm:
1722 if (new_mm)
1723 mmput(new_mm);
1724
1725bad_unshare_cleanup_sigh:
1726 if (new_sigh)
1727 if (atomic_dec_and_test(&new_sigh->count))
1728 kmem_cache_free(sighand_cachep, new_sigh);
1729
1730bad_unshare_cleanup_fs:
1731 if (new_fs)
1732 free_fs_struct(new_fs);
1733
1734bad_unshare_cleanup_thread:
1735bad_unshare_out:
1736 return err;
1737}
1738
1739/*
1740 * Helper to unshare the files of the current task.
1741 * We don't want to expose copy_files internals to
1742 * the exec layer of the kernel.
1743 */
1744
1745int unshare_files(struct files_struct **displaced)
1746{
1747 struct task_struct *task = current;
1748 struct files_struct *copy = NULL;
1749 int error;
1750
1751 error = unshare_fd(CLONE_FILES, &copy);
1752 if (error || !copy) {
1753 *displaced = NULL;
1754 return error;
1755 }
1756 *displaced = task->files;
1757 task_lock(task);
1758 task->files = copy;
1759 task_unlock(task);
1760 return 0;
1761}