projects/linux·blob v2.6.28-rc3 · refs

1704 lines · 40.8 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/mnt_namespace.h>
21#include <linux/personality.h>
22#include <linux/mempolicy.h>
23#include <linux/sem.h>
24#include <linux/file.h>
25#include <linux/fdtable.h>
26#include <linux/iocontext.h>
27#include <linux/key.h>
28#include <linux/binfmts.h>
29#include <linux/mman.h>
30#include <linux/mmu_notifier.h>
31#include <linux/fs.h>
32#include <linux/nsproxy.h>
33#include <linux/capability.h>
34#include <linux/cpu.h>
35#include <linux/cgroup.h>
36#include <linux/security.h>
37#include <linux/hugetlb.h>
38#include <linux/swap.h>
39#include <linux/syscalls.h>
40#include <linux/jiffies.h>
41#include <linux/tracehook.h>
42#include <linux/futex.h>
43#include <linux/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/profile.h>
50#include <linux/rmap.h>
51#include <linux/acct.h>
52#include <linux/tsacct_kern.h>
53#include <linux/cn_proc.h>
54#include <linux/freezer.h>
55#include <linux/delayacct.h>
56#include <linux/taskstats_kern.h>
57#include <linux/random.h>
58#include <linux/tty.h>
59#include <linux/proc_fs.h>
60#include <linux/blkdev.h>
61#include <trace/sched.h>
62
63#include <asm/pgtable.h>
64#include <asm/pgalloc.h>
65#include <asm/uaccess.h>
66#include <asm/mmu_context.h>
67#include <asm/cacheflush.h>
68#include <asm/tlbflush.h>
69
70/*
71 * Protected counters by write_lock_irq(&tasklist_lock)
72 */
73unsigned long total_forks; /* Handle normal Linux uptimes. */
74int nr_threads; /* The idle threads do not count.. */
75
76int max_threads; /* tunable limit on nr_threads */
77
78DEFINE_PER_CPU(unsigned long, process_counts) = 0;
79
80__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
81
82int nr_processes(void)
83{
84 int cpu;
85 int total = 0;
86
87 for_each_online_cpu(cpu)
88 total += per_cpu(process_counts, cpu);
89
90 return total;
91}
92
93#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
94# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
95# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
96static struct kmem_cache *task_struct_cachep;
97#endif
98
99#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
100static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
101{
102#ifdef CONFIG_DEBUG_STACK_USAGE
103 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
104#else
105 gfp_t mask = GFP_KERNEL;
106#endif
107 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
108}
109
110static inline void free_thread_info(struct thread_info *ti)
111{
112 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
113}
114#endif
115
116/* SLAB cache for signal_struct structures (tsk->signal) */
117static struct kmem_cache *signal_cachep;
118
119/* SLAB cache for sighand_struct structures (tsk->sighand) */
120struct kmem_cache *sighand_cachep;
121
122/* SLAB cache for files_struct structures (tsk->files) */
123struct kmem_cache *files_cachep;
124
125/* SLAB cache for fs_struct structures (tsk->fs) */
126struct kmem_cache *fs_cachep;
127
128/* SLAB cache for vm_area_struct structures */
129struct kmem_cache *vm_area_cachep;
130
131/* SLAB cache for mm_struct structures (tsk->mm) */
132static struct kmem_cache *mm_cachep;
133
134void free_task(struct task_struct *tsk)
135{
136 prop_local_destroy_single(&tsk->dirties);
137 free_thread_info(tsk->stack);
138 rt_mutex_debug_task_free(tsk);
139 free_task_struct(tsk);
140}
141EXPORT_SYMBOL(free_task);
142
143void __put_task_struct(struct task_struct *tsk)
144{
145 WARN_ON(!tsk->exit_state);
146 WARN_ON(atomic_read(&tsk->usage));
147 WARN_ON(tsk == current);
148
149 security_task_free(tsk);
150 free_uid(tsk->user);
151 put_group_info(tsk->group_info);
152 delayacct_tsk_free(tsk);
153
154 if (!profile_handoff_task(tsk))
155 free_task(tsk);
156}
157
158/*
159 * macro override instead of weak attribute alias, to workaround
160 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
161 */
162#ifndef arch_task_cache_init
163#define arch_task_cache_init()
164#endif
165
166void __init fork_init(unsigned long mempages)
167{
168#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
169#ifndef ARCH_MIN_TASKALIGN
170#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
171#endif
172 /* create a slab on which task_structs can be allocated */
173 task_struct_cachep =
174 kmem_cache_create("task_struct", sizeof(struct task_struct),
175 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
176#endif
177
178 /* do the arch specific task caches init */
179 arch_task_cache_init();
180
181 /*
182 * The default maximum number of threads is set to a safe
183 * value: the thread structures can take up at most half
184 * of memory.
185 */
186 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
187
188 /*
189 * we need to allow at least 20 threads to boot a system
190 */
191 if(max_threads < 20)
192 max_threads = 20;
193
194 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
195 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
196 init_task.signal->rlim[RLIMIT_SIGPENDING] =
197 init_task.signal->rlim[RLIMIT_NPROC];
198}
199
200int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
201 struct task_struct *src)
202{
203 *dst = *src;
204 return 0;
205}
206
207static struct task_struct *dup_task_struct(struct task_struct *orig)
208{
209 struct task_struct *tsk;
210 struct thread_info *ti;
211 int err;
212
213 prepare_to_copy(orig);
214
215 tsk = alloc_task_struct();
216 if (!tsk)
217 return NULL;
218
219 ti = alloc_thread_info(tsk);
220 if (!ti) {
221 free_task_struct(tsk);
222 return NULL;
223 }
224
225 err = arch_dup_task_struct(tsk, orig);
226 if (err)
227 goto out;
228
229 tsk->stack = ti;
230
231 err = prop_local_init_single(&tsk->dirties);
232 if (err)
233 goto out;
234
235 setup_thread_stack(tsk, orig);
236
237#ifdef CONFIG_CC_STACKPROTECTOR
238 tsk->stack_canary = get_random_int();
239#endif
240
241 /* One for us, one for whoever does the "release_task()" (usually parent) */
242 atomic_set(&tsk->usage,2);
243 atomic_set(&tsk->fs_excl, 0);
244#ifdef CONFIG_BLK_DEV_IO_TRACE
245 tsk->btrace_seq = 0;
246#endif
247 tsk->splice_pipe = NULL;
248 return tsk;
249
250out:
251 free_thread_info(ti);
252 free_task_struct(tsk);
253 return NULL;
254}
255
256#ifdef CONFIG_MMU
257static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
258{
259 struct vm_area_struct *mpnt, *tmp, **pprev;
260 struct rb_node **rb_link, *rb_parent;
261 int retval;
262 unsigned long charge;
263 struct mempolicy *pol;
264
265 down_write(&oldmm->mmap_sem);
266 flush_cache_dup_mm(oldmm);
267 /*
268 * Not linked in yet - no deadlock potential:
269 */
270 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
271
272 mm->locked_vm = 0;
273 mm->mmap = NULL;
274 mm->mmap_cache = NULL;
275 mm->free_area_cache = oldmm->mmap_base;
276 mm->cached_hole_size = ~0UL;
277 mm->map_count = 0;
278 cpus_clear(mm->cpu_vm_mask);
279 mm->mm_rb = RB_ROOT;
280 rb_link = &mm->mm_rb.rb_node;
281 rb_parent = NULL;
282 pprev = &mm->mmap;
283
284 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
285 struct file *file;
286
287 if (mpnt->vm_flags & VM_DONTCOPY) {
288 long pages = vma_pages(mpnt);
289 mm->total_vm -= pages;
290 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
291 -pages);
292 continue;
293 }
294 charge = 0;
295 if (mpnt->vm_flags & VM_ACCOUNT) {
296 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
297 if (security_vm_enough_memory(len))
298 goto fail_nomem;
299 charge = len;
300 }
301 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
302 if (!tmp)
303 goto fail_nomem;
304 *tmp = *mpnt;
305 pol = mpol_dup(vma_policy(mpnt));
306 retval = PTR_ERR(pol);
307 if (IS_ERR(pol))
308 goto fail_nomem_policy;
309 vma_set_policy(tmp, pol);
310 tmp->vm_flags &= ~VM_LOCKED;
311 tmp->vm_mm = mm;
312 tmp->vm_next = NULL;
313 anon_vma_link(tmp);
314 file = tmp->vm_file;
315 if (file) {
316 struct inode *inode = file->f_path.dentry->d_inode;
317 get_file(file);
318 if (tmp->vm_flags & VM_DENYWRITE)
319 atomic_dec(&inode->i_writecount);
320
321 /* insert tmp into the share list, just after mpnt */
322 spin_lock(&file->f_mapping->i_mmap_lock);
323 tmp->vm_truncate_count = mpnt->vm_truncate_count;
324 flush_dcache_mmap_lock(file->f_mapping);
325 vma_prio_tree_add(tmp, mpnt);
326 flush_dcache_mmap_unlock(file->f_mapping);
327 spin_unlock(&file->f_mapping->i_mmap_lock);
328 }
329
330 /*
331 * Clear hugetlb-related page reserves for children. This only
332 * affects MAP_PRIVATE mappings. Faults generated by the child
333 * are not guaranteed to succeed, even if read-only
334 */
335 if (is_vm_hugetlb_page(tmp))
336 reset_vma_resv_huge_pages(tmp);
337
338 /*
339 * Link in the new vma and copy the page table entries.
340 */
341 *pprev = tmp;
342 pprev = &tmp->vm_next;
343
344 __vma_link_rb(mm, tmp, rb_link, rb_parent);
345 rb_link = &tmp->vm_rb.rb_right;
346 rb_parent = &tmp->vm_rb;
347
348 mm->map_count++;
349 retval = copy_page_range(mm, oldmm, mpnt);
350
351 if (tmp->vm_ops && tmp->vm_ops->open)
352 tmp->vm_ops->open(tmp);
353
354 if (retval)
355 goto out;
356 }
357 /* a new mm has just been created */
358 arch_dup_mmap(oldmm, mm);
359 retval = 0;
360out:
361 up_write(&mm->mmap_sem);
362 flush_tlb_mm(oldmm);
363 up_write(&oldmm->mmap_sem);
364 return retval;
365fail_nomem_policy:
366 kmem_cache_free(vm_area_cachep, tmp);
367fail_nomem:
368 retval = -ENOMEM;
369 vm_unacct_memory(charge);
370 goto out;
371}
372
373static inline int mm_alloc_pgd(struct mm_struct * mm)
374{
375 mm->pgd = pgd_alloc(mm);
376 if (unlikely(!mm->pgd))
377 return -ENOMEM;
378 return 0;
379}
380
381static inline void mm_free_pgd(struct mm_struct * mm)
382{
383 pgd_free(mm, mm->pgd);
384}
385#else
386#define dup_mmap(mm, oldmm) (0)
387#define mm_alloc_pgd(mm) (0)
388#define mm_free_pgd(mm)
389#endif /* CONFIG_MMU */
390
391__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
392
393#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
394#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
395
396#include <linux/init_task.h>
397
398static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
399{
400 atomic_set(&mm->mm_users, 1);
401 atomic_set(&mm->mm_count, 1);
402 init_rwsem(&mm->mmap_sem);
403 INIT_LIST_HEAD(&mm->mmlist);
404 mm->flags = (current->mm) ? current->mm->flags
405 : MMF_DUMP_FILTER_DEFAULT;
406 mm->core_state = NULL;
407 mm->nr_ptes = 0;
408 set_mm_counter(mm, file_rss, 0);
409 set_mm_counter(mm, anon_rss, 0);
410 spin_lock_init(&mm->page_table_lock);
411 rwlock_init(&mm->ioctx_list_lock);
412 mm->ioctx_list = NULL;
413 mm->free_area_cache = TASK_UNMAPPED_BASE;
414 mm->cached_hole_size = ~0UL;
415 mm_init_owner(mm, p);
416
417 if (likely(!mm_alloc_pgd(mm))) {
418 mm->def_flags = 0;
419 mmu_notifier_mm_init(mm);
420 return mm;
421 }
422
423 free_mm(mm);
424 return NULL;
425}
426
427/*
428 * Allocate and initialize an mm_struct.
429 */
430struct mm_struct * mm_alloc(void)
431{
432 struct mm_struct * mm;
433
434 mm = allocate_mm();
435 if (mm) {
436 memset(mm, 0, sizeof(*mm));
437 mm = mm_init(mm, current);
438 }
439 return mm;
440}
441
442/*
443 * Called when the last reference to the mm
444 * is dropped: either by a lazy thread or by
445 * mmput. Free the page directory and the mm.
446 */
447void __mmdrop(struct mm_struct *mm)
448{
449 BUG_ON(mm == &init_mm);
450 mm_free_pgd(mm);
451 destroy_context(mm);
452 mmu_notifier_mm_destroy(mm);
453 free_mm(mm);
454}
455EXPORT_SYMBOL_GPL(__mmdrop);
456
457/*
458 * Decrement the use count and release all resources for an mm.
459 */
460void mmput(struct mm_struct *mm)
461{
462 might_sleep();
463
464 if (atomic_dec_and_test(&mm->mm_users)) {
465 exit_aio(mm);
466 exit_mmap(mm);
467 set_mm_exe_file(mm, NULL);
468 if (!list_empty(&mm->mmlist)) {
469 spin_lock(&mmlist_lock);
470 list_del(&mm->mmlist);
471 spin_unlock(&mmlist_lock);
472 }
473 put_swap_token(mm);
474 mmdrop(mm);
475 }
476}
477EXPORT_SYMBOL_GPL(mmput);
478
479/**
480 * get_task_mm - acquire a reference to the task's mm
481 *
482 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
483 * this kernel workthread has transiently adopted a user mm with use_mm,
484 * to do its AIO) is not set and if so returns a reference to it, after
485 * bumping up the use count. User must release the mm via mmput()
486 * after use. Typically used by /proc and ptrace.
487 */
488struct mm_struct *get_task_mm(struct task_struct *task)
489{
490 struct mm_struct *mm;
491
492 task_lock(task);
493 mm = task->mm;
494 if (mm) {
495 if (task->flags & PF_KTHREAD)
496 mm = NULL;
497 else
498 atomic_inc(&mm->mm_users);
499 }
500 task_unlock(task);
501 return mm;
502}
503EXPORT_SYMBOL_GPL(get_task_mm);
504
505/* Please note the differences between mmput and mm_release.
506 * mmput is called whenever we stop holding onto a mm_struct,
507 * error success whatever.
508 *
509 * mm_release is called after a mm_struct has been removed
510 * from the current process.
511 *
512 * This difference is important for error handling, when we
513 * only half set up a mm_struct for a new process and need to restore
514 * the old one. Because we mmput the new mm_struct before
515 * restoring the old one. . .
516 * Eric Biederman 10 January 1998
517 */
518void mm_release(struct task_struct *tsk, struct mm_struct *mm)
519{
520 struct completion *vfork_done = tsk->vfork_done;
521
522 /* Get rid of any cached register state */
523 deactivate_mm(tsk, mm);
524
525 /* notify parent sleeping on vfork() */
526 if (vfork_done) {
527 tsk->vfork_done = NULL;
528 complete(vfork_done);
529 }
530
531 /*
532 * If we're exiting normally, clear a user-space tid field if
533 * requested. We leave this alone when dying by signal, to leave
534 * the value intact in a core dump, and to save the unnecessary
535 * trouble otherwise. Userland only wants this done for a sys_exit.
536 */
537 if (tsk->clear_child_tid
538 && !(tsk->flags & PF_SIGNALED)
539 && atomic_read(&mm->mm_users) > 1) {
540 u32 __user * tidptr = tsk->clear_child_tid;
541 tsk->clear_child_tid = NULL;
542
543 /*
544 * We don't check the error code - if userspace has
545 * not set up a proper pointer then tough luck.
546 */
547 put_user(0, tidptr);
548 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
549 }
550}
551
552/*
553 * Allocate a new mm structure and copy contents from the
554 * mm structure of the passed in task structure.
555 */
556struct mm_struct *dup_mm(struct task_struct *tsk)
557{
558 struct mm_struct *mm, *oldmm = current->mm;
559 int err;
560
561 if (!oldmm)
562 return NULL;
563
564 mm = allocate_mm();
565 if (!mm)
566 goto fail_nomem;
567
568 memcpy(mm, oldmm, sizeof(*mm));
569
570 /* Initializing for Swap token stuff */
571 mm->token_priority = 0;
572 mm->last_interval = 0;
573
574 if (!mm_init(mm, tsk))
575 goto fail_nomem;
576
577 if (init_new_context(tsk, mm))
578 goto fail_nocontext;
579
580 dup_mm_exe_file(oldmm, mm);
581
582 err = dup_mmap(mm, oldmm);
583 if (err)
584 goto free_pt;
585
586 mm->hiwater_rss = get_mm_rss(mm);
587 mm->hiwater_vm = mm->total_vm;
588
589 return mm;
590
591free_pt:
592 mmput(mm);
593
594fail_nomem:
595 return NULL;
596
597fail_nocontext:
598 /*
599 * If init_new_context() failed, we cannot use mmput() to free the mm
600 * because it calls destroy_context()
601 */
602 mm_free_pgd(mm);
603 free_mm(mm);
604 return NULL;
605}
606
607static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
608{
609 struct mm_struct * mm, *oldmm;
610 int retval;
611
612 tsk->min_flt = tsk->maj_flt = 0;
613 tsk->nvcsw = tsk->nivcsw = 0;
614
615 tsk->mm = NULL;
616 tsk->active_mm = NULL;
617
618 /*
619 * Are we cloning a kernel thread?
620 *
621 * We need to steal a active VM for that..
622 */
623 oldmm = current->mm;
624 if (!oldmm)
625 return 0;
626
627 if (clone_flags & CLONE_VM) {
628 atomic_inc(&oldmm->mm_users);
629 mm = oldmm;
630 goto good_mm;
631 }
632
633 retval = -ENOMEM;
634 mm = dup_mm(tsk);
635 if (!mm)
636 goto fail_nomem;
637
638good_mm:
639 /* Initializing for Swap token stuff */
640 mm->token_priority = 0;
641 mm->last_interval = 0;
642
643 tsk->mm = mm;
644 tsk->active_mm = mm;
645 return 0;
646
647fail_nomem:
648 return retval;
649}
650
651static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
652{
653 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
654 /* We don't need to lock fs - think why ;-) */
655 if (fs) {
656 atomic_set(&fs->count, 1);
657 rwlock_init(&fs->lock);
658 fs->umask = old->umask;
659 read_lock(&old->lock);
660 fs->root = old->root;
661 path_get(&old->root);
662 fs->pwd = old->pwd;
663 path_get(&old->pwd);
664 read_unlock(&old->lock);
665 }
666 return fs;
667}
668
669struct fs_struct *copy_fs_struct(struct fs_struct *old)
670{
671 return __copy_fs_struct(old);
672}
673
674EXPORT_SYMBOL_GPL(copy_fs_struct);
675
676static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
677{
678 if (clone_flags & CLONE_FS) {
679 atomic_inc(&current->fs->count);
680 return 0;
681 }
682 tsk->fs = __copy_fs_struct(current->fs);
683 if (!tsk->fs)
684 return -ENOMEM;
685 return 0;
686}
687
688static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
689{
690 struct files_struct *oldf, *newf;
691 int error = 0;
692
693 /*
694 * A background process may not have any files ...
695 */
696 oldf = current->files;
697 if (!oldf)
698 goto out;
699
700 if (clone_flags & CLONE_FILES) {
701 atomic_inc(&oldf->count);
702 goto out;
703 }
704
705 newf = dup_fd(oldf, &error);
706 if (!newf)
707 goto out;
708
709 tsk->files = newf;
710 error = 0;
711out:
712 return error;
713}
714
715static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
716{
717#ifdef CONFIG_BLOCK
718 struct io_context *ioc = current->io_context;
719
720 if (!ioc)
721 return 0;
722 /*
723 * Share io context with parent, if CLONE_IO is set
724 */
725 if (clone_flags & CLONE_IO) {
726 tsk->io_context = ioc_task_link(ioc);
727 if (unlikely(!tsk->io_context))
728 return -ENOMEM;
729 } else if (ioprio_valid(ioc->ioprio)) {
730 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
731 if (unlikely(!tsk->io_context))
732 return -ENOMEM;
733
734 tsk->io_context->ioprio = ioc->ioprio;
735 }
736#endif
737 return 0;
738}
739
740static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
741{
742 struct sighand_struct *sig;
743
744 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
745 atomic_inc(&current->sighand->count);
746 return 0;
747 }
748 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
749 rcu_assign_pointer(tsk->sighand, sig);
750 if (!sig)
751 return -ENOMEM;
752 atomic_set(&sig->count, 1);
753 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
754 return 0;
755}
756
757void __cleanup_sighand(struct sighand_struct *sighand)
758{
759 if (atomic_dec_and_test(&sighand->count))
760 kmem_cache_free(sighand_cachep, sighand);
761}
762
763
764/*
765 * Initialize POSIX timer handling for a thread group.
766 */
767static void posix_cpu_timers_init_group(struct signal_struct *sig)
768{
769 /* Thread group counters. */
770 thread_group_cputime_init(sig);
771
772 /* Expiration times and increments. */
773 sig->it_virt_expires = cputime_zero;
774 sig->it_virt_incr = cputime_zero;
775 sig->it_prof_expires = cputime_zero;
776 sig->it_prof_incr = cputime_zero;
777
778 /* Cached expiration times. */
779 sig->cputime_expires.prof_exp = cputime_zero;
780 sig->cputime_expires.virt_exp = cputime_zero;
781 sig->cputime_expires.sched_exp = 0;
782
783 /* The timer lists. */
784 INIT_LIST_HEAD(&sig->cpu_timers[0]);
785 INIT_LIST_HEAD(&sig->cpu_timers[1]);
786 INIT_LIST_HEAD(&sig->cpu_timers[2]);
787}
788
789static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
790{
791 struct signal_struct *sig;
792 int ret;
793
794 if (clone_flags & CLONE_THREAD) {
795 ret = thread_group_cputime_clone_thread(current);
796 if (likely(!ret)) {
797 atomic_inc(&current->signal->count);
798 atomic_inc(&current->signal->live);
799 }
800 return ret;
801 }
802 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
803 tsk->signal = sig;
804 if (!sig)
805 return -ENOMEM;
806
807 ret = copy_thread_group_keys(tsk);
808 if (ret < 0) {
809 kmem_cache_free(signal_cachep, sig);
810 return ret;
811 }
812
813 atomic_set(&sig->count, 1);
814 atomic_set(&sig->live, 1);
815 init_waitqueue_head(&sig->wait_chldexit);
816 sig->flags = 0;
817 sig->group_exit_code = 0;
818 sig->group_exit_task = NULL;
819 sig->group_stop_count = 0;
820 sig->curr_target = tsk;
821 init_sigpending(&sig->shared_pending);
822 INIT_LIST_HEAD(&sig->posix_timers);
823
824 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
825 sig->it_real_incr.tv64 = 0;
826 sig->real_timer.function = it_real_fn;
827
828 sig->leader = 0; /* session leadership doesn't inherit */
829 sig->tty_old_pgrp = NULL;
830 sig->tty = NULL;
831
832 sig->cutime = sig->cstime = cputime_zero;
833 sig->gtime = cputime_zero;
834 sig->cgtime = cputime_zero;
835 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
836 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
837 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
838 task_io_accounting_init(&sig->ioac);
839 taskstats_tgid_init(sig);
840
841 task_lock(current->group_leader);
842 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
843 task_unlock(current->group_leader);
844
845 posix_cpu_timers_init_group(sig);
846
847 acct_init_pacct(&sig->pacct);
848
849 tty_audit_fork(sig);
850
851 return 0;
852}
853
854void __cleanup_signal(struct signal_struct *sig)
855{
856 thread_group_cputime_free(sig);
857 exit_thread_group_keys(sig);
858 tty_kref_put(sig->tty);
859 kmem_cache_free(signal_cachep, sig);
860}
861
862static void cleanup_signal(struct task_struct *tsk)
863{
864 struct signal_struct *sig = tsk->signal;
865
866 atomic_dec(&sig->live);
867
868 if (atomic_dec_and_test(&sig->count))
869 __cleanup_signal(sig);
870}
871
872static void copy_flags(unsigned long clone_flags, struct task_struct *p)
873{
874 unsigned long new_flags = p->flags;
875
876 new_flags &= ~PF_SUPERPRIV;
877 new_flags |= PF_FORKNOEXEC;
878 new_flags |= PF_STARTING;
879 p->flags = new_flags;
880 clear_freeze_flag(p);
881}
882
883asmlinkage long sys_set_tid_address(int __user *tidptr)
884{
885 current->clear_child_tid = tidptr;
886
887 return task_pid_vnr(current);
888}
889
890static void rt_mutex_init_task(struct task_struct *p)
891{
892 spin_lock_init(&p->pi_lock);
893#ifdef CONFIG_RT_MUTEXES
894 plist_head_init(&p->pi_waiters, &p->pi_lock);
895 p->pi_blocked_on = NULL;
896#endif
897}
898
899#ifdef CONFIG_MM_OWNER
900void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
901{
902 mm->owner = p;
903}
904#endif /* CONFIG_MM_OWNER */
905
906/*
907 * Initialize POSIX timer handling for a single task.
908 */
909static void posix_cpu_timers_init(struct task_struct *tsk)
910{
911 tsk->cputime_expires.prof_exp = cputime_zero;
912 tsk->cputime_expires.virt_exp = cputime_zero;
913 tsk->cputime_expires.sched_exp = 0;
914 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
915 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
916 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
917}
918
919/*
920 * This creates a new process as a copy of the old one,
921 * but does not actually start it yet.
922 *
923 * It copies the registers, and all the appropriate
924 * parts of the process environment (as per the clone
925 * flags). The actual kick-off is left to the caller.
926 */
927static struct task_struct *copy_process(unsigned long clone_flags,
928 unsigned long stack_start,
929 struct pt_regs *regs,
930 unsigned long stack_size,
931 int __user *child_tidptr,
932 struct pid *pid,
933 int trace)
934{
935 int retval;
936 struct task_struct *p;
937 int cgroup_callbacks_done = 0;
938
939 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
940 return ERR_PTR(-EINVAL);
941
942 /*
943 * Thread groups must share signals as well, and detached threads
944 * can only be started up within the thread group.
945 */
946 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
947 return ERR_PTR(-EINVAL);
948
949 /*
950 * Shared signal handlers imply shared VM. By way of the above,
951 * thread groups also imply shared VM. Blocking this case allows
952 * for various simplifications in other code.
953 */
954 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
955 return ERR_PTR(-EINVAL);
956
957 retval = security_task_create(clone_flags);
958 if (retval)
959 goto fork_out;
960
961 retval = -ENOMEM;
962 p = dup_task_struct(current);
963 if (!p)
964 goto fork_out;
965
966 rt_mutex_init_task(p);
967
968#ifdef CONFIG_PROVE_LOCKING
969 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
970 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
971#endif
972 retval = -EAGAIN;
973 if (atomic_read(&p->user->processes) >=
974 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
975 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
976 p->user != current->nsproxy->user_ns->root_user)
977 goto bad_fork_free;
978 }
979
980 atomic_inc(&p->user->__count);
981 atomic_inc(&p->user->processes);
982 get_group_info(p->group_info);
983
984 /*
985 * If multiple threads are within copy_process(), then this check
986 * triggers too late. This doesn't hurt, the check is only there
987 * to stop root fork bombs.
988 */
989 if (nr_threads >= max_threads)
990 goto bad_fork_cleanup_count;
991
992 if (!try_module_get(task_thread_info(p)->exec_domain->module))
993 goto bad_fork_cleanup_count;
994
995 if (p->binfmt && !try_module_get(p->binfmt->module))
996 goto bad_fork_cleanup_put_domain;
997
998 p->did_exec = 0;
999 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1000 copy_flags(clone_flags, p);
1001 INIT_LIST_HEAD(&p->children);
1002 INIT_LIST_HEAD(&p->sibling);
1003#ifdef CONFIG_PREEMPT_RCU
1004 p->rcu_read_lock_nesting = 0;
1005 p->rcu_flipctr_idx = 0;
1006#endif /* #ifdef CONFIG_PREEMPT_RCU */
1007 p->vfork_done = NULL;
1008 spin_lock_init(&p->alloc_lock);
1009
1010 clear_tsk_thread_flag(p, TIF_SIGPENDING);
1011 init_sigpending(&p->pending);
1012
1013 p->utime = cputime_zero;
1014 p->stime = cputime_zero;
1015 p->gtime = cputime_zero;
1016 p->utimescaled = cputime_zero;
1017 p->stimescaled = cputime_zero;
1018 p->prev_utime = cputime_zero;
1019 p->prev_stime = cputime_zero;
1020
1021 p->default_timer_slack_ns = current->timer_slack_ns;
1022
1023#ifdef CONFIG_DETECT_SOFTLOCKUP
1024 p->last_switch_count = 0;
1025 p->last_switch_timestamp = 0;
1026#endif
1027
1028 task_io_accounting_init(&p->ioac);
1029 acct_clear_integrals(p);
1030
1031 posix_cpu_timers_init(p);
1032
1033 p->lock_depth = -1; /* -1 = no lock */
1034 do_posix_clock_monotonic_gettime(&p->start_time);
1035 p->real_start_time = p->start_time;
1036 monotonic_to_bootbased(&p->real_start_time);
1037#ifdef CONFIG_SECURITY
1038 p->security = NULL;
1039#endif
1040 p->cap_bset = current->cap_bset;
1041 p->io_context = NULL;
1042 p->audit_context = NULL;
1043 cgroup_fork(p);
1044#ifdef CONFIG_NUMA
1045 p->mempolicy = mpol_dup(p->mempolicy);
1046 if (IS_ERR(p->mempolicy)) {
1047 retval = PTR_ERR(p->mempolicy);
1048 p->mempolicy = NULL;
1049 goto bad_fork_cleanup_cgroup;
1050 }
1051 mpol_fix_fork_child_flag(p);
1052#endif
1053#ifdef CONFIG_TRACE_IRQFLAGS
1054 p->irq_events = 0;
1055#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1056 p->hardirqs_enabled = 1;
1057#else
1058 p->hardirqs_enabled = 0;
1059#endif
1060 p->hardirq_enable_ip = 0;
1061 p->hardirq_enable_event = 0;
1062 p->hardirq_disable_ip = _THIS_IP_;
1063 p->hardirq_disable_event = 0;
1064 p->softirqs_enabled = 1;
1065 p->softirq_enable_ip = _THIS_IP_;
1066 p->softirq_enable_event = 0;
1067 p->softirq_disable_ip = 0;
1068 p->softirq_disable_event = 0;
1069 p->hardirq_context = 0;
1070 p->softirq_context = 0;
1071#endif
1072#ifdef CONFIG_LOCKDEP
1073 p->lockdep_depth = 0; /* no locks held yet */
1074 p->curr_chain_key = 0;
1075 p->lockdep_recursion = 0;
1076#endif
1077
1078#ifdef CONFIG_DEBUG_MUTEXES
1079 p->blocked_on = NULL; /* not blocked yet */
1080#endif
1081
1082 /* Perform scheduler related setup. Assign this task to a CPU. */
1083 sched_fork(p, clone_flags);
1084
1085 if ((retval = security_task_alloc(p)))
1086 goto bad_fork_cleanup_policy;
1087 if ((retval = audit_alloc(p)))
1088 goto bad_fork_cleanup_security;
1089 /* copy all the process information */
1090 if ((retval = copy_semundo(clone_flags, p)))
1091 goto bad_fork_cleanup_audit;
1092 if ((retval = copy_files(clone_flags, p)))
1093 goto bad_fork_cleanup_semundo;
1094 if ((retval = copy_fs(clone_flags, p)))
1095 goto bad_fork_cleanup_files;
1096 if ((retval = copy_sighand(clone_flags, p)))
1097 goto bad_fork_cleanup_fs;
1098 if ((retval = copy_signal(clone_flags, p)))
1099 goto bad_fork_cleanup_sighand;
1100 if ((retval = copy_mm(clone_flags, p)))
1101 goto bad_fork_cleanup_signal;
1102 if ((retval = copy_keys(clone_flags, p)))
1103 goto bad_fork_cleanup_mm;
1104 if ((retval = copy_namespaces(clone_flags, p)))
1105 goto bad_fork_cleanup_keys;
1106 if ((retval = copy_io(clone_flags, p)))
1107 goto bad_fork_cleanup_namespaces;
1108 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1109 if (retval)
1110 goto bad_fork_cleanup_io;
1111
1112 if (pid != &init_struct_pid) {
1113 retval = -ENOMEM;
1114 pid = alloc_pid(task_active_pid_ns(p));
1115 if (!pid)
1116 goto bad_fork_cleanup_io;
1117
1118 if (clone_flags & CLONE_NEWPID) {
1119 retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1120 if (retval < 0)
1121 goto bad_fork_free_pid;
1122 }
1123 }
1124
1125 p->pid = pid_nr(pid);
1126 p->tgid = p->pid;
1127 if (clone_flags & CLONE_THREAD)
1128 p->tgid = current->tgid;
1129
1130 if (current->nsproxy != p->nsproxy) {
1131 retval = ns_cgroup_clone(p, pid);
1132 if (retval)
1133 goto bad_fork_free_pid;
1134 }
1135
1136 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1137 /*
1138 * Clear TID on mm_release()?
1139 */
1140 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1141#ifdef CONFIG_FUTEX
1142 p->robust_list = NULL;
1143#ifdef CONFIG_COMPAT
1144 p->compat_robust_list = NULL;
1145#endif
1146 INIT_LIST_HEAD(&p->pi_state_list);
1147 p->pi_state_cache = NULL;
1148#endif
1149 /*
1150 * sigaltstack should be cleared when sharing the same VM
1151 */
1152 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1153 p->sas_ss_sp = p->sas_ss_size = 0;
1154
1155 /*
1156 * Syscall tracing should be turned off in the child regardless
1157 * of CLONE_PTRACE.
1158 */
1159 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1160#ifdef TIF_SYSCALL_EMU
1161 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1162#endif
1163 clear_all_latency_tracing(p);
1164
1165 /* Our parent execution domain becomes current domain
1166 These must match for thread signalling to apply */
1167 p->parent_exec_id = p->self_exec_id;
1168
1169 /* ok, now we should be set up.. */
1170 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1171 p->pdeath_signal = 0;
1172 p->exit_state = 0;
1173
1174 /*
1175 * Ok, make it visible to the rest of the system.
1176 * We dont wake it up yet.
1177 */
1178 p->group_leader = p;
1179 INIT_LIST_HEAD(&p->thread_group);
1180
1181 /* Now that the task is set up, run cgroup callbacks if
1182 * necessary. We need to run them before the task is visible
1183 * on the tasklist. */
1184 cgroup_fork_callbacks(p);
1185 cgroup_callbacks_done = 1;
1186
1187 /* Need tasklist lock for parent etc handling! */
1188 write_lock_irq(&tasklist_lock);
1189
1190 /*
1191 * The task hasn't been attached yet, so its cpus_allowed mask will
1192 * not be changed, nor will its assigned CPU.
1193 *
1194 * The cpus_allowed mask of the parent may have changed after it was
1195 * copied first time - so re-copy it here, then check the child's CPU
1196 * to ensure it is on a valid CPU (and if not, just force it back to
1197 * parent's CPU). This avoids alot of nasty races.
1198 */
1199 p->cpus_allowed = current->cpus_allowed;
1200 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1201 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1202 !cpu_online(task_cpu(p))))
1203 set_task_cpu(p, smp_processor_id());
1204
1205 /* CLONE_PARENT re-uses the old parent */
1206 if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1207 p->real_parent = current->real_parent;
1208 else
1209 p->real_parent = current;
1210
1211 spin_lock(&current->sighand->siglock);
1212
1213 /*
1214 * Process group and session signals need to be delivered to just the
1215 * parent before the fork or both the parent and the child after the
1216 * fork. Restart if a signal comes in before we add the new process to
1217 * it's process group.
1218 * A fatal signal pending means that current will exit, so the new
1219 * thread can't slip out of an OOM kill (or normal SIGKILL).
1220 */
1221 recalc_sigpending();
1222 if (signal_pending(current)) {
1223 spin_unlock(&current->sighand->siglock);
1224 write_unlock_irq(&tasklist_lock);
1225 retval = -ERESTARTNOINTR;
1226 goto bad_fork_free_pid;
1227 }
1228
1229 if (clone_flags & CLONE_THREAD) {
1230 p->group_leader = current->group_leader;
1231 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1232 }
1233
1234 if (likely(p->pid)) {
1235 list_add_tail(&p->sibling, &p->real_parent->children);
1236 tracehook_finish_clone(p, clone_flags, trace);
1237
1238 if (thread_group_leader(p)) {
1239 if (clone_flags & CLONE_NEWPID)
1240 p->nsproxy->pid_ns->child_reaper = p;
1241
1242 p->signal->leader_pid = pid;
1243 tty_kref_put(p->signal->tty);
1244 p->signal->tty = tty_kref_get(current->signal->tty);
1245 set_task_pgrp(p, task_pgrp_nr(current));
1246 set_task_session(p, task_session_nr(current));
1247 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1248 attach_pid(p, PIDTYPE_SID, task_session(current));
1249 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1250 __get_cpu_var(process_counts)++;
1251 }
1252 attach_pid(p, PIDTYPE_PID, pid);
1253 nr_threads++;
1254 }
1255
1256 total_forks++;
1257 spin_unlock(&current->sighand->siglock);
1258 write_unlock_irq(&tasklist_lock);
1259 proc_fork_connector(p);
1260 cgroup_post_fork(p);
1261 return p;
1262
1263bad_fork_free_pid:
1264 if (pid != &init_struct_pid)
1265 free_pid(pid);
1266bad_fork_cleanup_io:
1267 put_io_context(p->io_context);
1268bad_fork_cleanup_namespaces:
1269 exit_task_namespaces(p);
1270bad_fork_cleanup_keys:
1271 exit_keys(p);
1272bad_fork_cleanup_mm:
1273 if (p->mm)
1274 mmput(p->mm);
1275bad_fork_cleanup_signal:
1276 cleanup_signal(p);
1277bad_fork_cleanup_sighand:
1278 __cleanup_sighand(p->sighand);
1279bad_fork_cleanup_fs:
1280 exit_fs(p); /* blocking */
1281bad_fork_cleanup_files:
1282 exit_files(p); /* blocking */
1283bad_fork_cleanup_semundo:
1284 exit_sem(p);
1285bad_fork_cleanup_audit:
1286 audit_free(p);
1287bad_fork_cleanup_security:
1288 security_task_free(p);
1289bad_fork_cleanup_policy:
1290#ifdef CONFIG_NUMA
1291 mpol_put(p->mempolicy);
1292bad_fork_cleanup_cgroup:
1293#endif
1294 cgroup_exit(p, cgroup_callbacks_done);
1295 delayacct_tsk_free(p);
1296 if (p->binfmt)
1297 module_put(p->binfmt->module);
1298bad_fork_cleanup_put_domain:
1299 module_put(task_thread_info(p)->exec_domain->module);
1300bad_fork_cleanup_count:
1301 put_group_info(p->group_info);
1302 atomic_dec(&p->user->processes);
1303 free_uid(p->user);
1304bad_fork_free:
1305 free_task(p);
1306fork_out:
1307 return ERR_PTR(retval);
1308}
1309
1310noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1311{
1312 memset(regs, 0, sizeof(struct pt_regs));
1313 return regs;
1314}
1315
1316struct task_struct * __cpuinit fork_idle(int cpu)
1317{
1318 struct task_struct *task;
1319 struct pt_regs regs;
1320
1321 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1322 &init_struct_pid, 0);
1323 if (!IS_ERR(task))
1324 init_idle(task, cpu);
1325
1326 return task;
1327}
1328
1329/*
1330 * Ok, this is the main fork-routine.
1331 *
1332 * It copies the process, and if successful kick-starts
1333 * it and waits for it to finish using the VM if required.
1334 */
1335long do_fork(unsigned long clone_flags,
1336 unsigned long stack_start,
1337 struct pt_regs *regs,
1338 unsigned long stack_size,
1339 int __user *parent_tidptr,
1340 int __user *child_tidptr)
1341{
1342 struct task_struct *p;
1343 int trace = 0;
1344 long nr;
1345
1346 /*
1347 * We hope to recycle these flags after 2.6.26
1348 */
1349 if (unlikely(clone_flags & CLONE_STOPPED)) {
1350 static int __read_mostly count = 100;
1351
1352 if (count > 0 && printk_ratelimit()) {
1353 char comm[TASK_COMM_LEN];
1354
1355 count--;
1356 printk(KERN_INFO "fork(): process `%s' used deprecated "
1357 "clone flags 0x%lx\n",
1358 get_task_comm(comm, current),
1359 clone_flags & CLONE_STOPPED);
1360 }
1361 }
1362
1363 /*
1364 * When called from kernel_thread, don't do user tracing stuff.
1365 */
1366 if (likely(user_mode(regs)))
1367 trace = tracehook_prepare_clone(clone_flags);
1368
1369 p = copy_process(clone_flags, stack_start, regs, stack_size,
1370 child_tidptr, NULL, trace);
1371 /*
1372 * Do this prior waking up the new thread - the thread pointer
1373 * might get invalid after that point, if the thread exits quickly.
1374 */
1375 if (!IS_ERR(p)) {
1376 struct completion vfork;
1377
1378 trace_sched_process_fork(current, p);
1379
1380 nr = task_pid_vnr(p);
1381
1382 if (clone_flags & CLONE_PARENT_SETTID)
1383 put_user(nr, parent_tidptr);
1384
1385 if (clone_flags & CLONE_VFORK) {
1386 p->vfork_done = &vfork;
1387 init_completion(&vfork);
1388 }
1389
1390 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1391
1392 /*
1393 * We set PF_STARTING at creation in case tracing wants to
1394 * use this to distinguish a fully live task from one that
1395 * hasn't gotten to tracehook_report_clone() yet. Now we
1396 * clear it and set the child going.
1397 */
1398 p->flags &= ~PF_STARTING;
1399
1400 if (unlikely(clone_flags & CLONE_STOPPED)) {
1401 /*
1402 * We'll start up with an immediate SIGSTOP.
1403 */
1404 sigaddset(&p->pending.signal, SIGSTOP);
1405 set_tsk_thread_flag(p, TIF_SIGPENDING);
1406 __set_task_state(p, TASK_STOPPED);
1407 } else {
1408 wake_up_new_task(p, clone_flags);
1409 }
1410
1411 tracehook_report_clone_complete(trace, regs,
1412 clone_flags, nr, p);
1413
1414 if (clone_flags & CLONE_VFORK) {
1415 freezer_do_not_count();
1416 wait_for_completion(&vfork);
1417 freezer_count();
1418 tracehook_report_vfork_done(p, nr);
1419 }
1420 } else {
1421 nr = PTR_ERR(p);
1422 }
1423 return nr;
1424}
1425
1426#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1427#define ARCH_MIN_MMSTRUCT_ALIGN 0
1428#endif
1429
1430static void sighand_ctor(void *data)
1431{
1432 struct sighand_struct *sighand = data;
1433
1434 spin_lock_init(&sighand->siglock);
1435 init_waitqueue_head(&sighand->signalfd_wqh);
1436}
1437
1438void __init proc_caches_init(void)
1439{
1440 sighand_cachep = kmem_cache_create("sighand_cache",
1441 sizeof(struct sighand_struct), 0,
1442 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1443 sighand_ctor);
1444 signal_cachep = kmem_cache_create("signal_cache",
1445 sizeof(struct signal_struct), 0,
1446 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1447 files_cachep = kmem_cache_create("files_cache",
1448 sizeof(struct files_struct), 0,
1449 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1450 fs_cachep = kmem_cache_create("fs_cache",
1451 sizeof(struct fs_struct), 0,
1452 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1453 vm_area_cachep = kmem_cache_create("vm_area_struct",
1454 sizeof(struct vm_area_struct), 0,
1455 SLAB_PANIC, NULL);
1456 mm_cachep = kmem_cache_create("mm_struct",
1457 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1458 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1459}
1460
1461/*
1462 * Check constraints on flags passed to the unshare system call and
1463 * force unsharing of additional process context as appropriate.
1464 */
1465static void check_unshare_flags(unsigned long *flags_ptr)
1466{
1467 /*
1468 * If unsharing a thread from a thread group, must also
1469 * unshare vm.
1470 */
1471 if (*flags_ptr & CLONE_THREAD)
1472 *flags_ptr |= CLONE_VM;
1473
1474 /*
1475 * If unsharing vm, must also unshare signal handlers.
1476 */
1477 if (*flags_ptr & CLONE_VM)
1478 *flags_ptr |= CLONE_SIGHAND;
1479
1480 /*
1481 * If unsharing signal handlers and the task was created
1482 * using CLONE_THREAD, then must unshare the thread
1483 */
1484 if ((*flags_ptr & CLONE_SIGHAND) &&
1485 (atomic_read(&current->signal->count) > 1))
1486 *flags_ptr |= CLONE_THREAD;
1487
1488 /*
1489 * If unsharing namespace, must also unshare filesystem information.
1490 */
1491 if (*flags_ptr & CLONE_NEWNS)
1492 *flags_ptr |= CLONE_FS;
1493}
1494
1495/*
1496 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1497 */
1498static int unshare_thread(unsigned long unshare_flags)
1499{
1500 if (unshare_flags & CLONE_THREAD)
1501 return -EINVAL;
1502
1503 return 0;
1504}
1505
1506/*
1507 * Unshare the filesystem structure if it is being shared
1508 */
1509static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1510{
1511 struct fs_struct *fs = current->fs;
1512
1513 if ((unshare_flags & CLONE_FS) &&
1514 (fs && atomic_read(&fs->count) > 1)) {
1515 *new_fsp = __copy_fs_struct(current->fs);
1516 if (!*new_fsp)
1517 return -ENOMEM;
1518 }
1519
1520 return 0;
1521}
1522
1523/*
1524 * Unsharing of sighand is not supported yet
1525 */
1526static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1527{
1528 struct sighand_struct *sigh = current->sighand;
1529
1530 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1531 return -EINVAL;
1532 else
1533 return 0;
1534}
1535
1536/*
1537 * Unshare vm if it is being shared
1538 */
1539static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1540{
1541 struct mm_struct *mm = current->mm;
1542
1543 if ((unshare_flags & CLONE_VM) &&
1544 (mm && atomic_read(&mm->mm_users) > 1)) {
1545 return -EINVAL;
1546 }
1547
1548 return 0;
1549}
1550
1551/*
1552 * Unshare file descriptor table if it is being shared
1553 */
1554static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1555{
1556 struct files_struct *fd = current->files;
1557 int error = 0;
1558
1559 if ((unshare_flags & CLONE_FILES) &&
1560 (fd && atomic_read(&fd->count) > 1)) {
1561 *new_fdp = dup_fd(fd, &error);
1562 if (!*new_fdp)
1563 return error;
1564 }
1565
1566 return 0;
1567}
1568
1569/*
1570 * unshare allows a process to 'unshare' part of the process
1571 * context which was originally shared using clone. copy_*
1572 * functions used by do_fork() cannot be used here directly
1573 * because they modify an inactive task_struct that is being
1574 * constructed. Here we are modifying the current, active,
1575 * task_struct.
1576 */
1577asmlinkage long sys_unshare(unsigned long unshare_flags)
1578{
1579 int err = 0;
1580 struct fs_struct *fs, *new_fs = NULL;
1581 struct sighand_struct *new_sigh = NULL;
1582 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1583 struct files_struct *fd, *new_fd = NULL;
1584 struct nsproxy *new_nsproxy = NULL;
1585 int do_sysvsem = 0;
1586
1587 check_unshare_flags(&unshare_flags);
1588
1589 /* Return -EINVAL for all unsupported flags */
1590 err = -EINVAL;
1591 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1592 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1593 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1594 CLONE_NEWNET))
1595 goto bad_unshare_out;
1596
1597 /*
1598 * CLONE_NEWIPC must also detach from the undolist: after switching
1599 * to a new ipc namespace, the semaphore arrays from the old
1600 * namespace are unreachable.
1601 */
1602 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1603 do_sysvsem = 1;
1604 if ((err = unshare_thread(unshare_flags)))
1605 goto bad_unshare_out;
1606 if ((err = unshare_fs(unshare_flags, &new_fs)))
1607 goto bad_unshare_cleanup_thread;
1608 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1609 goto bad_unshare_cleanup_fs;
1610 if ((err = unshare_vm(unshare_flags, &new_mm)))
1611 goto bad_unshare_cleanup_sigh;
1612 if ((err = unshare_fd(unshare_flags, &new_fd)))
1613 goto bad_unshare_cleanup_vm;
1614 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1615 new_fs)))
1616 goto bad_unshare_cleanup_fd;
1617
1618 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1619 if (do_sysvsem) {
1620 /*
1621 * CLONE_SYSVSEM is equivalent to sys_exit().
1622 */
1623 exit_sem(current);
1624 }
1625
1626 if (new_nsproxy) {
1627 switch_task_namespaces(current, new_nsproxy);
1628 new_nsproxy = NULL;
1629 }
1630
1631 task_lock(current);
1632
1633 if (new_fs) {
1634 fs = current->fs;
1635 current->fs = new_fs;
1636 new_fs = fs;
1637 }
1638
1639 if (new_mm) {
1640 mm = current->mm;
1641 active_mm = current->active_mm;
1642 current->mm = new_mm;
1643 current->active_mm = new_mm;
1644 activate_mm(active_mm, new_mm);
1645 new_mm = mm;
1646 }
1647
1648 if (new_fd) {
1649 fd = current->files;
1650 current->files = new_fd;
1651 new_fd = fd;
1652 }
1653
1654 task_unlock(current);
1655 }
1656
1657 if (new_nsproxy)
1658 put_nsproxy(new_nsproxy);
1659
1660bad_unshare_cleanup_fd:
1661 if (new_fd)
1662 put_files_struct(new_fd);
1663
1664bad_unshare_cleanup_vm:
1665 if (new_mm)
1666 mmput(new_mm);
1667
1668bad_unshare_cleanup_sigh:
1669 if (new_sigh)
1670 if (atomic_dec_and_test(&new_sigh->count))
1671 kmem_cache_free(sighand_cachep, new_sigh);
1672
1673bad_unshare_cleanup_fs:
1674 if (new_fs)
1675 put_fs_struct(new_fs);
1676
1677bad_unshare_cleanup_thread:
1678bad_unshare_out:
1679 return err;
1680}
1681
1682/*
1683 * Helper to unshare the files of the current task.
1684 * We don't want to expose copy_files internals to
1685 * the exec layer of the kernel.
1686 */
1687
1688int unshare_files(struct files_struct **displaced)
1689{
1690 struct task_struct *task = current;
1691 struct files_struct *copy = NULL;
1692 int error;
1693
1694 error = unshare_fd(CLONE_FILES, &copy);
1695 if (error || !copy) {
1696 *displaced = NULL;
1697 return error;
1698 }
1699 *displaced = task->files;
1700 task_lock(task);
1701 task->files = copy;
1702 task_unlock(task);
1703 return 0;
1704}