projects/linux·blob v2.6.29-rc5 · refs

1732 lines · 41.4 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/compat.h>
44#include <linux/task_io_accounting_ops.h>
45#include <linux/rcupdate.h>
46#include <linux/ptrace.h>
47#include <linux/mount.h>
48#include <linux/audit.h>
49#include <linux/memcontrol.h>
50#include <linux/ftrace.h>
51#include <linux/profile.h>
52#include <linux/rmap.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 <trace/sched.h>
64
65#include <asm/pgtable.h>
66#include <asm/pgalloc.h>
67#include <asm/uaccess.h>
68#include <asm/mmu_context.h>
69#include <asm/cacheflush.h>
70#include <asm/tlbflush.h>
71
72/*
73 * Protected counters by write_lock_irq(&tasklist_lock)
74 */
75unsigned long total_forks; /* Handle normal Linux uptimes. */
76int nr_threads; /* The idle threads do not count.. */
77
78int max_threads; /* tunable limit on nr_threads */
79
80DEFINE_PER_CPU(unsigned long, process_counts) = 0;
81
82__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
83
84DEFINE_TRACE(sched_process_fork);
85
86int nr_processes(void)
87{
88 int cpu;
89 int total = 0;
90
91 for_each_online_cpu(cpu)
92 total += per_cpu(process_counts, cpu);
93
94 return total;
95}
96
97#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
98# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
99# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
100static struct kmem_cache *task_struct_cachep;
101#endif
102
103#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
104static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
105{
106#ifdef CONFIG_DEBUG_STACK_USAGE
107 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
108#else
109 gfp_t mask = GFP_KERNEL;
110#endif
111 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
112}
113
114static inline void free_thread_info(struct thread_info *ti)
115{
116 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
117}
118#endif
119
120/* SLAB cache for signal_struct structures (tsk->signal) */
121static struct kmem_cache *signal_cachep;
122
123/* SLAB cache for sighand_struct structures (tsk->sighand) */
124struct kmem_cache *sighand_cachep;
125
126/* SLAB cache for files_struct structures (tsk->files) */
127struct kmem_cache *files_cachep;
128
129/* SLAB cache for fs_struct structures (tsk->fs) */
130struct kmem_cache *fs_cachep;
131
132/* SLAB cache for vm_area_struct structures */
133struct kmem_cache *vm_area_cachep;
134
135/* SLAB cache for mm_struct structures (tsk->mm) */
136static struct kmem_cache *mm_cachep;
137
138void free_task(struct task_struct *tsk)
139{
140 prop_local_destroy_single(&tsk->dirties);
141 free_thread_info(tsk->stack);
142 rt_mutex_debug_task_free(tsk);
143 ftrace_graph_exit_task(tsk);
144 free_task_struct(tsk);
145}
146EXPORT_SYMBOL(free_task);
147
148void __put_task_struct(struct task_struct *tsk)
149{
150 WARN_ON(!tsk->exit_state);
151 WARN_ON(atomic_read(&tsk->usage));
152 WARN_ON(tsk == current);
153
154 put_cred(tsk->real_cred);
155 put_cred(tsk->cred);
156 delayacct_tsk_free(tsk);
157
158 if (!profile_handoff_task(tsk))
159 free_task(tsk);
160}
161
162/*
163 * macro override instead of weak attribute alias, to workaround
164 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
165 */
166#ifndef arch_task_cache_init
167#define arch_task_cache_init()
168#endif
169
170void __init fork_init(unsigned long mempages)
171{
172#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
173#ifndef ARCH_MIN_TASKALIGN
174#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
175#endif
176 /* create a slab on which task_structs can be allocated */
177 task_struct_cachep =
178 kmem_cache_create("task_struct", sizeof(struct task_struct),
179 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
180#endif
181
182 /* do the arch specific task caches init */
183 arch_task_cache_init();
184
185 /*
186 * The default maximum number of threads is set to a safe
187 * value: the thread structures can take up at most half
188 * of memory.
189 */
190 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
191
192 /*
193 * we need to allow at least 20 threads to boot a system
194 */
195 if(max_threads < 20)
196 max_threads = 20;
197
198 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
199 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
200 init_task.signal->rlim[RLIMIT_SIGPENDING] =
201 init_task.signal->rlim[RLIMIT_NPROC];
202}
203
204int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
205 struct task_struct *src)
206{
207 *dst = *src;
208 return 0;
209}
210
211static struct task_struct *dup_task_struct(struct task_struct *orig)
212{
213 struct task_struct *tsk;
214 struct thread_info *ti;
215 int err;
216
217 prepare_to_copy(orig);
218
219 tsk = alloc_task_struct();
220 if (!tsk)
221 return NULL;
222
223 ti = alloc_thread_info(tsk);
224 if (!ti) {
225 free_task_struct(tsk);
226 return NULL;
227 }
228
229 err = arch_dup_task_struct(tsk, orig);
230 if (err)
231 goto out;
232
233 tsk->stack = ti;
234
235 err = prop_local_init_single(&tsk->dirties);
236 if (err)
237 goto out;
238
239 setup_thread_stack(tsk, orig);
240
241#ifdef CONFIG_CC_STACKPROTECTOR
242 tsk->stack_canary = get_random_int();
243#endif
244
245 /* One for us, one for whoever does the "release_task()" (usually parent) */
246 atomic_set(&tsk->usage,2);
247 atomic_set(&tsk->fs_excl, 0);
248#ifdef CONFIG_BLK_DEV_IO_TRACE
249 tsk->btrace_seq = 0;
250#endif
251 tsk->splice_pipe = NULL;
252 return tsk;
253
254out:
255 free_thread_info(ti);
256 free_task_struct(tsk);
257 return NULL;
258}
259
260#ifdef CONFIG_MMU
261static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
262{
263 struct vm_area_struct *mpnt, *tmp, **pprev;
264 struct rb_node **rb_link, *rb_parent;
265 int retval;
266 unsigned long charge;
267 struct mempolicy *pol;
268
269 down_write(&oldmm->mmap_sem);
270 flush_cache_dup_mm(oldmm);
271 /*
272 * Not linked in yet - no deadlock potential:
273 */
274 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
275
276 mm->locked_vm = 0;
277 mm->mmap = NULL;
278 mm->mmap_cache = NULL;
279 mm->free_area_cache = oldmm->mmap_base;
280 mm->cached_hole_size = ~0UL;
281 mm->map_count = 0;
282 cpus_clear(mm->cpu_vm_mask);
283 mm->mm_rb = RB_ROOT;
284 rb_link = &mm->mm_rb.rb_node;
285 rb_parent = NULL;
286 pprev = &mm->mmap;
287
288 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
289 struct file *file;
290
291 if (mpnt->vm_flags & VM_DONTCOPY) {
292 long pages = vma_pages(mpnt);
293 mm->total_vm -= pages;
294 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
295 -pages);
296 continue;
297 }
298 charge = 0;
299 if (mpnt->vm_flags & VM_ACCOUNT) {
300 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
301 if (security_vm_enough_memory(len))
302 goto fail_nomem;
303 charge = len;
304 }
305 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
306 if (!tmp)
307 goto fail_nomem;
308 *tmp = *mpnt;
309 pol = mpol_dup(vma_policy(mpnt));
310 retval = PTR_ERR(pol);
311 if (IS_ERR(pol))
312 goto fail_nomem_policy;
313 vma_set_policy(tmp, pol);
314 tmp->vm_flags &= ~VM_LOCKED;
315 tmp->vm_mm = mm;
316 tmp->vm_next = NULL;
317 anon_vma_link(tmp);
318 file = tmp->vm_file;
319 if (file) {
320 struct inode *inode = file->f_path.dentry->d_inode;
321 struct address_space *mapping = file->f_mapping;
322
323 get_file(file);
324 if (tmp->vm_flags & VM_DENYWRITE)
325 atomic_dec(&inode->i_writecount);
326 spin_lock(&mapping->i_mmap_lock);
327 if (tmp->vm_flags & VM_SHARED)
328 mapping->i_mmap_writable++;
329 tmp->vm_truncate_count = mpnt->vm_truncate_count;
330 flush_dcache_mmap_lock(mapping);
331 /* insert tmp into the share list, just after mpnt */
332 vma_prio_tree_add(tmp, mpnt);
333 flush_dcache_mmap_unlock(mapping);
334 spin_unlock(&mapping->i_mmap_lock);
335 }
336
337 /*
338 * Clear hugetlb-related page reserves for children. This only
339 * affects MAP_PRIVATE mappings. Faults generated by the child
340 * are not guaranteed to succeed, even if read-only
341 */
342 if (is_vm_hugetlb_page(tmp))
343 reset_vma_resv_huge_pages(tmp);
344
345 /*
346 * Link in the new vma and copy the page table entries.
347 */
348 *pprev = tmp;
349 pprev = &tmp->vm_next;
350
351 __vma_link_rb(mm, tmp, rb_link, rb_parent);
352 rb_link = &tmp->vm_rb.rb_right;
353 rb_parent = &tmp->vm_rb;
354
355 mm->map_count++;
356 retval = copy_page_range(mm, oldmm, mpnt);
357
358 if (tmp->vm_ops && tmp->vm_ops->open)
359 tmp->vm_ops->open(tmp);
360
361 if (retval)
362 goto out;
363 }
364 /* a new mm has just been created */
365 arch_dup_mmap(oldmm, mm);
366 retval = 0;
367out:
368 up_write(&mm->mmap_sem);
369 flush_tlb_mm(oldmm);
370 up_write(&oldmm->mmap_sem);
371 return retval;
372fail_nomem_policy:
373 kmem_cache_free(vm_area_cachep, tmp);
374fail_nomem:
375 retval = -ENOMEM;
376 vm_unacct_memory(charge);
377 goto out;
378}
379
380static inline int mm_alloc_pgd(struct mm_struct * mm)
381{
382 mm->pgd = pgd_alloc(mm);
383 if (unlikely(!mm->pgd))
384 return -ENOMEM;
385 return 0;
386}
387
388static inline void mm_free_pgd(struct mm_struct * mm)
389{
390 pgd_free(mm, mm->pgd);
391}
392#else
393#define dup_mmap(mm, oldmm) (0)
394#define mm_alloc_pgd(mm) (0)
395#define mm_free_pgd(mm)
396#endif /* CONFIG_MMU */
397
398__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
399
400#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
401#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
402
403static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
404
405static int __init coredump_filter_setup(char *s)
406{
407 default_dump_filter =
408 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
409 MMF_DUMP_FILTER_MASK;
410 return 1;
411}
412
413__setup("coredump_filter=", coredump_filter_setup);
414
415#include <linux/init_task.h>
416
417static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
418{
419 atomic_set(&mm->mm_users, 1);
420 atomic_set(&mm->mm_count, 1);
421 init_rwsem(&mm->mmap_sem);
422 INIT_LIST_HEAD(&mm->mmlist);
423 mm->flags = (current->mm) ? current->mm->flags : default_dump_filter;
424 mm->core_state = NULL;
425 mm->nr_ptes = 0;
426 set_mm_counter(mm, file_rss, 0);
427 set_mm_counter(mm, anon_rss, 0);
428 spin_lock_init(&mm->page_table_lock);
429 spin_lock_init(&mm->ioctx_lock);
430 INIT_HLIST_HEAD(&mm->ioctx_list);
431 mm->free_area_cache = TASK_UNMAPPED_BASE;
432 mm->cached_hole_size = ~0UL;
433 mm_init_owner(mm, p);
434
435 if (likely(!mm_alloc_pgd(mm))) {
436 mm->def_flags = 0;
437 mmu_notifier_mm_init(mm);
438 return mm;
439 }
440
441 free_mm(mm);
442 return NULL;
443}
444
445/*
446 * Allocate and initialize an mm_struct.
447 */
448struct mm_struct * mm_alloc(void)
449{
450 struct mm_struct * mm;
451
452 mm = allocate_mm();
453 if (mm) {
454 memset(mm, 0, sizeof(*mm));
455 mm = mm_init(mm, current);
456 }
457 return mm;
458}
459
460/*
461 * Called when the last reference to the mm
462 * is dropped: either by a lazy thread or by
463 * mmput. Free the page directory and the mm.
464 */
465void __mmdrop(struct mm_struct *mm)
466{
467 BUG_ON(mm == &init_mm);
468 mm_free_pgd(mm);
469 destroy_context(mm);
470 mmu_notifier_mm_destroy(mm);
471 free_mm(mm);
472}
473EXPORT_SYMBOL_GPL(__mmdrop);
474
475/*
476 * Decrement the use count and release all resources for an mm.
477 */
478void mmput(struct mm_struct *mm)
479{
480 might_sleep();
481
482 if (atomic_dec_and_test(&mm->mm_users)) {
483 exit_aio(mm);
484 exit_mmap(mm);
485 set_mm_exe_file(mm, NULL);
486 if (!list_empty(&mm->mmlist)) {
487 spin_lock(&mmlist_lock);
488 list_del(&mm->mmlist);
489 spin_unlock(&mmlist_lock);
490 }
491 put_swap_token(mm);
492 mmdrop(mm);
493 }
494}
495EXPORT_SYMBOL_GPL(mmput);
496
497/**
498 * get_task_mm - acquire a reference to the task's mm
499 *
500 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
501 * this kernel workthread has transiently adopted a user mm with use_mm,
502 * to do its AIO) is not set and if so returns a reference to it, after
503 * bumping up the use count. User must release the mm via mmput()
504 * after use. Typically used by /proc and ptrace.
505 */
506struct mm_struct *get_task_mm(struct task_struct *task)
507{
508 struct mm_struct *mm;
509
510 task_lock(task);
511 mm = task->mm;
512 if (mm) {
513 if (task->flags & PF_KTHREAD)
514 mm = NULL;
515 else
516 atomic_inc(&mm->mm_users);
517 }
518 task_unlock(task);
519 return mm;
520}
521EXPORT_SYMBOL_GPL(get_task_mm);
522
523/* Please note the differences between mmput and mm_release.
524 * mmput is called whenever we stop holding onto a mm_struct,
525 * error success whatever.
526 *
527 * mm_release is called after a mm_struct has been removed
528 * from the current process.
529 *
530 * This difference is important for error handling, when we
531 * only half set up a mm_struct for a new process and need to restore
532 * the old one. Because we mmput the new mm_struct before
533 * restoring the old one. . .
534 * Eric Biederman 10 January 1998
535 */
536void mm_release(struct task_struct *tsk, struct mm_struct *mm)
537{
538 struct completion *vfork_done = tsk->vfork_done;
539
540 /* Get rid of any futexes when releasing the mm */
541#ifdef CONFIG_FUTEX
542 if (unlikely(tsk->robust_list))
543 exit_robust_list(tsk);
544#ifdef CONFIG_COMPAT
545 if (unlikely(tsk->compat_robust_list))
546 compat_exit_robust_list(tsk);
547#endif
548#endif
549
550 /* Get rid of any cached register state */
551 deactivate_mm(tsk, mm);
552
553 /* notify parent sleeping on vfork() */
554 if (vfork_done) {
555 tsk->vfork_done = NULL;
556 complete(vfork_done);
557 }
558
559 /*
560 * If we're exiting normally, clear a user-space tid field if
561 * requested. We leave this alone when dying by signal, to leave
562 * the value intact in a core dump, and to save the unnecessary
563 * trouble otherwise. Userland only wants this done for a sys_exit.
564 */
565 if (tsk->clear_child_tid
566 && !(tsk->flags & PF_SIGNALED)
567 && atomic_read(&mm->mm_users) > 1) {
568 u32 __user * tidptr = tsk->clear_child_tid;
569 tsk->clear_child_tid = NULL;
570
571 /*
572 * We don't check the error code - if userspace has
573 * not set up a proper pointer then tough luck.
574 */
575 put_user(0, tidptr);
576 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
577 }
578}
579
580/*
581 * Allocate a new mm structure and copy contents from the
582 * mm structure of the passed in task structure.
583 */
584struct mm_struct *dup_mm(struct task_struct *tsk)
585{
586 struct mm_struct *mm, *oldmm = current->mm;
587 int err;
588
589 if (!oldmm)
590 return NULL;
591
592 mm = allocate_mm();
593 if (!mm)
594 goto fail_nomem;
595
596 memcpy(mm, oldmm, sizeof(*mm));
597
598 /* Initializing for Swap token stuff */
599 mm->token_priority = 0;
600 mm->last_interval = 0;
601
602 if (!mm_init(mm, tsk))
603 goto fail_nomem;
604
605 if (init_new_context(tsk, mm))
606 goto fail_nocontext;
607
608 dup_mm_exe_file(oldmm, mm);
609
610 err = dup_mmap(mm, oldmm);
611 if (err)
612 goto free_pt;
613
614 mm->hiwater_rss = get_mm_rss(mm);
615 mm->hiwater_vm = mm->total_vm;
616
617 return mm;
618
619free_pt:
620 mmput(mm);
621
622fail_nomem:
623 return NULL;
624
625fail_nocontext:
626 /*
627 * If init_new_context() failed, we cannot use mmput() to free the mm
628 * because it calls destroy_context()
629 */
630 mm_free_pgd(mm);
631 free_mm(mm);
632 return NULL;
633}
634
635static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
636{
637 struct mm_struct * mm, *oldmm;
638 int retval;
639
640 tsk->min_flt = tsk->maj_flt = 0;
641 tsk->nvcsw = tsk->nivcsw = 0;
642
643 tsk->mm = NULL;
644 tsk->active_mm = NULL;
645
646 /*
647 * Are we cloning a kernel thread?
648 *
649 * We need to steal a active VM for that..
650 */
651 oldmm = current->mm;
652 if (!oldmm)
653 return 0;
654
655 if (clone_flags & CLONE_VM) {
656 atomic_inc(&oldmm->mm_users);
657 mm = oldmm;
658 goto good_mm;
659 }
660
661 retval = -ENOMEM;
662 mm = dup_mm(tsk);
663 if (!mm)
664 goto fail_nomem;
665
666good_mm:
667 /* Initializing for Swap token stuff */
668 mm->token_priority = 0;
669 mm->last_interval = 0;
670
671 tsk->mm = mm;
672 tsk->active_mm = mm;
673 return 0;
674
675fail_nomem:
676 return retval;
677}
678
679static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
680{
681 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
682 /* We don't need to lock fs - think why ;-) */
683 if (fs) {
684 atomic_set(&fs->count, 1);
685 rwlock_init(&fs->lock);
686 fs->umask = old->umask;
687 read_lock(&old->lock);
688 fs->root = old->root;
689 path_get(&old->root);
690 fs->pwd = old->pwd;
691 path_get(&old->pwd);
692 read_unlock(&old->lock);
693 }
694 return fs;
695}
696
697struct fs_struct *copy_fs_struct(struct fs_struct *old)
698{
699 return __copy_fs_struct(old);
700}
701
702EXPORT_SYMBOL_GPL(copy_fs_struct);
703
704static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
705{
706 if (clone_flags & CLONE_FS) {
707 atomic_inc(&current->fs->count);
708 return 0;
709 }
710 tsk->fs = __copy_fs_struct(current->fs);
711 if (!tsk->fs)
712 return -ENOMEM;
713 return 0;
714}
715
716static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
717{
718 struct files_struct *oldf, *newf;
719 int error = 0;
720
721 /*
722 * A background process may not have any files ...
723 */
724 oldf = current->files;
725 if (!oldf)
726 goto out;
727
728 if (clone_flags & CLONE_FILES) {
729 atomic_inc(&oldf->count);
730 goto out;
731 }
732
733 newf = dup_fd(oldf, &error);
734 if (!newf)
735 goto out;
736
737 tsk->files = newf;
738 error = 0;
739out:
740 return error;
741}
742
743static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
744{
745#ifdef CONFIG_BLOCK
746 struct io_context *ioc = current->io_context;
747
748 if (!ioc)
749 return 0;
750 /*
751 * Share io context with parent, if CLONE_IO is set
752 */
753 if (clone_flags & CLONE_IO) {
754 tsk->io_context = ioc_task_link(ioc);
755 if (unlikely(!tsk->io_context))
756 return -ENOMEM;
757 } else if (ioprio_valid(ioc->ioprio)) {
758 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
759 if (unlikely(!tsk->io_context))
760 return -ENOMEM;
761
762 tsk->io_context->ioprio = ioc->ioprio;
763 }
764#endif
765 return 0;
766}
767
768static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
769{
770 struct sighand_struct *sig;
771
772 if (clone_flags & CLONE_SIGHAND) {
773 atomic_inc(&current->sighand->count);
774 return 0;
775 }
776 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
777 rcu_assign_pointer(tsk->sighand, sig);
778 if (!sig)
779 return -ENOMEM;
780 atomic_set(&sig->count, 1);
781 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
782 return 0;
783}
784
785void __cleanup_sighand(struct sighand_struct *sighand)
786{
787 if (atomic_dec_and_test(&sighand->count))
788 kmem_cache_free(sighand_cachep, sighand);
789}
790
791
792/*
793 * Initialize POSIX timer handling for a thread group.
794 */
795static void posix_cpu_timers_init_group(struct signal_struct *sig)
796{
797 /* Thread group counters. */
798 thread_group_cputime_init(sig);
799
800 /* Expiration times and increments. */
801 sig->it_virt_expires = cputime_zero;
802 sig->it_virt_incr = cputime_zero;
803 sig->it_prof_expires = cputime_zero;
804 sig->it_prof_incr = cputime_zero;
805
806 /* Cached expiration times. */
807 sig->cputime_expires.prof_exp = cputime_zero;
808 sig->cputime_expires.virt_exp = cputime_zero;
809 sig->cputime_expires.sched_exp = 0;
810
811 /* The timer lists. */
812 INIT_LIST_HEAD(&sig->cpu_timers[0]);
813 INIT_LIST_HEAD(&sig->cpu_timers[1]);
814 INIT_LIST_HEAD(&sig->cpu_timers[2]);
815}
816
817static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
818{
819 struct signal_struct *sig;
820
821 if (clone_flags & CLONE_THREAD) {
822 atomic_inc(&current->signal->count);
823 atomic_inc(&current->signal->live);
824 return 0;
825 }
826 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
827
828 if (sig)
829 posix_cpu_timers_init_group(sig);
830
831 tsk->signal = sig;
832 if (!sig)
833 return -ENOMEM;
834
835 atomic_set(&sig->count, 1);
836 atomic_set(&sig->live, 1);
837 init_waitqueue_head(&sig->wait_chldexit);
838 sig->flags = 0;
839 sig->group_exit_code = 0;
840 sig->group_exit_task = NULL;
841 sig->group_stop_count = 0;
842 sig->curr_target = tsk;
843 init_sigpending(&sig->shared_pending);
844 INIT_LIST_HEAD(&sig->posix_timers);
845
846 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
847 sig->it_real_incr.tv64 = 0;
848 sig->real_timer.function = it_real_fn;
849
850 sig->leader = 0; /* session leadership doesn't inherit */
851 sig->tty_old_pgrp = NULL;
852 sig->tty = NULL;
853
854 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
855 sig->gtime = cputime_zero;
856 sig->cgtime = cputime_zero;
857 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
858 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
859 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
860 task_io_accounting_init(&sig->ioac);
861 sig->sum_sched_runtime = 0;
862 taskstats_tgid_init(sig);
863
864 task_lock(current->group_leader);
865 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
866 task_unlock(current->group_leader);
867
868 acct_init_pacct(&sig->pacct);
869
870 tty_audit_fork(sig);
871
872 return 0;
873}
874
875void __cleanup_signal(struct signal_struct *sig)
876{
877 thread_group_cputime_free(sig);
878 tty_kref_put(sig->tty);
879 kmem_cache_free(signal_cachep, sig);
880}
881
882static void cleanup_signal(struct task_struct *tsk)
883{
884 struct signal_struct *sig = tsk->signal;
885
886 atomic_dec(&sig->live);
887
888 if (atomic_dec_and_test(&sig->count))
889 __cleanup_signal(sig);
890}
891
892static void copy_flags(unsigned long clone_flags, struct task_struct *p)
893{
894 unsigned long new_flags = p->flags;
895
896 new_flags &= ~PF_SUPERPRIV;
897 new_flags |= PF_FORKNOEXEC;
898 new_flags |= PF_STARTING;
899 p->flags = new_flags;
900 clear_freeze_flag(p);
901}
902
903SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
904{
905 current->clear_child_tid = tidptr;
906
907 return task_pid_vnr(current);
908}
909
910static void rt_mutex_init_task(struct task_struct *p)
911{
912 spin_lock_init(&p->pi_lock);
913#ifdef CONFIG_RT_MUTEXES
914 plist_head_init(&p->pi_waiters, &p->pi_lock);
915 p->pi_blocked_on = NULL;
916#endif
917}
918
919#ifdef CONFIG_MM_OWNER
920void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
921{
922 mm->owner = p;
923}
924#endif /* CONFIG_MM_OWNER */
925
926/*
927 * Initialize POSIX timer handling for a single task.
928 */
929static void posix_cpu_timers_init(struct task_struct *tsk)
930{
931 tsk->cputime_expires.prof_exp = cputime_zero;
932 tsk->cputime_expires.virt_exp = cputime_zero;
933 tsk->cputime_expires.sched_exp = 0;
934 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
935 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
936 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
937}
938
939/*
940 * This creates a new process as a copy of the old one,
941 * but does not actually start it yet.
942 *
943 * It copies the registers, and all the appropriate
944 * parts of the process environment (as per the clone
945 * flags). The actual kick-off is left to the caller.
946 */
947static struct task_struct *copy_process(unsigned long clone_flags,
948 unsigned long stack_start,
949 struct pt_regs *regs,
950 unsigned long stack_size,
951 int __user *child_tidptr,
952 struct pid *pid,
953 int trace)
954{
955 int retval;
956 struct task_struct *p;
957 int cgroup_callbacks_done = 0;
958
959 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
960 return ERR_PTR(-EINVAL);
961
962 /*
963 * Thread groups must share signals as well, and detached threads
964 * can only be started up within the thread group.
965 */
966 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
967 return ERR_PTR(-EINVAL);
968
969 /*
970 * Shared signal handlers imply shared VM. By way of the above,
971 * thread groups also imply shared VM. Blocking this case allows
972 * for various simplifications in other code.
973 */
974 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
975 return ERR_PTR(-EINVAL);
976
977 retval = security_task_create(clone_flags);
978 if (retval)
979 goto fork_out;
980
981 retval = -ENOMEM;
982 p = dup_task_struct(current);
983 if (!p)
984 goto fork_out;
985
986 rt_mutex_init_task(p);
987
988#ifdef CONFIG_PROVE_LOCKING
989 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
990 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
991#endif
992 retval = -EAGAIN;
993 if (atomic_read(&p->real_cred->user->processes) >=
994 p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
995 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
996 p->real_cred->user != INIT_USER)
997 goto bad_fork_free;
998 }
999
1000 retval = copy_creds(p, clone_flags);
1001 if (retval < 0)
1002 goto bad_fork_free;
1003
1004 /*
1005 * If multiple threads are within copy_process(), then this check
1006 * triggers too late. This doesn't hurt, the check is only there
1007 * to stop root fork bombs.
1008 */
1009 retval = -EAGAIN;
1010 if (nr_threads >= max_threads)
1011 goto bad_fork_cleanup_count;
1012
1013 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1014 goto bad_fork_cleanup_count;
1015
1016 if (p->binfmt && !try_module_get(p->binfmt->module))
1017 goto bad_fork_cleanup_put_domain;
1018
1019 p->did_exec = 0;
1020 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1021 copy_flags(clone_flags, p);
1022 INIT_LIST_HEAD(&p->children);
1023 INIT_LIST_HEAD(&p->sibling);
1024#ifdef CONFIG_PREEMPT_RCU
1025 p->rcu_read_lock_nesting = 0;
1026 p->rcu_flipctr_idx = 0;
1027#endif /* #ifdef CONFIG_PREEMPT_RCU */
1028 p->vfork_done = NULL;
1029 spin_lock_init(&p->alloc_lock);
1030
1031 clear_tsk_thread_flag(p, TIF_SIGPENDING);
1032 init_sigpending(&p->pending);
1033
1034 p->utime = cputime_zero;
1035 p->stime = cputime_zero;
1036 p->gtime = cputime_zero;
1037 p->utimescaled = cputime_zero;
1038 p->stimescaled = cputime_zero;
1039 p->prev_utime = cputime_zero;
1040 p->prev_stime = cputime_zero;
1041
1042 p->default_timer_slack_ns = current->timer_slack_ns;
1043
1044#ifdef CONFIG_DETECT_SOFTLOCKUP
1045 p->last_switch_count = 0;
1046 p->last_switch_timestamp = 0;
1047#endif
1048
1049 task_io_accounting_init(&p->ioac);
1050 acct_clear_integrals(p);
1051
1052 posix_cpu_timers_init(p);
1053
1054 p->lock_depth = -1; /* -1 = no lock */
1055 do_posix_clock_monotonic_gettime(&p->start_time);
1056 p->real_start_time = p->start_time;
1057 monotonic_to_bootbased(&p->real_start_time);
1058 p->io_context = NULL;
1059 p->audit_context = NULL;
1060 cgroup_fork(p);
1061#ifdef CONFIG_NUMA
1062 p->mempolicy = mpol_dup(p->mempolicy);
1063 if (IS_ERR(p->mempolicy)) {
1064 retval = PTR_ERR(p->mempolicy);
1065 p->mempolicy = NULL;
1066 goto bad_fork_cleanup_cgroup;
1067 }
1068 mpol_fix_fork_child_flag(p);
1069#endif
1070#ifdef CONFIG_TRACE_IRQFLAGS
1071 p->irq_events = 0;
1072#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1073 p->hardirqs_enabled = 1;
1074#else
1075 p->hardirqs_enabled = 0;
1076#endif
1077 p->hardirq_enable_ip = 0;
1078 p->hardirq_enable_event = 0;
1079 p->hardirq_disable_ip = _THIS_IP_;
1080 p->hardirq_disable_event = 0;
1081 p->softirqs_enabled = 1;
1082 p->softirq_enable_ip = _THIS_IP_;
1083 p->softirq_enable_event = 0;
1084 p->softirq_disable_ip = 0;
1085 p->softirq_disable_event = 0;
1086 p->hardirq_context = 0;
1087 p->softirq_context = 0;
1088#endif
1089#ifdef CONFIG_LOCKDEP
1090 p->lockdep_depth = 0; /* no locks held yet */
1091 p->curr_chain_key = 0;
1092 p->lockdep_recursion = 0;
1093#endif
1094
1095#ifdef CONFIG_DEBUG_MUTEXES
1096 p->blocked_on = NULL; /* not blocked yet */
1097#endif
1098 if (unlikely(current->ptrace))
1099 ptrace_fork(p, clone_flags);
1100
1101 /* Perform scheduler related setup. Assign this task to a CPU. */
1102 sched_fork(p, clone_flags);
1103
1104 if ((retval = audit_alloc(p)))
1105 goto bad_fork_cleanup_policy;
1106 /* copy all the process information */
1107 if ((retval = copy_semundo(clone_flags, p)))
1108 goto bad_fork_cleanup_audit;
1109 if ((retval = copy_files(clone_flags, p)))
1110 goto bad_fork_cleanup_semundo;
1111 if ((retval = copy_fs(clone_flags, p)))
1112 goto bad_fork_cleanup_files;
1113 if ((retval = copy_sighand(clone_flags, p)))
1114 goto bad_fork_cleanup_fs;
1115 if ((retval = copy_signal(clone_flags, p)))
1116 goto bad_fork_cleanup_sighand;
1117 if ((retval = copy_mm(clone_flags, p)))
1118 goto bad_fork_cleanup_signal;
1119 if ((retval = copy_namespaces(clone_flags, p)))
1120 goto bad_fork_cleanup_mm;
1121 if ((retval = copy_io(clone_flags, p)))
1122 goto bad_fork_cleanup_namespaces;
1123 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1124 if (retval)
1125 goto bad_fork_cleanup_io;
1126
1127 if (pid != &init_struct_pid) {
1128 retval = -ENOMEM;
1129 pid = alloc_pid(p->nsproxy->pid_ns);
1130 if (!pid)
1131 goto bad_fork_cleanup_io;
1132
1133 if (clone_flags & CLONE_NEWPID) {
1134 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1135 if (retval < 0)
1136 goto bad_fork_free_pid;
1137 }
1138 }
1139
1140 ftrace_graph_init_task(p);
1141
1142 p->pid = pid_nr(pid);
1143 p->tgid = p->pid;
1144 if (clone_flags & CLONE_THREAD)
1145 p->tgid = current->tgid;
1146
1147 if (current->nsproxy != p->nsproxy) {
1148 retval = ns_cgroup_clone(p, pid);
1149 if (retval)
1150 goto bad_fork_free_graph;
1151 }
1152
1153 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1154 /*
1155 * Clear TID on mm_release()?
1156 */
1157 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1158#ifdef CONFIG_FUTEX
1159 p->robust_list = NULL;
1160#ifdef CONFIG_COMPAT
1161 p->compat_robust_list = NULL;
1162#endif
1163 INIT_LIST_HEAD(&p->pi_state_list);
1164 p->pi_state_cache = NULL;
1165#endif
1166 /*
1167 * sigaltstack should be cleared when sharing the same VM
1168 */
1169 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1170 p->sas_ss_sp = p->sas_ss_size = 0;
1171
1172 /*
1173 * Syscall tracing should be turned off in the child regardless
1174 * of CLONE_PTRACE.
1175 */
1176 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1177#ifdef TIF_SYSCALL_EMU
1178 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1179#endif
1180 clear_all_latency_tracing(p);
1181
1182 /* Our parent execution domain becomes current domain
1183 These must match for thread signalling to apply */
1184 p->parent_exec_id = p->self_exec_id;
1185
1186 /* ok, now we should be set up.. */
1187 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1188 p->pdeath_signal = 0;
1189 p->exit_state = 0;
1190
1191 /*
1192 * Ok, make it visible to the rest of the system.
1193 * We dont wake it up yet.
1194 */
1195 p->group_leader = p;
1196 INIT_LIST_HEAD(&p->thread_group);
1197
1198 /* Now that the task is set up, run cgroup callbacks if
1199 * necessary. We need to run them before the task is visible
1200 * on the tasklist. */
1201 cgroup_fork_callbacks(p);
1202 cgroup_callbacks_done = 1;
1203
1204 /* Need tasklist lock for parent etc handling! */
1205 write_lock_irq(&tasklist_lock);
1206
1207 /*
1208 * The task hasn't been attached yet, so its cpus_allowed mask will
1209 * not be changed, nor will its assigned CPU.
1210 *
1211 * The cpus_allowed mask of the parent may have changed after it was
1212 * copied first time - so re-copy it here, then check the child's CPU
1213 * to ensure it is on a valid CPU (and if not, just force it back to
1214 * parent's CPU). This avoids alot of nasty races.
1215 */
1216 p->cpus_allowed = current->cpus_allowed;
1217 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1218 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1219 !cpu_online(task_cpu(p))))
1220 set_task_cpu(p, smp_processor_id());
1221
1222 /* CLONE_PARENT re-uses the old parent */
1223 if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1224 p->real_parent = current->real_parent;
1225 else
1226 p->real_parent = current;
1227
1228 spin_lock(&current->sighand->siglock);
1229
1230 /*
1231 * Process group and session signals need to be delivered to just the
1232 * parent before the fork or both the parent and the child after the
1233 * fork. Restart if a signal comes in before we add the new process to
1234 * it's process group.
1235 * A fatal signal pending means that current will exit, so the new
1236 * thread can't slip out of an OOM kill (or normal SIGKILL).
1237 */
1238 recalc_sigpending();
1239 if (signal_pending(current)) {
1240 spin_unlock(&current->sighand->siglock);
1241 write_unlock_irq(&tasklist_lock);
1242 retval = -ERESTARTNOINTR;
1243 goto bad_fork_free_graph;
1244 }
1245
1246 if (clone_flags & CLONE_THREAD) {
1247 p->group_leader = current->group_leader;
1248 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1249 }
1250
1251 if (likely(p->pid)) {
1252 list_add_tail(&p->sibling, &p->real_parent->children);
1253 tracehook_finish_clone(p, clone_flags, trace);
1254
1255 if (thread_group_leader(p)) {
1256 if (clone_flags & CLONE_NEWPID)
1257 p->nsproxy->pid_ns->child_reaper = p;
1258
1259 p->signal->leader_pid = pid;
1260 tty_kref_put(p->signal->tty);
1261 p->signal->tty = tty_kref_get(current->signal->tty);
1262 set_task_pgrp(p, task_pgrp_nr(current));
1263 set_task_session(p, task_session_nr(current));
1264 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1265 attach_pid(p, PIDTYPE_SID, task_session(current));
1266 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1267 __get_cpu_var(process_counts)++;
1268 }
1269 attach_pid(p, PIDTYPE_PID, pid);
1270 nr_threads++;
1271 }
1272
1273 total_forks++;
1274 spin_unlock(&current->sighand->siglock);
1275 write_unlock_irq(&tasklist_lock);
1276 proc_fork_connector(p);
1277 cgroup_post_fork(p);
1278 return p;
1279
1280bad_fork_free_graph:
1281 ftrace_graph_exit_task(p);
1282bad_fork_free_pid:
1283 if (pid != &init_struct_pid)
1284 free_pid(pid);
1285bad_fork_cleanup_io:
1286 put_io_context(p->io_context);
1287bad_fork_cleanup_namespaces:
1288 exit_task_namespaces(p);
1289bad_fork_cleanup_mm:
1290 if (p->mm)
1291 mmput(p->mm);
1292bad_fork_cleanup_signal:
1293 cleanup_signal(p);
1294bad_fork_cleanup_sighand:
1295 __cleanup_sighand(p->sighand);
1296bad_fork_cleanup_fs:
1297 exit_fs(p); /* blocking */
1298bad_fork_cleanup_files:
1299 exit_files(p); /* blocking */
1300bad_fork_cleanup_semundo:
1301 exit_sem(p);
1302bad_fork_cleanup_audit:
1303 audit_free(p);
1304bad_fork_cleanup_policy:
1305#ifdef CONFIG_NUMA
1306 mpol_put(p->mempolicy);
1307bad_fork_cleanup_cgroup:
1308#endif
1309 cgroup_exit(p, cgroup_callbacks_done);
1310 delayacct_tsk_free(p);
1311 if (p->binfmt)
1312 module_put(p->binfmt->module);
1313bad_fork_cleanup_put_domain:
1314 module_put(task_thread_info(p)->exec_domain->module);
1315bad_fork_cleanup_count:
1316 atomic_dec(&p->cred->user->processes);
1317 put_cred(p->real_cred);
1318 put_cred(p->cred);
1319bad_fork_free:
1320 free_task(p);
1321fork_out:
1322 return ERR_PTR(retval);
1323}
1324
1325noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1326{
1327 memset(regs, 0, sizeof(struct pt_regs));
1328 return regs;
1329}
1330
1331struct task_struct * __cpuinit fork_idle(int cpu)
1332{
1333 struct task_struct *task;
1334 struct pt_regs regs;
1335
1336 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1337 &init_struct_pid, 0);
1338 if (!IS_ERR(task))
1339 init_idle(task, cpu);
1340
1341 return task;
1342}
1343
1344/*
1345 * Ok, this is the main fork-routine.
1346 *
1347 * It copies the process, and if successful kick-starts
1348 * it and waits for it to finish using the VM if required.
1349 */
1350long do_fork(unsigned long clone_flags,
1351 unsigned long stack_start,
1352 struct pt_regs *regs,
1353 unsigned long stack_size,
1354 int __user *parent_tidptr,
1355 int __user *child_tidptr)
1356{
1357 struct task_struct *p;
1358 int trace = 0;
1359 long nr;
1360
1361 /*
1362 * Do some preliminary argument and permissions checking before we
1363 * actually start allocating stuff
1364 */
1365 if (clone_flags & CLONE_NEWUSER) {
1366 if (clone_flags & CLONE_THREAD)
1367 return -EINVAL;
1368 /* hopefully this check will go away when userns support is
1369 * complete
1370 */
1371 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1372 !capable(CAP_SETGID))
1373 return -EPERM;
1374 }
1375
1376 /*
1377 * We hope to recycle these flags after 2.6.26
1378 */
1379 if (unlikely(clone_flags & CLONE_STOPPED)) {
1380 static int __read_mostly count = 100;
1381
1382 if (count > 0 && printk_ratelimit()) {
1383 char comm[TASK_COMM_LEN];
1384
1385 count--;
1386 printk(KERN_INFO "fork(): process `%s' used deprecated "
1387 "clone flags 0x%lx\n",
1388 get_task_comm(comm, current),
1389 clone_flags & CLONE_STOPPED);
1390 }
1391 }
1392
1393 /*
1394 * When called from kernel_thread, don't do user tracing stuff.
1395 */
1396 if (likely(user_mode(regs)))
1397 trace = tracehook_prepare_clone(clone_flags);
1398
1399 p = copy_process(clone_flags, stack_start, regs, stack_size,
1400 child_tidptr, NULL, trace);
1401 /*
1402 * Do this prior waking up the new thread - the thread pointer
1403 * might get invalid after that point, if the thread exits quickly.
1404 */
1405 if (!IS_ERR(p)) {
1406 struct completion vfork;
1407
1408 trace_sched_process_fork(current, p);
1409
1410 nr = task_pid_vnr(p);
1411
1412 if (clone_flags & CLONE_PARENT_SETTID)
1413 put_user(nr, parent_tidptr);
1414
1415 if (clone_flags & CLONE_VFORK) {
1416 p->vfork_done = &vfork;
1417 init_completion(&vfork);
1418 }
1419
1420 audit_finish_fork(p);
1421 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1422
1423 /*
1424 * We set PF_STARTING at creation in case tracing wants to
1425 * use this to distinguish a fully live task from one that
1426 * hasn't gotten to tracehook_report_clone() yet. Now we
1427 * clear it and set the child going.
1428 */
1429 p->flags &= ~PF_STARTING;
1430
1431 if (unlikely(clone_flags & CLONE_STOPPED)) {
1432 /*
1433 * We'll start up with an immediate SIGSTOP.
1434 */
1435 sigaddset(&p->pending.signal, SIGSTOP);
1436 set_tsk_thread_flag(p, TIF_SIGPENDING);
1437 __set_task_state(p, TASK_STOPPED);
1438 } else {
1439 wake_up_new_task(p, clone_flags);
1440 }
1441
1442 tracehook_report_clone_complete(trace, regs,
1443 clone_flags, nr, p);
1444
1445 if (clone_flags & CLONE_VFORK) {
1446 freezer_do_not_count();
1447 wait_for_completion(&vfork);
1448 freezer_count();
1449 tracehook_report_vfork_done(p, nr);
1450 }
1451 } else {
1452 nr = PTR_ERR(p);
1453 }
1454 return nr;
1455}
1456
1457#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1458#define ARCH_MIN_MMSTRUCT_ALIGN 0
1459#endif
1460
1461static void sighand_ctor(void *data)
1462{
1463 struct sighand_struct *sighand = data;
1464
1465 spin_lock_init(&sighand->siglock);
1466 init_waitqueue_head(&sighand->signalfd_wqh);
1467}
1468
1469void __init proc_caches_init(void)
1470{
1471 sighand_cachep = kmem_cache_create("sighand_cache",
1472 sizeof(struct sighand_struct), 0,
1473 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1474 sighand_ctor);
1475 signal_cachep = kmem_cache_create("signal_cache",
1476 sizeof(struct signal_struct), 0,
1477 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1478 files_cachep = kmem_cache_create("files_cache",
1479 sizeof(struct files_struct), 0,
1480 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1481 fs_cachep = kmem_cache_create("fs_cache",
1482 sizeof(struct fs_struct), 0,
1483 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1484 mm_cachep = kmem_cache_create("mm_struct",
1485 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1486 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1487 mmap_init();
1488}
1489
1490/*
1491 * Check constraints on flags passed to the unshare system call and
1492 * force unsharing of additional process context as appropriate.
1493 */
1494static void check_unshare_flags(unsigned long *flags_ptr)
1495{
1496 /*
1497 * If unsharing a thread from a thread group, must also
1498 * unshare vm.
1499 */
1500 if (*flags_ptr & CLONE_THREAD)
1501 *flags_ptr |= CLONE_VM;
1502
1503 /*
1504 * If unsharing vm, must also unshare signal handlers.
1505 */
1506 if (*flags_ptr & CLONE_VM)
1507 *flags_ptr |= CLONE_SIGHAND;
1508
1509 /*
1510 * If unsharing signal handlers and the task was created
1511 * using CLONE_THREAD, then must unshare the thread
1512 */
1513 if ((*flags_ptr & CLONE_SIGHAND) &&
1514 (atomic_read(&current->signal->count) > 1))
1515 *flags_ptr |= CLONE_THREAD;
1516
1517 /*
1518 * If unsharing namespace, must also unshare filesystem information.
1519 */
1520 if (*flags_ptr & CLONE_NEWNS)
1521 *flags_ptr |= CLONE_FS;
1522}
1523
1524/*
1525 * Unsharing of tasks created with CLONE_THREAD is not supported yet
1526 */
1527static int unshare_thread(unsigned long unshare_flags)
1528{
1529 if (unshare_flags & CLONE_THREAD)
1530 return -EINVAL;
1531
1532 return 0;
1533}
1534
1535/*
1536 * Unshare the filesystem structure if it is being shared
1537 */
1538static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1539{
1540 struct fs_struct *fs = current->fs;
1541
1542 if ((unshare_flags & CLONE_FS) &&
1543 (fs && atomic_read(&fs->count) > 1)) {
1544 *new_fsp = __copy_fs_struct(current->fs);
1545 if (!*new_fsp)
1546 return -ENOMEM;
1547 }
1548
1549 return 0;
1550}
1551
1552/*
1553 * Unsharing of sighand is not supported yet
1554 */
1555static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1556{
1557 struct sighand_struct *sigh = current->sighand;
1558
1559 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1560 return -EINVAL;
1561 else
1562 return 0;
1563}
1564
1565/*
1566 * Unshare vm if it is being shared
1567 */
1568static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1569{
1570 struct mm_struct *mm = current->mm;
1571
1572 if ((unshare_flags & CLONE_VM) &&
1573 (mm && atomic_read(&mm->mm_users) > 1)) {
1574 return -EINVAL;
1575 }
1576
1577 return 0;
1578}
1579
1580/*
1581 * Unshare file descriptor table if it is being shared
1582 */
1583static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1584{
1585 struct files_struct *fd = current->files;
1586 int error = 0;
1587
1588 if ((unshare_flags & CLONE_FILES) &&
1589 (fd && atomic_read(&fd->count) > 1)) {
1590 *new_fdp = dup_fd(fd, &error);
1591 if (!*new_fdp)
1592 return error;
1593 }
1594
1595 return 0;
1596}
1597
1598/*
1599 * unshare allows a process to 'unshare' part of the process
1600 * context which was originally shared using clone. copy_*
1601 * functions used by do_fork() cannot be used here directly
1602 * because they modify an inactive task_struct that is being
1603 * constructed. Here we are modifying the current, active,
1604 * task_struct.
1605 */
1606SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1607{
1608 int err = 0;
1609 struct fs_struct *fs, *new_fs = NULL;
1610 struct sighand_struct *new_sigh = NULL;
1611 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1612 struct files_struct *fd, *new_fd = NULL;
1613 struct nsproxy *new_nsproxy = NULL;
1614 int do_sysvsem = 0;
1615
1616 check_unshare_flags(&unshare_flags);
1617
1618 /* Return -EINVAL for all unsupported flags */
1619 err = -EINVAL;
1620 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1621 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1622 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1623 goto bad_unshare_out;
1624
1625 /*
1626 * CLONE_NEWIPC must also detach from the undolist: after switching
1627 * to a new ipc namespace, the semaphore arrays from the old
1628 * namespace are unreachable.
1629 */
1630 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1631 do_sysvsem = 1;
1632 if ((err = unshare_thread(unshare_flags)))
1633 goto bad_unshare_out;
1634 if ((err = unshare_fs(unshare_flags, &new_fs)))
1635 goto bad_unshare_cleanup_thread;
1636 if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1637 goto bad_unshare_cleanup_fs;
1638 if ((err = unshare_vm(unshare_flags, &new_mm)))
1639 goto bad_unshare_cleanup_sigh;
1640 if ((err = unshare_fd(unshare_flags, &new_fd)))
1641 goto bad_unshare_cleanup_vm;
1642 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1643 new_fs)))
1644 goto bad_unshare_cleanup_fd;
1645
1646 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) {
1647 if (do_sysvsem) {
1648 /*
1649 * CLONE_SYSVSEM is equivalent to sys_exit().
1650 */
1651 exit_sem(current);
1652 }
1653
1654 if (new_nsproxy) {
1655 switch_task_namespaces(current, new_nsproxy);
1656 new_nsproxy = NULL;
1657 }
1658
1659 task_lock(current);
1660
1661 if (new_fs) {
1662 fs = current->fs;
1663 current->fs = new_fs;
1664 new_fs = fs;
1665 }
1666
1667 if (new_mm) {
1668 mm = current->mm;
1669 active_mm = current->active_mm;
1670 current->mm = new_mm;
1671 current->active_mm = new_mm;
1672 activate_mm(active_mm, new_mm);
1673 new_mm = mm;
1674 }
1675
1676 if (new_fd) {
1677 fd = current->files;
1678 current->files = new_fd;
1679 new_fd = fd;
1680 }
1681
1682 task_unlock(current);
1683 }
1684
1685 if (new_nsproxy)
1686 put_nsproxy(new_nsproxy);
1687
1688bad_unshare_cleanup_fd:
1689 if (new_fd)
1690 put_files_struct(new_fd);
1691
1692bad_unshare_cleanup_vm:
1693 if (new_mm)
1694 mmput(new_mm);
1695
1696bad_unshare_cleanup_sigh:
1697 if (new_sigh)
1698 if (atomic_dec_and_test(&new_sigh->count))
1699 kmem_cache_free(sighand_cachep, new_sigh);
1700
1701bad_unshare_cleanup_fs:
1702 if (new_fs)
1703 put_fs_struct(new_fs);
1704
1705bad_unshare_cleanup_thread:
1706bad_unshare_out:
1707 return err;
1708}
1709
1710/*
1711 * Helper to unshare the files of the current task.
1712 * We don't want to expose copy_files internals to
1713 * the exec layer of the kernel.
1714 */
1715
1716int unshare_files(struct files_struct **displaced)
1717{
1718 struct task_struct *task = current;
1719 struct files_struct *copy = NULL;
1720 int error;
1721
1722 error = unshare_fd(CLONE_FILES, &copy);
1723 if (error || !copy) {
1724 *displaced = NULL;
1725 return error;
1726 }
1727 *displaced = task->files;
1728 task_lock(task);
1729 task->files = copy;
1730 task_unlock(task);
1731 return 0;
1732}