projects/linux·blob v3.3-rc2 · refs

1774 lines · 42.2 KiB

1/*
2 * linux/kernel/fork.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * 'fork.c' contains the help-routines for the 'fork' system call
9 * (see also entry.S and others).
10 * Fork is rather simple, once you get the hang of it, but the memory
11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12 */
13
14#include <linux/slab.h>
15#include <linux/init.h>
16#include <linux/unistd.h>
17#include <linux/module.h>
18#include <linux/vmalloc.h>
19#include <linux/completion.h>
20#include <linux/personality.h>
21#include <linux/mempolicy.h>
22#include <linux/sem.h>
23#include <linux/file.h>
24#include <linux/fdtable.h>
25#include <linux/iocontext.h>
26#include <linux/key.h>
27#include <linux/binfmts.h>
28#include <linux/mman.h>
29#include <linux/mmu_notifier.h>
30#include <linux/fs.h>
31#include <linux/nsproxy.h>
32#include <linux/capability.h>
33#include <linux/cpu.h>
34#include <linux/cgroup.h>
35#include <linux/security.h>
36#include <linux/hugetlb.h>
37#include <linux/swap.h>
38#include <linux/syscalls.h>
39#include <linux/jiffies.h>
40#include <linux/futex.h>
41#include <linux/compat.h>
42#include <linux/kthread.h>
43#include <linux/task_io_accounting_ops.h>
44#include <linux/rcupdate.h>
45#include <linux/ptrace.h>
46#include <linux/mount.h>
47#include <linux/audit.h>
48#include <linux/memcontrol.h>
49#include <linux/ftrace.h>
50#include <linux/profile.h>
51#include <linux/rmap.h>
52#include <linux/ksm.h>
53#include <linux/acct.h>
54#include <linux/tsacct_kern.h>
55#include <linux/cn_proc.h>
56#include <linux/freezer.h>
57#include <linux/delayacct.h>
58#include <linux/taskstats_kern.h>
59#include <linux/random.h>
60#include <linux/tty.h>
61#include <linux/blkdev.h>
62#include <linux/fs_struct.h>
63#include <linux/magic.h>
64#include <linux/perf_event.h>
65#include <linux/posix-timers.h>
66#include <linux/user-return-notifier.h>
67#include <linux/oom.h>
68#include <linux/khugepaged.h>
69
70#include <asm/pgtable.h>
71#include <asm/pgalloc.h>
72#include <asm/uaccess.h>
73#include <asm/mmu_context.h>
74#include <asm/cacheflush.h>
75#include <asm/tlbflush.h>
76
77#include <trace/events/sched.h>
78
79#define CREATE_TRACE_POINTS
80#include <trace/events/task.h>
81
82/*
83 * Protected counters by write_lock_irq(&tasklist_lock)
84 */
85unsigned long total_forks; /* Handle normal Linux uptimes. */
86int nr_threads; /* The idle threads do not count.. */
87
88int max_threads; /* tunable limit on nr_threads */
89
90DEFINE_PER_CPU(unsigned long, process_counts) = 0;
91
92__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
93
94#ifdef CONFIG_PROVE_RCU
95int lockdep_tasklist_lock_is_held(void)
96{
97 return lockdep_is_held(&tasklist_lock);
98}
99EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
100#endif /* #ifdef CONFIG_PROVE_RCU */
101
102int nr_processes(void)
103{
104 int cpu;
105 int total = 0;
106
107 for_each_possible_cpu(cpu)
108 total += per_cpu(process_counts, cpu);
109
110 return total;
111}
112
113#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
114# define alloc_task_struct_node(node) \
115 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
116# define free_task_struct(tsk) \
117 kmem_cache_free(task_struct_cachep, (tsk))
118static struct kmem_cache *task_struct_cachep;
119#endif
120
121#ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
122static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
123 int node)
124{
125#ifdef CONFIG_DEBUG_STACK_USAGE
126 gfp_t mask = GFP_KERNEL | __GFP_ZERO;
127#else
128 gfp_t mask = GFP_KERNEL;
129#endif
130 struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
131
132 return page ? page_address(page) : NULL;
133}
134
135static inline void free_thread_info(struct thread_info *ti)
136{
137 free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
138}
139#endif
140
141/* SLAB cache for signal_struct structures (tsk->signal) */
142static struct kmem_cache *signal_cachep;
143
144/* SLAB cache for sighand_struct structures (tsk->sighand) */
145struct kmem_cache *sighand_cachep;
146
147/* SLAB cache for files_struct structures (tsk->files) */
148struct kmem_cache *files_cachep;
149
150/* SLAB cache for fs_struct structures (tsk->fs) */
151struct kmem_cache *fs_cachep;
152
153/* SLAB cache for vm_area_struct structures */
154struct kmem_cache *vm_area_cachep;
155
156/* SLAB cache for mm_struct structures (tsk->mm) */
157static struct kmem_cache *mm_cachep;
158
159static void account_kernel_stack(struct thread_info *ti, int account)
160{
161 struct zone *zone = page_zone(virt_to_page(ti));
162
163 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
164}
165
166void free_task(struct task_struct *tsk)
167{
168 account_kernel_stack(tsk->stack, -1);
169 free_thread_info(tsk->stack);
170 rt_mutex_debug_task_free(tsk);
171 ftrace_graph_exit_task(tsk);
172 free_task_struct(tsk);
173}
174EXPORT_SYMBOL(free_task);
175
176static inline void free_signal_struct(struct signal_struct *sig)
177{
178 taskstats_tgid_free(sig);
179 sched_autogroup_exit(sig);
180 kmem_cache_free(signal_cachep, sig);
181}
182
183static inline void put_signal_struct(struct signal_struct *sig)
184{
185 if (atomic_dec_and_test(&sig->sigcnt))
186 free_signal_struct(sig);
187}
188
189void __put_task_struct(struct task_struct *tsk)
190{
191 WARN_ON(!tsk->exit_state);
192 WARN_ON(atomic_read(&tsk->usage));
193 WARN_ON(tsk == current);
194
195 exit_creds(tsk);
196 delayacct_tsk_free(tsk);
197 put_signal_struct(tsk->signal);
198
199 if (!profile_handoff_task(tsk))
200 free_task(tsk);
201}
202EXPORT_SYMBOL_GPL(__put_task_struct);
203
204/*
205 * macro override instead of weak attribute alias, to workaround
206 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
207 */
208#ifndef arch_task_cache_init
209#define arch_task_cache_init()
210#endif
211
212void __init fork_init(unsigned long mempages)
213{
214#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
215#ifndef ARCH_MIN_TASKALIGN
216#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
217#endif
218 /* create a slab on which task_structs can be allocated */
219 task_struct_cachep =
220 kmem_cache_create("task_struct", sizeof(struct task_struct),
221 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
222#endif
223
224 /* do the arch specific task caches init */
225 arch_task_cache_init();
226
227 /*
228 * The default maximum number of threads is set to a safe
229 * value: the thread structures can take up at most half
230 * of memory.
231 */
232 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
233
234 /*
235 * we need to allow at least 20 threads to boot a system
236 */
237 if (max_threads < 20)
238 max_threads = 20;
239
240 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
241 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
242 init_task.signal->rlim[RLIMIT_SIGPENDING] =
243 init_task.signal->rlim[RLIMIT_NPROC];
244}
245
246int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
247 struct task_struct *src)
248{
249 *dst = *src;
250 return 0;
251}
252
253static struct task_struct *dup_task_struct(struct task_struct *orig)
254{
255 struct task_struct *tsk;
256 struct thread_info *ti;
257 unsigned long *stackend;
258 int node = tsk_fork_get_node(orig);
259 int err;
260
261 prepare_to_copy(orig);
262
263 tsk = alloc_task_struct_node(node);
264 if (!tsk)
265 return NULL;
266
267 ti = alloc_thread_info_node(tsk, node);
268 if (!ti) {
269 free_task_struct(tsk);
270 return NULL;
271 }
272
273 err = arch_dup_task_struct(tsk, orig);
274 if (err)
275 goto out;
276
277 tsk->stack = ti;
278
279 setup_thread_stack(tsk, orig);
280 clear_user_return_notifier(tsk);
281 clear_tsk_need_resched(tsk);
282 stackend = end_of_stack(tsk);
283 *stackend = STACK_END_MAGIC; /* for overflow detection */
284
285#ifdef CONFIG_CC_STACKPROTECTOR
286 tsk->stack_canary = get_random_int();
287#endif
288
289 /*
290 * One for us, one for whoever does the "release_task()" (usually
291 * parent)
292 */
293 atomic_set(&tsk->usage, 2);
294#ifdef CONFIG_BLK_DEV_IO_TRACE
295 tsk->btrace_seq = 0;
296#endif
297 tsk->splice_pipe = NULL;
298
299 account_kernel_stack(ti, 1);
300
301 return tsk;
302
303out:
304 free_thread_info(ti);
305 free_task_struct(tsk);
306 return NULL;
307}
308
309#ifdef CONFIG_MMU
310static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
311{
312 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
313 struct rb_node **rb_link, *rb_parent;
314 int retval;
315 unsigned long charge;
316 struct mempolicy *pol;
317
318 down_write(&oldmm->mmap_sem);
319 flush_cache_dup_mm(oldmm);
320 /*
321 * Not linked in yet - no deadlock potential:
322 */
323 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
324
325 mm->locked_vm = 0;
326 mm->mmap = NULL;
327 mm->mmap_cache = NULL;
328 mm->free_area_cache = oldmm->mmap_base;
329 mm->cached_hole_size = ~0UL;
330 mm->map_count = 0;
331 cpumask_clear(mm_cpumask(mm));
332 mm->mm_rb = RB_ROOT;
333 rb_link = &mm->mm_rb.rb_node;
334 rb_parent = NULL;
335 pprev = &mm->mmap;
336 retval = ksm_fork(mm, oldmm);
337 if (retval)
338 goto out;
339 retval = khugepaged_fork(mm, oldmm);
340 if (retval)
341 goto out;
342
343 prev = NULL;
344 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
345 struct file *file;
346
347 if (mpnt->vm_flags & VM_DONTCOPY) {
348 long pages = vma_pages(mpnt);
349 mm->total_vm -= pages;
350 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
351 -pages);
352 continue;
353 }
354 charge = 0;
355 if (mpnt->vm_flags & VM_ACCOUNT) {
356 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
357 if (security_vm_enough_memory(len))
358 goto fail_nomem;
359 charge = len;
360 }
361 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
362 if (!tmp)
363 goto fail_nomem;
364 *tmp = *mpnt;
365 INIT_LIST_HEAD(&tmp->anon_vma_chain);
366 pol = mpol_dup(vma_policy(mpnt));
367 retval = PTR_ERR(pol);
368 if (IS_ERR(pol))
369 goto fail_nomem_policy;
370 vma_set_policy(tmp, pol);
371 tmp->vm_mm = mm;
372 if (anon_vma_fork(tmp, mpnt))
373 goto fail_nomem_anon_vma_fork;
374 tmp->vm_flags &= ~VM_LOCKED;
375 tmp->vm_next = tmp->vm_prev = NULL;
376 file = tmp->vm_file;
377 if (file) {
378 struct inode *inode = file->f_path.dentry->d_inode;
379 struct address_space *mapping = file->f_mapping;
380
381 get_file(file);
382 if (tmp->vm_flags & VM_DENYWRITE)
383 atomic_dec(&inode->i_writecount);
384 mutex_lock(&mapping->i_mmap_mutex);
385 if (tmp->vm_flags & VM_SHARED)
386 mapping->i_mmap_writable++;
387 flush_dcache_mmap_lock(mapping);
388 /* insert tmp into the share list, just after mpnt */
389 vma_prio_tree_add(tmp, mpnt);
390 flush_dcache_mmap_unlock(mapping);
391 mutex_unlock(&mapping->i_mmap_mutex);
392 }
393
394 /*
395 * Clear hugetlb-related page reserves for children. This only
396 * affects MAP_PRIVATE mappings. Faults generated by the child
397 * are not guaranteed to succeed, even if read-only
398 */
399 if (is_vm_hugetlb_page(tmp))
400 reset_vma_resv_huge_pages(tmp);
401
402 /*
403 * Link in the new vma and copy the page table entries.
404 */
405 *pprev = tmp;
406 pprev = &tmp->vm_next;
407 tmp->vm_prev = prev;
408 prev = tmp;
409
410 __vma_link_rb(mm, tmp, rb_link, rb_parent);
411 rb_link = &tmp->vm_rb.rb_right;
412 rb_parent = &tmp->vm_rb;
413
414 mm->map_count++;
415 retval = copy_page_range(mm, oldmm, mpnt);
416
417 if (tmp->vm_ops && tmp->vm_ops->open)
418 tmp->vm_ops->open(tmp);
419
420 if (retval)
421 goto out;
422 }
423 /* a new mm has just been created */
424 arch_dup_mmap(oldmm, mm);
425 retval = 0;
426out:
427 up_write(&mm->mmap_sem);
428 flush_tlb_mm(oldmm);
429 up_write(&oldmm->mmap_sem);
430 return retval;
431fail_nomem_anon_vma_fork:
432 mpol_put(pol);
433fail_nomem_policy:
434 kmem_cache_free(vm_area_cachep, tmp);
435fail_nomem:
436 retval = -ENOMEM;
437 vm_unacct_memory(charge);
438 goto out;
439}
440
441static inline int mm_alloc_pgd(struct mm_struct *mm)
442{
443 mm->pgd = pgd_alloc(mm);
444 if (unlikely(!mm->pgd))
445 return -ENOMEM;
446 return 0;
447}
448
449static inline void mm_free_pgd(struct mm_struct *mm)
450{
451 pgd_free(mm, mm->pgd);
452}
453#else
454#define dup_mmap(mm, oldmm) (0)
455#define mm_alloc_pgd(mm) (0)
456#define mm_free_pgd(mm)
457#endif /* CONFIG_MMU */
458
459__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
460
461#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
462#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
463
464static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
465
466static int __init coredump_filter_setup(char *s)
467{
468 default_dump_filter =
469 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
470 MMF_DUMP_FILTER_MASK;
471 return 1;
472}
473
474__setup("coredump_filter=", coredump_filter_setup);
475
476#include <linux/init_task.h>
477
478static void mm_init_aio(struct mm_struct *mm)
479{
480#ifdef CONFIG_AIO
481 spin_lock_init(&mm->ioctx_lock);
482 INIT_HLIST_HEAD(&mm->ioctx_list);
483#endif
484}
485
486static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
487{
488 atomic_set(&mm->mm_users, 1);
489 atomic_set(&mm->mm_count, 1);
490 init_rwsem(&mm->mmap_sem);
491 INIT_LIST_HEAD(&mm->mmlist);
492 mm->flags = (current->mm) ?
493 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
494 mm->core_state = NULL;
495 mm->nr_ptes = 0;
496 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
497 spin_lock_init(&mm->page_table_lock);
498 mm->free_area_cache = TASK_UNMAPPED_BASE;
499 mm->cached_hole_size = ~0UL;
500 mm_init_aio(mm);
501 mm_init_owner(mm, p);
502
503 if (likely(!mm_alloc_pgd(mm))) {
504 mm->def_flags = 0;
505 mmu_notifier_mm_init(mm);
506 return mm;
507 }
508
509 free_mm(mm);
510 return NULL;
511}
512
513/*
514 * Allocate and initialize an mm_struct.
515 */
516struct mm_struct *mm_alloc(void)
517{
518 struct mm_struct *mm;
519
520 mm = allocate_mm();
521 if (!mm)
522 return NULL;
523
524 memset(mm, 0, sizeof(*mm));
525 mm_init_cpumask(mm);
526 return mm_init(mm, current);
527}
528
529/*
530 * Called when the last reference to the mm
531 * is dropped: either by a lazy thread or by
532 * mmput. Free the page directory and the mm.
533 */
534void __mmdrop(struct mm_struct *mm)
535{
536 BUG_ON(mm == &init_mm);
537 mm_free_pgd(mm);
538 destroy_context(mm);
539 mmu_notifier_mm_destroy(mm);
540#ifdef CONFIG_TRANSPARENT_HUGEPAGE
541 VM_BUG_ON(mm->pmd_huge_pte);
542#endif
543 free_mm(mm);
544}
545EXPORT_SYMBOL_GPL(__mmdrop);
546
547/*
548 * Decrement the use count and release all resources for an mm.
549 */
550void mmput(struct mm_struct *mm)
551{
552 might_sleep();
553
554 if (atomic_dec_and_test(&mm->mm_users)) {
555 exit_aio(mm);
556 ksm_exit(mm);
557 khugepaged_exit(mm); /* must run before exit_mmap */
558 exit_mmap(mm);
559 set_mm_exe_file(mm, NULL);
560 if (!list_empty(&mm->mmlist)) {
561 spin_lock(&mmlist_lock);
562 list_del(&mm->mmlist);
563 spin_unlock(&mmlist_lock);
564 }
565 put_swap_token(mm);
566 if (mm->binfmt)
567 module_put(mm->binfmt->module);
568 mmdrop(mm);
569 }
570}
571EXPORT_SYMBOL_GPL(mmput);
572
573/*
574 * We added or removed a vma mapping the executable. The vmas are only mapped
575 * during exec and are not mapped with the mmap system call.
576 * Callers must hold down_write() on the mm's mmap_sem for these
577 */
578void added_exe_file_vma(struct mm_struct *mm)
579{
580 mm->num_exe_file_vmas++;
581}
582
583void removed_exe_file_vma(struct mm_struct *mm)
584{
585 mm->num_exe_file_vmas--;
586 if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
587 fput(mm->exe_file);
588 mm->exe_file = NULL;
589 }
590
591}
592
593void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
594{
595 if (new_exe_file)
596 get_file(new_exe_file);
597 if (mm->exe_file)
598 fput(mm->exe_file);
599 mm->exe_file = new_exe_file;
600 mm->num_exe_file_vmas = 0;
601}
602
603struct file *get_mm_exe_file(struct mm_struct *mm)
604{
605 struct file *exe_file;
606
607 /* We need mmap_sem to protect against races with removal of
608 * VM_EXECUTABLE vmas */
609 down_read(&mm->mmap_sem);
610 exe_file = mm->exe_file;
611 if (exe_file)
612 get_file(exe_file);
613 up_read(&mm->mmap_sem);
614 return exe_file;
615}
616
617static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
618{
619 /* It's safe to write the exe_file pointer without exe_file_lock because
620 * this is called during fork when the task is not yet in /proc */
621 newmm->exe_file = get_mm_exe_file(oldmm);
622}
623
624/**
625 * get_task_mm - acquire a reference to the task's mm
626 *
627 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
628 * this kernel workthread has transiently adopted a user mm with use_mm,
629 * to do its AIO) is not set and if so returns a reference to it, after
630 * bumping up the use count. User must release the mm via mmput()
631 * after use. Typically used by /proc and ptrace.
632 */
633struct mm_struct *get_task_mm(struct task_struct *task)
634{
635 struct mm_struct *mm;
636
637 task_lock(task);
638 mm = task->mm;
639 if (mm) {
640 if (task->flags & PF_KTHREAD)
641 mm = NULL;
642 else
643 atomic_inc(&mm->mm_users);
644 }
645 task_unlock(task);
646 return mm;
647}
648EXPORT_SYMBOL_GPL(get_task_mm);
649
650/* Please note the differences between mmput and mm_release.
651 * mmput is called whenever we stop holding onto a mm_struct,
652 * error success whatever.
653 *
654 * mm_release is called after a mm_struct has been removed
655 * from the current process.
656 *
657 * This difference is important for error handling, when we
658 * only half set up a mm_struct for a new process and need to restore
659 * the old one. Because we mmput the new mm_struct before
660 * restoring the old one. . .
661 * Eric Biederman 10 January 1998
662 */
663void mm_release(struct task_struct *tsk, struct mm_struct *mm)
664{
665 struct completion *vfork_done = tsk->vfork_done;
666
667 /* Get rid of any futexes when releasing the mm */
668#ifdef CONFIG_FUTEX
669 if (unlikely(tsk->robust_list)) {
670 exit_robust_list(tsk);
671 tsk->robust_list = NULL;
672 }
673#ifdef CONFIG_COMPAT
674 if (unlikely(tsk->compat_robust_list)) {
675 compat_exit_robust_list(tsk);
676 tsk->compat_robust_list = NULL;
677 }
678#endif
679 if (unlikely(!list_empty(&tsk->pi_state_list)))
680 exit_pi_state_list(tsk);
681#endif
682
683 /* Get rid of any cached register state */
684 deactivate_mm(tsk, mm);
685
686 /* notify parent sleeping on vfork() */
687 if (vfork_done) {
688 tsk->vfork_done = NULL;
689 complete(vfork_done);
690 }
691
692 /*
693 * If we're exiting normally, clear a user-space tid field if
694 * requested. We leave this alone when dying by signal, to leave
695 * the value intact in a core dump, and to save the unnecessary
696 * trouble otherwise. Userland only wants this done for a sys_exit.
697 */
698 if (tsk->clear_child_tid) {
699 if (!(tsk->flags & PF_SIGNALED) &&
700 atomic_read(&mm->mm_users) > 1) {
701 /*
702 * We don't check the error code - if userspace has
703 * not set up a proper pointer then tough luck.
704 */
705 put_user(0, tsk->clear_child_tid);
706 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
707 1, NULL, NULL, 0);
708 }
709 tsk->clear_child_tid = NULL;
710 }
711}
712
713/*
714 * Allocate a new mm structure and copy contents from the
715 * mm structure of the passed in task structure.
716 */
717struct mm_struct *dup_mm(struct task_struct *tsk)
718{
719 struct mm_struct *mm, *oldmm = current->mm;
720 int err;
721
722 if (!oldmm)
723 return NULL;
724
725 mm = allocate_mm();
726 if (!mm)
727 goto fail_nomem;
728
729 memcpy(mm, oldmm, sizeof(*mm));
730 mm_init_cpumask(mm);
731
732 /* Initializing for Swap token stuff */
733 mm->token_priority = 0;
734 mm->last_interval = 0;
735
736#ifdef CONFIG_TRANSPARENT_HUGEPAGE
737 mm->pmd_huge_pte = NULL;
738#endif
739
740 if (!mm_init(mm, tsk))
741 goto fail_nomem;
742
743 if (init_new_context(tsk, mm))
744 goto fail_nocontext;
745
746 dup_mm_exe_file(oldmm, mm);
747
748 err = dup_mmap(mm, oldmm);
749 if (err)
750 goto free_pt;
751
752 mm->hiwater_rss = get_mm_rss(mm);
753 mm->hiwater_vm = mm->total_vm;
754
755 if (mm->binfmt && !try_module_get(mm->binfmt->module))
756 goto free_pt;
757
758 return mm;
759
760free_pt:
761 /* don't put binfmt in mmput, we haven't got module yet */
762 mm->binfmt = NULL;
763 mmput(mm);
764
765fail_nomem:
766 return NULL;
767
768fail_nocontext:
769 /*
770 * If init_new_context() failed, we cannot use mmput() to free the mm
771 * because it calls destroy_context()
772 */
773 mm_free_pgd(mm);
774 free_mm(mm);
775 return NULL;
776}
777
778static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
779{
780 struct mm_struct *mm, *oldmm;
781 int retval;
782
783 tsk->min_flt = tsk->maj_flt = 0;
784 tsk->nvcsw = tsk->nivcsw = 0;
785#ifdef CONFIG_DETECT_HUNG_TASK
786 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
787#endif
788
789 tsk->mm = NULL;
790 tsk->active_mm = NULL;
791
792 /*
793 * Are we cloning a kernel thread?
794 *
795 * We need to steal a active VM for that..
796 */
797 oldmm = current->mm;
798 if (!oldmm)
799 return 0;
800
801 if (clone_flags & CLONE_VM) {
802 atomic_inc(&oldmm->mm_users);
803 mm = oldmm;
804 goto good_mm;
805 }
806
807 retval = -ENOMEM;
808 mm = dup_mm(tsk);
809 if (!mm)
810 goto fail_nomem;
811
812good_mm:
813 /* Initializing for Swap token stuff */
814 mm->token_priority = 0;
815 mm->last_interval = 0;
816
817 tsk->mm = mm;
818 tsk->active_mm = mm;
819 return 0;
820
821fail_nomem:
822 return retval;
823}
824
825static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
826{
827 struct fs_struct *fs = current->fs;
828 if (clone_flags & CLONE_FS) {
829 /* tsk->fs is already what we want */
830 spin_lock(&fs->lock);
831 if (fs->in_exec) {
832 spin_unlock(&fs->lock);
833 return -EAGAIN;
834 }
835 fs->users++;
836 spin_unlock(&fs->lock);
837 return 0;
838 }
839 tsk->fs = copy_fs_struct(fs);
840 if (!tsk->fs)
841 return -ENOMEM;
842 return 0;
843}
844
845static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
846{
847 struct files_struct *oldf, *newf;
848 int error = 0;
849
850 /*
851 * A background process may not have any files ...
852 */
853 oldf = current->files;
854 if (!oldf)
855 goto out;
856
857 if (clone_flags & CLONE_FILES) {
858 atomic_inc(&oldf->count);
859 goto out;
860 }
861
862 newf = dup_fd(oldf, &error);
863 if (!newf)
864 goto out;
865
866 tsk->files = newf;
867 error = 0;
868out:
869 return error;
870}
871
872static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
873{
874#ifdef CONFIG_BLOCK
875 struct io_context *ioc = current->io_context;
876 struct io_context *new_ioc;
877
878 if (!ioc)
879 return 0;
880 /*
881 * Share io context with parent, if CLONE_IO is set
882 */
883 if (clone_flags & CLONE_IO) {
884 tsk->io_context = ioc_task_link(ioc);
885 if (unlikely(!tsk->io_context))
886 return -ENOMEM;
887 } else if (ioprio_valid(ioc->ioprio)) {
888 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
889 if (unlikely(!new_ioc))
890 return -ENOMEM;
891
892 new_ioc->ioprio = ioc->ioprio;
893 put_io_context(new_ioc, NULL);
894 }
895#endif
896 return 0;
897}
898
899static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
900{
901 struct sighand_struct *sig;
902
903 if (clone_flags & CLONE_SIGHAND) {
904 atomic_inc(&current->sighand->count);
905 return 0;
906 }
907 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
908 rcu_assign_pointer(tsk->sighand, sig);
909 if (!sig)
910 return -ENOMEM;
911 atomic_set(&sig->count, 1);
912 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
913 return 0;
914}
915
916void __cleanup_sighand(struct sighand_struct *sighand)
917{
918 if (atomic_dec_and_test(&sighand->count))
919 kmem_cache_free(sighand_cachep, sighand);
920}
921
922
923/*
924 * Initialize POSIX timer handling for a thread group.
925 */
926static void posix_cpu_timers_init_group(struct signal_struct *sig)
927{
928 unsigned long cpu_limit;
929
930 /* Thread group counters. */
931 thread_group_cputime_init(sig);
932
933 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
934 if (cpu_limit != RLIM_INFINITY) {
935 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
936 sig->cputimer.running = 1;
937 }
938
939 /* The timer lists. */
940 INIT_LIST_HEAD(&sig->cpu_timers[0]);
941 INIT_LIST_HEAD(&sig->cpu_timers[1]);
942 INIT_LIST_HEAD(&sig->cpu_timers[2]);
943}
944
945static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
946{
947 struct signal_struct *sig;
948
949 if (clone_flags & CLONE_THREAD)
950 return 0;
951
952 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
953 tsk->signal = sig;
954 if (!sig)
955 return -ENOMEM;
956
957 sig->nr_threads = 1;
958 atomic_set(&sig->live, 1);
959 atomic_set(&sig->sigcnt, 1);
960 init_waitqueue_head(&sig->wait_chldexit);
961 if (clone_flags & CLONE_NEWPID)
962 sig->flags |= SIGNAL_UNKILLABLE;
963 sig->curr_target = tsk;
964 init_sigpending(&sig->shared_pending);
965 INIT_LIST_HEAD(&sig->posix_timers);
966
967 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
968 sig->real_timer.function = it_real_fn;
969
970 task_lock(current->group_leader);
971 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
972 task_unlock(current->group_leader);
973
974 posix_cpu_timers_init_group(sig);
975
976 tty_audit_fork(sig);
977 sched_autogroup_fork(sig);
978
979#ifdef CONFIG_CGROUPS
980 init_rwsem(&sig->group_rwsem);
981#endif
982
983 sig->oom_adj = current->signal->oom_adj;
984 sig->oom_score_adj = current->signal->oom_score_adj;
985 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
986
987 mutex_init(&sig->cred_guard_mutex);
988
989 return 0;
990}
991
992static void copy_flags(unsigned long clone_flags, struct task_struct *p)
993{
994 unsigned long new_flags = p->flags;
995
996 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
997 new_flags |= PF_FORKNOEXEC;
998 new_flags |= PF_STARTING;
999 p->flags = new_flags;
1000}
1001
1002SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1003{
1004 current->clear_child_tid = tidptr;
1005
1006 return task_pid_vnr(current);
1007}
1008
1009static void rt_mutex_init_task(struct task_struct *p)
1010{
1011 raw_spin_lock_init(&p->pi_lock);
1012#ifdef CONFIG_RT_MUTEXES
1013 plist_head_init(&p->pi_waiters);
1014 p->pi_blocked_on = NULL;
1015#endif
1016}
1017
1018#ifdef CONFIG_MM_OWNER
1019void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1020{
1021 mm->owner = p;
1022}
1023#endif /* CONFIG_MM_OWNER */
1024
1025/*
1026 * Initialize POSIX timer handling for a single task.
1027 */
1028static void posix_cpu_timers_init(struct task_struct *tsk)
1029{
1030 tsk->cputime_expires.prof_exp = 0;
1031 tsk->cputime_expires.virt_exp = 0;
1032 tsk->cputime_expires.sched_exp = 0;
1033 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1034 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1035 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1036}
1037
1038/*
1039 * This creates a new process as a copy of the old one,
1040 * but does not actually start it yet.
1041 *
1042 * It copies the registers, and all the appropriate
1043 * parts of the process environment (as per the clone
1044 * flags). The actual kick-off is left to the caller.
1045 */
1046static struct task_struct *copy_process(unsigned long clone_flags,
1047 unsigned long stack_start,
1048 struct pt_regs *regs,
1049 unsigned long stack_size,
1050 int __user *child_tidptr,
1051 struct pid *pid,
1052 int trace)
1053{
1054 int retval;
1055 struct task_struct *p;
1056 int cgroup_callbacks_done = 0;
1057
1058 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1059 return ERR_PTR(-EINVAL);
1060
1061 /*
1062 * Thread groups must share signals as well, and detached threads
1063 * can only be started up within the thread group.
1064 */
1065 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1066 return ERR_PTR(-EINVAL);
1067
1068 /*
1069 * Shared signal handlers imply shared VM. By way of the above,
1070 * thread groups also imply shared VM. Blocking this case allows
1071 * for various simplifications in other code.
1072 */
1073 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1074 return ERR_PTR(-EINVAL);
1075
1076 /*
1077 * Siblings of global init remain as zombies on exit since they are
1078 * not reaped by their parent (swapper). To solve this and to avoid
1079 * multi-rooted process trees, prevent global and container-inits
1080 * from creating siblings.
1081 */
1082 if ((clone_flags & CLONE_PARENT) &&
1083 current->signal->flags & SIGNAL_UNKILLABLE)
1084 return ERR_PTR(-EINVAL);
1085
1086 retval = security_task_create(clone_flags);
1087 if (retval)
1088 goto fork_out;
1089
1090 retval = -ENOMEM;
1091 p = dup_task_struct(current);
1092 if (!p)
1093 goto fork_out;
1094
1095 ftrace_graph_init_task(p);
1096
1097 rt_mutex_init_task(p);
1098
1099#ifdef CONFIG_PROVE_LOCKING
1100 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1101 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1102#endif
1103 retval = -EAGAIN;
1104 if (atomic_read(&p->real_cred->user->processes) >=
1105 task_rlimit(p, RLIMIT_NPROC)) {
1106 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1107 p->real_cred->user != INIT_USER)
1108 goto bad_fork_free;
1109 }
1110 current->flags &= ~PF_NPROC_EXCEEDED;
1111
1112 retval = copy_creds(p, clone_flags);
1113 if (retval < 0)
1114 goto bad_fork_free;
1115
1116 /*
1117 * If multiple threads are within copy_process(), then this check
1118 * triggers too late. This doesn't hurt, the check is only there
1119 * to stop root fork bombs.
1120 */
1121 retval = -EAGAIN;
1122 if (nr_threads >= max_threads)
1123 goto bad_fork_cleanup_count;
1124
1125 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1126 goto bad_fork_cleanup_count;
1127
1128 p->did_exec = 0;
1129 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1130 copy_flags(clone_flags, p);
1131 INIT_LIST_HEAD(&p->children);
1132 INIT_LIST_HEAD(&p->sibling);
1133 rcu_copy_process(p);
1134 p->vfork_done = NULL;
1135 spin_lock_init(&p->alloc_lock);
1136
1137 init_sigpending(&p->pending);
1138
1139 p->utime = p->stime = p->gtime = 0;
1140 p->utimescaled = p->stimescaled = 0;
1141#ifndef CONFIG_VIRT_CPU_ACCOUNTING
1142 p->prev_utime = p->prev_stime = 0;
1143#endif
1144#if defined(SPLIT_RSS_COUNTING)
1145 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1146#endif
1147
1148 p->default_timer_slack_ns = current->timer_slack_ns;
1149
1150 task_io_accounting_init(&p->ioac);
1151 acct_clear_integrals(p);
1152
1153 posix_cpu_timers_init(p);
1154
1155 do_posix_clock_monotonic_gettime(&p->start_time);
1156 p->real_start_time = p->start_time;
1157 monotonic_to_bootbased(&p->real_start_time);
1158 p->io_context = NULL;
1159 p->audit_context = NULL;
1160 if (clone_flags & CLONE_THREAD)
1161 threadgroup_change_begin(current);
1162 cgroup_fork(p);
1163#ifdef CONFIG_NUMA
1164 p->mempolicy = mpol_dup(p->mempolicy);
1165 if (IS_ERR(p->mempolicy)) {
1166 retval = PTR_ERR(p->mempolicy);
1167 p->mempolicy = NULL;
1168 goto bad_fork_cleanup_cgroup;
1169 }
1170 mpol_fix_fork_child_flag(p);
1171#endif
1172#ifdef CONFIG_CPUSETS
1173 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1174 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1175#endif
1176#ifdef CONFIG_TRACE_IRQFLAGS
1177 p->irq_events = 0;
1178#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1179 p->hardirqs_enabled = 1;
1180#else
1181 p->hardirqs_enabled = 0;
1182#endif
1183 p->hardirq_enable_ip = 0;
1184 p->hardirq_enable_event = 0;
1185 p->hardirq_disable_ip = _THIS_IP_;
1186 p->hardirq_disable_event = 0;
1187 p->softirqs_enabled = 1;
1188 p->softirq_enable_ip = _THIS_IP_;
1189 p->softirq_enable_event = 0;
1190 p->softirq_disable_ip = 0;
1191 p->softirq_disable_event = 0;
1192 p->hardirq_context = 0;
1193 p->softirq_context = 0;
1194#endif
1195#ifdef CONFIG_LOCKDEP
1196 p->lockdep_depth = 0; /* no locks held yet */
1197 p->curr_chain_key = 0;
1198 p->lockdep_recursion = 0;
1199#endif
1200
1201#ifdef CONFIG_DEBUG_MUTEXES
1202 p->blocked_on = NULL; /* not blocked yet */
1203#endif
1204#ifdef CONFIG_CGROUP_MEM_RES_CTLR
1205 p->memcg_batch.do_batch = 0;
1206 p->memcg_batch.memcg = NULL;
1207#endif
1208
1209 /* Perform scheduler related setup. Assign this task to a CPU. */
1210 sched_fork(p);
1211
1212 retval = perf_event_init_task(p);
1213 if (retval)
1214 goto bad_fork_cleanup_policy;
1215 retval = audit_alloc(p);
1216 if (retval)
1217 goto bad_fork_cleanup_policy;
1218 /* copy all the process information */
1219 retval = copy_semundo(clone_flags, p);
1220 if (retval)
1221 goto bad_fork_cleanup_audit;
1222 retval = copy_files(clone_flags, p);
1223 if (retval)
1224 goto bad_fork_cleanup_semundo;
1225 retval = copy_fs(clone_flags, p);
1226 if (retval)
1227 goto bad_fork_cleanup_files;
1228 retval = copy_sighand(clone_flags, p);
1229 if (retval)
1230 goto bad_fork_cleanup_fs;
1231 retval = copy_signal(clone_flags, p);
1232 if (retval)
1233 goto bad_fork_cleanup_sighand;
1234 retval = copy_mm(clone_flags, p);
1235 if (retval)
1236 goto bad_fork_cleanup_signal;
1237 retval = copy_namespaces(clone_flags, p);
1238 if (retval)
1239 goto bad_fork_cleanup_mm;
1240 retval = copy_io(clone_flags, p);
1241 if (retval)
1242 goto bad_fork_cleanup_namespaces;
1243 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1244 if (retval)
1245 goto bad_fork_cleanup_io;
1246
1247 if (pid != &init_struct_pid) {
1248 retval = -ENOMEM;
1249 pid = alloc_pid(p->nsproxy->pid_ns);
1250 if (!pid)
1251 goto bad_fork_cleanup_io;
1252 }
1253
1254 p->pid = pid_nr(pid);
1255 p->tgid = p->pid;
1256 if (clone_flags & CLONE_THREAD)
1257 p->tgid = current->tgid;
1258
1259 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1260 /*
1261 * Clear TID on mm_release()?
1262 */
1263 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1264#ifdef CONFIG_BLOCK
1265 p->plug = NULL;
1266#endif
1267#ifdef CONFIG_FUTEX
1268 p->robust_list = NULL;
1269#ifdef CONFIG_COMPAT
1270 p->compat_robust_list = NULL;
1271#endif
1272 INIT_LIST_HEAD(&p->pi_state_list);
1273 p->pi_state_cache = NULL;
1274#endif
1275 /*
1276 * sigaltstack should be cleared when sharing the same VM
1277 */
1278 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1279 p->sas_ss_sp = p->sas_ss_size = 0;
1280
1281 /*
1282 * Syscall tracing and stepping should be turned off in the
1283 * child regardless of CLONE_PTRACE.
1284 */
1285 user_disable_single_step(p);
1286 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1287#ifdef TIF_SYSCALL_EMU
1288 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1289#endif
1290 clear_all_latency_tracing(p);
1291
1292 /* ok, now we should be set up.. */
1293 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1294 p->pdeath_signal = 0;
1295 p->exit_state = 0;
1296
1297 p->nr_dirtied = 0;
1298 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1299 p->dirty_paused_when = 0;
1300
1301 /*
1302 * Ok, make it visible to the rest of the system.
1303 * We dont wake it up yet.
1304 */
1305 p->group_leader = p;
1306 INIT_LIST_HEAD(&p->thread_group);
1307
1308 /* Now that the task is set up, run cgroup callbacks if
1309 * necessary. We need to run them before the task is visible
1310 * on the tasklist. */
1311 cgroup_fork_callbacks(p);
1312 cgroup_callbacks_done = 1;
1313
1314 /* Need tasklist lock for parent etc handling! */
1315 write_lock_irq(&tasklist_lock);
1316
1317 /* CLONE_PARENT re-uses the old parent */
1318 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1319 p->real_parent = current->real_parent;
1320 p->parent_exec_id = current->parent_exec_id;
1321 } else {
1322 p->real_parent = current;
1323 p->parent_exec_id = current->self_exec_id;
1324 }
1325
1326 spin_lock(&current->sighand->siglock);
1327
1328 /*
1329 * Process group and session signals need to be delivered to just the
1330 * parent before the fork or both the parent and the child after the
1331 * fork. Restart if a signal comes in before we add the new process to
1332 * it's process group.
1333 * A fatal signal pending means that current will exit, so the new
1334 * thread can't slip out of an OOM kill (or normal SIGKILL).
1335 */
1336 recalc_sigpending();
1337 if (signal_pending(current)) {
1338 spin_unlock(&current->sighand->siglock);
1339 write_unlock_irq(&tasklist_lock);
1340 retval = -ERESTARTNOINTR;
1341 goto bad_fork_free_pid;
1342 }
1343
1344 if (clone_flags & CLONE_THREAD) {
1345 current->signal->nr_threads++;
1346 atomic_inc(&current->signal->live);
1347 atomic_inc(&current->signal->sigcnt);
1348 p->group_leader = current->group_leader;
1349 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1350 }
1351
1352 if (likely(p->pid)) {
1353 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1354
1355 if (thread_group_leader(p)) {
1356 if (is_child_reaper(pid))
1357 p->nsproxy->pid_ns->child_reaper = p;
1358
1359 p->signal->leader_pid = pid;
1360 p->signal->tty = tty_kref_get(current->signal->tty);
1361 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1362 attach_pid(p, PIDTYPE_SID, task_session(current));
1363 list_add_tail(&p->sibling, &p->real_parent->children);
1364 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1365 __this_cpu_inc(process_counts);
1366 }
1367 attach_pid(p, PIDTYPE_PID, pid);
1368 nr_threads++;
1369 }
1370
1371 total_forks++;
1372 spin_unlock(&current->sighand->siglock);
1373 write_unlock_irq(&tasklist_lock);
1374 proc_fork_connector(p);
1375 cgroup_post_fork(p);
1376 if (clone_flags & CLONE_THREAD)
1377 threadgroup_change_end(current);
1378 perf_event_fork(p);
1379
1380 trace_task_newtask(p, clone_flags);
1381
1382 return p;
1383
1384bad_fork_free_pid:
1385 if (pid != &init_struct_pid)
1386 free_pid(pid);
1387bad_fork_cleanup_io:
1388 if (p->io_context)
1389 exit_io_context(p);
1390bad_fork_cleanup_namespaces:
1391 exit_task_namespaces(p);
1392bad_fork_cleanup_mm:
1393 if (p->mm)
1394 mmput(p->mm);
1395bad_fork_cleanup_signal:
1396 if (!(clone_flags & CLONE_THREAD))
1397 free_signal_struct(p->signal);
1398bad_fork_cleanup_sighand:
1399 __cleanup_sighand(p->sighand);
1400bad_fork_cleanup_fs:
1401 exit_fs(p); /* blocking */
1402bad_fork_cleanup_files:
1403 exit_files(p); /* blocking */
1404bad_fork_cleanup_semundo:
1405 exit_sem(p);
1406bad_fork_cleanup_audit:
1407 audit_free(p);
1408bad_fork_cleanup_policy:
1409 perf_event_free_task(p);
1410#ifdef CONFIG_NUMA
1411 mpol_put(p->mempolicy);
1412bad_fork_cleanup_cgroup:
1413#endif
1414 if (clone_flags & CLONE_THREAD)
1415 threadgroup_change_end(current);
1416 cgroup_exit(p, cgroup_callbacks_done);
1417 delayacct_tsk_free(p);
1418 module_put(task_thread_info(p)->exec_domain->module);
1419bad_fork_cleanup_count:
1420 atomic_dec(&p->cred->user->processes);
1421 exit_creds(p);
1422bad_fork_free:
1423 free_task(p);
1424fork_out:
1425 return ERR_PTR(retval);
1426}
1427
1428noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1429{
1430 memset(regs, 0, sizeof(struct pt_regs));
1431 return regs;
1432}
1433
1434static inline void init_idle_pids(struct pid_link *links)
1435{
1436 enum pid_type type;
1437
1438 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1439 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1440 links[type].pid = &init_struct_pid;
1441 }
1442}
1443
1444struct task_struct * __cpuinit fork_idle(int cpu)
1445{
1446 struct task_struct *task;
1447 struct pt_regs regs;
1448
1449 task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1450 &init_struct_pid, 0);
1451 if (!IS_ERR(task)) {
1452 init_idle_pids(task->pids);
1453 init_idle(task, cpu);
1454 }
1455
1456 return task;
1457}
1458
1459/*
1460 * Ok, this is the main fork-routine.
1461 *
1462 * It copies the process, and if successful kick-starts
1463 * it and waits for it to finish using the VM if required.
1464 */
1465long do_fork(unsigned long clone_flags,
1466 unsigned long stack_start,
1467 struct pt_regs *regs,
1468 unsigned long stack_size,
1469 int __user *parent_tidptr,
1470 int __user *child_tidptr)
1471{
1472 struct task_struct *p;
1473 int trace = 0;
1474 long nr;
1475
1476 /*
1477 * Do some preliminary argument and permissions checking before we
1478 * actually start allocating stuff
1479 */
1480 if (clone_flags & CLONE_NEWUSER) {
1481 if (clone_flags & CLONE_THREAD)
1482 return -EINVAL;
1483 /* hopefully this check will go away when userns support is
1484 * complete
1485 */
1486 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1487 !capable(CAP_SETGID))
1488 return -EPERM;
1489 }
1490
1491 /*
1492 * Determine whether and which event to report to ptracer. When
1493 * called from kernel_thread or CLONE_UNTRACED is explicitly
1494 * requested, no event is reported; otherwise, report if the event
1495 * for the type of forking is enabled.
1496 */
1497 if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1498 if (clone_flags & CLONE_VFORK)
1499 trace = PTRACE_EVENT_VFORK;
1500 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1501 trace = PTRACE_EVENT_CLONE;
1502 else
1503 trace = PTRACE_EVENT_FORK;
1504
1505 if (likely(!ptrace_event_enabled(current, trace)))
1506 trace = 0;
1507 }
1508
1509 p = copy_process(clone_flags, stack_start, regs, stack_size,
1510 child_tidptr, NULL, trace);
1511 /*
1512 * Do this prior waking up the new thread - the thread pointer
1513 * might get invalid after that point, if the thread exits quickly.
1514 */
1515 if (!IS_ERR(p)) {
1516 struct completion vfork;
1517
1518 trace_sched_process_fork(current, p);
1519
1520 nr = task_pid_vnr(p);
1521
1522 if (clone_flags & CLONE_PARENT_SETTID)
1523 put_user(nr, parent_tidptr);
1524
1525 if (clone_flags & CLONE_VFORK) {
1526 p->vfork_done = &vfork;
1527 init_completion(&vfork);
1528 }
1529
1530 /*
1531 * We set PF_STARTING at creation in case tracing wants to
1532 * use this to distinguish a fully live task from one that
1533 * hasn't finished SIGSTOP raising yet. Now we clear it
1534 * and set the child going.
1535 */
1536 p->flags &= ~PF_STARTING;
1537
1538 wake_up_new_task(p);
1539
1540 /* forking complete and child started to run, tell ptracer */
1541 if (unlikely(trace))
1542 ptrace_event(trace, nr);
1543
1544 if (clone_flags & CLONE_VFORK) {
1545 freezer_do_not_count();
1546 wait_for_completion(&vfork);
1547 freezer_count();
1548 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1549 }
1550 } else {
1551 nr = PTR_ERR(p);
1552 }
1553 return nr;
1554}
1555
1556#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1557#define ARCH_MIN_MMSTRUCT_ALIGN 0
1558#endif
1559
1560static void sighand_ctor(void *data)
1561{
1562 struct sighand_struct *sighand = data;
1563
1564 spin_lock_init(&sighand->siglock);
1565 init_waitqueue_head(&sighand->signalfd_wqh);
1566}
1567
1568void __init proc_caches_init(void)
1569{
1570 sighand_cachep = kmem_cache_create("sighand_cache",
1571 sizeof(struct sighand_struct), 0,
1572 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1573 SLAB_NOTRACK, sighand_ctor);
1574 signal_cachep = kmem_cache_create("signal_cache",
1575 sizeof(struct signal_struct), 0,
1576 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1577 files_cachep = kmem_cache_create("files_cache",
1578 sizeof(struct files_struct), 0,
1579 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1580 fs_cachep = kmem_cache_create("fs_cache",
1581 sizeof(struct fs_struct), 0,
1582 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1583 /*
1584 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1585 * whole struct cpumask for the OFFSTACK case. We could change
1586 * this to *only* allocate as much of it as required by the
1587 * maximum number of CPU's we can ever have. The cpumask_allocation
1588 * is at the end of the structure, exactly for that reason.
1589 */
1590 mm_cachep = kmem_cache_create("mm_struct",
1591 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1592 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1593 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1594 mmap_init();
1595 nsproxy_cache_init();
1596}
1597
1598/*
1599 * Check constraints on flags passed to the unshare system call.
1600 */
1601static int check_unshare_flags(unsigned long unshare_flags)
1602{
1603 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1604 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1605 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1606 return -EINVAL;
1607 /*
1608 * Not implemented, but pretend it works if there is nothing to
1609 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1610 * needs to unshare vm.
1611 */
1612 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1613 /* FIXME: get_task_mm() increments ->mm_users */
1614 if (atomic_read(&current->mm->mm_users) > 1)
1615 return -EINVAL;
1616 }
1617
1618 return 0;
1619}
1620
1621/*
1622 * Unshare the filesystem structure if it is being shared
1623 */
1624static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1625{
1626 struct fs_struct *fs = current->fs;
1627
1628 if (!(unshare_flags & CLONE_FS) || !fs)
1629 return 0;
1630
1631 /* don't need lock here; in the worst case we'll do useless copy */
1632 if (fs->users == 1)
1633 return 0;
1634
1635 *new_fsp = copy_fs_struct(fs);
1636 if (!*new_fsp)
1637 return -ENOMEM;
1638
1639 return 0;
1640}
1641
1642/*
1643 * Unshare file descriptor table if it is being shared
1644 */
1645static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1646{
1647 struct files_struct *fd = current->files;
1648 int error = 0;
1649
1650 if ((unshare_flags & CLONE_FILES) &&
1651 (fd && atomic_read(&fd->count) > 1)) {
1652 *new_fdp = dup_fd(fd, &error);
1653 if (!*new_fdp)
1654 return error;
1655 }
1656
1657 return 0;
1658}
1659
1660/*
1661 * unshare allows a process to 'unshare' part of the process
1662 * context which was originally shared using clone. copy_*
1663 * functions used by do_fork() cannot be used here directly
1664 * because they modify an inactive task_struct that is being
1665 * constructed. Here we are modifying the current, active,
1666 * task_struct.
1667 */
1668SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1669{
1670 struct fs_struct *fs, *new_fs = NULL;
1671 struct files_struct *fd, *new_fd = NULL;
1672 struct nsproxy *new_nsproxy = NULL;
1673 int do_sysvsem = 0;
1674 int err;
1675
1676 err = check_unshare_flags(unshare_flags);
1677 if (err)
1678 goto bad_unshare_out;
1679
1680 /*
1681 * If unsharing namespace, must also unshare filesystem information.
1682 */
1683 if (unshare_flags & CLONE_NEWNS)
1684 unshare_flags |= CLONE_FS;
1685 /*
1686 * CLONE_NEWIPC must also detach from the undolist: after switching
1687 * to a new ipc namespace, the semaphore arrays from the old
1688 * namespace are unreachable.
1689 */
1690 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1691 do_sysvsem = 1;
1692 err = unshare_fs(unshare_flags, &new_fs);
1693 if (err)
1694 goto bad_unshare_out;
1695 err = unshare_fd(unshare_flags, &new_fd);
1696 if (err)
1697 goto bad_unshare_cleanup_fs;
1698 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1699 if (err)
1700 goto bad_unshare_cleanup_fd;
1701
1702 if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1703 if (do_sysvsem) {
1704 /*
1705 * CLONE_SYSVSEM is equivalent to sys_exit().
1706 */
1707 exit_sem(current);
1708 }
1709
1710 if (new_nsproxy) {
1711 switch_task_namespaces(current, new_nsproxy);
1712 new_nsproxy = NULL;
1713 }
1714
1715 task_lock(current);
1716
1717 if (new_fs) {
1718 fs = current->fs;
1719 spin_lock(&fs->lock);
1720 current->fs = new_fs;
1721 if (--fs->users)
1722 new_fs = NULL;
1723 else
1724 new_fs = fs;
1725 spin_unlock(&fs->lock);
1726 }
1727
1728 if (new_fd) {
1729 fd = current->files;
1730 current->files = new_fd;
1731 new_fd = fd;
1732 }
1733
1734 task_unlock(current);
1735 }
1736
1737 if (new_nsproxy)
1738 put_nsproxy(new_nsproxy);
1739
1740bad_unshare_cleanup_fd:
1741 if (new_fd)
1742 put_files_struct(new_fd);
1743
1744bad_unshare_cleanup_fs:
1745 if (new_fs)
1746 free_fs_struct(new_fs);
1747
1748bad_unshare_out:
1749 return err;
1750}
1751
1752/*
1753 * Helper to unshare the files of the current task.
1754 * We don't want to expose copy_files internals to
1755 * the exec layer of the kernel.
1756 */
1757
1758int unshare_files(struct files_struct **displaced)
1759{
1760 struct task_struct *task = current;
1761 struct files_struct *copy = NULL;
1762 int error;
1763
1764 error = unshare_fd(CLONE_FILES, &copy);
1765 if (error || !copy) {
1766 *displaced = NULL;
1767 return error;
1768 }
1769 *displaced = task->files;
1770 task_lock(task);
1771 task->files = copy;
1772 task_unlock(task);
1773 return 0;
1774}