projects/linux·blob v3.10-rc7 · refs

1937 lines · 45.7 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/seccomp.h>
38#include <linux/swap.h>
39#include <linux/syscalls.h>
40#include <linux/jiffies.h>
41#include <linux/futex.h>
42#include <linux/compat.h>
43#include <linux/kthread.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/proc_fs.h>
52#include <linux/profile.h>
53#include <linux/rmap.h>
54#include <linux/ksm.h>
55#include <linux/acct.h>
56#include <linux/tsacct_kern.h>
57#include <linux/cn_proc.h>
58#include <linux/freezer.h>
59#include <linux/delayacct.h>
60#include <linux/taskstats_kern.h>
61#include <linux/random.h>
62#include <linux/tty.h>
63#include <linux/blkdev.h>
64#include <linux/fs_struct.h>
65#include <linux/magic.h>
66#include <linux/perf_event.h>
67#include <linux/posix-timers.h>
68#include <linux/user-return-notifier.h>
69#include <linux/oom.h>
70#include <linux/khugepaged.h>
71#include <linux/signalfd.h>
72#include <linux/uprobes.h>
73#include <linux/aio.h>
74
75#include <asm/pgtable.h>
76#include <asm/pgalloc.h>
77#include <asm/uaccess.h>
78#include <asm/mmu_context.h>
79#include <asm/cacheflush.h>
80#include <asm/tlbflush.h>
81
82#include <trace/events/sched.h>
83
84#define CREATE_TRACE_POINTS
85#include <trace/events/task.h>
86
87/*
88 * Protected counters by write_lock_irq(&tasklist_lock)
89 */
90unsigned long total_forks; /* Handle normal Linux uptimes. */
91int nr_threads; /* The idle threads do not count.. */
92
93int max_threads; /* tunable limit on nr_threads */
94
95DEFINE_PER_CPU(unsigned long, process_counts) = 0;
96
97__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
98
99#ifdef CONFIG_PROVE_RCU
100int lockdep_tasklist_lock_is_held(void)
101{
102 return lockdep_is_held(&tasklist_lock);
103}
104EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
105#endif /* #ifdef CONFIG_PROVE_RCU */
106
107int nr_processes(void)
108{
109 int cpu;
110 int total = 0;
111
112 for_each_possible_cpu(cpu)
113 total += per_cpu(process_counts, cpu);
114
115 return total;
116}
117
118void __weak arch_release_task_struct(struct task_struct *tsk)
119{
120}
121
122#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
123static struct kmem_cache *task_struct_cachep;
124
125static inline struct task_struct *alloc_task_struct_node(int node)
126{
127 return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
128}
129
130static inline void free_task_struct(struct task_struct *tsk)
131{
132 kmem_cache_free(task_struct_cachep, tsk);
133}
134#endif
135
136void __weak arch_release_thread_info(struct thread_info *ti)
137{
138}
139
140#ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
141
142/*
143 * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
144 * kmemcache based allocator.
145 */
146# if THREAD_SIZE >= PAGE_SIZE
147static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
148 int node)
149{
150 struct page *page = alloc_pages_node(node, THREADINFO_GFP_ACCOUNTED,
151 THREAD_SIZE_ORDER);
152
153 return page ? page_address(page) : NULL;
154}
155
156static inline void free_thread_info(struct thread_info *ti)
157{
158 free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
159}
160# else
161static struct kmem_cache *thread_info_cache;
162
163static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
164 int node)
165{
166 return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
167}
168
169static void free_thread_info(struct thread_info *ti)
170{
171 kmem_cache_free(thread_info_cache, ti);
172}
173
174void thread_info_cache_init(void)
175{
176 thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
177 THREAD_SIZE, 0, NULL);
178 BUG_ON(thread_info_cache == NULL);
179}
180# endif
181#endif
182
183/* SLAB cache for signal_struct structures (tsk->signal) */
184static struct kmem_cache *signal_cachep;
185
186/* SLAB cache for sighand_struct structures (tsk->sighand) */
187struct kmem_cache *sighand_cachep;
188
189/* SLAB cache for files_struct structures (tsk->files) */
190struct kmem_cache *files_cachep;
191
192/* SLAB cache for fs_struct structures (tsk->fs) */
193struct kmem_cache *fs_cachep;
194
195/* SLAB cache for vm_area_struct structures */
196struct kmem_cache *vm_area_cachep;
197
198/* SLAB cache for mm_struct structures (tsk->mm) */
199static struct kmem_cache *mm_cachep;
200
201static void account_kernel_stack(struct thread_info *ti, int account)
202{
203 struct zone *zone = page_zone(virt_to_page(ti));
204
205 mod_zone_page_state(zone, NR_KERNEL_STACK, account);
206}
207
208void free_task(struct task_struct *tsk)
209{
210 account_kernel_stack(tsk->stack, -1);
211 arch_release_thread_info(tsk->stack);
212 free_thread_info(tsk->stack);
213 rt_mutex_debug_task_free(tsk);
214 ftrace_graph_exit_task(tsk);
215 put_seccomp_filter(tsk);
216 arch_release_task_struct(tsk);
217 free_task_struct(tsk);
218}
219EXPORT_SYMBOL(free_task);
220
221static inline void free_signal_struct(struct signal_struct *sig)
222{
223 taskstats_tgid_free(sig);
224 sched_autogroup_exit(sig);
225 kmem_cache_free(signal_cachep, sig);
226}
227
228static inline void put_signal_struct(struct signal_struct *sig)
229{
230 if (atomic_dec_and_test(&sig->sigcnt))
231 free_signal_struct(sig);
232}
233
234void __put_task_struct(struct task_struct *tsk)
235{
236 WARN_ON(!tsk->exit_state);
237 WARN_ON(atomic_read(&tsk->usage));
238 WARN_ON(tsk == current);
239
240 security_task_free(tsk);
241 exit_creds(tsk);
242 delayacct_tsk_free(tsk);
243 put_signal_struct(tsk->signal);
244
245 if (!profile_handoff_task(tsk))
246 free_task(tsk);
247}
248EXPORT_SYMBOL_GPL(__put_task_struct);
249
250void __init __weak arch_task_cache_init(void) { }
251
252void __init fork_init(unsigned long mempages)
253{
254#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
255#ifndef ARCH_MIN_TASKALIGN
256#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES
257#endif
258 /* create a slab on which task_structs can be allocated */
259 task_struct_cachep =
260 kmem_cache_create("task_struct", sizeof(struct task_struct),
261 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
262#endif
263
264 /* do the arch specific task caches init */
265 arch_task_cache_init();
266
267 /*
268 * The default maximum number of threads is set to a safe
269 * value: the thread structures can take up at most half
270 * of memory.
271 */
272 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
273
274 /*
275 * we need to allow at least 20 threads to boot a system
276 */
277 if (max_threads < 20)
278 max_threads = 20;
279
280 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
281 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
282 init_task.signal->rlim[RLIMIT_SIGPENDING] =
283 init_task.signal->rlim[RLIMIT_NPROC];
284}
285
286int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
287 struct task_struct *src)
288{
289 *dst = *src;
290 return 0;
291}
292
293static struct task_struct *dup_task_struct(struct task_struct *orig)
294{
295 struct task_struct *tsk;
296 struct thread_info *ti;
297 unsigned long *stackend;
298 int node = tsk_fork_get_node(orig);
299 int err;
300
301 tsk = alloc_task_struct_node(node);
302 if (!tsk)
303 return NULL;
304
305 ti = alloc_thread_info_node(tsk, node);
306 if (!ti)
307 goto free_tsk;
308
309 err = arch_dup_task_struct(tsk, orig);
310 if (err)
311 goto free_ti;
312
313 tsk->stack = ti;
314
315 setup_thread_stack(tsk, orig);
316 clear_user_return_notifier(tsk);
317 clear_tsk_need_resched(tsk);
318 stackend = end_of_stack(tsk);
319 *stackend = STACK_END_MAGIC; /* for overflow detection */
320
321#ifdef CONFIG_CC_STACKPROTECTOR
322 tsk->stack_canary = get_random_int();
323#endif
324
325 /*
326 * One for us, one for whoever does the "release_task()" (usually
327 * parent)
328 */
329 atomic_set(&tsk->usage, 2);
330#ifdef CONFIG_BLK_DEV_IO_TRACE
331 tsk->btrace_seq = 0;
332#endif
333 tsk->splice_pipe = NULL;
334 tsk->task_frag.page = NULL;
335
336 account_kernel_stack(ti, 1);
337
338 return tsk;
339
340free_ti:
341 free_thread_info(ti);
342free_tsk:
343 free_task_struct(tsk);
344 return NULL;
345}
346
347#ifdef CONFIG_MMU
348static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
349{
350 struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
351 struct rb_node **rb_link, *rb_parent;
352 int retval;
353 unsigned long charge;
354 struct mempolicy *pol;
355
356 uprobe_start_dup_mmap();
357 down_write(&oldmm->mmap_sem);
358 flush_cache_dup_mm(oldmm);
359 uprobe_dup_mmap(oldmm, mm);
360 /*
361 * Not linked in yet - no deadlock potential:
362 */
363 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
364
365 mm->locked_vm = 0;
366 mm->mmap = NULL;
367 mm->mmap_cache = NULL;
368 mm->free_area_cache = oldmm->mmap_base;
369 mm->cached_hole_size = ~0UL;
370 mm->map_count = 0;
371 cpumask_clear(mm_cpumask(mm));
372 mm->mm_rb = RB_ROOT;
373 rb_link = &mm->mm_rb.rb_node;
374 rb_parent = NULL;
375 pprev = &mm->mmap;
376 retval = ksm_fork(mm, oldmm);
377 if (retval)
378 goto out;
379 retval = khugepaged_fork(mm, oldmm);
380 if (retval)
381 goto out;
382
383 prev = NULL;
384 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
385 struct file *file;
386
387 if (mpnt->vm_flags & VM_DONTCOPY) {
388 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
389 -vma_pages(mpnt));
390 continue;
391 }
392 charge = 0;
393 if (mpnt->vm_flags & VM_ACCOUNT) {
394 unsigned long len = vma_pages(mpnt);
395
396 if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
397 goto fail_nomem;
398 charge = len;
399 }
400 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
401 if (!tmp)
402 goto fail_nomem;
403 *tmp = *mpnt;
404 INIT_LIST_HEAD(&tmp->anon_vma_chain);
405 pol = mpol_dup(vma_policy(mpnt));
406 retval = PTR_ERR(pol);
407 if (IS_ERR(pol))
408 goto fail_nomem_policy;
409 vma_set_policy(tmp, pol);
410 tmp->vm_mm = mm;
411 if (anon_vma_fork(tmp, mpnt))
412 goto fail_nomem_anon_vma_fork;
413 tmp->vm_flags &= ~VM_LOCKED;
414 tmp->vm_next = tmp->vm_prev = NULL;
415 file = tmp->vm_file;
416 if (file) {
417 struct inode *inode = file_inode(file);
418 struct address_space *mapping = file->f_mapping;
419
420 get_file(file);
421 if (tmp->vm_flags & VM_DENYWRITE)
422 atomic_dec(&inode->i_writecount);
423 mutex_lock(&mapping->i_mmap_mutex);
424 if (tmp->vm_flags & VM_SHARED)
425 mapping->i_mmap_writable++;
426 flush_dcache_mmap_lock(mapping);
427 /* insert tmp into the share list, just after mpnt */
428 if (unlikely(tmp->vm_flags & VM_NONLINEAR))
429 vma_nonlinear_insert(tmp,
430 &mapping->i_mmap_nonlinear);
431 else
432 vma_interval_tree_insert_after(tmp, mpnt,
433 &mapping->i_mmap);
434 flush_dcache_mmap_unlock(mapping);
435 mutex_unlock(&mapping->i_mmap_mutex);
436 }
437
438 /*
439 * Clear hugetlb-related page reserves for children. This only
440 * affects MAP_PRIVATE mappings. Faults generated by the child
441 * are not guaranteed to succeed, even if read-only
442 */
443 if (is_vm_hugetlb_page(tmp))
444 reset_vma_resv_huge_pages(tmp);
445
446 /*
447 * Link in the new vma and copy the page table entries.
448 */
449 *pprev = tmp;
450 pprev = &tmp->vm_next;
451 tmp->vm_prev = prev;
452 prev = tmp;
453
454 __vma_link_rb(mm, tmp, rb_link, rb_parent);
455 rb_link = &tmp->vm_rb.rb_right;
456 rb_parent = &tmp->vm_rb;
457
458 mm->map_count++;
459 retval = copy_page_range(mm, oldmm, mpnt);
460
461 if (tmp->vm_ops && tmp->vm_ops->open)
462 tmp->vm_ops->open(tmp);
463
464 if (retval)
465 goto out;
466 }
467 /* a new mm has just been created */
468 arch_dup_mmap(oldmm, mm);
469 retval = 0;
470out:
471 up_write(&mm->mmap_sem);
472 flush_tlb_mm(oldmm);
473 up_write(&oldmm->mmap_sem);
474 uprobe_end_dup_mmap();
475 return retval;
476fail_nomem_anon_vma_fork:
477 mpol_put(pol);
478fail_nomem_policy:
479 kmem_cache_free(vm_area_cachep, tmp);
480fail_nomem:
481 retval = -ENOMEM;
482 vm_unacct_memory(charge);
483 goto out;
484}
485
486static inline int mm_alloc_pgd(struct mm_struct *mm)
487{
488 mm->pgd = pgd_alloc(mm);
489 if (unlikely(!mm->pgd))
490 return -ENOMEM;
491 return 0;
492}
493
494static inline void mm_free_pgd(struct mm_struct *mm)
495{
496 pgd_free(mm, mm->pgd);
497}
498#else
499#define dup_mmap(mm, oldmm) (0)
500#define mm_alloc_pgd(mm) (0)
501#define mm_free_pgd(mm)
502#endif /* CONFIG_MMU */
503
504__cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
505
506#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
507#define free_mm(mm) (kmem_cache_free(mm_cachep, (mm)))
508
509static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
510
511static int __init coredump_filter_setup(char *s)
512{
513 default_dump_filter =
514 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
515 MMF_DUMP_FILTER_MASK;
516 return 1;
517}
518
519__setup("coredump_filter=", coredump_filter_setup);
520
521#include <linux/init_task.h>
522
523static void mm_init_aio(struct mm_struct *mm)
524{
525#ifdef CONFIG_AIO
526 spin_lock_init(&mm->ioctx_lock);
527 INIT_HLIST_HEAD(&mm->ioctx_list);
528#endif
529}
530
531static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
532{
533 atomic_set(&mm->mm_users, 1);
534 atomic_set(&mm->mm_count, 1);
535 init_rwsem(&mm->mmap_sem);
536 INIT_LIST_HEAD(&mm->mmlist);
537 mm->flags = (current->mm) ?
538 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
539 mm->core_state = NULL;
540 mm->nr_ptes = 0;
541 memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
542 spin_lock_init(&mm->page_table_lock);
543 mm->free_area_cache = TASK_UNMAPPED_BASE;
544 mm->cached_hole_size = ~0UL;
545 mm_init_aio(mm);
546 mm_init_owner(mm, p);
547
548 if (likely(!mm_alloc_pgd(mm))) {
549 mm->def_flags = 0;
550 mmu_notifier_mm_init(mm);
551 return mm;
552 }
553
554 free_mm(mm);
555 return NULL;
556}
557
558static void check_mm(struct mm_struct *mm)
559{
560 int i;
561
562 for (i = 0; i < NR_MM_COUNTERS; i++) {
563 long x = atomic_long_read(&mm->rss_stat.count[i]);
564
565 if (unlikely(x))
566 printk(KERN_ALERT "BUG: Bad rss-counter state "
567 "mm:%p idx:%d val:%ld\n", mm, i, x);
568 }
569
570#ifdef CONFIG_TRANSPARENT_HUGEPAGE
571 VM_BUG_ON(mm->pmd_huge_pte);
572#endif
573}
574
575/*
576 * Allocate and initialize an mm_struct.
577 */
578struct mm_struct *mm_alloc(void)
579{
580 struct mm_struct *mm;
581
582 mm = allocate_mm();
583 if (!mm)
584 return NULL;
585
586 memset(mm, 0, sizeof(*mm));
587 mm_init_cpumask(mm);
588 return mm_init(mm, current);
589}
590
591/*
592 * Called when the last reference to the mm
593 * is dropped: either by a lazy thread or by
594 * mmput. Free the page directory and the mm.
595 */
596void __mmdrop(struct mm_struct *mm)
597{
598 BUG_ON(mm == &init_mm);
599 mm_free_pgd(mm);
600 destroy_context(mm);
601 mmu_notifier_mm_destroy(mm);
602 check_mm(mm);
603 free_mm(mm);
604}
605EXPORT_SYMBOL_GPL(__mmdrop);
606
607/*
608 * Decrement the use count and release all resources for an mm.
609 */
610void mmput(struct mm_struct *mm)
611{
612 might_sleep();
613
614 if (atomic_dec_and_test(&mm->mm_users)) {
615 uprobe_clear_state(mm);
616 exit_aio(mm);
617 ksm_exit(mm);
618 khugepaged_exit(mm); /* must run before exit_mmap */
619 exit_mmap(mm);
620 set_mm_exe_file(mm, NULL);
621 if (!list_empty(&mm->mmlist)) {
622 spin_lock(&mmlist_lock);
623 list_del(&mm->mmlist);
624 spin_unlock(&mmlist_lock);
625 }
626 if (mm->binfmt)
627 module_put(mm->binfmt->module);
628 mmdrop(mm);
629 }
630}
631EXPORT_SYMBOL_GPL(mmput);
632
633void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
634{
635 if (new_exe_file)
636 get_file(new_exe_file);
637 if (mm->exe_file)
638 fput(mm->exe_file);
639 mm->exe_file = new_exe_file;
640}
641
642struct file *get_mm_exe_file(struct mm_struct *mm)
643{
644 struct file *exe_file;
645
646 /* We need mmap_sem to protect against races with removal of exe_file */
647 down_read(&mm->mmap_sem);
648 exe_file = mm->exe_file;
649 if (exe_file)
650 get_file(exe_file);
651 up_read(&mm->mmap_sem);
652 return exe_file;
653}
654
655static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
656{
657 /* It's safe to write the exe_file pointer without exe_file_lock because
658 * this is called during fork when the task is not yet in /proc */
659 newmm->exe_file = get_mm_exe_file(oldmm);
660}
661
662/**
663 * get_task_mm - acquire a reference to the task's mm
664 *
665 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning
666 * this kernel workthread has transiently adopted a user mm with use_mm,
667 * to do its AIO) is not set and if so returns a reference to it, after
668 * bumping up the use count. User must release the mm via mmput()
669 * after use. Typically used by /proc and ptrace.
670 */
671struct mm_struct *get_task_mm(struct task_struct *task)
672{
673 struct mm_struct *mm;
674
675 task_lock(task);
676 mm = task->mm;
677 if (mm) {
678 if (task->flags & PF_KTHREAD)
679 mm = NULL;
680 else
681 atomic_inc(&mm->mm_users);
682 }
683 task_unlock(task);
684 return mm;
685}
686EXPORT_SYMBOL_GPL(get_task_mm);
687
688struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
689{
690 struct mm_struct *mm;
691 int err;
692
693 err = mutex_lock_killable(&task->signal->cred_guard_mutex);
694 if (err)
695 return ERR_PTR(err);
696
697 mm = get_task_mm(task);
698 if (mm && mm != current->mm &&
699 !ptrace_may_access(task, mode)) {
700 mmput(mm);
701 mm = ERR_PTR(-EACCES);
702 }
703 mutex_unlock(&task->signal->cred_guard_mutex);
704
705 return mm;
706}
707
708static void complete_vfork_done(struct task_struct *tsk)
709{
710 struct completion *vfork;
711
712 task_lock(tsk);
713 vfork = tsk->vfork_done;
714 if (likely(vfork)) {
715 tsk->vfork_done = NULL;
716 complete(vfork);
717 }
718 task_unlock(tsk);
719}
720
721static int wait_for_vfork_done(struct task_struct *child,
722 struct completion *vfork)
723{
724 int killed;
725
726 freezer_do_not_count();
727 killed = wait_for_completion_killable(vfork);
728 freezer_count();
729
730 if (killed) {
731 task_lock(child);
732 child->vfork_done = NULL;
733 task_unlock(child);
734 }
735
736 put_task_struct(child);
737 return killed;
738}
739
740/* Please note the differences between mmput and mm_release.
741 * mmput is called whenever we stop holding onto a mm_struct,
742 * error success whatever.
743 *
744 * mm_release is called after a mm_struct has been removed
745 * from the current process.
746 *
747 * This difference is important for error handling, when we
748 * only half set up a mm_struct for a new process and need to restore
749 * the old one. Because we mmput the new mm_struct before
750 * restoring the old one. . .
751 * Eric Biederman 10 January 1998
752 */
753void mm_release(struct task_struct *tsk, struct mm_struct *mm)
754{
755 /* Get rid of any futexes when releasing the mm */
756#ifdef CONFIG_FUTEX
757 if (unlikely(tsk->robust_list)) {
758 exit_robust_list(tsk);
759 tsk->robust_list = NULL;
760 }
761#ifdef CONFIG_COMPAT
762 if (unlikely(tsk->compat_robust_list)) {
763 compat_exit_robust_list(tsk);
764 tsk->compat_robust_list = NULL;
765 }
766#endif
767 if (unlikely(!list_empty(&tsk->pi_state_list)))
768 exit_pi_state_list(tsk);
769#endif
770
771 uprobe_free_utask(tsk);
772
773 /* Get rid of any cached register state */
774 deactivate_mm(tsk, mm);
775
776 /*
777 * If we're exiting normally, clear a user-space tid field if
778 * requested. We leave this alone when dying by signal, to leave
779 * the value intact in a core dump, and to save the unnecessary
780 * trouble, say, a killed vfork parent shouldn't touch this mm.
781 * Userland only wants this done for a sys_exit.
782 */
783 if (tsk->clear_child_tid) {
784 if (!(tsk->flags & PF_SIGNALED) &&
785 atomic_read(&mm->mm_users) > 1) {
786 /*
787 * We don't check the error code - if userspace has
788 * not set up a proper pointer then tough luck.
789 */
790 put_user(0, tsk->clear_child_tid);
791 sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
792 1, NULL, NULL, 0);
793 }
794 tsk->clear_child_tid = NULL;
795 }
796
797 /*
798 * All done, finally we can wake up parent and return this mm to him.
799 * Also kthread_stop() uses this completion for synchronization.
800 */
801 if (tsk->vfork_done)
802 complete_vfork_done(tsk);
803}
804
805/*
806 * Allocate a new mm structure and copy contents from the
807 * mm structure of the passed in task structure.
808 */
809struct mm_struct *dup_mm(struct task_struct *tsk)
810{
811 struct mm_struct *mm, *oldmm = current->mm;
812 int err;
813
814 if (!oldmm)
815 return NULL;
816
817 mm = allocate_mm();
818 if (!mm)
819 goto fail_nomem;
820
821 memcpy(mm, oldmm, sizeof(*mm));
822 mm_init_cpumask(mm);
823
824#ifdef CONFIG_TRANSPARENT_HUGEPAGE
825 mm->pmd_huge_pte = NULL;
826#endif
827#ifdef CONFIG_NUMA_BALANCING
828 mm->first_nid = NUMA_PTE_SCAN_INIT;
829#endif
830 if (!mm_init(mm, tsk))
831 goto fail_nomem;
832
833 if (init_new_context(tsk, mm))
834 goto fail_nocontext;
835
836 dup_mm_exe_file(oldmm, mm);
837
838 err = dup_mmap(mm, oldmm);
839 if (err)
840 goto free_pt;
841
842 mm->hiwater_rss = get_mm_rss(mm);
843 mm->hiwater_vm = mm->total_vm;
844
845 if (mm->binfmt && !try_module_get(mm->binfmt->module))
846 goto free_pt;
847
848 return mm;
849
850free_pt:
851 /* don't put binfmt in mmput, we haven't got module yet */
852 mm->binfmt = NULL;
853 mmput(mm);
854
855fail_nomem:
856 return NULL;
857
858fail_nocontext:
859 /*
860 * If init_new_context() failed, we cannot use mmput() to free the mm
861 * because it calls destroy_context()
862 */
863 mm_free_pgd(mm);
864 free_mm(mm);
865 return NULL;
866}
867
868static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
869{
870 struct mm_struct *mm, *oldmm;
871 int retval;
872
873 tsk->min_flt = tsk->maj_flt = 0;
874 tsk->nvcsw = tsk->nivcsw = 0;
875#ifdef CONFIG_DETECT_HUNG_TASK
876 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
877#endif
878
879 tsk->mm = NULL;
880 tsk->active_mm = NULL;
881
882 /*
883 * Are we cloning a kernel thread?
884 *
885 * We need to steal a active VM for that..
886 */
887 oldmm = current->mm;
888 if (!oldmm)
889 return 0;
890
891 if (clone_flags & CLONE_VM) {
892 atomic_inc(&oldmm->mm_users);
893 mm = oldmm;
894 goto good_mm;
895 }
896
897 retval = -ENOMEM;
898 mm = dup_mm(tsk);
899 if (!mm)
900 goto fail_nomem;
901
902good_mm:
903 tsk->mm = mm;
904 tsk->active_mm = mm;
905 return 0;
906
907fail_nomem:
908 return retval;
909}
910
911static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
912{
913 struct fs_struct *fs = current->fs;
914 if (clone_flags & CLONE_FS) {
915 /* tsk->fs is already what we want */
916 spin_lock(&fs->lock);
917 if (fs->in_exec) {
918 spin_unlock(&fs->lock);
919 return -EAGAIN;
920 }
921 fs->users++;
922 spin_unlock(&fs->lock);
923 return 0;
924 }
925 tsk->fs = copy_fs_struct(fs);
926 if (!tsk->fs)
927 return -ENOMEM;
928 return 0;
929}
930
931static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
932{
933 struct files_struct *oldf, *newf;
934 int error = 0;
935
936 /*
937 * A background process may not have any files ...
938 */
939 oldf = current->files;
940 if (!oldf)
941 goto out;
942
943 if (clone_flags & CLONE_FILES) {
944 atomic_inc(&oldf->count);
945 goto out;
946 }
947
948 newf = dup_fd(oldf, &error);
949 if (!newf)
950 goto out;
951
952 tsk->files = newf;
953 error = 0;
954out:
955 return error;
956}
957
958static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
959{
960#ifdef CONFIG_BLOCK
961 struct io_context *ioc = current->io_context;
962 struct io_context *new_ioc;
963
964 if (!ioc)
965 return 0;
966 /*
967 * Share io context with parent, if CLONE_IO is set
968 */
969 if (clone_flags & CLONE_IO) {
970 ioc_task_link(ioc);
971 tsk->io_context = ioc;
972 } else if (ioprio_valid(ioc->ioprio)) {
973 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
974 if (unlikely(!new_ioc))
975 return -ENOMEM;
976
977 new_ioc->ioprio = ioc->ioprio;
978 put_io_context(new_ioc);
979 }
980#endif
981 return 0;
982}
983
984static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
985{
986 struct sighand_struct *sig;
987
988 if (clone_flags & CLONE_SIGHAND) {
989 atomic_inc(&current->sighand->count);
990 return 0;
991 }
992 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
993 rcu_assign_pointer(tsk->sighand, sig);
994 if (!sig)
995 return -ENOMEM;
996 atomic_set(&sig->count, 1);
997 memcpy(sig->action, current->sighand->action, sizeof(sig->action));
998 return 0;
999}
1000
1001void __cleanup_sighand(struct sighand_struct *sighand)
1002{
1003 if (atomic_dec_and_test(&sighand->count)) {
1004 signalfd_cleanup(sighand);
1005 kmem_cache_free(sighand_cachep, sighand);
1006 }
1007}
1008
1009
1010/*
1011 * Initialize POSIX timer handling for a thread group.
1012 */
1013static void posix_cpu_timers_init_group(struct signal_struct *sig)
1014{
1015 unsigned long cpu_limit;
1016
1017 /* Thread group counters. */
1018 thread_group_cputime_init(sig);
1019
1020 cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1021 if (cpu_limit != RLIM_INFINITY) {
1022 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1023 sig->cputimer.running = 1;
1024 }
1025
1026 /* The timer lists. */
1027 INIT_LIST_HEAD(&sig->cpu_timers[0]);
1028 INIT_LIST_HEAD(&sig->cpu_timers[1]);
1029 INIT_LIST_HEAD(&sig->cpu_timers[2]);
1030}
1031
1032static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1033{
1034 struct signal_struct *sig;
1035
1036 if (clone_flags & CLONE_THREAD)
1037 return 0;
1038
1039 sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1040 tsk->signal = sig;
1041 if (!sig)
1042 return -ENOMEM;
1043
1044 sig->nr_threads = 1;
1045 atomic_set(&sig->live, 1);
1046 atomic_set(&sig->sigcnt, 1);
1047 init_waitqueue_head(&sig->wait_chldexit);
1048 sig->curr_target = tsk;
1049 init_sigpending(&sig->shared_pending);
1050 INIT_LIST_HEAD(&sig->posix_timers);
1051
1052 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1053 sig->real_timer.function = it_real_fn;
1054
1055 task_lock(current->group_leader);
1056 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1057 task_unlock(current->group_leader);
1058
1059 posix_cpu_timers_init_group(sig);
1060
1061 tty_audit_fork(sig);
1062 sched_autogroup_fork(sig);
1063
1064#ifdef CONFIG_CGROUPS
1065 init_rwsem(&sig->group_rwsem);
1066#endif
1067
1068 sig->oom_score_adj = current->signal->oom_score_adj;
1069 sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1070
1071 sig->has_child_subreaper = current->signal->has_child_subreaper ||
1072 current->signal->is_child_subreaper;
1073
1074 mutex_init(&sig->cred_guard_mutex);
1075
1076 return 0;
1077}
1078
1079static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1080{
1081 unsigned long new_flags = p->flags;
1082
1083 new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1084 new_flags |= PF_FORKNOEXEC;
1085 p->flags = new_flags;
1086}
1087
1088SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1089{
1090 current->clear_child_tid = tidptr;
1091
1092 return task_pid_vnr(current);
1093}
1094
1095static void rt_mutex_init_task(struct task_struct *p)
1096{
1097 raw_spin_lock_init(&p->pi_lock);
1098#ifdef CONFIG_RT_MUTEXES
1099 plist_head_init(&p->pi_waiters);
1100 p->pi_blocked_on = NULL;
1101#endif
1102}
1103
1104#ifdef CONFIG_MM_OWNER
1105void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1106{
1107 mm->owner = p;
1108}
1109#endif /* CONFIG_MM_OWNER */
1110
1111/*
1112 * Initialize POSIX timer handling for a single task.
1113 */
1114static void posix_cpu_timers_init(struct task_struct *tsk)
1115{
1116 tsk->cputime_expires.prof_exp = 0;
1117 tsk->cputime_expires.virt_exp = 0;
1118 tsk->cputime_expires.sched_exp = 0;
1119 INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1120 INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1121 INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1122}
1123
1124/*
1125 * This creates a new process as a copy of the old one,
1126 * but does not actually start it yet.
1127 *
1128 * It copies the registers, and all the appropriate
1129 * parts of the process environment (as per the clone
1130 * flags). The actual kick-off is left to the caller.
1131 */
1132static struct task_struct *copy_process(unsigned long clone_flags,
1133 unsigned long stack_start,
1134 unsigned long stack_size,
1135 int __user *child_tidptr,
1136 struct pid *pid,
1137 int trace)
1138{
1139 int retval;
1140 struct task_struct *p;
1141
1142 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1143 return ERR_PTR(-EINVAL);
1144
1145 if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1146 return ERR_PTR(-EINVAL);
1147
1148 /*
1149 * Thread groups must share signals as well, and detached threads
1150 * can only be started up within the thread group.
1151 */
1152 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1153 return ERR_PTR(-EINVAL);
1154
1155 /*
1156 * Shared signal handlers imply shared VM. By way of the above,
1157 * thread groups also imply shared VM. Blocking this case allows
1158 * for various simplifications in other code.
1159 */
1160 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1161 return ERR_PTR(-EINVAL);
1162
1163 /*
1164 * Siblings of global init remain as zombies on exit since they are
1165 * not reaped by their parent (swapper). To solve this and to avoid
1166 * multi-rooted process trees, prevent global and container-inits
1167 * from creating siblings.
1168 */
1169 if ((clone_flags & CLONE_PARENT) &&
1170 current->signal->flags & SIGNAL_UNKILLABLE)
1171 return ERR_PTR(-EINVAL);
1172
1173 /*
1174 * If the new process will be in a different pid namespace
1175 * don't allow the creation of threads.
1176 */
1177 if ((clone_flags & (CLONE_VM|CLONE_NEWPID)) &&
1178 (task_active_pid_ns(current) != current->nsproxy->pid_ns))
1179 return ERR_PTR(-EINVAL);
1180
1181 retval = security_task_create(clone_flags);
1182 if (retval)
1183 goto fork_out;
1184
1185 retval = -ENOMEM;
1186 p = dup_task_struct(current);
1187 if (!p)
1188 goto fork_out;
1189
1190 ftrace_graph_init_task(p);
1191 get_seccomp_filter(p);
1192
1193 rt_mutex_init_task(p);
1194
1195#ifdef CONFIG_PROVE_LOCKING
1196 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1197 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1198#endif
1199 retval = -EAGAIN;
1200 if (atomic_read(&p->real_cred->user->processes) >=
1201 task_rlimit(p, RLIMIT_NPROC)) {
1202 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1203 p->real_cred->user != INIT_USER)
1204 goto bad_fork_free;
1205 }
1206 current->flags &= ~PF_NPROC_EXCEEDED;
1207
1208 retval = copy_creds(p, clone_flags);
1209 if (retval < 0)
1210 goto bad_fork_free;
1211
1212 /*
1213 * If multiple threads are within copy_process(), then this check
1214 * triggers too late. This doesn't hurt, the check is only there
1215 * to stop root fork bombs.
1216 */
1217 retval = -EAGAIN;
1218 if (nr_threads >= max_threads)
1219 goto bad_fork_cleanup_count;
1220
1221 if (!try_module_get(task_thread_info(p)->exec_domain->module))
1222 goto bad_fork_cleanup_count;
1223
1224 p->did_exec = 0;
1225 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */
1226 copy_flags(clone_flags, p);
1227 INIT_LIST_HEAD(&p->children);
1228 INIT_LIST_HEAD(&p->sibling);
1229 rcu_copy_process(p);
1230 p->vfork_done = NULL;
1231 spin_lock_init(&p->alloc_lock);
1232
1233 init_sigpending(&p->pending);
1234
1235 p->utime = p->stime = p->gtime = 0;
1236 p->utimescaled = p->stimescaled = 0;
1237#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1238 p->prev_cputime.utime = p->prev_cputime.stime = 0;
1239#endif
1240#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1241 seqlock_init(&p->vtime_seqlock);
1242 p->vtime_snap = 0;
1243 p->vtime_snap_whence = VTIME_SLEEPING;
1244#endif
1245
1246#if defined(SPLIT_RSS_COUNTING)
1247 memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1248#endif
1249
1250 p->default_timer_slack_ns = current->timer_slack_ns;
1251
1252 task_io_accounting_init(&p->ioac);
1253 acct_clear_integrals(p);
1254
1255 posix_cpu_timers_init(p);
1256
1257 do_posix_clock_monotonic_gettime(&p->start_time);
1258 p->real_start_time = p->start_time;
1259 monotonic_to_bootbased(&p->real_start_time);
1260 p->io_context = NULL;
1261 p->audit_context = NULL;
1262 if (clone_flags & CLONE_THREAD)
1263 threadgroup_change_begin(current);
1264 cgroup_fork(p);
1265#ifdef CONFIG_NUMA
1266 p->mempolicy = mpol_dup(p->mempolicy);
1267 if (IS_ERR(p->mempolicy)) {
1268 retval = PTR_ERR(p->mempolicy);
1269 p->mempolicy = NULL;
1270 goto bad_fork_cleanup_cgroup;
1271 }
1272 mpol_fix_fork_child_flag(p);
1273#endif
1274#ifdef CONFIG_CPUSETS
1275 p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1276 p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1277 seqcount_init(&p->mems_allowed_seq);
1278#endif
1279#ifdef CONFIG_TRACE_IRQFLAGS
1280 p->irq_events = 0;
1281 p->hardirqs_enabled = 0;
1282 p->hardirq_enable_ip = 0;
1283 p->hardirq_enable_event = 0;
1284 p->hardirq_disable_ip = _THIS_IP_;
1285 p->hardirq_disable_event = 0;
1286 p->softirqs_enabled = 1;
1287 p->softirq_enable_ip = _THIS_IP_;
1288 p->softirq_enable_event = 0;
1289 p->softirq_disable_ip = 0;
1290 p->softirq_disable_event = 0;
1291 p->hardirq_context = 0;
1292 p->softirq_context = 0;
1293#endif
1294#ifdef CONFIG_LOCKDEP
1295 p->lockdep_depth = 0; /* no locks held yet */
1296 p->curr_chain_key = 0;
1297 p->lockdep_recursion = 0;
1298#endif
1299
1300#ifdef CONFIG_DEBUG_MUTEXES
1301 p->blocked_on = NULL; /* not blocked yet */
1302#endif
1303#ifdef CONFIG_MEMCG
1304 p->memcg_batch.do_batch = 0;
1305 p->memcg_batch.memcg = NULL;
1306#endif
1307#ifdef CONFIG_BCACHE
1308 p->sequential_io = 0;
1309 p->sequential_io_avg = 0;
1310#endif
1311
1312 /* Perform scheduler related setup. Assign this task to a CPU. */
1313 sched_fork(p);
1314
1315 retval = perf_event_init_task(p);
1316 if (retval)
1317 goto bad_fork_cleanup_policy;
1318 retval = audit_alloc(p);
1319 if (retval)
1320 goto bad_fork_cleanup_policy;
1321 /* copy all the process information */
1322 retval = copy_semundo(clone_flags, p);
1323 if (retval)
1324 goto bad_fork_cleanup_audit;
1325 retval = copy_files(clone_flags, p);
1326 if (retval)
1327 goto bad_fork_cleanup_semundo;
1328 retval = copy_fs(clone_flags, p);
1329 if (retval)
1330 goto bad_fork_cleanup_files;
1331 retval = copy_sighand(clone_flags, p);
1332 if (retval)
1333 goto bad_fork_cleanup_fs;
1334 retval = copy_signal(clone_flags, p);
1335 if (retval)
1336 goto bad_fork_cleanup_sighand;
1337 retval = copy_mm(clone_flags, p);
1338 if (retval)
1339 goto bad_fork_cleanup_signal;
1340 retval = copy_namespaces(clone_flags, p);
1341 if (retval)
1342 goto bad_fork_cleanup_mm;
1343 retval = copy_io(clone_flags, p);
1344 if (retval)
1345 goto bad_fork_cleanup_namespaces;
1346 retval = copy_thread(clone_flags, stack_start, stack_size, p);
1347 if (retval)
1348 goto bad_fork_cleanup_io;
1349
1350 if (pid != &init_struct_pid) {
1351 retval = -ENOMEM;
1352 pid = alloc_pid(p->nsproxy->pid_ns);
1353 if (!pid)
1354 goto bad_fork_cleanup_io;
1355 }
1356
1357 p->pid = pid_nr(pid);
1358 p->tgid = p->pid;
1359 if (clone_flags & CLONE_THREAD)
1360 p->tgid = current->tgid;
1361
1362 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1363 /*
1364 * Clear TID on mm_release()?
1365 */
1366 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1367#ifdef CONFIG_BLOCK
1368 p->plug = NULL;
1369#endif
1370#ifdef CONFIG_FUTEX
1371 p->robust_list = NULL;
1372#ifdef CONFIG_COMPAT
1373 p->compat_robust_list = NULL;
1374#endif
1375 INIT_LIST_HEAD(&p->pi_state_list);
1376 p->pi_state_cache = NULL;
1377#endif
1378 uprobe_copy_process(p);
1379 /*
1380 * sigaltstack should be cleared when sharing the same VM
1381 */
1382 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1383 p->sas_ss_sp = p->sas_ss_size = 0;
1384
1385 /*
1386 * Syscall tracing and stepping should be turned off in the
1387 * child regardless of CLONE_PTRACE.
1388 */
1389 user_disable_single_step(p);
1390 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1391#ifdef TIF_SYSCALL_EMU
1392 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1393#endif
1394 clear_all_latency_tracing(p);
1395
1396 /* ok, now we should be set up.. */
1397 if (clone_flags & CLONE_THREAD)
1398 p->exit_signal = -1;
1399 else if (clone_flags & CLONE_PARENT)
1400 p->exit_signal = current->group_leader->exit_signal;
1401 else
1402 p->exit_signal = (clone_flags & CSIGNAL);
1403
1404 p->pdeath_signal = 0;
1405 p->exit_state = 0;
1406
1407 p->nr_dirtied = 0;
1408 p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1409 p->dirty_paused_when = 0;
1410
1411 /*
1412 * Ok, make it visible to the rest of the system.
1413 * We dont wake it up yet.
1414 */
1415 p->group_leader = p;
1416 INIT_LIST_HEAD(&p->thread_group);
1417 p->task_works = NULL;
1418
1419 /* Need tasklist lock for parent etc handling! */
1420 write_lock_irq(&tasklist_lock);
1421
1422 /* CLONE_PARENT re-uses the old parent */
1423 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1424 p->real_parent = current->real_parent;
1425 p->parent_exec_id = current->parent_exec_id;
1426 } else {
1427 p->real_parent = current;
1428 p->parent_exec_id = current->self_exec_id;
1429 }
1430
1431 spin_lock(&current->sighand->siglock);
1432
1433 /*
1434 * Process group and session signals need to be delivered to just the
1435 * parent before the fork or both the parent and the child after the
1436 * fork. Restart if a signal comes in before we add the new process to
1437 * it's process group.
1438 * A fatal signal pending means that current will exit, so the new
1439 * thread can't slip out of an OOM kill (or normal SIGKILL).
1440 */
1441 recalc_sigpending();
1442 if (signal_pending(current)) {
1443 spin_unlock(&current->sighand->siglock);
1444 write_unlock_irq(&tasklist_lock);
1445 retval = -ERESTARTNOINTR;
1446 goto bad_fork_free_pid;
1447 }
1448
1449 if (clone_flags & CLONE_THREAD) {
1450 current->signal->nr_threads++;
1451 atomic_inc(&current->signal->live);
1452 atomic_inc(&current->signal->sigcnt);
1453 p->group_leader = current->group_leader;
1454 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1455 }
1456
1457 if (likely(p->pid)) {
1458 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1459
1460 if (thread_group_leader(p)) {
1461 if (is_child_reaper(pid)) {
1462 ns_of_pid(pid)->child_reaper = p;
1463 p->signal->flags |= SIGNAL_UNKILLABLE;
1464 }
1465
1466 p->signal->leader_pid = pid;
1467 p->signal->tty = tty_kref_get(current->signal->tty);
1468 attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1469 attach_pid(p, PIDTYPE_SID, task_session(current));
1470 list_add_tail(&p->sibling, &p->real_parent->children);
1471 list_add_tail_rcu(&p->tasks, &init_task.tasks);
1472 __this_cpu_inc(process_counts);
1473 }
1474 attach_pid(p, PIDTYPE_PID, pid);
1475 nr_threads++;
1476 }
1477
1478 total_forks++;
1479 spin_unlock(&current->sighand->siglock);
1480 write_unlock_irq(&tasklist_lock);
1481 proc_fork_connector(p);
1482 cgroup_post_fork(p);
1483 if (clone_flags & CLONE_THREAD)
1484 threadgroup_change_end(current);
1485 perf_event_fork(p);
1486
1487 trace_task_newtask(p, clone_flags);
1488
1489 return p;
1490
1491bad_fork_free_pid:
1492 if (pid != &init_struct_pid)
1493 free_pid(pid);
1494bad_fork_cleanup_io:
1495 if (p->io_context)
1496 exit_io_context(p);
1497bad_fork_cleanup_namespaces:
1498 exit_task_namespaces(p);
1499bad_fork_cleanup_mm:
1500 if (p->mm)
1501 mmput(p->mm);
1502bad_fork_cleanup_signal:
1503 if (!(clone_flags & CLONE_THREAD))
1504 free_signal_struct(p->signal);
1505bad_fork_cleanup_sighand:
1506 __cleanup_sighand(p->sighand);
1507bad_fork_cleanup_fs:
1508 exit_fs(p); /* blocking */
1509bad_fork_cleanup_files:
1510 exit_files(p); /* blocking */
1511bad_fork_cleanup_semundo:
1512 exit_sem(p);
1513bad_fork_cleanup_audit:
1514 audit_free(p);
1515bad_fork_cleanup_policy:
1516 perf_event_free_task(p);
1517#ifdef CONFIG_NUMA
1518 mpol_put(p->mempolicy);
1519bad_fork_cleanup_cgroup:
1520#endif
1521 if (clone_flags & CLONE_THREAD)
1522 threadgroup_change_end(current);
1523 cgroup_exit(p, 0);
1524 delayacct_tsk_free(p);
1525 module_put(task_thread_info(p)->exec_domain->module);
1526bad_fork_cleanup_count:
1527 atomic_dec(&p->cred->user->processes);
1528 exit_creds(p);
1529bad_fork_free:
1530 free_task(p);
1531fork_out:
1532 return ERR_PTR(retval);
1533}
1534
1535static inline void init_idle_pids(struct pid_link *links)
1536{
1537 enum pid_type type;
1538
1539 for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1540 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1541 links[type].pid = &init_struct_pid;
1542 }
1543}
1544
1545struct task_struct * __cpuinit fork_idle(int cpu)
1546{
1547 struct task_struct *task;
1548 task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1549 if (!IS_ERR(task)) {
1550 init_idle_pids(task->pids);
1551 init_idle(task, cpu);
1552 }
1553
1554 return task;
1555}
1556
1557/*
1558 * Ok, this is the main fork-routine.
1559 *
1560 * It copies the process, and if successful kick-starts
1561 * it and waits for it to finish using the VM if required.
1562 */
1563long do_fork(unsigned long clone_flags,
1564 unsigned long stack_start,
1565 unsigned long stack_size,
1566 int __user *parent_tidptr,
1567 int __user *child_tidptr)
1568{
1569 struct task_struct *p;
1570 int trace = 0;
1571 long nr;
1572
1573 /*
1574 * Do some preliminary argument and permissions checking before we
1575 * actually start allocating stuff
1576 */
1577 if (clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) {
1578 if (clone_flags & (CLONE_THREAD|CLONE_PARENT))
1579 return -EINVAL;
1580 }
1581
1582 /*
1583 * Determine whether and which event to report to ptracer. When
1584 * called from kernel_thread or CLONE_UNTRACED is explicitly
1585 * requested, no event is reported; otherwise, report if the event
1586 * for the type of forking is enabled.
1587 */
1588 if (!(clone_flags & CLONE_UNTRACED)) {
1589 if (clone_flags & CLONE_VFORK)
1590 trace = PTRACE_EVENT_VFORK;
1591 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1592 trace = PTRACE_EVENT_CLONE;
1593 else
1594 trace = PTRACE_EVENT_FORK;
1595
1596 if (likely(!ptrace_event_enabled(current, trace)))
1597 trace = 0;
1598 }
1599
1600 p = copy_process(clone_flags, stack_start, stack_size,
1601 child_tidptr, NULL, trace);
1602 /*
1603 * Do this prior waking up the new thread - the thread pointer
1604 * might get invalid after that point, if the thread exits quickly.
1605 */
1606 if (!IS_ERR(p)) {
1607 struct completion vfork;
1608
1609 trace_sched_process_fork(current, p);
1610
1611 nr = task_pid_vnr(p);
1612
1613 if (clone_flags & CLONE_PARENT_SETTID)
1614 put_user(nr, parent_tidptr);
1615
1616 if (clone_flags & CLONE_VFORK) {
1617 p->vfork_done = &vfork;
1618 init_completion(&vfork);
1619 get_task_struct(p);
1620 }
1621
1622 wake_up_new_task(p);
1623
1624 /* forking complete and child started to run, tell ptracer */
1625 if (unlikely(trace))
1626 ptrace_event(trace, nr);
1627
1628 if (clone_flags & CLONE_VFORK) {
1629 if (!wait_for_vfork_done(p, &vfork))
1630 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1631 }
1632 } else {
1633 nr = PTR_ERR(p);
1634 }
1635 return nr;
1636}
1637
1638/*
1639 * Create a kernel thread.
1640 */
1641pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1642{
1643 return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1644 (unsigned long)arg, NULL, NULL);
1645}
1646
1647#ifdef __ARCH_WANT_SYS_FORK
1648SYSCALL_DEFINE0(fork)
1649{
1650#ifdef CONFIG_MMU
1651 return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1652#else
1653 /* can not support in nommu mode */
1654 return(-EINVAL);
1655#endif
1656}
1657#endif
1658
1659#ifdef __ARCH_WANT_SYS_VFORK
1660SYSCALL_DEFINE0(vfork)
1661{
1662 return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0,
1663 0, NULL, NULL);
1664}
1665#endif
1666
1667#ifdef __ARCH_WANT_SYS_CLONE
1668#ifdef CONFIG_CLONE_BACKWARDS
1669SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1670 int __user *, parent_tidptr,
1671 int, tls_val,
1672 int __user *, child_tidptr)
1673#elif defined(CONFIG_CLONE_BACKWARDS2)
1674SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1675 int __user *, parent_tidptr,
1676 int __user *, child_tidptr,
1677 int, tls_val)
1678#else
1679SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1680 int __user *, parent_tidptr,
1681 int __user *, child_tidptr,
1682 int, tls_val)
1683#endif
1684{
1685 return do_fork(clone_flags, newsp, 0, parent_tidptr, child_tidptr);
1686}
1687#endif
1688
1689#ifndef ARCH_MIN_MMSTRUCT_ALIGN
1690#define ARCH_MIN_MMSTRUCT_ALIGN 0
1691#endif
1692
1693static void sighand_ctor(void *data)
1694{
1695 struct sighand_struct *sighand = data;
1696
1697 spin_lock_init(&sighand->siglock);
1698 init_waitqueue_head(&sighand->signalfd_wqh);
1699}
1700
1701void __init proc_caches_init(void)
1702{
1703 sighand_cachep = kmem_cache_create("sighand_cache",
1704 sizeof(struct sighand_struct), 0,
1705 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1706 SLAB_NOTRACK, sighand_ctor);
1707 signal_cachep = kmem_cache_create("signal_cache",
1708 sizeof(struct signal_struct), 0,
1709 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1710 files_cachep = kmem_cache_create("files_cache",
1711 sizeof(struct files_struct), 0,
1712 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1713 fs_cachep = kmem_cache_create("fs_cache",
1714 sizeof(struct fs_struct), 0,
1715 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1716 /*
1717 * FIXME! The "sizeof(struct mm_struct)" currently includes the
1718 * whole struct cpumask for the OFFSTACK case. We could change
1719 * this to *only* allocate as much of it as required by the
1720 * maximum number of CPU's we can ever have. The cpumask_allocation
1721 * is at the end of the structure, exactly for that reason.
1722 */
1723 mm_cachep = kmem_cache_create("mm_struct",
1724 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1725 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1726 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1727 mmap_init();
1728 nsproxy_cache_init();
1729}
1730
1731/*
1732 * Check constraints on flags passed to the unshare system call.
1733 */
1734static int check_unshare_flags(unsigned long unshare_flags)
1735{
1736 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1737 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1738 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET|
1739 CLONE_NEWUSER|CLONE_NEWPID))
1740 return -EINVAL;
1741 /*
1742 * Not implemented, but pretend it works if there is nothing to
1743 * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1744 * needs to unshare vm.
1745 */
1746 if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1747 /* FIXME: get_task_mm() increments ->mm_users */
1748 if (atomic_read(&current->mm->mm_users) > 1)
1749 return -EINVAL;
1750 }
1751
1752 return 0;
1753}
1754
1755/*
1756 * Unshare the filesystem structure if it is being shared
1757 */
1758static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1759{
1760 struct fs_struct *fs = current->fs;
1761
1762 if (!(unshare_flags & CLONE_FS) || !fs)
1763 return 0;
1764
1765 /* don't need lock here; in the worst case we'll do useless copy */
1766 if (fs->users == 1)
1767 return 0;
1768
1769 *new_fsp = copy_fs_struct(fs);
1770 if (!*new_fsp)
1771 return -ENOMEM;
1772
1773 return 0;
1774}
1775
1776/*
1777 * Unshare file descriptor table if it is being shared
1778 */
1779static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1780{
1781 struct files_struct *fd = current->files;
1782 int error = 0;
1783
1784 if ((unshare_flags & CLONE_FILES) &&
1785 (fd && atomic_read(&fd->count) > 1)) {
1786 *new_fdp = dup_fd(fd, &error);
1787 if (!*new_fdp)
1788 return error;
1789 }
1790
1791 return 0;
1792}
1793
1794/*
1795 * unshare allows a process to 'unshare' part of the process
1796 * context which was originally shared using clone. copy_*
1797 * functions used by do_fork() cannot be used here directly
1798 * because they modify an inactive task_struct that is being
1799 * constructed. Here we are modifying the current, active,
1800 * task_struct.
1801 */
1802SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1803{
1804 struct fs_struct *fs, *new_fs = NULL;
1805 struct files_struct *fd, *new_fd = NULL;
1806 struct cred *new_cred = NULL;
1807 struct nsproxy *new_nsproxy = NULL;
1808 int do_sysvsem = 0;
1809 int err;
1810
1811 /*
1812 * If unsharing a user namespace must also unshare the thread.
1813 */
1814 if (unshare_flags & CLONE_NEWUSER)
1815 unshare_flags |= CLONE_THREAD | CLONE_FS;
1816 /*
1817 * If unsharing a pid namespace must also unshare the thread.
1818 */
1819 if (unshare_flags & CLONE_NEWPID)
1820 unshare_flags |= CLONE_THREAD;
1821 /*
1822 * If unsharing a thread from a thread group, must also unshare vm.
1823 */
1824 if (unshare_flags & CLONE_THREAD)
1825 unshare_flags |= CLONE_VM;
1826 /*
1827 * If unsharing vm, must also unshare signal handlers.
1828 */
1829 if (unshare_flags & CLONE_VM)
1830 unshare_flags |= CLONE_SIGHAND;
1831 /*
1832 * If unsharing namespace, must also unshare filesystem information.
1833 */
1834 if (unshare_flags & CLONE_NEWNS)
1835 unshare_flags |= CLONE_FS;
1836
1837 err = check_unshare_flags(unshare_flags);
1838 if (err)
1839 goto bad_unshare_out;
1840 /*
1841 * CLONE_NEWIPC must also detach from the undolist: after switching
1842 * to a new ipc namespace, the semaphore arrays from the old
1843 * namespace are unreachable.
1844 */
1845 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1846 do_sysvsem = 1;
1847 err = unshare_fs(unshare_flags, &new_fs);
1848 if (err)
1849 goto bad_unshare_out;
1850 err = unshare_fd(unshare_flags, &new_fd);
1851 if (err)
1852 goto bad_unshare_cleanup_fs;
1853 err = unshare_userns(unshare_flags, &new_cred);
1854 if (err)
1855 goto bad_unshare_cleanup_fd;
1856 err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1857 new_cred, new_fs);
1858 if (err)
1859 goto bad_unshare_cleanup_cred;
1860
1861 if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1862 if (do_sysvsem) {
1863 /*
1864 * CLONE_SYSVSEM is equivalent to sys_exit().
1865 */
1866 exit_sem(current);
1867 }
1868
1869 if (new_nsproxy)
1870 switch_task_namespaces(current, new_nsproxy);
1871
1872 task_lock(current);
1873
1874 if (new_fs) {
1875 fs = current->fs;
1876 spin_lock(&fs->lock);
1877 current->fs = new_fs;
1878 if (--fs->users)
1879 new_fs = NULL;
1880 else
1881 new_fs = fs;
1882 spin_unlock(&fs->lock);
1883 }
1884
1885 if (new_fd) {
1886 fd = current->files;
1887 current->files = new_fd;
1888 new_fd = fd;
1889 }
1890
1891 task_unlock(current);
1892
1893 if (new_cred) {
1894 /* Install the new user namespace */
1895 commit_creds(new_cred);
1896 new_cred = NULL;
1897 }
1898 }
1899
1900bad_unshare_cleanup_cred:
1901 if (new_cred)
1902 put_cred(new_cred);
1903bad_unshare_cleanup_fd:
1904 if (new_fd)
1905 put_files_struct(new_fd);
1906
1907bad_unshare_cleanup_fs:
1908 if (new_fs)
1909 free_fs_struct(new_fs);
1910
1911bad_unshare_out:
1912 return err;
1913}
1914
1915/*
1916 * Helper to unshare the files of the current task.
1917 * We don't want to expose copy_files internals to
1918 * the exec layer of the kernel.
1919 */
1920
1921int unshare_files(struct files_struct **displaced)
1922{
1923 struct task_struct *task = current;
1924 struct files_struct *copy = NULL;
1925 int error;
1926
1927 error = unshare_fd(CLONE_FILES, &copy);
1928 if (error || !copy) {
1929 *displaced = NULL;
1930 return error;
1931 }
1932 *displaced = task->files;
1933 task_lock(task);
1934 task->files = copy;
1935 task_unlock(task);
1936 return 0;
1937}