fork: Provide kmemcache based thread_info allocator
[linux-3.10.git] / kernel / fork.c
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 #include <linux/signalfd.h>
70
71 #include <asm/pgtable.h>
72 #include <asm/pgalloc.h>
73 #include <asm/uaccess.h>
74 #include <asm/mmu_context.h>
75 #include <asm/cacheflush.h>
76 #include <asm/tlbflush.h>
77
78 #include <trace/events/sched.h>
79
80 #define CREATE_TRACE_POINTS
81 #include <trace/events/task.h>
82
83 /*
84  * Protected counters by write_lock_irq(&tasklist_lock)
85  */
86 unsigned long total_forks;      /* Handle normal Linux uptimes. */
87 int nr_threads;                 /* The idle threads do not count.. */
88
89 int max_threads;                /* tunable limit on nr_threads */
90
91 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
92
93 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
94
95 #ifdef CONFIG_PROVE_RCU
96 int lockdep_tasklist_lock_is_held(void)
97 {
98         return lockdep_is_held(&tasklist_lock);
99 }
100 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
101 #endif /* #ifdef CONFIG_PROVE_RCU */
102
103 int nr_processes(void)
104 {
105         int cpu;
106         int total = 0;
107
108         for_each_possible_cpu(cpu)
109                 total += per_cpu(process_counts, cpu);
110
111         return total;
112 }
113
114 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
115 static struct kmem_cache *task_struct_cachep;
116
117 static inline struct task_struct *alloc_task_struct_node(int node)
118 {
119         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
120 }
121
122 void __weak arch_release_task_struct(struct task_struct *tsk) { }
123
124 static inline void free_task_struct(struct task_struct *tsk)
125 {
126         arch_release_task_struct(tsk);
127         kmem_cache_free(task_struct_cachep, tsk);
128 }
129 #endif
130
131 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
132
133 void __weak arch_release_thread_info(struct thread_info *ti) { }
134
135 /*
136  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
137  * kmemcache based allocator.
138  */
139 # if THREAD_SIZE >= PAGE_SIZE
140 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
141                                                   int node)
142 {
143         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
144                                              THREAD_SIZE_ORDER);
145
146         return page ? page_address(page) : NULL;
147 }
148
149 static inline void free_thread_info(struct thread_info *ti)
150 {
151         arch_release_thread_info(ti);
152         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
153 }
154 # else
155 static struct kmem_cache *thread_info_cache;
156
157 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
158                                                   int node)
159 {
160         return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
161 }
162
163 static void free_thread_info(struct thread_info *ti)
164 {
165         arch_release_thread_info(ti);
166         kmem_cache_free(thread_info_cache, ti);
167 }
168
169 void thread_info_cache_init(void)
170 {
171         thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
172                                               THREAD_SIZE, 0, NULL);
173         BUG_ON(thread_info_cache == NULL);
174 }
175 # endif
176 #endif
177
178 /* SLAB cache for signal_struct structures (tsk->signal) */
179 static struct kmem_cache *signal_cachep;
180
181 /* SLAB cache for sighand_struct structures (tsk->sighand) */
182 struct kmem_cache *sighand_cachep;
183
184 /* SLAB cache for files_struct structures (tsk->files) */
185 struct kmem_cache *files_cachep;
186
187 /* SLAB cache for fs_struct structures (tsk->fs) */
188 struct kmem_cache *fs_cachep;
189
190 /* SLAB cache for vm_area_struct structures */
191 struct kmem_cache *vm_area_cachep;
192
193 /* SLAB cache for mm_struct structures (tsk->mm) */
194 static struct kmem_cache *mm_cachep;
195
196 static void account_kernel_stack(struct thread_info *ti, int account)
197 {
198         struct zone *zone = page_zone(virt_to_page(ti));
199
200         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
201 }
202
203 void free_task(struct task_struct *tsk)
204 {
205         account_kernel_stack(tsk->stack, -1);
206         free_thread_info(tsk->stack);
207         rt_mutex_debug_task_free(tsk);
208         ftrace_graph_exit_task(tsk);
209         free_task_struct(tsk);
210 }
211 EXPORT_SYMBOL(free_task);
212
213 static inline void free_signal_struct(struct signal_struct *sig)
214 {
215         taskstats_tgid_free(sig);
216         sched_autogroup_exit(sig);
217         kmem_cache_free(signal_cachep, sig);
218 }
219
220 static inline void put_signal_struct(struct signal_struct *sig)
221 {
222         if (atomic_dec_and_test(&sig->sigcnt))
223                 free_signal_struct(sig);
224 }
225
226 void __put_task_struct(struct task_struct *tsk)
227 {
228         WARN_ON(!tsk->exit_state);
229         WARN_ON(atomic_read(&tsk->usage));
230         WARN_ON(tsk == current);
231
232         security_task_free(tsk);
233         exit_creds(tsk);
234         delayacct_tsk_free(tsk);
235         put_signal_struct(tsk->signal);
236
237         if (!profile_handoff_task(tsk))
238                 free_task(tsk);
239 }
240 EXPORT_SYMBOL_GPL(__put_task_struct);
241
242 void __init __weak arch_task_cache_init(void) { }
243
244 void __init fork_init(unsigned long mempages)
245 {
246 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
247 #ifndef ARCH_MIN_TASKALIGN
248 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
249 #endif
250         /* create a slab on which task_structs can be allocated */
251         task_struct_cachep =
252                 kmem_cache_create("task_struct", sizeof(struct task_struct),
253                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
254 #endif
255
256         /* do the arch specific task caches init */
257         arch_task_cache_init();
258
259         /*
260          * The default maximum number of threads is set to a safe
261          * value: the thread structures can take up at most half
262          * of memory.
263          */
264         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
265
266         /*
267          * we need to allow at least 20 threads to boot a system
268          */
269         if (max_threads < 20)
270                 max_threads = 20;
271
272         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
273         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
274         init_task.signal->rlim[RLIMIT_SIGPENDING] =
275                 init_task.signal->rlim[RLIMIT_NPROC];
276 }
277
278 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
279                                                struct task_struct *src)
280 {
281         *dst = *src;
282         return 0;
283 }
284
285 static struct task_struct *dup_task_struct(struct task_struct *orig)
286 {
287         struct task_struct *tsk;
288         struct thread_info *ti;
289         unsigned long *stackend;
290         int node = tsk_fork_get_node(orig);
291         int err;
292
293         prepare_to_copy(orig);
294
295         tsk = alloc_task_struct_node(node);
296         if (!tsk)
297                 return NULL;
298
299         ti = alloc_thread_info_node(tsk, node);
300         if (!ti) {
301                 free_task_struct(tsk);
302                 return NULL;
303         }
304
305         err = arch_dup_task_struct(tsk, orig);
306         if (err)
307                 goto out;
308
309         tsk->stack = ti;
310
311         setup_thread_stack(tsk, orig);
312         clear_user_return_notifier(tsk);
313         clear_tsk_need_resched(tsk);
314         stackend = end_of_stack(tsk);
315         *stackend = STACK_END_MAGIC;    /* for overflow detection */
316
317 #ifdef CONFIG_CC_STACKPROTECTOR
318         tsk->stack_canary = get_random_int();
319 #endif
320
321         /*
322          * One for us, one for whoever does the "release_task()" (usually
323          * parent)
324          */
325         atomic_set(&tsk->usage, 2);
326 #ifdef CONFIG_BLK_DEV_IO_TRACE
327         tsk->btrace_seq = 0;
328 #endif
329         tsk->splice_pipe = NULL;
330
331         account_kernel_stack(ti, 1);
332
333         return tsk;
334
335 out:
336         free_thread_info(ti);
337         free_task_struct(tsk);
338         return NULL;
339 }
340
341 #ifdef CONFIG_MMU
342 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
343 {
344         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
345         struct rb_node **rb_link, *rb_parent;
346         int retval;
347         unsigned long charge;
348         struct mempolicy *pol;
349
350         down_write(&oldmm->mmap_sem);
351         flush_cache_dup_mm(oldmm);
352         /*
353          * Not linked in yet - no deadlock potential:
354          */
355         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
356
357         mm->locked_vm = 0;
358         mm->mmap = NULL;
359         mm->mmap_cache = NULL;
360         mm->free_area_cache = oldmm->mmap_base;
361         mm->cached_hole_size = ~0UL;
362         mm->map_count = 0;
363         cpumask_clear(mm_cpumask(mm));
364         mm->mm_rb = RB_ROOT;
365         rb_link = &mm->mm_rb.rb_node;
366         rb_parent = NULL;
367         pprev = &mm->mmap;
368         retval = ksm_fork(mm, oldmm);
369         if (retval)
370                 goto out;
371         retval = khugepaged_fork(mm, oldmm);
372         if (retval)
373                 goto out;
374
375         prev = NULL;
376         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
377                 struct file *file;
378
379                 if (mpnt->vm_flags & VM_DONTCOPY) {
380                         long pages = vma_pages(mpnt);
381                         mm->total_vm -= pages;
382                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
383                                                                 -pages);
384                         continue;
385                 }
386                 charge = 0;
387                 if (mpnt->vm_flags & VM_ACCOUNT) {
388                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
389                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
390                                 goto fail_nomem;
391                         charge = len;
392                 }
393                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
394                 if (!tmp)
395                         goto fail_nomem;
396                 *tmp = *mpnt;
397                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
398                 pol = mpol_dup(vma_policy(mpnt));
399                 retval = PTR_ERR(pol);
400                 if (IS_ERR(pol))
401                         goto fail_nomem_policy;
402                 vma_set_policy(tmp, pol);
403                 tmp->vm_mm = mm;
404                 if (anon_vma_fork(tmp, mpnt))
405                         goto fail_nomem_anon_vma_fork;
406                 tmp->vm_flags &= ~VM_LOCKED;
407                 tmp->vm_next = tmp->vm_prev = NULL;
408                 file = tmp->vm_file;
409                 if (file) {
410                         struct inode *inode = file->f_path.dentry->d_inode;
411                         struct address_space *mapping = file->f_mapping;
412
413                         get_file(file);
414                         if (tmp->vm_flags & VM_DENYWRITE)
415                                 atomic_dec(&inode->i_writecount);
416                         mutex_lock(&mapping->i_mmap_mutex);
417                         if (tmp->vm_flags & VM_SHARED)
418                                 mapping->i_mmap_writable++;
419                         flush_dcache_mmap_lock(mapping);
420                         /* insert tmp into the share list, just after mpnt */
421                         vma_prio_tree_add(tmp, mpnt);
422                         flush_dcache_mmap_unlock(mapping);
423                         mutex_unlock(&mapping->i_mmap_mutex);
424                 }
425
426                 /*
427                  * Clear hugetlb-related page reserves for children. This only
428                  * affects MAP_PRIVATE mappings. Faults generated by the child
429                  * are not guaranteed to succeed, even if read-only
430                  */
431                 if (is_vm_hugetlb_page(tmp))
432                         reset_vma_resv_huge_pages(tmp);
433
434                 /*
435                  * Link in the new vma and copy the page table entries.
436                  */
437                 *pprev = tmp;
438                 pprev = &tmp->vm_next;
439                 tmp->vm_prev = prev;
440                 prev = tmp;
441
442                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
443                 rb_link = &tmp->vm_rb.rb_right;
444                 rb_parent = &tmp->vm_rb;
445
446                 mm->map_count++;
447                 retval = copy_page_range(mm, oldmm, mpnt);
448
449                 if (tmp->vm_ops && tmp->vm_ops->open)
450                         tmp->vm_ops->open(tmp);
451
452                 if (retval)
453                         goto out;
454         }
455         /* a new mm has just been created */
456         arch_dup_mmap(oldmm, mm);
457         retval = 0;
458 out:
459         up_write(&mm->mmap_sem);
460         flush_tlb_mm(oldmm);
461         up_write(&oldmm->mmap_sem);
462         return retval;
463 fail_nomem_anon_vma_fork:
464         mpol_put(pol);
465 fail_nomem_policy:
466         kmem_cache_free(vm_area_cachep, tmp);
467 fail_nomem:
468         retval = -ENOMEM;
469         vm_unacct_memory(charge);
470         goto out;
471 }
472
473 static inline int mm_alloc_pgd(struct mm_struct *mm)
474 {
475         mm->pgd = pgd_alloc(mm);
476         if (unlikely(!mm->pgd))
477                 return -ENOMEM;
478         return 0;
479 }
480
481 static inline void mm_free_pgd(struct mm_struct *mm)
482 {
483         pgd_free(mm, mm->pgd);
484 }
485 #else
486 #define dup_mmap(mm, oldmm)     (0)
487 #define mm_alloc_pgd(mm)        (0)
488 #define mm_free_pgd(mm)
489 #endif /* CONFIG_MMU */
490
491 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
492
493 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
494 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
495
496 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
497
498 static int __init coredump_filter_setup(char *s)
499 {
500         default_dump_filter =
501                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
502                 MMF_DUMP_FILTER_MASK;
503         return 1;
504 }
505
506 __setup("coredump_filter=", coredump_filter_setup);
507
508 #include <linux/init_task.h>
509
510 static void mm_init_aio(struct mm_struct *mm)
511 {
512 #ifdef CONFIG_AIO
513         spin_lock_init(&mm->ioctx_lock);
514         INIT_HLIST_HEAD(&mm->ioctx_list);
515 #endif
516 }
517
518 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
519 {
520         atomic_set(&mm->mm_users, 1);
521         atomic_set(&mm->mm_count, 1);
522         init_rwsem(&mm->mmap_sem);
523         INIT_LIST_HEAD(&mm->mmlist);
524         mm->flags = (current->mm) ?
525                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
526         mm->core_state = NULL;
527         mm->nr_ptes = 0;
528         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
529         spin_lock_init(&mm->page_table_lock);
530         mm->free_area_cache = TASK_UNMAPPED_BASE;
531         mm->cached_hole_size = ~0UL;
532         mm_init_aio(mm);
533         mm_init_owner(mm, p);
534
535         if (likely(!mm_alloc_pgd(mm))) {
536                 mm->def_flags = 0;
537                 mmu_notifier_mm_init(mm);
538                 return mm;
539         }
540
541         free_mm(mm);
542         return NULL;
543 }
544
545 static void check_mm(struct mm_struct *mm)
546 {
547         int i;
548
549         for (i = 0; i < NR_MM_COUNTERS; i++) {
550                 long x = atomic_long_read(&mm->rss_stat.count[i]);
551
552                 if (unlikely(x))
553                         printk(KERN_ALERT "BUG: Bad rss-counter state "
554                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
555         }
556
557 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
558         VM_BUG_ON(mm->pmd_huge_pte);
559 #endif
560 }
561
562 /*
563  * Allocate and initialize an mm_struct.
564  */
565 struct mm_struct *mm_alloc(void)
566 {
567         struct mm_struct *mm;
568
569         mm = allocate_mm();
570         if (!mm)
571                 return NULL;
572
573         memset(mm, 0, sizeof(*mm));
574         mm_init_cpumask(mm);
575         return mm_init(mm, current);
576 }
577
578 /*
579  * Called when the last reference to the mm
580  * is dropped: either by a lazy thread or by
581  * mmput. Free the page directory and the mm.
582  */
583 void __mmdrop(struct mm_struct *mm)
584 {
585         BUG_ON(mm == &init_mm);
586         mm_free_pgd(mm);
587         destroy_context(mm);
588         mmu_notifier_mm_destroy(mm);
589         check_mm(mm);
590         free_mm(mm);
591 }
592 EXPORT_SYMBOL_GPL(__mmdrop);
593
594 /*
595  * Decrement the use count and release all resources for an mm.
596  */
597 void mmput(struct mm_struct *mm)
598 {
599         might_sleep();
600
601         if (atomic_dec_and_test(&mm->mm_users)) {
602                 exit_aio(mm);
603                 ksm_exit(mm);
604                 khugepaged_exit(mm); /* must run before exit_mmap */
605                 exit_mmap(mm);
606                 set_mm_exe_file(mm, NULL);
607                 if (!list_empty(&mm->mmlist)) {
608                         spin_lock(&mmlist_lock);
609                         list_del(&mm->mmlist);
610                         spin_unlock(&mmlist_lock);
611                 }
612                 put_swap_token(mm);
613                 if (mm->binfmt)
614                         module_put(mm->binfmt->module);
615                 mmdrop(mm);
616         }
617 }
618 EXPORT_SYMBOL_GPL(mmput);
619
620 /*
621  * We added or removed a vma mapping the executable. The vmas are only mapped
622  * during exec and are not mapped with the mmap system call.
623  * Callers must hold down_write() on the mm's mmap_sem for these
624  */
625 void added_exe_file_vma(struct mm_struct *mm)
626 {
627         mm->num_exe_file_vmas++;
628 }
629
630 void removed_exe_file_vma(struct mm_struct *mm)
631 {
632         mm->num_exe_file_vmas--;
633         if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
634                 fput(mm->exe_file);
635                 mm->exe_file = NULL;
636         }
637
638 }
639
640 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
641 {
642         if (new_exe_file)
643                 get_file(new_exe_file);
644         if (mm->exe_file)
645                 fput(mm->exe_file);
646         mm->exe_file = new_exe_file;
647         mm->num_exe_file_vmas = 0;
648 }
649
650 struct file *get_mm_exe_file(struct mm_struct *mm)
651 {
652         struct file *exe_file;
653
654         /* We need mmap_sem to protect against races with removal of
655          * VM_EXECUTABLE vmas */
656         down_read(&mm->mmap_sem);
657         exe_file = mm->exe_file;
658         if (exe_file)
659                 get_file(exe_file);
660         up_read(&mm->mmap_sem);
661         return exe_file;
662 }
663
664 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
665 {
666         /* It's safe to write the exe_file pointer without exe_file_lock because
667          * this is called during fork when the task is not yet in /proc */
668         newmm->exe_file = get_mm_exe_file(oldmm);
669 }
670
671 /**
672  * get_task_mm - acquire a reference to the task's mm
673  *
674  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
675  * this kernel workthread has transiently adopted a user mm with use_mm,
676  * to do its AIO) is not set and if so returns a reference to it, after
677  * bumping up the use count.  User must release the mm via mmput()
678  * after use.  Typically used by /proc and ptrace.
679  */
680 struct mm_struct *get_task_mm(struct task_struct *task)
681 {
682         struct mm_struct *mm;
683
684         task_lock(task);
685         mm = task->mm;
686         if (mm) {
687                 if (task->flags & PF_KTHREAD)
688                         mm = NULL;
689                 else
690                         atomic_inc(&mm->mm_users);
691         }
692         task_unlock(task);
693         return mm;
694 }
695 EXPORT_SYMBOL_GPL(get_task_mm);
696
697 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
698 {
699         struct mm_struct *mm;
700         int err;
701
702         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
703         if (err)
704                 return ERR_PTR(err);
705
706         mm = get_task_mm(task);
707         if (mm && mm != current->mm &&
708                         !ptrace_may_access(task, mode)) {
709                 mmput(mm);
710                 mm = ERR_PTR(-EACCES);
711         }
712         mutex_unlock(&task->signal->cred_guard_mutex);
713
714         return mm;
715 }
716
717 static void complete_vfork_done(struct task_struct *tsk)
718 {
719         struct completion *vfork;
720
721         task_lock(tsk);
722         vfork = tsk->vfork_done;
723         if (likely(vfork)) {
724                 tsk->vfork_done = NULL;
725                 complete(vfork);
726         }
727         task_unlock(tsk);
728 }
729
730 static int wait_for_vfork_done(struct task_struct *child,
731                                 struct completion *vfork)
732 {
733         int killed;
734
735         freezer_do_not_count();
736         killed = wait_for_completion_killable(vfork);
737         freezer_count();
738
739         if (killed) {
740                 task_lock(child);
741                 child->vfork_done = NULL;
742                 task_unlock(child);
743         }
744
745         put_task_struct(child);
746         return killed;
747 }
748
749 /* Please note the differences between mmput and mm_release.
750  * mmput is called whenever we stop holding onto a mm_struct,
751  * error success whatever.
752  *
753  * mm_release is called after a mm_struct has been removed
754  * from the current process.
755  *
756  * This difference is important for error handling, when we
757  * only half set up a mm_struct for a new process and need to restore
758  * the old one.  Because we mmput the new mm_struct before
759  * restoring the old one. . .
760  * Eric Biederman 10 January 1998
761  */
762 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
763 {
764         /* Get rid of any futexes when releasing the mm */
765 #ifdef CONFIG_FUTEX
766         if (unlikely(tsk->robust_list)) {
767                 exit_robust_list(tsk);
768                 tsk->robust_list = NULL;
769         }
770 #ifdef CONFIG_COMPAT
771         if (unlikely(tsk->compat_robust_list)) {
772                 compat_exit_robust_list(tsk);
773                 tsk->compat_robust_list = NULL;
774         }
775 #endif
776         if (unlikely(!list_empty(&tsk->pi_state_list)))
777                 exit_pi_state_list(tsk);
778 #endif
779
780         /* Get rid of any cached register state */
781         deactivate_mm(tsk, mm);
782
783         if (tsk->vfork_done)
784                 complete_vfork_done(tsk);
785
786         /*
787          * If we're exiting normally, clear a user-space tid field if
788          * requested.  We leave this alone when dying by signal, to leave
789          * the value intact in a core dump, and to save the unnecessary
790          * trouble, say, a killed vfork parent shouldn't touch this mm.
791          * Userland only wants this done for a sys_exit.
792          */
793         if (tsk->clear_child_tid) {
794                 if (!(tsk->flags & PF_SIGNALED) &&
795                     atomic_read(&mm->mm_users) > 1) {
796                         /*
797                          * We don't check the error code - if userspace has
798                          * not set up a proper pointer then tough luck.
799                          */
800                         put_user(0, tsk->clear_child_tid);
801                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
802                                         1, NULL, NULL, 0);
803                 }
804                 tsk->clear_child_tid = NULL;
805         }
806 }
807
808 /*
809  * Allocate a new mm structure and copy contents from the
810  * mm structure of the passed in task structure.
811  */
812 struct mm_struct *dup_mm(struct task_struct *tsk)
813 {
814         struct mm_struct *mm, *oldmm = current->mm;
815         int err;
816
817         if (!oldmm)
818                 return NULL;
819
820         mm = allocate_mm();
821         if (!mm)
822                 goto fail_nomem;
823
824         memcpy(mm, oldmm, sizeof(*mm));
825         mm_init_cpumask(mm);
826
827         /* Initializing for Swap token stuff */
828         mm->token_priority = 0;
829         mm->last_interval = 0;
830
831 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
832         mm->pmd_huge_pte = NULL;
833 #endif
834
835         if (!mm_init(mm, tsk))
836                 goto fail_nomem;
837
838         if (init_new_context(tsk, mm))
839                 goto fail_nocontext;
840
841         dup_mm_exe_file(oldmm, mm);
842
843         err = dup_mmap(mm, oldmm);
844         if (err)
845                 goto free_pt;
846
847         mm->hiwater_rss = get_mm_rss(mm);
848         mm->hiwater_vm = mm->total_vm;
849
850         if (mm->binfmt && !try_module_get(mm->binfmt->module))
851                 goto free_pt;
852
853         return mm;
854
855 free_pt:
856         /* don't put binfmt in mmput, we haven't got module yet */
857         mm->binfmt = NULL;
858         mmput(mm);
859
860 fail_nomem:
861         return NULL;
862
863 fail_nocontext:
864         /*
865          * If init_new_context() failed, we cannot use mmput() to free the mm
866          * because it calls destroy_context()
867          */
868         mm_free_pgd(mm);
869         free_mm(mm);
870         return NULL;
871 }
872
873 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
874 {
875         struct mm_struct *mm, *oldmm;
876         int retval;
877
878         tsk->min_flt = tsk->maj_flt = 0;
879         tsk->nvcsw = tsk->nivcsw = 0;
880 #ifdef CONFIG_DETECT_HUNG_TASK
881         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
882 #endif
883
884         tsk->mm = NULL;
885         tsk->active_mm = NULL;
886
887         /*
888          * Are we cloning a kernel thread?
889          *
890          * We need to steal a active VM for that..
891          */
892         oldmm = current->mm;
893         if (!oldmm)
894                 return 0;
895
896         if (clone_flags & CLONE_VM) {
897                 atomic_inc(&oldmm->mm_users);
898                 mm = oldmm;
899                 goto good_mm;
900         }
901
902         retval = -ENOMEM;
903         mm = dup_mm(tsk);
904         if (!mm)
905                 goto fail_nomem;
906
907 good_mm:
908         /* Initializing for Swap token stuff */
909         mm->token_priority = 0;
910         mm->last_interval = 0;
911
912         tsk->mm = mm;
913         tsk->active_mm = mm;
914         return 0;
915
916 fail_nomem:
917         return retval;
918 }
919
920 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
921 {
922         struct fs_struct *fs = current->fs;
923         if (clone_flags & CLONE_FS) {
924                 /* tsk->fs is already what we want */
925                 spin_lock(&fs->lock);
926                 if (fs->in_exec) {
927                         spin_unlock(&fs->lock);
928                         return -EAGAIN;
929                 }
930                 fs->users++;
931                 spin_unlock(&fs->lock);
932                 return 0;
933         }
934         tsk->fs = copy_fs_struct(fs);
935         if (!tsk->fs)
936                 return -ENOMEM;
937         return 0;
938 }
939
940 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
941 {
942         struct files_struct *oldf, *newf;
943         int error = 0;
944
945         /*
946          * A background process may not have any files ...
947          */
948         oldf = current->files;
949         if (!oldf)
950                 goto out;
951
952         if (clone_flags & CLONE_FILES) {
953                 atomic_inc(&oldf->count);
954                 goto out;
955         }
956
957         newf = dup_fd(oldf, &error);
958         if (!newf)
959                 goto out;
960
961         tsk->files = newf;
962         error = 0;
963 out:
964         return error;
965 }
966
967 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
968 {
969 #ifdef CONFIG_BLOCK
970         struct io_context *ioc = current->io_context;
971         struct io_context *new_ioc;
972
973         if (!ioc)
974                 return 0;
975         /*
976          * Share io context with parent, if CLONE_IO is set
977          */
978         if (clone_flags & CLONE_IO) {
979                 tsk->io_context = ioc_task_link(ioc);
980                 if (unlikely(!tsk->io_context))
981                         return -ENOMEM;
982         } else if (ioprio_valid(ioc->ioprio)) {
983                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
984                 if (unlikely(!new_ioc))
985                         return -ENOMEM;
986
987                 new_ioc->ioprio = ioc->ioprio;
988                 put_io_context(new_ioc);
989         }
990 #endif
991         return 0;
992 }
993
994 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
995 {
996         struct sighand_struct *sig;
997
998         if (clone_flags & CLONE_SIGHAND) {
999                 atomic_inc(&current->sighand->count);
1000                 return 0;
1001         }
1002         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1003         rcu_assign_pointer(tsk->sighand, sig);
1004         if (!sig)
1005                 return -ENOMEM;
1006         atomic_set(&sig->count, 1);
1007         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1008         return 0;
1009 }
1010
1011 void __cleanup_sighand(struct sighand_struct *sighand)
1012 {
1013         if (atomic_dec_and_test(&sighand->count)) {
1014                 signalfd_cleanup(sighand);
1015                 kmem_cache_free(sighand_cachep, sighand);
1016         }
1017 }
1018
1019
1020 /*
1021  * Initialize POSIX timer handling for a thread group.
1022  */
1023 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1024 {
1025         unsigned long cpu_limit;
1026
1027         /* Thread group counters. */
1028         thread_group_cputime_init(sig);
1029
1030         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1031         if (cpu_limit != RLIM_INFINITY) {
1032                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1033                 sig->cputimer.running = 1;
1034         }
1035
1036         /* The timer lists. */
1037         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1038         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1039         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1040 }
1041
1042 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1043 {
1044         struct signal_struct *sig;
1045
1046         if (clone_flags & CLONE_THREAD)
1047                 return 0;
1048
1049         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1050         tsk->signal = sig;
1051         if (!sig)
1052                 return -ENOMEM;
1053
1054         sig->nr_threads = 1;
1055         atomic_set(&sig->live, 1);
1056         atomic_set(&sig->sigcnt, 1);
1057         init_waitqueue_head(&sig->wait_chldexit);
1058         if (clone_flags & CLONE_NEWPID)
1059                 sig->flags |= SIGNAL_UNKILLABLE;
1060         sig->curr_target = tsk;
1061         init_sigpending(&sig->shared_pending);
1062         INIT_LIST_HEAD(&sig->posix_timers);
1063
1064         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1065         sig->real_timer.function = it_real_fn;
1066
1067         task_lock(current->group_leader);
1068         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1069         task_unlock(current->group_leader);
1070
1071         posix_cpu_timers_init_group(sig);
1072
1073         tty_audit_fork(sig);
1074         sched_autogroup_fork(sig);
1075
1076 #ifdef CONFIG_CGROUPS
1077         init_rwsem(&sig->group_rwsem);
1078 #endif
1079
1080         sig->oom_adj = current->signal->oom_adj;
1081         sig->oom_score_adj = current->signal->oom_score_adj;
1082         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1083
1084         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1085                                    current->signal->is_child_subreaper;
1086
1087         mutex_init(&sig->cred_guard_mutex);
1088
1089         return 0;
1090 }
1091
1092 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1093 {
1094         unsigned long new_flags = p->flags;
1095
1096         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1097         new_flags |= PF_FORKNOEXEC;
1098         p->flags = new_flags;
1099 }
1100
1101 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1102 {
1103         current->clear_child_tid = tidptr;
1104
1105         return task_pid_vnr(current);
1106 }
1107
1108 static void rt_mutex_init_task(struct task_struct *p)
1109 {
1110         raw_spin_lock_init(&p->pi_lock);
1111 #ifdef CONFIG_RT_MUTEXES
1112         plist_head_init(&p->pi_waiters);
1113         p->pi_blocked_on = NULL;
1114 #endif
1115 }
1116
1117 #ifdef CONFIG_MM_OWNER
1118 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1119 {
1120         mm->owner = p;
1121 }
1122 #endif /* CONFIG_MM_OWNER */
1123
1124 /*
1125  * Initialize POSIX timer handling for a single task.
1126  */
1127 static void posix_cpu_timers_init(struct task_struct *tsk)
1128 {
1129         tsk->cputime_expires.prof_exp = 0;
1130         tsk->cputime_expires.virt_exp = 0;
1131         tsk->cputime_expires.sched_exp = 0;
1132         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1133         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1134         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1135 }
1136
1137 /*
1138  * This creates a new process as a copy of the old one,
1139  * but does not actually start it yet.
1140  *
1141  * It copies the registers, and all the appropriate
1142  * parts of the process environment (as per the clone
1143  * flags). The actual kick-off is left to the caller.
1144  */
1145 static struct task_struct *copy_process(unsigned long clone_flags,
1146                                         unsigned long stack_start,
1147                                         struct pt_regs *regs,
1148                                         unsigned long stack_size,
1149                                         int __user *child_tidptr,
1150                                         struct pid *pid,
1151                                         int trace)
1152 {
1153         int retval;
1154         struct task_struct *p;
1155         int cgroup_callbacks_done = 0;
1156
1157         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1158                 return ERR_PTR(-EINVAL);
1159
1160         /*
1161          * Thread groups must share signals as well, and detached threads
1162          * can only be started up within the thread group.
1163          */
1164         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1165                 return ERR_PTR(-EINVAL);
1166
1167         /*
1168          * Shared signal handlers imply shared VM. By way of the above,
1169          * thread groups also imply shared VM. Blocking this case allows
1170          * for various simplifications in other code.
1171          */
1172         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1173                 return ERR_PTR(-EINVAL);
1174
1175         /*
1176          * Siblings of global init remain as zombies on exit since they are
1177          * not reaped by their parent (swapper). To solve this and to avoid
1178          * multi-rooted process trees, prevent global and container-inits
1179          * from creating siblings.
1180          */
1181         if ((clone_flags & CLONE_PARENT) &&
1182                                 current->signal->flags & SIGNAL_UNKILLABLE)
1183                 return ERR_PTR(-EINVAL);
1184
1185         retval = security_task_create(clone_flags);
1186         if (retval)
1187                 goto fork_out;
1188
1189         retval = -ENOMEM;
1190         p = dup_task_struct(current);
1191         if (!p)
1192                 goto fork_out;
1193
1194         ftrace_graph_init_task(p);
1195
1196         rt_mutex_init_task(p);
1197
1198 #ifdef CONFIG_PROVE_LOCKING
1199         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1200         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1201 #endif
1202         retval = -EAGAIN;
1203         if (atomic_read(&p->real_cred->user->processes) >=
1204                         task_rlimit(p, RLIMIT_NPROC)) {
1205                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1206                     p->real_cred->user != INIT_USER)
1207                         goto bad_fork_free;
1208         }
1209         current->flags &= ~PF_NPROC_EXCEEDED;
1210
1211         retval = copy_creds(p, clone_flags);
1212         if (retval < 0)
1213                 goto bad_fork_free;
1214
1215         /*
1216          * If multiple threads are within copy_process(), then this check
1217          * triggers too late. This doesn't hurt, the check is only there
1218          * to stop root fork bombs.
1219          */
1220         retval = -EAGAIN;
1221         if (nr_threads >= max_threads)
1222                 goto bad_fork_cleanup_count;
1223
1224         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1225                 goto bad_fork_cleanup_count;
1226
1227         p->did_exec = 0;
1228         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1229         copy_flags(clone_flags, p);
1230         INIT_LIST_HEAD(&p->children);
1231         INIT_LIST_HEAD(&p->sibling);
1232         rcu_copy_process(p);
1233         p->vfork_done = NULL;
1234         spin_lock_init(&p->alloc_lock);
1235
1236         init_sigpending(&p->pending);
1237
1238         p->utime = p->stime = p->gtime = 0;
1239         p->utimescaled = p->stimescaled = 0;
1240 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1241         p->prev_utime = p->prev_stime = 0;
1242 #endif
1243 #if defined(SPLIT_RSS_COUNTING)
1244         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1245 #endif
1246
1247         p->default_timer_slack_ns = current->timer_slack_ns;
1248
1249         task_io_accounting_init(&p->ioac);
1250         acct_clear_integrals(p);
1251
1252         posix_cpu_timers_init(p);
1253
1254         do_posix_clock_monotonic_gettime(&p->start_time);
1255         p->real_start_time = p->start_time;
1256         monotonic_to_bootbased(&p->real_start_time);
1257         p->io_context = NULL;
1258         p->audit_context = NULL;
1259         if (clone_flags & CLONE_THREAD)
1260                 threadgroup_change_begin(current);
1261         cgroup_fork(p);
1262 #ifdef CONFIG_NUMA
1263         p->mempolicy = mpol_dup(p->mempolicy);
1264         if (IS_ERR(p->mempolicy)) {
1265                 retval = PTR_ERR(p->mempolicy);
1266                 p->mempolicy = NULL;
1267                 goto bad_fork_cleanup_cgroup;
1268         }
1269         mpol_fix_fork_child_flag(p);
1270 #endif
1271 #ifdef CONFIG_CPUSETS
1272         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1273         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1274         seqcount_init(&p->mems_allowed_seq);
1275 #endif
1276 #ifdef CONFIG_TRACE_IRQFLAGS
1277         p->irq_events = 0;
1278 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1279         p->hardirqs_enabled = 1;
1280 #else
1281         p->hardirqs_enabled = 0;
1282 #endif
1283         p->hardirq_enable_ip = 0;
1284         p->hardirq_enable_event = 0;
1285         p->hardirq_disable_ip = _THIS_IP_;
1286         p->hardirq_disable_event = 0;
1287         p->softirqs_enabled = 1;
1288         p->softirq_enable_ip = _THIS_IP_;
1289         p->softirq_enable_event = 0;
1290         p->softirq_disable_ip = 0;
1291         p->softirq_disable_event = 0;
1292         p->hardirq_context = 0;
1293         p->softirq_context = 0;
1294 #endif
1295 #ifdef CONFIG_LOCKDEP
1296         p->lockdep_depth = 0; /* no locks held yet */
1297         p->curr_chain_key = 0;
1298         p->lockdep_recursion = 0;
1299 #endif
1300
1301 #ifdef CONFIG_DEBUG_MUTEXES
1302         p->blocked_on = NULL; /* not blocked yet */
1303 #endif
1304 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1305         p->memcg_batch.do_batch = 0;
1306         p->memcg_batch.memcg = NULL;
1307 #endif
1308
1309         /* Perform scheduler related setup. Assign this task to a CPU. */
1310         sched_fork(p);
1311
1312         retval = perf_event_init_task(p);
1313         if (retval)
1314                 goto bad_fork_cleanup_policy;
1315         retval = audit_alloc(p);
1316         if (retval)
1317                 goto bad_fork_cleanup_policy;
1318         /* copy all the process information */
1319         retval = copy_semundo(clone_flags, p);
1320         if (retval)
1321                 goto bad_fork_cleanup_audit;
1322         retval = copy_files(clone_flags, p);
1323         if (retval)
1324                 goto bad_fork_cleanup_semundo;
1325         retval = copy_fs(clone_flags, p);
1326         if (retval)
1327                 goto bad_fork_cleanup_files;
1328         retval = copy_sighand(clone_flags, p);
1329         if (retval)
1330                 goto bad_fork_cleanup_fs;
1331         retval = copy_signal(clone_flags, p);
1332         if (retval)
1333                 goto bad_fork_cleanup_sighand;
1334         retval = copy_mm(clone_flags, p);
1335         if (retval)
1336                 goto bad_fork_cleanup_signal;
1337         retval = copy_namespaces(clone_flags, p);
1338         if (retval)
1339                 goto bad_fork_cleanup_mm;
1340         retval = copy_io(clone_flags, p);
1341         if (retval)
1342                 goto bad_fork_cleanup_namespaces;
1343         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1344         if (retval)
1345                 goto bad_fork_cleanup_io;
1346
1347         if (pid != &init_struct_pid) {
1348                 retval = -ENOMEM;
1349                 pid = alloc_pid(p->nsproxy->pid_ns);
1350                 if (!pid)
1351                         goto bad_fork_cleanup_io;
1352         }
1353
1354         p->pid = pid_nr(pid);
1355         p->tgid = p->pid;
1356         if (clone_flags & CLONE_THREAD)
1357                 p->tgid = current->tgid;
1358
1359         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1360         /*
1361          * Clear TID on mm_release()?
1362          */
1363         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1364 #ifdef CONFIG_BLOCK
1365         p->plug = NULL;
1366 #endif
1367 #ifdef CONFIG_FUTEX
1368         p->robust_list = NULL;
1369 #ifdef CONFIG_COMPAT
1370         p->compat_robust_list = NULL;
1371 #endif
1372         INIT_LIST_HEAD(&p->pi_state_list);
1373         p->pi_state_cache = NULL;
1374 #endif
1375         /*
1376          * sigaltstack should be cleared when sharing the same VM
1377          */
1378         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1379                 p->sas_ss_sp = p->sas_ss_size = 0;
1380
1381         /*
1382          * Syscall tracing and stepping should be turned off in the
1383          * child regardless of CLONE_PTRACE.
1384          */
1385         user_disable_single_step(p);
1386         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1387 #ifdef TIF_SYSCALL_EMU
1388         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1389 #endif
1390         clear_all_latency_tracing(p);
1391
1392         /* ok, now we should be set up.. */
1393         if (clone_flags & CLONE_THREAD)
1394                 p->exit_signal = -1;
1395         else if (clone_flags & CLONE_PARENT)
1396                 p->exit_signal = current->group_leader->exit_signal;
1397         else
1398                 p->exit_signal = (clone_flags & CSIGNAL);
1399
1400         p->pdeath_signal = 0;
1401         p->exit_state = 0;
1402
1403         p->nr_dirtied = 0;
1404         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1405         p->dirty_paused_when = 0;
1406
1407         /*
1408          * Ok, make it visible to the rest of the system.
1409          * We dont wake it up yet.
1410          */
1411         p->group_leader = p;
1412         INIT_LIST_HEAD(&p->thread_group);
1413
1414         /* Now that the task is set up, run cgroup callbacks if
1415          * necessary. We need to run them before the task is visible
1416          * on the tasklist. */
1417         cgroup_fork_callbacks(p);
1418         cgroup_callbacks_done = 1;
1419
1420         /* Need tasklist lock for parent etc handling! */
1421         write_lock_irq(&tasklist_lock);
1422
1423         /* CLONE_PARENT re-uses the old parent */
1424         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1425                 p->real_parent = current->real_parent;
1426                 p->parent_exec_id = current->parent_exec_id;
1427         } else {
1428                 p->real_parent = current;
1429                 p->parent_exec_id = current->self_exec_id;
1430         }
1431
1432         spin_lock(&current->sighand->siglock);
1433
1434         /*
1435          * Process group and session signals need to be delivered to just the
1436          * parent before the fork or both the parent and the child after the
1437          * fork. Restart if a signal comes in before we add the new process to
1438          * it's process group.
1439          * A fatal signal pending means that current will exit, so the new
1440          * thread can't slip out of an OOM kill (or normal SIGKILL).
1441         */
1442         recalc_sigpending();
1443         if (signal_pending(current)) {
1444                 spin_unlock(&current->sighand->siglock);
1445                 write_unlock_irq(&tasklist_lock);
1446                 retval = -ERESTARTNOINTR;
1447                 goto bad_fork_free_pid;
1448         }
1449
1450         if (clone_flags & CLONE_THREAD) {
1451                 current->signal->nr_threads++;
1452                 atomic_inc(&current->signal->live);
1453                 atomic_inc(&current->signal->sigcnt);
1454                 p->group_leader = current->group_leader;
1455                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1456         }
1457
1458         if (likely(p->pid)) {
1459                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1460
1461                 if (thread_group_leader(p)) {
1462                         if (is_child_reaper(pid))
1463                                 p->nsproxy->pid_ns->child_reaper = p;
1464
1465                         p->signal->leader_pid = pid;
1466                         p->signal->tty = tty_kref_get(current->signal->tty);
1467                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1468                         attach_pid(p, PIDTYPE_SID, task_session(current));
1469                         list_add_tail(&p->sibling, &p->real_parent->children);
1470                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1471                         __this_cpu_inc(process_counts);
1472                 }
1473                 attach_pid(p, PIDTYPE_PID, pid);
1474                 nr_threads++;
1475         }
1476
1477         total_forks++;
1478         spin_unlock(&current->sighand->siglock);
1479         write_unlock_irq(&tasklist_lock);
1480         proc_fork_connector(p);
1481         cgroup_post_fork(p);
1482         if (clone_flags & CLONE_THREAD)
1483                 threadgroup_change_end(current);
1484         perf_event_fork(p);
1485
1486         trace_task_newtask(p, clone_flags);
1487
1488         return p;
1489
1490 bad_fork_free_pid:
1491         if (pid != &init_struct_pid)
1492                 free_pid(pid);
1493 bad_fork_cleanup_io:
1494         if (p->io_context)
1495                 exit_io_context(p);
1496 bad_fork_cleanup_namespaces:
1497         exit_task_namespaces(p);
1498 bad_fork_cleanup_mm:
1499         if (p->mm)
1500                 mmput(p->mm);
1501 bad_fork_cleanup_signal:
1502         if (!(clone_flags & CLONE_THREAD))
1503                 free_signal_struct(p->signal);
1504 bad_fork_cleanup_sighand:
1505         __cleanup_sighand(p->sighand);
1506 bad_fork_cleanup_fs:
1507         exit_fs(p); /* blocking */
1508 bad_fork_cleanup_files:
1509         exit_files(p); /* blocking */
1510 bad_fork_cleanup_semundo:
1511         exit_sem(p);
1512 bad_fork_cleanup_audit:
1513         audit_free(p);
1514 bad_fork_cleanup_policy:
1515         perf_event_free_task(p);
1516 #ifdef CONFIG_NUMA
1517         mpol_put(p->mempolicy);
1518 bad_fork_cleanup_cgroup:
1519 #endif
1520         if (clone_flags & CLONE_THREAD)
1521                 threadgroup_change_end(current);
1522         cgroup_exit(p, cgroup_callbacks_done);
1523         delayacct_tsk_free(p);
1524         module_put(task_thread_info(p)->exec_domain->module);
1525 bad_fork_cleanup_count:
1526         atomic_dec(&p->cred->user->processes);
1527         exit_creds(p);
1528 bad_fork_free:
1529         free_task(p);
1530 fork_out:
1531         return ERR_PTR(retval);
1532 }
1533
1534 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1535 {
1536         memset(regs, 0, sizeof(struct pt_regs));
1537         return regs;
1538 }
1539
1540 static inline void init_idle_pids(struct pid_link *links)
1541 {
1542         enum pid_type type;
1543
1544         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1545                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1546                 links[type].pid = &init_struct_pid;
1547         }
1548 }
1549
1550 struct task_struct * __cpuinit fork_idle(int cpu)
1551 {
1552         struct task_struct *task;
1553         struct pt_regs regs;
1554
1555         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1556                             &init_struct_pid, 0);
1557         if (!IS_ERR(task)) {
1558                 init_idle_pids(task->pids);
1559                 init_idle(task, cpu);
1560         }
1561
1562         return task;
1563 }
1564
1565 /*
1566  *  Ok, this is the main fork-routine.
1567  *
1568  * It copies the process, and if successful kick-starts
1569  * it and waits for it to finish using the VM if required.
1570  */
1571 long do_fork(unsigned long clone_flags,
1572               unsigned long stack_start,
1573               struct pt_regs *regs,
1574               unsigned long stack_size,
1575               int __user *parent_tidptr,
1576               int __user *child_tidptr)
1577 {
1578         struct task_struct *p;
1579         int trace = 0;
1580         long nr;
1581
1582         /*
1583          * Do some preliminary argument and permissions checking before we
1584          * actually start allocating stuff
1585          */
1586         if (clone_flags & CLONE_NEWUSER) {
1587                 if (clone_flags & CLONE_THREAD)
1588                         return -EINVAL;
1589                 /* hopefully this check will go away when userns support is
1590                  * complete
1591                  */
1592                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1593                                 !capable(CAP_SETGID))
1594                         return -EPERM;
1595         }
1596
1597         /*
1598          * Determine whether and which event to report to ptracer.  When
1599          * called from kernel_thread or CLONE_UNTRACED is explicitly
1600          * requested, no event is reported; otherwise, report if the event
1601          * for the type of forking is enabled.
1602          */
1603         if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1604                 if (clone_flags & CLONE_VFORK)
1605                         trace = PTRACE_EVENT_VFORK;
1606                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1607                         trace = PTRACE_EVENT_CLONE;
1608                 else
1609                         trace = PTRACE_EVENT_FORK;
1610
1611                 if (likely(!ptrace_event_enabled(current, trace)))
1612                         trace = 0;
1613         }
1614
1615         p = copy_process(clone_flags, stack_start, regs, stack_size,
1616                          child_tidptr, NULL, trace);
1617         /*
1618          * Do this prior waking up the new thread - the thread pointer
1619          * might get invalid after that point, if the thread exits quickly.
1620          */
1621         if (!IS_ERR(p)) {
1622                 struct completion vfork;
1623
1624                 trace_sched_process_fork(current, p);
1625
1626                 nr = task_pid_vnr(p);
1627
1628                 if (clone_flags & CLONE_PARENT_SETTID)
1629                         put_user(nr, parent_tidptr);
1630
1631                 if (clone_flags & CLONE_VFORK) {
1632                         p->vfork_done = &vfork;
1633                         init_completion(&vfork);
1634                         get_task_struct(p);
1635                 }
1636
1637                 wake_up_new_task(p);
1638
1639                 /* forking complete and child started to run, tell ptracer */
1640                 if (unlikely(trace))
1641                         ptrace_event(trace, nr);
1642
1643                 if (clone_flags & CLONE_VFORK) {
1644                         if (!wait_for_vfork_done(p, &vfork))
1645                                 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1646                 }
1647         } else {
1648                 nr = PTR_ERR(p);
1649         }
1650         return nr;
1651 }
1652
1653 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1654 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1655 #endif
1656
1657 static void sighand_ctor(void *data)
1658 {
1659         struct sighand_struct *sighand = data;
1660
1661         spin_lock_init(&sighand->siglock);
1662         init_waitqueue_head(&sighand->signalfd_wqh);
1663 }
1664
1665 void __init proc_caches_init(void)
1666 {
1667         sighand_cachep = kmem_cache_create("sighand_cache",
1668                         sizeof(struct sighand_struct), 0,
1669                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1670                         SLAB_NOTRACK, sighand_ctor);
1671         signal_cachep = kmem_cache_create("signal_cache",
1672                         sizeof(struct signal_struct), 0,
1673                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1674         files_cachep = kmem_cache_create("files_cache",
1675                         sizeof(struct files_struct), 0,
1676                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1677         fs_cachep = kmem_cache_create("fs_cache",
1678                         sizeof(struct fs_struct), 0,
1679                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1680         /*
1681          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1682          * whole struct cpumask for the OFFSTACK case. We could change
1683          * this to *only* allocate as much of it as required by the
1684          * maximum number of CPU's we can ever have.  The cpumask_allocation
1685          * is at the end of the structure, exactly for that reason.
1686          */
1687         mm_cachep = kmem_cache_create("mm_struct",
1688                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1689                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1690         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1691         mmap_init();
1692         nsproxy_cache_init();
1693 }
1694
1695 /*
1696  * Check constraints on flags passed to the unshare system call.
1697  */
1698 static int check_unshare_flags(unsigned long unshare_flags)
1699 {
1700         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1701                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1702                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1703                 return -EINVAL;
1704         /*
1705          * Not implemented, but pretend it works if there is nothing to
1706          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1707          * needs to unshare vm.
1708          */
1709         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1710                 /* FIXME: get_task_mm() increments ->mm_users */
1711                 if (atomic_read(&current->mm->mm_users) > 1)
1712                         return -EINVAL;
1713         }
1714
1715         return 0;
1716 }
1717
1718 /*
1719  * Unshare the filesystem structure if it is being shared
1720  */
1721 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1722 {
1723         struct fs_struct *fs = current->fs;
1724
1725         if (!(unshare_flags & CLONE_FS) || !fs)
1726                 return 0;
1727
1728         /* don't need lock here; in the worst case we'll do useless copy */
1729         if (fs->users == 1)
1730                 return 0;
1731
1732         *new_fsp = copy_fs_struct(fs);
1733         if (!*new_fsp)
1734                 return -ENOMEM;
1735
1736         return 0;
1737 }
1738
1739 /*
1740  * Unshare file descriptor table if it is being shared
1741  */
1742 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1743 {
1744         struct files_struct *fd = current->files;
1745         int error = 0;
1746
1747         if ((unshare_flags & CLONE_FILES) &&
1748             (fd && atomic_read(&fd->count) > 1)) {
1749                 *new_fdp = dup_fd(fd, &error);
1750                 if (!*new_fdp)
1751                         return error;
1752         }
1753
1754         return 0;
1755 }
1756
1757 /*
1758  * unshare allows a process to 'unshare' part of the process
1759  * context which was originally shared using clone.  copy_*
1760  * functions used by do_fork() cannot be used here directly
1761  * because they modify an inactive task_struct that is being
1762  * constructed. Here we are modifying the current, active,
1763  * task_struct.
1764  */
1765 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1766 {
1767         struct fs_struct *fs, *new_fs = NULL;
1768         struct files_struct *fd, *new_fd = NULL;
1769         struct nsproxy *new_nsproxy = NULL;
1770         int do_sysvsem = 0;
1771         int err;
1772
1773         err = check_unshare_flags(unshare_flags);
1774         if (err)
1775                 goto bad_unshare_out;
1776
1777         /*
1778          * If unsharing namespace, must also unshare filesystem information.
1779          */
1780         if (unshare_flags & CLONE_NEWNS)
1781                 unshare_flags |= CLONE_FS;
1782         /*
1783          * CLONE_NEWIPC must also detach from the undolist: after switching
1784          * to a new ipc namespace, the semaphore arrays from the old
1785          * namespace are unreachable.
1786          */
1787         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1788                 do_sysvsem = 1;
1789         err = unshare_fs(unshare_flags, &new_fs);
1790         if (err)
1791                 goto bad_unshare_out;
1792         err = unshare_fd(unshare_flags, &new_fd);
1793         if (err)
1794                 goto bad_unshare_cleanup_fs;
1795         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1796         if (err)
1797                 goto bad_unshare_cleanup_fd;
1798
1799         if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1800                 if (do_sysvsem) {
1801                         /*
1802                          * CLONE_SYSVSEM is equivalent to sys_exit().
1803                          */
1804                         exit_sem(current);
1805                 }
1806
1807                 if (new_nsproxy) {
1808                         switch_task_namespaces(current, new_nsproxy);
1809                         new_nsproxy = NULL;
1810                 }
1811
1812                 task_lock(current);
1813
1814                 if (new_fs) {
1815                         fs = current->fs;
1816                         spin_lock(&fs->lock);
1817                         current->fs = new_fs;
1818                         if (--fs->users)
1819                                 new_fs = NULL;
1820                         else
1821                                 new_fs = fs;
1822                         spin_unlock(&fs->lock);
1823                 }
1824
1825                 if (new_fd) {
1826                         fd = current->files;
1827                         current->files = new_fd;
1828                         new_fd = fd;
1829                 }
1830
1831                 task_unlock(current);
1832         }
1833
1834         if (new_nsproxy)
1835                 put_nsproxy(new_nsproxy);
1836
1837 bad_unshare_cleanup_fd:
1838         if (new_fd)
1839                 put_files_struct(new_fd);
1840
1841 bad_unshare_cleanup_fs:
1842         if (new_fs)
1843                 free_fs_struct(new_fs);
1844
1845 bad_unshare_out:
1846         return err;
1847 }
1848
1849 /*
1850  *      Helper to unshare the files of the current task.
1851  *      We don't want to expose copy_files internals to
1852  *      the exec layer of the kernel.
1853  */
1854
1855 int unshare_files(struct files_struct **displaced)
1856 {
1857         struct task_struct *task = current;
1858         struct files_struct *copy = NULL;
1859         int error;
1860
1861         error = unshare_fd(CLONE_FILES, &copy);
1862         if (error || !copy) {
1863                 *displaced = NULL;
1864                 return error;
1865         }
1866         *displaced = task->files;
1867         task_lock(task);
1868         task->files = copy;
1869         task_unlock(task);
1870         return 0;
1871 }