Merge remote-tracking branch 'asoc/topic/dapm' into asoc-next
[platform/adaptation/renesas_rcar/renesas_kernel.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/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  */
90 unsigned long total_forks;      /* Handle normal Linux uptimes. */
91 int nr_threads;                 /* The idle threads do not count.. */
92
93 int max_threads;                /* tunable limit on nr_threads */
94
95 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
96
97 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
98
99 #ifdef CONFIG_PROVE_RCU
100 int lockdep_tasklist_lock_is_held(void)
101 {
102         return lockdep_is_held(&tasklist_lock);
103 }
104 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
105 #endif /* #ifdef CONFIG_PROVE_RCU */
106
107 int 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
118 void __weak arch_release_task_struct(struct task_struct *tsk)
119 {
120 }
121
122 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
123 static struct kmem_cache *task_struct_cachep;
124
125 static 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
130 static inline void free_task_struct(struct task_struct *tsk)
131 {
132         kmem_cache_free(task_struct_cachep, tsk);
133 }
134 #endif
135
136 void __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
147 static 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
156 static inline void free_thread_info(struct thread_info *ti)
157 {
158         free_memcg_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
159 }
160 # else
161 static struct kmem_cache *thread_info_cache;
162
163 static 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
169 static void free_thread_info(struct thread_info *ti)
170 {
171         kmem_cache_free(thread_info_cache, ti);
172 }
173
174 void 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) */
184 static struct kmem_cache *signal_cachep;
185
186 /* SLAB cache for sighand_struct structures (tsk->sighand) */
187 struct kmem_cache *sighand_cachep;
188
189 /* SLAB cache for files_struct structures (tsk->files) */
190 struct kmem_cache *files_cachep;
191
192 /* SLAB cache for fs_struct structures (tsk->fs) */
193 struct kmem_cache *fs_cachep;
194
195 /* SLAB cache for vm_area_struct structures */
196 struct kmem_cache *vm_area_cachep;
197
198 /* SLAB cache for mm_struct structures (tsk->mm) */
199 static struct kmem_cache *mm_cachep;
200
201 static 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
208 void 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 }
219 EXPORT_SYMBOL(free_task);
220
221 static 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
228 static 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
234 void __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 }
248 EXPORT_SYMBOL_GPL(__put_task_struct);
249
250 void __init __weak arch_task_cache_init(void) { }
251
252 void __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
286 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
287                                                struct task_struct *src)
288 {
289         *dst = *src;
290         return 0;
291 }
292
293 static 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
340 free_ti:
341         free_thread_info(ti);
342 free_tsk:
343         free_task_struct(tsk);
344         return NULL;
345 }
346
347 #ifdef CONFIG_MMU
348 static 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
355         uprobe_start_dup_mmap();
356         down_write(&oldmm->mmap_sem);
357         flush_cache_dup_mm(oldmm);
358         uprobe_dup_mmap(oldmm, mm);
359         /*
360          * Not linked in yet - no deadlock potential:
361          */
362         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
363
364         mm->locked_vm = 0;
365         mm->mmap = NULL;
366         mm->mmap_cache = NULL;
367         mm->map_count = 0;
368         cpumask_clear(mm_cpumask(mm));
369         mm->mm_rb = RB_ROOT;
370         rb_link = &mm->mm_rb.rb_node;
371         rb_parent = NULL;
372         pprev = &mm->mmap;
373         retval = ksm_fork(mm, oldmm);
374         if (retval)
375                 goto out;
376         retval = khugepaged_fork(mm, oldmm);
377         if (retval)
378                 goto out;
379
380         prev = NULL;
381         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
382                 struct file *file;
383
384                 if (mpnt->vm_flags & VM_DONTCOPY) {
385                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
386                                                         -vma_pages(mpnt));
387                         continue;
388                 }
389                 charge = 0;
390                 if (mpnt->vm_flags & VM_ACCOUNT) {
391                         unsigned long len = vma_pages(mpnt);
392
393                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
394                                 goto fail_nomem;
395                         charge = len;
396                 }
397                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
398                 if (!tmp)
399                         goto fail_nomem;
400                 *tmp = *mpnt;
401                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
402                 retval = vma_dup_policy(mpnt, tmp);
403                 if (retval)
404                         goto fail_nomem_policy;
405                 tmp->vm_mm = mm;
406                 if (anon_vma_fork(tmp, mpnt))
407                         goto fail_nomem_anon_vma_fork;
408                 tmp->vm_flags &= ~VM_LOCKED;
409                 tmp->vm_next = tmp->vm_prev = NULL;
410                 file = tmp->vm_file;
411                 if (file) {
412                         struct inode *inode = file_inode(file);
413                         struct address_space *mapping = file->f_mapping;
414
415                         get_file(file);
416                         if (tmp->vm_flags & VM_DENYWRITE)
417                                 atomic_dec(&inode->i_writecount);
418                         mutex_lock(&mapping->i_mmap_mutex);
419                         if (tmp->vm_flags & VM_SHARED)
420                                 mapping->i_mmap_writable++;
421                         flush_dcache_mmap_lock(mapping);
422                         /* insert tmp into the share list, just after mpnt */
423                         if (unlikely(tmp->vm_flags & VM_NONLINEAR))
424                                 vma_nonlinear_insert(tmp,
425                                                 &mapping->i_mmap_nonlinear);
426                         else
427                                 vma_interval_tree_insert_after(tmp, mpnt,
428                                                         &mapping->i_mmap);
429                         flush_dcache_mmap_unlock(mapping);
430                         mutex_unlock(&mapping->i_mmap_mutex);
431                 }
432
433                 /*
434                  * Clear hugetlb-related page reserves for children. This only
435                  * affects MAP_PRIVATE mappings. Faults generated by the child
436                  * are not guaranteed to succeed, even if read-only
437                  */
438                 if (is_vm_hugetlb_page(tmp))
439                         reset_vma_resv_huge_pages(tmp);
440
441                 /*
442                  * Link in the new vma and copy the page table entries.
443                  */
444                 *pprev = tmp;
445                 pprev = &tmp->vm_next;
446                 tmp->vm_prev = prev;
447                 prev = tmp;
448
449                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
450                 rb_link = &tmp->vm_rb.rb_right;
451                 rb_parent = &tmp->vm_rb;
452
453                 mm->map_count++;
454                 retval = copy_page_range(mm, oldmm, mpnt);
455
456                 if (tmp->vm_ops && tmp->vm_ops->open)
457                         tmp->vm_ops->open(tmp);
458
459                 if (retval)
460                         goto out;
461         }
462         /* a new mm has just been created */
463         arch_dup_mmap(oldmm, mm);
464         retval = 0;
465 out:
466         up_write(&mm->mmap_sem);
467         flush_tlb_mm(oldmm);
468         up_write(&oldmm->mmap_sem);
469         uprobe_end_dup_mmap();
470         return retval;
471 fail_nomem_anon_vma_fork:
472         mpol_put(vma_policy(tmp));
473 fail_nomem_policy:
474         kmem_cache_free(vm_area_cachep, tmp);
475 fail_nomem:
476         retval = -ENOMEM;
477         vm_unacct_memory(charge);
478         goto out;
479 }
480
481 static inline int mm_alloc_pgd(struct mm_struct *mm)
482 {
483         mm->pgd = pgd_alloc(mm);
484         if (unlikely(!mm->pgd))
485                 return -ENOMEM;
486         return 0;
487 }
488
489 static inline void mm_free_pgd(struct mm_struct *mm)
490 {
491         pgd_free(mm, mm->pgd);
492 }
493 #else
494 #define dup_mmap(mm, oldmm)     (0)
495 #define mm_alloc_pgd(mm)        (0)
496 #define mm_free_pgd(mm)
497 #endif /* CONFIG_MMU */
498
499 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
500
501 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
502 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
503
504 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
505
506 static int __init coredump_filter_setup(char *s)
507 {
508         default_dump_filter =
509                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
510                 MMF_DUMP_FILTER_MASK;
511         return 1;
512 }
513
514 __setup("coredump_filter=", coredump_filter_setup);
515
516 #include <linux/init_task.h>
517
518 static void mm_init_aio(struct mm_struct *mm)
519 {
520 #ifdef CONFIG_AIO
521         spin_lock_init(&mm->ioctx_lock);
522         mm->ioctx_table = NULL;
523 #endif
524 }
525
526 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
527 {
528         atomic_set(&mm->mm_users, 1);
529         atomic_set(&mm->mm_count, 1);
530         init_rwsem(&mm->mmap_sem);
531         INIT_LIST_HEAD(&mm->mmlist);
532         mm->flags = (current->mm) ?
533                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
534         mm->core_state = NULL;
535         atomic_long_set(&mm->nr_ptes, 0);
536         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
537         spin_lock_init(&mm->page_table_lock);
538         mm_init_aio(mm);
539         mm_init_owner(mm, p);
540         clear_tlb_flush_pending(mm);
541
542         if (likely(!mm_alloc_pgd(mm))) {
543                 mm->def_flags = 0;
544                 mmu_notifier_mm_init(mm);
545                 return mm;
546         }
547
548         free_mm(mm);
549         return NULL;
550 }
551
552 static void check_mm(struct mm_struct *mm)
553 {
554         int i;
555
556         for (i = 0; i < NR_MM_COUNTERS; i++) {
557                 long x = atomic_long_read(&mm->rss_stat.count[i]);
558
559                 if (unlikely(x))
560                         printk(KERN_ALERT "BUG: Bad rss-counter state "
561                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
562         }
563
564 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
565         VM_BUG_ON(mm->pmd_huge_pte);
566 #endif
567 }
568
569 /*
570  * Allocate and initialize an mm_struct.
571  */
572 struct mm_struct *mm_alloc(void)
573 {
574         struct mm_struct *mm;
575
576         mm = allocate_mm();
577         if (!mm)
578                 return NULL;
579
580         memset(mm, 0, sizeof(*mm));
581         mm_init_cpumask(mm);
582         return mm_init(mm, current);
583 }
584
585 /*
586  * Called when the last reference to the mm
587  * is dropped: either by a lazy thread or by
588  * mmput. Free the page directory and the mm.
589  */
590 void __mmdrop(struct mm_struct *mm)
591 {
592         BUG_ON(mm == &init_mm);
593         mm_free_pgd(mm);
594         destroy_context(mm);
595         mmu_notifier_mm_destroy(mm);
596         check_mm(mm);
597         free_mm(mm);
598 }
599 EXPORT_SYMBOL_GPL(__mmdrop);
600
601 /*
602  * Decrement the use count and release all resources for an mm.
603  */
604 void mmput(struct mm_struct *mm)
605 {
606         might_sleep();
607
608         if (atomic_dec_and_test(&mm->mm_users)) {
609                 uprobe_clear_state(mm);
610                 exit_aio(mm);
611                 ksm_exit(mm);
612                 khugepaged_exit(mm); /* must run before exit_mmap */
613                 exit_mmap(mm);
614                 set_mm_exe_file(mm, NULL);
615                 if (!list_empty(&mm->mmlist)) {
616                         spin_lock(&mmlist_lock);
617                         list_del(&mm->mmlist);
618                         spin_unlock(&mmlist_lock);
619                 }
620                 if (mm->binfmt)
621                         module_put(mm->binfmt->module);
622                 mmdrop(mm);
623         }
624 }
625 EXPORT_SYMBOL_GPL(mmput);
626
627 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
628 {
629         if (new_exe_file)
630                 get_file(new_exe_file);
631         if (mm->exe_file)
632                 fput(mm->exe_file);
633         mm->exe_file = new_exe_file;
634 }
635
636 struct file *get_mm_exe_file(struct mm_struct *mm)
637 {
638         struct file *exe_file;
639
640         /* We need mmap_sem to protect against races with removal of exe_file */
641         down_read(&mm->mmap_sem);
642         exe_file = mm->exe_file;
643         if (exe_file)
644                 get_file(exe_file);
645         up_read(&mm->mmap_sem);
646         return exe_file;
647 }
648
649 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
650 {
651         /* It's safe to write the exe_file pointer without exe_file_lock because
652          * this is called during fork when the task is not yet in /proc */
653         newmm->exe_file = get_mm_exe_file(oldmm);
654 }
655
656 /**
657  * get_task_mm - acquire a reference to the task's mm
658  *
659  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
660  * this kernel workthread has transiently adopted a user mm with use_mm,
661  * to do its AIO) is not set and if so returns a reference to it, after
662  * bumping up the use count.  User must release the mm via mmput()
663  * after use.  Typically used by /proc and ptrace.
664  */
665 struct mm_struct *get_task_mm(struct task_struct *task)
666 {
667         struct mm_struct *mm;
668
669         task_lock(task);
670         mm = task->mm;
671         if (mm) {
672                 if (task->flags & PF_KTHREAD)
673                         mm = NULL;
674                 else
675                         atomic_inc(&mm->mm_users);
676         }
677         task_unlock(task);
678         return mm;
679 }
680 EXPORT_SYMBOL_GPL(get_task_mm);
681
682 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
683 {
684         struct mm_struct *mm;
685         int err;
686
687         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
688         if (err)
689                 return ERR_PTR(err);
690
691         mm = get_task_mm(task);
692         if (mm && mm != current->mm &&
693                         !ptrace_may_access(task, mode)) {
694                 mmput(mm);
695                 mm = ERR_PTR(-EACCES);
696         }
697         mutex_unlock(&task->signal->cred_guard_mutex);
698
699         return mm;
700 }
701
702 static void complete_vfork_done(struct task_struct *tsk)
703 {
704         struct completion *vfork;
705
706         task_lock(tsk);
707         vfork = tsk->vfork_done;
708         if (likely(vfork)) {
709                 tsk->vfork_done = NULL;
710                 complete(vfork);
711         }
712         task_unlock(tsk);
713 }
714
715 static int wait_for_vfork_done(struct task_struct *child,
716                                 struct completion *vfork)
717 {
718         int killed;
719
720         freezer_do_not_count();
721         killed = wait_for_completion_killable(vfork);
722         freezer_count();
723
724         if (killed) {
725                 task_lock(child);
726                 child->vfork_done = NULL;
727                 task_unlock(child);
728         }
729
730         put_task_struct(child);
731         return killed;
732 }
733
734 /* Please note the differences between mmput and mm_release.
735  * mmput is called whenever we stop holding onto a mm_struct,
736  * error success whatever.
737  *
738  * mm_release is called after a mm_struct has been removed
739  * from the current process.
740  *
741  * This difference is important for error handling, when we
742  * only half set up a mm_struct for a new process and need to restore
743  * the old one.  Because we mmput the new mm_struct before
744  * restoring the old one. . .
745  * Eric Biederman 10 January 1998
746  */
747 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
748 {
749         /* Get rid of any futexes when releasing the mm */
750 #ifdef CONFIG_FUTEX
751         if (unlikely(tsk->robust_list)) {
752                 exit_robust_list(tsk);
753                 tsk->robust_list = NULL;
754         }
755 #ifdef CONFIG_COMPAT
756         if (unlikely(tsk->compat_robust_list)) {
757                 compat_exit_robust_list(tsk);
758                 tsk->compat_robust_list = NULL;
759         }
760 #endif
761         if (unlikely(!list_empty(&tsk->pi_state_list)))
762                 exit_pi_state_list(tsk);
763 #endif
764
765         uprobe_free_utask(tsk);
766
767         /* Get rid of any cached register state */
768         deactivate_mm(tsk, mm);
769
770         /*
771          * If we're exiting normally, clear a user-space tid field if
772          * requested.  We leave this alone when dying by signal, to leave
773          * the value intact in a core dump, and to save the unnecessary
774          * trouble, say, a killed vfork parent shouldn't touch this mm.
775          * Userland only wants this done for a sys_exit.
776          */
777         if (tsk->clear_child_tid) {
778                 if (!(tsk->flags & PF_SIGNALED) &&
779                     atomic_read(&mm->mm_users) > 1) {
780                         /*
781                          * We don't check the error code - if userspace has
782                          * not set up a proper pointer then tough luck.
783                          */
784                         put_user(0, tsk->clear_child_tid);
785                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
786                                         1, NULL, NULL, 0);
787                 }
788                 tsk->clear_child_tid = NULL;
789         }
790
791         /*
792          * All done, finally we can wake up parent and return this mm to him.
793          * Also kthread_stop() uses this completion for synchronization.
794          */
795         if (tsk->vfork_done)
796                 complete_vfork_done(tsk);
797 }
798
799 /*
800  * Allocate a new mm structure and copy contents from the
801  * mm structure of the passed in task structure.
802  */
803 struct mm_struct *dup_mm(struct task_struct *tsk)
804 {
805         struct mm_struct *mm, *oldmm = current->mm;
806         int err;
807
808         if (!oldmm)
809                 return NULL;
810
811         mm = allocate_mm();
812         if (!mm)
813                 goto fail_nomem;
814
815         memcpy(mm, oldmm, sizeof(*mm));
816         mm_init_cpumask(mm);
817
818 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
819         mm->pmd_huge_pte = NULL;
820 #endif
821         if (!mm_init(mm, tsk))
822                 goto fail_nomem;
823
824         if (init_new_context(tsk, mm))
825                 goto fail_nocontext;
826
827         dup_mm_exe_file(oldmm, mm);
828
829         err = dup_mmap(mm, oldmm);
830         if (err)
831                 goto free_pt;
832
833         mm->hiwater_rss = get_mm_rss(mm);
834         mm->hiwater_vm = mm->total_vm;
835
836         if (mm->binfmt && !try_module_get(mm->binfmt->module))
837                 goto free_pt;
838
839         return mm;
840
841 free_pt:
842         /* don't put binfmt in mmput, we haven't got module yet */
843         mm->binfmt = NULL;
844         mmput(mm);
845
846 fail_nomem:
847         return NULL;
848
849 fail_nocontext:
850         /*
851          * If init_new_context() failed, we cannot use mmput() to free the mm
852          * because it calls destroy_context()
853          */
854         mm_free_pgd(mm);
855         free_mm(mm);
856         return NULL;
857 }
858
859 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
860 {
861         struct mm_struct *mm, *oldmm;
862         int retval;
863
864         tsk->min_flt = tsk->maj_flt = 0;
865         tsk->nvcsw = tsk->nivcsw = 0;
866 #ifdef CONFIG_DETECT_HUNG_TASK
867         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
868 #endif
869
870         tsk->mm = NULL;
871         tsk->active_mm = NULL;
872
873         /*
874          * Are we cloning a kernel thread?
875          *
876          * We need to steal a active VM for that..
877          */
878         oldmm = current->mm;
879         if (!oldmm)
880                 return 0;
881
882         if (clone_flags & CLONE_VM) {
883                 atomic_inc(&oldmm->mm_users);
884                 mm = oldmm;
885                 goto good_mm;
886         }
887
888         retval = -ENOMEM;
889         mm = dup_mm(tsk);
890         if (!mm)
891                 goto fail_nomem;
892
893 good_mm:
894         tsk->mm = mm;
895         tsk->active_mm = mm;
896         return 0;
897
898 fail_nomem:
899         return retval;
900 }
901
902 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
903 {
904         struct fs_struct *fs = current->fs;
905         if (clone_flags & CLONE_FS) {
906                 /* tsk->fs is already what we want */
907                 spin_lock(&fs->lock);
908                 if (fs->in_exec) {
909                         spin_unlock(&fs->lock);
910                         return -EAGAIN;
911                 }
912                 fs->users++;
913                 spin_unlock(&fs->lock);
914                 return 0;
915         }
916         tsk->fs = copy_fs_struct(fs);
917         if (!tsk->fs)
918                 return -ENOMEM;
919         return 0;
920 }
921
922 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
923 {
924         struct files_struct *oldf, *newf;
925         int error = 0;
926
927         /*
928          * A background process may not have any files ...
929          */
930         oldf = current->files;
931         if (!oldf)
932                 goto out;
933
934         if (clone_flags & CLONE_FILES) {
935                 atomic_inc(&oldf->count);
936                 goto out;
937         }
938
939         newf = dup_fd(oldf, &error);
940         if (!newf)
941                 goto out;
942
943         tsk->files = newf;
944         error = 0;
945 out:
946         return error;
947 }
948
949 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
950 {
951 #ifdef CONFIG_BLOCK
952         struct io_context *ioc = current->io_context;
953         struct io_context *new_ioc;
954
955         if (!ioc)
956                 return 0;
957         /*
958          * Share io context with parent, if CLONE_IO is set
959          */
960         if (clone_flags & CLONE_IO) {
961                 ioc_task_link(ioc);
962                 tsk->io_context = ioc;
963         } else if (ioprio_valid(ioc->ioprio)) {
964                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
965                 if (unlikely(!new_ioc))
966                         return -ENOMEM;
967
968                 new_ioc->ioprio = ioc->ioprio;
969                 put_io_context(new_ioc);
970         }
971 #endif
972         return 0;
973 }
974
975 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
976 {
977         struct sighand_struct *sig;
978
979         if (clone_flags & CLONE_SIGHAND) {
980                 atomic_inc(&current->sighand->count);
981                 return 0;
982         }
983         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
984         rcu_assign_pointer(tsk->sighand, sig);
985         if (!sig)
986                 return -ENOMEM;
987         atomic_set(&sig->count, 1);
988         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
989         return 0;
990 }
991
992 void __cleanup_sighand(struct sighand_struct *sighand)
993 {
994         if (atomic_dec_and_test(&sighand->count)) {
995                 signalfd_cleanup(sighand);
996                 kmem_cache_free(sighand_cachep, sighand);
997         }
998 }
999
1000
1001 /*
1002  * Initialize POSIX timer handling for a thread group.
1003  */
1004 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1005 {
1006         unsigned long cpu_limit;
1007
1008         /* Thread group counters. */
1009         thread_group_cputime_init(sig);
1010
1011         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1012         if (cpu_limit != RLIM_INFINITY) {
1013                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1014                 sig->cputimer.running = 1;
1015         }
1016
1017         /* The timer lists. */
1018         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1019         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1020         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1021 }
1022
1023 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1024 {
1025         struct signal_struct *sig;
1026
1027         if (clone_flags & CLONE_THREAD)
1028                 return 0;
1029
1030         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1031         tsk->signal = sig;
1032         if (!sig)
1033                 return -ENOMEM;
1034
1035         sig->nr_threads = 1;
1036         atomic_set(&sig->live, 1);
1037         atomic_set(&sig->sigcnt, 1);
1038         init_waitqueue_head(&sig->wait_chldexit);
1039         sig->curr_target = tsk;
1040         init_sigpending(&sig->shared_pending);
1041         INIT_LIST_HEAD(&sig->posix_timers);
1042
1043         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1044         sig->real_timer.function = it_real_fn;
1045
1046         task_lock(current->group_leader);
1047         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1048         task_unlock(current->group_leader);
1049
1050         posix_cpu_timers_init_group(sig);
1051
1052         tty_audit_fork(sig);
1053         sched_autogroup_fork(sig);
1054
1055 #ifdef CONFIG_CGROUPS
1056         init_rwsem(&sig->group_rwsem);
1057 #endif
1058
1059         sig->oom_score_adj = current->signal->oom_score_adj;
1060         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1061
1062         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1063                                    current->signal->is_child_subreaper;
1064
1065         mutex_init(&sig->cred_guard_mutex);
1066
1067         return 0;
1068 }
1069
1070 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1071 {
1072         unsigned long new_flags = p->flags;
1073
1074         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1075         new_flags |= PF_FORKNOEXEC;
1076         p->flags = new_flags;
1077 }
1078
1079 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1080 {
1081         current->clear_child_tid = tidptr;
1082
1083         return task_pid_vnr(current);
1084 }
1085
1086 static void rt_mutex_init_task(struct task_struct *p)
1087 {
1088         raw_spin_lock_init(&p->pi_lock);
1089 #ifdef CONFIG_RT_MUTEXES
1090         plist_head_init(&p->pi_waiters);
1091         p->pi_blocked_on = NULL;
1092 #endif
1093 }
1094
1095 #ifdef CONFIG_MM_OWNER
1096 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1097 {
1098         mm->owner = p;
1099 }
1100 #endif /* CONFIG_MM_OWNER */
1101
1102 /*
1103  * Initialize POSIX timer handling for a single task.
1104  */
1105 static void posix_cpu_timers_init(struct task_struct *tsk)
1106 {
1107         tsk->cputime_expires.prof_exp = 0;
1108         tsk->cputime_expires.virt_exp = 0;
1109         tsk->cputime_expires.sched_exp = 0;
1110         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1111         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1112         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1113 }
1114
1115 static inline void
1116 init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid)
1117 {
1118          task->pids[type].pid = pid;
1119 }
1120
1121 /*
1122  * This creates a new process as a copy of the old one,
1123  * but does not actually start it yet.
1124  *
1125  * It copies the registers, and all the appropriate
1126  * parts of the process environment (as per the clone
1127  * flags). The actual kick-off is left to the caller.
1128  */
1129 static struct task_struct *copy_process(unsigned long clone_flags,
1130                                         unsigned long stack_start,
1131                                         unsigned long stack_size,
1132                                         int __user *child_tidptr,
1133                                         struct pid *pid,
1134                                         int trace)
1135 {
1136         int retval;
1137         struct task_struct *p;
1138
1139         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1140                 return ERR_PTR(-EINVAL);
1141
1142         if ((clone_flags & (CLONE_NEWUSER|CLONE_FS)) == (CLONE_NEWUSER|CLONE_FS))
1143                 return ERR_PTR(-EINVAL);
1144
1145         /*
1146          * Thread groups must share signals as well, and detached threads
1147          * can only be started up within the thread group.
1148          */
1149         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1150                 return ERR_PTR(-EINVAL);
1151
1152         /*
1153          * Shared signal handlers imply shared VM. By way of the above,
1154          * thread groups also imply shared VM. Blocking this case allows
1155          * for various simplifications in other code.
1156          */
1157         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1158                 return ERR_PTR(-EINVAL);
1159
1160         /*
1161          * Siblings of global init remain as zombies on exit since they are
1162          * not reaped by their parent (swapper). To solve this and to avoid
1163          * multi-rooted process trees, prevent global and container-inits
1164          * from creating siblings.
1165          */
1166         if ((clone_flags & CLONE_PARENT) &&
1167                                 current->signal->flags & SIGNAL_UNKILLABLE)
1168                 return ERR_PTR(-EINVAL);
1169
1170         /*
1171          * If the new process will be in a different pid or user namespace
1172          * do not allow it to share a thread group or signal handlers or
1173          * parent with the forking task.
1174          */
1175         if (clone_flags & (CLONE_SIGHAND | CLONE_PARENT)) {
1176                 if ((clone_flags & (CLONE_NEWUSER | CLONE_NEWPID)) ||
1177                     (task_active_pid_ns(current) !=
1178                                 current->nsproxy->pid_ns_for_children))
1179                         return ERR_PTR(-EINVAL);
1180         }
1181
1182         retval = security_task_create(clone_flags);
1183         if (retval)
1184                 goto fork_out;
1185
1186         retval = -ENOMEM;
1187         p = dup_task_struct(current);
1188         if (!p)
1189                 goto fork_out;
1190
1191         ftrace_graph_init_task(p);
1192         get_seccomp_filter(p);
1193
1194         rt_mutex_init_task(p);
1195
1196 #ifdef CONFIG_PROVE_LOCKING
1197         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1198         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1199 #endif
1200         retval = -EAGAIN;
1201         if (atomic_read(&p->real_cred->user->processes) >=
1202                         task_rlimit(p, RLIMIT_NPROC)) {
1203                 if (p->real_cred->user != INIT_USER &&
1204                     !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN))
1205                         goto bad_fork_free;
1206         }
1207         current->flags &= ~PF_NPROC_EXCEEDED;
1208
1209         retval = copy_creds(p, clone_flags);
1210         if (retval < 0)
1211                 goto bad_fork_free;
1212
1213         /*
1214          * If multiple threads are within copy_process(), then this check
1215          * triggers too late. This doesn't hurt, the check is only there
1216          * to stop root fork bombs.
1217          */
1218         retval = -EAGAIN;
1219         if (nr_threads >= max_threads)
1220                 goto bad_fork_cleanup_count;
1221
1222         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1223                 goto bad_fork_cleanup_count;
1224
1225         p->did_exec = 0;
1226         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1227         copy_flags(clone_flags, p);
1228         INIT_LIST_HEAD(&p->children);
1229         INIT_LIST_HEAD(&p->sibling);
1230         rcu_copy_process(p);
1231         p->vfork_done = NULL;
1232         spin_lock_init(&p->alloc_lock);
1233
1234         init_sigpending(&p->pending);
1235
1236         p->utime = p->stime = p->gtime = 0;
1237         p->utimescaled = p->stimescaled = 0;
1238 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1239         p->prev_cputime.utime = p->prev_cputime.stime = 0;
1240 #endif
1241 #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
1242         seqlock_init(&p->vtime_seqlock);
1243         p->vtime_snap = 0;
1244         p->vtime_snap_whence = VTIME_SLEEPING;
1245 #endif
1246
1247 #if defined(SPLIT_RSS_COUNTING)
1248         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1249 #endif
1250
1251         p->default_timer_slack_ns = current->timer_slack_ns;
1252
1253         task_io_accounting_init(&p->ioac);
1254         acct_clear_integrals(p);
1255
1256         posix_cpu_timers_init(p);
1257
1258         do_posix_clock_monotonic_gettime(&p->start_time);
1259         p->real_start_time = p->start_time;
1260         monotonic_to_bootbased(&p->real_start_time);
1261         p->io_context = NULL;
1262         p->audit_context = NULL;
1263         if (clone_flags & CLONE_THREAD)
1264                 threadgroup_change_begin(current);
1265         cgroup_fork(p);
1266 #ifdef CONFIG_NUMA
1267         p->mempolicy = mpol_dup(p->mempolicy);
1268         if (IS_ERR(p->mempolicy)) {
1269                 retval = PTR_ERR(p->mempolicy);
1270                 p->mempolicy = NULL;
1271                 goto bad_fork_cleanup_cgroup;
1272         }
1273         mpol_fix_fork_child_flag(p);
1274 #endif
1275 #ifdef CONFIG_CPUSETS
1276         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1277         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1278         seqcount_init(&p->mems_allowed_seq);
1279 #endif
1280 #ifdef CONFIG_TRACE_IRQFLAGS
1281         p->irq_events = 0;
1282         p->hardirqs_enabled = 0;
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_MEMCG
1305         p->memcg_batch.do_batch = 0;
1306         p->memcg_batch.memcg = NULL;
1307 #endif
1308 #ifdef CONFIG_BCACHE
1309         p->sequential_io        = 0;
1310         p->sequential_io_avg    = 0;
1311 #endif
1312
1313         /* Perform scheduler related setup. Assign this task to a CPU. */
1314         sched_fork(clone_flags, p);
1315
1316         retval = perf_event_init_task(p);
1317         if (retval)
1318                 goto bad_fork_cleanup_policy;
1319         retval = audit_alloc(p);
1320         if (retval)
1321                 goto bad_fork_cleanup_policy;
1322         /* copy all the process information */
1323         retval = copy_semundo(clone_flags, p);
1324         if (retval)
1325                 goto bad_fork_cleanup_audit;
1326         retval = copy_files(clone_flags, p);
1327         if (retval)
1328                 goto bad_fork_cleanup_semundo;
1329         retval = copy_fs(clone_flags, p);
1330         if (retval)
1331                 goto bad_fork_cleanup_files;
1332         retval = copy_sighand(clone_flags, p);
1333         if (retval)
1334                 goto bad_fork_cleanup_fs;
1335         retval = copy_signal(clone_flags, p);
1336         if (retval)
1337                 goto bad_fork_cleanup_sighand;
1338         retval = copy_mm(clone_flags, p);
1339         if (retval)
1340                 goto bad_fork_cleanup_signal;
1341         retval = copy_namespaces(clone_flags, p);
1342         if (retval)
1343                 goto bad_fork_cleanup_mm;
1344         retval = copy_io(clone_flags, p);
1345         if (retval)
1346                 goto bad_fork_cleanup_namespaces;
1347         retval = copy_thread(clone_flags, stack_start, stack_size, p);
1348         if (retval)
1349                 goto bad_fork_cleanup_io;
1350
1351         if (pid != &init_struct_pid) {
1352                 retval = -ENOMEM;
1353                 pid = alloc_pid(p->nsproxy->pid_ns_for_children);
1354                 if (!pid)
1355                         goto bad_fork_cleanup_io;
1356         }
1357
1358         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1359         /*
1360          * Clear TID on mm_release()?
1361          */
1362         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1363 #ifdef CONFIG_BLOCK
1364         p->plug = NULL;
1365 #endif
1366 #ifdef CONFIG_FUTEX
1367         p->robust_list = NULL;
1368 #ifdef CONFIG_COMPAT
1369         p->compat_robust_list = NULL;
1370 #endif
1371         INIT_LIST_HEAD(&p->pi_state_list);
1372         p->pi_state_cache = NULL;
1373 #endif
1374         /*
1375          * sigaltstack should be cleared when sharing the same VM
1376          */
1377         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1378                 p->sas_ss_sp = p->sas_ss_size = 0;
1379
1380         /*
1381          * Syscall tracing and stepping should be turned off in the
1382          * child regardless of CLONE_PTRACE.
1383          */
1384         user_disable_single_step(p);
1385         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1386 #ifdef TIF_SYSCALL_EMU
1387         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1388 #endif
1389         clear_all_latency_tracing(p);
1390
1391         /* ok, now we should be set up.. */
1392         p->pid = pid_nr(pid);
1393         if (clone_flags & CLONE_THREAD) {
1394                 p->exit_signal = -1;
1395                 p->group_leader = current->group_leader;
1396                 p->tgid = current->tgid;
1397         } else {
1398                 if (clone_flags & CLONE_PARENT)
1399                         p->exit_signal = current->group_leader->exit_signal;
1400                 else
1401                         p->exit_signal = (clone_flags & CSIGNAL);
1402                 p->group_leader = p;
1403                 p->tgid = p->pid;
1404         }
1405
1406         p->pdeath_signal = 0;
1407         p->exit_state = 0;
1408
1409         p->nr_dirtied = 0;
1410         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1411         p->dirty_paused_when = 0;
1412
1413         INIT_LIST_HEAD(&p->thread_group);
1414         p->task_works = NULL;
1415
1416         /*
1417          * Make it visible to the rest of the system, but dont wake it up yet.
1418          * Need tasklist lock for parent etc handling!
1419          */
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 (likely(p->pid)) {
1450                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1451
1452                 init_task_pid(p, PIDTYPE_PID, pid);
1453                 if (thread_group_leader(p)) {
1454                         init_task_pid(p, PIDTYPE_PGID, task_pgrp(current));
1455                         init_task_pid(p, PIDTYPE_SID, task_session(current));
1456
1457                         if (is_child_reaper(pid)) {
1458                                 ns_of_pid(pid)->child_reaper = p;
1459                                 p->signal->flags |= SIGNAL_UNKILLABLE;
1460                         }
1461
1462                         p->signal->leader_pid = pid;
1463                         p->signal->tty = tty_kref_get(current->signal->tty);
1464                         list_add_tail(&p->sibling, &p->real_parent->children);
1465                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1466                         attach_pid(p, PIDTYPE_PGID);
1467                         attach_pid(p, PIDTYPE_SID);
1468                         __this_cpu_inc(process_counts);
1469                 } else {
1470                         current->signal->nr_threads++;
1471                         atomic_inc(&current->signal->live);
1472                         atomic_inc(&current->signal->sigcnt);
1473                         list_add_tail_rcu(&p->thread_group,
1474                                           &p->group_leader->thread_group);
1475                 }
1476                 attach_pid(p, PIDTYPE_PID);
1477                 nr_threads++;
1478         }
1479
1480         total_forks++;
1481         spin_unlock(&current->sighand->siglock);
1482         write_unlock_irq(&tasklist_lock);
1483         proc_fork_connector(p);
1484         cgroup_post_fork(p);
1485         if (clone_flags & CLONE_THREAD)
1486                 threadgroup_change_end(current);
1487         perf_event_fork(p);
1488
1489         trace_task_newtask(p, clone_flags);
1490         uprobe_copy_process(p, clone_flags);
1491
1492         return p;
1493
1494 bad_fork_free_pid:
1495         if (pid != &init_struct_pid)
1496                 free_pid(pid);
1497 bad_fork_cleanup_io:
1498         if (p->io_context)
1499                 exit_io_context(p);
1500 bad_fork_cleanup_namespaces:
1501         exit_task_namespaces(p);
1502 bad_fork_cleanup_mm:
1503         if (p->mm)
1504                 mmput(p->mm);
1505 bad_fork_cleanup_signal:
1506         if (!(clone_flags & CLONE_THREAD))
1507                 free_signal_struct(p->signal);
1508 bad_fork_cleanup_sighand:
1509         __cleanup_sighand(p->sighand);
1510 bad_fork_cleanup_fs:
1511         exit_fs(p); /* blocking */
1512 bad_fork_cleanup_files:
1513         exit_files(p); /* blocking */
1514 bad_fork_cleanup_semundo:
1515         exit_sem(p);
1516 bad_fork_cleanup_audit:
1517         audit_free(p);
1518 bad_fork_cleanup_policy:
1519         perf_event_free_task(p);
1520 #ifdef CONFIG_NUMA
1521         mpol_put(p->mempolicy);
1522 bad_fork_cleanup_cgroup:
1523 #endif
1524         if (clone_flags & CLONE_THREAD)
1525                 threadgroup_change_end(current);
1526         cgroup_exit(p, 0);
1527         delayacct_tsk_free(p);
1528         module_put(task_thread_info(p)->exec_domain->module);
1529 bad_fork_cleanup_count:
1530         atomic_dec(&p->cred->user->processes);
1531         exit_creds(p);
1532 bad_fork_free:
1533         free_task(p);
1534 fork_out:
1535         return ERR_PTR(retval);
1536 }
1537
1538 static inline void init_idle_pids(struct pid_link *links)
1539 {
1540         enum pid_type type;
1541
1542         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1543                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1544                 links[type].pid = &init_struct_pid;
1545         }
1546 }
1547
1548 struct task_struct *fork_idle(int cpu)
1549 {
1550         struct task_struct *task;
1551         task = copy_process(CLONE_VM, 0, 0, NULL, &init_struct_pid, 0);
1552         if (!IS_ERR(task)) {
1553                 init_idle_pids(task->pids);
1554                 init_idle(task, cpu);
1555         }
1556
1557         return task;
1558 }
1559
1560 /*
1561  *  Ok, this is the main fork-routine.
1562  *
1563  * It copies the process, and if successful kick-starts
1564  * it and waits for it to finish using the VM if required.
1565  */
1566 long do_fork(unsigned long clone_flags,
1567               unsigned long stack_start,
1568               unsigned long stack_size,
1569               int __user *parent_tidptr,
1570               int __user *child_tidptr)
1571 {
1572         struct task_struct *p;
1573         int trace = 0;
1574         long nr;
1575
1576         /*
1577          * Determine whether and which event to report to ptracer.  When
1578          * called from kernel_thread or CLONE_UNTRACED is explicitly
1579          * requested, no event is reported; otherwise, report if the event
1580          * for the type of forking is enabled.
1581          */
1582         if (!(clone_flags & CLONE_UNTRACED)) {
1583                 if (clone_flags & CLONE_VFORK)
1584                         trace = PTRACE_EVENT_VFORK;
1585                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1586                         trace = PTRACE_EVENT_CLONE;
1587                 else
1588                         trace = PTRACE_EVENT_FORK;
1589
1590                 if (likely(!ptrace_event_enabled(current, trace)))
1591                         trace = 0;
1592         }
1593
1594         p = copy_process(clone_flags, stack_start, stack_size,
1595                          child_tidptr, NULL, trace);
1596         /*
1597          * Do this prior waking up the new thread - the thread pointer
1598          * might get invalid after that point, if the thread exits quickly.
1599          */
1600         if (!IS_ERR(p)) {
1601                 struct completion vfork;
1602
1603                 trace_sched_process_fork(current, p);
1604
1605                 nr = task_pid_vnr(p);
1606
1607                 if (clone_flags & CLONE_PARENT_SETTID)
1608                         put_user(nr, parent_tidptr);
1609
1610                 if (clone_flags & CLONE_VFORK) {
1611                         p->vfork_done = &vfork;
1612                         init_completion(&vfork);
1613                         get_task_struct(p);
1614                 }
1615
1616                 wake_up_new_task(p);
1617
1618                 /* forking complete and child started to run, tell ptracer */
1619                 if (unlikely(trace))
1620                         ptrace_event(trace, nr);
1621
1622                 if (clone_flags & CLONE_VFORK) {
1623                         if (!wait_for_vfork_done(p, &vfork))
1624                                 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1625                 }
1626         } else {
1627                 nr = PTR_ERR(p);
1628         }
1629         return nr;
1630 }
1631
1632 /*
1633  * Create a kernel thread.
1634  */
1635 pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
1636 {
1637         return do_fork(flags|CLONE_VM|CLONE_UNTRACED, (unsigned long)fn,
1638                 (unsigned long)arg, NULL, NULL);
1639 }
1640
1641 #ifdef __ARCH_WANT_SYS_FORK
1642 SYSCALL_DEFINE0(fork)
1643 {
1644 #ifdef CONFIG_MMU
1645         return do_fork(SIGCHLD, 0, 0, NULL, NULL);
1646 #else
1647         /* can not support in nommu mode */
1648         return(-EINVAL);
1649 #endif
1650 }
1651 #endif
1652
1653 #ifdef __ARCH_WANT_SYS_VFORK
1654 SYSCALL_DEFINE0(vfork)
1655 {
1656         return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, 0, 
1657                         0, NULL, NULL);
1658 }
1659 #endif
1660
1661 #ifdef __ARCH_WANT_SYS_CLONE
1662 #ifdef CONFIG_CLONE_BACKWARDS
1663 SYSCALL_DEFINE5(clone, unsigned long, clone_flags, unsigned long, newsp,
1664                  int __user *, parent_tidptr,
1665                  int, tls_val,
1666                  int __user *, child_tidptr)
1667 #elif defined(CONFIG_CLONE_BACKWARDS2)
1668 SYSCALL_DEFINE5(clone, unsigned long, newsp, unsigned long, clone_flags,
1669                  int __user *, parent_tidptr,
1670                  int __user *, child_tidptr,
1671                  int, tls_val)
1672 #elif defined(CONFIG_CLONE_BACKWARDS3)
1673 SYSCALL_DEFINE6(clone, unsigned long, clone_flags, unsigned long, newsp,
1674                 int, stack_size,
1675                 int __user *, parent_tidptr,
1676                 int __user *, child_tidptr,
1677                 int, tls_val)
1678 #else
1679 SYSCALL_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
1693 static 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
1701 void __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  */
1734 static 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  */
1758 static 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  */
1779 static 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  */
1802 SYSCALL_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 thread from a thread group, must also unshare vm.
1818          */
1819         if (unshare_flags & CLONE_THREAD)
1820                 unshare_flags |= CLONE_VM;
1821         /*
1822          * If unsharing vm, must also unshare signal handlers.
1823          */
1824         if (unshare_flags & CLONE_VM)
1825                 unshare_flags |= CLONE_SIGHAND;
1826         /*
1827          * If unsharing namespace, must also unshare filesystem information.
1828          */
1829         if (unshare_flags & CLONE_NEWNS)
1830                 unshare_flags |= CLONE_FS;
1831
1832         err = check_unshare_flags(unshare_flags);
1833         if (err)
1834                 goto bad_unshare_out;
1835         /*
1836          * CLONE_NEWIPC must also detach from the undolist: after switching
1837          * to a new ipc namespace, the semaphore arrays from the old
1838          * namespace are unreachable.
1839          */
1840         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1841                 do_sysvsem = 1;
1842         err = unshare_fs(unshare_flags, &new_fs);
1843         if (err)
1844                 goto bad_unshare_out;
1845         err = unshare_fd(unshare_flags, &new_fd);
1846         if (err)
1847                 goto bad_unshare_cleanup_fs;
1848         err = unshare_userns(unshare_flags, &new_cred);
1849         if (err)
1850                 goto bad_unshare_cleanup_fd;
1851         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1852                                          new_cred, new_fs);
1853         if (err)
1854                 goto bad_unshare_cleanup_cred;
1855
1856         if (new_fs || new_fd || do_sysvsem || new_cred || new_nsproxy) {
1857                 if (do_sysvsem) {
1858                         /*
1859                          * CLONE_SYSVSEM is equivalent to sys_exit().
1860                          */
1861                         exit_sem(current);
1862                 }
1863
1864                 if (new_nsproxy)
1865                         switch_task_namespaces(current, new_nsproxy);
1866
1867                 task_lock(current);
1868
1869                 if (new_fs) {
1870                         fs = current->fs;
1871                         spin_lock(&fs->lock);
1872                         current->fs = new_fs;
1873                         if (--fs->users)
1874                                 new_fs = NULL;
1875                         else
1876                                 new_fs = fs;
1877                         spin_unlock(&fs->lock);
1878                 }
1879
1880                 if (new_fd) {
1881                         fd = current->files;
1882                         current->files = new_fd;
1883                         new_fd = fd;
1884                 }
1885
1886                 task_unlock(current);
1887
1888                 if (new_cred) {
1889                         /* Install the new user namespace */
1890                         commit_creds(new_cred);
1891                         new_cred = NULL;
1892                 }
1893         }
1894
1895 bad_unshare_cleanup_cred:
1896         if (new_cred)
1897                 put_cred(new_cred);
1898 bad_unshare_cleanup_fd:
1899         if (new_fd)
1900                 put_files_struct(new_fd);
1901
1902 bad_unshare_cleanup_fs:
1903         if (new_fs)
1904                 free_fs_struct(new_fs);
1905
1906 bad_unshare_out:
1907         return err;
1908 }
1909
1910 /*
1911  *      Helper to unshare the files of the current task.
1912  *      We don't want to expose copy_files internals to
1913  *      the exec layer of the kernel.
1914  */
1915
1916 int unshare_files(struct files_struct **displaced)
1917 {
1918         struct task_struct *task = current;
1919         struct files_struct *copy = NULL;
1920         int error;
1921
1922         error = unshare_fd(CLONE_FILES, &copy);
1923         if (error || !copy) {
1924                 *displaced = NULL;
1925                 return error;
1926         }
1927         *displaced = task->files;
1928         task_lock(task);
1929         task->files = copy;
1930         task_unlock(task);
1931         return 0;
1932 }