Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6.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/tracehook.h>
41 #include <linux/futex.h>
42 #include <linux/compat.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/proc_fs.h>
62 #include <linux/blkdev.h>
63 #include <linux/fs_struct.h>
64 #include <linux/magic.h>
65 #include <linux/perf_event.h>
66 #include <linux/posix-timers.h>
67 #include <linux/user-return-notifier.h>
68
69 #include <asm/pgtable.h>
70 #include <asm/pgalloc.h>
71 #include <asm/uaccess.h>
72 #include <asm/mmu_context.h>
73 #include <asm/cacheflush.h>
74 #include <asm/tlbflush.h>
75
76 #include <trace/events/sched.h>
77
78 /*
79  * Protected counters by write_lock_irq(&tasklist_lock)
80  */
81 unsigned long total_forks;      /* Handle normal Linux uptimes. */
82 int nr_threads;                 /* The idle threads do not count.. */
83
84 int max_threads;                /* tunable limit on nr_threads */
85
86 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
87
88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
89
90 #ifdef CONFIG_PROVE_RCU
91 int lockdep_tasklist_lock_is_held(void)
92 {
93         return lockdep_is_held(&tasklist_lock);
94 }
95 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
96 #endif /* #ifdef CONFIG_PROVE_RCU */
97
98 int nr_processes(void)
99 {
100         int cpu;
101         int total = 0;
102
103         for_each_possible_cpu(cpu)
104                 total += per_cpu(process_counts, cpu);
105
106         return total;
107 }
108
109 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
110 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
111 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
112 static struct kmem_cache *task_struct_cachep;
113 #endif
114
115 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
116 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
117 {
118 #ifdef CONFIG_DEBUG_STACK_USAGE
119         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
120 #else
121         gfp_t mask = GFP_KERNEL;
122 #endif
123         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
124 }
125
126 static inline void free_thread_info(struct thread_info *ti)
127 {
128         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
129 }
130 #endif
131
132 /* SLAB cache for signal_struct structures (tsk->signal) */
133 static struct kmem_cache *signal_cachep;
134
135 /* SLAB cache for sighand_struct structures (tsk->sighand) */
136 struct kmem_cache *sighand_cachep;
137
138 /* SLAB cache for files_struct structures (tsk->files) */
139 struct kmem_cache *files_cachep;
140
141 /* SLAB cache for fs_struct structures (tsk->fs) */
142 struct kmem_cache *fs_cachep;
143
144 /* SLAB cache for vm_area_struct structures */
145 struct kmem_cache *vm_area_cachep;
146
147 /* SLAB cache for mm_struct structures (tsk->mm) */
148 static struct kmem_cache *mm_cachep;
149
150 static void account_kernel_stack(struct thread_info *ti, int account)
151 {
152         struct zone *zone = page_zone(virt_to_page(ti));
153
154         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
155 }
156
157 void free_task(struct task_struct *tsk)
158 {
159         prop_local_destroy_single(&tsk->dirties);
160         account_kernel_stack(tsk->stack, -1);
161         free_thread_info(tsk->stack);
162         rt_mutex_debug_task_free(tsk);
163         ftrace_graph_exit_task(tsk);
164         free_task_struct(tsk);
165 }
166 EXPORT_SYMBOL(free_task);
167
168 void __put_task_struct(struct task_struct *tsk)
169 {
170         WARN_ON(!tsk->exit_state);
171         WARN_ON(atomic_read(&tsk->usage));
172         WARN_ON(tsk == current);
173
174         exit_creds(tsk);
175         delayacct_tsk_free(tsk);
176
177         if (!profile_handoff_task(tsk))
178                 free_task(tsk);
179 }
180
181 /*
182  * macro override instead of weak attribute alias, to workaround
183  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
184  */
185 #ifndef arch_task_cache_init
186 #define arch_task_cache_init()
187 #endif
188
189 void __init fork_init(unsigned long mempages)
190 {
191 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
192 #ifndef ARCH_MIN_TASKALIGN
193 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
194 #endif
195         /* create a slab on which task_structs can be allocated */
196         task_struct_cachep =
197                 kmem_cache_create("task_struct", sizeof(struct task_struct),
198                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
199 #endif
200
201         /* do the arch specific task caches init */
202         arch_task_cache_init();
203
204         /*
205          * The default maximum number of threads is set to a safe
206          * value: the thread structures can take up at most half
207          * of memory.
208          */
209         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
210
211         /*
212          * we need to allow at least 20 threads to boot a system
213          */
214         if(max_threads < 20)
215                 max_threads = 20;
216
217         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
218         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
219         init_task.signal->rlim[RLIMIT_SIGPENDING] =
220                 init_task.signal->rlim[RLIMIT_NPROC];
221 }
222
223 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
224                                                struct task_struct *src)
225 {
226         *dst = *src;
227         return 0;
228 }
229
230 static struct task_struct *dup_task_struct(struct task_struct *orig)
231 {
232         struct task_struct *tsk;
233         struct thread_info *ti;
234         unsigned long *stackend;
235
236         int err;
237
238         prepare_to_copy(orig);
239
240         tsk = alloc_task_struct();
241         if (!tsk)
242                 return NULL;
243
244         ti = alloc_thread_info(tsk);
245         if (!ti) {
246                 free_task_struct(tsk);
247                 return NULL;
248         }
249
250         err = arch_dup_task_struct(tsk, orig);
251         if (err)
252                 goto out;
253
254         tsk->stack = ti;
255
256         err = prop_local_init_single(&tsk->dirties);
257         if (err)
258                 goto out;
259
260         setup_thread_stack(tsk, orig);
261         clear_user_return_notifier(tsk);
262         stackend = end_of_stack(tsk);
263         *stackend = STACK_END_MAGIC;    /* for overflow detection */
264
265 #ifdef CONFIG_CC_STACKPROTECTOR
266         tsk->stack_canary = get_random_int();
267 #endif
268
269         /* One for us, one for whoever does the "release_task()" (usually parent) */
270         atomic_set(&tsk->usage,2);
271         atomic_set(&tsk->fs_excl, 0);
272 #ifdef CONFIG_BLK_DEV_IO_TRACE
273         tsk->btrace_seq = 0;
274 #endif
275         tsk->splice_pipe = NULL;
276
277         account_kernel_stack(ti, 1);
278
279         return tsk;
280
281 out:
282         free_thread_info(ti);
283         free_task_struct(tsk);
284         return NULL;
285 }
286
287 #ifdef CONFIG_MMU
288 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
289 {
290         struct vm_area_struct *mpnt, *tmp, **pprev;
291         struct rb_node **rb_link, *rb_parent;
292         int retval;
293         unsigned long charge;
294         struct mempolicy *pol;
295
296         down_write(&oldmm->mmap_sem);
297         flush_cache_dup_mm(oldmm);
298         /*
299          * Not linked in yet - no deadlock potential:
300          */
301         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
302
303         mm->locked_vm = 0;
304         mm->mmap = NULL;
305         mm->mmap_cache = NULL;
306         mm->free_area_cache = oldmm->mmap_base;
307         mm->cached_hole_size = ~0UL;
308         mm->map_count = 0;
309         cpumask_clear(mm_cpumask(mm));
310         mm->mm_rb = RB_ROOT;
311         rb_link = &mm->mm_rb.rb_node;
312         rb_parent = NULL;
313         pprev = &mm->mmap;
314         retval = ksm_fork(mm, oldmm);
315         if (retval)
316                 goto out;
317
318         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
319                 struct file *file;
320
321                 if (mpnt->vm_flags & VM_DONTCOPY) {
322                         long pages = vma_pages(mpnt);
323                         mm->total_vm -= pages;
324                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
325                                                                 -pages);
326                         continue;
327                 }
328                 charge = 0;
329                 if (mpnt->vm_flags & VM_ACCOUNT) {
330                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
331                         if (security_vm_enough_memory(len))
332                                 goto fail_nomem;
333                         charge = len;
334                 }
335                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
336                 if (!tmp)
337                         goto fail_nomem;
338                 *tmp = *mpnt;
339                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
340                 pol = mpol_dup(vma_policy(mpnt));
341                 retval = PTR_ERR(pol);
342                 if (IS_ERR(pol))
343                         goto fail_nomem_policy;
344                 vma_set_policy(tmp, pol);
345                 if (anon_vma_fork(tmp, mpnt))
346                         goto fail_nomem_anon_vma_fork;
347                 tmp->vm_flags &= ~VM_LOCKED;
348                 tmp->vm_mm = mm;
349                 tmp->vm_next = NULL;
350                 file = tmp->vm_file;
351                 if (file) {
352                         struct inode *inode = file->f_path.dentry->d_inode;
353                         struct address_space *mapping = file->f_mapping;
354
355                         get_file(file);
356                         if (tmp->vm_flags & VM_DENYWRITE)
357                                 atomic_dec(&inode->i_writecount);
358                         spin_lock(&mapping->i_mmap_lock);
359                         if (tmp->vm_flags & VM_SHARED)
360                                 mapping->i_mmap_writable++;
361                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
362                         flush_dcache_mmap_lock(mapping);
363                         /* insert tmp into the share list, just after mpnt */
364                         vma_prio_tree_add(tmp, mpnt);
365                         flush_dcache_mmap_unlock(mapping);
366                         spin_unlock(&mapping->i_mmap_lock);
367                 }
368
369                 /*
370                  * Clear hugetlb-related page reserves for children. This only
371                  * affects MAP_PRIVATE mappings. Faults generated by the child
372                  * are not guaranteed to succeed, even if read-only
373                  */
374                 if (is_vm_hugetlb_page(tmp))
375                         reset_vma_resv_huge_pages(tmp);
376
377                 /*
378                  * Link in the new vma and copy the page table entries.
379                  */
380                 *pprev = tmp;
381                 pprev = &tmp->vm_next;
382
383                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
384                 rb_link = &tmp->vm_rb.rb_right;
385                 rb_parent = &tmp->vm_rb;
386
387                 mm->map_count++;
388                 retval = copy_page_range(mm, oldmm, mpnt);
389
390                 if (tmp->vm_ops && tmp->vm_ops->open)
391                         tmp->vm_ops->open(tmp);
392
393                 if (retval)
394                         goto out;
395         }
396         /* a new mm has just been created */
397         arch_dup_mmap(oldmm, mm);
398         retval = 0;
399 out:
400         up_write(&mm->mmap_sem);
401         flush_tlb_mm(oldmm);
402         up_write(&oldmm->mmap_sem);
403         return retval;
404 fail_nomem_anon_vma_fork:
405         mpol_put(pol);
406 fail_nomem_policy:
407         kmem_cache_free(vm_area_cachep, tmp);
408 fail_nomem:
409         retval = -ENOMEM;
410         vm_unacct_memory(charge);
411         goto out;
412 }
413
414 static inline int mm_alloc_pgd(struct mm_struct * mm)
415 {
416         mm->pgd = pgd_alloc(mm);
417         if (unlikely(!mm->pgd))
418                 return -ENOMEM;
419         return 0;
420 }
421
422 static inline void mm_free_pgd(struct mm_struct * mm)
423 {
424         pgd_free(mm, mm->pgd);
425 }
426 #else
427 #define dup_mmap(mm, oldmm)     (0)
428 #define mm_alloc_pgd(mm)        (0)
429 #define mm_free_pgd(mm)
430 #endif /* CONFIG_MMU */
431
432 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
433
434 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
435 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
436
437 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
438
439 static int __init coredump_filter_setup(char *s)
440 {
441         default_dump_filter =
442                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
443                 MMF_DUMP_FILTER_MASK;
444         return 1;
445 }
446
447 __setup("coredump_filter=", coredump_filter_setup);
448
449 #include <linux/init_task.h>
450
451 static void mm_init_aio(struct mm_struct *mm)
452 {
453 #ifdef CONFIG_AIO
454         spin_lock_init(&mm->ioctx_lock);
455         INIT_HLIST_HEAD(&mm->ioctx_list);
456 #endif
457 }
458
459 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
460 {
461         atomic_set(&mm->mm_users, 1);
462         atomic_set(&mm->mm_count, 1);
463         init_rwsem(&mm->mmap_sem);
464         INIT_LIST_HEAD(&mm->mmlist);
465         mm->flags = (current->mm) ?
466                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
467         mm->core_state = NULL;
468         mm->nr_ptes = 0;
469         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
470         spin_lock_init(&mm->page_table_lock);
471         mm->free_area_cache = TASK_UNMAPPED_BASE;
472         mm->cached_hole_size = ~0UL;
473         mm_init_aio(mm);
474         mm_init_owner(mm, p);
475
476         if (likely(!mm_alloc_pgd(mm))) {
477                 mm->def_flags = 0;
478                 mmu_notifier_mm_init(mm);
479                 return mm;
480         }
481
482         free_mm(mm);
483         return NULL;
484 }
485
486 /*
487  * Allocate and initialize an mm_struct.
488  */
489 struct mm_struct * mm_alloc(void)
490 {
491         struct mm_struct * mm;
492
493         mm = allocate_mm();
494         if (mm) {
495                 memset(mm, 0, sizeof(*mm));
496                 mm = mm_init(mm, current);
497         }
498         return mm;
499 }
500
501 /*
502  * Called when the last reference to the mm
503  * is dropped: either by a lazy thread or by
504  * mmput. Free the page directory and the mm.
505  */
506 void __mmdrop(struct mm_struct *mm)
507 {
508         BUG_ON(mm == &init_mm);
509         mm_free_pgd(mm);
510         destroy_context(mm);
511         mmu_notifier_mm_destroy(mm);
512         free_mm(mm);
513 }
514 EXPORT_SYMBOL_GPL(__mmdrop);
515
516 /*
517  * Decrement the use count and release all resources for an mm.
518  */
519 void mmput(struct mm_struct *mm)
520 {
521         might_sleep();
522
523         if (atomic_dec_and_test(&mm->mm_users)) {
524                 exit_aio(mm);
525                 ksm_exit(mm);
526                 exit_mmap(mm);
527                 set_mm_exe_file(mm, NULL);
528                 if (!list_empty(&mm->mmlist)) {
529                         spin_lock(&mmlist_lock);
530                         list_del(&mm->mmlist);
531                         spin_unlock(&mmlist_lock);
532                 }
533                 put_swap_token(mm);
534                 if (mm->binfmt)
535                         module_put(mm->binfmt->module);
536                 mmdrop(mm);
537         }
538 }
539 EXPORT_SYMBOL_GPL(mmput);
540
541 /**
542  * get_task_mm - acquire a reference to the task's mm
543  *
544  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
545  * this kernel workthread has transiently adopted a user mm with use_mm,
546  * to do its AIO) is not set and if so returns a reference to it, after
547  * bumping up the use count.  User must release the mm via mmput()
548  * after use.  Typically used by /proc and ptrace.
549  */
550 struct mm_struct *get_task_mm(struct task_struct *task)
551 {
552         struct mm_struct *mm;
553
554         task_lock(task);
555         mm = task->mm;
556         if (mm) {
557                 if (task->flags & PF_KTHREAD)
558                         mm = NULL;
559                 else
560                         atomic_inc(&mm->mm_users);
561         }
562         task_unlock(task);
563         return mm;
564 }
565 EXPORT_SYMBOL_GPL(get_task_mm);
566
567 /* Please note the differences between mmput and mm_release.
568  * mmput is called whenever we stop holding onto a mm_struct,
569  * error success whatever.
570  *
571  * mm_release is called after a mm_struct has been removed
572  * from the current process.
573  *
574  * This difference is important for error handling, when we
575  * only half set up a mm_struct for a new process and need to restore
576  * the old one.  Because we mmput the new mm_struct before
577  * restoring the old one. . .
578  * Eric Biederman 10 January 1998
579  */
580 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
581 {
582         struct completion *vfork_done = tsk->vfork_done;
583
584         /* Get rid of any futexes when releasing the mm */
585 #ifdef CONFIG_FUTEX
586         if (unlikely(tsk->robust_list)) {
587                 exit_robust_list(tsk);
588                 tsk->robust_list = NULL;
589         }
590 #ifdef CONFIG_COMPAT
591         if (unlikely(tsk->compat_robust_list)) {
592                 compat_exit_robust_list(tsk);
593                 tsk->compat_robust_list = NULL;
594         }
595 #endif
596         if (unlikely(!list_empty(&tsk->pi_state_list)))
597                 exit_pi_state_list(tsk);
598 #endif
599
600         /* Get rid of any cached register state */
601         deactivate_mm(tsk, mm);
602
603         /* notify parent sleeping on vfork() */
604         if (vfork_done) {
605                 tsk->vfork_done = NULL;
606                 complete(vfork_done);
607         }
608
609         /*
610          * If we're exiting normally, clear a user-space tid field if
611          * requested.  We leave this alone when dying by signal, to leave
612          * the value intact in a core dump, and to save the unnecessary
613          * trouble otherwise.  Userland only wants this done for a sys_exit.
614          */
615         if (tsk->clear_child_tid) {
616                 if (!(tsk->flags & PF_SIGNALED) &&
617                     atomic_read(&mm->mm_users) > 1) {
618                         /*
619                          * We don't check the error code - if userspace has
620                          * not set up a proper pointer then tough luck.
621                          */
622                         put_user(0, tsk->clear_child_tid);
623                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
624                                         1, NULL, NULL, 0);
625                 }
626                 tsk->clear_child_tid = NULL;
627         }
628 }
629
630 /*
631  * Allocate a new mm structure and copy contents from the
632  * mm structure of the passed in task structure.
633  */
634 struct mm_struct *dup_mm(struct task_struct *tsk)
635 {
636         struct mm_struct *mm, *oldmm = current->mm;
637         int err;
638
639         if (!oldmm)
640                 return NULL;
641
642         mm = allocate_mm();
643         if (!mm)
644                 goto fail_nomem;
645
646         memcpy(mm, oldmm, sizeof(*mm));
647
648         /* Initializing for Swap token stuff */
649         mm->token_priority = 0;
650         mm->last_interval = 0;
651
652         if (!mm_init(mm, tsk))
653                 goto fail_nomem;
654
655         if (init_new_context(tsk, mm))
656                 goto fail_nocontext;
657
658         dup_mm_exe_file(oldmm, mm);
659
660         err = dup_mmap(mm, oldmm);
661         if (err)
662                 goto free_pt;
663
664         mm->hiwater_rss = get_mm_rss(mm);
665         mm->hiwater_vm = mm->total_vm;
666
667         if (mm->binfmt && !try_module_get(mm->binfmt->module))
668                 goto free_pt;
669
670         return mm;
671
672 free_pt:
673         /* don't put binfmt in mmput, we haven't got module yet */
674         mm->binfmt = NULL;
675         mmput(mm);
676
677 fail_nomem:
678         return NULL;
679
680 fail_nocontext:
681         /*
682          * If init_new_context() failed, we cannot use mmput() to free the mm
683          * because it calls destroy_context()
684          */
685         mm_free_pgd(mm);
686         free_mm(mm);
687         return NULL;
688 }
689
690 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
691 {
692         struct mm_struct * mm, *oldmm;
693         int retval;
694
695         tsk->min_flt = tsk->maj_flt = 0;
696         tsk->nvcsw = tsk->nivcsw = 0;
697 #ifdef CONFIG_DETECT_HUNG_TASK
698         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
699 #endif
700
701         tsk->mm = NULL;
702         tsk->active_mm = NULL;
703
704         /*
705          * Are we cloning a kernel thread?
706          *
707          * We need to steal a active VM for that..
708          */
709         oldmm = current->mm;
710         if (!oldmm)
711                 return 0;
712
713         if (clone_flags & CLONE_VM) {
714                 atomic_inc(&oldmm->mm_users);
715                 mm = oldmm;
716                 goto good_mm;
717         }
718
719         retval = -ENOMEM;
720         mm = dup_mm(tsk);
721         if (!mm)
722                 goto fail_nomem;
723
724 good_mm:
725         /* Initializing for Swap token stuff */
726         mm->token_priority = 0;
727         mm->last_interval = 0;
728
729         tsk->mm = mm;
730         tsk->active_mm = mm;
731         return 0;
732
733 fail_nomem:
734         return retval;
735 }
736
737 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
738 {
739         struct fs_struct *fs = current->fs;
740         if (clone_flags & CLONE_FS) {
741                 /* tsk->fs is already what we want */
742                 write_lock(&fs->lock);
743                 if (fs->in_exec) {
744                         write_unlock(&fs->lock);
745                         return -EAGAIN;
746                 }
747                 fs->users++;
748                 write_unlock(&fs->lock);
749                 return 0;
750         }
751         tsk->fs = copy_fs_struct(fs);
752         if (!tsk->fs)
753                 return -ENOMEM;
754         return 0;
755 }
756
757 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
758 {
759         struct files_struct *oldf, *newf;
760         int error = 0;
761
762         /*
763          * A background process may not have any files ...
764          */
765         oldf = current->files;
766         if (!oldf)
767                 goto out;
768
769         if (clone_flags & CLONE_FILES) {
770                 atomic_inc(&oldf->count);
771                 goto out;
772         }
773
774         newf = dup_fd(oldf, &error);
775         if (!newf)
776                 goto out;
777
778         tsk->files = newf;
779         error = 0;
780 out:
781         return error;
782 }
783
784 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
785 {
786 #ifdef CONFIG_BLOCK
787         struct io_context *ioc = current->io_context;
788
789         if (!ioc)
790                 return 0;
791         /*
792          * Share io context with parent, if CLONE_IO is set
793          */
794         if (clone_flags & CLONE_IO) {
795                 tsk->io_context = ioc_task_link(ioc);
796                 if (unlikely(!tsk->io_context))
797                         return -ENOMEM;
798         } else if (ioprio_valid(ioc->ioprio)) {
799                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
800                 if (unlikely(!tsk->io_context))
801                         return -ENOMEM;
802
803                 tsk->io_context->ioprio = ioc->ioprio;
804         }
805 #endif
806         return 0;
807 }
808
809 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
810 {
811         struct sighand_struct *sig;
812
813         if (clone_flags & CLONE_SIGHAND) {
814                 atomic_inc(&current->sighand->count);
815                 return 0;
816         }
817         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
818         rcu_assign_pointer(tsk->sighand, sig);
819         if (!sig)
820                 return -ENOMEM;
821         atomic_set(&sig->count, 1);
822         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
823         return 0;
824 }
825
826 void __cleanup_sighand(struct sighand_struct *sighand)
827 {
828         if (atomic_dec_and_test(&sighand->count))
829                 kmem_cache_free(sighand_cachep, sighand);
830 }
831
832
833 /*
834  * Initialize POSIX timer handling for a thread group.
835  */
836 static void posix_cpu_timers_init_group(struct signal_struct *sig)
837 {
838         unsigned long cpu_limit;
839
840         /* Thread group counters. */
841         thread_group_cputime_init(sig);
842
843         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
844         if (cpu_limit != RLIM_INFINITY) {
845                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
846                 sig->cputimer.running = 1;
847         }
848
849         /* The timer lists. */
850         INIT_LIST_HEAD(&sig->cpu_timers[0]);
851         INIT_LIST_HEAD(&sig->cpu_timers[1]);
852         INIT_LIST_HEAD(&sig->cpu_timers[2]);
853 }
854
855 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
856 {
857         struct signal_struct *sig;
858
859         if (clone_flags & CLONE_THREAD)
860                 return 0;
861
862         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
863         tsk->signal = sig;
864         if (!sig)
865                 return -ENOMEM;
866
867         atomic_set(&sig->count, 1);
868         atomic_set(&sig->live, 1);
869         init_waitqueue_head(&sig->wait_chldexit);
870         if (clone_flags & CLONE_NEWPID)
871                 sig->flags |= SIGNAL_UNKILLABLE;
872         sig->curr_target = tsk;
873         init_sigpending(&sig->shared_pending);
874         INIT_LIST_HEAD(&sig->posix_timers);
875
876         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
877         sig->real_timer.function = it_real_fn;
878
879         task_lock(current->group_leader);
880         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
881         task_unlock(current->group_leader);
882
883         posix_cpu_timers_init_group(sig);
884
885         tty_audit_fork(sig);
886
887         sig->oom_adj = current->signal->oom_adj;
888
889         return 0;
890 }
891
892 void __cleanup_signal(struct signal_struct *sig)
893 {
894         thread_group_cputime_free(sig);
895         tty_kref_put(sig->tty);
896         kmem_cache_free(signal_cachep, sig);
897 }
898
899 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
900 {
901         unsigned long new_flags = p->flags;
902
903         new_flags &= ~PF_SUPERPRIV;
904         new_flags |= PF_FORKNOEXEC;
905         new_flags |= PF_STARTING;
906         p->flags = new_flags;
907         clear_freeze_flag(p);
908 }
909
910 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
911 {
912         current->clear_child_tid = tidptr;
913
914         return task_pid_vnr(current);
915 }
916
917 static void rt_mutex_init_task(struct task_struct *p)
918 {
919         raw_spin_lock_init(&p->pi_lock);
920 #ifdef CONFIG_RT_MUTEXES
921         plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
922         p->pi_blocked_on = NULL;
923 #endif
924 }
925
926 #ifdef CONFIG_MM_OWNER
927 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
928 {
929         mm->owner = p;
930 }
931 #endif /* CONFIG_MM_OWNER */
932
933 /*
934  * Initialize POSIX timer handling for a single task.
935  */
936 static void posix_cpu_timers_init(struct task_struct *tsk)
937 {
938         tsk->cputime_expires.prof_exp = cputime_zero;
939         tsk->cputime_expires.virt_exp = cputime_zero;
940         tsk->cputime_expires.sched_exp = 0;
941         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
942         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
943         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
944 }
945
946 /*
947  * This creates a new process as a copy of the old one,
948  * but does not actually start it yet.
949  *
950  * It copies the registers, and all the appropriate
951  * parts of the process environment (as per the clone
952  * flags). The actual kick-off is left to the caller.
953  */
954 static struct task_struct *copy_process(unsigned long clone_flags,
955                                         unsigned long stack_start,
956                                         struct pt_regs *regs,
957                                         unsigned long stack_size,
958                                         int __user *child_tidptr,
959                                         struct pid *pid,
960                                         int trace)
961 {
962         int retval;
963         struct task_struct *p;
964         int cgroup_callbacks_done = 0;
965
966         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
967                 return ERR_PTR(-EINVAL);
968
969         /*
970          * Thread groups must share signals as well, and detached threads
971          * can only be started up within the thread group.
972          */
973         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
974                 return ERR_PTR(-EINVAL);
975
976         /*
977          * Shared signal handlers imply shared VM. By way of the above,
978          * thread groups also imply shared VM. Blocking this case allows
979          * for various simplifications in other code.
980          */
981         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
982                 return ERR_PTR(-EINVAL);
983
984         /*
985          * Siblings of global init remain as zombies on exit since they are
986          * not reaped by their parent (swapper). To solve this and to avoid
987          * multi-rooted process trees, prevent global and container-inits
988          * from creating siblings.
989          */
990         if ((clone_flags & CLONE_PARENT) &&
991                                 current->signal->flags & SIGNAL_UNKILLABLE)
992                 return ERR_PTR(-EINVAL);
993
994         retval = security_task_create(clone_flags);
995         if (retval)
996                 goto fork_out;
997
998         retval = -ENOMEM;
999         p = dup_task_struct(current);
1000         if (!p)
1001                 goto fork_out;
1002
1003         ftrace_graph_init_task(p);
1004
1005         rt_mutex_init_task(p);
1006
1007 #ifdef CONFIG_PROVE_LOCKING
1008         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1009         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1010 #endif
1011         retval = -EAGAIN;
1012         if (atomic_read(&p->real_cred->user->processes) >=
1013                         task_rlimit(p, RLIMIT_NPROC)) {
1014                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1015                     p->real_cred->user != INIT_USER)
1016                         goto bad_fork_free;
1017         }
1018
1019         retval = copy_creds(p, clone_flags);
1020         if (retval < 0)
1021                 goto bad_fork_free;
1022
1023         /*
1024          * If multiple threads are within copy_process(), then this check
1025          * triggers too late. This doesn't hurt, the check is only there
1026          * to stop root fork bombs.
1027          */
1028         retval = -EAGAIN;
1029         if (nr_threads >= max_threads)
1030                 goto bad_fork_cleanup_count;
1031
1032         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1033                 goto bad_fork_cleanup_count;
1034
1035         p->did_exec = 0;
1036         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1037         copy_flags(clone_flags, p);
1038         INIT_LIST_HEAD(&p->children);
1039         INIT_LIST_HEAD(&p->sibling);
1040         rcu_copy_process(p);
1041         p->vfork_done = NULL;
1042         spin_lock_init(&p->alloc_lock);
1043
1044         init_sigpending(&p->pending);
1045
1046         p->utime = cputime_zero;
1047         p->stime = cputime_zero;
1048         p->gtime = cputime_zero;
1049         p->utimescaled = cputime_zero;
1050         p->stimescaled = cputime_zero;
1051 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1052         p->prev_utime = cputime_zero;
1053         p->prev_stime = cputime_zero;
1054 #endif
1055
1056         p->default_timer_slack_ns = current->timer_slack_ns;
1057
1058         task_io_accounting_init(&p->ioac);
1059         acct_clear_integrals(p);
1060
1061         posix_cpu_timers_init(p);
1062
1063         p->lock_depth = -1;             /* -1 = no lock */
1064         do_posix_clock_monotonic_gettime(&p->start_time);
1065         p->real_start_time = p->start_time;
1066         monotonic_to_bootbased(&p->real_start_time);
1067         p->io_context = NULL;
1068         p->audit_context = NULL;
1069         cgroup_fork(p);
1070 #ifdef CONFIG_NUMA
1071         p->mempolicy = mpol_dup(p->mempolicy);
1072         if (IS_ERR(p->mempolicy)) {
1073                 retval = PTR_ERR(p->mempolicy);
1074                 p->mempolicy = NULL;
1075                 goto bad_fork_cleanup_cgroup;
1076         }
1077         mpol_fix_fork_child_flag(p);
1078 #endif
1079 #ifdef CONFIG_TRACE_IRQFLAGS
1080         p->irq_events = 0;
1081 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1082         p->hardirqs_enabled = 1;
1083 #else
1084         p->hardirqs_enabled = 0;
1085 #endif
1086         p->hardirq_enable_ip = 0;
1087         p->hardirq_enable_event = 0;
1088         p->hardirq_disable_ip = _THIS_IP_;
1089         p->hardirq_disable_event = 0;
1090         p->softirqs_enabled = 1;
1091         p->softirq_enable_ip = _THIS_IP_;
1092         p->softirq_enable_event = 0;
1093         p->softirq_disable_ip = 0;
1094         p->softirq_disable_event = 0;
1095         p->hardirq_context = 0;
1096         p->softirq_context = 0;
1097 #endif
1098 #ifdef CONFIG_LOCKDEP
1099         p->lockdep_depth = 0; /* no locks held yet */
1100         p->curr_chain_key = 0;
1101         p->lockdep_recursion = 0;
1102 #endif
1103
1104 #ifdef CONFIG_DEBUG_MUTEXES
1105         p->blocked_on = NULL; /* not blocked yet */
1106 #endif
1107 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1108         p->memcg_batch.do_batch = 0;
1109         p->memcg_batch.memcg = NULL;
1110 #endif
1111
1112         p->bts = NULL;
1113
1114         p->stack_start = stack_start;
1115
1116         /* Perform scheduler related setup. Assign this task to a CPU. */
1117         sched_fork(p, clone_flags);
1118
1119         retval = perf_event_init_task(p);
1120         if (retval)
1121                 goto bad_fork_cleanup_policy;
1122
1123         if ((retval = audit_alloc(p)))
1124                 goto bad_fork_cleanup_policy;
1125         /* copy all the process information */
1126         if ((retval = copy_semundo(clone_flags, p)))
1127                 goto bad_fork_cleanup_audit;
1128         if ((retval = copy_files(clone_flags, p)))
1129                 goto bad_fork_cleanup_semundo;
1130         if ((retval = copy_fs(clone_flags, p)))
1131                 goto bad_fork_cleanup_files;
1132         if ((retval = copy_sighand(clone_flags, p)))
1133                 goto bad_fork_cleanup_fs;
1134         if ((retval = copy_signal(clone_flags, p)))
1135                 goto bad_fork_cleanup_sighand;
1136         if ((retval = copy_mm(clone_flags, p)))
1137                 goto bad_fork_cleanup_signal;
1138         if ((retval = copy_namespaces(clone_flags, p)))
1139                 goto bad_fork_cleanup_mm;
1140         if ((retval = copy_io(clone_flags, p)))
1141                 goto bad_fork_cleanup_namespaces;
1142         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1143         if (retval)
1144                 goto bad_fork_cleanup_io;
1145
1146         if (pid != &init_struct_pid) {
1147                 retval = -ENOMEM;
1148                 pid = alloc_pid(p->nsproxy->pid_ns);
1149                 if (!pid)
1150                         goto bad_fork_cleanup_io;
1151
1152                 if (clone_flags & CLONE_NEWPID) {
1153                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1154                         if (retval < 0)
1155                                 goto bad_fork_free_pid;
1156                 }
1157         }
1158
1159         p->pid = pid_nr(pid);
1160         p->tgid = p->pid;
1161         if (clone_flags & CLONE_THREAD)
1162                 p->tgid = current->tgid;
1163
1164         if (current->nsproxy != p->nsproxy) {
1165                 retval = ns_cgroup_clone(p, pid);
1166                 if (retval)
1167                         goto bad_fork_free_pid;
1168         }
1169
1170         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1171         /*
1172          * Clear TID on mm_release()?
1173          */
1174         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1175 #ifdef CONFIG_FUTEX
1176         p->robust_list = NULL;
1177 #ifdef CONFIG_COMPAT
1178         p->compat_robust_list = NULL;
1179 #endif
1180         INIT_LIST_HEAD(&p->pi_state_list);
1181         p->pi_state_cache = NULL;
1182 #endif
1183         /*
1184          * sigaltstack should be cleared when sharing the same VM
1185          */
1186         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1187                 p->sas_ss_sp = p->sas_ss_size = 0;
1188
1189         /*
1190          * Syscall tracing and stepping should be turned off in the
1191          * child regardless of CLONE_PTRACE.
1192          */
1193         user_disable_single_step(p);
1194         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1195 #ifdef TIF_SYSCALL_EMU
1196         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1197 #endif
1198         clear_all_latency_tracing(p);
1199
1200         /* ok, now we should be set up.. */
1201         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1202         p->pdeath_signal = 0;
1203         p->exit_state = 0;
1204
1205         /*
1206          * Ok, make it visible to the rest of the system.
1207          * We dont wake it up yet.
1208          */
1209         p->group_leader = p;
1210         INIT_LIST_HEAD(&p->thread_group);
1211
1212         /* Now that the task is set up, run cgroup callbacks if
1213          * necessary. We need to run them before the task is visible
1214          * on the tasklist. */
1215         cgroup_fork_callbacks(p);
1216         cgroup_callbacks_done = 1;
1217
1218         /* Need tasklist lock for parent etc handling! */
1219         write_lock_irq(&tasklist_lock);
1220
1221         /* CLONE_PARENT re-uses the old parent */
1222         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1223                 p->real_parent = current->real_parent;
1224                 p->parent_exec_id = current->parent_exec_id;
1225         } else {
1226                 p->real_parent = current;
1227                 p->parent_exec_id = current->self_exec_id;
1228         }
1229
1230         spin_lock(&current->sighand->siglock);
1231
1232         /*
1233          * Process group and session signals need to be delivered to just the
1234          * parent before the fork or both the parent and the child after the
1235          * fork. Restart if a signal comes in before we add the new process to
1236          * it's process group.
1237          * A fatal signal pending means that current will exit, so the new
1238          * thread can't slip out of an OOM kill (or normal SIGKILL).
1239          */
1240         recalc_sigpending();
1241         if (signal_pending(current)) {
1242                 spin_unlock(&current->sighand->siglock);
1243                 write_unlock_irq(&tasklist_lock);
1244                 retval = -ERESTARTNOINTR;
1245                 goto bad_fork_free_pid;
1246         }
1247
1248         if (clone_flags & CLONE_THREAD) {
1249                 atomic_inc(&current->signal->count);
1250                 atomic_inc(&current->signal->live);
1251                 p->group_leader = current->group_leader;
1252                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1253         }
1254
1255         if (likely(p->pid)) {
1256                 tracehook_finish_clone(p, clone_flags, trace);
1257
1258                 if (thread_group_leader(p)) {
1259                         if (clone_flags & CLONE_NEWPID)
1260                                 p->nsproxy->pid_ns->child_reaper = p;
1261
1262                         p->signal->leader_pid = pid;
1263                         tty_kref_put(p->signal->tty);
1264                         p->signal->tty = tty_kref_get(current->signal->tty);
1265                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1266                         attach_pid(p, PIDTYPE_SID, task_session(current));
1267                         list_add_tail(&p->sibling, &p->real_parent->children);
1268                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1269                         __get_cpu_var(process_counts)++;
1270                 }
1271                 attach_pid(p, PIDTYPE_PID, pid);
1272                 nr_threads++;
1273         }
1274
1275         total_forks++;
1276         spin_unlock(&current->sighand->siglock);
1277         write_unlock_irq(&tasklist_lock);
1278         proc_fork_connector(p);
1279         cgroup_post_fork(p);
1280         perf_event_fork(p);
1281         return p;
1282
1283 bad_fork_free_pid:
1284         if (pid != &init_struct_pid)
1285                 free_pid(pid);
1286 bad_fork_cleanup_io:
1287         if (p->io_context)
1288                 exit_io_context(p);
1289 bad_fork_cleanup_namespaces:
1290         exit_task_namespaces(p);
1291 bad_fork_cleanup_mm:
1292         if (p->mm)
1293                 mmput(p->mm);
1294 bad_fork_cleanup_signal:
1295         if (!(clone_flags & CLONE_THREAD))
1296                 __cleanup_signal(p->signal);
1297 bad_fork_cleanup_sighand:
1298         __cleanup_sighand(p->sighand);
1299 bad_fork_cleanup_fs:
1300         exit_fs(p); /* blocking */
1301 bad_fork_cleanup_files:
1302         exit_files(p); /* blocking */
1303 bad_fork_cleanup_semundo:
1304         exit_sem(p);
1305 bad_fork_cleanup_audit:
1306         audit_free(p);
1307 bad_fork_cleanup_policy:
1308         perf_event_free_task(p);
1309 #ifdef CONFIG_NUMA
1310         mpol_put(p->mempolicy);
1311 bad_fork_cleanup_cgroup:
1312 #endif
1313         cgroup_exit(p, cgroup_callbacks_done);
1314         delayacct_tsk_free(p);
1315         module_put(task_thread_info(p)->exec_domain->module);
1316 bad_fork_cleanup_count:
1317         atomic_dec(&p->cred->user->processes);
1318         exit_creds(p);
1319 bad_fork_free:
1320         free_task(p);
1321 fork_out:
1322         return ERR_PTR(retval);
1323 }
1324
1325 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1326 {
1327         memset(regs, 0, sizeof(struct pt_regs));
1328         return regs;
1329 }
1330
1331 struct task_struct * __cpuinit fork_idle(int cpu)
1332 {
1333         struct task_struct *task;
1334         struct pt_regs regs;
1335
1336         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1337                             &init_struct_pid, 0);
1338         if (!IS_ERR(task))
1339                 init_idle(task, cpu);
1340
1341         return task;
1342 }
1343
1344 /*
1345  *  Ok, this is the main fork-routine.
1346  *
1347  * It copies the process, and if successful kick-starts
1348  * it and waits for it to finish using the VM if required.
1349  */
1350 long do_fork(unsigned long clone_flags,
1351               unsigned long stack_start,
1352               struct pt_regs *regs,
1353               unsigned long stack_size,
1354               int __user *parent_tidptr,
1355               int __user *child_tidptr)
1356 {
1357         struct task_struct *p;
1358         int trace = 0;
1359         long nr;
1360
1361         /*
1362          * Do some preliminary argument and permissions checking before we
1363          * actually start allocating stuff
1364          */
1365         if (clone_flags & CLONE_NEWUSER) {
1366                 if (clone_flags & CLONE_THREAD)
1367                         return -EINVAL;
1368                 /* hopefully this check will go away when userns support is
1369                  * complete
1370                  */
1371                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1372                                 !capable(CAP_SETGID))
1373                         return -EPERM;
1374         }
1375
1376         /*
1377          * We hope to recycle these flags after 2.6.26
1378          */
1379         if (unlikely(clone_flags & CLONE_STOPPED)) {
1380                 static int __read_mostly count = 100;
1381
1382                 if (count > 0 && printk_ratelimit()) {
1383                         char comm[TASK_COMM_LEN];
1384
1385                         count--;
1386                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1387                                         "clone flags 0x%lx\n",
1388                                 get_task_comm(comm, current),
1389                                 clone_flags & CLONE_STOPPED);
1390                 }
1391         }
1392
1393         /*
1394          * When called from kernel_thread, don't do user tracing stuff.
1395          */
1396         if (likely(user_mode(regs)))
1397                 trace = tracehook_prepare_clone(clone_flags);
1398
1399         p = copy_process(clone_flags, stack_start, regs, stack_size,
1400                          child_tidptr, NULL, trace);
1401         /*
1402          * Do this prior waking up the new thread - the thread pointer
1403          * might get invalid after that point, if the thread exits quickly.
1404          */
1405         if (!IS_ERR(p)) {
1406                 struct completion vfork;
1407
1408                 trace_sched_process_fork(current, p);
1409
1410                 nr = task_pid_vnr(p);
1411
1412                 if (clone_flags & CLONE_PARENT_SETTID)
1413                         put_user(nr, parent_tidptr);
1414
1415                 if (clone_flags & CLONE_VFORK) {
1416                         p->vfork_done = &vfork;
1417                         init_completion(&vfork);
1418                 }
1419
1420                 audit_finish_fork(p);
1421                 tracehook_report_clone(regs, clone_flags, nr, p);
1422
1423                 /*
1424                  * We set PF_STARTING at creation in case tracing wants to
1425                  * use this to distinguish a fully live task from one that
1426                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1427                  * clear it and set the child going.
1428                  */
1429                 p->flags &= ~PF_STARTING;
1430
1431                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1432                         /*
1433                          * We'll start up with an immediate SIGSTOP.
1434                          */
1435                         sigaddset(&p->pending.signal, SIGSTOP);
1436                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1437                         __set_task_state(p, TASK_STOPPED);
1438                 } else {
1439                         wake_up_new_task(p, clone_flags);
1440                 }
1441
1442                 tracehook_report_clone_complete(trace, regs,
1443                                                 clone_flags, nr, p);
1444
1445                 if (clone_flags & CLONE_VFORK) {
1446                         freezer_do_not_count();
1447                         wait_for_completion(&vfork);
1448                         freezer_count();
1449                         tracehook_report_vfork_done(p, nr);
1450                 }
1451         } else {
1452                 nr = PTR_ERR(p);
1453         }
1454         return nr;
1455 }
1456
1457 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1458 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1459 #endif
1460
1461 static void sighand_ctor(void *data)
1462 {
1463         struct sighand_struct *sighand = data;
1464
1465         spin_lock_init(&sighand->siglock);
1466         init_waitqueue_head(&sighand->signalfd_wqh);
1467 }
1468
1469 void __init proc_caches_init(void)
1470 {
1471         sighand_cachep = kmem_cache_create("sighand_cache",
1472                         sizeof(struct sighand_struct), 0,
1473                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1474                         SLAB_NOTRACK, sighand_ctor);
1475         signal_cachep = kmem_cache_create("signal_cache",
1476                         sizeof(struct signal_struct), 0,
1477                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1478         files_cachep = kmem_cache_create("files_cache",
1479                         sizeof(struct files_struct), 0,
1480                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1481         fs_cachep = kmem_cache_create("fs_cache",
1482                         sizeof(struct fs_struct), 0,
1483                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1484         mm_cachep = kmem_cache_create("mm_struct",
1485                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1486                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1487         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1488         mmap_init();
1489 }
1490
1491 /*
1492  * Check constraints on flags passed to the unshare system call and
1493  * force unsharing of additional process context as appropriate.
1494  */
1495 static void check_unshare_flags(unsigned long *flags_ptr)
1496 {
1497         /*
1498          * If unsharing a thread from a thread group, must also
1499          * unshare vm.
1500          */
1501         if (*flags_ptr & CLONE_THREAD)
1502                 *flags_ptr |= CLONE_VM;
1503
1504         /*
1505          * If unsharing vm, must also unshare signal handlers.
1506          */
1507         if (*flags_ptr & CLONE_VM)
1508                 *flags_ptr |= CLONE_SIGHAND;
1509
1510         /*
1511          * If unsharing signal handlers and the task was created
1512          * using CLONE_THREAD, then must unshare the thread
1513          */
1514         if ((*flags_ptr & CLONE_SIGHAND) &&
1515             (atomic_read(&current->signal->count) > 1))
1516                 *flags_ptr |= CLONE_THREAD;
1517
1518         /*
1519          * If unsharing namespace, must also unshare filesystem information.
1520          */
1521         if (*flags_ptr & CLONE_NEWNS)
1522                 *flags_ptr |= CLONE_FS;
1523 }
1524
1525 /*
1526  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1527  */
1528 static int unshare_thread(unsigned long unshare_flags)
1529 {
1530         if (unshare_flags & CLONE_THREAD)
1531                 return -EINVAL;
1532
1533         return 0;
1534 }
1535
1536 /*
1537  * Unshare the filesystem structure if it is being shared
1538  */
1539 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1540 {
1541         struct fs_struct *fs = current->fs;
1542
1543         if (!(unshare_flags & CLONE_FS) || !fs)
1544                 return 0;
1545
1546         /* don't need lock here; in the worst case we'll do useless copy */
1547         if (fs->users == 1)
1548                 return 0;
1549
1550         *new_fsp = copy_fs_struct(fs);
1551         if (!*new_fsp)
1552                 return -ENOMEM;
1553
1554         return 0;
1555 }
1556
1557 /*
1558  * Unsharing of sighand is not supported yet
1559  */
1560 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1561 {
1562         struct sighand_struct *sigh = current->sighand;
1563
1564         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1565                 return -EINVAL;
1566         else
1567                 return 0;
1568 }
1569
1570 /*
1571  * Unshare vm if it is being shared
1572  */
1573 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1574 {
1575         struct mm_struct *mm = current->mm;
1576
1577         if ((unshare_flags & CLONE_VM) &&
1578             (mm && atomic_read(&mm->mm_users) > 1)) {
1579                 return -EINVAL;
1580         }
1581
1582         return 0;
1583 }
1584
1585 /*
1586  * Unshare file descriptor table if it is being shared
1587  */
1588 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1589 {
1590         struct files_struct *fd = current->files;
1591         int error = 0;
1592
1593         if ((unshare_flags & CLONE_FILES) &&
1594             (fd && atomic_read(&fd->count) > 1)) {
1595                 *new_fdp = dup_fd(fd, &error);
1596                 if (!*new_fdp)
1597                         return error;
1598         }
1599
1600         return 0;
1601 }
1602
1603 /*
1604  * unshare allows a process to 'unshare' part of the process
1605  * context which was originally shared using clone.  copy_*
1606  * functions used by do_fork() cannot be used here directly
1607  * because they modify an inactive task_struct that is being
1608  * constructed. Here we are modifying the current, active,
1609  * task_struct.
1610  */
1611 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1612 {
1613         int err = 0;
1614         struct fs_struct *fs, *new_fs = NULL;
1615         struct sighand_struct *new_sigh = NULL;
1616         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1617         struct files_struct *fd, *new_fd = NULL;
1618         struct nsproxy *new_nsproxy = NULL;
1619         int do_sysvsem = 0;
1620
1621         check_unshare_flags(&unshare_flags);
1622
1623         /* Return -EINVAL for all unsupported flags */
1624         err = -EINVAL;
1625         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1626                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1627                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1628                 goto bad_unshare_out;
1629
1630         /*
1631          * CLONE_NEWIPC must also detach from the undolist: after switching
1632          * to a new ipc namespace, the semaphore arrays from the old
1633          * namespace are unreachable.
1634          */
1635         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1636                 do_sysvsem = 1;
1637         if ((err = unshare_thread(unshare_flags)))
1638                 goto bad_unshare_out;
1639         if ((err = unshare_fs(unshare_flags, &new_fs)))
1640                 goto bad_unshare_cleanup_thread;
1641         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1642                 goto bad_unshare_cleanup_fs;
1643         if ((err = unshare_vm(unshare_flags, &new_mm)))
1644                 goto bad_unshare_cleanup_sigh;
1645         if ((err = unshare_fd(unshare_flags, &new_fd)))
1646                 goto bad_unshare_cleanup_vm;
1647         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1648                         new_fs)))
1649                 goto bad_unshare_cleanup_fd;
1650
1651         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1652                 if (do_sysvsem) {
1653                         /*
1654                          * CLONE_SYSVSEM is equivalent to sys_exit().
1655                          */
1656                         exit_sem(current);
1657                 }
1658
1659                 if (new_nsproxy) {
1660                         switch_task_namespaces(current, new_nsproxy);
1661                         new_nsproxy = NULL;
1662                 }
1663
1664                 task_lock(current);
1665
1666                 if (new_fs) {
1667                         fs = current->fs;
1668                         write_lock(&fs->lock);
1669                         current->fs = new_fs;
1670                         if (--fs->users)
1671                                 new_fs = NULL;
1672                         else
1673                                 new_fs = fs;
1674                         write_unlock(&fs->lock);
1675                 }
1676
1677                 if (new_mm) {
1678                         mm = current->mm;
1679                         active_mm = current->active_mm;
1680                         current->mm = new_mm;
1681                         current->active_mm = new_mm;
1682                         activate_mm(active_mm, new_mm);
1683                         new_mm = mm;
1684                 }
1685
1686                 if (new_fd) {
1687                         fd = current->files;
1688                         current->files = new_fd;
1689                         new_fd = fd;
1690                 }
1691
1692                 task_unlock(current);
1693         }
1694
1695         if (new_nsproxy)
1696                 put_nsproxy(new_nsproxy);
1697
1698 bad_unshare_cleanup_fd:
1699         if (new_fd)
1700                 put_files_struct(new_fd);
1701
1702 bad_unshare_cleanup_vm:
1703         if (new_mm)
1704                 mmput(new_mm);
1705
1706 bad_unshare_cleanup_sigh:
1707         if (new_sigh)
1708                 if (atomic_dec_and_test(&new_sigh->count))
1709                         kmem_cache_free(sighand_cachep, new_sigh);
1710
1711 bad_unshare_cleanup_fs:
1712         if (new_fs)
1713                 free_fs_struct(new_fs);
1714
1715 bad_unshare_cleanup_thread:
1716 bad_unshare_out:
1717         return err;
1718 }
1719
1720 /*
1721  *      Helper to unshare the files of the current task.
1722  *      We don't want to expose copy_files internals to
1723  *      the exec layer of the kernel.
1724  */
1725
1726 int unshare_files(struct files_struct **displaced)
1727 {
1728         struct task_struct *task = current;
1729         struct files_struct *copy = NULL;
1730         int error;
1731
1732         error = unshare_fd(CLONE_FILES, &copy);
1733         if (error || !copy) {
1734                 *displaced = NULL;
1735                 return error;
1736         }
1737         *displaced = task->files;
1738         task_lock(task);
1739         task->files = copy;
1740         task_unlock(task);
1741         return 0;
1742 }