Merge remote branch 'tip/x86/entry' into kvm-updates/2.6.33
[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 int nr_processes(void)
91 {
92         int cpu;
93         int total = 0;
94
95         for_each_possible_cpu(cpu)
96                 total += per_cpu(process_counts, cpu);
97
98         return total;
99 }
100
101 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
102 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
103 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
104 static struct kmem_cache *task_struct_cachep;
105 #endif
106
107 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
108 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
109 {
110 #ifdef CONFIG_DEBUG_STACK_USAGE
111         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
112 #else
113         gfp_t mask = GFP_KERNEL;
114 #endif
115         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
116 }
117
118 static inline void free_thread_info(struct thread_info *ti)
119 {
120         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
121 }
122 #endif
123
124 /* SLAB cache for signal_struct structures (tsk->signal) */
125 static struct kmem_cache *signal_cachep;
126
127 /* SLAB cache for sighand_struct structures (tsk->sighand) */
128 struct kmem_cache *sighand_cachep;
129
130 /* SLAB cache for files_struct structures (tsk->files) */
131 struct kmem_cache *files_cachep;
132
133 /* SLAB cache for fs_struct structures (tsk->fs) */
134 struct kmem_cache *fs_cachep;
135
136 /* SLAB cache for vm_area_struct structures */
137 struct kmem_cache *vm_area_cachep;
138
139 /* SLAB cache for mm_struct structures (tsk->mm) */
140 static struct kmem_cache *mm_cachep;
141
142 static void account_kernel_stack(struct thread_info *ti, int account)
143 {
144         struct zone *zone = page_zone(virt_to_page(ti));
145
146         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
147 }
148
149 void free_task(struct task_struct *tsk)
150 {
151         prop_local_destroy_single(&tsk->dirties);
152         account_kernel_stack(tsk->stack, -1);
153         free_thread_info(tsk->stack);
154         rt_mutex_debug_task_free(tsk);
155         ftrace_graph_exit_task(tsk);
156         free_task_struct(tsk);
157 }
158 EXPORT_SYMBOL(free_task);
159
160 void __put_task_struct(struct task_struct *tsk)
161 {
162         WARN_ON(!tsk->exit_state);
163         WARN_ON(atomic_read(&tsk->usage));
164         WARN_ON(tsk == current);
165
166         exit_creds(tsk);
167         delayacct_tsk_free(tsk);
168
169         if (!profile_handoff_task(tsk))
170                 free_task(tsk);
171 }
172
173 /*
174  * macro override instead of weak attribute alias, to workaround
175  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
176  */
177 #ifndef arch_task_cache_init
178 #define arch_task_cache_init()
179 #endif
180
181 void __init fork_init(unsigned long mempages)
182 {
183 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
184 #ifndef ARCH_MIN_TASKALIGN
185 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
186 #endif
187         /* create a slab on which task_structs can be allocated */
188         task_struct_cachep =
189                 kmem_cache_create("task_struct", sizeof(struct task_struct),
190                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
191 #endif
192
193         /* do the arch specific task caches init */
194         arch_task_cache_init();
195
196         /*
197          * The default maximum number of threads is set to a safe
198          * value: the thread structures can take up at most half
199          * of memory.
200          */
201         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
202
203         /*
204          * we need to allow at least 20 threads to boot a system
205          */
206         if(max_threads < 20)
207                 max_threads = 20;
208
209         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
210         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
211         init_task.signal->rlim[RLIMIT_SIGPENDING] =
212                 init_task.signal->rlim[RLIMIT_NPROC];
213 }
214
215 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
216                                                struct task_struct *src)
217 {
218         *dst = *src;
219         return 0;
220 }
221
222 static struct task_struct *dup_task_struct(struct task_struct *orig)
223 {
224         struct task_struct *tsk;
225         struct thread_info *ti;
226         unsigned long *stackend;
227
228         int err;
229
230         prepare_to_copy(orig);
231
232         tsk = alloc_task_struct();
233         if (!tsk)
234                 return NULL;
235
236         ti = alloc_thread_info(tsk);
237         if (!ti) {
238                 free_task_struct(tsk);
239                 return NULL;
240         }
241
242         err = arch_dup_task_struct(tsk, orig);
243         if (err)
244                 goto out;
245
246         tsk->stack = ti;
247
248         err = prop_local_init_single(&tsk->dirties);
249         if (err)
250                 goto out;
251
252         setup_thread_stack(tsk, orig);
253         clear_user_return_notifier(tsk);
254         stackend = end_of_stack(tsk);
255         *stackend = STACK_END_MAGIC;    /* for overflow detection */
256
257 #ifdef CONFIG_CC_STACKPROTECTOR
258         tsk->stack_canary = get_random_int();
259 #endif
260
261         /* One for us, one for whoever does the "release_task()" (usually parent) */
262         atomic_set(&tsk->usage,2);
263         atomic_set(&tsk->fs_excl, 0);
264 #ifdef CONFIG_BLK_DEV_IO_TRACE
265         tsk->btrace_seq = 0;
266 #endif
267         tsk->splice_pipe = NULL;
268
269         account_kernel_stack(ti, 1);
270
271         return tsk;
272
273 out:
274         free_thread_info(ti);
275         free_task_struct(tsk);
276         return NULL;
277 }
278
279 #ifdef CONFIG_MMU
280 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
281 {
282         struct vm_area_struct *mpnt, *tmp, **pprev;
283         struct rb_node **rb_link, *rb_parent;
284         int retval;
285         unsigned long charge;
286         struct mempolicy *pol;
287
288         down_write(&oldmm->mmap_sem);
289         flush_cache_dup_mm(oldmm);
290         /*
291          * Not linked in yet - no deadlock potential:
292          */
293         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
294
295         mm->locked_vm = 0;
296         mm->mmap = NULL;
297         mm->mmap_cache = NULL;
298         mm->free_area_cache = oldmm->mmap_base;
299         mm->cached_hole_size = ~0UL;
300         mm->map_count = 0;
301         cpumask_clear(mm_cpumask(mm));
302         mm->mm_rb = RB_ROOT;
303         rb_link = &mm->mm_rb.rb_node;
304         rb_parent = NULL;
305         pprev = &mm->mmap;
306         retval = ksm_fork(mm, oldmm);
307         if (retval)
308                 goto out;
309
310         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
311                 struct file *file;
312
313                 if (mpnt->vm_flags & VM_DONTCOPY) {
314                         long pages = vma_pages(mpnt);
315                         mm->total_vm -= pages;
316                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
317                                                                 -pages);
318                         continue;
319                 }
320                 charge = 0;
321                 if (mpnt->vm_flags & VM_ACCOUNT) {
322                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
323                         if (security_vm_enough_memory(len))
324                                 goto fail_nomem;
325                         charge = len;
326                 }
327                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
328                 if (!tmp)
329                         goto fail_nomem;
330                 *tmp = *mpnt;
331                 pol = mpol_dup(vma_policy(mpnt));
332                 retval = PTR_ERR(pol);
333                 if (IS_ERR(pol))
334                         goto fail_nomem_policy;
335                 vma_set_policy(tmp, pol);
336                 tmp->vm_flags &= ~VM_LOCKED;
337                 tmp->vm_mm = mm;
338                 tmp->vm_next = NULL;
339                 anon_vma_link(tmp);
340                 file = tmp->vm_file;
341                 if (file) {
342                         struct inode *inode = file->f_path.dentry->d_inode;
343                         struct address_space *mapping = file->f_mapping;
344
345                         get_file(file);
346                         if (tmp->vm_flags & VM_DENYWRITE)
347                                 atomic_dec(&inode->i_writecount);
348                         spin_lock(&mapping->i_mmap_lock);
349                         if (tmp->vm_flags & VM_SHARED)
350                                 mapping->i_mmap_writable++;
351                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
352                         flush_dcache_mmap_lock(mapping);
353                         /* insert tmp into the share list, just after mpnt */
354                         vma_prio_tree_add(tmp, mpnt);
355                         flush_dcache_mmap_unlock(mapping);
356                         spin_unlock(&mapping->i_mmap_lock);
357                 }
358
359                 /*
360                  * Clear hugetlb-related page reserves for children. This only
361                  * affects MAP_PRIVATE mappings. Faults generated by the child
362                  * are not guaranteed to succeed, even if read-only
363                  */
364                 if (is_vm_hugetlb_page(tmp))
365                         reset_vma_resv_huge_pages(tmp);
366
367                 /*
368                  * Link in the new vma and copy the page table entries.
369                  */
370                 *pprev = tmp;
371                 pprev = &tmp->vm_next;
372
373                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
374                 rb_link = &tmp->vm_rb.rb_right;
375                 rb_parent = &tmp->vm_rb;
376
377                 mm->map_count++;
378                 retval = copy_page_range(mm, oldmm, mpnt);
379
380                 if (tmp->vm_ops && tmp->vm_ops->open)
381                         tmp->vm_ops->open(tmp);
382
383                 if (retval)
384                         goto out;
385         }
386         /* a new mm has just been created */
387         arch_dup_mmap(oldmm, mm);
388         retval = 0;
389 out:
390         up_write(&mm->mmap_sem);
391         flush_tlb_mm(oldmm);
392         up_write(&oldmm->mmap_sem);
393         return retval;
394 fail_nomem_policy:
395         kmem_cache_free(vm_area_cachep, tmp);
396 fail_nomem:
397         retval = -ENOMEM;
398         vm_unacct_memory(charge);
399         goto out;
400 }
401
402 static inline int mm_alloc_pgd(struct mm_struct * mm)
403 {
404         mm->pgd = pgd_alloc(mm);
405         if (unlikely(!mm->pgd))
406                 return -ENOMEM;
407         return 0;
408 }
409
410 static inline void mm_free_pgd(struct mm_struct * mm)
411 {
412         pgd_free(mm, mm->pgd);
413 }
414 #else
415 #define dup_mmap(mm, oldmm)     (0)
416 #define mm_alloc_pgd(mm)        (0)
417 #define mm_free_pgd(mm)
418 #endif /* CONFIG_MMU */
419
420 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
421
422 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
423 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
424
425 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
426
427 static int __init coredump_filter_setup(char *s)
428 {
429         default_dump_filter =
430                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
431                 MMF_DUMP_FILTER_MASK;
432         return 1;
433 }
434
435 __setup("coredump_filter=", coredump_filter_setup);
436
437 #include <linux/init_task.h>
438
439 static void mm_init_aio(struct mm_struct *mm)
440 {
441 #ifdef CONFIG_AIO
442         spin_lock_init(&mm->ioctx_lock);
443         INIT_HLIST_HEAD(&mm->ioctx_list);
444 #endif
445 }
446
447 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
448 {
449         atomic_set(&mm->mm_users, 1);
450         atomic_set(&mm->mm_count, 1);
451         init_rwsem(&mm->mmap_sem);
452         INIT_LIST_HEAD(&mm->mmlist);
453         mm->flags = (current->mm) ?
454                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
455         mm->core_state = NULL;
456         mm->nr_ptes = 0;
457         set_mm_counter(mm, file_rss, 0);
458         set_mm_counter(mm, anon_rss, 0);
459         spin_lock_init(&mm->page_table_lock);
460         mm->free_area_cache = TASK_UNMAPPED_BASE;
461         mm->cached_hole_size = ~0UL;
462         mm_init_aio(mm);
463         mm_init_owner(mm, p);
464
465         if (likely(!mm_alloc_pgd(mm))) {
466                 mm->def_flags = 0;
467                 mmu_notifier_mm_init(mm);
468                 return mm;
469         }
470
471         free_mm(mm);
472         return NULL;
473 }
474
475 /*
476  * Allocate and initialize an mm_struct.
477  */
478 struct mm_struct * mm_alloc(void)
479 {
480         struct mm_struct * mm;
481
482         mm = allocate_mm();
483         if (mm) {
484                 memset(mm, 0, sizeof(*mm));
485                 mm = mm_init(mm, current);
486         }
487         return mm;
488 }
489
490 /*
491  * Called when the last reference to the mm
492  * is dropped: either by a lazy thread or by
493  * mmput. Free the page directory and the mm.
494  */
495 void __mmdrop(struct mm_struct *mm)
496 {
497         BUG_ON(mm == &init_mm);
498         mm_free_pgd(mm);
499         destroy_context(mm);
500         mmu_notifier_mm_destroy(mm);
501         free_mm(mm);
502 }
503 EXPORT_SYMBOL_GPL(__mmdrop);
504
505 /*
506  * Decrement the use count and release all resources for an mm.
507  */
508 void mmput(struct mm_struct *mm)
509 {
510         might_sleep();
511
512         if (atomic_dec_and_test(&mm->mm_users)) {
513                 exit_aio(mm);
514                 ksm_exit(mm);
515                 exit_mmap(mm);
516                 set_mm_exe_file(mm, NULL);
517                 if (!list_empty(&mm->mmlist)) {
518                         spin_lock(&mmlist_lock);
519                         list_del(&mm->mmlist);
520                         spin_unlock(&mmlist_lock);
521                 }
522                 put_swap_token(mm);
523                 if (mm->binfmt)
524                         module_put(mm->binfmt->module);
525                 mmdrop(mm);
526         }
527 }
528 EXPORT_SYMBOL_GPL(mmput);
529
530 /**
531  * get_task_mm - acquire a reference to the task's mm
532  *
533  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
534  * this kernel workthread has transiently adopted a user mm with use_mm,
535  * to do its AIO) is not set and if so returns a reference to it, after
536  * bumping up the use count.  User must release the mm via mmput()
537  * after use.  Typically used by /proc and ptrace.
538  */
539 struct mm_struct *get_task_mm(struct task_struct *task)
540 {
541         struct mm_struct *mm;
542
543         task_lock(task);
544         mm = task->mm;
545         if (mm) {
546                 if (task->flags & PF_KTHREAD)
547                         mm = NULL;
548                 else
549                         atomic_inc(&mm->mm_users);
550         }
551         task_unlock(task);
552         return mm;
553 }
554 EXPORT_SYMBOL_GPL(get_task_mm);
555
556 /* Please note the differences between mmput and mm_release.
557  * mmput is called whenever we stop holding onto a mm_struct,
558  * error success whatever.
559  *
560  * mm_release is called after a mm_struct has been removed
561  * from the current process.
562  *
563  * This difference is important for error handling, when we
564  * only half set up a mm_struct for a new process and need to restore
565  * the old one.  Because we mmput the new mm_struct before
566  * restoring the old one. . .
567  * Eric Biederman 10 January 1998
568  */
569 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
570 {
571         struct completion *vfork_done = tsk->vfork_done;
572
573         /* Get rid of any futexes when releasing the mm */
574 #ifdef CONFIG_FUTEX
575         if (unlikely(tsk->robust_list)) {
576                 exit_robust_list(tsk);
577                 tsk->robust_list = NULL;
578         }
579 #ifdef CONFIG_COMPAT
580         if (unlikely(tsk->compat_robust_list)) {
581                 compat_exit_robust_list(tsk);
582                 tsk->compat_robust_list = NULL;
583         }
584 #endif
585         if (unlikely(!list_empty(&tsk->pi_state_list)))
586                 exit_pi_state_list(tsk);
587 #endif
588
589         /* Get rid of any cached register state */
590         deactivate_mm(tsk, mm);
591
592         /* notify parent sleeping on vfork() */
593         if (vfork_done) {
594                 tsk->vfork_done = NULL;
595                 complete(vfork_done);
596         }
597
598         /*
599          * If we're exiting normally, clear a user-space tid field if
600          * requested.  We leave this alone when dying by signal, to leave
601          * the value intact in a core dump, and to save the unnecessary
602          * trouble otherwise.  Userland only wants this done for a sys_exit.
603          */
604         if (tsk->clear_child_tid) {
605                 if (!(tsk->flags & PF_SIGNALED) &&
606                     atomic_read(&mm->mm_users) > 1) {
607                         /*
608                          * We don't check the error code - if userspace has
609                          * not set up a proper pointer then tough luck.
610                          */
611                         put_user(0, tsk->clear_child_tid);
612                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
613                                         1, NULL, NULL, 0);
614                 }
615                 tsk->clear_child_tid = NULL;
616         }
617 }
618
619 /*
620  * Allocate a new mm structure and copy contents from the
621  * mm structure of the passed in task structure.
622  */
623 struct mm_struct *dup_mm(struct task_struct *tsk)
624 {
625         struct mm_struct *mm, *oldmm = current->mm;
626         int err;
627
628         if (!oldmm)
629                 return NULL;
630
631         mm = allocate_mm();
632         if (!mm)
633                 goto fail_nomem;
634
635         memcpy(mm, oldmm, sizeof(*mm));
636
637         /* Initializing for Swap token stuff */
638         mm->token_priority = 0;
639         mm->last_interval = 0;
640
641         if (!mm_init(mm, tsk))
642                 goto fail_nomem;
643
644         if (init_new_context(tsk, mm))
645                 goto fail_nocontext;
646
647         dup_mm_exe_file(oldmm, mm);
648
649         err = dup_mmap(mm, oldmm);
650         if (err)
651                 goto free_pt;
652
653         mm->hiwater_rss = get_mm_rss(mm);
654         mm->hiwater_vm = mm->total_vm;
655
656         if (mm->binfmt && !try_module_get(mm->binfmt->module))
657                 goto free_pt;
658
659         return mm;
660
661 free_pt:
662         /* don't put binfmt in mmput, we haven't got module yet */
663         mm->binfmt = NULL;
664         mmput(mm);
665
666 fail_nomem:
667         return NULL;
668
669 fail_nocontext:
670         /*
671          * If init_new_context() failed, we cannot use mmput() to free the mm
672          * because it calls destroy_context()
673          */
674         mm_free_pgd(mm);
675         free_mm(mm);
676         return NULL;
677 }
678
679 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
680 {
681         struct mm_struct * mm, *oldmm;
682         int retval;
683
684         tsk->min_flt = tsk->maj_flt = 0;
685         tsk->nvcsw = tsk->nivcsw = 0;
686 #ifdef CONFIG_DETECT_HUNG_TASK
687         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
688 #endif
689
690         tsk->mm = NULL;
691         tsk->active_mm = NULL;
692
693         /*
694          * Are we cloning a kernel thread?
695          *
696          * We need to steal a active VM for that..
697          */
698         oldmm = current->mm;
699         if (!oldmm)
700                 return 0;
701
702         if (clone_flags & CLONE_VM) {
703                 atomic_inc(&oldmm->mm_users);
704                 mm = oldmm;
705                 goto good_mm;
706         }
707
708         retval = -ENOMEM;
709         mm = dup_mm(tsk);
710         if (!mm)
711                 goto fail_nomem;
712
713 good_mm:
714         /* Initializing for Swap token stuff */
715         mm->token_priority = 0;
716         mm->last_interval = 0;
717
718         tsk->mm = mm;
719         tsk->active_mm = mm;
720         return 0;
721
722 fail_nomem:
723         return retval;
724 }
725
726 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
727 {
728         struct fs_struct *fs = current->fs;
729         if (clone_flags & CLONE_FS) {
730                 /* tsk->fs is already what we want */
731                 write_lock(&fs->lock);
732                 if (fs->in_exec) {
733                         write_unlock(&fs->lock);
734                         return -EAGAIN;
735                 }
736                 fs->users++;
737                 write_unlock(&fs->lock);
738                 return 0;
739         }
740         tsk->fs = copy_fs_struct(fs);
741         if (!tsk->fs)
742                 return -ENOMEM;
743         return 0;
744 }
745
746 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
747 {
748         struct files_struct *oldf, *newf;
749         int error = 0;
750
751         /*
752          * A background process may not have any files ...
753          */
754         oldf = current->files;
755         if (!oldf)
756                 goto out;
757
758         if (clone_flags & CLONE_FILES) {
759                 atomic_inc(&oldf->count);
760                 goto out;
761         }
762
763         newf = dup_fd(oldf, &error);
764         if (!newf)
765                 goto out;
766
767         tsk->files = newf;
768         error = 0;
769 out:
770         return error;
771 }
772
773 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
774 {
775 #ifdef CONFIG_BLOCK
776         struct io_context *ioc = current->io_context;
777
778         if (!ioc)
779                 return 0;
780         /*
781          * Share io context with parent, if CLONE_IO is set
782          */
783         if (clone_flags & CLONE_IO) {
784                 tsk->io_context = ioc_task_link(ioc);
785                 if (unlikely(!tsk->io_context))
786                         return -ENOMEM;
787         } else if (ioprio_valid(ioc->ioprio)) {
788                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
789                 if (unlikely(!tsk->io_context))
790                         return -ENOMEM;
791
792                 tsk->io_context->ioprio = ioc->ioprio;
793         }
794 #endif
795         return 0;
796 }
797
798 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
799 {
800         struct sighand_struct *sig;
801
802         if (clone_flags & CLONE_SIGHAND) {
803                 atomic_inc(&current->sighand->count);
804                 return 0;
805         }
806         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
807         rcu_assign_pointer(tsk->sighand, sig);
808         if (!sig)
809                 return -ENOMEM;
810         atomic_set(&sig->count, 1);
811         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
812         return 0;
813 }
814
815 void __cleanup_sighand(struct sighand_struct *sighand)
816 {
817         if (atomic_dec_and_test(&sighand->count))
818                 kmem_cache_free(sighand_cachep, sighand);
819 }
820
821
822 /*
823  * Initialize POSIX timer handling for a thread group.
824  */
825 static void posix_cpu_timers_init_group(struct signal_struct *sig)
826 {
827         /* Thread group counters. */
828         thread_group_cputime_init(sig);
829
830         /* Expiration times and increments. */
831         sig->it[CPUCLOCK_PROF].expires = cputime_zero;
832         sig->it[CPUCLOCK_PROF].incr = cputime_zero;
833         sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
834         sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
835
836         /* Cached expiration times. */
837         sig->cputime_expires.prof_exp = cputime_zero;
838         sig->cputime_expires.virt_exp = cputime_zero;
839         sig->cputime_expires.sched_exp = 0;
840
841         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
842                 sig->cputime_expires.prof_exp =
843                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
844                 sig->cputimer.running = 1;
845         }
846
847         /* The timer lists. */
848         INIT_LIST_HEAD(&sig->cpu_timers[0]);
849         INIT_LIST_HEAD(&sig->cpu_timers[1]);
850         INIT_LIST_HEAD(&sig->cpu_timers[2]);
851 }
852
853 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
854 {
855         struct signal_struct *sig;
856
857         if (clone_flags & CLONE_THREAD)
858                 return 0;
859
860         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
861         tsk->signal = sig;
862         if (!sig)
863                 return -ENOMEM;
864
865         atomic_set(&sig->count, 1);
866         atomic_set(&sig->live, 1);
867         init_waitqueue_head(&sig->wait_chldexit);
868         sig->flags = 0;
869         if (clone_flags & CLONE_NEWPID)
870                 sig->flags |= SIGNAL_UNKILLABLE;
871         sig->group_exit_code = 0;
872         sig->group_exit_task = NULL;
873         sig->group_stop_count = 0;
874         sig->curr_target = tsk;
875         init_sigpending(&sig->shared_pending);
876         INIT_LIST_HEAD(&sig->posix_timers);
877
878         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
879         sig->it_real_incr.tv64 = 0;
880         sig->real_timer.function = it_real_fn;
881
882         sig->leader = 0;        /* session leadership doesn't inherit */
883         sig->tty_old_pgrp = NULL;
884         sig->tty = NULL;
885
886         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
887         sig->gtime = cputime_zero;
888         sig->cgtime = cputime_zero;
889         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
890         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
891         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
892         sig->maxrss = sig->cmaxrss = 0;
893         task_io_accounting_init(&sig->ioac);
894         sig->sum_sched_runtime = 0;
895         taskstats_tgid_init(sig);
896
897         task_lock(current->group_leader);
898         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
899         task_unlock(current->group_leader);
900
901         posix_cpu_timers_init_group(sig);
902
903         acct_init_pacct(&sig->pacct);
904
905         tty_audit_fork(sig);
906
907         sig->oom_adj = current->signal->oom_adj;
908
909         return 0;
910 }
911
912 void __cleanup_signal(struct signal_struct *sig)
913 {
914         thread_group_cputime_free(sig);
915         tty_kref_put(sig->tty);
916         kmem_cache_free(signal_cachep, sig);
917 }
918
919 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
920 {
921         unsigned long new_flags = p->flags;
922
923         new_flags &= ~PF_SUPERPRIV;
924         new_flags |= PF_FORKNOEXEC;
925         new_flags |= PF_STARTING;
926         p->flags = new_flags;
927         clear_freeze_flag(p);
928 }
929
930 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
931 {
932         current->clear_child_tid = tidptr;
933
934         return task_pid_vnr(current);
935 }
936
937 static void rt_mutex_init_task(struct task_struct *p)
938 {
939         spin_lock_init(&p->pi_lock);
940 #ifdef CONFIG_RT_MUTEXES
941         plist_head_init(&p->pi_waiters, &p->pi_lock);
942         p->pi_blocked_on = NULL;
943 #endif
944 }
945
946 #ifdef CONFIG_MM_OWNER
947 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
948 {
949         mm->owner = p;
950 }
951 #endif /* CONFIG_MM_OWNER */
952
953 /*
954  * Initialize POSIX timer handling for a single task.
955  */
956 static void posix_cpu_timers_init(struct task_struct *tsk)
957 {
958         tsk->cputime_expires.prof_exp = cputime_zero;
959         tsk->cputime_expires.virt_exp = cputime_zero;
960         tsk->cputime_expires.sched_exp = 0;
961         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
962         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
963         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
964 }
965
966 /*
967  * This creates a new process as a copy of the old one,
968  * but does not actually start it yet.
969  *
970  * It copies the registers, and all the appropriate
971  * parts of the process environment (as per the clone
972  * flags). The actual kick-off is left to the caller.
973  */
974 static struct task_struct *copy_process(unsigned long clone_flags,
975                                         unsigned long stack_start,
976                                         struct pt_regs *regs,
977                                         unsigned long stack_size,
978                                         int __user *child_tidptr,
979                                         struct pid *pid,
980                                         int trace)
981 {
982         int retval;
983         struct task_struct *p;
984         int cgroup_callbacks_done = 0;
985
986         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
987                 return ERR_PTR(-EINVAL);
988
989         /*
990          * Thread groups must share signals as well, and detached threads
991          * can only be started up within the thread group.
992          */
993         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
994                 return ERR_PTR(-EINVAL);
995
996         /*
997          * Shared signal handlers imply shared VM. By way of the above,
998          * thread groups also imply shared VM. Blocking this case allows
999          * for various simplifications in other code.
1000          */
1001         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1002                 return ERR_PTR(-EINVAL);
1003
1004         /*
1005          * Siblings of global init remain as zombies on exit since they are
1006          * not reaped by their parent (swapper). To solve this and to avoid
1007          * multi-rooted process trees, prevent global and container-inits
1008          * from creating siblings.
1009          */
1010         if ((clone_flags & CLONE_PARENT) &&
1011                                 current->signal->flags & SIGNAL_UNKILLABLE)
1012                 return ERR_PTR(-EINVAL);
1013
1014         retval = security_task_create(clone_flags);
1015         if (retval)
1016                 goto fork_out;
1017
1018         retval = -ENOMEM;
1019         p = dup_task_struct(current);
1020         if (!p)
1021                 goto fork_out;
1022
1023         ftrace_graph_init_task(p);
1024
1025         rt_mutex_init_task(p);
1026
1027 #ifdef CONFIG_PROVE_LOCKING
1028         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1029         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1030 #endif
1031         retval = -EAGAIN;
1032         if (atomic_read(&p->real_cred->user->processes) >=
1033                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1034                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1035                     p->real_cred->user != INIT_USER)
1036                         goto bad_fork_free;
1037         }
1038
1039         retval = copy_creds(p, clone_flags);
1040         if (retval < 0)
1041                 goto bad_fork_free;
1042
1043         /*
1044          * If multiple threads are within copy_process(), then this check
1045          * triggers too late. This doesn't hurt, the check is only there
1046          * to stop root fork bombs.
1047          */
1048         retval = -EAGAIN;
1049         if (nr_threads >= max_threads)
1050                 goto bad_fork_cleanup_count;
1051
1052         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1053                 goto bad_fork_cleanup_count;
1054
1055         p->did_exec = 0;
1056         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1057         copy_flags(clone_flags, p);
1058         INIT_LIST_HEAD(&p->children);
1059         INIT_LIST_HEAD(&p->sibling);
1060         rcu_copy_process(p);
1061         p->vfork_done = NULL;
1062         spin_lock_init(&p->alloc_lock);
1063
1064         init_sigpending(&p->pending);
1065
1066         p->utime = cputime_zero;
1067         p->stime = cputime_zero;
1068         p->gtime = cputime_zero;
1069         p->utimescaled = cputime_zero;
1070         p->stimescaled = cputime_zero;
1071         p->prev_utime = cputime_zero;
1072         p->prev_stime = cputime_zero;
1073
1074         p->default_timer_slack_ns = current->timer_slack_ns;
1075
1076         task_io_accounting_init(&p->ioac);
1077         acct_clear_integrals(p);
1078
1079         posix_cpu_timers_init(p);
1080
1081         p->lock_depth = -1;             /* -1 = no lock */
1082         do_posix_clock_monotonic_gettime(&p->start_time);
1083         p->real_start_time = p->start_time;
1084         monotonic_to_bootbased(&p->real_start_time);
1085         p->io_context = NULL;
1086         p->audit_context = NULL;
1087         cgroup_fork(p);
1088 #ifdef CONFIG_NUMA
1089         p->mempolicy = mpol_dup(p->mempolicy);
1090         if (IS_ERR(p->mempolicy)) {
1091                 retval = PTR_ERR(p->mempolicy);
1092                 p->mempolicy = NULL;
1093                 goto bad_fork_cleanup_cgroup;
1094         }
1095         mpol_fix_fork_child_flag(p);
1096 #endif
1097 #ifdef CONFIG_TRACE_IRQFLAGS
1098         p->irq_events = 0;
1099 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1100         p->hardirqs_enabled = 1;
1101 #else
1102         p->hardirqs_enabled = 0;
1103 #endif
1104         p->hardirq_enable_ip = 0;
1105         p->hardirq_enable_event = 0;
1106         p->hardirq_disable_ip = _THIS_IP_;
1107         p->hardirq_disable_event = 0;
1108         p->softirqs_enabled = 1;
1109         p->softirq_enable_ip = _THIS_IP_;
1110         p->softirq_enable_event = 0;
1111         p->softirq_disable_ip = 0;
1112         p->softirq_disable_event = 0;
1113         p->hardirq_context = 0;
1114         p->softirq_context = 0;
1115 #endif
1116 #ifdef CONFIG_LOCKDEP
1117         p->lockdep_depth = 0; /* no locks held yet */
1118         p->curr_chain_key = 0;
1119         p->lockdep_recursion = 0;
1120 #endif
1121
1122 #ifdef CONFIG_DEBUG_MUTEXES
1123         p->blocked_on = NULL; /* not blocked yet */
1124 #endif
1125
1126         p->bts = NULL;
1127
1128         p->stack_start = stack_start;
1129
1130         /* Perform scheduler related setup. Assign this task to a CPU. */
1131         sched_fork(p, clone_flags);
1132
1133         retval = perf_event_init_task(p);
1134         if (retval)
1135                 goto bad_fork_cleanup_policy;
1136
1137         if ((retval = audit_alloc(p)))
1138                 goto bad_fork_cleanup_policy;
1139         /* copy all the process information */
1140         if ((retval = copy_semundo(clone_flags, p)))
1141                 goto bad_fork_cleanup_audit;
1142         if ((retval = copy_files(clone_flags, p)))
1143                 goto bad_fork_cleanup_semundo;
1144         if ((retval = copy_fs(clone_flags, p)))
1145                 goto bad_fork_cleanup_files;
1146         if ((retval = copy_sighand(clone_flags, p)))
1147                 goto bad_fork_cleanup_fs;
1148         if ((retval = copy_signal(clone_flags, p)))
1149                 goto bad_fork_cleanup_sighand;
1150         if ((retval = copy_mm(clone_flags, p)))
1151                 goto bad_fork_cleanup_signal;
1152         if ((retval = copy_namespaces(clone_flags, p)))
1153                 goto bad_fork_cleanup_mm;
1154         if ((retval = copy_io(clone_flags, p)))
1155                 goto bad_fork_cleanup_namespaces;
1156         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1157         if (retval)
1158                 goto bad_fork_cleanup_io;
1159
1160         if (pid != &init_struct_pid) {
1161                 retval = -ENOMEM;
1162                 pid = alloc_pid(p->nsproxy->pid_ns);
1163                 if (!pid)
1164                         goto bad_fork_cleanup_io;
1165
1166                 if (clone_flags & CLONE_NEWPID) {
1167                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1168                         if (retval < 0)
1169                                 goto bad_fork_free_pid;
1170                 }
1171         }
1172
1173         p->pid = pid_nr(pid);
1174         p->tgid = p->pid;
1175         if (clone_flags & CLONE_THREAD)
1176                 p->tgid = current->tgid;
1177
1178         if (current->nsproxy != p->nsproxy) {
1179                 retval = ns_cgroup_clone(p, pid);
1180                 if (retval)
1181                         goto bad_fork_free_pid;
1182         }
1183
1184         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1185         /*
1186          * Clear TID on mm_release()?
1187          */
1188         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1189 #ifdef CONFIG_FUTEX
1190         p->robust_list = NULL;
1191 #ifdef CONFIG_COMPAT
1192         p->compat_robust_list = NULL;
1193 #endif
1194         INIT_LIST_HEAD(&p->pi_state_list);
1195         p->pi_state_cache = NULL;
1196 #endif
1197         /*
1198          * sigaltstack should be cleared when sharing the same VM
1199          */
1200         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1201                 p->sas_ss_sp = p->sas_ss_size = 0;
1202
1203         /*
1204          * Syscall tracing should be turned off in the child regardless
1205          * of CLONE_PTRACE.
1206          */
1207         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1208 #ifdef TIF_SYSCALL_EMU
1209         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1210 #endif
1211         clear_all_latency_tracing(p);
1212
1213         /* ok, now we should be set up.. */
1214         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1215         p->pdeath_signal = 0;
1216         p->exit_state = 0;
1217
1218         /*
1219          * Ok, make it visible to the rest of the system.
1220          * We dont wake it up yet.
1221          */
1222         p->group_leader = p;
1223         INIT_LIST_HEAD(&p->thread_group);
1224
1225         /* Now that the task is set up, run cgroup callbacks if
1226          * necessary. We need to run them before the task is visible
1227          * on the tasklist. */
1228         cgroup_fork_callbacks(p);
1229         cgroup_callbacks_done = 1;
1230
1231         /* Need tasklist lock for parent etc handling! */
1232         write_lock_irq(&tasklist_lock);
1233
1234         /*
1235          * The task hasn't been attached yet, so its cpus_allowed mask will
1236          * not be changed, nor will its assigned CPU.
1237          *
1238          * The cpus_allowed mask of the parent may have changed after it was
1239          * copied first time - so re-copy it here, then check the child's CPU
1240          * to ensure it is on a valid CPU (and if not, just force it back to
1241          * parent's CPU). This avoids alot of nasty races.
1242          */
1243         p->cpus_allowed = current->cpus_allowed;
1244         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1245         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1246                         !cpu_online(task_cpu(p))))
1247                 set_task_cpu(p, smp_processor_id());
1248
1249         /* CLONE_PARENT re-uses the old parent */
1250         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1251                 p->real_parent = current->real_parent;
1252                 p->parent_exec_id = current->parent_exec_id;
1253         } else {
1254                 p->real_parent = current;
1255                 p->parent_exec_id = current->self_exec_id;
1256         }
1257
1258         spin_lock(&current->sighand->siglock);
1259
1260         /*
1261          * Process group and session signals need to be delivered to just the
1262          * parent before the fork or both the parent and the child after the
1263          * fork. Restart if a signal comes in before we add the new process to
1264          * it's process group.
1265          * A fatal signal pending means that current will exit, so the new
1266          * thread can't slip out of an OOM kill (or normal SIGKILL).
1267          */
1268         recalc_sigpending();
1269         if (signal_pending(current)) {
1270                 spin_unlock(&current->sighand->siglock);
1271                 write_unlock_irq(&tasklist_lock);
1272                 retval = -ERESTARTNOINTR;
1273                 goto bad_fork_free_pid;
1274         }
1275
1276         if (clone_flags & CLONE_THREAD) {
1277                 atomic_inc(&current->signal->count);
1278                 atomic_inc(&current->signal->live);
1279                 p->group_leader = current->group_leader;
1280                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1281         }
1282
1283         if (likely(p->pid)) {
1284                 list_add_tail(&p->sibling, &p->real_parent->children);
1285                 tracehook_finish_clone(p, clone_flags, trace);
1286
1287                 if (thread_group_leader(p)) {
1288                         if (clone_flags & CLONE_NEWPID)
1289                                 p->nsproxy->pid_ns->child_reaper = p;
1290
1291                         p->signal->leader_pid = pid;
1292                         tty_kref_put(p->signal->tty);
1293                         p->signal->tty = tty_kref_get(current->signal->tty);
1294                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1295                         attach_pid(p, PIDTYPE_SID, task_session(current));
1296                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1297                         __get_cpu_var(process_counts)++;
1298                 }
1299                 attach_pid(p, PIDTYPE_PID, pid);
1300                 nr_threads++;
1301         }
1302
1303         total_forks++;
1304         spin_unlock(&current->sighand->siglock);
1305         write_unlock_irq(&tasklist_lock);
1306         proc_fork_connector(p);
1307         cgroup_post_fork(p);
1308         perf_event_fork(p);
1309         return p;
1310
1311 bad_fork_free_pid:
1312         if (pid != &init_struct_pid)
1313                 free_pid(pid);
1314 bad_fork_cleanup_io:
1315         put_io_context(p->io_context);
1316 bad_fork_cleanup_namespaces:
1317         exit_task_namespaces(p);
1318 bad_fork_cleanup_mm:
1319         if (p->mm)
1320                 mmput(p->mm);
1321 bad_fork_cleanup_signal:
1322         if (!(clone_flags & CLONE_THREAD))
1323                 __cleanup_signal(p->signal);
1324 bad_fork_cleanup_sighand:
1325         __cleanup_sighand(p->sighand);
1326 bad_fork_cleanup_fs:
1327         exit_fs(p); /* blocking */
1328 bad_fork_cleanup_files:
1329         exit_files(p); /* blocking */
1330 bad_fork_cleanup_semundo:
1331         exit_sem(p);
1332 bad_fork_cleanup_audit:
1333         audit_free(p);
1334 bad_fork_cleanup_policy:
1335         perf_event_free_task(p);
1336 #ifdef CONFIG_NUMA
1337         mpol_put(p->mempolicy);
1338 bad_fork_cleanup_cgroup:
1339 #endif
1340         cgroup_exit(p, cgroup_callbacks_done);
1341         delayacct_tsk_free(p);
1342         module_put(task_thread_info(p)->exec_domain->module);
1343 bad_fork_cleanup_count:
1344         atomic_dec(&p->cred->user->processes);
1345         exit_creds(p);
1346 bad_fork_free:
1347         free_task(p);
1348 fork_out:
1349         return ERR_PTR(retval);
1350 }
1351
1352 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1353 {
1354         memset(regs, 0, sizeof(struct pt_regs));
1355         return regs;
1356 }
1357
1358 struct task_struct * __cpuinit fork_idle(int cpu)
1359 {
1360         struct task_struct *task;
1361         struct pt_regs regs;
1362
1363         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1364                             &init_struct_pid, 0);
1365         if (!IS_ERR(task))
1366                 init_idle(task, cpu);
1367
1368         return task;
1369 }
1370
1371 /*
1372  *  Ok, this is the main fork-routine.
1373  *
1374  * It copies the process, and if successful kick-starts
1375  * it and waits for it to finish using the VM if required.
1376  */
1377 long do_fork(unsigned long clone_flags,
1378               unsigned long stack_start,
1379               struct pt_regs *regs,
1380               unsigned long stack_size,
1381               int __user *parent_tidptr,
1382               int __user *child_tidptr)
1383 {
1384         struct task_struct *p;
1385         int trace = 0;
1386         long nr;
1387
1388         /*
1389          * Do some preliminary argument and permissions checking before we
1390          * actually start allocating stuff
1391          */
1392         if (clone_flags & CLONE_NEWUSER) {
1393                 if (clone_flags & CLONE_THREAD)
1394                         return -EINVAL;
1395                 /* hopefully this check will go away when userns support is
1396                  * complete
1397                  */
1398                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1399                                 !capable(CAP_SETGID))
1400                         return -EPERM;
1401         }
1402
1403         /*
1404          * We hope to recycle these flags after 2.6.26
1405          */
1406         if (unlikely(clone_flags & CLONE_STOPPED)) {
1407                 static int __read_mostly count = 100;
1408
1409                 if (count > 0 && printk_ratelimit()) {
1410                         char comm[TASK_COMM_LEN];
1411
1412                         count--;
1413                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1414                                         "clone flags 0x%lx\n",
1415                                 get_task_comm(comm, current),
1416                                 clone_flags & CLONE_STOPPED);
1417                 }
1418         }
1419
1420         /*
1421          * When called from kernel_thread, don't do user tracing stuff.
1422          */
1423         if (likely(user_mode(regs)))
1424                 trace = tracehook_prepare_clone(clone_flags);
1425
1426         p = copy_process(clone_flags, stack_start, regs, stack_size,
1427                          child_tidptr, NULL, trace);
1428         /*
1429          * Do this prior waking up the new thread - the thread pointer
1430          * might get invalid after that point, if the thread exits quickly.
1431          */
1432         if (!IS_ERR(p)) {
1433                 struct completion vfork;
1434
1435                 trace_sched_process_fork(current, p);
1436
1437                 nr = task_pid_vnr(p);
1438
1439                 if (clone_flags & CLONE_PARENT_SETTID)
1440                         put_user(nr, parent_tidptr);
1441
1442                 if (clone_flags & CLONE_VFORK) {
1443                         p->vfork_done = &vfork;
1444                         init_completion(&vfork);
1445                 }
1446
1447                 audit_finish_fork(p);
1448                 tracehook_report_clone(regs, clone_flags, nr, p);
1449
1450                 /*
1451                  * We set PF_STARTING at creation in case tracing wants to
1452                  * use this to distinguish a fully live task from one that
1453                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1454                  * clear it and set the child going.
1455                  */
1456                 p->flags &= ~PF_STARTING;
1457
1458                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1459                         /*
1460                          * We'll start up with an immediate SIGSTOP.
1461                          */
1462                         sigaddset(&p->pending.signal, SIGSTOP);
1463                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1464                         __set_task_state(p, TASK_STOPPED);
1465                 } else {
1466                         wake_up_new_task(p, clone_flags);
1467                 }
1468
1469                 tracehook_report_clone_complete(trace, regs,
1470                                                 clone_flags, nr, p);
1471
1472                 if (clone_flags & CLONE_VFORK) {
1473                         freezer_do_not_count();
1474                         wait_for_completion(&vfork);
1475                         freezer_count();
1476                         tracehook_report_vfork_done(p, nr);
1477                 }
1478         } else {
1479                 nr = PTR_ERR(p);
1480         }
1481         return nr;
1482 }
1483
1484 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1485 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1486 #endif
1487
1488 static void sighand_ctor(void *data)
1489 {
1490         struct sighand_struct *sighand = data;
1491
1492         spin_lock_init(&sighand->siglock);
1493         init_waitqueue_head(&sighand->signalfd_wqh);
1494 }
1495
1496 void __init proc_caches_init(void)
1497 {
1498         sighand_cachep = kmem_cache_create("sighand_cache",
1499                         sizeof(struct sighand_struct), 0,
1500                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1501                         SLAB_NOTRACK, sighand_ctor);
1502         signal_cachep = kmem_cache_create("signal_cache",
1503                         sizeof(struct signal_struct), 0,
1504                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1505         files_cachep = kmem_cache_create("files_cache",
1506                         sizeof(struct files_struct), 0,
1507                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1508         fs_cachep = kmem_cache_create("fs_cache",
1509                         sizeof(struct fs_struct), 0,
1510                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1511         mm_cachep = kmem_cache_create("mm_struct",
1512                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1513                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1514         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1515         mmap_init();
1516 }
1517
1518 /*
1519  * Check constraints on flags passed to the unshare system call and
1520  * force unsharing of additional process context as appropriate.
1521  */
1522 static void check_unshare_flags(unsigned long *flags_ptr)
1523 {
1524         /*
1525          * If unsharing a thread from a thread group, must also
1526          * unshare vm.
1527          */
1528         if (*flags_ptr & CLONE_THREAD)
1529                 *flags_ptr |= CLONE_VM;
1530
1531         /*
1532          * If unsharing vm, must also unshare signal handlers.
1533          */
1534         if (*flags_ptr & CLONE_VM)
1535                 *flags_ptr |= CLONE_SIGHAND;
1536
1537         /*
1538          * If unsharing signal handlers and the task was created
1539          * using CLONE_THREAD, then must unshare the thread
1540          */
1541         if ((*flags_ptr & CLONE_SIGHAND) &&
1542             (atomic_read(&current->signal->count) > 1))
1543                 *flags_ptr |= CLONE_THREAD;
1544
1545         /*
1546          * If unsharing namespace, must also unshare filesystem information.
1547          */
1548         if (*flags_ptr & CLONE_NEWNS)
1549                 *flags_ptr |= CLONE_FS;
1550 }
1551
1552 /*
1553  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1554  */
1555 static int unshare_thread(unsigned long unshare_flags)
1556 {
1557         if (unshare_flags & CLONE_THREAD)
1558                 return -EINVAL;
1559
1560         return 0;
1561 }
1562
1563 /*
1564  * Unshare the filesystem structure if it is being shared
1565  */
1566 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1567 {
1568         struct fs_struct *fs = current->fs;
1569
1570         if (!(unshare_flags & CLONE_FS) || !fs)
1571                 return 0;
1572
1573         /* don't need lock here; in the worst case we'll do useless copy */
1574         if (fs->users == 1)
1575                 return 0;
1576
1577         *new_fsp = copy_fs_struct(fs);
1578         if (!*new_fsp)
1579                 return -ENOMEM;
1580
1581         return 0;
1582 }
1583
1584 /*
1585  * Unsharing of sighand is not supported yet
1586  */
1587 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1588 {
1589         struct sighand_struct *sigh = current->sighand;
1590
1591         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1592                 return -EINVAL;
1593         else
1594                 return 0;
1595 }
1596
1597 /*
1598  * Unshare vm if it is being shared
1599  */
1600 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1601 {
1602         struct mm_struct *mm = current->mm;
1603
1604         if ((unshare_flags & CLONE_VM) &&
1605             (mm && atomic_read(&mm->mm_users) > 1)) {
1606                 return -EINVAL;
1607         }
1608
1609         return 0;
1610 }
1611
1612 /*
1613  * Unshare file descriptor table if it is being shared
1614  */
1615 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1616 {
1617         struct files_struct *fd = current->files;
1618         int error = 0;
1619
1620         if ((unshare_flags & CLONE_FILES) &&
1621             (fd && atomic_read(&fd->count) > 1)) {
1622                 *new_fdp = dup_fd(fd, &error);
1623                 if (!*new_fdp)
1624                         return error;
1625         }
1626
1627         return 0;
1628 }
1629
1630 /*
1631  * unshare allows a process to 'unshare' part of the process
1632  * context which was originally shared using clone.  copy_*
1633  * functions used by do_fork() cannot be used here directly
1634  * because they modify an inactive task_struct that is being
1635  * constructed. Here we are modifying the current, active,
1636  * task_struct.
1637  */
1638 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1639 {
1640         int err = 0;
1641         struct fs_struct *fs, *new_fs = NULL;
1642         struct sighand_struct *new_sigh = NULL;
1643         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1644         struct files_struct *fd, *new_fd = NULL;
1645         struct nsproxy *new_nsproxy = NULL;
1646         int do_sysvsem = 0;
1647
1648         check_unshare_flags(&unshare_flags);
1649
1650         /* Return -EINVAL for all unsupported flags */
1651         err = -EINVAL;
1652         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1653                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1654                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1655                 goto bad_unshare_out;
1656
1657         /*
1658          * CLONE_NEWIPC must also detach from the undolist: after switching
1659          * to a new ipc namespace, the semaphore arrays from the old
1660          * namespace are unreachable.
1661          */
1662         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1663                 do_sysvsem = 1;
1664         if ((err = unshare_thread(unshare_flags)))
1665                 goto bad_unshare_out;
1666         if ((err = unshare_fs(unshare_flags, &new_fs)))
1667                 goto bad_unshare_cleanup_thread;
1668         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1669                 goto bad_unshare_cleanup_fs;
1670         if ((err = unshare_vm(unshare_flags, &new_mm)))
1671                 goto bad_unshare_cleanup_sigh;
1672         if ((err = unshare_fd(unshare_flags, &new_fd)))
1673                 goto bad_unshare_cleanup_vm;
1674         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1675                         new_fs)))
1676                 goto bad_unshare_cleanup_fd;
1677
1678         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1679                 if (do_sysvsem) {
1680                         /*
1681                          * CLONE_SYSVSEM is equivalent to sys_exit().
1682                          */
1683                         exit_sem(current);
1684                 }
1685
1686                 if (new_nsproxy) {
1687                         switch_task_namespaces(current, new_nsproxy);
1688                         new_nsproxy = NULL;
1689                 }
1690
1691                 task_lock(current);
1692
1693                 if (new_fs) {
1694                         fs = current->fs;
1695                         write_lock(&fs->lock);
1696                         current->fs = new_fs;
1697                         if (--fs->users)
1698                                 new_fs = NULL;
1699                         else
1700                                 new_fs = fs;
1701                         write_unlock(&fs->lock);
1702                 }
1703
1704                 if (new_mm) {
1705                         mm = current->mm;
1706                         active_mm = current->active_mm;
1707                         current->mm = new_mm;
1708                         current->active_mm = new_mm;
1709                         activate_mm(active_mm, new_mm);
1710                         new_mm = mm;
1711                 }
1712
1713                 if (new_fd) {
1714                         fd = current->files;
1715                         current->files = new_fd;
1716                         new_fd = fd;
1717                 }
1718
1719                 task_unlock(current);
1720         }
1721
1722         if (new_nsproxy)
1723                 put_nsproxy(new_nsproxy);
1724
1725 bad_unshare_cleanup_fd:
1726         if (new_fd)
1727                 put_files_struct(new_fd);
1728
1729 bad_unshare_cleanup_vm:
1730         if (new_mm)
1731                 mmput(new_mm);
1732
1733 bad_unshare_cleanup_sigh:
1734         if (new_sigh)
1735                 if (atomic_dec_and_test(&new_sigh->count))
1736                         kmem_cache_free(sighand_cachep, new_sigh);
1737
1738 bad_unshare_cleanup_fs:
1739         if (new_fs)
1740                 free_fs_struct(new_fs);
1741
1742 bad_unshare_cleanup_thread:
1743 bad_unshare_out:
1744         return err;
1745 }
1746
1747 /*
1748  *      Helper to unshare the files of the current task.
1749  *      We don't want to expose copy_files internals to
1750  *      the exec layer of the kernel.
1751  */
1752
1753 int unshare_files(struct files_struct **displaced)
1754 {
1755         struct task_struct *task = current;
1756         struct files_struct *copy = NULL;
1757         int error;
1758
1759         error = unshare_fd(CLONE_FILES, &copy);
1760         if (error || !copy) {
1761                 *displaced = NULL;
1762                 return error;
1763         }
1764         *displaced = task->files;
1765         task_lock(task);
1766         task->files = copy;
1767         task_unlock(task);
1768         return 0;
1769 }