7ce2ebe847964ecd0701c3c74c18994e3eebcf26
[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/mnt_namespace.h>
21 #include <linux/personality.h>
22 #include <linux/mempolicy.h>
23 #include <linux/sem.h>
24 #include <linux/file.h>
25 #include <linux/fdtable.h>
26 #include <linux/iocontext.h>
27 #include <linux/key.h>
28 #include <linux/binfmts.h>
29 #include <linux/mman.h>
30 #include <linux/mmu_notifier.h>
31 #include <linux/fs.h>
32 #include <linux/nsproxy.h>
33 #include <linux/capability.h>
34 #include <linux/cpu.h>
35 #include <linux/cgroup.h>
36 #include <linux/security.h>
37 #include <linux/hugetlb.h>
38 #include <linux/swap.h>
39 #include <linux/syscalls.h>
40 #include <linux/jiffies.h>
41 #include <linux/tracehook.h>
42 #include <linux/futex.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/profile.h>
50 #include <linux/rmap.h>
51 #include <linux/acct.h>
52 #include <linux/tsacct_kern.h>
53 #include <linux/cn_proc.h>
54 #include <linux/freezer.h>
55 #include <linux/delayacct.h>
56 #include <linux/taskstats_kern.h>
57 #include <linux/random.h>
58 #include <linux/tty.h>
59 #include <linux/proc_fs.h>
60 #include <linux/blkdev.h>
61
62 #include <asm/pgtable.h>
63 #include <asm/pgalloc.h>
64 #include <asm/uaccess.h>
65 #include <asm/mmu_context.h>
66 #include <asm/cacheflush.h>
67 #include <asm/tlbflush.h>
68
69 /*
70  * Protected counters by write_lock_irq(&tasklist_lock)
71  */
72 unsigned long total_forks;      /* Handle normal Linux uptimes. */
73 int nr_threads;                 /* The idle threads do not count.. */
74
75 int max_threads;                /* tunable limit on nr_threads */
76
77 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
78
79 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
80
81 int nr_processes(void)
82 {
83         int cpu;
84         int total = 0;
85
86         for_each_online_cpu(cpu)
87                 total += per_cpu(process_counts, cpu);
88
89         return total;
90 }
91
92 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
93 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
94 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
95 static struct kmem_cache *task_struct_cachep;
96 #endif
97
98 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
99 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
100 {
101 #ifdef CONFIG_DEBUG_STACK_USAGE
102         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
103 #else
104         gfp_t mask = GFP_KERNEL;
105 #endif
106         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
107 }
108
109 static inline void free_thread_info(struct thread_info *ti)
110 {
111         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
112 }
113 #endif
114
115 /* SLAB cache for signal_struct structures (tsk->signal) */
116 static struct kmem_cache *signal_cachep;
117
118 /* SLAB cache for sighand_struct structures (tsk->sighand) */
119 struct kmem_cache *sighand_cachep;
120
121 /* SLAB cache for files_struct structures (tsk->files) */
122 struct kmem_cache *files_cachep;
123
124 /* SLAB cache for fs_struct structures (tsk->fs) */
125 struct kmem_cache *fs_cachep;
126
127 /* SLAB cache for vm_area_struct structures */
128 struct kmem_cache *vm_area_cachep;
129
130 /* SLAB cache for mm_struct structures (tsk->mm) */
131 static struct kmem_cache *mm_cachep;
132
133 void free_task(struct task_struct *tsk)
134 {
135         prop_local_destroy_single(&tsk->dirties);
136         free_thread_info(tsk->stack);
137         rt_mutex_debug_task_free(tsk);
138         free_task_struct(tsk);
139 }
140 EXPORT_SYMBOL(free_task);
141
142 void __put_task_struct(struct task_struct *tsk)
143 {
144         WARN_ON(!tsk->exit_state);
145         WARN_ON(atomic_read(&tsk->usage));
146         WARN_ON(tsk == current);
147
148         security_task_free(tsk);
149         free_uid(tsk->user);
150         put_group_info(tsk->group_info);
151         delayacct_tsk_free(tsk);
152
153         if (!profile_handoff_task(tsk))
154                 free_task(tsk);
155 }
156
157 /*
158  * macro override instead of weak attribute alias, to workaround
159  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
160  */
161 #ifndef arch_task_cache_init
162 #define arch_task_cache_init()
163 #endif
164
165 void __init fork_init(unsigned long mempages)
166 {
167 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
168 #ifndef ARCH_MIN_TASKALIGN
169 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
170 #endif
171         /* create a slab on which task_structs can be allocated */
172         task_struct_cachep =
173                 kmem_cache_create("task_struct", sizeof(struct task_struct),
174                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
175 #endif
176
177         /* do the arch specific task caches init */
178         arch_task_cache_init();
179
180         /*
181          * The default maximum number of threads is set to a safe
182          * value: the thread structures can take up at most half
183          * of memory.
184          */
185         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
186
187         /*
188          * we need to allow at least 20 threads to boot a system
189          */
190         if(max_threads < 20)
191                 max_threads = 20;
192
193         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
194         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
195         init_task.signal->rlim[RLIMIT_SIGPENDING] =
196                 init_task.signal->rlim[RLIMIT_NPROC];
197 }
198
199 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
200                                                struct task_struct *src)
201 {
202         *dst = *src;
203         return 0;
204 }
205
206 static struct task_struct *dup_task_struct(struct task_struct *orig)
207 {
208         struct task_struct *tsk;
209         struct thread_info *ti;
210         int err;
211
212         prepare_to_copy(orig);
213
214         tsk = alloc_task_struct();
215         if (!tsk)
216                 return NULL;
217
218         ti = alloc_thread_info(tsk);
219         if (!ti) {
220                 free_task_struct(tsk);
221                 return NULL;
222         }
223
224         err = arch_dup_task_struct(tsk, orig);
225         if (err)
226                 goto out;
227
228         tsk->stack = ti;
229
230         err = prop_local_init_single(&tsk->dirties);
231         if (err)
232                 goto out;
233
234         setup_thread_stack(tsk, orig);
235
236 #ifdef CONFIG_CC_STACKPROTECTOR
237         tsk->stack_canary = get_random_int();
238 #endif
239
240         /* One for us, one for whoever does the "release_task()" (usually parent) */
241         atomic_set(&tsk->usage,2);
242         atomic_set(&tsk->fs_excl, 0);
243 #ifdef CONFIG_BLK_DEV_IO_TRACE
244         tsk->btrace_seq = 0;
245 #endif
246         tsk->splice_pipe = NULL;
247         return tsk;
248
249 out:
250         free_thread_info(ti);
251         free_task_struct(tsk);
252         return NULL;
253 }
254
255 #ifdef CONFIG_MMU
256 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
257 {
258         struct vm_area_struct *mpnt, *tmp, **pprev;
259         struct rb_node **rb_link, *rb_parent;
260         int retval;
261         unsigned long charge;
262         struct mempolicy *pol;
263
264         down_write(&oldmm->mmap_sem);
265         flush_cache_dup_mm(oldmm);
266         /*
267          * Not linked in yet - no deadlock potential:
268          */
269         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
270
271         mm->locked_vm = 0;
272         mm->mmap = NULL;
273         mm->mmap_cache = NULL;
274         mm->free_area_cache = oldmm->mmap_base;
275         mm->cached_hole_size = ~0UL;
276         mm->map_count = 0;
277         cpus_clear(mm->cpu_vm_mask);
278         mm->mm_rb = RB_ROOT;
279         rb_link = &mm->mm_rb.rb_node;
280         rb_parent = NULL;
281         pprev = &mm->mmap;
282
283         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
284                 struct file *file;
285
286                 if (mpnt->vm_flags & VM_DONTCOPY) {
287                         long pages = vma_pages(mpnt);
288                         mm->total_vm -= pages;
289                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
290                                                                 -pages);
291                         continue;
292                 }
293                 charge = 0;
294                 if (mpnt->vm_flags & VM_ACCOUNT) {
295                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
296                         if (security_vm_enough_memory(len))
297                                 goto fail_nomem;
298                         charge = len;
299                 }
300                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
301                 if (!tmp)
302                         goto fail_nomem;
303                 *tmp = *mpnt;
304                 pol = mpol_dup(vma_policy(mpnt));
305                 retval = PTR_ERR(pol);
306                 if (IS_ERR(pol))
307                         goto fail_nomem_policy;
308                 vma_set_policy(tmp, pol);
309                 tmp->vm_flags &= ~VM_LOCKED;
310                 tmp->vm_mm = mm;
311                 tmp->vm_next = NULL;
312                 anon_vma_link(tmp);
313                 file = tmp->vm_file;
314                 if (file) {
315                         struct inode *inode = file->f_path.dentry->d_inode;
316                         get_file(file);
317                         if (tmp->vm_flags & VM_DENYWRITE)
318                                 atomic_dec(&inode->i_writecount);
319
320                         /* insert tmp into the share list, just after mpnt */
321                         spin_lock(&file->f_mapping->i_mmap_lock);
322                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
323                         flush_dcache_mmap_lock(file->f_mapping);
324                         vma_prio_tree_add(tmp, mpnt);
325                         flush_dcache_mmap_unlock(file->f_mapping);
326                         spin_unlock(&file->f_mapping->i_mmap_lock);
327                 }
328
329                 /*
330                  * Clear hugetlb-related page reserves for children. This only
331                  * affects MAP_PRIVATE mappings. Faults generated by the child
332                  * are not guaranteed to succeed, even if read-only
333                  */
334                 if (is_vm_hugetlb_page(tmp))
335                         reset_vma_resv_huge_pages(tmp);
336
337                 /*
338                  * Link in the new vma and copy the page table entries.
339                  */
340                 *pprev = tmp;
341                 pprev = &tmp->vm_next;
342
343                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
344                 rb_link = &tmp->vm_rb.rb_right;
345                 rb_parent = &tmp->vm_rb;
346
347                 mm->map_count++;
348                 retval = copy_page_range(mm, oldmm, mpnt);
349
350                 if (tmp->vm_ops && tmp->vm_ops->open)
351                         tmp->vm_ops->open(tmp);
352
353                 if (retval)
354                         goto out;
355         }
356         /* a new mm has just been created */
357         arch_dup_mmap(oldmm, mm);
358         retval = 0;
359 out:
360         up_write(&mm->mmap_sem);
361         flush_tlb_mm(oldmm);
362         up_write(&oldmm->mmap_sem);
363         return retval;
364 fail_nomem_policy:
365         kmem_cache_free(vm_area_cachep, tmp);
366 fail_nomem:
367         retval = -ENOMEM;
368         vm_unacct_memory(charge);
369         goto out;
370 }
371
372 static inline int mm_alloc_pgd(struct mm_struct * mm)
373 {
374         mm->pgd = pgd_alloc(mm);
375         if (unlikely(!mm->pgd))
376                 return -ENOMEM;
377         return 0;
378 }
379
380 static inline void mm_free_pgd(struct mm_struct * mm)
381 {
382         pgd_free(mm, mm->pgd);
383 }
384 #else
385 #define dup_mmap(mm, oldmm)     (0)
386 #define mm_alloc_pgd(mm)        (0)
387 #define mm_free_pgd(mm)
388 #endif /* CONFIG_MMU */
389
390 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
391
392 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
393 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
394
395 #include <linux/init_task.h>
396
397 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
398 {
399         atomic_set(&mm->mm_users, 1);
400         atomic_set(&mm->mm_count, 1);
401         init_rwsem(&mm->mmap_sem);
402         INIT_LIST_HEAD(&mm->mmlist);
403         mm->flags = (current->mm) ? current->mm->flags
404                                   : MMF_DUMP_FILTER_DEFAULT;
405         mm->core_state = NULL;
406         mm->nr_ptes = 0;
407         set_mm_counter(mm, file_rss, 0);
408         set_mm_counter(mm, anon_rss, 0);
409         spin_lock_init(&mm->page_table_lock);
410         rwlock_init(&mm->ioctx_list_lock);
411         mm->ioctx_list = NULL;
412         mm->free_area_cache = TASK_UNMAPPED_BASE;
413         mm->cached_hole_size = ~0UL;
414         mm_init_owner(mm, p);
415
416         if (likely(!mm_alloc_pgd(mm))) {
417                 mm->def_flags = 0;
418                 mmu_notifier_mm_init(mm);
419                 return mm;
420         }
421
422         free_mm(mm);
423         return NULL;
424 }
425
426 /*
427  * Allocate and initialize an mm_struct.
428  */
429 struct mm_struct * mm_alloc(void)
430 {
431         struct mm_struct * mm;
432
433         mm = allocate_mm();
434         if (mm) {
435                 memset(mm, 0, sizeof(*mm));
436                 mm = mm_init(mm, current);
437         }
438         return mm;
439 }
440
441 /*
442  * Called when the last reference to the mm
443  * is dropped: either by a lazy thread or by
444  * mmput. Free the page directory and the mm.
445  */
446 void __mmdrop(struct mm_struct *mm)
447 {
448         BUG_ON(mm == &init_mm);
449         mm_free_pgd(mm);
450         destroy_context(mm);
451         mmu_notifier_mm_destroy(mm);
452         free_mm(mm);
453 }
454 EXPORT_SYMBOL_GPL(__mmdrop);
455
456 /*
457  * Decrement the use count and release all resources for an mm.
458  */
459 void mmput(struct mm_struct *mm)
460 {
461         might_sleep();
462
463         if (atomic_dec_and_test(&mm->mm_users)) {
464                 exit_aio(mm);
465                 exit_mmap(mm);
466                 set_mm_exe_file(mm, NULL);
467                 if (!list_empty(&mm->mmlist)) {
468                         spin_lock(&mmlist_lock);
469                         list_del(&mm->mmlist);
470                         spin_unlock(&mmlist_lock);
471                 }
472                 put_swap_token(mm);
473                 mmdrop(mm);
474         }
475 }
476 EXPORT_SYMBOL_GPL(mmput);
477
478 /**
479  * get_task_mm - acquire a reference to the task's mm
480  *
481  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
482  * this kernel workthread has transiently adopted a user mm with use_mm,
483  * to do its AIO) is not set and if so returns a reference to it, after
484  * bumping up the use count.  User must release the mm via mmput()
485  * after use.  Typically used by /proc and ptrace.
486  */
487 struct mm_struct *get_task_mm(struct task_struct *task)
488 {
489         struct mm_struct *mm;
490
491         task_lock(task);
492         mm = task->mm;
493         if (mm) {
494                 if (task->flags & PF_KTHREAD)
495                         mm = NULL;
496                 else
497                         atomic_inc(&mm->mm_users);
498         }
499         task_unlock(task);
500         return mm;
501 }
502 EXPORT_SYMBOL_GPL(get_task_mm);
503
504 /* Please note the differences between mmput and mm_release.
505  * mmput is called whenever we stop holding onto a mm_struct,
506  * error success whatever.
507  *
508  * mm_release is called after a mm_struct has been removed
509  * from the current process.
510  *
511  * This difference is important for error handling, when we
512  * only half set up a mm_struct for a new process and need to restore
513  * the old one.  Because we mmput the new mm_struct before
514  * restoring the old one. . .
515  * Eric Biederman 10 January 1998
516  */
517 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
518 {
519         struct completion *vfork_done = tsk->vfork_done;
520
521         /* Get rid of any cached register state */
522         deactivate_mm(tsk, mm);
523
524         /* notify parent sleeping on vfork() */
525         if (vfork_done) {
526                 tsk->vfork_done = NULL;
527                 complete(vfork_done);
528         }
529
530         /*
531          * If we're exiting normally, clear a user-space tid field if
532          * requested.  We leave this alone when dying by signal, to leave
533          * the value intact in a core dump, and to save the unnecessary
534          * trouble otherwise.  Userland only wants this done for a sys_exit.
535          */
536         if (tsk->clear_child_tid
537             && !(tsk->flags & PF_SIGNALED)
538             && atomic_read(&mm->mm_users) > 1) {
539                 u32 __user * tidptr = tsk->clear_child_tid;
540                 tsk->clear_child_tid = NULL;
541
542                 /*
543                  * We don't check the error code - if userspace has
544                  * not set up a proper pointer then tough luck.
545                  */
546                 put_user(0, tidptr);
547                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
548         }
549 }
550
551 /*
552  * Allocate a new mm structure and copy contents from the
553  * mm structure of the passed in task structure.
554  */
555 struct mm_struct *dup_mm(struct task_struct *tsk)
556 {
557         struct mm_struct *mm, *oldmm = current->mm;
558         int err;
559
560         if (!oldmm)
561                 return NULL;
562
563         mm = allocate_mm();
564         if (!mm)
565                 goto fail_nomem;
566
567         memcpy(mm, oldmm, sizeof(*mm));
568
569         /* Initializing for Swap token stuff */
570         mm->token_priority = 0;
571         mm->last_interval = 0;
572
573         if (!mm_init(mm, tsk))
574                 goto fail_nomem;
575
576         if (init_new_context(tsk, mm))
577                 goto fail_nocontext;
578
579         dup_mm_exe_file(oldmm, mm);
580
581         err = dup_mmap(mm, oldmm);
582         if (err)
583                 goto free_pt;
584
585         mm->hiwater_rss = get_mm_rss(mm);
586         mm->hiwater_vm = mm->total_vm;
587
588         return mm;
589
590 free_pt:
591         mmput(mm);
592
593 fail_nomem:
594         return NULL;
595
596 fail_nocontext:
597         /*
598          * If init_new_context() failed, we cannot use mmput() to free the mm
599          * because it calls destroy_context()
600          */
601         mm_free_pgd(mm);
602         free_mm(mm);
603         return NULL;
604 }
605
606 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
607 {
608         struct mm_struct * mm, *oldmm;
609         int retval;
610
611         tsk->min_flt = tsk->maj_flt = 0;
612         tsk->nvcsw = tsk->nivcsw = 0;
613
614         tsk->mm = NULL;
615         tsk->active_mm = NULL;
616
617         /*
618          * Are we cloning a kernel thread?
619          *
620          * We need to steal a active VM for that..
621          */
622         oldmm = current->mm;
623         if (!oldmm)
624                 return 0;
625
626         if (clone_flags & CLONE_VM) {
627                 atomic_inc(&oldmm->mm_users);
628                 mm = oldmm;
629                 goto good_mm;
630         }
631
632         retval = -ENOMEM;
633         mm = dup_mm(tsk);
634         if (!mm)
635                 goto fail_nomem;
636
637 good_mm:
638         /* Initializing for Swap token stuff */
639         mm->token_priority = 0;
640         mm->last_interval = 0;
641
642         tsk->mm = mm;
643         tsk->active_mm = mm;
644         return 0;
645
646 fail_nomem:
647         return retval;
648 }
649
650 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
651 {
652         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
653         /* We don't need to lock fs - think why ;-) */
654         if (fs) {
655                 atomic_set(&fs->count, 1);
656                 rwlock_init(&fs->lock);
657                 fs->umask = old->umask;
658                 read_lock(&old->lock);
659                 fs->root = old->root;
660                 path_get(&old->root);
661                 fs->pwd = old->pwd;
662                 path_get(&old->pwd);
663                 read_unlock(&old->lock);
664         }
665         return fs;
666 }
667
668 struct fs_struct *copy_fs_struct(struct fs_struct *old)
669 {
670         return __copy_fs_struct(old);
671 }
672
673 EXPORT_SYMBOL_GPL(copy_fs_struct);
674
675 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
676 {
677         if (clone_flags & CLONE_FS) {
678                 atomic_inc(&current->fs->count);
679                 return 0;
680         }
681         tsk->fs = __copy_fs_struct(current->fs);
682         if (!tsk->fs)
683                 return -ENOMEM;
684         return 0;
685 }
686
687 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
688 {
689         struct files_struct *oldf, *newf;
690         int error = 0;
691
692         /*
693          * A background process may not have any files ...
694          */
695         oldf = current->files;
696         if (!oldf)
697                 goto out;
698
699         if (clone_flags & CLONE_FILES) {
700                 atomic_inc(&oldf->count);
701                 goto out;
702         }
703
704         newf = dup_fd(oldf, &error);
705         if (!newf)
706                 goto out;
707
708         tsk->files = newf;
709         error = 0;
710 out:
711         return error;
712 }
713
714 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
715 {
716 #ifdef CONFIG_BLOCK
717         struct io_context *ioc = current->io_context;
718
719         if (!ioc)
720                 return 0;
721         /*
722          * Share io context with parent, if CLONE_IO is set
723          */
724         if (clone_flags & CLONE_IO) {
725                 tsk->io_context = ioc_task_link(ioc);
726                 if (unlikely(!tsk->io_context))
727                         return -ENOMEM;
728         } else if (ioprio_valid(ioc->ioprio)) {
729                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
730                 if (unlikely(!tsk->io_context))
731                         return -ENOMEM;
732
733                 tsk->io_context->ioprio = ioc->ioprio;
734         }
735 #endif
736         return 0;
737 }
738
739 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
740 {
741         struct sighand_struct *sig;
742
743         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
744                 atomic_inc(&current->sighand->count);
745                 return 0;
746         }
747         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
748         rcu_assign_pointer(tsk->sighand, sig);
749         if (!sig)
750                 return -ENOMEM;
751         atomic_set(&sig->count, 1);
752         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
753         return 0;
754 }
755
756 void __cleanup_sighand(struct sighand_struct *sighand)
757 {
758         if (atomic_dec_and_test(&sighand->count))
759                 kmem_cache_free(sighand_cachep, sighand);
760 }
761
762 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
763 {
764         struct signal_struct *sig;
765         int ret;
766
767         if (clone_flags & CLONE_THREAD) {
768                 atomic_inc(&current->signal->count);
769                 atomic_inc(&current->signal->live);
770                 return 0;
771         }
772         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
773         tsk->signal = sig;
774         if (!sig)
775                 return -ENOMEM;
776
777         ret = copy_thread_group_keys(tsk);
778         if (ret < 0) {
779                 kmem_cache_free(signal_cachep, sig);
780                 return ret;
781         }
782
783         atomic_set(&sig->count, 1);
784         atomic_set(&sig->live, 1);
785         init_waitqueue_head(&sig->wait_chldexit);
786         sig->flags = 0;
787         sig->group_exit_code = 0;
788         sig->group_exit_task = NULL;
789         sig->group_stop_count = 0;
790         sig->curr_target = tsk;
791         init_sigpending(&sig->shared_pending);
792         INIT_LIST_HEAD(&sig->posix_timers);
793
794         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
795         sig->it_real_incr.tv64 = 0;
796         sig->real_timer.function = it_real_fn;
797
798         sig->it_virt_expires = cputime_zero;
799         sig->it_virt_incr = cputime_zero;
800         sig->it_prof_expires = cputime_zero;
801         sig->it_prof_incr = cputime_zero;
802
803         sig->leader = 0;        /* session leadership doesn't inherit */
804         sig->tty_old_pgrp = NULL;
805
806         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
807         sig->gtime = cputime_zero;
808         sig->cgtime = cputime_zero;
809         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
810         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
811         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
812         task_io_accounting_init(&sig->ioac);
813         sig->sum_sched_runtime = 0;
814         INIT_LIST_HEAD(&sig->cpu_timers[0]);
815         INIT_LIST_HEAD(&sig->cpu_timers[1]);
816         INIT_LIST_HEAD(&sig->cpu_timers[2]);
817         taskstats_tgid_init(sig);
818
819         task_lock(current->group_leader);
820         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
821         task_unlock(current->group_leader);
822
823         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
824                 /*
825                  * New sole thread in the process gets an expiry time
826                  * of the whole CPU time limit.
827                  */
828                 tsk->it_prof_expires =
829                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
830         }
831         acct_init_pacct(&sig->pacct);
832
833         tty_audit_fork(sig);
834
835         return 0;
836 }
837
838 void __cleanup_signal(struct signal_struct *sig)
839 {
840         exit_thread_group_keys(sig);
841         kmem_cache_free(signal_cachep, sig);
842 }
843
844 static void cleanup_signal(struct task_struct *tsk)
845 {
846         struct signal_struct *sig = tsk->signal;
847
848         atomic_dec(&sig->live);
849
850         if (atomic_dec_and_test(&sig->count))
851                 __cleanup_signal(sig);
852 }
853
854 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
855 {
856         unsigned long new_flags = p->flags;
857
858         new_flags &= ~PF_SUPERPRIV;
859         new_flags |= PF_FORKNOEXEC;
860         new_flags |= PF_STARTING;
861         p->flags = new_flags;
862         clear_freeze_flag(p);
863 }
864
865 asmlinkage long sys_set_tid_address(int __user *tidptr)
866 {
867         current->clear_child_tid = tidptr;
868
869         return task_pid_vnr(current);
870 }
871
872 static void rt_mutex_init_task(struct task_struct *p)
873 {
874         spin_lock_init(&p->pi_lock);
875 #ifdef CONFIG_RT_MUTEXES
876         plist_head_init(&p->pi_waiters, &p->pi_lock);
877         p->pi_blocked_on = NULL;
878 #endif
879 }
880
881 #ifdef CONFIG_MM_OWNER
882 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
883 {
884         mm->owner = p;
885 }
886 #endif /* CONFIG_MM_OWNER */
887
888 /*
889  * This creates a new process as a copy of the old one,
890  * but does not actually start it yet.
891  *
892  * It copies the registers, and all the appropriate
893  * parts of the process environment (as per the clone
894  * flags). The actual kick-off is left to the caller.
895  */
896 static struct task_struct *copy_process(unsigned long clone_flags,
897                                         unsigned long stack_start,
898                                         struct pt_regs *regs,
899                                         unsigned long stack_size,
900                                         int __user *child_tidptr,
901                                         struct pid *pid,
902                                         int trace)
903 {
904         int retval;
905         struct task_struct *p;
906         int cgroup_callbacks_done = 0;
907
908         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
909                 return ERR_PTR(-EINVAL);
910
911         /*
912          * Thread groups must share signals as well, and detached threads
913          * can only be started up within the thread group.
914          */
915         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
916                 return ERR_PTR(-EINVAL);
917
918         /*
919          * Shared signal handlers imply shared VM. By way of the above,
920          * thread groups also imply shared VM. Blocking this case allows
921          * for various simplifications in other code.
922          */
923         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
924                 return ERR_PTR(-EINVAL);
925
926         retval = security_task_create(clone_flags);
927         if (retval)
928                 goto fork_out;
929
930         retval = -ENOMEM;
931         p = dup_task_struct(current);
932         if (!p)
933                 goto fork_out;
934
935         rt_mutex_init_task(p);
936
937 #ifdef CONFIG_PROVE_LOCKING
938         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
939         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
940 #endif
941         retval = -EAGAIN;
942         if (atomic_read(&p->user->processes) >=
943                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
944                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
945                     p->user != current->nsproxy->user_ns->root_user)
946                         goto bad_fork_free;
947         }
948
949         atomic_inc(&p->user->__count);
950         atomic_inc(&p->user->processes);
951         get_group_info(p->group_info);
952
953         /*
954          * If multiple threads are within copy_process(), then this check
955          * triggers too late. This doesn't hurt, the check is only there
956          * to stop root fork bombs.
957          */
958         if (nr_threads >= max_threads)
959                 goto bad_fork_cleanup_count;
960
961         if (!try_module_get(task_thread_info(p)->exec_domain->module))
962                 goto bad_fork_cleanup_count;
963
964         if (p->binfmt && !try_module_get(p->binfmt->module))
965                 goto bad_fork_cleanup_put_domain;
966
967         p->did_exec = 0;
968         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
969         copy_flags(clone_flags, p);
970         INIT_LIST_HEAD(&p->children);
971         INIT_LIST_HEAD(&p->sibling);
972 #ifdef CONFIG_PREEMPT_RCU
973         p->rcu_read_lock_nesting = 0;
974         p->rcu_flipctr_idx = 0;
975 #endif /* #ifdef CONFIG_PREEMPT_RCU */
976         p->vfork_done = NULL;
977         spin_lock_init(&p->alloc_lock);
978
979         clear_tsk_thread_flag(p, TIF_SIGPENDING);
980         init_sigpending(&p->pending);
981
982         p->utime = cputime_zero;
983         p->stime = cputime_zero;
984         p->gtime = cputime_zero;
985         p->utimescaled = cputime_zero;
986         p->stimescaled = cputime_zero;
987         p->prev_utime = cputime_zero;
988         p->prev_stime = cputime_zero;
989
990 #ifdef CONFIG_DETECT_SOFTLOCKUP
991         p->last_switch_count = 0;
992         p->last_switch_timestamp = 0;
993 #endif
994
995         task_io_accounting_init(&p->ioac);
996         acct_clear_integrals(p);
997
998         p->it_virt_expires = cputime_zero;
999         p->it_prof_expires = cputime_zero;
1000         p->it_sched_expires = 0;
1001         INIT_LIST_HEAD(&p->cpu_timers[0]);
1002         INIT_LIST_HEAD(&p->cpu_timers[1]);
1003         INIT_LIST_HEAD(&p->cpu_timers[2]);
1004
1005         p->lock_depth = -1;             /* -1 = no lock */
1006         do_posix_clock_monotonic_gettime(&p->start_time);
1007         p->real_start_time = p->start_time;
1008         monotonic_to_bootbased(&p->real_start_time);
1009 #ifdef CONFIG_SECURITY
1010         p->security = NULL;
1011 #endif
1012         p->cap_bset = current->cap_bset;
1013         p->io_context = NULL;
1014         p->audit_context = NULL;
1015         cgroup_fork(p);
1016 #ifdef CONFIG_NUMA
1017         p->mempolicy = mpol_dup(p->mempolicy);
1018         if (IS_ERR(p->mempolicy)) {
1019                 retval = PTR_ERR(p->mempolicy);
1020                 p->mempolicy = NULL;
1021                 goto bad_fork_cleanup_cgroup;
1022         }
1023         mpol_fix_fork_child_flag(p);
1024 #endif
1025 #ifdef CONFIG_TRACE_IRQFLAGS
1026         p->irq_events = 0;
1027 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1028         p->hardirqs_enabled = 1;
1029 #else
1030         p->hardirqs_enabled = 0;
1031 #endif
1032         p->hardirq_enable_ip = 0;
1033         p->hardirq_enable_event = 0;
1034         p->hardirq_disable_ip = _THIS_IP_;
1035         p->hardirq_disable_event = 0;
1036         p->softirqs_enabled = 1;
1037         p->softirq_enable_ip = _THIS_IP_;
1038         p->softirq_enable_event = 0;
1039         p->softirq_disable_ip = 0;
1040         p->softirq_disable_event = 0;
1041         p->hardirq_context = 0;
1042         p->softirq_context = 0;
1043 #endif
1044 #ifdef CONFIG_LOCKDEP
1045         p->lockdep_depth = 0; /* no locks held yet */
1046         p->curr_chain_key = 0;
1047         p->lockdep_recursion = 0;
1048 #endif
1049
1050 #ifdef CONFIG_DEBUG_MUTEXES
1051         p->blocked_on = NULL; /* not blocked yet */
1052 #endif
1053
1054         /* Perform scheduler related setup. Assign this task to a CPU. */
1055         sched_fork(p, clone_flags);
1056
1057         if ((retval = security_task_alloc(p)))
1058                 goto bad_fork_cleanup_policy;
1059         if ((retval = audit_alloc(p)))
1060                 goto bad_fork_cleanup_security;
1061         /* copy all the process information */
1062         if ((retval = copy_semundo(clone_flags, p)))
1063                 goto bad_fork_cleanup_audit;
1064         if ((retval = copy_files(clone_flags, p)))
1065                 goto bad_fork_cleanup_semundo;
1066         if ((retval = copy_fs(clone_flags, p)))
1067                 goto bad_fork_cleanup_files;
1068         if ((retval = copy_sighand(clone_flags, p)))
1069                 goto bad_fork_cleanup_fs;
1070         if ((retval = copy_signal(clone_flags, p)))
1071                 goto bad_fork_cleanup_sighand;
1072         if ((retval = copy_mm(clone_flags, p)))
1073                 goto bad_fork_cleanup_signal;
1074         if ((retval = copy_keys(clone_flags, p)))
1075                 goto bad_fork_cleanup_mm;
1076         if ((retval = copy_namespaces(clone_flags, p)))
1077                 goto bad_fork_cleanup_keys;
1078         if ((retval = copy_io(clone_flags, p)))
1079                 goto bad_fork_cleanup_namespaces;
1080         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1081         if (retval)
1082                 goto bad_fork_cleanup_io;
1083
1084         if (pid != &init_struct_pid) {
1085                 retval = -ENOMEM;
1086                 pid = alloc_pid(task_active_pid_ns(p));
1087                 if (!pid)
1088                         goto bad_fork_cleanup_io;
1089
1090                 if (clone_flags & CLONE_NEWPID) {
1091                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1092                         if (retval < 0)
1093                                 goto bad_fork_free_pid;
1094                 }
1095         }
1096
1097         p->pid = pid_nr(pid);
1098         p->tgid = p->pid;
1099         if (clone_flags & CLONE_THREAD)
1100                 p->tgid = current->tgid;
1101
1102         if (current->nsproxy != p->nsproxy) {
1103                 retval = ns_cgroup_clone(p, pid);
1104                 if (retval)
1105                         goto bad_fork_free_pid;
1106         }
1107
1108         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1109         /*
1110          * Clear TID on mm_release()?
1111          */
1112         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1113 #ifdef CONFIG_FUTEX
1114         p->robust_list = NULL;
1115 #ifdef CONFIG_COMPAT
1116         p->compat_robust_list = NULL;
1117 #endif
1118         INIT_LIST_HEAD(&p->pi_state_list);
1119         p->pi_state_cache = NULL;
1120 #endif
1121         /*
1122          * sigaltstack should be cleared when sharing the same VM
1123          */
1124         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1125                 p->sas_ss_sp = p->sas_ss_size = 0;
1126
1127         /*
1128          * Syscall tracing should be turned off in the child regardless
1129          * of CLONE_PTRACE.
1130          */
1131         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1132 #ifdef TIF_SYSCALL_EMU
1133         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1134 #endif
1135         clear_all_latency_tracing(p);
1136
1137         /* Our parent execution domain becomes current domain
1138            These must match for thread signalling to apply */
1139         p->parent_exec_id = p->self_exec_id;
1140
1141         /* ok, now we should be set up.. */
1142         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1143         p->pdeath_signal = 0;
1144         p->exit_state = 0;
1145
1146         /*
1147          * Ok, make it visible to the rest of the system.
1148          * We dont wake it up yet.
1149          */
1150         p->group_leader = p;
1151         INIT_LIST_HEAD(&p->thread_group);
1152
1153         /* Now that the task is set up, run cgroup callbacks if
1154          * necessary. We need to run them before the task is visible
1155          * on the tasklist. */
1156         cgroup_fork_callbacks(p);
1157         cgroup_callbacks_done = 1;
1158
1159         /* Need tasklist lock for parent etc handling! */
1160         write_lock_irq(&tasklist_lock);
1161
1162         /*
1163          * The task hasn't been attached yet, so its cpus_allowed mask will
1164          * not be changed, nor will its assigned CPU.
1165          *
1166          * The cpus_allowed mask of the parent may have changed after it was
1167          * copied first time - so re-copy it here, then check the child's CPU
1168          * to ensure it is on a valid CPU (and if not, just force it back to
1169          * parent's CPU). This avoids alot of nasty races.
1170          */
1171         p->cpus_allowed = current->cpus_allowed;
1172         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1173         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1174                         !cpu_online(task_cpu(p))))
1175                 set_task_cpu(p, smp_processor_id());
1176
1177         /* CLONE_PARENT re-uses the old parent */
1178         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1179                 p->real_parent = current->real_parent;
1180         else
1181                 p->real_parent = current;
1182
1183         spin_lock(&current->sighand->siglock);
1184
1185         /*
1186          * Process group and session signals need to be delivered to just the
1187          * parent before the fork or both the parent and the child after the
1188          * fork. Restart if a signal comes in before we add the new process to
1189          * it's process group.
1190          * A fatal signal pending means that current will exit, so the new
1191          * thread can't slip out of an OOM kill (or normal SIGKILL).
1192          */
1193         recalc_sigpending();
1194         if (signal_pending(current)) {
1195                 spin_unlock(&current->sighand->siglock);
1196                 write_unlock_irq(&tasklist_lock);
1197                 retval = -ERESTARTNOINTR;
1198                 goto bad_fork_free_pid;
1199         }
1200
1201         if (clone_flags & CLONE_THREAD) {
1202                 p->group_leader = current->group_leader;
1203                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1204
1205                 if (!cputime_eq(current->signal->it_virt_expires,
1206                                 cputime_zero) ||
1207                     !cputime_eq(current->signal->it_prof_expires,
1208                                 cputime_zero) ||
1209                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1210                     !list_empty(&current->signal->cpu_timers[0]) ||
1211                     !list_empty(&current->signal->cpu_timers[1]) ||
1212                     !list_empty(&current->signal->cpu_timers[2])) {
1213                         /*
1214                          * Have child wake up on its first tick to check
1215                          * for process CPU timers.
1216                          */
1217                         p->it_prof_expires = jiffies_to_cputime(1);
1218                 }
1219         }
1220
1221         if (likely(p->pid)) {
1222                 list_add_tail(&p->sibling, &p->real_parent->children);
1223                 tracehook_finish_clone(p, clone_flags, trace);
1224
1225                 if (thread_group_leader(p)) {
1226                         if (clone_flags & CLONE_NEWPID)
1227                                 p->nsproxy->pid_ns->child_reaper = p;
1228
1229                         p->signal->leader_pid = pid;
1230                         p->signal->tty = current->signal->tty;
1231                         set_task_pgrp(p, task_pgrp_nr(current));
1232                         set_task_session(p, task_session_nr(current));
1233                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1234                         attach_pid(p, PIDTYPE_SID, task_session(current));
1235                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1236                         __get_cpu_var(process_counts)++;
1237                 }
1238                 attach_pid(p, PIDTYPE_PID, pid);
1239                 nr_threads++;
1240         }
1241
1242         total_forks++;
1243         spin_unlock(&current->sighand->siglock);
1244         write_unlock_irq(&tasklist_lock);
1245         proc_fork_connector(p);
1246         cgroup_post_fork(p);
1247         return p;
1248
1249 bad_fork_free_pid:
1250         if (pid != &init_struct_pid)
1251                 free_pid(pid);
1252 bad_fork_cleanup_io:
1253         put_io_context(p->io_context);
1254 bad_fork_cleanup_namespaces:
1255         exit_task_namespaces(p);
1256 bad_fork_cleanup_keys:
1257         exit_keys(p);
1258 bad_fork_cleanup_mm:
1259         if (p->mm)
1260                 mmput(p->mm);
1261 bad_fork_cleanup_signal:
1262         cleanup_signal(p);
1263 bad_fork_cleanup_sighand:
1264         __cleanup_sighand(p->sighand);
1265 bad_fork_cleanup_fs:
1266         exit_fs(p); /* blocking */
1267 bad_fork_cleanup_files:
1268         exit_files(p); /* blocking */
1269 bad_fork_cleanup_semundo:
1270         exit_sem(p);
1271 bad_fork_cleanup_audit:
1272         audit_free(p);
1273 bad_fork_cleanup_security:
1274         security_task_free(p);
1275 bad_fork_cleanup_policy:
1276 #ifdef CONFIG_NUMA
1277         mpol_put(p->mempolicy);
1278 bad_fork_cleanup_cgroup:
1279 #endif
1280         cgroup_exit(p, cgroup_callbacks_done);
1281         delayacct_tsk_free(p);
1282         if (p->binfmt)
1283                 module_put(p->binfmt->module);
1284 bad_fork_cleanup_put_domain:
1285         module_put(task_thread_info(p)->exec_domain->module);
1286 bad_fork_cleanup_count:
1287         put_group_info(p->group_info);
1288         atomic_dec(&p->user->processes);
1289         free_uid(p->user);
1290 bad_fork_free:
1291         free_task(p);
1292 fork_out:
1293         return ERR_PTR(retval);
1294 }
1295
1296 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1297 {
1298         memset(regs, 0, sizeof(struct pt_regs));
1299         return regs;
1300 }
1301
1302 struct task_struct * __cpuinit fork_idle(int cpu)
1303 {
1304         struct task_struct *task;
1305         struct pt_regs regs;
1306
1307         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1308                             &init_struct_pid, 0);
1309         if (!IS_ERR(task))
1310                 init_idle(task, cpu);
1311
1312         return task;
1313 }
1314
1315 /*
1316  *  Ok, this is the main fork-routine.
1317  *
1318  * It copies the process, and if successful kick-starts
1319  * it and waits for it to finish using the VM if required.
1320  */
1321 long do_fork(unsigned long clone_flags,
1322               unsigned long stack_start,
1323               struct pt_regs *regs,
1324               unsigned long stack_size,
1325               int __user *parent_tidptr,
1326               int __user *child_tidptr)
1327 {
1328         struct task_struct *p;
1329         int trace = 0;
1330         long nr;
1331
1332         /*
1333          * We hope to recycle these flags after 2.6.26
1334          */
1335         if (unlikely(clone_flags & CLONE_STOPPED)) {
1336                 static int __read_mostly count = 100;
1337
1338                 if (count > 0 && printk_ratelimit()) {
1339                         char comm[TASK_COMM_LEN];
1340
1341                         count--;
1342                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1343                                         "clone flags 0x%lx\n",
1344                                 get_task_comm(comm, current),
1345                                 clone_flags & CLONE_STOPPED);
1346                 }
1347         }
1348
1349         /*
1350          * When called from kernel_thread, don't do user tracing stuff.
1351          */
1352         if (likely(user_mode(regs)))
1353                 trace = tracehook_prepare_clone(clone_flags);
1354
1355         p = copy_process(clone_flags, stack_start, regs, stack_size,
1356                          child_tidptr, NULL, trace);
1357         /*
1358          * Do this prior waking up the new thread - the thread pointer
1359          * might get invalid after that point, if the thread exits quickly.
1360          */
1361         if (!IS_ERR(p)) {
1362                 struct completion vfork;
1363
1364                 nr = task_pid_vnr(p);
1365
1366                 if (clone_flags & CLONE_PARENT_SETTID)
1367                         put_user(nr, parent_tidptr);
1368
1369                 if (clone_flags & CLONE_VFORK) {
1370                         p->vfork_done = &vfork;
1371                         init_completion(&vfork);
1372                 }
1373
1374                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1375
1376                 /*
1377                  * We set PF_STARTING at creation in case tracing wants to
1378                  * use this to distinguish a fully live task from one that
1379                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1380                  * clear it and set the child going.
1381                  */
1382                 p->flags &= ~PF_STARTING;
1383
1384                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1385                         /*
1386                          * We'll start up with an immediate SIGSTOP.
1387                          */
1388                         sigaddset(&p->pending.signal, SIGSTOP);
1389                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1390                         __set_task_state(p, TASK_STOPPED);
1391                 } else {
1392                         wake_up_new_task(p, clone_flags);
1393                 }
1394
1395                 tracehook_report_clone_complete(trace, regs,
1396                                                 clone_flags, nr, p);
1397
1398                 if (clone_flags & CLONE_VFORK) {
1399                         freezer_do_not_count();
1400                         wait_for_completion(&vfork);
1401                         freezer_count();
1402                         tracehook_report_vfork_done(p, nr);
1403                 }
1404         } else {
1405                 nr = PTR_ERR(p);
1406         }
1407         return nr;
1408 }
1409
1410 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1411 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1412 #endif
1413
1414 static void sighand_ctor(void *data)
1415 {
1416         struct sighand_struct *sighand = data;
1417
1418         spin_lock_init(&sighand->siglock);
1419         init_waitqueue_head(&sighand->signalfd_wqh);
1420 }
1421
1422 void __init proc_caches_init(void)
1423 {
1424         sighand_cachep = kmem_cache_create("sighand_cache",
1425                         sizeof(struct sighand_struct), 0,
1426                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1427                         sighand_ctor);
1428         signal_cachep = kmem_cache_create("signal_cache",
1429                         sizeof(struct signal_struct), 0,
1430                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1431         files_cachep = kmem_cache_create("files_cache",
1432                         sizeof(struct files_struct), 0,
1433                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1434         fs_cachep = kmem_cache_create("fs_cache",
1435                         sizeof(struct fs_struct), 0,
1436                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1437         vm_area_cachep = kmem_cache_create("vm_area_struct",
1438                         sizeof(struct vm_area_struct), 0,
1439                         SLAB_PANIC, NULL);
1440         mm_cachep = kmem_cache_create("mm_struct",
1441                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1442                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1443 }
1444
1445 /*
1446  * Check constraints on flags passed to the unshare system call and
1447  * force unsharing of additional process context as appropriate.
1448  */
1449 static void check_unshare_flags(unsigned long *flags_ptr)
1450 {
1451         /*
1452          * If unsharing a thread from a thread group, must also
1453          * unshare vm.
1454          */
1455         if (*flags_ptr & CLONE_THREAD)
1456                 *flags_ptr |= CLONE_VM;
1457
1458         /*
1459          * If unsharing vm, must also unshare signal handlers.
1460          */
1461         if (*flags_ptr & CLONE_VM)
1462                 *flags_ptr |= CLONE_SIGHAND;
1463
1464         /*
1465          * If unsharing signal handlers and the task was created
1466          * using CLONE_THREAD, then must unshare the thread
1467          */
1468         if ((*flags_ptr & CLONE_SIGHAND) &&
1469             (atomic_read(&current->signal->count) > 1))
1470                 *flags_ptr |= CLONE_THREAD;
1471
1472         /*
1473          * If unsharing namespace, must also unshare filesystem information.
1474          */
1475         if (*flags_ptr & CLONE_NEWNS)
1476                 *flags_ptr |= CLONE_FS;
1477 }
1478
1479 /*
1480  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1481  */
1482 static int unshare_thread(unsigned long unshare_flags)
1483 {
1484         if (unshare_flags & CLONE_THREAD)
1485                 return -EINVAL;
1486
1487         return 0;
1488 }
1489
1490 /*
1491  * Unshare the filesystem structure if it is being shared
1492  */
1493 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1494 {
1495         struct fs_struct *fs = current->fs;
1496
1497         if ((unshare_flags & CLONE_FS) &&
1498             (fs && atomic_read(&fs->count) > 1)) {
1499                 *new_fsp = __copy_fs_struct(current->fs);
1500                 if (!*new_fsp)
1501                         return -ENOMEM;
1502         }
1503
1504         return 0;
1505 }
1506
1507 /*
1508  * Unsharing of sighand is not supported yet
1509  */
1510 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1511 {
1512         struct sighand_struct *sigh = current->sighand;
1513
1514         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1515                 return -EINVAL;
1516         else
1517                 return 0;
1518 }
1519
1520 /*
1521  * Unshare vm if it is being shared
1522  */
1523 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1524 {
1525         struct mm_struct *mm = current->mm;
1526
1527         if ((unshare_flags & CLONE_VM) &&
1528             (mm && atomic_read(&mm->mm_users) > 1)) {
1529                 return -EINVAL;
1530         }
1531
1532         return 0;
1533 }
1534
1535 /*
1536  * Unshare file descriptor table if it is being shared
1537  */
1538 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1539 {
1540         struct files_struct *fd = current->files;
1541         int error = 0;
1542
1543         if ((unshare_flags & CLONE_FILES) &&
1544             (fd && atomic_read(&fd->count) > 1)) {
1545                 *new_fdp = dup_fd(fd, &error);
1546                 if (!*new_fdp)
1547                         return error;
1548         }
1549
1550         return 0;
1551 }
1552
1553 /*
1554  * unshare allows a process to 'unshare' part of the process
1555  * context which was originally shared using clone.  copy_*
1556  * functions used by do_fork() cannot be used here directly
1557  * because they modify an inactive task_struct that is being
1558  * constructed. Here we are modifying the current, active,
1559  * task_struct.
1560  */
1561 asmlinkage long sys_unshare(unsigned long unshare_flags)
1562 {
1563         int err = 0;
1564         struct fs_struct *fs, *new_fs = NULL;
1565         struct sighand_struct *new_sigh = NULL;
1566         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1567         struct files_struct *fd, *new_fd = NULL;
1568         struct nsproxy *new_nsproxy = NULL;
1569         int do_sysvsem = 0;
1570
1571         check_unshare_flags(&unshare_flags);
1572
1573         /* Return -EINVAL for all unsupported flags */
1574         err = -EINVAL;
1575         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1576                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1577                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1578                                 CLONE_NEWNET))
1579                 goto bad_unshare_out;
1580
1581         /*
1582          * CLONE_NEWIPC must also detach from the undolist: after switching
1583          * to a new ipc namespace, the semaphore arrays from the old
1584          * namespace are unreachable.
1585          */
1586         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1587                 do_sysvsem = 1;
1588         if ((err = unshare_thread(unshare_flags)))
1589                 goto bad_unshare_out;
1590         if ((err = unshare_fs(unshare_flags, &new_fs)))
1591                 goto bad_unshare_cleanup_thread;
1592         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1593                 goto bad_unshare_cleanup_fs;
1594         if ((err = unshare_vm(unshare_flags, &new_mm)))
1595                 goto bad_unshare_cleanup_sigh;
1596         if ((err = unshare_fd(unshare_flags, &new_fd)))
1597                 goto bad_unshare_cleanup_vm;
1598         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1599                         new_fs)))
1600                 goto bad_unshare_cleanup_fd;
1601
1602         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1603                 if (do_sysvsem) {
1604                         /*
1605                          * CLONE_SYSVSEM is equivalent to sys_exit().
1606                          */
1607                         exit_sem(current);
1608                 }
1609
1610                 if (new_nsproxy) {
1611                         switch_task_namespaces(current, new_nsproxy);
1612                         new_nsproxy = NULL;
1613                 }
1614
1615                 task_lock(current);
1616
1617                 if (new_fs) {
1618                         fs = current->fs;
1619                         current->fs = new_fs;
1620                         new_fs = fs;
1621                 }
1622
1623                 if (new_mm) {
1624                         mm = current->mm;
1625                         active_mm = current->active_mm;
1626                         current->mm = new_mm;
1627                         current->active_mm = new_mm;
1628                         activate_mm(active_mm, new_mm);
1629                         new_mm = mm;
1630                 }
1631
1632                 if (new_fd) {
1633                         fd = current->files;
1634                         current->files = new_fd;
1635                         new_fd = fd;
1636                 }
1637
1638                 task_unlock(current);
1639         }
1640
1641         if (new_nsproxy)
1642                 put_nsproxy(new_nsproxy);
1643
1644 bad_unshare_cleanup_fd:
1645         if (new_fd)
1646                 put_files_struct(new_fd);
1647
1648 bad_unshare_cleanup_vm:
1649         if (new_mm)
1650                 mmput(new_mm);
1651
1652 bad_unshare_cleanup_sigh:
1653         if (new_sigh)
1654                 if (atomic_dec_and_test(&new_sigh->count))
1655                         kmem_cache_free(sighand_cachep, new_sigh);
1656
1657 bad_unshare_cleanup_fs:
1658         if (new_fs)
1659                 put_fs_struct(new_fs);
1660
1661 bad_unshare_cleanup_thread:
1662 bad_unshare_out:
1663         return err;
1664 }
1665
1666 /*
1667  *      Helper to unshare the files of the current task.
1668  *      We don't want to expose copy_files internals to
1669  *      the exec layer of the kernel.
1670  */
1671
1672 int unshare_files(struct files_struct **displaced)
1673 {
1674         struct task_struct *task = current;
1675         struct files_struct *copy = NULL;
1676         int error;
1677
1678         error = unshare_fd(CLONE_FILES, &copy);
1679         if (error || !copy) {
1680                 *displaced = NULL;
1681                 return error;
1682         }
1683         *displaced = task->files;
1684         task_lock(task);
1685         task->files = copy;
1686         task_unlock(task);
1687         return 0;
1688 }