fork(): disable CLONE_PARENT for init
[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
68 #include <asm/pgtable.h>
69 #include <asm/pgalloc.h>
70 #include <asm/uaccess.h>
71 #include <asm/mmu_context.h>
72 #include <asm/cacheflush.h>
73 #include <asm/tlbflush.h>
74
75 #include <trace/events/sched.h>
76
77 /*
78  * Protected counters by write_lock_irq(&tasklist_lock)
79  */
80 unsigned long total_forks;      /* Handle normal Linux uptimes. */
81 int nr_threads;                 /* The idle threads do not count.. */
82
83 int max_threads;                /* tunable limit on nr_threads */
84
85 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
86
87 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
88
89 int nr_processes(void)
90 {
91         int cpu;
92         int total = 0;
93
94         for_each_online_cpu(cpu)
95                 total += per_cpu(process_counts, cpu);
96
97         return total;
98 }
99
100 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
101 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
102 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
103 static struct kmem_cache *task_struct_cachep;
104 #endif
105
106 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
107 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
108 {
109 #ifdef CONFIG_DEBUG_STACK_USAGE
110         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
111 #else
112         gfp_t mask = GFP_KERNEL;
113 #endif
114         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
115 }
116
117 static inline void free_thread_info(struct thread_info *ti)
118 {
119         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
120 }
121 #endif
122
123 /* SLAB cache for signal_struct structures (tsk->signal) */
124 static struct kmem_cache *signal_cachep;
125
126 /* SLAB cache for sighand_struct structures (tsk->sighand) */
127 struct kmem_cache *sighand_cachep;
128
129 /* SLAB cache for files_struct structures (tsk->files) */
130 struct kmem_cache *files_cachep;
131
132 /* SLAB cache for fs_struct structures (tsk->fs) */
133 struct kmem_cache *fs_cachep;
134
135 /* SLAB cache for vm_area_struct structures */
136 struct kmem_cache *vm_area_cachep;
137
138 /* SLAB cache for mm_struct structures (tsk->mm) */
139 static struct kmem_cache *mm_cachep;
140
141 static void account_kernel_stack(struct thread_info *ti, int account)
142 {
143         struct zone *zone = page_zone(virt_to_page(ti));
144
145         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
146 }
147
148 void free_task(struct task_struct *tsk)
149 {
150         prop_local_destroy_single(&tsk->dirties);
151         account_kernel_stack(tsk->stack, -1);
152         free_thread_info(tsk->stack);
153         rt_mutex_debug_task_free(tsk);
154         ftrace_graph_exit_task(tsk);
155         free_task_struct(tsk);
156 }
157 EXPORT_SYMBOL(free_task);
158
159 void __put_task_struct(struct task_struct *tsk)
160 {
161         WARN_ON(!tsk->exit_state);
162         WARN_ON(atomic_read(&tsk->usage));
163         WARN_ON(tsk == current);
164
165         exit_creds(tsk);
166         delayacct_tsk_free(tsk);
167
168         if (!profile_handoff_task(tsk))
169                 free_task(tsk);
170 }
171
172 /*
173  * macro override instead of weak attribute alias, to workaround
174  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
175  */
176 #ifndef arch_task_cache_init
177 #define arch_task_cache_init()
178 #endif
179
180 void __init fork_init(unsigned long mempages)
181 {
182 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
183 #ifndef ARCH_MIN_TASKALIGN
184 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
185 #endif
186         /* create a slab on which task_structs can be allocated */
187         task_struct_cachep =
188                 kmem_cache_create("task_struct", sizeof(struct task_struct),
189                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
190 #endif
191
192         /* do the arch specific task caches init */
193         arch_task_cache_init();
194
195         /*
196          * The default maximum number of threads is set to a safe
197          * value: the thread structures can take up at most half
198          * of memory.
199          */
200         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
201
202         /*
203          * we need to allow at least 20 threads to boot a system
204          */
205         if(max_threads < 20)
206                 max_threads = 20;
207
208         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
209         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
210         init_task.signal->rlim[RLIMIT_SIGPENDING] =
211                 init_task.signal->rlim[RLIMIT_NPROC];
212 }
213
214 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
215                                                struct task_struct *src)
216 {
217         *dst = *src;
218         return 0;
219 }
220
221 static struct task_struct *dup_task_struct(struct task_struct *orig)
222 {
223         struct task_struct *tsk;
224         struct thread_info *ti;
225         unsigned long *stackend;
226
227         int err;
228
229         prepare_to_copy(orig);
230
231         tsk = alloc_task_struct();
232         if (!tsk)
233                 return NULL;
234
235         ti = alloc_thread_info(tsk);
236         if (!ti) {
237                 free_task_struct(tsk);
238                 return NULL;
239         }
240
241         err = arch_dup_task_struct(tsk, orig);
242         if (err)
243                 goto out;
244
245         tsk->stack = ti;
246
247         err = prop_local_init_single(&tsk->dirties);
248         if (err)
249                 goto out;
250
251         setup_thread_stack(tsk, orig);
252         stackend = end_of_stack(tsk);
253         *stackend = STACK_END_MAGIC;    /* for overflow detection */
254
255 #ifdef CONFIG_CC_STACKPROTECTOR
256         tsk->stack_canary = get_random_int();
257 #endif
258
259         /* One for us, one for whoever does the "release_task()" (usually parent) */
260         atomic_set(&tsk->usage,2);
261         atomic_set(&tsk->fs_excl, 0);
262 #ifdef CONFIG_BLK_DEV_IO_TRACE
263         tsk->btrace_seq = 0;
264 #endif
265         tsk->splice_pipe = NULL;
266
267         account_kernel_stack(ti, 1);
268
269         return tsk;
270
271 out:
272         free_thread_info(ti);
273         free_task_struct(tsk);
274         return NULL;
275 }
276
277 #ifdef CONFIG_MMU
278 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
279 {
280         struct vm_area_struct *mpnt, *tmp, **pprev;
281         struct rb_node **rb_link, *rb_parent;
282         int retval;
283         unsigned long charge;
284         struct mempolicy *pol;
285
286         down_write(&oldmm->mmap_sem);
287         flush_cache_dup_mm(oldmm);
288         /*
289          * Not linked in yet - no deadlock potential:
290          */
291         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
292
293         mm->locked_vm = 0;
294         mm->mmap = NULL;
295         mm->mmap_cache = NULL;
296         mm->free_area_cache = oldmm->mmap_base;
297         mm->cached_hole_size = ~0UL;
298         mm->map_count = 0;
299         cpumask_clear(mm_cpumask(mm));
300         mm->mm_rb = RB_ROOT;
301         rb_link = &mm->mm_rb.rb_node;
302         rb_parent = NULL;
303         pprev = &mm->mmap;
304         retval = ksm_fork(mm, oldmm);
305         if (retval)
306                 goto out;
307
308         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
309                 struct file *file;
310
311                 if (mpnt->vm_flags & VM_DONTCOPY) {
312                         long pages = vma_pages(mpnt);
313                         mm->total_vm -= pages;
314                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
315                                                                 -pages);
316                         continue;
317                 }
318                 charge = 0;
319                 if (mpnt->vm_flags & VM_ACCOUNT) {
320                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
321                         if (security_vm_enough_memory(len))
322                                 goto fail_nomem;
323                         charge = len;
324                 }
325                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
326                 if (!tmp)
327                         goto fail_nomem;
328                 *tmp = *mpnt;
329                 pol = mpol_dup(vma_policy(mpnt));
330                 retval = PTR_ERR(pol);
331                 if (IS_ERR(pol))
332                         goto fail_nomem_policy;
333                 vma_set_policy(tmp, pol);
334                 tmp->vm_flags &= ~VM_LOCKED;
335                 tmp->vm_mm = mm;
336                 tmp->vm_next = NULL;
337                 anon_vma_link(tmp);
338                 file = tmp->vm_file;
339                 if (file) {
340                         struct inode *inode = file->f_path.dentry->d_inode;
341                         struct address_space *mapping = file->f_mapping;
342
343                         get_file(file);
344                         if (tmp->vm_flags & VM_DENYWRITE)
345                                 atomic_dec(&inode->i_writecount);
346                         spin_lock(&mapping->i_mmap_lock);
347                         if (tmp->vm_flags & VM_SHARED)
348                                 mapping->i_mmap_writable++;
349                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
350                         flush_dcache_mmap_lock(mapping);
351                         /* insert tmp into the share list, just after mpnt */
352                         vma_prio_tree_add(tmp, mpnt);
353                         flush_dcache_mmap_unlock(mapping);
354                         spin_unlock(&mapping->i_mmap_lock);
355                 }
356
357                 /*
358                  * Clear hugetlb-related page reserves for children. This only
359                  * affects MAP_PRIVATE mappings. Faults generated by the child
360                  * are not guaranteed to succeed, even if read-only
361                  */
362                 if (is_vm_hugetlb_page(tmp))
363                         reset_vma_resv_huge_pages(tmp);
364
365                 /*
366                  * Link in the new vma and copy the page table entries.
367                  */
368                 *pprev = tmp;
369                 pprev = &tmp->vm_next;
370
371                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
372                 rb_link = &tmp->vm_rb.rb_right;
373                 rb_parent = &tmp->vm_rb;
374
375                 mm->map_count++;
376                 retval = copy_page_range(mm, oldmm, mpnt);
377
378                 if (tmp->vm_ops && tmp->vm_ops->open)
379                         tmp->vm_ops->open(tmp);
380
381                 if (retval)
382                         goto out;
383         }
384         /* a new mm has just been created */
385         arch_dup_mmap(oldmm, mm);
386         retval = 0;
387 out:
388         up_write(&mm->mmap_sem);
389         flush_tlb_mm(oldmm);
390         up_write(&oldmm->mmap_sem);
391         return retval;
392 fail_nomem_policy:
393         kmem_cache_free(vm_area_cachep, tmp);
394 fail_nomem:
395         retval = -ENOMEM;
396         vm_unacct_memory(charge);
397         goto out;
398 }
399
400 static inline int mm_alloc_pgd(struct mm_struct * mm)
401 {
402         mm->pgd = pgd_alloc(mm);
403         if (unlikely(!mm->pgd))
404                 return -ENOMEM;
405         return 0;
406 }
407
408 static inline void mm_free_pgd(struct mm_struct * mm)
409 {
410         pgd_free(mm, mm->pgd);
411 }
412 #else
413 #define dup_mmap(mm, oldmm)     (0)
414 #define mm_alloc_pgd(mm)        (0)
415 #define mm_free_pgd(mm)
416 #endif /* CONFIG_MMU */
417
418 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
419
420 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
421 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
422
423 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
424
425 static int __init coredump_filter_setup(char *s)
426 {
427         default_dump_filter =
428                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
429                 MMF_DUMP_FILTER_MASK;
430         return 1;
431 }
432
433 __setup("coredump_filter=", coredump_filter_setup);
434
435 #include <linux/init_task.h>
436
437 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
438 {
439         atomic_set(&mm->mm_users, 1);
440         atomic_set(&mm->mm_count, 1);
441         init_rwsem(&mm->mmap_sem);
442         INIT_LIST_HEAD(&mm->mmlist);
443         mm->flags = (current->mm) ?
444                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
445         mm->core_state = NULL;
446         mm->nr_ptes = 0;
447         set_mm_counter(mm, file_rss, 0);
448         set_mm_counter(mm, anon_rss, 0);
449         spin_lock_init(&mm->page_table_lock);
450         spin_lock_init(&mm->ioctx_lock);
451         INIT_HLIST_HEAD(&mm->ioctx_list);
452         mm->free_area_cache = TASK_UNMAPPED_BASE;
453         mm->cached_hole_size = ~0UL;
454         mm_init_owner(mm, p);
455
456         if (likely(!mm_alloc_pgd(mm))) {
457                 mm->def_flags = 0;
458                 mmu_notifier_mm_init(mm);
459                 return mm;
460         }
461
462         free_mm(mm);
463         return NULL;
464 }
465
466 /*
467  * Allocate and initialize an mm_struct.
468  */
469 struct mm_struct * mm_alloc(void)
470 {
471         struct mm_struct * mm;
472
473         mm = allocate_mm();
474         if (mm) {
475                 memset(mm, 0, sizeof(*mm));
476                 mm = mm_init(mm, current);
477         }
478         return mm;
479 }
480
481 /*
482  * Called when the last reference to the mm
483  * is dropped: either by a lazy thread or by
484  * mmput. Free the page directory and the mm.
485  */
486 void __mmdrop(struct mm_struct *mm)
487 {
488         BUG_ON(mm == &init_mm);
489         mm_free_pgd(mm);
490         destroy_context(mm);
491         mmu_notifier_mm_destroy(mm);
492         free_mm(mm);
493 }
494 EXPORT_SYMBOL_GPL(__mmdrop);
495
496 /*
497  * Decrement the use count and release all resources for an mm.
498  */
499 void mmput(struct mm_struct *mm)
500 {
501         might_sleep();
502
503         if (atomic_dec_and_test(&mm->mm_users)) {
504                 exit_aio(mm);
505                 ksm_exit(mm);
506                 exit_mmap(mm);
507                 set_mm_exe_file(mm, NULL);
508                 if (!list_empty(&mm->mmlist)) {
509                         spin_lock(&mmlist_lock);
510                         list_del(&mm->mmlist);
511                         spin_unlock(&mmlist_lock);
512                 }
513                 put_swap_token(mm);
514                 mmdrop(mm);
515         }
516 }
517 EXPORT_SYMBOL_GPL(mmput);
518
519 /**
520  * get_task_mm - acquire a reference to the task's mm
521  *
522  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
523  * this kernel workthread has transiently adopted a user mm with use_mm,
524  * to do its AIO) is not set and if so returns a reference to it, after
525  * bumping up the use count.  User must release the mm via mmput()
526  * after use.  Typically used by /proc and ptrace.
527  */
528 struct mm_struct *get_task_mm(struct task_struct *task)
529 {
530         struct mm_struct *mm;
531
532         task_lock(task);
533         mm = task->mm;
534         if (mm) {
535                 if (task->flags & PF_KTHREAD)
536                         mm = NULL;
537                 else
538                         atomic_inc(&mm->mm_users);
539         }
540         task_unlock(task);
541         return mm;
542 }
543 EXPORT_SYMBOL_GPL(get_task_mm);
544
545 /* Please note the differences between mmput and mm_release.
546  * mmput is called whenever we stop holding onto a mm_struct,
547  * error success whatever.
548  *
549  * mm_release is called after a mm_struct has been removed
550  * from the current process.
551  *
552  * This difference is important for error handling, when we
553  * only half set up a mm_struct for a new process and need to restore
554  * the old one.  Because we mmput the new mm_struct before
555  * restoring the old one. . .
556  * Eric Biederman 10 January 1998
557  */
558 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
559 {
560         struct completion *vfork_done = tsk->vfork_done;
561
562         /* Get rid of any futexes when releasing the mm */
563 #ifdef CONFIG_FUTEX
564         if (unlikely(tsk->robust_list))
565                 exit_robust_list(tsk);
566 #ifdef CONFIG_COMPAT
567         if (unlikely(tsk->compat_robust_list))
568                 compat_exit_robust_list(tsk);
569 #endif
570 #endif
571
572         /* Get rid of any cached register state */
573         deactivate_mm(tsk, mm);
574
575         /* notify parent sleeping on vfork() */
576         if (vfork_done) {
577                 tsk->vfork_done = NULL;
578                 complete(vfork_done);
579         }
580
581         /*
582          * If we're exiting normally, clear a user-space tid field if
583          * requested.  We leave this alone when dying by signal, to leave
584          * the value intact in a core dump, and to save the unnecessary
585          * trouble otherwise.  Userland only wants this done for a sys_exit.
586          */
587         if (tsk->clear_child_tid) {
588                 if (!(tsk->flags & PF_SIGNALED) &&
589                     atomic_read(&mm->mm_users) > 1) {
590                         /*
591                          * We don't check the error code - if userspace has
592                          * not set up a proper pointer then tough luck.
593                          */
594                         put_user(0, tsk->clear_child_tid);
595                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
596                                         1, NULL, NULL, 0);
597                 }
598                 tsk->clear_child_tid = NULL;
599         }
600 }
601
602 /*
603  * Allocate a new mm structure and copy contents from the
604  * mm structure of the passed in task structure.
605  */
606 struct mm_struct *dup_mm(struct task_struct *tsk)
607 {
608         struct mm_struct *mm, *oldmm = current->mm;
609         int err;
610
611         if (!oldmm)
612                 return NULL;
613
614         mm = allocate_mm();
615         if (!mm)
616                 goto fail_nomem;
617
618         memcpy(mm, oldmm, sizeof(*mm));
619
620         /* Initializing for Swap token stuff */
621         mm->token_priority = 0;
622         mm->last_interval = 0;
623
624         if (!mm_init(mm, tsk))
625                 goto fail_nomem;
626
627         if (init_new_context(tsk, mm))
628                 goto fail_nocontext;
629
630         dup_mm_exe_file(oldmm, mm);
631
632         err = dup_mmap(mm, oldmm);
633         if (err)
634                 goto free_pt;
635
636         mm->hiwater_rss = get_mm_rss(mm);
637         mm->hiwater_vm = mm->total_vm;
638
639         return mm;
640
641 free_pt:
642         mmput(mm);
643
644 fail_nomem:
645         return NULL;
646
647 fail_nocontext:
648         /*
649          * If init_new_context() failed, we cannot use mmput() to free the mm
650          * because it calls destroy_context()
651          */
652         mm_free_pgd(mm);
653         free_mm(mm);
654         return NULL;
655 }
656
657 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
658 {
659         struct mm_struct * mm, *oldmm;
660         int retval;
661
662         tsk->min_flt = tsk->maj_flt = 0;
663         tsk->nvcsw = tsk->nivcsw = 0;
664 #ifdef CONFIG_DETECT_HUNG_TASK
665         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
666 #endif
667
668         tsk->mm = NULL;
669         tsk->active_mm = NULL;
670
671         /*
672          * Are we cloning a kernel thread?
673          *
674          * We need to steal a active VM for that..
675          */
676         oldmm = current->mm;
677         if (!oldmm)
678                 return 0;
679
680         if (clone_flags & CLONE_VM) {
681                 atomic_inc(&oldmm->mm_users);
682                 mm = oldmm;
683                 goto good_mm;
684         }
685
686         retval = -ENOMEM;
687         mm = dup_mm(tsk);
688         if (!mm)
689                 goto fail_nomem;
690
691 good_mm:
692         /* Initializing for Swap token stuff */
693         mm->token_priority = 0;
694         mm->last_interval = 0;
695
696         tsk->mm = mm;
697         tsk->active_mm = mm;
698         return 0;
699
700 fail_nomem:
701         return retval;
702 }
703
704 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
705 {
706         struct fs_struct *fs = current->fs;
707         if (clone_flags & CLONE_FS) {
708                 /* tsk->fs is already what we want */
709                 write_lock(&fs->lock);
710                 if (fs->in_exec) {
711                         write_unlock(&fs->lock);
712                         return -EAGAIN;
713                 }
714                 fs->users++;
715                 write_unlock(&fs->lock);
716                 return 0;
717         }
718         tsk->fs = copy_fs_struct(fs);
719         if (!tsk->fs)
720                 return -ENOMEM;
721         return 0;
722 }
723
724 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
725 {
726         struct files_struct *oldf, *newf;
727         int error = 0;
728
729         /*
730          * A background process may not have any files ...
731          */
732         oldf = current->files;
733         if (!oldf)
734                 goto out;
735
736         if (clone_flags & CLONE_FILES) {
737                 atomic_inc(&oldf->count);
738                 goto out;
739         }
740
741         newf = dup_fd(oldf, &error);
742         if (!newf)
743                 goto out;
744
745         tsk->files = newf;
746         error = 0;
747 out:
748         return error;
749 }
750
751 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
752 {
753 #ifdef CONFIG_BLOCK
754         struct io_context *ioc = current->io_context;
755
756         if (!ioc)
757                 return 0;
758         /*
759          * Share io context with parent, if CLONE_IO is set
760          */
761         if (clone_flags & CLONE_IO) {
762                 tsk->io_context = ioc_task_link(ioc);
763                 if (unlikely(!tsk->io_context))
764                         return -ENOMEM;
765         } else if (ioprio_valid(ioc->ioprio)) {
766                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
767                 if (unlikely(!tsk->io_context))
768                         return -ENOMEM;
769
770                 tsk->io_context->ioprio = ioc->ioprio;
771         }
772 #endif
773         return 0;
774 }
775
776 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
777 {
778         struct sighand_struct *sig;
779
780         if (clone_flags & CLONE_SIGHAND) {
781                 atomic_inc(&current->sighand->count);
782                 return 0;
783         }
784         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
785         rcu_assign_pointer(tsk->sighand, sig);
786         if (!sig)
787                 return -ENOMEM;
788         atomic_set(&sig->count, 1);
789         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
790         return 0;
791 }
792
793 void __cleanup_sighand(struct sighand_struct *sighand)
794 {
795         if (atomic_dec_and_test(&sighand->count))
796                 kmem_cache_free(sighand_cachep, sighand);
797 }
798
799
800 /*
801  * Initialize POSIX timer handling for a thread group.
802  */
803 static void posix_cpu_timers_init_group(struct signal_struct *sig)
804 {
805         /* Thread group counters. */
806         thread_group_cputime_init(sig);
807
808         /* Expiration times and increments. */
809         sig->it[CPUCLOCK_PROF].expires = cputime_zero;
810         sig->it[CPUCLOCK_PROF].incr = cputime_zero;
811         sig->it[CPUCLOCK_VIRT].expires = cputime_zero;
812         sig->it[CPUCLOCK_VIRT].incr = cputime_zero;
813
814         /* Cached expiration times. */
815         sig->cputime_expires.prof_exp = cputime_zero;
816         sig->cputime_expires.virt_exp = cputime_zero;
817         sig->cputime_expires.sched_exp = 0;
818
819         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
820                 sig->cputime_expires.prof_exp =
821                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
822                 sig->cputimer.running = 1;
823         }
824
825         /* The timer lists. */
826         INIT_LIST_HEAD(&sig->cpu_timers[0]);
827         INIT_LIST_HEAD(&sig->cpu_timers[1]);
828         INIT_LIST_HEAD(&sig->cpu_timers[2]);
829 }
830
831 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
832 {
833         struct signal_struct *sig;
834
835         if (clone_flags & CLONE_THREAD)
836                 return 0;
837
838         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
839         tsk->signal = sig;
840         if (!sig)
841                 return -ENOMEM;
842
843         atomic_set(&sig->count, 1);
844         atomic_set(&sig->live, 1);
845         init_waitqueue_head(&sig->wait_chldexit);
846         sig->flags = 0;
847         if (clone_flags & CLONE_NEWPID)
848                 sig->flags |= SIGNAL_UNKILLABLE;
849         sig->group_exit_code = 0;
850         sig->group_exit_task = NULL;
851         sig->group_stop_count = 0;
852         sig->curr_target = tsk;
853         init_sigpending(&sig->shared_pending);
854         INIT_LIST_HEAD(&sig->posix_timers);
855
856         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
857         sig->it_real_incr.tv64 = 0;
858         sig->real_timer.function = it_real_fn;
859
860         sig->leader = 0;        /* session leadership doesn't inherit */
861         sig->tty_old_pgrp = NULL;
862         sig->tty = NULL;
863
864         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
865         sig->gtime = cputime_zero;
866         sig->cgtime = cputime_zero;
867         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
868         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
869         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
870         sig->maxrss = sig->cmaxrss = 0;
871         task_io_accounting_init(&sig->ioac);
872         sig->sum_sched_runtime = 0;
873         taskstats_tgid_init(sig);
874
875         task_lock(current->group_leader);
876         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
877         task_unlock(current->group_leader);
878
879         posix_cpu_timers_init_group(sig);
880
881         acct_init_pacct(&sig->pacct);
882
883         tty_audit_fork(sig);
884
885         sig->oom_adj = current->signal->oom_adj;
886
887         return 0;
888 }
889
890 void __cleanup_signal(struct signal_struct *sig)
891 {
892         thread_group_cputime_free(sig);
893         tty_kref_put(sig->tty);
894         kmem_cache_free(signal_cachep, sig);
895 }
896
897 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
898 {
899         unsigned long new_flags = p->flags;
900
901         new_flags &= ~PF_SUPERPRIV;
902         new_flags |= PF_FORKNOEXEC;
903         new_flags |= PF_STARTING;
904         p->flags = new_flags;
905         clear_freeze_flag(p);
906 }
907
908 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
909 {
910         current->clear_child_tid = tidptr;
911
912         return task_pid_vnr(current);
913 }
914
915 static void rt_mutex_init_task(struct task_struct *p)
916 {
917         spin_lock_init(&p->pi_lock);
918 #ifdef CONFIG_RT_MUTEXES
919         plist_head_init(&p->pi_waiters, &p->pi_lock);
920         p->pi_blocked_on = NULL;
921 #endif
922 }
923
924 #ifdef CONFIG_MM_OWNER
925 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
926 {
927         mm->owner = p;
928 }
929 #endif /* CONFIG_MM_OWNER */
930
931 /*
932  * Initialize POSIX timer handling for a single task.
933  */
934 static void posix_cpu_timers_init(struct task_struct *tsk)
935 {
936         tsk->cputime_expires.prof_exp = cputime_zero;
937         tsk->cputime_expires.virt_exp = cputime_zero;
938         tsk->cputime_expires.sched_exp = 0;
939         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
940         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
941         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
942 }
943
944 /*
945  * This creates a new process as a copy of the old one,
946  * but does not actually start it yet.
947  *
948  * It copies the registers, and all the appropriate
949  * parts of the process environment (as per the clone
950  * flags). The actual kick-off is left to the caller.
951  */
952 static struct task_struct *copy_process(unsigned long clone_flags,
953                                         unsigned long stack_start,
954                                         struct pt_regs *regs,
955                                         unsigned long stack_size,
956                                         int __user *child_tidptr,
957                                         struct pid *pid,
958                                         int trace)
959 {
960         int retval;
961         struct task_struct *p;
962         int cgroup_callbacks_done = 0;
963
964         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
965                 return ERR_PTR(-EINVAL);
966
967         /*
968          * Thread groups must share signals as well, and detached threads
969          * can only be started up within the thread group.
970          */
971         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
972                 return ERR_PTR(-EINVAL);
973
974         /*
975          * Shared signal handlers imply shared VM. By way of the above,
976          * thread groups also imply shared VM. Blocking this case allows
977          * for various simplifications in other code.
978          */
979         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
980                 return ERR_PTR(-EINVAL);
981
982         /*
983          * Siblings of global init remain as zombies on exit since they are
984          * not reaped by their parent (swapper). To solve this and to avoid
985          * multi-rooted process trees, prevent global and container-inits
986          * from creating siblings.
987          */
988         if ((clone_flags & CLONE_PARENT) &&
989                                 current->signal->flags & SIGNAL_UNKILLABLE)
990                 return ERR_PTR(-EINVAL);
991
992         retval = security_task_create(clone_flags);
993         if (retval)
994                 goto fork_out;
995
996         retval = -ENOMEM;
997         p = dup_task_struct(current);
998         if (!p)
999                 goto fork_out;
1000
1001         ftrace_graph_init_task(p);
1002
1003         rt_mutex_init_task(p);
1004
1005 #ifdef CONFIG_PROVE_LOCKING
1006         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1007         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1008 #endif
1009         retval = -EAGAIN;
1010         if (atomic_read(&p->real_cred->user->processes) >=
1011                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1012                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1013                     p->real_cred->user != INIT_USER)
1014                         goto bad_fork_free;
1015         }
1016
1017         retval = copy_creds(p, clone_flags);
1018         if (retval < 0)
1019                 goto bad_fork_free;
1020
1021         /*
1022          * If multiple threads are within copy_process(), then this check
1023          * triggers too late. This doesn't hurt, the check is only there
1024          * to stop root fork bombs.
1025          */
1026         retval = -EAGAIN;
1027         if (nr_threads >= max_threads)
1028                 goto bad_fork_cleanup_count;
1029
1030         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1031                 goto bad_fork_cleanup_count;
1032
1033         if (p->binfmt && !try_module_get(p->binfmt->module))
1034                 goto bad_fork_cleanup_put_domain;
1035
1036         p->did_exec = 0;
1037         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1038         copy_flags(clone_flags, p);
1039         INIT_LIST_HEAD(&p->children);
1040         INIT_LIST_HEAD(&p->sibling);
1041         rcu_copy_process(p);
1042         p->vfork_done = NULL;
1043         spin_lock_init(&p->alloc_lock);
1044
1045         init_sigpending(&p->pending);
1046
1047         p->utime = cputime_zero;
1048         p->stime = cputime_zero;
1049         p->gtime = cputime_zero;
1050         p->utimescaled = cputime_zero;
1051         p->stimescaled = cputime_zero;
1052         p->prev_utime = cputime_zero;
1053         p->prev_stime = cputime_zero;
1054
1055         p->default_timer_slack_ns = current->timer_slack_ns;
1056
1057         task_io_accounting_init(&p->ioac);
1058         acct_clear_integrals(p);
1059
1060         posix_cpu_timers_init(p);
1061
1062         p->lock_depth = -1;             /* -1 = no lock */
1063         do_posix_clock_monotonic_gettime(&p->start_time);
1064         p->real_start_time = p->start_time;
1065         monotonic_to_bootbased(&p->real_start_time);
1066         p->io_context = NULL;
1067         p->audit_context = NULL;
1068         cgroup_fork(p);
1069 #ifdef CONFIG_NUMA
1070         p->mempolicy = mpol_dup(p->mempolicy);
1071         if (IS_ERR(p->mempolicy)) {
1072                 retval = PTR_ERR(p->mempolicy);
1073                 p->mempolicy = NULL;
1074                 goto bad_fork_cleanup_cgroup;
1075         }
1076         mpol_fix_fork_child_flag(p);
1077 #endif
1078 #ifdef CONFIG_TRACE_IRQFLAGS
1079         p->irq_events = 0;
1080 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1081         p->hardirqs_enabled = 1;
1082 #else
1083         p->hardirqs_enabled = 0;
1084 #endif
1085         p->hardirq_enable_ip = 0;
1086         p->hardirq_enable_event = 0;
1087         p->hardirq_disable_ip = _THIS_IP_;
1088         p->hardirq_disable_event = 0;
1089         p->softirqs_enabled = 1;
1090         p->softirq_enable_ip = _THIS_IP_;
1091         p->softirq_enable_event = 0;
1092         p->softirq_disable_ip = 0;
1093         p->softirq_disable_event = 0;
1094         p->hardirq_context = 0;
1095         p->softirq_context = 0;
1096 #endif
1097 #ifdef CONFIG_LOCKDEP
1098         p->lockdep_depth = 0; /* no locks held yet */
1099         p->curr_chain_key = 0;
1100         p->lockdep_recursion = 0;
1101 #endif
1102
1103 #ifdef CONFIG_DEBUG_MUTEXES
1104         p->blocked_on = NULL; /* not blocked yet */
1105 #endif
1106
1107         p->bts = NULL;
1108
1109         p->stack_start = stack_start;
1110
1111         /* Perform scheduler related setup. Assign this task to a CPU. */
1112         sched_fork(p, clone_flags);
1113
1114         retval = perf_event_init_task(p);
1115         if (retval)
1116                 goto bad_fork_cleanup_policy;
1117
1118         if ((retval = audit_alloc(p)))
1119                 goto bad_fork_cleanup_policy;
1120         /* copy all the process information */
1121         if ((retval = copy_semundo(clone_flags, p)))
1122                 goto bad_fork_cleanup_audit;
1123         if ((retval = copy_files(clone_flags, p)))
1124                 goto bad_fork_cleanup_semundo;
1125         if ((retval = copy_fs(clone_flags, p)))
1126                 goto bad_fork_cleanup_files;
1127         if ((retval = copy_sighand(clone_flags, p)))
1128                 goto bad_fork_cleanup_fs;
1129         if ((retval = copy_signal(clone_flags, p)))
1130                 goto bad_fork_cleanup_sighand;
1131         if ((retval = copy_mm(clone_flags, p)))
1132                 goto bad_fork_cleanup_signal;
1133         if ((retval = copy_namespaces(clone_flags, p)))
1134                 goto bad_fork_cleanup_mm;
1135         if ((retval = copy_io(clone_flags, p)))
1136                 goto bad_fork_cleanup_namespaces;
1137         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1138         if (retval)
1139                 goto bad_fork_cleanup_io;
1140
1141         if (pid != &init_struct_pid) {
1142                 retval = -ENOMEM;
1143                 pid = alloc_pid(p->nsproxy->pid_ns);
1144                 if (!pid)
1145                         goto bad_fork_cleanup_io;
1146
1147                 if (clone_flags & CLONE_NEWPID) {
1148                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1149                         if (retval < 0)
1150                                 goto bad_fork_free_pid;
1151                 }
1152         }
1153
1154         p->pid = pid_nr(pid);
1155         p->tgid = p->pid;
1156         if (clone_flags & CLONE_THREAD)
1157                 p->tgid = current->tgid;
1158
1159         if (current->nsproxy != p->nsproxy) {
1160                 retval = ns_cgroup_clone(p, pid);
1161                 if (retval)
1162                         goto bad_fork_free_pid;
1163         }
1164
1165         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1166         /*
1167          * Clear TID on mm_release()?
1168          */
1169         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1170 #ifdef CONFIG_FUTEX
1171         p->robust_list = NULL;
1172 #ifdef CONFIG_COMPAT
1173         p->compat_robust_list = NULL;
1174 #endif
1175         INIT_LIST_HEAD(&p->pi_state_list);
1176         p->pi_state_cache = NULL;
1177 #endif
1178         /*
1179          * sigaltstack should be cleared when sharing the same VM
1180          */
1181         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1182                 p->sas_ss_sp = p->sas_ss_size = 0;
1183
1184         /*
1185          * Syscall tracing should be turned off in the child regardless
1186          * of CLONE_PTRACE.
1187          */
1188         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1189 #ifdef TIF_SYSCALL_EMU
1190         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1191 #endif
1192         clear_all_latency_tracing(p);
1193
1194         /* ok, now we should be set up.. */
1195         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1196         p->pdeath_signal = 0;
1197         p->exit_state = 0;
1198
1199         /*
1200          * Ok, make it visible to the rest of the system.
1201          * We dont wake it up yet.
1202          */
1203         p->group_leader = p;
1204         INIT_LIST_HEAD(&p->thread_group);
1205
1206         /* Now that the task is set up, run cgroup callbacks if
1207          * necessary. We need to run them before the task is visible
1208          * on the tasklist. */
1209         cgroup_fork_callbacks(p);
1210         cgroup_callbacks_done = 1;
1211
1212         /* Need tasklist lock for parent etc handling! */
1213         write_lock_irq(&tasklist_lock);
1214
1215         /*
1216          * The task hasn't been attached yet, so its cpus_allowed mask will
1217          * not be changed, nor will its assigned CPU.
1218          *
1219          * The cpus_allowed mask of the parent may have changed after it was
1220          * copied first time - so re-copy it here, then check the child's CPU
1221          * to ensure it is on a valid CPU (and if not, just force it back to
1222          * parent's CPU). This avoids alot of nasty races.
1223          */
1224         p->cpus_allowed = current->cpus_allowed;
1225         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1226         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1227                         !cpu_online(task_cpu(p))))
1228                 set_task_cpu(p, smp_processor_id());
1229
1230         /* CLONE_PARENT re-uses the old parent */
1231         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1232                 p->real_parent = current->real_parent;
1233                 p->parent_exec_id = current->parent_exec_id;
1234         } else {
1235                 p->real_parent = current;
1236                 p->parent_exec_id = current->self_exec_id;
1237         }
1238
1239         spin_lock(&current->sighand->siglock);
1240
1241         /*
1242          * Process group and session signals need to be delivered to just the
1243          * parent before the fork or both the parent and the child after the
1244          * fork. Restart if a signal comes in before we add the new process to
1245          * it's process group.
1246          * A fatal signal pending means that current will exit, so the new
1247          * thread can't slip out of an OOM kill (or normal SIGKILL).
1248          */
1249         recalc_sigpending();
1250         if (signal_pending(current)) {
1251                 spin_unlock(&current->sighand->siglock);
1252                 write_unlock_irq(&tasklist_lock);
1253                 retval = -ERESTARTNOINTR;
1254                 goto bad_fork_free_pid;
1255         }
1256
1257         if (clone_flags & CLONE_THREAD) {
1258                 atomic_inc(&current->signal->count);
1259                 atomic_inc(&current->signal->live);
1260                 p->group_leader = current->group_leader;
1261                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1262         }
1263
1264         if (likely(p->pid)) {
1265                 list_add_tail(&p->sibling, &p->real_parent->children);
1266                 tracehook_finish_clone(p, clone_flags, trace);
1267
1268                 if (thread_group_leader(p)) {
1269                         if (clone_flags & CLONE_NEWPID)
1270                                 p->nsproxy->pid_ns->child_reaper = p;
1271
1272                         p->signal->leader_pid = pid;
1273                         tty_kref_put(p->signal->tty);
1274                         p->signal->tty = tty_kref_get(current->signal->tty);
1275                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1276                         attach_pid(p, PIDTYPE_SID, task_session(current));
1277                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1278                         __get_cpu_var(process_counts)++;
1279                 }
1280                 attach_pid(p, PIDTYPE_PID, pid);
1281                 nr_threads++;
1282         }
1283
1284         total_forks++;
1285         spin_unlock(&current->sighand->siglock);
1286         write_unlock_irq(&tasklist_lock);
1287         proc_fork_connector(p);
1288         cgroup_post_fork(p);
1289         perf_event_fork(p);
1290         return p;
1291
1292 bad_fork_free_pid:
1293         if (pid != &init_struct_pid)
1294                 free_pid(pid);
1295 bad_fork_cleanup_io:
1296         put_io_context(p->io_context);
1297 bad_fork_cleanup_namespaces:
1298         exit_task_namespaces(p);
1299 bad_fork_cleanup_mm:
1300         if (p->mm)
1301                 mmput(p->mm);
1302 bad_fork_cleanup_signal:
1303         if (!(clone_flags & CLONE_THREAD))
1304                 __cleanup_signal(p->signal);
1305 bad_fork_cleanup_sighand:
1306         __cleanup_sighand(p->sighand);
1307 bad_fork_cleanup_fs:
1308         exit_fs(p); /* blocking */
1309 bad_fork_cleanup_files:
1310         exit_files(p); /* blocking */
1311 bad_fork_cleanup_semundo:
1312         exit_sem(p);
1313 bad_fork_cleanup_audit:
1314         audit_free(p);
1315 bad_fork_cleanup_policy:
1316         perf_event_free_task(p);
1317 #ifdef CONFIG_NUMA
1318         mpol_put(p->mempolicy);
1319 bad_fork_cleanup_cgroup:
1320 #endif
1321         cgroup_exit(p, cgroup_callbacks_done);
1322         delayacct_tsk_free(p);
1323         if (p->binfmt)
1324                 module_put(p->binfmt->module);
1325 bad_fork_cleanup_put_domain:
1326         module_put(task_thread_info(p)->exec_domain->module);
1327 bad_fork_cleanup_count:
1328         atomic_dec(&p->cred->user->processes);
1329         exit_creds(p);
1330 bad_fork_free:
1331         free_task(p);
1332 fork_out:
1333         return ERR_PTR(retval);
1334 }
1335
1336 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1337 {
1338         memset(regs, 0, sizeof(struct pt_regs));
1339         return regs;
1340 }
1341
1342 struct task_struct * __cpuinit fork_idle(int cpu)
1343 {
1344         struct task_struct *task;
1345         struct pt_regs regs;
1346
1347         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1348                             &init_struct_pid, 0);
1349         if (!IS_ERR(task))
1350                 init_idle(task, cpu);
1351
1352         return task;
1353 }
1354
1355 /*
1356  *  Ok, this is the main fork-routine.
1357  *
1358  * It copies the process, and if successful kick-starts
1359  * it and waits for it to finish using the VM if required.
1360  */
1361 long do_fork(unsigned long clone_flags,
1362               unsigned long stack_start,
1363               struct pt_regs *regs,
1364               unsigned long stack_size,
1365               int __user *parent_tidptr,
1366               int __user *child_tidptr)
1367 {
1368         struct task_struct *p;
1369         int trace = 0;
1370         long nr;
1371
1372         /*
1373          * Do some preliminary argument and permissions checking before we
1374          * actually start allocating stuff
1375          */
1376         if (clone_flags & CLONE_NEWUSER) {
1377                 if (clone_flags & CLONE_THREAD)
1378                         return -EINVAL;
1379                 /* hopefully this check will go away when userns support is
1380                  * complete
1381                  */
1382                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1383                                 !capable(CAP_SETGID))
1384                         return -EPERM;
1385         }
1386
1387         /*
1388          * We hope to recycle these flags after 2.6.26
1389          */
1390         if (unlikely(clone_flags & CLONE_STOPPED)) {
1391                 static int __read_mostly count = 100;
1392
1393                 if (count > 0 && printk_ratelimit()) {
1394                         char comm[TASK_COMM_LEN];
1395
1396                         count--;
1397                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1398                                         "clone flags 0x%lx\n",
1399                                 get_task_comm(comm, current),
1400                                 clone_flags & CLONE_STOPPED);
1401                 }
1402         }
1403
1404         /*
1405          * When called from kernel_thread, don't do user tracing stuff.
1406          */
1407         if (likely(user_mode(regs)))
1408                 trace = tracehook_prepare_clone(clone_flags);
1409
1410         p = copy_process(clone_flags, stack_start, regs, stack_size,
1411                          child_tidptr, NULL, trace);
1412         /*
1413          * Do this prior waking up the new thread - the thread pointer
1414          * might get invalid after that point, if the thread exits quickly.
1415          */
1416         if (!IS_ERR(p)) {
1417                 struct completion vfork;
1418
1419                 trace_sched_process_fork(current, p);
1420
1421                 nr = task_pid_vnr(p);
1422
1423                 if (clone_flags & CLONE_PARENT_SETTID)
1424                         put_user(nr, parent_tidptr);
1425
1426                 if (clone_flags & CLONE_VFORK) {
1427                         p->vfork_done = &vfork;
1428                         init_completion(&vfork);
1429                 }
1430
1431                 audit_finish_fork(p);
1432                 tracehook_report_clone(regs, clone_flags, nr, p);
1433
1434                 /*
1435                  * We set PF_STARTING at creation in case tracing wants to
1436                  * use this to distinguish a fully live task from one that
1437                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1438                  * clear it and set the child going.
1439                  */
1440                 p->flags &= ~PF_STARTING;
1441
1442                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1443                         /*
1444                          * We'll start up with an immediate SIGSTOP.
1445                          */
1446                         sigaddset(&p->pending.signal, SIGSTOP);
1447                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1448                         __set_task_state(p, TASK_STOPPED);
1449                 } else {
1450                         wake_up_new_task(p, clone_flags);
1451                 }
1452
1453                 tracehook_report_clone_complete(trace, regs,
1454                                                 clone_flags, nr, p);
1455
1456                 if (clone_flags & CLONE_VFORK) {
1457                         freezer_do_not_count();
1458                         wait_for_completion(&vfork);
1459                         freezer_count();
1460                         tracehook_report_vfork_done(p, nr);
1461                 }
1462         } else {
1463                 nr = PTR_ERR(p);
1464         }
1465         return nr;
1466 }
1467
1468 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1469 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1470 #endif
1471
1472 static void sighand_ctor(void *data)
1473 {
1474         struct sighand_struct *sighand = data;
1475
1476         spin_lock_init(&sighand->siglock);
1477         init_waitqueue_head(&sighand->signalfd_wqh);
1478 }
1479
1480 void __init proc_caches_init(void)
1481 {
1482         sighand_cachep = kmem_cache_create("sighand_cache",
1483                         sizeof(struct sighand_struct), 0,
1484                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1485                         SLAB_NOTRACK, sighand_ctor);
1486         signal_cachep = kmem_cache_create("signal_cache",
1487                         sizeof(struct signal_struct), 0,
1488                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1489         files_cachep = kmem_cache_create("files_cache",
1490                         sizeof(struct files_struct), 0,
1491                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1492         fs_cachep = kmem_cache_create("fs_cache",
1493                         sizeof(struct fs_struct), 0,
1494                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1495         mm_cachep = kmem_cache_create("mm_struct",
1496                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1497                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1498         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1499         mmap_init();
1500 }
1501
1502 /*
1503  * Check constraints on flags passed to the unshare system call and
1504  * force unsharing of additional process context as appropriate.
1505  */
1506 static void check_unshare_flags(unsigned long *flags_ptr)
1507 {
1508         /*
1509          * If unsharing a thread from a thread group, must also
1510          * unshare vm.
1511          */
1512         if (*flags_ptr & CLONE_THREAD)
1513                 *flags_ptr |= CLONE_VM;
1514
1515         /*
1516          * If unsharing vm, must also unshare signal handlers.
1517          */
1518         if (*flags_ptr & CLONE_VM)
1519                 *flags_ptr |= CLONE_SIGHAND;
1520
1521         /*
1522          * If unsharing signal handlers and the task was created
1523          * using CLONE_THREAD, then must unshare the thread
1524          */
1525         if ((*flags_ptr & CLONE_SIGHAND) &&
1526             (atomic_read(&current->signal->count) > 1))
1527                 *flags_ptr |= CLONE_THREAD;
1528
1529         /*
1530          * If unsharing namespace, must also unshare filesystem information.
1531          */
1532         if (*flags_ptr & CLONE_NEWNS)
1533                 *flags_ptr |= CLONE_FS;
1534 }
1535
1536 /*
1537  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1538  */
1539 static int unshare_thread(unsigned long unshare_flags)
1540 {
1541         if (unshare_flags & CLONE_THREAD)
1542                 return -EINVAL;
1543
1544         return 0;
1545 }
1546
1547 /*
1548  * Unshare the filesystem structure if it is being shared
1549  */
1550 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1551 {
1552         struct fs_struct *fs = current->fs;
1553
1554         if (!(unshare_flags & CLONE_FS) || !fs)
1555                 return 0;
1556
1557         /* don't need lock here; in the worst case we'll do useless copy */
1558         if (fs->users == 1)
1559                 return 0;
1560
1561         *new_fsp = copy_fs_struct(fs);
1562         if (!*new_fsp)
1563                 return -ENOMEM;
1564
1565         return 0;
1566 }
1567
1568 /*
1569  * Unsharing of sighand is not supported yet
1570  */
1571 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1572 {
1573         struct sighand_struct *sigh = current->sighand;
1574
1575         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1576                 return -EINVAL;
1577         else
1578                 return 0;
1579 }
1580
1581 /*
1582  * Unshare vm if it is being shared
1583  */
1584 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1585 {
1586         struct mm_struct *mm = current->mm;
1587
1588         if ((unshare_flags & CLONE_VM) &&
1589             (mm && atomic_read(&mm->mm_users) > 1)) {
1590                 return -EINVAL;
1591         }
1592
1593         return 0;
1594 }
1595
1596 /*
1597  * Unshare file descriptor table if it is being shared
1598  */
1599 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1600 {
1601         struct files_struct *fd = current->files;
1602         int error = 0;
1603
1604         if ((unshare_flags & CLONE_FILES) &&
1605             (fd && atomic_read(&fd->count) > 1)) {
1606                 *new_fdp = dup_fd(fd, &error);
1607                 if (!*new_fdp)
1608                         return error;
1609         }
1610
1611         return 0;
1612 }
1613
1614 /*
1615  * unshare allows a process to 'unshare' part of the process
1616  * context which was originally shared using clone.  copy_*
1617  * functions used by do_fork() cannot be used here directly
1618  * because they modify an inactive task_struct that is being
1619  * constructed. Here we are modifying the current, active,
1620  * task_struct.
1621  */
1622 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1623 {
1624         int err = 0;
1625         struct fs_struct *fs, *new_fs = NULL;
1626         struct sighand_struct *new_sigh = NULL;
1627         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1628         struct files_struct *fd, *new_fd = NULL;
1629         struct nsproxy *new_nsproxy = NULL;
1630         int do_sysvsem = 0;
1631
1632         check_unshare_flags(&unshare_flags);
1633
1634         /* Return -EINVAL for all unsupported flags */
1635         err = -EINVAL;
1636         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1637                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1638                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1639                 goto bad_unshare_out;
1640
1641         /*
1642          * CLONE_NEWIPC must also detach from the undolist: after switching
1643          * to a new ipc namespace, the semaphore arrays from the old
1644          * namespace are unreachable.
1645          */
1646         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1647                 do_sysvsem = 1;
1648         if ((err = unshare_thread(unshare_flags)))
1649                 goto bad_unshare_out;
1650         if ((err = unshare_fs(unshare_flags, &new_fs)))
1651                 goto bad_unshare_cleanup_thread;
1652         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1653                 goto bad_unshare_cleanup_fs;
1654         if ((err = unshare_vm(unshare_flags, &new_mm)))
1655                 goto bad_unshare_cleanup_sigh;
1656         if ((err = unshare_fd(unshare_flags, &new_fd)))
1657                 goto bad_unshare_cleanup_vm;
1658         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1659                         new_fs)))
1660                 goto bad_unshare_cleanup_fd;
1661
1662         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1663                 if (do_sysvsem) {
1664                         /*
1665                          * CLONE_SYSVSEM is equivalent to sys_exit().
1666                          */
1667                         exit_sem(current);
1668                 }
1669
1670                 if (new_nsproxy) {
1671                         switch_task_namespaces(current, new_nsproxy);
1672                         new_nsproxy = NULL;
1673                 }
1674
1675                 task_lock(current);
1676
1677                 if (new_fs) {
1678                         fs = current->fs;
1679                         write_lock(&fs->lock);
1680                         current->fs = new_fs;
1681                         if (--fs->users)
1682                                 new_fs = NULL;
1683                         else
1684                                 new_fs = fs;
1685                         write_unlock(&fs->lock);
1686                 }
1687
1688                 if (new_mm) {
1689                         mm = current->mm;
1690                         active_mm = current->active_mm;
1691                         current->mm = new_mm;
1692                         current->active_mm = new_mm;
1693                         activate_mm(active_mm, new_mm);
1694                         new_mm = mm;
1695                 }
1696
1697                 if (new_fd) {
1698                         fd = current->files;
1699                         current->files = new_fd;
1700                         new_fd = fd;
1701                 }
1702
1703                 task_unlock(current);
1704         }
1705
1706         if (new_nsproxy)
1707                 put_nsproxy(new_nsproxy);
1708
1709 bad_unshare_cleanup_fd:
1710         if (new_fd)
1711                 put_files_struct(new_fd);
1712
1713 bad_unshare_cleanup_vm:
1714         if (new_mm)
1715                 mmput(new_mm);
1716
1717 bad_unshare_cleanup_sigh:
1718         if (new_sigh)
1719                 if (atomic_dec_and_test(&new_sigh->count))
1720                         kmem_cache_free(sighand_cachep, new_sigh);
1721
1722 bad_unshare_cleanup_fs:
1723         if (new_fs)
1724                 free_fs_struct(new_fs);
1725
1726 bad_unshare_cleanup_thread:
1727 bad_unshare_out:
1728         return err;
1729 }
1730
1731 /*
1732  *      Helper to unshare the files of the current task.
1733  *      We don't want to expose copy_files internals to
1734  *      the exec layer of the kernel.
1735  */
1736
1737 int unshare_files(struct files_struct **displaced)
1738 {
1739         struct task_struct *task = current;
1740         struct files_struct *copy = NULL;
1741         int error;
1742
1743         error = unshare_fd(CLONE_FILES, &copy);
1744         if (error || !copy) {
1745                 *displaced = NULL;
1746                 return error;
1747         }
1748         *displaced = task->files;
1749         task_lock(task);
1750         task->files = copy;
1751         task_unlock(task);
1752         return 0;
1753 }