Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6.git] / kernel / fork.c
1 /*
2  *  linux/kernel/fork.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6
7 /*
8  *  'fork.c' contains the help-routines for the 'fork' system call
9  * (see also entry.S and others).
10  * Fork is rather simple, once you get the hang of it, but the memory
11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12  */
13
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/personality.h>
21 #include <linux/mempolicy.h>
22 #include <linux/sem.h>
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/iocontext.h>
26 #include <linux/key.h>
27 #include <linux/binfmts.h>
28 #include <linux/mman.h>
29 #include <linux/mmu_notifier.h>
30 #include <linux/fs.h>
31 #include <linux/nsproxy.h>
32 #include <linux/capability.h>
33 #include <linux/cpu.h>
34 #include <linux/cgroup.h>
35 #include <linux/security.h>
36 #include <linux/hugetlb.h>
37 #include <linux/swap.h>
38 #include <linux/syscalls.h>
39 #include <linux/jiffies.h>
40 #include <linux/tracehook.h>
41 #include <linux/futex.h>
42 #include <linux/compat.h>
43 #include <linux/kthread.h>
44 #include <linux/task_io_accounting_ops.h>
45 #include <linux/rcupdate.h>
46 #include <linux/ptrace.h>
47 #include <linux/mount.h>
48 #include <linux/audit.h>
49 #include <linux/memcontrol.h>
50 #include <linux/ftrace.h>
51 #include <linux/profile.h>
52 #include <linux/rmap.h>
53 #include <linux/ksm.h>
54 #include <linux/acct.h>
55 #include <linux/tsacct_kern.h>
56 #include <linux/cn_proc.h>
57 #include <linux/freezer.h>
58 #include <linux/delayacct.h>
59 #include <linux/taskstats_kern.h>
60 #include <linux/random.h>
61 #include <linux/tty.h>
62 #include <linux/proc_fs.h>
63 #include <linux/blkdev.h>
64 #include <linux/fs_struct.h>
65 #include <linux/magic.h>
66 #include <linux/perf_event.h>
67 #include <linux/posix-timers.h>
68 #include <linux/user-return-notifier.h>
69 #include <linux/oom.h>
70 #include <linux/khugepaged.h>
71
72 #include <asm/pgtable.h>
73 #include <asm/pgalloc.h>
74 #include <asm/uaccess.h>
75 #include <asm/mmu_context.h>
76 #include <asm/cacheflush.h>
77 #include <asm/tlbflush.h>
78
79 #include <trace/events/sched.h>
80
81 /*
82  * Protected counters by write_lock_irq(&tasklist_lock)
83  */
84 unsigned long total_forks;      /* Handle normal Linux uptimes. */
85 int nr_threads;                 /* The idle threads do not count.. */
86
87 int max_threads;                /* tunable limit on nr_threads */
88
89 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
90
91 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
92
93 #ifdef CONFIG_PROVE_RCU
94 int lockdep_tasklist_lock_is_held(void)
95 {
96         return lockdep_is_held(&tasklist_lock);
97 }
98 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
99 #endif /* #ifdef CONFIG_PROVE_RCU */
100
101 int nr_processes(void)
102 {
103         int cpu;
104         int total = 0;
105
106         for_each_possible_cpu(cpu)
107                 total += per_cpu(process_counts, cpu);
108
109         return total;
110 }
111
112 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
113 # define alloc_task_struct_node(node)           \
114                 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
115 # define free_task_struct(tsk)                  \
116                 kmem_cache_free(task_struct_cachep, (tsk))
117 static struct kmem_cache *task_struct_cachep;
118 #endif
119
120 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
121 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
122                                                   int node)
123 {
124 #ifdef CONFIG_DEBUG_STACK_USAGE
125         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
126 #else
127         gfp_t mask = GFP_KERNEL;
128 #endif
129         struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
130
131         return page ? page_address(page) : NULL;
132 }
133
134 static inline void free_thread_info(struct thread_info *ti)
135 {
136         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
137 }
138 #endif
139
140 /* SLAB cache for signal_struct structures (tsk->signal) */
141 static struct kmem_cache *signal_cachep;
142
143 /* SLAB cache for sighand_struct structures (tsk->sighand) */
144 struct kmem_cache *sighand_cachep;
145
146 /* SLAB cache for files_struct structures (tsk->files) */
147 struct kmem_cache *files_cachep;
148
149 /* SLAB cache for fs_struct structures (tsk->fs) */
150 struct kmem_cache *fs_cachep;
151
152 /* SLAB cache for vm_area_struct structures */
153 struct kmem_cache *vm_area_cachep;
154
155 /* SLAB cache for mm_struct structures (tsk->mm) */
156 static struct kmem_cache *mm_cachep;
157
158 static void account_kernel_stack(struct thread_info *ti, int account)
159 {
160         struct zone *zone = page_zone(virt_to_page(ti));
161
162         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
163 }
164
165 void free_task(struct task_struct *tsk)
166 {
167         prop_local_destroy_single(&tsk->dirties);
168         account_kernel_stack(tsk->stack, -1);
169         free_thread_info(tsk->stack);
170         rt_mutex_debug_task_free(tsk);
171         ftrace_graph_exit_task(tsk);
172         free_task_struct(tsk);
173 }
174 EXPORT_SYMBOL(free_task);
175
176 static inline void free_signal_struct(struct signal_struct *sig)
177 {
178         taskstats_tgid_free(sig);
179         sched_autogroup_exit(sig);
180         kmem_cache_free(signal_cachep, sig);
181 }
182
183 static inline void put_signal_struct(struct signal_struct *sig)
184 {
185         if (atomic_dec_and_test(&sig->sigcnt))
186                 free_signal_struct(sig);
187 }
188
189 void __put_task_struct(struct task_struct *tsk)
190 {
191         WARN_ON(!tsk->exit_state);
192         WARN_ON(atomic_read(&tsk->usage));
193         WARN_ON(tsk == current);
194
195         exit_creds(tsk);
196         delayacct_tsk_free(tsk);
197         put_signal_struct(tsk->signal);
198
199         if (!profile_handoff_task(tsk))
200                 free_task(tsk);
201 }
202 EXPORT_SYMBOL_GPL(__put_task_struct);
203
204 /*
205  * macro override instead of weak attribute alias, to workaround
206  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
207  */
208 #ifndef arch_task_cache_init
209 #define arch_task_cache_init()
210 #endif
211
212 void __init fork_init(unsigned long mempages)
213 {
214 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
215 #ifndef ARCH_MIN_TASKALIGN
216 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
217 #endif
218         /* create a slab on which task_structs can be allocated */
219         task_struct_cachep =
220                 kmem_cache_create("task_struct", sizeof(struct task_struct),
221                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
222 #endif
223
224         /* do the arch specific task caches init */
225         arch_task_cache_init();
226
227         /*
228          * The default maximum number of threads is set to a safe
229          * value: the thread structures can take up at most half
230          * of memory.
231          */
232         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
233
234         /*
235          * we need to allow at least 20 threads to boot a system
236          */
237         if(max_threads < 20)
238                 max_threads = 20;
239
240         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
241         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
242         init_task.signal->rlim[RLIMIT_SIGPENDING] =
243                 init_task.signal->rlim[RLIMIT_NPROC];
244 }
245
246 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
247                                                struct task_struct *src)
248 {
249         *dst = *src;
250         return 0;
251 }
252
253 static struct task_struct *dup_task_struct(struct task_struct *orig)
254 {
255         struct task_struct *tsk;
256         struct thread_info *ti;
257         unsigned long *stackend;
258         int node = tsk_fork_get_node(orig);
259         int err;
260
261         prepare_to_copy(orig);
262
263         tsk = alloc_task_struct_node(node);
264         if (!tsk)
265                 return NULL;
266
267         ti = alloc_thread_info_node(tsk, node);
268         if (!ti) {
269                 free_task_struct(tsk);
270                 return NULL;
271         }
272
273         err = arch_dup_task_struct(tsk, orig);
274         if (err)
275                 goto out;
276
277         tsk->stack = ti;
278
279         err = prop_local_init_single(&tsk->dirties);
280         if (err)
281                 goto out;
282
283         setup_thread_stack(tsk, orig);
284         clear_user_return_notifier(tsk);
285         clear_tsk_need_resched(tsk);
286         stackend = end_of_stack(tsk);
287         *stackend = STACK_END_MAGIC;    /* for overflow detection */
288
289 #ifdef CONFIG_CC_STACKPROTECTOR
290         tsk->stack_canary = get_random_int();
291 #endif
292
293         /* One for us, one for whoever does the "release_task()" (usually parent) */
294         atomic_set(&tsk->usage,2);
295         atomic_set(&tsk->fs_excl, 0);
296 #ifdef CONFIG_BLK_DEV_IO_TRACE
297         tsk->btrace_seq = 0;
298 #endif
299         tsk->splice_pipe = NULL;
300
301         account_kernel_stack(ti, 1);
302
303         return tsk;
304
305 out:
306         free_thread_info(ti);
307         free_task_struct(tsk);
308         return NULL;
309 }
310
311 #ifdef CONFIG_MMU
312 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
313 {
314         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
315         struct rb_node **rb_link, *rb_parent;
316         int retval;
317         unsigned long charge;
318         struct mempolicy *pol;
319
320         down_write(&oldmm->mmap_sem);
321         flush_cache_dup_mm(oldmm);
322         /*
323          * Not linked in yet - no deadlock potential:
324          */
325         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
326
327         mm->locked_vm = 0;
328         mm->mmap = NULL;
329         mm->mmap_cache = NULL;
330         mm->free_area_cache = oldmm->mmap_base;
331         mm->cached_hole_size = ~0UL;
332         mm->map_count = 0;
333         cpumask_clear(mm_cpumask(mm));
334         mm->mm_rb = RB_ROOT;
335         rb_link = &mm->mm_rb.rb_node;
336         rb_parent = NULL;
337         pprev = &mm->mmap;
338         retval = ksm_fork(mm, oldmm);
339         if (retval)
340                 goto out;
341         retval = khugepaged_fork(mm, oldmm);
342         if (retval)
343                 goto out;
344
345         prev = NULL;
346         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
347                 struct file *file;
348
349                 if (mpnt->vm_flags & VM_DONTCOPY) {
350                         long pages = vma_pages(mpnt);
351                         mm->total_vm -= pages;
352                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
353                                                                 -pages);
354                         continue;
355                 }
356                 charge = 0;
357                 if (mpnt->vm_flags & VM_ACCOUNT) {
358                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
359                         if (security_vm_enough_memory(len))
360                                 goto fail_nomem;
361                         charge = len;
362                 }
363                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
364                 if (!tmp)
365                         goto fail_nomem;
366                 *tmp = *mpnt;
367                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
368                 pol = mpol_dup(vma_policy(mpnt));
369                 retval = PTR_ERR(pol);
370                 if (IS_ERR(pol))
371                         goto fail_nomem_policy;
372                 vma_set_policy(tmp, pol);
373                 tmp->vm_mm = mm;
374                 if (anon_vma_fork(tmp, mpnt))
375                         goto fail_nomem_anon_vma_fork;
376                 tmp->vm_flags &= ~VM_LOCKED;
377                 tmp->vm_next = tmp->vm_prev = NULL;
378                 file = tmp->vm_file;
379                 if (file) {
380                         struct inode *inode = file->f_path.dentry->d_inode;
381                         struct address_space *mapping = file->f_mapping;
382
383                         get_file(file);
384                         if (tmp->vm_flags & VM_DENYWRITE)
385                                 atomic_dec(&inode->i_writecount);
386                         spin_lock(&mapping->i_mmap_lock);
387                         if (tmp->vm_flags & VM_SHARED)
388                                 mapping->i_mmap_writable++;
389                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
390                         flush_dcache_mmap_lock(mapping);
391                         /* insert tmp into the share list, just after mpnt */
392                         vma_prio_tree_add(tmp, mpnt);
393                         flush_dcache_mmap_unlock(mapping);
394                         spin_unlock(&mapping->i_mmap_lock);
395                 }
396
397                 /*
398                  * Clear hugetlb-related page reserves for children. This only
399                  * affects MAP_PRIVATE mappings. Faults generated by the child
400                  * are not guaranteed to succeed, even if read-only
401                  */
402                 if (is_vm_hugetlb_page(tmp))
403                         reset_vma_resv_huge_pages(tmp);
404
405                 /*
406                  * Link in the new vma and copy the page table entries.
407                  */
408                 *pprev = tmp;
409                 pprev = &tmp->vm_next;
410                 tmp->vm_prev = prev;
411                 prev = tmp;
412
413                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
414                 rb_link = &tmp->vm_rb.rb_right;
415                 rb_parent = &tmp->vm_rb;
416
417                 mm->map_count++;
418                 retval = copy_page_range(mm, oldmm, mpnt);
419
420                 if (tmp->vm_ops && tmp->vm_ops->open)
421                         tmp->vm_ops->open(tmp);
422
423                 if (retval)
424                         goto out;
425         }
426         /* a new mm has just been created */
427         arch_dup_mmap(oldmm, mm);
428         retval = 0;
429 out:
430         up_write(&mm->mmap_sem);
431         flush_tlb_mm(oldmm);
432         up_write(&oldmm->mmap_sem);
433         return retval;
434 fail_nomem_anon_vma_fork:
435         mpol_put(pol);
436 fail_nomem_policy:
437         kmem_cache_free(vm_area_cachep, tmp);
438 fail_nomem:
439         retval = -ENOMEM;
440         vm_unacct_memory(charge);
441         goto out;
442 }
443
444 static inline int mm_alloc_pgd(struct mm_struct * mm)
445 {
446         mm->pgd = pgd_alloc(mm);
447         if (unlikely(!mm->pgd))
448                 return -ENOMEM;
449         return 0;
450 }
451
452 static inline void mm_free_pgd(struct mm_struct * mm)
453 {
454         pgd_free(mm, mm->pgd);
455 }
456 #else
457 #define dup_mmap(mm, oldmm)     (0)
458 #define mm_alloc_pgd(mm)        (0)
459 #define mm_free_pgd(mm)
460 #endif /* CONFIG_MMU */
461
462 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
463
464 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
465 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
466
467 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
468
469 static int __init coredump_filter_setup(char *s)
470 {
471         default_dump_filter =
472                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
473                 MMF_DUMP_FILTER_MASK;
474         return 1;
475 }
476
477 __setup("coredump_filter=", coredump_filter_setup);
478
479 #include <linux/init_task.h>
480
481 static void mm_init_aio(struct mm_struct *mm)
482 {
483 #ifdef CONFIG_AIO
484         spin_lock_init(&mm->ioctx_lock);
485         INIT_HLIST_HEAD(&mm->ioctx_list);
486 #endif
487 }
488
489 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
490 {
491         atomic_set(&mm->mm_users, 1);
492         atomic_set(&mm->mm_count, 1);
493         init_rwsem(&mm->mmap_sem);
494         INIT_LIST_HEAD(&mm->mmlist);
495         mm->flags = (current->mm) ?
496                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
497         mm->core_state = NULL;
498         mm->nr_ptes = 0;
499         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
500         spin_lock_init(&mm->page_table_lock);
501         mm->free_area_cache = TASK_UNMAPPED_BASE;
502         mm->cached_hole_size = ~0UL;
503         mm_init_aio(mm);
504         mm_init_owner(mm, p);
505         atomic_set(&mm->oom_disable_count, 0);
506
507         if (likely(!mm_alloc_pgd(mm))) {
508                 mm->def_flags = 0;
509                 mmu_notifier_mm_init(mm);
510                 return mm;
511         }
512
513         free_mm(mm);
514         return NULL;
515 }
516
517 /*
518  * Allocate and initialize an mm_struct.
519  */
520 struct mm_struct * mm_alloc(void)
521 {
522         struct mm_struct * mm;
523
524         mm = allocate_mm();
525         if (mm) {
526                 memset(mm, 0, sizeof(*mm));
527                 mm = mm_init(mm, current);
528         }
529         return mm;
530 }
531
532 /*
533  * Called when the last reference to the mm
534  * is dropped: either by a lazy thread or by
535  * mmput. Free the page directory and the mm.
536  */
537 void __mmdrop(struct mm_struct *mm)
538 {
539         BUG_ON(mm == &init_mm);
540         mm_free_pgd(mm);
541         destroy_context(mm);
542         mmu_notifier_mm_destroy(mm);
543 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
544         VM_BUG_ON(mm->pmd_huge_pte);
545 #endif
546         free_mm(mm);
547 }
548 EXPORT_SYMBOL_GPL(__mmdrop);
549
550 /*
551  * Decrement the use count and release all resources for an mm.
552  */
553 void mmput(struct mm_struct *mm)
554 {
555         might_sleep();
556
557         if (atomic_dec_and_test(&mm->mm_users)) {
558                 exit_aio(mm);
559                 ksm_exit(mm);
560                 khugepaged_exit(mm); /* must run before exit_mmap */
561                 exit_mmap(mm);
562                 set_mm_exe_file(mm, NULL);
563                 if (!list_empty(&mm->mmlist)) {
564                         spin_lock(&mmlist_lock);
565                         list_del(&mm->mmlist);
566                         spin_unlock(&mmlist_lock);
567                 }
568                 put_swap_token(mm);
569                 if (mm->binfmt)
570                         module_put(mm->binfmt->module);
571                 mmdrop(mm);
572         }
573 }
574 EXPORT_SYMBOL_GPL(mmput);
575
576 /**
577  * get_task_mm - acquire a reference to the task's mm
578  *
579  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
580  * this kernel workthread has transiently adopted a user mm with use_mm,
581  * to do its AIO) is not set and if so returns a reference to it, after
582  * bumping up the use count.  User must release the mm via mmput()
583  * after use.  Typically used by /proc and ptrace.
584  */
585 struct mm_struct *get_task_mm(struct task_struct *task)
586 {
587         struct mm_struct *mm;
588
589         task_lock(task);
590         mm = task->mm;
591         if (mm) {
592                 if (task->flags & PF_KTHREAD)
593                         mm = NULL;
594                 else
595                         atomic_inc(&mm->mm_users);
596         }
597         task_unlock(task);
598         return mm;
599 }
600 EXPORT_SYMBOL_GPL(get_task_mm);
601
602 /* Please note the differences between mmput and mm_release.
603  * mmput is called whenever we stop holding onto a mm_struct,
604  * error success whatever.
605  *
606  * mm_release is called after a mm_struct has been removed
607  * from the current process.
608  *
609  * This difference is important for error handling, when we
610  * only half set up a mm_struct for a new process and need to restore
611  * the old one.  Because we mmput the new mm_struct before
612  * restoring the old one. . .
613  * Eric Biederman 10 January 1998
614  */
615 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
616 {
617         struct completion *vfork_done = tsk->vfork_done;
618
619         /* Get rid of any futexes when releasing the mm */
620 #ifdef CONFIG_FUTEX
621         if (unlikely(tsk->robust_list)) {
622                 exit_robust_list(tsk);
623                 tsk->robust_list = NULL;
624         }
625 #ifdef CONFIG_COMPAT
626         if (unlikely(tsk->compat_robust_list)) {
627                 compat_exit_robust_list(tsk);
628                 tsk->compat_robust_list = NULL;
629         }
630 #endif
631         if (unlikely(!list_empty(&tsk->pi_state_list)))
632                 exit_pi_state_list(tsk);
633 #endif
634
635         /* Get rid of any cached register state */
636         deactivate_mm(tsk, mm);
637
638         /* notify parent sleeping on vfork() */
639         if (vfork_done) {
640                 tsk->vfork_done = NULL;
641                 complete(vfork_done);
642         }
643
644         /*
645          * If we're exiting normally, clear a user-space tid field if
646          * requested.  We leave this alone when dying by signal, to leave
647          * the value intact in a core dump, and to save the unnecessary
648          * trouble otherwise.  Userland only wants this done for a sys_exit.
649          */
650         if (tsk->clear_child_tid) {
651                 if (!(tsk->flags & PF_SIGNALED) &&
652                     atomic_read(&mm->mm_users) > 1) {
653                         /*
654                          * We don't check the error code - if userspace has
655                          * not set up a proper pointer then tough luck.
656                          */
657                         put_user(0, tsk->clear_child_tid);
658                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
659                                         1, NULL, NULL, 0);
660                 }
661                 tsk->clear_child_tid = NULL;
662         }
663 }
664
665 /*
666  * Allocate a new mm structure and copy contents from the
667  * mm structure of the passed in task structure.
668  */
669 struct mm_struct *dup_mm(struct task_struct *tsk)
670 {
671         struct mm_struct *mm, *oldmm = current->mm;
672         int err;
673
674         if (!oldmm)
675                 return NULL;
676
677         mm = allocate_mm();
678         if (!mm)
679                 goto fail_nomem;
680
681         memcpy(mm, oldmm, sizeof(*mm));
682
683         /* Initializing for Swap token stuff */
684         mm->token_priority = 0;
685         mm->last_interval = 0;
686
687 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
688         mm->pmd_huge_pte = NULL;
689 #endif
690
691         if (!mm_init(mm, tsk))
692                 goto fail_nomem;
693
694         if (init_new_context(tsk, mm))
695                 goto fail_nocontext;
696
697         dup_mm_exe_file(oldmm, mm);
698
699         err = dup_mmap(mm, oldmm);
700         if (err)
701                 goto free_pt;
702
703         mm->hiwater_rss = get_mm_rss(mm);
704         mm->hiwater_vm = mm->total_vm;
705
706         if (mm->binfmt && !try_module_get(mm->binfmt->module))
707                 goto free_pt;
708
709         return mm;
710
711 free_pt:
712         /* don't put binfmt in mmput, we haven't got module yet */
713         mm->binfmt = NULL;
714         mmput(mm);
715
716 fail_nomem:
717         return NULL;
718
719 fail_nocontext:
720         /*
721          * If init_new_context() failed, we cannot use mmput() to free the mm
722          * because it calls destroy_context()
723          */
724         mm_free_pgd(mm);
725         free_mm(mm);
726         return NULL;
727 }
728
729 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
730 {
731         struct mm_struct * mm, *oldmm;
732         int retval;
733
734         tsk->min_flt = tsk->maj_flt = 0;
735         tsk->nvcsw = tsk->nivcsw = 0;
736 #ifdef CONFIG_DETECT_HUNG_TASK
737         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
738 #endif
739
740         tsk->mm = NULL;
741         tsk->active_mm = NULL;
742
743         /*
744          * Are we cloning a kernel thread?
745          *
746          * We need to steal a active VM for that..
747          */
748         oldmm = current->mm;
749         if (!oldmm)
750                 return 0;
751
752         if (clone_flags & CLONE_VM) {
753                 atomic_inc(&oldmm->mm_users);
754                 mm = oldmm;
755                 goto good_mm;
756         }
757
758         retval = -ENOMEM;
759         mm = dup_mm(tsk);
760         if (!mm)
761                 goto fail_nomem;
762
763 good_mm:
764         /* Initializing for Swap token stuff */
765         mm->token_priority = 0;
766         mm->last_interval = 0;
767         if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
768                 atomic_inc(&mm->oom_disable_count);
769
770         tsk->mm = mm;
771         tsk->active_mm = mm;
772         return 0;
773
774 fail_nomem:
775         return retval;
776 }
777
778 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
779 {
780         struct fs_struct *fs = current->fs;
781         if (clone_flags & CLONE_FS) {
782                 /* tsk->fs is already what we want */
783                 spin_lock(&fs->lock);
784                 if (fs->in_exec) {
785                         spin_unlock(&fs->lock);
786                         return -EAGAIN;
787                 }
788                 fs->users++;
789                 spin_unlock(&fs->lock);
790                 return 0;
791         }
792         tsk->fs = copy_fs_struct(fs);
793         if (!tsk->fs)
794                 return -ENOMEM;
795         return 0;
796 }
797
798 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
799 {
800         struct files_struct *oldf, *newf;
801         int error = 0;
802
803         /*
804          * A background process may not have any files ...
805          */
806         oldf = current->files;
807         if (!oldf)
808                 goto out;
809
810         if (clone_flags & CLONE_FILES) {
811                 atomic_inc(&oldf->count);
812                 goto out;
813         }
814
815         newf = dup_fd(oldf, &error);
816         if (!newf)
817                 goto out;
818
819         tsk->files = newf;
820         error = 0;
821 out:
822         return error;
823 }
824
825 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
826 {
827 #ifdef CONFIG_BLOCK
828         struct io_context *ioc = current->io_context;
829
830         if (!ioc)
831                 return 0;
832         /*
833          * Share io context with parent, if CLONE_IO is set
834          */
835         if (clone_flags & CLONE_IO) {
836                 tsk->io_context = ioc_task_link(ioc);
837                 if (unlikely(!tsk->io_context))
838                         return -ENOMEM;
839         } else if (ioprio_valid(ioc->ioprio)) {
840                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
841                 if (unlikely(!tsk->io_context))
842                         return -ENOMEM;
843
844                 tsk->io_context->ioprio = ioc->ioprio;
845         }
846 #endif
847         return 0;
848 }
849
850 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
851 {
852         struct sighand_struct *sig;
853
854         if (clone_flags & CLONE_SIGHAND) {
855                 atomic_inc(&current->sighand->count);
856                 return 0;
857         }
858         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
859         rcu_assign_pointer(tsk->sighand, sig);
860         if (!sig)
861                 return -ENOMEM;
862         atomic_set(&sig->count, 1);
863         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
864         return 0;
865 }
866
867 void __cleanup_sighand(struct sighand_struct *sighand)
868 {
869         if (atomic_dec_and_test(&sighand->count))
870                 kmem_cache_free(sighand_cachep, sighand);
871 }
872
873
874 /*
875  * Initialize POSIX timer handling for a thread group.
876  */
877 static void posix_cpu_timers_init_group(struct signal_struct *sig)
878 {
879         unsigned long cpu_limit;
880
881         /* Thread group counters. */
882         thread_group_cputime_init(sig);
883
884         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
885         if (cpu_limit != RLIM_INFINITY) {
886                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
887                 sig->cputimer.running = 1;
888         }
889
890         /* The timer lists. */
891         INIT_LIST_HEAD(&sig->cpu_timers[0]);
892         INIT_LIST_HEAD(&sig->cpu_timers[1]);
893         INIT_LIST_HEAD(&sig->cpu_timers[2]);
894 }
895
896 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
897 {
898         struct signal_struct *sig;
899
900         if (clone_flags & CLONE_THREAD)
901                 return 0;
902
903         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
904         tsk->signal = sig;
905         if (!sig)
906                 return -ENOMEM;
907
908         sig->nr_threads = 1;
909         atomic_set(&sig->live, 1);
910         atomic_set(&sig->sigcnt, 1);
911         init_waitqueue_head(&sig->wait_chldexit);
912         if (clone_flags & CLONE_NEWPID)
913                 sig->flags |= SIGNAL_UNKILLABLE;
914         sig->curr_target = tsk;
915         init_sigpending(&sig->shared_pending);
916         INIT_LIST_HEAD(&sig->posix_timers);
917
918         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
919         sig->real_timer.function = it_real_fn;
920
921         task_lock(current->group_leader);
922         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
923         task_unlock(current->group_leader);
924
925         posix_cpu_timers_init_group(sig);
926
927         tty_audit_fork(sig);
928         sched_autogroup_fork(sig);
929
930         sig->oom_adj = current->signal->oom_adj;
931         sig->oom_score_adj = current->signal->oom_score_adj;
932         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
933
934         mutex_init(&sig->cred_guard_mutex);
935
936         return 0;
937 }
938
939 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
940 {
941         unsigned long new_flags = p->flags;
942
943         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
944         new_flags |= PF_FORKNOEXEC;
945         new_flags |= PF_STARTING;
946         p->flags = new_flags;
947         clear_freeze_flag(p);
948 }
949
950 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
951 {
952         current->clear_child_tid = tidptr;
953
954         return task_pid_vnr(current);
955 }
956
957 static void rt_mutex_init_task(struct task_struct *p)
958 {
959         raw_spin_lock_init(&p->pi_lock);
960 #ifdef CONFIG_RT_MUTEXES
961         plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
962         p->pi_blocked_on = NULL;
963 #endif
964 }
965
966 #ifdef CONFIG_MM_OWNER
967 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
968 {
969         mm->owner = p;
970 }
971 #endif /* CONFIG_MM_OWNER */
972
973 /*
974  * Initialize POSIX timer handling for a single task.
975  */
976 static void posix_cpu_timers_init(struct task_struct *tsk)
977 {
978         tsk->cputime_expires.prof_exp = cputime_zero;
979         tsk->cputime_expires.virt_exp = cputime_zero;
980         tsk->cputime_expires.sched_exp = 0;
981         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
982         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
983         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
984 }
985
986 /*
987  * This creates a new process as a copy of the old one,
988  * but does not actually start it yet.
989  *
990  * It copies the registers, and all the appropriate
991  * parts of the process environment (as per the clone
992  * flags). The actual kick-off is left to the caller.
993  */
994 static struct task_struct *copy_process(unsigned long clone_flags,
995                                         unsigned long stack_start,
996                                         struct pt_regs *regs,
997                                         unsigned long stack_size,
998                                         int __user *child_tidptr,
999                                         struct pid *pid,
1000                                         int trace)
1001 {
1002         int retval;
1003         struct task_struct *p;
1004         int cgroup_callbacks_done = 0;
1005
1006         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1007                 return ERR_PTR(-EINVAL);
1008
1009         /*
1010          * Thread groups must share signals as well, and detached threads
1011          * can only be started up within the thread group.
1012          */
1013         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1014                 return ERR_PTR(-EINVAL);
1015
1016         /*
1017          * Shared signal handlers imply shared VM. By way of the above,
1018          * thread groups also imply shared VM. Blocking this case allows
1019          * for various simplifications in other code.
1020          */
1021         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1022                 return ERR_PTR(-EINVAL);
1023
1024         /*
1025          * Siblings of global init remain as zombies on exit since they are
1026          * not reaped by their parent (swapper). To solve this and to avoid
1027          * multi-rooted process trees, prevent global and container-inits
1028          * from creating siblings.
1029          */
1030         if ((clone_flags & CLONE_PARENT) &&
1031                                 current->signal->flags & SIGNAL_UNKILLABLE)
1032                 return ERR_PTR(-EINVAL);
1033
1034         retval = security_task_create(clone_flags);
1035         if (retval)
1036                 goto fork_out;
1037
1038         retval = -ENOMEM;
1039         p = dup_task_struct(current);
1040         if (!p)
1041                 goto fork_out;
1042
1043         ftrace_graph_init_task(p);
1044
1045         rt_mutex_init_task(p);
1046
1047 #ifdef CONFIG_PROVE_LOCKING
1048         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1049         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1050 #endif
1051         retval = -EAGAIN;
1052         if (atomic_read(&p->real_cred->user->processes) >=
1053                         task_rlimit(p, RLIMIT_NPROC)) {
1054                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1055                     p->real_cred->user != INIT_USER)
1056                         goto bad_fork_free;
1057         }
1058
1059         retval = copy_creds(p, clone_flags);
1060         if (retval < 0)
1061                 goto bad_fork_free;
1062
1063         /*
1064          * If multiple threads are within copy_process(), then this check
1065          * triggers too late. This doesn't hurt, the check is only there
1066          * to stop root fork bombs.
1067          */
1068         retval = -EAGAIN;
1069         if (nr_threads >= max_threads)
1070                 goto bad_fork_cleanup_count;
1071
1072         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1073                 goto bad_fork_cleanup_count;
1074
1075         p->did_exec = 0;
1076         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1077         copy_flags(clone_flags, p);
1078         INIT_LIST_HEAD(&p->children);
1079         INIT_LIST_HEAD(&p->sibling);
1080         rcu_copy_process(p);
1081         p->vfork_done = NULL;
1082         spin_lock_init(&p->alloc_lock);
1083
1084         init_sigpending(&p->pending);
1085
1086         p->utime = cputime_zero;
1087         p->stime = cputime_zero;
1088         p->gtime = cputime_zero;
1089         p->utimescaled = cputime_zero;
1090         p->stimescaled = cputime_zero;
1091 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1092         p->prev_utime = cputime_zero;
1093         p->prev_stime = cputime_zero;
1094 #endif
1095 #if defined(SPLIT_RSS_COUNTING)
1096         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1097 #endif
1098
1099         p->default_timer_slack_ns = current->timer_slack_ns;
1100
1101         task_io_accounting_init(&p->ioac);
1102         acct_clear_integrals(p);
1103
1104         posix_cpu_timers_init(p);
1105
1106         p->lock_depth = -1;             /* -1 = no lock */
1107         do_posix_clock_monotonic_gettime(&p->start_time);
1108         p->real_start_time = p->start_time;
1109         monotonic_to_bootbased(&p->real_start_time);
1110         p->io_context = NULL;
1111         p->audit_context = NULL;
1112         cgroup_fork(p);
1113 #ifdef CONFIG_NUMA
1114         p->mempolicy = mpol_dup(p->mempolicy);
1115         if (IS_ERR(p->mempolicy)) {
1116                 retval = PTR_ERR(p->mempolicy);
1117                 p->mempolicy = NULL;
1118                 goto bad_fork_cleanup_cgroup;
1119         }
1120         mpol_fix_fork_child_flag(p);
1121 #endif
1122 #ifdef CONFIG_TRACE_IRQFLAGS
1123         p->irq_events = 0;
1124 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1125         p->hardirqs_enabled = 1;
1126 #else
1127         p->hardirqs_enabled = 0;
1128 #endif
1129         p->hardirq_enable_ip = 0;
1130         p->hardirq_enable_event = 0;
1131         p->hardirq_disable_ip = _THIS_IP_;
1132         p->hardirq_disable_event = 0;
1133         p->softirqs_enabled = 1;
1134         p->softirq_enable_ip = _THIS_IP_;
1135         p->softirq_enable_event = 0;
1136         p->softirq_disable_ip = 0;
1137         p->softirq_disable_event = 0;
1138         p->hardirq_context = 0;
1139         p->softirq_context = 0;
1140 #endif
1141 #ifdef CONFIG_LOCKDEP
1142         p->lockdep_depth = 0; /* no locks held yet */
1143         p->curr_chain_key = 0;
1144         p->lockdep_recursion = 0;
1145 #endif
1146
1147 #ifdef CONFIG_DEBUG_MUTEXES
1148         p->blocked_on = NULL; /* not blocked yet */
1149 #endif
1150 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1151         p->memcg_batch.do_batch = 0;
1152         p->memcg_batch.memcg = NULL;
1153 #endif
1154
1155         /* Perform scheduler related setup. Assign this task to a CPU. */
1156         sched_fork(p, clone_flags);
1157
1158         retval = perf_event_init_task(p);
1159         if (retval)
1160                 goto bad_fork_cleanup_policy;
1161
1162         if ((retval = audit_alloc(p)))
1163                 goto bad_fork_cleanup_policy;
1164         /* copy all the process information */
1165         if ((retval = copy_semundo(clone_flags, p)))
1166                 goto bad_fork_cleanup_audit;
1167         if ((retval = copy_files(clone_flags, p)))
1168                 goto bad_fork_cleanup_semundo;
1169         if ((retval = copy_fs(clone_flags, p)))
1170                 goto bad_fork_cleanup_files;
1171         if ((retval = copy_sighand(clone_flags, p)))
1172                 goto bad_fork_cleanup_fs;
1173         if ((retval = copy_signal(clone_flags, p)))
1174                 goto bad_fork_cleanup_sighand;
1175         if ((retval = copy_mm(clone_flags, p)))
1176                 goto bad_fork_cleanup_signal;
1177         if ((retval = copy_namespaces(clone_flags, p)))
1178                 goto bad_fork_cleanup_mm;
1179         if ((retval = copy_io(clone_flags, p)))
1180                 goto bad_fork_cleanup_namespaces;
1181         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1182         if (retval)
1183                 goto bad_fork_cleanup_io;
1184
1185         if (pid != &init_struct_pid) {
1186                 retval = -ENOMEM;
1187                 pid = alloc_pid(p->nsproxy->pid_ns);
1188                 if (!pid)
1189                         goto bad_fork_cleanup_io;
1190         }
1191
1192         p->pid = pid_nr(pid);
1193         p->tgid = p->pid;
1194         if (clone_flags & CLONE_THREAD)
1195                 p->tgid = current->tgid;
1196
1197         if (current->nsproxy != p->nsproxy) {
1198                 retval = ns_cgroup_clone(p, pid);
1199                 if (retval)
1200                         goto bad_fork_free_pid;
1201         }
1202
1203         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1204         /*
1205          * Clear TID on mm_release()?
1206          */
1207         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1208 #ifdef CONFIG_BLOCK
1209         p->plug = NULL;
1210 #endif
1211 #ifdef CONFIG_FUTEX
1212         p->robust_list = NULL;
1213 #ifdef CONFIG_COMPAT
1214         p->compat_robust_list = NULL;
1215 #endif
1216         INIT_LIST_HEAD(&p->pi_state_list);
1217         p->pi_state_cache = NULL;
1218 #endif
1219         /*
1220          * sigaltstack should be cleared when sharing the same VM
1221          */
1222         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1223                 p->sas_ss_sp = p->sas_ss_size = 0;
1224
1225         /*
1226          * Syscall tracing and stepping should be turned off in the
1227          * child regardless of CLONE_PTRACE.
1228          */
1229         user_disable_single_step(p);
1230         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1231 #ifdef TIF_SYSCALL_EMU
1232         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1233 #endif
1234         clear_all_latency_tracing(p);
1235
1236         /* ok, now we should be set up.. */
1237         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1238         p->pdeath_signal = 0;
1239         p->exit_state = 0;
1240
1241         /*
1242          * Ok, make it visible to the rest of the system.
1243          * We dont wake it up yet.
1244          */
1245         p->group_leader = p;
1246         INIT_LIST_HEAD(&p->thread_group);
1247
1248         /* Now that the task is set up, run cgroup callbacks if
1249          * necessary. We need to run them before the task is visible
1250          * on the tasklist. */
1251         cgroup_fork_callbacks(p);
1252         cgroup_callbacks_done = 1;
1253
1254         /* Need tasklist lock for parent etc handling! */
1255         write_lock_irq(&tasklist_lock);
1256
1257         /* CLONE_PARENT re-uses the old parent */
1258         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1259                 p->real_parent = current->real_parent;
1260                 p->parent_exec_id = current->parent_exec_id;
1261         } else {
1262                 p->real_parent = current;
1263                 p->parent_exec_id = current->self_exec_id;
1264         }
1265
1266         spin_lock(&current->sighand->siglock);
1267
1268         /*
1269          * Process group and session signals need to be delivered to just the
1270          * parent before the fork or both the parent and the child after the
1271          * fork. Restart if a signal comes in before we add the new process to
1272          * it's process group.
1273          * A fatal signal pending means that current will exit, so the new
1274          * thread can't slip out of an OOM kill (or normal SIGKILL).
1275          */
1276         recalc_sigpending();
1277         if (signal_pending(current)) {
1278                 spin_unlock(&current->sighand->siglock);
1279                 write_unlock_irq(&tasklist_lock);
1280                 retval = -ERESTARTNOINTR;
1281                 goto bad_fork_free_pid;
1282         }
1283
1284         if (clone_flags & CLONE_THREAD) {
1285                 current->signal->nr_threads++;
1286                 atomic_inc(&current->signal->live);
1287                 atomic_inc(&current->signal->sigcnt);
1288                 p->group_leader = current->group_leader;
1289                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1290         }
1291
1292         if (likely(p->pid)) {
1293                 tracehook_finish_clone(p, clone_flags, trace);
1294
1295                 if (thread_group_leader(p)) {
1296                         if (is_child_reaper(pid))
1297                                 p->nsproxy->pid_ns->child_reaper = p;
1298
1299                         p->signal->leader_pid = pid;
1300                         p->signal->tty = tty_kref_get(current->signal->tty);
1301                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1302                         attach_pid(p, PIDTYPE_SID, task_session(current));
1303                         list_add_tail(&p->sibling, &p->real_parent->children);
1304                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1305                         __this_cpu_inc(process_counts);
1306                 }
1307                 attach_pid(p, PIDTYPE_PID, pid);
1308                 nr_threads++;
1309         }
1310
1311         total_forks++;
1312         spin_unlock(&current->sighand->siglock);
1313         write_unlock_irq(&tasklist_lock);
1314         proc_fork_connector(p);
1315         cgroup_post_fork(p);
1316         perf_event_fork(p);
1317         return p;
1318
1319 bad_fork_free_pid:
1320         if (pid != &init_struct_pid)
1321                 free_pid(pid);
1322 bad_fork_cleanup_io:
1323         if (p->io_context)
1324                 exit_io_context(p);
1325 bad_fork_cleanup_namespaces:
1326         exit_task_namespaces(p);
1327 bad_fork_cleanup_mm:
1328         if (p->mm) {
1329                 task_lock(p);
1330                 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1331                         atomic_dec(&p->mm->oom_disable_count);
1332                 task_unlock(p);
1333                 mmput(p->mm);
1334         }
1335 bad_fork_cleanup_signal:
1336         if (!(clone_flags & CLONE_THREAD))
1337                 free_signal_struct(p->signal);
1338 bad_fork_cleanup_sighand:
1339         __cleanup_sighand(p->sighand);
1340 bad_fork_cleanup_fs:
1341         exit_fs(p); /* blocking */
1342 bad_fork_cleanup_files:
1343         exit_files(p); /* blocking */
1344 bad_fork_cleanup_semundo:
1345         exit_sem(p);
1346 bad_fork_cleanup_audit:
1347         audit_free(p);
1348 bad_fork_cleanup_policy:
1349         perf_event_free_task(p);
1350 #ifdef CONFIG_NUMA
1351         mpol_put(p->mempolicy);
1352 bad_fork_cleanup_cgroup:
1353 #endif
1354         cgroup_exit(p, cgroup_callbacks_done);
1355         delayacct_tsk_free(p);
1356         module_put(task_thread_info(p)->exec_domain->module);
1357 bad_fork_cleanup_count:
1358         atomic_dec(&p->cred->user->processes);
1359         exit_creds(p);
1360 bad_fork_free:
1361         free_task(p);
1362 fork_out:
1363         return ERR_PTR(retval);
1364 }
1365
1366 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1367 {
1368         memset(regs, 0, sizeof(struct pt_regs));
1369         return regs;
1370 }
1371
1372 static inline void init_idle_pids(struct pid_link *links)
1373 {
1374         enum pid_type type;
1375
1376         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1377                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1378                 links[type].pid = &init_struct_pid;
1379         }
1380 }
1381
1382 struct task_struct * __cpuinit fork_idle(int cpu)
1383 {
1384         struct task_struct *task;
1385         struct pt_regs regs;
1386
1387         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1388                             &init_struct_pid, 0);
1389         if (!IS_ERR(task)) {
1390                 init_idle_pids(task->pids);
1391                 init_idle(task, cpu);
1392         }
1393
1394         return task;
1395 }
1396
1397 /*
1398  *  Ok, this is the main fork-routine.
1399  *
1400  * It copies the process, and if successful kick-starts
1401  * it and waits for it to finish using the VM if required.
1402  */
1403 long do_fork(unsigned long clone_flags,
1404               unsigned long stack_start,
1405               struct pt_regs *regs,
1406               unsigned long stack_size,
1407               int __user *parent_tidptr,
1408               int __user *child_tidptr)
1409 {
1410         struct task_struct *p;
1411         int trace = 0;
1412         long nr;
1413
1414         /*
1415          * Do some preliminary argument and permissions checking before we
1416          * actually start allocating stuff
1417          */
1418         if (clone_flags & CLONE_NEWUSER) {
1419                 if (clone_flags & CLONE_THREAD)
1420                         return -EINVAL;
1421                 /* hopefully this check will go away when userns support is
1422                  * complete
1423                  */
1424                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1425                                 !capable(CAP_SETGID))
1426                         return -EPERM;
1427         }
1428
1429         /*
1430          * When called from kernel_thread, don't do user tracing stuff.
1431          */
1432         if (likely(user_mode(regs)))
1433                 trace = tracehook_prepare_clone(clone_flags);
1434
1435         p = copy_process(clone_flags, stack_start, regs, stack_size,
1436                          child_tidptr, NULL, trace);
1437         /*
1438          * Do this prior waking up the new thread - the thread pointer
1439          * might get invalid after that point, if the thread exits quickly.
1440          */
1441         if (!IS_ERR(p)) {
1442                 struct completion vfork;
1443
1444                 trace_sched_process_fork(current, p);
1445
1446                 nr = task_pid_vnr(p);
1447
1448                 if (clone_flags & CLONE_PARENT_SETTID)
1449                         put_user(nr, parent_tidptr);
1450
1451                 if (clone_flags & CLONE_VFORK) {
1452                         p->vfork_done = &vfork;
1453                         init_completion(&vfork);
1454                 }
1455
1456                 audit_finish_fork(p);
1457                 tracehook_report_clone(regs, clone_flags, nr, p);
1458
1459                 /*
1460                  * We set PF_STARTING at creation in case tracing wants to
1461                  * use this to distinguish a fully live task from one that
1462                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1463                  * clear it and set the child going.
1464                  */
1465                 p->flags &= ~PF_STARTING;
1466
1467                 wake_up_new_task(p, clone_flags);
1468
1469                 tracehook_report_clone_complete(trace, regs,
1470                                                 clone_flags, nr, p);
1471
1472                 if (clone_flags & CLONE_VFORK) {
1473                         freezer_do_not_count();
1474                         wait_for_completion(&vfork);
1475                         freezer_count();
1476                         tracehook_report_vfork_done(p, nr);
1477                 }
1478         } else {
1479                 nr = PTR_ERR(p);
1480         }
1481         return nr;
1482 }
1483
1484 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1485 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1486 #endif
1487
1488 static void sighand_ctor(void *data)
1489 {
1490         struct sighand_struct *sighand = data;
1491
1492         spin_lock_init(&sighand->siglock);
1493         init_waitqueue_head(&sighand->signalfd_wqh);
1494 }
1495
1496 void __init proc_caches_init(void)
1497 {
1498         sighand_cachep = kmem_cache_create("sighand_cache",
1499                         sizeof(struct sighand_struct), 0,
1500                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1501                         SLAB_NOTRACK, sighand_ctor);
1502         signal_cachep = kmem_cache_create("signal_cache",
1503                         sizeof(struct signal_struct), 0,
1504                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1505         files_cachep = kmem_cache_create("files_cache",
1506                         sizeof(struct files_struct), 0,
1507                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1508         fs_cachep = kmem_cache_create("fs_cache",
1509                         sizeof(struct fs_struct), 0,
1510                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1511         mm_cachep = kmem_cache_create("mm_struct",
1512                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1513                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1514         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1515         mmap_init();
1516 }
1517
1518 /*
1519  * Check constraints on flags passed to the unshare system call.
1520  */
1521 static int check_unshare_flags(unsigned long unshare_flags)
1522 {
1523         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1524                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1525                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1526                 return -EINVAL;
1527         /*
1528          * Not implemented, but pretend it works if there is nothing to
1529          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1530          * needs to unshare vm.
1531          */
1532         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1533                 /* FIXME: get_task_mm() increments ->mm_users */
1534                 if (atomic_read(&current->mm->mm_users) > 1)
1535                         return -EINVAL;
1536         }
1537
1538         return 0;
1539 }
1540
1541 /*
1542  * Unshare the filesystem structure if it is being shared
1543  */
1544 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1545 {
1546         struct fs_struct *fs = current->fs;
1547
1548         if (!(unshare_flags & CLONE_FS) || !fs)
1549                 return 0;
1550
1551         /* don't need lock here; in the worst case we'll do useless copy */
1552         if (fs->users == 1)
1553                 return 0;
1554
1555         *new_fsp = copy_fs_struct(fs);
1556         if (!*new_fsp)
1557                 return -ENOMEM;
1558
1559         return 0;
1560 }
1561
1562 /*
1563  * Unshare file descriptor table if it is being shared
1564  */
1565 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1566 {
1567         struct files_struct *fd = current->files;
1568         int error = 0;
1569
1570         if ((unshare_flags & CLONE_FILES) &&
1571             (fd && atomic_read(&fd->count) > 1)) {
1572                 *new_fdp = dup_fd(fd, &error);
1573                 if (!*new_fdp)
1574                         return error;
1575         }
1576
1577         return 0;
1578 }
1579
1580 /*
1581  * unshare allows a process to 'unshare' part of the process
1582  * context which was originally shared using clone.  copy_*
1583  * functions used by do_fork() cannot be used here directly
1584  * because they modify an inactive task_struct that is being
1585  * constructed. Here we are modifying the current, active,
1586  * task_struct.
1587  */
1588 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1589 {
1590         struct fs_struct *fs, *new_fs = NULL;
1591         struct files_struct *fd, *new_fd = NULL;
1592         struct nsproxy *new_nsproxy = NULL;
1593         int do_sysvsem = 0;
1594         int err;
1595
1596         err = check_unshare_flags(unshare_flags);
1597         if (err)
1598                 goto bad_unshare_out;
1599
1600         /*
1601          * If unsharing namespace, must also unshare filesystem information.
1602          */
1603         if (unshare_flags & CLONE_NEWNS)
1604                 unshare_flags |= CLONE_FS;
1605         /*
1606          * CLONE_NEWIPC must also detach from the undolist: after switching
1607          * to a new ipc namespace, the semaphore arrays from the old
1608          * namespace are unreachable.
1609          */
1610         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1611                 do_sysvsem = 1;
1612         if ((err = unshare_fs(unshare_flags, &new_fs)))
1613                 goto bad_unshare_out;
1614         if ((err = unshare_fd(unshare_flags, &new_fd)))
1615                 goto bad_unshare_cleanup_fs;
1616         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1617                         new_fs)))
1618                 goto bad_unshare_cleanup_fd;
1619
1620         if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1621                 if (do_sysvsem) {
1622                         /*
1623                          * CLONE_SYSVSEM is equivalent to sys_exit().
1624                          */
1625                         exit_sem(current);
1626                 }
1627
1628                 if (new_nsproxy) {
1629                         switch_task_namespaces(current, new_nsproxy);
1630                         new_nsproxy = NULL;
1631                 }
1632
1633                 task_lock(current);
1634
1635                 if (new_fs) {
1636                         fs = current->fs;
1637                         spin_lock(&fs->lock);
1638                         current->fs = new_fs;
1639                         if (--fs->users)
1640                                 new_fs = NULL;
1641                         else
1642                                 new_fs = fs;
1643                         spin_unlock(&fs->lock);
1644                 }
1645
1646                 if (new_fd) {
1647                         fd = current->files;
1648                         current->files = new_fd;
1649                         new_fd = fd;
1650                 }
1651
1652                 task_unlock(current);
1653         }
1654
1655         if (new_nsproxy)
1656                 put_nsproxy(new_nsproxy);
1657
1658 bad_unshare_cleanup_fd:
1659         if (new_fd)
1660                 put_files_struct(new_fd);
1661
1662 bad_unshare_cleanup_fs:
1663         if (new_fs)
1664                 free_fs_struct(new_fs);
1665
1666 bad_unshare_out:
1667         return err;
1668 }
1669
1670 /*
1671  *      Helper to unshare the files of the current task.
1672  *      We don't want to expose copy_files internals to
1673  *      the exec layer of the kernel.
1674  */
1675
1676 int unshare_files(struct files_struct **displaced)
1677 {
1678         struct task_struct *task = current;
1679         struct files_struct *copy = NULL;
1680         int error;
1681
1682         error = unshare_fd(CLONE_FILES, &copy);
1683         if (error || !copy) {
1684                 *displaced = NULL;
1685                 return error;
1686         }
1687         *displaced = task->files;
1688         task_lock(task);
1689         task->files = copy;
1690         task_unlock(task);
1691         return 0;
1692 }