2c1802948a38034598459e8d9b8cfeb533095679
[linux-3.10.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/seccomp.h>
38 #include <linux/swap.h>
39 #include <linux/syscalls.h>
40 #include <linux/jiffies.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/proc_fs.h>
52 #include <linux/profile.h>
53 #include <linux/rmap.h>
54 #include <linux/ksm.h>
55 #include <linux/acct.h>
56 #include <linux/tsacct_kern.h>
57 #include <linux/cn_proc.h>
58 #include <linux/freezer.h>
59 #include <linux/delayacct.h>
60 #include <linux/taskstats_kern.h>
61 #include <linux/random.h>
62 #include <linux/tty.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 #include <linux/signalfd.h>
72 #include <linux/uprobes.h>
73
74 #include <asm/pgtable.h>
75 #include <asm/pgalloc.h>
76 #include <asm/uaccess.h>
77 #include <asm/mmu_context.h>
78 #include <asm/cacheflush.h>
79 #include <asm/tlbflush.h>
80
81 #include <trace/events/sched.h>
82
83 #define CREATE_TRACE_POINTS
84 #include <trace/events/task.h>
85
86 /*
87  * Protected counters by write_lock_irq(&tasklist_lock)
88  */
89 unsigned long total_forks;      /* Handle normal Linux uptimes. */
90 int nr_threads;                 /* The idle threads do not count.. */
91
92 int max_threads;                /* tunable limit on nr_threads */
93
94 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
95
96 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
97
98 #ifdef CONFIG_PROVE_RCU
99 int lockdep_tasklist_lock_is_held(void)
100 {
101         return lockdep_is_held(&tasklist_lock);
102 }
103 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
104 #endif /* #ifdef CONFIG_PROVE_RCU */
105
106 int nr_processes(void)
107 {
108         int cpu;
109         int total = 0;
110
111         for_each_possible_cpu(cpu)
112                 total += per_cpu(process_counts, cpu);
113
114         return total;
115 }
116
117 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
118 static struct kmem_cache *task_struct_cachep;
119
120 static inline struct task_struct *alloc_task_struct_node(int node)
121 {
122         return kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node);
123 }
124
125 void __weak arch_release_task_struct(struct task_struct *tsk) { }
126
127 static inline void free_task_struct(struct task_struct *tsk)
128 {
129         arch_release_task_struct(tsk);
130         kmem_cache_free(task_struct_cachep, tsk);
131 }
132 #endif
133
134 #ifndef CONFIG_ARCH_THREAD_INFO_ALLOCATOR
135 void __weak arch_release_thread_info(struct thread_info *ti) { }
136
137 /*
138  * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
139  * kmemcache based allocator.
140  */
141 # if THREAD_SIZE >= PAGE_SIZE
142 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
143                                                   int node)
144 {
145         struct page *page = alloc_pages_node(node, THREADINFO_GFP,
146                                              THREAD_SIZE_ORDER);
147
148         return page ? page_address(page) : NULL;
149 }
150
151 static inline void free_thread_info(struct thread_info *ti)
152 {
153         arch_release_thread_info(ti);
154         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
155 }
156 # else
157 static struct kmem_cache *thread_info_cache;
158
159 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
160                                                   int node)
161 {
162         return kmem_cache_alloc_node(thread_info_cache, THREADINFO_GFP, node);
163 }
164
165 static void free_thread_info(struct thread_info *ti)
166 {
167         arch_release_thread_info(ti);
168         kmem_cache_free(thread_info_cache, ti);
169 }
170
171 void thread_info_cache_init(void)
172 {
173         thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,
174                                               THREAD_SIZE, 0, NULL);
175         BUG_ON(thread_info_cache == NULL);
176 }
177 # endif
178 #endif
179
180 /* SLAB cache for signal_struct structures (tsk->signal) */
181 static struct kmem_cache *signal_cachep;
182
183 /* SLAB cache for sighand_struct structures (tsk->sighand) */
184 struct kmem_cache *sighand_cachep;
185
186 /* SLAB cache for files_struct structures (tsk->files) */
187 struct kmem_cache *files_cachep;
188
189 /* SLAB cache for fs_struct structures (tsk->fs) */
190 struct kmem_cache *fs_cachep;
191
192 /* SLAB cache for vm_area_struct structures */
193 struct kmem_cache *vm_area_cachep;
194
195 /* SLAB cache for mm_struct structures (tsk->mm) */
196 static struct kmem_cache *mm_cachep;
197
198 static void account_kernel_stack(struct thread_info *ti, int account)
199 {
200         struct zone *zone = page_zone(virt_to_page(ti));
201
202         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
203 }
204
205 void free_task(struct task_struct *tsk)
206 {
207         account_kernel_stack(tsk->stack, -1);
208         free_thread_info(tsk->stack);
209         rt_mutex_debug_task_free(tsk);
210         ftrace_graph_exit_task(tsk);
211         put_seccomp_filter(tsk);
212         free_task_struct(tsk);
213 }
214 EXPORT_SYMBOL(free_task);
215
216 static inline void free_signal_struct(struct signal_struct *sig)
217 {
218         taskstats_tgid_free(sig);
219         sched_autogroup_exit(sig);
220         kmem_cache_free(signal_cachep, sig);
221 }
222
223 static inline void put_signal_struct(struct signal_struct *sig)
224 {
225         if (atomic_dec_and_test(&sig->sigcnt))
226                 free_signal_struct(sig);
227 }
228
229 void __put_task_struct(struct task_struct *tsk)
230 {
231         WARN_ON(!tsk->exit_state);
232         WARN_ON(atomic_read(&tsk->usage));
233         WARN_ON(tsk == current);
234
235         security_task_free(tsk);
236         exit_creds(tsk);
237         delayacct_tsk_free(tsk);
238         put_signal_struct(tsk->signal);
239
240         if (!profile_handoff_task(tsk))
241                 free_task(tsk);
242 }
243 EXPORT_SYMBOL_GPL(__put_task_struct);
244
245 void __init __weak arch_task_cache_init(void) { }
246
247 void __init fork_init(unsigned long mempages)
248 {
249 #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR
250 #ifndef ARCH_MIN_TASKALIGN
251 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
252 #endif
253         /* create a slab on which task_structs can be allocated */
254         task_struct_cachep =
255                 kmem_cache_create("task_struct", sizeof(struct task_struct),
256                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
257 #endif
258
259         /* do the arch specific task caches init */
260         arch_task_cache_init();
261
262         /*
263          * The default maximum number of threads is set to a safe
264          * value: the thread structures can take up at most half
265          * of memory.
266          */
267         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
268
269         /*
270          * we need to allow at least 20 threads to boot a system
271          */
272         if (max_threads < 20)
273                 max_threads = 20;
274
275         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
276         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
277         init_task.signal->rlim[RLIMIT_SIGPENDING] =
278                 init_task.signal->rlim[RLIMIT_NPROC];
279 }
280
281 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
282                                                struct task_struct *src)
283 {
284         *dst = *src;
285         return 0;
286 }
287
288 static struct task_struct *dup_task_struct(struct task_struct *orig)
289 {
290         struct task_struct *tsk;
291         struct thread_info *ti;
292         unsigned long *stackend;
293         int node = tsk_fork_get_node(orig);
294         int err;
295
296         tsk = alloc_task_struct_node(node);
297         if (!tsk)
298                 return NULL;
299
300         ti = alloc_thread_info_node(tsk, node);
301         if (!ti) {
302                 free_task_struct(tsk);
303                 return NULL;
304         }
305
306         err = arch_dup_task_struct(tsk, orig);
307
308         /*
309          * We defer looking at err, because we will need this setup
310          * for the clean up path to work correctly.
311          */
312         tsk->stack = ti;
313         setup_thread_stack(tsk, orig);
314
315         if (err)
316                 goto out;
317
318         clear_user_return_notifier(tsk);
319         clear_tsk_need_resched(tsk);
320         stackend = end_of_stack(tsk);
321         *stackend = STACK_END_MAGIC;    /* for overflow detection */
322
323 #ifdef CONFIG_CC_STACKPROTECTOR
324         tsk->stack_canary = get_random_int();
325 #endif
326
327         /*
328          * One for us, one for whoever does the "release_task()" (usually
329          * parent)
330          */
331         atomic_set(&tsk->usage, 2);
332 #ifdef CONFIG_BLK_DEV_IO_TRACE
333         tsk->btrace_seq = 0;
334 #endif
335         tsk->splice_pipe = NULL;
336
337         account_kernel_stack(ti, 1);
338
339         return tsk;
340
341 out:
342         free_thread_info(ti);
343         free_task_struct(tsk);
344         return NULL;
345 }
346
347 #ifdef CONFIG_MMU
348 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
349 {
350         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
351         struct rb_node **rb_link, *rb_parent;
352         int retval;
353         unsigned long charge;
354         struct mempolicy *pol;
355
356         down_write(&oldmm->mmap_sem);
357         flush_cache_dup_mm(oldmm);
358         /*
359          * Not linked in yet - no deadlock potential:
360          */
361         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
362
363         mm->locked_vm = 0;
364         mm->mmap = NULL;
365         mm->mmap_cache = NULL;
366         mm->free_area_cache = oldmm->mmap_base;
367         mm->cached_hole_size = ~0UL;
368         mm->map_count = 0;
369         cpumask_clear(mm_cpumask(mm));
370         mm->mm_rb = RB_ROOT;
371         rb_link = &mm->mm_rb.rb_node;
372         rb_parent = NULL;
373         pprev = &mm->mmap;
374         retval = ksm_fork(mm, oldmm);
375         if (retval)
376                 goto out;
377         retval = khugepaged_fork(mm, oldmm);
378         if (retval)
379                 goto out;
380
381         prev = NULL;
382         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
383                 struct file *file;
384
385                 if (mpnt->vm_flags & VM_DONTCOPY) {
386                         long pages = vma_pages(mpnt);
387                         mm->total_vm -= pages;
388                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
389                                                                 -pages);
390                         continue;
391                 }
392                 charge = 0;
393                 if (mpnt->vm_flags & VM_ACCOUNT) {
394                         unsigned long len = vma_pages(mpnt);
395
396                         if (security_vm_enough_memory_mm(oldmm, len)) /* sic */
397                                 goto fail_nomem;
398                         charge = len;
399                 }
400                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
401                 if (!tmp)
402                         goto fail_nomem;
403                 *tmp = *mpnt;
404                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
405                 pol = mpol_dup(vma_policy(mpnt));
406                 retval = PTR_ERR(pol);
407                 if (IS_ERR(pol))
408                         goto fail_nomem_policy;
409                 vma_set_policy(tmp, pol);
410                 tmp->vm_mm = mm;
411                 if (anon_vma_fork(tmp, mpnt))
412                         goto fail_nomem_anon_vma_fork;
413                 tmp->vm_flags &= ~VM_LOCKED;
414                 tmp->vm_next = tmp->vm_prev = NULL;
415                 file = tmp->vm_file;
416                 if (file) {
417                         struct inode *inode = file->f_path.dentry->d_inode;
418                         struct address_space *mapping = file->f_mapping;
419
420                         get_file(file);
421                         if (tmp->vm_flags & VM_DENYWRITE)
422                                 atomic_dec(&inode->i_writecount);
423                         mutex_lock(&mapping->i_mmap_mutex);
424                         if (tmp->vm_flags & VM_SHARED)
425                                 mapping->i_mmap_writable++;
426                         flush_dcache_mmap_lock(mapping);
427                         /* insert tmp into the share list, just after mpnt */
428                         vma_prio_tree_add(tmp, mpnt);
429                         flush_dcache_mmap_unlock(mapping);
430                         mutex_unlock(&mapping->i_mmap_mutex);
431                 }
432
433                 /*
434                  * Clear hugetlb-related page reserves for children. This only
435                  * affects MAP_PRIVATE mappings. Faults generated by the child
436                  * are not guaranteed to succeed, even if read-only
437                  */
438                 if (is_vm_hugetlb_page(tmp))
439                         reset_vma_resv_huge_pages(tmp);
440
441                 /*
442                  * Link in the new vma and copy the page table entries.
443                  */
444                 *pprev = tmp;
445                 pprev = &tmp->vm_next;
446                 tmp->vm_prev = prev;
447                 prev = tmp;
448
449                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
450                 rb_link = &tmp->vm_rb.rb_right;
451                 rb_parent = &tmp->vm_rb;
452
453                 mm->map_count++;
454                 retval = copy_page_range(mm, oldmm, mpnt);
455
456                 if (tmp->vm_ops && tmp->vm_ops->open)
457                         tmp->vm_ops->open(tmp);
458
459                 if (retval)
460                         goto out;
461
462                 if (file && uprobe_mmap(tmp))
463                         goto out;
464         }
465         /* a new mm has just been created */
466         arch_dup_mmap(oldmm, mm);
467         retval = 0;
468 out:
469         up_write(&mm->mmap_sem);
470         flush_tlb_mm(oldmm);
471         up_write(&oldmm->mmap_sem);
472         return retval;
473 fail_nomem_anon_vma_fork:
474         mpol_put(pol);
475 fail_nomem_policy:
476         kmem_cache_free(vm_area_cachep, tmp);
477 fail_nomem:
478         retval = -ENOMEM;
479         vm_unacct_memory(charge);
480         goto out;
481 }
482
483 static inline int mm_alloc_pgd(struct mm_struct *mm)
484 {
485         mm->pgd = pgd_alloc(mm);
486         if (unlikely(!mm->pgd))
487                 return -ENOMEM;
488         return 0;
489 }
490
491 static inline void mm_free_pgd(struct mm_struct *mm)
492 {
493         pgd_free(mm, mm->pgd);
494 }
495 #else
496 #define dup_mmap(mm, oldmm)     (0)
497 #define mm_alloc_pgd(mm)        (0)
498 #define mm_free_pgd(mm)
499 #endif /* CONFIG_MMU */
500
501 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
502
503 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
504 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
505
506 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
507
508 static int __init coredump_filter_setup(char *s)
509 {
510         default_dump_filter =
511                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
512                 MMF_DUMP_FILTER_MASK;
513         return 1;
514 }
515
516 __setup("coredump_filter=", coredump_filter_setup);
517
518 #include <linux/init_task.h>
519
520 static void mm_init_aio(struct mm_struct *mm)
521 {
522 #ifdef CONFIG_AIO
523         spin_lock_init(&mm->ioctx_lock);
524         INIT_HLIST_HEAD(&mm->ioctx_list);
525 #endif
526 }
527
528 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
529 {
530         atomic_set(&mm->mm_users, 1);
531         atomic_set(&mm->mm_count, 1);
532         init_rwsem(&mm->mmap_sem);
533         INIT_LIST_HEAD(&mm->mmlist);
534         mm->flags = (current->mm) ?
535                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
536         mm->core_state = NULL;
537         mm->nr_ptes = 0;
538         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
539         spin_lock_init(&mm->page_table_lock);
540         mm->free_area_cache = TASK_UNMAPPED_BASE;
541         mm->cached_hole_size = ~0UL;
542         mm_init_aio(mm);
543         mm_init_owner(mm, p);
544
545         if (likely(!mm_alloc_pgd(mm))) {
546                 mm->def_flags = 0;
547                 mmu_notifier_mm_init(mm);
548                 return mm;
549         }
550
551         free_mm(mm);
552         return NULL;
553 }
554
555 static void check_mm(struct mm_struct *mm)
556 {
557         int i;
558
559         for (i = 0; i < NR_MM_COUNTERS; i++) {
560                 long x = atomic_long_read(&mm->rss_stat.count[i]);
561
562                 if (unlikely(x))
563                         printk(KERN_ALERT "BUG: Bad rss-counter state "
564                                           "mm:%p idx:%d val:%ld\n", mm, i, x);
565         }
566
567 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
568         VM_BUG_ON(mm->pmd_huge_pte);
569 #endif
570 }
571
572 /*
573  * Allocate and initialize an mm_struct.
574  */
575 struct mm_struct *mm_alloc(void)
576 {
577         struct mm_struct *mm;
578
579         mm = allocate_mm();
580         if (!mm)
581                 return NULL;
582
583         memset(mm, 0, sizeof(*mm));
584         mm_init_cpumask(mm);
585         return mm_init(mm, current);
586 }
587
588 /*
589  * Called when the last reference to the mm
590  * is dropped: either by a lazy thread or by
591  * mmput. Free the page directory and the mm.
592  */
593 void __mmdrop(struct mm_struct *mm)
594 {
595         BUG_ON(mm == &init_mm);
596         mm_free_pgd(mm);
597         destroy_context(mm);
598         mmu_notifier_mm_destroy(mm);
599         check_mm(mm);
600         free_mm(mm);
601 }
602 EXPORT_SYMBOL_GPL(__mmdrop);
603
604 /*
605  * Decrement the use count and release all resources for an mm.
606  */
607 void mmput(struct mm_struct *mm)
608 {
609         might_sleep();
610
611         if (atomic_dec_and_test(&mm->mm_users)) {
612                 uprobe_clear_state(mm);
613                 exit_aio(mm);
614                 ksm_exit(mm);
615                 khugepaged_exit(mm); /* must run before exit_mmap */
616                 exit_mmap(mm);
617                 set_mm_exe_file(mm, NULL);
618                 if (!list_empty(&mm->mmlist)) {
619                         spin_lock(&mmlist_lock);
620                         list_del(&mm->mmlist);
621                         spin_unlock(&mmlist_lock);
622                 }
623                 if (mm->binfmt)
624                         module_put(mm->binfmt->module);
625                 mmdrop(mm);
626         }
627 }
628 EXPORT_SYMBOL_GPL(mmput);
629
630 /*
631  * We added or removed a vma mapping the executable. The vmas are only mapped
632  * during exec and are not mapped with the mmap system call.
633  * Callers must hold down_write() on the mm's mmap_sem for these
634  */
635 void added_exe_file_vma(struct mm_struct *mm)
636 {
637         mm->num_exe_file_vmas++;
638 }
639
640 void removed_exe_file_vma(struct mm_struct *mm)
641 {
642         mm->num_exe_file_vmas--;
643         if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
644                 fput(mm->exe_file);
645                 mm->exe_file = NULL;
646         }
647
648 }
649
650 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
651 {
652         if (new_exe_file)
653                 get_file(new_exe_file);
654         if (mm->exe_file)
655                 fput(mm->exe_file);
656         mm->exe_file = new_exe_file;
657         mm->num_exe_file_vmas = 0;
658 }
659
660 struct file *get_mm_exe_file(struct mm_struct *mm)
661 {
662         struct file *exe_file;
663
664         /* We need mmap_sem to protect against races with removal of
665          * VM_EXECUTABLE vmas */
666         down_read(&mm->mmap_sem);
667         exe_file = mm->exe_file;
668         if (exe_file)
669                 get_file(exe_file);
670         up_read(&mm->mmap_sem);
671         return exe_file;
672 }
673
674 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
675 {
676         /* It's safe to write the exe_file pointer without exe_file_lock because
677          * this is called during fork when the task is not yet in /proc */
678         newmm->exe_file = get_mm_exe_file(oldmm);
679 }
680
681 /**
682  * get_task_mm - acquire a reference to the task's mm
683  *
684  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
685  * this kernel workthread has transiently adopted a user mm with use_mm,
686  * to do its AIO) is not set and if so returns a reference to it, after
687  * bumping up the use count.  User must release the mm via mmput()
688  * after use.  Typically used by /proc and ptrace.
689  */
690 struct mm_struct *get_task_mm(struct task_struct *task)
691 {
692         struct mm_struct *mm;
693
694         task_lock(task);
695         mm = task->mm;
696         if (mm) {
697                 if (task->flags & PF_KTHREAD)
698                         mm = NULL;
699                 else
700                         atomic_inc(&mm->mm_users);
701         }
702         task_unlock(task);
703         return mm;
704 }
705 EXPORT_SYMBOL_GPL(get_task_mm);
706
707 struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
708 {
709         struct mm_struct *mm;
710         int err;
711
712         err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
713         if (err)
714                 return ERR_PTR(err);
715
716         mm = get_task_mm(task);
717         if (mm && mm != current->mm &&
718                         !ptrace_may_access(task, mode)) {
719                 mmput(mm);
720                 mm = ERR_PTR(-EACCES);
721         }
722         mutex_unlock(&task->signal->cred_guard_mutex);
723
724         return mm;
725 }
726
727 static void complete_vfork_done(struct task_struct *tsk)
728 {
729         struct completion *vfork;
730
731         task_lock(tsk);
732         vfork = tsk->vfork_done;
733         if (likely(vfork)) {
734                 tsk->vfork_done = NULL;
735                 complete(vfork);
736         }
737         task_unlock(tsk);
738 }
739
740 static int wait_for_vfork_done(struct task_struct *child,
741                                 struct completion *vfork)
742 {
743         int killed;
744
745         freezer_do_not_count();
746         killed = wait_for_completion_killable(vfork);
747         freezer_count();
748
749         if (killed) {
750                 task_lock(child);
751                 child->vfork_done = NULL;
752                 task_unlock(child);
753         }
754
755         put_task_struct(child);
756         return killed;
757 }
758
759 /* Please note the differences between mmput and mm_release.
760  * mmput is called whenever we stop holding onto a mm_struct,
761  * error success whatever.
762  *
763  * mm_release is called after a mm_struct has been removed
764  * from the current process.
765  *
766  * This difference is important for error handling, when we
767  * only half set up a mm_struct for a new process and need to restore
768  * the old one.  Because we mmput the new mm_struct before
769  * restoring the old one. . .
770  * Eric Biederman 10 January 1998
771  */
772 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
773 {
774         /* Get rid of any futexes when releasing the mm */
775 #ifdef CONFIG_FUTEX
776         if (unlikely(tsk->robust_list)) {
777                 exit_robust_list(tsk);
778                 tsk->robust_list = NULL;
779         }
780 #ifdef CONFIG_COMPAT
781         if (unlikely(tsk->compat_robust_list)) {
782                 compat_exit_robust_list(tsk);
783                 tsk->compat_robust_list = NULL;
784         }
785 #endif
786         if (unlikely(!list_empty(&tsk->pi_state_list)))
787                 exit_pi_state_list(tsk);
788 #endif
789
790         uprobe_free_utask(tsk);
791
792         /* Get rid of any cached register state */
793         deactivate_mm(tsk, mm);
794
795         /*
796          * If we're exiting normally, clear a user-space tid field if
797          * requested.  We leave this alone when dying by signal, to leave
798          * the value intact in a core dump, and to save the unnecessary
799          * trouble, say, a killed vfork parent shouldn't touch this mm.
800          * Userland only wants this done for a sys_exit.
801          */
802         if (tsk->clear_child_tid) {
803                 if (!(tsk->flags & PF_SIGNALED) &&
804                     atomic_read(&mm->mm_users) > 1) {
805                         /*
806                          * We don't check the error code - if userspace has
807                          * not set up a proper pointer then tough luck.
808                          */
809                         put_user(0, tsk->clear_child_tid);
810                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
811                                         1, NULL, NULL, 0);
812                 }
813                 tsk->clear_child_tid = NULL;
814         }
815
816         /*
817          * All done, finally we can wake up parent and return this mm to him.
818          * Also kthread_stop() uses this completion for synchronization.
819          */
820         if (tsk->vfork_done)
821                 complete_vfork_done(tsk);
822 }
823
824 /*
825  * Allocate a new mm structure and copy contents from the
826  * mm structure of the passed in task structure.
827  */
828 struct mm_struct *dup_mm(struct task_struct *tsk)
829 {
830         struct mm_struct *mm, *oldmm = current->mm;
831         int err;
832
833         if (!oldmm)
834                 return NULL;
835
836         mm = allocate_mm();
837         if (!mm)
838                 goto fail_nomem;
839
840         memcpy(mm, oldmm, sizeof(*mm));
841         mm_init_cpumask(mm);
842
843 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
844         mm->pmd_huge_pte = NULL;
845 #endif
846         uprobe_reset_state(mm);
847
848         if (!mm_init(mm, tsk))
849                 goto fail_nomem;
850
851         if (init_new_context(tsk, mm))
852                 goto fail_nocontext;
853
854         dup_mm_exe_file(oldmm, mm);
855
856         err = dup_mmap(mm, oldmm);
857         if (err)
858                 goto free_pt;
859
860         mm->hiwater_rss = get_mm_rss(mm);
861         mm->hiwater_vm = mm->total_vm;
862
863         if (mm->binfmt && !try_module_get(mm->binfmt->module))
864                 goto free_pt;
865
866         return mm;
867
868 free_pt:
869         /* don't put binfmt in mmput, we haven't got module yet */
870         mm->binfmt = NULL;
871         mmput(mm);
872
873 fail_nomem:
874         return NULL;
875
876 fail_nocontext:
877         /*
878          * If init_new_context() failed, we cannot use mmput() to free the mm
879          * because it calls destroy_context()
880          */
881         mm_free_pgd(mm);
882         free_mm(mm);
883         return NULL;
884 }
885
886 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
887 {
888         struct mm_struct *mm, *oldmm;
889         int retval;
890
891         tsk->min_flt = tsk->maj_flt = 0;
892         tsk->nvcsw = tsk->nivcsw = 0;
893 #ifdef CONFIG_DETECT_HUNG_TASK
894         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
895 #endif
896
897         tsk->mm = NULL;
898         tsk->active_mm = NULL;
899
900         /*
901          * Are we cloning a kernel thread?
902          *
903          * We need to steal a active VM for that..
904          */
905         oldmm = current->mm;
906         if (!oldmm)
907                 return 0;
908
909         if (clone_flags & CLONE_VM) {
910                 atomic_inc(&oldmm->mm_users);
911                 mm = oldmm;
912                 goto good_mm;
913         }
914
915         retval = -ENOMEM;
916         mm = dup_mm(tsk);
917         if (!mm)
918                 goto fail_nomem;
919
920 good_mm:
921         tsk->mm = mm;
922         tsk->active_mm = mm;
923         return 0;
924
925 fail_nomem:
926         return retval;
927 }
928
929 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
930 {
931         struct fs_struct *fs = current->fs;
932         if (clone_flags & CLONE_FS) {
933                 /* tsk->fs is already what we want */
934                 spin_lock(&fs->lock);
935                 if (fs->in_exec) {
936                         spin_unlock(&fs->lock);
937                         return -EAGAIN;
938                 }
939                 fs->users++;
940                 spin_unlock(&fs->lock);
941                 return 0;
942         }
943         tsk->fs = copy_fs_struct(fs);
944         if (!tsk->fs)
945                 return -ENOMEM;
946         return 0;
947 }
948
949 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
950 {
951         struct files_struct *oldf, *newf;
952         int error = 0;
953
954         /*
955          * A background process may not have any files ...
956          */
957         oldf = current->files;
958         if (!oldf)
959                 goto out;
960
961         if (clone_flags & CLONE_FILES) {
962                 atomic_inc(&oldf->count);
963                 goto out;
964         }
965
966         newf = dup_fd(oldf, &error);
967         if (!newf)
968                 goto out;
969
970         tsk->files = newf;
971         error = 0;
972 out:
973         return error;
974 }
975
976 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
977 {
978 #ifdef CONFIG_BLOCK
979         struct io_context *ioc = current->io_context;
980         struct io_context *new_ioc;
981
982         if (!ioc)
983                 return 0;
984         /*
985          * Share io context with parent, if CLONE_IO is set
986          */
987         if (clone_flags & CLONE_IO) {
988                 ioc_task_link(ioc);
989                 tsk->io_context = ioc;
990         } else if (ioprio_valid(ioc->ioprio)) {
991                 new_ioc = get_task_io_context(tsk, GFP_KERNEL, NUMA_NO_NODE);
992                 if (unlikely(!new_ioc))
993                         return -ENOMEM;
994
995                 new_ioc->ioprio = ioc->ioprio;
996                 put_io_context(new_ioc);
997         }
998 #endif
999         return 0;
1000 }
1001
1002 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
1003 {
1004         struct sighand_struct *sig;
1005
1006         if (clone_flags & CLONE_SIGHAND) {
1007                 atomic_inc(&current->sighand->count);
1008                 return 0;
1009         }
1010         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
1011         rcu_assign_pointer(tsk->sighand, sig);
1012         if (!sig)
1013                 return -ENOMEM;
1014         atomic_set(&sig->count, 1);
1015         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
1016         return 0;
1017 }
1018
1019 void __cleanup_sighand(struct sighand_struct *sighand)
1020 {
1021         if (atomic_dec_and_test(&sighand->count)) {
1022                 signalfd_cleanup(sighand);
1023                 kmem_cache_free(sighand_cachep, sighand);
1024         }
1025 }
1026
1027
1028 /*
1029  * Initialize POSIX timer handling for a thread group.
1030  */
1031 static void posix_cpu_timers_init_group(struct signal_struct *sig)
1032 {
1033         unsigned long cpu_limit;
1034
1035         /* Thread group counters. */
1036         thread_group_cputime_init(sig);
1037
1038         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1039         if (cpu_limit != RLIM_INFINITY) {
1040                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
1041                 sig->cputimer.running = 1;
1042         }
1043
1044         /* The timer lists. */
1045         INIT_LIST_HEAD(&sig->cpu_timers[0]);
1046         INIT_LIST_HEAD(&sig->cpu_timers[1]);
1047         INIT_LIST_HEAD(&sig->cpu_timers[2]);
1048 }
1049
1050 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
1051 {
1052         struct signal_struct *sig;
1053
1054         if (clone_flags & CLONE_THREAD)
1055                 return 0;
1056
1057         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
1058         tsk->signal = sig;
1059         if (!sig)
1060                 return -ENOMEM;
1061
1062         sig->nr_threads = 1;
1063         atomic_set(&sig->live, 1);
1064         atomic_set(&sig->sigcnt, 1);
1065         init_waitqueue_head(&sig->wait_chldexit);
1066         if (clone_flags & CLONE_NEWPID)
1067                 sig->flags |= SIGNAL_UNKILLABLE;
1068         sig->curr_target = tsk;
1069         init_sigpending(&sig->shared_pending);
1070         INIT_LIST_HEAD(&sig->posix_timers);
1071
1072         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
1073         sig->real_timer.function = it_real_fn;
1074
1075         task_lock(current->group_leader);
1076         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
1077         task_unlock(current->group_leader);
1078
1079         posix_cpu_timers_init_group(sig);
1080
1081         tty_audit_fork(sig);
1082         sched_autogroup_fork(sig);
1083
1084 #ifdef CONFIG_CGROUPS
1085         init_rwsem(&sig->group_rwsem);
1086 #endif
1087
1088         sig->oom_adj = current->signal->oom_adj;
1089         sig->oom_score_adj = current->signal->oom_score_adj;
1090         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1091
1092         sig->has_child_subreaper = current->signal->has_child_subreaper ||
1093                                    current->signal->is_child_subreaper;
1094
1095         mutex_init(&sig->cred_guard_mutex);
1096
1097         return 0;
1098 }
1099
1100 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1101 {
1102         unsigned long new_flags = p->flags;
1103
1104         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1105         new_flags |= PF_FORKNOEXEC;
1106         p->flags = new_flags;
1107 }
1108
1109 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1110 {
1111         current->clear_child_tid = tidptr;
1112
1113         return task_pid_vnr(current);
1114 }
1115
1116 static void rt_mutex_init_task(struct task_struct *p)
1117 {
1118         raw_spin_lock_init(&p->pi_lock);
1119 #ifdef CONFIG_RT_MUTEXES
1120         plist_head_init(&p->pi_waiters);
1121         p->pi_blocked_on = NULL;
1122 #endif
1123 }
1124
1125 #ifdef CONFIG_MM_OWNER
1126 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1127 {
1128         mm->owner = p;
1129 }
1130 #endif /* CONFIG_MM_OWNER */
1131
1132 /*
1133  * Initialize POSIX timer handling for a single task.
1134  */
1135 static void posix_cpu_timers_init(struct task_struct *tsk)
1136 {
1137         tsk->cputime_expires.prof_exp = 0;
1138         tsk->cputime_expires.virt_exp = 0;
1139         tsk->cputime_expires.sched_exp = 0;
1140         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1141         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1142         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1143 }
1144
1145 /*
1146  * This creates a new process as a copy of the old one,
1147  * but does not actually start it yet.
1148  *
1149  * It copies the registers, and all the appropriate
1150  * parts of the process environment (as per the clone
1151  * flags). The actual kick-off is left to the caller.
1152  */
1153 static struct task_struct *copy_process(unsigned long clone_flags,
1154                                         unsigned long stack_start,
1155                                         struct pt_regs *regs,
1156                                         unsigned long stack_size,
1157                                         int __user *child_tidptr,
1158                                         struct pid *pid,
1159                                         int trace)
1160 {
1161         int retval;
1162         struct task_struct *p;
1163         int cgroup_callbacks_done = 0;
1164
1165         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1166                 return ERR_PTR(-EINVAL);
1167
1168         /*
1169          * Thread groups must share signals as well, and detached threads
1170          * can only be started up within the thread group.
1171          */
1172         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1173                 return ERR_PTR(-EINVAL);
1174
1175         /*
1176          * Shared signal handlers imply shared VM. By way of the above,
1177          * thread groups also imply shared VM. Blocking this case allows
1178          * for various simplifications in other code.
1179          */
1180         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1181                 return ERR_PTR(-EINVAL);
1182
1183         /*
1184          * Siblings of global init remain as zombies on exit since they are
1185          * not reaped by their parent (swapper). To solve this and to avoid
1186          * multi-rooted process trees, prevent global and container-inits
1187          * from creating siblings.
1188          */
1189         if ((clone_flags & CLONE_PARENT) &&
1190                                 current->signal->flags & SIGNAL_UNKILLABLE)
1191                 return ERR_PTR(-EINVAL);
1192
1193         retval = security_task_create(clone_flags);
1194         if (retval)
1195                 goto fork_out;
1196
1197         retval = -ENOMEM;
1198         p = dup_task_struct(current);
1199         if (!p)
1200                 goto fork_out;
1201
1202         ftrace_graph_init_task(p);
1203         get_seccomp_filter(p);
1204
1205         rt_mutex_init_task(p);
1206
1207 #ifdef CONFIG_PROVE_LOCKING
1208         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1209         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1210 #endif
1211         retval = -EAGAIN;
1212         if (atomic_read(&p->real_cred->user->processes) >=
1213                         task_rlimit(p, RLIMIT_NPROC)) {
1214                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1215                     p->real_cred->user != INIT_USER)
1216                         goto bad_fork_free;
1217         }
1218         current->flags &= ~PF_NPROC_EXCEEDED;
1219
1220         retval = copy_creds(p, clone_flags);
1221         if (retval < 0)
1222                 goto bad_fork_free;
1223
1224         /*
1225          * If multiple threads are within copy_process(), then this check
1226          * triggers too late. This doesn't hurt, the check is only there
1227          * to stop root fork bombs.
1228          */
1229         retval = -EAGAIN;
1230         if (nr_threads >= max_threads)
1231                 goto bad_fork_cleanup_count;
1232
1233         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1234                 goto bad_fork_cleanup_count;
1235
1236         p->did_exec = 0;
1237         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1238         copy_flags(clone_flags, p);
1239         INIT_LIST_HEAD(&p->children);
1240         INIT_LIST_HEAD(&p->sibling);
1241         rcu_copy_process(p);
1242         p->vfork_done = NULL;
1243         spin_lock_init(&p->alloc_lock);
1244
1245         init_sigpending(&p->pending);
1246
1247         p->utime = p->stime = p->gtime = 0;
1248         p->utimescaled = p->stimescaled = 0;
1249 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1250         p->prev_utime = p->prev_stime = 0;
1251 #endif
1252 #if defined(SPLIT_RSS_COUNTING)
1253         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1254 #endif
1255
1256         p->default_timer_slack_ns = current->timer_slack_ns;
1257
1258         task_io_accounting_init(&p->ioac);
1259         acct_clear_integrals(p);
1260
1261         posix_cpu_timers_init(p);
1262
1263         do_posix_clock_monotonic_gettime(&p->start_time);
1264         p->real_start_time = p->start_time;
1265         monotonic_to_bootbased(&p->real_start_time);
1266         p->io_context = NULL;
1267         p->audit_context = NULL;
1268         if (clone_flags & CLONE_THREAD)
1269                 threadgroup_change_begin(current);
1270         cgroup_fork(p);
1271 #ifdef CONFIG_NUMA
1272         p->mempolicy = mpol_dup(p->mempolicy);
1273         if (IS_ERR(p->mempolicy)) {
1274                 retval = PTR_ERR(p->mempolicy);
1275                 p->mempolicy = NULL;
1276                 goto bad_fork_cleanup_cgroup;
1277         }
1278         mpol_fix_fork_child_flag(p);
1279 #endif
1280 #ifdef CONFIG_CPUSETS
1281         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1282         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1283         seqcount_init(&p->mems_allowed_seq);
1284 #endif
1285 #ifdef CONFIG_TRACE_IRQFLAGS
1286         p->irq_events = 0;
1287 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1288         p->hardirqs_enabled = 1;
1289 #else
1290         p->hardirqs_enabled = 0;
1291 #endif
1292         p->hardirq_enable_ip = 0;
1293         p->hardirq_enable_event = 0;
1294         p->hardirq_disable_ip = _THIS_IP_;
1295         p->hardirq_disable_event = 0;
1296         p->softirqs_enabled = 1;
1297         p->softirq_enable_ip = _THIS_IP_;
1298         p->softirq_enable_event = 0;
1299         p->softirq_disable_ip = 0;
1300         p->softirq_disable_event = 0;
1301         p->hardirq_context = 0;
1302         p->softirq_context = 0;
1303 #endif
1304 #ifdef CONFIG_LOCKDEP
1305         p->lockdep_depth = 0; /* no locks held yet */
1306         p->curr_chain_key = 0;
1307         p->lockdep_recursion = 0;
1308 #endif
1309
1310 #ifdef CONFIG_DEBUG_MUTEXES
1311         p->blocked_on = NULL; /* not blocked yet */
1312 #endif
1313 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1314         p->memcg_batch.do_batch = 0;
1315         p->memcg_batch.memcg = NULL;
1316 #endif
1317
1318         /* Perform scheduler related setup. Assign this task to a CPU. */
1319         sched_fork(p);
1320
1321         retval = perf_event_init_task(p);
1322         if (retval)
1323                 goto bad_fork_cleanup_policy;
1324         retval = audit_alloc(p);
1325         if (retval)
1326                 goto bad_fork_cleanup_policy;
1327         /* copy all the process information */
1328         retval = copy_semundo(clone_flags, p);
1329         if (retval)
1330                 goto bad_fork_cleanup_audit;
1331         retval = copy_files(clone_flags, p);
1332         if (retval)
1333                 goto bad_fork_cleanup_semundo;
1334         retval = copy_fs(clone_flags, p);
1335         if (retval)
1336                 goto bad_fork_cleanup_files;
1337         retval = copy_sighand(clone_flags, p);
1338         if (retval)
1339                 goto bad_fork_cleanup_fs;
1340         retval = copy_signal(clone_flags, p);
1341         if (retval)
1342                 goto bad_fork_cleanup_sighand;
1343         retval = copy_mm(clone_flags, p);
1344         if (retval)
1345                 goto bad_fork_cleanup_signal;
1346         retval = copy_namespaces(clone_flags, p);
1347         if (retval)
1348                 goto bad_fork_cleanup_mm;
1349         retval = copy_io(clone_flags, p);
1350         if (retval)
1351                 goto bad_fork_cleanup_namespaces;
1352         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1353         if (retval)
1354                 goto bad_fork_cleanup_io;
1355
1356         if (pid != &init_struct_pid) {
1357                 retval = -ENOMEM;
1358                 pid = alloc_pid(p->nsproxy->pid_ns);
1359                 if (!pid)
1360                         goto bad_fork_cleanup_io;
1361         }
1362
1363         p->pid = pid_nr(pid);
1364         p->tgid = p->pid;
1365         if (clone_flags & CLONE_THREAD)
1366                 p->tgid = current->tgid;
1367
1368         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1369         /*
1370          * Clear TID on mm_release()?
1371          */
1372         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1373 #ifdef CONFIG_BLOCK
1374         p->plug = NULL;
1375 #endif
1376 #ifdef CONFIG_FUTEX
1377         p->robust_list = NULL;
1378 #ifdef CONFIG_COMPAT
1379         p->compat_robust_list = NULL;
1380 #endif
1381         INIT_LIST_HEAD(&p->pi_state_list);
1382         p->pi_state_cache = NULL;
1383 #endif
1384         uprobe_copy_process(p);
1385         /*
1386          * sigaltstack should be cleared when sharing the same VM
1387          */
1388         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1389                 p->sas_ss_sp = p->sas_ss_size = 0;
1390
1391         /*
1392          * Syscall tracing and stepping should be turned off in the
1393          * child regardless of CLONE_PTRACE.
1394          */
1395         user_disable_single_step(p);
1396         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1397 #ifdef TIF_SYSCALL_EMU
1398         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1399 #endif
1400         clear_all_latency_tracing(p);
1401
1402         /* ok, now we should be set up.. */
1403         if (clone_flags & CLONE_THREAD)
1404                 p->exit_signal = -1;
1405         else if (clone_flags & CLONE_PARENT)
1406                 p->exit_signal = current->group_leader->exit_signal;
1407         else
1408                 p->exit_signal = (clone_flags & CSIGNAL);
1409
1410         p->pdeath_signal = 0;
1411         p->exit_state = 0;
1412
1413         p->nr_dirtied = 0;
1414         p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
1415         p->dirty_paused_when = 0;
1416
1417         /*
1418          * Ok, make it visible to the rest of the system.
1419          * We dont wake it up yet.
1420          */
1421         p->group_leader = p;
1422         INIT_LIST_HEAD(&p->thread_group);
1423         p->task_works = NULL;
1424
1425         /* Now that the task is set up, run cgroup callbacks if
1426          * necessary. We need to run them before the task is visible
1427          * on the tasklist. */
1428         cgroup_fork_callbacks(p);
1429         cgroup_callbacks_done = 1;
1430
1431         /* Need tasklist lock for parent etc handling! */
1432         write_lock_irq(&tasklist_lock);
1433
1434         /* CLONE_PARENT re-uses the old parent */
1435         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1436                 p->real_parent = current->real_parent;
1437                 p->parent_exec_id = current->parent_exec_id;
1438         } else {
1439                 p->real_parent = current;
1440                 p->parent_exec_id = current->self_exec_id;
1441         }
1442
1443         spin_lock(&current->sighand->siglock);
1444
1445         /*
1446          * Process group and session signals need to be delivered to just the
1447          * parent before the fork or both the parent and the child after the
1448          * fork. Restart if a signal comes in before we add the new process to
1449          * it's process group.
1450          * A fatal signal pending means that current will exit, so the new
1451          * thread can't slip out of an OOM kill (or normal SIGKILL).
1452         */
1453         recalc_sigpending();
1454         if (signal_pending(current)) {
1455                 spin_unlock(&current->sighand->siglock);
1456                 write_unlock_irq(&tasklist_lock);
1457                 retval = -ERESTARTNOINTR;
1458                 goto bad_fork_free_pid;
1459         }
1460
1461         if (clone_flags & CLONE_THREAD) {
1462                 current->signal->nr_threads++;
1463                 atomic_inc(&current->signal->live);
1464                 atomic_inc(&current->signal->sigcnt);
1465                 p->group_leader = current->group_leader;
1466                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1467         }
1468
1469         if (likely(p->pid)) {
1470                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1471
1472                 if (thread_group_leader(p)) {
1473                         if (is_child_reaper(pid))
1474                                 p->nsproxy->pid_ns->child_reaper = p;
1475
1476                         p->signal->leader_pid = pid;
1477                         p->signal->tty = tty_kref_get(current->signal->tty);
1478                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1479                         attach_pid(p, PIDTYPE_SID, task_session(current));
1480                         list_add_tail(&p->sibling, &p->real_parent->children);
1481                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1482                         __this_cpu_inc(process_counts);
1483                 }
1484                 attach_pid(p, PIDTYPE_PID, pid);
1485                 nr_threads++;
1486         }
1487
1488         total_forks++;
1489         spin_unlock(&current->sighand->siglock);
1490         write_unlock_irq(&tasklist_lock);
1491         proc_fork_connector(p);
1492         cgroup_post_fork(p);
1493         if (clone_flags & CLONE_THREAD)
1494                 threadgroup_change_end(current);
1495         perf_event_fork(p);
1496
1497         trace_task_newtask(p, clone_flags);
1498
1499         return p;
1500
1501 bad_fork_free_pid:
1502         if (pid != &init_struct_pid)
1503                 free_pid(pid);
1504 bad_fork_cleanup_io:
1505         if (p->io_context)
1506                 exit_io_context(p);
1507 bad_fork_cleanup_namespaces:
1508         if (unlikely(clone_flags & CLONE_NEWPID))
1509                 pid_ns_release_proc(p->nsproxy->pid_ns);
1510         exit_task_namespaces(p);
1511 bad_fork_cleanup_mm:
1512         if (p->mm)
1513                 mmput(p->mm);
1514 bad_fork_cleanup_signal:
1515         if (!(clone_flags & CLONE_THREAD))
1516                 free_signal_struct(p->signal);
1517 bad_fork_cleanup_sighand:
1518         __cleanup_sighand(p->sighand);
1519 bad_fork_cleanup_fs:
1520         exit_fs(p); /* blocking */
1521 bad_fork_cleanup_files:
1522         exit_files(p); /* blocking */
1523 bad_fork_cleanup_semundo:
1524         exit_sem(p);
1525 bad_fork_cleanup_audit:
1526         audit_free(p);
1527 bad_fork_cleanup_policy:
1528         perf_event_free_task(p);
1529 #ifdef CONFIG_NUMA
1530         mpol_put(p->mempolicy);
1531 bad_fork_cleanup_cgroup:
1532 #endif
1533         if (clone_flags & CLONE_THREAD)
1534                 threadgroup_change_end(current);
1535         cgroup_exit(p, cgroup_callbacks_done);
1536         delayacct_tsk_free(p);
1537         module_put(task_thread_info(p)->exec_domain->module);
1538 bad_fork_cleanup_count:
1539         atomic_dec(&p->cred->user->processes);
1540         exit_creds(p);
1541 bad_fork_free:
1542         free_task(p);
1543 fork_out:
1544         return ERR_PTR(retval);
1545 }
1546
1547 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1548 {
1549         memset(regs, 0, sizeof(struct pt_regs));
1550         return regs;
1551 }
1552
1553 static inline void init_idle_pids(struct pid_link *links)
1554 {
1555         enum pid_type type;
1556
1557         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1558                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1559                 links[type].pid = &init_struct_pid;
1560         }
1561 }
1562
1563 struct task_struct * __cpuinit fork_idle(int cpu)
1564 {
1565         struct task_struct *task;
1566         struct pt_regs regs;
1567
1568         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1569                             &init_struct_pid, 0);
1570         if (!IS_ERR(task)) {
1571                 init_idle_pids(task->pids);
1572                 init_idle(task, cpu);
1573         }
1574
1575         return task;
1576 }
1577
1578 /*
1579  *  Ok, this is the main fork-routine.
1580  *
1581  * It copies the process, and if successful kick-starts
1582  * it and waits for it to finish using the VM if required.
1583  */
1584 long do_fork(unsigned long clone_flags,
1585               unsigned long stack_start,
1586               struct pt_regs *regs,
1587               unsigned long stack_size,
1588               int __user *parent_tidptr,
1589               int __user *child_tidptr)
1590 {
1591         struct task_struct *p;
1592         int trace = 0;
1593         long nr;
1594
1595         /*
1596          * Do some preliminary argument and permissions checking before we
1597          * actually start allocating stuff
1598          */
1599         if (clone_flags & CLONE_NEWUSER) {
1600                 if (clone_flags & CLONE_THREAD)
1601                         return -EINVAL;
1602                 /* hopefully this check will go away when userns support is
1603                  * complete
1604                  */
1605                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1606                                 !capable(CAP_SETGID))
1607                         return -EPERM;
1608         }
1609
1610         /*
1611          * Determine whether and which event to report to ptracer.  When
1612          * called from kernel_thread or CLONE_UNTRACED is explicitly
1613          * requested, no event is reported; otherwise, report if the event
1614          * for the type of forking is enabled.
1615          */
1616         if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1617                 if (clone_flags & CLONE_VFORK)
1618                         trace = PTRACE_EVENT_VFORK;
1619                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1620                         trace = PTRACE_EVENT_CLONE;
1621                 else
1622                         trace = PTRACE_EVENT_FORK;
1623
1624                 if (likely(!ptrace_event_enabled(current, trace)))
1625                         trace = 0;
1626         }
1627
1628         p = copy_process(clone_flags, stack_start, regs, stack_size,
1629                          child_tidptr, NULL, trace);
1630         /*
1631          * Do this prior waking up the new thread - the thread pointer
1632          * might get invalid after that point, if the thread exits quickly.
1633          */
1634         if (!IS_ERR(p)) {
1635                 struct completion vfork;
1636
1637                 trace_sched_process_fork(current, p);
1638
1639                 nr = task_pid_vnr(p);
1640
1641                 if (clone_flags & CLONE_PARENT_SETTID)
1642                         put_user(nr, parent_tidptr);
1643
1644                 if (clone_flags & CLONE_VFORK) {
1645                         p->vfork_done = &vfork;
1646                         init_completion(&vfork);
1647                         get_task_struct(p);
1648                 }
1649
1650                 wake_up_new_task(p);
1651
1652                 /* forking complete and child started to run, tell ptracer */
1653                 if (unlikely(trace))
1654                         ptrace_event(trace, nr);
1655
1656                 if (clone_flags & CLONE_VFORK) {
1657                         if (!wait_for_vfork_done(p, &vfork))
1658                                 ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1659                 }
1660         } else {
1661                 nr = PTR_ERR(p);
1662         }
1663         return nr;
1664 }
1665
1666 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1667 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1668 #endif
1669
1670 static void sighand_ctor(void *data)
1671 {
1672         struct sighand_struct *sighand = data;
1673
1674         spin_lock_init(&sighand->siglock);
1675         init_waitqueue_head(&sighand->signalfd_wqh);
1676 }
1677
1678 void __init proc_caches_init(void)
1679 {
1680         sighand_cachep = kmem_cache_create("sighand_cache",
1681                         sizeof(struct sighand_struct), 0,
1682                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1683                         SLAB_NOTRACK, sighand_ctor);
1684         signal_cachep = kmem_cache_create("signal_cache",
1685                         sizeof(struct signal_struct), 0,
1686                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1687         files_cachep = kmem_cache_create("files_cache",
1688                         sizeof(struct files_struct), 0,
1689                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1690         fs_cachep = kmem_cache_create("fs_cache",
1691                         sizeof(struct fs_struct), 0,
1692                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1693         /*
1694          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1695          * whole struct cpumask for the OFFSTACK case. We could change
1696          * this to *only* allocate as much of it as required by the
1697          * maximum number of CPU's we can ever have.  The cpumask_allocation
1698          * is at the end of the structure, exactly for that reason.
1699          */
1700         mm_cachep = kmem_cache_create("mm_struct",
1701                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1702                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1703         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1704         mmap_init();
1705         nsproxy_cache_init();
1706 }
1707
1708 /*
1709  * Check constraints on flags passed to the unshare system call.
1710  */
1711 static int check_unshare_flags(unsigned long unshare_flags)
1712 {
1713         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1714                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1715                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1716                 return -EINVAL;
1717         /*
1718          * Not implemented, but pretend it works if there is nothing to
1719          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1720          * needs to unshare vm.
1721          */
1722         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1723                 /* FIXME: get_task_mm() increments ->mm_users */
1724                 if (atomic_read(&current->mm->mm_users) > 1)
1725                         return -EINVAL;
1726         }
1727
1728         return 0;
1729 }
1730
1731 /*
1732  * Unshare the filesystem structure if it is being shared
1733  */
1734 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1735 {
1736         struct fs_struct *fs = current->fs;
1737
1738         if (!(unshare_flags & CLONE_FS) || !fs)
1739                 return 0;
1740
1741         /* don't need lock here; in the worst case we'll do useless copy */
1742         if (fs->users == 1)
1743                 return 0;
1744
1745         *new_fsp = copy_fs_struct(fs);
1746         if (!*new_fsp)
1747                 return -ENOMEM;
1748
1749         return 0;
1750 }
1751
1752 /*
1753  * Unshare file descriptor table if it is being shared
1754  */
1755 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1756 {
1757         struct files_struct *fd = current->files;
1758         int error = 0;
1759
1760         if ((unshare_flags & CLONE_FILES) &&
1761             (fd && atomic_read(&fd->count) > 1)) {
1762                 *new_fdp = dup_fd(fd, &error);
1763                 if (!*new_fdp)
1764                         return error;
1765         }
1766
1767         return 0;
1768 }
1769
1770 /*
1771  * unshare allows a process to 'unshare' part of the process
1772  * context which was originally shared using clone.  copy_*
1773  * functions used by do_fork() cannot be used here directly
1774  * because they modify an inactive task_struct that is being
1775  * constructed. Here we are modifying the current, active,
1776  * task_struct.
1777  */
1778 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1779 {
1780         struct fs_struct *fs, *new_fs = NULL;
1781         struct files_struct *fd, *new_fd = NULL;
1782         struct nsproxy *new_nsproxy = NULL;
1783         int do_sysvsem = 0;
1784         int err;
1785
1786         err = check_unshare_flags(unshare_flags);
1787         if (err)
1788                 goto bad_unshare_out;
1789
1790         /*
1791          * If unsharing namespace, must also unshare filesystem information.
1792          */
1793         if (unshare_flags & CLONE_NEWNS)
1794                 unshare_flags |= CLONE_FS;
1795         /*
1796          * CLONE_NEWIPC must also detach from the undolist: after switching
1797          * to a new ipc namespace, the semaphore arrays from the old
1798          * namespace are unreachable.
1799          */
1800         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1801                 do_sysvsem = 1;
1802         err = unshare_fs(unshare_flags, &new_fs);
1803         if (err)
1804                 goto bad_unshare_out;
1805         err = unshare_fd(unshare_flags, &new_fd);
1806         if (err)
1807                 goto bad_unshare_cleanup_fs;
1808         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1809         if (err)
1810                 goto bad_unshare_cleanup_fd;
1811
1812         if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1813                 if (do_sysvsem) {
1814                         /*
1815                          * CLONE_SYSVSEM is equivalent to sys_exit().
1816                          */
1817                         exit_sem(current);
1818                 }
1819
1820                 if (new_nsproxy) {
1821                         switch_task_namespaces(current, new_nsproxy);
1822                         new_nsproxy = NULL;
1823                 }
1824
1825                 task_lock(current);
1826
1827                 if (new_fs) {
1828                         fs = current->fs;
1829                         spin_lock(&fs->lock);
1830                         current->fs = new_fs;
1831                         if (--fs->users)
1832                                 new_fs = NULL;
1833                         else
1834                                 new_fs = fs;
1835                         spin_unlock(&fs->lock);
1836                 }
1837
1838                 if (new_fd) {
1839                         fd = current->files;
1840                         current->files = new_fd;
1841                         new_fd = fd;
1842                 }
1843
1844                 task_unlock(current);
1845         }
1846
1847         if (new_nsproxy)
1848                 put_nsproxy(new_nsproxy);
1849
1850 bad_unshare_cleanup_fd:
1851         if (new_fd)
1852                 put_files_struct(new_fd);
1853
1854 bad_unshare_cleanup_fs:
1855         if (new_fs)
1856                 free_fs_struct(new_fs);
1857
1858 bad_unshare_out:
1859         return err;
1860 }
1861
1862 /*
1863  *      Helper to unshare the files of the current task.
1864  *      We don't want to expose copy_files internals to
1865  *      the exec layer of the kernel.
1866  */
1867
1868 int unshare_files(struct files_struct **displaced)
1869 {
1870         struct task_struct *task = current;
1871         struct files_struct *copy = NULL;
1872         int error;
1873
1874         error = unshare_fd(CLONE_FILES, &copy);
1875         if (error || !copy) {
1876                 *displaced = NULL;
1877                 return error;
1878         }
1879         *displaced = task->files;
1880         task_lock(task);
1881         task->files = copy;
1882         task_unlock(task);
1883         return 0;
1884 }