kernel/printk: do not turn off bootconsole in printk_late_init() if keep_bootcon
[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/futex.h>
41 #include <linux/compat.h>
42 #include <linux/kthread.h>
43 #include <linux/task_io_accounting_ops.h>
44 #include <linux/rcupdate.h>
45 #include <linux/ptrace.h>
46 #include <linux/mount.h>
47 #include <linux/audit.h>
48 #include <linux/memcontrol.h>
49 #include <linux/ftrace.h>
50 #include <linux/profile.h>
51 #include <linux/rmap.h>
52 #include <linux/ksm.h>
53 #include <linux/acct.h>
54 #include <linux/tsacct_kern.h>
55 #include <linux/cn_proc.h>
56 #include <linux/freezer.h>
57 #include <linux/delayacct.h>
58 #include <linux/taskstats_kern.h>
59 #include <linux/random.h>
60 #include <linux/tty.h>
61 #include <linux/blkdev.h>
62 #include <linux/fs_struct.h>
63 #include <linux/magic.h>
64 #include <linux/perf_event.h>
65 #include <linux/posix-timers.h>
66 #include <linux/user-return-notifier.h>
67 #include <linux/oom.h>
68 #include <linux/khugepaged.h>
69
70 #include <asm/pgtable.h>
71 #include <asm/pgalloc.h>
72 #include <asm/uaccess.h>
73 #include <asm/mmu_context.h>
74 #include <asm/cacheflush.h>
75 #include <asm/tlbflush.h>
76
77 #include <trace/events/sched.h>
78
79 /*
80  * Protected counters by write_lock_irq(&tasklist_lock)
81  */
82 unsigned long total_forks;      /* Handle normal Linux uptimes. */
83 int nr_threads;                 /* The idle threads do not count.. */
84
85 int max_threads;                /* tunable limit on nr_threads */
86
87 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
88
89 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
90
91 #ifdef CONFIG_PROVE_RCU
92 int lockdep_tasklist_lock_is_held(void)
93 {
94         return lockdep_is_held(&tasklist_lock);
95 }
96 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
97 #endif /* #ifdef CONFIG_PROVE_RCU */
98
99 int nr_processes(void)
100 {
101         int cpu;
102         int total = 0;
103
104         for_each_possible_cpu(cpu)
105                 total += per_cpu(process_counts, cpu);
106
107         return total;
108 }
109
110 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
111 # define alloc_task_struct_node(node)           \
112                 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
113 # define free_task_struct(tsk)                  \
114                 kmem_cache_free(task_struct_cachep, (tsk))
115 static struct kmem_cache *task_struct_cachep;
116 #endif
117
118 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
119 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
120                                                   int node)
121 {
122 #ifdef CONFIG_DEBUG_STACK_USAGE
123         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
124 #else
125         gfp_t mask = GFP_KERNEL;
126 #endif
127         struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
128
129         return page ? page_address(page) : NULL;
130 }
131
132 static inline void free_thread_info(struct thread_info *ti)
133 {
134         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
135 }
136 #endif
137
138 /* SLAB cache for signal_struct structures (tsk->signal) */
139 static struct kmem_cache *signal_cachep;
140
141 /* SLAB cache for sighand_struct structures (tsk->sighand) */
142 struct kmem_cache *sighand_cachep;
143
144 /* SLAB cache for files_struct structures (tsk->files) */
145 struct kmem_cache *files_cachep;
146
147 /* SLAB cache for fs_struct structures (tsk->fs) */
148 struct kmem_cache *fs_cachep;
149
150 /* SLAB cache for vm_area_struct structures */
151 struct kmem_cache *vm_area_cachep;
152
153 /* SLAB cache for mm_struct structures (tsk->mm) */
154 static struct kmem_cache *mm_cachep;
155
156 static void account_kernel_stack(struct thread_info *ti, int account)
157 {
158         struct zone *zone = page_zone(virt_to_page(ti));
159
160         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
161 }
162
163 void free_task(struct task_struct *tsk)
164 {
165         prop_local_destroy_single(&tsk->dirties);
166         account_kernel_stack(tsk->stack, -1);
167         free_thread_info(tsk->stack);
168         rt_mutex_debug_task_free(tsk);
169         ftrace_graph_exit_task(tsk);
170         free_task_struct(tsk);
171 }
172 EXPORT_SYMBOL(free_task);
173
174 static inline void free_signal_struct(struct signal_struct *sig)
175 {
176         taskstats_tgid_free(sig);
177         sched_autogroup_exit(sig);
178         kmem_cache_free(signal_cachep, sig);
179 }
180
181 static inline void put_signal_struct(struct signal_struct *sig)
182 {
183         if (atomic_dec_and_test(&sig->sigcnt))
184                 free_signal_struct(sig);
185 }
186
187 void __put_task_struct(struct task_struct *tsk)
188 {
189         WARN_ON(!tsk->exit_state);
190         WARN_ON(atomic_read(&tsk->usage));
191         WARN_ON(tsk == current);
192
193         exit_creds(tsk);
194         delayacct_tsk_free(tsk);
195         put_signal_struct(tsk->signal);
196
197         if (!profile_handoff_task(tsk))
198                 free_task(tsk);
199 }
200 EXPORT_SYMBOL_GPL(__put_task_struct);
201
202 /*
203  * macro override instead of weak attribute alias, to workaround
204  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
205  */
206 #ifndef arch_task_cache_init
207 #define arch_task_cache_init()
208 #endif
209
210 void __init fork_init(unsigned long mempages)
211 {
212 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
213 #ifndef ARCH_MIN_TASKALIGN
214 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
215 #endif
216         /* create a slab on which task_structs can be allocated */
217         task_struct_cachep =
218                 kmem_cache_create("task_struct", sizeof(struct task_struct),
219                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
220 #endif
221
222         /* do the arch specific task caches init */
223         arch_task_cache_init();
224
225         /*
226          * The default maximum number of threads is set to a safe
227          * value: the thread structures can take up at most half
228          * of memory.
229          */
230         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
231
232         /*
233          * we need to allow at least 20 threads to boot a system
234          */
235         if (max_threads < 20)
236                 max_threads = 20;
237
238         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
239         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
240         init_task.signal->rlim[RLIMIT_SIGPENDING] =
241                 init_task.signal->rlim[RLIMIT_NPROC];
242 }
243
244 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
245                                                struct task_struct *src)
246 {
247         *dst = *src;
248         return 0;
249 }
250
251 static struct task_struct *dup_task_struct(struct task_struct *orig)
252 {
253         struct task_struct *tsk;
254         struct thread_info *ti;
255         unsigned long *stackend;
256         int node = tsk_fork_get_node(orig);
257         int err;
258
259         prepare_to_copy(orig);
260
261         tsk = alloc_task_struct_node(node);
262         if (!tsk)
263                 return NULL;
264
265         ti = alloc_thread_info_node(tsk, node);
266         if (!ti) {
267                 free_task_struct(tsk);
268                 return NULL;
269         }
270
271         err = arch_dup_task_struct(tsk, orig);
272         if (err)
273                 goto out;
274
275         tsk->stack = ti;
276
277         err = prop_local_init_single(&tsk->dirties);
278         if (err)
279                 goto out;
280
281         setup_thread_stack(tsk, orig);
282         clear_user_return_notifier(tsk);
283         clear_tsk_need_resched(tsk);
284         stackend = end_of_stack(tsk);
285         *stackend = STACK_END_MAGIC;    /* for overflow detection */
286
287 #ifdef CONFIG_CC_STACKPROTECTOR
288         tsk->stack_canary = get_random_int();
289 #endif
290
291         /*
292          * One for us, one for whoever does the "release_task()" (usually
293          * parent)
294          */
295         atomic_set(&tsk->usage, 2);
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                         mutex_lock(&mapping->i_mmap_mutex);
387                         if (tmp->vm_flags & VM_SHARED)
388                                 mapping->i_mmap_writable++;
389                         flush_dcache_mmap_lock(mapping);
390                         /* insert tmp into the share list, just after mpnt */
391                         vma_prio_tree_add(tmp, mpnt);
392                         flush_dcache_mmap_unlock(mapping);
393                         mutex_unlock(&mapping->i_mmap_mutex);
394                 }
395
396                 /*
397                  * Clear hugetlb-related page reserves for children. This only
398                  * affects MAP_PRIVATE mappings. Faults generated by the child
399                  * are not guaranteed to succeed, even if read-only
400                  */
401                 if (is_vm_hugetlb_page(tmp))
402                         reset_vma_resv_huge_pages(tmp);
403
404                 /*
405                  * Link in the new vma and copy the page table entries.
406                  */
407                 *pprev = tmp;
408                 pprev = &tmp->vm_next;
409                 tmp->vm_prev = prev;
410                 prev = tmp;
411
412                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
413                 rb_link = &tmp->vm_rb.rb_right;
414                 rb_parent = &tmp->vm_rb;
415
416                 mm->map_count++;
417                 retval = copy_page_range(mm, oldmm, mpnt);
418
419                 if (tmp->vm_ops && tmp->vm_ops->open)
420                         tmp->vm_ops->open(tmp);
421
422                 if (retval)
423                         goto out;
424         }
425         /* a new mm has just been created */
426         arch_dup_mmap(oldmm, mm);
427         retval = 0;
428 out:
429         up_write(&mm->mmap_sem);
430         flush_tlb_mm(oldmm);
431         up_write(&oldmm->mmap_sem);
432         return retval;
433 fail_nomem_anon_vma_fork:
434         mpol_put(pol);
435 fail_nomem_policy:
436         kmem_cache_free(vm_area_cachep, tmp);
437 fail_nomem:
438         retval = -ENOMEM;
439         vm_unacct_memory(charge);
440         goto out;
441 }
442
443 static inline int mm_alloc_pgd(struct mm_struct *mm)
444 {
445         mm->pgd = pgd_alloc(mm);
446         if (unlikely(!mm->pgd))
447                 return -ENOMEM;
448         return 0;
449 }
450
451 static inline void mm_free_pgd(struct mm_struct *mm)
452 {
453         pgd_free(mm, mm->pgd);
454 }
455 #else
456 #define dup_mmap(mm, oldmm)     (0)
457 #define mm_alloc_pgd(mm)        (0)
458 #define mm_free_pgd(mm)
459 #endif /* CONFIG_MMU */
460
461 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
462
463 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
464 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
465
466 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
467
468 static int __init coredump_filter_setup(char *s)
469 {
470         default_dump_filter =
471                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
472                 MMF_DUMP_FILTER_MASK;
473         return 1;
474 }
475
476 __setup("coredump_filter=", coredump_filter_setup);
477
478 #include <linux/init_task.h>
479
480 static void mm_init_aio(struct mm_struct *mm)
481 {
482 #ifdef CONFIG_AIO
483         spin_lock_init(&mm->ioctx_lock);
484         INIT_HLIST_HEAD(&mm->ioctx_list);
485 #endif
486 }
487
488 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
489 {
490         atomic_set(&mm->mm_users, 1);
491         atomic_set(&mm->mm_count, 1);
492         init_rwsem(&mm->mmap_sem);
493         INIT_LIST_HEAD(&mm->mmlist);
494         mm->flags = (current->mm) ?
495                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
496         mm->core_state = NULL;
497         mm->nr_ptes = 0;
498         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
499         spin_lock_init(&mm->page_table_lock);
500         mm->free_area_cache = TASK_UNMAPPED_BASE;
501         mm->cached_hole_size = ~0UL;
502         mm_init_aio(mm);
503         mm_init_owner(mm, p);
504         atomic_set(&mm->oom_disable_count, 0);
505
506         if (likely(!mm_alloc_pgd(mm))) {
507                 mm->def_flags = 0;
508                 mmu_notifier_mm_init(mm);
509                 return mm;
510         }
511
512         free_mm(mm);
513         return NULL;
514 }
515
516 /*
517  * Allocate and initialize an mm_struct.
518  */
519 struct mm_struct *mm_alloc(void)
520 {
521         struct mm_struct *mm;
522
523         mm = allocate_mm();
524         if (!mm)
525                 return NULL;
526
527         memset(mm, 0, sizeof(*mm));
528         mm_init_cpumask(mm);
529         return mm_init(mm, current);
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  * We added or removed a vma mapping the executable. The vmas are only mapped
578  * during exec and are not mapped with the mmap system call.
579  * Callers must hold down_write() on the mm's mmap_sem for these
580  */
581 void added_exe_file_vma(struct mm_struct *mm)
582 {
583         mm->num_exe_file_vmas++;
584 }
585
586 void removed_exe_file_vma(struct mm_struct *mm)
587 {
588         mm->num_exe_file_vmas--;
589         if ((mm->num_exe_file_vmas == 0) && mm->exe_file) {
590                 fput(mm->exe_file);
591                 mm->exe_file = NULL;
592         }
593
594 }
595
596 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
597 {
598         if (new_exe_file)
599                 get_file(new_exe_file);
600         if (mm->exe_file)
601                 fput(mm->exe_file);
602         mm->exe_file = new_exe_file;
603         mm->num_exe_file_vmas = 0;
604 }
605
606 struct file *get_mm_exe_file(struct mm_struct *mm)
607 {
608         struct file *exe_file;
609
610         /* We need mmap_sem to protect against races with removal of
611          * VM_EXECUTABLE vmas */
612         down_read(&mm->mmap_sem);
613         exe_file = mm->exe_file;
614         if (exe_file)
615                 get_file(exe_file);
616         up_read(&mm->mmap_sem);
617         return exe_file;
618 }
619
620 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
621 {
622         /* It's safe to write the exe_file pointer without exe_file_lock because
623          * this is called during fork when the task is not yet in /proc */
624         newmm->exe_file = get_mm_exe_file(oldmm);
625 }
626
627 /**
628  * get_task_mm - acquire a reference to the task's mm
629  *
630  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
631  * this kernel workthread has transiently adopted a user mm with use_mm,
632  * to do its AIO) is not set and if so returns a reference to it, after
633  * bumping up the use count.  User must release the mm via mmput()
634  * after use.  Typically used by /proc and ptrace.
635  */
636 struct mm_struct *get_task_mm(struct task_struct *task)
637 {
638         struct mm_struct *mm;
639
640         task_lock(task);
641         mm = task->mm;
642         if (mm) {
643                 if (task->flags & PF_KTHREAD)
644                         mm = NULL;
645                 else
646                         atomic_inc(&mm->mm_users);
647         }
648         task_unlock(task);
649         return mm;
650 }
651 EXPORT_SYMBOL_GPL(get_task_mm);
652
653 /* Please note the differences between mmput and mm_release.
654  * mmput is called whenever we stop holding onto a mm_struct,
655  * error success whatever.
656  *
657  * mm_release is called after a mm_struct has been removed
658  * from the current process.
659  *
660  * This difference is important for error handling, when we
661  * only half set up a mm_struct for a new process and need to restore
662  * the old one.  Because we mmput the new mm_struct before
663  * restoring the old one. . .
664  * Eric Biederman 10 January 1998
665  */
666 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
667 {
668         struct completion *vfork_done = tsk->vfork_done;
669
670         /* Get rid of any futexes when releasing the mm */
671 #ifdef CONFIG_FUTEX
672         if (unlikely(tsk->robust_list)) {
673                 exit_robust_list(tsk);
674                 tsk->robust_list = NULL;
675         }
676 #ifdef CONFIG_COMPAT
677         if (unlikely(tsk->compat_robust_list)) {
678                 compat_exit_robust_list(tsk);
679                 tsk->compat_robust_list = NULL;
680         }
681 #endif
682         if (unlikely(!list_empty(&tsk->pi_state_list)))
683                 exit_pi_state_list(tsk);
684 #endif
685
686         /* Get rid of any cached register state */
687         deactivate_mm(tsk, mm);
688
689         /* notify parent sleeping on vfork() */
690         if (vfork_done) {
691                 tsk->vfork_done = NULL;
692                 complete(vfork_done);
693         }
694
695         /*
696          * If we're exiting normally, clear a user-space tid field if
697          * requested.  We leave this alone when dying by signal, to leave
698          * the value intact in a core dump, and to save the unnecessary
699          * trouble otherwise.  Userland only wants this done for a sys_exit.
700          */
701         if (tsk->clear_child_tid) {
702                 if (!(tsk->flags & PF_SIGNALED) &&
703                     atomic_read(&mm->mm_users) > 1) {
704                         /*
705                          * We don't check the error code - if userspace has
706                          * not set up a proper pointer then tough luck.
707                          */
708                         put_user(0, tsk->clear_child_tid);
709                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
710                                         1, NULL, NULL, 0);
711                 }
712                 tsk->clear_child_tid = NULL;
713         }
714 }
715
716 /*
717  * Allocate a new mm structure and copy contents from the
718  * mm structure of the passed in task structure.
719  */
720 struct mm_struct *dup_mm(struct task_struct *tsk)
721 {
722         struct mm_struct *mm, *oldmm = current->mm;
723         int err;
724
725         if (!oldmm)
726                 return NULL;
727
728         mm = allocate_mm();
729         if (!mm)
730                 goto fail_nomem;
731
732         memcpy(mm, oldmm, sizeof(*mm));
733         mm_init_cpumask(mm);
734
735         /* Initializing for Swap token stuff */
736         mm->token_priority = 0;
737         mm->last_interval = 0;
738
739 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
740         mm->pmd_huge_pte = NULL;
741 #endif
742
743         if (!mm_init(mm, tsk))
744                 goto fail_nomem;
745
746         if (init_new_context(tsk, mm))
747                 goto fail_nocontext;
748
749         dup_mm_exe_file(oldmm, mm);
750
751         err = dup_mmap(mm, oldmm);
752         if (err)
753                 goto free_pt;
754
755         mm->hiwater_rss = get_mm_rss(mm);
756         mm->hiwater_vm = mm->total_vm;
757
758         if (mm->binfmt && !try_module_get(mm->binfmt->module))
759                 goto free_pt;
760
761         return mm;
762
763 free_pt:
764         /* don't put binfmt in mmput, we haven't got module yet */
765         mm->binfmt = NULL;
766         mmput(mm);
767
768 fail_nomem:
769         return NULL;
770
771 fail_nocontext:
772         /*
773          * If init_new_context() failed, we cannot use mmput() to free the mm
774          * because it calls destroy_context()
775          */
776         mm_free_pgd(mm);
777         free_mm(mm);
778         return NULL;
779 }
780
781 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
782 {
783         struct mm_struct *mm, *oldmm;
784         int retval;
785
786         tsk->min_flt = tsk->maj_flt = 0;
787         tsk->nvcsw = tsk->nivcsw = 0;
788 #ifdef CONFIG_DETECT_HUNG_TASK
789         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
790 #endif
791
792         tsk->mm = NULL;
793         tsk->active_mm = NULL;
794
795         /*
796          * Are we cloning a kernel thread?
797          *
798          * We need to steal a active VM for that..
799          */
800         oldmm = current->mm;
801         if (!oldmm)
802                 return 0;
803
804         if (clone_flags & CLONE_VM) {
805                 atomic_inc(&oldmm->mm_users);
806                 mm = oldmm;
807                 goto good_mm;
808         }
809
810         retval = -ENOMEM;
811         mm = dup_mm(tsk);
812         if (!mm)
813                 goto fail_nomem;
814
815 good_mm:
816         /* Initializing for Swap token stuff */
817         mm->token_priority = 0;
818         mm->last_interval = 0;
819         if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
820                 atomic_inc(&mm->oom_disable_count);
821
822         tsk->mm = mm;
823         tsk->active_mm = mm;
824         return 0;
825
826 fail_nomem:
827         return retval;
828 }
829
830 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
831 {
832         struct fs_struct *fs = current->fs;
833         if (clone_flags & CLONE_FS) {
834                 /* tsk->fs is already what we want */
835                 spin_lock(&fs->lock);
836                 if (fs->in_exec) {
837                         spin_unlock(&fs->lock);
838                         return -EAGAIN;
839                 }
840                 fs->users++;
841                 spin_unlock(&fs->lock);
842                 return 0;
843         }
844         tsk->fs = copy_fs_struct(fs);
845         if (!tsk->fs)
846                 return -ENOMEM;
847         return 0;
848 }
849
850 static int copy_files(unsigned long clone_flags, struct task_struct *tsk)
851 {
852         struct files_struct *oldf, *newf;
853         int error = 0;
854
855         /*
856          * A background process may not have any files ...
857          */
858         oldf = current->files;
859         if (!oldf)
860                 goto out;
861
862         if (clone_flags & CLONE_FILES) {
863                 atomic_inc(&oldf->count);
864                 goto out;
865         }
866
867         newf = dup_fd(oldf, &error);
868         if (!newf)
869                 goto out;
870
871         tsk->files = newf;
872         error = 0;
873 out:
874         return error;
875 }
876
877 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
878 {
879 #ifdef CONFIG_BLOCK
880         struct io_context *ioc = current->io_context;
881
882         if (!ioc)
883                 return 0;
884         /*
885          * Share io context with parent, if CLONE_IO is set
886          */
887         if (clone_flags & CLONE_IO) {
888                 tsk->io_context = ioc_task_link(ioc);
889                 if (unlikely(!tsk->io_context))
890                         return -ENOMEM;
891         } else if (ioprio_valid(ioc->ioprio)) {
892                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
893                 if (unlikely(!tsk->io_context))
894                         return -ENOMEM;
895
896                 tsk->io_context->ioprio = ioc->ioprio;
897         }
898 #endif
899         return 0;
900 }
901
902 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
903 {
904         struct sighand_struct *sig;
905
906         if (clone_flags & CLONE_SIGHAND) {
907                 atomic_inc(&current->sighand->count);
908                 return 0;
909         }
910         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
911         rcu_assign_pointer(tsk->sighand, sig);
912         if (!sig)
913                 return -ENOMEM;
914         atomic_set(&sig->count, 1);
915         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
916         return 0;
917 }
918
919 void __cleanup_sighand(struct sighand_struct *sighand)
920 {
921         if (atomic_dec_and_test(&sighand->count))
922                 kmem_cache_free(sighand_cachep, sighand);
923 }
924
925
926 /*
927  * Initialize POSIX timer handling for a thread group.
928  */
929 static void posix_cpu_timers_init_group(struct signal_struct *sig)
930 {
931         unsigned long cpu_limit;
932
933         /* Thread group counters. */
934         thread_group_cputime_init(sig);
935
936         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
937         if (cpu_limit != RLIM_INFINITY) {
938                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
939                 sig->cputimer.running = 1;
940         }
941
942         /* The timer lists. */
943         INIT_LIST_HEAD(&sig->cpu_timers[0]);
944         INIT_LIST_HEAD(&sig->cpu_timers[1]);
945         INIT_LIST_HEAD(&sig->cpu_timers[2]);
946 }
947
948 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
949 {
950         struct signal_struct *sig;
951
952         if (clone_flags & CLONE_THREAD)
953                 return 0;
954
955         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
956         tsk->signal = sig;
957         if (!sig)
958                 return -ENOMEM;
959
960         sig->nr_threads = 1;
961         atomic_set(&sig->live, 1);
962         atomic_set(&sig->sigcnt, 1);
963         init_waitqueue_head(&sig->wait_chldexit);
964         if (clone_flags & CLONE_NEWPID)
965                 sig->flags |= SIGNAL_UNKILLABLE;
966         sig->curr_target = tsk;
967         init_sigpending(&sig->shared_pending);
968         INIT_LIST_HEAD(&sig->posix_timers);
969
970         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
971         sig->real_timer.function = it_real_fn;
972
973         task_lock(current->group_leader);
974         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
975         task_unlock(current->group_leader);
976
977         posix_cpu_timers_init_group(sig);
978
979         tty_audit_fork(sig);
980         sched_autogroup_fork(sig);
981
982 #ifdef CONFIG_CGROUPS
983         init_rwsem(&sig->threadgroup_fork_lock);
984 #endif
985
986         sig->oom_adj = current->signal->oom_adj;
987         sig->oom_score_adj = current->signal->oom_score_adj;
988         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
989
990         mutex_init(&sig->cred_guard_mutex);
991
992         return 0;
993 }
994
995 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
996 {
997         unsigned long new_flags = p->flags;
998
999         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1000         new_flags |= PF_FORKNOEXEC;
1001         new_flags |= PF_STARTING;
1002         p->flags = new_flags;
1003         clear_freeze_flag(p);
1004 }
1005
1006 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1007 {
1008         current->clear_child_tid = tidptr;
1009
1010         return task_pid_vnr(current);
1011 }
1012
1013 static void rt_mutex_init_task(struct task_struct *p)
1014 {
1015         raw_spin_lock_init(&p->pi_lock);
1016 #ifdef CONFIG_RT_MUTEXES
1017         plist_head_init(&p->pi_waiters);
1018         p->pi_blocked_on = NULL;
1019 #endif
1020 }
1021
1022 #ifdef CONFIG_MM_OWNER
1023 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1024 {
1025         mm->owner = p;
1026 }
1027 #endif /* CONFIG_MM_OWNER */
1028
1029 /*
1030  * Initialize POSIX timer handling for a single task.
1031  */
1032 static void posix_cpu_timers_init(struct task_struct *tsk)
1033 {
1034         tsk->cputime_expires.prof_exp = cputime_zero;
1035         tsk->cputime_expires.virt_exp = cputime_zero;
1036         tsk->cputime_expires.sched_exp = 0;
1037         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1038         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1039         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1040 }
1041
1042 /*
1043  * This creates a new process as a copy of the old one,
1044  * but does not actually start it yet.
1045  *
1046  * It copies the registers, and all the appropriate
1047  * parts of the process environment (as per the clone
1048  * flags). The actual kick-off is left to the caller.
1049  */
1050 static struct task_struct *copy_process(unsigned long clone_flags,
1051                                         unsigned long stack_start,
1052                                         struct pt_regs *regs,
1053                                         unsigned long stack_size,
1054                                         int __user *child_tidptr,
1055                                         struct pid *pid,
1056                                         int trace)
1057 {
1058         int retval;
1059         struct task_struct *p;
1060         int cgroup_callbacks_done = 0;
1061
1062         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1063                 return ERR_PTR(-EINVAL);
1064
1065         /*
1066          * Thread groups must share signals as well, and detached threads
1067          * can only be started up within the thread group.
1068          */
1069         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1070                 return ERR_PTR(-EINVAL);
1071
1072         /*
1073          * Shared signal handlers imply shared VM. By way of the above,
1074          * thread groups also imply shared VM. Blocking this case allows
1075          * for various simplifications in other code.
1076          */
1077         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1078                 return ERR_PTR(-EINVAL);
1079
1080         /*
1081          * Siblings of global init remain as zombies on exit since they are
1082          * not reaped by their parent (swapper). To solve this and to avoid
1083          * multi-rooted process trees, prevent global and container-inits
1084          * from creating siblings.
1085          */
1086         if ((clone_flags & CLONE_PARENT) &&
1087                                 current->signal->flags & SIGNAL_UNKILLABLE)
1088                 return ERR_PTR(-EINVAL);
1089
1090         retval = security_task_create(clone_flags);
1091         if (retval)
1092                 goto fork_out;
1093
1094         retval = -ENOMEM;
1095         p = dup_task_struct(current);
1096         if (!p)
1097                 goto fork_out;
1098
1099         ftrace_graph_init_task(p);
1100
1101         rt_mutex_init_task(p);
1102
1103 #ifdef CONFIG_PROVE_LOCKING
1104         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1105         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1106 #endif
1107         retval = -EAGAIN;
1108         if (atomic_read(&p->real_cred->user->processes) >=
1109                         task_rlimit(p, RLIMIT_NPROC)) {
1110                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1111                     p->real_cred->user != INIT_USER)
1112                         goto bad_fork_free;
1113         }
1114         current->flags &= ~PF_NPROC_EXCEEDED;
1115
1116         retval = copy_creds(p, clone_flags);
1117         if (retval < 0)
1118                 goto bad_fork_free;
1119
1120         /*
1121          * If multiple threads are within copy_process(), then this check
1122          * triggers too late. This doesn't hurt, the check is only there
1123          * to stop root fork bombs.
1124          */
1125         retval = -EAGAIN;
1126         if (nr_threads >= max_threads)
1127                 goto bad_fork_cleanup_count;
1128
1129         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1130                 goto bad_fork_cleanup_count;
1131
1132         p->did_exec = 0;
1133         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1134         copy_flags(clone_flags, p);
1135         INIT_LIST_HEAD(&p->children);
1136         INIT_LIST_HEAD(&p->sibling);
1137         rcu_copy_process(p);
1138         p->vfork_done = NULL;
1139         spin_lock_init(&p->alloc_lock);
1140
1141         init_sigpending(&p->pending);
1142
1143         p->utime = cputime_zero;
1144         p->stime = cputime_zero;
1145         p->gtime = cputime_zero;
1146         p->utimescaled = cputime_zero;
1147         p->stimescaled = cputime_zero;
1148 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1149         p->prev_utime = cputime_zero;
1150         p->prev_stime = cputime_zero;
1151 #endif
1152 #if defined(SPLIT_RSS_COUNTING)
1153         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1154 #endif
1155
1156         p->default_timer_slack_ns = current->timer_slack_ns;
1157
1158         task_io_accounting_init(&p->ioac);
1159         acct_clear_integrals(p);
1160
1161         posix_cpu_timers_init(p);
1162
1163         do_posix_clock_monotonic_gettime(&p->start_time);
1164         p->real_start_time = p->start_time;
1165         monotonic_to_bootbased(&p->real_start_time);
1166         p->io_context = NULL;
1167         p->audit_context = NULL;
1168         if (clone_flags & CLONE_THREAD)
1169                 threadgroup_fork_read_lock(current);
1170         cgroup_fork(p);
1171 #ifdef CONFIG_NUMA
1172         p->mempolicy = mpol_dup(p->mempolicy);
1173         if (IS_ERR(p->mempolicy)) {
1174                 retval = PTR_ERR(p->mempolicy);
1175                 p->mempolicy = NULL;
1176                 goto bad_fork_cleanup_cgroup;
1177         }
1178         mpol_fix_fork_child_flag(p);
1179 #endif
1180 #ifdef CONFIG_CPUSETS
1181         p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
1182         p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
1183 #endif
1184 #ifdef CONFIG_TRACE_IRQFLAGS
1185         p->irq_events = 0;
1186 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1187         p->hardirqs_enabled = 1;
1188 #else
1189         p->hardirqs_enabled = 0;
1190 #endif
1191         p->hardirq_enable_ip = 0;
1192         p->hardirq_enable_event = 0;
1193         p->hardirq_disable_ip = _THIS_IP_;
1194         p->hardirq_disable_event = 0;
1195         p->softirqs_enabled = 1;
1196         p->softirq_enable_ip = _THIS_IP_;
1197         p->softirq_enable_event = 0;
1198         p->softirq_disable_ip = 0;
1199         p->softirq_disable_event = 0;
1200         p->hardirq_context = 0;
1201         p->softirq_context = 0;
1202 #endif
1203 #ifdef CONFIG_LOCKDEP
1204         p->lockdep_depth = 0; /* no locks held yet */
1205         p->curr_chain_key = 0;
1206         p->lockdep_recursion = 0;
1207 #endif
1208
1209 #ifdef CONFIG_DEBUG_MUTEXES
1210         p->blocked_on = NULL; /* not blocked yet */
1211 #endif
1212 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1213         p->memcg_batch.do_batch = 0;
1214         p->memcg_batch.memcg = NULL;
1215 #endif
1216
1217         /* Perform scheduler related setup. Assign this task to a CPU. */
1218         sched_fork(p);
1219
1220         retval = perf_event_init_task(p);
1221         if (retval)
1222                 goto bad_fork_cleanup_policy;
1223         retval = audit_alloc(p);
1224         if (retval)
1225                 goto bad_fork_cleanup_policy;
1226         /* copy all the process information */
1227         retval = copy_semundo(clone_flags, p);
1228         if (retval)
1229                 goto bad_fork_cleanup_audit;
1230         retval = copy_files(clone_flags, p);
1231         if (retval)
1232                 goto bad_fork_cleanup_semundo;
1233         retval = copy_fs(clone_flags, p);
1234         if (retval)
1235                 goto bad_fork_cleanup_files;
1236         retval = copy_sighand(clone_flags, p);
1237         if (retval)
1238                 goto bad_fork_cleanup_fs;
1239         retval = copy_signal(clone_flags, p);
1240         if (retval)
1241                 goto bad_fork_cleanup_sighand;
1242         retval = copy_mm(clone_flags, p);
1243         if (retval)
1244                 goto bad_fork_cleanup_signal;
1245         retval = copy_namespaces(clone_flags, p);
1246         if (retval)
1247                 goto bad_fork_cleanup_mm;
1248         retval = copy_io(clone_flags, p);
1249         if (retval)
1250                 goto bad_fork_cleanup_namespaces;
1251         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1252         if (retval)
1253                 goto bad_fork_cleanup_io;
1254
1255         if (pid != &init_struct_pid) {
1256                 retval = -ENOMEM;
1257                 pid = alloc_pid(p->nsproxy->pid_ns);
1258                 if (!pid)
1259                         goto bad_fork_cleanup_io;
1260         }
1261
1262         p->pid = pid_nr(pid);
1263         p->tgid = p->pid;
1264         if (clone_flags & CLONE_THREAD)
1265                 p->tgid = current->tgid;
1266
1267         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1268         /*
1269          * Clear TID on mm_release()?
1270          */
1271         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
1272 #ifdef CONFIG_BLOCK
1273         p->plug = NULL;
1274 #endif
1275 #ifdef CONFIG_FUTEX
1276         p->robust_list = NULL;
1277 #ifdef CONFIG_COMPAT
1278         p->compat_robust_list = NULL;
1279 #endif
1280         INIT_LIST_HEAD(&p->pi_state_list);
1281         p->pi_state_cache = NULL;
1282 #endif
1283         /*
1284          * sigaltstack should be cleared when sharing the same VM
1285          */
1286         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1287                 p->sas_ss_sp = p->sas_ss_size = 0;
1288
1289         /*
1290          * Syscall tracing and stepping should be turned off in the
1291          * child regardless of CLONE_PTRACE.
1292          */
1293         user_disable_single_step(p);
1294         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1295 #ifdef TIF_SYSCALL_EMU
1296         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1297 #endif
1298         clear_all_latency_tracing(p);
1299
1300         /* ok, now we should be set up.. */
1301         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1302         p->pdeath_signal = 0;
1303         p->exit_state = 0;
1304
1305         /*
1306          * Ok, make it visible to the rest of the system.
1307          * We dont wake it up yet.
1308          */
1309         p->group_leader = p;
1310         INIT_LIST_HEAD(&p->thread_group);
1311
1312         /* Now that the task is set up, run cgroup callbacks if
1313          * necessary. We need to run them before the task is visible
1314          * on the tasklist. */
1315         cgroup_fork_callbacks(p);
1316         cgroup_callbacks_done = 1;
1317
1318         /* Need tasklist lock for parent etc handling! */
1319         write_lock_irq(&tasklist_lock);
1320
1321         /* CLONE_PARENT re-uses the old parent */
1322         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1323                 p->real_parent = current->real_parent;
1324                 p->parent_exec_id = current->parent_exec_id;
1325         } else {
1326                 p->real_parent = current;
1327                 p->parent_exec_id = current->self_exec_id;
1328         }
1329
1330         spin_lock(&current->sighand->siglock);
1331
1332         /*
1333          * Process group and session signals need to be delivered to just the
1334          * parent before the fork or both the parent and the child after the
1335          * fork. Restart if a signal comes in before we add the new process to
1336          * it's process group.
1337          * A fatal signal pending means that current will exit, so the new
1338          * thread can't slip out of an OOM kill (or normal SIGKILL).
1339         */
1340         recalc_sigpending();
1341         if (signal_pending(current)) {
1342                 spin_unlock(&current->sighand->siglock);
1343                 write_unlock_irq(&tasklist_lock);
1344                 retval = -ERESTARTNOINTR;
1345                 goto bad_fork_free_pid;
1346         }
1347
1348         if (clone_flags & CLONE_THREAD) {
1349                 current->signal->nr_threads++;
1350                 atomic_inc(&current->signal->live);
1351                 atomic_inc(&current->signal->sigcnt);
1352                 p->group_leader = current->group_leader;
1353                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1354         }
1355
1356         if (likely(p->pid)) {
1357                 ptrace_init_task(p, (clone_flags & CLONE_PTRACE) || trace);
1358
1359                 if (thread_group_leader(p)) {
1360                         if (is_child_reaper(pid))
1361                                 p->nsproxy->pid_ns->child_reaper = p;
1362
1363                         p->signal->leader_pid = pid;
1364                         p->signal->tty = tty_kref_get(current->signal->tty);
1365                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1366                         attach_pid(p, PIDTYPE_SID, task_session(current));
1367                         list_add_tail(&p->sibling, &p->real_parent->children);
1368                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1369                         __this_cpu_inc(process_counts);
1370                 }
1371                 attach_pid(p, PIDTYPE_PID, pid);
1372                 nr_threads++;
1373         }
1374
1375         total_forks++;
1376         spin_unlock(&current->sighand->siglock);
1377         write_unlock_irq(&tasklist_lock);
1378         proc_fork_connector(p);
1379         cgroup_post_fork(p);
1380         if (clone_flags & CLONE_THREAD)
1381                 threadgroup_fork_read_unlock(current);
1382         perf_event_fork(p);
1383         return p;
1384
1385 bad_fork_free_pid:
1386         if (pid != &init_struct_pid)
1387                 free_pid(pid);
1388 bad_fork_cleanup_io:
1389         if (p->io_context)
1390                 exit_io_context(p);
1391 bad_fork_cleanup_namespaces:
1392         exit_task_namespaces(p);
1393 bad_fork_cleanup_mm:
1394         if (p->mm) {
1395                 task_lock(p);
1396                 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1397                         atomic_dec(&p->mm->oom_disable_count);
1398                 task_unlock(p);
1399                 mmput(p->mm);
1400         }
1401 bad_fork_cleanup_signal:
1402         if (!(clone_flags & CLONE_THREAD))
1403                 free_signal_struct(p->signal);
1404 bad_fork_cleanup_sighand:
1405         __cleanup_sighand(p->sighand);
1406 bad_fork_cleanup_fs:
1407         exit_fs(p); /* blocking */
1408 bad_fork_cleanup_files:
1409         exit_files(p); /* blocking */
1410 bad_fork_cleanup_semundo:
1411         exit_sem(p);
1412 bad_fork_cleanup_audit:
1413         audit_free(p);
1414 bad_fork_cleanup_policy:
1415         perf_event_free_task(p);
1416 #ifdef CONFIG_NUMA
1417         mpol_put(p->mempolicy);
1418 bad_fork_cleanup_cgroup:
1419 #endif
1420         if (clone_flags & CLONE_THREAD)
1421                 threadgroup_fork_read_unlock(current);
1422         cgroup_exit(p, cgroup_callbacks_done);
1423         delayacct_tsk_free(p);
1424         module_put(task_thread_info(p)->exec_domain->module);
1425 bad_fork_cleanup_count:
1426         atomic_dec(&p->cred->user->processes);
1427         exit_creds(p);
1428 bad_fork_free:
1429         free_task(p);
1430 fork_out:
1431         return ERR_PTR(retval);
1432 }
1433
1434 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1435 {
1436         memset(regs, 0, sizeof(struct pt_regs));
1437         return regs;
1438 }
1439
1440 static inline void init_idle_pids(struct pid_link *links)
1441 {
1442         enum pid_type type;
1443
1444         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1445                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1446                 links[type].pid = &init_struct_pid;
1447         }
1448 }
1449
1450 struct task_struct * __cpuinit fork_idle(int cpu)
1451 {
1452         struct task_struct *task;
1453         struct pt_regs regs;
1454
1455         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1456                             &init_struct_pid, 0);
1457         if (!IS_ERR(task)) {
1458                 init_idle_pids(task->pids);
1459                 init_idle(task, cpu);
1460         }
1461
1462         return task;
1463 }
1464
1465 /*
1466  *  Ok, this is the main fork-routine.
1467  *
1468  * It copies the process, and if successful kick-starts
1469  * it and waits for it to finish using the VM if required.
1470  */
1471 long do_fork(unsigned long clone_flags,
1472               unsigned long stack_start,
1473               struct pt_regs *regs,
1474               unsigned long stack_size,
1475               int __user *parent_tidptr,
1476               int __user *child_tidptr)
1477 {
1478         struct task_struct *p;
1479         int trace = 0;
1480         long nr;
1481
1482         /*
1483          * Do some preliminary argument and permissions checking before we
1484          * actually start allocating stuff
1485          */
1486         if (clone_flags & CLONE_NEWUSER) {
1487                 if (clone_flags & CLONE_THREAD)
1488                         return -EINVAL;
1489                 /* hopefully this check will go away when userns support is
1490                  * complete
1491                  */
1492                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1493                                 !capable(CAP_SETGID))
1494                         return -EPERM;
1495         }
1496
1497         /*
1498          * Determine whether and which event to report to ptracer.  When
1499          * called from kernel_thread or CLONE_UNTRACED is explicitly
1500          * requested, no event is reported; otherwise, report if the event
1501          * for the type of forking is enabled.
1502          */
1503         if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
1504                 if (clone_flags & CLONE_VFORK)
1505                         trace = PTRACE_EVENT_VFORK;
1506                 else if ((clone_flags & CSIGNAL) != SIGCHLD)
1507                         trace = PTRACE_EVENT_CLONE;
1508                 else
1509                         trace = PTRACE_EVENT_FORK;
1510
1511                 if (likely(!ptrace_event_enabled(current, trace)))
1512                         trace = 0;
1513         }
1514
1515         p = copy_process(clone_flags, stack_start, regs, stack_size,
1516                          child_tidptr, NULL, trace);
1517         /*
1518          * Do this prior waking up the new thread - the thread pointer
1519          * might get invalid after that point, if the thread exits quickly.
1520          */
1521         if (!IS_ERR(p)) {
1522                 struct completion vfork;
1523
1524                 trace_sched_process_fork(current, p);
1525
1526                 nr = task_pid_vnr(p);
1527
1528                 if (clone_flags & CLONE_PARENT_SETTID)
1529                         put_user(nr, parent_tidptr);
1530
1531                 if (clone_flags & CLONE_VFORK) {
1532                         p->vfork_done = &vfork;
1533                         init_completion(&vfork);
1534                 }
1535
1536                 audit_finish_fork(p);
1537
1538                 /*
1539                  * We set PF_STARTING at creation in case tracing wants to
1540                  * use this to distinguish a fully live task from one that
1541                  * hasn't finished SIGSTOP raising yet.  Now we clear it
1542                  * and set the child going.
1543                  */
1544                 p->flags &= ~PF_STARTING;
1545
1546                 wake_up_new_task(p);
1547
1548                 /* forking complete and child started to run, tell ptracer */
1549                 if (unlikely(trace))
1550                         ptrace_event(trace, nr);
1551
1552                 if (clone_flags & CLONE_VFORK) {
1553                         freezer_do_not_count();
1554                         wait_for_completion(&vfork);
1555                         freezer_count();
1556                         ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
1557                 }
1558         } else {
1559                 nr = PTR_ERR(p);
1560         }
1561         return nr;
1562 }
1563
1564 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1565 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1566 #endif
1567
1568 static void sighand_ctor(void *data)
1569 {
1570         struct sighand_struct *sighand = data;
1571
1572         spin_lock_init(&sighand->siglock);
1573         init_waitqueue_head(&sighand->signalfd_wqh);
1574 }
1575
1576 void __init proc_caches_init(void)
1577 {
1578         sighand_cachep = kmem_cache_create("sighand_cache",
1579                         sizeof(struct sighand_struct), 0,
1580                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1581                         SLAB_NOTRACK, sighand_ctor);
1582         signal_cachep = kmem_cache_create("signal_cache",
1583                         sizeof(struct signal_struct), 0,
1584                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1585         files_cachep = kmem_cache_create("files_cache",
1586                         sizeof(struct files_struct), 0,
1587                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1588         fs_cachep = kmem_cache_create("fs_cache",
1589                         sizeof(struct fs_struct), 0,
1590                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1591         /*
1592          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1593          * whole struct cpumask for the OFFSTACK case. We could change
1594          * this to *only* allocate as much of it as required by the
1595          * maximum number of CPU's we can ever have.  The cpumask_allocation
1596          * is at the end of the structure, exactly for that reason.
1597          */
1598         mm_cachep = kmem_cache_create("mm_struct",
1599                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1600                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1601         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1602         mmap_init();
1603         nsproxy_cache_init();
1604 }
1605
1606 /*
1607  * Check constraints on flags passed to the unshare system call.
1608  */
1609 static int check_unshare_flags(unsigned long unshare_flags)
1610 {
1611         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1612                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1613                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1614                 return -EINVAL;
1615         /*
1616          * Not implemented, but pretend it works if there is nothing to
1617          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1618          * needs to unshare vm.
1619          */
1620         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1621                 /* FIXME: get_task_mm() increments ->mm_users */
1622                 if (atomic_read(&current->mm->mm_users) > 1)
1623                         return -EINVAL;
1624         }
1625
1626         return 0;
1627 }
1628
1629 /*
1630  * Unshare the filesystem structure if it is being shared
1631  */
1632 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1633 {
1634         struct fs_struct *fs = current->fs;
1635
1636         if (!(unshare_flags & CLONE_FS) || !fs)
1637                 return 0;
1638
1639         /* don't need lock here; in the worst case we'll do useless copy */
1640         if (fs->users == 1)
1641                 return 0;
1642
1643         *new_fsp = copy_fs_struct(fs);
1644         if (!*new_fsp)
1645                 return -ENOMEM;
1646
1647         return 0;
1648 }
1649
1650 /*
1651  * Unshare file descriptor table if it is being shared
1652  */
1653 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1654 {
1655         struct files_struct *fd = current->files;
1656         int error = 0;
1657
1658         if ((unshare_flags & CLONE_FILES) &&
1659             (fd && atomic_read(&fd->count) > 1)) {
1660                 *new_fdp = dup_fd(fd, &error);
1661                 if (!*new_fdp)
1662                         return error;
1663         }
1664
1665         return 0;
1666 }
1667
1668 /*
1669  * unshare allows a process to 'unshare' part of the process
1670  * context which was originally shared using clone.  copy_*
1671  * functions used by do_fork() cannot be used here directly
1672  * because they modify an inactive task_struct that is being
1673  * constructed. Here we are modifying the current, active,
1674  * task_struct.
1675  */
1676 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1677 {
1678         struct fs_struct *fs, *new_fs = NULL;
1679         struct files_struct *fd, *new_fd = NULL;
1680         struct nsproxy *new_nsproxy = NULL;
1681         int do_sysvsem = 0;
1682         int err;
1683
1684         err = check_unshare_flags(unshare_flags);
1685         if (err)
1686                 goto bad_unshare_out;
1687
1688         /*
1689          * If unsharing namespace, must also unshare filesystem information.
1690          */
1691         if (unshare_flags & CLONE_NEWNS)
1692                 unshare_flags |= CLONE_FS;
1693         /*
1694          * CLONE_NEWIPC must also detach from the undolist: after switching
1695          * to a new ipc namespace, the semaphore arrays from the old
1696          * namespace are unreachable.
1697          */
1698         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1699                 do_sysvsem = 1;
1700         err = unshare_fs(unshare_flags, &new_fs);
1701         if (err)
1702                 goto bad_unshare_out;
1703         err = unshare_fd(unshare_flags, &new_fd);
1704         if (err)
1705                 goto bad_unshare_cleanup_fs;
1706         err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, new_fs);
1707         if (err)
1708                 goto bad_unshare_cleanup_fd;
1709
1710         if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1711                 if (do_sysvsem) {
1712                         /*
1713                          * CLONE_SYSVSEM is equivalent to sys_exit().
1714                          */
1715                         exit_sem(current);
1716                 }
1717
1718                 if (new_nsproxy) {
1719                         switch_task_namespaces(current, new_nsproxy);
1720                         new_nsproxy = NULL;
1721                 }
1722
1723                 task_lock(current);
1724
1725                 if (new_fs) {
1726                         fs = current->fs;
1727                         spin_lock(&fs->lock);
1728                         current->fs = new_fs;
1729                         if (--fs->users)
1730                                 new_fs = NULL;
1731                         else
1732                                 new_fs = fs;
1733                         spin_unlock(&fs->lock);
1734                 }
1735
1736                 if (new_fd) {
1737                         fd = current->files;
1738                         current->files = new_fd;
1739                         new_fd = fd;
1740                 }
1741
1742                 task_unlock(current);
1743         }
1744
1745         if (new_nsproxy)
1746                 put_nsproxy(new_nsproxy);
1747
1748 bad_unshare_cleanup_fd:
1749         if (new_fd)
1750                 put_files_struct(new_fd);
1751
1752 bad_unshare_cleanup_fs:
1753         if (new_fs)
1754                 free_fs_struct(new_fs);
1755
1756 bad_unshare_out:
1757         return err;
1758 }
1759
1760 /*
1761  *      Helper to unshare the files of the current task.
1762  *      We don't want to expose copy_files internals to
1763  *      the exec layer of the kernel.
1764  */
1765
1766 int unshare_files(struct files_struct **displaced)
1767 {
1768         struct task_struct *task = current;
1769         struct files_struct *copy = NULL;
1770         int error;
1771
1772         error = unshare_fd(CLONE_FILES, &copy);
1773         if (error || !copy) {
1774                 *displaced = NULL;
1775                 return error;
1776         }
1777         *displaced = task->files;
1778         task_lock(task);
1779         task->files = copy;
1780         task_unlock(task);
1781         return 0;
1782 }