New locking/refcounting for fs_struct
[linux-2.6.git] / kernel / fork.c
1 /*
2  *  linux/kernel/fork.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6
7 /*
8  *  'fork.c' contains the help-routines for the 'fork' system call
9  * (see also entry.S and others).
10  * Fork is rather simple, once you get the hang of it, but the memory
11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12  */
13
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/mnt_namespace.h>
21 #include <linux/personality.h>
22 #include <linux/mempolicy.h>
23 #include <linux/sem.h>
24 #include <linux/file.h>
25 #include <linux/fdtable.h>
26 #include <linux/iocontext.h>
27 #include <linux/key.h>
28 #include <linux/binfmts.h>
29 #include <linux/mman.h>
30 #include <linux/mmu_notifier.h>
31 #include <linux/fs.h>
32 #include <linux/nsproxy.h>
33 #include <linux/capability.h>
34 #include <linux/cpu.h>
35 #include <linux/cgroup.h>
36 #include <linux/security.h>
37 #include <linux/hugetlb.h>
38 #include <linux/swap.h>
39 #include <linux/syscalls.h>
40 #include <linux/jiffies.h>
41 #include <linux/tracehook.h>
42 #include <linux/futex.h>
43 #include <linux/compat.h>
44 #include <linux/task_io_accounting_ops.h>
45 #include <linux/rcupdate.h>
46 #include <linux/ptrace.h>
47 #include <linux/mount.h>
48 #include <linux/audit.h>
49 #include <linux/memcontrol.h>
50 #include <linux/ftrace.h>
51 #include <linux/profile.h>
52 #include <linux/rmap.h>
53 #include <linux/acct.h>
54 #include <linux/tsacct_kern.h>
55 #include <linux/cn_proc.h>
56 #include <linux/freezer.h>
57 #include <linux/delayacct.h>
58 #include <linux/taskstats_kern.h>
59 #include <linux/random.h>
60 #include <linux/tty.h>
61 #include <linux/proc_fs.h>
62 #include <linux/blkdev.h>
63 #include <trace/sched.h>
64 #include <linux/magic.h>
65
66 #include <asm/pgtable.h>
67 #include <asm/pgalloc.h>
68 #include <asm/uaccess.h>
69 #include <asm/mmu_context.h>
70 #include <asm/cacheflush.h>
71 #include <asm/tlbflush.h>
72
73 /*
74  * Protected counters by write_lock_irq(&tasklist_lock)
75  */
76 unsigned long total_forks;      /* Handle normal Linux uptimes. */
77 int nr_threads;                 /* The idle threads do not count.. */
78
79 int max_threads;                /* tunable limit on nr_threads */
80
81 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
82
83 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
84
85 DEFINE_TRACE(sched_process_fork);
86
87 int nr_processes(void)
88 {
89         int cpu;
90         int total = 0;
91
92         for_each_online_cpu(cpu)
93                 total += per_cpu(process_counts, cpu);
94
95         return total;
96 }
97
98 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
99 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
100 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
101 static struct kmem_cache *task_struct_cachep;
102 #endif
103
104 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
105 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
106 {
107 #ifdef CONFIG_DEBUG_STACK_USAGE
108         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
109 #else
110         gfp_t mask = GFP_KERNEL;
111 #endif
112         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
113 }
114
115 static inline void free_thread_info(struct thread_info *ti)
116 {
117         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
118 }
119 #endif
120
121 /* SLAB cache for signal_struct structures (tsk->signal) */
122 static struct kmem_cache *signal_cachep;
123
124 /* SLAB cache for sighand_struct structures (tsk->sighand) */
125 struct kmem_cache *sighand_cachep;
126
127 /* SLAB cache for files_struct structures (tsk->files) */
128 struct kmem_cache *files_cachep;
129
130 /* SLAB cache for fs_struct structures (tsk->fs) */
131 struct kmem_cache *fs_cachep;
132
133 /* SLAB cache for vm_area_struct structures */
134 struct kmem_cache *vm_area_cachep;
135
136 /* SLAB cache for mm_struct structures (tsk->mm) */
137 static struct kmem_cache *mm_cachep;
138
139 void free_task(struct task_struct *tsk)
140 {
141         prop_local_destroy_single(&tsk->dirties);
142         free_thread_info(tsk->stack);
143         rt_mutex_debug_task_free(tsk);
144         ftrace_graph_exit_task(tsk);
145         free_task_struct(tsk);
146 }
147 EXPORT_SYMBOL(free_task);
148
149 void __put_task_struct(struct task_struct *tsk)
150 {
151         WARN_ON(!tsk->exit_state);
152         WARN_ON(atomic_read(&tsk->usage));
153         WARN_ON(tsk == current);
154
155         put_cred(tsk->real_cred);
156         put_cred(tsk->cred);
157         delayacct_tsk_free(tsk);
158
159         if (!profile_handoff_task(tsk))
160                 free_task(tsk);
161 }
162
163 /*
164  * macro override instead of weak attribute alias, to workaround
165  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
166  */
167 #ifndef arch_task_cache_init
168 #define arch_task_cache_init()
169 #endif
170
171 void __init fork_init(unsigned long mempages)
172 {
173 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
174 #ifndef ARCH_MIN_TASKALIGN
175 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
176 #endif
177         /* create a slab on which task_structs can be allocated */
178         task_struct_cachep =
179                 kmem_cache_create("task_struct", sizeof(struct task_struct),
180                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
181 #endif
182
183         /* do the arch specific task caches init */
184         arch_task_cache_init();
185
186         /*
187          * The default maximum number of threads is set to a safe
188          * value: the thread structures can take up at most half
189          * of memory.
190          */
191         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
192
193         /*
194          * we need to allow at least 20 threads to boot a system
195          */
196         if(max_threads < 20)
197                 max_threads = 20;
198
199         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
200         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
201         init_task.signal->rlim[RLIMIT_SIGPENDING] =
202                 init_task.signal->rlim[RLIMIT_NPROC];
203 }
204
205 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
206                                                struct task_struct *src)
207 {
208         *dst = *src;
209         return 0;
210 }
211
212 static struct task_struct *dup_task_struct(struct task_struct *orig)
213 {
214         struct task_struct *tsk;
215         struct thread_info *ti;
216         unsigned long *stackend;
217
218         int err;
219
220         prepare_to_copy(orig);
221
222         tsk = alloc_task_struct();
223         if (!tsk)
224                 return NULL;
225
226         ti = alloc_thread_info(tsk);
227         if (!ti) {
228                 free_task_struct(tsk);
229                 return NULL;
230         }
231
232         err = arch_dup_task_struct(tsk, orig);
233         if (err)
234                 goto out;
235
236         tsk->stack = ti;
237
238         err = prop_local_init_single(&tsk->dirties);
239         if (err)
240                 goto out;
241
242         setup_thread_stack(tsk, orig);
243         stackend = end_of_stack(tsk);
244         *stackend = STACK_END_MAGIC;    /* for overflow detection */
245
246 #ifdef CONFIG_CC_STACKPROTECTOR
247         tsk->stack_canary = get_random_int();
248 #endif
249
250         /* One for us, one for whoever does the "release_task()" (usually parent) */
251         atomic_set(&tsk->usage,2);
252         atomic_set(&tsk->fs_excl, 0);
253 #ifdef CONFIG_BLK_DEV_IO_TRACE
254         tsk->btrace_seq = 0;
255 #endif
256         tsk->splice_pipe = NULL;
257         return tsk;
258
259 out:
260         free_thread_info(ti);
261         free_task_struct(tsk);
262         return NULL;
263 }
264
265 #ifdef CONFIG_MMU
266 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
267 {
268         struct vm_area_struct *mpnt, *tmp, **pprev;
269         struct rb_node **rb_link, *rb_parent;
270         int retval;
271         unsigned long charge;
272         struct mempolicy *pol;
273
274         down_write(&oldmm->mmap_sem);
275         flush_cache_dup_mm(oldmm);
276         /*
277          * Not linked in yet - no deadlock potential:
278          */
279         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
280
281         mm->locked_vm = 0;
282         mm->mmap = NULL;
283         mm->mmap_cache = NULL;
284         mm->free_area_cache = oldmm->mmap_base;
285         mm->cached_hole_size = ~0UL;
286         mm->map_count = 0;
287         cpumask_clear(mm_cpumask(mm));
288         mm->mm_rb = RB_ROOT;
289         rb_link = &mm->mm_rb.rb_node;
290         rb_parent = NULL;
291         pprev = &mm->mmap;
292
293         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
294                 struct file *file;
295
296                 if (mpnt->vm_flags & VM_DONTCOPY) {
297                         long pages = vma_pages(mpnt);
298                         mm->total_vm -= pages;
299                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
300                                                                 -pages);
301                         continue;
302                 }
303                 charge = 0;
304                 if (mpnt->vm_flags & VM_ACCOUNT) {
305                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
306                         if (security_vm_enough_memory(len))
307                                 goto fail_nomem;
308                         charge = len;
309                 }
310                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
311                 if (!tmp)
312                         goto fail_nomem;
313                 *tmp = *mpnt;
314                 pol = mpol_dup(vma_policy(mpnt));
315                 retval = PTR_ERR(pol);
316                 if (IS_ERR(pol))
317                         goto fail_nomem_policy;
318                 vma_set_policy(tmp, pol);
319                 tmp->vm_flags &= ~VM_LOCKED;
320                 tmp->vm_mm = mm;
321                 tmp->vm_next = NULL;
322                 anon_vma_link(tmp);
323                 file = tmp->vm_file;
324                 if (file) {
325                         struct inode *inode = file->f_path.dentry->d_inode;
326                         struct address_space *mapping = file->f_mapping;
327
328                         get_file(file);
329                         if (tmp->vm_flags & VM_DENYWRITE)
330                                 atomic_dec(&inode->i_writecount);
331                         spin_lock(&mapping->i_mmap_lock);
332                         if (tmp->vm_flags & VM_SHARED)
333                                 mapping->i_mmap_writable++;
334                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
335                         flush_dcache_mmap_lock(mapping);
336                         /* insert tmp into the share list, just after mpnt */
337                         vma_prio_tree_add(tmp, mpnt);
338                         flush_dcache_mmap_unlock(mapping);
339                         spin_unlock(&mapping->i_mmap_lock);
340                 }
341
342                 /*
343                  * Clear hugetlb-related page reserves for children. This only
344                  * affects MAP_PRIVATE mappings. Faults generated by the child
345                  * are not guaranteed to succeed, even if read-only
346                  */
347                 if (is_vm_hugetlb_page(tmp))
348                         reset_vma_resv_huge_pages(tmp);
349
350                 /*
351                  * Link in the new vma and copy the page table entries.
352                  */
353                 *pprev = tmp;
354                 pprev = &tmp->vm_next;
355
356                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
357                 rb_link = &tmp->vm_rb.rb_right;
358                 rb_parent = &tmp->vm_rb;
359
360                 mm->map_count++;
361                 retval = copy_page_range(mm, oldmm, mpnt);
362
363                 if (tmp->vm_ops && tmp->vm_ops->open)
364                         tmp->vm_ops->open(tmp);
365
366                 if (retval)
367                         goto out;
368         }
369         /* a new mm has just been created */
370         arch_dup_mmap(oldmm, mm);
371         retval = 0;
372 out:
373         up_write(&mm->mmap_sem);
374         flush_tlb_mm(oldmm);
375         up_write(&oldmm->mmap_sem);
376         return retval;
377 fail_nomem_policy:
378         kmem_cache_free(vm_area_cachep, tmp);
379 fail_nomem:
380         retval = -ENOMEM;
381         vm_unacct_memory(charge);
382         goto out;
383 }
384
385 static inline int mm_alloc_pgd(struct mm_struct * mm)
386 {
387         mm->pgd = pgd_alloc(mm);
388         if (unlikely(!mm->pgd))
389                 return -ENOMEM;
390         return 0;
391 }
392
393 static inline void mm_free_pgd(struct mm_struct * mm)
394 {
395         pgd_free(mm, mm->pgd);
396 }
397 #else
398 #define dup_mmap(mm, oldmm)     (0)
399 #define mm_alloc_pgd(mm)        (0)
400 #define mm_free_pgd(mm)
401 #endif /* CONFIG_MMU */
402
403 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
404
405 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
406 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
407
408 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
409
410 static int __init coredump_filter_setup(char *s)
411 {
412         default_dump_filter =
413                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
414                 MMF_DUMP_FILTER_MASK;
415         return 1;
416 }
417
418 __setup("coredump_filter=", coredump_filter_setup);
419
420 #include <linux/init_task.h>
421
422 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
423 {
424         atomic_set(&mm->mm_users, 1);
425         atomic_set(&mm->mm_count, 1);
426         init_rwsem(&mm->mmap_sem);
427         INIT_LIST_HEAD(&mm->mmlist);
428         mm->flags = (current->mm) ? current->mm->flags : default_dump_filter;
429         mm->core_state = NULL;
430         mm->nr_ptes = 0;
431         set_mm_counter(mm, file_rss, 0);
432         set_mm_counter(mm, anon_rss, 0);
433         spin_lock_init(&mm->page_table_lock);
434         spin_lock_init(&mm->ioctx_lock);
435         INIT_HLIST_HEAD(&mm->ioctx_list);
436         mm->free_area_cache = TASK_UNMAPPED_BASE;
437         mm->cached_hole_size = ~0UL;
438         mm_init_owner(mm, p);
439
440         if (likely(!mm_alloc_pgd(mm))) {
441                 mm->def_flags = 0;
442                 mmu_notifier_mm_init(mm);
443                 return mm;
444         }
445
446         free_mm(mm);
447         return NULL;
448 }
449
450 /*
451  * Allocate and initialize an mm_struct.
452  */
453 struct mm_struct * mm_alloc(void)
454 {
455         struct mm_struct * mm;
456
457         mm = allocate_mm();
458         if (mm) {
459                 memset(mm, 0, sizeof(*mm));
460                 mm = mm_init(mm, current);
461         }
462         return mm;
463 }
464
465 /*
466  * Called when the last reference to the mm
467  * is dropped: either by a lazy thread or by
468  * mmput. Free the page directory and the mm.
469  */
470 void __mmdrop(struct mm_struct *mm)
471 {
472         BUG_ON(mm == &init_mm);
473         mm_free_pgd(mm);
474         destroy_context(mm);
475         mmu_notifier_mm_destroy(mm);
476         free_mm(mm);
477 }
478 EXPORT_SYMBOL_GPL(__mmdrop);
479
480 /*
481  * Decrement the use count and release all resources for an mm.
482  */
483 void mmput(struct mm_struct *mm)
484 {
485         might_sleep();
486
487         if (atomic_dec_and_test(&mm->mm_users)) {
488                 exit_aio(mm);
489                 exit_mmap(mm);
490                 set_mm_exe_file(mm, NULL);
491                 if (!list_empty(&mm->mmlist)) {
492                         spin_lock(&mmlist_lock);
493                         list_del(&mm->mmlist);
494                         spin_unlock(&mmlist_lock);
495                 }
496                 put_swap_token(mm);
497                 mmdrop(mm);
498         }
499 }
500 EXPORT_SYMBOL_GPL(mmput);
501
502 /**
503  * get_task_mm - acquire a reference to the task's mm
504  *
505  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
506  * this kernel workthread has transiently adopted a user mm with use_mm,
507  * to do its AIO) is not set and if so returns a reference to it, after
508  * bumping up the use count.  User must release the mm via mmput()
509  * after use.  Typically used by /proc and ptrace.
510  */
511 struct mm_struct *get_task_mm(struct task_struct *task)
512 {
513         struct mm_struct *mm;
514
515         task_lock(task);
516         mm = task->mm;
517         if (mm) {
518                 if (task->flags & PF_KTHREAD)
519                         mm = NULL;
520                 else
521                         atomic_inc(&mm->mm_users);
522         }
523         task_unlock(task);
524         return mm;
525 }
526 EXPORT_SYMBOL_GPL(get_task_mm);
527
528 /* Please note the differences between mmput and mm_release.
529  * mmput is called whenever we stop holding onto a mm_struct,
530  * error success whatever.
531  *
532  * mm_release is called after a mm_struct has been removed
533  * from the current process.
534  *
535  * This difference is important for error handling, when we
536  * only half set up a mm_struct for a new process and need to restore
537  * the old one.  Because we mmput the new mm_struct before
538  * restoring the old one. . .
539  * Eric Biederman 10 January 1998
540  */
541 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
542 {
543         struct completion *vfork_done = tsk->vfork_done;
544
545         /* Get rid of any futexes when releasing the mm */
546 #ifdef CONFIG_FUTEX
547         if (unlikely(tsk->robust_list))
548                 exit_robust_list(tsk);
549 #ifdef CONFIG_COMPAT
550         if (unlikely(tsk->compat_robust_list))
551                 compat_exit_robust_list(tsk);
552 #endif
553 #endif
554
555         /* Get rid of any cached register state */
556         deactivate_mm(tsk, mm);
557
558         /* notify parent sleeping on vfork() */
559         if (vfork_done) {
560                 tsk->vfork_done = NULL;
561                 complete(vfork_done);
562         }
563
564         /*
565          * If we're exiting normally, clear a user-space tid field if
566          * requested.  We leave this alone when dying by signal, to leave
567          * the value intact in a core dump, and to save the unnecessary
568          * trouble otherwise.  Userland only wants this done for a sys_exit.
569          */
570         if (tsk->clear_child_tid
571             && !(tsk->flags & PF_SIGNALED)
572             && atomic_read(&mm->mm_users) > 1) {
573                 u32 __user * tidptr = tsk->clear_child_tid;
574                 tsk->clear_child_tid = NULL;
575
576                 /*
577                  * We don't check the error code - if userspace has
578                  * not set up a proper pointer then tough luck.
579                  */
580                 put_user(0, tidptr);
581                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
582         }
583 }
584
585 /*
586  * Allocate a new mm structure and copy contents from the
587  * mm structure of the passed in task structure.
588  */
589 struct mm_struct *dup_mm(struct task_struct *tsk)
590 {
591         struct mm_struct *mm, *oldmm = current->mm;
592         int err;
593
594         if (!oldmm)
595                 return NULL;
596
597         mm = allocate_mm();
598         if (!mm)
599                 goto fail_nomem;
600
601         memcpy(mm, oldmm, sizeof(*mm));
602
603         /* Initializing for Swap token stuff */
604         mm->token_priority = 0;
605         mm->last_interval = 0;
606
607         if (!mm_init(mm, tsk))
608                 goto fail_nomem;
609
610         if (init_new_context(tsk, mm))
611                 goto fail_nocontext;
612
613         dup_mm_exe_file(oldmm, mm);
614
615         err = dup_mmap(mm, oldmm);
616         if (err)
617                 goto free_pt;
618
619         mm->hiwater_rss = get_mm_rss(mm);
620         mm->hiwater_vm = mm->total_vm;
621
622         return mm;
623
624 free_pt:
625         mmput(mm);
626
627 fail_nomem:
628         return NULL;
629
630 fail_nocontext:
631         /*
632          * If init_new_context() failed, we cannot use mmput() to free the mm
633          * because it calls destroy_context()
634          */
635         mm_free_pgd(mm);
636         free_mm(mm);
637         return NULL;
638 }
639
640 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
641 {
642         struct mm_struct * mm, *oldmm;
643         int retval;
644
645         tsk->min_flt = tsk->maj_flt = 0;
646         tsk->nvcsw = tsk->nivcsw = 0;
647
648         tsk->mm = NULL;
649         tsk->active_mm = NULL;
650
651         /*
652          * Are we cloning a kernel thread?
653          *
654          * We need to steal a active VM for that..
655          */
656         oldmm = current->mm;
657         if (!oldmm)
658                 return 0;
659
660         if (clone_flags & CLONE_VM) {
661                 atomic_inc(&oldmm->mm_users);
662                 mm = oldmm;
663                 goto good_mm;
664         }
665
666         retval = -ENOMEM;
667         mm = dup_mm(tsk);
668         if (!mm)
669                 goto fail_nomem;
670
671 good_mm:
672         /* Initializing for Swap token stuff */
673         mm->token_priority = 0;
674         mm->last_interval = 0;
675
676         tsk->mm = mm;
677         tsk->active_mm = mm;
678         return 0;
679
680 fail_nomem:
681         return retval;
682 }
683
684 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
685 {
686         struct fs_struct *fs = current->fs;
687         if (clone_flags & CLONE_FS) {
688                 /* tsk->fs is already what we want */
689                 write_lock(&fs->lock);
690                 if (fs->in_exec) {
691                         write_unlock(&fs->lock);
692                         return -EAGAIN;
693                 }
694                 fs->users++;
695                 write_unlock(&fs->lock);
696                 return 0;
697         }
698         tsk->fs = copy_fs_struct(fs);
699         if (!tsk->fs)
700                 return -ENOMEM;
701         return 0;
702 }
703
704 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
705 {
706         struct files_struct *oldf, *newf;
707         int error = 0;
708
709         /*
710          * A background process may not have any files ...
711          */
712         oldf = current->files;
713         if (!oldf)
714                 goto out;
715
716         if (clone_flags & CLONE_FILES) {
717                 atomic_inc(&oldf->count);
718                 goto out;
719         }
720
721         newf = dup_fd(oldf, &error);
722         if (!newf)
723                 goto out;
724
725         tsk->files = newf;
726         error = 0;
727 out:
728         return error;
729 }
730
731 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
732 {
733 #ifdef CONFIG_BLOCK
734         struct io_context *ioc = current->io_context;
735
736         if (!ioc)
737                 return 0;
738         /*
739          * Share io context with parent, if CLONE_IO is set
740          */
741         if (clone_flags & CLONE_IO) {
742                 tsk->io_context = ioc_task_link(ioc);
743                 if (unlikely(!tsk->io_context))
744                         return -ENOMEM;
745         } else if (ioprio_valid(ioc->ioprio)) {
746                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
747                 if (unlikely(!tsk->io_context))
748                         return -ENOMEM;
749
750                 tsk->io_context->ioprio = ioc->ioprio;
751         }
752 #endif
753         return 0;
754 }
755
756 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
757 {
758         struct sighand_struct *sig;
759
760         if (clone_flags & CLONE_SIGHAND) {
761                 atomic_inc(&current->sighand->count);
762                 return 0;
763         }
764         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
765         rcu_assign_pointer(tsk->sighand, sig);
766         if (!sig)
767                 return -ENOMEM;
768         atomic_set(&sig->count, 1);
769         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
770         return 0;
771 }
772
773 void __cleanup_sighand(struct sighand_struct *sighand)
774 {
775         if (atomic_dec_and_test(&sighand->count))
776                 kmem_cache_free(sighand_cachep, sighand);
777 }
778
779
780 /*
781  * Initialize POSIX timer handling for a thread group.
782  */
783 static void posix_cpu_timers_init_group(struct signal_struct *sig)
784 {
785         /* Thread group counters. */
786         thread_group_cputime_init(sig);
787
788         /* Expiration times and increments. */
789         sig->it_virt_expires = cputime_zero;
790         sig->it_virt_incr = cputime_zero;
791         sig->it_prof_expires = cputime_zero;
792         sig->it_prof_incr = cputime_zero;
793
794         /* Cached expiration times. */
795         sig->cputime_expires.prof_exp = cputime_zero;
796         sig->cputime_expires.virt_exp = cputime_zero;
797         sig->cputime_expires.sched_exp = 0;
798
799         /* The timer lists. */
800         INIT_LIST_HEAD(&sig->cpu_timers[0]);
801         INIT_LIST_HEAD(&sig->cpu_timers[1]);
802         INIT_LIST_HEAD(&sig->cpu_timers[2]);
803 }
804
805 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
806 {
807         struct signal_struct *sig;
808
809         if (clone_flags & CLONE_THREAD) {
810                 atomic_inc(&current->signal->count);
811                 atomic_inc(&current->signal->live);
812                 return 0;
813         }
814         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
815
816         if (sig)
817                 posix_cpu_timers_init_group(sig);
818
819         tsk->signal = sig;
820         if (!sig)
821                 return -ENOMEM;
822
823         atomic_set(&sig->count, 1);
824         atomic_set(&sig->live, 1);
825         init_waitqueue_head(&sig->wait_chldexit);
826         sig->flags = 0;
827         sig->group_exit_code = 0;
828         sig->group_exit_task = NULL;
829         sig->group_stop_count = 0;
830         sig->curr_target = tsk;
831         init_sigpending(&sig->shared_pending);
832         INIT_LIST_HEAD(&sig->posix_timers);
833
834         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
835         sig->it_real_incr.tv64 = 0;
836         sig->real_timer.function = it_real_fn;
837
838         sig->leader = 0;        /* session leadership doesn't inherit */
839         sig->tty_old_pgrp = NULL;
840         sig->tty = NULL;
841
842         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
843         sig->gtime = cputime_zero;
844         sig->cgtime = cputime_zero;
845         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
846         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
847         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
848         task_io_accounting_init(&sig->ioac);
849         sig->sum_sched_runtime = 0;
850         taskstats_tgid_init(sig);
851
852         task_lock(current->group_leader);
853         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
854         task_unlock(current->group_leader);
855
856         acct_init_pacct(&sig->pacct);
857
858         tty_audit_fork(sig);
859
860         return 0;
861 }
862
863 void __cleanup_signal(struct signal_struct *sig)
864 {
865         thread_group_cputime_free(sig);
866         tty_kref_put(sig->tty);
867         kmem_cache_free(signal_cachep, sig);
868 }
869
870 static void cleanup_signal(struct task_struct *tsk)
871 {
872         struct signal_struct *sig = tsk->signal;
873
874         atomic_dec(&sig->live);
875
876         if (atomic_dec_and_test(&sig->count))
877                 __cleanup_signal(sig);
878 }
879
880 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
881 {
882         unsigned long new_flags = p->flags;
883
884         new_flags &= ~PF_SUPERPRIV;
885         new_flags |= PF_FORKNOEXEC;
886         new_flags |= PF_STARTING;
887         p->flags = new_flags;
888         clear_freeze_flag(p);
889 }
890
891 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
892 {
893         current->clear_child_tid = tidptr;
894
895         return task_pid_vnr(current);
896 }
897
898 static void rt_mutex_init_task(struct task_struct *p)
899 {
900         spin_lock_init(&p->pi_lock);
901 #ifdef CONFIG_RT_MUTEXES
902         plist_head_init(&p->pi_waiters, &p->pi_lock);
903         p->pi_blocked_on = NULL;
904 #endif
905 }
906
907 #ifdef CONFIG_MM_OWNER
908 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
909 {
910         mm->owner = p;
911 }
912 #endif /* CONFIG_MM_OWNER */
913
914 /*
915  * Initialize POSIX timer handling for a single task.
916  */
917 static void posix_cpu_timers_init(struct task_struct *tsk)
918 {
919         tsk->cputime_expires.prof_exp = cputime_zero;
920         tsk->cputime_expires.virt_exp = cputime_zero;
921         tsk->cputime_expires.sched_exp = 0;
922         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
923         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
924         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
925 }
926
927 /*
928  * This creates a new process as a copy of the old one,
929  * but does not actually start it yet.
930  *
931  * It copies the registers, and all the appropriate
932  * parts of the process environment (as per the clone
933  * flags). The actual kick-off is left to the caller.
934  */
935 static struct task_struct *copy_process(unsigned long clone_flags,
936                                         unsigned long stack_start,
937                                         struct pt_regs *regs,
938                                         unsigned long stack_size,
939                                         int __user *child_tidptr,
940                                         struct pid *pid,
941                                         int trace)
942 {
943         int retval;
944         struct task_struct *p;
945         int cgroup_callbacks_done = 0;
946
947         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
948                 return ERR_PTR(-EINVAL);
949
950         /*
951          * Thread groups must share signals as well, and detached threads
952          * can only be started up within the thread group.
953          */
954         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
955                 return ERR_PTR(-EINVAL);
956
957         /*
958          * Shared signal handlers imply shared VM. By way of the above,
959          * thread groups also imply shared VM. Blocking this case allows
960          * for various simplifications in other code.
961          */
962         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
963                 return ERR_PTR(-EINVAL);
964
965         retval = security_task_create(clone_flags);
966         if (retval)
967                 goto fork_out;
968
969         retval = -ENOMEM;
970         p = dup_task_struct(current);
971         if (!p)
972                 goto fork_out;
973
974         rt_mutex_init_task(p);
975
976 #ifdef CONFIG_PROVE_LOCKING
977         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
978         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
979 #endif
980         retval = -EAGAIN;
981         if (atomic_read(&p->real_cred->user->processes) >=
982                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
983                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
984                     p->real_cred->user != INIT_USER)
985                         goto bad_fork_free;
986         }
987
988         retval = copy_creds(p, clone_flags);
989         if (retval < 0)
990                 goto bad_fork_free;
991
992         /*
993          * If multiple threads are within copy_process(), then this check
994          * triggers too late. This doesn't hurt, the check is only there
995          * to stop root fork bombs.
996          */
997         retval = -EAGAIN;
998         if (nr_threads >= max_threads)
999                 goto bad_fork_cleanup_count;
1000
1001         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1002                 goto bad_fork_cleanup_count;
1003
1004         if (p->binfmt && !try_module_get(p->binfmt->module))
1005                 goto bad_fork_cleanup_put_domain;
1006
1007         p->did_exec = 0;
1008         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1009         copy_flags(clone_flags, p);
1010         INIT_LIST_HEAD(&p->children);
1011         INIT_LIST_HEAD(&p->sibling);
1012 #ifdef CONFIG_PREEMPT_RCU
1013         p->rcu_read_lock_nesting = 0;
1014         p->rcu_flipctr_idx = 0;
1015 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1016         p->vfork_done = NULL;
1017         spin_lock_init(&p->alloc_lock);
1018
1019         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1020         init_sigpending(&p->pending);
1021
1022         p->utime = cputime_zero;
1023         p->stime = cputime_zero;
1024         p->gtime = cputime_zero;
1025         p->utimescaled = cputime_zero;
1026         p->stimescaled = cputime_zero;
1027         p->prev_utime = cputime_zero;
1028         p->prev_stime = cputime_zero;
1029
1030         p->default_timer_slack_ns = current->timer_slack_ns;
1031
1032 #ifdef CONFIG_DETECT_SOFTLOCKUP
1033         p->last_switch_count = 0;
1034         p->last_switch_timestamp = 0;
1035 #endif
1036
1037         task_io_accounting_init(&p->ioac);
1038         acct_clear_integrals(p);
1039
1040         posix_cpu_timers_init(p);
1041
1042         p->lock_depth = -1;             /* -1 = no lock */
1043         do_posix_clock_monotonic_gettime(&p->start_time);
1044         p->real_start_time = p->start_time;
1045         monotonic_to_bootbased(&p->real_start_time);
1046         p->io_context = NULL;
1047         p->audit_context = NULL;
1048         cgroup_fork(p);
1049 #ifdef CONFIG_NUMA
1050         p->mempolicy = mpol_dup(p->mempolicy);
1051         if (IS_ERR(p->mempolicy)) {
1052                 retval = PTR_ERR(p->mempolicy);
1053                 p->mempolicy = NULL;
1054                 goto bad_fork_cleanup_cgroup;
1055         }
1056         mpol_fix_fork_child_flag(p);
1057 #endif
1058 #ifdef CONFIG_TRACE_IRQFLAGS
1059         p->irq_events = 0;
1060 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1061         p->hardirqs_enabled = 1;
1062 #else
1063         p->hardirqs_enabled = 0;
1064 #endif
1065         p->hardirq_enable_ip = 0;
1066         p->hardirq_enable_event = 0;
1067         p->hardirq_disable_ip = _THIS_IP_;
1068         p->hardirq_disable_event = 0;
1069         p->softirqs_enabled = 1;
1070         p->softirq_enable_ip = _THIS_IP_;
1071         p->softirq_enable_event = 0;
1072         p->softirq_disable_ip = 0;
1073         p->softirq_disable_event = 0;
1074         p->hardirq_context = 0;
1075         p->softirq_context = 0;
1076 #endif
1077 #ifdef CONFIG_LOCKDEP
1078         p->lockdep_depth = 0; /* no locks held yet */
1079         p->curr_chain_key = 0;
1080         p->lockdep_recursion = 0;
1081 #endif
1082
1083 #ifdef CONFIG_DEBUG_MUTEXES
1084         p->blocked_on = NULL; /* not blocked yet */
1085 #endif
1086         if (unlikely(current->ptrace))
1087                 ptrace_fork(p, clone_flags);
1088
1089         /* Perform scheduler related setup. Assign this task to a CPU. */
1090         sched_fork(p, clone_flags);
1091
1092         if ((retval = audit_alloc(p)))
1093                 goto bad_fork_cleanup_policy;
1094         /* copy all the process information */
1095         if ((retval = copy_semundo(clone_flags, p)))
1096                 goto bad_fork_cleanup_audit;
1097         if ((retval = copy_files(clone_flags, p)))
1098                 goto bad_fork_cleanup_semundo;
1099         if ((retval = copy_fs(clone_flags, p)))
1100                 goto bad_fork_cleanup_files;
1101         if ((retval = copy_sighand(clone_flags, p)))
1102                 goto bad_fork_cleanup_fs;
1103         if ((retval = copy_signal(clone_flags, p)))
1104                 goto bad_fork_cleanup_sighand;
1105         if ((retval = copy_mm(clone_flags, p)))
1106                 goto bad_fork_cleanup_signal;
1107         if ((retval = copy_namespaces(clone_flags, p)))
1108                 goto bad_fork_cleanup_mm;
1109         if ((retval = copy_io(clone_flags, p)))
1110                 goto bad_fork_cleanup_namespaces;
1111         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1112         if (retval)
1113                 goto bad_fork_cleanup_io;
1114
1115         if (pid != &init_struct_pid) {
1116                 retval = -ENOMEM;
1117                 pid = alloc_pid(p->nsproxy->pid_ns);
1118                 if (!pid)
1119                         goto bad_fork_cleanup_io;
1120
1121                 if (clone_flags & CLONE_NEWPID) {
1122                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1123                         if (retval < 0)
1124                                 goto bad_fork_free_pid;
1125                 }
1126         }
1127
1128         ftrace_graph_init_task(p);
1129
1130         p->pid = pid_nr(pid);
1131         p->tgid = p->pid;
1132         if (clone_flags & CLONE_THREAD)
1133                 p->tgid = current->tgid;
1134
1135         if (current->nsproxy != p->nsproxy) {
1136                 retval = ns_cgroup_clone(p, pid);
1137                 if (retval)
1138                         goto bad_fork_free_graph;
1139         }
1140
1141         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1142         /*
1143          * Clear TID on mm_release()?
1144          */
1145         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1146 #ifdef CONFIG_FUTEX
1147         p->robust_list = NULL;
1148 #ifdef CONFIG_COMPAT
1149         p->compat_robust_list = NULL;
1150 #endif
1151         INIT_LIST_HEAD(&p->pi_state_list);
1152         p->pi_state_cache = NULL;
1153 #endif
1154         /*
1155          * sigaltstack should be cleared when sharing the same VM
1156          */
1157         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1158                 p->sas_ss_sp = p->sas_ss_size = 0;
1159
1160         /*
1161          * Syscall tracing should be turned off in the child regardless
1162          * of CLONE_PTRACE.
1163          */
1164         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1165 #ifdef TIF_SYSCALL_EMU
1166         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1167 #endif
1168         clear_all_latency_tracing(p);
1169
1170         /* ok, now we should be set up.. */
1171         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1172         p->pdeath_signal = 0;
1173         p->exit_state = 0;
1174
1175         /*
1176          * Ok, make it visible to the rest of the system.
1177          * We dont wake it up yet.
1178          */
1179         p->group_leader = p;
1180         INIT_LIST_HEAD(&p->thread_group);
1181
1182         /* Now that the task is set up, run cgroup callbacks if
1183          * necessary. We need to run them before the task is visible
1184          * on the tasklist. */
1185         cgroup_fork_callbacks(p);
1186         cgroup_callbacks_done = 1;
1187
1188         /* Need tasklist lock for parent etc handling! */
1189         write_lock_irq(&tasklist_lock);
1190
1191         /*
1192          * The task hasn't been attached yet, so its cpus_allowed mask will
1193          * not be changed, nor will its assigned CPU.
1194          *
1195          * The cpus_allowed mask of the parent may have changed after it was
1196          * copied first time - so re-copy it here, then check the child's CPU
1197          * to ensure it is on a valid CPU (and if not, just force it back to
1198          * parent's CPU). This avoids alot of nasty races.
1199          */
1200         p->cpus_allowed = current->cpus_allowed;
1201         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1202         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1203                         !cpu_online(task_cpu(p))))
1204                 set_task_cpu(p, smp_processor_id());
1205
1206         /* CLONE_PARENT re-uses the old parent */
1207         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1208                 p->real_parent = current->real_parent;
1209                 p->parent_exec_id = current->parent_exec_id;
1210         } else {
1211                 p->real_parent = current;
1212                 p->parent_exec_id = current->self_exec_id;
1213         }
1214
1215         spin_lock(&current->sighand->siglock);
1216
1217         /*
1218          * Process group and session signals need to be delivered to just the
1219          * parent before the fork or both the parent and the child after the
1220          * fork. Restart if a signal comes in before we add the new process to
1221          * it's process group.
1222          * A fatal signal pending means that current will exit, so the new
1223          * thread can't slip out of an OOM kill (or normal SIGKILL).
1224          */
1225         recalc_sigpending();
1226         if (signal_pending(current)) {
1227                 spin_unlock(&current->sighand->siglock);
1228                 write_unlock_irq(&tasklist_lock);
1229                 retval = -ERESTARTNOINTR;
1230                 goto bad_fork_free_graph;
1231         }
1232
1233         if (clone_flags & CLONE_THREAD) {
1234                 p->group_leader = current->group_leader;
1235                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1236         }
1237
1238         if (likely(p->pid)) {
1239                 list_add_tail(&p->sibling, &p->real_parent->children);
1240                 tracehook_finish_clone(p, clone_flags, trace);
1241
1242                 if (thread_group_leader(p)) {
1243                         if (clone_flags & CLONE_NEWPID)
1244                                 p->nsproxy->pid_ns->child_reaper = p;
1245
1246                         p->signal->leader_pid = pid;
1247                         tty_kref_put(p->signal->tty);
1248                         p->signal->tty = tty_kref_get(current->signal->tty);
1249                         set_task_pgrp(p, task_pgrp_nr(current));
1250                         set_task_session(p, task_session_nr(current));
1251                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1252                         attach_pid(p, PIDTYPE_SID, task_session(current));
1253                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1254                         __get_cpu_var(process_counts)++;
1255                 }
1256                 attach_pid(p, PIDTYPE_PID, pid);
1257                 nr_threads++;
1258         }
1259
1260         total_forks++;
1261         spin_unlock(&current->sighand->siglock);
1262         write_unlock_irq(&tasklist_lock);
1263         proc_fork_connector(p);
1264         cgroup_post_fork(p);
1265         return p;
1266
1267 bad_fork_free_graph:
1268         ftrace_graph_exit_task(p);
1269 bad_fork_free_pid:
1270         if (pid != &init_struct_pid)
1271                 free_pid(pid);
1272 bad_fork_cleanup_io:
1273         put_io_context(p->io_context);
1274 bad_fork_cleanup_namespaces:
1275         exit_task_namespaces(p);
1276 bad_fork_cleanup_mm:
1277         if (p->mm)
1278                 mmput(p->mm);
1279 bad_fork_cleanup_signal:
1280         cleanup_signal(p);
1281 bad_fork_cleanup_sighand:
1282         __cleanup_sighand(p->sighand);
1283 bad_fork_cleanup_fs:
1284         exit_fs(p); /* blocking */
1285 bad_fork_cleanup_files:
1286         exit_files(p); /* blocking */
1287 bad_fork_cleanup_semundo:
1288         exit_sem(p);
1289 bad_fork_cleanup_audit:
1290         audit_free(p);
1291 bad_fork_cleanup_policy:
1292 #ifdef CONFIG_NUMA
1293         mpol_put(p->mempolicy);
1294 bad_fork_cleanup_cgroup:
1295 #endif
1296         cgroup_exit(p, cgroup_callbacks_done);
1297         delayacct_tsk_free(p);
1298         if (p->binfmt)
1299                 module_put(p->binfmt->module);
1300 bad_fork_cleanup_put_domain:
1301         module_put(task_thread_info(p)->exec_domain->module);
1302 bad_fork_cleanup_count:
1303         atomic_dec(&p->cred->user->processes);
1304         put_cred(p->real_cred);
1305         put_cred(p->cred);
1306 bad_fork_free:
1307         free_task(p);
1308 fork_out:
1309         return ERR_PTR(retval);
1310 }
1311
1312 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1313 {
1314         memset(regs, 0, sizeof(struct pt_regs));
1315         return regs;
1316 }
1317
1318 struct task_struct * __cpuinit fork_idle(int cpu)
1319 {
1320         struct task_struct *task;
1321         struct pt_regs regs;
1322
1323         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1324                             &init_struct_pid, 0);
1325         if (!IS_ERR(task))
1326                 init_idle(task, cpu);
1327
1328         return task;
1329 }
1330
1331 /*
1332  *  Ok, this is the main fork-routine.
1333  *
1334  * It copies the process, and if successful kick-starts
1335  * it and waits for it to finish using the VM if required.
1336  */
1337 long do_fork(unsigned long clone_flags,
1338               unsigned long stack_start,
1339               struct pt_regs *regs,
1340               unsigned long stack_size,
1341               int __user *parent_tidptr,
1342               int __user *child_tidptr)
1343 {
1344         struct task_struct *p;
1345         int trace = 0;
1346         long nr;
1347
1348         /*
1349          * Do some preliminary argument and permissions checking before we
1350          * actually start allocating stuff
1351          */
1352         if (clone_flags & CLONE_NEWUSER) {
1353                 if (clone_flags & CLONE_THREAD)
1354                         return -EINVAL;
1355                 /* hopefully this check will go away when userns support is
1356                  * complete
1357                  */
1358                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1359                                 !capable(CAP_SETGID))
1360                         return -EPERM;
1361         }
1362
1363         /*
1364          * We hope to recycle these flags after 2.6.26
1365          */
1366         if (unlikely(clone_flags & CLONE_STOPPED)) {
1367                 static int __read_mostly count = 100;
1368
1369                 if (count > 0 && printk_ratelimit()) {
1370                         char comm[TASK_COMM_LEN];
1371
1372                         count--;
1373                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1374                                         "clone flags 0x%lx\n",
1375                                 get_task_comm(comm, current),
1376                                 clone_flags & CLONE_STOPPED);
1377                 }
1378         }
1379
1380         /*
1381          * When called from kernel_thread, don't do user tracing stuff.
1382          */
1383         if (likely(user_mode(regs)))
1384                 trace = tracehook_prepare_clone(clone_flags);
1385
1386         p = copy_process(clone_flags, stack_start, regs, stack_size,
1387                          child_tidptr, NULL, trace);
1388         /*
1389          * Do this prior waking up the new thread - the thread pointer
1390          * might get invalid after that point, if the thread exits quickly.
1391          */
1392         if (!IS_ERR(p)) {
1393                 struct completion vfork;
1394
1395                 trace_sched_process_fork(current, p);
1396
1397                 nr = task_pid_vnr(p);
1398
1399                 if (clone_flags & CLONE_PARENT_SETTID)
1400                         put_user(nr, parent_tidptr);
1401
1402                 if (clone_flags & CLONE_VFORK) {
1403                         p->vfork_done = &vfork;
1404                         init_completion(&vfork);
1405                 }
1406
1407                 audit_finish_fork(p);
1408                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1409
1410                 /*
1411                  * We set PF_STARTING at creation in case tracing wants to
1412                  * use this to distinguish a fully live task from one that
1413                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1414                  * clear it and set the child going.
1415                  */
1416                 p->flags &= ~PF_STARTING;
1417
1418                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1419                         /*
1420                          * We'll start up with an immediate SIGSTOP.
1421                          */
1422                         sigaddset(&p->pending.signal, SIGSTOP);
1423                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1424                         __set_task_state(p, TASK_STOPPED);
1425                 } else {
1426                         wake_up_new_task(p, clone_flags);
1427                 }
1428
1429                 tracehook_report_clone_complete(trace, regs,
1430                                                 clone_flags, nr, p);
1431
1432                 if (clone_flags & CLONE_VFORK) {
1433                         freezer_do_not_count();
1434                         wait_for_completion(&vfork);
1435                         freezer_count();
1436                         tracehook_report_vfork_done(p, nr);
1437                 }
1438         } else {
1439                 nr = PTR_ERR(p);
1440         }
1441         return nr;
1442 }
1443
1444 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1445 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1446 #endif
1447
1448 static void sighand_ctor(void *data)
1449 {
1450         struct sighand_struct *sighand = data;
1451
1452         spin_lock_init(&sighand->siglock);
1453         init_waitqueue_head(&sighand->signalfd_wqh);
1454 }
1455
1456 void __init proc_caches_init(void)
1457 {
1458         sighand_cachep = kmem_cache_create("sighand_cache",
1459                         sizeof(struct sighand_struct), 0,
1460                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1461                         sighand_ctor);
1462         signal_cachep = kmem_cache_create("signal_cache",
1463                         sizeof(struct signal_struct), 0,
1464                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1465         files_cachep = kmem_cache_create("files_cache",
1466                         sizeof(struct files_struct), 0,
1467                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1468         fs_cachep = kmem_cache_create("fs_cache",
1469                         sizeof(struct fs_struct), 0,
1470                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1471         mm_cachep = kmem_cache_create("mm_struct",
1472                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1473                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1474         mmap_init();
1475 }
1476
1477 /*
1478  * Check constraints on flags passed to the unshare system call and
1479  * force unsharing of additional process context as appropriate.
1480  */
1481 static void check_unshare_flags(unsigned long *flags_ptr)
1482 {
1483         /*
1484          * If unsharing a thread from a thread group, must also
1485          * unshare vm.
1486          */
1487         if (*flags_ptr & CLONE_THREAD)
1488                 *flags_ptr |= CLONE_VM;
1489
1490         /*
1491          * If unsharing vm, must also unshare signal handlers.
1492          */
1493         if (*flags_ptr & CLONE_VM)
1494                 *flags_ptr |= CLONE_SIGHAND;
1495
1496         /*
1497          * If unsharing signal handlers and the task was created
1498          * using CLONE_THREAD, then must unshare the thread
1499          */
1500         if ((*flags_ptr & CLONE_SIGHAND) &&
1501             (atomic_read(&current->signal->count) > 1))
1502                 *flags_ptr |= CLONE_THREAD;
1503
1504         /*
1505          * If unsharing namespace, must also unshare filesystem information.
1506          */
1507         if (*flags_ptr & CLONE_NEWNS)
1508                 *flags_ptr |= CLONE_FS;
1509 }
1510
1511 /*
1512  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1513  */
1514 static int unshare_thread(unsigned long unshare_flags)
1515 {
1516         if (unshare_flags & CLONE_THREAD)
1517                 return -EINVAL;
1518
1519         return 0;
1520 }
1521
1522 /*
1523  * Unshare the filesystem structure if it is being shared
1524  */
1525 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1526 {
1527         struct fs_struct *fs = current->fs;
1528
1529         if (!(unshare_flags & CLONE_FS) || !fs)
1530                 return 0;
1531
1532         /* don't need lock here; in the worst case we'll do useless copy */
1533         if (fs->users == 1)
1534                 return 0;
1535
1536         *new_fsp = copy_fs_struct(fs);
1537         if (!*new_fsp)
1538                 return -ENOMEM;
1539
1540         return 0;
1541 }
1542
1543 /*
1544  * Unsharing of sighand is not supported yet
1545  */
1546 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1547 {
1548         struct sighand_struct *sigh = current->sighand;
1549
1550         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1551                 return -EINVAL;
1552         else
1553                 return 0;
1554 }
1555
1556 /*
1557  * Unshare vm if it is being shared
1558  */
1559 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1560 {
1561         struct mm_struct *mm = current->mm;
1562
1563         if ((unshare_flags & CLONE_VM) &&
1564             (mm && atomic_read(&mm->mm_users) > 1)) {
1565                 return -EINVAL;
1566         }
1567
1568         return 0;
1569 }
1570
1571 /*
1572  * Unshare file descriptor table if it is being shared
1573  */
1574 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1575 {
1576         struct files_struct *fd = current->files;
1577         int error = 0;
1578
1579         if ((unshare_flags & CLONE_FILES) &&
1580             (fd && atomic_read(&fd->count) > 1)) {
1581                 *new_fdp = dup_fd(fd, &error);
1582                 if (!*new_fdp)
1583                         return error;
1584         }
1585
1586         return 0;
1587 }
1588
1589 /*
1590  * unshare allows a process to 'unshare' part of the process
1591  * context which was originally shared using clone.  copy_*
1592  * functions used by do_fork() cannot be used here directly
1593  * because they modify an inactive task_struct that is being
1594  * constructed. Here we are modifying the current, active,
1595  * task_struct.
1596  */
1597 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1598 {
1599         int err = 0;
1600         struct fs_struct *fs, *new_fs = NULL;
1601         struct sighand_struct *new_sigh = NULL;
1602         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1603         struct files_struct *fd, *new_fd = NULL;
1604         struct nsproxy *new_nsproxy = NULL;
1605         int do_sysvsem = 0;
1606
1607         check_unshare_flags(&unshare_flags);
1608
1609         /* Return -EINVAL for all unsupported flags */
1610         err = -EINVAL;
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                 goto bad_unshare_out;
1615
1616         /*
1617          * CLONE_NEWIPC must also detach from the undolist: after switching
1618          * to a new ipc namespace, the semaphore arrays from the old
1619          * namespace are unreachable.
1620          */
1621         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1622                 do_sysvsem = 1;
1623         if ((err = unshare_thread(unshare_flags)))
1624                 goto bad_unshare_out;
1625         if ((err = unshare_fs(unshare_flags, &new_fs)))
1626                 goto bad_unshare_cleanup_thread;
1627         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1628                 goto bad_unshare_cleanup_fs;
1629         if ((err = unshare_vm(unshare_flags, &new_mm)))
1630                 goto bad_unshare_cleanup_sigh;
1631         if ((err = unshare_fd(unshare_flags, &new_fd)))
1632                 goto bad_unshare_cleanup_vm;
1633         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1634                         new_fs)))
1635                 goto bad_unshare_cleanup_fd;
1636
1637         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1638                 if (do_sysvsem) {
1639                         /*
1640                          * CLONE_SYSVSEM is equivalent to sys_exit().
1641                          */
1642                         exit_sem(current);
1643                 }
1644
1645                 if (new_nsproxy) {
1646                         switch_task_namespaces(current, new_nsproxy);
1647                         new_nsproxy = NULL;
1648                 }
1649
1650                 task_lock(current);
1651
1652                 if (new_fs) {
1653                         fs = current->fs;
1654                         write_lock(&fs->lock);
1655                         current->fs = new_fs;
1656                         if (--fs->users)
1657                                 new_fs = NULL;
1658                         else
1659                                 new_fs = fs;
1660                         write_unlock(&fs->lock);
1661                 }
1662
1663                 if (new_mm) {
1664                         mm = current->mm;
1665                         active_mm = current->active_mm;
1666                         current->mm = new_mm;
1667                         current->active_mm = new_mm;
1668                         activate_mm(active_mm, new_mm);
1669                         new_mm = mm;
1670                 }
1671
1672                 if (new_fd) {
1673                         fd = current->files;
1674                         current->files = new_fd;
1675                         new_fd = fd;
1676                 }
1677
1678                 task_unlock(current);
1679         }
1680
1681         if (new_nsproxy)
1682                 put_nsproxy(new_nsproxy);
1683
1684 bad_unshare_cleanup_fd:
1685         if (new_fd)
1686                 put_files_struct(new_fd);
1687
1688 bad_unshare_cleanup_vm:
1689         if (new_mm)
1690                 mmput(new_mm);
1691
1692 bad_unshare_cleanup_sigh:
1693         if (new_sigh)
1694                 if (atomic_dec_and_test(&new_sigh->count))
1695                         kmem_cache_free(sighand_cachep, new_sigh);
1696
1697 bad_unshare_cleanup_fs:
1698         if (new_fs)
1699                 free_fs_struct(new_fs);
1700
1701 bad_unshare_cleanup_thread:
1702 bad_unshare_out:
1703         return err;
1704 }
1705
1706 /*
1707  *      Helper to unshare the files of the current task.
1708  *      We don't want to expose copy_files internals to
1709  *      the exec layer of the kernel.
1710  */
1711
1712 int unshare_files(struct files_struct **displaced)
1713 {
1714         struct task_struct *task = current;
1715         struct files_struct *copy = NULL;
1716         int error;
1717
1718         error = unshare_fd(CLONE_FILES, &copy);
1719         if (error || !copy) {
1720                 *displaced = NULL;
1721                 return error;
1722         }
1723         *displaced = task->files;
1724         task_lock(task);
1725         task->files = copy;
1726         task_unlock(task);
1727         return 0;
1728 }