b664a081fffa07f179b2af22350c992311563436
[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/config.h>
15 #include <linux/slab.h>
16 #include <linux/init.h>
17 #include <linux/unistd.h>
18 #include <linux/smp_lock.h>
19 #include <linux/module.h>
20 #include <linux/vmalloc.h>
21 #include <linux/completion.h>
22 #include <linux/namespace.h>
23 #include <linux/personality.h>
24 #include <linux/mempolicy.h>
25 #include <linux/sem.h>
26 #include <linux/file.h>
27 #include <linux/key.h>
28 #include <linux/binfmts.h>
29 #include <linux/mman.h>
30 #include <linux/fs.h>
31 #include <linux/capability.h>
32 #include <linux/cpu.h>
33 #include <linux/cpuset.h>
34 #include <linux/security.h>
35 #include <linux/swap.h>
36 #include <linux/syscalls.h>
37 #include <linux/jiffies.h>
38 #include <linux/futex.h>
39 #include <linux/rcupdate.h>
40 #include <linux/ptrace.h>
41 #include <linux/mount.h>
42 #include <linux/audit.h>
43 #include <linux/profile.h>
44 #include <linux/rmap.h>
45 #include <linux/acct.h>
46 #include <linux/cn_proc.h>
47
48 #include <asm/pgtable.h>
49 #include <asm/pgalloc.h>
50 #include <asm/uaccess.h>
51 #include <asm/mmu_context.h>
52 #include <asm/cacheflush.h>
53 #include <asm/tlbflush.h>
54
55 /*
56  * Protected counters by write_lock_irq(&tasklist_lock)
57  */
58 unsigned long total_forks;      /* Handle normal Linux uptimes. */
59 int nr_threads;                 /* The idle threads do not count.. */
60
61 int max_threads;                /* tunable limit on nr_threads */
62
63 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
64
65  __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
66
67 EXPORT_SYMBOL(tasklist_lock);
68
69 int nr_processes(void)
70 {
71         int cpu;
72         int total = 0;
73
74         for_each_online_cpu(cpu)
75                 total += per_cpu(process_counts, cpu);
76
77         return total;
78 }
79
80 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
81 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
82 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
83 static kmem_cache_t *task_struct_cachep;
84 #endif
85
86 /* SLAB cache for signal_struct structures (tsk->signal) */
87 static kmem_cache_t *signal_cachep;
88
89 /* SLAB cache for sighand_struct structures (tsk->sighand) */
90 kmem_cache_t *sighand_cachep;
91
92 /* SLAB cache for files_struct structures (tsk->files) */
93 kmem_cache_t *files_cachep;
94
95 /* SLAB cache for fs_struct structures (tsk->fs) */
96 kmem_cache_t *fs_cachep;
97
98 /* SLAB cache for vm_area_struct structures */
99 kmem_cache_t *vm_area_cachep;
100
101 /* SLAB cache for mm_struct structures (tsk->mm) */
102 static kmem_cache_t *mm_cachep;
103
104 void free_task(struct task_struct *tsk)
105 {
106         free_thread_info(tsk->thread_info);
107         rt_mutex_debug_task_free(tsk);
108         free_task_struct(tsk);
109 }
110 EXPORT_SYMBOL(free_task);
111
112 void __put_task_struct(struct task_struct *tsk)
113 {
114         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
115         WARN_ON(atomic_read(&tsk->usage));
116         WARN_ON(tsk == current);
117
118         security_task_free(tsk);
119         free_uid(tsk->user);
120         put_group_info(tsk->group_info);
121
122         if (!profile_handoff_task(tsk))
123                 free_task(tsk);
124 }
125
126 void __init fork_init(unsigned long mempages)
127 {
128 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
129 #ifndef ARCH_MIN_TASKALIGN
130 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
131 #endif
132         /* create a slab on which task_structs can be allocated */
133         task_struct_cachep =
134                 kmem_cache_create("task_struct", sizeof(struct task_struct),
135                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
136 #endif
137
138         /*
139          * The default maximum number of threads is set to a safe
140          * value: the thread structures can take up at most half
141          * of memory.
142          */
143         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
144
145         /*
146          * we need to allow at least 20 threads to boot a system
147          */
148         if(max_threads < 20)
149                 max_threads = 20;
150
151         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
152         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
153         init_task.signal->rlim[RLIMIT_SIGPENDING] =
154                 init_task.signal->rlim[RLIMIT_NPROC];
155 }
156
157 static struct task_struct *dup_task_struct(struct task_struct *orig)
158 {
159         struct task_struct *tsk;
160         struct thread_info *ti;
161
162         prepare_to_copy(orig);
163
164         tsk = alloc_task_struct();
165         if (!tsk)
166                 return NULL;
167
168         ti = alloc_thread_info(tsk);
169         if (!ti) {
170                 free_task_struct(tsk);
171                 return NULL;
172         }
173
174         *tsk = *orig;
175         tsk->thread_info = ti;
176         setup_thread_stack(tsk, orig);
177
178         /* One for us, one for whoever does the "release_task()" (usually parent) */
179         atomic_set(&tsk->usage,2);
180         atomic_set(&tsk->fs_excl, 0);
181         tsk->btrace_seq = 0;
182         tsk->splice_pipe = NULL;
183         return tsk;
184 }
185
186 #ifdef CONFIG_MMU
187 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
188 {
189         struct vm_area_struct *mpnt, *tmp, **pprev;
190         struct rb_node **rb_link, *rb_parent;
191         int retval;
192         unsigned long charge;
193         struct mempolicy *pol;
194
195         down_write(&oldmm->mmap_sem);
196         flush_cache_mm(oldmm);
197         down_write(&mm->mmap_sem);
198
199         mm->locked_vm = 0;
200         mm->mmap = NULL;
201         mm->mmap_cache = NULL;
202         mm->free_area_cache = oldmm->mmap_base;
203         mm->cached_hole_size = ~0UL;
204         mm->map_count = 0;
205         cpus_clear(mm->cpu_vm_mask);
206         mm->mm_rb = RB_ROOT;
207         rb_link = &mm->mm_rb.rb_node;
208         rb_parent = NULL;
209         pprev = &mm->mmap;
210
211         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
212                 struct file *file;
213
214                 if (mpnt->vm_flags & VM_DONTCOPY) {
215                         long pages = vma_pages(mpnt);
216                         mm->total_vm -= pages;
217                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
218                                                                 -pages);
219                         continue;
220                 }
221                 charge = 0;
222                 if (mpnt->vm_flags & VM_ACCOUNT) {
223                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
224                         if (security_vm_enough_memory(len))
225                                 goto fail_nomem;
226                         charge = len;
227                 }
228                 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
229                 if (!tmp)
230                         goto fail_nomem;
231                 *tmp = *mpnt;
232                 pol = mpol_copy(vma_policy(mpnt));
233                 retval = PTR_ERR(pol);
234                 if (IS_ERR(pol))
235                         goto fail_nomem_policy;
236                 vma_set_policy(tmp, pol);
237                 tmp->vm_flags &= ~VM_LOCKED;
238                 tmp->vm_mm = mm;
239                 tmp->vm_next = NULL;
240                 anon_vma_link(tmp);
241                 file = tmp->vm_file;
242                 if (file) {
243                         struct inode *inode = file->f_dentry->d_inode;
244                         get_file(file);
245                         if (tmp->vm_flags & VM_DENYWRITE)
246                                 atomic_dec(&inode->i_writecount);
247       
248                         /* insert tmp into the share list, just after mpnt */
249                         spin_lock(&file->f_mapping->i_mmap_lock);
250                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
251                         flush_dcache_mmap_lock(file->f_mapping);
252                         vma_prio_tree_add(tmp, mpnt);
253                         flush_dcache_mmap_unlock(file->f_mapping);
254                         spin_unlock(&file->f_mapping->i_mmap_lock);
255                 }
256
257                 /*
258                  * Link in the new vma and copy the page table entries.
259                  */
260                 *pprev = tmp;
261                 pprev = &tmp->vm_next;
262
263                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
264                 rb_link = &tmp->vm_rb.rb_right;
265                 rb_parent = &tmp->vm_rb;
266
267                 mm->map_count++;
268                 retval = copy_page_range(mm, oldmm, mpnt);
269
270                 if (tmp->vm_ops && tmp->vm_ops->open)
271                         tmp->vm_ops->open(tmp);
272
273                 if (retval)
274                         goto out;
275         }
276         retval = 0;
277 out:
278         up_write(&mm->mmap_sem);
279         flush_tlb_mm(oldmm);
280         up_write(&oldmm->mmap_sem);
281         return retval;
282 fail_nomem_policy:
283         kmem_cache_free(vm_area_cachep, tmp);
284 fail_nomem:
285         retval = -ENOMEM;
286         vm_unacct_memory(charge);
287         goto out;
288 }
289
290 static inline int mm_alloc_pgd(struct mm_struct * mm)
291 {
292         mm->pgd = pgd_alloc(mm);
293         if (unlikely(!mm->pgd))
294                 return -ENOMEM;
295         return 0;
296 }
297
298 static inline void mm_free_pgd(struct mm_struct * mm)
299 {
300         pgd_free(mm->pgd);
301 }
302 #else
303 #define dup_mmap(mm, oldmm)     (0)
304 #define mm_alloc_pgd(mm)        (0)
305 #define mm_free_pgd(mm)
306 #endif /* CONFIG_MMU */
307
308  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
309
310 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
311 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
312
313 #include <linux/init_task.h>
314
315 static struct mm_struct * mm_init(struct mm_struct * mm)
316 {
317         atomic_set(&mm->mm_users, 1);
318         atomic_set(&mm->mm_count, 1);
319         init_rwsem(&mm->mmap_sem);
320         INIT_LIST_HEAD(&mm->mmlist);
321         mm->core_waiters = 0;
322         mm->nr_ptes = 0;
323         set_mm_counter(mm, file_rss, 0);
324         set_mm_counter(mm, anon_rss, 0);
325         spin_lock_init(&mm->page_table_lock);
326         rwlock_init(&mm->ioctx_list_lock);
327         mm->ioctx_list = NULL;
328         mm->free_area_cache = TASK_UNMAPPED_BASE;
329         mm->cached_hole_size = ~0UL;
330
331         if (likely(!mm_alloc_pgd(mm))) {
332                 mm->def_flags = 0;
333                 return mm;
334         }
335         free_mm(mm);
336         return NULL;
337 }
338
339 /*
340  * Allocate and initialize an mm_struct.
341  */
342 struct mm_struct * mm_alloc(void)
343 {
344         struct mm_struct * mm;
345
346         mm = allocate_mm();
347         if (mm) {
348                 memset(mm, 0, sizeof(*mm));
349                 mm = mm_init(mm);
350         }
351         return mm;
352 }
353
354 /*
355  * Called when the last reference to the mm
356  * is dropped: either by a lazy thread or by
357  * mmput. Free the page directory and the mm.
358  */
359 void fastcall __mmdrop(struct mm_struct *mm)
360 {
361         BUG_ON(mm == &init_mm);
362         mm_free_pgd(mm);
363         destroy_context(mm);
364         free_mm(mm);
365 }
366
367 /*
368  * Decrement the use count and release all resources for an mm.
369  */
370 void mmput(struct mm_struct *mm)
371 {
372         might_sleep();
373
374         if (atomic_dec_and_test(&mm->mm_users)) {
375                 exit_aio(mm);
376                 exit_mmap(mm);
377                 if (!list_empty(&mm->mmlist)) {
378                         spin_lock(&mmlist_lock);
379                         list_del(&mm->mmlist);
380                         spin_unlock(&mmlist_lock);
381                 }
382                 put_swap_token(mm);
383                 mmdrop(mm);
384         }
385 }
386 EXPORT_SYMBOL_GPL(mmput);
387
388 /**
389  * get_task_mm - acquire a reference to the task's mm
390  *
391  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
392  * this kernel workthread has transiently adopted a user mm with use_mm,
393  * to do its AIO) is not set and if so returns a reference to it, after
394  * bumping up the use count.  User must release the mm via mmput()
395  * after use.  Typically used by /proc and ptrace.
396  */
397 struct mm_struct *get_task_mm(struct task_struct *task)
398 {
399         struct mm_struct *mm;
400
401         task_lock(task);
402         mm = task->mm;
403         if (mm) {
404                 if (task->flags & PF_BORROWED_MM)
405                         mm = NULL;
406                 else
407                         atomic_inc(&mm->mm_users);
408         }
409         task_unlock(task);
410         return mm;
411 }
412 EXPORT_SYMBOL_GPL(get_task_mm);
413
414 /* Please note the differences between mmput and mm_release.
415  * mmput is called whenever we stop holding onto a mm_struct,
416  * error success whatever.
417  *
418  * mm_release is called after a mm_struct has been removed
419  * from the current process.
420  *
421  * This difference is important for error handling, when we
422  * only half set up a mm_struct for a new process and need to restore
423  * the old one.  Because we mmput the new mm_struct before
424  * restoring the old one. . .
425  * Eric Biederman 10 January 1998
426  */
427 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
428 {
429         struct completion *vfork_done = tsk->vfork_done;
430
431         /* Get rid of any cached register state */
432         deactivate_mm(tsk, mm);
433
434         /* notify parent sleeping on vfork() */
435         if (vfork_done) {
436                 tsk->vfork_done = NULL;
437                 complete(vfork_done);
438         }
439         if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
440                 u32 __user * tidptr = tsk->clear_child_tid;
441                 tsk->clear_child_tid = NULL;
442
443                 /*
444                  * We don't check the error code - if userspace has
445                  * not set up a proper pointer then tough luck.
446                  */
447                 put_user(0, tidptr);
448                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
449         }
450 }
451
452 /*
453  * Allocate a new mm structure and copy contents from the
454  * mm structure of the passed in task structure.
455  */
456 static struct mm_struct *dup_mm(struct task_struct *tsk)
457 {
458         struct mm_struct *mm, *oldmm = current->mm;
459         int err;
460
461         if (!oldmm)
462                 return NULL;
463
464         mm = allocate_mm();
465         if (!mm)
466                 goto fail_nomem;
467
468         memcpy(mm, oldmm, sizeof(*mm));
469
470         if (!mm_init(mm))
471                 goto fail_nomem;
472
473         if (init_new_context(tsk, mm))
474                 goto fail_nocontext;
475
476         err = dup_mmap(mm, oldmm);
477         if (err)
478                 goto free_pt;
479
480         mm->hiwater_rss = get_mm_rss(mm);
481         mm->hiwater_vm = mm->total_vm;
482
483         return mm;
484
485 free_pt:
486         mmput(mm);
487
488 fail_nomem:
489         return NULL;
490
491 fail_nocontext:
492         /*
493          * If init_new_context() failed, we cannot use mmput() to free the mm
494          * because it calls destroy_context()
495          */
496         mm_free_pgd(mm);
497         free_mm(mm);
498         return NULL;
499 }
500
501 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
502 {
503         struct mm_struct * mm, *oldmm;
504         int retval;
505
506         tsk->min_flt = tsk->maj_flt = 0;
507         tsk->nvcsw = tsk->nivcsw = 0;
508
509         tsk->mm = NULL;
510         tsk->active_mm = NULL;
511
512         /*
513          * Are we cloning a kernel thread?
514          *
515          * We need to steal a active VM for that..
516          */
517         oldmm = current->mm;
518         if (!oldmm)
519                 return 0;
520
521         if (clone_flags & CLONE_VM) {
522                 atomic_inc(&oldmm->mm_users);
523                 mm = oldmm;
524                 goto good_mm;
525         }
526
527         retval = -ENOMEM;
528         mm = dup_mm(tsk);
529         if (!mm)
530                 goto fail_nomem;
531
532 good_mm:
533         tsk->mm = mm;
534         tsk->active_mm = mm;
535         return 0;
536
537 fail_nomem:
538         return retval;
539 }
540
541 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
542 {
543         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
544         /* We don't need to lock fs - think why ;-) */
545         if (fs) {
546                 atomic_set(&fs->count, 1);
547                 rwlock_init(&fs->lock);
548                 fs->umask = old->umask;
549                 read_lock(&old->lock);
550                 fs->rootmnt = mntget(old->rootmnt);
551                 fs->root = dget(old->root);
552                 fs->pwdmnt = mntget(old->pwdmnt);
553                 fs->pwd = dget(old->pwd);
554                 if (old->altroot) {
555                         fs->altrootmnt = mntget(old->altrootmnt);
556                         fs->altroot = dget(old->altroot);
557                 } else {
558                         fs->altrootmnt = NULL;
559                         fs->altroot = NULL;
560                 }
561                 read_unlock(&old->lock);
562         }
563         return fs;
564 }
565
566 struct fs_struct *copy_fs_struct(struct fs_struct *old)
567 {
568         return __copy_fs_struct(old);
569 }
570
571 EXPORT_SYMBOL_GPL(copy_fs_struct);
572
573 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
574 {
575         if (clone_flags & CLONE_FS) {
576                 atomic_inc(&current->fs->count);
577                 return 0;
578         }
579         tsk->fs = __copy_fs_struct(current->fs);
580         if (!tsk->fs)
581                 return -ENOMEM;
582         return 0;
583 }
584
585 static int count_open_files(struct fdtable *fdt)
586 {
587         int size = fdt->max_fdset;
588         int i;
589
590         /* Find the last open fd */
591         for (i = size/(8*sizeof(long)); i > 0; ) {
592                 if (fdt->open_fds->fds_bits[--i])
593                         break;
594         }
595         i = (i+1) * 8 * sizeof(long);
596         return i;
597 }
598
599 static struct files_struct *alloc_files(void)
600 {
601         struct files_struct *newf;
602         struct fdtable *fdt;
603
604         newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
605         if (!newf)
606                 goto out;
607
608         atomic_set(&newf->count, 1);
609
610         spin_lock_init(&newf->file_lock);
611         newf->next_fd = 0;
612         fdt = &newf->fdtab;
613         fdt->max_fds = NR_OPEN_DEFAULT;
614         fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
615         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
616         fdt->open_fds = (fd_set *)&newf->open_fds_init;
617         fdt->fd = &newf->fd_array[0];
618         INIT_RCU_HEAD(&fdt->rcu);
619         fdt->free_files = NULL;
620         fdt->next = NULL;
621         rcu_assign_pointer(newf->fdt, fdt);
622 out:
623         return newf;
624 }
625
626 /*
627  * Allocate a new files structure and copy contents from the
628  * passed in files structure.
629  * errorp will be valid only when the returned files_struct is NULL.
630  */
631 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
632 {
633         struct files_struct *newf;
634         struct file **old_fds, **new_fds;
635         int open_files, size, i, expand;
636         struct fdtable *old_fdt, *new_fdt;
637
638         *errorp = -ENOMEM;
639         newf = alloc_files();
640         if (!newf)
641                 goto out;
642
643         spin_lock(&oldf->file_lock);
644         old_fdt = files_fdtable(oldf);
645         new_fdt = files_fdtable(newf);
646         size = old_fdt->max_fdset;
647         open_files = count_open_files(old_fdt);
648         expand = 0;
649
650         /*
651          * Check whether we need to allocate a larger fd array or fd set.
652          * Note: we're not a clone task, so the open count won't  change.
653          */
654         if (open_files > new_fdt->max_fdset) {
655                 new_fdt->max_fdset = 0;
656                 expand = 1;
657         }
658         if (open_files > new_fdt->max_fds) {
659                 new_fdt->max_fds = 0;
660                 expand = 1;
661         }
662
663         /* if the old fdset gets grown now, we'll only copy up to "size" fds */
664         if (expand) {
665                 spin_unlock(&oldf->file_lock);
666                 spin_lock(&newf->file_lock);
667                 *errorp = expand_files(newf, open_files-1);
668                 spin_unlock(&newf->file_lock);
669                 if (*errorp < 0)
670                         goto out_release;
671                 new_fdt = files_fdtable(newf);
672                 /*
673                  * Reacquire the oldf lock and a pointer to its fd table
674                  * who knows it may have a new bigger fd table. We need
675                  * the latest pointer.
676                  */
677                 spin_lock(&oldf->file_lock);
678                 old_fdt = files_fdtable(oldf);
679         }
680
681         old_fds = old_fdt->fd;
682         new_fds = new_fdt->fd;
683
684         memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
685         memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
686
687         for (i = open_files; i != 0; i--) {
688                 struct file *f = *old_fds++;
689                 if (f) {
690                         get_file(f);
691                 } else {
692                         /*
693                          * The fd may be claimed in the fd bitmap but not yet
694                          * instantiated in the files array if a sibling thread
695                          * is partway through open().  So make sure that this
696                          * fd is available to the new process.
697                          */
698                         FD_CLR(open_files - i, new_fdt->open_fds);
699                 }
700                 rcu_assign_pointer(*new_fds++, f);
701         }
702         spin_unlock(&oldf->file_lock);
703
704         /* compute the remainder to be cleared */
705         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
706
707         /* This is long word aligned thus could use a optimized version */ 
708         memset(new_fds, 0, size); 
709
710         if (new_fdt->max_fdset > open_files) {
711                 int left = (new_fdt->max_fdset-open_files)/8;
712                 int start = open_files / (8 * sizeof(unsigned long));
713
714                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
715                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
716         }
717
718 out:
719         return newf;
720
721 out_release:
722         free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
723         free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
724         free_fd_array(new_fdt->fd, new_fdt->max_fds);
725         kmem_cache_free(files_cachep, newf);
726         return NULL;
727 }
728
729 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
730 {
731         struct files_struct *oldf, *newf;
732         int error = 0;
733
734         /*
735          * A background process may not have any files ...
736          */
737         oldf = current->files;
738         if (!oldf)
739                 goto out;
740
741         if (clone_flags & CLONE_FILES) {
742                 atomic_inc(&oldf->count);
743                 goto out;
744         }
745
746         /*
747          * Note: we may be using current for both targets (See exec.c)
748          * This works because we cache current->files (old) as oldf. Don't
749          * break this.
750          */
751         tsk->files = NULL;
752         newf = dup_fd(oldf, &error);
753         if (!newf)
754                 goto out;
755
756         tsk->files = newf;
757         error = 0;
758 out:
759         return error;
760 }
761
762 /*
763  *      Helper to unshare the files of the current task.
764  *      We don't want to expose copy_files internals to
765  *      the exec layer of the kernel.
766  */
767
768 int unshare_files(void)
769 {
770         struct files_struct *files  = current->files;
771         int rc;
772
773         BUG_ON(!files);
774
775         /* This can race but the race causes us to copy when we don't
776            need to and drop the copy */
777         if(atomic_read(&files->count) == 1)
778         {
779                 atomic_inc(&files->count);
780                 return 0;
781         }
782         rc = copy_files(0, current);
783         if(rc)
784                 current->files = files;
785         return rc;
786 }
787
788 EXPORT_SYMBOL(unshare_files);
789
790 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
791 {
792         struct sighand_struct *sig;
793
794         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
795                 atomic_inc(&current->sighand->count);
796                 return 0;
797         }
798         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
799         rcu_assign_pointer(tsk->sighand, sig);
800         if (!sig)
801                 return -ENOMEM;
802         atomic_set(&sig->count, 1);
803         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
804         return 0;
805 }
806
807 void __cleanup_sighand(struct sighand_struct *sighand)
808 {
809         if (atomic_dec_and_test(&sighand->count))
810                 kmem_cache_free(sighand_cachep, sighand);
811 }
812
813 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
814 {
815         struct signal_struct *sig;
816         int ret;
817
818         if (clone_flags & CLONE_THREAD) {
819                 atomic_inc(&current->signal->count);
820                 atomic_inc(&current->signal->live);
821                 return 0;
822         }
823         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
824         tsk->signal = sig;
825         if (!sig)
826                 return -ENOMEM;
827
828         ret = copy_thread_group_keys(tsk);
829         if (ret < 0) {
830                 kmem_cache_free(signal_cachep, sig);
831                 return ret;
832         }
833
834         atomic_set(&sig->count, 1);
835         atomic_set(&sig->live, 1);
836         init_waitqueue_head(&sig->wait_chldexit);
837         sig->flags = 0;
838         sig->group_exit_code = 0;
839         sig->group_exit_task = NULL;
840         sig->group_stop_count = 0;
841         sig->curr_target = NULL;
842         init_sigpending(&sig->shared_pending);
843         INIT_LIST_HEAD(&sig->posix_timers);
844
845         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
846         sig->it_real_incr.tv64 = 0;
847         sig->real_timer.function = it_real_fn;
848         sig->tsk = tsk;
849
850         sig->it_virt_expires = cputime_zero;
851         sig->it_virt_incr = cputime_zero;
852         sig->it_prof_expires = cputime_zero;
853         sig->it_prof_incr = cputime_zero;
854
855         sig->leader = 0;        /* session leadership doesn't inherit */
856         sig->tty_old_pgrp = 0;
857
858         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
859         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
860         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
861         sig->sched_time = 0;
862         INIT_LIST_HEAD(&sig->cpu_timers[0]);
863         INIT_LIST_HEAD(&sig->cpu_timers[1]);
864         INIT_LIST_HEAD(&sig->cpu_timers[2]);
865
866         task_lock(current->group_leader);
867         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
868         task_unlock(current->group_leader);
869
870         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
871                 /*
872                  * New sole thread in the process gets an expiry time
873                  * of the whole CPU time limit.
874                  */
875                 tsk->it_prof_expires =
876                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
877         }
878         acct_init_pacct(&sig->pacct);
879
880         return 0;
881 }
882
883 void __cleanup_signal(struct signal_struct *sig)
884 {
885         exit_thread_group_keys(sig);
886         kmem_cache_free(signal_cachep, sig);
887 }
888
889 static inline void cleanup_signal(struct task_struct *tsk)
890 {
891         struct signal_struct *sig = tsk->signal;
892
893         atomic_dec(&sig->live);
894
895         if (atomic_dec_and_test(&sig->count))
896                 __cleanup_signal(sig);
897 }
898
899 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
900 {
901         unsigned long new_flags = p->flags;
902
903         new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
904         new_flags |= PF_FORKNOEXEC;
905         if (!(clone_flags & CLONE_PTRACE))
906                 p->ptrace = 0;
907         p->flags = new_flags;
908 }
909
910 asmlinkage long sys_set_tid_address(int __user *tidptr)
911 {
912         current->clear_child_tid = tidptr;
913
914         return current->pid;
915 }
916
917 static inline void rt_mutex_init_task(struct task_struct *p)
918 {
919 #ifdef CONFIG_RT_MUTEXES
920         spin_lock_init(&p->pi_lock);
921         plist_head_init(&p->pi_waiters, &p->pi_lock);
922         p->pi_blocked_on = NULL;
923 # ifdef CONFIG_DEBUG_RT_MUTEXES
924         spin_lock_init(&p->held_list_lock);
925         INIT_LIST_HEAD(&p->held_list_head);
926 # endif
927 #endif
928 }
929
930 /*
931  * This creates a new process as a copy of the old one,
932  * but does not actually start it yet.
933  *
934  * It copies the registers, and all the appropriate
935  * parts of the process environment (as per the clone
936  * flags). The actual kick-off is left to the caller.
937  */
938 static task_t *copy_process(unsigned long clone_flags,
939                                  unsigned long stack_start,
940                                  struct pt_regs *regs,
941                                  unsigned long stack_size,
942                                  int __user *parent_tidptr,
943                                  int __user *child_tidptr,
944                                  int pid)
945 {
946         int retval;
947         struct task_struct *p = NULL;
948
949         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
950                 return ERR_PTR(-EINVAL);
951
952         /*
953          * Thread groups must share signals as well, and detached threads
954          * can only be started up within the thread group.
955          */
956         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
957                 return ERR_PTR(-EINVAL);
958
959         /*
960          * Shared signal handlers imply shared VM. By way of the above,
961          * thread groups also imply shared VM. Blocking this case allows
962          * for various simplifications in other code.
963          */
964         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
965                 return ERR_PTR(-EINVAL);
966
967         retval = security_task_create(clone_flags);
968         if (retval)
969                 goto fork_out;
970
971         retval = -ENOMEM;
972         p = dup_task_struct(current);
973         if (!p)
974                 goto fork_out;
975
976         retval = -EAGAIN;
977         if (atomic_read(&p->user->processes) >=
978                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
979                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
980                                 p->user != &root_user)
981                         goto bad_fork_free;
982         }
983
984         atomic_inc(&p->user->__count);
985         atomic_inc(&p->user->processes);
986         get_group_info(p->group_info);
987
988         /*
989          * If multiple threads are within copy_process(), then this check
990          * triggers too late. This doesn't hurt, the check is only there
991          * to stop root fork bombs.
992          */
993         if (nr_threads >= max_threads)
994                 goto bad_fork_cleanup_count;
995
996         if (!try_module_get(task_thread_info(p)->exec_domain->module))
997                 goto bad_fork_cleanup_count;
998
999         if (p->binfmt && !try_module_get(p->binfmt->module))
1000                 goto bad_fork_cleanup_put_domain;
1001
1002         p->did_exec = 0;
1003         copy_flags(clone_flags, p);
1004         p->pid = pid;
1005         retval = -EFAULT;
1006         if (clone_flags & CLONE_PARENT_SETTID)
1007                 if (put_user(p->pid, parent_tidptr))
1008                         goto bad_fork_cleanup;
1009
1010         INIT_LIST_HEAD(&p->children);
1011         INIT_LIST_HEAD(&p->sibling);
1012         p->vfork_done = NULL;
1013         spin_lock_init(&p->alloc_lock);
1014
1015         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1016         init_sigpending(&p->pending);
1017
1018         p->utime = cputime_zero;
1019         p->stime = cputime_zero;
1020         p->sched_time = 0;
1021         p->rchar = 0;           /* I/O counter: bytes read */
1022         p->wchar = 0;           /* I/O counter: bytes written */
1023         p->syscr = 0;           /* I/O counter: read syscalls */
1024         p->syscw = 0;           /* I/O counter: write syscalls */
1025         acct_clear_integrals(p);
1026
1027         p->it_virt_expires = cputime_zero;
1028         p->it_prof_expires = cputime_zero;
1029         p->it_sched_expires = 0;
1030         INIT_LIST_HEAD(&p->cpu_timers[0]);
1031         INIT_LIST_HEAD(&p->cpu_timers[1]);
1032         INIT_LIST_HEAD(&p->cpu_timers[2]);
1033
1034         p->lock_depth = -1;             /* -1 = no lock */
1035         do_posix_clock_monotonic_gettime(&p->start_time);
1036         p->security = NULL;
1037         p->io_context = NULL;
1038         p->io_wait = NULL;
1039         p->audit_context = NULL;
1040         cpuset_fork(p);
1041 #ifdef CONFIG_NUMA
1042         p->mempolicy = mpol_copy(p->mempolicy);
1043         if (IS_ERR(p->mempolicy)) {
1044                 retval = PTR_ERR(p->mempolicy);
1045                 p->mempolicy = NULL;
1046                 goto bad_fork_cleanup_cpuset;
1047         }
1048         mpol_fix_fork_child_flag(p);
1049 #endif
1050
1051         rt_mutex_init_task(p);
1052
1053 #ifdef CONFIG_DEBUG_MUTEXES
1054         p->blocked_on = NULL; /* not blocked yet */
1055 #endif
1056
1057         p->tgid = p->pid;
1058         if (clone_flags & CLONE_THREAD)
1059                 p->tgid = current->tgid;
1060
1061         if ((retval = security_task_alloc(p)))
1062                 goto bad_fork_cleanup_policy;
1063         if ((retval = audit_alloc(p)))
1064                 goto bad_fork_cleanup_security;
1065         /* copy all the process information */
1066         if ((retval = copy_semundo(clone_flags, p)))
1067                 goto bad_fork_cleanup_audit;
1068         if ((retval = copy_files(clone_flags, p)))
1069                 goto bad_fork_cleanup_semundo;
1070         if ((retval = copy_fs(clone_flags, p)))
1071                 goto bad_fork_cleanup_files;
1072         if ((retval = copy_sighand(clone_flags, p)))
1073                 goto bad_fork_cleanup_fs;
1074         if ((retval = copy_signal(clone_flags, p)))
1075                 goto bad_fork_cleanup_sighand;
1076         if ((retval = copy_mm(clone_flags, p)))
1077                 goto bad_fork_cleanup_signal;
1078         if ((retval = copy_keys(clone_flags, p)))
1079                 goto bad_fork_cleanup_mm;
1080         if ((retval = copy_namespace(clone_flags, p)))
1081                 goto bad_fork_cleanup_keys;
1082         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1083         if (retval)
1084                 goto bad_fork_cleanup_namespace;
1085
1086         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1087         /*
1088          * Clear TID on mm_release()?
1089          */
1090         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1091         p->robust_list = NULL;
1092 #ifdef CONFIG_COMPAT
1093         p->compat_robust_list = NULL;
1094 #endif
1095         /*
1096          * sigaltstack should be cleared when sharing the same VM
1097          */
1098         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1099                 p->sas_ss_sp = p->sas_ss_size = 0;
1100
1101         /*
1102          * Syscall tracing should be turned off in the child regardless
1103          * of CLONE_PTRACE.
1104          */
1105         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1106 #ifdef TIF_SYSCALL_EMU
1107         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1108 #endif
1109
1110         /* Our parent execution domain becomes current domain
1111            These must match for thread signalling to apply */
1112            
1113         p->parent_exec_id = p->self_exec_id;
1114
1115         /* ok, now we should be set up.. */
1116         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1117         p->pdeath_signal = 0;
1118         p->exit_state = 0;
1119
1120         /*
1121          * Ok, make it visible to the rest of the system.
1122          * We dont wake it up yet.
1123          */
1124         p->group_leader = p;
1125         INIT_LIST_HEAD(&p->thread_group);
1126         INIT_LIST_HEAD(&p->ptrace_children);
1127         INIT_LIST_HEAD(&p->ptrace_list);
1128
1129         /* Perform scheduler related setup. Assign this task to a CPU. */
1130         sched_fork(p, clone_flags);
1131
1132         /* Need tasklist lock for parent etc handling! */
1133         write_lock_irq(&tasklist_lock);
1134
1135         /*
1136          * The task hasn't been attached yet, so its cpus_allowed mask will
1137          * not be changed, nor will its assigned CPU.
1138          *
1139          * The cpus_allowed mask of the parent may have changed after it was
1140          * copied first time - so re-copy it here, then check the child's CPU
1141          * to ensure it is on a valid CPU (and if not, just force it back to
1142          * parent's CPU). This avoids alot of nasty races.
1143          */
1144         p->cpus_allowed = current->cpus_allowed;
1145         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1146                         !cpu_online(task_cpu(p))))
1147                 set_task_cpu(p, smp_processor_id());
1148
1149         /* CLONE_PARENT re-uses the old parent */
1150         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1151                 p->real_parent = current->real_parent;
1152         else
1153                 p->real_parent = current;
1154         p->parent = p->real_parent;
1155
1156         spin_lock(&current->sighand->siglock);
1157
1158         /*
1159          * Process group and session signals need to be delivered to just the
1160          * parent before the fork or both the parent and the child after the
1161          * fork. Restart if a signal comes in before we add the new process to
1162          * it's process group.
1163          * A fatal signal pending means that current will exit, so the new
1164          * thread can't slip out of an OOM kill (or normal SIGKILL).
1165          */
1166         recalc_sigpending();
1167         if (signal_pending(current)) {
1168                 spin_unlock(&current->sighand->siglock);
1169                 write_unlock_irq(&tasklist_lock);
1170                 retval = -ERESTARTNOINTR;
1171                 goto bad_fork_cleanup_namespace;
1172         }
1173
1174         if (clone_flags & CLONE_THREAD) {
1175                 p->group_leader = current->group_leader;
1176                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1177
1178                 if (!cputime_eq(current->signal->it_virt_expires,
1179                                 cputime_zero) ||
1180                     !cputime_eq(current->signal->it_prof_expires,
1181                                 cputime_zero) ||
1182                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1183                     !list_empty(&current->signal->cpu_timers[0]) ||
1184                     !list_empty(&current->signal->cpu_timers[1]) ||
1185                     !list_empty(&current->signal->cpu_timers[2])) {
1186                         /*
1187                          * Have child wake up on its first tick to check
1188                          * for process CPU timers.
1189                          */
1190                         p->it_prof_expires = jiffies_to_cputime(1);
1191                 }
1192         }
1193
1194         /*
1195          * inherit ioprio
1196          */
1197         p->ioprio = current->ioprio;
1198
1199         if (likely(p->pid)) {
1200                 add_parent(p);
1201                 if (unlikely(p->ptrace & PT_PTRACED))
1202                         __ptrace_link(p, current->parent);
1203
1204                 if (thread_group_leader(p)) {
1205                         p->signal->tty = current->signal->tty;
1206                         p->signal->pgrp = process_group(current);
1207                         p->signal->session = current->signal->session;
1208                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1209                         attach_pid(p, PIDTYPE_SID, p->signal->session);
1210
1211                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1212                         __get_cpu_var(process_counts)++;
1213                 }
1214                 attach_pid(p, PIDTYPE_PID, p->pid);
1215                 nr_threads++;
1216         }
1217
1218         total_forks++;
1219         spin_unlock(&current->sighand->siglock);
1220         write_unlock_irq(&tasklist_lock);
1221         proc_fork_connector(p);
1222         return p;
1223
1224 bad_fork_cleanup_namespace:
1225         exit_namespace(p);
1226 bad_fork_cleanup_keys:
1227         exit_keys(p);
1228 bad_fork_cleanup_mm:
1229         if (p->mm)
1230                 mmput(p->mm);
1231 bad_fork_cleanup_signal:
1232         cleanup_signal(p);
1233 bad_fork_cleanup_sighand:
1234         __cleanup_sighand(p->sighand);
1235 bad_fork_cleanup_fs:
1236         exit_fs(p); /* blocking */
1237 bad_fork_cleanup_files:
1238         exit_files(p); /* blocking */
1239 bad_fork_cleanup_semundo:
1240         exit_sem(p);
1241 bad_fork_cleanup_audit:
1242         audit_free(p);
1243 bad_fork_cleanup_security:
1244         security_task_free(p);
1245 bad_fork_cleanup_policy:
1246 #ifdef CONFIG_NUMA
1247         mpol_free(p->mempolicy);
1248 bad_fork_cleanup_cpuset:
1249 #endif
1250         cpuset_exit(p);
1251 bad_fork_cleanup:
1252         if (p->binfmt)
1253                 module_put(p->binfmt->module);
1254 bad_fork_cleanup_put_domain:
1255         module_put(task_thread_info(p)->exec_domain->module);
1256 bad_fork_cleanup_count:
1257         put_group_info(p->group_info);
1258         atomic_dec(&p->user->processes);
1259         free_uid(p->user);
1260 bad_fork_free:
1261         free_task(p);
1262 fork_out:
1263         return ERR_PTR(retval);
1264 }
1265
1266 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1267 {
1268         memset(regs, 0, sizeof(struct pt_regs));
1269         return regs;
1270 }
1271
1272 task_t * __devinit fork_idle(int cpu)
1273 {
1274         task_t *task;
1275         struct pt_regs regs;
1276
1277         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1278         if (!task)
1279                 return ERR_PTR(-ENOMEM);
1280         init_idle(task, cpu);
1281
1282         return task;
1283 }
1284
1285 static inline int fork_traceflag (unsigned clone_flags)
1286 {
1287         if (clone_flags & CLONE_UNTRACED)
1288                 return 0;
1289         else if (clone_flags & CLONE_VFORK) {
1290                 if (current->ptrace & PT_TRACE_VFORK)
1291                         return PTRACE_EVENT_VFORK;
1292         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1293                 if (current->ptrace & PT_TRACE_CLONE)
1294                         return PTRACE_EVENT_CLONE;
1295         } else if (current->ptrace & PT_TRACE_FORK)
1296                 return PTRACE_EVENT_FORK;
1297
1298         return 0;
1299 }
1300
1301 /*
1302  *  Ok, this is the main fork-routine.
1303  *
1304  * It copies the process, and if successful kick-starts
1305  * it and waits for it to finish using the VM if required.
1306  */
1307 long do_fork(unsigned long clone_flags,
1308               unsigned long stack_start,
1309               struct pt_regs *regs,
1310               unsigned long stack_size,
1311               int __user *parent_tidptr,
1312               int __user *child_tidptr)
1313 {
1314         struct task_struct *p;
1315         int trace = 0;
1316         struct pid *pid = alloc_pid();
1317         long nr;
1318
1319         if (!pid)
1320                 return -EAGAIN;
1321         nr = pid->nr;
1322         if (unlikely(current->ptrace)) {
1323                 trace = fork_traceflag (clone_flags);
1324                 if (trace)
1325                         clone_flags |= CLONE_PTRACE;
1326         }
1327
1328         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1329         /*
1330          * Do this prior waking up the new thread - the thread pointer
1331          * might get invalid after that point, if the thread exits quickly.
1332          */
1333         if (!IS_ERR(p)) {
1334                 struct completion vfork;
1335
1336                 if (clone_flags & CLONE_VFORK) {
1337                         p->vfork_done = &vfork;
1338                         init_completion(&vfork);
1339                 }
1340
1341                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1342                         /*
1343                          * We'll start up with an immediate SIGSTOP.
1344                          */
1345                         sigaddset(&p->pending.signal, SIGSTOP);
1346                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1347                 }
1348
1349                 if (!(clone_flags & CLONE_STOPPED))
1350                         wake_up_new_task(p, clone_flags);
1351                 else
1352                         p->state = TASK_STOPPED;
1353
1354                 if (unlikely (trace)) {
1355                         current->ptrace_message = nr;
1356                         ptrace_notify ((trace << 8) | SIGTRAP);
1357                 }
1358
1359                 if (clone_flags & CLONE_VFORK) {
1360                         wait_for_completion(&vfork);
1361                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
1362                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1363                 }
1364         } else {
1365                 free_pid(pid);
1366                 nr = PTR_ERR(p);
1367         }
1368         return nr;
1369 }
1370
1371 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1372 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1373 #endif
1374
1375 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1376 {
1377         struct sighand_struct *sighand = data;
1378
1379         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1380                                         SLAB_CTOR_CONSTRUCTOR)
1381                 spin_lock_init(&sighand->siglock);
1382 }
1383
1384 void __init proc_caches_init(void)
1385 {
1386         sighand_cachep = kmem_cache_create("sighand_cache",
1387                         sizeof(struct sighand_struct), 0,
1388                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1389                         sighand_ctor, NULL);
1390         signal_cachep = kmem_cache_create("signal_cache",
1391                         sizeof(struct signal_struct), 0,
1392                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1393         files_cachep = kmem_cache_create("files_cache", 
1394                         sizeof(struct files_struct), 0,
1395                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1396         fs_cachep = kmem_cache_create("fs_cache", 
1397                         sizeof(struct fs_struct), 0,
1398                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1399         vm_area_cachep = kmem_cache_create("vm_area_struct",
1400                         sizeof(struct vm_area_struct), 0,
1401                         SLAB_PANIC, NULL, NULL);
1402         mm_cachep = kmem_cache_create("mm_struct",
1403                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1404                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1405 }
1406
1407
1408 /*
1409  * Check constraints on flags passed to the unshare system call and
1410  * force unsharing of additional process context as appropriate.
1411  */
1412 static inline void check_unshare_flags(unsigned long *flags_ptr)
1413 {
1414         /*
1415          * If unsharing a thread from a thread group, must also
1416          * unshare vm.
1417          */
1418         if (*flags_ptr & CLONE_THREAD)
1419                 *flags_ptr |= CLONE_VM;
1420
1421         /*
1422          * If unsharing vm, must also unshare signal handlers.
1423          */
1424         if (*flags_ptr & CLONE_VM)
1425                 *flags_ptr |= CLONE_SIGHAND;
1426
1427         /*
1428          * If unsharing signal handlers and the task was created
1429          * using CLONE_THREAD, then must unshare the thread
1430          */
1431         if ((*flags_ptr & CLONE_SIGHAND) &&
1432             (atomic_read(&current->signal->count) > 1))
1433                 *flags_ptr |= CLONE_THREAD;
1434
1435         /*
1436          * If unsharing namespace, must also unshare filesystem information.
1437          */
1438         if (*flags_ptr & CLONE_NEWNS)
1439                 *flags_ptr |= CLONE_FS;
1440 }
1441
1442 /*
1443  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1444  */
1445 static int unshare_thread(unsigned long unshare_flags)
1446 {
1447         if (unshare_flags & CLONE_THREAD)
1448                 return -EINVAL;
1449
1450         return 0;
1451 }
1452
1453 /*
1454  * Unshare the filesystem structure if it is being shared
1455  */
1456 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1457 {
1458         struct fs_struct *fs = current->fs;
1459
1460         if ((unshare_flags & CLONE_FS) &&
1461             (fs && atomic_read(&fs->count) > 1)) {
1462                 *new_fsp = __copy_fs_struct(current->fs);
1463                 if (!*new_fsp)
1464                         return -ENOMEM;
1465         }
1466
1467         return 0;
1468 }
1469
1470 /*
1471  * Unshare the namespace structure if it is being shared
1472  */
1473 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1474 {
1475         struct namespace *ns = current->namespace;
1476
1477         if ((unshare_flags & CLONE_NEWNS) &&
1478             (ns && atomic_read(&ns->count) > 1)) {
1479                 if (!capable(CAP_SYS_ADMIN))
1480                         return -EPERM;
1481
1482                 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1483                 if (!*new_nsp)
1484                         return -ENOMEM;
1485         }
1486
1487         return 0;
1488 }
1489
1490 /*
1491  * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1492  * supported yet
1493  */
1494 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1495 {
1496         struct sighand_struct *sigh = current->sighand;
1497
1498         if ((unshare_flags & CLONE_SIGHAND) &&
1499             (sigh && atomic_read(&sigh->count) > 1))
1500                 return -EINVAL;
1501         else
1502                 return 0;
1503 }
1504
1505 /*
1506  * Unshare vm if it is being shared
1507  */
1508 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1509 {
1510         struct mm_struct *mm = current->mm;
1511
1512         if ((unshare_flags & CLONE_VM) &&
1513             (mm && atomic_read(&mm->mm_users) > 1)) {
1514                 return -EINVAL;
1515         }
1516
1517         return 0;
1518 }
1519
1520 /*
1521  * Unshare file descriptor table if it is being shared
1522  */
1523 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1524 {
1525         struct files_struct *fd = current->files;
1526         int error = 0;
1527
1528         if ((unshare_flags & CLONE_FILES) &&
1529             (fd && atomic_read(&fd->count) > 1)) {
1530                 *new_fdp = dup_fd(fd, &error);
1531                 if (!*new_fdp)
1532                         return error;
1533         }
1534
1535         return 0;
1536 }
1537
1538 /*
1539  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1540  * supported yet
1541  */
1542 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1543 {
1544         if (unshare_flags & CLONE_SYSVSEM)
1545                 return -EINVAL;
1546
1547         return 0;
1548 }
1549
1550 /*
1551  * unshare allows a process to 'unshare' part of the process
1552  * context which was originally shared using clone.  copy_*
1553  * functions used by do_fork() cannot be used here directly
1554  * because they modify an inactive task_struct that is being
1555  * constructed. Here we are modifying the current, active,
1556  * task_struct.
1557  */
1558 asmlinkage long sys_unshare(unsigned long unshare_flags)
1559 {
1560         int err = 0;
1561         struct fs_struct *fs, *new_fs = NULL;
1562         struct namespace *ns, *new_ns = NULL;
1563         struct sighand_struct *sigh, *new_sigh = NULL;
1564         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1565         struct files_struct *fd, *new_fd = NULL;
1566         struct sem_undo_list *new_ulist = NULL;
1567
1568         check_unshare_flags(&unshare_flags);
1569
1570         /* Return -EINVAL for all unsupported flags */
1571         err = -EINVAL;
1572         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1573                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
1574                 goto bad_unshare_out;
1575
1576         if ((err = unshare_thread(unshare_flags)))
1577                 goto bad_unshare_out;
1578         if ((err = unshare_fs(unshare_flags, &new_fs)))
1579                 goto bad_unshare_cleanup_thread;
1580         if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1581                 goto bad_unshare_cleanup_fs;
1582         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1583                 goto bad_unshare_cleanup_ns;
1584         if ((err = unshare_vm(unshare_flags, &new_mm)))
1585                 goto bad_unshare_cleanup_sigh;
1586         if ((err = unshare_fd(unshare_flags, &new_fd)))
1587                 goto bad_unshare_cleanup_vm;
1588         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1589                 goto bad_unshare_cleanup_fd;
1590
1591         if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1592
1593                 task_lock(current);
1594
1595                 if (new_fs) {
1596                         fs = current->fs;
1597                         current->fs = new_fs;
1598                         new_fs = fs;
1599                 }
1600
1601                 if (new_ns) {
1602                         ns = current->namespace;
1603                         current->namespace = new_ns;
1604                         new_ns = ns;
1605                 }
1606
1607                 if (new_sigh) {
1608                         sigh = current->sighand;
1609                         rcu_assign_pointer(current->sighand, new_sigh);
1610                         new_sigh = sigh;
1611                 }
1612
1613                 if (new_mm) {
1614                         mm = current->mm;
1615                         active_mm = current->active_mm;
1616                         current->mm = new_mm;
1617                         current->active_mm = new_mm;
1618                         activate_mm(active_mm, new_mm);
1619                         new_mm = mm;
1620                 }
1621
1622                 if (new_fd) {
1623                         fd = current->files;
1624                         current->files = new_fd;
1625                         new_fd = fd;
1626                 }
1627
1628                 task_unlock(current);
1629         }
1630
1631 bad_unshare_cleanup_fd:
1632         if (new_fd)
1633                 put_files_struct(new_fd);
1634
1635 bad_unshare_cleanup_vm:
1636         if (new_mm)
1637                 mmput(new_mm);
1638
1639 bad_unshare_cleanup_sigh:
1640         if (new_sigh)
1641                 if (atomic_dec_and_test(&new_sigh->count))
1642                         kmem_cache_free(sighand_cachep, new_sigh);
1643
1644 bad_unshare_cleanup_ns:
1645         if (new_ns)
1646                 put_namespace(new_ns);
1647
1648 bad_unshare_cleanup_fs:
1649         if (new_fs)
1650                 put_fs_struct(new_fs);
1651
1652 bad_unshare_cleanup_thread:
1653 bad_unshare_out:
1654         return err;
1655 }