49adc0e8d47ccf3b51af4e5b32ffd4210aeaf955
[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         free_task_struct(tsk);
108 }
109 EXPORT_SYMBOL(free_task);
110
111 void __put_task_struct(struct task_struct *tsk)
112 {
113         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
114         WARN_ON(atomic_read(&tsk->usage));
115         WARN_ON(tsk == current);
116
117         security_task_free(tsk);
118         free_uid(tsk->user);
119         put_group_info(tsk->group_info);
120
121         if (!profile_handoff_task(tsk))
122                 free_task(tsk);
123 }
124
125 void __init fork_init(unsigned long mempages)
126 {
127 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
128 #ifndef ARCH_MIN_TASKALIGN
129 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
130 #endif
131         /* create a slab on which task_structs can be allocated */
132         task_struct_cachep =
133                 kmem_cache_create("task_struct", sizeof(struct task_struct),
134                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
135 #endif
136
137         /*
138          * The default maximum number of threads is set to a safe
139          * value: the thread structures can take up at most half
140          * of memory.
141          */
142         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
143
144         /*
145          * we need to allow at least 20 threads to boot a system
146          */
147         if(max_threads < 20)
148                 max_threads = 20;
149
150         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
151         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
152         init_task.signal->rlim[RLIMIT_SIGPENDING] =
153                 init_task.signal->rlim[RLIMIT_NPROC];
154 }
155
156 static struct task_struct *dup_task_struct(struct task_struct *orig)
157 {
158         struct task_struct *tsk;
159         struct thread_info *ti;
160
161         prepare_to_copy(orig);
162
163         tsk = alloc_task_struct();
164         if (!tsk)
165                 return NULL;
166
167         ti = alloc_thread_info(tsk);
168         if (!ti) {
169                 free_task_struct(tsk);
170                 return NULL;
171         }
172
173         *tsk = *orig;
174         tsk->thread_info = ti;
175         setup_thread_stack(tsk, orig);
176
177         /* One for us, one for whoever does the "release_task()" (usually parent) */
178         atomic_set(&tsk->usage,2);
179         atomic_set(&tsk->fs_excl, 0);
180         tsk->btrace_seq = 0;
181         tsk->splice_pipe = NULL;
182         return tsk;
183 }
184
185 #ifdef CONFIG_MMU
186 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
187 {
188         struct vm_area_struct *mpnt, *tmp, **pprev;
189         struct rb_node **rb_link, *rb_parent;
190         int retval;
191         unsigned long charge;
192         struct mempolicy *pol;
193
194         down_write(&oldmm->mmap_sem);
195         flush_cache_mm(oldmm);
196         down_write(&mm->mmap_sem);
197
198         mm->locked_vm = 0;
199         mm->mmap = NULL;
200         mm->mmap_cache = NULL;
201         mm->free_area_cache = oldmm->mmap_base;
202         mm->cached_hole_size = ~0UL;
203         mm->map_count = 0;
204         cpus_clear(mm->cpu_vm_mask);
205         mm->mm_rb = RB_ROOT;
206         rb_link = &mm->mm_rb.rb_node;
207         rb_parent = NULL;
208         pprev = &mm->mmap;
209
210         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
211                 struct file *file;
212
213                 if (mpnt->vm_flags & VM_DONTCOPY) {
214                         long pages = vma_pages(mpnt);
215                         mm->total_vm -= pages;
216                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
217                                                                 -pages);
218                         continue;
219                 }
220                 charge = 0;
221                 if (mpnt->vm_flags & VM_ACCOUNT) {
222                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
223                         if (security_vm_enough_memory(len))
224                                 goto fail_nomem;
225                         charge = len;
226                 }
227                 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
228                 if (!tmp)
229                         goto fail_nomem;
230                 *tmp = *mpnt;
231                 pol = mpol_copy(vma_policy(mpnt));
232                 retval = PTR_ERR(pol);
233                 if (IS_ERR(pol))
234                         goto fail_nomem_policy;
235                 vma_set_policy(tmp, pol);
236                 tmp->vm_flags &= ~VM_LOCKED;
237                 tmp->vm_mm = mm;
238                 tmp->vm_next = NULL;
239                 anon_vma_link(tmp);
240                 file = tmp->vm_file;
241                 if (file) {
242                         struct inode *inode = file->f_dentry->d_inode;
243                         get_file(file);
244                         if (tmp->vm_flags & VM_DENYWRITE)
245                                 atomic_dec(&inode->i_writecount);
246       
247                         /* insert tmp into the share list, just after mpnt */
248                         spin_lock(&file->f_mapping->i_mmap_lock);
249                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
250                         flush_dcache_mmap_lock(file->f_mapping);
251                         vma_prio_tree_add(tmp, mpnt);
252                         flush_dcache_mmap_unlock(file->f_mapping);
253                         spin_unlock(&file->f_mapping->i_mmap_lock);
254                 }
255
256                 /*
257                  * Link in the new vma and copy the page table entries.
258                  */
259                 *pprev = tmp;
260                 pprev = &tmp->vm_next;
261
262                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
263                 rb_link = &tmp->vm_rb.rb_right;
264                 rb_parent = &tmp->vm_rb;
265
266                 mm->map_count++;
267                 retval = copy_page_range(mm, oldmm, mpnt);
268
269                 if (tmp->vm_ops && tmp->vm_ops->open)
270                         tmp->vm_ops->open(tmp);
271
272                 if (retval)
273                         goto out;
274         }
275         retval = 0;
276 out:
277         up_write(&mm->mmap_sem);
278         flush_tlb_mm(oldmm);
279         up_write(&oldmm->mmap_sem);
280         return retval;
281 fail_nomem_policy:
282         kmem_cache_free(vm_area_cachep, tmp);
283 fail_nomem:
284         retval = -ENOMEM;
285         vm_unacct_memory(charge);
286         goto out;
287 }
288
289 static inline int mm_alloc_pgd(struct mm_struct * mm)
290 {
291         mm->pgd = pgd_alloc(mm);
292         if (unlikely(!mm->pgd))
293                 return -ENOMEM;
294         return 0;
295 }
296
297 static inline void mm_free_pgd(struct mm_struct * mm)
298 {
299         pgd_free(mm->pgd);
300 }
301 #else
302 #define dup_mmap(mm, oldmm)     (0)
303 #define mm_alloc_pgd(mm)        (0)
304 #define mm_free_pgd(mm)
305 #endif /* CONFIG_MMU */
306
307  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
308
309 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
310 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
311
312 #include <linux/init_task.h>
313
314 static struct mm_struct * mm_init(struct mm_struct * mm)
315 {
316         atomic_set(&mm->mm_users, 1);
317         atomic_set(&mm->mm_count, 1);
318         init_rwsem(&mm->mmap_sem);
319         INIT_LIST_HEAD(&mm->mmlist);
320         mm->core_waiters = 0;
321         mm->nr_ptes = 0;
322         set_mm_counter(mm, file_rss, 0);
323         set_mm_counter(mm, anon_rss, 0);
324         spin_lock_init(&mm->page_table_lock);
325         rwlock_init(&mm->ioctx_list_lock);
326         mm->ioctx_list = NULL;
327         mm->free_area_cache = TASK_UNMAPPED_BASE;
328         mm->cached_hole_size = ~0UL;
329
330         if (likely(!mm_alloc_pgd(mm))) {
331                 mm->def_flags = 0;
332                 return mm;
333         }
334         free_mm(mm);
335         return NULL;
336 }
337
338 /*
339  * Allocate and initialize an mm_struct.
340  */
341 struct mm_struct * mm_alloc(void)
342 {
343         struct mm_struct * mm;
344
345         mm = allocate_mm();
346         if (mm) {
347                 memset(mm, 0, sizeof(*mm));
348                 mm = mm_init(mm);
349         }
350         return mm;
351 }
352
353 /*
354  * Called when the last reference to the mm
355  * is dropped: either by a lazy thread or by
356  * mmput. Free the page directory and the mm.
357  */
358 void fastcall __mmdrop(struct mm_struct *mm)
359 {
360         BUG_ON(mm == &init_mm);
361         mm_free_pgd(mm);
362         destroy_context(mm);
363         free_mm(mm);
364 }
365
366 /*
367  * Decrement the use count and release all resources for an mm.
368  */
369 void mmput(struct mm_struct *mm)
370 {
371         might_sleep();
372
373         if (atomic_dec_and_test(&mm->mm_users)) {
374                 exit_aio(mm);
375                 exit_mmap(mm);
376                 if (!list_empty(&mm->mmlist)) {
377                         spin_lock(&mmlist_lock);
378                         list_del(&mm->mmlist);
379                         spin_unlock(&mmlist_lock);
380                 }
381                 put_swap_token(mm);
382                 mmdrop(mm);
383         }
384 }
385 EXPORT_SYMBOL_GPL(mmput);
386
387 /**
388  * get_task_mm - acquire a reference to the task's mm
389  *
390  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
391  * this kernel workthread has transiently adopted a user mm with use_mm,
392  * to do its AIO) is not set and if so returns a reference to it, after
393  * bumping up the use count.  User must release the mm via mmput()
394  * after use.  Typically used by /proc and ptrace.
395  */
396 struct mm_struct *get_task_mm(struct task_struct *task)
397 {
398         struct mm_struct *mm;
399
400         task_lock(task);
401         mm = task->mm;
402         if (mm) {
403                 if (task->flags & PF_BORROWED_MM)
404                         mm = NULL;
405                 else
406                         atomic_inc(&mm->mm_users);
407         }
408         task_unlock(task);
409         return mm;
410 }
411 EXPORT_SYMBOL_GPL(get_task_mm);
412
413 /* Please note the differences between mmput and mm_release.
414  * mmput is called whenever we stop holding onto a mm_struct,
415  * error success whatever.
416  *
417  * mm_release is called after a mm_struct has been removed
418  * from the current process.
419  *
420  * This difference is important for error handling, when we
421  * only half set up a mm_struct for a new process and need to restore
422  * the old one.  Because we mmput the new mm_struct before
423  * restoring the old one. . .
424  * Eric Biederman 10 January 1998
425  */
426 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
427 {
428         struct completion *vfork_done = tsk->vfork_done;
429
430         /* Get rid of any cached register state */
431         deactivate_mm(tsk, mm);
432
433         /* notify parent sleeping on vfork() */
434         if (vfork_done) {
435                 tsk->vfork_done = NULL;
436                 complete(vfork_done);
437         }
438         if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
439                 u32 __user * tidptr = tsk->clear_child_tid;
440                 tsk->clear_child_tid = NULL;
441
442                 /*
443                  * We don't check the error code - if userspace has
444                  * not set up a proper pointer then tough luck.
445                  */
446                 put_user(0, tidptr);
447                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
448         }
449 }
450
451 /*
452  * Allocate a new mm structure and copy contents from the
453  * mm structure of the passed in task structure.
454  */
455 static struct mm_struct *dup_mm(struct task_struct *tsk)
456 {
457         struct mm_struct *mm, *oldmm = current->mm;
458         int err;
459
460         if (!oldmm)
461                 return NULL;
462
463         mm = allocate_mm();
464         if (!mm)
465                 goto fail_nomem;
466
467         memcpy(mm, oldmm, sizeof(*mm));
468
469         if (!mm_init(mm))
470                 goto fail_nomem;
471
472         if (init_new_context(tsk, mm))
473                 goto fail_nocontext;
474
475         err = dup_mmap(mm, oldmm);
476         if (err)
477                 goto free_pt;
478
479         mm->hiwater_rss = get_mm_rss(mm);
480         mm->hiwater_vm = mm->total_vm;
481
482         return mm;
483
484 free_pt:
485         mmput(mm);
486
487 fail_nomem:
488         return NULL;
489
490 fail_nocontext:
491         /*
492          * If init_new_context() failed, we cannot use mmput() to free the mm
493          * because it calls destroy_context()
494          */
495         mm_free_pgd(mm);
496         free_mm(mm);
497         return NULL;
498 }
499
500 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
501 {
502         struct mm_struct * mm, *oldmm;
503         int retval;
504
505         tsk->min_flt = tsk->maj_flt = 0;
506         tsk->nvcsw = tsk->nivcsw = 0;
507
508         tsk->mm = NULL;
509         tsk->active_mm = NULL;
510
511         /*
512          * Are we cloning a kernel thread?
513          *
514          * We need to steal a active VM for that..
515          */
516         oldmm = current->mm;
517         if (!oldmm)
518                 return 0;
519
520         if (clone_flags & CLONE_VM) {
521                 atomic_inc(&oldmm->mm_users);
522                 mm = oldmm;
523                 goto good_mm;
524         }
525
526         retval = -ENOMEM;
527         mm = dup_mm(tsk);
528         if (!mm)
529                 goto fail_nomem;
530
531 good_mm:
532         tsk->mm = mm;
533         tsk->active_mm = mm;
534         return 0;
535
536 fail_nomem:
537         return retval;
538 }
539
540 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
541 {
542         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
543         /* We don't need to lock fs - think why ;-) */
544         if (fs) {
545                 atomic_set(&fs->count, 1);
546                 rwlock_init(&fs->lock);
547                 fs->umask = old->umask;
548                 read_lock(&old->lock);
549                 fs->rootmnt = mntget(old->rootmnt);
550                 fs->root = dget(old->root);
551                 fs->pwdmnt = mntget(old->pwdmnt);
552                 fs->pwd = dget(old->pwd);
553                 if (old->altroot) {
554                         fs->altrootmnt = mntget(old->altrootmnt);
555                         fs->altroot = dget(old->altroot);
556                 } else {
557                         fs->altrootmnt = NULL;
558                         fs->altroot = NULL;
559                 }
560                 read_unlock(&old->lock);
561         }
562         return fs;
563 }
564
565 struct fs_struct *copy_fs_struct(struct fs_struct *old)
566 {
567         return __copy_fs_struct(old);
568 }
569
570 EXPORT_SYMBOL_GPL(copy_fs_struct);
571
572 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
573 {
574         if (clone_flags & CLONE_FS) {
575                 atomic_inc(&current->fs->count);
576                 return 0;
577         }
578         tsk->fs = __copy_fs_struct(current->fs);
579         if (!tsk->fs)
580                 return -ENOMEM;
581         return 0;
582 }
583
584 static int count_open_files(struct fdtable *fdt)
585 {
586         int size = fdt->max_fdset;
587         int i;
588
589         /* Find the last open fd */
590         for (i = size/(8*sizeof(long)); i > 0; ) {
591                 if (fdt->open_fds->fds_bits[--i])
592                         break;
593         }
594         i = (i+1) * 8 * sizeof(long);
595         return i;
596 }
597
598 static struct files_struct *alloc_files(void)
599 {
600         struct files_struct *newf;
601         struct fdtable *fdt;
602
603         newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
604         if (!newf)
605                 goto out;
606
607         atomic_set(&newf->count, 1);
608
609         spin_lock_init(&newf->file_lock);
610         newf->next_fd = 0;
611         fdt = &newf->fdtab;
612         fdt->max_fds = NR_OPEN_DEFAULT;
613         fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
614         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
615         fdt->open_fds = (fd_set *)&newf->open_fds_init;
616         fdt->fd = &newf->fd_array[0];
617         INIT_RCU_HEAD(&fdt->rcu);
618         fdt->free_files = NULL;
619         fdt->next = NULL;
620         rcu_assign_pointer(newf->fdt, fdt);
621 out:
622         return newf;
623 }
624
625 /*
626  * Allocate a new files structure and copy contents from the
627  * passed in files structure.
628  * errorp will be valid only when the returned files_struct is NULL.
629  */
630 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
631 {
632         struct files_struct *newf;
633         struct file **old_fds, **new_fds;
634         int open_files, size, i, expand;
635         struct fdtable *old_fdt, *new_fdt;
636
637         *errorp = -ENOMEM;
638         newf = alloc_files();
639         if (!newf)
640                 goto out;
641
642         spin_lock(&oldf->file_lock);
643         old_fdt = files_fdtable(oldf);
644         new_fdt = files_fdtable(newf);
645         size = old_fdt->max_fdset;
646         open_files = count_open_files(old_fdt);
647         expand = 0;
648
649         /*
650          * Check whether we need to allocate a larger fd array or fd set.
651          * Note: we're not a clone task, so the open count won't  change.
652          */
653         if (open_files > new_fdt->max_fdset) {
654                 new_fdt->max_fdset = 0;
655                 expand = 1;
656         }
657         if (open_files > new_fdt->max_fds) {
658                 new_fdt->max_fds = 0;
659                 expand = 1;
660         }
661
662         /* if the old fdset gets grown now, we'll only copy up to "size" fds */
663         if (expand) {
664                 spin_unlock(&oldf->file_lock);
665                 spin_lock(&newf->file_lock);
666                 *errorp = expand_files(newf, open_files-1);
667                 spin_unlock(&newf->file_lock);
668                 if (*errorp < 0)
669                         goto out_release;
670                 new_fdt = files_fdtable(newf);
671                 /*
672                  * Reacquire the oldf lock and a pointer to its fd table
673                  * who knows it may have a new bigger fd table. We need
674                  * the latest pointer.
675                  */
676                 spin_lock(&oldf->file_lock);
677                 old_fdt = files_fdtable(oldf);
678         }
679
680         old_fds = old_fdt->fd;
681         new_fds = new_fdt->fd;
682
683         memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
684         memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
685
686         for (i = open_files; i != 0; i--) {
687                 struct file *f = *old_fds++;
688                 if (f) {
689                         get_file(f);
690                 } else {
691                         /*
692                          * The fd may be claimed in the fd bitmap but not yet
693                          * instantiated in the files array if a sibling thread
694                          * is partway through open().  So make sure that this
695                          * fd is available to the new process.
696                          */
697                         FD_CLR(open_files - i, new_fdt->open_fds);
698                 }
699                 rcu_assign_pointer(*new_fds++, f);
700         }
701         spin_unlock(&oldf->file_lock);
702
703         /* compute the remainder to be cleared */
704         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
705
706         /* This is long word aligned thus could use a optimized version */ 
707         memset(new_fds, 0, size); 
708
709         if (new_fdt->max_fdset > open_files) {
710                 int left = (new_fdt->max_fdset-open_files)/8;
711                 int start = open_files / (8 * sizeof(unsigned long));
712
713                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
714                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
715         }
716
717 out:
718         return newf;
719
720 out_release:
721         free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
722         free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
723         free_fd_array(new_fdt->fd, new_fdt->max_fds);
724         kmem_cache_free(files_cachep, newf);
725         return NULL;
726 }
727
728 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
729 {
730         struct files_struct *oldf, *newf;
731         int error = 0;
732
733         /*
734          * A background process may not have any files ...
735          */
736         oldf = current->files;
737         if (!oldf)
738                 goto out;
739
740         if (clone_flags & CLONE_FILES) {
741                 atomic_inc(&oldf->count);
742                 goto out;
743         }
744
745         /*
746          * Note: we may be using current for both targets (See exec.c)
747          * This works because we cache current->files (old) as oldf. Don't
748          * break this.
749          */
750         tsk->files = NULL;
751         newf = dup_fd(oldf, &error);
752         if (!newf)
753                 goto out;
754
755         tsk->files = newf;
756         error = 0;
757 out:
758         return error;
759 }
760
761 /*
762  *      Helper to unshare the files of the current task.
763  *      We don't want to expose copy_files internals to
764  *      the exec layer of the kernel.
765  */
766
767 int unshare_files(void)
768 {
769         struct files_struct *files  = current->files;
770         int rc;
771
772         BUG_ON(!files);
773
774         /* This can race but the race causes us to copy when we don't
775            need to and drop the copy */
776         if(atomic_read(&files->count) == 1)
777         {
778                 atomic_inc(&files->count);
779                 return 0;
780         }
781         rc = copy_files(0, current);
782         if(rc)
783                 current->files = files;
784         return rc;
785 }
786
787 EXPORT_SYMBOL(unshare_files);
788
789 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
790 {
791         struct sighand_struct *sig;
792
793         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
794                 atomic_inc(&current->sighand->count);
795                 return 0;
796         }
797         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
798         rcu_assign_pointer(tsk->sighand, sig);
799         if (!sig)
800                 return -ENOMEM;
801         atomic_set(&sig->count, 1);
802         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
803         return 0;
804 }
805
806 void __cleanup_sighand(struct sighand_struct *sighand)
807 {
808         if (atomic_dec_and_test(&sighand->count))
809                 kmem_cache_free(sighand_cachep, sighand);
810 }
811
812 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
813 {
814         struct signal_struct *sig;
815         int ret;
816
817         if (clone_flags & CLONE_THREAD) {
818                 atomic_inc(&current->signal->count);
819                 atomic_inc(&current->signal->live);
820                 return 0;
821         }
822         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
823         tsk->signal = sig;
824         if (!sig)
825                 return -ENOMEM;
826
827         ret = copy_thread_group_keys(tsk);
828         if (ret < 0) {
829                 kmem_cache_free(signal_cachep, sig);
830                 return ret;
831         }
832
833         atomic_set(&sig->count, 1);
834         atomic_set(&sig->live, 1);
835         init_waitqueue_head(&sig->wait_chldexit);
836         sig->flags = 0;
837         sig->group_exit_code = 0;
838         sig->group_exit_task = NULL;
839         sig->group_stop_count = 0;
840         sig->curr_target = NULL;
841         init_sigpending(&sig->shared_pending);
842         INIT_LIST_HEAD(&sig->posix_timers);
843
844         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
845         sig->it_real_incr.tv64 = 0;
846         sig->real_timer.function = it_real_fn;
847         sig->tsk = tsk;
848
849         sig->it_virt_expires = cputime_zero;
850         sig->it_virt_incr = cputime_zero;
851         sig->it_prof_expires = cputime_zero;
852         sig->it_prof_incr = cputime_zero;
853
854         sig->leader = 0;        /* session leadership doesn't inherit */
855         sig->tty_old_pgrp = 0;
856
857         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
858         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
859         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
860         sig->sched_time = 0;
861         INIT_LIST_HEAD(&sig->cpu_timers[0]);
862         INIT_LIST_HEAD(&sig->cpu_timers[1]);
863         INIT_LIST_HEAD(&sig->cpu_timers[2]);
864
865         task_lock(current->group_leader);
866         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
867         task_unlock(current->group_leader);
868
869         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
870                 /*
871                  * New sole thread in the process gets an expiry time
872                  * of the whole CPU time limit.
873                  */
874                 tsk->it_prof_expires =
875                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
876         }
877
878         return 0;
879 }
880
881 void __cleanup_signal(struct signal_struct *sig)
882 {
883         exit_thread_group_keys(sig);
884         kmem_cache_free(signal_cachep, sig);
885 }
886
887 static inline void cleanup_signal(struct task_struct *tsk)
888 {
889         struct signal_struct *sig = tsk->signal;
890
891         atomic_dec(&sig->live);
892
893         if (atomic_dec_and_test(&sig->count))
894                 __cleanup_signal(sig);
895 }
896
897 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
898 {
899         unsigned long new_flags = p->flags;
900
901         new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
902         new_flags |= PF_FORKNOEXEC;
903         if (!(clone_flags & CLONE_PTRACE))
904                 p->ptrace = 0;
905         p->flags = new_flags;
906 }
907
908 asmlinkage long sys_set_tid_address(int __user *tidptr)
909 {
910         current->clear_child_tid = tidptr;
911
912         return current->pid;
913 }
914
915 /*
916  * This creates a new process as a copy of the old one,
917  * but does not actually start it yet.
918  *
919  * It copies the registers, and all the appropriate
920  * parts of the process environment (as per the clone
921  * flags). The actual kick-off is left to the caller.
922  */
923 static task_t *copy_process(unsigned long clone_flags,
924                                  unsigned long stack_start,
925                                  struct pt_regs *regs,
926                                  unsigned long stack_size,
927                                  int __user *parent_tidptr,
928                                  int __user *child_tidptr,
929                                  int pid)
930 {
931         int retval;
932         struct task_struct *p = NULL;
933
934         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
935                 return ERR_PTR(-EINVAL);
936
937         /*
938          * Thread groups must share signals as well, and detached threads
939          * can only be started up within the thread group.
940          */
941         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
942                 return ERR_PTR(-EINVAL);
943
944         /*
945          * Shared signal handlers imply shared VM. By way of the above,
946          * thread groups also imply shared VM. Blocking this case allows
947          * for various simplifications in other code.
948          */
949         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
950                 return ERR_PTR(-EINVAL);
951
952         retval = security_task_create(clone_flags);
953         if (retval)
954                 goto fork_out;
955
956         retval = -ENOMEM;
957         p = dup_task_struct(current);
958         if (!p)
959                 goto fork_out;
960
961         retval = -EAGAIN;
962         if (atomic_read(&p->user->processes) >=
963                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
964                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
965                                 p->user != &root_user)
966                         goto bad_fork_free;
967         }
968
969         atomic_inc(&p->user->__count);
970         atomic_inc(&p->user->processes);
971         get_group_info(p->group_info);
972
973         /*
974          * If multiple threads are within copy_process(), then this check
975          * triggers too late. This doesn't hurt, the check is only there
976          * to stop root fork bombs.
977          */
978         if (nr_threads >= max_threads)
979                 goto bad_fork_cleanup_count;
980
981         if (!try_module_get(task_thread_info(p)->exec_domain->module))
982                 goto bad_fork_cleanup_count;
983
984         if (p->binfmt && !try_module_get(p->binfmt->module))
985                 goto bad_fork_cleanup_put_domain;
986
987         p->did_exec = 0;
988         copy_flags(clone_flags, p);
989         p->pid = pid;
990         retval = -EFAULT;
991         if (clone_flags & CLONE_PARENT_SETTID)
992                 if (put_user(p->pid, parent_tidptr))
993                         goto bad_fork_cleanup;
994
995         p->proc_dentry = NULL;
996
997         INIT_LIST_HEAD(&p->children);
998         INIT_LIST_HEAD(&p->sibling);
999         p->vfork_done = NULL;
1000         spin_lock_init(&p->alloc_lock);
1001         spin_lock_init(&p->proc_lock);
1002
1003         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1004         init_sigpending(&p->pending);
1005
1006         p->utime = cputime_zero;
1007         p->stime = cputime_zero;
1008         p->sched_time = 0;
1009         p->rchar = 0;           /* I/O counter: bytes read */
1010         p->wchar = 0;           /* I/O counter: bytes written */
1011         p->syscr = 0;           /* I/O counter: read syscalls */
1012         p->syscw = 0;           /* I/O counter: write syscalls */
1013         acct_clear_integrals(p);
1014
1015         p->it_virt_expires = cputime_zero;
1016         p->it_prof_expires = cputime_zero;
1017         p->it_sched_expires = 0;
1018         INIT_LIST_HEAD(&p->cpu_timers[0]);
1019         INIT_LIST_HEAD(&p->cpu_timers[1]);
1020         INIT_LIST_HEAD(&p->cpu_timers[2]);
1021
1022         p->lock_depth = -1;             /* -1 = no lock */
1023         do_posix_clock_monotonic_gettime(&p->start_time);
1024         p->security = NULL;
1025         p->io_context = NULL;
1026         p->io_wait = NULL;
1027         p->audit_context = NULL;
1028         cpuset_fork(p);
1029 #ifdef CONFIG_NUMA
1030         p->mempolicy = mpol_copy(p->mempolicy);
1031         if (IS_ERR(p->mempolicy)) {
1032                 retval = PTR_ERR(p->mempolicy);
1033                 p->mempolicy = NULL;
1034                 goto bad_fork_cleanup_cpuset;
1035         }
1036         mpol_fix_fork_child_flag(p);
1037 #endif
1038
1039 #ifdef CONFIG_DEBUG_MUTEXES
1040         p->blocked_on = NULL; /* not blocked yet */
1041 #endif
1042
1043         p->tgid = p->pid;
1044         if (clone_flags & CLONE_THREAD)
1045                 p->tgid = current->tgid;
1046
1047         if ((retval = security_task_alloc(p)))
1048                 goto bad_fork_cleanup_policy;
1049         if ((retval = audit_alloc(p)))
1050                 goto bad_fork_cleanup_security;
1051         /* copy all the process information */
1052         if ((retval = copy_semundo(clone_flags, p)))
1053                 goto bad_fork_cleanup_audit;
1054         if ((retval = copy_files(clone_flags, p)))
1055                 goto bad_fork_cleanup_semundo;
1056         if ((retval = copy_fs(clone_flags, p)))
1057                 goto bad_fork_cleanup_files;
1058         if ((retval = copy_sighand(clone_flags, p)))
1059                 goto bad_fork_cleanup_fs;
1060         if ((retval = copy_signal(clone_flags, p)))
1061                 goto bad_fork_cleanup_sighand;
1062         if ((retval = copy_mm(clone_flags, p)))
1063                 goto bad_fork_cleanup_signal;
1064         if ((retval = copy_keys(clone_flags, p)))
1065                 goto bad_fork_cleanup_mm;
1066         if ((retval = copy_namespace(clone_flags, p)))
1067                 goto bad_fork_cleanup_keys;
1068         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1069         if (retval)
1070                 goto bad_fork_cleanup_namespace;
1071
1072         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1073         /*
1074          * Clear TID on mm_release()?
1075          */
1076         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1077         p->robust_list = NULL;
1078 #ifdef CONFIG_COMPAT
1079         p->compat_robust_list = NULL;
1080 #endif
1081         /*
1082          * sigaltstack should be cleared when sharing the same VM
1083          */
1084         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1085                 p->sas_ss_sp = p->sas_ss_size = 0;
1086
1087         /*
1088          * Syscall tracing should be turned off in the child regardless
1089          * of CLONE_PTRACE.
1090          */
1091         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1092 #ifdef TIF_SYSCALL_EMU
1093         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1094 #endif
1095
1096         /* Our parent execution domain becomes current domain
1097            These must match for thread signalling to apply */
1098            
1099         p->parent_exec_id = p->self_exec_id;
1100
1101         /* ok, now we should be set up.. */
1102         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1103         p->pdeath_signal = 0;
1104         p->exit_state = 0;
1105
1106         /*
1107          * Ok, make it visible to the rest of the system.
1108          * We dont wake it up yet.
1109          */
1110         p->group_leader = p;
1111         INIT_LIST_HEAD(&p->thread_group);
1112         INIT_LIST_HEAD(&p->ptrace_children);
1113         INIT_LIST_HEAD(&p->ptrace_list);
1114
1115         /* Perform scheduler related setup. Assign this task to a CPU. */
1116         sched_fork(p, clone_flags);
1117
1118         /* Need tasklist lock for parent etc handling! */
1119         write_lock_irq(&tasklist_lock);
1120
1121         /*
1122          * The task hasn't been attached yet, so its cpus_allowed mask will
1123          * not be changed, nor will its assigned CPU.
1124          *
1125          * The cpus_allowed mask of the parent may have changed after it was
1126          * copied first time - so re-copy it here, then check the child's CPU
1127          * to ensure it is on a valid CPU (and if not, just force it back to
1128          * parent's CPU). This avoids alot of nasty races.
1129          */
1130         p->cpus_allowed = current->cpus_allowed;
1131         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1132                         !cpu_online(task_cpu(p))))
1133                 set_task_cpu(p, smp_processor_id());
1134
1135         /* CLONE_PARENT re-uses the old parent */
1136         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1137                 p->real_parent = current->real_parent;
1138         else
1139                 p->real_parent = current;
1140         p->parent = p->real_parent;
1141
1142         spin_lock(&current->sighand->siglock);
1143
1144         /*
1145          * Process group and session signals need to be delivered to just the
1146          * parent before the fork or both the parent and the child after the
1147          * fork. Restart if a signal comes in before we add the new process to
1148          * it's process group.
1149          * A fatal signal pending means that current will exit, so the new
1150          * thread can't slip out of an OOM kill (or normal SIGKILL).
1151          */
1152         recalc_sigpending();
1153         if (signal_pending(current)) {
1154                 spin_unlock(&current->sighand->siglock);
1155                 write_unlock_irq(&tasklist_lock);
1156                 retval = -ERESTARTNOINTR;
1157                 goto bad_fork_cleanup_namespace;
1158         }
1159
1160         if (clone_flags & CLONE_THREAD) {
1161                 /*
1162                  * Important: if an exit-all has been started then
1163                  * do not create this new thread - the whole thread
1164                  * group is supposed to exit anyway.
1165                  */
1166                 if (current->signal->flags & SIGNAL_GROUP_EXIT) {
1167                         spin_unlock(&current->sighand->siglock);
1168                         write_unlock_irq(&tasklist_lock);
1169                         retval = -EAGAIN;
1170                         goto bad_fork_cleanup_namespace;
1171                 }
1172
1173                 p->group_leader = current->group_leader;
1174                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1175
1176                 if (!cputime_eq(current->signal->it_virt_expires,
1177                                 cputime_zero) ||
1178                     !cputime_eq(current->signal->it_prof_expires,
1179                                 cputime_zero) ||
1180                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1181                     !list_empty(&current->signal->cpu_timers[0]) ||
1182                     !list_empty(&current->signal->cpu_timers[1]) ||
1183                     !list_empty(&current->signal->cpu_timers[2])) {
1184                         /*
1185                          * Have child wake up on its first tick to check
1186                          * for process CPU timers.
1187                          */
1188                         p->it_prof_expires = jiffies_to_cputime(1);
1189                 }
1190         }
1191
1192         /*
1193          * inherit ioprio
1194          */
1195         p->ioprio = current->ioprio;
1196
1197         if (likely(p->pid)) {
1198                 add_parent(p);
1199                 if (unlikely(p->ptrace & PT_PTRACED))
1200                         __ptrace_link(p, current->parent);
1201
1202                 if (thread_group_leader(p)) {
1203                         p->signal->tty = current->signal->tty;
1204                         p->signal->pgrp = process_group(current);
1205                         p->signal->session = current->signal->session;
1206                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1207                         attach_pid(p, PIDTYPE_SID, p->signal->session);
1208
1209                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1210                         __get_cpu_var(process_counts)++;
1211                 }
1212                 attach_pid(p, PIDTYPE_PID, p->pid);
1213                 nr_threads++;
1214         }
1215
1216         total_forks++;
1217         spin_unlock(&current->sighand->siglock);
1218         write_unlock_irq(&tasklist_lock);
1219         proc_fork_connector(p);
1220         return p;
1221
1222 bad_fork_cleanup_namespace:
1223         exit_namespace(p);
1224 bad_fork_cleanup_keys:
1225         exit_keys(p);
1226 bad_fork_cleanup_mm:
1227         if (p->mm)
1228                 mmput(p->mm);
1229 bad_fork_cleanup_signal:
1230         cleanup_signal(p);
1231 bad_fork_cleanup_sighand:
1232         __cleanup_sighand(p->sighand);
1233 bad_fork_cleanup_fs:
1234         exit_fs(p); /* blocking */
1235 bad_fork_cleanup_files:
1236         exit_files(p); /* blocking */
1237 bad_fork_cleanup_semundo:
1238         exit_sem(p);
1239 bad_fork_cleanup_audit:
1240         audit_free(p);
1241 bad_fork_cleanup_security:
1242         security_task_free(p);
1243 bad_fork_cleanup_policy:
1244 #ifdef CONFIG_NUMA
1245         mpol_free(p->mempolicy);
1246 bad_fork_cleanup_cpuset:
1247 #endif
1248         cpuset_exit(p);
1249 bad_fork_cleanup:
1250         if (p->binfmt)
1251                 module_put(p->binfmt->module);
1252 bad_fork_cleanup_put_domain:
1253         module_put(task_thread_info(p)->exec_domain->module);
1254 bad_fork_cleanup_count:
1255         put_group_info(p->group_info);
1256         atomic_dec(&p->user->processes);
1257         free_uid(p->user);
1258 bad_fork_free:
1259         free_task(p);
1260 fork_out:
1261         return ERR_PTR(retval);
1262 }
1263
1264 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1265 {
1266         memset(regs, 0, sizeof(struct pt_regs));
1267         return regs;
1268 }
1269
1270 task_t * __devinit fork_idle(int cpu)
1271 {
1272         task_t *task;
1273         struct pt_regs regs;
1274
1275         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1276         if (!task)
1277                 return ERR_PTR(-ENOMEM);
1278         init_idle(task, cpu);
1279
1280         return task;
1281 }
1282
1283 static inline int fork_traceflag (unsigned clone_flags)
1284 {
1285         if (clone_flags & CLONE_UNTRACED)
1286                 return 0;
1287         else if (clone_flags & CLONE_VFORK) {
1288                 if (current->ptrace & PT_TRACE_VFORK)
1289                         return PTRACE_EVENT_VFORK;
1290         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1291                 if (current->ptrace & PT_TRACE_CLONE)
1292                         return PTRACE_EVENT_CLONE;
1293         } else if (current->ptrace & PT_TRACE_FORK)
1294                 return PTRACE_EVENT_FORK;
1295
1296         return 0;
1297 }
1298
1299 /*
1300  *  Ok, this is the main fork-routine.
1301  *
1302  * It copies the process, and if successful kick-starts
1303  * it and waits for it to finish using the VM if required.
1304  */
1305 long do_fork(unsigned long clone_flags,
1306               unsigned long stack_start,
1307               struct pt_regs *regs,
1308               unsigned long stack_size,
1309               int __user *parent_tidptr,
1310               int __user *child_tidptr)
1311 {
1312         struct task_struct *p;
1313         int trace = 0;
1314         struct pid *pid = alloc_pid();
1315         long nr;
1316
1317         if (!pid)
1318                 return -EAGAIN;
1319         nr = pid->nr;
1320         if (unlikely(current->ptrace)) {
1321                 trace = fork_traceflag (clone_flags);
1322                 if (trace)
1323                         clone_flags |= CLONE_PTRACE;
1324         }
1325
1326         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1327         /*
1328          * Do this prior waking up the new thread - the thread pointer
1329          * might get invalid after that point, if the thread exits quickly.
1330          */
1331         if (!IS_ERR(p)) {
1332                 struct completion vfork;
1333
1334                 if (clone_flags & CLONE_VFORK) {
1335                         p->vfork_done = &vfork;
1336                         init_completion(&vfork);
1337                 }
1338
1339                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1340                         /*
1341                          * We'll start up with an immediate SIGSTOP.
1342                          */
1343                         sigaddset(&p->pending.signal, SIGSTOP);
1344                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1345                 }
1346
1347                 if (!(clone_flags & CLONE_STOPPED))
1348                         wake_up_new_task(p, clone_flags);
1349                 else
1350                         p->state = TASK_STOPPED;
1351
1352                 if (unlikely (trace)) {
1353                         current->ptrace_message = nr;
1354                         ptrace_notify ((trace << 8) | SIGTRAP);
1355                 }
1356
1357                 if (clone_flags & CLONE_VFORK) {
1358                         wait_for_completion(&vfork);
1359                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
1360                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1361                 }
1362         } else {
1363                 free_pid(pid);
1364                 nr = PTR_ERR(p);
1365         }
1366         return nr;
1367 }
1368
1369 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1370 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1371 #endif
1372
1373 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1374 {
1375         struct sighand_struct *sighand = data;
1376
1377         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1378                                         SLAB_CTOR_CONSTRUCTOR)
1379                 spin_lock_init(&sighand->siglock);
1380 }
1381
1382 void __init proc_caches_init(void)
1383 {
1384         sighand_cachep = kmem_cache_create("sighand_cache",
1385                         sizeof(struct sighand_struct), 0,
1386                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1387                         sighand_ctor, NULL);
1388         signal_cachep = kmem_cache_create("signal_cache",
1389                         sizeof(struct signal_struct), 0,
1390                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1391         files_cachep = kmem_cache_create("files_cache", 
1392                         sizeof(struct files_struct), 0,
1393                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1394         fs_cachep = kmem_cache_create("fs_cache", 
1395                         sizeof(struct fs_struct), 0,
1396                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1397         vm_area_cachep = kmem_cache_create("vm_area_struct",
1398                         sizeof(struct vm_area_struct), 0,
1399                         SLAB_PANIC, NULL, NULL);
1400         mm_cachep = kmem_cache_create("mm_struct",
1401                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1402                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1403 }
1404
1405
1406 /*
1407  * Check constraints on flags passed to the unshare system call and
1408  * force unsharing of additional process context as appropriate.
1409  */
1410 static inline void check_unshare_flags(unsigned long *flags_ptr)
1411 {
1412         /*
1413          * If unsharing a thread from a thread group, must also
1414          * unshare vm.
1415          */
1416         if (*flags_ptr & CLONE_THREAD)
1417                 *flags_ptr |= CLONE_VM;
1418
1419         /*
1420          * If unsharing vm, must also unshare signal handlers.
1421          */
1422         if (*flags_ptr & CLONE_VM)
1423                 *flags_ptr |= CLONE_SIGHAND;
1424
1425         /*
1426          * If unsharing signal handlers and the task was created
1427          * using CLONE_THREAD, then must unshare the thread
1428          */
1429         if ((*flags_ptr & CLONE_SIGHAND) &&
1430             (atomic_read(&current->signal->count) > 1))
1431                 *flags_ptr |= CLONE_THREAD;
1432
1433         /*
1434          * If unsharing namespace, must also unshare filesystem information.
1435          */
1436         if (*flags_ptr & CLONE_NEWNS)
1437                 *flags_ptr |= CLONE_FS;
1438 }
1439
1440 /*
1441  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1442  */
1443 static int unshare_thread(unsigned long unshare_flags)
1444 {
1445         if (unshare_flags & CLONE_THREAD)
1446                 return -EINVAL;
1447
1448         return 0;
1449 }
1450
1451 /*
1452  * Unshare the filesystem structure if it is being shared
1453  */
1454 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1455 {
1456         struct fs_struct *fs = current->fs;
1457
1458         if ((unshare_flags & CLONE_FS) &&
1459             (fs && atomic_read(&fs->count) > 1)) {
1460                 *new_fsp = __copy_fs_struct(current->fs);
1461                 if (!*new_fsp)
1462                         return -ENOMEM;
1463         }
1464
1465         return 0;
1466 }
1467
1468 /*
1469  * Unshare the namespace structure if it is being shared
1470  */
1471 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1472 {
1473         struct namespace *ns = current->namespace;
1474
1475         if ((unshare_flags & CLONE_NEWNS) &&
1476             (ns && atomic_read(&ns->count) > 1)) {
1477                 if (!capable(CAP_SYS_ADMIN))
1478                         return -EPERM;
1479
1480                 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1481                 if (!*new_nsp)
1482                         return -ENOMEM;
1483         }
1484
1485         return 0;
1486 }
1487
1488 /*
1489  * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1490  * supported yet
1491  */
1492 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1493 {
1494         struct sighand_struct *sigh = current->sighand;
1495
1496         if ((unshare_flags & CLONE_SIGHAND) &&
1497             (sigh && atomic_read(&sigh->count) > 1))
1498                 return -EINVAL;
1499         else
1500                 return 0;
1501 }
1502
1503 /*
1504  * Unshare vm if it is being shared
1505  */
1506 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1507 {
1508         struct mm_struct *mm = current->mm;
1509
1510         if ((unshare_flags & CLONE_VM) &&
1511             (mm && atomic_read(&mm->mm_users) > 1)) {
1512                 return -EINVAL;
1513         }
1514
1515         return 0;
1516 }
1517
1518 /*
1519  * Unshare file descriptor table if it is being shared
1520  */
1521 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1522 {
1523         struct files_struct *fd = current->files;
1524         int error = 0;
1525
1526         if ((unshare_flags & CLONE_FILES) &&
1527             (fd && atomic_read(&fd->count) > 1)) {
1528                 *new_fdp = dup_fd(fd, &error);
1529                 if (!*new_fdp)
1530                         return error;
1531         }
1532
1533         return 0;
1534 }
1535
1536 /*
1537  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1538  * supported yet
1539  */
1540 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1541 {
1542         if (unshare_flags & CLONE_SYSVSEM)
1543                 return -EINVAL;
1544
1545         return 0;
1546 }
1547
1548 /*
1549  * unshare allows a process to 'unshare' part of the process
1550  * context which was originally shared using clone.  copy_*
1551  * functions used by do_fork() cannot be used here directly
1552  * because they modify an inactive task_struct that is being
1553  * constructed. Here we are modifying the current, active,
1554  * task_struct.
1555  */
1556 asmlinkage long sys_unshare(unsigned long unshare_flags)
1557 {
1558         int err = 0;
1559         struct fs_struct *fs, *new_fs = NULL;
1560         struct namespace *ns, *new_ns = NULL;
1561         struct sighand_struct *sigh, *new_sigh = NULL;
1562         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1563         struct files_struct *fd, *new_fd = NULL;
1564         struct sem_undo_list *new_ulist = NULL;
1565
1566         check_unshare_flags(&unshare_flags);
1567
1568         /* Return -EINVAL for all unsupported flags */
1569         err = -EINVAL;
1570         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1571                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
1572                 goto bad_unshare_out;
1573
1574         if ((err = unshare_thread(unshare_flags)))
1575                 goto bad_unshare_out;
1576         if ((err = unshare_fs(unshare_flags, &new_fs)))
1577                 goto bad_unshare_cleanup_thread;
1578         if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1579                 goto bad_unshare_cleanup_fs;
1580         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1581                 goto bad_unshare_cleanup_ns;
1582         if ((err = unshare_vm(unshare_flags, &new_mm)))
1583                 goto bad_unshare_cleanup_sigh;
1584         if ((err = unshare_fd(unshare_flags, &new_fd)))
1585                 goto bad_unshare_cleanup_vm;
1586         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1587                 goto bad_unshare_cleanup_fd;
1588
1589         if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1590
1591                 task_lock(current);
1592
1593                 if (new_fs) {
1594                         fs = current->fs;
1595                         current->fs = new_fs;
1596                         new_fs = fs;
1597                 }
1598
1599                 if (new_ns) {
1600                         ns = current->namespace;
1601                         current->namespace = new_ns;
1602                         new_ns = ns;
1603                 }
1604
1605                 if (new_sigh) {
1606                         sigh = current->sighand;
1607                         rcu_assign_pointer(current->sighand, new_sigh);
1608                         new_sigh = sigh;
1609                 }
1610
1611                 if (new_mm) {
1612                         mm = current->mm;
1613                         active_mm = current->active_mm;
1614                         current->mm = new_mm;
1615                         current->active_mm = new_mm;
1616                         activate_mm(active_mm, new_mm);
1617                         new_mm = mm;
1618                 }
1619
1620                 if (new_fd) {
1621                         fd = current->files;
1622                         current->files = new_fd;
1623                         new_fd = fd;
1624                 }
1625
1626                 task_unlock(current);
1627         }
1628
1629 bad_unshare_cleanup_fd:
1630         if (new_fd)
1631                 put_files_struct(new_fd);
1632
1633 bad_unshare_cleanup_vm:
1634         if (new_mm)
1635                 mmput(new_mm);
1636
1637 bad_unshare_cleanup_sigh:
1638         if (new_sigh)
1639                 if (atomic_dec_and_test(&new_sigh->count))
1640                         kmem_cache_free(sighand_cachep, new_sigh);
1641
1642 bad_unshare_cleanup_ns:
1643         if (new_ns)
1644                 put_namespace(new_ns);
1645
1646 bad_unshare_cleanup_fs:
1647         if (new_fs)
1648                 put_fs_struct(new_fs);
1649
1650 bad_unshare_cleanup_thread:
1651 bad_unshare_out:
1652         return err;
1653 }