Merge master.kernel.org:/home/rmk/linux-2.6-serial
[linux-2.6] / 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         if (unlikely(tsk->audit_context))
118                 audit_free(tsk);
119         security_task_free(tsk);
120         free_uid(tsk->user);
121         put_group_info(tsk->group_info);
122
123         if (!profile_handoff_task(tsk))
124                 free_task(tsk);
125 }
126
127 void __put_task_struct_cb(struct rcu_head *rhp)
128 {
129         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
130         __put_task_struct(tsk);
131 }
132
133 void __init fork_init(unsigned long mempages)
134 {
135 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
136 #ifndef ARCH_MIN_TASKALIGN
137 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
138 #endif
139         /* create a slab on which task_structs can be allocated */
140         task_struct_cachep =
141                 kmem_cache_create("task_struct", sizeof(struct task_struct),
142                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
143 #endif
144
145         /*
146          * The default maximum number of threads is set to a safe
147          * value: the thread structures can take up at most half
148          * of memory.
149          */
150         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
151
152         /*
153          * we need to allow at least 20 threads to boot a system
154          */
155         if(max_threads < 20)
156                 max_threads = 20;
157
158         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
159         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
160         init_task.signal->rlim[RLIMIT_SIGPENDING] =
161                 init_task.signal->rlim[RLIMIT_NPROC];
162 }
163
164 static struct task_struct *dup_task_struct(struct task_struct *orig)
165 {
166         struct task_struct *tsk;
167         struct thread_info *ti;
168
169         prepare_to_copy(orig);
170
171         tsk = alloc_task_struct();
172         if (!tsk)
173                 return NULL;
174
175         ti = alloc_thread_info(tsk);
176         if (!ti) {
177                 free_task_struct(tsk);
178                 return NULL;
179         }
180
181         *tsk = *orig;
182         tsk->thread_info = ti;
183         setup_thread_stack(tsk, orig);
184
185         /* One for us, one for whoever does the "release_task()" (usually parent) */
186         atomic_set(&tsk->usage,2);
187         atomic_set(&tsk->fs_excl, 0);
188         tsk->btrace_seq = 0;
189         return tsk;
190 }
191
192 #ifdef CONFIG_MMU
193 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
194 {
195         struct vm_area_struct *mpnt, *tmp, **pprev;
196         struct rb_node **rb_link, *rb_parent;
197         int retval;
198         unsigned long charge;
199         struct mempolicy *pol;
200
201         down_write(&oldmm->mmap_sem);
202         flush_cache_mm(oldmm);
203         down_write(&mm->mmap_sem);
204
205         mm->locked_vm = 0;
206         mm->mmap = NULL;
207         mm->mmap_cache = NULL;
208         mm->free_area_cache = oldmm->mmap_base;
209         mm->cached_hole_size = ~0UL;
210         mm->map_count = 0;
211         cpus_clear(mm->cpu_vm_mask);
212         mm->mm_rb = RB_ROOT;
213         rb_link = &mm->mm_rb.rb_node;
214         rb_parent = NULL;
215         pprev = &mm->mmap;
216
217         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
218                 struct file *file;
219
220                 if (mpnt->vm_flags & VM_DONTCOPY) {
221                         long pages = vma_pages(mpnt);
222                         mm->total_vm -= pages;
223                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
224                                                                 -pages);
225                         continue;
226                 }
227                 charge = 0;
228                 if (mpnt->vm_flags & VM_ACCOUNT) {
229                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
230                         if (security_vm_enough_memory(len))
231                                 goto fail_nomem;
232                         charge = len;
233                 }
234                 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
235                 if (!tmp)
236                         goto fail_nomem;
237                 *tmp = *mpnt;
238                 pol = mpol_copy(vma_policy(mpnt));
239                 retval = PTR_ERR(pol);
240                 if (IS_ERR(pol))
241                         goto fail_nomem_policy;
242                 vma_set_policy(tmp, pol);
243                 tmp->vm_flags &= ~VM_LOCKED;
244                 tmp->vm_mm = mm;
245                 tmp->vm_next = NULL;
246                 anon_vma_link(tmp);
247                 file = tmp->vm_file;
248                 if (file) {
249                         struct inode *inode = file->f_dentry->d_inode;
250                         get_file(file);
251                         if (tmp->vm_flags & VM_DENYWRITE)
252                                 atomic_dec(&inode->i_writecount);
253       
254                         /* insert tmp into the share list, just after mpnt */
255                         spin_lock(&file->f_mapping->i_mmap_lock);
256                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
257                         flush_dcache_mmap_lock(file->f_mapping);
258                         vma_prio_tree_add(tmp, mpnt);
259                         flush_dcache_mmap_unlock(file->f_mapping);
260                         spin_unlock(&file->f_mapping->i_mmap_lock);
261                 }
262
263                 /*
264                  * Link in the new vma and copy the page table entries.
265                  */
266                 *pprev = tmp;
267                 pprev = &tmp->vm_next;
268
269                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
270                 rb_link = &tmp->vm_rb.rb_right;
271                 rb_parent = &tmp->vm_rb;
272
273                 mm->map_count++;
274                 retval = copy_page_range(mm, oldmm, mpnt);
275
276                 if (tmp->vm_ops && tmp->vm_ops->open)
277                         tmp->vm_ops->open(tmp);
278
279                 if (retval)
280                         goto out;
281         }
282         retval = 0;
283 out:
284         up_write(&mm->mmap_sem);
285         flush_tlb_mm(oldmm);
286         up_write(&oldmm->mmap_sem);
287         return retval;
288 fail_nomem_policy:
289         kmem_cache_free(vm_area_cachep, tmp);
290 fail_nomem:
291         retval = -ENOMEM;
292         vm_unacct_memory(charge);
293         goto out;
294 }
295
296 static inline int mm_alloc_pgd(struct mm_struct * mm)
297 {
298         mm->pgd = pgd_alloc(mm);
299         if (unlikely(!mm->pgd))
300                 return -ENOMEM;
301         return 0;
302 }
303
304 static inline void mm_free_pgd(struct mm_struct * mm)
305 {
306         pgd_free(mm->pgd);
307 }
308 #else
309 #define dup_mmap(mm, oldmm)     (0)
310 #define mm_alloc_pgd(mm)        (0)
311 #define mm_free_pgd(mm)
312 #endif /* CONFIG_MMU */
313
314  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
315
316 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
317 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
318
319 #include <linux/init_task.h>
320
321 static struct mm_struct * mm_init(struct mm_struct * mm)
322 {
323         atomic_set(&mm->mm_users, 1);
324         atomic_set(&mm->mm_count, 1);
325         init_rwsem(&mm->mmap_sem);
326         INIT_LIST_HEAD(&mm->mmlist);
327         mm->core_waiters = 0;
328         mm->nr_ptes = 0;
329         set_mm_counter(mm, file_rss, 0);
330         set_mm_counter(mm, anon_rss, 0);
331         spin_lock_init(&mm->page_table_lock);
332         rwlock_init(&mm->ioctx_list_lock);
333         mm->ioctx_list = NULL;
334         mm->free_area_cache = TASK_UNMAPPED_BASE;
335         mm->cached_hole_size = ~0UL;
336
337         if (likely(!mm_alloc_pgd(mm))) {
338                 mm->def_flags = 0;
339                 return mm;
340         }
341         free_mm(mm);
342         return NULL;
343 }
344
345 /*
346  * Allocate and initialize an mm_struct.
347  */
348 struct mm_struct * mm_alloc(void)
349 {
350         struct mm_struct * mm;
351
352         mm = allocate_mm();
353         if (mm) {
354                 memset(mm, 0, sizeof(*mm));
355                 mm = mm_init(mm);
356         }
357         return mm;
358 }
359
360 /*
361  * Called when the last reference to the mm
362  * is dropped: either by a lazy thread or by
363  * mmput. Free the page directory and the mm.
364  */
365 void fastcall __mmdrop(struct mm_struct *mm)
366 {
367         BUG_ON(mm == &init_mm);
368         mm_free_pgd(mm);
369         destroy_context(mm);
370         free_mm(mm);
371 }
372
373 /*
374  * Decrement the use count and release all resources for an mm.
375  */
376 void mmput(struct mm_struct *mm)
377 {
378         if (atomic_dec_and_test(&mm->mm_users)) {
379                 exit_aio(mm);
380                 exit_mmap(mm);
381                 if (!list_empty(&mm->mmlist)) {
382                         spin_lock(&mmlist_lock);
383                         list_del(&mm->mmlist);
384                         spin_unlock(&mmlist_lock);
385                 }
386                 put_swap_token(mm);
387                 mmdrop(mm);
388         }
389 }
390 EXPORT_SYMBOL_GPL(mmput);
391
392 /**
393  * get_task_mm - acquire a reference to the task's mm
394  *
395  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
396  * this kernel workthread has transiently adopted a user mm with use_mm,
397  * to do its AIO) is not set and if so returns a reference to it, after
398  * bumping up the use count.  User must release the mm via mmput()
399  * after use.  Typically used by /proc and ptrace.
400  */
401 struct mm_struct *get_task_mm(struct task_struct *task)
402 {
403         struct mm_struct *mm;
404
405         task_lock(task);
406         mm = task->mm;
407         if (mm) {
408                 if (task->flags & PF_BORROWED_MM)
409                         mm = NULL;
410                 else
411                         atomic_inc(&mm->mm_users);
412         }
413         task_unlock(task);
414         return mm;
415 }
416 EXPORT_SYMBOL_GPL(get_task_mm);
417
418 /* Please note the differences between mmput and mm_release.
419  * mmput is called whenever we stop holding onto a mm_struct,
420  * error success whatever.
421  *
422  * mm_release is called after a mm_struct has been removed
423  * from the current process.
424  *
425  * This difference is important for error handling, when we
426  * only half set up a mm_struct for a new process and need to restore
427  * the old one.  Because we mmput the new mm_struct before
428  * restoring the old one. . .
429  * Eric Biederman 10 January 1998
430  */
431 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
432 {
433         struct completion *vfork_done = tsk->vfork_done;
434
435         /* Get rid of any cached register state */
436         deactivate_mm(tsk, mm);
437
438         /* notify parent sleeping on vfork() */
439         if (vfork_done) {
440                 tsk->vfork_done = NULL;
441                 complete(vfork_done);
442         }
443         if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
444                 u32 __user * tidptr = tsk->clear_child_tid;
445                 tsk->clear_child_tid = NULL;
446
447                 /*
448                  * We don't check the error code - if userspace has
449                  * not set up a proper pointer then tough luck.
450                  */
451                 put_user(0, tidptr);
452                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
453         }
454 }
455
456 /*
457  * Allocate a new mm structure and copy contents from the
458  * mm structure of the passed in task structure.
459  */
460 static struct mm_struct *dup_mm(struct task_struct *tsk)
461 {
462         struct mm_struct *mm, *oldmm = current->mm;
463         int err;
464
465         if (!oldmm)
466                 return NULL;
467
468         mm = allocate_mm();
469         if (!mm)
470                 goto fail_nomem;
471
472         memcpy(mm, oldmm, sizeof(*mm));
473
474         if (!mm_init(mm))
475                 goto fail_nomem;
476
477         if (init_new_context(tsk, mm))
478                 goto fail_nocontext;
479
480         err = dup_mmap(mm, oldmm);
481         if (err)
482                 goto free_pt;
483
484         mm->hiwater_rss = get_mm_rss(mm);
485         mm->hiwater_vm = mm->total_vm;
486
487         return mm;
488
489 free_pt:
490         mmput(mm);
491
492 fail_nomem:
493         return NULL;
494
495 fail_nocontext:
496         /*
497          * If init_new_context() failed, we cannot use mmput() to free the mm
498          * because it calls destroy_context()
499          */
500         mm_free_pgd(mm);
501         free_mm(mm);
502         return NULL;
503 }
504
505 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
506 {
507         struct mm_struct * mm, *oldmm;
508         int retval;
509
510         tsk->min_flt = tsk->maj_flt = 0;
511         tsk->nvcsw = tsk->nivcsw = 0;
512
513         tsk->mm = NULL;
514         tsk->active_mm = NULL;
515
516         /*
517          * Are we cloning a kernel thread?
518          *
519          * We need to steal a active VM for that..
520          */
521         oldmm = current->mm;
522         if (!oldmm)
523                 return 0;
524
525         if (clone_flags & CLONE_VM) {
526                 atomic_inc(&oldmm->mm_users);
527                 mm = oldmm;
528                 goto good_mm;
529         }
530
531         retval = -ENOMEM;
532         mm = dup_mm(tsk);
533         if (!mm)
534                 goto fail_nomem;
535
536 good_mm:
537         tsk->mm = mm;
538         tsk->active_mm = mm;
539         return 0;
540
541 fail_nomem:
542         return retval;
543 }
544
545 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
546 {
547         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
548         /* We don't need to lock fs - think why ;-) */
549         if (fs) {
550                 atomic_set(&fs->count, 1);
551                 rwlock_init(&fs->lock);
552                 fs->umask = old->umask;
553                 read_lock(&old->lock);
554                 fs->rootmnt = mntget(old->rootmnt);
555                 fs->root = dget(old->root);
556                 fs->pwdmnt = mntget(old->pwdmnt);
557                 fs->pwd = dget(old->pwd);
558                 if (old->altroot) {
559                         fs->altrootmnt = mntget(old->altrootmnt);
560                         fs->altroot = dget(old->altroot);
561                 } else {
562                         fs->altrootmnt = NULL;
563                         fs->altroot = NULL;
564                 }
565                 read_unlock(&old->lock);
566         }
567         return fs;
568 }
569
570 struct fs_struct *copy_fs_struct(struct fs_struct *old)
571 {
572         return __copy_fs_struct(old);
573 }
574
575 EXPORT_SYMBOL_GPL(copy_fs_struct);
576
577 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
578 {
579         if (clone_flags & CLONE_FS) {
580                 atomic_inc(&current->fs->count);
581                 return 0;
582         }
583         tsk->fs = __copy_fs_struct(current->fs);
584         if (!tsk->fs)
585                 return -ENOMEM;
586         return 0;
587 }
588
589 static int count_open_files(struct fdtable *fdt)
590 {
591         int size = fdt->max_fdset;
592         int i;
593
594         /* Find the last open fd */
595         for (i = size/(8*sizeof(long)); i > 0; ) {
596                 if (fdt->open_fds->fds_bits[--i])
597                         break;
598         }
599         i = (i+1) * 8 * sizeof(long);
600         return i;
601 }
602
603 static struct files_struct *alloc_files(void)
604 {
605         struct files_struct *newf;
606         struct fdtable *fdt;
607
608         newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
609         if (!newf)
610                 goto out;
611
612         atomic_set(&newf->count, 1);
613
614         spin_lock_init(&newf->file_lock);
615         newf->next_fd = 0;
616         fdt = &newf->fdtab;
617         fdt->max_fds = NR_OPEN_DEFAULT;
618         fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
619         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
620         fdt->open_fds = (fd_set *)&newf->open_fds_init;
621         fdt->fd = &newf->fd_array[0];
622         INIT_RCU_HEAD(&fdt->rcu);
623         fdt->free_files = NULL;
624         fdt->next = NULL;
625         rcu_assign_pointer(newf->fdt, fdt);
626 out:
627         return newf;
628 }
629
630 /*
631  * Allocate a new files structure and copy contents from the
632  * passed in files structure.
633  */
634 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
635 {
636         struct files_struct *newf;
637         struct file **old_fds, **new_fds;
638         int open_files, size, i, expand;
639         struct fdtable *old_fdt, *new_fdt;
640
641         newf = alloc_files();
642         if (!newf)
643                 goto out;
644
645         spin_lock(&oldf->file_lock);
646         old_fdt = files_fdtable(oldf);
647         new_fdt = files_fdtable(newf);
648         size = old_fdt->max_fdset;
649         open_files = count_open_files(old_fdt);
650         expand = 0;
651
652         /*
653          * Check whether we need to allocate a larger fd array or fd set.
654          * Note: we're not a clone task, so the open count won't  change.
655          */
656         if (open_files > new_fdt->max_fdset) {
657                 new_fdt->max_fdset = 0;
658                 expand = 1;
659         }
660         if (open_files > new_fdt->max_fds) {
661                 new_fdt->max_fds = 0;
662                 expand = 1;
663         }
664
665         /* if the old fdset gets grown now, we'll only copy up to "size" fds */
666         if (expand) {
667                 spin_unlock(&oldf->file_lock);
668                 spin_lock(&newf->file_lock);
669                 *errorp = expand_files(newf, open_files-1);
670                 spin_unlock(&newf->file_lock);
671                 if (*errorp < 0)
672                         goto out_release;
673                 new_fdt = files_fdtable(newf);
674                 /*
675                  * Reacquire the oldf lock and a pointer to its fd table
676                  * who knows it may have a new bigger fd table. We need
677                  * the latest pointer.
678                  */
679                 spin_lock(&oldf->file_lock);
680                 old_fdt = files_fdtable(oldf);
681         }
682
683         old_fds = old_fdt->fd;
684         new_fds = new_fdt->fd;
685
686         memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
687         memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
688
689         for (i = open_files; i != 0; i--) {
690                 struct file *f = *old_fds++;
691                 if (f) {
692                         get_file(f);
693                 } else {
694                         /*
695                          * The fd may be claimed in the fd bitmap but not yet
696                          * instantiated in the files array if a sibling thread
697                          * is partway through open().  So make sure that this
698                          * fd is available to the new process.
699                          */
700                         FD_CLR(open_files - i, new_fdt->open_fds);
701                 }
702                 rcu_assign_pointer(*new_fds++, f);
703         }
704         spin_unlock(&oldf->file_lock);
705
706         /* compute the remainder to be cleared */
707         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
708
709         /* This is long word aligned thus could use a optimized version */ 
710         memset(new_fds, 0, size); 
711
712         if (new_fdt->max_fdset > open_files) {
713                 int left = (new_fdt->max_fdset-open_files)/8;
714                 int start = open_files / (8 * sizeof(unsigned long));
715
716                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
717                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
718         }
719
720 out:
721         return newf;
722
723 out_release:
724         free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
725         free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
726         free_fd_array(new_fdt->fd, new_fdt->max_fds);
727         kmem_cache_free(files_cachep, newf);
728         return NULL;
729 }
730
731 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
732 {
733         struct files_struct *oldf, *newf;
734         int error = 0;
735
736         /*
737          * A background process may not have any files ...
738          */
739         oldf = current->files;
740         if (!oldf)
741                 goto out;
742
743         if (clone_flags & CLONE_FILES) {
744                 atomic_inc(&oldf->count);
745                 goto out;
746         }
747
748         /*
749          * Note: we may be using current for both targets (See exec.c)
750          * This works because we cache current->files (old) as oldf. Don't
751          * break this.
752          */
753         tsk->files = NULL;
754         error = -ENOMEM;
755         newf = dup_fd(oldf, &error);
756         if (!newf)
757                 goto out;
758
759         tsk->files = newf;
760         error = 0;
761 out:
762         return error;
763 }
764
765 /*
766  *      Helper to unshare the files of the current task.
767  *      We don't want to expose copy_files internals to
768  *      the exec layer of the kernel.
769  */
770
771 int unshare_files(void)
772 {
773         struct files_struct *files  = current->files;
774         int rc;
775
776         BUG_ON(!files);
777
778         /* This can race but the race causes us to copy when we don't
779            need to and drop the copy */
780         if(atomic_read(&files->count) == 1)
781         {
782                 atomic_inc(&files->count);
783                 return 0;
784         }
785         rc = copy_files(0, current);
786         if(rc)
787                 current->files = files;
788         return rc;
789 }
790
791 EXPORT_SYMBOL(unshare_files);
792
793 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
794 {
795         struct sighand_struct *sig;
796
797         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
798                 atomic_inc(&current->sighand->count);
799                 return 0;
800         }
801         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
802         rcu_assign_pointer(tsk->sighand, sig);
803         if (!sig)
804                 return -ENOMEM;
805         atomic_set(&sig->count, 1);
806         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
807         return 0;
808 }
809
810 void __cleanup_sighand(struct sighand_struct *sighand)
811 {
812         if (atomic_dec_and_test(&sighand->count))
813                 kmem_cache_free(sighand_cachep, sighand);
814 }
815
816 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
817 {
818         struct signal_struct *sig;
819         int ret;
820
821         if (clone_flags & CLONE_THREAD) {
822                 atomic_inc(&current->signal->count);
823                 atomic_inc(&current->signal->live);
824                 return 0;
825         }
826         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
827         tsk->signal = sig;
828         if (!sig)
829                 return -ENOMEM;
830
831         ret = copy_thread_group_keys(tsk);
832         if (ret < 0) {
833                 kmem_cache_free(signal_cachep, sig);
834                 return ret;
835         }
836
837         atomic_set(&sig->count, 1);
838         atomic_set(&sig->live, 1);
839         init_waitqueue_head(&sig->wait_chldexit);
840         sig->flags = 0;
841         sig->group_exit_code = 0;
842         sig->group_exit_task = NULL;
843         sig->group_stop_count = 0;
844         sig->curr_target = NULL;
845         init_sigpending(&sig->shared_pending);
846         INIT_LIST_HEAD(&sig->posix_timers);
847
848         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
849         sig->it_real_incr.tv64 = 0;
850         sig->real_timer.function = it_real_fn;
851         sig->tsk = tsk;
852
853         sig->it_virt_expires = cputime_zero;
854         sig->it_virt_incr = cputime_zero;
855         sig->it_prof_expires = cputime_zero;
856         sig->it_prof_incr = cputime_zero;
857
858         sig->leader = 0;        /* session leadership doesn't inherit */
859         sig->tty_old_pgrp = 0;
860
861         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
862         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
863         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
864         sig->sched_time = 0;
865         INIT_LIST_HEAD(&sig->cpu_timers[0]);
866         INIT_LIST_HEAD(&sig->cpu_timers[1]);
867         INIT_LIST_HEAD(&sig->cpu_timers[2]);
868
869         task_lock(current->group_leader);
870         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
871         task_unlock(current->group_leader);
872
873         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
874                 /*
875                  * New sole thread in the process gets an expiry time
876                  * of the whole CPU time limit.
877                  */
878                 tsk->it_prof_expires =
879                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
880         }
881
882         return 0;
883 }
884
885 void __cleanup_signal(struct signal_struct *sig)
886 {
887         exit_thread_group_keys(sig);
888         kmem_cache_free(signal_cachep, sig);
889 }
890
891 static inline void cleanup_signal(struct task_struct *tsk)
892 {
893         struct signal_struct *sig = tsk->signal;
894
895         atomic_dec(&sig->live);
896
897         if (atomic_dec_and_test(&sig->count))
898                 __cleanup_signal(sig);
899 }
900
901 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
902 {
903         unsigned long new_flags = p->flags;
904
905         new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
906         new_flags |= PF_FORKNOEXEC;
907         if (!(clone_flags & CLONE_PTRACE))
908                 p->ptrace = 0;
909         p->flags = new_flags;
910 }
911
912 asmlinkage long sys_set_tid_address(int __user *tidptr)
913 {
914         current->clear_child_tid = tidptr;
915
916         return current->pid;
917 }
918
919 /*
920  * This creates a new process as a copy of the old one,
921  * but does not actually start it yet.
922  *
923  * It copies the registers, and all the appropriate
924  * parts of the process environment (as per the clone
925  * flags). The actual kick-off is left to the caller.
926  */
927 static task_t *copy_process(unsigned long clone_flags,
928                                  unsigned long stack_start,
929                                  struct pt_regs *regs,
930                                  unsigned long stack_size,
931                                  int __user *parent_tidptr,
932                                  int __user *child_tidptr,
933                                  int pid)
934 {
935         int retval;
936         struct task_struct *p = NULL;
937
938         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
939                 return ERR_PTR(-EINVAL);
940
941         /*
942          * Thread groups must share signals as well, and detached threads
943          * can only be started up within the thread group.
944          */
945         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
946                 return ERR_PTR(-EINVAL);
947
948         /*
949          * Shared signal handlers imply shared VM. By way of the above,
950          * thread groups also imply shared VM. Blocking this case allows
951          * for various simplifications in other code.
952          */
953         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
954                 return ERR_PTR(-EINVAL);
955
956         retval = security_task_create(clone_flags);
957         if (retval)
958                 goto fork_out;
959
960         retval = -ENOMEM;
961         p = dup_task_struct(current);
962         if (!p)
963                 goto fork_out;
964
965         retval = -EAGAIN;
966         if (atomic_read(&p->user->processes) >=
967                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
968                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
969                                 p->user != &root_user)
970                         goto bad_fork_free;
971         }
972
973         atomic_inc(&p->user->__count);
974         atomic_inc(&p->user->processes);
975         get_group_info(p->group_info);
976
977         /*
978          * If multiple threads are within copy_process(), then this check
979          * triggers too late. This doesn't hurt, the check is only there
980          * to stop root fork bombs.
981          */
982         if (nr_threads >= max_threads)
983                 goto bad_fork_cleanup_count;
984
985         if (!try_module_get(task_thread_info(p)->exec_domain->module))
986                 goto bad_fork_cleanup_count;
987
988         if (p->binfmt && !try_module_get(p->binfmt->module))
989                 goto bad_fork_cleanup_put_domain;
990
991         p->did_exec = 0;
992         copy_flags(clone_flags, p);
993         p->pid = pid;
994         retval = -EFAULT;
995         if (clone_flags & CLONE_PARENT_SETTID)
996                 if (put_user(p->pid, parent_tidptr))
997                         goto bad_fork_cleanup;
998
999         p->proc_dentry = NULL;
1000
1001         INIT_LIST_HEAD(&p->children);
1002         INIT_LIST_HEAD(&p->sibling);
1003         p->vfork_done = NULL;
1004         spin_lock_init(&p->alloc_lock);
1005         spin_lock_init(&p->proc_lock);
1006
1007         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1008         init_sigpending(&p->pending);
1009
1010         p->utime = cputime_zero;
1011         p->stime = cputime_zero;
1012         p->sched_time = 0;
1013         p->rchar = 0;           /* I/O counter: bytes read */
1014         p->wchar = 0;           /* I/O counter: bytes written */
1015         p->syscr = 0;           /* I/O counter: read syscalls */
1016         p->syscw = 0;           /* I/O counter: write syscalls */
1017         acct_clear_integrals(p);
1018
1019         p->it_virt_expires = cputime_zero;
1020         p->it_prof_expires = cputime_zero;
1021         p->it_sched_expires = 0;
1022         INIT_LIST_HEAD(&p->cpu_timers[0]);
1023         INIT_LIST_HEAD(&p->cpu_timers[1]);
1024         INIT_LIST_HEAD(&p->cpu_timers[2]);
1025
1026         p->lock_depth = -1;             /* -1 = no lock */
1027         do_posix_clock_monotonic_gettime(&p->start_time);
1028         p->security = NULL;
1029         p->io_context = NULL;
1030         p->io_wait = NULL;
1031         p->audit_context = NULL;
1032         cpuset_fork(p);
1033 #ifdef CONFIG_NUMA
1034         p->mempolicy = mpol_copy(p->mempolicy);
1035         if (IS_ERR(p->mempolicy)) {
1036                 retval = PTR_ERR(p->mempolicy);
1037                 p->mempolicy = NULL;
1038                 goto bad_fork_cleanup_cpuset;
1039         }
1040         mpol_fix_fork_child_flag(p);
1041 #endif
1042
1043 #ifdef CONFIG_DEBUG_MUTEXES
1044         p->blocked_on = NULL; /* not blocked yet */
1045 #endif
1046
1047         p->tgid = p->pid;
1048         if (clone_flags & CLONE_THREAD)
1049                 p->tgid = current->tgid;
1050
1051         if ((retval = security_task_alloc(p)))
1052                 goto bad_fork_cleanup_policy;
1053         if ((retval = audit_alloc(p)))
1054                 goto bad_fork_cleanup_security;
1055         /* copy all the process information */
1056         if ((retval = copy_semundo(clone_flags, p)))
1057                 goto bad_fork_cleanup_audit;
1058         if ((retval = copy_files(clone_flags, p)))
1059                 goto bad_fork_cleanup_semundo;
1060         if ((retval = copy_fs(clone_flags, p)))
1061                 goto bad_fork_cleanup_files;
1062         if ((retval = copy_sighand(clone_flags, p)))
1063                 goto bad_fork_cleanup_fs;
1064         if ((retval = copy_signal(clone_flags, p)))
1065                 goto bad_fork_cleanup_sighand;
1066         if ((retval = copy_mm(clone_flags, p)))
1067                 goto bad_fork_cleanup_signal;
1068         if ((retval = copy_keys(clone_flags, p)))
1069                 goto bad_fork_cleanup_mm;
1070         if ((retval = copy_namespace(clone_flags, p)))
1071                 goto bad_fork_cleanup_keys;
1072         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1073         if (retval)
1074                 goto bad_fork_cleanup_namespace;
1075
1076         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1077         /*
1078          * Clear TID on mm_release()?
1079          */
1080         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1081         p->robust_list = NULL;
1082 #ifdef CONFIG_COMPAT
1083         p->compat_robust_list = NULL;
1084 #endif
1085         /*
1086          * sigaltstack should be cleared when sharing the same VM
1087          */
1088         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1089                 p->sas_ss_sp = p->sas_ss_size = 0;
1090
1091         /*
1092          * Syscall tracing should be turned off in the child regardless
1093          * of CLONE_PTRACE.
1094          */
1095         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1096 #ifdef TIF_SYSCALL_EMU
1097         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1098 #endif
1099
1100         /* Our parent execution domain becomes current domain
1101            These must match for thread signalling to apply */
1102            
1103         p->parent_exec_id = p->self_exec_id;
1104
1105         /* ok, now we should be set up.. */
1106         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1107         p->pdeath_signal = 0;
1108         p->exit_state = 0;
1109
1110         /*
1111          * Ok, make it visible to the rest of the system.
1112          * We dont wake it up yet.
1113          */
1114         p->group_leader = p;
1115         INIT_LIST_HEAD(&p->thread_group);
1116         INIT_LIST_HEAD(&p->ptrace_children);
1117         INIT_LIST_HEAD(&p->ptrace_list);
1118
1119         /* Perform scheduler related setup. Assign this task to a CPU. */
1120         sched_fork(p, clone_flags);
1121
1122         /* Need tasklist lock for parent etc handling! */
1123         write_lock_irq(&tasklist_lock);
1124
1125         /*
1126          * The task hasn't been attached yet, so its cpus_allowed mask will
1127          * not be changed, nor will its assigned CPU.
1128          *
1129          * The cpus_allowed mask of the parent may have changed after it was
1130          * copied first time - so re-copy it here, then check the child's CPU
1131          * to ensure it is on a valid CPU (and if not, just force it back to
1132          * parent's CPU). This avoids alot of nasty races.
1133          */
1134         p->cpus_allowed = current->cpus_allowed;
1135         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1136                         !cpu_online(task_cpu(p))))
1137                 set_task_cpu(p, smp_processor_id());
1138
1139         /* CLONE_PARENT re-uses the old parent */
1140         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1141                 p->real_parent = current->real_parent;
1142         else
1143                 p->real_parent = current;
1144         p->parent = p->real_parent;
1145
1146         spin_lock(&current->sighand->siglock);
1147
1148         /*
1149          * Process group and session signals need to be delivered to just the
1150          * parent before the fork or both the parent and the child after the
1151          * fork. Restart if a signal comes in before we add the new process to
1152          * it's process group.
1153          * A fatal signal pending means that current will exit, so the new
1154          * thread can't slip out of an OOM kill (or normal SIGKILL).
1155          */
1156         recalc_sigpending();
1157         if (signal_pending(current)) {
1158                 spin_unlock(&current->sighand->siglock);
1159                 write_unlock_irq(&tasklist_lock);
1160                 retval = -ERESTARTNOINTR;
1161                 goto bad_fork_cleanup_namespace;
1162         }
1163
1164         if (clone_flags & CLONE_THREAD) {
1165                 /*
1166                  * Important: if an exit-all has been started then
1167                  * do not create this new thread - the whole thread
1168                  * group is supposed to exit anyway.
1169                  */
1170                 if (current->signal->flags & SIGNAL_GROUP_EXIT) {
1171                         spin_unlock(&current->sighand->siglock);
1172                         write_unlock_irq(&tasklist_lock);
1173                         retval = -EAGAIN;
1174                         goto bad_fork_cleanup_namespace;
1175                 }
1176
1177                 p->group_leader = current->group_leader;
1178                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1179
1180                 if (!cputime_eq(current->signal->it_virt_expires,
1181                                 cputime_zero) ||
1182                     !cputime_eq(current->signal->it_prof_expires,
1183                                 cputime_zero) ||
1184                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1185                     !list_empty(&current->signal->cpu_timers[0]) ||
1186                     !list_empty(&current->signal->cpu_timers[1]) ||
1187                     !list_empty(&current->signal->cpu_timers[2])) {
1188                         /*
1189                          * Have child wake up on its first tick to check
1190                          * for process CPU timers.
1191                          */
1192                         p->it_prof_expires = jiffies_to_cputime(1);
1193                 }
1194         }
1195
1196         /*
1197          * inherit ioprio
1198          */
1199         p->ioprio = current->ioprio;
1200
1201         if (likely(p->pid)) {
1202                 add_parent(p);
1203                 if (unlikely(p->ptrace & PT_PTRACED))
1204                         __ptrace_link(p, current->parent);
1205
1206                 if (thread_group_leader(p)) {
1207                         p->signal->tty = current->signal->tty;
1208                         p->signal->pgrp = process_group(current);
1209                         p->signal->session = current->signal->session;
1210                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1211                         attach_pid(p, PIDTYPE_SID, p->signal->session);
1212
1213                         list_add_tail(&p->tasks, &init_task.tasks);
1214                         __get_cpu_var(process_counts)++;
1215                 }
1216                 attach_pid(p, PIDTYPE_PID, p->pid);
1217                 nr_threads++;
1218         }
1219
1220         total_forks++;
1221         spin_unlock(&current->sighand->siglock);
1222         write_unlock_irq(&tasklist_lock);
1223         proc_fork_connector(p);
1224         return p;
1225
1226 bad_fork_cleanup_namespace:
1227         exit_namespace(p);
1228 bad_fork_cleanup_keys:
1229         exit_keys(p);
1230 bad_fork_cleanup_mm:
1231         if (p->mm)
1232                 mmput(p->mm);
1233 bad_fork_cleanup_signal:
1234         cleanup_signal(p);
1235 bad_fork_cleanup_sighand:
1236         __cleanup_sighand(p->sighand);
1237 bad_fork_cleanup_fs:
1238         exit_fs(p); /* blocking */
1239 bad_fork_cleanup_files:
1240         exit_files(p); /* blocking */
1241 bad_fork_cleanup_semundo:
1242         exit_sem(p);
1243 bad_fork_cleanup_audit:
1244         audit_free(p);
1245 bad_fork_cleanup_security:
1246         security_task_free(p);
1247 bad_fork_cleanup_policy:
1248 #ifdef CONFIG_NUMA
1249         mpol_free(p->mempolicy);
1250 bad_fork_cleanup_cpuset:
1251 #endif
1252         cpuset_exit(p);
1253 bad_fork_cleanup:
1254         if (p->binfmt)
1255                 module_put(p->binfmt->module);
1256 bad_fork_cleanup_put_domain:
1257         module_put(task_thread_info(p)->exec_domain->module);
1258 bad_fork_cleanup_count:
1259         put_group_info(p->group_info);
1260         atomic_dec(&p->user->processes);
1261         free_uid(p->user);
1262 bad_fork_free:
1263         free_task(p);
1264 fork_out:
1265         return ERR_PTR(retval);
1266 }
1267
1268 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1269 {
1270         memset(regs, 0, sizeof(struct pt_regs));
1271         return regs;
1272 }
1273
1274 task_t * __devinit fork_idle(int cpu)
1275 {
1276         task_t *task;
1277         struct pt_regs regs;
1278
1279         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1280         if (!task)
1281                 return ERR_PTR(-ENOMEM);
1282         init_idle(task, cpu);
1283
1284         return task;
1285 }
1286
1287 static inline int fork_traceflag (unsigned clone_flags)
1288 {
1289         if (clone_flags & CLONE_UNTRACED)
1290                 return 0;
1291         else if (clone_flags & CLONE_VFORK) {
1292                 if (current->ptrace & PT_TRACE_VFORK)
1293                         return PTRACE_EVENT_VFORK;
1294         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1295                 if (current->ptrace & PT_TRACE_CLONE)
1296                         return PTRACE_EVENT_CLONE;
1297         } else if (current->ptrace & PT_TRACE_FORK)
1298                 return PTRACE_EVENT_FORK;
1299
1300         return 0;
1301 }
1302
1303 /*
1304  *  Ok, this is the main fork-routine.
1305  *
1306  * It copies the process, and if successful kick-starts
1307  * it and waits for it to finish using the VM if required.
1308  */
1309 long do_fork(unsigned long clone_flags,
1310               unsigned long stack_start,
1311               struct pt_regs *regs,
1312               unsigned long stack_size,
1313               int __user *parent_tidptr,
1314               int __user *child_tidptr)
1315 {
1316         struct task_struct *p;
1317         int trace = 0;
1318         struct pid *pid = alloc_pid();
1319         long nr;
1320
1321         if (!pid)
1322                 return -EAGAIN;
1323         nr = pid->nr;
1324         if (unlikely(current->ptrace)) {
1325                 trace = fork_traceflag (clone_flags);
1326                 if (trace)
1327                         clone_flags |= CLONE_PTRACE;
1328         }
1329
1330         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1331         /*
1332          * Do this prior waking up the new thread - the thread pointer
1333          * might get invalid after that point, if the thread exits quickly.
1334          */
1335         if (!IS_ERR(p)) {
1336                 struct completion vfork;
1337
1338                 if (clone_flags & CLONE_VFORK) {
1339                         p->vfork_done = &vfork;
1340                         init_completion(&vfork);
1341                 }
1342
1343                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1344                         /*
1345                          * We'll start up with an immediate SIGSTOP.
1346                          */
1347                         sigaddset(&p->pending.signal, SIGSTOP);
1348                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1349                 }
1350
1351                 if (!(clone_flags & CLONE_STOPPED))
1352                         wake_up_new_task(p, clone_flags);
1353                 else
1354                         p->state = TASK_STOPPED;
1355
1356                 if (unlikely (trace)) {
1357                         current->ptrace_message = nr;
1358                         ptrace_notify ((trace << 8) | SIGTRAP);
1359                 }
1360
1361                 if (clone_flags & CLONE_VFORK) {
1362                         wait_for_completion(&vfork);
1363                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
1364                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1365                 }
1366         } else {
1367                 free_pid(pid);
1368                 nr = PTR_ERR(p);
1369         }
1370         return nr;
1371 }
1372
1373 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1374 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1375 #endif
1376
1377 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1378 {
1379         struct sighand_struct *sighand = data;
1380
1381         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1382                                         SLAB_CTOR_CONSTRUCTOR)
1383                 spin_lock_init(&sighand->siglock);
1384 }
1385
1386 void __init proc_caches_init(void)
1387 {
1388         sighand_cachep = kmem_cache_create("sighand_cache",
1389                         sizeof(struct sighand_struct), 0,
1390                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1391                         sighand_ctor, NULL);
1392         signal_cachep = kmem_cache_create("signal_cache",
1393                         sizeof(struct signal_struct), 0,
1394                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1395         files_cachep = kmem_cache_create("files_cache", 
1396                         sizeof(struct files_struct), 0,
1397                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1398         fs_cachep = kmem_cache_create("fs_cache", 
1399                         sizeof(struct fs_struct), 0,
1400                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1401         vm_area_cachep = kmem_cache_create("vm_area_struct",
1402                         sizeof(struct vm_area_struct), 0,
1403                         SLAB_PANIC, NULL, NULL);
1404         mm_cachep = kmem_cache_create("mm_struct",
1405                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1406                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1407 }
1408
1409
1410 /*
1411  * Check constraints on flags passed to the unshare system call and
1412  * force unsharing of additional process context as appropriate.
1413  */
1414 static inline void check_unshare_flags(unsigned long *flags_ptr)
1415 {
1416         /*
1417          * If unsharing a thread from a thread group, must also
1418          * unshare vm.
1419          */
1420         if (*flags_ptr & CLONE_THREAD)
1421                 *flags_ptr |= CLONE_VM;
1422
1423         /*
1424          * If unsharing vm, must also unshare signal handlers.
1425          */
1426         if (*flags_ptr & CLONE_VM)
1427                 *flags_ptr |= CLONE_SIGHAND;
1428
1429         /*
1430          * If unsharing signal handlers and the task was created
1431          * using CLONE_THREAD, then must unshare the thread
1432          */
1433         if ((*flags_ptr & CLONE_SIGHAND) &&
1434             (atomic_read(&current->signal->count) > 1))
1435                 *flags_ptr |= CLONE_THREAD;
1436
1437         /*
1438          * If unsharing namespace, must also unshare filesystem information.
1439          */
1440         if (*flags_ptr & CLONE_NEWNS)
1441                 *flags_ptr |= CLONE_FS;
1442 }
1443
1444 /*
1445  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1446  */
1447 static int unshare_thread(unsigned long unshare_flags)
1448 {
1449         if (unshare_flags & CLONE_THREAD)
1450                 return -EINVAL;
1451
1452         return 0;
1453 }
1454
1455 /*
1456  * Unshare the filesystem structure if it is being shared
1457  */
1458 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1459 {
1460         struct fs_struct *fs = current->fs;
1461
1462         if ((unshare_flags & CLONE_FS) &&
1463             (fs && atomic_read(&fs->count) > 1)) {
1464                 *new_fsp = __copy_fs_struct(current->fs);
1465                 if (!*new_fsp)
1466                         return -ENOMEM;
1467         }
1468
1469         return 0;
1470 }
1471
1472 /*
1473  * Unshare the namespace structure if it is being shared
1474  */
1475 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1476 {
1477         struct namespace *ns = current->namespace;
1478
1479         if ((unshare_flags & CLONE_NEWNS) &&
1480             (ns && atomic_read(&ns->count) > 1)) {
1481                 if (!capable(CAP_SYS_ADMIN))
1482                         return -EPERM;
1483
1484                 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1485                 if (!*new_nsp)
1486                         return -ENOMEM;
1487         }
1488
1489         return 0;
1490 }
1491
1492 /*
1493  * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1494  * supported yet
1495  */
1496 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1497 {
1498         struct sighand_struct *sigh = current->sighand;
1499
1500         if ((unshare_flags & CLONE_SIGHAND) &&
1501             (sigh && atomic_read(&sigh->count) > 1))
1502                 return -EINVAL;
1503         else
1504                 return 0;
1505 }
1506
1507 /*
1508  * Unshare vm if it is being shared
1509  */
1510 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1511 {
1512         struct mm_struct *mm = current->mm;
1513
1514         if ((unshare_flags & CLONE_VM) &&
1515             (mm && atomic_read(&mm->mm_users) > 1)) {
1516                 return -EINVAL;
1517         }
1518
1519         return 0;
1520 }
1521
1522 /*
1523  * Unshare file descriptor table if it is being shared
1524  */
1525 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1526 {
1527         struct files_struct *fd = current->files;
1528         int error = 0;
1529
1530         if ((unshare_flags & CLONE_FILES) &&
1531             (fd && atomic_read(&fd->count) > 1)) {
1532                 *new_fdp = dup_fd(fd, &error);
1533                 if (!*new_fdp)
1534                         return error;
1535         }
1536
1537         return 0;
1538 }
1539
1540 /*
1541  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1542  * supported yet
1543  */
1544 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1545 {
1546         if (unshare_flags & CLONE_SYSVSEM)
1547                 return -EINVAL;
1548
1549         return 0;
1550 }
1551
1552 /*
1553  * unshare allows a process to 'unshare' part of the process
1554  * context which was originally shared using clone.  copy_*
1555  * functions used by do_fork() cannot be used here directly
1556  * because they modify an inactive task_struct that is being
1557  * constructed. Here we are modifying the current, active,
1558  * task_struct.
1559  */
1560 asmlinkage long sys_unshare(unsigned long unshare_flags)
1561 {
1562         int err = 0;
1563         struct fs_struct *fs, *new_fs = NULL;
1564         struct namespace *ns, *new_ns = NULL;
1565         struct sighand_struct *sigh, *new_sigh = NULL;
1566         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1567         struct files_struct *fd, *new_fd = NULL;
1568         struct sem_undo_list *new_ulist = NULL;
1569
1570         check_unshare_flags(&unshare_flags);
1571
1572         /* Return -EINVAL for all unsupported flags */
1573         err = -EINVAL;
1574         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1575                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
1576                 goto bad_unshare_out;
1577
1578         if ((err = unshare_thread(unshare_flags)))
1579                 goto bad_unshare_out;
1580         if ((err = unshare_fs(unshare_flags, &new_fs)))
1581                 goto bad_unshare_cleanup_thread;
1582         if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1583                 goto bad_unshare_cleanup_fs;
1584         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1585                 goto bad_unshare_cleanup_ns;
1586         if ((err = unshare_vm(unshare_flags, &new_mm)))
1587                 goto bad_unshare_cleanup_sigh;
1588         if ((err = unshare_fd(unshare_flags, &new_fd)))
1589                 goto bad_unshare_cleanup_vm;
1590         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1591                 goto bad_unshare_cleanup_fd;
1592
1593         if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1594
1595                 task_lock(current);
1596
1597                 if (new_fs) {
1598                         fs = current->fs;
1599                         current->fs = new_fs;
1600                         new_fs = fs;
1601                 }
1602
1603                 if (new_ns) {
1604                         ns = current->namespace;
1605                         current->namespace = new_ns;
1606                         new_ns = ns;
1607                 }
1608
1609                 if (new_sigh) {
1610                         sigh = current->sighand;
1611                         rcu_assign_pointer(current->sighand, new_sigh);
1612                         new_sigh = sigh;
1613                 }
1614
1615                 if (new_mm) {
1616                         mm = current->mm;
1617                         active_mm = current->active_mm;
1618                         current->mm = new_mm;
1619                         current->active_mm = new_mm;
1620                         activate_mm(active_mm, new_mm);
1621                         new_mm = mm;
1622                 }
1623
1624                 if (new_fd) {
1625                         fd = current->files;
1626                         current->files = new_fd;
1627                         new_fd = fd;
1628                 }
1629
1630                 task_unlock(current);
1631         }
1632
1633 bad_unshare_cleanup_fd:
1634         if (new_fd)
1635                 put_files_struct(new_fd);
1636
1637 bad_unshare_cleanup_vm:
1638         if (new_mm)
1639                 mmput(new_mm);
1640
1641 bad_unshare_cleanup_sigh:
1642         if (new_sigh)
1643                 if (atomic_dec_and_test(&new_sigh->count))
1644                         kmem_cache_free(sighand_cachep, new_sigh);
1645
1646 bad_unshare_cleanup_ns:
1647         if (new_ns)
1648                 put_namespace(new_ns);
1649
1650 bad_unshare_cleanup_fs:
1651         if (new_fs)
1652                 put_fs_struct(new_fs);
1653
1654 bad_unshare_cleanup_thread:
1655 bad_unshare_out:
1656         return err;
1657 }