[PATCH] pids: kill PIDTYPE_TGID
[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_cb(struct rcu_head *rhp)
112 {
113         struct task_struct *tsk = container_of(rhp, struct task_struct, rcu);
114
115         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
116         WARN_ON(atomic_read(&tsk->usage));
117         WARN_ON(tsk == current);
118
119         if (unlikely(tsk->audit_context))
120                 audit_free(tsk);
121         security_task_free(tsk);
122         free_uid(tsk->user);
123         put_group_info(tsk->group_info);
124
125         if (!profile_handoff_task(tsk))
126                 free_task(tsk);
127 }
128
129 void __init fork_init(unsigned long mempages)
130 {
131 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
132 #ifndef ARCH_MIN_TASKALIGN
133 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
134 #endif
135         /* create a slab on which task_structs can be allocated */
136         task_struct_cachep =
137                 kmem_cache_create("task_struct", sizeof(struct task_struct),
138                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
139 #endif
140
141         /*
142          * The default maximum number of threads is set to a safe
143          * value: the thread structures can take up at most half
144          * of memory.
145          */
146         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
147
148         /*
149          * we need to allow at least 20 threads to boot a system
150          */
151         if(max_threads < 20)
152                 max_threads = 20;
153
154         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
155         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
156         init_task.signal->rlim[RLIMIT_SIGPENDING] =
157                 init_task.signal->rlim[RLIMIT_NPROC];
158 }
159
160 static struct task_struct *dup_task_struct(struct task_struct *orig)
161 {
162         struct task_struct *tsk;
163         struct thread_info *ti;
164
165         prepare_to_copy(orig);
166
167         tsk = alloc_task_struct();
168         if (!tsk)
169                 return NULL;
170
171         ti = alloc_thread_info(tsk);
172         if (!ti) {
173                 free_task_struct(tsk);
174                 return NULL;
175         }
176
177         *tsk = *orig;
178         tsk->thread_info = ti;
179         setup_thread_stack(tsk, orig);
180
181         /* One for us, one for whoever does the "release_task()" (usually parent) */
182         atomic_set(&tsk->usage,2);
183         atomic_set(&tsk->fs_excl, 0);
184         tsk->btrace_seq = 0;
185         return tsk;
186 }
187
188 #ifdef CONFIG_MMU
189 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
190 {
191         struct vm_area_struct *mpnt, *tmp, **pprev;
192         struct rb_node **rb_link, *rb_parent;
193         int retval;
194         unsigned long charge;
195         struct mempolicy *pol;
196
197         down_write(&oldmm->mmap_sem);
198         flush_cache_mm(oldmm);
199         down_write(&mm->mmap_sem);
200
201         mm->locked_vm = 0;
202         mm->mmap = NULL;
203         mm->mmap_cache = NULL;
204         mm->free_area_cache = oldmm->mmap_base;
205         mm->cached_hole_size = ~0UL;
206         mm->map_count = 0;
207         cpus_clear(mm->cpu_vm_mask);
208         mm->mm_rb = RB_ROOT;
209         rb_link = &mm->mm_rb.rb_node;
210         rb_parent = NULL;
211         pprev = &mm->mmap;
212
213         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
214                 struct file *file;
215
216                 if (mpnt->vm_flags & VM_DONTCOPY) {
217                         long pages = vma_pages(mpnt);
218                         mm->total_vm -= pages;
219                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
220                                                                 -pages);
221                         continue;
222                 }
223                 charge = 0;
224                 if (mpnt->vm_flags & VM_ACCOUNT) {
225                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
226                         if (security_vm_enough_memory(len))
227                                 goto fail_nomem;
228                         charge = len;
229                 }
230                 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
231                 if (!tmp)
232                         goto fail_nomem;
233                 *tmp = *mpnt;
234                 pol = mpol_copy(vma_policy(mpnt));
235                 retval = PTR_ERR(pol);
236                 if (IS_ERR(pol))
237                         goto fail_nomem_policy;
238                 vma_set_policy(tmp, pol);
239                 tmp->vm_flags &= ~VM_LOCKED;
240                 tmp->vm_mm = mm;
241                 tmp->vm_next = NULL;
242                 anon_vma_link(tmp);
243                 file = tmp->vm_file;
244                 if (file) {
245                         struct inode *inode = file->f_dentry->d_inode;
246                         get_file(file);
247                         if (tmp->vm_flags & VM_DENYWRITE)
248                                 atomic_dec(&inode->i_writecount);
249       
250                         /* insert tmp into the share list, just after mpnt */
251                         spin_lock(&file->f_mapping->i_mmap_lock);
252                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
253                         flush_dcache_mmap_lock(file->f_mapping);
254                         vma_prio_tree_add(tmp, mpnt);
255                         flush_dcache_mmap_unlock(file->f_mapping);
256                         spin_unlock(&file->f_mapping->i_mmap_lock);
257                 }
258
259                 /*
260                  * Link in the new vma and copy the page table entries.
261                  */
262                 *pprev = tmp;
263                 pprev = &tmp->vm_next;
264
265                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
266                 rb_link = &tmp->vm_rb.rb_right;
267                 rb_parent = &tmp->vm_rb;
268
269                 mm->map_count++;
270                 retval = copy_page_range(mm, oldmm, mpnt);
271
272                 if (tmp->vm_ops && tmp->vm_ops->open)
273                         tmp->vm_ops->open(tmp);
274
275                 if (retval)
276                         goto out;
277         }
278         retval = 0;
279 out:
280         up_write(&mm->mmap_sem);
281         flush_tlb_mm(oldmm);
282         up_write(&oldmm->mmap_sem);
283         return retval;
284 fail_nomem_policy:
285         kmem_cache_free(vm_area_cachep, tmp);
286 fail_nomem:
287         retval = -ENOMEM;
288         vm_unacct_memory(charge);
289         goto out;
290 }
291
292 static inline int mm_alloc_pgd(struct mm_struct * mm)
293 {
294         mm->pgd = pgd_alloc(mm);
295         if (unlikely(!mm->pgd))
296                 return -ENOMEM;
297         return 0;
298 }
299
300 static inline void mm_free_pgd(struct mm_struct * mm)
301 {
302         pgd_free(mm->pgd);
303 }
304 #else
305 #define dup_mmap(mm, oldmm)     (0)
306 #define mm_alloc_pgd(mm)        (0)
307 #define mm_free_pgd(mm)
308 #endif /* CONFIG_MMU */
309
310  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
311
312 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
313 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
314
315 #include <linux/init_task.h>
316
317 static struct mm_struct * mm_init(struct mm_struct * mm)
318 {
319         atomic_set(&mm->mm_users, 1);
320         atomic_set(&mm->mm_count, 1);
321         init_rwsem(&mm->mmap_sem);
322         INIT_LIST_HEAD(&mm->mmlist);
323         mm->core_waiters = 0;
324         mm->nr_ptes = 0;
325         set_mm_counter(mm, file_rss, 0);
326         set_mm_counter(mm, anon_rss, 0);
327         spin_lock_init(&mm->page_table_lock);
328         rwlock_init(&mm->ioctx_list_lock);
329         mm->ioctx_list = NULL;
330         mm->free_area_cache = TASK_UNMAPPED_BASE;
331         mm->cached_hole_size = ~0UL;
332
333         if (likely(!mm_alloc_pgd(mm))) {
334                 mm->def_flags = 0;
335                 return mm;
336         }
337         free_mm(mm);
338         return NULL;
339 }
340
341 /*
342  * Allocate and initialize an mm_struct.
343  */
344 struct mm_struct * mm_alloc(void)
345 {
346         struct mm_struct * mm;
347
348         mm = allocate_mm();
349         if (mm) {
350                 memset(mm, 0, sizeof(*mm));
351                 mm = mm_init(mm);
352         }
353         return mm;
354 }
355
356 /*
357  * Called when the last reference to the mm
358  * is dropped: either by a lazy thread or by
359  * mmput. Free the page directory and the mm.
360  */
361 void fastcall __mmdrop(struct mm_struct *mm)
362 {
363         BUG_ON(mm == &init_mm);
364         mm_free_pgd(mm);
365         destroy_context(mm);
366         free_mm(mm);
367 }
368
369 /*
370  * Decrement the use count and release all resources for an mm.
371  */
372 void mmput(struct mm_struct *mm)
373 {
374         if (atomic_dec_and_test(&mm->mm_users)) {
375                 exit_aio(mm);
376                 exit_mmap(mm);
377                 if (!list_empty(&mm->mmlist)) {
378                         spin_lock(&mmlist_lock);
379                         list_del(&mm->mmlist);
380                         spin_unlock(&mmlist_lock);
381                 }
382                 put_swap_token(mm);
383                 mmdrop(mm);
384         }
385 }
386 EXPORT_SYMBOL_GPL(mmput);
387
388 /**
389  * get_task_mm - acquire a reference to the task's mm
390  *
391  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
392  * this kernel workthread has transiently adopted a user mm with use_mm,
393  * to do its AIO) is not set and if so returns a reference to it, after
394  * bumping up the use count.  User must release the mm via mmput()
395  * after use.  Typically used by /proc and ptrace.
396  */
397 struct mm_struct *get_task_mm(struct task_struct *task)
398 {
399         struct mm_struct *mm;
400
401         task_lock(task);
402         mm = task->mm;
403         if (mm) {
404                 if (task->flags & PF_BORROWED_MM)
405                         mm = NULL;
406                 else
407                         atomic_inc(&mm->mm_users);
408         }
409         task_unlock(task);
410         return mm;
411 }
412 EXPORT_SYMBOL_GPL(get_task_mm);
413
414 /* Please note the differences between mmput and mm_release.
415  * mmput is called whenever we stop holding onto a mm_struct,
416  * error success whatever.
417  *
418  * mm_release is called after a mm_struct has been removed
419  * from the current process.
420  *
421  * This difference is important for error handling, when we
422  * only half set up a mm_struct for a new process and need to restore
423  * the old one.  Because we mmput the new mm_struct before
424  * restoring the old one. . .
425  * Eric Biederman 10 January 1998
426  */
427 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
428 {
429         struct completion *vfork_done = tsk->vfork_done;
430
431         /* Get rid of any cached register state */
432         deactivate_mm(tsk, mm);
433
434         /* notify parent sleeping on vfork() */
435         if (vfork_done) {
436                 tsk->vfork_done = NULL;
437                 complete(vfork_done);
438         }
439         if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
440                 u32 __user * tidptr = tsk->clear_child_tid;
441                 tsk->clear_child_tid = NULL;
442
443                 /*
444                  * We don't check the error code - if userspace has
445                  * not set up a proper pointer then tough luck.
446                  */
447                 put_user(0, tidptr);
448                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
449         }
450 }
451
452 /*
453  * Allocate a new mm structure and copy contents from the
454  * mm structure of the passed in task structure.
455  */
456 static struct mm_struct *dup_mm(struct task_struct *tsk)
457 {
458         struct mm_struct *mm, *oldmm = current->mm;
459         int err;
460
461         if (!oldmm)
462                 return NULL;
463
464         mm = allocate_mm();
465         if (!mm)
466                 goto fail_nomem;
467
468         memcpy(mm, oldmm, sizeof(*mm));
469
470         if (!mm_init(mm))
471                 goto fail_nomem;
472
473         if (init_new_context(tsk, mm))
474                 goto fail_nocontext;
475
476         err = dup_mmap(mm, oldmm);
477         if (err)
478                 goto free_pt;
479
480         mm->hiwater_rss = get_mm_rss(mm);
481         mm->hiwater_vm = mm->total_vm;
482
483         return mm;
484
485 free_pt:
486         mmput(mm);
487
488 fail_nomem:
489         return NULL;
490
491 fail_nocontext:
492         /*
493          * If init_new_context() failed, we cannot use mmput() to free the mm
494          * because it calls destroy_context()
495          */
496         mm_free_pgd(mm);
497         free_mm(mm);
498         return NULL;
499 }
500
501 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
502 {
503         struct mm_struct * mm, *oldmm;
504         int retval;
505
506         tsk->min_flt = tsk->maj_flt = 0;
507         tsk->nvcsw = tsk->nivcsw = 0;
508
509         tsk->mm = NULL;
510         tsk->active_mm = NULL;
511
512         /*
513          * Are we cloning a kernel thread?
514          *
515          * We need to steal a active VM for that..
516          */
517         oldmm = current->mm;
518         if (!oldmm)
519                 return 0;
520
521         if (clone_flags & CLONE_VM) {
522                 atomic_inc(&oldmm->mm_users);
523                 mm = oldmm;
524                 goto good_mm;
525         }
526
527         retval = -ENOMEM;
528         mm = dup_mm(tsk);
529         if (!mm)
530                 goto fail_nomem;
531
532 good_mm:
533         tsk->mm = mm;
534         tsk->active_mm = mm;
535         return 0;
536
537 fail_nomem:
538         return retval;
539 }
540
541 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
542 {
543         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
544         /* We don't need to lock fs - think why ;-) */
545         if (fs) {
546                 atomic_set(&fs->count, 1);
547                 rwlock_init(&fs->lock);
548                 fs->umask = old->umask;
549                 read_lock(&old->lock);
550                 fs->rootmnt = mntget(old->rootmnt);
551                 fs->root = dget(old->root);
552                 fs->pwdmnt = mntget(old->pwdmnt);
553                 fs->pwd = dget(old->pwd);
554                 if (old->altroot) {
555                         fs->altrootmnt = mntget(old->altrootmnt);
556                         fs->altroot = dget(old->altroot);
557                 } else {
558                         fs->altrootmnt = NULL;
559                         fs->altroot = NULL;
560                 }
561                 read_unlock(&old->lock);
562         }
563         return fs;
564 }
565
566 struct fs_struct *copy_fs_struct(struct fs_struct *old)
567 {
568         return __copy_fs_struct(old);
569 }
570
571 EXPORT_SYMBOL_GPL(copy_fs_struct);
572
573 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
574 {
575         if (clone_flags & CLONE_FS) {
576                 atomic_inc(&current->fs->count);
577                 return 0;
578         }
579         tsk->fs = __copy_fs_struct(current->fs);
580         if (!tsk->fs)
581                 return -ENOMEM;
582         return 0;
583 }
584
585 static int count_open_files(struct fdtable *fdt)
586 {
587         int size = fdt->max_fdset;
588         int i;
589
590         /* Find the last open fd */
591         for (i = size/(8*sizeof(long)); i > 0; ) {
592                 if (fdt->open_fds->fds_bits[--i])
593                         break;
594         }
595         i = (i+1) * 8 * sizeof(long);
596         return i;
597 }
598
599 static struct files_struct *alloc_files(void)
600 {
601         struct files_struct *newf;
602         struct fdtable *fdt;
603
604         newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
605         if (!newf)
606                 goto out;
607
608         atomic_set(&newf->count, 1);
609
610         spin_lock_init(&newf->file_lock);
611         newf->next_fd = 0;
612         fdt = &newf->fdtab;
613         fdt->max_fds = NR_OPEN_DEFAULT;
614         fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
615         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
616         fdt->open_fds = (fd_set *)&newf->open_fds_init;
617         fdt->fd = &newf->fd_array[0];
618         INIT_RCU_HEAD(&fdt->rcu);
619         fdt->free_files = NULL;
620         fdt->next = NULL;
621         rcu_assign_pointer(newf->fdt, fdt);
622 out:
623         return newf;
624 }
625
626 /*
627  * Allocate a new files structure and copy contents from the
628  * passed in files structure.
629  */
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         newf = alloc_files();
638         if (!newf)
639                 goto out;
640
641         spin_lock(&oldf->file_lock);
642         old_fdt = files_fdtable(oldf);
643         new_fdt = files_fdtable(newf);
644         size = old_fdt->max_fdset;
645         open_files = count_open_files(old_fdt);
646         expand = 0;
647
648         /*
649          * Check whether we need to allocate a larger fd array or fd set.
650          * Note: we're not a clone task, so the open count won't  change.
651          */
652         if (open_files > new_fdt->max_fdset) {
653                 new_fdt->max_fdset = 0;
654                 expand = 1;
655         }
656         if (open_files > new_fdt->max_fds) {
657                 new_fdt->max_fds = 0;
658                 expand = 1;
659         }
660
661         /* if the old fdset gets grown now, we'll only copy up to "size" fds */
662         if (expand) {
663                 spin_unlock(&oldf->file_lock);
664                 spin_lock(&newf->file_lock);
665                 *errorp = expand_files(newf, open_files-1);
666                 spin_unlock(&newf->file_lock);
667                 if (*errorp < 0)
668                         goto out_release;
669                 new_fdt = files_fdtable(newf);
670                 /*
671                  * Reacquire the oldf lock and a pointer to its fd table
672                  * who knows it may have a new bigger fd table. We need
673                  * the latest pointer.
674                  */
675                 spin_lock(&oldf->file_lock);
676                 old_fdt = files_fdtable(oldf);
677         }
678
679         old_fds = old_fdt->fd;
680         new_fds = new_fdt->fd;
681
682         memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
683         memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
684
685         for (i = open_files; i != 0; i--) {
686                 struct file *f = *old_fds++;
687                 if (f) {
688                         get_file(f);
689                 } else {
690                         /*
691                          * The fd may be claimed in the fd bitmap but not yet
692                          * instantiated in the files array if a sibling thread
693                          * is partway through open().  So make sure that this
694                          * fd is available to the new process.
695                          */
696                         FD_CLR(open_files - i, new_fdt->open_fds);
697                 }
698                 rcu_assign_pointer(*new_fds++, f);
699         }
700         spin_unlock(&oldf->file_lock);
701
702         /* compute the remainder to be cleared */
703         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
704
705         /* This is long word aligned thus could use a optimized version */ 
706         memset(new_fds, 0, size); 
707
708         if (new_fdt->max_fdset > open_files) {
709                 int left = (new_fdt->max_fdset-open_files)/8;
710                 int start = open_files / (8 * sizeof(unsigned long));
711
712                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
713                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
714         }
715
716 out:
717         return newf;
718
719 out_release:
720         free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
721         free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
722         free_fd_array(new_fdt->fd, new_fdt->max_fds);
723         kmem_cache_free(files_cachep, newf);
724         goto out;
725 }
726
727 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
728 {
729         struct files_struct *oldf, *newf;
730         int error = 0;
731
732         /*
733          * A background process may not have any files ...
734          */
735         oldf = current->files;
736         if (!oldf)
737                 goto out;
738
739         if (clone_flags & CLONE_FILES) {
740                 atomic_inc(&oldf->count);
741                 goto out;
742         }
743
744         /*
745          * Note: we may be using current for both targets (See exec.c)
746          * This works because we cache current->files (old) as oldf. Don't
747          * break this.
748          */
749         tsk->files = NULL;
750         error = -ENOMEM;
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 task_struct *tsk)
807 {
808         struct sighand_struct * sighand = tsk->sighand;
809
810         /* Ok, we're done with the signal handlers */
811         tsk->sighand = NULL;
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         /*
1140          * Check for pending SIGKILL! The new thread should not be allowed
1141          * to slip out of an OOM kill. (or normal SIGKILL.)
1142          */
1143         if (sigismember(&current->pending.signal, SIGKILL)) {
1144                 write_unlock_irq(&tasklist_lock);
1145                 retval = -EINTR;
1146                 goto bad_fork_cleanup_namespace;
1147         }
1148
1149         /* CLONE_PARENT re-uses the old parent */
1150         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1151                 p->real_parent = current->real_parent;
1152         else
1153                 p->real_parent = current;
1154         p->parent = p->real_parent;
1155
1156         spin_lock(&current->sighand->siglock);
1157         if (clone_flags & CLONE_THREAD) {
1158                 /*
1159                  * Important: if an exit-all has been started then
1160                  * do not create this new thread - the whole thread
1161                  * group is supposed to exit anyway.
1162                  */
1163                 if (current->signal->flags & SIGNAL_GROUP_EXIT) {
1164                         spin_unlock(&current->sighand->siglock);
1165                         write_unlock_irq(&tasklist_lock);
1166                         retval = -EAGAIN;
1167                         goto bad_fork_cleanup_namespace;
1168                 }
1169
1170                 p->group_leader = current->group_leader;
1171                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1172
1173                 if (current->signal->group_stop_count > 0) {
1174                         /*
1175                          * There is an all-stop in progress for the group.
1176                          * We ourselves will stop as soon as we check signals.
1177                          * Make the new thread part of that group stop too.
1178                          */
1179                         current->signal->group_stop_count++;
1180                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1181                 }
1182
1183                 if (!cputime_eq(current->signal->it_virt_expires,
1184                                 cputime_zero) ||
1185                     !cputime_eq(current->signal->it_prof_expires,
1186                                 cputime_zero) ||
1187                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1188                     !list_empty(&current->signal->cpu_timers[0]) ||
1189                     !list_empty(&current->signal->cpu_timers[1]) ||
1190                     !list_empty(&current->signal->cpu_timers[2])) {
1191                         /*
1192                          * Have child wake up on its first tick to check
1193                          * for process CPU timers.
1194                          */
1195                         p->it_prof_expires = jiffies_to_cputime(1);
1196                 }
1197         }
1198
1199         /*
1200          * inherit ioprio
1201          */
1202         p->ioprio = current->ioprio;
1203
1204         if (likely(p->pid)) {
1205                 add_parent(p);
1206                 if (unlikely(p->ptrace & PT_PTRACED))
1207                         __ptrace_link(p, current->parent);
1208
1209                 if (thread_group_leader(p)) {
1210                         p->signal->tty = current->signal->tty;
1211                         p->signal->pgrp = process_group(current);
1212                         p->signal->session = current->signal->session;
1213                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1214                         attach_pid(p, PIDTYPE_SID, p->signal->session);
1215
1216                         list_add_tail(&p->tasks, &init_task.tasks);
1217                         __get_cpu_var(process_counts)++;
1218                 }
1219                 attach_pid(p, PIDTYPE_PID, p->pid);
1220                 nr_threads++;
1221         }
1222
1223         total_forks++;
1224         spin_unlock(&current->sighand->siglock);
1225         write_unlock_irq(&tasklist_lock);
1226         proc_fork_connector(p);
1227         return p;
1228
1229 bad_fork_cleanup_namespace:
1230         exit_namespace(p);
1231 bad_fork_cleanup_keys:
1232         exit_keys(p);
1233 bad_fork_cleanup_mm:
1234         if (p->mm)
1235                 mmput(p->mm);
1236 bad_fork_cleanup_signal:
1237         cleanup_signal(p);
1238 bad_fork_cleanup_sighand:
1239         cleanup_sighand(p);
1240 bad_fork_cleanup_fs:
1241         exit_fs(p); /* blocking */
1242 bad_fork_cleanup_files:
1243         exit_files(p); /* blocking */
1244 bad_fork_cleanup_semundo:
1245         exit_sem(p);
1246 bad_fork_cleanup_audit:
1247         audit_free(p);
1248 bad_fork_cleanup_security:
1249         security_task_free(p);
1250 bad_fork_cleanup_policy:
1251 #ifdef CONFIG_NUMA
1252         mpol_free(p->mempolicy);
1253 bad_fork_cleanup_cpuset:
1254 #endif
1255         cpuset_exit(p);
1256 bad_fork_cleanup:
1257         if (p->binfmt)
1258                 module_put(p->binfmt->module);
1259 bad_fork_cleanup_put_domain:
1260         module_put(task_thread_info(p)->exec_domain->module);
1261 bad_fork_cleanup_count:
1262         put_group_info(p->group_info);
1263         atomic_dec(&p->user->processes);
1264         free_uid(p->user);
1265 bad_fork_free:
1266         free_task(p);
1267 fork_out:
1268         return ERR_PTR(retval);
1269 }
1270
1271 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1272 {
1273         memset(regs, 0, sizeof(struct pt_regs));
1274         return regs;
1275 }
1276
1277 task_t * __devinit fork_idle(int cpu)
1278 {
1279         task_t *task;
1280         struct pt_regs regs;
1281
1282         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1283         if (!task)
1284                 return ERR_PTR(-ENOMEM);
1285         init_idle(task, cpu);
1286
1287         return task;
1288 }
1289
1290 static inline int fork_traceflag (unsigned clone_flags)
1291 {
1292         if (clone_flags & CLONE_UNTRACED)
1293                 return 0;
1294         else if (clone_flags & CLONE_VFORK) {
1295                 if (current->ptrace & PT_TRACE_VFORK)
1296                         return PTRACE_EVENT_VFORK;
1297         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1298                 if (current->ptrace & PT_TRACE_CLONE)
1299                         return PTRACE_EVENT_CLONE;
1300         } else if (current->ptrace & PT_TRACE_FORK)
1301                 return PTRACE_EVENT_FORK;
1302
1303         return 0;
1304 }
1305
1306 /*
1307  *  Ok, this is the main fork-routine.
1308  *
1309  * It copies the process, and if successful kick-starts
1310  * it and waits for it to finish using the VM if required.
1311  */
1312 long do_fork(unsigned long clone_flags,
1313               unsigned long stack_start,
1314               struct pt_regs *regs,
1315               unsigned long stack_size,
1316               int __user *parent_tidptr,
1317               int __user *child_tidptr)
1318 {
1319         struct task_struct *p;
1320         int trace = 0;
1321         long pid = alloc_pidmap();
1322
1323         if (pid < 0)
1324                 return -EAGAIN;
1325         if (unlikely(current->ptrace)) {
1326                 trace = fork_traceflag (clone_flags);
1327                 if (trace)
1328                         clone_flags |= CLONE_PTRACE;
1329         }
1330
1331         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
1332         /*
1333          * Do this prior waking up the new thread - the thread pointer
1334          * might get invalid after that point, if the thread exits quickly.
1335          */
1336         if (!IS_ERR(p)) {
1337                 struct completion vfork;
1338
1339                 if (clone_flags & CLONE_VFORK) {
1340                         p->vfork_done = &vfork;
1341                         init_completion(&vfork);
1342                 }
1343
1344                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1345                         /*
1346                          * We'll start up with an immediate SIGSTOP.
1347                          */
1348                         sigaddset(&p->pending.signal, SIGSTOP);
1349                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1350                 }
1351
1352                 if (!(clone_flags & CLONE_STOPPED))
1353                         wake_up_new_task(p, clone_flags);
1354                 else
1355                         p->state = TASK_STOPPED;
1356
1357                 if (unlikely (trace)) {
1358                         current->ptrace_message = pid;
1359                         ptrace_notify ((trace << 8) | SIGTRAP);
1360                 }
1361
1362                 if (clone_flags & CLONE_VFORK) {
1363                         wait_for_completion(&vfork);
1364                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
1365                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1366                 }
1367         } else {
1368                 free_pidmap(pid);
1369                 pid = PTR_ERR(p);
1370         }
1371         return pid;
1372 }
1373
1374 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1375 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1376 #endif
1377
1378 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1379 {
1380         struct sighand_struct *sighand = data;
1381
1382         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1383                                         SLAB_CTOR_CONSTRUCTOR)
1384                 spin_lock_init(&sighand->siglock);
1385 }
1386
1387 void __init proc_caches_init(void)
1388 {
1389         sighand_cachep = kmem_cache_create("sighand_cache",
1390                         sizeof(struct sighand_struct), 0,
1391                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1392                         sighand_ctor, NULL);
1393         signal_cachep = kmem_cache_create("signal_cache",
1394                         sizeof(struct signal_struct), 0,
1395                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1396         files_cachep = kmem_cache_create("files_cache", 
1397                         sizeof(struct files_struct), 0,
1398                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1399         fs_cachep = kmem_cache_create("fs_cache", 
1400                         sizeof(struct fs_struct), 0,
1401                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1402         vm_area_cachep = kmem_cache_create("vm_area_struct",
1403                         sizeof(struct vm_area_struct), 0,
1404                         SLAB_PANIC, NULL, NULL);
1405         mm_cachep = kmem_cache_create("mm_struct",
1406                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1407                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1408 }
1409
1410
1411 /*
1412  * Check constraints on flags passed to the unshare system call and
1413  * force unsharing of additional process context as appropriate.
1414  */
1415 static inline void check_unshare_flags(unsigned long *flags_ptr)
1416 {
1417         /*
1418          * If unsharing a thread from a thread group, must also
1419          * unshare vm.
1420          */
1421         if (*flags_ptr & CLONE_THREAD)
1422                 *flags_ptr |= CLONE_VM;
1423
1424         /*
1425          * If unsharing vm, must also unshare signal handlers.
1426          */
1427         if (*flags_ptr & CLONE_VM)
1428                 *flags_ptr |= CLONE_SIGHAND;
1429
1430         /*
1431          * If unsharing signal handlers and the task was created
1432          * using CLONE_THREAD, then must unshare the thread
1433          */
1434         if ((*flags_ptr & CLONE_SIGHAND) &&
1435             (atomic_read(&current->signal->count) > 1))
1436                 *flags_ptr |= CLONE_THREAD;
1437
1438         /*
1439          * If unsharing namespace, must also unshare filesystem information.
1440          */
1441         if (*flags_ptr & CLONE_NEWNS)
1442                 *flags_ptr |= CLONE_FS;
1443 }
1444
1445 /*
1446  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1447  */
1448 static int unshare_thread(unsigned long unshare_flags)
1449 {
1450         if (unshare_flags & CLONE_THREAD)
1451                 return -EINVAL;
1452
1453         return 0;
1454 }
1455
1456 /*
1457  * Unshare the filesystem structure if it is being shared
1458  */
1459 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1460 {
1461         struct fs_struct *fs = current->fs;
1462
1463         if ((unshare_flags & CLONE_FS) &&
1464             (fs && atomic_read(&fs->count) > 1)) {
1465                 *new_fsp = __copy_fs_struct(current->fs);
1466                 if (!*new_fsp)
1467                         return -ENOMEM;
1468         }
1469
1470         return 0;
1471 }
1472
1473 /*
1474  * Unshare the namespace structure if it is being shared
1475  */
1476 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1477 {
1478         struct namespace *ns = current->namespace;
1479
1480         if ((unshare_flags & CLONE_NEWNS) &&
1481             (ns && atomic_read(&ns->count) > 1)) {
1482                 if (!capable(CAP_SYS_ADMIN))
1483                         return -EPERM;
1484
1485                 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1486                 if (!*new_nsp)
1487                         return -ENOMEM;
1488         }
1489
1490         return 0;
1491 }
1492
1493 /*
1494  * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1495  * supported yet
1496  */
1497 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1498 {
1499         struct sighand_struct *sigh = current->sighand;
1500
1501         if ((unshare_flags & CLONE_SIGHAND) &&
1502             (sigh && atomic_read(&sigh->count) > 1))
1503                 return -EINVAL;
1504         else
1505                 return 0;
1506 }
1507
1508 /*
1509  * Unshare vm if it is being shared
1510  */
1511 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1512 {
1513         struct mm_struct *mm = current->mm;
1514
1515         if ((unshare_flags & CLONE_VM) &&
1516             (mm && atomic_read(&mm->mm_users) > 1)) {
1517                 return -EINVAL;
1518         }
1519
1520         return 0;
1521 }
1522
1523 /*
1524  * Unshare file descriptor table if it is being shared
1525  */
1526 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1527 {
1528         struct files_struct *fd = current->files;
1529         int error = 0;
1530
1531         if ((unshare_flags & CLONE_FILES) &&
1532             (fd && atomic_read(&fd->count) > 1)) {
1533                 *new_fdp = dup_fd(fd, &error);
1534                 if (!*new_fdp)
1535                         return error;
1536         }
1537
1538         return 0;
1539 }
1540
1541 /*
1542  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1543  * supported yet
1544  */
1545 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1546 {
1547         if (unshare_flags & CLONE_SYSVSEM)
1548                 return -EINVAL;
1549
1550         return 0;
1551 }
1552
1553 /*
1554  * unshare allows a process to 'unshare' part of the process
1555  * context which was originally shared using clone.  copy_*
1556  * functions used by do_fork() cannot be used here directly
1557  * because they modify an inactive task_struct that is being
1558  * constructed. Here we are modifying the current, active,
1559  * task_struct.
1560  */
1561 asmlinkage long sys_unshare(unsigned long unshare_flags)
1562 {
1563         int err = 0;
1564         struct fs_struct *fs, *new_fs = NULL;
1565         struct namespace *ns, *new_ns = NULL;
1566         struct sighand_struct *sigh, *new_sigh = NULL;
1567         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1568         struct files_struct *fd, *new_fd = NULL;
1569         struct sem_undo_list *new_ulist = NULL;
1570
1571         check_unshare_flags(&unshare_flags);
1572
1573         /* Return -EINVAL for all unsupported flags */
1574         err = -EINVAL;
1575         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1576                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
1577                 goto bad_unshare_out;
1578
1579         if ((err = unshare_thread(unshare_flags)))
1580                 goto bad_unshare_out;
1581         if ((err = unshare_fs(unshare_flags, &new_fs)))
1582                 goto bad_unshare_cleanup_thread;
1583         if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1584                 goto bad_unshare_cleanup_fs;
1585         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1586                 goto bad_unshare_cleanup_ns;
1587         if ((err = unshare_vm(unshare_flags, &new_mm)))
1588                 goto bad_unshare_cleanup_sigh;
1589         if ((err = unshare_fd(unshare_flags, &new_fd)))
1590                 goto bad_unshare_cleanup_vm;
1591         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1592                 goto bad_unshare_cleanup_fd;
1593
1594         if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1595
1596                 task_lock(current);
1597
1598                 if (new_fs) {
1599                         fs = current->fs;
1600                         current->fs = new_fs;
1601                         new_fs = fs;
1602                 }
1603
1604                 if (new_ns) {
1605                         ns = current->namespace;
1606                         current->namespace = new_ns;
1607                         new_ns = ns;
1608                 }
1609
1610                 if (new_sigh) {
1611                         sigh = current->sighand;
1612                         rcu_assign_pointer(current->sighand, new_sigh);
1613                         new_sigh = sigh;
1614                 }
1615
1616                 if (new_mm) {
1617                         mm = current->mm;
1618                         active_mm = current->active_mm;
1619                         current->mm = new_mm;
1620                         current->active_mm = new_mm;
1621                         activate_mm(active_mm, new_mm);
1622                         new_mm = mm;
1623                 }
1624
1625                 if (new_fd) {
1626                         fd = current->files;
1627                         current->files = new_fd;
1628                         new_fd = fd;
1629                 }
1630
1631                 task_unlock(current);
1632         }
1633
1634 bad_unshare_cleanup_fd:
1635         if (new_fd)
1636                 put_files_struct(new_fd);
1637
1638 bad_unshare_cleanup_vm:
1639         if (new_mm)
1640                 mmput(new_mm);
1641
1642 bad_unshare_cleanup_sigh:
1643         if (new_sigh)
1644                 if (atomic_dec_and_test(&new_sigh->count))
1645                         kmem_cache_free(sighand_cachep, new_sigh);
1646
1647 bad_unshare_cleanup_ns:
1648         if (new_ns)
1649                 put_namespace(new_ns);
1650
1651 bad_unshare_cleanup_fs:
1652         if (new_fs)
1653                 put_fs_struct(new_fs);
1654
1655 bad_unshare_cleanup_thread:
1656 bad_unshare_out:
1657         return err;
1658 }