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1 /*
2  *  linux/kernel/fork.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6
7 /*
8  *  'fork.c' contains the help-routines for the 'fork' system call
9  * (see also entry.S and others).
10  * Fork is rather simple, once you get the hang of it, but the memory
11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
12  */
13
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/unistd.h>
17 #include <linux/module.h>
18 #include <linux/vmalloc.h>
19 #include <linux/completion.h>
20 #include <linux/mnt_namespace.h>
21 #include <linux/personality.h>
22 #include <linux/mempolicy.h>
23 #include <linux/sem.h>
24 #include <linux/file.h>
25 #include <linux/key.h>
26 #include <linux/binfmts.h>
27 #include <linux/mman.h>
28 #include <linux/fs.h>
29 #include <linux/nsproxy.h>
30 #include <linux/capability.h>
31 #include <linux/cpu.h>
32 #include <linux/cpuset.h>
33 #include <linux/security.h>
34 #include <linux/swap.h>
35 #include <linux/syscalls.h>
36 #include <linux/jiffies.h>
37 #include <linux/futex.h>
38 #include <linux/task_io_accounting_ops.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/tsacct_kern.h>
47 #include <linux/cn_proc.h>
48 #include <linux/delayacct.h>
49 #include <linux/taskstats_kern.h>
50 #include <linux/random.h>
51
52 #include <asm/pgtable.h>
53 #include <asm/pgalloc.h>
54 #include <asm/uaccess.h>
55 #include <asm/mmu_context.h>
56 #include <asm/cacheflush.h>
57 #include <asm/tlbflush.h>
58
59 /*
60  * Protected counters by write_lock_irq(&tasklist_lock)
61  */
62 unsigned long total_forks;      /* Handle normal Linux uptimes. */
63 int nr_threads;                 /* The idle threads do not count.. */
64
65 int max_threads;                /* tunable limit on nr_threads */
66
67 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
68
69 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
70
71 int nr_processes(void)
72 {
73         int cpu;
74         int total = 0;
75
76         for_each_online_cpu(cpu)
77                 total += per_cpu(process_counts, cpu);
78
79         return total;
80 }
81
82 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
83 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
84 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
85 static struct kmem_cache *task_struct_cachep;
86 #endif
87
88 /* SLAB cache for signal_struct structures (tsk->signal) */
89 static struct kmem_cache *signal_cachep;
90
91 /* SLAB cache for sighand_struct structures (tsk->sighand) */
92 struct kmem_cache *sighand_cachep;
93
94 /* SLAB cache for files_struct structures (tsk->files) */
95 struct kmem_cache *files_cachep;
96
97 /* SLAB cache for fs_struct structures (tsk->fs) */
98 struct kmem_cache *fs_cachep;
99
100 /* SLAB cache for vm_area_struct structures */
101 struct kmem_cache *vm_area_cachep;
102
103 /* SLAB cache for mm_struct structures (tsk->mm) */
104 static struct kmem_cache *mm_cachep;
105
106 void free_task(struct task_struct *tsk)
107 {
108         free_thread_info(tsk->thread_info);
109         rt_mutex_debug_task_free(tsk);
110         free_task_struct(tsk);
111 }
112 EXPORT_SYMBOL(free_task);
113
114 void __put_task_struct(struct task_struct *tsk)
115 {
116         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
117         WARN_ON(atomic_read(&tsk->usage));
118         WARN_ON(tsk == current);
119
120         security_task_free(tsk);
121         free_uid(tsk->user);
122         put_group_info(tsk->group_info);
123         delayacct_tsk_free(tsk);
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 #ifdef CONFIG_CC_STACKPROTECTOR
182         tsk->stack_canary = get_random_int();
183 #endif
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 #ifdef CONFIG_BLK_DEV_IO_TRACE
189         tsk->btrace_seq = 0;
190 #endif
191         tsk->splice_pipe = NULL;
192         return tsk;
193 }
194
195 #ifdef CONFIG_MMU
196 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
197 {
198         struct vm_area_struct *mpnt, *tmp, **pprev;
199         struct rb_node **rb_link, *rb_parent;
200         int retval;
201         unsigned long charge;
202         struct mempolicy *pol;
203
204         down_write(&oldmm->mmap_sem);
205         flush_cache_dup_mm(oldmm);
206         /*
207          * Not linked in yet - no deadlock potential:
208          */
209         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
210
211         mm->locked_vm = 0;
212         mm->mmap = NULL;
213         mm->mmap_cache = NULL;
214         mm->free_area_cache = oldmm->mmap_base;
215         mm->cached_hole_size = ~0UL;
216         mm->map_count = 0;
217         cpus_clear(mm->cpu_vm_mask);
218         mm->mm_rb = RB_ROOT;
219         rb_link = &mm->mm_rb.rb_node;
220         rb_parent = NULL;
221         pprev = &mm->mmap;
222
223         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
224                 struct file *file;
225
226                 if (mpnt->vm_flags & VM_DONTCOPY) {
227                         long pages = vma_pages(mpnt);
228                         mm->total_vm -= pages;
229                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
230                                                                 -pages);
231                         continue;
232                 }
233                 charge = 0;
234                 if (mpnt->vm_flags & VM_ACCOUNT) {
235                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
236                         if (security_vm_enough_memory(len))
237                                 goto fail_nomem;
238                         charge = len;
239                 }
240                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
241                 if (!tmp)
242                         goto fail_nomem;
243                 *tmp = *mpnt;
244                 pol = mpol_copy(vma_policy(mpnt));
245                 retval = PTR_ERR(pol);
246                 if (IS_ERR(pol))
247                         goto fail_nomem_policy;
248                 vma_set_policy(tmp, pol);
249                 tmp->vm_flags &= ~VM_LOCKED;
250                 tmp->vm_mm = mm;
251                 tmp->vm_next = NULL;
252                 anon_vma_link(tmp);
253                 file = tmp->vm_file;
254                 if (file) {
255                         struct inode *inode = file->f_path.dentry->d_inode;
256                         get_file(file);
257                         if (tmp->vm_flags & VM_DENYWRITE)
258                                 atomic_dec(&inode->i_writecount);
259       
260                         /* insert tmp into the share list, just after mpnt */
261                         spin_lock(&file->f_mapping->i_mmap_lock);
262                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
263                         flush_dcache_mmap_lock(file->f_mapping);
264                         vma_prio_tree_add(tmp, mpnt);
265                         flush_dcache_mmap_unlock(file->f_mapping);
266                         spin_unlock(&file->f_mapping->i_mmap_lock);
267                 }
268
269                 /*
270                  * Link in the new vma and copy the page table entries.
271                  */
272                 *pprev = tmp;
273                 pprev = &tmp->vm_next;
274
275                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
276                 rb_link = &tmp->vm_rb.rb_right;
277                 rb_parent = &tmp->vm_rb;
278
279                 mm->map_count++;
280                 retval = copy_page_range(mm, oldmm, mpnt);
281
282                 if (tmp->vm_ops && tmp->vm_ops->open)
283                         tmp->vm_ops->open(tmp);
284
285                 if (retval)
286                         goto out;
287         }
288         /* a new mm has just been created */
289         arch_dup_mmap(oldmm, mm);
290         retval = 0;
291 out:
292         up_write(&mm->mmap_sem);
293         flush_tlb_mm(oldmm);
294         up_write(&oldmm->mmap_sem);
295         return retval;
296 fail_nomem_policy:
297         kmem_cache_free(vm_area_cachep, tmp);
298 fail_nomem:
299         retval = -ENOMEM;
300         vm_unacct_memory(charge);
301         goto out;
302 }
303
304 static inline int mm_alloc_pgd(struct mm_struct * mm)
305 {
306         mm->pgd = pgd_alloc(mm);
307         if (unlikely(!mm->pgd))
308                 return -ENOMEM;
309         return 0;
310 }
311
312 static inline void mm_free_pgd(struct mm_struct * mm)
313 {
314         pgd_free(mm->pgd);
315 }
316 #else
317 #define dup_mmap(mm, oldmm)     (0)
318 #define mm_alloc_pgd(mm)        (0)
319 #define mm_free_pgd(mm)
320 #endif /* CONFIG_MMU */
321
322  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
323
324 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
325 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
326
327 #include <linux/init_task.h>
328
329 static struct mm_struct * mm_init(struct mm_struct * mm)
330 {
331         atomic_set(&mm->mm_users, 1);
332         atomic_set(&mm->mm_count, 1);
333         init_rwsem(&mm->mmap_sem);
334         INIT_LIST_HEAD(&mm->mmlist);
335         mm->core_waiters = 0;
336         mm->nr_ptes = 0;
337         set_mm_counter(mm, file_rss, 0);
338         set_mm_counter(mm, anon_rss, 0);
339         spin_lock_init(&mm->page_table_lock);
340         rwlock_init(&mm->ioctx_list_lock);
341         mm->ioctx_list = NULL;
342         mm->free_area_cache = TASK_UNMAPPED_BASE;
343         mm->cached_hole_size = ~0UL;
344
345         if (likely(!mm_alloc_pgd(mm))) {
346                 mm->def_flags = 0;
347                 return mm;
348         }
349         free_mm(mm);
350         return NULL;
351 }
352
353 /*
354  * Allocate and initialize an mm_struct.
355  */
356 struct mm_struct * mm_alloc(void)
357 {
358         struct mm_struct * mm;
359
360         mm = allocate_mm();
361         if (mm) {
362                 memset(mm, 0, sizeof(*mm));
363                 mm = mm_init(mm);
364         }
365         return mm;
366 }
367
368 /*
369  * Called when the last reference to the mm
370  * is dropped: either by a lazy thread or by
371  * mmput. Free the page directory and the mm.
372  */
373 void fastcall __mmdrop(struct mm_struct *mm)
374 {
375         BUG_ON(mm == &init_mm);
376         mm_free_pgd(mm);
377         destroy_context(mm);
378         free_mm(mm);
379 }
380
381 /*
382  * Decrement the use count and release all resources for an mm.
383  */
384 void mmput(struct mm_struct *mm)
385 {
386         might_sleep();
387
388         if (atomic_dec_and_test(&mm->mm_users)) {
389                 exit_aio(mm);
390                 exit_mmap(mm);
391                 if (!list_empty(&mm->mmlist)) {
392                         spin_lock(&mmlist_lock);
393                         list_del(&mm->mmlist);
394                         spin_unlock(&mmlist_lock);
395                 }
396                 put_swap_token(mm);
397                 mmdrop(mm);
398         }
399 }
400 EXPORT_SYMBOL_GPL(mmput);
401
402 /**
403  * get_task_mm - acquire a reference to the task's mm
404  *
405  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
406  * this kernel workthread has transiently adopted a user mm with use_mm,
407  * to do its AIO) is not set and if so returns a reference to it, after
408  * bumping up the use count.  User must release the mm via mmput()
409  * after use.  Typically used by /proc and ptrace.
410  */
411 struct mm_struct *get_task_mm(struct task_struct *task)
412 {
413         struct mm_struct *mm;
414
415         task_lock(task);
416         mm = task->mm;
417         if (mm) {
418                 if (task->flags & PF_BORROWED_MM)
419                         mm = NULL;
420                 else
421                         atomic_inc(&mm->mm_users);
422         }
423         task_unlock(task);
424         return mm;
425 }
426 EXPORT_SYMBOL_GPL(get_task_mm);
427
428 /* Please note the differences between mmput and mm_release.
429  * mmput is called whenever we stop holding onto a mm_struct,
430  * error success whatever.
431  *
432  * mm_release is called after a mm_struct has been removed
433  * from the current process.
434  *
435  * This difference is important for error handling, when we
436  * only half set up a mm_struct for a new process and need to restore
437  * the old one.  Because we mmput the new mm_struct before
438  * restoring the old one. . .
439  * Eric Biederman 10 January 1998
440  */
441 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
442 {
443         struct completion *vfork_done = tsk->vfork_done;
444
445         /* Get rid of any cached register state */
446         deactivate_mm(tsk, mm);
447
448         /* notify parent sleeping on vfork() */
449         if (vfork_done) {
450                 tsk->vfork_done = NULL;
451                 complete(vfork_done);
452         }
453
454         /*
455          * If we're exiting normally, clear a user-space tid field if
456          * requested.  We leave this alone when dying by signal, to leave
457          * the value intact in a core dump, and to save the unnecessary
458          * trouble otherwise.  Userland only wants this done for a sys_exit.
459          */
460         if (tsk->clear_child_tid
461             && !(tsk->flags & PF_SIGNALED)
462             && atomic_read(&mm->mm_users) > 1) {
463                 u32 __user * tidptr = tsk->clear_child_tid;
464                 tsk->clear_child_tid = NULL;
465
466                 /*
467                  * We don't check the error code - if userspace has
468                  * not set up a proper pointer then tough luck.
469                  */
470                 put_user(0, tidptr);
471                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
472         }
473 }
474
475 /*
476  * Allocate a new mm structure and copy contents from the
477  * mm structure of the passed in task structure.
478  */
479 static struct mm_struct *dup_mm(struct task_struct *tsk)
480 {
481         struct mm_struct *mm, *oldmm = current->mm;
482         int err;
483
484         if (!oldmm)
485                 return NULL;
486
487         mm = allocate_mm();
488         if (!mm)
489                 goto fail_nomem;
490
491         memcpy(mm, oldmm, sizeof(*mm));
492
493         /* Initializing for Swap token stuff */
494         mm->token_priority = 0;
495         mm->last_interval = 0;
496
497         if (!mm_init(mm))
498                 goto fail_nomem;
499
500         if (init_new_context(tsk, mm))
501                 goto fail_nocontext;
502
503         err = dup_mmap(mm, oldmm);
504         if (err)
505                 goto free_pt;
506
507         mm->hiwater_rss = get_mm_rss(mm);
508         mm->hiwater_vm = mm->total_vm;
509
510         return mm;
511
512 free_pt:
513         mmput(mm);
514
515 fail_nomem:
516         return NULL;
517
518 fail_nocontext:
519         /*
520          * If init_new_context() failed, we cannot use mmput() to free the mm
521          * because it calls destroy_context()
522          */
523         mm_free_pgd(mm);
524         free_mm(mm);
525         return NULL;
526 }
527
528 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
529 {
530         struct mm_struct * mm, *oldmm;
531         int retval;
532
533         tsk->min_flt = tsk->maj_flt = 0;
534         tsk->nvcsw = tsk->nivcsw = 0;
535
536         tsk->mm = NULL;
537         tsk->active_mm = NULL;
538
539         /*
540          * Are we cloning a kernel thread?
541          *
542          * We need to steal a active VM for that..
543          */
544         oldmm = current->mm;
545         if (!oldmm)
546                 return 0;
547
548         if (clone_flags & CLONE_VM) {
549                 atomic_inc(&oldmm->mm_users);
550                 mm = oldmm;
551                 goto good_mm;
552         }
553
554         retval = -ENOMEM;
555         mm = dup_mm(tsk);
556         if (!mm)
557                 goto fail_nomem;
558
559 good_mm:
560         /* Initializing for Swap token stuff */
561         mm->token_priority = 0;
562         mm->last_interval = 0;
563
564         tsk->mm = mm;
565         tsk->active_mm = mm;
566         return 0;
567
568 fail_nomem:
569         return retval;
570 }
571
572 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
573 {
574         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
575         /* We don't need to lock fs - think why ;-) */
576         if (fs) {
577                 atomic_set(&fs->count, 1);
578                 rwlock_init(&fs->lock);
579                 fs->umask = old->umask;
580                 read_lock(&old->lock);
581                 fs->rootmnt = mntget(old->rootmnt);
582                 fs->root = dget(old->root);
583                 fs->pwdmnt = mntget(old->pwdmnt);
584                 fs->pwd = dget(old->pwd);
585                 if (old->altroot) {
586                         fs->altrootmnt = mntget(old->altrootmnt);
587                         fs->altroot = dget(old->altroot);
588                 } else {
589                         fs->altrootmnt = NULL;
590                         fs->altroot = NULL;
591                 }
592                 read_unlock(&old->lock);
593         }
594         return fs;
595 }
596
597 struct fs_struct *copy_fs_struct(struct fs_struct *old)
598 {
599         return __copy_fs_struct(old);
600 }
601
602 EXPORT_SYMBOL_GPL(copy_fs_struct);
603
604 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
605 {
606         if (clone_flags & CLONE_FS) {
607                 atomic_inc(&current->fs->count);
608                 return 0;
609         }
610         tsk->fs = __copy_fs_struct(current->fs);
611         if (!tsk->fs)
612                 return -ENOMEM;
613         return 0;
614 }
615
616 static int count_open_files(struct fdtable *fdt)
617 {
618         int size = fdt->max_fds;
619         int i;
620
621         /* Find the last open fd */
622         for (i = size/(8*sizeof(long)); i > 0; ) {
623                 if (fdt->open_fds->fds_bits[--i])
624                         break;
625         }
626         i = (i+1) * 8 * sizeof(long);
627         return i;
628 }
629
630 static struct files_struct *alloc_files(void)
631 {
632         struct files_struct *newf;
633         struct fdtable *fdt;
634
635         newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
636         if (!newf)
637                 goto out;
638
639         atomic_set(&newf->count, 1);
640
641         spin_lock_init(&newf->file_lock);
642         newf->next_fd = 0;
643         fdt = &newf->fdtab;
644         fdt->max_fds = NR_OPEN_DEFAULT;
645         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
646         fdt->open_fds = (fd_set *)&newf->open_fds_init;
647         fdt->fd = &newf->fd_array[0];
648         INIT_RCU_HEAD(&fdt->rcu);
649         fdt->next = NULL;
650         rcu_assign_pointer(newf->fdt, fdt);
651 out:
652         return newf;
653 }
654
655 /*
656  * Allocate a new files structure and copy contents from the
657  * passed in files structure.
658  * errorp will be valid only when the returned files_struct is NULL.
659  */
660 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
661 {
662         struct files_struct *newf;
663         struct file **old_fds, **new_fds;
664         int open_files, size, i;
665         struct fdtable *old_fdt, *new_fdt;
666
667         *errorp = -ENOMEM;
668         newf = alloc_files();
669         if (!newf)
670                 goto out;
671
672         spin_lock(&oldf->file_lock);
673         old_fdt = files_fdtable(oldf);
674         new_fdt = files_fdtable(newf);
675         open_files = count_open_files(old_fdt);
676
677         /*
678          * Check whether we need to allocate a larger fd array and fd set.
679          * Note: we're not a clone task, so the open count won't change.
680          */
681         if (open_files > new_fdt->max_fds) {
682                 new_fdt->max_fds = 0;
683                 spin_unlock(&oldf->file_lock);
684                 spin_lock(&newf->file_lock);
685                 *errorp = expand_files(newf, open_files-1);
686                 spin_unlock(&newf->file_lock);
687                 if (*errorp < 0)
688                         goto out_release;
689                 new_fdt = files_fdtable(newf);
690                 /*
691                  * Reacquire the oldf lock and a pointer to its fd table
692                  * who knows it may have a new bigger fd table. We need
693                  * the latest pointer.
694                  */
695                 spin_lock(&oldf->file_lock);
696                 old_fdt = files_fdtable(oldf);
697         }
698
699         old_fds = old_fdt->fd;
700         new_fds = new_fdt->fd;
701
702         memcpy(new_fdt->open_fds->fds_bits,
703                 old_fdt->open_fds->fds_bits, open_files/8);
704         memcpy(new_fdt->close_on_exec->fds_bits,
705                 old_fdt->close_on_exec->fds_bits, open_files/8);
706
707         for (i = open_files; i != 0; i--) {
708                 struct file *f = *old_fds++;
709                 if (f) {
710                         get_file(f);
711                 } else {
712                         /*
713                          * The fd may be claimed in the fd bitmap but not yet
714                          * instantiated in the files array if a sibling thread
715                          * is partway through open().  So make sure that this
716                          * fd is available to the new process.
717                          */
718                         FD_CLR(open_files - i, new_fdt->open_fds);
719                 }
720                 rcu_assign_pointer(*new_fds++, f);
721         }
722         spin_unlock(&oldf->file_lock);
723
724         /* compute the remainder to be cleared */
725         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
726
727         /* This is long word aligned thus could use a optimized version */ 
728         memset(new_fds, 0, size); 
729
730         if (new_fdt->max_fds > open_files) {
731                 int left = (new_fdt->max_fds-open_files)/8;
732                 int start = open_files / (8 * sizeof(unsigned long));
733
734                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
735                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
736         }
737
738         return newf;
739
740 out_release:
741         kmem_cache_free(files_cachep, newf);
742 out:
743         return NULL;
744 }
745
746 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
747 {
748         struct files_struct *oldf, *newf;
749         int error = 0;
750
751         /*
752          * A background process may not have any files ...
753          */
754         oldf = current->files;
755         if (!oldf)
756                 goto out;
757
758         if (clone_flags & CLONE_FILES) {
759                 atomic_inc(&oldf->count);
760                 goto out;
761         }
762
763         /*
764          * Note: we may be using current for both targets (See exec.c)
765          * This works because we cache current->files (old) as oldf. Don't
766          * break this.
767          */
768         tsk->files = NULL;
769         newf = dup_fd(oldf, &error);
770         if (!newf)
771                 goto out;
772
773         tsk->files = newf;
774         error = 0;
775 out:
776         return error;
777 }
778
779 /*
780  *      Helper to unshare the files of the current task.
781  *      We don't want to expose copy_files internals to
782  *      the exec layer of the kernel.
783  */
784
785 int unshare_files(void)
786 {
787         struct files_struct *files  = current->files;
788         int rc;
789
790         BUG_ON(!files);
791
792         /* This can race but the race causes us to copy when we don't
793            need to and drop the copy */
794         if(atomic_read(&files->count) == 1)
795         {
796                 atomic_inc(&files->count);
797                 return 0;
798         }
799         rc = copy_files(0, current);
800         if(rc)
801                 current->files = files;
802         return rc;
803 }
804
805 EXPORT_SYMBOL(unshare_files);
806
807 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
808 {
809         struct sighand_struct *sig;
810
811         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
812                 atomic_inc(&current->sighand->count);
813                 return 0;
814         }
815         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
816         rcu_assign_pointer(tsk->sighand, sig);
817         if (!sig)
818                 return -ENOMEM;
819         atomic_set(&sig->count, 1);
820         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
821         return 0;
822 }
823
824 void __cleanup_sighand(struct sighand_struct *sighand)
825 {
826         if (atomic_dec_and_test(&sighand->count))
827                 kmem_cache_free(sighand_cachep, sighand);
828 }
829
830 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
831 {
832         struct signal_struct *sig;
833         int ret;
834
835         if (clone_flags & CLONE_THREAD) {
836                 atomic_inc(&current->signal->count);
837                 atomic_inc(&current->signal->live);
838                 return 0;
839         }
840         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
841         tsk->signal = sig;
842         if (!sig)
843                 return -ENOMEM;
844
845         ret = copy_thread_group_keys(tsk);
846         if (ret < 0) {
847                 kmem_cache_free(signal_cachep, sig);
848                 return ret;
849         }
850
851         atomic_set(&sig->count, 1);
852         atomic_set(&sig->live, 1);
853         init_waitqueue_head(&sig->wait_chldexit);
854         sig->flags = 0;
855         sig->group_exit_code = 0;
856         sig->group_exit_task = NULL;
857         sig->group_stop_count = 0;
858         sig->curr_target = NULL;
859         init_sigpending(&sig->shared_pending);
860         INIT_LIST_HEAD(&sig->posix_timers);
861
862         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
863         sig->it_real_incr.tv64 = 0;
864         sig->real_timer.function = it_real_fn;
865         sig->tsk = tsk;
866
867         sig->it_virt_expires = cputime_zero;
868         sig->it_virt_incr = cputime_zero;
869         sig->it_prof_expires = cputime_zero;
870         sig->it_prof_incr = cputime_zero;
871
872         sig->leader = 0;        /* session leadership doesn't inherit */
873         sig->tty_old_pgrp = NULL;
874
875         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
876         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
877         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
878         sig->sched_time = 0;
879         INIT_LIST_HEAD(&sig->cpu_timers[0]);
880         INIT_LIST_HEAD(&sig->cpu_timers[1]);
881         INIT_LIST_HEAD(&sig->cpu_timers[2]);
882         taskstats_tgid_init(sig);
883
884         task_lock(current->group_leader);
885         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
886         task_unlock(current->group_leader);
887
888         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
889                 /*
890                  * New sole thread in the process gets an expiry time
891                  * of the whole CPU time limit.
892                  */
893                 tsk->it_prof_expires =
894                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
895         }
896         acct_init_pacct(&sig->pacct);
897
898         return 0;
899 }
900
901 void __cleanup_signal(struct signal_struct *sig)
902 {
903         exit_thread_group_keys(sig);
904         kmem_cache_free(signal_cachep, sig);
905 }
906
907 static inline void cleanup_signal(struct task_struct *tsk)
908 {
909         struct signal_struct *sig = tsk->signal;
910
911         atomic_dec(&sig->live);
912
913         if (atomic_dec_and_test(&sig->count))
914                 __cleanup_signal(sig);
915 }
916
917 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
918 {
919         unsigned long new_flags = p->flags;
920
921         new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
922         new_flags |= PF_FORKNOEXEC;
923         if (!(clone_flags & CLONE_PTRACE))
924                 p->ptrace = 0;
925         p->flags = new_flags;
926 }
927
928 asmlinkage long sys_set_tid_address(int __user *tidptr)
929 {
930         current->clear_child_tid = tidptr;
931
932         return current->pid;
933 }
934
935 static inline void rt_mutex_init_task(struct task_struct *p)
936 {
937         spin_lock_init(&p->pi_lock);
938 #ifdef CONFIG_RT_MUTEXES
939         plist_head_init(&p->pi_waiters, &p->pi_lock);
940         p->pi_blocked_on = NULL;
941 #endif
942 }
943
944 /*
945  * This creates a new process as a copy of the old one,
946  * but does not actually start it yet.
947  *
948  * It copies the registers, and all the appropriate
949  * parts of the process environment (as per the clone
950  * flags). The actual kick-off is left to the caller.
951  */
952 static struct task_struct *copy_process(unsigned long clone_flags,
953                                         unsigned long stack_start,
954                                         struct pt_regs *regs,
955                                         unsigned long stack_size,
956                                         int __user *parent_tidptr,
957                                         int __user *child_tidptr,
958                                         int pid)
959 {
960         int retval;
961         struct task_struct *p = NULL;
962
963         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
964                 return ERR_PTR(-EINVAL);
965
966         /*
967          * Thread groups must share signals as well, and detached threads
968          * can only be started up within the thread group.
969          */
970         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
971                 return ERR_PTR(-EINVAL);
972
973         /*
974          * Shared signal handlers imply shared VM. By way of the above,
975          * thread groups also imply shared VM. Blocking this case allows
976          * for various simplifications in other code.
977          */
978         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
979                 return ERR_PTR(-EINVAL);
980
981         retval = security_task_create(clone_flags);
982         if (retval)
983                 goto fork_out;
984
985         retval = -ENOMEM;
986         p = dup_task_struct(current);
987         if (!p)
988                 goto fork_out;
989
990         rt_mutex_init_task(p);
991
992 #ifdef CONFIG_TRACE_IRQFLAGS
993         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
994         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
995 #endif
996         retval = -EAGAIN;
997         if (atomic_read(&p->user->processes) >=
998                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
999                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1000                                 p->user != &root_user)
1001                         goto bad_fork_free;
1002         }
1003
1004         atomic_inc(&p->user->__count);
1005         atomic_inc(&p->user->processes);
1006         get_group_info(p->group_info);
1007
1008         /*
1009          * If multiple threads are within copy_process(), then this check
1010          * triggers too late. This doesn't hurt, the check is only there
1011          * to stop root fork bombs.
1012          */
1013         if (nr_threads >= max_threads)
1014                 goto bad_fork_cleanup_count;
1015
1016         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1017                 goto bad_fork_cleanup_count;
1018
1019         if (p->binfmt && !try_module_get(p->binfmt->module))
1020                 goto bad_fork_cleanup_put_domain;
1021
1022         p->did_exec = 0;
1023         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1024         copy_flags(clone_flags, p);
1025         p->pid = pid;
1026         retval = -EFAULT;
1027         if (clone_flags & CLONE_PARENT_SETTID)
1028                 if (put_user(p->pid, parent_tidptr))
1029                         goto bad_fork_cleanup_delays_binfmt;
1030
1031         INIT_LIST_HEAD(&p->children);
1032         INIT_LIST_HEAD(&p->sibling);
1033         p->vfork_done = NULL;
1034         spin_lock_init(&p->alloc_lock);
1035
1036         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1037         init_sigpending(&p->pending);
1038
1039         p->utime = cputime_zero;
1040         p->stime = cputime_zero;
1041         p->sched_time = 0;
1042 #ifdef CONFIG_TASK_XACCT
1043         p->rchar = 0;           /* I/O counter: bytes read */
1044         p->wchar = 0;           /* I/O counter: bytes written */
1045         p->syscr = 0;           /* I/O counter: read syscalls */
1046         p->syscw = 0;           /* I/O counter: write syscalls */
1047 #endif
1048         task_io_accounting_init(p);
1049         acct_clear_integrals(p);
1050
1051         p->it_virt_expires = cputime_zero;
1052         p->it_prof_expires = cputime_zero;
1053         p->it_sched_expires = 0;
1054         INIT_LIST_HEAD(&p->cpu_timers[0]);
1055         INIT_LIST_HEAD(&p->cpu_timers[1]);
1056         INIT_LIST_HEAD(&p->cpu_timers[2]);
1057
1058         p->lock_depth = -1;             /* -1 = no lock */
1059         do_posix_clock_monotonic_gettime(&p->start_time);
1060         p->security = NULL;
1061         p->io_context = NULL;
1062         p->io_wait = NULL;
1063         p->audit_context = NULL;
1064         cpuset_fork(p);
1065 #ifdef CONFIG_NUMA
1066         p->mempolicy = mpol_copy(p->mempolicy);
1067         if (IS_ERR(p->mempolicy)) {
1068                 retval = PTR_ERR(p->mempolicy);
1069                 p->mempolicy = NULL;
1070                 goto bad_fork_cleanup_cpuset;
1071         }
1072         mpol_fix_fork_child_flag(p);
1073 #endif
1074 #ifdef CONFIG_TRACE_IRQFLAGS
1075         p->irq_events = 0;
1076 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1077         p->hardirqs_enabled = 1;
1078 #else
1079         p->hardirqs_enabled = 0;
1080 #endif
1081         p->hardirq_enable_ip = 0;
1082         p->hardirq_enable_event = 0;
1083         p->hardirq_disable_ip = _THIS_IP_;
1084         p->hardirq_disable_event = 0;
1085         p->softirqs_enabled = 1;
1086         p->softirq_enable_ip = _THIS_IP_;
1087         p->softirq_enable_event = 0;
1088         p->softirq_disable_ip = 0;
1089         p->softirq_disable_event = 0;
1090         p->hardirq_context = 0;
1091         p->softirq_context = 0;
1092 #endif
1093 #ifdef CONFIG_LOCKDEP
1094         p->lockdep_depth = 0; /* no locks held yet */
1095         p->curr_chain_key = 0;
1096         p->lockdep_recursion = 0;
1097 #endif
1098
1099 #ifdef CONFIG_DEBUG_MUTEXES
1100         p->blocked_on = NULL; /* not blocked yet */
1101 #endif
1102
1103         p->tgid = p->pid;
1104         if (clone_flags & CLONE_THREAD)
1105                 p->tgid = current->tgid;
1106
1107         if ((retval = security_task_alloc(p)))
1108                 goto bad_fork_cleanup_policy;
1109         if ((retval = audit_alloc(p)))
1110                 goto bad_fork_cleanup_security;
1111         /* copy all the process information */
1112         if ((retval = copy_semundo(clone_flags, p)))
1113                 goto bad_fork_cleanup_audit;
1114         if ((retval = copy_files(clone_flags, p)))
1115                 goto bad_fork_cleanup_semundo;
1116         if ((retval = copy_fs(clone_flags, p)))
1117                 goto bad_fork_cleanup_files;
1118         if ((retval = copy_sighand(clone_flags, p)))
1119                 goto bad_fork_cleanup_fs;
1120         if ((retval = copy_signal(clone_flags, p)))
1121                 goto bad_fork_cleanup_sighand;
1122         if ((retval = copy_mm(clone_flags, p)))
1123                 goto bad_fork_cleanup_signal;
1124         if ((retval = copy_keys(clone_flags, p)))
1125                 goto bad_fork_cleanup_mm;
1126         if ((retval = copy_namespaces(clone_flags, p)))
1127                 goto bad_fork_cleanup_keys;
1128         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1129         if (retval)
1130                 goto bad_fork_cleanup_namespaces;
1131
1132         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1133         /*
1134          * Clear TID on mm_release()?
1135          */
1136         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1137         p->robust_list = NULL;
1138 #ifdef CONFIG_COMPAT
1139         p->compat_robust_list = NULL;
1140 #endif
1141         INIT_LIST_HEAD(&p->pi_state_list);
1142         p->pi_state_cache = NULL;
1143
1144         /*
1145          * sigaltstack should be cleared when sharing the same VM
1146          */
1147         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1148                 p->sas_ss_sp = p->sas_ss_size = 0;
1149
1150         /*
1151          * Syscall tracing should be turned off in the child regardless
1152          * of CLONE_PTRACE.
1153          */
1154         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1155 #ifdef TIF_SYSCALL_EMU
1156         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1157 #endif
1158
1159         /* Our parent execution domain becomes current domain
1160            These must match for thread signalling to apply */
1161         p->parent_exec_id = p->self_exec_id;
1162
1163         /* ok, now we should be set up.. */
1164         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1165         p->pdeath_signal = 0;
1166         p->exit_state = 0;
1167
1168         /*
1169          * Ok, make it visible to the rest of the system.
1170          * We dont wake it up yet.
1171          */
1172         p->group_leader = p;
1173         INIT_LIST_HEAD(&p->thread_group);
1174         INIT_LIST_HEAD(&p->ptrace_children);
1175         INIT_LIST_HEAD(&p->ptrace_list);
1176
1177         /* Perform scheduler related setup. Assign this task to a CPU. */
1178         sched_fork(p, clone_flags);
1179
1180         /* Need tasklist lock for parent etc handling! */
1181         write_lock_irq(&tasklist_lock);
1182
1183         /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
1184         p->ioprio = current->ioprio;
1185
1186         /*
1187          * The task hasn't been attached yet, so its cpus_allowed mask will
1188          * not be changed, nor will its assigned CPU.
1189          *
1190          * The cpus_allowed mask of the parent may have changed after it was
1191          * copied first time - so re-copy it here, then check the child's CPU
1192          * to ensure it is on a valid CPU (and if not, just force it back to
1193          * parent's CPU). This avoids alot of nasty races.
1194          */
1195         p->cpus_allowed = current->cpus_allowed;
1196         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1197                         !cpu_online(task_cpu(p))))
1198                 set_task_cpu(p, smp_processor_id());
1199
1200         /* CLONE_PARENT re-uses the old parent */
1201         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1202                 p->real_parent = current->real_parent;
1203         else
1204                 p->real_parent = current;
1205         p->parent = p->real_parent;
1206
1207         spin_lock(&current->sighand->siglock);
1208
1209         /*
1210          * Process group and session signals need to be delivered to just the
1211          * parent before the fork or both the parent and the child after the
1212          * fork. Restart if a signal comes in before we add the new process to
1213          * it's process group.
1214          * A fatal signal pending means that current will exit, so the new
1215          * thread can't slip out of an OOM kill (or normal SIGKILL).
1216          */
1217         recalc_sigpending();
1218         if (signal_pending(current)) {
1219                 spin_unlock(&current->sighand->siglock);
1220                 write_unlock_irq(&tasklist_lock);
1221                 retval = -ERESTARTNOINTR;
1222                 goto bad_fork_cleanup_namespaces;
1223         }
1224
1225         if (clone_flags & CLONE_THREAD) {
1226                 p->group_leader = current->group_leader;
1227                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1228
1229                 if (!cputime_eq(current->signal->it_virt_expires,
1230                                 cputime_zero) ||
1231                     !cputime_eq(current->signal->it_prof_expires,
1232                                 cputime_zero) ||
1233                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1234                     !list_empty(&current->signal->cpu_timers[0]) ||
1235                     !list_empty(&current->signal->cpu_timers[1]) ||
1236                     !list_empty(&current->signal->cpu_timers[2])) {
1237                         /*
1238                          * Have child wake up on its first tick to check
1239                          * for process CPU timers.
1240                          */
1241                         p->it_prof_expires = jiffies_to_cputime(1);
1242                 }
1243         }
1244
1245         if (likely(p->pid)) {
1246                 add_parent(p);
1247                 if (unlikely(p->ptrace & PT_PTRACED))
1248                         __ptrace_link(p, current->parent);
1249
1250                 if (thread_group_leader(p)) {
1251                         p->signal->tty = current->signal->tty;
1252                         p->signal->pgrp = process_group(current);
1253                         set_signal_session(p->signal, process_session(current));
1254                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1255                         attach_pid(p, PIDTYPE_SID, process_session(p));
1256
1257                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1258                         __get_cpu_var(process_counts)++;
1259                 }
1260                 attach_pid(p, PIDTYPE_PID, p->pid);
1261                 nr_threads++;
1262         }
1263
1264         total_forks++;
1265         spin_unlock(&current->sighand->siglock);
1266         write_unlock_irq(&tasklist_lock);
1267         proc_fork_connector(p);
1268         return p;
1269
1270 bad_fork_cleanup_namespaces:
1271         exit_task_namespaces(p);
1272 bad_fork_cleanup_keys:
1273         exit_keys(p);
1274 bad_fork_cleanup_mm:
1275         if (p->mm)
1276                 mmput(p->mm);
1277 bad_fork_cleanup_signal:
1278         cleanup_signal(p);
1279 bad_fork_cleanup_sighand:
1280         __cleanup_sighand(p->sighand);
1281 bad_fork_cleanup_fs:
1282         exit_fs(p); /* blocking */
1283 bad_fork_cleanup_files:
1284         exit_files(p); /* blocking */
1285 bad_fork_cleanup_semundo:
1286         exit_sem(p);
1287 bad_fork_cleanup_audit:
1288         audit_free(p);
1289 bad_fork_cleanup_security:
1290         security_task_free(p);
1291 bad_fork_cleanup_policy:
1292 #ifdef CONFIG_NUMA
1293         mpol_free(p->mempolicy);
1294 bad_fork_cleanup_cpuset:
1295 #endif
1296         cpuset_exit(p);
1297 bad_fork_cleanup_delays_binfmt:
1298         delayacct_tsk_free(p);
1299         if (p->binfmt)
1300                 module_put(p->binfmt->module);
1301 bad_fork_cleanup_put_domain:
1302         module_put(task_thread_info(p)->exec_domain->module);
1303 bad_fork_cleanup_count:
1304         put_group_info(p->group_info);
1305         atomic_dec(&p->user->processes);
1306         free_uid(p->user);
1307 bad_fork_free:
1308         free_task(p);
1309 fork_out:
1310         return ERR_PTR(retval);
1311 }
1312
1313 noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1314 {
1315         memset(regs, 0, sizeof(struct pt_regs));
1316         return regs;
1317 }
1318
1319 struct task_struct * __cpuinit fork_idle(int cpu)
1320 {
1321         struct task_struct *task;
1322         struct pt_regs regs;
1323
1324         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1325         if (!IS_ERR(task))
1326                 init_idle(task, cpu);
1327
1328         return task;
1329 }
1330
1331 static inline int fork_traceflag (unsigned clone_flags)
1332 {
1333         if (clone_flags & CLONE_UNTRACED)
1334                 return 0;
1335         else if (clone_flags & CLONE_VFORK) {
1336                 if (current->ptrace & PT_TRACE_VFORK)
1337                         return PTRACE_EVENT_VFORK;
1338         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1339                 if (current->ptrace & PT_TRACE_CLONE)
1340                         return PTRACE_EVENT_CLONE;
1341         } else if (current->ptrace & PT_TRACE_FORK)
1342                 return PTRACE_EVENT_FORK;
1343
1344         return 0;
1345 }
1346
1347 /*
1348  *  Ok, this is the main fork-routine.
1349  *
1350  * It copies the process, and if successful kick-starts
1351  * it and waits for it to finish using the VM if required.
1352  */
1353 long do_fork(unsigned long clone_flags,
1354               unsigned long stack_start,
1355               struct pt_regs *regs,
1356               unsigned long stack_size,
1357               int __user *parent_tidptr,
1358               int __user *child_tidptr)
1359 {
1360         struct task_struct *p;
1361         int trace = 0;
1362         struct pid *pid = alloc_pid();
1363         long nr;
1364
1365         if (!pid)
1366                 return -EAGAIN;
1367         nr = pid->nr;
1368         if (unlikely(current->ptrace)) {
1369                 trace = fork_traceflag (clone_flags);
1370                 if (trace)
1371                         clone_flags |= CLONE_PTRACE;
1372         }
1373
1374         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1375         /*
1376          * Do this prior waking up the new thread - the thread pointer
1377          * might get invalid after that point, if the thread exits quickly.
1378          */
1379         if (!IS_ERR(p)) {
1380                 struct completion vfork;
1381
1382                 if (clone_flags & CLONE_VFORK) {
1383                         p->vfork_done = &vfork;
1384                         init_completion(&vfork);
1385                 }
1386
1387                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1388                         /*
1389                          * We'll start up with an immediate SIGSTOP.
1390                          */
1391                         sigaddset(&p->pending.signal, SIGSTOP);
1392                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1393                 }
1394
1395                 if (!(clone_flags & CLONE_STOPPED))
1396                         wake_up_new_task(p, clone_flags);
1397                 else
1398                         p->state = TASK_STOPPED;
1399
1400                 if (unlikely (trace)) {
1401                         current->ptrace_message = nr;
1402                         ptrace_notify ((trace << 8) | SIGTRAP);
1403                 }
1404
1405                 if (clone_flags & CLONE_VFORK) {
1406                         wait_for_completion(&vfork);
1407                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1408                                 current->ptrace_message = nr;
1409                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1410                         }
1411                 }
1412         } else {
1413                 free_pid(pid);
1414                 nr = PTR_ERR(p);
1415         }
1416         return nr;
1417 }
1418
1419 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1420 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1421 #endif
1422
1423 static void sighand_ctor(void *data, struct kmem_cache *cachep, unsigned long flags)
1424 {
1425         struct sighand_struct *sighand = data;
1426
1427         if (flags & SLAB_CTOR_CONSTRUCTOR)
1428                 spin_lock_init(&sighand->siglock);
1429 }
1430
1431 void __init proc_caches_init(void)
1432 {
1433         sighand_cachep = kmem_cache_create("sighand_cache",
1434                         sizeof(struct sighand_struct), 0,
1435                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1436                         sighand_ctor, NULL);
1437         signal_cachep = kmem_cache_create("signal_cache",
1438                         sizeof(struct signal_struct), 0,
1439                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1440         files_cachep = kmem_cache_create("files_cache", 
1441                         sizeof(struct files_struct), 0,
1442                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1443         fs_cachep = kmem_cache_create("fs_cache", 
1444                         sizeof(struct fs_struct), 0,
1445                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1446         vm_area_cachep = kmem_cache_create("vm_area_struct",
1447                         sizeof(struct vm_area_struct), 0,
1448                         SLAB_PANIC, NULL, NULL);
1449         mm_cachep = kmem_cache_create("mm_struct",
1450                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1451                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1452 }
1453
1454
1455 /*
1456  * Check constraints on flags passed to the unshare system call and
1457  * force unsharing of additional process context as appropriate.
1458  */
1459 static inline void check_unshare_flags(unsigned long *flags_ptr)
1460 {
1461         /*
1462          * If unsharing a thread from a thread group, must also
1463          * unshare vm.
1464          */
1465         if (*flags_ptr & CLONE_THREAD)
1466                 *flags_ptr |= CLONE_VM;
1467
1468         /*
1469          * If unsharing vm, must also unshare signal handlers.
1470          */
1471         if (*flags_ptr & CLONE_VM)
1472                 *flags_ptr |= CLONE_SIGHAND;
1473
1474         /*
1475          * If unsharing signal handlers and the task was created
1476          * using CLONE_THREAD, then must unshare the thread
1477          */
1478         if ((*flags_ptr & CLONE_SIGHAND) &&
1479             (atomic_read(&current->signal->count) > 1))
1480                 *flags_ptr |= CLONE_THREAD;
1481
1482         /*
1483          * If unsharing namespace, must also unshare filesystem information.
1484          */
1485         if (*flags_ptr & CLONE_NEWNS)
1486                 *flags_ptr |= CLONE_FS;
1487 }
1488
1489 /*
1490  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1491  */
1492 static int unshare_thread(unsigned long unshare_flags)
1493 {
1494         if (unshare_flags & CLONE_THREAD)
1495                 return -EINVAL;
1496
1497         return 0;
1498 }
1499
1500 /*
1501  * Unshare the filesystem structure if it is being shared
1502  */
1503 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1504 {
1505         struct fs_struct *fs = current->fs;
1506
1507         if ((unshare_flags & CLONE_FS) &&
1508             (fs && atomic_read(&fs->count) > 1)) {
1509                 *new_fsp = __copy_fs_struct(current->fs);
1510                 if (!*new_fsp)
1511                         return -ENOMEM;
1512         }
1513
1514         return 0;
1515 }
1516
1517 /*
1518  * Unsharing of sighand is not supported yet
1519  */
1520 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1521 {
1522         struct sighand_struct *sigh = current->sighand;
1523
1524         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1525                 return -EINVAL;
1526         else
1527                 return 0;
1528 }
1529
1530 /*
1531  * Unshare vm if it is being shared
1532  */
1533 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1534 {
1535         struct mm_struct *mm = current->mm;
1536
1537         if ((unshare_flags & CLONE_VM) &&
1538             (mm && atomic_read(&mm->mm_users) > 1)) {
1539                 return -EINVAL;
1540         }
1541
1542         return 0;
1543 }
1544
1545 /*
1546  * Unshare file descriptor table if it is being shared
1547  */
1548 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1549 {
1550         struct files_struct *fd = current->files;
1551         int error = 0;
1552
1553         if ((unshare_flags & CLONE_FILES) &&
1554             (fd && atomic_read(&fd->count) > 1)) {
1555                 *new_fdp = dup_fd(fd, &error);
1556                 if (!*new_fdp)
1557                         return error;
1558         }
1559
1560         return 0;
1561 }
1562
1563 /*
1564  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1565  * supported yet
1566  */
1567 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1568 {
1569         if (unshare_flags & CLONE_SYSVSEM)
1570                 return -EINVAL;
1571
1572         return 0;
1573 }
1574
1575 /*
1576  * unshare allows a process to 'unshare' part of the process
1577  * context which was originally shared using clone.  copy_*
1578  * functions used by do_fork() cannot be used here directly
1579  * because they modify an inactive task_struct that is being
1580  * constructed. Here we are modifying the current, active,
1581  * task_struct.
1582  */
1583 asmlinkage long sys_unshare(unsigned long unshare_flags)
1584 {
1585         int err = 0;
1586         struct fs_struct *fs, *new_fs = NULL;
1587         struct sighand_struct *new_sigh = NULL;
1588         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1589         struct files_struct *fd, *new_fd = NULL;
1590         struct sem_undo_list *new_ulist = NULL;
1591         struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
1592
1593         check_unshare_flags(&unshare_flags);
1594
1595         /* Return -EINVAL for all unsupported flags */
1596         err = -EINVAL;
1597         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1598                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1599                                 CLONE_NEWUTS|CLONE_NEWIPC))
1600                 goto bad_unshare_out;
1601
1602         if ((err = unshare_thread(unshare_flags)))
1603                 goto bad_unshare_out;
1604         if ((err = unshare_fs(unshare_flags, &new_fs)))
1605                 goto bad_unshare_cleanup_thread;
1606         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1607                 goto bad_unshare_cleanup_fs;
1608         if ((err = unshare_vm(unshare_flags, &new_mm)))
1609                 goto bad_unshare_cleanup_sigh;
1610         if ((err = unshare_fd(unshare_flags, &new_fd)))
1611                 goto bad_unshare_cleanup_vm;
1612         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1613                 goto bad_unshare_cleanup_fd;
1614         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1615                         new_fs)))
1616                 goto bad_unshare_cleanup_semundo;
1617
1618         if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
1619
1620                 task_lock(current);
1621
1622                 if (new_nsproxy) {
1623                         old_nsproxy = current->nsproxy;
1624                         current->nsproxy = new_nsproxy;
1625                         new_nsproxy = old_nsproxy;
1626                 }
1627
1628                 if (new_fs) {
1629                         fs = current->fs;
1630                         current->fs = new_fs;
1631                         new_fs = fs;
1632                 }
1633
1634                 if (new_mm) {
1635                         mm = current->mm;
1636                         active_mm = current->active_mm;
1637                         current->mm = new_mm;
1638                         current->active_mm = new_mm;
1639                         activate_mm(active_mm, new_mm);
1640                         new_mm = mm;
1641                 }
1642
1643                 if (new_fd) {
1644                         fd = current->files;
1645                         current->files = new_fd;
1646                         new_fd = fd;
1647                 }
1648
1649                 task_unlock(current);
1650         }
1651
1652         if (new_nsproxy)
1653                 put_nsproxy(new_nsproxy);
1654
1655 bad_unshare_cleanup_semundo:
1656 bad_unshare_cleanup_fd:
1657         if (new_fd)
1658                 put_files_struct(new_fd);
1659
1660 bad_unshare_cleanup_vm:
1661         if (new_mm)
1662                 mmput(new_mm);
1663
1664 bad_unshare_cleanup_sigh:
1665         if (new_sigh)
1666                 if (atomic_dec_and_test(&new_sigh->count))
1667                         kmem_cache_free(sighand_cachep, new_sigh);
1668
1669 bad_unshare_cleanup_fs:
1670         if (new_fs)
1671                 put_fs_struct(new_fs);
1672
1673 bad_unshare_cleanup_thread:
1674 bad_unshare_out:
1675         return err;
1676 }