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/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/smp_lock.h>
  18 #include <linux/module.h>
  19 #include <linux/vmalloc.h>
  20 #include <linux/completion.h>
  21 #include <linux/mnt_namespace.h>
  22 #include <linux/personality.h>
  23 #include <linux/mempolicy.h>
  24 #include <linux/sem.h>
  25 #include <linux/file.h>
  26 #include <linux/key.h>
  27 #include <linux/binfmts.h>
  28 #include <linux/mman.h>
  29 #include <linux/fs.h>
  30 #include <linux/nsproxy.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/task_io_accounting_ops.h>
  40 #include <linux/rcupdate.h>
  41 #include <linux/ptrace.h>
  42 #include <linux/mount.h>
  43 #include <linux/audit.h>
  44 #include <linux/profile.h>
  45 #include <linux/rmap.h>
  46 #include <linux/acct.h>
  47 #include <linux/tsacct_kern.h>
  48 #include <linux/cn_proc.h>
  49 #include <linux/delayacct.h>
  50 #include <linux/taskstats_kern.h>
  51 #include <linux/random.h>
  52
  53 #include <asm/pgtable.h>
  54 #include <asm/pgalloc.h>
  55 #include <asm/uaccess.h>
  56 #include <asm/mmu_context.h>
  57 #include <asm/cacheflush.h>
  58 #include <asm/tlbflush.h>
  59
  60 /*
  61  * Protected counters by write_lock_irq(&tasklist_lock)
  62  */
  63 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  64 int nr_threads;                 /* The idle threads do not count.. */
  65
  66 int max_threads;                /* tunable limit on nr_threads */
  67
  68 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  69
  70 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  71
  72 int nr_processes(void)
  73 {
  74         int cpu;
  75         int total = 0;
  76
  77         for_each_online_cpu(cpu)
  78                 total += per_cpu(process_counts, cpu);
  79
  80         return total;
  81 }
  82
  83 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  84 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  85 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  86 static struct kmem_cache *task_struct_cachep;
  87 #endif
  88
  89 /* SLAB cache for signal_struct structures (tsk->signal) */
  90 static struct kmem_cache *signal_cachep;
  91
  92 /* SLAB cache for sighand_struct structures (tsk->sighand) */
  93 struct kmem_cache *sighand_cachep;
  94
  95 /* SLAB cache for files_struct structures (tsk->files) */
  96 struct kmem_cache *files_cachep;
  97
  98 /* SLAB cache for fs_struct structures (tsk->fs) */
  99 struct kmem_cache *fs_cachep;
 100
 101 /* SLAB cache for vm_area_struct structures */
 102 struct kmem_cache *vm_area_cachep;
 103
 104 /* SLAB cache for mm_struct structures (tsk->mm) */
 105 static struct kmem_cache *mm_cachep;
 106
 107 void free_task(struct task_struct *tsk)
 108 {
 109         free_thread_info(tsk->thread_info);
 110         rt_mutex_debug_task_free(tsk);
 111         free_task_struct(tsk);
 112 }
 113 EXPORT_SYMBOL(free_task);
 114
 115 void __put_task_struct(struct task_struct *tsk)
 116 {
 117         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
 118         WARN_ON(atomic_read(&tsk->usage));
 119         WARN_ON(tsk == current);
 120
 121         security_task_free(tsk);
 122         free_uid(tsk->user);
 123         put_group_info(tsk->group_info);
 124         delayacct_tsk_free(tsk);
 125
 126         if (!profile_handoff_task(tsk))
 127                 free_task(tsk);
 128 }
 129
 130 void __init fork_init(unsigned long mempages)
 131 {
 132 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 133 #ifndef ARCH_MIN_TASKALIGN
 134 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 135 #endif
 136         /* create a slab on which task_structs can be allocated */
 137         task_struct_cachep =
 138                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 139                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
 140 #endif
 141
 142         /*
 143          * The default maximum number of threads is set to a safe
 144          * value: the thread structures can take up at most half
 145          * of memory.
 146          */
 147         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 148
 149         /*
 150          * we need to allow at least 20 threads to boot a system
 151          */
 152         if(max_threads < 20)
 153                 max_threads = 20;
 154
 155         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 156         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 157         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 158                 init_task.signal->rlim[RLIMIT_NPROC];
 159 }
 160
 161 static struct task_struct *dup_task_struct(struct task_struct *orig)
 162 {
 163         struct task_struct *tsk;
 164         struct thread_info *ti;
 165
 166         prepare_to_copy(orig);
 167
 168         tsk = alloc_task_struct();
 169         if (!tsk)
 170                 return NULL;
 171
 172         ti = alloc_thread_info(tsk);
 173         if (!ti) {
 174                 free_task_struct(tsk);
 175                 return NULL;
 176         }
 177
 178         *tsk = *orig;
 179         tsk->thread_info = ti;
 180         setup_thread_stack(tsk, orig);
 181
 182 #ifdef CONFIG_CC_STACKPROTECTOR
 183         tsk->stack_canary = get_random_int();
 184 #endif
 185
 186         /* One for us, one for whoever does the "release_task()" (usually parent) */
 187         atomic_set(&tsk->usage,2);
 188         atomic_set(&tsk->fs_excl, 0);
 189 #ifdef CONFIG_BLK_DEV_IO_TRACE
 190         tsk->btrace_seq = 0;
 191 #endif
 192         tsk->splice_pipe = NULL;
 193         return tsk;
 194 }
 195
 196 #ifdef CONFIG_MMU
 197 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 198 {
 199         struct vm_area_struct *mpnt, *tmp, **pprev;
 200         struct rb_node **rb_link, *rb_parent;
 201         int retval;
 202         unsigned long charge;
 203         struct mempolicy *pol;
 204
 205         down_write(&oldmm->mmap_sem);
 206         flush_cache_dup_mm(oldmm);
 207         /*
 208          * Not linked in yet - no deadlock potential:
 209          */
 210         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 211
 212         mm->locked_vm = 0;
 213         mm->mmap = NULL;
 214         mm->mmap_cache = NULL;
 215         mm->free_area_cache = oldmm->mmap_base;
 216         mm->cached_hole_size = ~0UL;
 217         mm->map_count = 0;
 218         cpus_clear(mm->cpu_vm_mask);
 219         mm->mm_rb = RB_ROOT;
 220         rb_link = &mm->mm_rb.rb_node;
 221         rb_parent = NULL;
 222         pprev = &mm->mmap;
 223
 224         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 225                 struct file *file;
 226
 227                 if (mpnt->vm_flags & VM_DONTCOPY) {
 228                         long pages = vma_pages(mpnt);
 229                         mm->total_vm -= pages;
 230                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 231                                                                 -pages);
 232                         continue;
 233                 }
 234                 charge = 0;
 235                 if (mpnt->vm_flags & VM_ACCOUNT) {
 236                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 237                         if (security_vm_enough_memory(len))
 238                                 goto fail_nomem;
 239                         charge = len;
 240                 }
 241                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 242                 if (!tmp)
 243                         goto fail_nomem;
 244                 *tmp = *mpnt;
 245                 pol = mpol_copy(vma_policy(mpnt));
 246                 retval = PTR_ERR(pol);
 247                 if (IS_ERR(pol))
 248                         goto fail_nomem_policy;
 249                 vma_set_policy(tmp, pol);
 250                 tmp->vm_flags &= ~VM_LOCKED;
 251                 tmp->vm_mm = mm;
 252                 tmp->vm_next = NULL;
 253                 anon_vma_link(tmp);
 254                 file = tmp->vm_file;
 255                 if (file) {
 256                         struct inode *inode = file->f_path.dentry->d_inode;
 257                         get_file(file);
 258                         if (tmp->vm_flags & VM_DENYWRITE)
 259                                 atomic_dec(&inode->i_writecount);
 260
 261                         /* insert tmp into the share list, just after mpnt */
 262                         spin_lock(&file->f_mapping->i_mmap_lock);
 263                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 264                         flush_dcache_mmap_lock(file->f_mapping);
 265                         vma_prio_tree_add(tmp, mpnt);
 266                         flush_dcache_mmap_unlock(file->f_mapping);
 267                         spin_unlock(&file->f_mapping->i_mmap_lock);
 268                 }
 269
 270                 /*
 271                  * Link in the new vma and copy the page table entries.
 272                  */
 273                 *pprev = tmp;
 274                 pprev = &tmp->vm_next;
 275
 276                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 277                 rb_link = &tmp->vm_rb.rb_right;
 278                 rb_parent = &tmp->vm_rb;
 279
 280                 mm->map_count++;
 281                 retval = copy_page_range(mm, oldmm, mpnt);
 282
 283                 if (tmp->vm_ops && tmp->vm_ops->open)
 284                         tmp->vm_ops->open(tmp);
 285
 286                 if (retval)
 287                         goto out;
 288         }
 289         retval = 0;
 290 out:
 291         up_write(&mm->mmap_sem);
 292         flush_tlb_mm(oldmm);
 293         up_write(&oldmm->mmap_sem);
 294         return retval;
 295 fail_nomem_policy:
 296         kmem_cache_free(vm_area_cachep, tmp);
 297 fail_nomem:
 298         retval = -ENOMEM;
 299         vm_unacct_memory(charge);
 300         goto out;
 301 }
 302
 303 static inline int mm_alloc_pgd(struct mm_struct * mm)
 304 {
 305         mm->pgd = pgd_alloc(mm);
 306         if (unlikely(!mm->pgd))
 307                 return -ENOMEM;
 308         return 0;
 309 }
 310
 311 static inline void mm_free_pgd(struct mm_struct * mm)
 312 {
 313         pgd_free(mm->pgd);
 314 }
 315 #else
 316 #define dup_mmap(mm, oldmm)     (0)
 317 #define mm_alloc_pgd(mm)        (0)
 318 #define mm_free_pgd(mm)
 319 #endif /* CONFIG_MMU */
 320
 321  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 322
 323 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 324 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 325
 326 #include <linux/init_task.h>
 327
 328 static struct mm_struct * mm_init(struct mm_struct * mm)
 329 {
 330         atomic_set(&mm->mm_users, 1);
 331         atomic_set(&mm->mm_count, 1);
 332         init_rwsem(&mm->mmap_sem);
 333         INIT_LIST_HEAD(&mm->mmlist);
 334         mm->core_waiters = 0;
 335         mm->nr_ptes = 0;
 336         set_mm_counter(mm, file_rss, 0);
 337         set_mm_counter(mm, anon_rss, 0);
 338         spin_lock_init(&mm->page_table_lock);
 339         rwlock_init(&mm->ioctx_list_lock);
 340         mm->ioctx_list = NULL;
 341         mm->free_area_cache = TASK_UNMAPPED_BASE;
 342         mm->cached_hole_size = ~0UL;
 343
 344         if (likely(!mm_alloc_pgd(mm))) {
 345                 mm->def_flags = 0;
 346                 return mm;
 347         }
 348         free_mm(mm);
 349         return NULL;
 350 }
 351
 352 /*
 353  * Allocate and initialize an mm_struct.
 354  */
 355 struct mm_struct * mm_alloc(void)
 356 {
 357         struct mm_struct * mm;
 358
 359         mm = allocate_mm();
 360         if (mm) {
 361                 memset(mm, 0, sizeof(*mm));
 362                 mm = mm_init(mm);
 363         }
 364         return mm;
 365 }
 366
 367 /*
 368  * Called when the last reference to the mm
 369  * is dropped: either by a lazy thread or by
 370  * mmput. Free the page directory and the mm.
 371  */
 372 void fastcall __mmdrop(struct mm_struct *mm)
 373 {
 374         BUG_ON(mm == &init_mm);
 375         mm_free_pgd(mm);
 376         destroy_context(mm);
 377         free_mm(mm);
 378 }
 379
 380 /*
 381  * Decrement the use count and release all resources for an mm.
 382  */
 383 void mmput(struct mm_struct *mm)
 384 {
 385         might_sleep();
 386
 387         if (atomic_dec_and_test(&mm->mm_users)) {
 388                 exit_aio(mm);
 389                 exit_mmap(mm);
 390                 if (!list_empty(&mm->mmlist)) {
 391                         spin_lock(&mmlist_lock);
 392                         list_del(&mm->mmlist);
 393                         spin_unlock(&mmlist_lock);
 394                 }
 395                 put_swap_token(mm);
 396                 mmdrop(mm);
 397         }
 398 }
 399 EXPORT_SYMBOL_GPL(mmput);
 400
 401 /**
 402  * get_task_mm - acquire a reference to the task's mm
 403  *
 404  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 405  * this kernel workthread has transiently adopted a user mm with use_mm,
 406  * to do its AIO) is not set and if so returns a reference to it, after
 407  * bumping up the use count.  User must release the mm via mmput()
 408  * after use.  Typically used by /proc and ptrace.
 409  */
 410 struct mm_struct *get_task_mm(struct task_struct *task)
 411 {
 412         struct mm_struct *mm;
 413
 414         task_lock(task);
 415         mm = task->mm;
 416         if (mm) {
 417                 if (task->flags & PF_BORROWED_MM)
 418                         mm = NULL;
 419                 else
 420                         atomic_inc(&mm->mm_users);
 421         }
 422         task_unlock(task);
 423         return mm;
 424 }
 425 EXPORT_SYMBOL_GPL(get_task_mm);
 426
 427 /* Please note the differences between mmput and mm_release.
 428  * mmput is called whenever we stop holding onto a mm_struct,
 429  * error success whatever.
 430  *
 431  * mm_release is called after a mm_struct has been removed
 432  * from the current process.
 433  *
 434  * This difference is important for error handling, when we
 435  * only half set up a mm_struct for a new process and need to restore
 436  * the old one.  Because we mmput the new mm_struct before
 437  * restoring the old one. . .
 438  * Eric Biederman 10 January 1998
 439  */
 440 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 441 {
 442         struct completion *vfork_done = tsk->vfork_done;
 443
 444         /* Get rid of any cached register state */
 445         deactivate_mm(tsk, mm);
 446
 447         /* notify parent sleeping on vfork() */
 448         if (vfork_done) {
 449                 tsk->vfork_done = NULL;
 450                 complete(vfork_done);
 451         }
 452
 453         /*
 454          * If we're exiting normally, clear a user-space tid field if
 455          * requested.  We leave this alone when dying by signal, to leave
 456          * the value intact in a core dump, and to save the unnecessary
 457          * trouble otherwise.  Userland only wants this done for a sys_exit.
 458          */
 459         if (tsk->clear_child_tid
 460             && !(tsk->flags & PF_SIGNALED)
 461             && atomic_read(&mm->mm_users) > 1) {
 462                 u32 __user * tidptr = tsk->clear_child_tid;
 463                 tsk->clear_child_tid = NULL;
 464
 465                 /*
 466                  * We don't check the error code - if userspace has
 467                  * not set up a proper pointer then tough luck.
 468                  */
 469                 put_user(0, tidptr);
 470                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 471         }
 472 }
 473
 474 /*
 475  * Allocate a new mm structure and copy contents from the
 476  * mm structure of the passed in task structure.
 477  */
 478 static struct mm_struct *dup_mm(struct task_struct *tsk)
 479 {
 480         struct mm_struct *mm, *oldmm = current->mm;
 481         int err;
 482
 483         if (!oldmm)
 484                 return NULL;
 485
 486         mm = allocate_mm();
 487         if (!mm)
 488                 goto fail_nomem;
 489
 490         memcpy(mm, oldmm, sizeof(*mm));
 491
 492         /* Initializing for Swap token stuff */
 493         mm->token_priority = 0;
 494         mm->last_interval = 0;
 495
 496         if (!mm_init(mm))
 497                 goto fail_nomem;
 498
 499         if (init_new_context(tsk, mm))
 500                 goto fail_nocontext;
 501
 502         err = dup_mmap(mm, oldmm);
 503         if (err)
 504                 goto free_pt;
 505
 506         mm->hiwater_rss = get_mm_rss(mm);
 507         mm->hiwater_vm = mm->total_vm;
 508
 509         return mm;
 510
 511 free_pt:
 512         mmput(mm);
 513
 514 fail_nomem:
 515         return NULL;
 516
 517 fail_nocontext:
 518         /*
 519          * If init_new_context() failed, we cannot use mmput() to free the mm
 520          * because it calls destroy_context()
 521          */
 522         mm_free_pgd(mm);
 523         free_mm(mm);
 524         return NULL;
 525 }
 526
 527 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 528 {
 529         struct mm_struct * mm, *oldmm;
 530         int retval;
 531
 532         tsk->min_flt = tsk->maj_flt = 0;
 533         tsk->nvcsw = tsk->nivcsw = 0;
 534
 535         tsk->mm = NULL;
 536         tsk->active_mm = NULL;
 537
 538         /*
 539          * Are we cloning a kernel thread?
 540          *
 541          * We need to steal a active VM for that..
 542          */
 543         oldmm = current->mm;
 544         if (!oldmm)
 545                 return 0;
 546
 547         if (clone_flags & CLONE_VM) {
 548                 atomic_inc(&oldmm->mm_users);
 549                 mm = oldmm;
 550                 goto good_mm;
 551         }
 552
 553         retval = -ENOMEM;
 554         mm = dup_mm(tsk);
 555         if (!mm)
 556                 goto fail_nomem;
 557
 558 good_mm:
 559         /* Initializing for Swap token stuff */
 560         mm->token_priority = 0;
 561         mm->last_interval = 0;
 562
 563         tsk->mm = mm;
 564         tsk->active_mm = mm;
 565         return 0;
 566
 567 fail_nomem:
 568         return retval;
 569 }
 570
 571 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 572 {
 573         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 574         /* We don't need to lock fs - think why ;-) */
 575         if (fs) {
 576                 atomic_set(&fs->count, 1);
 577                 rwlock_init(&fs->lock);
 578                 fs->umask = old->umask;
 579                 read_lock(&old->lock);
 580                 fs->rootmnt = mntget(old->rootmnt);
 581                 fs->root = dget(old->root);
 582                 fs->pwdmnt = mntget(old->pwdmnt);
 583                 fs->pwd = dget(old->pwd);
 584                 if (old->altroot) {
 585                         fs->altrootmnt = mntget(old->altrootmnt);
 586                         fs->altroot = dget(old->altroot);
 587                 } else {
 588                         fs->altrootmnt = NULL;
 589                         fs->altroot = NULL;
 590                 }
 591                 read_unlock(&old->lock);
 592         }
 593         return fs;
 594 }
 595
 596 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 597 {
 598         return __copy_fs_struct(old);
 599 }
 600
 601 EXPORT_SYMBOL_GPL(copy_fs_struct);
 602
 603 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
 604 {
 605         if (clone_flags & CLONE_FS) {
 606                 atomic_inc(&current->fs->count);
 607                 return 0;
 608         }
 609         tsk->fs = __copy_fs_struct(current->fs);
 610         if (!tsk->fs)
 611                 return -ENOMEM;
 612         return 0;
 613 }
 614
 615 static int count_open_files(struct fdtable *fdt)
 616 {
 617         int size = fdt->max_fds;
 618         int i;
 619
 620         /* Find the last open fd */
 621         for (i = size/(8*sizeof(long)); i > 0; ) {
 622                 if (fdt->open_fds->fds_bits[--i])
 623                         break;
 624         }
 625         i = (i+1) * 8 * sizeof(long);
 626         return i;
 627 }
 628
 629 static struct files_struct *alloc_files(void)
 630 {
 631         struct files_struct *newf;
 632         struct fdtable *fdt;
 633
 634         newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 635         if (!newf)
 636                 goto out;
 637
 638         atomic_set(&newf->count, 1);
 639
 640         spin_lock_init(&newf->file_lock);
 641         newf->next_fd = 0;
 642         fdt = &newf->fdtab;
 643         fdt->max_fds = NR_OPEN_DEFAULT;
 644         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
 645         fdt->open_fds = (fd_set *)&newf->open_fds_init;
 646         fdt->fd = &newf->fd_array[0];
 647         INIT_RCU_HEAD(&fdt->rcu);
 648         fdt->next = NULL;
 649         rcu_assign_pointer(newf->fdt, fdt);
 650 out:
 651         return newf;
 652 }
 653
 654 /*
 655  * Allocate a new files structure and copy contents from the
 656  * passed in files structure.
 657  * errorp will be valid only when the returned files_struct is NULL.
 658  */
 659 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 660 {
 661         struct files_struct *newf;
 662         struct file **old_fds, **new_fds;
 663         int open_files, size, i;
 664         struct fdtable *old_fdt, *new_fdt;
 665
 666         *errorp = -ENOMEM;
 667         newf = alloc_files();
 668         if (!newf)
 669                 goto out;
 670
 671         spin_lock(&oldf->file_lock);
 672         old_fdt = files_fdtable(oldf);
 673         new_fdt = files_fdtable(newf);
 674         open_files = count_open_files(old_fdt);
 675
 676         /*
 677          * Check whether we need to allocate a larger fd array and fd set.
 678          * Note: we're not a clone task, so the open count won't change.
 679          */
 680         if (open_files > new_fdt->max_fds) {
 681                 new_fdt->max_fds = 0;
 682                 spin_unlock(&oldf->file_lock);
 683                 spin_lock(&newf->file_lock);
 684                 *errorp = expand_files(newf, open_files-1);
 685                 spin_unlock(&newf->file_lock);
 686                 if (*errorp < 0)
 687                         goto out_release;
 688                 new_fdt = files_fdtable(newf);
 689                 /*
 690                  * Reacquire the oldf lock and a pointer to its fd table
 691                  * who knows it may have a new bigger fd table. We need
 692                  * the latest pointer.
 693                  */
 694                 spin_lock(&oldf->file_lock);
 695                 old_fdt = files_fdtable(oldf);
 696         }
 697
 698         old_fds = old_fdt->fd;
 699         new_fds = new_fdt->fd;
 700
 701         memcpy(new_fdt->open_fds->fds_bits,
 702                 old_fdt->open_fds->fds_bits, open_files/8);
 703         memcpy(new_fdt->close_on_exec->fds_bits,
 704                 old_fdt->close_on_exec->fds_bits, open_files/8);
 705
 706         for (i = open_files; i != 0; i--) {
 707                 struct file *f = *old_fds++;
 708                 if (f) {
 709                         get_file(f);
 710                 } else {
 711                         /*
 712                          * The fd may be claimed in the fd bitmap but not yet
 713                          * instantiated in the files array if a sibling thread
 714                          * is partway through open().  So make sure that this
 715                          * fd is available to the new process.
 716                          */
 717                         FD_CLR(open_files - i, new_fdt->open_fds);
 718                 }
 719                 rcu_assign_pointer(*new_fds++, f);
 720         }
 721         spin_unlock(&oldf->file_lock);
 722
 723         /* compute the remainder to be cleared */
 724         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 725
 726         /* This is long word aligned thus could use a optimized version */
 727         memset(new_fds, 0, size);
 728
 729         if (new_fdt->max_fds > open_files) {
 730                 int left = (new_fdt->max_fds-open_files)/8;
 731                 int start = open_files / (8 * sizeof(unsigned long));
 732
 733                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
 734                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 735         }
 736
 737         return newf;
 738
 739 out_release:
 740         kmem_cache_free(files_cachep, newf);
 741 out:
 742         return NULL;
 743 }
 744
 745 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 746 {
 747         struct files_struct *oldf, *newf;
 748         int error = 0;
 749
 750         /*
 751          * A background process may not have any files ...
 752          */
 753         oldf = current->files;
 754         if (!oldf)
 755                 goto out;
 756
 757         if (clone_flags & CLONE_FILES) {
 758                 atomic_inc(&oldf->count);
 759                 goto out;
 760         }
 761
 762         /*
 763          * Note: we may be using current for both targets (See exec.c)
 764          * This works because we cache current->files (old) as oldf. Don't
 765          * break this.
 766          */
 767         tsk->files = NULL;
 768         newf = dup_fd(oldf, &error);
 769         if (!newf)
 770                 goto out;
 771
 772         tsk->files = newf;
 773         error = 0;
 774 out:
 775         return error;
 776 }
 777
 778 /*
 779  *      Helper to unshare the files of the current task.
 780  *      We don't want to expose copy_files internals to
 781  *      the exec layer of the kernel.
 782  */
 783
 784 int unshare_files(void)
 785 {
 786         struct files_struct *files  = current->files;
 787         int rc;
 788
 789         BUG_ON(!files);
 790
 791         /* This can race but the race causes us to copy when we don't
 792            need to and drop the copy */
 793         if(atomic_read(&files->count) == 1)
 794         {
 795                 atomic_inc(&files->count);
 796                 return 0;
 797         }
 798         rc = copy_files(0, current);
 799         if(rc)
 800                 current->files = files;
 801         return rc;
 802 }
 803
 804 EXPORT_SYMBOL(unshare_files);
 805
 806 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
 807 {
 808         struct sighand_struct *sig;
 809
 810         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 811                 atomic_inc(&current->sighand->count);
 812                 return 0;
 813         }
 814         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 815         rcu_assign_pointer(tsk->sighand, sig);
 816         if (!sig)
 817                 return -ENOMEM;
 818         atomic_set(&sig->count, 1);
 819         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 820         return 0;
 821 }
 822
 823 void __cleanup_sighand(struct sighand_struct *sighand)
 824 {
 825         if (atomic_dec_and_test(&sighand->count))
 826                 kmem_cache_free(sighand_cachep, sighand);
 827 }
 828
 829 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
 830 {
 831         struct signal_struct *sig;
 832         int ret;
 833
 834         if (clone_flags & CLONE_THREAD) {
 835                 atomic_inc(&current->signal->count);
 836                 atomic_inc(&current->signal->live);
 837                 return 0;
 838         }
 839         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 840         tsk->signal = sig;
 841         if (!sig)
 842                 return -ENOMEM;
 843
 844         ret = copy_thread_group_keys(tsk);
 845         if (ret < 0) {
 846                 kmem_cache_free(signal_cachep, sig);
 847                 return ret;
 848         }
 849
 850         atomic_set(&sig->count, 1);
 851         atomic_set(&sig->live, 1);
 852         init_waitqueue_head(&sig->wait_chldexit);
 853         sig->flags = 0;
 854         sig->group_exit_code = 0;
 855         sig->group_exit_task = NULL;
 856         sig->group_stop_count = 0;
 857         sig->curr_target = NULL;
 858         init_sigpending(&sig->shared_pending);
 859         INIT_LIST_HEAD(&sig->posix_timers);
 860
 861         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
 862         sig->it_real_incr.tv64 = 0;
 863         sig->real_timer.function = it_real_fn;
 864         sig->tsk = tsk;
 865
 866         sig->it_virt_expires = cputime_zero;
 867         sig->it_virt_incr = cputime_zero;
 868         sig->it_prof_expires = cputime_zero;
 869         sig->it_prof_incr = cputime_zero;
 870
 871         sig->leader = 0;        /* session leadership doesn't inherit */
 872         sig->tty_old_pgrp = NULL;
 873
 874         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 875         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 876         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 877         sig->sched_time = 0;
 878         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 879         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 880         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 881         taskstats_tgid_init(sig);
 882
 883         task_lock(current->group_leader);
 884         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 885         task_unlock(current->group_leader);
 886
 887         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 888                 /*
 889                  * New sole thread in the process gets an expiry time
 890                  * of the whole CPU time limit.
 891                  */
 892                 tsk->it_prof_expires =
 893                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 894         }
 895         acct_init_pacct(&sig->pacct);
 896
 897         return 0;
 898 }
 899
 900 void __cleanup_signal(struct signal_struct *sig)
 901 {
 902         exit_thread_group_keys(sig);
 903         kmem_cache_free(signal_cachep, sig);
 904 }
 905
 906 static inline void cleanup_signal(struct task_struct *tsk)
 907 {
 908         struct signal_struct *sig = tsk->signal;
 909
 910         atomic_dec(&sig->live);
 911
 912         if (atomic_dec_and_test(&sig->count))
 913                 __cleanup_signal(sig);
 914 }
 915
 916 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
 917 {
 918         unsigned long new_flags = p->flags;
 919
 920         new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
 921         new_flags |= PF_FORKNOEXEC;
 922         if (!(clone_flags & CLONE_PTRACE))
 923                 p->ptrace = 0;
 924         p->flags = new_flags;
 925 }
 926
 927 asmlinkage long sys_set_tid_address(int __user *tidptr)
 928 {
 929         current->clear_child_tid = tidptr;
 930
 931         return current->pid;
 932 }
 933
 934 static inline void rt_mutex_init_task(struct task_struct *p)
 935 {
 936 #ifdef CONFIG_RT_MUTEXES
 937         spin_lock_init(&p->pi_lock);
 938         plist_head_init(&p->pi_waiters, &p->pi_lock);
 939         p->pi_blocked_on = NULL;
 940 #endif
 941 }
 942
 943 /*
 944  * This creates a new process as a copy of the old one,
 945  * but does not actually start it yet.
 946  *
 947  * It copies the registers, and all the appropriate
 948  * parts of the process environment (as per the clone
 949  * flags). The actual kick-off is left to the caller.
 950  */
 951 static struct task_struct *copy_process(unsigned long clone_flags,
 952                                         unsigned long stack_start,
 953                                         struct pt_regs *regs,
 954                                         unsigned long stack_size,
 955                                         int __user *parent_tidptr,
 956                                         int __user *child_tidptr,
 957                                         int pid)
 958 {
 959         int retval;
 960         struct task_struct *p = NULL;
 961
 962         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 963                 return ERR_PTR(-EINVAL);
 964
 965         /*
 966          * Thread groups must share signals as well, and detached threads
 967          * can only be started up within the thread group.
 968          */
 969         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 970                 return ERR_PTR(-EINVAL);
 971
 972         /*
 973          * Shared signal handlers imply shared VM. By way of the above,
 974          * thread groups also imply shared VM. Blocking this case allows
 975          * for various simplifications in other code.
 976          */
 977         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 978                 return ERR_PTR(-EINVAL);
 979
 980         retval = security_task_create(clone_flags);
 981         if (retval)
 982                 goto fork_out;
 983
 984         retval = -ENOMEM;
 985         p = dup_task_struct(current);
 986         if (!p)
 987                 goto fork_out;
 988
 989         rt_mutex_init_task(p);
 990
 991 #ifdef CONFIG_TRACE_IRQFLAGS
 992         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 993         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 994 #endif
 995         retval = -EAGAIN;
 996         if (atomic_read(&p->user->processes) >=
 997                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 998                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 999                                 p->user != &root_user)
1000                         goto bad_fork_free;
1001         }
1002
1003         atomic_inc(&p->user->__count);
1004         atomic_inc(&p->user->processes);
1005         get_group_info(p->group_info);
1006
1007         /*
1008          * If multiple threads are within copy_process(), then this check
1009          * triggers too late. This doesn't hurt, the check is only there
1010          * to stop root fork bombs.
1011          */
1012         if (nr_threads >= max_threads)
1013                 goto bad_fork_cleanup_count;
1014
1015         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1016                 goto bad_fork_cleanup_count;
1017
1018         if (p->binfmt && !try_module_get(p->binfmt->module))
1019                 goto bad_fork_cleanup_put_domain;
1020
1021         p->did_exec = 0;
1022         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1023         copy_flags(clone_flags, p);
1024         p->pid = pid;
1025         retval = -EFAULT;
1026         if (clone_flags & CLONE_PARENT_SETTID)
1027                 if (put_user(p->pid, parent_tidptr))
1028                         goto bad_fork_cleanup_delays_binfmt;
1029
1030         INIT_LIST_HEAD(&p->children);
1031         INIT_LIST_HEAD(&p->sibling);
1032         p->vfork_done = NULL;
1033         spin_lock_init(&p->alloc_lock);
1034
1035         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1036         init_sigpending(&p->pending);
1037
1038         p->utime = cputime_zero;
1039         p->stime = cputime_zero;
1040         p->sched_time = 0;
1041 #ifdef CONFIG_TASK_XACCT
1042         p->rchar = 0;           /* I/O counter: bytes read */
1043         p->wchar = 0;           /* I/O counter: bytes written */
1044         p->syscr = 0;           /* I/O counter: read syscalls */
1045         p->syscw = 0;           /* I/O counter: write syscalls */
1046 #endif
1047         task_io_accounting_init(p);
1048         acct_clear_integrals(p);
1049
1050         p->it_virt_expires = cputime_zero;
1051         p->it_prof_expires = cputime_zero;
1052         p->it_sched_expires = 0;
1053         INIT_LIST_HEAD(&p->cpu_timers[0]);
1054         INIT_LIST_HEAD(&p->cpu_timers[1]);
1055         INIT_LIST_HEAD(&p->cpu_timers[2]);
1056
1057         p->lock_depth = -1;             /* -1 = no lock */
1058         do_posix_clock_monotonic_gettime(&p->start_time);
1059         p->security = NULL;
1060         p->io_context = NULL;
1061         p->io_wait = NULL;
1062         p->audit_context = NULL;
1063         cpuset_fork(p);
1064 #ifdef CONFIG_NUMA
1065         p->mempolicy = mpol_copy(p->mempolicy);
1066         if (IS_ERR(p->mempolicy)) {
1067                 retval = PTR_ERR(p->mempolicy);
1068                 p->mempolicy = NULL;
1069                 goto bad_fork_cleanup_cpuset;
1070         }
1071         mpol_fix_fork_child_flag(p);
1072 #endif
1073 #ifdef CONFIG_TRACE_IRQFLAGS
1074         p->irq_events = 0;
1075 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1076         p->hardirqs_enabled = 1;
1077 #else
1078         p->hardirqs_enabled = 0;
1079 #endif
1080         p->hardirq_enable_ip = 0;
1081         p->hardirq_enable_event = 0;
1082         p->hardirq_disable_ip = _THIS_IP_;
1083         p->hardirq_disable_event = 0;
1084         p->softirqs_enabled = 1;
1085         p->softirq_enable_ip = _THIS_IP_;
1086         p->softirq_enable_event = 0;
1087         p->softirq_disable_ip = 0;
1088         p->softirq_disable_event = 0;
1089         p->hardirq_context = 0;
1090         p->softirq_context = 0;
1091 #endif
1092 #ifdef CONFIG_LOCKDEP
1093         p->lockdep_depth = 0; /* no locks held yet */
1094         p->curr_chain_key = 0;
1095         p->lockdep_recursion = 0;
1096 #endif
1097
1098 #ifdef CONFIG_DEBUG_MUTEXES
1099         p->blocked_on = NULL; /* not blocked yet */
1100 #endif
1101
1102         p->tgid = p->pid;
1103         if (clone_flags & CLONE_THREAD)
1104                 p->tgid = current->tgid;
1105
1106         if ((retval = security_task_alloc(p)))
1107                 goto bad_fork_cleanup_policy;
1108         if ((retval = audit_alloc(p)))
1109                 goto bad_fork_cleanup_security;
1110         /* copy all the process information */
1111         if ((retval = copy_semundo(clone_flags, p)))
1112                 goto bad_fork_cleanup_audit;
1113         if ((retval = copy_files(clone_flags, p)))
1114                 goto bad_fork_cleanup_semundo;
1115         if ((retval = copy_fs(clone_flags, p)))
1116                 goto bad_fork_cleanup_files;
1117         if ((retval = copy_sighand(clone_flags, p)))
1118                 goto bad_fork_cleanup_fs;
1119         if ((retval = copy_signal(clone_flags, p)))
1120                 goto bad_fork_cleanup_sighand;
1121         if ((retval = copy_mm(clone_flags, p)))
1122                 goto bad_fork_cleanup_signal;
1123         if ((retval = copy_keys(clone_flags, p)))
1124                 goto bad_fork_cleanup_mm;
1125         if ((retval = copy_namespaces(clone_flags, p)))
1126                 goto bad_fork_cleanup_keys;
1127         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1128         if (retval)
1129                 goto bad_fork_cleanup_namespaces;
1130
1131         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1132         /*
1133          * Clear TID on mm_release()?
1134          */
1135         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1136         p->robust_list = NULL;
1137 #ifdef CONFIG_COMPAT
1138         p->compat_robust_list = NULL;
1139 #endif
1140         INIT_LIST_HEAD(&p->pi_state_list);
1141         p->pi_state_cache = NULL;
1142
1143         /*
1144          * sigaltstack should be cleared when sharing the same VM
1145          */
1146         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1147                 p->sas_ss_sp = p->sas_ss_size = 0;
1148
1149         /*
1150          * Syscall tracing should be turned off in the child regardless
1151          * of CLONE_PTRACE.
1152          */
1153         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1154 #ifdef TIF_SYSCALL_EMU
1155         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1156 #endif
1157
1158         /* Our parent execution domain becomes current domain
1159            These must match for thread signalling to apply */
1160         p->parent_exec_id = p->self_exec_id;
1161
1162         /* ok, now we should be set up.. */
1163         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1164         p->pdeath_signal = 0;
1165         p->exit_state = 0;
1166
1167         /*
1168          * Ok, make it visible to the rest of the system.
1169          * We dont wake it up yet.
1170          */
1171         p->group_leader = p;
1172         INIT_LIST_HEAD(&p->thread_group);
1173         INIT_LIST_HEAD(&p->ptrace_children);
1174         INIT_LIST_HEAD(&p->ptrace_list);
1175
1176         /* Perform scheduler related setup. Assign this task to a CPU. */
1177         sched_fork(p, clone_flags);
1178
1179         /* Need tasklist lock for parent etc handling! */
1180         write_lock_irq(&tasklist_lock);
1181
1182         /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
1183         p->ioprio = current->ioprio;
1184
1185         /*
1186          * The task hasn't been attached yet, so its cpus_allowed mask will
1187          * not be changed, nor will its assigned CPU.
1188          *
1189          * The cpus_allowed mask of the parent may have changed after it was
1190          * copied first time - so re-copy it here, then check the child's CPU
1191          * to ensure it is on a valid CPU (and if not, just force it back to
1192          * parent's CPU). This avoids alot of nasty races.
1193          */
1194         p->cpus_allowed = current->cpus_allowed;
1195         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1196                         !cpu_online(task_cpu(p))))
1197                 set_task_cpu(p, smp_processor_id());
1198
1199         /* CLONE_PARENT re-uses the old parent */
1200         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1201                 p->real_parent = current->real_parent;
1202         else
1203                 p->real_parent = current;
1204         p->parent = p->real_parent;
1205
1206         spin_lock(&current->sighand->siglock);
1207
1208         /*
1209          * Process group and session signals need to be delivered to just the
1210          * parent before the fork or both the parent and the child after the
1211          * fork. Restart if a signal comes in before we add the new process to
1212          * it's process group.
1213          * A fatal signal pending means that current will exit, so the new
1214          * thread can't slip out of an OOM kill (or normal SIGKILL).
1215          */
1216         recalc_sigpending();
1217         if (signal_pending(current)) {
1218                 spin_unlock(&current->sighand->siglock);
1219                 write_unlock_irq(&tasklist_lock);
1220                 retval = -ERESTARTNOINTR;
1221                 goto bad_fork_cleanup_namespaces;
1222         }
1223
1224         if (clone_flags & CLONE_THREAD) {
1225                 p->group_leader = current->group_leader;
1226                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1227
1228                 if (!cputime_eq(current->signal->it_virt_expires,
1229                                 cputime_zero) ||
1230                     !cputime_eq(current->signal->it_prof_expires,
1231                                 cputime_zero) ||
1232                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1233                     !list_empty(&current->signal->cpu_timers[0]) ||
1234                     !list_empty(&current->signal->cpu_timers[1]) ||
1235                     !list_empty(&current->signal->cpu_timers[2])) {
1236                         /*
1237                          * Have child wake up on its first tick to check
1238                          * for process CPU timers.
1239                          */
1240                         p->it_prof_expires = jiffies_to_cputime(1);
1241                 }
1242         }
1243
1244         if (likely(p->pid)) {
1245                 add_parent(p);
1246                 if (unlikely(p->ptrace & PT_PTRACED))
1247                         __ptrace_link(p, current->parent);
1248
1249                 if (thread_group_leader(p)) {
1250                         p->signal->tty = current->signal->tty;
1251                         p->signal->pgrp = process_group(current);
1252                         set_signal_session(p->signal, process_session(current));
1253                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1254                         attach_pid(p, PIDTYPE_SID, process_session(p));
1255
1256                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1257                         __get_cpu_var(process_counts)++;
1258                 }
1259                 attach_pid(p, PIDTYPE_PID, p->pid);
1260                 nr_threads++;
1261         }
1262
1263         total_forks++;
1264         spin_unlock(&current->sighand->siglock);
1265         write_unlock_irq(&tasklist_lock);
1266         proc_fork_connector(p);
1267         return p;
1268
1269 bad_fork_cleanup_namespaces:
1270         exit_task_namespaces(p);
1271 bad_fork_cleanup_keys:
1272         exit_keys(p);
1273 bad_fork_cleanup_mm:
1274         if (p->mm)
1275                 mmput(p->mm);
1276 bad_fork_cleanup_signal:
1277         cleanup_signal(p);
1278 bad_fork_cleanup_sighand:
1279         __cleanup_sighand(p->sighand);
1280 bad_fork_cleanup_fs:
1281         exit_fs(p); /* blocking */
1282 bad_fork_cleanup_files:
1283         exit_files(p); /* blocking */
1284 bad_fork_cleanup_semundo:
1285         exit_sem(p);
1286 bad_fork_cleanup_audit:
1287         audit_free(p);
1288 bad_fork_cleanup_security:
1289         security_task_free(p);
1290 bad_fork_cleanup_policy:
1291 #ifdef CONFIG_NUMA
1292         mpol_free(p->mempolicy);
1293 bad_fork_cleanup_cpuset:
1294 #endif
1295         cpuset_exit(p);
1296 bad_fork_cleanup_delays_binfmt:
1297         delayacct_tsk_free(p);
1298         if (p->binfmt)
1299                 module_put(p->binfmt->module);
1300 bad_fork_cleanup_put_domain:
1301         module_put(task_thread_info(p)->exec_domain->module);
1302 bad_fork_cleanup_count:
1303         put_group_info(p->group_info);
1304         atomic_dec(&p->user->processes);
1305         free_uid(p->user);
1306 bad_fork_free:
1307         free_task(p);
1308 fork_out:
1309         return ERR_PTR(retval);
1310 }
1311
1312 noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1313 {
1314         memset(regs, 0, sizeof(struct pt_regs));
1315         return regs;
1316 }
1317
1318 struct task_struct * __cpuinit fork_idle(int cpu)
1319 {
1320         struct task_struct *task;
1321         struct pt_regs regs;
1322
1323         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1324         if (!IS_ERR(task))
1325                 init_idle(task, cpu);
1326
1327         return task;
1328 }
1329
1330 static inline int fork_traceflag (unsigned clone_flags)
1331 {
1332         if (clone_flags & CLONE_UNTRACED)
1333                 return 0;
1334         else if (clone_flags & CLONE_VFORK) {
1335                 if (current->ptrace & PT_TRACE_VFORK)
1336                         return PTRACE_EVENT_VFORK;
1337         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1338                 if (current->ptrace & PT_TRACE_CLONE)
1339                         return PTRACE_EVENT_CLONE;
1340         } else if (current->ptrace & PT_TRACE_FORK)
1341                 return PTRACE_EVENT_FORK;
1342
1343         return 0;
1344 }
1345
1346 /*
1347  *  Ok, this is the main fork-routine.
1348  *
1349  * It copies the process, and if successful kick-starts
1350  * it and waits for it to finish using the VM if required.
1351  */
1352 long do_fork(unsigned long clone_flags,
1353               unsigned long stack_start,
1354               struct pt_regs *regs,
1355               unsigned long stack_size,
1356               int __user *parent_tidptr,
1357               int __user *child_tidptr)
1358 {
1359         struct task_struct *p;
1360         int trace = 0;
1361         struct pid *pid = alloc_pid();
1362         long nr;
1363
1364         if (!pid)
1365                 return -EAGAIN;
1366         nr = pid->nr;
1367         if (unlikely(current->ptrace)) {
1368                 trace = fork_traceflag (clone_flags);
1369                 if (trace)
1370                         clone_flags |= CLONE_PTRACE;
1371         }
1372
1373         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1374         /*
1375          * Do this prior waking up the new thread - the thread pointer
1376          * might get invalid after that point, if the thread exits quickly.
1377          */
1378         if (!IS_ERR(p)) {
1379                 struct completion vfork;
1380
1381                 if (clone_flags & CLONE_VFORK) {
1382                         p->vfork_done = &vfork;
1383                         init_completion(&vfork);
1384                 }
1385
1386                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1387                         /*
1388                          * We'll start up with an immediate SIGSTOP.
1389                          */
1390                         sigaddset(&p->pending.signal, SIGSTOP);
1391                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1392                 }
1393
1394                 if (!(clone_flags & CLONE_STOPPED))
1395                         wake_up_new_task(p, clone_flags);
1396                 else
1397                         p->state = TASK_STOPPED;
1398
1399                 if (unlikely (trace)) {
1400                         current->ptrace_message = nr;
1401                         ptrace_notify ((trace << 8) | SIGTRAP);
1402                 }
1403
1404                 if (clone_flags & CLONE_VFORK) {
1405                         wait_for_completion(&vfork);
1406                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1407                                 current->ptrace_message = nr;
1408                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1409                         }
1410                 }
1411         } else {
1412                 free_pid(pid);
1413                 nr = PTR_ERR(p);
1414         }
1415         return nr;
1416 }
1417
1418 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1419 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1420 #endif
1421
1422 static void sighand_ctor(void *data, struct kmem_cache *cachep, unsigned long flags)
1423 {
1424         struct sighand_struct *sighand = data;
1425
1426         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1427                                         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  * Unshare the mnt_namespace structure if it is being shared
1519  */
1520 static int unshare_mnt_namespace(unsigned long unshare_flags,
1521                 struct mnt_namespace **new_nsp, struct fs_struct *new_fs)
1522 {
1523         struct mnt_namespace *ns = current->nsproxy->mnt_ns;
1524
1525         if ((unshare_flags & CLONE_NEWNS) && ns) {
1526                 if (!capable(CAP_SYS_ADMIN))
1527                         return -EPERM;
1528
1529                 *new_nsp = dup_mnt_ns(current, new_fs ? new_fs : current->fs);
1530                 if (!*new_nsp)
1531                         return -ENOMEM;
1532         }
1533
1534         return 0;
1535 }
1536
1537 /*
1538  * Unsharing of sighand is not supported yet
1539  */
1540 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1541 {
1542         struct sighand_struct *sigh = current->sighand;
1543
1544         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1545                 return -EINVAL;
1546         else
1547                 return 0;
1548 }
1549
1550 /*
1551  * Unshare vm if it is being shared
1552  */
1553 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1554 {
1555         struct mm_struct *mm = current->mm;
1556
1557         if ((unshare_flags & CLONE_VM) &&
1558             (mm && atomic_read(&mm->mm_users) > 1)) {
1559                 return -EINVAL;
1560         }
1561
1562         return 0;
1563 }
1564
1565 /*
1566  * Unshare file descriptor table if it is being shared
1567  */
1568 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1569 {
1570         struct files_struct *fd = current->files;
1571         int error = 0;
1572
1573         if ((unshare_flags & CLONE_FILES) &&
1574             (fd && atomic_read(&fd->count) > 1)) {
1575                 *new_fdp = dup_fd(fd, &error);
1576                 if (!*new_fdp)
1577                         return error;
1578         }
1579
1580         return 0;
1581 }
1582
1583 /*
1584  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1585  * supported yet
1586  */
1587 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1588 {
1589         if (unshare_flags & CLONE_SYSVSEM)
1590                 return -EINVAL;
1591
1592         return 0;
1593 }
1594
1595 #ifndef CONFIG_IPC_NS
1596 static inline int unshare_ipcs(unsigned long flags, struct ipc_namespace **ns)
1597 {
1598         if (flags & CLONE_NEWIPC)
1599                 return -EINVAL;
1600
1601         return 0;
1602 }
1603 #endif
1604
1605 /*
1606  * unshare allows a process to 'unshare' part of the process
1607  * context which was originally shared using clone.  copy_*
1608  * functions used by do_fork() cannot be used here directly
1609  * because they modify an inactive task_struct that is being
1610  * constructed. Here we are modifying the current, active,
1611  * task_struct.
1612  */
1613 asmlinkage long sys_unshare(unsigned long unshare_flags)
1614 {
1615         int err = 0;
1616         struct fs_struct *fs, *new_fs = NULL;
1617         struct mnt_namespace *ns, *new_ns = NULL;
1618         struct sighand_struct *new_sigh = NULL;
1619         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1620         struct files_struct *fd, *new_fd = NULL;
1621         struct sem_undo_list *new_ulist = NULL;
1622         struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
1623         struct uts_namespace *uts, *new_uts = NULL;
1624         struct ipc_namespace *ipc, *new_ipc = NULL;
1625
1626         check_unshare_flags(&unshare_flags);
1627
1628         /* Return -EINVAL for all unsupported flags */
1629         err = -EINVAL;
1630         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1631                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1632                                 CLONE_NEWUTS|CLONE_NEWIPC))
1633                 goto bad_unshare_out;
1634
1635         if ((err = unshare_thread(unshare_flags)))
1636                 goto bad_unshare_out;
1637         if ((err = unshare_fs(unshare_flags, &new_fs)))
1638                 goto bad_unshare_cleanup_thread;
1639         if ((err = unshare_mnt_namespace(unshare_flags, &new_ns, new_fs)))
1640                 goto bad_unshare_cleanup_fs;
1641         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1642                 goto bad_unshare_cleanup_ns;
1643         if ((err = unshare_vm(unshare_flags, &new_mm)))
1644                 goto bad_unshare_cleanup_sigh;
1645         if ((err = unshare_fd(unshare_flags, &new_fd)))
1646                 goto bad_unshare_cleanup_vm;
1647         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1648                 goto bad_unshare_cleanup_fd;
1649         if ((err = unshare_utsname(unshare_flags, &new_uts)))
1650                 goto bad_unshare_cleanup_semundo;
1651         if ((err = unshare_ipcs(unshare_flags, &new_ipc)))
1652                 goto bad_unshare_cleanup_uts;
1653
1654         if (new_ns || new_uts || new_ipc) {
1655                 old_nsproxy = current->nsproxy;
1656                 new_nsproxy = dup_namespaces(old_nsproxy);
1657                 if (!new_nsproxy) {
1658                         err = -ENOMEM;
1659                         goto bad_unshare_cleanup_ipc;
1660                 }
1661         }
1662
1663         if (new_fs || new_ns || new_mm || new_fd || new_ulist ||
1664                                 new_uts || new_ipc) {
1665
1666                 task_lock(current);
1667
1668                 if (new_nsproxy) {
1669                         current->nsproxy = new_nsproxy;
1670                         new_nsproxy = old_nsproxy;
1671                 }
1672
1673                 if (new_fs) {
1674                         fs = current->fs;
1675                         current->fs = new_fs;
1676                         new_fs = fs;
1677                 }
1678
1679                 if (new_ns) {
1680                         ns = current->nsproxy->mnt_ns;
1681                         current->nsproxy->mnt_ns = new_ns;
1682                         new_ns = ns;
1683                 }
1684
1685                 if (new_mm) {
1686                         mm = current->mm;
1687                         active_mm = current->active_mm;
1688                         current->mm = new_mm;
1689                         current->active_mm = new_mm;
1690                         activate_mm(active_mm, new_mm);
1691                         new_mm = mm;
1692                 }
1693
1694                 if (new_fd) {
1695                         fd = current->files;
1696                         current->files = new_fd;
1697                         new_fd = fd;
1698                 }
1699
1700                 if (new_uts) {
1701                         uts = current->nsproxy->uts_ns;
1702                         current->nsproxy->uts_ns = new_uts;
1703                         new_uts = uts;
1704                 }
1705
1706                 if (new_ipc) {
1707                         ipc = current->nsproxy->ipc_ns;
1708                         current->nsproxy->ipc_ns = new_ipc;
1709                         new_ipc = ipc;
1710                 }
1711
1712                 task_unlock(current);
1713         }
1714
1715         if (new_nsproxy)
1716                 put_nsproxy(new_nsproxy);
1717
1718 bad_unshare_cleanup_ipc:
1719         if (new_ipc)
1720                 put_ipc_ns(new_ipc);
1721
1722 bad_unshare_cleanup_uts:
1723         if (new_uts)
1724                 put_uts_ns(new_uts);
1725
1726 bad_unshare_cleanup_semundo:
1727 bad_unshare_cleanup_fd:
1728         if (new_fd)
1729                 put_files_struct(new_fd);
1730
1731 bad_unshare_cleanup_vm:
1732         if (new_mm)
1733                 mmput(new_mm);
1734
1735 bad_unshare_cleanup_sigh:
1736         if (new_sigh)
1737                 if (atomic_dec_and_test(&new_sigh->count))
1738                         kmem_cache_free(sighand_cachep, new_sigh);
1739
1740 bad_unshare_cleanup_ns:
1741         if (new_ns)
1742                 put_mnt_ns(new_ns);
1743
1744 bad_unshare_cleanup_fs:
1745         if (new_fs)
1746                 put_fs_struct(new_fs);
1747
1748 bad_unshare_cleanup_thread:
1749 bad_unshare_out:
1750         return err;
1751 }