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/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/cgroup.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/freezer.h>
  49 #include <linux/delayacct.h>
  50 #include <linux/taskstats_kern.h>
  51 #include <linux/random.h>
  52 #include <linux/tty.h>
  53 #include <linux/proc_fs.h>
  54 #include <linux/blkdev.h>
  55
  56 #include <asm/pgtable.h>
  57 #include <asm/pgalloc.h>
  58 #include <asm/uaccess.h>
  59 #include <asm/mmu_context.h>
  60 #include <asm/cacheflush.h>
  61 #include <asm/tlbflush.h>
  62
  63 /*
  64  * Protected counters by write_lock_irq(&tasklist_lock)
  65  */
  66 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  67 int nr_threads;                 /* The idle threads do not count.. */
  68
  69 int max_threads;                /* tunable limit on nr_threads */
  70
  71 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  72
  73 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  74
  75 int nr_processes(void)
  76 {
  77         int cpu;
  78         int total = 0;
  79
  80         for_each_online_cpu(cpu)
  81                 total += per_cpu(process_counts, cpu);
  82
  83         return total;
  84 }
  85
  86 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  87 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  88 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  89 static struct kmem_cache *task_struct_cachep;
  90 #endif
  91
  92 /* SLAB cache for signal_struct structures (tsk->signal) */
  93 static struct kmem_cache *signal_cachep;
  94
  95 /* SLAB cache for sighand_struct structures (tsk->sighand) */
  96 struct kmem_cache *sighand_cachep;
  97
  98 /* SLAB cache for files_struct structures (tsk->files) */
  99 struct kmem_cache *files_cachep;
 100
 101 /* SLAB cache for fs_struct structures (tsk->fs) */
 102 struct kmem_cache *fs_cachep;
 103
 104 /* SLAB cache for vm_area_struct structures */
 105 struct kmem_cache *vm_area_cachep;
 106
 107 /* SLAB cache for mm_struct structures (tsk->mm) */
 108 static struct kmem_cache *mm_cachep;
 109
 110 void free_task(struct task_struct *tsk)
 111 {
 112         prop_local_destroy_single(&tsk->dirties);
 113         free_thread_info(tsk->stack);
 114         rt_mutex_debug_task_free(tsk);
 115         free_task_struct(tsk);
 116 }
 117 EXPORT_SYMBOL(free_task);
 118
 119 void __put_task_struct(struct task_struct *tsk)
 120 {
 121         WARN_ON(!tsk->exit_state);
 122         WARN_ON(atomic_read(&tsk->usage));
 123         WARN_ON(tsk == current);
 124
 125         security_task_free(tsk);
 126         free_uid(tsk->user);
 127         put_group_info(tsk->group_info);
 128         delayacct_tsk_free(tsk);
 129
 130         if (!profile_handoff_task(tsk))
 131                 free_task(tsk);
 132 }
 133
 134 void __init fork_init(unsigned long mempages)
 135 {
 136 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 137 #ifndef ARCH_MIN_TASKALIGN
 138 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 139 #endif
 140         /* create a slab on which task_structs can be allocated */
 141         task_struct_cachep =
 142                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 143                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
 144 #endif
 145
 146         /*
 147          * The default maximum number of threads is set to a safe
 148          * value: the thread structures can take up at most half
 149          * of memory.
 150          */
 151         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 152
 153         /*
 154          * we need to allow at least 20 threads to boot a system
 155          */
 156         if(max_threads < 20)
 157                 max_threads = 20;
 158
 159         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 160         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 161         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 162                 init_task.signal->rlim[RLIMIT_NPROC];
 163 }
 164
 165 static struct task_struct *dup_task_struct(struct task_struct *orig)
 166 {
 167         struct task_struct *tsk;
 168         struct thread_info *ti;
 169         int err;
 170
 171         prepare_to_copy(orig);
 172
 173         tsk = alloc_task_struct();
 174         if (!tsk)
 175                 return NULL;
 176
 177         ti = alloc_thread_info(tsk);
 178         if (!ti) {
 179                 free_task_struct(tsk);
 180                 return NULL;
 181         }
 182
 183         *tsk = *orig;
 184         tsk->stack = ti;
 185
 186         err = prop_local_init_single(&tsk->dirties);
 187         if (err) {
 188                 free_thread_info(ti);
 189                 free_task_struct(tsk);
 190                 return NULL;
 191         }
 192
 193         setup_thread_stack(tsk, orig);
 194
 195 #ifdef CONFIG_CC_STACKPROTECTOR
 196         tsk->stack_canary = get_random_int();
 197 #endif
 198
 199         /* One for us, one for whoever does the "release_task()" (usually parent) */
 200         atomic_set(&tsk->usage,2);
 201         atomic_set(&tsk->fs_excl, 0);
 202 #ifdef CONFIG_BLK_DEV_IO_TRACE
 203         tsk->btrace_seq = 0;
 204 #endif
 205         tsk->splice_pipe = NULL;
 206         return tsk;
 207 }
 208
 209 #ifdef CONFIG_MMU
 210 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 211 {
 212         struct vm_area_struct *mpnt, *tmp, **pprev;
 213         struct rb_node **rb_link, *rb_parent;
 214         int retval;
 215         unsigned long charge;
 216         struct mempolicy *pol;
 217
 218         down_write(&oldmm->mmap_sem);
 219         flush_cache_dup_mm(oldmm);
 220         /*
 221          * Not linked in yet - no deadlock potential:
 222          */
 223         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 224
 225         mm->locked_vm = 0;
 226         mm->mmap = NULL;
 227         mm->mmap_cache = NULL;
 228         mm->free_area_cache = oldmm->mmap_base;
 229         mm->cached_hole_size = ~0UL;
 230         mm->map_count = 0;
 231         cpus_clear(mm->cpu_vm_mask);
 232         mm->mm_rb = RB_ROOT;
 233         rb_link = &mm->mm_rb.rb_node;
 234         rb_parent = NULL;
 235         pprev = &mm->mmap;
 236
 237         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 238                 struct file *file;
 239
 240                 if (mpnt->vm_flags & VM_DONTCOPY) {
 241                         long pages = vma_pages(mpnt);
 242                         mm->total_vm -= pages;
 243                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 244                                                                 -pages);
 245                         continue;
 246                 }
 247                 charge = 0;
 248                 if (mpnt->vm_flags & VM_ACCOUNT) {
 249                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 250                         if (security_vm_enough_memory(len))
 251                                 goto fail_nomem;
 252                         charge = len;
 253                 }
 254                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 255                 if (!tmp)
 256                         goto fail_nomem;
 257                 *tmp = *mpnt;
 258                 pol = mpol_copy(vma_policy(mpnt));
 259                 retval = PTR_ERR(pol);
 260                 if (IS_ERR(pol))
 261                         goto fail_nomem_policy;
 262                 vma_set_policy(tmp, pol);
 263                 tmp->vm_flags &= ~VM_LOCKED;
 264                 tmp->vm_mm = mm;
 265                 tmp->vm_next = NULL;
 266                 anon_vma_link(tmp);
 267                 file = tmp->vm_file;
 268                 if (file) {
 269                         struct inode *inode = file->f_path.dentry->d_inode;
 270                         get_file(file);
 271                         if (tmp->vm_flags & VM_DENYWRITE)
 272                                 atomic_dec(&inode->i_writecount);
 273
 274                         /* insert tmp into the share list, just after mpnt */
 275                         spin_lock(&file->f_mapping->i_mmap_lock);
 276                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 277                         flush_dcache_mmap_lock(file->f_mapping);
 278                         vma_prio_tree_add(tmp, mpnt);
 279                         flush_dcache_mmap_unlock(file->f_mapping);
 280                         spin_unlock(&file->f_mapping->i_mmap_lock);
 281                 }
 282
 283                 /*
 284                  * Link in the new vma and copy the page table entries.
 285                  */
 286                 *pprev = tmp;
 287                 pprev = &tmp->vm_next;
 288
 289                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 290                 rb_link = &tmp->vm_rb.rb_right;
 291                 rb_parent = &tmp->vm_rb;
 292
 293                 mm->map_count++;
 294                 retval = copy_page_range(mm, oldmm, mpnt);
 295
 296                 if (tmp->vm_ops && tmp->vm_ops->open)
 297                         tmp->vm_ops->open(tmp);
 298
 299                 if (retval)
 300                         goto out;
 301         }
 302         /* a new mm has just been created */
 303         arch_dup_mmap(oldmm, mm);
 304         retval = 0;
 305 out:
 306         up_write(&mm->mmap_sem);
 307         flush_tlb_mm(oldmm);
 308         up_write(&oldmm->mmap_sem);
 309         return retval;
 310 fail_nomem_policy:
 311         kmem_cache_free(vm_area_cachep, tmp);
 312 fail_nomem:
 313         retval = -ENOMEM;
 314         vm_unacct_memory(charge);
 315         goto out;
 316 }
 317
 318 static inline int mm_alloc_pgd(struct mm_struct * mm)
 319 {
 320         mm->pgd = pgd_alloc(mm);
 321         if (unlikely(!mm->pgd))
 322                 return -ENOMEM;
 323         return 0;
 324 }
 325
 326 static inline void mm_free_pgd(struct mm_struct * mm)
 327 {
 328         pgd_free(mm, mm->pgd);
 329 }
 330 #else
 331 #define dup_mmap(mm, oldmm)     (0)
 332 #define mm_alloc_pgd(mm)        (0)
 333 #define mm_free_pgd(mm)
 334 #endif /* CONFIG_MMU */
 335
 336 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 337
 338 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 339 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 340
 341 #include <linux/init_task.h>
 342
 343 static struct mm_struct * mm_init(struct mm_struct * mm)
 344 {
 345         atomic_set(&mm->mm_users, 1);
 346         atomic_set(&mm->mm_count, 1);
 347         init_rwsem(&mm->mmap_sem);
 348         INIT_LIST_HEAD(&mm->mmlist);
 349         mm->flags = (current->mm) ? current->mm->flags
 350                                   : MMF_DUMP_FILTER_DEFAULT;
 351         mm->core_waiters = 0;
 352         mm->nr_ptes = 0;
 353         set_mm_counter(mm, file_rss, 0);
 354         set_mm_counter(mm, anon_rss, 0);
 355         spin_lock_init(&mm->page_table_lock);
 356         rwlock_init(&mm->ioctx_list_lock);
 357         mm->ioctx_list = NULL;
 358         mm->free_area_cache = TASK_UNMAPPED_BASE;
 359         mm->cached_hole_size = ~0UL;
 360
 361         if (likely(!mm_alloc_pgd(mm))) {
 362                 mm->def_flags = 0;
 363                 return mm;
 364         }
 365         free_mm(mm);
 366         return NULL;
 367 }
 368
 369 /*
 370  * Allocate and initialize an mm_struct.
 371  */
 372 struct mm_struct * mm_alloc(void)
 373 {
 374         struct mm_struct * mm;
 375
 376         mm = allocate_mm();
 377         if (mm) {
 378                 memset(mm, 0, sizeof(*mm));
 379                 mm = mm_init(mm);
 380         }
 381         return mm;
 382 }
 383
 384 /*
 385  * Called when the last reference to the mm
 386  * is dropped: either by a lazy thread or by
 387  * mmput. Free the page directory and the mm.
 388  */
 389 void fastcall __mmdrop(struct mm_struct *mm)
 390 {
 391         BUG_ON(mm == &init_mm);
 392         mm_free_pgd(mm);
 393         destroy_context(mm);
 394         free_mm(mm);
 395 }
 396 EXPORT_SYMBOL_GPL(__mmdrop);
 397
 398 /*
 399  * Decrement the use count and release all resources for an mm.
 400  */
 401 void mmput(struct mm_struct *mm)
 402 {
 403         might_sleep();
 404
 405         if (atomic_dec_and_test(&mm->mm_users)) {
 406                 exit_aio(mm);
 407                 exit_mmap(mm);
 408                 if (!list_empty(&mm->mmlist)) {
 409                         spin_lock(&mmlist_lock);
 410                         list_del(&mm->mmlist);
 411                         spin_unlock(&mmlist_lock);
 412                 }
 413                 put_swap_token(mm);
 414                 mmdrop(mm);
 415         }
 416 }
 417 EXPORT_SYMBOL_GPL(mmput);
 418
 419 /**
 420  * get_task_mm - acquire a reference to the task's mm
 421  *
 422  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 423  * this kernel workthread has transiently adopted a user mm with use_mm,
 424  * to do its AIO) is not set and if so returns a reference to it, after
 425  * bumping up the use count.  User must release the mm via mmput()
 426  * after use.  Typically used by /proc and ptrace.
 427  */
 428 struct mm_struct *get_task_mm(struct task_struct *task)
 429 {
 430         struct mm_struct *mm;
 431
 432         task_lock(task);
 433         mm = task->mm;
 434         if (mm) {
 435                 if (task->flags & PF_BORROWED_MM)
 436                         mm = NULL;
 437                 else
 438                         atomic_inc(&mm->mm_users);
 439         }
 440         task_unlock(task);
 441         return mm;
 442 }
 443 EXPORT_SYMBOL_GPL(get_task_mm);
 444
 445 /* Please note the differences between mmput and mm_release.
 446  * mmput is called whenever we stop holding onto a mm_struct,
 447  * error success whatever.
 448  *
 449  * mm_release is called after a mm_struct has been removed
 450  * from the current process.
 451  *
 452  * This difference is important for error handling, when we
 453  * only half set up a mm_struct for a new process and need to restore
 454  * the old one.  Because we mmput the new mm_struct before
 455  * restoring the old one. . .
 456  * Eric Biederman 10 January 1998
 457  */
 458 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 459 {
 460         struct completion *vfork_done = tsk->vfork_done;
 461
 462         /* Get rid of any cached register state */
 463         deactivate_mm(tsk, mm);
 464
 465         /* notify parent sleeping on vfork() */
 466         if (vfork_done) {
 467                 tsk->vfork_done = NULL;
 468                 complete(vfork_done);
 469         }
 470
 471         /*
 472          * If we're exiting normally, clear a user-space tid field if
 473          * requested.  We leave this alone when dying by signal, to leave
 474          * the value intact in a core dump, and to save the unnecessary
 475          * trouble otherwise.  Userland only wants this done for a sys_exit.
 476          */
 477         if (tsk->clear_child_tid
 478             && !(tsk->flags & PF_SIGNALED)
 479             && atomic_read(&mm->mm_users) > 1) {
 480                 u32 __user * tidptr = tsk->clear_child_tid;
 481                 tsk->clear_child_tid = NULL;
 482
 483                 /*
 484                  * We don't check the error code - if userspace has
 485                  * not set up a proper pointer then tough luck.
 486                  */
 487                 put_user(0, tidptr);
 488                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 489         }
 490 }
 491
 492 /*
 493  * Allocate a new mm structure and copy contents from the
 494  * mm structure of the passed in task structure.
 495  */
 496 static struct mm_struct *dup_mm(struct task_struct *tsk)
 497 {
 498         struct mm_struct *mm, *oldmm = current->mm;
 499         int err;
 500
 501         if (!oldmm)
 502                 return NULL;
 503
 504         mm = allocate_mm();
 505         if (!mm)
 506                 goto fail_nomem;
 507
 508         memcpy(mm, oldmm, sizeof(*mm));
 509
 510         /* Initializing for Swap token stuff */
 511         mm->token_priority = 0;
 512         mm->last_interval = 0;
 513
 514         if (!mm_init(mm))
 515                 goto fail_nomem;
 516
 517         if (init_new_context(tsk, mm))
 518                 goto fail_nocontext;
 519
 520         err = dup_mmap(mm, oldmm);
 521         if (err)
 522                 goto free_pt;
 523
 524         mm->hiwater_rss = get_mm_rss(mm);
 525         mm->hiwater_vm = mm->total_vm;
 526
 527         return mm;
 528
 529 free_pt:
 530         mmput(mm);
 531
 532 fail_nomem:
 533         return NULL;
 534
 535 fail_nocontext:
 536         /*
 537          * If init_new_context() failed, we cannot use mmput() to free the mm
 538          * because it calls destroy_context()
 539          */
 540         mm_free_pgd(mm);
 541         free_mm(mm);
 542         return NULL;
 543 }
 544
 545 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 546 {
 547         struct mm_struct * mm, *oldmm;
 548         int retval;
 549
 550         tsk->min_flt = tsk->maj_flt = 0;
 551         tsk->nvcsw = tsk->nivcsw = 0;
 552
 553         tsk->mm = NULL;
 554         tsk->active_mm = NULL;
 555
 556         /*
 557          * Are we cloning a kernel thread?
 558          *
 559          * We need to steal a active VM for that..
 560          */
 561         oldmm = current->mm;
 562         if (!oldmm)
 563                 return 0;
 564
 565         if (clone_flags & CLONE_VM) {
 566                 atomic_inc(&oldmm->mm_users);
 567                 mm = oldmm;
 568                 goto good_mm;
 569         }
 570
 571         retval = -ENOMEM;
 572         mm = dup_mm(tsk);
 573         if (!mm)
 574                 goto fail_nomem;
 575
 576 good_mm:
 577         /* Initializing for Swap token stuff */
 578         mm->token_priority = 0;
 579         mm->last_interval = 0;
 580
 581         tsk->mm = mm;
 582         tsk->active_mm = mm;
 583         return 0;
 584
 585 fail_nomem:
 586         return retval;
 587 }
 588
 589 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 590 {
 591         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 592         /* We don't need to lock fs - think why ;-) */
 593         if (fs) {
 594                 atomic_set(&fs->count, 1);
 595                 rwlock_init(&fs->lock);
 596                 fs->umask = old->umask;
 597                 read_lock(&old->lock);
 598                 fs->rootmnt = mntget(old->rootmnt);
 599                 fs->root = dget(old->root);
 600                 fs->pwdmnt = mntget(old->pwdmnt);
 601                 fs->pwd = dget(old->pwd);
 602                 if (old->altroot) {
 603                         fs->altrootmnt = mntget(old->altrootmnt);
 604                         fs->altroot = dget(old->altroot);
 605                 } else {
 606                         fs->altrootmnt = NULL;
 607                         fs->altroot = NULL;
 608                 }
 609                 read_unlock(&old->lock);
 610         }
 611         return fs;
 612 }
 613
 614 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 615 {
 616         return __copy_fs_struct(old);
 617 }
 618
 619 EXPORT_SYMBOL_GPL(copy_fs_struct);
 620
 621 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 622 {
 623         if (clone_flags & CLONE_FS) {
 624                 atomic_inc(&current->fs->count);
 625                 return 0;
 626         }
 627         tsk->fs = __copy_fs_struct(current->fs);
 628         if (!tsk->fs)
 629                 return -ENOMEM;
 630         return 0;
 631 }
 632
 633 static int count_open_files(struct fdtable *fdt)
 634 {
 635         int size = fdt->max_fds;
 636         int i;
 637
 638         /* Find the last open fd */
 639         for (i = size/(8*sizeof(long)); i > 0; ) {
 640                 if (fdt->open_fds->fds_bits[--i])
 641                         break;
 642         }
 643         i = (i+1) * 8 * sizeof(long);
 644         return i;
 645 }
 646
 647 static struct files_struct *alloc_files(void)
 648 {
 649         struct files_struct *newf;
 650         struct fdtable *fdt;
 651
 652         newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 653         if (!newf)
 654                 goto out;
 655
 656         atomic_set(&newf->count, 1);
 657
 658         spin_lock_init(&newf->file_lock);
 659         newf->next_fd = 0;
 660         fdt = &newf->fdtab;
 661         fdt->max_fds = NR_OPEN_DEFAULT;
 662         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
 663         fdt->open_fds = (fd_set *)&newf->open_fds_init;
 664         fdt->fd = &newf->fd_array[0];
 665         INIT_RCU_HEAD(&fdt->rcu);
 666         fdt->next = NULL;
 667         rcu_assign_pointer(newf->fdt, fdt);
 668 out:
 669         return newf;
 670 }
 671
 672 /*
 673  * Allocate a new files structure and copy contents from the
 674  * passed in files structure.
 675  * errorp will be valid only when the returned files_struct is NULL.
 676  */
 677 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 678 {
 679         struct files_struct *newf;
 680         struct file **old_fds, **new_fds;
 681         int open_files, size, i;
 682         struct fdtable *old_fdt, *new_fdt;
 683
 684         *errorp = -ENOMEM;
 685         newf = alloc_files();
 686         if (!newf)
 687                 goto out;
 688
 689         spin_lock(&oldf->file_lock);
 690         old_fdt = files_fdtable(oldf);
 691         new_fdt = files_fdtable(newf);
 692         open_files = count_open_files(old_fdt);
 693
 694         /*
 695          * Check whether we need to allocate a larger fd array and fd set.
 696          * Note: we're not a clone task, so the open count won't change.
 697          */
 698         if (open_files > new_fdt->max_fds) {
 699                 new_fdt->max_fds = 0;
 700                 spin_unlock(&oldf->file_lock);
 701                 spin_lock(&newf->file_lock);
 702                 *errorp = expand_files(newf, open_files-1);
 703                 spin_unlock(&newf->file_lock);
 704                 if (*errorp < 0)
 705                         goto out_release;
 706                 new_fdt = files_fdtable(newf);
 707                 /*
 708                  * Reacquire the oldf lock and a pointer to its fd table
 709                  * who knows it may have a new bigger fd table. We need
 710                  * the latest pointer.
 711                  */
 712                 spin_lock(&oldf->file_lock);
 713                 old_fdt = files_fdtable(oldf);
 714         }
 715
 716         old_fds = old_fdt->fd;
 717         new_fds = new_fdt->fd;
 718
 719         memcpy(new_fdt->open_fds->fds_bits,
 720                 old_fdt->open_fds->fds_bits, open_files/8);
 721         memcpy(new_fdt->close_on_exec->fds_bits,
 722                 old_fdt->close_on_exec->fds_bits, open_files/8);
 723
 724         for (i = open_files; i != 0; i--) {
 725                 struct file *f = *old_fds++;
 726                 if (f) {
 727                         get_file(f);
 728                 } else {
 729                         /*
 730                          * The fd may be claimed in the fd bitmap but not yet
 731                          * instantiated in the files array if a sibling thread
 732                          * is partway through open().  So make sure that this
 733                          * fd is available to the new process.
 734                          */
 735                         FD_CLR(open_files - i, new_fdt->open_fds);
 736                 }
 737                 rcu_assign_pointer(*new_fds++, f);
 738         }
 739         spin_unlock(&oldf->file_lock);
 740
 741         /* compute the remainder to be cleared */
 742         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 743
 744         /* This is long word aligned thus could use a optimized version */
 745         memset(new_fds, 0, size);
 746
 747         if (new_fdt->max_fds > open_files) {
 748                 int left = (new_fdt->max_fds-open_files)/8;
 749                 int start = open_files / (8 * sizeof(unsigned long));
 750
 751                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
 752                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 753         }
 754
 755         return newf;
 756
 757 out_release:
 758         kmem_cache_free(files_cachep, newf);
 759 out:
 760         return NULL;
 761 }
 762
 763 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 764 {
 765         struct files_struct *oldf, *newf;
 766         int error = 0;
 767
 768         /*
 769          * A background process may not have any files ...
 770          */
 771         oldf = current->files;
 772         if (!oldf)
 773                 goto out;
 774
 775         if (clone_flags & CLONE_FILES) {
 776                 atomic_inc(&oldf->count);
 777                 goto out;
 778         }
 779
 780         /*
 781          * Note: we may be using current for both targets (See exec.c)
 782          * This works because we cache current->files (old) as oldf. Don't
 783          * break this.
 784          */
 785         tsk->files = NULL;
 786         newf = dup_fd(oldf, &error);
 787         if (!newf)
 788                 goto out;
 789
 790         tsk->files = newf;
 791         error = 0;
 792 out:
 793         return error;
 794 }
 795
 796 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 797 {
 798 #ifdef CONFIG_BLOCK
 799         struct io_context *ioc = current->io_context;
 800
 801         if (!ioc)
 802                 return 0;
 803         /*
 804          * Share io context with parent, if CLONE_IO is set
 805          */
 806         if (clone_flags & CLONE_IO) {
 807                 tsk->io_context = ioc_task_link(ioc);
 808                 if (unlikely(!tsk->io_context))
 809                         return -ENOMEM;
 810         } else if (ioprio_valid(ioc->ioprio)) {
 811                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 812                 if (unlikely(!tsk->io_context))
 813                         return -ENOMEM;
 814
 815                 tsk->io_context->ioprio = ioc->ioprio;
 816         }
 817 #endif
 818         return 0;
 819 }
 820
 821 /*
 822  *      Helper to unshare the files of the current task.
 823  *      We don't want to expose copy_files internals to
 824  *      the exec layer of the kernel.
 825  */
 826
 827 int unshare_files(void)
 828 {
 829         struct files_struct *files  = current->files;
 830         int rc;
 831
 832         BUG_ON(!files);
 833
 834         /* This can race but the race causes us to copy when we don't
 835            need to and drop the copy */
 836         if(atomic_read(&files->count) == 1)
 837         {
 838                 atomic_inc(&files->count);
 839                 return 0;
 840         }
 841         rc = copy_files(0, current);
 842         if(rc)
 843                 current->files = files;
 844         return rc;
 845 }
 846
 847 EXPORT_SYMBOL(unshare_files);
 848
 849 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 850 {
 851         struct sighand_struct *sig;
 852
 853         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 854                 atomic_inc(&current->sighand->count);
 855                 return 0;
 856         }
 857         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 858         rcu_assign_pointer(tsk->sighand, sig);
 859         if (!sig)
 860                 return -ENOMEM;
 861         atomic_set(&sig->count, 1);
 862         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 863         return 0;
 864 }
 865
 866 void __cleanup_sighand(struct sighand_struct *sighand)
 867 {
 868         if (atomic_dec_and_test(&sighand->count))
 869                 kmem_cache_free(sighand_cachep, sighand);
 870 }
 871
 872 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 873 {
 874         struct signal_struct *sig;
 875         int ret;
 876
 877         if (clone_flags & CLONE_THREAD) {
 878                 atomic_inc(&current->signal->count);
 879                 atomic_inc(&current->signal->live);
 880                 return 0;
 881         }
 882         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 883         tsk->signal = sig;
 884         if (!sig)
 885                 return -ENOMEM;
 886
 887         ret = copy_thread_group_keys(tsk);
 888         if (ret < 0) {
 889                 kmem_cache_free(signal_cachep, sig);
 890                 return ret;
 891         }
 892
 893         atomic_set(&sig->count, 1);
 894         atomic_set(&sig->live, 1);
 895         init_waitqueue_head(&sig->wait_chldexit);
 896         sig->flags = 0;
 897         sig->group_exit_code = 0;
 898         sig->group_exit_task = NULL;
 899         sig->group_stop_count = 0;
 900         sig->curr_target = NULL;
 901         init_sigpending(&sig->shared_pending);
 902         INIT_LIST_HEAD(&sig->posix_timers);
 903
 904         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 905         sig->it_real_incr.tv64 = 0;
 906         sig->real_timer.function = it_real_fn;
 907         sig->tsk = tsk;
 908
 909         sig->it_virt_expires = cputime_zero;
 910         sig->it_virt_incr = cputime_zero;
 911         sig->it_prof_expires = cputime_zero;
 912         sig->it_prof_incr = cputime_zero;
 913
 914         sig->leader = 0;        /* session leadership doesn't inherit */
 915         sig->tty_old_pgrp = NULL;
 916
 917         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 918         sig->gtime = cputime_zero;
 919         sig->cgtime = cputime_zero;
 920         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 921         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 922         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 923         sig->sum_sched_runtime = 0;
 924         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 925         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 926         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 927         taskstats_tgid_init(sig);
 928
 929         task_lock(current->group_leader);
 930         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 931         task_unlock(current->group_leader);
 932
 933         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 934                 /*
 935                  * New sole thread in the process gets an expiry time
 936                  * of the whole CPU time limit.
 937                  */
 938                 tsk->it_prof_expires =
 939                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 940         }
 941         acct_init_pacct(&sig->pacct);
 942
 943         tty_audit_fork(sig);
 944
 945         return 0;
 946 }
 947
 948 void __cleanup_signal(struct signal_struct *sig)
 949 {
 950         exit_thread_group_keys(sig);
 951         kmem_cache_free(signal_cachep, sig);
 952 }
 953
 954 static void cleanup_signal(struct task_struct *tsk)
 955 {
 956         struct signal_struct *sig = tsk->signal;
 957
 958         atomic_dec(&sig->live);
 959
 960         if (atomic_dec_and_test(&sig->count))
 961                 __cleanup_signal(sig);
 962 }
 963
 964 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 965 {
 966         unsigned long new_flags = p->flags;
 967
 968         new_flags &= ~PF_SUPERPRIV;
 969         new_flags |= PF_FORKNOEXEC;
 970         if (!(clone_flags & CLONE_PTRACE))
 971                 p->ptrace = 0;
 972         p->flags = new_flags;
 973         clear_freeze_flag(p);
 974 }
 975
 976 asmlinkage long sys_set_tid_address(int __user *tidptr)
 977 {
 978         current->clear_child_tid = tidptr;
 979
 980         return task_pid_vnr(current);
 981 }
 982
 983 static void rt_mutex_init_task(struct task_struct *p)
 984 {
 985         spin_lock_init(&p->pi_lock);
 986 #ifdef CONFIG_RT_MUTEXES
 987         plist_head_init(&p->pi_waiters, &p->pi_lock);
 988         p->pi_blocked_on = NULL;
 989 #endif
 990 }
 991
 992 /*
 993  * This creates a new process as a copy of the old one,
 994  * but does not actually start it yet.
 995  *
 996  * It copies the registers, and all the appropriate
 997  * parts of the process environment (as per the clone
 998  * flags). The actual kick-off is left to the caller.
 999  */
1000 static struct task_struct *copy_process(unsigned long clone_flags,
1001                                         unsigned long stack_start,
1002                                         struct pt_regs *regs,
1003                                         unsigned long stack_size,
1004                                         int __user *child_tidptr,
1005                                         struct pid *pid)
1006 {
1007         int retval;
1008         struct task_struct *p;
1009         int cgroup_callbacks_done = 0;
1010
1011         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1012                 return ERR_PTR(-EINVAL);
1013
1014         /*
1015          * Thread groups must share signals as well, and detached threads
1016          * can only be started up within the thread group.
1017          */
1018         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1019                 return ERR_PTR(-EINVAL);
1020
1021         /*
1022          * Shared signal handlers imply shared VM. By way of the above,
1023          * thread groups also imply shared VM. Blocking this case allows
1024          * for various simplifications in other code.
1025          */
1026         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1027                 return ERR_PTR(-EINVAL);
1028
1029         retval = security_task_create(clone_flags);
1030         if (retval)
1031                 goto fork_out;
1032
1033         retval = -ENOMEM;
1034         p = dup_task_struct(current);
1035         if (!p)
1036                 goto fork_out;
1037
1038         rt_mutex_init_task(p);
1039
1040 #ifdef CONFIG_TRACE_IRQFLAGS
1041         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1042         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1043 #endif
1044         retval = -EAGAIN;
1045         if (atomic_read(&p->user->processes) >=
1046                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1047                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1048                     p->user != current->nsproxy->user_ns->root_user)
1049                         goto bad_fork_free;
1050         }
1051
1052         atomic_inc(&p->user->__count);
1053         atomic_inc(&p->user->processes);
1054         get_group_info(p->group_info);
1055
1056         /*
1057          * If multiple threads are within copy_process(), then this check
1058          * triggers too late. This doesn't hurt, the check is only there
1059          * to stop root fork bombs.
1060          */
1061         if (nr_threads >= max_threads)
1062                 goto bad_fork_cleanup_count;
1063
1064         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1065                 goto bad_fork_cleanup_count;
1066
1067         if (p->binfmt && !try_module_get(p->binfmt->module))
1068                 goto bad_fork_cleanup_put_domain;
1069
1070         p->did_exec = 0;
1071         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1072         copy_flags(clone_flags, p);
1073         INIT_LIST_HEAD(&p->children);
1074         INIT_LIST_HEAD(&p->sibling);
1075 #ifdef CONFIG_PREEMPT_RCU
1076         p->rcu_read_lock_nesting = 0;
1077         p->rcu_flipctr_idx = 0;
1078 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1079         p->vfork_done = NULL;
1080         spin_lock_init(&p->alloc_lock);
1081
1082         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1083         init_sigpending(&p->pending);
1084
1085         p->utime = cputime_zero;
1086         p->stime = cputime_zero;
1087         p->gtime = cputime_zero;
1088         p->utimescaled = cputime_zero;
1089         p->stimescaled = cputime_zero;
1090         p->prev_utime = cputime_zero;
1091         p->prev_stime = cputime_zero;
1092
1093 #ifdef CONFIG_DETECT_SOFTLOCKUP
1094         p->last_switch_count = 0;
1095         p->last_switch_timestamp = 0;
1096 #endif
1097
1098 #ifdef CONFIG_TASK_XACCT
1099         p->rchar = 0;           /* I/O counter: bytes read */
1100         p->wchar = 0;           /* I/O counter: bytes written */
1101         p->syscr = 0;           /* I/O counter: read syscalls */
1102         p->syscw = 0;           /* I/O counter: write syscalls */
1103 #endif
1104         task_io_accounting_init(p);
1105         acct_clear_integrals(p);
1106
1107         p->it_virt_expires = cputime_zero;
1108         p->it_prof_expires = cputime_zero;
1109         p->it_sched_expires = 0;
1110         INIT_LIST_HEAD(&p->cpu_timers[0]);
1111         INIT_LIST_HEAD(&p->cpu_timers[1]);
1112         INIT_LIST_HEAD(&p->cpu_timers[2]);
1113
1114         p->lock_depth = -1;             /* -1 = no lock */
1115         do_posix_clock_monotonic_gettime(&p->start_time);
1116         p->real_start_time = p->start_time;
1117         monotonic_to_bootbased(&p->real_start_time);
1118 #ifdef CONFIG_SECURITY
1119         p->security = NULL;
1120 #endif
1121         p->io_context = NULL;
1122         p->audit_context = NULL;
1123         cgroup_fork(p);
1124 #ifdef CONFIG_NUMA
1125         p->mempolicy = mpol_copy(p->mempolicy);
1126         if (IS_ERR(p->mempolicy)) {
1127                 retval = PTR_ERR(p->mempolicy);
1128                 p->mempolicy = NULL;
1129                 goto bad_fork_cleanup_cgroup;
1130         }
1131         mpol_fix_fork_child_flag(p);
1132 #endif
1133 #ifdef CONFIG_TRACE_IRQFLAGS
1134         p->irq_events = 0;
1135 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1136         p->hardirqs_enabled = 1;
1137 #else
1138         p->hardirqs_enabled = 0;
1139 #endif
1140         p->hardirq_enable_ip = 0;
1141         p->hardirq_enable_event = 0;
1142         p->hardirq_disable_ip = _THIS_IP_;
1143         p->hardirq_disable_event = 0;
1144         p->softirqs_enabled = 1;
1145         p->softirq_enable_ip = _THIS_IP_;
1146         p->softirq_enable_event = 0;
1147         p->softirq_disable_ip = 0;
1148         p->softirq_disable_event = 0;
1149         p->hardirq_context = 0;
1150         p->softirq_context = 0;
1151 #endif
1152 #ifdef CONFIG_LOCKDEP
1153         p->lockdep_depth = 0; /* no locks held yet */
1154         p->curr_chain_key = 0;
1155         p->lockdep_recursion = 0;
1156 #endif
1157
1158 #ifdef CONFIG_DEBUG_MUTEXES
1159         p->blocked_on = NULL; /* not blocked yet */
1160 #endif
1161
1162         /* Perform scheduler related setup. Assign this task to a CPU. */
1163         sched_fork(p, clone_flags);
1164
1165         if ((retval = security_task_alloc(p)))
1166                 goto bad_fork_cleanup_policy;
1167         if ((retval = audit_alloc(p)))
1168                 goto bad_fork_cleanup_security;
1169         /* copy all the process information */
1170         if ((retval = copy_semundo(clone_flags, p)))
1171                 goto bad_fork_cleanup_audit;
1172         if ((retval = copy_files(clone_flags, p)))
1173                 goto bad_fork_cleanup_semundo;
1174         if ((retval = copy_fs(clone_flags, p)))
1175                 goto bad_fork_cleanup_files;
1176         if ((retval = copy_sighand(clone_flags, p)))
1177                 goto bad_fork_cleanup_fs;
1178         if ((retval = copy_signal(clone_flags, p)))
1179                 goto bad_fork_cleanup_sighand;
1180         if ((retval = copy_mm(clone_flags, p)))
1181                 goto bad_fork_cleanup_signal;
1182         if ((retval = copy_keys(clone_flags, p)))
1183                 goto bad_fork_cleanup_mm;
1184         if ((retval = copy_namespaces(clone_flags, p)))
1185                 goto bad_fork_cleanup_keys;
1186         if ((retval = copy_io(clone_flags, p)))
1187                 goto bad_fork_cleanup_namespaces;
1188         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1189         if (retval)
1190                 goto bad_fork_cleanup_io;
1191
1192         if (pid != &init_struct_pid) {
1193                 retval = -ENOMEM;
1194                 pid = alloc_pid(task_active_pid_ns(p));
1195                 if (!pid)
1196                         goto bad_fork_cleanup_io;
1197
1198                 if (clone_flags & CLONE_NEWPID) {
1199                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1200                         if (retval < 0)
1201                                 goto bad_fork_free_pid;
1202                 }
1203         }
1204
1205         p->pid = pid_nr(pid);
1206         p->tgid = p->pid;
1207         if (clone_flags & CLONE_THREAD)
1208                 p->tgid = current->tgid;
1209
1210         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1211         /*
1212          * Clear TID on mm_release()?
1213          */
1214         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1215 #ifdef CONFIG_FUTEX
1216         p->robust_list = NULL;
1217 #ifdef CONFIG_COMPAT
1218         p->compat_robust_list = NULL;
1219 #endif
1220         INIT_LIST_HEAD(&p->pi_state_list);
1221         p->pi_state_cache = NULL;
1222 #endif
1223         /*
1224          * sigaltstack should be cleared when sharing the same VM
1225          */
1226         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1227                 p->sas_ss_sp = p->sas_ss_size = 0;
1228
1229         /*
1230          * Syscall tracing should be turned off in the child regardless
1231          * of CLONE_PTRACE.
1232          */
1233         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1234 #ifdef TIF_SYSCALL_EMU
1235         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1236 #endif
1237         clear_all_latency_tracing(p);
1238
1239         /* Our parent execution domain becomes current domain
1240            These must match for thread signalling to apply */
1241         p->parent_exec_id = p->self_exec_id;
1242
1243         /* ok, now we should be set up.. */
1244         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1245         p->pdeath_signal = 0;
1246         p->exit_state = 0;
1247
1248         /*
1249          * Ok, make it visible to the rest of the system.
1250          * We dont wake it up yet.
1251          */
1252         p->group_leader = p;
1253         INIT_LIST_HEAD(&p->thread_group);
1254         INIT_LIST_HEAD(&p->ptrace_children);
1255         INIT_LIST_HEAD(&p->ptrace_list);
1256
1257         /* Now that the task is set up, run cgroup callbacks if
1258          * necessary. We need to run them before the task is visible
1259          * on the tasklist. */
1260         cgroup_fork_callbacks(p);
1261         cgroup_callbacks_done = 1;
1262
1263         /* Need tasklist lock for parent etc handling! */
1264         write_lock_irq(&tasklist_lock);
1265
1266         /*
1267          * The task hasn't been attached yet, so its cpus_allowed mask will
1268          * not be changed, nor will its assigned CPU.
1269          *
1270          * The cpus_allowed mask of the parent may have changed after it was
1271          * copied first time - so re-copy it here, then check the child's CPU
1272          * to ensure it is on a valid CPU (and if not, just force it back to
1273          * parent's CPU). This avoids alot of nasty races.
1274          */
1275         p->cpus_allowed = current->cpus_allowed;
1276         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1277         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1278                         !cpu_online(task_cpu(p))))
1279                 set_task_cpu(p, smp_processor_id());
1280
1281         /* CLONE_PARENT re-uses the old parent */
1282         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1283                 p->real_parent = current->real_parent;
1284         else
1285                 p->real_parent = current;
1286         p->parent = p->real_parent;
1287
1288         spin_lock(&current->sighand->siglock);
1289
1290         /*
1291          * Process group and session signals need to be delivered to just the
1292          * parent before the fork or both the parent and the child after the
1293          * fork. Restart if a signal comes in before we add the new process to
1294          * it's process group.
1295          * A fatal signal pending means that current will exit, so the new
1296          * thread can't slip out of an OOM kill (or normal SIGKILL).
1297          */
1298         recalc_sigpending();
1299         if (signal_pending(current)) {
1300                 spin_unlock(&current->sighand->siglock);
1301                 write_unlock_irq(&tasklist_lock);
1302                 retval = -ERESTARTNOINTR;
1303                 goto bad_fork_free_pid;
1304         }
1305
1306         if (clone_flags & CLONE_THREAD) {
1307                 p->group_leader = current->group_leader;
1308                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1309
1310                 if (!cputime_eq(current->signal->it_virt_expires,
1311                                 cputime_zero) ||
1312                     !cputime_eq(current->signal->it_prof_expires,
1313                                 cputime_zero) ||
1314                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1315                     !list_empty(&current->signal->cpu_timers[0]) ||
1316                     !list_empty(&current->signal->cpu_timers[1]) ||
1317                     !list_empty(&current->signal->cpu_timers[2])) {
1318                         /*
1319                          * Have child wake up on its first tick to check
1320                          * for process CPU timers.
1321                          */
1322                         p->it_prof_expires = jiffies_to_cputime(1);
1323                 }
1324         }
1325
1326         if (likely(p->pid)) {
1327                 add_parent(p);
1328                 if (unlikely(p->ptrace & PT_PTRACED))
1329                         __ptrace_link(p, current->parent);
1330
1331                 if (thread_group_leader(p)) {
1332                         if (clone_flags & CLONE_NEWPID)
1333                                 p->nsproxy->pid_ns->child_reaper = p;
1334
1335                         p->signal->tty = current->signal->tty;
1336                         set_task_pgrp(p, task_pgrp_nr(current));
1337                         set_task_session(p, task_session_nr(current));
1338                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1339                         attach_pid(p, PIDTYPE_SID, task_session(current));
1340                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1341                         __get_cpu_var(process_counts)++;
1342                 }
1343                 attach_pid(p, PIDTYPE_PID, pid);
1344                 nr_threads++;
1345         }
1346
1347         total_forks++;
1348         spin_unlock(&current->sighand->siglock);
1349         write_unlock_irq(&tasklist_lock);
1350         proc_fork_connector(p);
1351         cgroup_post_fork(p);
1352         return p;
1353
1354 bad_fork_free_pid:
1355         if (pid != &init_struct_pid)
1356                 free_pid(pid);
1357 bad_fork_cleanup_io:
1358         put_io_context(p->io_context);
1359 bad_fork_cleanup_namespaces:
1360         exit_task_namespaces(p);
1361 bad_fork_cleanup_keys:
1362         exit_keys(p);
1363 bad_fork_cleanup_mm:
1364         if (p->mm)
1365                 mmput(p->mm);
1366 bad_fork_cleanup_signal:
1367         cleanup_signal(p);
1368 bad_fork_cleanup_sighand:
1369         __cleanup_sighand(p->sighand);
1370 bad_fork_cleanup_fs:
1371         exit_fs(p); /* blocking */
1372 bad_fork_cleanup_files:
1373         exit_files(p); /* blocking */
1374 bad_fork_cleanup_semundo:
1375         exit_sem(p);
1376 bad_fork_cleanup_audit:
1377         audit_free(p);
1378 bad_fork_cleanup_security:
1379         security_task_free(p);
1380 bad_fork_cleanup_policy:
1381 #ifdef CONFIG_NUMA
1382         mpol_free(p->mempolicy);
1383 bad_fork_cleanup_cgroup:
1384 #endif
1385         cgroup_exit(p, cgroup_callbacks_done);
1386         delayacct_tsk_free(p);
1387         if (p->binfmt)
1388                 module_put(p->binfmt->module);
1389 bad_fork_cleanup_put_domain:
1390         module_put(task_thread_info(p)->exec_domain->module);
1391 bad_fork_cleanup_count:
1392         put_group_info(p->group_info);
1393         atomic_dec(&p->user->processes);
1394         free_uid(p->user);
1395 bad_fork_free:
1396         free_task(p);
1397 fork_out:
1398         return ERR_PTR(retval);
1399 }
1400
1401 noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1402 {
1403         memset(regs, 0, sizeof(struct pt_regs));
1404         return regs;
1405 }
1406
1407 struct task_struct * __cpuinit fork_idle(int cpu)
1408 {
1409         struct task_struct *task;
1410         struct pt_regs regs;
1411
1412         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1413                                 &init_struct_pid);
1414         if (!IS_ERR(task))
1415                 init_idle(task, cpu);
1416
1417         return task;
1418 }
1419
1420 static int fork_traceflag(unsigned clone_flags)
1421 {
1422         if (clone_flags & CLONE_UNTRACED)
1423                 return 0;
1424         else if (clone_flags & CLONE_VFORK) {
1425                 if (current->ptrace & PT_TRACE_VFORK)
1426                         return PTRACE_EVENT_VFORK;
1427         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1428                 if (current->ptrace & PT_TRACE_CLONE)
1429                         return PTRACE_EVENT_CLONE;
1430         } else if (current->ptrace & PT_TRACE_FORK)
1431                 return PTRACE_EVENT_FORK;
1432
1433         return 0;
1434 }
1435
1436 /*
1437  *  Ok, this is the main fork-routine.
1438  *
1439  * It copies the process, and if successful kick-starts
1440  * it and waits for it to finish using the VM if required.
1441  */
1442 long do_fork(unsigned long clone_flags,
1443               unsigned long stack_start,
1444               struct pt_regs *regs,
1445               unsigned long stack_size,
1446               int __user *parent_tidptr,
1447               int __user *child_tidptr)
1448 {
1449         struct task_struct *p;
1450         int trace = 0;
1451         long nr;
1452
1453         /*
1454          * We hope to recycle these flags after 2.6.26
1455          */
1456         if (unlikely(clone_flags & CLONE_STOPPED)) {
1457                 static int __read_mostly count = 100;
1458
1459                 if (count > 0 && printk_ratelimit()) {
1460                         char comm[TASK_COMM_LEN];
1461
1462                         count--;
1463                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1464                                         "clone flags 0x%lx\n",
1465                                 get_task_comm(comm, current),
1466                                 clone_flags & CLONE_STOPPED);
1467                 }
1468         }
1469
1470         if (unlikely(current->ptrace)) {
1471                 trace = fork_traceflag (clone_flags);
1472                 if (trace)
1473                         clone_flags |= CLONE_PTRACE;
1474         }
1475
1476         p = copy_process(clone_flags, stack_start, regs, stack_size,
1477                         child_tidptr, NULL);
1478         /*
1479          * Do this prior waking up the new thread - the thread pointer
1480          * might get invalid after that point, if the thread exits quickly.
1481          */
1482         if (!IS_ERR(p)) {
1483                 struct completion vfork;
1484
1485                 /*
1486                  * this is enough to call pid_nr_ns here, but this if
1487                  * improves optimisation of regular fork()
1488                  */
1489                 nr = (clone_flags & CLONE_NEWPID) ?
1490                         task_pid_nr_ns(p, current->nsproxy->pid_ns) :
1491                                 task_pid_vnr(p);
1492
1493                 if (clone_flags & CLONE_PARENT_SETTID)
1494                         put_user(nr, parent_tidptr);
1495
1496                 if (clone_flags & CLONE_VFORK) {
1497                         p->vfork_done = &vfork;
1498                         init_completion(&vfork);
1499                 }
1500
1501                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1502                         /*
1503                          * We'll start up with an immediate SIGSTOP.
1504                          */
1505                         sigaddset(&p->pending.signal, SIGSTOP);
1506                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1507                 }
1508
1509                 if (!(clone_flags & CLONE_STOPPED))
1510                         wake_up_new_task(p, clone_flags);
1511                 else
1512                         p->state = TASK_STOPPED;
1513
1514                 if (unlikely (trace)) {
1515                         current->ptrace_message = nr;
1516                         ptrace_notify ((trace << 8) | SIGTRAP);
1517                 }
1518
1519                 if (clone_flags & CLONE_VFORK) {
1520                         freezer_do_not_count();
1521                         wait_for_completion(&vfork);
1522                         freezer_count();
1523                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1524                                 current->ptrace_message = nr;
1525                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1526                         }
1527                 }
1528         } else {
1529                 nr = PTR_ERR(p);
1530         }
1531         return nr;
1532 }
1533
1534 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1535 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1536 #endif
1537
1538 static void sighand_ctor(struct kmem_cache *cachep, void *data)
1539 {
1540         struct sighand_struct *sighand = data;
1541
1542         spin_lock_init(&sighand->siglock);
1543         init_waitqueue_head(&sighand->signalfd_wqh);
1544 }
1545
1546 void __init proc_caches_init(void)
1547 {
1548         sighand_cachep = kmem_cache_create("sighand_cache",
1549                         sizeof(struct sighand_struct), 0,
1550                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1551                         sighand_ctor);
1552         signal_cachep = kmem_cache_create("signal_cache",
1553                         sizeof(struct signal_struct), 0,
1554                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1555         files_cachep = kmem_cache_create("files_cache",
1556                         sizeof(struct files_struct), 0,
1557                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1558         fs_cachep = kmem_cache_create("fs_cache",
1559                         sizeof(struct fs_struct), 0,
1560                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1561         vm_area_cachep = kmem_cache_create("vm_area_struct",
1562                         sizeof(struct vm_area_struct), 0,
1563                         SLAB_PANIC, NULL);
1564         mm_cachep = kmem_cache_create("mm_struct",
1565                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1566                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1567 }
1568
1569 /*
1570  * Check constraints on flags passed to the unshare system call and
1571  * force unsharing of additional process context as appropriate.
1572  */
1573 static void check_unshare_flags(unsigned long *flags_ptr)
1574 {
1575         /*
1576          * If unsharing a thread from a thread group, must also
1577          * unshare vm.
1578          */
1579         if (*flags_ptr & CLONE_THREAD)
1580                 *flags_ptr |= CLONE_VM;
1581
1582         /*
1583          * If unsharing vm, must also unshare signal handlers.
1584          */
1585         if (*flags_ptr & CLONE_VM)
1586                 *flags_ptr |= CLONE_SIGHAND;
1587
1588         /*
1589          * If unsharing signal handlers and the task was created
1590          * using CLONE_THREAD, then must unshare the thread
1591          */
1592         if ((*flags_ptr & CLONE_SIGHAND) &&
1593             (atomic_read(&current->signal->count) > 1))
1594                 *flags_ptr |= CLONE_THREAD;
1595
1596         /*
1597          * If unsharing namespace, must also unshare filesystem information.
1598          */
1599         if (*flags_ptr & CLONE_NEWNS)
1600                 *flags_ptr |= CLONE_FS;
1601 }
1602
1603 /*
1604  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1605  */
1606 static int unshare_thread(unsigned long unshare_flags)
1607 {
1608         if (unshare_flags & CLONE_THREAD)
1609                 return -EINVAL;
1610
1611         return 0;
1612 }
1613
1614 /*
1615  * Unshare the filesystem structure if it is being shared
1616  */
1617 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1618 {
1619         struct fs_struct *fs = current->fs;
1620
1621         if ((unshare_flags & CLONE_FS) &&
1622             (fs && atomic_read(&fs->count) > 1)) {
1623                 *new_fsp = __copy_fs_struct(current->fs);
1624                 if (!*new_fsp)
1625                         return -ENOMEM;
1626         }
1627
1628         return 0;
1629 }
1630
1631 /*
1632  * Unsharing of sighand is not supported yet
1633  */
1634 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1635 {
1636         struct sighand_struct *sigh = current->sighand;
1637
1638         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1639                 return -EINVAL;
1640         else
1641                 return 0;
1642 }
1643
1644 /*
1645  * Unshare vm if it is being shared
1646  */
1647 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1648 {
1649         struct mm_struct *mm = current->mm;
1650
1651         if ((unshare_flags & CLONE_VM) &&
1652             (mm && atomic_read(&mm->mm_users) > 1)) {
1653                 return -EINVAL;
1654         }
1655
1656         return 0;
1657 }
1658
1659 /*
1660  * Unshare file descriptor table if it is being shared
1661  */
1662 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1663 {
1664         struct files_struct *fd = current->files;
1665         int error = 0;
1666
1667         if ((unshare_flags & CLONE_FILES) &&
1668             (fd && atomic_read(&fd->count) > 1)) {
1669                 *new_fdp = dup_fd(fd, &error);
1670                 if (!*new_fdp)
1671                         return error;
1672         }
1673
1674         return 0;
1675 }
1676
1677 /*
1678  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1679  * supported yet
1680  */
1681 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1682 {
1683         if (unshare_flags & CLONE_SYSVSEM)
1684                 return -EINVAL;
1685
1686         return 0;
1687 }
1688
1689 /*
1690  * unshare allows a process to 'unshare' part of the process
1691  * context which was originally shared using clone.  copy_*
1692  * functions used by do_fork() cannot be used here directly
1693  * because they modify an inactive task_struct that is being
1694  * constructed. Here we are modifying the current, active,
1695  * task_struct.
1696  */
1697 asmlinkage long sys_unshare(unsigned long unshare_flags)
1698 {
1699         int err = 0;
1700         struct fs_struct *fs, *new_fs = NULL;
1701         struct sighand_struct *new_sigh = NULL;
1702         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1703         struct files_struct *fd, *new_fd = NULL;
1704         struct sem_undo_list *new_ulist = NULL;
1705         struct nsproxy *new_nsproxy = NULL;
1706
1707         check_unshare_flags(&unshare_flags);
1708
1709         /* Return -EINVAL for all unsupported flags */
1710         err = -EINVAL;
1711         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1712                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1713                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1714                                 CLONE_NEWNET))
1715                 goto bad_unshare_out;
1716
1717         if ((err = unshare_thread(unshare_flags)))
1718                 goto bad_unshare_out;
1719         if ((err = unshare_fs(unshare_flags, &new_fs)))
1720                 goto bad_unshare_cleanup_thread;
1721         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1722                 goto bad_unshare_cleanup_fs;
1723         if ((err = unshare_vm(unshare_flags, &new_mm)))
1724                 goto bad_unshare_cleanup_sigh;
1725         if ((err = unshare_fd(unshare_flags, &new_fd)))
1726                 goto bad_unshare_cleanup_vm;
1727         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1728                 goto bad_unshare_cleanup_fd;
1729         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1730                         new_fs)))
1731                 goto bad_unshare_cleanup_semundo;
1732
1733         if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
1734
1735                 if (new_nsproxy) {
1736                         switch_task_namespaces(current, new_nsproxy);
1737                         new_nsproxy = NULL;
1738                 }
1739
1740                 task_lock(current);
1741
1742                 if (new_fs) {
1743                         fs = current->fs;
1744                         current->fs = new_fs;
1745                         new_fs = fs;
1746                 }
1747
1748                 if (new_mm) {
1749                         mm = current->mm;
1750                         active_mm = current->active_mm;
1751                         current->mm = new_mm;
1752                         current->active_mm = new_mm;
1753                         activate_mm(active_mm, new_mm);
1754                         new_mm = mm;
1755                 }
1756
1757                 if (new_fd) {
1758                         fd = current->files;
1759                         current->files = new_fd;
1760                         new_fd = fd;
1761                 }
1762
1763                 task_unlock(current);
1764         }
1765
1766         if (new_nsproxy)
1767                 put_nsproxy(new_nsproxy);
1768
1769 bad_unshare_cleanup_semundo:
1770 bad_unshare_cleanup_fd:
1771         if (new_fd)
1772                 put_files_struct(new_fd);
1773
1774 bad_unshare_cleanup_vm:
1775         if (new_mm)
1776                 mmput(new_mm);
1777
1778 bad_unshare_cleanup_sigh:
1779         if (new_sigh)
1780                 if (atomic_dec_and_test(&new_sigh->count))
1781                         kmem_cache_free(sighand_cachep, new_sigh);
1782
1783 bad_unshare_cleanup_fs:
1784         if (new_fs)
1785                 put_fs_struct(new_fs);
1786
1787 bad_unshare_cleanup_thread:
1788 bad_unshare_out:
1789         return err;
1790 }