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