kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/config.h>
  15 #include <linux/slab.h>
  16 #include <linux/init.h>
  17 #include <linux/unistd.h>
  18 #include <linux/smp_lock.h>
  19 #include <linux/module.h>
  20 #include <linux/vmalloc.h>
  21 #include <linux/completion.h>
  22 #include <linux/namespace.h>
  23 #include <linux/personality.h>
  24 #include <linux/mempolicy.h>
  25 #include <linux/sem.h>
  26 #include <linux/file.h>
  27 #include <linux/key.h>
  28 #include <linux/binfmts.h>
  29 #include <linux/mman.h>
  30 #include <linux/fs.h>
  31 #include <linux/capability.h>
  32 #include <linux/cpu.h>
  33 #include <linux/cpuset.h>
  34 #include <linux/security.h>
  35 #include <linux/swap.h>
  36 #include <linux/syscalls.h>
  37 #include <linux/jiffies.h>
  38 #include <linux/futex.h>
  39 #include <linux/rcupdate.h>
  40 #include <linux/ptrace.h>
  41 #include <linux/mount.h>
  42 #include <linux/audit.h>
  43 #include <linux/profile.h>
  44 #include <linux/rmap.h>
  45 #include <linux/acct.h>
  46 #include <linux/cn_proc.h>
  47 #include <linux/vs_context.h>
  48 #include <linux/vs_network.h>
  49 #include <linux/vs_limit.h>
  50 #include <linux/vs_memory.h>
  51
  52 #include <asm/pgtable.h>
  53 #include <asm/pgalloc.h>
  54 #include <asm/uaccess.h>
  55 #include <asm/mmu_context.h>
  56 #include <asm/cacheflush.h>
  57 #include <asm/tlbflush.h>
  58
  59 /*
  60  * Protected counters by write_lock_irq(&tasklist_lock)
  61  */
  62 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  63 int nr_threads;                 /* The idle threads do not count.. */
  64
  65 int max_threads;                /* tunable limit on nr_threads */
  66
  67 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  68
  69  __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  70
  71 EXPORT_SYMBOL(tasklist_lock);
  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         clr_vx_info(&tsk->vx_info);
 112         clr_nx_info(&tsk->nx_info);
 113         free_task_struct(tsk);
 114 }
 115 EXPORT_SYMBOL(free_task);
 116
 117 void __put_task_struct(struct task_struct *tsk)
 118 {
 119         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
 120         WARN_ON(atomic_read(&tsk->usage));
 121         WARN_ON(tsk == current);
 122
 123         security_task_free(tsk);
 124         free_uid(tsk->user);
 125         put_group_info(tsk->group_info);
 126
 127         if (!profile_handoff_task(tsk))
 128                 free_task(tsk);
 129 }
 130
 131 void __init fork_init(unsigned long mempages)
 132 {
 133 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 134 #ifndef ARCH_MIN_TASKALIGN
 135 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 136 #endif
 137         /* create a slab on which task_structs can be allocated */
 138         task_struct_cachep =
 139                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 140                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
 141 #endif
 142
 143         /*
 144          * The default maximum number of threads is set to a safe
 145          * value: the thread structures can take up at most half
 146          * of memory.
 147          */
 148         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 149
 150         /*
 151          * we need to allow at least 20 threads to boot a system
 152          */
 153         if(max_threads < 20)
 154                 max_threads = 20;
 155
 156         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 157         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 158         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 159                 init_task.signal->rlim[RLIMIT_NPROC];
 160 }
 161
 162 static struct task_struct *dup_task_struct(struct task_struct *orig)
 163 {
 164         struct task_struct *tsk;
 165         struct thread_info *ti;
 166
 167         prepare_to_copy(orig);
 168
 169         tsk = alloc_task_struct();
 170         if (!tsk)
 171                 return NULL;
 172
 173         ti = alloc_thread_info(tsk);
 174         if (!ti) {
 175                 free_task_struct(tsk);
 176                 return NULL;
 177         }
 178
 179         *tsk = *orig;
 180         tsk->thread_info = ti;
 181         setup_thread_stack(tsk, orig);
 182
 183         /* One for us, one for whoever does the "release_task()" (usually parent) */
 184         atomic_set(&tsk->usage,2);
 185         atomic_set(&tsk->fs_excl, 0);
 186         tsk->btrace_seq = 0;
 187         tsk->splice_pipe = NULL;
 188         return tsk;
 189 }
 190
 191 #ifdef CONFIG_MMU
 192 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 193 {
 194         struct vm_area_struct *mpnt, *tmp, **pprev;
 195         struct rb_node **rb_link, *rb_parent;
 196         int retval;
 197         unsigned long charge;
 198         struct mempolicy *pol;
 199
 200         down_write(&oldmm->mmap_sem);
 201         flush_cache_mm(oldmm);
 202         down_write(&mm->mmap_sem);
 203
 204         mm->locked_vm = 0;
 205         mm->mmap = NULL;
 206         mm->mmap_cache = NULL;
 207         mm->free_area_cache = oldmm->mmap_base;
 208         mm->cached_hole_size = ~0UL;
 209         mm->map_count = 0;
 210         __set_mm_counter(mm, file_rss, 0);
 211         __set_mm_counter(mm, anon_rss, 0);
 212         cpus_clear(mm->cpu_vm_mask);
 213         mm->mm_rb = RB_ROOT;
 214         rb_link = &mm->mm_rb.rb_node;
 215         rb_parent = NULL;
 216         pprev = &mm->mmap;
 217
 218         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 219                 struct file *file;
 220
 221                 if (mpnt->vm_flags & VM_DONTCOPY) {
 222                         long pages = vma_pages(mpnt);
 223                         vx_vmpages_sub(mm, pages);
 224                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 225                                                                 -pages);
 226                         continue;
 227                 }
 228                 charge = 0;
 229                 if (mpnt->vm_flags & VM_ACCOUNT) {
 230                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 231                         if (security_vm_enough_memory(len))
 232                                 goto fail_nomem;
 233                         charge = len;
 234                 }
 235                 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL);
 236                 if (!tmp)
 237                         goto fail_nomem;
 238                 *tmp = *mpnt;
 239                 pol = mpol_copy(vma_policy(mpnt));
 240                 retval = PTR_ERR(pol);
 241                 if (IS_ERR(pol))
 242                         goto fail_nomem_policy;
 243                 vma_set_policy(tmp, pol);
 244                 tmp->vm_flags &= ~VM_LOCKED;
 245                 tmp->vm_mm = mm;
 246                 tmp->vm_next = NULL;
 247                 anon_vma_link(tmp);
 248                 file = tmp->vm_file;
 249                 if (file) {
 250                         struct inode *inode = file->f_dentry->d_inode;
 251                         get_file(file);
 252                         if (tmp->vm_flags & VM_DENYWRITE)
 253                                 atomic_dec(&inode->i_writecount);
 254
 255                         /* insert tmp into the share list, just after mpnt */
 256                         spin_lock(&file->f_mapping->i_mmap_lock);
 257                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 258                         flush_dcache_mmap_lock(file->f_mapping);
 259                         vma_prio_tree_add(tmp, mpnt);
 260                         flush_dcache_mmap_unlock(file->f_mapping);
 261                         spin_unlock(&file->f_mapping->i_mmap_lock);
 262                 }
 263
 264                 /*
 265                  * Link in the new vma and copy the page table entries.
 266                  */
 267                 *pprev = tmp;
 268                 pprev = &tmp->vm_next;
 269
 270                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 271                 rb_link = &tmp->vm_rb.rb_right;
 272                 rb_parent = &tmp->vm_rb;
 273
 274                 mm->map_count++;
 275                 retval = copy_page_range(mm, oldmm, mpnt);
 276
 277                 if (tmp->vm_ops && tmp->vm_ops->open)
 278                         tmp->vm_ops->open(tmp);
 279
 280                 if (retval)
 281                         goto out;
 282         }
 283 #ifdef arch_dup_mmap
 284         arch_dup_mmap(mm, oldmm);
 285 #endif
 286         retval = 0;
 287 out:
 288         up_write(&mm->mmap_sem);
 289         flush_tlb_mm(oldmm);
 290         up_write(&oldmm->mmap_sem);
 291         return retval;
 292 fail_nomem_policy:
 293         kmem_cache_free(vm_area_cachep, tmp);
 294 fail_nomem:
 295         retval = -ENOMEM;
 296         vm_unacct_memory(charge);
 297         goto out;
 298 }
 299
 300 static inline int mm_alloc_pgd(struct mm_struct * mm)
 301 {
 302         mm->pgd = pgd_alloc(mm);
 303         if (unlikely(!mm->pgd))
 304                 return -ENOMEM;
 305         return 0;
 306 }
 307
 308 static inline void mm_free_pgd(struct mm_struct * mm)
 309 {
 310         pgd_free(mm->pgd);
 311 }
 312 #else
 313 #define dup_mmap(mm, oldmm)     (0)
 314 #define mm_alloc_pgd(mm)        (0)
 315 #define mm_free_pgd(mm)
 316 #endif /* CONFIG_MMU */
 317
 318  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 319
 320 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, SLAB_KERNEL))
 321 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 322
 323 #include <linux/init_task.h>
 324
 325 static struct mm_struct * mm_init(struct mm_struct * mm)
 326 {
 327         atomic_set(&mm->mm_users, 1);
 328         atomic_set(&mm->mm_count, 1);
 329         init_rwsem(&mm->mmap_sem);
 330         INIT_LIST_HEAD(&mm->mmlist);
 331         mm->core_waiters = 0;
 332         mm->nr_ptes = 0;
 333         spin_lock_init(&mm->page_table_lock);
 334         rwlock_init(&mm->ioctx_list_lock);
 335         mm->ioctx_list = NULL;
 336         mm->free_area_cache = TASK_UNMAPPED_BASE;
 337         mm->cached_hole_size = ~0UL;
 338
 339         if (likely(!mm_alloc_pgd(mm))) {
 340                 mm->def_flags = 0;
 341                 set_vx_info(&mm->mm_vx_info, current->vx_info);
 342                 return mm;
 343         }
 344         free_mm(mm);
 345         return NULL;
 346 }
 347
 348 /*
 349  * Allocate and initialize an mm_struct.
 350  */
 351 struct mm_struct * mm_alloc(void)
 352 {
 353         struct mm_struct * mm;
 354
 355         mm = allocate_mm();
 356         if (mm) {
 357                 memset(mm, 0, sizeof(*mm));
 358                 mm = mm_init(mm);
 359         }
 360         return mm;
 361 }
 362
 363 /*
 364  * Called when the last reference to the mm
 365  * is dropped: either by a lazy thread or by
 366  * mmput. Free the page directory and the mm.
 367  */
 368 void fastcall __mmdrop(struct mm_struct *mm)
 369 {
 370         BUG_ON(mm == &init_mm);
 371         mm_free_pgd(mm);
 372         destroy_context(mm);
 373         clr_vx_info(&mm->mm_vx_info);
 374         free_mm(mm);
 375 }
 376
 377 /*
 378  * Decrement the use count and release all resources for an mm.
 379  */
 380 void mmput(struct mm_struct *mm)
 381 {
 382         if (atomic_dec_and_test(&mm->mm_users)) {
 383                 exit_aio(mm);
 384                 exit_mmap(mm);
 385                 if (!list_empty(&mm->mmlist)) {
 386                         spin_lock(&mmlist_lock);
 387                         list_del(&mm->mmlist);
 388                         spin_unlock(&mmlist_lock);
 389                 }
 390                 put_swap_token(mm);
 391                 mmdrop(mm);
 392         }
 393 }
 394 EXPORT_SYMBOL_GPL(mmput);
 395
 396 /**
 397  * get_task_mm - acquire a reference to the task's mm
 398  *
 399  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 400  * this kernel workthread has transiently adopted a user mm with use_mm,
 401  * to do its AIO) is not set and if so returns a reference to it, after
 402  * bumping up the use count.  User must release the mm via mmput()
 403  * after use.  Typically used by /proc and ptrace.
 404  */
 405 struct mm_struct *get_task_mm(struct task_struct *task)
 406 {
 407         struct mm_struct *mm;
 408
 409         task_lock(task);
 410         mm = task->mm;
 411         if (mm) {
 412                 if (task->flags & PF_BORROWED_MM)
 413                         mm = NULL;
 414                 else
 415                         atomic_inc(&mm->mm_users);
 416         }
 417         task_unlock(task);
 418         return mm;
 419 }
 420 EXPORT_SYMBOL_GPL(get_task_mm);
 421
 422 /* Please note the differences between mmput and mm_release.
 423  * mmput is called whenever we stop holding onto a mm_struct,
 424  * error success whatever.
 425  *
 426  * mm_release is called after a mm_struct has been removed
 427  * from the current process.
 428  *
 429  * This difference is important for error handling, when we
 430  * only half set up a mm_struct for a new process and need to restore
 431  * the old one.  Because we mmput the new mm_struct before
 432  * restoring the old one. . .
 433  * Eric Biederman 10 January 1998
 434  */
 435 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 436 {
 437         struct completion *vfork_done = tsk->vfork_done;
 438
 439         /* Get rid of any cached register state */
 440         deactivate_mm(tsk, mm);
 441
 442         /* notify parent sleeping on vfork() */
 443         if (vfork_done) {
 444                 tsk->vfork_done = NULL;
 445                 complete(vfork_done);
 446         }
 447         if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) {
 448                 u32 __user * tidptr = tsk->clear_child_tid;
 449                 tsk->clear_child_tid = NULL;
 450
 451                 /*
 452                  * We don't check the error code - if userspace has
 453                  * not set up a proper pointer then tough luck.
 454                  */
 455                 put_user(0, tidptr);
 456                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 457         }
 458 }
 459
 460 /*
 461  * Allocate a new mm structure and copy contents from the
 462  * mm structure of the passed in task structure.
 463  */
 464 static struct mm_struct *dup_mm(struct task_struct *tsk)
 465 {
 466         struct mm_struct *mm, *oldmm = current->mm;
 467         int err;
 468
 469         if (!oldmm)
 470                 return NULL;
 471
 472         mm = allocate_mm();
 473         if (!mm)
 474                 goto fail_nomem;
 475
 476         memcpy(mm, oldmm, sizeof(*mm));
 477         mm->mm_vx_info = NULL;
 478
 479         if (!mm_init(mm))
 480                 goto fail_nomem;
 481
 482         if (init_new_context(tsk, mm))
 483                 goto fail_nocontext;
 484
 485         err = dup_mmap(mm, oldmm);
 486         if (err)
 487                 goto free_pt;
 488
 489         mm->hiwater_rss = get_mm_rss(mm);
 490         mm->hiwater_vm = mm->total_vm;
 491
 492         return mm;
 493
 494 free_pt:
 495         mmput(mm);
 496
 497 fail_nomem:
 498         return NULL;
 499
 500 fail_nocontext:
 501         /*
 502          * If init_new_context() failed, we cannot use mmput() to free the mm
 503          * because it calls destroy_context()
 504          */
 505         clr_vx_info(&mm->mm_vx_info);
 506         mm_free_pgd(mm);
 507         free_mm(mm);
 508         return NULL;
 509 }
 510
 511 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 512 {
 513         struct mm_struct * mm, *oldmm;
 514         int retval;
 515
 516         tsk->min_flt = tsk->maj_flt = 0;
 517         tsk->nvcsw = tsk->nivcsw = 0;
 518
 519         tsk->mm = NULL;
 520         tsk->active_mm = NULL;
 521
 522         /*
 523          * Are we cloning a kernel thread?
 524          *
 525          * We need to steal a active VM for that..
 526          */
 527         oldmm = current->mm;
 528         if (!oldmm)
 529                 return 0;
 530
 531         if (clone_flags & CLONE_VM) {
 532                 atomic_inc(&oldmm->mm_users);
 533                 mm = oldmm;
 534                 goto good_mm;
 535         }
 536
 537         retval = -ENOMEM;
 538         mm = dup_mm(tsk);
 539         if (!mm)
 540                 goto fail_nomem;
 541
 542 good_mm:
 543         tsk->mm = mm;
 544         tsk->active_mm = mm;
 545         return 0;
 546
 547 fail_nomem:
 548         return retval;
 549 }
 550
 551 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 552 {
 553         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 554         /* We don't need to lock fs - think why ;-) */
 555         if (fs) {
 556                 atomic_set(&fs->count, 1);
 557                 rwlock_init(&fs->lock);
 558                 fs->umask = old->umask;
 559                 read_lock(&old->lock);
 560                 fs->rootmnt = mntget(old->rootmnt);
 561                 fs->root = dget(old->root);
 562                 fs->pwdmnt = mntget(old->pwdmnt);
 563                 fs->pwd = dget(old->pwd);
 564                 if (old->altroot) {
 565                         fs->altrootmnt = mntget(old->altrootmnt);
 566                         fs->altroot = dget(old->altroot);
 567                 } else {
 568                         fs->altrootmnt = NULL;
 569                         fs->altroot = NULL;
 570                 }
 571                 read_unlock(&old->lock);
 572         }
 573         return fs;
 574 }
 575
 576 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 577 {
 578         return __copy_fs_struct(old);
 579 }
 580
 581 EXPORT_SYMBOL_GPL(copy_fs_struct);
 582
 583 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
 584 {
 585         if (clone_flags & CLONE_FS) {
 586                 atomic_inc(&current->fs->count);
 587                 return 0;
 588         }
 589         tsk->fs = __copy_fs_struct(current->fs);
 590         if (!tsk->fs)
 591                 return -ENOMEM;
 592         return 0;
 593 }
 594
 595 static int count_open_files(struct fdtable *fdt)
 596 {
 597         int size = fdt->max_fdset;
 598         int i;
 599
 600         /* Find the last open fd */
 601         for (i = size/(8*sizeof(long)); i > 0; ) {
 602                 if (fdt->open_fds->fds_bits[--i])
 603                         break;
 604         }
 605         i = (i+1) * 8 * sizeof(long);
 606         return i;
 607 }
 608
 609 static struct files_struct *alloc_files(void)
 610 {
 611         struct files_struct *newf;
 612         struct fdtable *fdt;
 613
 614         newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
 615         if (!newf)
 616                 goto out;
 617
 618         atomic_set(&newf->count, 1);
 619
 620         spin_lock_init(&newf->file_lock);
 621         newf->next_fd = 0;
 622         fdt = &newf->fdtab;
 623         fdt->max_fds = NR_OPEN_DEFAULT;
 624         fdt->max_fdset = EMBEDDED_FD_SET_SIZE;
 625         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
 626         fdt->open_fds = (fd_set *)&newf->open_fds_init;
 627         fdt->fd = &newf->fd_array[0];
 628         INIT_RCU_HEAD(&fdt->rcu);
 629         fdt->free_files = NULL;
 630         fdt->next = NULL;
 631         rcu_assign_pointer(newf->fdt, fdt);
 632 out:
 633         return newf;
 634 }
 635
 636 /*
 637  * Allocate a new files structure and copy contents from the
 638  * passed in files structure.
 639  */
 640 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 641 {
 642         struct files_struct *newf;
 643         struct file **old_fds, **new_fds;
 644         int open_files, size, i, expand;
 645         struct fdtable *old_fdt, *new_fdt;
 646
 647         newf = alloc_files();
 648         if (!newf)
 649                 goto out;
 650
 651         spin_lock(&oldf->file_lock);
 652         old_fdt = files_fdtable(oldf);
 653         new_fdt = files_fdtable(newf);
 654         size = old_fdt->max_fdset;
 655         open_files = count_open_files(old_fdt);
 656         expand = 0;
 657
 658         /*
 659          * Check whether we need to allocate a larger fd array or fd set.
 660          * Note: we're not a clone task, so the open count won't  change.
 661          */
 662         if (open_files > new_fdt->max_fdset) {
 663                 new_fdt->max_fdset = 0;
 664                 expand = 1;
 665         }
 666         if (open_files > new_fdt->max_fds) {
 667                 new_fdt->max_fds = 0;
 668                 expand = 1;
 669         }
 670
 671         /* if the old fdset gets grown now, we'll only copy up to "size" fds */
 672         if (expand) {
 673                 spin_unlock(&oldf->file_lock);
 674                 spin_lock(&newf->file_lock);
 675                 *errorp = expand_files(newf, open_files-1);
 676                 spin_unlock(&newf->file_lock);
 677                 if (*errorp < 0)
 678                         goto out_release;
 679                 new_fdt = files_fdtable(newf);
 680                 /*
 681                  * Reacquire the oldf lock and a pointer to its fd table
 682                  * who knows it may have a new bigger fd table. We need
 683                  * the latest pointer.
 684                  */
 685                 spin_lock(&oldf->file_lock);
 686                 old_fdt = files_fdtable(oldf);
 687         }
 688
 689         old_fds = old_fdt->fd;
 690         new_fds = new_fdt->fd;
 691
 692         memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8);
 693         memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8);
 694
 695         for (i = open_files; i != 0; i--) {
 696                 struct file *f = *old_fds++;
 697                 if (f) {
 698                         get_file(f);
 699                         /* FIXME: sum it first for check and performance */
 700                         vx_openfd_inc(open_files - i);
 701                 } else {
 702                         /*
 703                          * The fd may be claimed in the fd bitmap but not yet
 704                          * instantiated in the files array if a sibling thread
 705                          * is partway through open().  So make sure that this
 706                          * fd is available to the new process.
 707                          */
 708                         FD_CLR(open_files - i, new_fdt->open_fds);
 709                 }
 710                 rcu_assign_pointer(*new_fds++, f);
 711         }
 712         spin_unlock(&oldf->file_lock);
 713
 714         /* compute the remainder to be cleared */
 715         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 716
 717         /* This is long word aligned thus could use a optimized version */
 718         memset(new_fds, 0, size);
 719
 720         if (new_fdt->max_fdset > open_files) {
 721                 int left = (new_fdt->max_fdset-open_files)/8;
 722                 int start = open_files / (8 * sizeof(unsigned long));
 723
 724                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
 725                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 726         }
 727
 728 out:
 729         return newf;
 730
 731 out_release:
 732         free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset);
 733         free_fdset (new_fdt->open_fds, new_fdt->max_fdset);
 734         free_fd_array(new_fdt->fd, new_fdt->max_fds);
 735         kmem_cache_free(files_cachep, newf);
 736         return NULL;
 737 }
 738
 739 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 740 {
 741         struct files_struct *oldf, *newf;
 742         int error = 0;
 743
 744         /*
 745          * A background process may not have any files ...
 746          */
 747         oldf = current->files;
 748         if (!oldf)
 749                 goto out;
 750
 751         if (clone_flags & CLONE_FILES) {
 752                 atomic_inc(&oldf->count);
 753                 goto out;
 754         }
 755
 756         /*
 757          * Note: we may be using current for both targets (See exec.c)
 758          * This works because we cache current->files (old) as oldf. Don't
 759          * break this.
 760          */
 761         tsk->files = NULL;
 762         error = -ENOMEM;
 763         newf = dup_fd(oldf, &error);
 764         if (!newf)
 765                 goto out;
 766
 767         tsk->files = newf;
 768         error = 0;
 769 out:
 770         return error;
 771 }
 772
 773 /*
 774  *      Helper to unshare the files of the current task.
 775  *      We don't want to expose copy_files internals to
 776  *      the exec layer of the kernel.
 777  */
 778
 779 int unshare_files(void)
 780 {
 781         struct files_struct *files  = current->files;
 782         int rc;
 783
 784         BUG_ON(!files);
 785
 786         /* This can race but the race causes us to copy when we don't
 787            need to and drop the copy */
 788         if(atomic_read(&files->count) == 1)
 789         {
 790                 atomic_inc(&files->count);
 791                 return 0;
 792         }
 793         rc = copy_files(0, current);
 794         if(rc)
 795                 current->files = files;
 796         return rc;
 797 }
 798
 799 EXPORT_SYMBOL(unshare_files);
 800
 801 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
 802 {
 803         struct sighand_struct *sig;
 804
 805         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 806                 atomic_inc(&current->sighand->count);
 807                 return 0;
 808         }
 809         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 810         rcu_assign_pointer(tsk->sighand, sig);
 811         if (!sig)
 812                 return -ENOMEM;
 813         atomic_set(&sig->count, 1);
 814         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 815         return 0;
 816 }
 817
 818 void __cleanup_sighand(struct sighand_struct *sighand)
 819 {
 820         if (atomic_dec_and_test(&sighand->count))
 821                 kmem_cache_free(sighand_cachep, sighand);
 822 }
 823
 824 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
 825 {
 826         struct signal_struct *sig;
 827         int ret;
 828
 829         if (clone_flags & CLONE_THREAD) {
 830                 atomic_inc(&current->signal->count);
 831                 atomic_inc(&current->signal->live);
 832                 return 0;
 833         }
 834         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 835         tsk->signal = sig;
 836         if (!sig)
 837                 return -ENOMEM;
 838
 839         ret = copy_thread_group_keys(tsk);
 840         if (ret < 0) {
 841                 kmem_cache_free(signal_cachep, sig);
 842                 return ret;
 843         }
 844
 845         atomic_set(&sig->count, 1);
 846         atomic_set(&sig->live, 1);
 847         init_waitqueue_head(&sig->wait_chldexit);
 848         sig->flags = 0;
 849         sig->group_exit_code = 0;
 850         sig->group_exit_task = NULL;
 851         sig->group_stop_count = 0;
 852         sig->curr_target = NULL;
 853         init_sigpending(&sig->shared_pending);
 854         INIT_LIST_HEAD(&sig->posix_timers);
 855
 856         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_REL);
 857         sig->it_real_incr.tv64 = 0;
 858         sig->real_timer.function = it_real_fn;
 859         sig->tsk = tsk;
 860
 861         sig->it_virt_expires = cputime_zero;
 862         sig->it_virt_incr = cputime_zero;
 863         sig->it_prof_expires = cputime_zero;
 864         sig->it_prof_incr = cputime_zero;
 865
 866         sig->leader = 0;        /* session leadership doesn't inherit */
 867         sig->tty_old_pgrp = 0;
 868
 869         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 870         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 871         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 872         sig->sched_time = 0;
 873         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 874         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 875         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 876
 877         task_lock(current->group_leader);
 878         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 879         task_unlock(current->group_leader);
 880
 881         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 882                 /*
 883                  * New sole thread in the process gets an expiry time
 884                  * of the whole CPU time limit.
 885                  */
 886                 tsk->it_prof_expires =
 887                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 888         }
 889
 890         return 0;
 891 }
 892
 893 void __cleanup_signal(struct signal_struct *sig)
 894 {
 895         exit_thread_group_keys(sig);
 896         kmem_cache_free(signal_cachep, sig);
 897 }
 898
 899 static inline void cleanup_signal(struct task_struct *tsk)
 900 {
 901         struct signal_struct *sig = tsk->signal;
 902
 903         atomic_dec(&sig->live);
 904
 905         if (atomic_dec_and_test(&sig->count))
 906                 __cleanup_signal(sig);
 907 }
 908
 909 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
 910 {
 911         unsigned long new_flags = p->flags;
 912
 913         new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE);
 914         new_flags |= PF_FORKNOEXEC;
 915         if (!(clone_flags & CLONE_PTRACE))
 916                 p->ptrace = 0;
 917         p->flags = new_flags;
 918 }
 919
 920 asmlinkage long sys_set_tid_address(int __user *tidptr)
 921 {
 922         current->clear_child_tid = tidptr;
 923
 924         return current->pid;
 925 }
 926
 927 /*
 928  * This creates a new process as a copy of the old one,
 929  * but does not actually start it yet.
 930  *
 931  * It copies the registers, and all the appropriate
 932  * parts of the process environment (as per the clone
 933  * flags). The actual kick-off is left to the caller.
 934  */
 935 static task_t *copy_process(unsigned long clone_flags,
 936                                  unsigned long stack_start,
 937                                  struct pt_regs *regs,
 938                                  unsigned long stack_size,
 939                                  int __user *parent_tidptr,
 940                                  int __user *child_tidptr,
 941                                  int pid)
 942 {
 943         int retval;
 944         struct task_struct *p = NULL;
 945         struct vx_info *vxi;
 946         struct nx_info *nxi;
 947
 948         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 949                 return ERR_PTR(-EINVAL);
 950
 951         /*
 952          * Thread groups must share signals as well, and detached threads
 953          * can only be started up within the thread group.
 954          */
 955         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 956                 return ERR_PTR(-EINVAL);
 957
 958         /*
 959          * Shared signal handlers imply shared VM. By way of the above,
 960          * thread groups also imply shared VM. Blocking this case allows
 961          * for various simplifications in other code.
 962          */
 963         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 964                 return ERR_PTR(-EINVAL);
 965
 966         retval = security_task_create(clone_flags);
 967         if (retval)
 968                 goto fork_out;
 969
 970         retval = -ENOMEM;
 971         p = dup_task_struct(current);
 972         if (!p)
 973                 goto fork_out;
 974         p->tux_info = NULL;
 975
 976         init_vx_info(&p->vx_info, current->vx_info);
 977         init_nx_info(&p->nx_info, current->nx_info);
 978
 979         /* check vserver memory */
 980         if (p->mm && !(clone_flags & CLONE_VM)) {
 981                 if (vx_vmpages_avail(p->mm, p->mm->total_vm))
 982                         vx_pages_add(p->vx_info, RLIMIT_AS, p->mm->total_vm);
 983                 else
 984                         goto bad_fork_free;
 985         }
 986         if (p->mm && vx_flags(VXF_FORK_RSS, 0)) {
 987                 if (!vx_rsspages_avail(p->mm, get_mm_counter(p->mm, file_rss)))
 988                         goto bad_fork_cleanup_vm;
 989         }
 990
 991         retval = -EAGAIN;
 992         if (!vx_nproc_avail(1))
 993                 goto bad_fork_cleanup_vm;
 994
 995         if (atomic_read(&p->user->processes) >=
 996                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 997                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 998                                 p->user != &root_user)
 999                         goto bad_fork_cleanup_vm;
1000         }
1001
1002         atomic_inc(&p->user->__count);
1003         atomic_inc(&p->user->processes);
1004         get_group_info(p->group_info);
1005
1006         /*
1007          * If multiple threads are within copy_process(), then this check
1008          * triggers too late. This doesn't hurt, the check is only there
1009          * to stop root fork bombs.
1010          */
1011         if (nr_threads >= max_threads)
1012                 goto bad_fork_cleanup_count;
1013
1014         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1015                 goto bad_fork_cleanup_count;
1016
1017         if (p->binfmt && !try_module_get(p->binfmt->module))
1018                 goto bad_fork_cleanup_put_domain;
1019
1020         p->did_exec = 0;
1021         copy_flags(clone_flags, p);
1022         p->pid = pid;
1023         retval = -EFAULT;
1024         if (clone_flags & CLONE_PARENT_SETTID)
1025                 if (put_user(p->pid, parent_tidptr))
1026                         goto bad_fork_cleanup;
1027
1028         p->proc_dentry = NULL;
1029
1030         INIT_LIST_HEAD(&p->children);
1031         INIT_LIST_HEAD(&p->sibling);
1032         p->vfork_done = NULL;
1033         spin_lock_init(&p->alloc_lock);
1034         spin_lock_init(&p->proc_lock);
1035
1036         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1037         init_sigpending(&p->pending);
1038
1039         p->utime = cputime_zero;
1040         p->stime = cputime_zero;
1041         p->sched_time = 0;
1042         p->rchar = 0;           /* I/O counter: bytes read */
1043         p->wchar = 0;           /* I/O counter: bytes written */
1044         p->syscr = 0;           /* I/O counter: read syscalls */
1045         p->syscw = 0;           /* I/O counter: write syscalls */
1046         acct_clear_integrals(p);
1047
1048         p->it_virt_expires = cputime_zero;
1049         p->it_prof_expires = cputime_zero;
1050         p->it_sched_expires = 0;
1051         INIT_LIST_HEAD(&p->cpu_timers[0]);
1052         INIT_LIST_HEAD(&p->cpu_timers[1]);
1053         INIT_LIST_HEAD(&p->cpu_timers[2]);
1054
1055         p->lock_depth = -1;             /* -1 = no lock */
1056         do_posix_clock_monotonic_gettime(&p->start_time);
1057         p->security = NULL;
1058         p->io_context = NULL;
1059         p->io_wait = NULL;
1060         p->audit_context = NULL;
1061         cpuset_fork(p);
1062 #ifdef CONFIG_NUMA
1063         p->mempolicy = mpol_copy(p->mempolicy);
1064         if (IS_ERR(p->mempolicy)) {
1065                 retval = PTR_ERR(p->mempolicy);
1066                 p->mempolicy = NULL;
1067                 goto bad_fork_cleanup_cpuset;
1068         }
1069         mpol_fix_fork_child_flag(p);
1070 #endif
1071
1072 #ifdef CONFIG_DEBUG_MUTEXES
1073         p->blocked_on = NULL; /* not blocked yet */
1074 #endif
1075
1076         p->tgid = p->pid;
1077         if (clone_flags & CLONE_THREAD)
1078                 p->tgid = current->tgid;
1079
1080         if ((retval = security_task_alloc(p)))
1081                 goto bad_fork_cleanup_policy;
1082         if ((retval = audit_alloc(p)))
1083                 goto bad_fork_cleanup_security;
1084         /* copy all the process information */
1085         if ((retval = copy_semundo(clone_flags, p)))
1086                 goto bad_fork_cleanup_audit;
1087         if ((retval = copy_files(clone_flags, p)))
1088                 goto bad_fork_cleanup_semundo;
1089         if ((retval = copy_fs(clone_flags, p)))
1090                 goto bad_fork_cleanup_files;
1091         if ((retval = copy_sighand(clone_flags, p)))
1092                 goto bad_fork_cleanup_fs;
1093         if ((retval = copy_signal(clone_flags, p)))
1094                 goto bad_fork_cleanup_sighand;
1095         if ((retval = copy_mm(clone_flags, p)))
1096                 goto bad_fork_cleanup_signal;
1097         if ((retval = copy_keys(clone_flags, p)))
1098                 goto bad_fork_cleanup_mm;
1099         if ((retval = copy_namespace(clone_flags, p)))
1100                 goto bad_fork_cleanup_keys;
1101         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1102         if (retval)
1103                 goto bad_fork_cleanup_namespace;
1104
1105         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1106         /*
1107          * Clear TID on mm_release()?
1108          */
1109         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1110         p->robust_list = NULL;
1111 #ifdef CONFIG_COMPAT
1112         p->compat_robust_list = NULL;
1113 #endif
1114         /*
1115          * sigaltstack should be cleared when sharing the same VM
1116          */
1117         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1118                 p->sas_ss_sp = p->sas_ss_size = 0;
1119
1120         /*
1121          * Syscall tracing should be turned off in the child regardless
1122          * of CLONE_PTRACE.
1123          */
1124         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1125 #ifdef TIF_SYSCALL_EMU
1126         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1127 #endif
1128
1129         /* Our parent execution domain becomes current domain
1130            These must match for thread signalling to apply */
1131
1132         p->parent_exec_id = p->self_exec_id;
1133
1134         /* ok, now we should be set up.. */
1135         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1136         p->pdeath_signal = 0;
1137         p->exit_state = 0;
1138
1139         /*
1140          * Ok, make it visible to the rest of the system.
1141          * We dont wake it up yet.
1142          */
1143         p->group_leader = p;
1144         INIT_LIST_HEAD(&p->thread_group);
1145         INIT_LIST_HEAD(&p->ptrace_children);
1146         INIT_LIST_HEAD(&p->ptrace_list);
1147
1148         /* Perform scheduler related setup. Assign this task to a CPU. */
1149         sched_fork(p, clone_flags);
1150
1151         /* Need tasklist lock for parent etc handling! */
1152         write_lock_irq(&tasklist_lock);
1153
1154         /*
1155          * The task hasn't been attached yet, so its cpus_allowed mask will
1156          * not be changed, nor will its assigned CPU.
1157          *
1158          * The cpus_allowed mask of the parent may have changed after it was
1159          * copied first time - so re-copy it here, then check the child's CPU
1160          * to ensure it is on a valid CPU (and if not, just force it back to
1161          * parent's CPU). This avoids alot of nasty races.
1162          */
1163         p->cpus_allowed = current->cpus_allowed;
1164         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1165                         !cpu_online(task_cpu(p))))
1166                 set_task_cpu(p, smp_processor_id());
1167
1168         /* CLONE_PARENT re-uses the old parent */
1169         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1170                 p->real_parent = current->real_parent;
1171         else
1172                 p->real_parent = current;
1173         p->parent = p->real_parent;
1174
1175         spin_lock(&current->sighand->siglock);
1176
1177         /*
1178          * Process group and session signals need to be delivered to just the
1179          * parent before the fork or both the parent and the child after the
1180          * fork. Restart if a signal comes in before we add the new process to
1181          * it's process group.
1182          * A fatal signal pending means that current will exit, so the new
1183          * thread can't slip out of an OOM kill (or normal SIGKILL).
1184          */
1185         recalc_sigpending();
1186         if (signal_pending(current)) {
1187                 spin_unlock(&current->sighand->siglock);
1188                 write_unlock_irq(&tasklist_lock);
1189                 retval = -ERESTARTNOINTR;
1190                 goto bad_fork_cleanup_namespace;
1191         }
1192
1193         if (clone_flags & CLONE_THREAD) {
1194                 /*
1195                  * Important: if an exit-all has been started then
1196                  * do not create this new thread - the whole thread
1197                  * group is supposed to exit anyway.
1198                  */
1199                 if (current->signal->flags & SIGNAL_GROUP_EXIT) {
1200                         spin_unlock(&current->sighand->siglock);
1201                         write_unlock_irq(&tasklist_lock);
1202                         retval = -EAGAIN;
1203                         goto bad_fork_cleanup_namespace;
1204                 }
1205
1206                 p->group_leader = current->group_leader;
1207                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1208
1209                 if (!cputime_eq(current->signal->it_virt_expires,
1210                                 cputime_zero) ||
1211                     !cputime_eq(current->signal->it_prof_expires,
1212                                 cputime_zero) ||
1213                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1214                     !list_empty(&current->signal->cpu_timers[0]) ||
1215                     !list_empty(&current->signal->cpu_timers[1]) ||
1216                     !list_empty(&current->signal->cpu_timers[2])) {
1217                         /*
1218                          * Have child wake up on its first tick to check
1219                          * for process CPU timers.
1220                          */
1221                         p->it_prof_expires = jiffies_to_cputime(1);
1222                 }
1223         }
1224
1225         /*
1226          * inherit ioprio
1227          */
1228         p->ioprio = current->ioprio;
1229
1230         if (likely(p->pid)) {
1231                 add_parent(p);
1232                 if (unlikely(p->ptrace & PT_PTRACED))
1233                         __ptrace_link(p, current->parent);
1234
1235                 if (thread_group_leader(p)) {
1236                         p->signal->tty = current->signal->tty;
1237                         p->signal->pgrp = process_group(current);
1238                         p->signal->session = current->signal->session;
1239                         attach_pid(p, PIDTYPE_PGID, process_group(p));
1240                         attach_pid(p, PIDTYPE_SID, p->signal->session);
1241
1242                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1243                         __get_cpu_var(process_counts)++;
1244                 }
1245                 attach_pid(p, PIDTYPE_PID, p->pid);
1246                 nr_threads++;
1247         }
1248
1249         total_forks++;
1250         spin_unlock(&current->sighand->siglock);
1251
1252         /* p is copy of current */
1253         vxi = p->vx_info;
1254         if (vxi) {
1255                 claim_vx_info(vxi, p);
1256                 atomic_inc(&vxi->cvirt.nr_threads);
1257                 atomic_inc(&vxi->cvirt.total_forks);
1258                 vx_nproc_inc(p);
1259         }
1260         nxi = p->nx_info;
1261         if (nxi)
1262                 claim_nx_info(nxi, p);
1263         write_unlock_irq(&tasklist_lock);
1264         proc_fork_connector(p);
1265         return p;
1266
1267 bad_fork_cleanup_namespace:
1268         exit_namespace(p);
1269 bad_fork_cleanup_keys:
1270         exit_keys(p);
1271 bad_fork_cleanup_mm:
1272         if (p->mm)
1273                 mmput(p->mm);
1274 bad_fork_cleanup_signal:
1275         cleanup_signal(p);
1276 bad_fork_cleanup_sighand:
1277         __cleanup_sighand(p->sighand);
1278 bad_fork_cleanup_fs:
1279         exit_fs(p); /* blocking */
1280 bad_fork_cleanup_files:
1281         exit_files(p); /* blocking */
1282 bad_fork_cleanup_semundo:
1283         exit_sem(p);
1284 bad_fork_cleanup_audit:
1285         audit_free(p);
1286 bad_fork_cleanup_security:
1287         security_task_free(p);
1288 bad_fork_cleanup_policy:
1289 #ifdef CONFIG_NUMA
1290         mpol_free(p->mempolicy);
1291 bad_fork_cleanup_cpuset:
1292 #endif
1293         cpuset_exit(p);
1294 bad_fork_cleanup:
1295         if (p->binfmt)
1296                 module_put(p->binfmt->module);
1297 bad_fork_cleanup_put_domain:
1298         module_put(task_thread_info(p)->exec_domain->module);
1299 bad_fork_cleanup_count:
1300         put_group_info(p->group_info);
1301         atomic_dec(&p->user->processes);
1302         free_uid(p->user);
1303 bad_fork_cleanup_vm:
1304         if (p->mm && !(clone_flags & CLONE_VM))
1305                 vx_pages_sub(p->vx_info, RLIMIT_AS, p->mm->total_vm);
1306 bad_fork_free:
1307         free_task(p);
1308 fork_out:
1309         return ERR_PTR(retval);
1310 }
1311
1312 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1313 {
1314         memset(regs, 0, sizeof(struct pt_regs));
1315         return regs;
1316 }
1317
1318 task_t * __devinit fork_idle(int cpu)
1319 {
1320         task_t *task;
1321         struct pt_regs regs;
1322
1323         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
1324         if (!task)
1325                 return ERR_PTR(-ENOMEM);
1326         init_idle(task, cpu);
1327
1328         return task;
1329 }
1330
1331 static inline int fork_traceflag (unsigned clone_flags)
1332 {
1333         if (clone_flags & CLONE_UNTRACED)
1334                 return 0;
1335         else if (clone_flags & CLONE_VFORK) {
1336                 if (current->ptrace & PT_TRACE_VFORK)
1337                         return PTRACE_EVENT_VFORK;
1338         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1339                 if (current->ptrace & PT_TRACE_CLONE)
1340                         return PTRACE_EVENT_CLONE;
1341         } else if (current->ptrace & PT_TRACE_FORK)
1342                 return PTRACE_EVENT_FORK;
1343
1344         return 0;
1345 }
1346
1347 /*
1348  *  Ok, this is the main fork-routine.
1349  *
1350  * It copies the process, and if successful kick-starts
1351  * it and waits for it to finish using the VM if required.
1352  */
1353 long do_fork(unsigned long clone_flags,
1354               unsigned long stack_start,
1355               struct pt_regs *regs,
1356               unsigned long stack_size,
1357               int __user *parent_tidptr,
1358               int __user *child_tidptr)
1359 {
1360         struct task_struct *p;
1361         int trace = 0;
1362         struct pid *pid = alloc_pid();
1363         long nr;
1364
1365         if (!pid)
1366                 return -EAGAIN;
1367         nr = pid->nr;
1368         if (unlikely(current->ptrace)) {
1369                 trace = fork_traceflag (clone_flags);
1370                 if (trace)
1371                         clone_flags |= CLONE_PTRACE;
1372         }
1373
1374         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
1375         /*
1376          * Do this prior waking up the new thread - the thread pointer
1377          * might get invalid after that point, if the thread exits quickly.
1378          */
1379         if (!IS_ERR(p)) {
1380                 struct completion vfork;
1381
1382                 if (clone_flags & CLONE_VFORK) {
1383                         p->vfork_done = &vfork;
1384                         init_completion(&vfork);
1385                 }
1386
1387                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1388                         /*
1389                          * We'll start up with an immediate SIGSTOP.
1390                          */
1391                         sigaddset(&p->pending.signal, SIGSTOP);
1392                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1393                 }
1394
1395                 if (!(clone_flags & CLONE_STOPPED))
1396                         wake_up_new_task(p, clone_flags);
1397                 else
1398                         p->state = TASK_STOPPED;
1399
1400                 if (unlikely (trace)) {
1401                         current->ptrace_message = nr;
1402                         ptrace_notify ((trace << 8) | SIGTRAP);
1403                 }
1404
1405                 if (clone_flags & CLONE_VFORK) {
1406                         wait_for_completion(&vfork);
1407                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE))
1408                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1409                 }
1410         } else {
1411                 free_pid(pid);
1412                 nr = PTR_ERR(p);
1413         }
1414         return nr;
1415 }
1416
1417 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1418 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1419 #endif
1420
1421 static void sighand_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
1422 {
1423         struct sighand_struct *sighand = data;
1424
1425         if ((flags & (SLAB_CTOR_VERIFY | SLAB_CTOR_CONSTRUCTOR)) ==
1426                                         SLAB_CTOR_CONSTRUCTOR)
1427                 spin_lock_init(&sighand->siglock);
1428 }
1429
1430 void __init proc_caches_init(void)
1431 {
1432         sighand_cachep = kmem_cache_create("sighand_cache",
1433                         sizeof(struct sighand_struct), 0,
1434                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1435                         sighand_ctor, NULL);
1436         signal_cachep = kmem_cache_create("signal_cache",
1437                         sizeof(struct signal_struct), 0,
1438                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1439         files_cachep = kmem_cache_create("files_cache",
1440                         sizeof(struct files_struct), 0,
1441                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1442         fs_cachep = kmem_cache_create("fs_cache",
1443                         sizeof(struct fs_struct), 0,
1444                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1445         vm_area_cachep = kmem_cache_create("vm_area_struct",
1446                         sizeof(struct vm_area_struct), 0,
1447                         SLAB_PANIC, NULL, NULL);
1448         mm_cachep = kmem_cache_create("mm_struct",
1449                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1450                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1451 }
1452
1453
1454 /*
1455  * Check constraints on flags passed to the unshare system call and
1456  * force unsharing of additional process context as appropriate.
1457  */
1458 static inline void check_unshare_flags(unsigned long *flags_ptr)
1459 {
1460         /*
1461          * If unsharing a thread from a thread group, must also
1462          * unshare vm.
1463          */
1464         if (*flags_ptr & CLONE_THREAD)
1465                 *flags_ptr |= CLONE_VM;
1466
1467         /*
1468          * If unsharing vm, must also unshare signal handlers.
1469          */
1470         if (*flags_ptr & CLONE_VM)
1471                 *flags_ptr |= CLONE_SIGHAND;
1472
1473         /*
1474          * If unsharing signal handlers and the task was created
1475          * using CLONE_THREAD, then must unshare the thread
1476          */
1477         if ((*flags_ptr & CLONE_SIGHAND) &&
1478             (atomic_read(&current->signal->count) > 1))
1479                 *flags_ptr |= CLONE_THREAD;
1480
1481         /*
1482          * If unsharing namespace, must also unshare filesystem information.
1483          */
1484         if (*flags_ptr & CLONE_NEWNS)
1485                 *flags_ptr |= CLONE_FS;
1486 }
1487
1488 /*
1489  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1490  */
1491 static int unshare_thread(unsigned long unshare_flags)
1492 {
1493         if (unshare_flags & CLONE_THREAD)
1494                 return -EINVAL;
1495
1496         return 0;
1497 }
1498
1499 /*
1500  * Unshare the filesystem structure if it is being shared
1501  */
1502 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1503 {
1504         struct fs_struct *fs = current->fs;
1505
1506         if ((unshare_flags & CLONE_FS) &&
1507             (fs && atomic_read(&fs->count) > 1)) {
1508                 *new_fsp = __copy_fs_struct(current->fs);
1509                 if (!*new_fsp)
1510                         return -ENOMEM;
1511         }
1512
1513         return 0;
1514 }
1515
1516 /*
1517  * Unshare the namespace structure if it is being shared
1518  */
1519 static int unshare_namespace(unsigned long unshare_flags, struct namespace **new_nsp, struct fs_struct *new_fs)
1520 {
1521         struct namespace *ns = current->namespace;
1522
1523         if ((unshare_flags & CLONE_NEWNS) &&
1524             (ns && atomic_read(&ns->count) > 1)) {
1525                 if (!capable(CAP_SYS_ADMIN))
1526                         return -EPERM;
1527
1528                 *new_nsp = dup_namespace(current, new_fs ? new_fs : current->fs);
1529                 if (!*new_nsp)
1530                         return -ENOMEM;
1531         }
1532
1533         return 0;
1534 }
1535
1536 /*
1537  * Unsharing of sighand for tasks created with CLONE_SIGHAND is not
1538  * supported yet
1539  */
1540 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1541 {
1542         struct sighand_struct *sigh = current->sighand;
1543
1544         if ((unshare_flags & CLONE_SIGHAND) &&
1545             (sigh && atomic_read(&sigh->count) > 1))
1546                 return -EINVAL;
1547         else
1548                 return 0;
1549 }
1550
1551 /*
1552  * Unshare vm if it is being shared
1553  */
1554 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1555 {
1556         struct mm_struct *mm = current->mm;
1557
1558         if ((unshare_flags & CLONE_VM) &&
1559             (mm && atomic_read(&mm->mm_users) > 1)) {
1560                 return -EINVAL;
1561         }
1562
1563         return 0;
1564 }
1565
1566 /*
1567  * Unshare file descriptor table if it is being shared
1568  */
1569 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1570 {
1571         struct files_struct *fd = current->files;
1572         int error = 0;
1573
1574         if ((unshare_flags & CLONE_FILES) &&
1575             (fd && atomic_read(&fd->count) > 1)) {
1576                 *new_fdp = dup_fd(fd, &error);
1577                 if (!*new_fdp)
1578                         return error;
1579         }
1580
1581         return 0;
1582 }
1583
1584 /*
1585  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1586  * supported yet
1587  */
1588 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1589 {
1590         if (unshare_flags & CLONE_SYSVSEM)
1591                 return -EINVAL;
1592
1593         return 0;
1594 }
1595
1596 /*
1597  * unshare allows a process to 'unshare' part of the process
1598  * context which was originally shared using clone.  copy_*
1599  * functions used by do_fork() cannot be used here directly
1600  * because they modify an inactive task_struct that is being
1601  * constructed. Here we are modifying the current, active,
1602  * task_struct.
1603  */
1604 asmlinkage long sys_unshare(unsigned long unshare_flags)
1605 {
1606         int err = 0;
1607         struct fs_struct *fs, *new_fs = NULL;
1608         struct namespace *ns, *new_ns = NULL;
1609         struct sighand_struct *sigh, *new_sigh = NULL;
1610         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1611         struct files_struct *fd, *new_fd = NULL;
1612         struct sem_undo_list *new_ulist = NULL;
1613
1614         check_unshare_flags(&unshare_flags);
1615
1616         /* Return -EINVAL for all unsupported flags */
1617         err = -EINVAL;
1618         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1619                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM))
1620                 goto bad_unshare_out;
1621
1622         if ((err = unshare_thread(unshare_flags)))
1623                 goto bad_unshare_out;
1624         if ((err = unshare_fs(unshare_flags, &new_fs)))
1625                 goto bad_unshare_cleanup_thread;
1626         if ((err = unshare_namespace(unshare_flags, &new_ns, new_fs)))
1627                 goto bad_unshare_cleanup_fs;
1628         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1629                 goto bad_unshare_cleanup_ns;
1630         if ((err = unshare_vm(unshare_flags, &new_mm)))
1631                 goto bad_unshare_cleanup_sigh;
1632         if ((err = unshare_fd(unshare_flags, &new_fd)))
1633                 goto bad_unshare_cleanup_vm;
1634         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1635                 goto bad_unshare_cleanup_fd;
1636
1637         if (new_fs || new_ns || new_sigh || new_mm || new_fd || new_ulist) {
1638
1639                 task_lock(current);
1640
1641                 if (new_fs) {
1642                         fs = current->fs;
1643                         current->fs = new_fs;
1644                         new_fs = fs;
1645                 }
1646
1647                 if (new_ns) {
1648                         ns = current->namespace;
1649                         current->namespace = new_ns;
1650                         new_ns = ns;
1651                 }
1652
1653                 if (new_sigh) {
1654                         sigh = current->sighand;
1655                         rcu_assign_pointer(current->sighand, new_sigh);
1656                         new_sigh = sigh;
1657                 }
1658
1659                 if (new_mm) {
1660                         mm = current->mm;
1661                         active_mm = current->active_mm;
1662                         current->mm = new_mm;
1663                         current->active_mm = new_mm;
1664                         activate_mm(active_mm, new_mm);
1665                         new_mm = mm;
1666                 }
1667
1668                 if (new_fd) {
1669                         fd = current->files;
1670                         current->files = new_fd;
1671                         new_fd = fd;
1672                 }
1673
1674                 task_unlock(current);
1675         }
1676
1677 bad_unshare_cleanup_fd:
1678         if (new_fd)
1679                 put_files_struct(new_fd);
1680
1681 bad_unshare_cleanup_vm:
1682         if (new_mm)
1683                 mmput(new_mm);
1684
1685 bad_unshare_cleanup_sigh:
1686         if (new_sigh)
1687                 if (atomic_dec_and_test(&new_sigh->count))
1688                         kmem_cache_free(sighand_cachep, new_sigh);
1689
1690 bad_unshare_cleanup_ns:
1691         if (new_ns)
1692                 put_namespace(new_ns);
1693
1694 bad_unshare_cleanup_fs:
1695         if (new_fs)
1696                 put_fs_struct(new_fs);
1697
1698 bad_unshare_cleanup_thread:
1699 bad_unshare_out:
1700         return err;
1701 }