kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/module.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/completion.h>
  20 #include <linux/mnt_namespace.h>
  21 #include <linux/personality.h>
  22 #include <linux/mempolicy.h>
  23 #include <linux/sem.h>
  24 #include <linux/file.h>
  25 #include <linux/key.h>
  26 #include <linux/binfmts.h>
  27 #include <linux/mman.h>
  28 #include <linux/fs.h>
  29 #include <linux/nsproxy.h>
  30 #include <linux/capability.h>
  31 #include <linux/cpu.h>
  32 #include <linux/cpuset.h>
  33 #include <linux/security.h>
  34 #include <linux/swap.h>
  35 #include <linux/syscalls.h>
  36 #include <linux/jiffies.h>
  37 #include <linux/futex.h>
  38 #include <linux/task_io_accounting_ops.h>
  39 #include <linux/rcupdate.h>
  40 #include <linux/ptrace.h>
  41 #include <linux/mount.h>
  42 #include <linux/audit.h>
  43 #include <linux/profile.h>
  44 #include <linux/rmap.h>
  45 #include <linux/acct.h>
  46 #include <linux/tsacct_kern.h>
  47 #include <linux/cn_proc.h>
  48 #include <linux/freezer.h>
  49 #include <linux/delayacct.h>
  50 #include <linux/taskstats_kern.h>
  51 #include <linux/random.h>
  52 #include <linux/tty.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 struct kmem_cache *task_struct_cachep;
  88 #endif
  89
  90 /* SLAB cache for signal_struct structures (tsk->signal) */
  91 static struct kmem_cache *signal_cachep;
  92
  93 /* SLAB cache for sighand_struct structures (tsk->sighand) */
  94 struct kmem_cache *sighand_cachep;
  95
  96 /* SLAB cache for files_struct structures (tsk->files) */
  97 struct kmem_cache *files_cachep;
  98
  99 /* SLAB cache for fs_struct structures (tsk->fs) */
 100 struct kmem_cache *fs_cachep;
 101
 102 /* SLAB cache for vm_area_struct structures */
 103 struct kmem_cache *vm_area_cachep;
 104
 105 /* SLAB cache for mm_struct structures (tsk->mm) */
 106 static struct kmem_cache *mm_cachep;
 107
 108 void free_task(struct task_struct *tsk)
 109 {
 110         free_thread_info(tsk->stack);
 111         rt_mutex_debug_task_free(tsk);
 112         free_task_struct(tsk);
 113 }
 114 EXPORT_SYMBOL(free_task);
 115
 116 void __put_task_struct(struct task_struct *tsk)
 117 {
 118         WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE)));
 119         WARN_ON(atomic_read(&tsk->usage));
 120         WARN_ON(tsk == current);
 121
 122         security_task_free(tsk);
 123         free_uid(tsk->user);
 124         put_group_info(tsk->group_info);
 125         delayacct_tsk_free(tsk);
 126
 127         if (!profile_handoff_task(tsk))
 128                 free_task(tsk);
 129 }
 130 EXPORT_SYMBOL_GPL(__put_task_struct);
 131
 132 void __init fork_init(unsigned long mempages)
 133 {
 134 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 135 #ifndef ARCH_MIN_TASKALIGN
 136 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 137 #endif
 138         /* create a slab on which task_structs can be allocated */
 139         task_struct_cachep =
 140                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 141                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL);
 142 #endif
 143
 144         /*
 145          * The default maximum number of threads is set to a safe
 146          * value: the thread structures can take up at most half
 147          * of memory.
 148          */
 149         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 150
 151         /*
 152          * we need to allow at least 20 threads to boot a system
 153          */
 154         if(max_threads < 20)
 155                 max_threads = 20;
 156
 157         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 158         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 159         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 160                 init_task.signal->rlim[RLIMIT_NPROC];
 161 }
 162
 163 static struct task_struct *dup_task_struct(struct task_struct *orig)
 164 {
 165         struct task_struct *tsk;
 166         struct thread_info *ti;
 167
 168         prepare_to_copy(orig);
 169
 170         tsk = alloc_task_struct();
 171         if (!tsk)
 172                 return NULL;
 173
 174         ti = alloc_thread_info(tsk);
 175         if (!ti) {
 176                 free_task_struct(tsk);
 177                 return NULL;
 178         }
 179
 180         *tsk = *orig;
 181         tsk->stack = ti;
 182         setup_thread_stack(tsk, orig);
 183
 184 #ifdef CONFIG_CC_STACKPROTECTOR
 185         tsk->stack_canary = get_random_int();
 186 #endif
 187
 188         /* One for us, one for whoever does the "release_task()" (usually parent) */
 189         atomic_set(&tsk->usage,2);
 190         atomic_set(&tsk->fs_excl, 0);
 191 #ifdef CONFIG_BLK_DEV_IO_TRACE
 192         tsk->btrace_seq = 0;
 193 #endif
 194         tsk->splice_pipe = NULL;
 195         return tsk;
 196 }
 197
 198 #ifdef CONFIG_MMU
 199 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 200 {
 201         struct vm_area_struct *mpnt, *tmp, **pprev;
 202         struct rb_node **rb_link, *rb_parent;
 203         int retval;
 204         unsigned long charge;
 205         struct mempolicy *pol;
 206
 207         down_write(&oldmm->mmap_sem);
 208         flush_cache_dup_mm(oldmm);
 209         /*
 210          * Not linked in yet - no deadlock potential:
 211          */
 212         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 213
 214         mm->locked_vm = 0;
 215         mm->mmap = NULL;
 216         mm->mmap_cache = NULL;
 217         mm->free_area_cache = oldmm->mmap_base;
 218         mm->cached_hole_size = ~0UL;
 219         mm->map_count = 0;
 220         cpus_clear(mm->cpu_vm_mask);
 221         mm->mm_rb = RB_ROOT;
 222         rb_link = &mm->mm_rb.rb_node;
 223         rb_parent = NULL;
 224         pprev = &mm->mmap;
 225
 226         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 227                 struct file *file;
 228
 229                 if (mpnt->vm_flags & VM_DONTCOPY) {
 230                         long pages = vma_pages(mpnt);
 231                         mm->total_vm -= pages;
 232                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 233                                                                 -pages);
 234                         continue;
 235                 }
 236                 charge = 0;
 237                 if (mpnt->vm_flags & VM_ACCOUNT) {
 238                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 239                         if (security_vm_enough_memory(len))
 240                                 goto fail_nomem;
 241                         charge = len;
 242                 }
 243                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 244                 if (!tmp)
 245                         goto fail_nomem;
 246                 *tmp = *mpnt;
 247                 pol = mpol_copy(vma_policy(mpnt));
 248                 retval = PTR_ERR(pol);
 249                 if (IS_ERR(pol))
 250                         goto fail_nomem_policy;
 251                 vma_set_policy(tmp, pol);
 252                 tmp->vm_flags &= ~VM_LOCKED;
 253                 tmp->vm_mm = mm;
 254                 tmp->vm_next = NULL;
 255                 anon_vma_link(tmp);
 256                 file = tmp->vm_file;
 257                 if (file) {
 258                         struct inode *inode = file->f_path.dentry->d_inode;
 259                         get_file(file);
 260                         if (tmp->vm_flags & VM_DENYWRITE)
 261                                 atomic_dec(&inode->i_writecount);
 262
 263                         /* insert tmp into the share list, just after mpnt */
 264                         spin_lock(&file->f_mapping->i_mmap_lock);
 265                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 266                         flush_dcache_mmap_lock(file->f_mapping);
 267                         vma_prio_tree_add(tmp, mpnt);
 268                         flush_dcache_mmap_unlock(file->f_mapping);
 269                         spin_unlock(&file->f_mapping->i_mmap_lock);
 270                 }
 271
 272                 /*
 273                  * Link in the new vma and copy the page table entries.
 274                  */
 275                 *pprev = tmp;
 276                 pprev = &tmp->vm_next;
 277
 278                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 279                 rb_link = &tmp->vm_rb.rb_right;
 280                 rb_parent = &tmp->vm_rb;
 281
 282                 mm->map_count++;
 283                 retval = copy_page_range(mm, oldmm, mpnt);
 284
 285                 if (tmp->vm_ops && tmp->vm_ops->open)
 286                         tmp->vm_ops->open(tmp);
 287
 288                 if (retval)
 289                         goto out;
 290         }
 291         /* a new mm has just been created */
 292         arch_dup_mmap(oldmm, mm);
 293         retval = 0;
 294 out:
 295         up_write(&mm->mmap_sem);
 296         flush_tlb_mm(oldmm);
 297         up_write(&oldmm->mmap_sem);
 298         return retval;
 299 fail_nomem_policy:
 300         kmem_cache_free(vm_area_cachep, tmp);
 301 fail_nomem:
 302         retval = -ENOMEM;
 303         vm_unacct_memory(charge);
 304         goto out;
 305 }
 306
 307 static inline int mm_alloc_pgd(struct mm_struct * mm)
 308 {
 309         mm->pgd = pgd_alloc(mm);
 310         if (unlikely(!mm->pgd))
 311                 return -ENOMEM;
 312         return 0;
 313 }
 314
 315 static inline void mm_free_pgd(struct mm_struct * mm)
 316 {
 317         pgd_free(mm->pgd);
 318 }
 319 #else
 320 #define dup_mmap(mm, oldmm)     (0)
 321 #define mm_alloc_pgd(mm)        (0)
 322 #define mm_free_pgd(mm)
 323 #endif /* CONFIG_MMU */
 324
 325  __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 326
 327 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 328 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 329
 330 #include <linux/init_task.h>
 331
 332 static struct mm_struct * mm_init(struct mm_struct * mm)
 333 {
 334         atomic_set(&mm->mm_users, 1);
 335         atomic_set(&mm->mm_count, 1);
 336         init_rwsem(&mm->mmap_sem);
 337         INIT_LIST_HEAD(&mm->mmlist);
 338         mm->flags = (current->mm) ? current->mm->flags
 339                                   : MMF_DUMP_FILTER_DEFAULT;
 340         mm->core_waiters = 0;
 341         mm->nr_ptes = 0;
 342         set_mm_counter(mm, file_rss, 0);
 343         set_mm_counter(mm, anon_rss, 0);
 344         spin_lock_init(&mm->page_table_lock);
 345         rwlock_init(&mm->ioctx_list_lock);
 346         mm->ioctx_list = NULL;
 347         mm->free_area_cache = TASK_UNMAPPED_BASE;
 348         mm->cached_hole_size = ~0UL;
 349
 350         if (likely(!mm_alloc_pgd(mm))) {
 351                 mm->def_flags = 0;
 352                 return mm;
 353         }
 354         free_mm(mm);
 355         return NULL;
 356 }
 357
 358 /*
 359  * Allocate and initialize an mm_struct.
 360  */
 361 struct mm_struct * mm_alloc(void)
 362 {
 363         struct mm_struct * mm;
 364
 365         mm = allocate_mm();
 366         if (mm) {
 367                 memset(mm, 0, sizeof(*mm));
 368                 mm = mm_init(mm);
 369         }
 370         return mm;
 371 }
 372
 373 /*
 374  * Called when the last reference to the mm
 375  * is dropped: either by a lazy thread or by
 376  * mmput. Free the page directory and the mm.
 377  */
 378 void fastcall __mmdrop(struct mm_struct *mm)
 379 {
 380         BUG_ON(mm == &init_mm);
 381         mm_free_pgd(mm);
 382         destroy_context(mm);
 383         free_mm(mm);
 384 }
 385
 386 /*
 387  * Decrement the use count and release all resources for an mm.
 388  */
 389 void mmput(struct mm_struct *mm)
 390 {
 391         might_sleep();
 392
 393         if (atomic_dec_and_test(&mm->mm_users)) {
 394                 exit_aio(mm);
 395                 exit_mmap(mm);
 396                 if (!list_empty(&mm->mmlist)) {
 397                         spin_lock(&mmlist_lock);
 398                         list_del(&mm->mmlist);
 399                         spin_unlock(&mmlist_lock);
 400                 }
 401                 put_swap_token(mm);
 402                 mmdrop(mm);
 403         }
 404 }
 405 EXPORT_SYMBOL_GPL(mmput);
 406
 407 /**
 408  * get_task_mm - acquire a reference to the task's mm
 409  *
 410  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 411  * this kernel workthread has transiently adopted a user mm with use_mm,
 412  * to do its AIO) is not set and if so returns a reference to it, after
 413  * bumping up the use count.  User must release the mm via mmput()
 414  * after use.  Typically used by /proc and ptrace.
 415  */
 416 struct mm_struct *get_task_mm(struct task_struct *task)
 417 {
 418         struct mm_struct *mm;
 419
 420         task_lock(task);
 421         mm = task->mm;
 422         if (mm) {
 423                 if (task->flags & PF_BORROWED_MM)
 424                         mm = NULL;
 425                 else
 426                         atomic_inc(&mm->mm_users);
 427         }
 428         task_unlock(task);
 429         return mm;
 430 }
 431 EXPORT_SYMBOL_GPL(get_task_mm);
 432
 433 /* Please note the differences between mmput and mm_release.
 434  * mmput is called whenever we stop holding onto a mm_struct,
 435  * error success whatever.
 436  *
 437  * mm_release is called after a mm_struct has been removed
 438  * from the current process.
 439  *
 440  * This difference is important for error handling, when we
 441  * only half set up a mm_struct for a new process and need to restore
 442  * the old one.  Because we mmput the new mm_struct before
 443  * restoring the old one. . .
 444  * Eric Biederman 10 January 1998
 445  */
 446 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 447 {
 448         struct completion *vfork_done = tsk->vfork_done;
 449
 450         /* Get rid of any cached register state */
 451         deactivate_mm(tsk, mm);
 452
 453         /* notify parent sleeping on vfork() */
 454         if (vfork_done) {
 455                 tsk->vfork_done = NULL;
 456                 complete(vfork_done);
 457         }
 458
 459         /*
 460          * If we're exiting normally, clear a user-space tid field if
 461          * requested.  We leave this alone when dying by signal, to leave
 462          * the value intact in a core dump, and to save the unnecessary
 463          * trouble otherwise.  Userland only wants this done for a sys_exit.
 464          */
 465         if (tsk->clear_child_tid
 466             && !(tsk->flags & PF_SIGNALED)
 467             && atomic_read(&mm->mm_users) > 1) {
 468                 u32 __user * tidptr = tsk->clear_child_tid;
 469                 tsk->clear_child_tid = NULL;
 470
 471                 /*
 472                  * We don't check the error code - if userspace has
 473                  * not set up a proper pointer then tough luck.
 474                  */
 475                 put_user(0, tidptr);
 476                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 477         }
 478 }
 479
 480 /*
 481  * Allocate a new mm structure and copy contents from the
 482  * mm structure of the passed in task structure.
 483  */
 484 static struct mm_struct *dup_mm(struct task_struct *tsk)
 485 {
 486         struct mm_struct *mm, *oldmm = current->mm;
 487         int err;
 488
 489         if (!oldmm)
 490                 return NULL;
 491
 492         mm = allocate_mm();
 493         if (!mm)
 494                 goto fail_nomem;
 495
 496         memcpy(mm, oldmm, sizeof(*mm));
 497
 498         /* Initializing for Swap token stuff */
 499         mm->token_priority = 0;
 500         mm->last_interval = 0;
 501
 502         if (!mm_init(mm))
 503                 goto fail_nomem;
 504
 505         if (init_new_context(tsk, mm))
 506                 goto fail_nocontext;
 507
 508         err = dup_mmap(mm, oldmm);
 509         if (err)
 510                 goto free_pt;
 511
 512         mm->hiwater_rss = get_mm_rss(mm);
 513         mm->hiwater_vm = mm->total_vm;
 514
 515         return mm;
 516
 517 free_pt:
 518         mmput(mm);
 519
 520 fail_nomem:
 521         return NULL;
 522
 523 fail_nocontext:
 524         /*
 525          * If init_new_context() failed, we cannot use mmput() to free the mm
 526          * because it calls destroy_context()
 527          */
 528         mm_free_pgd(mm);
 529         free_mm(mm);
 530         return NULL;
 531 }
 532
 533 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 534 {
 535         struct mm_struct * mm, *oldmm;
 536         int retval;
 537
 538         tsk->min_flt = tsk->maj_flt = 0;
 539         tsk->nvcsw = tsk->nivcsw = 0;
 540
 541         tsk->mm = NULL;
 542         tsk->active_mm = NULL;
 543
 544         /*
 545          * Are we cloning a kernel thread?
 546          *
 547          * We need to steal a active VM for that..
 548          */
 549         oldmm = current->mm;
 550         if (!oldmm)
 551                 return 0;
 552
 553         if (clone_flags & CLONE_VM) {
 554                 atomic_inc(&oldmm->mm_users);
 555                 mm = oldmm;
 556                 goto good_mm;
 557         }
 558
 559         retval = -ENOMEM;
 560         mm = dup_mm(tsk);
 561         if (!mm)
 562                 goto fail_nomem;
 563
 564 good_mm:
 565         /* Initializing for Swap token stuff */
 566         mm->token_priority = 0;
 567         mm->last_interval = 0;
 568
 569         tsk->mm = mm;
 570         tsk->active_mm = mm;
 571         return 0;
 572
 573 fail_nomem:
 574         return retval;
 575 }
 576
 577 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 578 {
 579         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 580         /* We don't need to lock fs - think why ;-) */
 581         if (fs) {
 582                 atomic_set(&fs->count, 1);
 583                 rwlock_init(&fs->lock);
 584                 fs->umask = old->umask;
 585                 read_lock(&old->lock);
 586                 fs->rootmnt = mntget(old->rootmnt);
 587                 fs->root = dget(old->root);
 588                 fs->pwdmnt = mntget(old->pwdmnt);
 589                 fs->pwd = dget(old->pwd);
 590                 if (old->altroot) {
 591                         fs->altrootmnt = mntget(old->altrootmnt);
 592                         fs->altroot = dget(old->altroot);
 593                 } else {
 594                         fs->altrootmnt = NULL;
 595                         fs->altroot = NULL;
 596                 }
 597                 read_unlock(&old->lock);
 598         }
 599         return fs;
 600 }
 601
 602 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 603 {
 604         return __copy_fs_struct(old);
 605 }
 606
 607 EXPORT_SYMBOL_GPL(copy_fs_struct);
 608
 609 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk)
 610 {
 611         if (clone_flags & CLONE_FS) {
 612                 atomic_inc(&current->fs->count);
 613                 return 0;
 614         }
 615         tsk->fs = __copy_fs_struct(current->fs);
 616         if (!tsk->fs)
 617                 return -ENOMEM;
 618         return 0;
 619 }
 620
 621 static int count_open_files(struct fdtable *fdt)
 622 {
 623         int size = fdt->max_fds;
 624         int i;
 625
 626         /* Find the last open fd */
 627         for (i = size/(8*sizeof(long)); i > 0; ) {
 628                 if (fdt->open_fds->fds_bits[--i])
 629                         break;
 630         }
 631         i = (i+1) * 8 * sizeof(long);
 632         return i;
 633 }
 634
 635 static struct files_struct *alloc_files(void)
 636 {
 637         struct files_struct *newf;
 638         struct fdtable *fdt;
 639
 640         newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 641         if (!newf)
 642                 goto out;
 643
 644         atomic_set(&newf->count, 1);
 645
 646         spin_lock_init(&newf->file_lock);
 647         newf->next_fd = 0;
 648         fdt = &newf->fdtab;
 649         fdt->max_fds = NR_OPEN_DEFAULT;
 650         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
 651         fdt->open_fds = (fd_set *)&newf->open_fds_init;
 652         fdt->fd = &newf->fd_array[0];
 653         INIT_RCU_HEAD(&fdt->rcu);
 654         fdt->next = NULL;
 655         rcu_assign_pointer(newf->fdt, fdt);
 656 out:
 657         return newf;
 658 }
 659
 660 /*
 661  * Allocate a new files structure and copy contents from the
 662  * passed in files structure.
 663  * errorp will be valid only when the returned files_struct is NULL.
 664  */
 665 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 666 {
 667         struct files_struct *newf;
 668         struct file **old_fds, **new_fds;
 669         int open_files, size, i;
 670         struct fdtable *old_fdt, *new_fdt;
 671
 672         *errorp = -ENOMEM;
 673         newf = alloc_files();
 674         if (!newf)
 675                 goto out;
 676
 677         spin_lock(&oldf->file_lock);
 678         old_fdt = files_fdtable(oldf);
 679         new_fdt = files_fdtable(newf);
 680         open_files = count_open_files(old_fdt);
 681
 682         /*
 683          * Check whether we need to allocate a larger fd array and fd set.
 684          * Note: we're not a clone task, so the open count won't change.
 685          */
 686         if (open_files > new_fdt->max_fds) {
 687                 new_fdt->max_fds = 0;
 688                 spin_unlock(&oldf->file_lock);
 689                 spin_lock(&newf->file_lock);
 690                 *errorp = expand_files(newf, open_files-1);
 691                 spin_unlock(&newf->file_lock);
 692                 if (*errorp < 0)
 693                         goto out_release;
 694                 new_fdt = files_fdtable(newf);
 695                 /*
 696                  * Reacquire the oldf lock and a pointer to its fd table
 697                  * who knows it may have a new bigger fd table. We need
 698                  * the latest pointer.
 699                  */
 700                 spin_lock(&oldf->file_lock);
 701                 old_fdt = files_fdtable(oldf);
 702         }
 703
 704         old_fds = old_fdt->fd;
 705         new_fds = new_fdt->fd;
 706
 707         memcpy(new_fdt->open_fds->fds_bits,
 708                 old_fdt->open_fds->fds_bits, open_files/8);
 709         memcpy(new_fdt->close_on_exec->fds_bits,
 710                 old_fdt->close_on_exec->fds_bits, open_files/8);
 711
 712         for (i = open_files; i != 0; i--) {
 713                 struct file *f = *old_fds++;
 714                 if (f) {
 715                         get_file(f);
 716                 } else {
 717                         /*
 718                          * The fd may be claimed in the fd bitmap but not yet
 719                          * instantiated in the files array if a sibling thread
 720                          * is partway through open().  So make sure that this
 721                          * fd is available to the new process.
 722                          */
 723                         FD_CLR(open_files - i, new_fdt->open_fds);
 724                 }
 725                 rcu_assign_pointer(*new_fds++, f);
 726         }
 727         spin_unlock(&oldf->file_lock);
 728
 729         /* compute the remainder to be cleared */
 730         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 731
 732         /* This is long word aligned thus could use a optimized version */
 733         memset(new_fds, 0, size);
 734
 735         if (new_fdt->max_fds > open_files) {
 736                 int left = (new_fdt->max_fds-open_files)/8;
 737                 int start = open_files / (8 * sizeof(unsigned long));
 738
 739                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
 740                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 741         }
 742
 743         return newf;
 744
 745 out_release:
 746         kmem_cache_free(files_cachep, newf);
 747 out:
 748         return NULL;
 749 }
 750
 751 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 752 {
 753         struct files_struct *oldf, *newf;
 754         int error = 0;
 755
 756         /*
 757          * A background process may not have any files ...
 758          */
 759         oldf = current->files;
 760         if (!oldf)
 761                 goto out;
 762
 763         if (clone_flags & CLONE_FILES) {
 764                 atomic_inc(&oldf->count);
 765                 goto out;
 766         }
 767
 768         /*
 769          * Note: we may be using current for both targets (See exec.c)
 770          * This works because we cache current->files (old) as oldf. Don't
 771          * break this.
 772          */
 773         tsk->files = NULL;
 774         newf = dup_fd(oldf, &error);
 775         if (!newf)
 776                 goto out;
 777
 778         tsk->files = newf;
 779         error = 0;
 780 out:
 781         return error;
 782 }
 783
 784 /*
 785  *      Helper to unshare the files of the current task.
 786  *      We don't want to expose copy_files internals to
 787  *      the exec layer of the kernel.
 788  */
 789
 790 int unshare_files(void)
 791 {
 792         struct files_struct *files  = current->files;
 793         int rc;
 794
 795         BUG_ON(!files);
 796
 797         /* This can race but the race causes us to copy when we don't
 798            need to and drop the copy */
 799         if(atomic_read(&files->count) == 1)
 800         {
 801                 atomic_inc(&files->count);
 802                 return 0;
 803         }
 804         rc = copy_files(0, current);
 805         if(rc)
 806                 current->files = files;
 807         return rc;
 808 }
 809
 810 EXPORT_SYMBOL(unshare_files);
 811
 812 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
 813 {
 814         struct sighand_struct *sig;
 815
 816         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 817                 atomic_inc(&current->sighand->count);
 818                 return 0;
 819         }
 820         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 821         rcu_assign_pointer(tsk->sighand, sig);
 822         if (!sig)
 823                 return -ENOMEM;
 824         atomic_set(&sig->count, 1);
 825         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 826         return 0;
 827 }
 828
 829 void __cleanup_sighand(struct sighand_struct *sighand)
 830 {
 831         if (atomic_dec_and_test(&sighand->count))
 832                 kmem_cache_free(sighand_cachep, sighand);
 833 }
 834
 835 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk)
 836 {
 837         struct signal_struct *sig;
 838         int ret;
 839
 840         if (clone_flags & CLONE_THREAD) {
 841                 atomic_inc(&current->signal->count);
 842                 atomic_inc(&current->signal->live);
 843                 return 0;
 844         }
 845         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 846         tsk->signal = sig;
 847         if (!sig)
 848                 return -ENOMEM;
 849
 850         ret = copy_thread_group_keys(tsk);
 851         if (ret < 0) {
 852                 kmem_cache_free(signal_cachep, sig);
 853                 return ret;
 854         }
 855
 856         atomic_set(&sig->count, 1);
 857         atomic_set(&sig->live, 1);
 858         init_waitqueue_head(&sig->wait_chldexit);
 859         sig->flags = 0;
 860         sig->group_exit_code = 0;
 861         sig->group_exit_task = NULL;
 862         sig->group_stop_count = 0;
 863         sig->curr_target = NULL;
 864         init_sigpending(&sig->shared_pending);
 865         INIT_LIST_HEAD(&sig->posix_timers);
 866
 867         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 868         sig->it_real_incr.tv64 = 0;
 869         sig->real_timer.function = it_real_fn;
 870         sig->tsk = tsk;
 871
 872         sig->it_virt_expires = cputime_zero;
 873         sig->it_virt_incr = cputime_zero;
 874         sig->it_prof_expires = cputime_zero;
 875         sig->it_prof_incr = cputime_zero;
 876
 877         sig->leader = 0;        /* session leadership doesn't inherit */
 878         sig->tty_old_pgrp = NULL;
 879
 880         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 881         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 882         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 883         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 884         sig->sum_sched_runtime = 0;
 885         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 886         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 887         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 888         taskstats_tgid_init(sig);
 889
 890         task_lock(current->group_leader);
 891         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 892         task_unlock(current->group_leader);
 893
 894         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 895                 /*
 896                  * New sole thread in the process gets an expiry time
 897                  * of the whole CPU time limit.
 898                  */
 899                 tsk->it_prof_expires =
 900                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 901         }
 902         acct_init_pacct(&sig->pacct);
 903
 904         tty_audit_fork(sig);
 905
 906         return 0;
 907 }
 908
 909 void __cleanup_signal(struct signal_struct *sig)
 910 {
 911         exit_thread_group_keys(sig);
 912         kmem_cache_free(signal_cachep, sig);
 913 }
 914
 915 static inline void cleanup_signal(struct task_struct *tsk)
 916 {
 917         struct signal_struct *sig = tsk->signal;
 918
 919         atomic_dec(&sig->live);
 920
 921         if (atomic_dec_and_test(&sig->count))
 922                 __cleanup_signal(sig);
 923 }
 924
 925 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
 926 {
 927         unsigned long new_flags = p->flags;
 928
 929         new_flags &= ~PF_SUPERPRIV;
 930         new_flags |= PF_FORKNOEXEC;
 931         if (!(clone_flags & CLONE_PTRACE))
 932                 p->ptrace = 0;
 933         p->flags = new_flags;
 934 }
 935
 936 asmlinkage long sys_set_tid_address(int __user *tidptr)
 937 {
 938         current->clear_child_tid = tidptr;
 939
 940         return current->pid;
 941 }
 942
 943 static inline void rt_mutex_init_task(struct task_struct *p)
 944 {
 945         spin_lock_init(&p->pi_lock);
 946 #ifdef CONFIG_RT_MUTEXES
 947         plist_head_init(&p->pi_waiters, &p->pi_lock);
 948         p->pi_blocked_on = NULL;
 949 #endif
 950 }
 951
 952 /*
 953  * This creates a new process as a copy of the old one,
 954  * but does not actually start it yet.
 955  *
 956  * It copies the registers, and all the appropriate
 957  * parts of the process environment (as per the clone
 958  * flags). The actual kick-off is left to the caller.
 959  */
 960 static struct task_struct *copy_process(unsigned long clone_flags,
 961                                         unsigned long stack_start,
 962                                         struct pt_regs *regs,
 963                                         unsigned long stack_size,
 964                                         int __user *parent_tidptr,
 965                                         int __user *child_tidptr,
 966                                         struct pid *pid)
 967 {
 968         int retval;
 969         struct task_struct *p = NULL;
 970
 971         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 972                 return ERR_PTR(-EINVAL);
 973
 974         /*
 975          * Thread groups must share signals as well, and detached threads
 976          * can only be started up within the thread group.
 977          */
 978         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 979                 return ERR_PTR(-EINVAL);
 980
 981         /*
 982          * Shared signal handlers imply shared VM. By way of the above,
 983          * thread groups also imply shared VM. Blocking this case allows
 984          * for various simplifications in other code.
 985          */
 986         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 987                 return ERR_PTR(-EINVAL);
 988
 989         retval = security_task_create(clone_flags);
 990         if (retval)
 991                 goto fork_out;
 992
 993         retval = -ENOMEM;
 994         p = dup_task_struct(current);
 995         if (!p)
 996                 goto fork_out;
 997
 998         rt_mutex_init_task(p);
 999
1000 #ifdef CONFIG_TRACE_IRQFLAGS
1001         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1002         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1003 #endif
1004         retval = -EAGAIN;
1005         if (atomic_read(&p->user->processes) >=
1006                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1007                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1008                     p->user != current->nsproxy->user_ns->root_user)
1009                         goto bad_fork_free;
1010         }
1011
1012         atomic_inc(&p->user->__count);
1013         atomic_inc(&p->user->processes);
1014         get_group_info(p->group_info);
1015
1016         /*
1017          * If multiple threads are within copy_process(), then this check
1018          * triggers too late. This doesn't hurt, the check is only there
1019          * to stop root fork bombs.
1020          */
1021         if (nr_threads >= max_threads)
1022                 goto bad_fork_cleanup_count;
1023
1024         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1025                 goto bad_fork_cleanup_count;
1026
1027         if (p->binfmt && !try_module_get(p->binfmt->module))
1028                 goto bad_fork_cleanup_put_domain;
1029
1030         p->did_exec = 0;
1031         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1032         copy_flags(clone_flags, p);
1033         p->pid = pid_nr(pid);
1034         retval = -EFAULT;
1035         if (clone_flags & CLONE_PARENT_SETTID)
1036                 if (put_user(p->pid, parent_tidptr))
1037                         goto bad_fork_cleanup_delays_binfmt;
1038
1039         INIT_LIST_HEAD(&p->children);
1040         INIT_LIST_HEAD(&p->sibling);
1041         p->vfork_done = NULL;
1042         spin_lock_init(&p->alloc_lock);
1043
1044         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1045         init_sigpending(&p->pending);
1046
1047         p->utime = cputime_zero;
1048         p->stime = cputime_zero;
1049
1050 #ifdef CONFIG_TASK_XACCT
1051         p->rchar = 0;           /* I/O counter: bytes read */
1052         p->wchar = 0;           /* I/O counter: bytes written */
1053         p->syscr = 0;           /* I/O counter: read syscalls */
1054         p->syscw = 0;           /* I/O counter: write syscalls */
1055 #endif
1056         task_io_accounting_init(p);
1057         acct_clear_integrals(p);
1058
1059         p->it_virt_expires = cputime_zero;
1060         p->it_prof_expires = cputime_zero;
1061         p->it_sched_expires = 0;
1062         INIT_LIST_HEAD(&p->cpu_timers[0]);
1063         INIT_LIST_HEAD(&p->cpu_timers[1]);
1064         INIT_LIST_HEAD(&p->cpu_timers[2]);
1065
1066         p->lock_depth = -1;             /* -1 = no lock */
1067         do_posix_clock_monotonic_gettime(&p->start_time);
1068         p->real_start_time = p->start_time;
1069         monotonic_to_bootbased(&p->real_start_time);
1070         p->security = NULL;
1071         p->io_context = NULL;
1072         p->io_wait = NULL;
1073         p->audit_context = NULL;
1074         cpuset_fork(p);
1075 #ifdef CONFIG_NUMA
1076         p->mempolicy = mpol_copy(p->mempolicy);
1077         if (IS_ERR(p->mempolicy)) {
1078                 retval = PTR_ERR(p->mempolicy);
1079                 p->mempolicy = NULL;
1080                 goto bad_fork_cleanup_cpuset;
1081         }
1082         mpol_fix_fork_child_flag(p);
1083 #endif
1084 #ifdef CONFIG_TRACE_IRQFLAGS
1085         p->irq_events = 0;
1086 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1087         p->hardirqs_enabled = 1;
1088 #else
1089         p->hardirqs_enabled = 0;
1090 #endif
1091         p->hardirq_enable_ip = 0;
1092         p->hardirq_enable_event = 0;
1093         p->hardirq_disable_ip = _THIS_IP_;
1094         p->hardirq_disable_event = 0;
1095         p->softirqs_enabled = 1;
1096         p->softirq_enable_ip = _THIS_IP_;
1097         p->softirq_enable_event = 0;
1098         p->softirq_disable_ip = 0;
1099         p->softirq_disable_event = 0;
1100         p->hardirq_context = 0;
1101         p->softirq_context = 0;
1102 #endif
1103 #ifdef CONFIG_LOCKDEP
1104         p->lockdep_depth = 0; /* no locks held yet */
1105         p->curr_chain_key = 0;
1106         p->lockdep_recursion = 0;
1107 #endif
1108
1109 #ifdef CONFIG_DEBUG_MUTEXES
1110         p->blocked_on = NULL; /* not blocked yet */
1111 #endif
1112
1113         p->tgid = p->pid;
1114         if (clone_flags & CLONE_THREAD)
1115                 p->tgid = current->tgid;
1116
1117         if ((retval = security_task_alloc(p)))
1118                 goto bad_fork_cleanup_policy;
1119         if ((retval = audit_alloc(p)))
1120                 goto bad_fork_cleanup_security;
1121         /* copy all the process information */
1122         if ((retval = copy_semundo(clone_flags, p)))
1123                 goto bad_fork_cleanup_audit;
1124         if ((retval = copy_files(clone_flags, p)))
1125                 goto bad_fork_cleanup_semundo;
1126         if ((retval = copy_fs(clone_flags, p)))
1127                 goto bad_fork_cleanup_files;
1128         if ((retval = copy_sighand(clone_flags, p)))
1129                 goto bad_fork_cleanup_fs;
1130         if ((retval = copy_signal(clone_flags, p)))
1131                 goto bad_fork_cleanup_sighand;
1132         if ((retval = copy_mm(clone_flags, p)))
1133                 goto bad_fork_cleanup_signal;
1134         if ((retval = copy_keys(clone_flags, p)))
1135                 goto bad_fork_cleanup_mm;
1136         if ((retval = copy_namespaces(clone_flags, p)))
1137                 goto bad_fork_cleanup_keys;
1138         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1139         if (retval)
1140                 goto bad_fork_cleanup_namespaces;
1141
1142         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1143         /*
1144          * Clear TID on mm_release()?
1145          */
1146         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1147         p->robust_list = NULL;
1148 #ifdef CONFIG_COMPAT
1149         p->compat_robust_list = NULL;
1150 #endif
1151         INIT_LIST_HEAD(&p->pi_state_list);
1152         p->pi_state_cache = NULL;
1153
1154         /*
1155          * sigaltstack should be cleared when sharing the same VM
1156          */
1157         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1158                 p->sas_ss_sp = p->sas_ss_size = 0;
1159
1160         /*
1161          * Syscall tracing should be turned off in the child regardless
1162          * of CLONE_PTRACE.
1163          */
1164         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1165 #ifdef TIF_SYSCALL_EMU
1166         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1167 #endif
1168
1169         /* Our parent execution domain becomes current domain
1170            These must match for thread signalling to apply */
1171         p->parent_exec_id = p->self_exec_id;
1172
1173         /* ok, now we should be set up.. */
1174         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1175         p->pdeath_signal = 0;
1176         p->exit_state = 0;
1177
1178         /*
1179          * Ok, make it visible to the rest of the system.
1180          * We dont wake it up yet.
1181          */
1182         p->group_leader = p;
1183         INIT_LIST_HEAD(&p->thread_group);
1184         INIT_LIST_HEAD(&p->ptrace_children);
1185         INIT_LIST_HEAD(&p->ptrace_list);
1186
1187         /* Perform scheduler related setup. Assign this task to a CPU. */
1188         sched_fork(p, clone_flags);
1189
1190         /* Need tasklist lock for parent etc handling! */
1191         write_lock_irq(&tasklist_lock);
1192
1193         /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */
1194         p->ioprio = current->ioprio;
1195
1196         /*
1197          * The task hasn't been attached yet, so its cpus_allowed mask will
1198          * not be changed, nor will its assigned CPU.
1199          *
1200          * The cpus_allowed mask of the parent may have changed after it was
1201          * copied first time - so re-copy it here, then check the child's CPU
1202          * to ensure it is on a valid CPU (and if not, just force it back to
1203          * parent's CPU). This avoids alot of nasty races.
1204          */
1205         p->cpus_allowed = current->cpus_allowed;
1206         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1207                         !cpu_online(task_cpu(p))))
1208                 set_task_cpu(p, smp_processor_id());
1209
1210         /* CLONE_PARENT re-uses the old parent */
1211         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1212                 p->real_parent = current->real_parent;
1213         else
1214                 p->real_parent = current;
1215         p->parent = p->real_parent;
1216
1217         spin_lock(&current->sighand->siglock);
1218
1219         /*
1220          * Process group and session signals need to be delivered to just the
1221          * parent before the fork or both the parent and the child after the
1222          * fork. Restart if a signal comes in before we add the new process to
1223          * it's process group.
1224          * A fatal signal pending means that current will exit, so the new
1225          * thread can't slip out of an OOM kill (or normal SIGKILL).
1226          */
1227         recalc_sigpending();
1228         if (signal_pending(current)) {
1229                 spin_unlock(&current->sighand->siglock);
1230                 write_unlock_irq(&tasklist_lock);
1231                 retval = -ERESTARTNOINTR;
1232                 goto bad_fork_cleanup_namespaces;
1233         }
1234
1235         if (clone_flags & CLONE_THREAD) {
1236                 p->group_leader = current->group_leader;
1237                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1238
1239                 if (!cputime_eq(current->signal->it_virt_expires,
1240                                 cputime_zero) ||
1241                     !cputime_eq(current->signal->it_prof_expires,
1242                                 cputime_zero) ||
1243                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1244                     !list_empty(&current->signal->cpu_timers[0]) ||
1245                     !list_empty(&current->signal->cpu_timers[1]) ||
1246                     !list_empty(&current->signal->cpu_timers[2])) {
1247                         /*
1248                          * Have child wake up on its first tick to check
1249                          * for process CPU timers.
1250                          */
1251                         p->it_prof_expires = jiffies_to_cputime(1);
1252                 }
1253         }
1254
1255         if (likely(p->pid)) {
1256                 add_parent(p);
1257                 if (unlikely(p->ptrace & PT_PTRACED))
1258                         __ptrace_link(p, current->parent);
1259
1260                 if (thread_group_leader(p)) {
1261                         p->signal->tty = current->signal->tty;
1262                         p->signal->pgrp = process_group(current);
1263                         set_signal_session(p->signal, process_session(current));
1264                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1265                         attach_pid(p, PIDTYPE_SID, task_session(current));
1266
1267                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1268                         __get_cpu_var(process_counts)++;
1269                 }
1270                 attach_pid(p, PIDTYPE_PID, pid);
1271                 nr_threads++;
1272         }
1273
1274         total_forks++;
1275         spin_unlock(&current->sighand->siglock);
1276         write_unlock_irq(&tasklist_lock);
1277         proc_fork_connector(p);
1278         return p;
1279
1280 bad_fork_cleanup_namespaces:
1281         exit_task_namespaces(p);
1282 bad_fork_cleanup_keys:
1283         exit_keys(p);
1284 bad_fork_cleanup_mm:
1285         if (p->mm)
1286                 mmput(p->mm);
1287 bad_fork_cleanup_signal:
1288         cleanup_signal(p);
1289 bad_fork_cleanup_sighand:
1290         __cleanup_sighand(p->sighand);
1291 bad_fork_cleanup_fs:
1292         exit_fs(p); /* blocking */
1293 bad_fork_cleanup_files:
1294         exit_files(p); /* blocking */
1295 bad_fork_cleanup_semundo:
1296         exit_sem(p);
1297 bad_fork_cleanup_audit:
1298         audit_free(p);
1299 bad_fork_cleanup_security:
1300         security_task_free(p);
1301 bad_fork_cleanup_policy:
1302 #ifdef CONFIG_NUMA
1303         mpol_free(p->mempolicy);
1304 bad_fork_cleanup_cpuset:
1305 #endif
1306         cpuset_exit(p);
1307 bad_fork_cleanup_delays_binfmt:
1308         delayacct_tsk_free(p);
1309         if (p->binfmt)
1310                 module_put(p->binfmt->module);
1311 bad_fork_cleanup_put_domain:
1312         module_put(task_thread_info(p)->exec_domain->module);
1313 bad_fork_cleanup_count:
1314         put_group_info(p->group_info);
1315         atomic_dec(&p->user->processes);
1316         free_uid(p->user);
1317 bad_fork_free:
1318         free_task(p);
1319 fork_out:
1320         return ERR_PTR(retval);
1321 }
1322
1323 noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1324 {
1325         memset(regs, 0, sizeof(struct pt_regs));
1326         return regs;
1327 }
1328
1329 struct task_struct * __cpuinit fork_idle(int cpu)
1330 {
1331         struct task_struct *task;
1332         struct pt_regs regs;
1333
1334         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL,
1335                                 &init_struct_pid);
1336         if (!IS_ERR(task))
1337                 init_idle(task, cpu);
1338
1339         return task;
1340 }
1341
1342 static inline int fork_traceflag (unsigned clone_flags)
1343 {
1344         if (clone_flags & CLONE_UNTRACED)
1345                 return 0;
1346         else if (clone_flags & CLONE_VFORK) {
1347                 if (current->ptrace & PT_TRACE_VFORK)
1348                         return PTRACE_EVENT_VFORK;
1349         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1350                 if (current->ptrace & PT_TRACE_CLONE)
1351                         return PTRACE_EVENT_CLONE;
1352         } else if (current->ptrace & PT_TRACE_FORK)
1353                 return PTRACE_EVENT_FORK;
1354
1355         return 0;
1356 }
1357
1358 /*
1359  *  Ok, this is the main fork-routine.
1360  *
1361  * It copies the process, and if successful kick-starts
1362  * it and waits for it to finish using the VM if required.
1363  */
1364 long do_fork(unsigned long clone_flags,
1365               unsigned long stack_start,
1366               struct pt_regs *regs,
1367               unsigned long stack_size,
1368               int __user *parent_tidptr,
1369               int __user *child_tidptr)
1370 {
1371         struct task_struct *p;
1372         int trace = 0;
1373         struct pid *pid = alloc_pid();
1374         long nr;
1375
1376         if (!pid)
1377                 return -EAGAIN;
1378         nr = pid->nr;
1379         if (unlikely(current->ptrace)) {
1380                 trace = fork_traceflag (clone_flags);
1381                 if (trace)
1382                         clone_flags |= CLONE_PTRACE;
1383         }
1384
1385         p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
1386         /*
1387          * Do this prior waking up the new thread - the thread pointer
1388          * might get invalid after that point, if the thread exits quickly.
1389          */
1390         if (!IS_ERR(p)) {
1391                 struct completion vfork;
1392
1393                 if (clone_flags & CLONE_VFORK) {
1394                         p->vfork_done = &vfork;
1395                         init_completion(&vfork);
1396                 }
1397
1398                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1399                         /*
1400                          * We'll start up with an immediate SIGSTOP.
1401                          */
1402                         sigaddset(&p->pending.signal, SIGSTOP);
1403                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1404                 }
1405
1406                 if (!(clone_flags & CLONE_STOPPED))
1407                         wake_up_new_task(p, clone_flags);
1408                 else
1409                         p->state = TASK_STOPPED;
1410
1411                 if (unlikely (trace)) {
1412                         current->ptrace_message = nr;
1413                         ptrace_notify ((trace << 8) | SIGTRAP);
1414                 }
1415
1416                 if (clone_flags & CLONE_VFORK) {
1417                         freezer_do_not_count();
1418                         wait_for_completion(&vfork);
1419                         freezer_count();
1420                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1421                                 current->ptrace_message = nr;
1422                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1423                         }
1424                 }
1425         } else {
1426                 free_pid(pid);
1427                 nr = PTR_ERR(p);
1428         }
1429         return nr;
1430 }
1431
1432 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1433 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1434 #endif
1435
1436 static void sighand_ctor(void *data, struct kmem_cache *cachep,
1437                         unsigned long flags)
1438 {
1439         struct sighand_struct *sighand = data;
1440
1441         spin_lock_init(&sighand->siglock);
1442         INIT_LIST_HEAD(&sighand->signalfd_list);
1443 }
1444
1445 void __init proc_caches_init(void)
1446 {
1447         sighand_cachep = kmem_cache_create("sighand_cache",
1448                         sizeof(struct sighand_struct), 0,
1449                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1450                         sighand_ctor, NULL);
1451         signal_cachep = kmem_cache_create("signal_cache",
1452                         sizeof(struct signal_struct), 0,
1453                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1454         files_cachep = kmem_cache_create("files_cache",
1455                         sizeof(struct files_struct), 0,
1456                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1457         fs_cachep = kmem_cache_create("fs_cache",
1458                         sizeof(struct fs_struct), 0,
1459                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1460         vm_area_cachep = kmem_cache_create("vm_area_struct",
1461                         sizeof(struct vm_area_struct), 0,
1462                         SLAB_PANIC, NULL, NULL);
1463         mm_cachep = kmem_cache_create("mm_struct",
1464                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1465                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL);
1466 }
1467
1468 /*
1469  * Check constraints on flags passed to the unshare system call and
1470  * force unsharing of additional process context as appropriate.
1471  */
1472 static inline void check_unshare_flags(unsigned long *flags_ptr)
1473 {
1474         /*
1475          * If unsharing a thread from a thread group, must also
1476          * unshare vm.
1477          */
1478         if (*flags_ptr & CLONE_THREAD)
1479                 *flags_ptr |= CLONE_VM;
1480
1481         /*
1482          * If unsharing vm, must also unshare signal handlers.
1483          */
1484         if (*flags_ptr & CLONE_VM)
1485                 *flags_ptr |= CLONE_SIGHAND;
1486
1487         /*
1488          * If unsharing signal handlers and the task was created
1489          * using CLONE_THREAD, then must unshare the thread
1490          */
1491         if ((*flags_ptr & CLONE_SIGHAND) &&
1492             (atomic_read(&current->signal->count) > 1))
1493                 *flags_ptr |= CLONE_THREAD;
1494
1495         /*
1496          * If unsharing namespace, must also unshare filesystem information.
1497          */
1498         if (*flags_ptr & CLONE_NEWNS)
1499                 *flags_ptr |= CLONE_FS;
1500 }
1501
1502 /*
1503  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1504  */
1505 static int unshare_thread(unsigned long unshare_flags)
1506 {
1507         if (unshare_flags & CLONE_THREAD)
1508                 return -EINVAL;
1509
1510         return 0;
1511 }
1512
1513 /*
1514  * Unshare the filesystem structure if it is being shared
1515  */
1516 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1517 {
1518         struct fs_struct *fs = current->fs;
1519
1520         if ((unshare_flags & CLONE_FS) &&
1521             (fs && atomic_read(&fs->count) > 1)) {
1522                 *new_fsp = __copy_fs_struct(current->fs);
1523                 if (!*new_fsp)
1524                         return -ENOMEM;
1525         }
1526
1527         return 0;
1528 }
1529
1530 /*
1531  * Unsharing of sighand is not supported yet
1532  */
1533 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1534 {
1535         struct sighand_struct *sigh = current->sighand;
1536
1537         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1538                 return -EINVAL;
1539         else
1540                 return 0;
1541 }
1542
1543 /*
1544  * Unshare vm if it is being shared
1545  */
1546 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1547 {
1548         struct mm_struct *mm = current->mm;
1549
1550         if ((unshare_flags & CLONE_VM) &&
1551             (mm && atomic_read(&mm->mm_users) > 1)) {
1552                 return -EINVAL;
1553         }
1554
1555         return 0;
1556 }
1557
1558 /*
1559  * Unshare file descriptor table if it is being shared
1560  */
1561 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1562 {
1563         struct files_struct *fd = current->files;
1564         int error = 0;
1565
1566         if ((unshare_flags & CLONE_FILES) &&
1567             (fd && atomic_read(&fd->count) > 1)) {
1568                 *new_fdp = dup_fd(fd, &error);
1569                 if (!*new_fdp)
1570                         return error;
1571         }
1572
1573         return 0;
1574 }
1575
1576 /*
1577  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1578  * supported yet
1579  */
1580 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1581 {
1582         if (unshare_flags & CLONE_SYSVSEM)
1583                 return -EINVAL;
1584
1585         return 0;
1586 }
1587
1588 /*
1589  * unshare allows a process to 'unshare' part of the process
1590  * context which was originally shared using clone.  copy_*
1591  * functions used by do_fork() cannot be used here directly
1592  * because they modify an inactive task_struct that is being
1593  * constructed. Here we are modifying the current, active,
1594  * task_struct.
1595  */
1596 asmlinkage long sys_unshare(unsigned long unshare_flags)
1597 {
1598         int err = 0;
1599         struct fs_struct *fs, *new_fs = NULL;
1600         struct sighand_struct *new_sigh = NULL;
1601         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1602         struct files_struct *fd, *new_fd = NULL;
1603         struct sem_undo_list *new_ulist = NULL;
1604         struct nsproxy *new_nsproxy = NULL, *old_nsproxy = NULL;
1605
1606         check_unshare_flags(&unshare_flags);
1607
1608         /* Return -EINVAL for all unsupported flags */
1609         err = -EINVAL;
1610         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1611                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1612                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER))
1613                 goto bad_unshare_out;
1614
1615         if ((err = unshare_thread(unshare_flags)))
1616                 goto bad_unshare_out;
1617         if ((err = unshare_fs(unshare_flags, &new_fs)))
1618                 goto bad_unshare_cleanup_thread;
1619         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1620                 goto bad_unshare_cleanup_fs;
1621         if ((err = unshare_vm(unshare_flags, &new_mm)))
1622                 goto bad_unshare_cleanup_sigh;
1623         if ((err = unshare_fd(unshare_flags, &new_fd)))
1624                 goto bad_unshare_cleanup_vm;
1625         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1626                 goto bad_unshare_cleanup_fd;
1627         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1628                         new_fs)))
1629                 goto bad_unshare_cleanup_semundo;
1630
1631         if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
1632
1633                 task_lock(current);
1634
1635                 if (new_nsproxy) {
1636                         old_nsproxy = current->nsproxy;
1637                         current->nsproxy = new_nsproxy;
1638                         new_nsproxy = old_nsproxy;
1639                 }
1640
1641                 if (new_fs) {
1642                         fs = current->fs;
1643                         current->fs = new_fs;
1644                         new_fs = fs;
1645                 }
1646
1647                 if (new_mm) {
1648                         mm = current->mm;
1649                         active_mm = current->active_mm;
1650                         current->mm = new_mm;
1651                         current->active_mm = new_mm;
1652                         activate_mm(active_mm, new_mm);
1653                         new_mm = mm;
1654                 }
1655
1656                 if (new_fd) {
1657                         fd = current->files;
1658                         current->files = new_fd;
1659                         new_fd = fd;
1660                 }
1661
1662                 task_unlock(current);
1663         }
1664
1665         if (new_nsproxy)
1666                 put_nsproxy(new_nsproxy);
1667
1668 bad_unshare_cleanup_semundo:
1669 bad_unshare_cleanup_fd:
1670         if (new_fd)
1671                 put_files_struct(new_fd);
1672
1673 bad_unshare_cleanup_vm:
1674         if (new_mm)
1675                 mmput(new_mm);
1676
1677 bad_unshare_cleanup_sigh:
1678         if (new_sigh)
1679                 if (atomic_dec_and_test(&new_sigh->count))
1680                         kmem_cache_free(sighand_cachep, new_sigh);
1681
1682 bad_unshare_cleanup_fs:
1683         if (new_fs)
1684                 put_fs_struct(new_fs);
1685
1686 bad_unshare_cleanup_thread:
1687 bad_unshare_out:
1688         return err;
1689 }