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