err.no Git - linux-2.6/blob - kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/module.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/completion.h>
  20 #include <linux/mnt_namespace.h>
  21 #include <linux/personality.h>
  22 #include <linux/mempolicy.h>
  23 #include <linux/sem.h>
  24 #include <linux/file.h>
  25 #include <linux/key.h>
  26 #include <linux/binfmts.h>
  27 #include <linux/mman.h>
  28 #include <linux/fs.h>
  29 #include <linux/nsproxy.h>
  30 #include <linux/capability.h>
  31 #include <linux/cpu.h>
  32 #include <linux/cgroup.h>
  33 #include <linux/security.h>
  34 #include <linux/swap.h>
  35 #include <linux/syscalls.h>
  36 #include <linux/jiffies.h>
  37 #include <linux/futex.h>
  38 #include <linux/task_io_accounting_ops.h>
  39 #include <linux/rcupdate.h>
  40 #include <linux/ptrace.h>
  41 #include <linux/mount.h>
  42 #include <linux/audit.h>
  43 #include <linux/memcontrol.h>
  44 #include <linux/profile.h>
  45 #include <linux/rmap.h>
  46 #include <linux/acct.h>
  47 #include <linux/tsacct_kern.h>
  48 #include <linux/cn_proc.h>
  49 #include <linux/freezer.h>
  50 #include <linux/delayacct.h>
  51 #include <linux/taskstats_kern.h>
  52 #include <linux/random.h>
  53 #include <linux/tty.h>
  54 #include <linux/proc_fs.h>
  55 #include <linux/blkdev.h>
  56
  57 #include <asm/pgtable.h>
  58 #include <asm/pgalloc.h>
  59 #include <asm/uaccess.h>
  60 #include <asm/mmu_context.h>
  61 #include <asm/cacheflush.h>
  62 #include <asm/tlbflush.h>
  63
  64 /*
  65  * Protected counters by write_lock_irq(&tasklist_lock)
  66  */
  67 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  68 int nr_threads;                 /* The idle threads do not count.. */
  69
  70 int max_threads;                /* tunable limit on nr_threads */
  71
  72 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  73
  74 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  75
  76 int nr_processes(void)
  77 {
  78         int cpu;
  79         int total = 0;
  80
  81         for_each_online_cpu(cpu)
  82                 total += per_cpu(process_counts, cpu);
  83
  84         return total;
  85 }
  86
  87 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  88 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  89 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  90 static struct kmem_cache *task_struct_cachep;
  91 #endif
  92
  93 /* SLAB cache for signal_struct structures (tsk->signal) */
  94 static struct kmem_cache *signal_cachep;
  95
  96 /* SLAB cache for sighand_struct structures (tsk->sighand) */
  97 struct kmem_cache *sighand_cachep;
  98
  99 /* SLAB cache for files_struct structures (tsk->files) */
 100 struct kmem_cache *files_cachep;
 101
 102 /* SLAB cache for fs_struct structures (tsk->fs) */
 103 struct kmem_cache *fs_cachep;
 104
 105 /* SLAB cache for vm_area_struct structures */
 106 struct kmem_cache *vm_area_cachep;
 107
 108 /* SLAB cache for mm_struct structures (tsk->mm) */
 109 static struct kmem_cache *mm_cachep;
 110
 111 void free_task(struct task_struct *tsk)
 112 {
 113         prop_local_destroy_single(&tsk->dirties);
 114         free_thread_info(tsk->stack);
 115         rt_mutex_debug_task_free(tsk);
 116         free_task_struct(tsk);
 117 }
 118 EXPORT_SYMBOL(free_task);
 119
 120 void __put_task_struct(struct task_struct *tsk)
 121 {
 122         WARN_ON(!tsk->exit_state);
 123         WARN_ON(atomic_read(&tsk->usage));
 124         WARN_ON(tsk == current);
 125
 126         security_task_free(tsk);
 127         free_uid(tsk->user);
 128         put_group_info(tsk->group_info);
 129         delayacct_tsk_free(tsk);
 130
 131         if (!profile_handoff_task(tsk))
 132                 free_task(tsk);
 133 }
 134
 135 void __attribute__((weak)) arch_task_cache_init(void)
 136 {
 137 }
 138
 139 void __init fork_init(unsigned long mempages)
 140 {
 141 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 142 #ifndef ARCH_MIN_TASKALIGN
 143 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 144 #endif
 145         /* create a slab on which task_structs can be allocated */
 146         task_struct_cachep =
 147                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 148                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
 149 #endif
 150
 151         /* do the arch specific task caches init */
 152         arch_task_cache_init();
 153
 154         /*
 155          * The default maximum number of threads is set to a safe
 156          * value: the thread structures can take up at most half
 157          * of memory.
 158          */
 159         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 160
 161         /*
 162          * we need to allow at least 20 threads to boot a system
 163          */
 164         if(max_threads < 20)
 165                 max_threads = 20;
 166
 167         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 168         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 169         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 170                 init_task.signal->rlim[RLIMIT_NPROC];
 171 }
 172
 173 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 174                                                struct task_struct *src)
 175 {
 176         *dst = *src;
 177         return 0;
 178 }
 179
 180 static struct task_struct *dup_task_struct(struct task_struct *orig)
 181 {
 182         struct task_struct *tsk;
 183         struct thread_info *ti;
 184         int err;
 185
 186         prepare_to_copy(orig);
 187
 188         tsk = alloc_task_struct();
 189         if (!tsk)
 190                 return NULL;
 191
 192         ti = alloc_thread_info(tsk);
 193         if (!ti) {
 194                 free_task_struct(tsk);
 195                 return NULL;
 196         }
 197
 198         err = arch_dup_task_struct(tsk, orig);
 199         if (err)
 200                 goto out;
 201
 202         tsk->stack = ti;
 203
 204         err = prop_local_init_single(&tsk->dirties);
 205         if (err)
 206                 goto out;
 207
 208         setup_thread_stack(tsk, orig);
 209
 210 #ifdef CONFIG_CC_STACKPROTECTOR
 211         tsk->stack_canary = get_random_int();
 212 #endif
 213
 214         /* One for us, one for whoever does the "release_task()" (usually parent) */
 215         atomic_set(&tsk->usage,2);
 216         atomic_set(&tsk->fs_excl, 0);
 217 #ifdef CONFIG_BLK_DEV_IO_TRACE
 218         tsk->btrace_seq = 0;
 219 #endif
 220         tsk->splice_pipe = NULL;
 221         return tsk;
 222
 223 out:
 224         free_thread_info(ti);
 225         free_task_struct(tsk);
 226         return NULL;
 227 }
 228
 229 #ifdef CONFIG_MMU
 230 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 231 {
 232         struct vm_area_struct *mpnt, *tmp, **pprev;
 233         struct rb_node **rb_link, *rb_parent;
 234         int retval;
 235         unsigned long charge;
 236         struct mempolicy *pol;
 237
 238         down_write(&oldmm->mmap_sem);
 239         flush_cache_dup_mm(oldmm);
 240         /*
 241          * Not linked in yet - no deadlock potential:
 242          */
 243         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 244
 245         mm->locked_vm = 0;
 246         mm->mmap = NULL;
 247         mm->mmap_cache = NULL;
 248         mm->free_area_cache = oldmm->mmap_base;
 249         mm->cached_hole_size = ~0UL;
 250         mm->map_count = 0;
 251         cpus_clear(mm->cpu_vm_mask);
 252         mm->mm_rb = RB_ROOT;
 253         rb_link = &mm->mm_rb.rb_node;
 254         rb_parent = NULL;
 255         pprev = &mm->mmap;
 256
 257         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 258                 struct file *file;
 259
 260                 if (mpnt->vm_flags & VM_DONTCOPY) {
 261                         long pages = vma_pages(mpnt);
 262                         mm->total_vm -= pages;
 263                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 264                                                                 -pages);
 265                         continue;
 266                 }
 267                 charge = 0;
 268                 if (mpnt->vm_flags & VM_ACCOUNT) {
 269                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 270                         if (security_vm_enough_memory(len))
 271                                 goto fail_nomem;
 272                         charge = len;
 273                 }
 274                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 275                 if (!tmp)
 276                         goto fail_nomem;
 277                 *tmp = *mpnt;
 278                 pol = mpol_copy(vma_policy(mpnt));
 279                 retval = PTR_ERR(pol);
 280                 if (IS_ERR(pol))
 281                         goto fail_nomem_policy;
 282                 vma_set_policy(tmp, pol);
 283                 tmp->vm_flags &= ~VM_LOCKED;
 284                 tmp->vm_mm = mm;
 285                 tmp->vm_next = NULL;
 286                 anon_vma_link(tmp);
 287                 file = tmp->vm_file;
 288                 if (file) {
 289                         struct inode *inode = file->f_path.dentry->d_inode;
 290                         get_file(file);
 291                         if (tmp->vm_flags & VM_DENYWRITE)
 292                                 atomic_dec(&inode->i_writecount);
 293
 294                         /* insert tmp into the share list, just after mpnt */
 295                         spin_lock(&file->f_mapping->i_mmap_lock);
 296                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 297                         flush_dcache_mmap_lock(file->f_mapping);
 298                         vma_prio_tree_add(tmp, mpnt);
 299                         flush_dcache_mmap_unlock(file->f_mapping);
 300                         spin_unlock(&file->f_mapping->i_mmap_lock);
 301                 }
 302
 303                 /*
 304                  * Link in the new vma and copy the page table entries.
 305                  */
 306                 *pprev = tmp;
 307                 pprev = &tmp->vm_next;
 308
 309                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 310                 rb_link = &tmp->vm_rb.rb_right;
 311                 rb_parent = &tmp->vm_rb;
 312
 313                 mm->map_count++;
 314                 retval = copy_page_range(mm, oldmm, mpnt);
 315
 316                 if (tmp->vm_ops && tmp->vm_ops->open)
 317                         tmp->vm_ops->open(tmp);
 318
 319                 if (retval)
 320                         goto out;
 321         }
 322         /* a new mm has just been created */
 323         arch_dup_mmap(oldmm, mm);
 324         retval = 0;
 325 out:
 326         up_write(&mm->mmap_sem);
 327         flush_tlb_mm(oldmm);
 328         up_write(&oldmm->mmap_sem);
 329         return retval;
 330 fail_nomem_policy:
 331         kmem_cache_free(vm_area_cachep, tmp);
 332 fail_nomem:
 333         retval = -ENOMEM;
 334         vm_unacct_memory(charge);
 335         goto out;
 336 }
 337
 338 static inline int mm_alloc_pgd(struct mm_struct * mm)
 339 {
 340         mm->pgd = pgd_alloc(mm);
 341         if (unlikely(!mm->pgd))
 342                 return -ENOMEM;
 343         return 0;
 344 }
 345
 346 static inline void mm_free_pgd(struct mm_struct * mm)
 347 {
 348         pgd_free(mm, mm->pgd);
 349 }
 350 #else
 351 #define dup_mmap(mm, oldmm)     (0)
 352 #define mm_alloc_pgd(mm)        (0)
 353 #define mm_free_pgd(mm)
 354 #endif /* CONFIG_MMU */
 355
 356 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 357
 358 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 359 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 360
 361 #include <linux/init_task.h>
 362
 363 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 364 {
 365         atomic_set(&mm->mm_users, 1);
 366         atomic_set(&mm->mm_count, 1);
 367         init_rwsem(&mm->mmap_sem);
 368         INIT_LIST_HEAD(&mm->mmlist);
 369         mm->flags = (current->mm) ? current->mm->flags
 370                                   : MMF_DUMP_FILTER_DEFAULT;
 371         mm->core_waiters = 0;
 372         mm->nr_ptes = 0;
 373         set_mm_counter(mm, file_rss, 0);
 374         set_mm_counter(mm, anon_rss, 0);
 375         spin_lock_init(&mm->page_table_lock);
 376         rwlock_init(&mm->ioctx_list_lock);
 377         mm->ioctx_list = NULL;
 378         mm->free_area_cache = TASK_UNMAPPED_BASE;
 379         mm->cached_hole_size = ~0UL;
 380         mm_init_cgroup(mm, p);
 381
 382         if (likely(!mm_alloc_pgd(mm))) {
 383                 mm->def_flags = 0;
 384                 return mm;
 385         }
 386
 387         mm_free_cgroup(mm);
 388         free_mm(mm);
 389         return NULL;
 390 }
 391
 392 /*
 393  * Allocate and initialize an mm_struct.
 394  */
 395 struct mm_struct * mm_alloc(void)
 396 {
 397         struct mm_struct * mm;
 398
 399         mm = allocate_mm();
 400         if (mm) {
 401                 memset(mm, 0, sizeof(*mm));
 402                 mm = mm_init(mm, current);
 403         }
 404         return mm;
 405 }
 406
 407 /*
 408  * Called when the last reference to the mm
 409  * is dropped: either by a lazy thread or by
 410  * mmput. Free the page directory and the mm.
 411  */
 412 void __mmdrop(struct mm_struct *mm)
 413 {
 414         BUG_ON(mm == &init_mm);
 415         mm_free_pgd(mm);
 416         destroy_context(mm);
 417         free_mm(mm);
 418 }
 419 EXPORT_SYMBOL_GPL(__mmdrop);
 420
 421 /*
 422  * Decrement the use count and release all resources for an mm.
 423  */
 424 void mmput(struct mm_struct *mm)
 425 {
 426         might_sleep();
 427
 428         if (atomic_dec_and_test(&mm->mm_users)) {
 429                 exit_aio(mm);
 430                 exit_mmap(mm);
 431                 if (!list_empty(&mm->mmlist)) {
 432                         spin_lock(&mmlist_lock);
 433                         list_del(&mm->mmlist);
 434                         spin_unlock(&mmlist_lock);
 435                 }
 436                 put_swap_token(mm);
 437                 mm_free_cgroup(mm);
 438                 mmdrop(mm);
 439         }
 440 }
 441 EXPORT_SYMBOL_GPL(mmput);
 442
 443 /**
 444  * get_task_mm - acquire a reference to the task's mm
 445  *
 446  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 447  * this kernel workthread has transiently adopted a user mm with use_mm,
 448  * to do its AIO) is not set and if so returns a reference to it, after
 449  * bumping up the use count.  User must release the mm via mmput()
 450  * after use.  Typically used by /proc and ptrace.
 451  */
 452 struct mm_struct *get_task_mm(struct task_struct *task)
 453 {
 454         struct mm_struct *mm;
 455
 456         task_lock(task);
 457         mm = task->mm;
 458         if (mm) {
 459                 if (task->flags & PF_BORROWED_MM)
 460                         mm = NULL;
 461                 else
 462                         atomic_inc(&mm->mm_users);
 463         }
 464         task_unlock(task);
 465         return mm;
 466 }
 467 EXPORT_SYMBOL_GPL(get_task_mm);
 468
 469 /* Please note the differences between mmput and mm_release.
 470  * mmput is called whenever we stop holding onto a mm_struct,
 471  * error success whatever.
 472  *
 473  * mm_release is called after a mm_struct has been removed
 474  * from the current process.
 475  *
 476  * This difference is important for error handling, when we
 477  * only half set up a mm_struct for a new process and need to restore
 478  * the old one.  Because we mmput the new mm_struct before
 479  * restoring the old one. . .
 480  * Eric Biederman 10 January 1998
 481  */
 482 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 483 {
 484         struct completion *vfork_done = tsk->vfork_done;
 485
 486         /* Get rid of any cached register state */
 487         deactivate_mm(tsk, mm);
 488
 489         /* notify parent sleeping on vfork() */
 490         if (vfork_done) {
 491                 tsk->vfork_done = NULL;
 492                 complete(vfork_done);
 493         }
 494
 495         /*
 496          * If we're exiting normally, clear a user-space tid field if
 497          * requested.  We leave this alone when dying by signal, to leave
 498          * the value intact in a core dump, and to save the unnecessary
 499          * trouble otherwise.  Userland only wants this done for a sys_exit.
 500          */
 501         if (tsk->clear_child_tid
 502             && !(tsk->flags & PF_SIGNALED)
 503             && atomic_read(&mm->mm_users) > 1) {
 504                 u32 __user * tidptr = tsk->clear_child_tid;
 505                 tsk->clear_child_tid = NULL;
 506
 507                 /*
 508                  * We don't check the error code - if userspace has
 509                  * not set up a proper pointer then tough luck.
 510                  */
 511                 put_user(0, tidptr);
 512                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 513         }
 514 }
 515
 516 /*
 517  * Allocate a new mm structure and copy contents from the
 518  * mm structure of the passed in task structure.
 519  */
 520 static struct mm_struct *dup_mm(struct task_struct *tsk)
 521 {
 522         struct mm_struct *mm, *oldmm = current->mm;
 523         int err;
 524
 525         if (!oldmm)
 526                 return NULL;
 527
 528         mm = allocate_mm();
 529         if (!mm)
 530                 goto fail_nomem;
 531
 532         memcpy(mm, oldmm, sizeof(*mm));
 533
 534         /* Initializing for Swap token stuff */
 535         mm->token_priority = 0;
 536         mm->last_interval = 0;
 537
 538         if (!mm_init(mm, tsk))
 539                 goto fail_nomem;
 540
 541         if (init_new_context(tsk, mm))
 542                 goto fail_nocontext;
 543
 544         err = dup_mmap(mm, oldmm);
 545         if (err)
 546                 goto free_pt;
 547
 548         mm->hiwater_rss = get_mm_rss(mm);
 549         mm->hiwater_vm = mm->total_vm;
 550
 551         return mm;
 552
 553 free_pt:
 554         mmput(mm);
 555
 556 fail_nomem:
 557         return NULL;
 558
 559 fail_nocontext:
 560         /*
 561          * If init_new_context() failed, we cannot use mmput() to free the mm
 562          * because it calls destroy_context()
 563          */
 564         mm_free_pgd(mm);
 565         free_mm(mm);
 566         return NULL;
 567 }
 568
 569 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 570 {
 571         struct mm_struct * mm, *oldmm;
 572         int retval;
 573
 574         tsk->min_flt = tsk->maj_flt = 0;
 575         tsk->nvcsw = tsk->nivcsw = 0;
 576
 577         tsk->mm = NULL;
 578         tsk->active_mm = NULL;
 579
 580         /*
 581          * Are we cloning a kernel thread?
 582          *
 583          * We need to steal a active VM for that..
 584          */
 585         oldmm = current->mm;
 586         if (!oldmm)
 587                 return 0;
 588
 589         if (clone_flags & CLONE_VM) {
 590                 atomic_inc(&oldmm->mm_users);
 591                 mm = oldmm;
 592                 goto good_mm;
 593         }
 594
 595         retval = -ENOMEM;
 596         mm = dup_mm(tsk);
 597         if (!mm)
 598                 goto fail_nomem;
 599
 600 good_mm:
 601         /* Initializing for Swap token stuff */
 602         mm->token_priority = 0;
 603         mm->last_interval = 0;
 604
 605         tsk->mm = mm;
 606         tsk->active_mm = mm;
 607         return 0;
 608
 609 fail_nomem:
 610         return retval;
 611 }
 612
 613 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 614 {
 615         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 616         /* We don't need to lock fs - think why ;-) */
 617         if (fs) {
 618                 atomic_set(&fs->count, 1);
 619                 rwlock_init(&fs->lock);
 620                 fs->umask = old->umask;
 621                 read_lock(&old->lock);
 622                 fs->root = old->root;
 623                 path_get(&old->root);
 624                 fs->pwd = old->pwd;
 625                 path_get(&old->pwd);
 626                 if (old->altroot.dentry) {
 627                         fs->altroot = old->altroot;
 628                         path_get(&old->altroot);
 629                 } else {
 630                         fs->altroot.mnt = NULL;
 631                         fs->altroot.dentry = NULL;
 632                 }
 633                 read_unlock(&old->lock);
 634         }
 635         return fs;
 636 }
 637
 638 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 639 {
 640         return __copy_fs_struct(old);
 641 }
 642
 643 EXPORT_SYMBOL_GPL(copy_fs_struct);
 644
 645 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 646 {
 647         if (clone_flags & CLONE_FS) {
 648                 atomic_inc(&current->fs->count);
 649                 return 0;
 650         }
 651         tsk->fs = __copy_fs_struct(current->fs);
 652         if (!tsk->fs)
 653                 return -ENOMEM;
 654         return 0;
 655 }
 656
 657 static int count_open_files(struct fdtable *fdt)
 658 {
 659         int size = fdt->max_fds;
 660         int i;
 661
 662         /* Find the last open fd */
 663         for (i = size/(8*sizeof(long)); i > 0; ) {
 664                 if (fdt->open_fds->fds_bits[--i])
 665                         break;
 666         }
 667         i = (i+1) * 8 * sizeof(long);
 668         return i;
 669 }
 670
 671 static struct files_struct *alloc_files(void)
 672 {
 673         struct files_struct *newf;
 674         struct fdtable *fdt;
 675
 676         newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 677         if (!newf)
 678                 goto out;
 679
 680         atomic_set(&newf->count, 1);
 681
 682         spin_lock_init(&newf->file_lock);
 683         newf->next_fd = 0;
 684         fdt = &newf->fdtab;
 685         fdt->max_fds = NR_OPEN_DEFAULT;
 686         fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
 687         fdt->open_fds = (fd_set *)&newf->open_fds_init;
 688         fdt->fd = &newf->fd_array[0];
 689         INIT_RCU_HEAD(&fdt->rcu);
 690         fdt->next = NULL;
 691         rcu_assign_pointer(newf->fdt, fdt);
 692 out:
 693         return newf;
 694 }
 695
 696 /*
 697  * Allocate a new files structure and copy contents from the
 698  * passed in files structure.
 699  * errorp will be valid only when the returned files_struct is NULL.
 700  */
 701 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 702 {
 703         struct files_struct *newf;
 704         struct file **old_fds, **new_fds;
 705         int open_files, size, i;
 706         struct fdtable *old_fdt, *new_fdt;
 707
 708         *errorp = -ENOMEM;
 709         newf = alloc_files();
 710         if (!newf)
 711                 goto out;
 712
 713         spin_lock(&oldf->file_lock);
 714         old_fdt = files_fdtable(oldf);
 715         new_fdt = files_fdtable(newf);
 716         open_files = count_open_files(old_fdt);
 717
 718         /*
 719          * Check whether we need to allocate a larger fd array and fd set.
 720          * Note: we're not a clone task, so the open count won't change.
 721          */
 722         if (open_files > new_fdt->max_fds) {
 723                 new_fdt->max_fds = 0;
 724                 spin_unlock(&oldf->file_lock);
 725                 spin_lock(&newf->file_lock);
 726                 *errorp = expand_files(newf, open_files-1);
 727                 spin_unlock(&newf->file_lock);
 728                 if (*errorp < 0)
 729                         goto out_release;
 730                 new_fdt = files_fdtable(newf);
 731                 /*
 732                  * Reacquire the oldf lock and a pointer to its fd table
 733                  * who knows it may have a new bigger fd table. We need
 734                  * the latest pointer.
 735                  */
 736                 spin_lock(&oldf->file_lock);
 737                 old_fdt = files_fdtable(oldf);
 738         }
 739
 740         old_fds = old_fdt->fd;
 741         new_fds = new_fdt->fd;
 742
 743         memcpy(new_fdt->open_fds->fds_bits,
 744                 old_fdt->open_fds->fds_bits, open_files/8);
 745         memcpy(new_fdt->close_on_exec->fds_bits,
 746                 old_fdt->close_on_exec->fds_bits, open_files/8);
 747
 748         for (i = open_files; i != 0; i--) {
 749                 struct file *f = *old_fds++;
 750                 if (f) {
 751                         get_file(f);
 752                 } else {
 753                         /*
 754                          * The fd may be claimed in the fd bitmap but not yet
 755                          * instantiated in the files array if a sibling thread
 756                          * is partway through open().  So make sure that this
 757                          * fd is available to the new process.
 758                          */
 759                         FD_CLR(open_files - i, new_fdt->open_fds);
 760                 }
 761                 rcu_assign_pointer(*new_fds++, f);
 762         }
 763         spin_unlock(&oldf->file_lock);
 764
 765         /* compute the remainder to be cleared */
 766         size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
 767
 768         /* This is long word aligned thus could use a optimized version */
 769         memset(new_fds, 0, size);
 770
 771         if (new_fdt->max_fds > open_files) {
 772                 int left = (new_fdt->max_fds-open_files)/8;
 773                 int start = open_files / (8 * sizeof(unsigned long));
 774
 775                 memset(&new_fdt->open_fds->fds_bits[start], 0, left);
 776                 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
 777         }
 778
 779         return newf;
 780
 781 out_release:
 782         kmem_cache_free(files_cachep, newf);
 783 out:
 784         return NULL;
 785 }
 786
 787 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 788 {
 789         struct files_struct *oldf, *newf;
 790         int error = 0;
 791
 792         /*
 793          * A background process may not have any files ...
 794          */
 795         oldf = current->files;
 796         if (!oldf)
 797                 goto out;
 798
 799         if (clone_flags & CLONE_FILES) {
 800                 atomic_inc(&oldf->count);
 801                 goto out;
 802         }
 803
 804         /*
 805          * Note: we may be using current for both targets (See exec.c)
 806          * This works because we cache current->files (old) as oldf. Don't
 807          * break this.
 808          */
 809         tsk->files = NULL;
 810         newf = dup_fd(oldf, &error);
 811         if (!newf)
 812                 goto out;
 813
 814         tsk->files = newf;
 815         error = 0;
 816 out:
 817         return error;
 818 }
 819
 820 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 821 {
 822 #ifdef CONFIG_BLOCK
 823         struct io_context *ioc = current->io_context;
 824
 825         if (!ioc)
 826                 return 0;
 827         /*
 828          * Share io context with parent, if CLONE_IO is set
 829          */
 830         if (clone_flags & CLONE_IO) {
 831                 tsk->io_context = ioc_task_link(ioc);
 832                 if (unlikely(!tsk->io_context))
 833                         return -ENOMEM;
 834         } else if (ioprio_valid(ioc->ioprio)) {
 835                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 836                 if (unlikely(!tsk->io_context))
 837                         return -ENOMEM;
 838
 839                 tsk->io_context->ioprio = ioc->ioprio;
 840         }
 841 #endif
 842         return 0;
 843 }
 844
 845 /*
 846  *      Helper to unshare the files of the current task.
 847  *      We don't want to expose copy_files internals to
 848  *      the exec layer of the kernel.
 849  */
 850
 851 int unshare_files(void)
 852 {
 853         struct files_struct *files  = current->files;
 854         int rc;
 855
 856         BUG_ON(!files);
 857
 858         /* This can race but the race causes us to copy when we don't
 859            need to and drop the copy */
 860         if(atomic_read(&files->count) == 1)
 861         {
 862                 atomic_inc(&files->count);
 863                 return 0;
 864         }
 865         rc = copy_files(0, current);
 866         if(rc)
 867                 current->files = files;
 868         return rc;
 869 }
 870
 871 EXPORT_SYMBOL(unshare_files);
 872
 873 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 874 {
 875         struct sighand_struct *sig;
 876
 877         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 878                 atomic_inc(&current->sighand->count);
 879                 return 0;
 880         }
 881         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 882         rcu_assign_pointer(tsk->sighand, sig);
 883         if (!sig)
 884                 return -ENOMEM;
 885         atomic_set(&sig->count, 1);
 886         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 887         return 0;
 888 }
 889
 890 void __cleanup_sighand(struct sighand_struct *sighand)
 891 {
 892         if (atomic_dec_and_test(&sighand->count))
 893                 kmem_cache_free(sighand_cachep, sighand);
 894 }
 895
 896 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 897 {
 898         struct signal_struct *sig;
 899         int ret;
 900
 901         if (clone_flags & CLONE_THREAD) {
 902                 atomic_inc(&current->signal->count);
 903                 atomic_inc(&current->signal->live);
 904                 return 0;
 905         }
 906         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 907         tsk->signal = sig;
 908         if (!sig)
 909                 return -ENOMEM;
 910
 911         ret = copy_thread_group_keys(tsk);
 912         if (ret < 0) {
 913                 kmem_cache_free(signal_cachep, sig);
 914                 return ret;
 915         }
 916
 917         atomic_set(&sig->count, 1);
 918         atomic_set(&sig->live, 1);
 919         init_waitqueue_head(&sig->wait_chldexit);
 920         sig->flags = 0;
 921         sig->group_exit_code = 0;
 922         sig->group_exit_task = NULL;
 923         sig->group_stop_count = 0;
 924         sig->curr_target = NULL;
 925         init_sigpending(&sig->shared_pending);
 926         INIT_LIST_HEAD(&sig->posix_timers);
 927
 928         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 929         sig->it_real_incr.tv64 = 0;
 930         sig->real_timer.function = it_real_fn;
 931
 932         sig->it_virt_expires = cputime_zero;
 933         sig->it_virt_incr = cputime_zero;
 934         sig->it_prof_expires = cputime_zero;
 935         sig->it_prof_incr = cputime_zero;
 936
 937         sig->leader = 0;        /* session leadership doesn't inherit */
 938         sig->tty_old_pgrp = NULL;
 939
 940         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 941         sig->gtime = cputime_zero;
 942         sig->cgtime = cputime_zero;
 943         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 944         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 945         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 946         sig->sum_sched_runtime = 0;
 947         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 948         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 949         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 950         taskstats_tgid_init(sig);
 951
 952         task_lock(current->group_leader);
 953         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 954         task_unlock(current->group_leader);
 955
 956         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 957                 /*
 958                  * New sole thread in the process gets an expiry time
 959                  * of the whole CPU time limit.
 960                  */
 961                 tsk->it_prof_expires =
 962                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 963         }
 964         acct_init_pacct(&sig->pacct);
 965
 966         tty_audit_fork(sig);
 967
 968         return 0;
 969 }
 970
 971 void __cleanup_signal(struct signal_struct *sig)
 972 {
 973         exit_thread_group_keys(sig);
 974         kmem_cache_free(signal_cachep, sig);
 975 }
 976
 977 static void cleanup_signal(struct task_struct *tsk)
 978 {
 979         struct signal_struct *sig = tsk->signal;
 980
 981         atomic_dec(&sig->live);
 982
 983         if (atomic_dec_and_test(&sig->count))
 984                 __cleanup_signal(sig);
 985 }
 986
 987 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 988 {
 989         unsigned long new_flags = p->flags;
 990
 991         new_flags &= ~PF_SUPERPRIV;
 992         new_flags |= PF_FORKNOEXEC;
 993         if (!(clone_flags & CLONE_PTRACE))
 994                 p->ptrace = 0;
 995         p->flags = new_flags;
 996         clear_freeze_flag(p);
 997 }
 998
 999 asmlinkage long sys_set_tid_address(int __user *tidptr)
1000 {
1001         current->clear_child_tid = tidptr;
1002
1003         return task_pid_vnr(current);
1004 }
1005
1006 static void rt_mutex_init_task(struct task_struct *p)
1007 {
1008         spin_lock_init(&p->pi_lock);
1009 #ifdef CONFIG_RT_MUTEXES
1010         plist_head_init(&p->pi_waiters, &p->pi_lock);
1011         p->pi_blocked_on = NULL;
1012 #endif
1013 }
1014
1015 /*
1016  * This creates a new process as a copy of the old one,
1017  * but does not actually start it yet.
1018  *
1019  * It copies the registers, and all the appropriate
1020  * parts of the process environment (as per the clone
1021  * flags). The actual kick-off is left to the caller.
1022  */
1023 static struct task_struct *copy_process(unsigned long clone_flags,
1024                                         unsigned long stack_start,
1025                                         struct pt_regs *regs,
1026                                         unsigned long stack_size,
1027                                         int __user *child_tidptr,
1028                                         struct pid *pid)
1029 {
1030         int retval;
1031         struct task_struct *p;
1032         int cgroup_callbacks_done = 0;
1033
1034         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1035                 return ERR_PTR(-EINVAL);
1036
1037         /*
1038          * Thread groups must share signals as well, and detached threads
1039          * can only be started up within the thread group.
1040          */
1041         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1042                 return ERR_PTR(-EINVAL);
1043
1044         /*
1045          * Shared signal handlers imply shared VM. By way of the above,
1046          * thread groups also imply shared VM. Blocking this case allows
1047          * for various simplifications in other code.
1048          */
1049         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1050                 return ERR_PTR(-EINVAL);
1051
1052         retval = security_task_create(clone_flags);
1053         if (retval)
1054                 goto fork_out;
1055
1056         retval = -ENOMEM;
1057         p = dup_task_struct(current);
1058         if (!p)
1059                 goto fork_out;
1060
1061         rt_mutex_init_task(p);
1062
1063 #ifdef CONFIG_TRACE_IRQFLAGS
1064         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1065         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1066 #endif
1067         retval = -EAGAIN;
1068         if (atomic_read(&p->user->processes) >=
1069                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
1070                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1071                     p->user != current->nsproxy->user_ns->root_user)
1072                         goto bad_fork_free;
1073         }
1074
1075         atomic_inc(&p->user->__count);
1076         atomic_inc(&p->user->processes);
1077         get_group_info(p->group_info);
1078
1079         /*
1080          * If multiple threads are within copy_process(), then this check
1081          * triggers too late. This doesn't hurt, the check is only there
1082          * to stop root fork bombs.
1083          */
1084         if (nr_threads >= max_threads)
1085                 goto bad_fork_cleanup_count;
1086
1087         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1088                 goto bad_fork_cleanup_count;
1089
1090         if (p->binfmt && !try_module_get(p->binfmt->module))
1091                 goto bad_fork_cleanup_put_domain;
1092
1093         p->did_exec = 0;
1094         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1095         copy_flags(clone_flags, p);
1096         INIT_LIST_HEAD(&p->children);
1097         INIT_LIST_HEAD(&p->sibling);
1098 #ifdef CONFIG_PREEMPT_RCU
1099         p->rcu_read_lock_nesting = 0;
1100         p->rcu_flipctr_idx = 0;
1101 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1102         p->vfork_done = NULL;
1103         spin_lock_init(&p->alloc_lock);
1104
1105         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1106         init_sigpending(&p->pending);
1107
1108         p->utime = cputime_zero;
1109         p->stime = cputime_zero;
1110         p->gtime = cputime_zero;
1111         p->utimescaled = cputime_zero;
1112         p->stimescaled = cputime_zero;
1113         p->prev_utime = cputime_zero;
1114         p->prev_stime = cputime_zero;
1115
1116 #ifdef CONFIG_DETECT_SOFTLOCKUP
1117         p->last_switch_count = 0;
1118         p->last_switch_timestamp = 0;
1119 #endif
1120
1121 #ifdef CONFIG_TASK_XACCT
1122         p->rchar = 0;           /* I/O counter: bytes read */
1123         p->wchar = 0;           /* I/O counter: bytes written */
1124         p->syscr = 0;           /* I/O counter: read syscalls */
1125         p->syscw = 0;           /* I/O counter: write syscalls */
1126 #endif
1127         task_io_accounting_init(p);
1128         acct_clear_integrals(p);
1129
1130         p->it_virt_expires = cputime_zero;
1131         p->it_prof_expires = cputime_zero;
1132         p->it_sched_expires = 0;
1133         INIT_LIST_HEAD(&p->cpu_timers[0]);
1134         INIT_LIST_HEAD(&p->cpu_timers[1]);
1135         INIT_LIST_HEAD(&p->cpu_timers[2]);
1136
1137         p->lock_depth = -1;             /* -1 = no lock */
1138         do_posix_clock_monotonic_gettime(&p->start_time);
1139         p->real_start_time = p->start_time;
1140         monotonic_to_bootbased(&p->real_start_time);
1141 #ifdef CONFIG_SECURITY
1142         p->security = NULL;
1143 #endif
1144         p->cap_bset = current->cap_bset;
1145         p->io_context = NULL;
1146         p->audit_context = NULL;
1147         cgroup_fork(p);
1148 #ifdef CONFIG_NUMA
1149         p->mempolicy = mpol_copy(p->mempolicy);
1150         if (IS_ERR(p->mempolicy)) {
1151                 retval = PTR_ERR(p->mempolicy);
1152                 p->mempolicy = NULL;
1153                 goto bad_fork_cleanup_cgroup;
1154         }
1155         mpol_fix_fork_child_flag(p);
1156 #endif
1157 #ifdef CONFIG_TRACE_IRQFLAGS
1158         p->irq_events = 0;
1159 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1160         p->hardirqs_enabled = 1;
1161 #else
1162         p->hardirqs_enabled = 0;
1163 #endif
1164         p->hardirq_enable_ip = 0;
1165         p->hardirq_enable_event = 0;
1166         p->hardirq_disable_ip = _THIS_IP_;
1167         p->hardirq_disable_event = 0;
1168         p->softirqs_enabled = 1;
1169         p->softirq_enable_ip = _THIS_IP_;
1170         p->softirq_enable_event = 0;
1171         p->softirq_disable_ip = 0;
1172         p->softirq_disable_event = 0;
1173         p->hardirq_context = 0;
1174         p->softirq_context = 0;
1175 #endif
1176 #ifdef CONFIG_LOCKDEP
1177         p->lockdep_depth = 0; /* no locks held yet */
1178         p->curr_chain_key = 0;
1179         p->lockdep_recursion = 0;
1180 #endif
1181
1182 #ifdef CONFIG_DEBUG_MUTEXES
1183         p->blocked_on = NULL; /* not blocked yet */
1184 #endif
1185
1186         /* Perform scheduler related setup. Assign this task to a CPU. */
1187         sched_fork(p, clone_flags);
1188
1189         if ((retval = security_task_alloc(p)))
1190                 goto bad_fork_cleanup_policy;
1191         if ((retval = audit_alloc(p)))
1192                 goto bad_fork_cleanup_security;
1193         /* copy all the process information */
1194         if ((retval = copy_semundo(clone_flags, p)))
1195                 goto bad_fork_cleanup_audit;
1196         if ((retval = copy_files(clone_flags, p)))
1197                 goto bad_fork_cleanup_semundo;
1198         if ((retval = copy_fs(clone_flags, p)))
1199                 goto bad_fork_cleanup_files;
1200         if ((retval = copy_sighand(clone_flags, p)))
1201                 goto bad_fork_cleanup_fs;
1202         if ((retval = copy_signal(clone_flags, p)))
1203                 goto bad_fork_cleanup_sighand;
1204         if ((retval = copy_mm(clone_flags, p)))
1205                 goto bad_fork_cleanup_signal;
1206         if ((retval = copy_keys(clone_flags, p)))
1207                 goto bad_fork_cleanup_mm;
1208         if ((retval = copy_namespaces(clone_flags, p)))
1209                 goto bad_fork_cleanup_keys;
1210         if ((retval = copy_io(clone_flags, p)))
1211                 goto bad_fork_cleanup_namespaces;
1212         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1213         if (retval)
1214                 goto bad_fork_cleanup_io;
1215
1216         if (pid != &init_struct_pid) {
1217                 retval = -ENOMEM;
1218                 pid = alloc_pid(task_active_pid_ns(p));
1219                 if (!pid)
1220                         goto bad_fork_cleanup_io;
1221
1222                 if (clone_flags & CLONE_NEWPID) {
1223                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1224                         if (retval < 0)
1225                                 goto bad_fork_free_pid;
1226                 }
1227         }
1228
1229         p->pid = pid_nr(pid);
1230         p->tgid = p->pid;
1231         if (clone_flags & CLONE_THREAD)
1232                 p->tgid = current->tgid;
1233
1234         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1235         /*
1236          * Clear TID on mm_release()?
1237          */
1238         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1239 #ifdef CONFIG_FUTEX
1240         p->robust_list = NULL;
1241 #ifdef CONFIG_COMPAT
1242         p->compat_robust_list = NULL;
1243 #endif
1244         INIT_LIST_HEAD(&p->pi_state_list);
1245         p->pi_state_cache = NULL;
1246 #endif
1247         /*
1248          * sigaltstack should be cleared when sharing the same VM
1249          */
1250         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1251                 p->sas_ss_sp = p->sas_ss_size = 0;
1252
1253         /*
1254          * Syscall tracing should be turned off in the child regardless
1255          * of CLONE_PTRACE.
1256          */
1257         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1258 #ifdef TIF_SYSCALL_EMU
1259         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1260 #endif
1261         clear_all_latency_tracing(p);
1262
1263         /* Our parent execution domain becomes current domain
1264            These must match for thread signalling to apply */
1265         p->parent_exec_id = p->self_exec_id;
1266
1267         /* ok, now we should be set up.. */
1268         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1269         p->pdeath_signal = 0;
1270         p->exit_state = 0;
1271
1272         /*
1273          * Ok, make it visible to the rest of the system.
1274          * We dont wake it up yet.
1275          */
1276         p->group_leader = p;
1277         INIT_LIST_HEAD(&p->thread_group);
1278         INIT_LIST_HEAD(&p->ptrace_children);
1279         INIT_LIST_HEAD(&p->ptrace_list);
1280
1281         /* Now that the task is set up, run cgroup callbacks if
1282          * necessary. We need to run them before the task is visible
1283          * on the tasklist. */
1284         cgroup_fork_callbacks(p);
1285         cgroup_callbacks_done = 1;
1286
1287         /* Need tasklist lock for parent etc handling! */
1288         write_lock_irq(&tasklist_lock);
1289
1290         /*
1291          * The task hasn't been attached yet, so its cpus_allowed mask will
1292          * not be changed, nor will its assigned CPU.
1293          *
1294          * The cpus_allowed mask of the parent may have changed after it was
1295          * copied first time - so re-copy it here, then check the child's CPU
1296          * to ensure it is on a valid CPU (and if not, just force it back to
1297          * parent's CPU). This avoids alot of nasty races.
1298          */
1299         p->cpus_allowed = current->cpus_allowed;
1300         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1301         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1302                         !cpu_online(task_cpu(p))))
1303                 set_task_cpu(p, smp_processor_id());
1304
1305         /* CLONE_PARENT re-uses the old parent */
1306         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1307                 p->real_parent = current->real_parent;
1308         else
1309                 p->real_parent = current;
1310         p->parent = p->real_parent;
1311
1312         spin_lock(&current->sighand->siglock);
1313
1314         /*
1315          * Process group and session signals need to be delivered to just the
1316          * parent before the fork or both the parent and the child after the
1317          * fork. Restart if a signal comes in before we add the new process to
1318          * it's process group.
1319          * A fatal signal pending means that current will exit, so the new
1320          * thread can't slip out of an OOM kill (or normal SIGKILL).
1321          */
1322         recalc_sigpending();
1323         if (signal_pending(current)) {
1324                 spin_unlock(&current->sighand->siglock);
1325                 write_unlock_irq(&tasklist_lock);
1326                 retval = -ERESTARTNOINTR;
1327                 goto bad_fork_free_pid;
1328         }
1329
1330         if (clone_flags & CLONE_THREAD) {
1331                 p->group_leader = current->group_leader;
1332                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1333
1334                 if (!cputime_eq(current->signal->it_virt_expires,
1335                                 cputime_zero) ||
1336                     !cputime_eq(current->signal->it_prof_expires,
1337                                 cputime_zero) ||
1338                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1339                     !list_empty(&current->signal->cpu_timers[0]) ||
1340                     !list_empty(&current->signal->cpu_timers[1]) ||
1341                     !list_empty(&current->signal->cpu_timers[2])) {
1342                         /*
1343                          * Have child wake up on its first tick to check
1344                          * for process CPU timers.
1345                          */
1346                         p->it_prof_expires = jiffies_to_cputime(1);
1347                 }
1348         }
1349
1350         if (likely(p->pid)) {
1351                 add_parent(p);
1352                 if (unlikely(p->ptrace & PT_PTRACED))
1353                         __ptrace_link(p, current->parent);
1354
1355                 if (thread_group_leader(p)) {
1356                         if (clone_flags & CLONE_NEWPID)
1357                                 p->nsproxy->pid_ns->child_reaper = p;
1358
1359                         p->signal->leader_pid = pid;
1360                         p->signal->tty = current->signal->tty;
1361                         set_task_pgrp(p, task_pgrp_nr(current));
1362                         set_task_session(p, task_session_nr(current));
1363                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1364                         attach_pid(p, PIDTYPE_SID, task_session(current));
1365                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1366                         __get_cpu_var(process_counts)++;
1367                 }
1368                 attach_pid(p, PIDTYPE_PID, pid);
1369                 nr_threads++;
1370         }
1371
1372         total_forks++;
1373         spin_unlock(&current->sighand->siglock);
1374         write_unlock_irq(&tasklist_lock);
1375         proc_fork_connector(p);
1376         cgroup_post_fork(p);
1377         return p;
1378
1379 bad_fork_free_pid:
1380         if (pid != &init_struct_pid)
1381                 free_pid(pid);
1382 bad_fork_cleanup_io:
1383         put_io_context(p->io_context);
1384 bad_fork_cleanup_namespaces:
1385         exit_task_namespaces(p);
1386 bad_fork_cleanup_keys:
1387         exit_keys(p);
1388 bad_fork_cleanup_mm:
1389         if (p->mm)
1390                 mmput(p->mm);
1391 bad_fork_cleanup_signal:
1392         cleanup_signal(p);
1393 bad_fork_cleanup_sighand:
1394         __cleanup_sighand(p->sighand);
1395 bad_fork_cleanup_fs:
1396         exit_fs(p); /* blocking */
1397 bad_fork_cleanup_files:
1398         exit_files(p); /* blocking */
1399 bad_fork_cleanup_semundo:
1400         exit_sem(p);
1401 bad_fork_cleanup_audit:
1402         audit_free(p);
1403 bad_fork_cleanup_security:
1404         security_task_free(p);
1405 bad_fork_cleanup_policy:
1406 #ifdef CONFIG_NUMA
1407         mpol_free(p->mempolicy);
1408 bad_fork_cleanup_cgroup:
1409 #endif
1410         cgroup_exit(p, cgroup_callbacks_done);
1411         delayacct_tsk_free(p);
1412         if (p->binfmt)
1413                 module_put(p->binfmt->module);
1414 bad_fork_cleanup_put_domain:
1415         module_put(task_thread_info(p)->exec_domain->module);
1416 bad_fork_cleanup_count:
1417         put_group_info(p->group_info);
1418         atomic_dec(&p->user->processes);
1419         free_uid(p->user);
1420 bad_fork_free:
1421         free_task(p);
1422 fork_out:
1423         return ERR_PTR(retval);
1424 }
1425
1426 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1427 {
1428         memset(regs, 0, sizeof(struct pt_regs));
1429         return regs;
1430 }
1431
1432 struct task_struct * __cpuinit fork_idle(int cpu)
1433 {
1434         struct task_struct *task;
1435         struct pt_regs regs;
1436
1437         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1438                                 &init_struct_pid);
1439         if (!IS_ERR(task))
1440                 init_idle(task, cpu);
1441
1442         return task;
1443 }
1444
1445 static int fork_traceflag(unsigned clone_flags)
1446 {
1447         if (clone_flags & CLONE_UNTRACED)
1448                 return 0;
1449         else if (clone_flags & CLONE_VFORK) {
1450                 if (current->ptrace & PT_TRACE_VFORK)
1451                         return PTRACE_EVENT_VFORK;
1452         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1453                 if (current->ptrace & PT_TRACE_CLONE)
1454                         return PTRACE_EVENT_CLONE;
1455         } else if (current->ptrace & PT_TRACE_FORK)
1456                 return PTRACE_EVENT_FORK;
1457
1458         return 0;
1459 }
1460
1461 /*
1462  *  Ok, this is the main fork-routine.
1463  *
1464  * It copies the process, and if successful kick-starts
1465  * it and waits for it to finish using the VM if required.
1466  */
1467 long do_fork(unsigned long clone_flags,
1468               unsigned long stack_start,
1469               struct pt_regs *regs,
1470               unsigned long stack_size,
1471               int __user *parent_tidptr,
1472               int __user *child_tidptr)
1473 {
1474         struct task_struct *p;
1475         int trace = 0;
1476         long nr;
1477
1478         /*
1479          * We hope to recycle these flags after 2.6.26
1480          */
1481         if (unlikely(clone_flags & CLONE_STOPPED)) {
1482                 static int __read_mostly count = 100;
1483
1484                 if (count > 0 && printk_ratelimit()) {
1485                         char comm[TASK_COMM_LEN];
1486
1487                         count--;
1488                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1489                                         "clone flags 0x%lx\n",
1490                                 get_task_comm(comm, current),
1491                                 clone_flags & CLONE_STOPPED);
1492                 }
1493         }
1494
1495         if (unlikely(current->ptrace)) {
1496                 trace = fork_traceflag (clone_flags);
1497                 if (trace)
1498                         clone_flags |= CLONE_PTRACE;
1499         }
1500
1501         p = copy_process(clone_flags, stack_start, regs, stack_size,
1502                         child_tidptr, NULL);
1503         /*
1504          * Do this prior waking up the new thread - the thread pointer
1505          * might get invalid after that point, if the thread exits quickly.
1506          */
1507         if (!IS_ERR(p)) {
1508                 struct completion vfork;
1509
1510                 nr = task_pid_vnr(p);
1511
1512                 if (clone_flags & CLONE_PARENT_SETTID)
1513                         put_user(nr, parent_tidptr);
1514
1515                 if (clone_flags & CLONE_VFORK) {
1516                         p->vfork_done = &vfork;
1517                         init_completion(&vfork);
1518                 }
1519
1520                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1521                         /*
1522                          * We'll start up with an immediate SIGSTOP.
1523                          */
1524                         sigaddset(&p->pending.signal, SIGSTOP);
1525                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1526                 }
1527
1528                 if (!(clone_flags & CLONE_STOPPED))
1529                         wake_up_new_task(p, clone_flags);
1530                 else
1531                         __set_task_state(p, TASK_STOPPED);
1532
1533                 if (unlikely (trace)) {
1534                         current->ptrace_message = nr;
1535                         ptrace_notify ((trace << 8) | SIGTRAP);
1536                 }
1537
1538                 if (clone_flags & CLONE_VFORK) {
1539                         freezer_do_not_count();
1540                         wait_for_completion(&vfork);
1541                         freezer_count();
1542                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1543                                 current->ptrace_message = nr;
1544                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1545                         }
1546                 }
1547         } else {
1548                 nr = PTR_ERR(p);
1549         }
1550         return nr;
1551 }
1552
1553 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1554 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1555 #endif
1556
1557 static void sighand_ctor(struct kmem_cache *cachep, void *data)
1558 {
1559         struct sighand_struct *sighand = data;
1560
1561         spin_lock_init(&sighand->siglock);
1562         init_waitqueue_head(&sighand->signalfd_wqh);
1563 }
1564
1565 void __init proc_caches_init(void)
1566 {
1567         sighand_cachep = kmem_cache_create("sighand_cache",
1568                         sizeof(struct sighand_struct), 0,
1569                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1570                         sighand_ctor);
1571         signal_cachep = kmem_cache_create("signal_cache",
1572                         sizeof(struct signal_struct), 0,
1573                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1574         files_cachep = kmem_cache_create("files_cache",
1575                         sizeof(struct files_struct), 0,
1576                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1577         fs_cachep = kmem_cache_create("fs_cache",
1578                         sizeof(struct fs_struct), 0,
1579                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1580         vm_area_cachep = kmem_cache_create("vm_area_struct",
1581                         sizeof(struct vm_area_struct), 0,
1582                         SLAB_PANIC, NULL);
1583         mm_cachep = kmem_cache_create("mm_struct",
1584                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1585                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1586 }
1587
1588 /*
1589  * Check constraints on flags passed to the unshare system call and
1590  * force unsharing of additional process context as appropriate.
1591  */
1592 static void check_unshare_flags(unsigned long *flags_ptr)
1593 {
1594         /*
1595          * If unsharing a thread from a thread group, must also
1596          * unshare vm.
1597          */
1598         if (*flags_ptr & CLONE_THREAD)
1599                 *flags_ptr |= CLONE_VM;
1600
1601         /*
1602          * If unsharing vm, must also unshare signal handlers.
1603          */
1604         if (*flags_ptr & CLONE_VM)
1605                 *flags_ptr |= CLONE_SIGHAND;
1606
1607         /*
1608          * If unsharing signal handlers and the task was created
1609          * using CLONE_THREAD, then must unshare the thread
1610          */
1611         if ((*flags_ptr & CLONE_SIGHAND) &&
1612             (atomic_read(&current->signal->count) > 1))
1613                 *flags_ptr |= CLONE_THREAD;
1614
1615         /*
1616          * If unsharing namespace, must also unshare filesystem information.
1617          */
1618         if (*flags_ptr & CLONE_NEWNS)
1619                 *flags_ptr |= CLONE_FS;
1620 }
1621
1622 /*
1623  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1624  */
1625 static int unshare_thread(unsigned long unshare_flags)
1626 {
1627         if (unshare_flags & CLONE_THREAD)
1628                 return -EINVAL;
1629
1630         return 0;
1631 }
1632
1633 /*
1634  * Unshare the filesystem structure if it is being shared
1635  */
1636 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1637 {
1638         struct fs_struct *fs = current->fs;
1639
1640         if ((unshare_flags & CLONE_FS) &&
1641             (fs && atomic_read(&fs->count) > 1)) {
1642                 *new_fsp = __copy_fs_struct(current->fs);
1643                 if (!*new_fsp)
1644                         return -ENOMEM;
1645         }
1646
1647         return 0;
1648 }
1649
1650 /*
1651  * Unsharing of sighand is not supported yet
1652  */
1653 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1654 {
1655         struct sighand_struct *sigh = current->sighand;
1656
1657         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1658                 return -EINVAL;
1659         else
1660                 return 0;
1661 }
1662
1663 /*
1664  * Unshare vm if it is being shared
1665  */
1666 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1667 {
1668         struct mm_struct *mm = current->mm;
1669
1670         if ((unshare_flags & CLONE_VM) &&
1671             (mm && atomic_read(&mm->mm_users) > 1)) {
1672                 return -EINVAL;
1673         }
1674
1675         return 0;
1676 }
1677
1678 /*
1679  * Unshare file descriptor table if it is being shared
1680  */
1681 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1682 {
1683         struct files_struct *fd = current->files;
1684         int error = 0;
1685
1686         if ((unshare_flags & CLONE_FILES) &&
1687             (fd && atomic_read(&fd->count) > 1)) {
1688                 *new_fdp = dup_fd(fd, &error);
1689                 if (!*new_fdp)
1690                         return error;
1691         }
1692
1693         return 0;
1694 }
1695
1696 /*
1697  * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not
1698  * supported yet
1699  */
1700 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp)
1701 {
1702         if (unshare_flags & CLONE_SYSVSEM)
1703                 return -EINVAL;
1704
1705         return 0;
1706 }
1707
1708 /*
1709  * unshare allows a process to 'unshare' part of the process
1710  * context which was originally shared using clone.  copy_*
1711  * functions used by do_fork() cannot be used here directly
1712  * because they modify an inactive task_struct that is being
1713  * constructed. Here we are modifying the current, active,
1714  * task_struct.
1715  */
1716 asmlinkage long sys_unshare(unsigned long unshare_flags)
1717 {
1718         int err = 0;
1719         struct fs_struct *fs, *new_fs = NULL;
1720         struct sighand_struct *new_sigh = NULL;
1721         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1722         struct files_struct *fd, *new_fd = NULL;
1723         struct sem_undo_list *new_ulist = NULL;
1724         struct nsproxy *new_nsproxy = NULL;
1725
1726         check_unshare_flags(&unshare_flags);
1727
1728         /* Return -EINVAL for all unsupported flags */
1729         err = -EINVAL;
1730         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1731                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1732                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1733                                 CLONE_NEWNET))
1734                 goto bad_unshare_out;
1735
1736         if ((err = unshare_thread(unshare_flags)))
1737                 goto bad_unshare_out;
1738         if ((err = unshare_fs(unshare_flags, &new_fs)))
1739                 goto bad_unshare_cleanup_thread;
1740         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1741                 goto bad_unshare_cleanup_fs;
1742         if ((err = unshare_vm(unshare_flags, &new_mm)))
1743                 goto bad_unshare_cleanup_sigh;
1744         if ((err = unshare_fd(unshare_flags, &new_fd)))
1745                 goto bad_unshare_cleanup_vm;
1746         if ((err = unshare_semundo(unshare_flags, &new_ulist)))
1747                 goto bad_unshare_cleanup_fd;
1748         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1749                         new_fs)))
1750                 goto bad_unshare_cleanup_semundo;
1751
1752         if (new_fs ||  new_mm || new_fd || new_ulist || new_nsproxy) {
1753
1754                 if (new_nsproxy) {
1755                         switch_task_namespaces(current, new_nsproxy);
1756                         new_nsproxy = NULL;
1757                 }
1758
1759                 task_lock(current);
1760
1761                 if (new_fs) {
1762                         fs = current->fs;
1763                         current->fs = new_fs;
1764                         new_fs = fs;
1765                 }
1766
1767                 if (new_mm) {
1768                         mm = current->mm;
1769                         active_mm = current->active_mm;
1770                         current->mm = new_mm;
1771                         current->active_mm = new_mm;
1772                         activate_mm(active_mm, new_mm);
1773                         new_mm = mm;
1774                 }
1775
1776                 if (new_fd) {
1777                         fd = current->files;
1778                         current->files = new_fd;
1779                         new_fd = fd;
1780                 }
1781
1782                 task_unlock(current);
1783         }
1784
1785         if (new_nsproxy)
1786                 put_nsproxy(new_nsproxy);
1787
1788 bad_unshare_cleanup_semundo:
1789 bad_unshare_cleanup_fd:
1790         if (new_fd)
1791                 put_files_struct(new_fd);
1792
1793 bad_unshare_cleanup_vm:
1794         if (new_mm)
1795                 mmput(new_mm);
1796
1797 bad_unshare_cleanup_sigh:
1798         if (new_sigh)
1799                 if (atomic_dec_and_test(&new_sigh->count))
1800                         kmem_cache_free(sighand_cachep, new_sigh);
1801
1802 bad_unshare_cleanup_fs:
1803         if (new_fs)
1804                 put_fs_struct(new_fs);
1805
1806 bad_unshare_cleanup_thread:
1807 bad_unshare_out:
1808         return err;
1809 }