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   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/fdtable.h>
  26 #include <linux/iocontext.h>
  27 #include <linux/key.h>
  28 #include <linux/binfmts.h>
  29 #include <linux/mman.h>
  30 #include <linux/mmu_notifier.h>
  31 #include <linux/fs.h>
  32 #include <linux/nsproxy.h>
  33 #include <linux/capability.h>
  34 #include <linux/cpu.h>
  35 #include <linux/cgroup.h>
  36 #include <linux/security.h>
  37 #include <linux/hugetlb.h>
  38 #include <linux/swap.h>
  39 #include <linux/syscalls.h>
  40 #include <linux/jiffies.h>
  41 #include <linux/tracehook.h>
  42 #include <linux/futex.h>
  43 #include <linux/compat.h>
  44 #include <linux/task_io_accounting_ops.h>
  45 #include <linux/rcupdate.h>
  46 #include <linux/ptrace.h>
  47 #include <linux/mount.h>
  48 #include <linux/audit.h>
  49 #include <linux/memcontrol.h>
  50 #include <linux/ftrace.h>
  51 #include <linux/profile.h>
  52 #include <linux/rmap.h>
  53 #include <linux/acct.h>
  54 #include <linux/tsacct_kern.h>
  55 #include <linux/cn_proc.h>
  56 #include <linux/freezer.h>
  57 #include <linux/delayacct.h>
  58 #include <linux/taskstats_kern.h>
  59 #include <linux/random.h>
  60 #include <linux/tty.h>
  61 #include <linux/proc_fs.h>
  62 #include <linux/blkdev.h>
  63 #include <linux/fs_struct.h>
  64 #include <linux/magic.h>
  65 #include <linux/perf_counter.h>
  66
  67 #include <asm/pgtable.h>
  68 #include <asm/pgalloc.h>
  69 #include <asm/uaccess.h>
  70 #include <asm/mmu_context.h>
  71 #include <asm/cacheflush.h>
  72 #include <asm/tlbflush.h>
  73
  74 #include <trace/events/sched.h>
  75
  76 /*
  77  * Protected counters by write_lock_irq(&tasklist_lock)
  78  */
  79 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  80 int nr_threads;                 /* The idle threads do not count.. */
  81
  82 int max_threads;                /* tunable limit on nr_threads */
  83
  84 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  85
  86 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  87
  88 int nr_processes(void)
  89 {
  90         int cpu;
  91         int total = 0;
  92
  93         for_each_online_cpu(cpu)
  94                 total += per_cpu(process_counts, cpu);
  95
  96         return total;
  97 }
  98
  99 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 100 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
 101 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
 102 static struct kmem_cache *task_struct_cachep;
 103 #endif
 104
 105 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 106 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 107 {
 108 #ifdef CONFIG_DEBUG_STACK_USAGE
 109         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 110 #else
 111         gfp_t mask = GFP_KERNEL;
 112 #endif
 113         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 114 }
 115
 116 static inline void free_thread_info(struct thread_info *ti)
 117 {
 118         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 119 }
 120 #endif
 121
 122 /* SLAB cache for signal_struct structures (tsk->signal) */
 123 static struct kmem_cache *signal_cachep;
 124
 125 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 126 struct kmem_cache *sighand_cachep;
 127
 128 /* SLAB cache for files_struct structures (tsk->files) */
 129 struct kmem_cache *files_cachep;
 130
 131 /* SLAB cache for fs_struct structures (tsk->fs) */
 132 struct kmem_cache *fs_cachep;
 133
 134 /* SLAB cache for vm_area_struct structures */
 135 struct kmem_cache *vm_area_cachep;
 136
 137 /* SLAB cache for mm_struct structures (tsk->mm) */
 138 static struct kmem_cache *mm_cachep;
 139
 140 void free_task(struct task_struct *tsk)
 141 {
 142         prop_local_destroy_single(&tsk->dirties);
 143         free_thread_info(tsk->stack);
 144         rt_mutex_debug_task_free(tsk);
 145         ftrace_graph_exit_task(tsk);
 146         free_task_struct(tsk);
 147 }
 148 EXPORT_SYMBOL(free_task);
 149
 150 void __put_task_struct(struct task_struct *tsk)
 151 {
 152         WARN_ON(!tsk->exit_state);
 153         WARN_ON(atomic_read(&tsk->usage));
 154         WARN_ON(tsk == current);
 155
 156         put_cred(tsk->real_cred);
 157         put_cred(tsk->cred);
 158         delayacct_tsk_free(tsk);
 159
 160         if (!profile_handoff_task(tsk))
 161                 free_task(tsk);
 162 }
 163
 164 /*
 165  * macro override instead of weak attribute alias, to workaround
 166  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 167  */
 168 #ifndef arch_task_cache_init
 169 #define arch_task_cache_init()
 170 #endif
 171
 172 void __init fork_init(unsigned long mempages)
 173 {
 174 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 175 #ifndef ARCH_MIN_TASKALIGN
 176 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 177 #endif
 178         /* create a slab on which task_structs can be allocated */
 179         task_struct_cachep =
 180                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 181                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 182 #endif
 183
 184         /* do the arch specific task caches init */
 185         arch_task_cache_init();
 186
 187         /*
 188          * The default maximum number of threads is set to a safe
 189          * value: the thread structures can take up at most half
 190          * of memory.
 191          */
 192         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 193
 194         /*
 195          * we need to allow at least 20 threads to boot a system
 196          */
 197         if(max_threads < 20)
 198                 max_threads = 20;
 199
 200         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 201         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 202         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 203                 init_task.signal->rlim[RLIMIT_NPROC];
 204 }
 205
 206 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 207                                                struct task_struct *src)
 208 {
 209         *dst = *src;
 210         return 0;
 211 }
 212
 213 static struct task_struct *dup_task_struct(struct task_struct *orig)
 214 {
 215         struct task_struct *tsk;
 216         struct thread_info *ti;
 217         unsigned long *stackend;
 218
 219         int err;
 220
 221         prepare_to_copy(orig);
 222
 223         tsk = alloc_task_struct();
 224         if (!tsk)
 225                 return NULL;
 226
 227         ti = alloc_thread_info(tsk);
 228         if (!ti) {
 229                 free_task_struct(tsk);
 230                 return NULL;
 231         }
 232
 233         err = arch_dup_task_struct(tsk, orig);
 234         if (err)
 235                 goto out;
 236
 237         tsk->stack = ti;
 238
 239         err = prop_local_init_single(&tsk->dirties);
 240         if (err)
 241                 goto out;
 242
 243         setup_thread_stack(tsk, orig);
 244         stackend = end_of_stack(tsk);
 245         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 246
 247 #ifdef CONFIG_CC_STACKPROTECTOR
 248         tsk->stack_canary = get_random_int();
 249 #endif
 250
 251         /* One for us, one for whoever does the "release_task()" (usually parent) */
 252         atomic_set(&tsk->usage,2);
 253         atomic_set(&tsk->fs_excl, 0);
 254 #ifdef CONFIG_BLK_DEV_IO_TRACE
 255         tsk->btrace_seq = 0;
 256 #endif
 257         tsk->splice_pipe = NULL;
 258         return tsk;
 259
 260 out:
 261         free_thread_info(ti);
 262         free_task_struct(tsk);
 263         return NULL;
 264 }
 265
 266 #ifdef CONFIG_MMU
 267 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 268 {
 269         struct vm_area_struct *mpnt, *tmp, **pprev;
 270         struct rb_node **rb_link, *rb_parent;
 271         int retval;
 272         unsigned long charge;
 273         struct mempolicy *pol;
 274
 275         down_write(&oldmm->mmap_sem);
 276         flush_cache_dup_mm(oldmm);
 277         /*
 278          * Not linked in yet - no deadlock potential:
 279          */
 280         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 281
 282         mm->locked_vm = 0;
 283         mm->mmap = NULL;
 284         mm->mmap_cache = NULL;
 285         mm->free_area_cache = oldmm->mmap_base;
 286         mm->cached_hole_size = ~0UL;
 287         mm->map_count = 0;
 288         cpumask_clear(mm_cpumask(mm));
 289         mm->mm_rb = RB_ROOT;
 290         rb_link = &mm->mm_rb.rb_node;
 291         rb_parent = NULL;
 292         pprev = &mm->mmap;
 293
 294         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 295                 struct file *file;
 296
 297                 if (mpnt->vm_flags & VM_DONTCOPY) {
 298                         long pages = vma_pages(mpnt);
 299                         mm->total_vm -= pages;
 300                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 301                                                                 -pages);
 302                         continue;
 303                 }
 304                 charge = 0;
 305                 if (mpnt->vm_flags & VM_ACCOUNT) {
 306                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 307                         if (security_vm_enough_memory(len))
 308                                 goto fail_nomem;
 309                         charge = len;
 310                 }
 311                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 312                 if (!tmp)
 313                         goto fail_nomem;
 314                 *tmp = *mpnt;
 315                 pol = mpol_dup(vma_policy(mpnt));
 316                 retval = PTR_ERR(pol);
 317                 if (IS_ERR(pol))
 318                         goto fail_nomem_policy;
 319                 vma_set_policy(tmp, pol);
 320                 tmp->vm_flags &= ~VM_LOCKED;
 321                 tmp->vm_mm = mm;
 322                 tmp->vm_next = NULL;
 323                 anon_vma_link(tmp);
 324                 file = tmp->vm_file;
 325                 if (file) {
 326                         struct inode *inode = file->f_path.dentry->d_inode;
 327                         struct address_space *mapping = file->f_mapping;
 328
 329                         get_file(file);
 330                         if (tmp->vm_flags & VM_DENYWRITE)
 331                                 atomic_dec(&inode->i_writecount);
 332                         spin_lock(&mapping->i_mmap_lock);
 333                         if (tmp->vm_flags & VM_SHARED)
 334                                 mapping->i_mmap_writable++;
 335                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 336                         flush_dcache_mmap_lock(mapping);
 337                         /* insert tmp into the share list, just after mpnt */
 338                         vma_prio_tree_add(tmp, mpnt);
 339                         flush_dcache_mmap_unlock(mapping);
 340                         spin_unlock(&mapping->i_mmap_lock);
 341                 }
 342
 343                 /*
 344                  * Clear hugetlb-related page reserves for children. This only
 345                  * affects MAP_PRIVATE mappings. Faults generated by the child
 346                  * are not guaranteed to succeed, even if read-only
 347                  */
 348                 if (is_vm_hugetlb_page(tmp))
 349                         reset_vma_resv_huge_pages(tmp);
 350
 351                 /*
 352                  * Link in the new vma and copy the page table entries.
 353                  */
 354                 *pprev = tmp;
 355                 pprev = &tmp->vm_next;
 356
 357                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 358                 rb_link = &tmp->vm_rb.rb_right;
 359                 rb_parent = &tmp->vm_rb;
 360
 361                 mm->map_count++;
 362                 retval = copy_page_range(mm, oldmm, mpnt);
 363
 364                 if (tmp->vm_ops && tmp->vm_ops->open)
 365                         tmp->vm_ops->open(tmp);
 366
 367                 if (retval)
 368                         goto out;
 369         }
 370         /* a new mm has just been created */
 371         arch_dup_mmap(oldmm, mm);
 372         retval = 0;
 373 out:
 374         up_write(&mm->mmap_sem);
 375         flush_tlb_mm(oldmm);
 376         up_write(&oldmm->mmap_sem);
 377         return retval;
 378 fail_nomem_policy:
 379         kmem_cache_free(vm_area_cachep, tmp);
 380 fail_nomem:
 381         retval = -ENOMEM;
 382         vm_unacct_memory(charge);
 383         goto out;
 384 }
 385
 386 static inline int mm_alloc_pgd(struct mm_struct * mm)
 387 {
 388         mm->pgd = pgd_alloc(mm);
 389         if (unlikely(!mm->pgd))
 390                 return -ENOMEM;
 391         return 0;
 392 }
 393
 394 static inline void mm_free_pgd(struct mm_struct * mm)
 395 {
 396         pgd_free(mm, mm->pgd);
 397 }
 398 #else
 399 #define dup_mmap(mm, oldmm)     (0)
 400 #define mm_alloc_pgd(mm)        (0)
 401 #define mm_free_pgd(mm)
 402 #endif /* CONFIG_MMU */
 403
 404 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 405
 406 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 407 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 408
 409 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 410
 411 static int __init coredump_filter_setup(char *s)
 412 {
 413         default_dump_filter =
 414                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 415                 MMF_DUMP_FILTER_MASK;
 416         return 1;
 417 }
 418
 419 __setup("coredump_filter=", coredump_filter_setup);
 420
 421 #include <linux/init_task.h>
 422
 423 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 424 {
 425         atomic_set(&mm->mm_users, 1);
 426         atomic_set(&mm->mm_count, 1);
 427         init_rwsem(&mm->mmap_sem);
 428         INIT_LIST_HEAD(&mm->mmlist);
 429         mm->flags = (current->mm) ? current->mm->flags : default_dump_filter;
 430         mm->core_state = NULL;
 431         mm->nr_ptes = 0;
 432         set_mm_counter(mm, file_rss, 0);
 433         set_mm_counter(mm, anon_rss, 0);
 434         spin_lock_init(&mm->page_table_lock);
 435         spin_lock_init(&mm->ioctx_lock);
 436         INIT_HLIST_HEAD(&mm->ioctx_list);
 437         mm->free_area_cache = TASK_UNMAPPED_BASE;
 438         mm->cached_hole_size = ~0UL;
 439         mm_init_owner(mm, p);
 440
 441         if (likely(!mm_alloc_pgd(mm))) {
 442                 mm->def_flags = 0;
 443                 mmu_notifier_mm_init(mm);
 444                 return mm;
 445         }
 446
 447         free_mm(mm);
 448         return NULL;
 449 }
 450
 451 /*
 452  * Allocate and initialize an mm_struct.
 453  */
 454 struct mm_struct * mm_alloc(void)
 455 {
 456         struct mm_struct * mm;
 457
 458         mm = allocate_mm();
 459         if (mm) {
 460                 memset(mm, 0, sizeof(*mm));
 461                 mm = mm_init(mm, current);
 462         }
 463         return mm;
 464 }
 465
 466 /*
 467  * Called when the last reference to the mm
 468  * is dropped: either by a lazy thread or by
 469  * mmput. Free the page directory and the mm.
 470  */
 471 void __mmdrop(struct mm_struct *mm)
 472 {
 473         BUG_ON(mm == &init_mm);
 474         mm_free_pgd(mm);
 475         destroy_context(mm);
 476         mmu_notifier_mm_destroy(mm);
 477         free_mm(mm);
 478 }
 479 EXPORT_SYMBOL_GPL(__mmdrop);
 480
 481 /*
 482  * Decrement the use count and release all resources for an mm.
 483  */
 484 void mmput(struct mm_struct *mm)
 485 {
 486         might_sleep();
 487
 488         if (atomic_dec_and_test(&mm->mm_users)) {
 489                 exit_aio(mm);
 490                 exit_mmap(mm);
 491                 set_mm_exe_file(mm, NULL);
 492                 if (!list_empty(&mm->mmlist)) {
 493                         spin_lock(&mmlist_lock);
 494                         list_del(&mm->mmlist);
 495                         spin_unlock(&mmlist_lock);
 496                 }
 497                 put_swap_token(mm);
 498                 mmdrop(mm);
 499         }
 500 }
 501 EXPORT_SYMBOL_GPL(mmput);
 502
 503 /**
 504  * get_task_mm - acquire a reference to the task's mm
 505  *
 506  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 507  * this kernel workthread has transiently adopted a user mm with use_mm,
 508  * to do its AIO) is not set and if so returns a reference to it, after
 509  * bumping up the use count.  User must release the mm via mmput()
 510  * after use.  Typically used by /proc and ptrace.
 511  */
 512 struct mm_struct *get_task_mm(struct task_struct *task)
 513 {
 514         struct mm_struct *mm;
 515
 516         task_lock(task);
 517         mm = task->mm;
 518         if (mm) {
 519                 if (task->flags & PF_KTHREAD)
 520                         mm = NULL;
 521                 else
 522                         atomic_inc(&mm->mm_users);
 523         }
 524         task_unlock(task);
 525         return mm;
 526 }
 527 EXPORT_SYMBOL_GPL(get_task_mm);
 528
 529 /* Please note the differences between mmput and mm_release.
 530  * mmput is called whenever we stop holding onto a mm_struct,
 531  * error success whatever.
 532  *
 533  * mm_release is called after a mm_struct has been removed
 534  * from the current process.
 535  *
 536  * This difference is important for error handling, when we
 537  * only half set up a mm_struct for a new process and need to restore
 538  * the old one.  Because we mmput the new mm_struct before
 539  * restoring the old one. . .
 540  * Eric Biederman 10 January 1998
 541  */
 542 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 543 {
 544         struct completion *vfork_done = tsk->vfork_done;
 545
 546         /* Get rid of any futexes when releasing the mm */
 547 #ifdef CONFIG_FUTEX
 548         if (unlikely(tsk->robust_list))
 549                 exit_robust_list(tsk);
 550 #ifdef CONFIG_COMPAT
 551         if (unlikely(tsk->compat_robust_list))
 552                 compat_exit_robust_list(tsk);
 553 #endif
 554 #endif
 555
 556         /* Get rid of any cached register state */
 557         deactivate_mm(tsk, mm);
 558
 559         /* notify parent sleeping on vfork() */
 560         if (vfork_done) {
 561                 tsk->vfork_done = NULL;
 562                 complete(vfork_done);
 563         }
 564
 565         /*
 566          * If we're exiting normally, clear a user-space tid field if
 567          * requested.  We leave this alone when dying by signal, to leave
 568          * the value intact in a core dump, and to save the unnecessary
 569          * trouble otherwise.  Userland only wants this done for a sys_exit.
 570          */
 571         if (tsk->clear_child_tid
 572             && !(tsk->flags & PF_SIGNALED)
 573             && atomic_read(&mm->mm_users) > 1) {
 574                 u32 __user * tidptr = tsk->clear_child_tid;
 575                 tsk->clear_child_tid = NULL;
 576
 577                 /*
 578                  * We don't check the error code - if userspace has
 579                  * not set up a proper pointer then tough luck.
 580                  */
 581                 put_user(0, tidptr);
 582                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 583         }
 584 }
 585
 586 /*
 587  * Allocate a new mm structure and copy contents from the
 588  * mm structure of the passed in task structure.
 589  */
 590 struct mm_struct *dup_mm(struct task_struct *tsk)
 591 {
 592         struct mm_struct *mm, *oldmm = current->mm;
 593         int err;
 594
 595         if (!oldmm)
 596                 return NULL;
 597
 598         mm = allocate_mm();
 599         if (!mm)
 600                 goto fail_nomem;
 601
 602         memcpy(mm, oldmm, sizeof(*mm));
 603
 604         /* Initializing for Swap token stuff */
 605         mm->token_priority = 0;
 606         mm->last_interval = 0;
 607
 608         if (!mm_init(mm, tsk))
 609                 goto fail_nomem;
 610
 611         if (init_new_context(tsk, mm))
 612                 goto fail_nocontext;
 613
 614         dup_mm_exe_file(oldmm, mm);
 615
 616         err = dup_mmap(mm, oldmm);
 617         if (err)
 618                 goto free_pt;
 619
 620         mm->hiwater_rss = get_mm_rss(mm);
 621         mm->hiwater_vm = mm->total_vm;
 622
 623         return mm;
 624
 625 free_pt:
 626         mmput(mm);
 627
 628 fail_nomem:
 629         return NULL;
 630
 631 fail_nocontext:
 632         /*
 633          * If init_new_context() failed, we cannot use mmput() to free the mm
 634          * because it calls destroy_context()
 635          */
 636         mm_free_pgd(mm);
 637         free_mm(mm);
 638         return NULL;
 639 }
 640
 641 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 642 {
 643         struct mm_struct * mm, *oldmm;
 644         int retval;
 645
 646         tsk->min_flt = tsk->maj_flt = 0;
 647         tsk->nvcsw = tsk->nivcsw = 0;
 648 #ifdef CONFIG_DETECT_HUNG_TASK
 649         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 650 #endif
 651
 652         tsk->mm = NULL;
 653         tsk->active_mm = NULL;
 654
 655         /*
 656          * Are we cloning a kernel thread?
 657          *
 658          * We need to steal a active VM for that..
 659          */
 660         oldmm = current->mm;
 661         if (!oldmm)
 662                 return 0;
 663
 664         if (clone_flags & CLONE_VM) {
 665                 atomic_inc(&oldmm->mm_users);
 666                 mm = oldmm;
 667                 goto good_mm;
 668         }
 669
 670         retval = -ENOMEM;
 671         mm = dup_mm(tsk);
 672         if (!mm)
 673                 goto fail_nomem;
 674
 675 good_mm:
 676         /* Initializing for Swap token stuff */
 677         mm->token_priority = 0;
 678         mm->last_interval = 0;
 679
 680         tsk->mm = mm;
 681         tsk->active_mm = mm;
 682         return 0;
 683
 684 fail_nomem:
 685         return retval;
 686 }
 687
 688 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 689 {
 690         struct fs_struct *fs = current->fs;
 691         if (clone_flags & CLONE_FS) {
 692                 /* tsk->fs is already what we want */
 693                 write_lock(&fs->lock);
 694                 if (fs->in_exec) {
 695                         write_unlock(&fs->lock);
 696                         return -EAGAIN;
 697                 }
 698                 fs->users++;
 699                 write_unlock(&fs->lock);
 700                 return 0;
 701         }
 702         tsk->fs = copy_fs_struct(fs);
 703         if (!tsk->fs)
 704                 return -ENOMEM;
 705         return 0;
 706 }
 707
 708 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 709 {
 710         struct files_struct *oldf, *newf;
 711         int error = 0;
 712
 713         /*
 714          * A background process may not have any files ...
 715          */
 716         oldf = current->files;
 717         if (!oldf)
 718                 goto out;
 719
 720         if (clone_flags & CLONE_FILES) {
 721                 atomic_inc(&oldf->count);
 722                 goto out;
 723         }
 724
 725         newf = dup_fd(oldf, &error);
 726         if (!newf)
 727                 goto out;
 728
 729         tsk->files = newf;
 730         error = 0;
 731 out:
 732         return error;
 733 }
 734
 735 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 736 {
 737 #ifdef CONFIG_BLOCK
 738         struct io_context *ioc = current->io_context;
 739
 740         if (!ioc)
 741                 return 0;
 742         /*
 743          * Share io context with parent, if CLONE_IO is set
 744          */
 745         if (clone_flags & CLONE_IO) {
 746                 tsk->io_context = ioc_task_link(ioc);
 747                 if (unlikely(!tsk->io_context))
 748                         return -ENOMEM;
 749         } else if (ioprio_valid(ioc->ioprio)) {
 750                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 751                 if (unlikely(!tsk->io_context))
 752                         return -ENOMEM;
 753
 754                 tsk->io_context->ioprio = ioc->ioprio;
 755         }
 756 #endif
 757         return 0;
 758 }
 759
 760 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 761 {
 762         struct sighand_struct *sig;
 763
 764         if (clone_flags & CLONE_SIGHAND) {
 765                 atomic_inc(&current->sighand->count);
 766                 return 0;
 767         }
 768         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 769         rcu_assign_pointer(tsk->sighand, sig);
 770         if (!sig)
 771                 return -ENOMEM;
 772         atomic_set(&sig->count, 1);
 773         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 774         return 0;
 775 }
 776
 777 void __cleanup_sighand(struct sighand_struct *sighand)
 778 {
 779         if (atomic_dec_and_test(&sighand->count))
 780                 kmem_cache_free(sighand_cachep, sighand);
 781 }
 782
 783
 784 /*
 785  * Initialize POSIX timer handling for a thread group.
 786  */
 787 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 788 {
 789         /* Thread group counters. */
 790         thread_group_cputime_init(sig);
 791
 792         /* Expiration times and increments. */
 793         sig->it_virt_expires = cputime_zero;
 794         sig->it_virt_incr = cputime_zero;
 795         sig->it_prof_expires = cputime_zero;
 796         sig->it_prof_incr = cputime_zero;
 797
 798         /* Cached expiration times. */
 799         sig->cputime_expires.prof_exp = cputime_zero;
 800         sig->cputime_expires.virt_exp = cputime_zero;
 801         sig->cputime_expires.sched_exp = 0;
 802
 803         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 804                 sig->cputime_expires.prof_exp =
 805                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 806                 sig->cputimer.running = 1;
 807         }
 808
 809         /* The timer lists. */
 810         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 811         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 812         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 813 }
 814
 815 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 816 {
 817         struct signal_struct *sig;
 818
 819         if (clone_flags & CLONE_THREAD) {
 820                 atomic_inc(&current->signal->count);
 821                 atomic_inc(&current->signal->live);
 822                 return 0;
 823         }
 824
 825         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 826         tsk->signal = sig;
 827         if (!sig)
 828                 return -ENOMEM;
 829
 830         atomic_set(&sig->count, 1);
 831         atomic_set(&sig->live, 1);
 832         init_waitqueue_head(&sig->wait_chldexit);
 833         sig->flags = 0;
 834         if (clone_flags & CLONE_NEWPID)
 835                 sig->flags |= SIGNAL_UNKILLABLE;
 836         sig->group_exit_code = 0;
 837         sig->group_exit_task = NULL;
 838         sig->group_stop_count = 0;
 839         sig->curr_target = tsk;
 840         init_sigpending(&sig->shared_pending);
 841         INIT_LIST_HEAD(&sig->posix_timers);
 842
 843         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 844         sig->it_real_incr.tv64 = 0;
 845         sig->real_timer.function = it_real_fn;
 846
 847         sig->leader = 0;        /* session leadership doesn't inherit */
 848         sig->tty_old_pgrp = NULL;
 849         sig->tty = NULL;
 850
 851         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 852         sig->gtime = cputime_zero;
 853         sig->cgtime = cputime_zero;
 854         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 855         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 856         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 857         task_io_accounting_init(&sig->ioac);
 858         sig->sum_sched_runtime = 0;
 859         taskstats_tgid_init(sig);
 860
 861         task_lock(current->group_leader);
 862         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 863         task_unlock(current->group_leader);
 864
 865         posix_cpu_timers_init_group(sig);
 866
 867         acct_init_pacct(&sig->pacct);
 868
 869         tty_audit_fork(sig);
 870
 871         return 0;
 872 }
 873
 874 void __cleanup_signal(struct signal_struct *sig)
 875 {
 876         thread_group_cputime_free(sig);
 877         tty_kref_put(sig->tty);
 878         kmem_cache_free(signal_cachep, sig);
 879 }
 880
 881 static 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 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;
 896         new_flags |= PF_FORKNOEXEC;
 897         new_flags |= PF_STARTING;
 898         p->flags = new_flags;
 899         clear_freeze_flag(p);
 900 }
 901
 902 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 903 {
 904         current->clear_child_tid = tidptr;
 905
 906         return task_pid_vnr(current);
 907 }
 908
 909 static void rt_mutex_init_task(struct task_struct *p)
 910 {
 911         spin_lock_init(&p->pi_lock);
 912 #ifdef CONFIG_RT_MUTEXES
 913         plist_head_init(&p->pi_waiters, &p->pi_lock);
 914         p->pi_blocked_on = NULL;
 915 #endif
 916 }
 917
 918 #ifdef CONFIG_MM_OWNER
 919 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 920 {
 921         mm->owner = p;
 922 }
 923 #endif /* CONFIG_MM_OWNER */
 924
 925 /*
 926  * Initialize POSIX timer handling for a single task.
 927  */
 928 static void posix_cpu_timers_init(struct task_struct *tsk)
 929 {
 930         tsk->cputime_expires.prof_exp = cputime_zero;
 931         tsk->cputime_expires.virt_exp = cputime_zero;
 932         tsk->cputime_expires.sched_exp = 0;
 933         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 934         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
 935         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
 936 }
 937
 938 /*
 939  * This creates a new process as a copy of the old one,
 940  * but does not actually start it yet.
 941  *
 942  * It copies the registers, and all the appropriate
 943  * parts of the process environment (as per the clone
 944  * flags). The actual kick-off is left to the caller.
 945  */
 946 static struct task_struct *copy_process(unsigned long clone_flags,
 947                                         unsigned long stack_start,
 948                                         struct pt_regs *regs,
 949                                         unsigned long stack_size,
 950                                         int __user *child_tidptr,
 951                                         struct pid *pid,
 952                                         int trace)
 953 {
 954         int retval;
 955         struct task_struct *p;
 956         int cgroup_callbacks_done = 0;
 957
 958         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 959                 return ERR_PTR(-EINVAL);
 960
 961         /*
 962          * Thread groups must share signals as well, and detached threads
 963          * can only be started up within the thread group.
 964          */
 965         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 966                 return ERR_PTR(-EINVAL);
 967
 968         /*
 969          * Shared signal handlers imply shared VM. By way of the above,
 970          * thread groups also imply shared VM. Blocking this case allows
 971          * for various simplifications in other code.
 972          */
 973         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 974                 return ERR_PTR(-EINVAL);
 975
 976         retval = security_task_create(clone_flags);
 977         if (retval)
 978                 goto fork_out;
 979
 980         retval = -ENOMEM;
 981         p = dup_task_struct(current);
 982         if (!p)
 983                 goto fork_out;
 984
 985         ftrace_graph_init_task(p);
 986
 987         rt_mutex_init_task(p);
 988
 989 #ifdef CONFIG_PROVE_LOCKING
 990         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 991         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 992 #endif
 993         retval = -EAGAIN;
 994         if (atomic_read(&p->real_cred->user->processes) >=
 995                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 996                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 997                     p->real_cred->user != INIT_USER)
 998                         goto bad_fork_free;
 999         }
1000
1001         retval = copy_creds(p, clone_flags);
1002         if (retval < 0)
1003                 goto bad_fork_free;
1004
1005         /*
1006          * If multiple threads are within copy_process(), then this check
1007          * triggers too late. This doesn't hurt, the check is only there
1008          * to stop root fork bombs.
1009          */
1010         retval = -EAGAIN;
1011         if (nr_threads >= max_threads)
1012                 goto bad_fork_cleanup_count;
1013
1014         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1015                 goto bad_fork_cleanup_count;
1016
1017         if (p->binfmt && !try_module_get(p->binfmt->module))
1018                 goto bad_fork_cleanup_put_domain;
1019
1020         p->did_exec = 0;
1021         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1022         copy_flags(clone_flags, p);
1023         INIT_LIST_HEAD(&p->children);
1024         INIT_LIST_HEAD(&p->sibling);
1025 #ifdef CONFIG_PREEMPT_RCU
1026         p->rcu_read_lock_nesting = 0;
1027         p->rcu_flipctr_idx = 0;
1028 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1029         p->vfork_done = NULL;
1030         spin_lock_init(&p->alloc_lock);
1031
1032         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1033         init_sigpending(&p->pending);
1034
1035         p->utime = cputime_zero;
1036         p->stime = cputime_zero;
1037         p->gtime = cputime_zero;
1038         p->utimescaled = cputime_zero;
1039         p->stimescaled = cputime_zero;
1040         p->prev_utime = cputime_zero;
1041         p->prev_stime = cputime_zero;
1042
1043         p->default_timer_slack_ns = current->timer_slack_ns;
1044
1045         task_io_accounting_init(&p->ioac);
1046         acct_clear_integrals(p);
1047
1048         posix_cpu_timers_init(p);
1049
1050         p->lock_depth = -1;             /* -1 = no lock */
1051         do_posix_clock_monotonic_gettime(&p->start_time);
1052         p->real_start_time = p->start_time;
1053         monotonic_to_bootbased(&p->real_start_time);
1054         p->io_context = NULL;
1055         p->audit_context = NULL;
1056         cgroup_fork(p);
1057 #ifdef CONFIG_NUMA
1058         p->mempolicy = mpol_dup(p->mempolicy);
1059         if (IS_ERR(p->mempolicy)) {
1060                 retval = PTR_ERR(p->mempolicy);
1061                 p->mempolicy = NULL;
1062                 goto bad_fork_cleanup_cgroup;
1063         }
1064         mpol_fix_fork_child_flag(p);
1065 #endif
1066 #ifdef CONFIG_TRACE_IRQFLAGS
1067         p->irq_events = 0;
1068 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1069         p->hardirqs_enabled = 1;
1070 #else
1071         p->hardirqs_enabled = 0;
1072 #endif
1073         p->hardirq_enable_ip = 0;
1074         p->hardirq_enable_event = 0;
1075         p->hardirq_disable_ip = _THIS_IP_;
1076         p->hardirq_disable_event = 0;
1077         p->softirqs_enabled = 1;
1078         p->softirq_enable_ip = _THIS_IP_;
1079         p->softirq_enable_event = 0;
1080         p->softirq_disable_ip = 0;
1081         p->softirq_disable_event = 0;
1082         p->hardirq_context = 0;
1083         p->softirq_context = 0;
1084 #endif
1085 #ifdef CONFIG_LOCKDEP
1086         p->lockdep_depth = 0; /* no locks held yet */
1087         p->curr_chain_key = 0;
1088         p->lockdep_recursion = 0;
1089 #endif
1090
1091 #ifdef CONFIG_DEBUG_MUTEXES
1092         p->blocked_on = NULL; /* not blocked yet */
1093 #endif
1094
1095         p->bts = NULL;
1096
1097         /* Perform scheduler related setup. Assign this task to a CPU. */
1098         sched_fork(p, clone_flags);
1099
1100         retval = perf_counter_init_task(p);
1101         if (retval)
1102                 goto bad_fork_cleanup_policy;
1103
1104         if ((retval = audit_alloc(p)))
1105                 goto bad_fork_cleanup_policy;
1106         /* copy all the process information */
1107         if ((retval = copy_semundo(clone_flags, p)))
1108                 goto bad_fork_cleanup_audit;
1109         if ((retval = copy_files(clone_flags, p)))
1110                 goto bad_fork_cleanup_semundo;
1111         if ((retval = copy_fs(clone_flags, p)))
1112                 goto bad_fork_cleanup_files;
1113         if ((retval = copy_sighand(clone_flags, p)))
1114                 goto bad_fork_cleanup_fs;
1115         if ((retval = copy_signal(clone_flags, p)))
1116                 goto bad_fork_cleanup_sighand;
1117         if ((retval = copy_mm(clone_flags, p)))
1118                 goto bad_fork_cleanup_signal;
1119         if ((retval = copy_namespaces(clone_flags, p)))
1120                 goto bad_fork_cleanup_mm;
1121         if ((retval = copy_io(clone_flags, p)))
1122                 goto bad_fork_cleanup_namespaces;
1123         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1124         if (retval)
1125                 goto bad_fork_cleanup_io;
1126
1127         if (pid != &init_struct_pid) {
1128                 retval = -ENOMEM;
1129                 pid = alloc_pid(p->nsproxy->pid_ns);
1130                 if (!pid)
1131                         goto bad_fork_cleanup_io;
1132
1133                 if (clone_flags & CLONE_NEWPID) {
1134                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1135                         if (retval < 0)
1136                                 goto bad_fork_free_pid;
1137                 }
1138         }
1139
1140         p->pid = pid_nr(pid);
1141         p->tgid = p->pid;
1142         if (clone_flags & CLONE_THREAD)
1143                 p->tgid = current->tgid;
1144
1145         if (current->nsproxy != p->nsproxy) {
1146                 retval = ns_cgroup_clone(p, pid);
1147                 if (retval)
1148                         goto bad_fork_free_pid;
1149         }
1150
1151         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1152         /*
1153          * Clear TID on mm_release()?
1154          */
1155         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1156 #ifdef CONFIG_FUTEX
1157         p->robust_list = NULL;
1158 #ifdef CONFIG_COMPAT
1159         p->compat_robust_list = NULL;
1160 #endif
1161         INIT_LIST_HEAD(&p->pi_state_list);
1162         p->pi_state_cache = NULL;
1163 #endif
1164         /*
1165          * sigaltstack should be cleared when sharing the same VM
1166          */
1167         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1168                 p->sas_ss_sp = p->sas_ss_size = 0;
1169
1170         /*
1171          * Syscall tracing should be turned off in the child regardless
1172          * of CLONE_PTRACE.
1173          */
1174         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1175 #ifdef TIF_SYSCALL_EMU
1176         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1177 #endif
1178         clear_all_latency_tracing(p);
1179
1180         /* ok, now we should be set up.. */
1181         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1182         p->pdeath_signal = 0;
1183         p->exit_state = 0;
1184
1185         /*
1186          * Ok, make it visible to the rest of the system.
1187          * We dont wake it up yet.
1188          */
1189         p->group_leader = p;
1190         INIT_LIST_HEAD(&p->thread_group);
1191
1192         /* Now that the task is set up, run cgroup callbacks if
1193          * necessary. We need to run them before the task is visible
1194          * on the tasklist. */
1195         cgroup_fork_callbacks(p);
1196         cgroup_callbacks_done = 1;
1197
1198         /* Need tasklist lock for parent etc handling! */
1199         write_lock_irq(&tasklist_lock);
1200
1201         /*
1202          * The task hasn't been attached yet, so its cpus_allowed mask will
1203          * not be changed, nor will its assigned CPU.
1204          *
1205          * The cpus_allowed mask of the parent may have changed after it was
1206          * copied first time - so re-copy it here, then check the child's CPU
1207          * to ensure it is on a valid CPU (and if not, just force it back to
1208          * parent's CPU). This avoids alot of nasty races.
1209          */
1210         p->cpus_allowed = current->cpus_allowed;
1211         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1212         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1213                         !cpu_online(task_cpu(p))))
1214                 set_task_cpu(p, smp_processor_id());
1215
1216         /* CLONE_PARENT re-uses the old parent */
1217         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1218                 p->real_parent = current->real_parent;
1219                 p->parent_exec_id = current->parent_exec_id;
1220         } else {
1221                 p->real_parent = current;
1222                 p->parent_exec_id = current->self_exec_id;
1223         }
1224
1225         spin_lock(&current->sighand->siglock);
1226
1227         /*
1228          * Process group and session signals need to be delivered to just the
1229          * parent before the fork or both the parent and the child after the
1230          * fork. Restart if a signal comes in before we add the new process to
1231          * it's process group.
1232          * A fatal signal pending means that current will exit, so the new
1233          * thread can't slip out of an OOM kill (or normal SIGKILL).
1234          */
1235         recalc_sigpending();
1236         if (signal_pending(current)) {
1237                 spin_unlock(&current->sighand->siglock);
1238                 write_unlock_irq(&tasklist_lock);
1239                 retval = -ERESTARTNOINTR;
1240                 goto bad_fork_free_pid;
1241         }
1242
1243         if (clone_flags & CLONE_THREAD) {
1244                 p->group_leader = current->group_leader;
1245                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1246         }
1247
1248         if (likely(p->pid)) {
1249                 list_add_tail(&p->sibling, &p->real_parent->children);
1250                 tracehook_finish_clone(p, clone_flags, trace);
1251
1252                 if (thread_group_leader(p)) {
1253                         if (clone_flags & CLONE_NEWPID)
1254                                 p->nsproxy->pid_ns->child_reaper = p;
1255
1256                         p->signal->leader_pid = pid;
1257                         tty_kref_put(p->signal->tty);
1258                         p->signal->tty = tty_kref_get(current->signal->tty);
1259                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1260                         attach_pid(p, PIDTYPE_SID, task_session(current));
1261                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1262                         __get_cpu_var(process_counts)++;
1263                 }
1264                 attach_pid(p, PIDTYPE_PID, pid);
1265                 nr_threads++;
1266         }
1267
1268         total_forks++;
1269         spin_unlock(&current->sighand->siglock);
1270         write_unlock_irq(&tasklist_lock);
1271         proc_fork_connector(p);
1272         cgroup_post_fork(p);
1273         return p;
1274
1275 bad_fork_free_pid:
1276         if (pid != &init_struct_pid)
1277                 free_pid(pid);
1278 bad_fork_cleanup_io:
1279         put_io_context(p->io_context);
1280 bad_fork_cleanup_namespaces:
1281         exit_task_namespaces(p);
1282 bad_fork_cleanup_mm:
1283         if (p->mm)
1284                 mmput(p->mm);
1285 bad_fork_cleanup_signal:
1286         cleanup_signal(p);
1287 bad_fork_cleanup_sighand:
1288         __cleanup_sighand(p->sighand);
1289 bad_fork_cleanup_fs:
1290         exit_fs(p); /* blocking */
1291 bad_fork_cleanup_files:
1292         exit_files(p); /* blocking */
1293 bad_fork_cleanup_semundo:
1294         exit_sem(p);
1295 bad_fork_cleanup_audit:
1296         audit_free(p);
1297 bad_fork_cleanup_policy:
1298         perf_counter_free_task(p);
1299 #ifdef CONFIG_NUMA
1300         mpol_put(p->mempolicy);
1301 bad_fork_cleanup_cgroup:
1302 #endif
1303         cgroup_exit(p, cgroup_callbacks_done);
1304         delayacct_tsk_free(p);
1305         if (p->binfmt)
1306                 module_put(p->binfmt->module);
1307 bad_fork_cleanup_put_domain:
1308         module_put(task_thread_info(p)->exec_domain->module);
1309 bad_fork_cleanup_count:
1310         atomic_dec(&p->cred->user->processes);
1311         put_cred(p->real_cred);
1312         put_cred(p->cred);
1313 bad_fork_free:
1314         free_task(p);
1315 fork_out:
1316         return ERR_PTR(retval);
1317 }
1318
1319 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1320 {
1321         memset(regs, 0, sizeof(struct pt_regs));
1322         return regs;
1323 }
1324
1325 struct task_struct * __cpuinit fork_idle(int cpu)
1326 {
1327         struct task_struct *task;
1328         struct pt_regs regs;
1329
1330         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1331                             &init_struct_pid, 0);
1332         if (!IS_ERR(task))
1333                 init_idle(task, cpu);
1334
1335         return task;
1336 }
1337
1338 /*
1339  *  Ok, this is the main fork-routine.
1340  *
1341  * It copies the process, and if successful kick-starts
1342  * it and waits for it to finish using the VM if required.
1343  */
1344 long do_fork(unsigned long clone_flags,
1345               unsigned long stack_start,
1346               struct pt_regs *regs,
1347               unsigned long stack_size,
1348               int __user *parent_tidptr,
1349               int __user *child_tidptr)
1350 {
1351         struct task_struct *p;
1352         int trace = 0;
1353         long nr;
1354
1355         /*
1356          * Do some preliminary argument and permissions checking before we
1357          * actually start allocating stuff
1358          */
1359         if (clone_flags & CLONE_NEWUSER) {
1360                 if (clone_flags & CLONE_THREAD)
1361                         return -EINVAL;
1362                 /* hopefully this check will go away when userns support is
1363                  * complete
1364                  */
1365                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1366                                 !capable(CAP_SETGID))
1367                         return -EPERM;
1368         }
1369
1370         /*
1371          * We hope to recycle these flags after 2.6.26
1372          */
1373         if (unlikely(clone_flags & CLONE_STOPPED)) {
1374                 static int __read_mostly count = 100;
1375
1376                 if (count > 0 && printk_ratelimit()) {
1377                         char comm[TASK_COMM_LEN];
1378
1379                         count--;
1380                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1381                                         "clone flags 0x%lx\n",
1382                                 get_task_comm(comm, current),
1383                                 clone_flags & CLONE_STOPPED);
1384                 }
1385         }
1386
1387         /*
1388          * When called from kernel_thread, don't do user tracing stuff.
1389          */
1390         if (likely(user_mode(regs)))
1391                 trace = tracehook_prepare_clone(clone_flags);
1392
1393         p = copy_process(clone_flags, stack_start, regs, stack_size,
1394                          child_tidptr, NULL, trace);
1395         /*
1396          * Do this prior waking up the new thread - the thread pointer
1397          * might get invalid after that point, if the thread exits quickly.
1398          */
1399         if (!IS_ERR(p)) {
1400                 struct completion vfork;
1401
1402                 trace_sched_process_fork(current, p);
1403
1404                 nr = task_pid_vnr(p);
1405
1406                 if (clone_flags & CLONE_PARENT_SETTID)
1407                         put_user(nr, parent_tidptr);
1408
1409                 if (clone_flags & CLONE_VFORK) {
1410                         p->vfork_done = &vfork;
1411                         init_completion(&vfork);
1412                 } else if (!(clone_flags & CLONE_VM)) {
1413                         /*
1414                          * vfork will do an exec which will call
1415                          * set_task_comm()
1416                          */
1417                         perf_counter_fork(p);
1418                 }
1419
1420                 audit_finish_fork(p);
1421                 tracehook_report_clone(regs, clone_flags, nr, p);
1422
1423                 /*
1424                  * We set PF_STARTING at creation in case tracing wants to
1425                  * use this to distinguish a fully live task from one that
1426                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1427                  * clear it and set the child going.
1428                  */
1429                 p->flags &= ~PF_STARTING;
1430
1431                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1432                         /*
1433                          * We'll start up with an immediate SIGSTOP.
1434                          */
1435                         sigaddset(&p->pending.signal, SIGSTOP);
1436                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1437                         __set_task_state(p, TASK_STOPPED);
1438                 } else {
1439                         wake_up_new_task(p, clone_flags);
1440                 }
1441
1442                 tracehook_report_clone_complete(trace, regs,
1443                                                 clone_flags, nr, p);
1444
1445                 if (clone_flags & CLONE_VFORK) {
1446                         freezer_do_not_count();
1447                         wait_for_completion(&vfork);
1448                         freezer_count();
1449                         tracehook_report_vfork_done(p, nr);
1450                 }
1451         } else {
1452                 nr = PTR_ERR(p);
1453         }
1454         return nr;
1455 }
1456
1457 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1458 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1459 #endif
1460
1461 static void sighand_ctor(void *data)
1462 {
1463         struct sighand_struct *sighand = data;
1464
1465         spin_lock_init(&sighand->siglock);
1466         init_waitqueue_head(&sighand->signalfd_wqh);
1467 }
1468
1469 void __init proc_caches_init(void)
1470 {
1471         sighand_cachep = kmem_cache_create("sighand_cache",
1472                         sizeof(struct sighand_struct), 0,
1473                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1474                         SLAB_NOTRACK, sighand_ctor);
1475         signal_cachep = kmem_cache_create("signal_cache",
1476                         sizeof(struct signal_struct), 0,
1477                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1478         files_cachep = kmem_cache_create("files_cache",
1479                         sizeof(struct files_struct), 0,
1480                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1481         fs_cachep = kmem_cache_create("fs_cache",
1482                         sizeof(struct fs_struct), 0,
1483                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1484         mm_cachep = kmem_cache_create("mm_struct",
1485                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1486                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1487         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1488         mmap_init();
1489 }
1490
1491 /*
1492  * Check constraints on flags passed to the unshare system call and
1493  * force unsharing of additional process context as appropriate.
1494  */
1495 static void check_unshare_flags(unsigned long *flags_ptr)
1496 {
1497         /*
1498          * If unsharing a thread from a thread group, must also
1499          * unshare vm.
1500          */
1501         if (*flags_ptr & CLONE_THREAD)
1502                 *flags_ptr |= CLONE_VM;
1503
1504         /*
1505          * If unsharing vm, must also unshare signal handlers.
1506          */
1507         if (*flags_ptr & CLONE_VM)
1508                 *flags_ptr |= CLONE_SIGHAND;
1509
1510         /*
1511          * If unsharing signal handlers and the task was created
1512          * using CLONE_THREAD, then must unshare the thread
1513          */
1514         if ((*flags_ptr & CLONE_SIGHAND) &&
1515             (atomic_read(&current->signal->count) > 1))
1516                 *flags_ptr |= CLONE_THREAD;
1517
1518         /*
1519          * If unsharing namespace, must also unshare filesystem information.
1520          */
1521         if (*flags_ptr & CLONE_NEWNS)
1522                 *flags_ptr |= CLONE_FS;
1523 }
1524
1525 /*
1526  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1527  */
1528 static int unshare_thread(unsigned long unshare_flags)
1529 {
1530         if (unshare_flags & CLONE_THREAD)
1531                 return -EINVAL;
1532
1533         return 0;
1534 }
1535
1536 /*
1537  * Unshare the filesystem structure if it is being shared
1538  */
1539 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1540 {
1541         struct fs_struct *fs = current->fs;
1542
1543         if (!(unshare_flags & CLONE_FS) || !fs)
1544                 return 0;
1545
1546         /* don't need lock here; in the worst case we'll do useless copy */
1547         if (fs->users == 1)
1548                 return 0;
1549
1550         *new_fsp = copy_fs_struct(fs);
1551         if (!*new_fsp)
1552                 return -ENOMEM;
1553
1554         return 0;
1555 }
1556
1557 /*
1558  * Unsharing of sighand is not supported yet
1559  */
1560 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1561 {
1562         struct sighand_struct *sigh = current->sighand;
1563
1564         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1565                 return -EINVAL;
1566         else
1567                 return 0;
1568 }
1569
1570 /*
1571  * Unshare vm if it is being shared
1572  */
1573 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1574 {
1575         struct mm_struct *mm = current->mm;
1576
1577         if ((unshare_flags & CLONE_VM) &&
1578             (mm && atomic_read(&mm->mm_users) > 1)) {
1579                 return -EINVAL;
1580         }
1581
1582         return 0;
1583 }
1584
1585 /*
1586  * Unshare file descriptor table if it is being shared
1587  */
1588 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1589 {
1590         struct files_struct *fd = current->files;
1591         int error = 0;
1592
1593         if ((unshare_flags & CLONE_FILES) &&
1594             (fd && atomic_read(&fd->count) > 1)) {
1595                 *new_fdp = dup_fd(fd, &error);
1596                 if (!*new_fdp)
1597                         return error;
1598         }
1599
1600         return 0;
1601 }
1602
1603 /*
1604  * unshare allows a process to 'unshare' part of the process
1605  * context which was originally shared using clone.  copy_*
1606  * functions used by do_fork() cannot be used here directly
1607  * because they modify an inactive task_struct that is being
1608  * constructed. Here we are modifying the current, active,
1609  * task_struct.
1610  */
1611 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1612 {
1613         int err = 0;
1614         struct fs_struct *fs, *new_fs = NULL;
1615         struct sighand_struct *new_sigh = NULL;
1616         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1617         struct files_struct *fd, *new_fd = NULL;
1618         struct nsproxy *new_nsproxy = NULL;
1619         int do_sysvsem = 0;
1620
1621         check_unshare_flags(&unshare_flags);
1622
1623         /* Return -EINVAL for all unsupported flags */
1624         err = -EINVAL;
1625         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1626                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1627                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1628                 goto bad_unshare_out;
1629
1630         /*
1631          * CLONE_NEWIPC must also detach from the undolist: after switching
1632          * to a new ipc namespace, the semaphore arrays from the old
1633          * namespace are unreachable.
1634          */
1635         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1636                 do_sysvsem = 1;
1637         if ((err = unshare_thread(unshare_flags)))
1638                 goto bad_unshare_out;
1639         if ((err = unshare_fs(unshare_flags, &new_fs)))
1640                 goto bad_unshare_cleanup_thread;
1641         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1642                 goto bad_unshare_cleanup_fs;
1643         if ((err = unshare_vm(unshare_flags, &new_mm)))
1644                 goto bad_unshare_cleanup_sigh;
1645         if ((err = unshare_fd(unshare_flags, &new_fd)))
1646                 goto bad_unshare_cleanup_vm;
1647         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1648                         new_fs)))
1649                 goto bad_unshare_cleanup_fd;
1650
1651         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1652                 if (do_sysvsem) {
1653                         /*
1654                          * CLONE_SYSVSEM is equivalent to sys_exit().
1655                          */
1656                         exit_sem(current);
1657                 }
1658
1659                 if (new_nsproxy) {
1660                         switch_task_namespaces(current, new_nsproxy);
1661                         new_nsproxy = NULL;
1662                 }
1663
1664                 task_lock(current);
1665
1666                 if (new_fs) {
1667                         fs = current->fs;
1668                         write_lock(&fs->lock);
1669                         current->fs = new_fs;
1670                         if (--fs->users)
1671                                 new_fs = NULL;
1672                         else
1673                                 new_fs = fs;
1674                         write_unlock(&fs->lock);
1675                 }
1676
1677                 if (new_mm) {
1678                         mm = current->mm;
1679                         active_mm = current->active_mm;
1680                         current->mm = new_mm;
1681                         current->active_mm = new_mm;
1682                         activate_mm(active_mm, new_mm);
1683                         new_mm = mm;
1684                 }
1685
1686                 if (new_fd) {
1687                         fd = current->files;
1688                         current->files = new_fd;
1689                         new_fd = fd;
1690                 }
1691
1692                 task_unlock(current);
1693         }
1694
1695         if (new_nsproxy)
1696                 put_nsproxy(new_nsproxy);
1697
1698 bad_unshare_cleanup_fd:
1699         if (new_fd)
1700                 put_files_struct(new_fd);
1701
1702 bad_unshare_cleanup_vm:
1703         if (new_mm)
1704                 mmput(new_mm);
1705
1706 bad_unshare_cleanup_sigh:
1707         if (new_sigh)
1708                 if (atomic_dec_and_test(&new_sigh->count))
1709                         kmem_cache_free(sighand_cachep, new_sigh);
1710
1711 bad_unshare_cleanup_fs:
1712         if (new_fs)
1713                 free_fs_struct(new_fs);
1714
1715 bad_unshare_cleanup_thread:
1716 bad_unshare_out:
1717         return err;
1718 }
1719
1720 /*
1721  *      Helper to unshare the files of the current task.
1722  *      We don't want to expose copy_files internals to
1723  *      the exec layer of the kernel.
1724  */
1725
1726 int unshare_files(struct files_struct **displaced)
1727 {
1728         struct task_struct *task = current;
1729         struct files_struct *copy = NULL;
1730         int error;
1731
1732         error = unshare_fd(CLONE_FILES, &copy);
1733         if (error || !copy) {
1734                 *displaced = NULL;
1735                 return error;
1736         }
1737         *displaced = task->files;
1738         task_lock(task);
1739         task->files = copy;
1740         task_unlock(task);
1741         return 0;
1742 }