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/personality.h>
  21 #include <linux/mempolicy.h>
  22 #include <linux/sem.h>
  23 #include <linux/file.h>
  24 #include <linux/fdtable.h>
  25 #include <linux/iocontext.h>
  26 #include <linux/key.h>
  27 #include <linux/binfmts.h>
  28 #include <linux/mman.h>
  29 #include <linux/mmu_notifier.h>
  30 #include <linux/fs.h>
  31 #include <linux/nsproxy.h>
  32 #include <linux/capability.h>
  33 #include <linux/cpu.h>
  34 #include <linux/cgroup.h>
  35 #include <linux/security.h>
  36 #include <linux/hugetlb.h>
  37 #include <linux/swap.h>
  38 #include <linux/syscalls.h>
  39 #include <linux/jiffies.h>
  40 #include <linux/tracehook.h>
  41 #include <linux/futex.h>
  42 #include <linux/compat.h>
  43 #include <linux/task_io_accounting_ops.h>
  44 #include <linux/rcupdate.h>
  45 #include <linux/ptrace.h>
  46 #include <linux/mount.h>
  47 #include <linux/audit.h>
  48 #include <linux/memcontrol.h>
  49 #include <linux/ftrace.h>
  50 #include <linux/profile.h>
  51 #include <linux/rmap.h>
  52 #include <linux/ksm.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_event.h>
  66 #include <linux/posix-timers.h>
  67 #include <linux/user-return-notifier.h>
  68
  69 #include <asm/pgtable.h>
  70 #include <asm/pgalloc.h>
  71 #include <asm/uaccess.h>
  72 #include <asm/mmu_context.h>
  73 #include <asm/cacheflush.h>
  74 #include <asm/tlbflush.h>
  75
  76 #include <trace/events/sched.h>
  77
  78 /*
  79  * Protected counters by write_lock_irq(&tasklist_lock)
  80  */
  81 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  82 int nr_threads;                 /* The idle threads do not count.. */
  83
  84 int max_threads;                /* tunable limit on nr_threads */
  85
  86 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  87
  88 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  89
  90 #ifdef CONFIG_PROVE_RCU
  91 int lockdep_tasklist_lock_is_held(void)
  92 {
  93         return lockdep_is_held(&tasklist_lock);
  94 }
  95 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
  96 #endif /* #ifdef CONFIG_PROVE_RCU */
  97
  98 int nr_processes(void)
  99 {
 100         int cpu;
 101         int total = 0;
 102
 103         for_each_possible_cpu(cpu)
 104                 total += per_cpu(process_counts, cpu);
 105
 106         return total;
 107 }
 108
 109 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 110 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
 111 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
 112 static struct kmem_cache *task_struct_cachep;
 113 #endif
 114
 115 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 116 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 117 {
 118 #ifdef CONFIG_DEBUG_STACK_USAGE
 119         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 120 #else
 121         gfp_t mask = GFP_KERNEL;
 122 #endif
 123         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 124 }
 125
 126 static inline void free_thread_info(struct thread_info *ti)
 127 {
 128         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 129 }
 130 #endif
 131
 132 /* SLAB cache for signal_struct structures (tsk->signal) */
 133 static struct kmem_cache *signal_cachep;
 134
 135 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 136 struct kmem_cache *sighand_cachep;
 137
 138 /* SLAB cache for files_struct structures (tsk->files) */
 139 struct kmem_cache *files_cachep;
 140
 141 /* SLAB cache for fs_struct structures (tsk->fs) */
 142 struct kmem_cache *fs_cachep;
 143
 144 /* SLAB cache for vm_area_struct structures */
 145 struct kmem_cache *vm_area_cachep;
 146
 147 /* SLAB cache for mm_struct structures (tsk->mm) */
 148 static struct kmem_cache *mm_cachep;
 149
 150 static void account_kernel_stack(struct thread_info *ti, int account)
 151 {
 152         struct zone *zone = page_zone(virt_to_page(ti));
 153
 154         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 155 }
 156
 157 void free_task(struct task_struct *tsk)
 158 {
 159         prop_local_destroy_single(&tsk->dirties);
 160         account_kernel_stack(tsk->stack, -1);
 161         free_thread_info(tsk->stack);
 162         rt_mutex_debug_task_free(tsk);
 163         ftrace_graph_exit_task(tsk);
 164         free_task_struct(tsk);
 165 }
 166 EXPORT_SYMBOL(free_task);
 167
 168 static inline void free_signal_struct(struct signal_struct *sig)
 169 {
 170         taskstats_tgid_free(sig);
 171         kmem_cache_free(signal_cachep, sig);
 172 }
 173
 174 static inline void put_signal_struct(struct signal_struct *sig)
 175 {
 176         if (atomic_dec_and_test(&sig->sigcnt))
 177                 free_signal_struct(sig);
 178 }
 179
 180 void __put_task_struct(struct task_struct *tsk)
 181 {
 182         WARN_ON(!tsk->exit_state);
 183         WARN_ON(atomic_read(&tsk->usage));
 184         WARN_ON(tsk == current);
 185
 186         exit_creds(tsk);
 187         delayacct_tsk_free(tsk);
 188         put_signal_struct(tsk->signal);
 189
 190         if (!profile_handoff_task(tsk))
 191                 free_task(tsk);
 192 }
 193
 194 /*
 195  * macro override instead of weak attribute alias, to workaround
 196  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 197  */
 198 #ifndef arch_task_cache_init
 199 #define arch_task_cache_init()
 200 #endif
 201
 202 void __init fork_init(unsigned long mempages)
 203 {
 204 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 205 #ifndef ARCH_MIN_TASKALIGN
 206 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 207 #endif
 208         /* create a slab on which task_structs can be allocated */
 209         task_struct_cachep =
 210                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 211                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 212 #endif
 213
 214         /* do the arch specific task caches init */
 215         arch_task_cache_init();
 216
 217         /*
 218          * The default maximum number of threads is set to a safe
 219          * value: the thread structures can take up at most half
 220          * of memory.
 221          */
 222         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 223
 224         /*
 225          * we need to allow at least 20 threads to boot a system
 226          */
 227         if(max_threads < 20)
 228                 max_threads = 20;
 229
 230         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 231         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 232         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 233                 init_task.signal->rlim[RLIMIT_NPROC];
 234 }
 235
 236 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 237                                                struct task_struct *src)
 238 {
 239         *dst = *src;
 240         return 0;
 241 }
 242
 243 static struct task_struct *dup_task_struct(struct task_struct *orig)
 244 {
 245         struct task_struct *tsk;
 246         struct thread_info *ti;
 247         unsigned long *stackend;
 248
 249         int err;
 250
 251         prepare_to_copy(orig);
 252
 253         tsk = alloc_task_struct();
 254         if (!tsk)
 255                 return NULL;
 256
 257         ti = alloc_thread_info(tsk);
 258         if (!ti) {
 259                 free_task_struct(tsk);
 260                 return NULL;
 261         }
 262
 263         err = arch_dup_task_struct(tsk, orig);
 264         if (err)
 265                 goto out;
 266
 267         tsk->stack = ti;
 268
 269         err = prop_local_init_single(&tsk->dirties);
 270         if (err)
 271                 goto out;
 272
 273         setup_thread_stack(tsk, orig);
 274         clear_user_return_notifier(tsk);
 275         stackend = end_of_stack(tsk);
 276         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 277
 278 #ifdef CONFIG_CC_STACKPROTECTOR
 279         tsk->stack_canary = get_random_int();
 280 #endif
 281
 282         /* One for us, one for whoever does the "release_task()" (usually parent) */
 283         atomic_set(&tsk->usage,2);
 284         atomic_set(&tsk->fs_excl, 0);
 285 #ifdef CONFIG_BLK_DEV_IO_TRACE
 286         tsk->btrace_seq = 0;
 287 #endif
 288         tsk->splice_pipe = NULL;
 289
 290         account_kernel_stack(ti, 1);
 291
 292         return tsk;
 293
 294 out:
 295         free_thread_info(ti);
 296         free_task_struct(tsk);
 297         return NULL;
 298 }
 299
 300 #ifdef CONFIG_MMU
 301 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 302 {
 303         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 304         struct rb_node **rb_link, *rb_parent;
 305         int retval;
 306         unsigned long charge;
 307         struct mempolicy *pol;
 308
 309         down_write(&oldmm->mmap_sem);
 310         flush_cache_dup_mm(oldmm);
 311         /*
 312          * Not linked in yet - no deadlock potential:
 313          */
 314         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 315
 316         mm->locked_vm = 0;
 317         mm->mmap = NULL;
 318         mm->mmap_cache = NULL;
 319         mm->free_area_cache = oldmm->mmap_base;
 320         mm->cached_hole_size = ~0UL;
 321         mm->map_count = 0;
 322         cpumask_clear(mm_cpumask(mm));
 323         mm->mm_rb = RB_ROOT;
 324         rb_link = &mm->mm_rb.rb_node;
 325         rb_parent = NULL;
 326         pprev = &mm->mmap;
 327         retval = ksm_fork(mm, oldmm);
 328         if (retval)
 329                 goto out;
 330
 331         prev = NULL;
 332         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 333                 struct file *file;
 334
 335                 if (mpnt->vm_flags & VM_DONTCOPY) {
 336                         long pages = vma_pages(mpnt);
 337                         mm->total_vm -= pages;
 338                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 339                                                                 -pages);
 340                         continue;
 341                 }
 342                 charge = 0;
 343                 if (mpnt->vm_flags & VM_ACCOUNT) {
 344                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 345                         if (security_vm_enough_memory(len))
 346                                 goto fail_nomem;
 347                         charge = len;
 348                 }
 349                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 350                 if (!tmp)
 351                         goto fail_nomem;
 352                 *tmp = *mpnt;
 353                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 354                 pol = mpol_dup(vma_policy(mpnt));
 355                 retval = PTR_ERR(pol);
 356                 if (IS_ERR(pol))
 357                         goto fail_nomem_policy;
 358                 vma_set_policy(tmp, pol);
 359                 if (anon_vma_fork(tmp, mpnt))
 360                         goto fail_nomem_anon_vma_fork;
 361                 tmp->vm_flags &= ~VM_LOCKED;
 362                 tmp->vm_mm = mm;
 363                 tmp->vm_next = tmp->vm_prev = NULL;
 364                 file = tmp->vm_file;
 365                 if (file) {
 366                         struct inode *inode = file->f_path.dentry->d_inode;
 367                         struct address_space *mapping = file->f_mapping;
 368
 369                         get_file(file);
 370                         if (tmp->vm_flags & VM_DENYWRITE)
 371                                 atomic_dec(&inode->i_writecount);
 372                         spin_lock(&mapping->i_mmap_lock);
 373                         if (tmp->vm_flags & VM_SHARED)
 374                                 mapping->i_mmap_writable++;
 375                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 376                         flush_dcache_mmap_lock(mapping);
 377                         /* insert tmp into the share list, just after mpnt */
 378                         vma_prio_tree_add(tmp, mpnt);
 379                         flush_dcache_mmap_unlock(mapping);
 380                         spin_unlock(&mapping->i_mmap_lock);
 381                 }
 382
 383                 /*
 384                  * Clear hugetlb-related page reserves for children. This only
 385                  * affects MAP_PRIVATE mappings. Faults generated by the child
 386                  * are not guaranteed to succeed, even if read-only
 387                  */
 388                 if (is_vm_hugetlb_page(tmp))
 389                         reset_vma_resv_huge_pages(tmp);
 390
 391                 /*
 392                  * Link in the new vma and copy the page table entries.
 393                  */
 394                 *pprev = tmp;
 395                 pprev = &tmp->vm_next;
 396                 tmp->vm_prev = prev;
 397                 prev = tmp;
 398
 399                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 400                 rb_link = &tmp->vm_rb.rb_right;
 401                 rb_parent = &tmp->vm_rb;
 402
 403                 mm->map_count++;
 404                 retval = copy_page_range(mm, oldmm, mpnt);
 405
 406                 if (tmp->vm_ops && tmp->vm_ops->open)
 407                         tmp->vm_ops->open(tmp);
 408
 409                 if (retval)
 410                         goto out;
 411         }
 412         /* a new mm has just been created */
 413         arch_dup_mmap(oldmm, mm);
 414         retval = 0;
 415 out:
 416         up_write(&mm->mmap_sem);
 417         flush_tlb_mm(oldmm);
 418         up_write(&oldmm->mmap_sem);
 419         return retval;
 420 fail_nomem_anon_vma_fork:
 421         mpol_put(pol);
 422 fail_nomem_policy:
 423         kmem_cache_free(vm_area_cachep, tmp);
 424 fail_nomem:
 425         retval = -ENOMEM;
 426         vm_unacct_memory(charge);
 427         goto out;
 428 }
 429
 430 static inline int mm_alloc_pgd(struct mm_struct * mm)
 431 {
 432         mm->pgd = pgd_alloc(mm);
 433         if (unlikely(!mm->pgd))
 434                 return -ENOMEM;
 435         return 0;
 436 }
 437
 438 static inline void mm_free_pgd(struct mm_struct * mm)
 439 {
 440         pgd_free(mm, mm->pgd);
 441 }
 442 #else
 443 #define dup_mmap(mm, oldmm)     (0)
 444 #define mm_alloc_pgd(mm)        (0)
 445 #define mm_free_pgd(mm)
 446 #endif /* CONFIG_MMU */
 447
 448 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 449
 450 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 451 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 452
 453 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 454
 455 static int __init coredump_filter_setup(char *s)
 456 {
 457         default_dump_filter =
 458                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 459                 MMF_DUMP_FILTER_MASK;
 460         return 1;
 461 }
 462
 463 __setup("coredump_filter=", coredump_filter_setup);
 464
 465 #include <linux/init_task.h>
 466
 467 static void mm_init_aio(struct mm_struct *mm)
 468 {
 469 #ifdef CONFIG_AIO
 470         spin_lock_init(&mm->ioctx_lock);
 471         INIT_HLIST_HEAD(&mm->ioctx_list);
 472 #endif
 473 }
 474
 475 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 476 {
 477         atomic_set(&mm->mm_users, 1);
 478         atomic_set(&mm->mm_count, 1);
 479         init_rwsem(&mm->mmap_sem);
 480         INIT_LIST_HEAD(&mm->mmlist);
 481         mm->flags = (current->mm) ?
 482                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 483         mm->core_state = NULL;
 484         mm->nr_ptes = 0;
 485         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 486         spin_lock_init(&mm->page_table_lock);
 487         mm->free_area_cache = TASK_UNMAPPED_BASE;
 488         mm->cached_hole_size = ~0UL;
 489         mm_init_aio(mm);
 490         mm_init_owner(mm, p);
 491
 492         if (likely(!mm_alloc_pgd(mm))) {
 493                 mm->def_flags = 0;
 494                 mmu_notifier_mm_init(mm);
 495                 return mm;
 496         }
 497
 498         free_mm(mm);
 499         return NULL;
 500 }
 501
 502 /*
 503  * Allocate and initialize an mm_struct.
 504  */
 505 struct mm_struct * mm_alloc(void)
 506 {
 507         struct mm_struct * mm;
 508
 509         mm = allocate_mm();
 510         if (mm) {
 511                 memset(mm, 0, sizeof(*mm));
 512                 mm = mm_init(mm, current);
 513         }
 514         return mm;
 515 }
 516
 517 /*
 518  * Called when the last reference to the mm
 519  * is dropped: either by a lazy thread or by
 520  * mmput. Free the page directory and the mm.
 521  */
 522 void __mmdrop(struct mm_struct *mm)
 523 {
 524         BUG_ON(mm == &init_mm);
 525         mm_free_pgd(mm);
 526         destroy_context(mm);
 527         mmu_notifier_mm_destroy(mm);
 528         free_mm(mm);
 529 }
 530 EXPORT_SYMBOL_GPL(__mmdrop);
 531
 532 /*
 533  * Decrement the use count and release all resources for an mm.
 534  */
 535 void mmput(struct mm_struct *mm)
 536 {
 537         might_sleep();
 538
 539         if (atomic_dec_and_test(&mm->mm_users)) {
 540                 exit_aio(mm);
 541                 ksm_exit(mm);
 542                 exit_mmap(mm);
 543                 set_mm_exe_file(mm, NULL);
 544                 if (!list_empty(&mm->mmlist)) {
 545                         spin_lock(&mmlist_lock);
 546                         list_del(&mm->mmlist);
 547                         spin_unlock(&mmlist_lock);
 548                 }
 549                 put_swap_token(mm);
 550                 if (mm->binfmt)
 551                         module_put(mm->binfmt->module);
 552                 mmdrop(mm);
 553         }
 554 }
 555 EXPORT_SYMBOL_GPL(mmput);
 556
 557 /**
 558  * get_task_mm - acquire a reference to the task's mm
 559  *
 560  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 561  * this kernel workthread has transiently adopted a user mm with use_mm,
 562  * to do its AIO) is not set and if so returns a reference to it, after
 563  * bumping up the use count.  User must release the mm via mmput()
 564  * after use.  Typically used by /proc and ptrace.
 565  */
 566 struct mm_struct *get_task_mm(struct task_struct *task)
 567 {
 568         struct mm_struct *mm;
 569
 570         task_lock(task);
 571         mm = task->mm;
 572         if (mm) {
 573                 if (task->flags & PF_KTHREAD)
 574                         mm = NULL;
 575                 else
 576                         atomic_inc(&mm->mm_users);
 577         }
 578         task_unlock(task);
 579         return mm;
 580 }
 581 EXPORT_SYMBOL_GPL(get_task_mm);
 582
 583 /* Please note the differences between mmput and mm_release.
 584  * mmput is called whenever we stop holding onto a mm_struct,
 585  * error success whatever.
 586  *
 587  * mm_release is called after a mm_struct has been removed
 588  * from the current process.
 589  *
 590  * This difference is important for error handling, when we
 591  * only half set up a mm_struct for a new process and need to restore
 592  * the old one.  Because we mmput the new mm_struct before
 593  * restoring the old one. . .
 594  * Eric Biederman 10 January 1998
 595  */
 596 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 597 {
 598         struct completion *vfork_done = tsk->vfork_done;
 599
 600         /* Get rid of any futexes when releasing the mm */
 601 #ifdef CONFIG_FUTEX
 602         if (unlikely(tsk->robust_list)) {
 603                 exit_robust_list(tsk);
 604                 tsk->robust_list = NULL;
 605         }
 606 #ifdef CONFIG_COMPAT
 607         if (unlikely(tsk->compat_robust_list)) {
 608                 compat_exit_robust_list(tsk);
 609                 tsk->compat_robust_list = NULL;
 610         }
 611 #endif
 612         if (unlikely(!list_empty(&tsk->pi_state_list)))
 613                 exit_pi_state_list(tsk);
 614 #endif
 615
 616         /* Get rid of any cached register state */
 617         deactivate_mm(tsk, mm);
 618
 619         /* notify parent sleeping on vfork() */
 620         if (vfork_done) {
 621                 tsk->vfork_done = NULL;
 622                 complete(vfork_done);
 623         }
 624
 625         /*
 626          * If we're exiting normally, clear a user-space tid field if
 627          * requested.  We leave this alone when dying by signal, to leave
 628          * the value intact in a core dump, and to save the unnecessary
 629          * trouble otherwise.  Userland only wants this done for a sys_exit.
 630          */
 631         if (tsk->clear_child_tid) {
 632                 if (!(tsk->flags & PF_SIGNALED) &&
 633                     atomic_read(&mm->mm_users) > 1) {
 634                         /*
 635                          * We don't check the error code - if userspace has
 636                          * not set up a proper pointer then tough luck.
 637                          */
 638                         put_user(0, tsk->clear_child_tid);
 639                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 640                                         1, NULL, NULL, 0);
 641                 }
 642                 tsk->clear_child_tid = NULL;
 643         }
 644 }
 645
 646 /*
 647  * Allocate a new mm structure and copy contents from the
 648  * mm structure of the passed in task structure.
 649  */
 650 struct mm_struct *dup_mm(struct task_struct *tsk)
 651 {
 652         struct mm_struct *mm, *oldmm = current->mm;
 653         int err;
 654
 655         if (!oldmm)
 656                 return NULL;
 657
 658         mm = allocate_mm();
 659         if (!mm)
 660                 goto fail_nomem;
 661
 662         memcpy(mm, oldmm, sizeof(*mm));
 663
 664         /* Initializing for Swap token stuff */
 665         mm->token_priority = 0;
 666         mm->last_interval = 0;
 667
 668         if (!mm_init(mm, tsk))
 669                 goto fail_nomem;
 670
 671         if (init_new_context(tsk, mm))
 672                 goto fail_nocontext;
 673
 674         dup_mm_exe_file(oldmm, mm);
 675
 676         err = dup_mmap(mm, oldmm);
 677         if (err)
 678                 goto free_pt;
 679
 680         mm->hiwater_rss = get_mm_rss(mm);
 681         mm->hiwater_vm = mm->total_vm;
 682
 683         if (mm->binfmt && !try_module_get(mm->binfmt->module))
 684                 goto free_pt;
 685
 686         return mm;
 687
 688 free_pt:
 689         /* don't put binfmt in mmput, we haven't got module yet */
 690         mm->binfmt = NULL;
 691         mmput(mm);
 692
 693 fail_nomem:
 694         return NULL;
 695
 696 fail_nocontext:
 697         /*
 698          * If init_new_context() failed, we cannot use mmput() to free the mm
 699          * because it calls destroy_context()
 700          */
 701         mm_free_pgd(mm);
 702         free_mm(mm);
 703         return NULL;
 704 }
 705
 706 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 707 {
 708         struct mm_struct * mm, *oldmm;
 709         int retval;
 710
 711         tsk->min_flt = tsk->maj_flt = 0;
 712         tsk->nvcsw = tsk->nivcsw = 0;
 713 #ifdef CONFIG_DETECT_HUNG_TASK
 714         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 715 #endif
 716
 717         tsk->mm = NULL;
 718         tsk->active_mm = NULL;
 719
 720         /*
 721          * Are we cloning a kernel thread?
 722          *
 723          * We need to steal a active VM for that..
 724          */
 725         oldmm = current->mm;
 726         if (!oldmm)
 727                 return 0;
 728
 729         if (clone_flags & CLONE_VM) {
 730                 atomic_inc(&oldmm->mm_users);
 731                 mm = oldmm;
 732                 goto good_mm;
 733         }
 734
 735         retval = -ENOMEM;
 736         mm = dup_mm(tsk);
 737         if (!mm)
 738                 goto fail_nomem;
 739
 740 good_mm:
 741         /* Initializing for Swap token stuff */
 742         mm->token_priority = 0;
 743         mm->last_interval = 0;
 744
 745         tsk->mm = mm;
 746         tsk->active_mm = mm;
 747         return 0;
 748
 749 fail_nomem:
 750         return retval;
 751 }
 752
 753 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 754 {
 755         struct fs_struct *fs = current->fs;
 756         if (clone_flags & CLONE_FS) {
 757                 /* tsk->fs is already what we want */
 758                 write_lock(&fs->lock);
 759                 if (fs->in_exec) {
 760                         write_unlock(&fs->lock);
 761                         return -EAGAIN;
 762                 }
 763                 fs->users++;
 764                 write_unlock(&fs->lock);
 765                 return 0;
 766         }
 767         tsk->fs = copy_fs_struct(fs);
 768         if (!tsk->fs)
 769                 return -ENOMEM;
 770         return 0;
 771 }
 772
 773 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 774 {
 775         struct files_struct *oldf, *newf;
 776         int error = 0;
 777
 778         /*
 779          * A background process may not have any files ...
 780          */
 781         oldf = current->files;
 782         if (!oldf)
 783                 goto out;
 784
 785         if (clone_flags & CLONE_FILES) {
 786                 atomic_inc(&oldf->count);
 787                 goto out;
 788         }
 789
 790         newf = dup_fd(oldf, &error);
 791         if (!newf)
 792                 goto out;
 793
 794         tsk->files = newf;
 795         error = 0;
 796 out:
 797         return error;
 798 }
 799
 800 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 801 {
 802 #ifdef CONFIG_BLOCK
 803         struct io_context *ioc = current->io_context;
 804
 805         if (!ioc)
 806                 return 0;
 807         /*
 808          * Share io context with parent, if CLONE_IO is set
 809          */
 810         if (clone_flags & CLONE_IO) {
 811                 tsk->io_context = ioc_task_link(ioc);
 812                 if (unlikely(!tsk->io_context))
 813                         return -ENOMEM;
 814         } else if (ioprio_valid(ioc->ioprio)) {
 815                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 816                 if (unlikely(!tsk->io_context))
 817                         return -ENOMEM;
 818
 819                 tsk->io_context->ioprio = ioc->ioprio;
 820         }
 821 #endif
 822         return 0;
 823 }
 824
 825 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 826 {
 827         struct sighand_struct *sig;
 828
 829         if (clone_flags & CLONE_SIGHAND) {
 830                 atomic_inc(&current->sighand->count);
 831                 return 0;
 832         }
 833         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 834         rcu_assign_pointer(tsk->sighand, sig);
 835         if (!sig)
 836                 return -ENOMEM;
 837         atomic_set(&sig->count, 1);
 838         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 839         return 0;
 840 }
 841
 842 void __cleanup_sighand(struct sighand_struct *sighand)
 843 {
 844         if (atomic_dec_and_test(&sighand->count))
 845                 kmem_cache_free(sighand_cachep, sighand);
 846 }
 847
 848
 849 /*
 850  * Initialize POSIX timer handling for a thread group.
 851  */
 852 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 853 {
 854         unsigned long cpu_limit;
 855
 856         /* Thread group counters. */
 857         thread_group_cputime_init(sig);
 858
 859         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
 860         if (cpu_limit != RLIM_INFINITY) {
 861                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
 862                 sig->cputimer.running = 1;
 863         }
 864
 865         /* The timer lists. */
 866         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 867         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 868         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 869 }
 870
 871 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 872 {
 873         struct signal_struct *sig;
 874
 875         if (clone_flags & CLONE_THREAD)
 876                 return 0;
 877
 878         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
 879         tsk->signal = sig;
 880         if (!sig)
 881                 return -ENOMEM;
 882
 883         sig->nr_threads = 1;
 884         atomic_set(&sig->live, 1);
 885         atomic_set(&sig->sigcnt, 1);
 886         init_waitqueue_head(&sig->wait_chldexit);
 887         if (clone_flags & CLONE_NEWPID)
 888                 sig->flags |= SIGNAL_UNKILLABLE;
 889         sig->curr_target = tsk;
 890         init_sigpending(&sig->shared_pending);
 891         INIT_LIST_HEAD(&sig->posix_timers);
 892
 893         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 894         sig->real_timer.function = it_real_fn;
 895
 896         task_lock(current->group_leader);
 897         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 898         task_unlock(current->group_leader);
 899
 900         posix_cpu_timers_init_group(sig);
 901
 902         tty_audit_fork(sig);
 903
 904         sig->oom_adj = current->signal->oom_adj;
 905
 906         return 0;
 907 }
 908
 909 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 910 {
 911         unsigned long new_flags = p->flags;
 912
 913         new_flags &= ~PF_SUPERPRIV;
 914         new_flags |= PF_FORKNOEXEC;
 915         new_flags |= PF_STARTING;
 916         p->flags = new_flags;
 917         clear_freeze_flag(p);
 918 }
 919
 920 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
 921 {
 922         current->clear_child_tid = tidptr;
 923
 924         return task_pid_vnr(current);
 925 }
 926
 927 static void rt_mutex_init_task(struct task_struct *p)
 928 {
 929         raw_spin_lock_init(&p->pi_lock);
 930 #ifdef CONFIG_RT_MUTEXES
 931         plist_head_init_raw(&p->pi_waiters, &p->pi_lock);
 932         p->pi_blocked_on = NULL;
 933 #endif
 934 }
 935
 936 #ifdef CONFIG_MM_OWNER
 937 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 938 {
 939         mm->owner = p;
 940 }
 941 #endif /* CONFIG_MM_OWNER */
 942
 943 /*
 944  * Initialize POSIX timer handling for a single task.
 945  */
 946 static void posix_cpu_timers_init(struct task_struct *tsk)
 947 {
 948         tsk->cputime_expires.prof_exp = cputime_zero;
 949         tsk->cputime_expires.virt_exp = cputime_zero;
 950         tsk->cputime_expires.sched_exp = 0;
 951         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 952         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
 953         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
 954 }
 955
 956 /*
 957  * This creates a new process as a copy of the old one,
 958  * but does not actually start it yet.
 959  *
 960  * It copies the registers, and all the appropriate
 961  * parts of the process environment (as per the clone
 962  * flags). The actual kick-off is left to the caller.
 963  */
 964 static struct task_struct *copy_process(unsigned long clone_flags,
 965                                         unsigned long stack_start,
 966                                         struct pt_regs *regs,
 967                                         unsigned long stack_size,
 968                                         int __user *child_tidptr,
 969                                         struct pid *pid,
 970                                         int trace)
 971 {
 972         int retval;
 973         struct task_struct *p;
 974         int cgroup_callbacks_done = 0;
 975
 976         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 977                 return ERR_PTR(-EINVAL);
 978
 979         /*
 980          * Thread groups must share signals as well, and detached threads
 981          * can only be started up within the thread group.
 982          */
 983         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 984                 return ERR_PTR(-EINVAL);
 985
 986         /*
 987          * Shared signal handlers imply shared VM. By way of the above,
 988          * thread groups also imply shared VM. Blocking this case allows
 989          * for various simplifications in other code.
 990          */
 991         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 992                 return ERR_PTR(-EINVAL);
 993
 994         /*
 995          * Siblings of global init remain as zombies on exit since they are
 996          * not reaped by their parent (swapper). To solve this and to avoid
 997          * multi-rooted process trees, prevent global and container-inits
 998          * from creating siblings.
 999          */
1000         if ((clone_flags & CLONE_PARENT) &&
1001                                 current->signal->flags & SIGNAL_UNKILLABLE)
1002                 return ERR_PTR(-EINVAL);
1003
1004         retval = security_task_create(clone_flags);
1005         if (retval)
1006                 goto fork_out;
1007
1008         retval = -ENOMEM;
1009         p = dup_task_struct(current);
1010         if (!p)
1011                 goto fork_out;
1012
1013         ftrace_graph_init_task(p);
1014
1015         rt_mutex_init_task(p);
1016
1017 #ifdef CONFIG_PROVE_LOCKING
1018         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1019         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1020 #endif
1021         retval = -EAGAIN;
1022         if (atomic_read(&p->real_cred->user->processes) >=
1023                         task_rlimit(p, RLIMIT_NPROC)) {
1024                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1025                     p->real_cred->user != INIT_USER)
1026                         goto bad_fork_free;
1027         }
1028
1029         retval = copy_creds(p, clone_flags);
1030         if (retval < 0)
1031                 goto bad_fork_free;
1032
1033         /*
1034          * If multiple threads are within copy_process(), then this check
1035          * triggers too late. This doesn't hurt, the check is only there
1036          * to stop root fork bombs.
1037          */
1038         retval = -EAGAIN;
1039         if (nr_threads >= max_threads)
1040                 goto bad_fork_cleanup_count;
1041
1042         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1043                 goto bad_fork_cleanup_count;
1044
1045         p->did_exec = 0;
1046         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1047         copy_flags(clone_flags, p);
1048         INIT_LIST_HEAD(&p->children);
1049         INIT_LIST_HEAD(&p->sibling);
1050         rcu_copy_process(p);
1051         p->vfork_done = NULL;
1052         spin_lock_init(&p->alloc_lock);
1053
1054         init_sigpending(&p->pending);
1055
1056         p->utime = cputime_zero;
1057         p->stime = cputime_zero;
1058         p->gtime = cputime_zero;
1059         p->utimescaled = cputime_zero;
1060         p->stimescaled = cputime_zero;
1061 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1062         p->prev_utime = cputime_zero;
1063         p->prev_stime = cputime_zero;
1064 #endif
1065 #if defined(SPLIT_RSS_COUNTING)
1066         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1067 #endif
1068
1069         p->default_timer_slack_ns = current->timer_slack_ns;
1070
1071         task_io_accounting_init(&p->ioac);
1072         acct_clear_integrals(p);
1073
1074         posix_cpu_timers_init(p);
1075
1076         p->lock_depth = -1;             /* -1 = no lock */
1077         do_posix_clock_monotonic_gettime(&p->start_time);
1078         p->real_start_time = p->start_time;
1079         monotonic_to_bootbased(&p->real_start_time);
1080         p->io_context = NULL;
1081         p->audit_context = NULL;
1082         cgroup_fork(p);
1083 #ifdef CONFIG_NUMA
1084         p->mempolicy = mpol_dup(p->mempolicy);
1085         if (IS_ERR(p->mempolicy)) {
1086                 retval = PTR_ERR(p->mempolicy);
1087                 p->mempolicy = NULL;
1088                 goto bad_fork_cleanup_cgroup;
1089         }
1090         mpol_fix_fork_child_flag(p);
1091 #endif
1092 #ifdef CONFIG_TRACE_IRQFLAGS
1093         p->irq_events = 0;
1094 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1095         p->hardirqs_enabled = 1;
1096 #else
1097         p->hardirqs_enabled = 0;
1098 #endif
1099         p->hardirq_enable_ip = 0;
1100         p->hardirq_enable_event = 0;
1101         p->hardirq_disable_ip = _THIS_IP_;
1102         p->hardirq_disable_event = 0;
1103         p->softirqs_enabled = 1;
1104         p->softirq_enable_ip = _THIS_IP_;
1105         p->softirq_enable_event = 0;
1106         p->softirq_disable_ip = 0;
1107         p->softirq_disable_event = 0;
1108         p->hardirq_context = 0;
1109         p->softirq_context = 0;
1110 #endif
1111 #ifdef CONFIG_LOCKDEP
1112         p->lockdep_depth = 0; /* no locks held yet */
1113         p->curr_chain_key = 0;
1114         p->lockdep_recursion = 0;
1115 #endif
1116
1117 #ifdef CONFIG_DEBUG_MUTEXES
1118         p->blocked_on = NULL; /* not blocked yet */
1119 #endif
1120 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1121         p->memcg_batch.do_batch = 0;
1122         p->memcg_batch.memcg = NULL;
1123 #endif
1124
1125         /* Perform scheduler related setup. Assign this task to a CPU. */
1126         sched_fork(p, clone_flags);
1127
1128         retval = perf_event_init_task(p);
1129         if (retval)
1130                 goto bad_fork_cleanup_policy;
1131
1132         if ((retval = audit_alloc(p)))
1133                 goto bad_fork_cleanup_policy;
1134         /* copy all the process information */
1135         if ((retval = copy_semundo(clone_flags, p)))
1136                 goto bad_fork_cleanup_audit;
1137         if ((retval = copy_files(clone_flags, p)))
1138                 goto bad_fork_cleanup_semundo;
1139         if ((retval = copy_fs(clone_flags, p)))
1140                 goto bad_fork_cleanup_files;
1141         if ((retval = copy_sighand(clone_flags, p)))
1142                 goto bad_fork_cleanup_fs;
1143         if ((retval = copy_signal(clone_flags, p)))
1144                 goto bad_fork_cleanup_sighand;
1145         if ((retval = copy_mm(clone_flags, p)))
1146                 goto bad_fork_cleanup_signal;
1147         if ((retval = copy_namespaces(clone_flags, p)))
1148                 goto bad_fork_cleanup_mm;
1149         if ((retval = copy_io(clone_flags, p)))
1150                 goto bad_fork_cleanup_namespaces;
1151         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1152         if (retval)
1153                 goto bad_fork_cleanup_io;
1154
1155         if (pid != &init_struct_pid) {
1156                 retval = -ENOMEM;
1157                 pid = alloc_pid(p->nsproxy->pid_ns);
1158                 if (!pid)
1159                         goto bad_fork_cleanup_io;
1160
1161                 if (clone_flags & CLONE_NEWPID) {
1162                         retval = pid_ns_prepare_proc(p->nsproxy->pid_ns);
1163                         if (retval < 0)
1164                                 goto bad_fork_free_pid;
1165                 }
1166         }
1167
1168         p->pid = pid_nr(pid);
1169         p->tgid = p->pid;
1170         if (clone_flags & CLONE_THREAD)
1171                 p->tgid = current->tgid;
1172
1173         if (current->nsproxy != p->nsproxy) {
1174                 retval = ns_cgroup_clone(p, pid);
1175                 if (retval)
1176                         goto bad_fork_free_pid;
1177         }
1178
1179         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1180         /*
1181          * Clear TID on mm_release()?
1182          */
1183         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1184 #ifdef CONFIG_FUTEX
1185         p->robust_list = NULL;
1186 #ifdef CONFIG_COMPAT
1187         p->compat_robust_list = NULL;
1188 #endif
1189         INIT_LIST_HEAD(&p->pi_state_list);
1190         p->pi_state_cache = NULL;
1191 #endif
1192         /*
1193          * sigaltstack should be cleared when sharing the same VM
1194          */
1195         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1196                 p->sas_ss_sp = p->sas_ss_size = 0;
1197
1198         /*
1199          * Syscall tracing and stepping should be turned off in the
1200          * child regardless of CLONE_PTRACE.
1201          */
1202         user_disable_single_step(p);
1203         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1204 #ifdef TIF_SYSCALL_EMU
1205         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1206 #endif
1207         clear_all_latency_tracing(p);
1208
1209         /* ok, now we should be set up.. */
1210         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1211         p->pdeath_signal = 0;
1212         p->exit_state = 0;
1213
1214         /*
1215          * Ok, make it visible to the rest of the system.
1216          * We dont wake it up yet.
1217          */
1218         p->group_leader = p;
1219         INIT_LIST_HEAD(&p->thread_group);
1220
1221         /* Now that the task is set up, run cgroup callbacks if
1222          * necessary. We need to run them before the task is visible
1223          * on the tasklist. */
1224         cgroup_fork_callbacks(p);
1225         cgroup_callbacks_done = 1;
1226
1227         /* Need tasklist lock for parent etc handling! */
1228         write_lock_irq(&tasklist_lock);
1229
1230         /* CLONE_PARENT re-uses the old parent */
1231         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1232                 p->real_parent = current->real_parent;
1233                 p->parent_exec_id = current->parent_exec_id;
1234         } else {
1235                 p->real_parent = current;
1236                 p->parent_exec_id = current->self_exec_id;
1237         }
1238
1239         spin_lock(&current->sighand->siglock);
1240
1241         /*
1242          * Process group and session signals need to be delivered to just the
1243          * parent before the fork or both the parent and the child after the
1244          * fork. Restart if a signal comes in before we add the new process to
1245          * it's process group.
1246          * A fatal signal pending means that current will exit, so the new
1247          * thread can't slip out of an OOM kill (or normal SIGKILL).
1248          */
1249         recalc_sigpending();
1250         if (signal_pending(current)) {
1251                 spin_unlock(&current->sighand->siglock);
1252                 write_unlock_irq(&tasklist_lock);
1253                 retval = -ERESTARTNOINTR;
1254                 goto bad_fork_free_pid;
1255         }
1256
1257         if (clone_flags & CLONE_THREAD) {
1258                 current->signal->nr_threads++;
1259                 atomic_inc(&current->signal->live);
1260                 atomic_inc(&current->signal->sigcnt);
1261                 p->group_leader = current->group_leader;
1262                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1263         }
1264
1265         if (likely(p->pid)) {
1266                 tracehook_finish_clone(p, clone_flags, trace);
1267
1268                 if (thread_group_leader(p)) {
1269                         if (clone_flags & CLONE_NEWPID)
1270                                 p->nsproxy->pid_ns->child_reaper = p;
1271
1272                         p->signal->leader_pid = pid;
1273                         p->signal->tty = tty_kref_get(current->signal->tty);
1274                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1275                         attach_pid(p, PIDTYPE_SID, task_session(current));
1276                         list_add_tail(&p->sibling, &p->real_parent->children);
1277                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1278                         __get_cpu_var(process_counts)++;
1279                 }
1280                 attach_pid(p, PIDTYPE_PID, pid);
1281                 nr_threads++;
1282         }
1283
1284         total_forks++;
1285         spin_unlock(&current->sighand->siglock);
1286         write_unlock_irq(&tasklist_lock);
1287         proc_fork_connector(p);
1288         cgroup_post_fork(p);
1289         perf_event_fork(p);
1290         return p;
1291
1292 bad_fork_free_pid:
1293         if (pid != &init_struct_pid)
1294                 free_pid(pid);
1295 bad_fork_cleanup_io:
1296         if (p->io_context)
1297                 exit_io_context(p);
1298 bad_fork_cleanup_namespaces:
1299         exit_task_namespaces(p);
1300 bad_fork_cleanup_mm:
1301         if (p->mm)
1302                 mmput(p->mm);
1303 bad_fork_cleanup_signal:
1304         if (!(clone_flags & CLONE_THREAD))
1305                 free_signal_struct(p->signal);
1306 bad_fork_cleanup_sighand:
1307         __cleanup_sighand(p->sighand);
1308 bad_fork_cleanup_fs:
1309         exit_fs(p); /* blocking */
1310 bad_fork_cleanup_files:
1311         exit_files(p); /* blocking */
1312 bad_fork_cleanup_semundo:
1313         exit_sem(p);
1314 bad_fork_cleanup_audit:
1315         audit_free(p);
1316 bad_fork_cleanup_policy:
1317         perf_event_free_task(p);
1318 #ifdef CONFIG_NUMA
1319         mpol_put(p->mempolicy);
1320 bad_fork_cleanup_cgroup:
1321 #endif
1322         cgroup_exit(p, cgroup_callbacks_done);
1323         delayacct_tsk_free(p);
1324         module_put(task_thread_info(p)->exec_domain->module);
1325 bad_fork_cleanup_count:
1326         atomic_dec(&p->cred->user->processes);
1327         exit_creds(p);
1328 bad_fork_free:
1329         free_task(p);
1330 fork_out:
1331         return ERR_PTR(retval);
1332 }
1333
1334 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1335 {
1336         memset(regs, 0, sizeof(struct pt_regs));
1337         return regs;
1338 }
1339
1340 static inline void init_idle_pids(struct pid_link *links)
1341 {
1342         enum pid_type type;
1343
1344         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1345                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1346                 links[type].pid = &init_struct_pid;
1347         }
1348 }
1349
1350 struct task_struct * __cpuinit fork_idle(int cpu)
1351 {
1352         struct task_struct *task;
1353         struct pt_regs regs;
1354
1355         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1356                             &init_struct_pid, 0);
1357         if (!IS_ERR(task)) {
1358                 init_idle_pids(task->pids);
1359                 init_idle(task, cpu);
1360         }
1361
1362         return task;
1363 }
1364
1365 /*
1366  *  Ok, this is the main fork-routine.
1367  *
1368  * It copies the process, and if successful kick-starts
1369  * it and waits for it to finish using the VM if required.
1370  */
1371 long do_fork(unsigned long clone_flags,
1372               unsigned long stack_start,
1373               struct pt_regs *regs,
1374               unsigned long stack_size,
1375               int __user *parent_tidptr,
1376               int __user *child_tidptr)
1377 {
1378         struct task_struct *p;
1379         int trace = 0;
1380         long nr;
1381
1382         /*
1383          * Do some preliminary argument and permissions checking before we
1384          * actually start allocating stuff
1385          */
1386         if (clone_flags & CLONE_NEWUSER) {
1387                 if (clone_flags & CLONE_THREAD)
1388                         return -EINVAL;
1389                 /* hopefully this check will go away when userns support is
1390                  * complete
1391                  */
1392                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1393                                 !capable(CAP_SETGID))
1394                         return -EPERM;
1395         }
1396
1397         /*
1398          * We hope to recycle these flags after 2.6.26
1399          */
1400         if (unlikely(clone_flags & CLONE_STOPPED)) {
1401                 static int __read_mostly count = 100;
1402
1403                 if (count > 0 && printk_ratelimit()) {
1404                         char comm[TASK_COMM_LEN];
1405
1406                         count--;
1407                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1408                                         "clone flags 0x%lx\n",
1409                                 get_task_comm(comm, current),
1410                                 clone_flags & CLONE_STOPPED);
1411                 }
1412         }
1413
1414         /*
1415          * When called from kernel_thread, don't do user tracing stuff.
1416          */
1417         if (likely(user_mode(regs)))
1418                 trace = tracehook_prepare_clone(clone_flags);
1419
1420         p = copy_process(clone_flags, stack_start, regs, stack_size,
1421                          child_tidptr, NULL, trace);
1422         /*
1423          * Do this prior waking up the new thread - the thread pointer
1424          * might get invalid after that point, if the thread exits quickly.
1425          */
1426         if (!IS_ERR(p)) {
1427                 struct completion vfork;
1428
1429                 trace_sched_process_fork(current, p);
1430
1431                 nr = task_pid_vnr(p);
1432
1433                 if (clone_flags & CLONE_PARENT_SETTID)
1434                         put_user(nr, parent_tidptr);
1435
1436                 if (clone_flags & CLONE_VFORK) {
1437                         p->vfork_done = &vfork;
1438                         init_completion(&vfork);
1439                 }
1440
1441                 audit_finish_fork(p);
1442                 tracehook_report_clone(regs, clone_flags, nr, p);
1443
1444                 /*
1445                  * We set PF_STARTING at creation in case tracing wants to
1446                  * use this to distinguish a fully live task from one that
1447                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1448                  * clear it and set the child going.
1449                  */
1450                 p->flags &= ~PF_STARTING;
1451
1452                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1453                         /*
1454                          * We'll start up with an immediate SIGSTOP.
1455                          */
1456                         sigaddset(&p->pending.signal, SIGSTOP);
1457                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1458                         __set_task_state(p, TASK_STOPPED);
1459                 } else {
1460                         wake_up_new_task(p, clone_flags);
1461                 }
1462
1463                 tracehook_report_clone_complete(trace, regs,
1464                                                 clone_flags, nr, p);
1465
1466                 if (clone_flags & CLONE_VFORK) {
1467                         freezer_do_not_count();
1468                         wait_for_completion(&vfork);
1469                         freezer_count();
1470                         tracehook_report_vfork_done(p, nr);
1471                 }
1472         } else {
1473                 nr = PTR_ERR(p);
1474         }
1475         return nr;
1476 }
1477
1478 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1479 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1480 #endif
1481
1482 static void sighand_ctor(void *data)
1483 {
1484         struct sighand_struct *sighand = data;
1485
1486         spin_lock_init(&sighand->siglock);
1487         init_waitqueue_head(&sighand->signalfd_wqh);
1488 }
1489
1490 void __init proc_caches_init(void)
1491 {
1492         sighand_cachep = kmem_cache_create("sighand_cache",
1493                         sizeof(struct sighand_struct), 0,
1494                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1495                         SLAB_NOTRACK, sighand_ctor);
1496         signal_cachep = kmem_cache_create("signal_cache",
1497                         sizeof(struct signal_struct), 0,
1498                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1499         files_cachep = kmem_cache_create("files_cache",
1500                         sizeof(struct files_struct), 0,
1501                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1502         fs_cachep = kmem_cache_create("fs_cache",
1503                         sizeof(struct fs_struct), 0,
1504                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1505         mm_cachep = kmem_cache_create("mm_struct",
1506                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1507                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1508         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1509         mmap_init();
1510 }
1511
1512 /*
1513  * Check constraints on flags passed to the unshare system call and
1514  * force unsharing of additional process context as appropriate.
1515  */
1516 static void check_unshare_flags(unsigned long *flags_ptr)
1517 {
1518         /*
1519          * If unsharing a thread from a thread group, must also
1520          * unshare vm.
1521          */
1522         if (*flags_ptr & CLONE_THREAD)
1523                 *flags_ptr |= CLONE_VM;
1524
1525         /*
1526          * If unsharing vm, must also unshare signal handlers.
1527          */
1528         if (*flags_ptr & CLONE_VM)
1529                 *flags_ptr |= CLONE_SIGHAND;
1530
1531         /*
1532          * If unsharing namespace, must also unshare filesystem information.
1533          */
1534         if (*flags_ptr & CLONE_NEWNS)
1535                 *flags_ptr |= CLONE_FS;
1536 }
1537
1538 /*
1539  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1540  */
1541 static int unshare_thread(unsigned long unshare_flags)
1542 {
1543         if (unshare_flags & CLONE_THREAD)
1544                 return -EINVAL;
1545
1546         return 0;
1547 }
1548
1549 /*
1550  * Unshare the filesystem structure if it is being shared
1551  */
1552 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1553 {
1554         struct fs_struct *fs = current->fs;
1555
1556         if (!(unshare_flags & CLONE_FS) || !fs)
1557                 return 0;
1558
1559         /* don't need lock here; in the worst case we'll do useless copy */
1560         if (fs->users == 1)
1561                 return 0;
1562
1563         *new_fsp = copy_fs_struct(fs);
1564         if (!*new_fsp)
1565                 return -ENOMEM;
1566
1567         return 0;
1568 }
1569
1570 /*
1571  * Unsharing of sighand is not supported yet
1572  */
1573 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1574 {
1575         struct sighand_struct *sigh = current->sighand;
1576
1577         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1578                 return -EINVAL;
1579         else
1580                 return 0;
1581 }
1582
1583 /*
1584  * Unshare vm if it is being shared
1585  */
1586 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1587 {
1588         struct mm_struct *mm = current->mm;
1589
1590         if ((unshare_flags & CLONE_VM) &&
1591             (mm && atomic_read(&mm->mm_users) > 1)) {
1592                 return -EINVAL;
1593         }
1594
1595         return 0;
1596 }
1597
1598 /*
1599  * Unshare file descriptor table if it is being shared
1600  */
1601 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1602 {
1603         struct files_struct *fd = current->files;
1604         int error = 0;
1605
1606         if ((unshare_flags & CLONE_FILES) &&
1607             (fd && atomic_read(&fd->count) > 1)) {
1608                 *new_fdp = dup_fd(fd, &error);
1609                 if (!*new_fdp)
1610                         return error;
1611         }
1612
1613         return 0;
1614 }
1615
1616 /*
1617  * unshare allows a process to 'unshare' part of the process
1618  * context which was originally shared using clone.  copy_*
1619  * functions used by do_fork() cannot be used here directly
1620  * because they modify an inactive task_struct that is being
1621  * constructed. Here we are modifying the current, active,
1622  * task_struct.
1623  */
1624 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1625 {
1626         int err = 0;
1627         struct fs_struct *fs, *new_fs = NULL;
1628         struct sighand_struct *new_sigh = NULL;
1629         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1630         struct files_struct *fd, *new_fd = NULL;
1631         struct nsproxy *new_nsproxy = NULL;
1632         int do_sysvsem = 0;
1633
1634         check_unshare_flags(&unshare_flags);
1635
1636         /* Return -EINVAL for all unsupported flags */
1637         err = -EINVAL;
1638         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1639                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1640                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1641                 goto bad_unshare_out;
1642
1643         /*
1644          * CLONE_NEWIPC must also detach from the undolist: after switching
1645          * to a new ipc namespace, the semaphore arrays from the old
1646          * namespace are unreachable.
1647          */
1648         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1649                 do_sysvsem = 1;
1650         if ((err = unshare_thread(unshare_flags)))
1651                 goto bad_unshare_out;
1652         if ((err = unshare_fs(unshare_flags, &new_fs)))
1653                 goto bad_unshare_cleanup_thread;
1654         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1655                 goto bad_unshare_cleanup_fs;
1656         if ((err = unshare_vm(unshare_flags, &new_mm)))
1657                 goto bad_unshare_cleanup_sigh;
1658         if ((err = unshare_fd(unshare_flags, &new_fd)))
1659                 goto bad_unshare_cleanup_vm;
1660         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1661                         new_fs)))
1662                 goto bad_unshare_cleanup_fd;
1663
1664         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1665                 if (do_sysvsem) {
1666                         /*
1667                          * CLONE_SYSVSEM is equivalent to sys_exit().
1668                          */
1669                         exit_sem(current);
1670                 }
1671
1672                 if (new_nsproxy) {
1673                         switch_task_namespaces(current, new_nsproxy);
1674                         new_nsproxy = NULL;
1675                 }
1676
1677                 task_lock(current);
1678
1679                 if (new_fs) {
1680                         fs = current->fs;
1681                         write_lock(&fs->lock);
1682                         current->fs = new_fs;
1683                         if (--fs->users)
1684                                 new_fs = NULL;
1685                         else
1686                                 new_fs = fs;
1687                         write_unlock(&fs->lock);
1688                 }
1689
1690                 if (new_mm) {
1691                         mm = current->mm;
1692                         active_mm = current->active_mm;
1693                         current->mm = new_mm;
1694                         current->active_mm = new_mm;
1695                         activate_mm(active_mm, new_mm);
1696                         new_mm = mm;
1697                 }
1698
1699                 if (new_fd) {
1700                         fd = current->files;
1701                         current->files = new_fd;
1702                         new_fd = fd;
1703                 }
1704
1705                 task_unlock(current);
1706         }
1707
1708         if (new_nsproxy)
1709                 put_nsproxy(new_nsproxy);
1710
1711 bad_unshare_cleanup_fd:
1712         if (new_fd)
1713                 put_files_struct(new_fd);
1714
1715 bad_unshare_cleanup_vm:
1716         if (new_mm)
1717                 mmput(new_mm);
1718
1719 bad_unshare_cleanup_sigh:
1720         if (new_sigh)
1721                 if (atomic_dec_and_test(&new_sigh->count))
1722                         kmem_cache_free(sighand_cachep, new_sigh);
1723
1724 bad_unshare_cleanup_fs:
1725         if (new_fs)
1726                 free_fs_struct(new_fs);
1727
1728 bad_unshare_cleanup_thread:
1729 bad_unshare_out:
1730         return err;
1731 }
1732
1733 /*
1734  *      Helper to unshare the files of the current task.
1735  *      We don't want to expose copy_files internals to
1736  *      the exec layer of the kernel.
1737  */
1738
1739 int unshare_files(struct files_struct **displaced)
1740 {
1741         struct task_struct *task = current;
1742         struct files_struct *copy = NULL;
1743         int error;
1744
1745         error = unshare_fd(CLONE_FILES, &copy);
1746         if (error || !copy) {
1747                 *displaced = NULL;
1748                 return error;
1749         }
1750         *displaced = task->files;
1751         task_lock(task);
1752         task->files = copy;
1753         task_unlock(task);
1754         return 0;
1755 }