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/kthread.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/proc_fs.h>
  52 #include <linux/profile.h>
  53 #include <linux/rmap.h>
  54 #include <linux/ksm.h>
  55 #include <linux/acct.h>
  56 #include <linux/tsacct_kern.h>
  57 #include <linux/cn_proc.h>
  58 #include <linux/freezer.h>
  59 #include <linux/delayacct.h>
  60 #include <linux/taskstats_kern.h>
  61 #include <linux/random.h>
  62 #include <linux/tty.h>
  63 #include <linux/blkdev.h>
  64 #include <linux/fs_struct.h>
  65 #include <linux/magic.h>
  66 #include <linux/perf_event.h>
  67 #include <linux/posix-timers.h>
  68 #include <linux/user-return-notifier.h>
  69 #include <linux/oom.h>
  70 #include <linux/khugepaged.h>
  71 #include <linux/signalfd.h>
  72
  73 #include <asm/pgtable.h>
  74 #include <asm/pgalloc.h>
  75 #include <asm/uaccess.h>
  76 #include <asm/mmu_context.h>
  77 #include <asm/cacheflush.h>
  78 #include <asm/tlbflush.h>
  79
  80 #include <trace/events/sched.h>
  81
  82 /*
  83  * Protected counters by write_lock_irq(&tasklist_lock)
  84  */
  85 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  86 int nr_threads;                 /* The idle threads do not count.. */
  87
  88 int max_threads;                /* tunable limit on nr_threads */
  89
  90 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  91
  92 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  93
  94 #ifdef CONFIG_PROVE_RCU
  95 int lockdep_tasklist_lock_is_held(void)
  96 {
  97         return lockdep_is_held(&tasklist_lock);
  98 }
  99 EXPORT_SYMBOL_GPL(lockdep_tasklist_lock_is_held);
 100 #endif /* #ifdef CONFIG_PROVE_RCU */
 101
 102 int nr_processes(void)
 103 {
 104         int cpu;
 105         int total = 0;
 106
 107         for_each_possible_cpu(cpu)
 108                 total += per_cpu(process_counts, cpu);
 109
 110         return total;
 111 }
 112
 113 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 114 # define alloc_task_struct_node(node)           \
 115                 kmem_cache_alloc_node(task_struct_cachep, GFP_KERNEL, node)
 116 # define free_task_struct(tsk)                  \
 117                 kmem_cache_free(task_struct_cachep, (tsk))
 118 static struct kmem_cache *task_struct_cachep;
 119 #endif
 120
 121 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 122 static struct thread_info *alloc_thread_info_node(struct task_struct *tsk,
 123                                                   int node)
 124 {
 125 #ifdef CONFIG_DEBUG_STACK_USAGE
 126         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 127 #else
 128         gfp_t mask = GFP_KERNEL;
 129 #endif
 130         struct page *page = alloc_pages_node(node, mask, THREAD_SIZE_ORDER);
 131
 132         return page ? page_address(page) : NULL;
 133 }
 134
 135 static inline void free_thread_info(struct thread_info *ti)
 136 {
 137         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 138 }
 139 #endif
 140
 141 /* SLAB cache for signal_struct structures (tsk->signal) */
 142 static struct kmem_cache *signal_cachep;
 143
 144 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 145 struct kmem_cache *sighand_cachep;
 146
 147 /* SLAB cache for files_struct structures (tsk->files) */
 148 struct kmem_cache *files_cachep;
 149
 150 /* SLAB cache for fs_struct structures (tsk->fs) */
 151 struct kmem_cache *fs_cachep;
 152
 153 /* SLAB cache for vm_area_struct structures */
 154 struct kmem_cache *vm_area_cachep;
 155
 156 /* SLAB cache for mm_struct structures (tsk->mm) */
 157 static struct kmem_cache *mm_cachep;
 158
 159 /* Notifier list called when a task struct is freed */
 160 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 161
 162 static void account_kernel_stack(struct thread_info *ti, int account)
 163 {
 164         struct zone *zone = page_zone(virt_to_page(ti));
 165
 166         mod_zone_page_state(zone, NR_KERNEL_STACK, account);
 167 }
 168
 169 void free_task(struct task_struct *tsk)
 170 {
 171         prop_local_destroy_single(&tsk->dirties);
 172         account_kernel_stack(tsk->stack, -1);
 173         free_thread_info(tsk->stack);
 174         rt_mutex_debug_task_free(tsk);
 175         ftrace_graph_exit_task(tsk);
 176         free_task_struct(tsk);
 177 }
 178 EXPORT_SYMBOL(free_task);
 179
 180 static inline void free_signal_struct(struct signal_struct *sig)
 181 {
 182         taskstats_tgid_free(sig);
 183         sched_autogroup_exit(sig);
 184         kmem_cache_free(signal_cachep, sig);
 185 }
 186
 187 static inline void put_signal_struct(struct signal_struct *sig)
 188 {
 189         if (atomic_dec_and_test(&sig->sigcnt))
 190                 free_signal_struct(sig);
 191 }
 192
 193 int task_free_register(struct notifier_block *n)
 194 {
 195         return atomic_notifier_chain_register(&task_free_notifier, n);
 196 }
 197 EXPORT_SYMBOL(task_free_register);
 198
 199 int task_free_unregister(struct notifier_block *n)
 200 {
 201         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 202 }
 203 EXPORT_SYMBOL(task_free_unregister);
 204
 205 void __put_task_struct(struct task_struct *tsk)
 206 {
 207         WARN_ON(!tsk->exit_state);
 208         WARN_ON(atomic_read(&tsk->usage));
 209         WARN_ON(tsk == current);
 210
 211         exit_creds(tsk);
 212         delayacct_tsk_free(tsk);
 213         put_signal_struct(tsk->signal);
 214
 215         atomic_notifier_call_chain(&task_free_notifier, 0, tsk);
 216         if (!profile_handoff_task(tsk))
 217                 free_task(tsk);
 218 }
 219 EXPORT_SYMBOL_GPL(__put_task_struct);
 220
 221 /*
 222  * macro override instead of weak attribute alias, to workaround
 223  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 224  */
 225 #ifndef arch_task_cache_init
 226 #define arch_task_cache_init()
 227 #endif
 228
 229 void __init fork_init(unsigned long mempages)
 230 {
 231 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 232 #ifndef ARCH_MIN_TASKALIGN
 233 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 234 #endif
 235         /* create a slab on which task_structs can be allocated */
 236         task_struct_cachep =
 237                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 238                         ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL);
 239 #endif
 240
 241         /* do the arch specific task caches init */
 242         arch_task_cache_init();
 243
 244         /*
 245          * The default maximum number of threads is set to a safe
 246          * value: the thread structures can take up at most half
 247          * of memory.
 248          */
 249         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 250
 251         /*
 252          * we need to allow at least 20 threads to boot a system
 253          */
 254         if(max_threads < 20)
 255                 max_threads = 20;
 256
 257         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 258         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 259         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 260                 init_task.signal->rlim[RLIMIT_NPROC];
 261 }
 262
 263 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 264                                                struct task_struct *src)
 265 {
 266         *dst = *src;
 267         return 0;
 268 }
 269
 270 static struct task_struct *dup_task_struct(struct task_struct *orig)
 271 {
 272         struct task_struct *tsk;
 273         struct thread_info *ti;
 274         unsigned long *stackend;
 275         int node = tsk_fork_get_node(orig);
 276         int err;
 277
 278         prepare_to_copy(orig);
 279
 280         tsk = alloc_task_struct_node(node);
 281         if (!tsk)
 282                 return NULL;
 283
 284         ti = alloc_thread_info_node(tsk, node);
 285         if (!ti) {
 286                 free_task_struct(tsk);
 287                 return NULL;
 288         }
 289
 290         err = arch_dup_task_struct(tsk, orig);
 291         if (err)
 292                 goto out;
 293
 294         tsk->stack = ti;
 295
 296         err = prop_local_init_single(&tsk->dirties);
 297         if (err)
 298                 goto out;
 299
 300         setup_thread_stack(tsk, orig);
 301         clear_user_return_notifier(tsk);
 302         clear_tsk_need_resched(tsk);
 303         stackend = end_of_stack(tsk);
 304         *stackend = STACK_END_MAGIC;    /* for overflow detection */
 305
 306 #ifdef CONFIG_CC_STACKPROTECTOR
 307         tsk->stack_canary = get_random_int();
 308 #endif
 309
 310         /* One for us, one for whoever does the "release_task()" (usually parent) */
 311         atomic_set(&tsk->usage,2);
 312         atomic_set(&tsk->fs_excl, 0);
 313 #ifdef CONFIG_BLK_DEV_IO_TRACE
 314         tsk->btrace_seq = 0;
 315 #endif
 316         tsk->splice_pipe = NULL;
 317
 318         account_kernel_stack(ti, 1);
 319
 320         return tsk;
 321
 322 out:
 323         free_thread_info(ti);
 324         free_task_struct(tsk);
 325         return NULL;
 326 }
 327
 328 #ifdef CONFIG_MMU
 329 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 330 {
 331         struct vm_area_struct *mpnt, *tmp, *prev, **pprev;
 332         struct rb_node **rb_link, *rb_parent;
 333         int retval;
 334         unsigned long charge;
 335         struct mempolicy *pol;
 336
 337         down_write(&oldmm->mmap_sem);
 338         flush_cache_dup_mm(oldmm);
 339         /*
 340          * Not linked in yet - no deadlock potential:
 341          */
 342         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 343
 344         mm->locked_vm = 0;
 345         mm->mmap = NULL;
 346         mm->mmap_cache = NULL;
 347         mm->free_area_cache = oldmm->mmap_base;
 348         mm->cached_hole_size = ~0UL;
 349         mm->map_count = 0;
 350         cpumask_clear(mm_cpumask(mm));
 351         mm->mm_rb = RB_ROOT;
 352         rb_link = &mm->mm_rb.rb_node;
 353         rb_parent = NULL;
 354         pprev = &mm->mmap;
 355         retval = ksm_fork(mm, oldmm);
 356         if (retval)
 357                 goto out;
 358         retval = khugepaged_fork(mm, oldmm);
 359         if (retval)
 360                 goto out;
 361
 362         prev = NULL;
 363         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 364                 struct file *file;
 365
 366                 if (mpnt->vm_flags & VM_DONTCOPY) {
 367                         long pages = vma_pages(mpnt);
 368                         mm->total_vm -= pages;
 369                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 370                                                                 -pages);
 371                         continue;
 372                 }
 373                 charge = 0;
 374                 if (mpnt->vm_flags & VM_ACCOUNT) {
 375                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 376                         if (security_vm_enough_memory(len))
 377                                 goto fail_nomem;
 378                         charge = len;
 379                 }
 380                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 381                 if (!tmp)
 382                         goto fail_nomem;
 383                 *tmp = *mpnt;
 384                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
 385                 pol = mpol_dup(vma_policy(mpnt));
 386                 retval = PTR_ERR(pol);
 387                 if (IS_ERR(pol))
 388                         goto fail_nomem_policy;
 389                 vma_set_policy(tmp, pol);
 390                 tmp->vm_mm = mm;
 391                 if (anon_vma_fork(tmp, mpnt))
 392                         goto fail_nomem_anon_vma_fork;
 393                 tmp->vm_flags &= ~VM_LOCKED;
 394                 tmp->vm_next = tmp->vm_prev = NULL;
 395                 file = tmp->vm_file;
 396                 if (file) {
 397                         struct inode *inode = file->f_path.dentry->d_inode;
 398                         struct address_space *mapping = file->f_mapping;
 399
 400                         get_file(file);
 401                         if (tmp->vm_flags & VM_DENYWRITE)
 402                                 atomic_dec(&inode->i_writecount);
 403                         mutex_lock(&mapping->i_mmap_mutex);
 404                         if (tmp->vm_flags & VM_SHARED)
 405                                 mapping->i_mmap_writable++;
 406                         flush_dcache_mmap_lock(mapping);
 407                         /* insert tmp into the share list, just after mpnt */
 408                         vma_prio_tree_add(tmp, mpnt);
 409                         flush_dcache_mmap_unlock(mapping);
 410                         mutex_unlock(&mapping->i_mmap_mutex);
 411                 }
 412
 413                 /*
 414                  * Clear hugetlb-related page reserves for children. This only
 415                  * affects MAP_PRIVATE mappings. Faults generated by the child
 416                  * are not guaranteed to succeed, even if read-only
 417                  */
 418                 if (is_vm_hugetlb_page(tmp))
 419                         reset_vma_resv_huge_pages(tmp);
 420
 421                 /*
 422                  * Link in the new vma and copy the page table entries.
 423                  */
 424                 *pprev = tmp;
 425                 pprev = &tmp->vm_next;
 426                 tmp->vm_prev = prev;
 427                 prev = tmp;
 428
 429                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 430                 rb_link = &tmp->vm_rb.rb_right;
 431                 rb_parent = &tmp->vm_rb;
 432
 433                 mm->map_count++;
 434                 retval = copy_page_range(mm, oldmm, mpnt);
 435
 436                 if (tmp->vm_ops && tmp->vm_ops->open)
 437                         tmp->vm_ops->open(tmp);
 438
 439                 if (retval)
 440                         goto out;
 441         }
 442         /* a new mm has just been created */
 443         arch_dup_mmap(oldmm, mm);
 444         retval = 0;
 445 out:
 446         up_write(&mm->mmap_sem);
 447         flush_tlb_mm(oldmm);
 448         up_write(&oldmm->mmap_sem);
 449         return retval;
 450 fail_nomem_anon_vma_fork:
 451         mpol_put(pol);
 452 fail_nomem_policy:
 453         kmem_cache_free(vm_area_cachep, tmp);
 454 fail_nomem:
 455         retval = -ENOMEM;
 456         vm_unacct_memory(charge);
 457         goto out;
 458 }
 459
 460 static inline int mm_alloc_pgd(struct mm_struct * mm)
 461 {
 462         mm->pgd = pgd_alloc(mm);
 463         if (unlikely(!mm->pgd))
 464                 return -ENOMEM;
 465         return 0;
 466 }
 467
 468 static inline void mm_free_pgd(struct mm_struct * mm)
 469 {
 470         pgd_free(mm, mm->pgd);
 471 }
 472 #else
 473 #define dup_mmap(mm, oldmm)     (0)
 474 #define mm_alloc_pgd(mm)        (0)
 475 #define mm_free_pgd(mm)
 476 #endif /* CONFIG_MMU */
 477
 478 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 479
 480 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 481 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 482
 483 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT;
 484
 485 static int __init coredump_filter_setup(char *s)
 486 {
 487         default_dump_filter =
 488                 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) &
 489                 MMF_DUMP_FILTER_MASK;
 490         return 1;
 491 }
 492
 493 __setup("coredump_filter=", coredump_filter_setup);
 494
 495 #include <linux/init_task.h>
 496
 497 static void mm_init_aio(struct mm_struct *mm)
 498 {
 499 #ifdef CONFIG_AIO
 500         spin_lock_init(&mm->ioctx_lock);
 501         INIT_HLIST_HEAD(&mm->ioctx_list);
 502 #endif
 503 }
 504
 505 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 506 {
 507         atomic_set(&mm->mm_users, 1);
 508         atomic_set(&mm->mm_count, 1);
 509         init_rwsem(&mm->mmap_sem);
 510         INIT_LIST_HEAD(&mm->mmlist);
 511         mm->flags = (current->mm) ?
 512                 (current->mm->flags & MMF_INIT_MASK) : default_dump_filter;
 513         mm->core_state = NULL;
 514         mm->nr_ptes = 0;
 515         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
 516         spin_lock_init(&mm->page_table_lock);
 517         mm->free_area_cache = TASK_UNMAPPED_BASE;
 518         mm->cached_hole_size = ~0UL;
 519         mm_init_aio(mm);
 520         mm_init_owner(mm, p);
 521         atomic_set(&mm->oom_disable_count, 0);
 522
 523         if (likely(!mm_alloc_pgd(mm))) {
 524                 mm->def_flags = 0;
 525                 mmu_notifier_mm_init(mm);
 526                 return mm;
 527         }
 528
 529         free_mm(mm);
 530         return NULL;
 531 }
 532
 533 /*
 534  * Allocate and initialize an mm_struct.
 535  */
 536 struct mm_struct * mm_alloc(void)
 537 {
 538         struct mm_struct * mm;
 539
 540         mm = allocate_mm();
 541         if (!mm)
 542                 return NULL;
 543
 544         memset(mm, 0, sizeof(*mm));
 545         mm_init_cpumask(mm);
 546         return mm_init(mm, current);
 547 }
 548
 549 /*
 550  * Called when the last reference to the mm
 551  * is dropped: either by a lazy thread or by
 552  * mmput. Free the page directory and the mm.
 553  */
 554 void __mmdrop(struct mm_struct *mm)
 555 {
 556         BUG_ON(mm == &init_mm);
 557         mm_free_pgd(mm);
 558         destroy_context(mm);
 559         mmu_notifier_mm_destroy(mm);
 560 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 561         VM_BUG_ON(mm->pmd_huge_pte);
 562 #endif
 563         free_mm(mm);
 564 }
 565 EXPORT_SYMBOL_GPL(__mmdrop);
 566
 567 /*
 568  * Decrement the use count and release all resources for an mm.
 569  */
 570 void mmput(struct mm_struct *mm)
 571 {
 572         might_sleep();
 573
 574         if (atomic_dec_and_test(&mm->mm_users)) {
 575                 exit_aio(mm);
 576                 ksm_exit(mm);
 577                 khugepaged_exit(mm); /* must run before exit_mmap */
 578                 exit_mmap(mm);
 579                 set_mm_exe_file(mm, NULL);
 580                 if (!list_empty(&mm->mmlist)) {
 581                         spin_lock(&mmlist_lock);
 582                         list_del(&mm->mmlist);
 583                         spin_unlock(&mmlist_lock);
 584                 }
 585                 put_swap_token(mm);
 586                 if (mm->binfmt)
 587                         module_put(mm->binfmt->module);
 588                 mmdrop(mm);
 589         }
 590 }
 591 EXPORT_SYMBOL_GPL(mmput);
 592
 593 /*
 594  * We added or removed a vma mapping the executable. The vmas are only mapped
 595  * during exec and are not mapped with the mmap system call.
 596  * Callers must hold down_write() on the mm's mmap_sem for these
 597  */
 598 void added_exe_file_vma(struct mm_struct *mm)
 599 {
 600         mm->num_exe_file_vmas++;
 601 }
 602
 603 void removed_exe_file_vma(struct mm_struct *mm)
 604 {
 605         mm->num_exe_file_vmas--;
 606         if ((mm->num_exe_file_vmas == 0) && mm->exe_file){
 607                 fput(mm->exe_file);
 608                 mm->exe_file = NULL;
 609         }
 610
 611 }
 612
 613 void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
 614 {
 615         if (new_exe_file)
 616                 get_file(new_exe_file);
 617         if (mm->exe_file)
 618                 fput(mm->exe_file);
 619         mm->exe_file = new_exe_file;
 620         mm->num_exe_file_vmas = 0;
 621 }
 622
 623 struct file *get_mm_exe_file(struct mm_struct *mm)
 624 {
 625         struct file *exe_file;
 626
 627         /* We need mmap_sem to protect against races with removal of
 628          * VM_EXECUTABLE vmas */
 629         down_read(&mm->mmap_sem);
 630         exe_file = mm->exe_file;
 631         if (exe_file)
 632                 get_file(exe_file);
 633         up_read(&mm->mmap_sem);
 634         return exe_file;
 635 }
 636
 637 static void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm)
 638 {
 639         /* It's safe to write the exe_file pointer without exe_file_lock because
 640          * this is called during fork when the task is not yet in /proc */
 641         newmm->exe_file = get_mm_exe_file(oldmm);
 642 }
 643
 644 /**
 645  * get_task_mm - acquire a reference to the task's mm
 646  *
 647  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 648  * this kernel workthread has transiently adopted a user mm with use_mm,
 649  * to do its AIO) is not set and if so returns a reference to it, after
 650  * bumping up the use count.  User must release the mm via mmput()
 651  * after use.  Typically used by /proc and ptrace.
 652  */
 653 struct mm_struct *get_task_mm(struct task_struct *task)
 654 {
 655         struct mm_struct *mm;
 656
 657         task_lock(task);
 658         mm = task->mm;
 659         if (mm) {
 660                 if (task->flags & PF_KTHREAD)
 661                         mm = NULL;
 662                 else
 663                         atomic_inc(&mm->mm_users);
 664         }
 665         task_unlock(task);
 666         return mm;
 667 }
 668 EXPORT_SYMBOL_GPL(get_task_mm);
 669
 670 /* Please note the differences between mmput and mm_release.
 671  * mmput is called whenever we stop holding onto a mm_struct,
 672  * error success whatever.
 673  *
 674  * mm_release is called after a mm_struct has been removed
 675  * from the current process.
 676  *
 677  * This difference is important for error handling, when we
 678  * only half set up a mm_struct for a new process and need to restore
 679  * the old one.  Because we mmput the new mm_struct before
 680  * restoring the old one. . .
 681  * Eric Biederman 10 January 1998
 682  */
 683 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 684 {
 685         struct completion *vfork_done = tsk->vfork_done;
 686
 687         /* Get rid of any futexes when releasing the mm */
 688 #ifdef CONFIG_FUTEX
 689         if (unlikely(tsk->robust_list)) {
 690                 exit_robust_list(tsk);
 691                 tsk->robust_list = NULL;
 692         }
 693 #ifdef CONFIG_COMPAT
 694         if (unlikely(tsk->compat_robust_list)) {
 695                 compat_exit_robust_list(tsk);
 696                 tsk->compat_robust_list = NULL;
 697         }
 698 #endif
 699         if (unlikely(!list_empty(&tsk->pi_state_list)))
 700                 exit_pi_state_list(tsk);
 701 #endif
 702
 703         /* Get rid of any cached register state */
 704         deactivate_mm(tsk, mm);
 705
 706         /* notify parent sleeping on vfork() */
 707         if (vfork_done) {
 708                 tsk->vfork_done = NULL;
 709                 complete(vfork_done);
 710         }
 711
 712         /*
 713          * If we're exiting normally, clear a user-space tid field if
 714          * requested.  We leave this alone when dying by signal, to leave
 715          * the value intact in a core dump, and to save the unnecessary
 716          * trouble otherwise.  Userland only wants this done for a sys_exit.
 717          */
 718         if (tsk->clear_child_tid) {
 719                 if (!(tsk->flags & PF_SIGNALED) &&
 720                     atomic_read(&mm->mm_users) > 1) {
 721                         /*
 722                          * We don't check the error code - if userspace has
 723                          * not set up a proper pointer then tough luck.
 724                          */
 725                         put_user(0, tsk->clear_child_tid);
 726                         sys_futex(tsk->clear_child_tid, FUTEX_WAKE,
 727                                         1, NULL, NULL, 0);
 728                 }
 729                 tsk->clear_child_tid = NULL;
 730         }
 731 }
 732
 733 /*
 734  * Allocate a new mm structure and copy contents from the
 735  * mm structure of the passed in task structure.
 736  */
 737 struct mm_struct *dup_mm(struct task_struct *tsk)
 738 {
 739         struct mm_struct *mm, *oldmm = current->mm;
 740         int err;
 741
 742         if (!oldmm)
 743                 return NULL;
 744
 745         mm = allocate_mm();
 746         if (!mm)
 747                 goto fail_nomem;
 748
 749         memcpy(mm, oldmm, sizeof(*mm));
 750         mm_init_cpumask(mm);
 751
 752         /* Initializing for Swap token stuff */
 753         mm->token_priority = 0;
 754         mm->last_interval = 0;
 755
 756 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 757         mm->pmd_huge_pte = NULL;
 758 #endif
 759
 760         if (!mm_init(mm, tsk))
 761                 goto fail_nomem;
 762
 763         if (init_new_context(tsk, mm))
 764                 goto fail_nocontext;
 765
 766         dup_mm_exe_file(oldmm, mm);
 767
 768         err = dup_mmap(mm, oldmm);
 769         if (err)
 770                 goto free_pt;
 771
 772         mm->hiwater_rss = get_mm_rss(mm);
 773         mm->hiwater_vm = mm->total_vm;
 774
 775         if (mm->binfmt && !try_module_get(mm->binfmt->module))
 776                 goto free_pt;
 777
 778         return mm;
 779
 780 free_pt:
 781         /* don't put binfmt in mmput, we haven't got module yet */
 782         mm->binfmt = NULL;
 783         mmput(mm);
 784
 785 fail_nomem:
 786         return NULL;
 787
 788 fail_nocontext:
 789         /*
 790          * If init_new_context() failed, we cannot use mmput() to free the mm
 791          * because it calls destroy_context()
 792          */
 793         mm_free_pgd(mm);
 794         free_mm(mm);
 795         return NULL;
 796 }
 797
 798 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 799 {
 800         struct mm_struct * mm, *oldmm;
 801         int retval;
 802
 803         tsk->min_flt = tsk->maj_flt = 0;
 804         tsk->nvcsw = tsk->nivcsw = 0;
 805 #ifdef CONFIG_DETECT_HUNG_TASK
 806         tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
 807 #endif
 808
 809         tsk->mm = NULL;
 810         tsk->active_mm = NULL;
 811
 812         /*
 813          * Are we cloning a kernel thread?
 814          *
 815          * We need to steal a active VM for that..
 816          */
 817         oldmm = current->mm;
 818         if (!oldmm)
 819                 return 0;
 820
 821         if (clone_flags & CLONE_VM) {
 822                 atomic_inc(&oldmm->mm_users);
 823                 mm = oldmm;
 824                 goto good_mm;
 825         }
 826
 827         retval = -ENOMEM;
 828         mm = dup_mm(tsk);
 829         if (!mm)
 830                 goto fail_nomem;
 831
 832 good_mm:
 833         /* Initializing for Swap token stuff */
 834         mm->token_priority = 0;
 835         mm->last_interval = 0;
 836         if (tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 837                 atomic_inc(&mm->oom_disable_count);
 838
 839         tsk->mm = mm;
 840         tsk->active_mm = mm;
 841         return 0;
 842
 843 fail_nomem:
 844         return retval;
 845 }
 846
 847 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 848 {
 849         struct fs_struct *fs = current->fs;
 850         if (clone_flags & CLONE_FS) {
 851                 /* tsk->fs is already what we want */
 852                 spin_lock(&fs->lock);
 853                 if (fs->in_exec) {
 854                         spin_unlock(&fs->lock);
 855                         return -EAGAIN;
 856                 }
 857                 fs->users++;
 858                 spin_unlock(&fs->lock);
 859                 return 0;
 860         }
 861         tsk->fs = copy_fs_struct(fs);
 862         if (!tsk->fs)
 863                 return -ENOMEM;
 864         return 0;
 865 }
 866
 867 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 868 {
 869         struct files_struct *oldf, *newf;
 870         int error = 0;
 871
 872         /*
 873          * A background process may not have any files ...
 874          */
 875         oldf = current->files;
 876         if (!oldf)
 877                 goto out;
 878
 879         if (clone_flags & CLONE_FILES) {
 880                 atomic_inc(&oldf->count);
 881                 goto out;
 882         }
 883
 884         newf = dup_fd(oldf, &error);
 885         if (!newf)
 886                 goto out;
 887
 888         tsk->files = newf;
 889         error = 0;
 890 out:
 891         return error;
 892 }
 893
 894 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 895 {
 896 #ifdef CONFIG_BLOCK
 897         struct io_context *ioc = current->io_context;
 898
 899         if (!ioc)
 900                 return 0;
 901         /*
 902          * Share io context with parent, if CLONE_IO is set
 903          */
 904         if (clone_flags & CLONE_IO) {
 905                 tsk->io_context = ioc_task_link(ioc);
 906                 if (unlikely(!tsk->io_context))
 907                         return -ENOMEM;
 908         } else if (ioprio_valid(ioc->ioprio)) {
 909                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 910                 if (unlikely(!tsk->io_context))
 911                         return -ENOMEM;
 912
 913                 tsk->io_context->ioprio = ioc->ioprio;
 914         }
 915 #endif
 916         return 0;
 917 }
 918
 919 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 920 {
 921         struct sighand_struct *sig;
 922
 923         if (clone_flags & CLONE_SIGHAND) {
 924                 atomic_inc(&current->sighand->count);
 925                 return 0;
 926         }
 927         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 928         rcu_assign_pointer(tsk->sighand, sig);
 929         if (!sig)
 930                 return -ENOMEM;
 931         atomic_set(&sig->count, 1);
 932         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 933         return 0;
 934 }
 935
 936 void __cleanup_sighand(struct sighand_struct *sighand)
 937 {
 938         if (atomic_dec_and_test(&sighand->count)) {
 939                 signalfd_cleanup(sighand);
 940                 kmem_cache_free(sighand_cachep, sighand);
 941         }
 942 }
 943
 944
 945 /*
 946  * Initialize POSIX timer handling for a thread group.
 947  */
 948 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 949 {
 950         unsigned long cpu_limit;
 951
 952         /* Thread group counters. */
 953         thread_group_cputime_init(sig);
 954
 955         cpu_limit = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
 956         if (cpu_limit != RLIM_INFINITY) {
 957                 sig->cputime_expires.prof_exp = secs_to_cputime(cpu_limit);
 958                 sig->cputimer.running = 1;
 959         }
 960
 961         /* The timer lists. */
 962         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 963         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 964         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 965 }
 966
 967 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 968 {
 969         struct signal_struct *sig;
 970
 971         if (clone_flags & CLONE_THREAD)
 972                 return 0;
 973
 974         sig = kmem_cache_zalloc(signal_cachep, GFP_KERNEL);
 975         tsk->signal = sig;
 976         if (!sig)
 977                 return -ENOMEM;
 978
 979         sig->nr_threads = 1;
 980         atomic_set(&sig->live, 1);
 981         atomic_set(&sig->sigcnt, 1);
 982         init_waitqueue_head(&sig->wait_chldexit);
 983         if (clone_flags & CLONE_NEWPID)
 984                 sig->flags |= SIGNAL_UNKILLABLE;
 985         sig->curr_target = tsk;
 986         init_sigpending(&sig->shared_pending);
 987         INIT_LIST_HEAD(&sig->posix_timers);
 988
 989         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 990         sig->real_timer.function = it_real_fn;
 991
 992         task_lock(current->group_leader);
 993         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 994         task_unlock(current->group_leader);
 995
 996         posix_cpu_timers_init_group(sig);
 997
 998         tty_audit_fork(sig);
 999         sched_autogroup_fork(sig);
1000
1001 #ifdef CONFIG_CGROUPS
1002         init_rwsem(&sig->threadgroup_fork_lock);
1003 #endif
1004
1005         sig->oom_adj = current->signal->oom_adj;
1006         sig->oom_score_adj = current->signal->oom_score_adj;
1007         sig->oom_score_adj_min = current->signal->oom_score_adj_min;
1008
1009         mutex_init(&sig->cred_guard_mutex);
1010
1011         return 0;
1012 }
1013
1014 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
1015 {
1016         unsigned long new_flags = p->flags;
1017
1018         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
1019         new_flags |= PF_FORKNOEXEC;
1020         new_flags |= PF_STARTING;
1021         p->flags = new_flags;
1022         clear_freeze_flag(p);
1023 }
1024
1025 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr)
1026 {
1027         current->clear_child_tid = tidptr;
1028
1029         return task_pid_vnr(current);
1030 }
1031
1032 static void rt_mutex_init_task(struct task_struct *p)
1033 {
1034         raw_spin_lock_init(&p->pi_lock);
1035 #ifdef CONFIG_RT_MUTEXES
1036         plist_head_init(&p->pi_waiters);
1037         p->pi_blocked_on = NULL;
1038 #endif
1039 }
1040
1041 #ifdef CONFIG_MM_OWNER
1042 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
1043 {
1044         mm->owner = p;
1045 }
1046 #endif /* CONFIG_MM_OWNER */
1047
1048 /*
1049  * Initialize POSIX timer handling for a single task.
1050  */
1051 static void posix_cpu_timers_init(struct task_struct *tsk)
1052 {
1053         tsk->cputime_expires.prof_exp = cputime_zero;
1054         tsk->cputime_expires.virt_exp = cputime_zero;
1055         tsk->cputime_expires.sched_exp = 0;
1056         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
1057         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
1058         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
1059 }
1060
1061 /*
1062  * This creates a new process as a copy of the old one,
1063  * but does not actually start it yet.
1064  *
1065  * It copies the registers, and all the appropriate
1066  * parts of the process environment (as per the clone
1067  * flags). The actual kick-off is left to the caller.
1068  */
1069 static struct task_struct *copy_process(unsigned long clone_flags,
1070                                         unsigned long stack_start,
1071                                         struct pt_regs *regs,
1072                                         unsigned long stack_size,
1073                                         int __user *child_tidptr,
1074                                         struct pid *pid,
1075                                         int trace)
1076 {
1077         int retval;
1078         struct task_struct *p;
1079         int cgroup_callbacks_done = 0;
1080
1081         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
1082                 return ERR_PTR(-EINVAL);
1083
1084         /*
1085          * Thread groups must share signals as well, and detached threads
1086          * can only be started up within the thread group.
1087          */
1088         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
1089                 return ERR_PTR(-EINVAL);
1090
1091         /*
1092          * Shared signal handlers imply shared VM. By way of the above,
1093          * thread groups also imply shared VM. Blocking this case allows
1094          * for various simplifications in other code.
1095          */
1096         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
1097                 return ERR_PTR(-EINVAL);
1098
1099         /*
1100          * Siblings of global init remain as zombies on exit since they are
1101          * not reaped by their parent (swapper). To solve this and to avoid
1102          * multi-rooted process trees, prevent global and container-inits
1103          * from creating siblings.
1104          */
1105         if ((clone_flags & CLONE_PARENT) &&
1106                                 current->signal->flags & SIGNAL_UNKILLABLE)
1107                 return ERR_PTR(-EINVAL);
1108
1109         retval = security_task_create(clone_flags);
1110         if (retval)
1111                 goto fork_out;
1112
1113         retval = -ENOMEM;
1114         p = dup_task_struct(current);
1115         if (!p)
1116                 goto fork_out;
1117
1118         ftrace_graph_init_task(p);
1119
1120         rt_mutex_init_task(p);
1121
1122 #ifdef CONFIG_PROVE_LOCKING
1123         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
1124         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
1125 #endif
1126         retval = -EAGAIN;
1127         if (atomic_read(&p->real_cred->user->processes) >=
1128                         task_rlimit(p, RLIMIT_NPROC)) {
1129                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
1130                     p->real_cred->user != INIT_USER)
1131                         goto bad_fork_free;
1132         }
1133
1134         retval = copy_creds(p, clone_flags);
1135         if (retval < 0)
1136                 goto bad_fork_free;
1137
1138         /*
1139          * If multiple threads are within copy_process(), then this check
1140          * triggers too late. This doesn't hurt, the check is only there
1141          * to stop root fork bombs.
1142          */
1143         retval = -EAGAIN;
1144         if (nr_threads >= max_threads)
1145                 goto bad_fork_cleanup_count;
1146
1147         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1148                 goto bad_fork_cleanup_count;
1149
1150         p->did_exec = 0;
1151         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1152         copy_flags(clone_flags, p);
1153         INIT_LIST_HEAD(&p->children);
1154         INIT_LIST_HEAD(&p->sibling);
1155         rcu_copy_process(p);
1156         p->vfork_done = NULL;
1157         spin_lock_init(&p->alloc_lock);
1158
1159         init_sigpending(&p->pending);
1160
1161         p->utime = cputime_zero;
1162         p->stime = cputime_zero;
1163         p->gtime = cputime_zero;
1164         p->utimescaled = cputime_zero;
1165         p->stimescaled = cputime_zero;
1166 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
1167         p->prev_utime = cputime_zero;
1168         p->prev_stime = cputime_zero;
1169 #endif
1170 #if defined(SPLIT_RSS_COUNTING)
1171         memset(&p->rss_stat, 0, sizeof(p->rss_stat));
1172 #endif
1173
1174         p->default_timer_slack_ns = current->timer_slack_ns;
1175
1176         task_io_accounting_init(&p->ioac);
1177         acct_clear_integrals(p);
1178
1179         posix_cpu_timers_init(p);
1180
1181         do_posix_clock_monotonic_gettime(&p->start_time);
1182         p->real_start_time = p->start_time;
1183         monotonic_to_bootbased(&p->real_start_time);
1184         p->io_context = NULL;
1185         p->audit_context = NULL;
1186         if (clone_flags & CLONE_THREAD)
1187                 threadgroup_fork_read_lock(current);
1188         cgroup_fork(p);
1189 #ifdef CONFIG_NUMA
1190         p->mempolicy = mpol_dup(p->mempolicy);
1191         if (IS_ERR(p->mempolicy)) {
1192                 retval = PTR_ERR(p->mempolicy);
1193                 p->mempolicy = NULL;
1194                 goto bad_fork_cleanup_cgroup;
1195         }
1196         mpol_fix_fork_child_flag(p);
1197 #endif
1198 #ifdef CONFIG_TRACE_IRQFLAGS
1199         p->irq_events = 0;
1200 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1201         p->hardirqs_enabled = 1;
1202 #else
1203         p->hardirqs_enabled = 0;
1204 #endif
1205         p->hardirq_enable_ip = 0;
1206         p->hardirq_enable_event = 0;
1207         p->hardirq_disable_ip = _THIS_IP_;
1208         p->hardirq_disable_event = 0;
1209         p->softirqs_enabled = 1;
1210         p->softirq_enable_ip = _THIS_IP_;
1211         p->softirq_enable_event = 0;
1212         p->softirq_disable_ip = 0;
1213         p->softirq_disable_event = 0;
1214         p->hardirq_context = 0;
1215         p->softirq_context = 0;
1216 #endif
1217 #ifdef CONFIG_LOCKDEP
1218         p->lockdep_depth = 0; /* no locks held yet */
1219         p->curr_chain_key = 0;
1220         p->lockdep_recursion = 0;
1221 #endif
1222
1223 #ifdef CONFIG_DEBUG_MUTEXES
1224         p->blocked_on = NULL; /* not blocked yet */
1225 #endif
1226 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
1227         p->memcg_batch.do_batch = 0;
1228         p->memcg_batch.memcg = NULL;
1229 #endif
1230
1231         /* Perform scheduler related setup. Assign this task to a CPU. */
1232         sched_fork(p);
1233
1234         retval = perf_event_init_task(p);
1235         if (retval)
1236                 goto bad_fork_cleanup_policy;
1237
1238         if ((retval = audit_alloc(p)))
1239                 goto bad_fork_cleanup_policy;
1240         /* copy all the process information */
1241         if ((retval = copy_semundo(clone_flags, p)))
1242                 goto bad_fork_cleanup_audit;
1243         if ((retval = copy_files(clone_flags, p)))
1244                 goto bad_fork_cleanup_semundo;
1245         if ((retval = copy_fs(clone_flags, p)))
1246                 goto bad_fork_cleanup_files;
1247         if ((retval = copy_sighand(clone_flags, p)))
1248                 goto bad_fork_cleanup_fs;
1249         if ((retval = copy_signal(clone_flags, p)))
1250                 goto bad_fork_cleanup_sighand;
1251         if ((retval = copy_mm(clone_flags, p)))
1252                 goto bad_fork_cleanup_signal;
1253         if ((retval = copy_namespaces(clone_flags, p)))
1254                 goto bad_fork_cleanup_mm;
1255         if ((retval = copy_io(clone_flags, p)))
1256                 goto bad_fork_cleanup_namespaces;
1257         retval = copy_thread(clone_flags, stack_start, stack_size, p, regs);
1258         if (retval)
1259                 goto bad_fork_cleanup_io;
1260
1261         if (pid != &init_struct_pid) {
1262                 retval = -ENOMEM;
1263                 pid = alloc_pid(p->nsproxy->pid_ns);
1264                 if (!pid)
1265                         goto bad_fork_cleanup_io;
1266         }
1267
1268         p->pid = pid_nr(pid);
1269         p->tgid = p->pid;
1270         if (clone_flags & CLONE_THREAD)
1271                 p->tgid = current->tgid;
1272
1273         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1274         /*
1275          * Clear TID on mm_release()?
1276          */
1277         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1278 #ifdef CONFIG_BLOCK
1279         p->plug = NULL;
1280 #endif
1281 #ifdef CONFIG_FUTEX
1282         p->robust_list = NULL;
1283 #ifdef CONFIG_COMPAT
1284         p->compat_robust_list = NULL;
1285 #endif
1286         INIT_LIST_HEAD(&p->pi_state_list);
1287         p->pi_state_cache = NULL;
1288 #endif
1289         /*
1290          * sigaltstack should be cleared when sharing the same VM
1291          */
1292         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1293                 p->sas_ss_sp = p->sas_ss_size = 0;
1294
1295         /*
1296          * Syscall tracing and stepping should be turned off in the
1297          * child regardless of CLONE_PTRACE.
1298          */
1299         user_disable_single_step(p);
1300         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1301 #ifdef TIF_SYSCALL_EMU
1302         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1303 #endif
1304         clear_all_latency_tracing(p);
1305
1306         /* ok, now we should be set up.. */
1307         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1308         p->pdeath_signal = 0;
1309         p->exit_state = 0;
1310
1311         /*
1312          * Ok, make it visible to the rest of the system.
1313          * We dont wake it up yet.
1314          */
1315         p->group_leader = p;
1316         INIT_LIST_HEAD(&p->thread_group);
1317
1318         /* Now that the task is set up, run cgroup callbacks if
1319          * necessary. We need to run them before the task is visible
1320          * on the tasklist. */
1321         cgroup_fork_callbacks(p);
1322         cgroup_callbacks_done = 1;
1323
1324         /* Need tasklist lock for parent etc handling! */
1325         write_lock_irq(&tasklist_lock);
1326
1327         /* CLONE_PARENT re-uses the old parent */
1328         if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
1329                 p->real_parent = current->real_parent;
1330                 p->parent_exec_id = current->parent_exec_id;
1331         } else {
1332                 p->real_parent = current;
1333                 p->parent_exec_id = current->self_exec_id;
1334         }
1335
1336         spin_lock(&current->sighand->siglock);
1337
1338         /*
1339          * Process group and session signals need to be delivered to just the
1340          * parent before the fork or both the parent and the child after the
1341          * fork. Restart if a signal comes in before we add the new process to
1342          * it's process group.
1343          * A fatal signal pending means that current will exit, so the new
1344          * thread can't slip out of an OOM kill (or normal SIGKILL).
1345          */
1346         recalc_sigpending();
1347         if (signal_pending(current)) {
1348                 spin_unlock(&current->sighand->siglock);
1349                 write_unlock_irq(&tasklist_lock);
1350                 retval = -ERESTARTNOINTR;
1351                 goto bad_fork_free_pid;
1352         }
1353
1354         if (clone_flags & CLONE_THREAD) {
1355                 current->signal->nr_threads++;
1356                 atomic_inc(&current->signal->live);
1357                 atomic_inc(&current->signal->sigcnt);
1358                 p->group_leader = current->group_leader;
1359                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1360         }
1361
1362         if (likely(p->pid)) {
1363                 tracehook_finish_clone(p, clone_flags, trace);
1364
1365                 if (thread_group_leader(p)) {
1366                         if (is_child_reaper(pid))
1367                                 p->nsproxy->pid_ns->child_reaper = p;
1368
1369                         p->signal->leader_pid = pid;
1370                         p->signal->tty = tty_kref_get(current->signal->tty);
1371                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1372                         attach_pid(p, PIDTYPE_SID, task_session(current));
1373                         list_add_tail(&p->sibling, &p->real_parent->children);
1374                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1375                         __this_cpu_inc(process_counts);
1376                 }
1377                 attach_pid(p, PIDTYPE_PID, pid);
1378                 nr_threads++;
1379         }
1380
1381         total_forks++;
1382         spin_unlock(&current->sighand->siglock);
1383         write_unlock_irq(&tasklist_lock);
1384         proc_fork_connector(p);
1385         cgroup_post_fork(p);
1386         if (clone_flags & CLONE_THREAD)
1387                 threadgroup_fork_read_unlock(current);
1388         perf_event_fork(p);
1389         return p;
1390
1391 bad_fork_free_pid:
1392         if (pid != &init_struct_pid)
1393                 free_pid(pid);
1394 bad_fork_cleanup_io:
1395         if (p->io_context)
1396                 exit_io_context(p);
1397 bad_fork_cleanup_namespaces:
1398         if (unlikely(clone_flags & CLONE_NEWPID))
1399                 pid_ns_release_proc(p->nsproxy->pid_ns);
1400         exit_task_namespaces(p);
1401 bad_fork_cleanup_mm:
1402         if (p->mm) {
1403                 task_lock(p);
1404                 if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
1405                         atomic_dec(&p->mm->oom_disable_count);
1406                 task_unlock(p);
1407                 mmput(p->mm);
1408         }
1409 bad_fork_cleanup_signal:
1410         if (!(clone_flags & CLONE_THREAD))
1411                 free_signal_struct(p->signal);
1412 bad_fork_cleanup_sighand:
1413         __cleanup_sighand(p->sighand);
1414 bad_fork_cleanup_fs:
1415         exit_fs(p); /* blocking */
1416 bad_fork_cleanup_files:
1417         exit_files(p); /* blocking */
1418 bad_fork_cleanup_semundo:
1419         exit_sem(p);
1420 bad_fork_cleanup_audit:
1421         audit_free(p);
1422 bad_fork_cleanup_policy:
1423         perf_event_free_task(p);
1424 #ifdef CONFIG_NUMA
1425         mpol_put(p->mempolicy);
1426 bad_fork_cleanup_cgroup:
1427 #endif
1428         if (clone_flags & CLONE_THREAD)
1429                 threadgroup_fork_read_unlock(current);
1430         cgroup_exit(p, cgroup_callbacks_done);
1431         delayacct_tsk_free(p);
1432         module_put(task_thread_info(p)->exec_domain->module);
1433 bad_fork_cleanup_count:
1434         atomic_dec(&p->cred->user->processes);
1435         exit_creds(p);
1436 bad_fork_free:
1437         free_task(p);
1438 fork_out:
1439         return ERR_PTR(retval);
1440 }
1441
1442 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1443 {
1444         memset(regs, 0, sizeof(struct pt_regs));
1445         return regs;
1446 }
1447
1448 static inline void init_idle_pids(struct pid_link *links)
1449 {
1450         enum pid_type type;
1451
1452         for (type = PIDTYPE_PID; type < PIDTYPE_MAX; ++type) {
1453                 INIT_HLIST_NODE(&links[type].node); /* not really needed */
1454                 links[type].pid = &init_struct_pid;
1455         }
1456 }
1457
1458 struct task_struct * __cpuinit fork_idle(int cpu)
1459 {
1460         struct task_struct *task;
1461         struct pt_regs regs;
1462
1463         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1464                             &init_struct_pid, 0);
1465         if (!IS_ERR(task)) {
1466                 init_idle_pids(task->pids);
1467                 init_idle(task, cpu);
1468         }
1469
1470         return task;
1471 }
1472
1473 /*
1474  *  Ok, this is the main fork-routine.
1475  *
1476  * It copies the process, and if successful kick-starts
1477  * it and waits for it to finish using the VM if required.
1478  */
1479 long do_fork(unsigned long clone_flags,
1480               unsigned long stack_start,
1481               struct pt_regs *regs,
1482               unsigned long stack_size,
1483               int __user *parent_tidptr,
1484               int __user *child_tidptr)
1485 {
1486         struct task_struct *p;
1487         int trace = 0;
1488         long nr;
1489
1490         /*
1491          * Do some preliminary argument and permissions checking before we
1492          * actually start allocating stuff
1493          */
1494         if (clone_flags & CLONE_NEWUSER) {
1495                 if (clone_flags & CLONE_THREAD)
1496                         return -EINVAL;
1497                 /* hopefully this check will go away when userns support is
1498                  * complete
1499                  */
1500                 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) ||
1501                                 !capable(CAP_SETGID))
1502                         return -EPERM;
1503         }
1504
1505         /*
1506          * When called from kernel_thread, don't do user tracing stuff.
1507          */
1508         if (likely(user_mode(regs)))
1509                 trace = tracehook_prepare_clone(clone_flags);
1510
1511         p = copy_process(clone_flags, stack_start, regs, stack_size,
1512                          child_tidptr, NULL, trace);
1513         /*
1514          * Do this prior waking up the new thread - the thread pointer
1515          * might get invalid after that point, if the thread exits quickly.
1516          */
1517         if (!IS_ERR(p)) {
1518                 struct completion vfork;
1519
1520                 trace_sched_process_fork(current, p);
1521
1522                 nr = task_pid_vnr(p);
1523
1524                 if (clone_flags & CLONE_PARENT_SETTID)
1525                         put_user(nr, parent_tidptr);
1526
1527                 if (clone_flags & CLONE_VFORK) {
1528                         p->vfork_done = &vfork;
1529                         init_completion(&vfork);
1530                 }
1531
1532                 audit_finish_fork(p);
1533                 tracehook_report_clone(regs, clone_flags, nr, p);
1534
1535                 /*
1536                  * We set PF_STARTING at creation in case tracing wants to
1537                  * use this to distinguish a fully live task from one that
1538                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1539                  * clear it and set the child going.
1540                  */
1541                 p->flags &= ~PF_STARTING;
1542
1543                 wake_up_new_task(p);
1544
1545                 tracehook_report_clone_complete(trace, regs,
1546                                                 clone_flags, nr, p);
1547
1548                 if (clone_flags & CLONE_VFORK) {
1549                         freezer_do_not_count();
1550                         wait_for_completion(&vfork);
1551                         freezer_count();
1552                         tracehook_report_vfork_done(p, nr);
1553                 }
1554         } else {
1555                 nr = PTR_ERR(p);
1556         }
1557         return nr;
1558 }
1559
1560 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1561 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1562 #endif
1563
1564 static void sighand_ctor(void *data)
1565 {
1566         struct sighand_struct *sighand = data;
1567
1568         spin_lock_init(&sighand->siglock);
1569         init_waitqueue_head(&sighand->signalfd_wqh);
1570 }
1571
1572 void __init proc_caches_init(void)
1573 {
1574         sighand_cachep = kmem_cache_create("sighand_cache",
1575                         sizeof(struct sighand_struct), 0,
1576                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU|
1577                         SLAB_NOTRACK, sighand_ctor);
1578         signal_cachep = kmem_cache_create("signal_cache",
1579                         sizeof(struct signal_struct), 0,
1580                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1581         files_cachep = kmem_cache_create("files_cache",
1582                         sizeof(struct files_struct), 0,
1583                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1584         fs_cachep = kmem_cache_create("fs_cache",
1585                         sizeof(struct fs_struct), 0,
1586                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1587         /*
1588          * FIXME! The "sizeof(struct mm_struct)" currently includes the
1589          * whole struct cpumask for the OFFSTACK case. We could change
1590          * this to *only* allocate as much of it as required by the
1591          * maximum number of CPU's we can ever have.  The cpumask_allocation
1592          * is at the end of the structure, exactly for that reason.
1593          */
1594         mm_cachep = kmem_cache_create("mm_struct",
1595                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1596                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
1597         vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
1598         mmap_init();
1599 }
1600
1601 /*
1602  * Check constraints on flags passed to the unshare system call.
1603  */
1604 static int check_unshare_flags(unsigned long unshare_flags)
1605 {
1606         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1607                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1608                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET))
1609                 return -EINVAL;
1610         /*
1611          * Not implemented, but pretend it works if there is nothing to
1612          * unshare. Note that unsharing CLONE_THREAD or CLONE_SIGHAND
1613          * needs to unshare vm.
1614          */
1615         if (unshare_flags & (CLONE_THREAD | CLONE_SIGHAND | CLONE_VM)) {
1616                 /* FIXME: get_task_mm() increments ->mm_users */
1617                 if (atomic_read(&current->mm->mm_users) > 1)
1618                         return -EINVAL;
1619         }
1620
1621         return 0;
1622 }
1623
1624 /*
1625  * Unshare the filesystem structure if it is being shared
1626  */
1627 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1628 {
1629         struct fs_struct *fs = current->fs;
1630
1631         if (!(unshare_flags & CLONE_FS) || !fs)
1632                 return 0;
1633
1634         /* don't need lock here; in the worst case we'll do useless copy */
1635         if (fs->users == 1)
1636                 return 0;
1637
1638         *new_fsp = copy_fs_struct(fs);
1639         if (!*new_fsp)
1640                 return -ENOMEM;
1641
1642         return 0;
1643 }
1644
1645 /*
1646  * Unshare file descriptor table if it is being shared
1647  */
1648 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1649 {
1650         struct files_struct *fd = current->files;
1651         int error = 0;
1652
1653         if ((unshare_flags & CLONE_FILES) &&
1654             (fd && atomic_read(&fd->count) > 1)) {
1655                 *new_fdp = dup_fd(fd, &error);
1656                 if (!*new_fdp)
1657                         return error;
1658         }
1659
1660         return 0;
1661 }
1662
1663 /*
1664  * unshare allows a process to 'unshare' part of the process
1665  * context which was originally shared using clone.  copy_*
1666  * functions used by do_fork() cannot be used here directly
1667  * because they modify an inactive task_struct that is being
1668  * constructed. Here we are modifying the current, active,
1669  * task_struct.
1670  */
1671 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags)
1672 {
1673         struct fs_struct *fs, *new_fs = NULL;
1674         struct files_struct *fd, *new_fd = NULL;
1675         struct nsproxy *new_nsproxy = NULL;
1676         int do_sysvsem = 0;
1677         int err;
1678
1679         err = check_unshare_flags(unshare_flags);
1680         if (err)
1681                 goto bad_unshare_out;
1682
1683         /*
1684          * If unsharing namespace, must also unshare filesystem information.
1685          */
1686         if (unshare_flags & CLONE_NEWNS)
1687                 unshare_flags |= CLONE_FS;
1688         /*
1689          * CLONE_NEWIPC must also detach from the undolist: after switching
1690          * to a new ipc namespace, the semaphore arrays from the old
1691          * namespace are unreachable.
1692          */
1693         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1694                 do_sysvsem = 1;
1695         if ((err = unshare_fs(unshare_flags, &new_fs)))
1696                 goto bad_unshare_out;
1697         if ((err = unshare_fd(unshare_flags, &new_fd)))
1698                 goto bad_unshare_cleanup_fs;
1699         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1700                         new_fs)))
1701                 goto bad_unshare_cleanup_fd;
1702
1703         if (new_fs || new_fd || do_sysvsem || new_nsproxy) {
1704                 if (do_sysvsem) {
1705                         /*
1706                          * CLONE_SYSVSEM is equivalent to sys_exit().
1707                          */
1708                         exit_sem(current);
1709                 }
1710
1711                 if (new_nsproxy) {
1712                         switch_task_namespaces(current, new_nsproxy);
1713                         new_nsproxy = NULL;
1714                 }
1715
1716                 task_lock(current);
1717
1718                 if (new_fs) {
1719                         fs = current->fs;
1720                         spin_lock(&fs->lock);
1721                         current->fs = new_fs;
1722                         if (--fs->users)
1723                                 new_fs = NULL;
1724                         else
1725                                 new_fs = fs;
1726                         spin_unlock(&fs->lock);
1727                 }
1728
1729                 if (new_fd) {
1730                         fd = current->files;
1731                         current->files = new_fd;
1732                         new_fd = fd;
1733                 }
1734
1735                 task_unlock(current);
1736         }
1737
1738         if (new_nsproxy)
1739                 put_nsproxy(new_nsproxy);
1740
1741 bad_unshare_cleanup_fd:
1742         if (new_fd)
1743                 put_files_struct(new_fd);
1744
1745 bad_unshare_cleanup_fs:
1746         if (new_fs)
1747                 free_fs_struct(new_fs);
1748
1749 bad_unshare_out:
1750         return err;
1751 }
1752
1753 /*
1754  *      Helper to unshare the files of the current task.
1755  *      We don't want to expose copy_files internals to
1756  *      the exec layer of the kernel.
1757  */
1758
1759 int unshare_files(struct files_struct **displaced)
1760 {
1761         struct task_struct *task = current;
1762         struct files_struct *copy = NULL;
1763         int error;
1764
1765         error = unshare_fd(CLONE_FILES, &copy);
1766         if (error || !copy) {
1767                 *displaced = NULL;
1768                 return error;
1769         }
1770         *displaced = task->files;
1771         task_lock(task);
1772         task->files = copy;
1773         task_unlock(task);
1774         return 0;
1775 }