kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/module.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/completion.h>
  20 #include <linux/mnt_namespace.h>
  21 #include <linux/personality.h>
  22 #include <linux/mempolicy.h>
  23 #include <linux/sem.h>
  24 #include <linux/file.h>
  25 #include <linux/fdtable.h>
  26 #include <linux/iocontext.h>
  27 #include <linux/key.h>
  28 #include <linux/binfmts.h>
  29 #include <linux/mman.h>
  30 #include <linux/mmu_notifier.h>
  31 #include <linux/fs.h>
  32 #include <linux/nsproxy.h>
  33 #include <linux/capability.h>
  34 #include <linux/cpu.h>
  35 #include <linux/cgroup.h>
  36 #include <linux/security.h>
  37 #include <linux/hugetlb.h>
  38 #include <linux/swap.h>
  39 #include <linux/syscalls.h>
  40 #include <linux/jiffies.h>
  41 #include <linux/tracehook.h>
  42 #include <linux/futex.h>
  43 #include <linux/compat.h>
  44 #include <linux/task_io_accounting_ops.h>
  45 #include <linux/rcupdate.h>
  46 #include <linux/ptrace.h>
  47 #include <linux/mount.h>
  48 #include <linux/audit.h>
  49 #include <linux/memcontrol.h>
  50 #include <linux/profile.h>
  51 #include <linux/rmap.h>
  52 #include <linux/acct.h>
  53 #include <linux/tsacct_kern.h>
  54 #include <linux/cn_proc.h>
  55 #include <linux/freezer.h>
  56 #include <linux/delayacct.h>
  57 #include <linux/taskstats_kern.h>
  58 #include <linux/random.h>
  59 #include <linux/tty.h>
  60 #include <linux/proc_fs.h>
  61 #include <linux/blkdev.h>
  62 #include <trace/sched.h>
  63
  64 #include <asm/pgtable.h>
  65 #include <asm/pgalloc.h>
  66 #include <asm/uaccess.h>
  67 #include <asm/mmu_context.h>
  68 #include <asm/cacheflush.h>
  69 #include <asm/tlbflush.h>
  70
  71 /*
  72  * Protected counters by write_lock_irq(&tasklist_lock)
  73  */
  74 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  75 int nr_threads;                 /* The idle threads do not count.. */
  76
  77 int max_threads;                /* tunable limit on nr_threads */
  78
  79 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  80
  81 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  82
  83 int nr_processes(void)
  84 {
  85         int cpu;
  86         int total = 0;
  87
  88         for_each_online_cpu(cpu)
  89                 total += per_cpu(process_counts, cpu);
  90
  91         return total;
  92 }
  93
  94 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  95 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  96 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  97 static struct kmem_cache *task_struct_cachep;
  98 #endif
  99
 100 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 101 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 102 {
 103 #ifdef CONFIG_DEBUG_STACK_USAGE
 104         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 105 #else
 106         gfp_t mask = GFP_KERNEL;
 107 #endif
 108         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 109 }
 110
 111 static inline void free_thread_info(struct thread_info *ti)
 112 {
 113         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 114 }
 115 #endif
 116
 117 /* SLAB cache for signal_struct structures (tsk->signal) */
 118 static struct kmem_cache *signal_cachep;
 119
 120 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 121 struct kmem_cache *sighand_cachep;
 122
 123 /* SLAB cache for files_struct structures (tsk->files) */
 124 struct kmem_cache *files_cachep;
 125
 126 /* SLAB cache for fs_struct structures (tsk->fs) */
 127 struct kmem_cache *fs_cachep;
 128
 129 /* SLAB cache for vm_area_struct structures */
 130 struct kmem_cache *vm_area_cachep;
 131
 132 /* SLAB cache for mm_struct structures (tsk->mm) */
 133 static struct kmem_cache *mm_cachep;
 134
 135 void free_task(struct task_struct *tsk)
 136 {
 137         prop_local_destroy_single(&tsk->dirties);
 138         free_thread_info(tsk->stack);
 139         rt_mutex_debug_task_free(tsk);
 140         free_task_struct(tsk);
 141 }
 142 EXPORT_SYMBOL(free_task);
 143
 144 void __put_task_struct(struct task_struct *tsk)
 145 {
 146         WARN_ON(!tsk->exit_state);
 147         WARN_ON(atomic_read(&tsk->usage));
 148         WARN_ON(tsk == current);
 149
 150         security_task_free(tsk);
 151         free_uid(tsk->user);
 152         put_group_info(tsk->group_info);
 153         delayacct_tsk_free(tsk);
 154
 155         if (!profile_handoff_task(tsk))
 156                 free_task(tsk);
 157 }
 158
 159 /*
 160  * macro override instead of weak attribute alias, to workaround
 161  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 162  */
 163 #ifndef arch_task_cache_init
 164 #define arch_task_cache_init()
 165 #endif
 166
 167 void __init fork_init(unsigned long mempages)
 168 {
 169 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 170 #ifndef ARCH_MIN_TASKALIGN
 171 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 172 #endif
 173         /* create a slab on which task_structs can be allocated */
 174         task_struct_cachep =
 175                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 176                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
 177 #endif
 178
 179         /* do the arch specific task caches init */
 180         arch_task_cache_init();
 181
 182         /*
 183          * The default maximum number of threads is set to a safe
 184          * value: the thread structures can take up at most half
 185          * of memory.
 186          */
 187         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 188
 189         /*
 190          * we need to allow at least 20 threads to boot a system
 191          */
 192         if(max_threads < 20)
 193                 max_threads = 20;
 194
 195         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 196         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 197         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 198                 init_task.signal->rlim[RLIMIT_NPROC];
 199 }
 200
 201 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 202                                                struct task_struct *src)
 203 {
 204         *dst = *src;
 205         return 0;
 206 }
 207
 208 static struct task_struct *dup_task_struct(struct task_struct *orig)
 209 {
 210         struct task_struct *tsk;
 211         struct thread_info *ti;
 212         int err;
 213
 214         prepare_to_copy(orig);
 215
 216         tsk = alloc_task_struct();
 217         if (!tsk)
 218                 return NULL;
 219
 220         ti = alloc_thread_info(tsk);
 221         if (!ti) {
 222                 free_task_struct(tsk);
 223                 return NULL;
 224         }
 225
 226         err = arch_dup_task_struct(tsk, orig);
 227         if (err)
 228                 goto out;
 229
 230         tsk->stack = ti;
 231
 232         err = prop_local_init_single(&tsk->dirties);
 233         if (err)
 234                 goto out;
 235
 236         setup_thread_stack(tsk, orig);
 237
 238 #ifdef CONFIG_CC_STACKPROTECTOR
 239         tsk->stack_canary = get_random_int();
 240 #endif
 241
 242         /* One for us, one for whoever does the "release_task()" (usually parent) */
 243         atomic_set(&tsk->usage,2);
 244         atomic_set(&tsk->fs_excl, 0);
 245 #ifdef CONFIG_BLK_DEV_IO_TRACE
 246         tsk->btrace_seq = 0;
 247 #endif
 248         tsk->splice_pipe = NULL;
 249         return tsk;
 250
 251 out:
 252         free_thread_info(ti);
 253         free_task_struct(tsk);
 254         return NULL;
 255 }
 256
 257 #ifdef CONFIG_MMU
 258 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 259 {
 260         struct vm_area_struct *mpnt, *tmp, **pprev;
 261         struct rb_node **rb_link, *rb_parent;
 262         int retval;
 263         unsigned long charge;
 264         struct mempolicy *pol;
 265
 266         down_write(&oldmm->mmap_sem);
 267         flush_cache_dup_mm(oldmm);
 268         /*
 269          * Not linked in yet - no deadlock potential:
 270          */
 271         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 272
 273         mm->locked_vm = 0;
 274         mm->mmap = NULL;
 275         mm->mmap_cache = NULL;
 276         mm->free_area_cache = oldmm->mmap_base;
 277         mm->cached_hole_size = ~0UL;
 278         mm->map_count = 0;
 279         cpus_clear(mm->cpu_vm_mask);
 280         mm->mm_rb = RB_ROOT;
 281         rb_link = &mm->mm_rb.rb_node;
 282         rb_parent = NULL;
 283         pprev = &mm->mmap;
 284
 285         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 286                 struct file *file;
 287
 288                 if (mpnt->vm_flags & VM_DONTCOPY) {
 289                         long pages = vma_pages(mpnt);
 290                         mm->total_vm -= pages;
 291                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 292                                                                 -pages);
 293                         continue;
 294                 }
 295                 charge = 0;
 296                 if (mpnt->vm_flags & VM_ACCOUNT) {
 297                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 298                         if (security_vm_enough_memory(len))
 299                                 goto fail_nomem;
 300                         charge = len;
 301                 }
 302                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 303                 if (!tmp)
 304                         goto fail_nomem;
 305                 *tmp = *mpnt;
 306                 pol = mpol_dup(vma_policy(mpnt));
 307                 retval = PTR_ERR(pol);
 308                 if (IS_ERR(pol))
 309                         goto fail_nomem_policy;
 310                 vma_set_policy(tmp, pol);
 311                 tmp->vm_flags &= ~VM_LOCKED;
 312                 tmp->vm_mm = mm;
 313                 tmp->vm_next = NULL;
 314                 anon_vma_link(tmp);
 315                 file = tmp->vm_file;
 316                 if (file) {
 317                         struct inode *inode = file->f_path.dentry->d_inode;
 318                         struct address_space *mapping = file->f_mapping;
 319
 320                         get_file(file);
 321                         if (tmp->vm_flags & VM_DENYWRITE)
 322                                 atomic_dec(&inode->i_writecount);
 323                         spin_lock(&mapping->i_mmap_lock);
 324                         if (tmp->vm_flags & VM_SHARED)
 325                                 mapping->i_mmap_writable++;
 326                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 327                         flush_dcache_mmap_lock(mapping);
 328                         /* insert tmp into the share list, just after mpnt */
 329                         vma_prio_tree_add(tmp, mpnt);
 330                         flush_dcache_mmap_unlock(mapping);
 331                         spin_unlock(&mapping->i_mmap_lock);
 332                 }
 333
 334                 /*
 335                  * Clear hugetlb-related page reserves for children. This only
 336                  * affects MAP_PRIVATE mappings. Faults generated by the child
 337                  * are not guaranteed to succeed, even if read-only
 338                  */
 339                 if (is_vm_hugetlb_page(tmp))
 340                         reset_vma_resv_huge_pages(tmp);
 341
 342                 /*
 343                  * Link in the new vma and copy the page table entries.
 344                  */
 345                 *pprev = tmp;
 346                 pprev = &tmp->vm_next;
 347
 348                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 349                 rb_link = &tmp->vm_rb.rb_right;
 350                 rb_parent = &tmp->vm_rb;
 351
 352                 mm->map_count++;
 353                 retval = copy_page_range(mm, oldmm, mpnt);
 354
 355                 if (tmp->vm_ops && tmp->vm_ops->open)
 356                         tmp->vm_ops->open(tmp);
 357
 358                 if (retval)
 359                         goto out;
 360         }
 361         /* a new mm has just been created */
 362         arch_dup_mmap(oldmm, mm);
 363         retval = 0;
 364 out:
 365         up_write(&mm->mmap_sem);
 366         flush_tlb_mm(oldmm);
 367         up_write(&oldmm->mmap_sem);
 368         return retval;
 369 fail_nomem_policy:
 370         kmem_cache_free(vm_area_cachep, tmp);
 371 fail_nomem:
 372         retval = -ENOMEM;
 373         vm_unacct_memory(charge);
 374         goto out;
 375 }
 376
 377 static inline int mm_alloc_pgd(struct mm_struct * mm)
 378 {
 379         mm->pgd = pgd_alloc(mm);
 380         if (unlikely(!mm->pgd))
 381                 return -ENOMEM;
 382         return 0;
 383 }
 384
 385 static inline void mm_free_pgd(struct mm_struct * mm)
 386 {
 387         pgd_free(mm, mm->pgd);
 388 }
 389 #else
 390 #define dup_mmap(mm, oldmm)     (0)
 391 #define mm_alloc_pgd(mm)        (0)
 392 #define mm_free_pgd(mm)
 393 #endif /* CONFIG_MMU */
 394
 395 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 396
 397 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 398 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 399
 400 #include <linux/init_task.h>
 401
 402 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 403 {
 404         atomic_set(&mm->mm_users, 1);
 405         atomic_set(&mm->mm_count, 1);
 406         init_rwsem(&mm->mmap_sem);
 407         INIT_LIST_HEAD(&mm->mmlist);
 408         mm->flags = (current->mm) ? current->mm->flags
 409                                   : MMF_DUMP_FILTER_DEFAULT;
 410         mm->core_state = NULL;
 411         mm->nr_ptes = 0;
 412         set_mm_counter(mm, file_rss, 0);
 413         set_mm_counter(mm, anon_rss, 0);
 414         spin_lock_init(&mm->page_table_lock);
 415         rwlock_init(&mm->ioctx_list_lock);
 416         mm->ioctx_list = NULL;
 417         mm->free_area_cache = TASK_UNMAPPED_BASE;
 418         mm->cached_hole_size = ~0UL;
 419         mm_init_owner(mm, p);
 420
 421         if (likely(!mm_alloc_pgd(mm))) {
 422                 mm->def_flags = 0;
 423                 mmu_notifier_mm_init(mm);
 424                 return mm;
 425         }
 426
 427         free_mm(mm);
 428         return NULL;
 429 }
 430
 431 /*
 432  * Allocate and initialize an mm_struct.
 433  */
 434 struct mm_struct * mm_alloc(void)
 435 {
 436         struct mm_struct * mm;
 437
 438         mm = allocate_mm();
 439         if (mm) {
 440                 memset(mm, 0, sizeof(*mm));
 441                 mm = mm_init(mm, current);
 442         }
 443         return mm;
 444 }
 445
 446 /*
 447  * Called when the last reference to the mm
 448  * is dropped: either by a lazy thread or by
 449  * mmput. Free the page directory and the mm.
 450  */
 451 void __mmdrop(struct mm_struct *mm)
 452 {
 453         BUG_ON(mm == &init_mm);
 454         mm_free_pgd(mm);
 455         destroy_context(mm);
 456         mmu_notifier_mm_destroy(mm);
 457         free_mm(mm);
 458 }
 459 EXPORT_SYMBOL_GPL(__mmdrop);
 460
 461 /*
 462  * Decrement the use count and release all resources for an mm.
 463  */
 464 void mmput(struct mm_struct *mm)
 465 {
 466         might_sleep();
 467
 468         if (atomic_dec_and_test(&mm->mm_users)) {
 469                 exit_aio(mm);
 470                 exit_mmap(mm);
 471                 set_mm_exe_file(mm, NULL);
 472                 if (!list_empty(&mm->mmlist)) {
 473                         spin_lock(&mmlist_lock);
 474                         list_del(&mm->mmlist);
 475                         spin_unlock(&mmlist_lock);
 476                 }
 477                 put_swap_token(mm);
 478                 mmdrop(mm);
 479         }
 480 }
 481 EXPORT_SYMBOL_GPL(mmput);
 482
 483 /**
 484  * get_task_mm - acquire a reference to the task's mm
 485  *
 486  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 487  * this kernel workthread has transiently adopted a user mm with use_mm,
 488  * to do its AIO) is not set and if so returns a reference to it, after
 489  * bumping up the use count.  User must release the mm via mmput()
 490  * after use.  Typically used by /proc and ptrace.
 491  */
 492 struct mm_struct *get_task_mm(struct task_struct *task)
 493 {
 494         struct mm_struct *mm;
 495
 496         task_lock(task);
 497         mm = task->mm;
 498         if (mm) {
 499                 if (task->flags & PF_KTHREAD)
 500                         mm = NULL;
 501                 else
 502                         atomic_inc(&mm->mm_users);
 503         }
 504         task_unlock(task);
 505         return mm;
 506 }
 507 EXPORT_SYMBOL_GPL(get_task_mm);
 508
 509 /* Please note the differences between mmput and mm_release.
 510  * mmput is called whenever we stop holding onto a mm_struct,
 511  * error success whatever.
 512  *
 513  * mm_release is called after a mm_struct has been removed
 514  * from the current process.
 515  *
 516  * This difference is important for error handling, when we
 517  * only half set up a mm_struct for a new process and need to restore
 518  * the old one.  Because we mmput the new mm_struct before
 519  * restoring the old one. . .
 520  * Eric Biederman 10 January 1998
 521  */
 522 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 523 {
 524         struct completion *vfork_done = tsk->vfork_done;
 525
 526         /* Get rid of any futexes when releasing the mm */
 527 #ifdef CONFIG_FUTEX
 528         if (unlikely(tsk->robust_list))
 529                 exit_robust_list(tsk);
 530 #ifdef CONFIG_COMPAT
 531         if (unlikely(tsk->compat_robust_list))
 532                 compat_exit_robust_list(tsk);
 533 #endif
 534 #endif
 535
 536         /* Get rid of any cached register state */
 537         deactivate_mm(tsk, mm);
 538
 539         /* notify parent sleeping on vfork() */
 540         if (vfork_done) {
 541                 tsk->vfork_done = NULL;
 542                 complete(vfork_done);
 543         }
 544
 545         /*
 546          * If we're exiting normally, clear a user-space tid field if
 547          * requested.  We leave this alone when dying by signal, to leave
 548          * the value intact in a core dump, and to save the unnecessary
 549          * trouble otherwise.  Userland only wants this done for a sys_exit.
 550          */
 551         if (tsk->clear_child_tid
 552             && !(tsk->flags & PF_SIGNALED)
 553             && atomic_read(&mm->mm_users) > 1) {
 554                 u32 __user * tidptr = tsk->clear_child_tid;
 555                 tsk->clear_child_tid = NULL;
 556
 557                 /*
 558                  * We don't check the error code - if userspace has
 559                  * not set up a proper pointer then tough luck.
 560                  */
 561                 put_user(0, tidptr);
 562                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 563         }
 564 }
 565
 566 /*
 567  * Allocate a new mm structure and copy contents from the
 568  * mm structure of the passed in task structure.
 569  */
 570 struct mm_struct *dup_mm(struct task_struct *tsk)
 571 {
 572         struct mm_struct *mm, *oldmm = current->mm;
 573         int err;
 574
 575         if (!oldmm)
 576                 return NULL;
 577
 578         mm = allocate_mm();
 579         if (!mm)
 580                 goto fail_nomem;
 581
 582         memcpy(mm, oldmm, sizeof(*mm));
 583
 584         /* Initializing for Swap token stuff */
 585         mm->token_priority = 0;
 586         mm->last_interval = 0;
 587
 588         if (!mm_init(mm, tsk))
 589                 goto fail_nomem;
 590
 591         if (init_new_context(tsk, mm))
 592                 goto fail_nocontext;
 593
 594         dup_mm_exe_file(oldmm, mm);
 595
 596         err = dup_mmap(mm, oldmm);
 597         if (err)
 598                 goto free_pt;
 599
 600         mm->hiwater_rss = get_mm_rss(mm);
 601         mm->hiwater_vm = mm->total_vm;
 602
 603         return mm;
 604
 605 free_pt:
 606         mmput(mm);
 607
 608 fail_nomem:
 609         return NULL;
 610
 611 fail_nocontext:
 612         /*
 613          * If init_new_context() failed, we cannot use mmput() to free the mm
 614          * because it calls destroy_context()
 615          */
 616         mm_free_pgd(mm);
 617         free_mm(mm);
 618         return NULL;
 619 }
 620
 621 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 622 {
 623         struct mm_struct * mm, *oldmm;
 624         int retval;
 625
 626         tsk->min_flt = tsk->maj_flt = 0;
 627         tsk->nvcsw = tsk->nivcsw = 0;
 628
 629         tsk->mm = NULL;
 630         tsk->active_mm = NULL;
 631
 632         /*
 633          * Are we cloning a kernel thread?
 634          *
 635          * We need to steal a active VM for that..
 636          */
 637         oldmm = current->mm;
 638         if (!oldmm)
 639                 return 0;
 640
 641         if (clone_flags & CLONE_VM) {
 642                 atomic_inc(&oldmm->mm_users);
 643                 mm = oldmm;
 644                 goto good_mm;
 645         }
 646
 647         retval = -ENOMEM;
 648         mm = dup_mm(tsk);
 649         if (!mm)
 650                 goto fail_nomem;
 651
 652 good_mm:
 653         /* Initializing for Swap token stuff */
 654         mm->token_priority = 0;
 655         mm->last_interval = 0;
 656
 657         tsk->mm = mm;
 658         tsk->active_mm = mm;
 659         return 0;
 660
 661 fail_nomem:
 662         return retval;
 663 }
 664
 665 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 666 {
 667         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 668         /* We don't need to lock fs - think why ;-) */
 669         if (fs) {
 670                 atomic_set(&fs->count, 1);
 671                 rwlock_init(&fs->lock);
 672                 fs->umask = old->umask;
 673                 read_lock(&old->lock);
 674                 fs->root = old->root;
 675                 path_get(&old->root);
 676                 fs->pwd = old->pwd;
 677                 path_get(&old->pwd);
 678                 read_unlock(&old->lock);
 679         }
 680         return fs;
 681 }
 682
 683 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 684 {
 685         return __copy_fs_struct(old);
 686 }
 687
 688 EXPORT_SYMBOL_GPL(copy_fs_struct);
 689
 690 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 691 {
 692         if (clone_flags & CLONE_FS) {
 693                 atomic_inc(&current->fs->count);
 694                 return 0;
 695         }
 696         tsk->fs = __copy_fs_struct(current->fs);
 697         if (!tsk->fs)
 698                 return -ENOMEM;
 699         return 0;
 700 }
 701
 702 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 703 {
 704         struct files_struct *oldf, *newf;
 705         int error = 0;
 706
 707         /*
 708          * A background process may not have any files ...
 709          */
 710         oldf = current->files;
 711         if (!oldf)
 712                 goto out;
 713
 714         if (clone_flags & CLONE_FILES) {
 715                 atomic_inc(&oldf->count);
 716                 goto out;
 717         }
 718
 719         newf = dup_fd(oldf, &error);
 720         if (!newf)
 721                 goto out;
 722
 723         tsk->files = newf;
 724         error = 0;
 725 out:
 726         return error;
 727 }
 728
 729 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 730 {
 731 #ifdef CONFIG_BLOCK
 732         struct io_context *ioc = current->io_context;
 733
 734         if (!ioc)
 735                 return 0;
 736         /*
 737          * Share io context with parent, if CLONE_IO is set
 738          */
 739         if (clone_flags & CLONE_IO) {
 740                 tsk->io_context = ioc_task_link(ioc);
 741                 if (unlikely(!tsk->io_context))
 742                         return -ENOMEM;
 743         } else if (ioprio_valid(ioc->ioprio)) {
 744                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 745                 if (unlikely(!tsk->io_context))
 746                         return -ENOMEM;
 747
 748                 tsk->io_context->ioprio = ioc->ioprio;
 749         }
 750 #endif
 751         return 0;
 752 }
 753
 754 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 755 {
 756         struct sighand_struct *sig;
 757
 758         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 759                 atomic_inc(&current->sighand->count);
 760                 return 0;
 761         }
 762         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 763         rcu_assign_pointer(tsk->sighand, sig);
 764         if (!sig)
 765                 return -ENOMEM;
 766         atomic_set(&sig->count, 1);
 767         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 768         return 0;
 769 }
 770
 771 void __cleanup_sighand(struct sighand_struct *sighand)
 772 {
 773         if (atomic_dec_and_test(&sighand->count))
 774                 kmem_cache_free(sighand_cachep, sighand);
 775 }
 776
 777
 778 /*
 779  * Initialize POSIX timer handling for a thread group.
 780  */
 781 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 782 {
 783         /* Thread group counters. */
 784         thread_group_cputime_init(sig);
 785
 786         /* Expiration times and increments. */
 787         sig->it_virt_expires = cputime_zero;
 788         sig->it_virt_incr = cputime_zero;
 789         sig->it_prof_expires = cputime_zero;
 790         sig->it_prof_incr = cputime_zero;
 791
 792         /* Cached expiration times. */
 793         sig->cputime_expires.prof_exp = cputime_zero;
 794         sig->cputime_expires.virt_exp = cputime_zero;
 795         sig->cputime_expires.sched_exp = 0;
 796
 797         /* The timer lists. */
 798         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 799         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 800         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 801 }
 802
 803 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 804 {
 805         struct signal_struct *sig;
 806         int ret;
 807
 808         if (clone_flags & CLONE_THREAD) {
 809                 ret = thread_group_cputime_clone_thread(current);
 810                 if (likely(!ret)) {
 811                         atomic_inc(&current->signal->count);
 812                         atomic_inc(&current->signal->live);
 813                 }
 814                 return ret;
 815         }
 816         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 817         tsk->signal = sig;
 818         if (!sig)
 819                 return -ENOMEM;
 820
 821         ret = copy_thread_group_keys(tsk);
 822         if (ret < 0) {
 823                 kmem_cache_free(signal_cachep, sig);
 824                 return ret;
 825         }
 826
 827         atomic_set(&sig->count, 1);
 828         atomic_set(&sig->live, 1);
 829         init_waitqueue_head(&sig->wait_chldexit);
 830         sig->flags = 0;
 831         sig->group_exit_code = 0;
 832         sig->group_exit_task = NULL;
 833         sig->group_stop_count = 0;
 834         sig->curr_target = tsk;
 835         init_sigpending(&sig->shared_pending);
 836         INIT_LIST_HEAD(&sig->posix_timers);
 837
 838         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 839         sig->it_real_incr.tv64 = 0;
 840         sig->real_timer.function = it_real_fn;
 841
 842         sig->leader = 0;        /* session leadership doesn't inherit */
 843         sig->tty_old_pgrp = NULL;
 844         sig->tty = NULL;
 845
 846         sig->cutime = sig->cstime = cputime_zero;
 847         sig->gtime = cputime_zero;
 848         sig->cgtime = cputime_zero;
 849         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 850         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 851         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 852         task_io_accounting_init(&sig->ioac);
 853         taskstats_tgid_init(sig);
 854
 855         task_lock(current->group_leader);
 856         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 857         task_unlock(current->group_leader);
 858
 859         posix_cpu_timers_init_group(sig);
 860
 861         acct_init_pacct(&sig->pacct);
 862
 863         tty_audit_fork(sig);
 864
 865         return 0;
 866 }
 867
 868 void __cleanup_signal(struct signal_struct *sig)
 869 {
 870         thread_group_cputime_free(sig);
 871         exit_thread_group_keys(sig);
 872         tty_kref_put(sig->tty);
 873         kmem_cache_free(signal_cachep, sig);
 874 }
 875
 876 static void cleanup_signal(struct task_struct *tsk)
 877 {
 878         struct signal_struct *sig = tsk->signal;
 879
 880         atomic_dec(&sig->live);
 881
 882         if (atomic_dec_and_test(&sig->count))
 883                 __cleanup_signal(sig);
 884 }
 885
 886 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 887 {
 888         unsigned long new_flags = p->flags;
 889
 890         new_flags &= ~PF_SUPERPRIV;
 891         new_flags |= PF_FORKNOEXEC;
 892         new_flags |= PF_STARTING;
 893         p->flags = new_flags;
 894         clear_freeze_flag(p);
 895 }
 896
 897 asmlinkage long sys_set_tid_address(int __user *tidptr)
 898 {
 899         current->clear_child_tid = tidptr;
 900
 901         return task_pid_vnr(current);
 902 }
 903
 904 static void rt_mutex_init_task(struct task_struct *p)
 905 {
 906         spin_lock_init(&p->pi_lock);
 907 #ifdef CONFIG_RT_MUTEXES
 908         plist_head_init(&p->pi_waiters, &p->pi_lock);
 909         p->pi_blocked_on = NULL;
 910 #endif
 911 }
 912
 913 #ifdef CONFIG_MM_OWNER
 914 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 915 {
 916         mm->owner = p;
 917 }
 918 #endif /* CONFIG_MM_OWNER */
 919
 920 /*
 921  * Initialize POSIX timer handling for a single task.
 922  */
 923 static void posix_cpu_timers_init(struct task_struct *tsk)
 924 {
 925         tsk->cputime_expires.prof_exp = cputime_zero;
 926         tsk->cputime_expires.virt_exp = cputime_zero;
 927         tsk->cputime_expires.sched_exp = 0;
 928         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 929         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
 930         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
 931 }
 932
 933 /*
 934  * This creates a new process as a copy of the old one,
 935  * but does not actually start it yet.
 936  *
 937  * It copies the registers, and all the appropriate
 938  * parts of the process environment (as per the clone
 939  * flags). The actual kick-off is left to the caller.
 940  */
 941 static struct task_struct *copy_process(unsigned long clone_flags,
 942                                         unsigned long stack_start,
 943                                         struct pt_regs *regs,
 944                                         unsigned long stack_size,
 945                                         int __user *child_tidptr,
 946                                         struct pid *pid,
 947                                         int trace)
 948 {
 949         int retval;
 950         struct task_struct *p;
 951         int cgroup_callbacks_done = 0;
 952
 953         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 954                 return ERR_PTR(-EINVAL);
 955
 956         /*
 957          * Thread groups must share signals as well, and detached threads
 958          * can only be started up within the thread group.
 959          */
 960         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 961                 return ERR_PTR(-EINVAL);
 962
 963         /*
 964          * Shared signal handlers imply shared VM. By way of the above,
 965          * thread groups also imply shared VM. Blocking this case allows
 966          * for various simplifications in other code.
 967          */
 968         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 969                 return ERR_PTR(-EINVAL);
 970
 971         retval = security_task_create(clone_flags);
 972         if (retval)
 973                 goto fork_out;
 974
 975         retval = -ENOMEM;
 976         p = dup_task_struct(current);
 977         if (!p)
 978                 goto fork_out;
 979
 980         rt_mutex_init_task(p);
 981
 982 #ifdef CONFIG_PROVE_LOCKING
 983         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 984         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 985 #endif
 986         retval = -EAGAIN;
 987         if (atomic_read(&p->user->processes) >=
 988                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 989                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 990                     p->user != current->nsproxy->user_ns->root_user)
 991                         goto bad_fork_free;
 992         }
 993
 994         atomic_inc(&p->user->__count);
 995         atomic_inc(&p->user->processes);
 996         get_group_info(p->group_info);
 997
 998         /*
 999          * If multiple threads are within copy_process(), then this check
1000          * triggers too late. This doesn't hurt, the check is only there
1001          * to stop root fork bombs.
1002          */
1003         if (nr_threads >= max_threads)
1004                 goto bad_fork_cleanup_count;
1005
1006         if (!try_module_get(task_thread_info(p)->exec_domain->module))
1007                 goto bad_fork_cleanup_count;
1008
1009         if (p->binfmt && !try_module_get(p->binfmt->module))
1010                 goto bad_fork_cleanup_put_domain;
1011
1012         p->did_exec = 0;
1013         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
1014         copy_flags(clone_flags, p);
1015         INIT_LIST_HEAD(&p->children);
1016         INIT_LIST_HEAD(&p->sibling);
1017 #ifdef CONFIG_PREEMPT_RCU
1018         p->rcu_read_lock_nesting = 0;
1019         p->rcu_flipctr_idx = 0;
1020 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1021         p->vfork_done = NULL;
1022         spin_lock_init(&p->alloc_lock);
1023
1024         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1025         init_sigpending(&p->pending);
1026
1027         p->utime = cputime_zero;
1028         p->stime = cputime_zero;
1029         p->gtime = cputime_zero;
1030         p->utimescaled = cputime_zero;
1031         p->stimescaled = cputime_zero;
1032         p->prev_utime = cputime_zero;
1033         p->prev_stime = cputime_zero;
1034
1035         p->default_timer_slack_ns = current->timer_slack_ns;
1036
1037 #ifdef CONFIG_DETECT_SOFTLOCKUP
1038         p->last_switch_count = 0;
1039         p->last_switch_timestamp = 0;
1040 #endif
1041
1042         task_io_accounting_init(&p->ioac);
1043         acct_clear_integrals(p);
1044
1045         posix_cpu_timers_init(p);
1046
1047         p->lock_depth = -1;             /* -1 = no lock */
1048         do_posix_clock_monotonic_gettime(&p->start_time);
1049         p->real_start_time = p->start_time;
1050         monotonic_to_bootbased(&p->real_start_time);
1051 #ifdef CONFIG_SECURITY
1052         p->security = NULL;
1053 #endif
1054         p->cap_bset = current->cap_bset;
1055         p->io_context = NULL;
1056         p->audit_context = NULL;
1057         cgroup_fork(p);
1058 #ifdef CONFIG_NUMA
1059         p->mempolicy = mpol_dup(p->mempolicy);
1060         if (IS_ERR(p->mempolicy)) {
1061                 retval = PTR_ERR(p->mempolicy);
1062                 p->mempolicy = NULL;
1063                 goto bad_fork_cleanup_cgroup;
1064         }
1065         mpol_fix_fork_child_flag(p);
1066 #endif
1067 #ifdef CONFIG_TRACE_IRQFLAGS
1068         p->irq_events = 0;
1069 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1070         p->hardirqs_enabled = 1;
1071 #else
1072         p->hardirqs_enabled = 0;
1073 #endif
1074         p->hardirq_enable_ip = 0;
1075         p->hardirq_enable_event = 0;
1076         p->hardirq_disable_ip = _THIS_IP_;
1077         p->hardirq_disable_event = 0;
1078         p->softirqs_enabled = 1;
1079         p->softirq_enable_ip = _THIS_IP_;
1080         p->softirq_enable_event = 0;
1081         p->softirq_disable_ip = 0;
1082         p->softirq_disable_event = 0;
1083         p->hardirq_context = 0;
1084         p->softirq_context = 0;
1085 #endif
1086 #ifdef CONFIG_LOCKDEP
1087         p->lockdep_depth = 0; /* no locks held yet */
1088         p->curr_chain_key = 0;
1089         p->lockdep_recursion = 0;
1090 #endif
1091
1092 #ifdef CONFIG_DEBUG_MUTEXES
1093         p->blocked_on = NULL; /* not blocked yet */
1094 #endif
1095
1096         /* Perform scheduler related setup. Assign this task to a CPU. */
1097         sched_fork(p, clone_flags);
1098
1099         if ((retval = security_task_alloc(p)))
1100                 goto bad_fork_cleanup_policy;
1101         if ((retval = audit_alloc(p)))
1102                 goto bad_fork_cleanup_security;
1103         /* copy all the process information */
1104         if ((retval = copy_semundo(clone_flags, p)))
1105                 goto bad_fork_cleanup_audit;
1106         if ((retval = copy_files(clone_flags, p)))
1107                 goto bad_fork_cleanup_semundo;
1108         if ((retval = copy_fs(clone_flags, p)))
1109                 goto bad_fork_cleanup_files;
1110         if ((retval = copy_sighand(clone_flags, p)))
1111                 goto bad_fork_cleanup_fs;
1112         if ((retval = copy_signal(clone_flags, p)))
1113                 goto bad_fork_cleanup_sighand;
1114         if ((retval = copy_mm(clone_flags, p)))
1115                 goto bad_fork_cleanup_signal;
1116         if ((retval = copy_keys(clone_flags, p)))
1117                 goto bad_fork_cleanup_mm;
1118         if ((retval = copy_namespaces(clone_flags, p)))
1119                 goto bad_fork_cleanup_keys;
1120         if ((retval = copy_io(clone_flags, p)))
1121                 goto bad_fork_cleanup_namespaces;
1122         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1123         if (retval)
1124                 goto bad_fork_cleanup_io;
1125
1126         if (pid != &init_struct_pid) {
1127                 retval = -ENOMEM;
1128                 pid = alloc_pid(task_active_pid_ns(p));
1129                 if (!pid)
1130                         goto bad_fork_cleanup_io;
1131
1132                 if (clone_flags & CLONE_NEWPID) {
1133                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1134                         if (retval < 0)
1135                                 goto bad_fork_free_pid;
1136                 }
1137         }
1138
1139         p->pid = pid_nr(pid);
1140         p->tgid = p->pid;
1141         if (clone_flags & CLONE_THREAD)
1142                 p->tgid = current->tgid;
1143
1144         if (current->nsproxy != p->nsproxy) {
1145                 retval = ns_cgroup_clone(p, pid);
1146                 if (retval)
1147                         goto bad_fork_free_pid;
1148         }
1149
1150         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1151         /*
1152          * Clear TID on mm_release()?
1153          */
1154         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1155 #ifdef CONFIG_FUTEX
1156         p->robust_list = NULL;
1157 #ifdef CONFIG_COMPAT
1158         p->compat_robust_list = NULL;
1159 #endif
1160         INIT_LIST_HEAD(&p->pi_state_list);
1161         p->pi_state_cache = NULL;
1162 #endif
1163         /*
1164          * sigaltstack should be cleared when sharing the same VM
1165          */
1166         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1167                 p->sas_ss_sp = p->sas_ss_size = 0;
1168
1169         /*
1170          * Syscall tracing should be turned off in the child regardless
1171          * of CLONE_PTRACE.
1172          */
1173         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1174 #ifdef TIF_SYSCALL_EMU
1175         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1176 #endif
1177         clear_all_latency_tracing(p);
1178
1179         /* Our parent execution domain becomes current domain
1180            These must match for thread signalling to apply */
1181         p->parent_exec_id = p->self_exec_id;
1182
1183         /* ok, now we should be set up.. */
1184         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1185         p->pdeath_signal = 0;
1186         p->exit_state = 0;
1187
1188         /*
1189          * Ok, make it visible to the rest of the system.
1190          * We dont wake it up yet.
1191          */
1192         p->group_leader = p;
1193         INIT_LIST_HEAD(&p->thread_group);
1194
1195         /* Now that the task is set up, run cgroup callbacks if
1196          * necessary. We need to run them before the task is visible
1197          * on the tasklist. */
1198         cgroup_fork_callbacks(p);
1199         cgroup_callbacks_done = 1;
1200
1201         /* Need tasklist lock for parent etc handling! */
1202         write_lock_irq(&tasklist_lock);
1203
1204         /*
1205          * The task hasn't been attached yet, so its cpus_allowed mask will
1206          * not be changed, nor will its assigned CPU.
1207          *
1208          * The cpus_allowed mask of the parent may have changed after it was
1209          * copied first time - so re-copy it here, then check the child's CPU
1210          * to ensure it is on a valid CPU (and if not, just force it back to
1211          * parent's CPU). This avoids alot of nasty races.
1212          */
1213         p->cpus_allowed = current->cpus_allowed;
1214         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1215         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1216                         !cpu_online(task_cpu(p))))
1217                 set_task_cpu(p, smp_processor_id());
1218
1219         /* CLONE_PARENT re-uses the old parent */
1220         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1221                 p->real_parent = current->real_parent;
1222         else
1223                 p->real_parent = current;
1224
1225         spin_lock(&current->sighand->siglock);
1226
1227         /*
1228          * Process group and session signals need to be delivered to just the
1229          * parent before the fork or both the parent and the child after the
1230          * fork. Restart if a signal comes in before we add the new process to
1231          * it's process group.
1232          * A fatal signal pending means that current will exit, so the new
1233          * thread can't slip out of an OOM kill (or normal SIGKILL).
1234          */
1235         recalc_sigpending();
1236         if (signal_pending(current)) {
1237                 spin_unlock(&current->sighand->siglock);
1238                 write_unlock_irq(&tasklist_lock);
1239                 retval = -ERESTARTNOINTR;
1240                 goto bad_fork_free_pid;
1241         }
1242
1243         if (clone_flags & CLONE_THREAD) {
1244                 p->group_leader = current->group_leader;
1245                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1246         }
1247
1248         if (likely(p->pid)) {
1249                 list_add_tail(&p->sibling, &p->real_parent->children);
1250                 tracehook_finish_clone(p, clone_flags, trace);
1251
1252                 if (thread_group_leader(p)) {
1253                         if (clone_flags & CLONE_NEWPID)
1254                                 p->nsproxy->pid_ns->child_reaper = p;
1255
1256                         p->signal->leader_pid = pid;
1257                         tty_kref_put(p->signal->tty);
1258                         p->signal->tty = tty_kref_get(current->signal->tty);
1259                         set_task_pgrp(p, task_pgrp_nr(current));
1260                         set_task_session(p, task_session_nr(current));
1261                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1262                         attach_pid(p, PIDTYPE_SID, task_session(current));
1263                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1264                         __get_cpu_var(process_counts)++;
1265                 }
1266                 attach_pid(p, PIDTYPE_PID, pid);
1267                 nr_threads++;
1268         }
1269
1270         total_forks++;
1271         spin_unlock(&current->sighand->siglock);
1272         write_unlock_irq(&tasklist_lock);
1273         proc_fork_connector(p);
1274         cgroup_post_fork(p);
1275         return p;
1276
1277 bad_fork_free_pid:
1278         if (pid != &init_struct_pid)
1279                 free_pid(pid);
1280 bad_fork_cleanup_io:
1281         put_io_context(p->io_context);
1282 bad_fork_cleanup_namespaces:
1283         exit_task_namespaces(p);
1284 bad_fork_cleanup_keys:
1285         exit_keys(p);
1286 bad_fork_cleanup_mm:
1287         if (p->mm)
1288                 mmput(p->mm);
1289 bad_fork_cleanup_signal:
1290         cleanup_signal(p);
1291 bad_fork_cleanup_sighand:
1292         __cleanup_sighand(p->sighand);
1293 bad_fork_cleanup_fs:
1294         exit_fs(p); /* blocking */
1295 bad_fork_cleanup_files:
1296         exit_files(p); /* blocking */
1297 bad_fork_cleanup_semundo:
1298         exit_sem(p);
1299 bad_fork_cleanup_audit:
1300         audit_free(p);
1301 bad_fork_cleanup_security:
1302         security_task_free(p);
1303 bad_fork_cleanup_policy:
1304 #ifdef CONFIG_NUMA
1305         mpol_put(p->mempolicy);
1306 bad_fork_cleanup_cgroup:
1307 #endif
1308         cgroup_exit(p, cgroup_callbacks_done);
1309         delayacct_tsk_free(p);
1310         if (p->binfmt)
1311                 module_put(p->binfmt->module);
1312 bad_fork_cleanup_put_domain:
1313         module_put(task_thread_info(p)->exec_domain->module);
1314 bad_fork_cleanup_count:
1315         put_group_info(p->group_info);
1316         atomic_dec(&p->user->processes);
1317         free_uid(p->user);
1318 bad_fork_free:
1319         free_task(p);
1320 fork_out:
1321         return ERR_PTR(retval);
1322 }
1323
1324 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1325 {
1326         memset(regs, 0, sizeof(struct pt_regs));
1327         return regs;
1328 }
1329
1330 struct task_struct * __cpuinit fork_idle(int cpu)
1331 {
1332         struct task_struct *task;
1333         struct pt_regs regs;
1334
1335         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1336                             &init_struct_pid, 0);
1337         if (!IS_ERR(task))
1338                 init_idle(task, cpu);
1339
1340         return task;
1341 }
1342
1343 /*
1344  *  Ok, this is the main fork-routine.
1345  *
1346  * It copies the process, and if successful kick-starts
1347  * it and waits for it to finish using the VM if required.
1348  */
1349 long do_fork(unsigned long clone_flags,
1350               unsigned long stack_start,
1351               struct pt_regs *regs,
1352               unsigned long stack_size,
1353               int __user *parent_tidptr,
1354               int __user *child_tidptr)
1355 {
1356         struct task_struct *p;
1357         int trace = 0;
1358         long nr;
1359
1360         /*
1361          * We hope to recycle these flags after 2.6.26
1362          */
1363         if (unlikely(clone_flags & CLONE_STOPPED)) {
1364                 static int __read_mostly count = 100;
1365
1366                 if (count > 0 && printk_ratelimit()) {
1367                         char comm[TASK_COMM_LEN];
1368
1369                         count--;
1370                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1371                                         "clone flags 0x%lx\n",
1372                                 get_task_comm(comm, current),
1373                                 clone_flags & CLONE_STOPPED);
1374                 }
1375         }
1376
1377         /*
1378          * When called from kernel_thread, don't do user tracing stuff.
1379          */
1380         if (likely(user_mode(regs)))
1381                 trace = tracehook_prepare_clone(clone_flags);
1382
1383         p = copy_process(clone_flags, stack_start, regs, stack_size,
1384                          child_tidptr, NULL, trace);
1385         /*
1386          * Do this prior waking up the new thread - the thread pointer
1387          * might get invalid after that point, if the thread exits quickly.
1388          */
1389         if (!IS_ERR(p)) {
1390                 struct completion vfork;
1391
1392                 trace_sched_process_fork(current, p);
1393
1394                 nr = task_pid_vnr(p);
1395
1396                 if (clone_flags & CLONE_PARENT_SETTID)
1397                         put_user(nr, parent_tidptr);
1398
1399                 if (clone_flags & CLONE_VFORK) {
1400                         p->vfork_done = &vfork;
1401                         init_completion(&vfork);
1402                 }
1403
1404                 audit_finish_fork(p);
1405                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1406
1407                 /*
1408                  * We set PF_STARTING at creation in case tracing wants to
1409                  * use this to distinguish a fully live task from one that
1410                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1411                  * clear it and set the child going.
1412                  */
1413                 p->flags &= ~PF_STARTING;
1414
1415                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1416                         /*
1417                          * We'll start up with an immediate SIGSTOP.
1418                          */
1419                         sigaddset(&p->pending.signal, SIGSTOP);
1420                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1421                         __set_task_state(p, TASK_STOPPED);
1422                 } else {
1423                         wake_up_new_task(p, clone_flags);
1424                 }
1425
1426                 tracehook_report_clone_complete(trace, regs,
1427                                                 clone_flags, nr, p);
1428
1429                 if (clone_flags & CLONE_VFORK) {
1430                         freezer_do_not_count();
1431                         wait_for_completion(&vfork);
1432                         freezer_count();
1433                         tracehook_report_vfork_done(p, nr);
1434                 }
1435         } else {
1436                 nr = PTR_ERR(p);
1437         }
1438         return nr;
1439 }
1440
1441 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1442 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1443 #endif
1444
1445 static void sighand_ctor(void *data)
1446 {
1447         struct sighand_struct *sighand = data;
1448
1449         spin_lock_init(&sighand->siglock);
1450         init_waitqueue_head(&sighand->signalfd_wqh);
1451 }
1452
1453 void __init proc_caches_init(void)
1454 {
1455         sighand_cachep = kmem_cache_create("sighand_cache",
1456                         sizeof(struct sighand_struct), 0,
1457                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1458                         sighand_ctor);
1459         signal_cachep = kmem_cache_create("signal_cache",
1460                         sizeof(struct signal_struct), 0,
1461                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1462         files_cachep = kmem_cache_create("files_cache",
1463                         sizeof(struct files_struct), 0,
1464                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1465         fs_cachep = kmem_cache_create("fs_cache",
1466                         sizeof(struct fs_struct), 0,
1467                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1468         vm_area_cachep = kmem_cache_create("vm_area_struct",
1469                         sizeof(struct vm_area_struct), 0,
1470                         SLAB_PANIC, NULL);
1471         mm_cachep = kmem_cache_create("mm_struct",
1472                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1473                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1474 }
1475
1476 /*
1477  * Check constraints on flags passed to the unshare system call and
1478  * force unsharing of additional process context as appropriate.
1479  */
1480 static void check_unshare_flags(unsigned long *flags_ptr)
1481 {
1482         /*
1483          * If unsharing a thread from a thread group, must also
1484          * unshare vm.
1485          */
1486         if (*flags_ptr & CLONE_THREAD)
1487                 *flags_ptr |= CLONE_VM;
1488
1489         /*
1490          * If unsharing vm, must also unshare signal handlers.
1491          */
1492         if (*flags_ptr & CLONE_VM)
1493                 *flags_ptr |= CLONE_SIGHAND;
1494
1495         /*
1496          * If unsharing signal handlers and the task was created
1497          * using CLONE_THREAD, then must unshare the thread
1498          */
1499         if ((*flags_ptr & CLONE_SIGHAND) &&
1500             (atomic_read(&current->signal->count) > 1))
1501                 *flags_ptr |= CLONE_THREAD;
1502
1503         /*
1504          * If unsharing namespace, must also unshare filesystem information.
1505          */
1506         if (*flags_ptr & CLONE_NEWNS)
1507                 *flags_ptr |= CLONE_FS;
1508 }
1509
1510 /*
1511  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1512  */
1513 static int unshare_thread(unsigned long unshare_flags)
1514 {
1515         if (unshare_flags & CLONE_THREAD)
1516                 return -EINVAL;
1517
1518         return 0;
1519 }
1520
1521 /*
1522  * Unshare the filesystem structure if it is being shared
1523  */
1524 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1525 {
1526         struct fs_struct *fs = current->fs;
1527
1528         if ((unshare_flags & CLONE_FS) &&
1529             (fs && atomic_read(&fs->count) > 1)) {
1530                 *new_fsp = __copy_fs_struct(current->fs);
1531                 if (!*new_fsp)
1532                         return -ENOMEM;
1533         }
1534
1535         return 0;
1536 }
1537
1538 /*
1539  * Unsharing of sighand is not supported yet
1540  */
1541 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1542 {
1543         struct sighand_struct *sigh = current->sighand;
1544
1545         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1546                 return -EINVAL;
1547         else
1548                 return 0;
1549 }
1550
1551 /*
1552  * Unshare vm if it is being shared
1553  */
1554 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1555 {
1556         struct mm_struct *mm = current->mm;
1557
1558         if ((unshare_flags & CLONE_VM) &&
1559             (mm && atomic_read(&mm->mm_users) > 1)) {
1560                 return -EINVAL;
1561         }
1562
1563         return 0;
1564 }
1565
1566 /*
1567  * Unshare file descriptor table if it is being shared
1568  */
1569 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1570 {
1571         struct files_struct *fd = current->files;
1572         int error = 0;
1573
1574         if ((unshare_flags & CLONE_FILES) &&
1575             (fd && atomic_read(&fd->count) > 1)) {
1576                 *new_fdp = dup_fd(fd, &error);
1577                 if (!*new_fdp)
1578                         return error;
1579         }
1580
1581         return 0;
1582 }
1583
1584 /*
1585  * unshare allows a process to 'unshare' part of the process
1586  * context which was originally shared using clone.  copy_*
1587  * functions used by do_fork() cannot be used here directly
1588  * because they modify an inactive task_struct that is being
1589  * constructed. Here we are modifying the current, active,
1590  * task_struct.
1591  */
1592 asmlinkage long sys_unshare(unsigned long unshare_flags)
1593 {
1594         int err = 0;
1595         struct fs_struct *fs, *new_fs = NULL;
1596         struct sighand_struct *new_sigh = NULL;
1597         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1598         struct files_struct *fd, *new_fd = NULL;
1599         struct nsproxy *new_nsproxy = NULL;
1600         int do_sysvsem = 0;
1601
1602         check_unshare_flags(&unshare_flags);
1603
1604         /* Return -EINVAL for all unsupported flags */
1605         err = -EINVAL;
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_NEWUSER|
1609                                 CLONE_NEWNET))
1610                 goto bad_unshare_out;
1611
1612         /*
1613          * CLONE_NEWIPC must also detach from the undolist: after switching
1614          * to a new ipc namespace, the semaphore arrays from the old
1615          * namespace are unreachable.
1616          */
1617         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1618                 do_sysvsem = 1;
1619         if ((err = unshare_thread(unshare_flags)))
1620                 goto bad_unshare_out;
1621         if ((err = unshare_fs(unshare_flags, &new_fs)))
1622                 goto bad_unshare_cleanup_thread;
1623         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1624                 goto bad_unshare_cleanup_fs;
1625         if ((err = unshare_vm(unshare_flags, &new_mm)))
1626                 goto bad_unshare_cleanup_sigh;
1627         if ((err = unshare_fd(unshare_flags, &new_fd)))
1628                 goto bad_unshare_cleanup_vm;
1629         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1630                         new_fs)))
1631                 goto bad_unshare_cleanup_fd;
1632
1633         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1634                 if (do_sysvsem) {
1635                         /*
1636                          * CLONE_SYSVSEM is equivalent to sys_exit().
1637                          */
1638                         exit_sem(current);
1639                 }
1640
1641                 if (new_nsproxy) {
1642                         switch_task_namespaces(current, new_nsproxy);
1643                         new_nsproxy = NULL;
1644                 }
1645
1646                 task_lock(current);
1647
1648                 if (new_fs) {
1649                         fs = current->fs;
1650                         current->fs = new_fs;
1651                         new_fs = fs;
1652                 }
1653
1654                 if (new_mm) {
1655                         mm = current->mm;
1656                         active_mm = current->active_mm;
1657                         current->mm = new_mm;
1658                         current->active_mm = new_mm;
1659                         activate_mm(active_mm, new_mm);
1660                         new_mm = mm;
1661                 }
1662
1663                 if (new_fd) {
1664                         fd = current->files;
1665                         current->files = new_fd;
1666                         new_fd = fd;
1667                 }
1668
1669                 task_unlock(current);
1670         }
1671
1672         if (new_nsproxy)
1673                 put_nsproxy(new_nsproxy);
1674
1675 bad_unshare_cleanup_fd:
1676         if (new_fd)
1677                 put_files_struct(new_fd);
1678
1679 bad_unshare_cleanup_vm:
1680         if (new_mm)
1681                 mmput(new_mm);
1682
1683 bad_unshare_cleanup_sigh:
1684         if (new_sigh)
1685                 if (atomic_dec_and_test(&new_sigh->count))
1686                         kmem_cache_free(sighand_cachep, new_sigh);
1687
1688 bad_unshare_cleanup_fs:
1689         if (new_fs)
1690                 put_fs_struct(new_fs);
1691
1692 bad_unshare_cleanup_thread:
1693 bad_unshare_out:
1694         return err;
1695 }
1696
1697 /*
1698  *      Helper to unshare the files of the current task.
1699  *      We don't want to expose copy_files internals to
1700  *      the exec layer of the kernel.
1701  */
1702
1703 int unshare_files(struct files_struct **displaced)
1704 {
1705         struct task_struct *task = current;
1706         struct files_struct *copy = NULL;
1707         int error;
1708
1709         error = unshare_fd(CLONE_FILES, &copy);
1710         if (error || !copy) {
1711                 *displaced = NULL;
1712                 return error;
1713         }
1714         *displaced = task->files;
1715         task_lock(task);
1716         task->files = copy;
1717         task_unlock(task);
1718         return 0;
1719 }