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/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/futex.h>
  41 #include <linux/task_io_accounting_ops.h>
  42 #include <linux/rcupdate.h>
  43 #include <linux/ptrace.h>
  44 #include <linux/mount.h>
  45 #include <linux/audit.h>
  46 #include <linux/memcontrol.h>
  47 #include <linux/profile.h>
  48 #include <linux/rmap.h>
  49 #include <linux/acct.h>
  50 #include <linux/tsacct_kern.h>
  51 #include <linux/cn_proc.h>
  52 #include <linux/freezer.h>
  53 #include <linux/delayacct.h>
  54 #include <linux/taskstats_kern.h>
  55 #include <linux/random.h>
  56 #include <linux/tty.h>
  57 #include <linux/proc_fs.h>
  58 #include <linux/blkdev.h>
  59
  60 #include <asm/pgtable.h>
  61 #include <asm/pgalloc.h>
  62 #include <asm/uaccess.h>
  63 #include <asm/mmu_context.h>
  64 #include <asm/cacheflush.h>
  65 #include <asm/tlbflush.h>
  66
  67 /*
  68  * Protected counters by write_lock_irq(&tasklist_lock)
  69  */
  70 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  71 int nr_threads;                 /* The idle threads do not count.. */
  72
  73 int max_threads;                /* tunable limit on nr_threads */
  74
  75 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  76
  77 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  78
  79 int nr_processes(void)
  80 {
  81         int cpu;
  82         int total = 0;
  83
  84         for_each_online_cpu(cpu)
  85                 total += per_cpu(process_counts, cpu);
  86
  87         return total;
  88 }
  89
  90 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  91 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  92 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  93 static struct kmem_cache *task_struct_cachep;
  94 #endif
  95
  96 /* SLAB cache for signal_struct structures (tsk->signal) */
  97 static struct kmem_cache *signal_cachep;
  98
  99 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 100 struct kmem_cache *sighand_cachep;
 101
 102 /* SLAB cache for files_struct structures (tsk->files) */
 103 struct kmem_cache *files_cachep;
 104
 105 /* SLAB cache for fs_struct structures (tsk->fs) */
 106 struct kmem_cache *fs_cachep;
 107
 108 /* SLAB cache for vm_area_struct structures */
 109 struct kmem_cache *vm_area_cachep;
 110
 111 /* SLAB cache for mm_struct structures (tsk->mm) */
 112 static struct kmem_cache *mm_cachep;
 113
 114 void free_task(struct task_struct *tsk)
 115 {
 116         prop_local_destroy_single(&tsk->dirties);
 117         free_thread_info(tsk->stack);
 118         rt_mutex_debug_task_free(tsk);
 119         free_task_struct(tsk);
 120 }
 121 EXPORT_SYMBOL(free_task);
 122
 123 void __put_task_struct(struct task_struct *tsk)
 124 {
 125         WARN_ON(!tsk->exit_state);
 126         WARN_ON(atomic_read(&tsk->usage));
 127         WARN_ON(tsk == current);
 128
 129         security_task_free(tsk);
 130         free_uid(tsk->user);
 131         put_group_info(tsk->group_info);
 132         delayacct_tsk_free(tsk);
 133
 134         if (!profile_handoff_task(tsk))
 135                 free_task(tsk);
 136 }
 137
 138 /*
 139  * macro override instead of weak attribute alias, to workaround
 140  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 141  */
 142 #ifndef arch_task_cache_init
 143 #define arch_task_cache_init()
 144 #endif
 145
 146 void __init fork_init(unsigned long mempages)
 147 {
 148 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 149 #ifndef ARCH_MIN_TASKALIGN
 150 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 151 #endif
 152         /* create a slab on which task_structs can be allocated */
 153         task_struct_cachep =
 154                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 155                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
 156 #endif
 157
 158         /* do the arch specific task caches init */
 159         arch_task_cache_init();
 160
 161         /*
 162          * The default maximum number of threads is set to a safe
 163          * value: the thread structures can take up at most half
 164          * of memory.
 165          */
 166         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 167
 168         /*
 169          * we need to allow at least 20 threads to boot a system
 170          */
 171         if(max_threads < 20)
 172                 max_threads = 20;
 173
 174         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 175         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 176         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 177                 init_task.signal->rlim[RLIMIT_NPROC];
 178 }
 179
 180 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 181                                                struct task_struct *src)
 182 {
 183         *dst = *src;
 184         return 0;
 185 }
 186
 187 static struct task_struct *dup_task_struct(struct task_struct *orig)
 188 {
 189         struct task_struct *tsk;
 190         struct thread_info *ti;
 191         int err;
 192
 193         prepare_to_copy(orig);
 194
 195         tsk = alloc_task_struct();
 196         if (!tsk)
 197                 return NULL;
 198
 199         ti = alloc_thread_info(tsk);
 200         if (!ti) {
 201                 free_task_struct(tsk);
 202                 return NULL;
 203         }
 204
 205         err = arch_dup_task_struct(tsk, orig);
 206         if (err)
 207                 goto out;
 208
 209         tsk->stack = ti;
 210
 211         err = prop_local_init_single(&tsk->dirties);
 212         if (err)
 213                 goto out;
 214
 215         setup_thread_stack(tsk, orig);
 216
 217 #ifdef CONFIG_CC_STACKPROTECTOR
 218         tsk->stack_canary = get_random_int();
 219 #endif
 220
 221         /* One for us, one for whoever does the "release_task()" (usually parent) */
 222         atomic_set(&tsk->usage,2);
 223         atomic_set(&tsk->fs_excl, 0);
 224 #ifdef CONFIG_BLK_DEV_IO_TRACE
 225         tsk->btrace_seq = 0;
 226 #endif
 227         tsk->splice_pipe = NULL;
 228         return tsk;
 229
 230 out:
 231         free_thread_info(ti);
 232         free_task_struct(tsk);
 233         return NULL;
 234 }
 235
 236 #ifdef CONFIG_MMU
 237 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 238 {
 239         struct vm_area_struct *mpnt, *tmp, **pprev;
 240         struct rb_node **rb_link, *rb_parent;
 241         int retval;
 242         unsigned long charge;
 243         struct mempolicy *pol;
 244
 245         down_write(&oldmm->mmap_sem);
 246         flush_cache_dup_mm(oldmm);
 247         /*
 248          * Not linked in yet - no deadlock potential:
 249          */
 250         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 251
 252         mm->locked_vm = 0;
 253         mm->mmap = NULL;
 254         mm->mmap_cache = NULL;
 255         mm->free_area_cache = oldmm->mmap_base;
 256         mm->cached_hole_size = ~0UL;
 257         mm->map_count = 0;
 258         cpus_clear(mm->cpu_vm_mask);
 259         mm->mm_rb = RB_ROOT;
 260         rb_link = &mm->mm_rb.rb_node;
 261         rb_parent = NULL;
 262         pprev = &mm->mmap;
 263
 264         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 265                 struct file *file;
 266
 267                 if (mpnt->vm_flags & VM_DONTCOPY) {
 268                         long pages = vma_pages(mpnt);
 269                         mm->total_vm -= pages;
 270                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 271                                                                 -pages);
 272                         continue;
 273                 }
 274                 charge = 0;
 275                 if (mpnt->vm_flags & VM_ACCOUNT) {
 276                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 277                         if (security_vm_enough_memory(len))
 278                                 goto fail_nomem;
 279                         charge = len;
 280                 }
 281                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 282                 if (!tmp)
 283                         goto fail_nomem;
 284                 *tmp = *mpnt;
 285                 pol = mpol_dup(vma_policy(mpnt));
 286                 retval = PTR_ERR(pol);
 287                 if (IS_ERR(pol))
 288                         goto fail_nomem_policy;
 289                 vma_set_policy(tmp, pol);
 290                 tmp->vm_flags &= ~VM_LOCKED;
 291                 tmp->vm_mm = mm;
 292                 tmp->vm_next = NULL;
 293                 anon_vma_link(tmp);
 294                 file = tmp->vm_file;
 295                 if (file) {
 296                         struct inode *inode = file->f_path.dentry->d_inode;
 297                         get_file(file);
 298                         if (tmp->vm_flags & VM_DENYWRITE)
 299                                 atomic_dec(&inode->i_writecount);
 300
 301                         /* insert tmp into the share list, just after mpnt */
 302                         spin_lock(&file->f_mapping->i_mmap_lock);
 303                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 304                         flush_dcache_mmap_lock(file->f_mapping);
 305                         vma_prio_tree_add(tmp, mpnt);
 306                         flush_dcache_mmap_unlock(file->f_mapping);
 307                         spin_unlock(&file->f_mapping->i_mmap_lock);
 308                 }
 309
 310                 /*
 311                  * Clear hugetlb-related page reserves for children. This only
 312                  * affects MAP_PRIVATE mappings. Faults generated by the child
 313                  * are not guaranteed to succeed, even if read-only
 314                  */
 315                 if (is_vm_hugetlb_page(tmp))
 316                         reset_vma_resv_huge_pages(tmp);
 317
 318                 /*
 319                  * Link in the new vma and copy the page table entries.
 320                  */
 321                 *pprev = tmp;
 322                 pprev = &tmp->vm_next;
 323
 324                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 325                 rb_link = &tmp->vm_rb.rb_right;
 326                 rb_parent = &tmp->vm_rb;
 327
 328                 mm->map_count++;
 329                 retval = copy_page_range(mm, oldmm, mpnt);
 330
 331                 if (tmp->vm_ops && tmp->vm_ops->open)
 332                         tmp->vm_ops->open(tmp);
 333
 334                 if (retval)
 335                         goto out;
 336         }
 337         /* a new mm has just been created */
 338         arch_dup_mmap(oldmm, mm);
 339         retval = 0;
 340 out:
 341         up_write(&mm->mmap_sem);
 342         flush_tlb_mm(oldmm);
 343         up_write(&oldmm->mmap_sem);
 344         return retval;
 345 fail_nomem_policy:
 346         kmem_cache_free(vm_area_cachep, tmp);
 347 fail_nomem:
 348         retval = -ENOMEM;
 349         vm_unacct_memory(charge);
 350         goto out;
 351 }
 352
 353 static inline int mm_alloc_pgd(struct mm_struct * mm)
 354 {
 355         mm->pgd = pgd_alloc(mm);
 356         if (unlikely(!mm->pgd))
 357                 return -ENOMEM;
 358         return 0;
 359 }
 360
 361 static inline void mm_free_pgd(struct mm_struct * mm)
 362 {
 363         pgd_free(mm, mm->pgd);
 364 }
 365 #else
 366 #define dup_mmap(mm, oldmm)     (0)
 367 #define mm_alloc_pgd(mm)        (0)
 368 #define mm_free_pgd(mm)
 369 #endif /* CONFIG_MMU */
 370
 371 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 372
 373 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 374 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 375
 376 #include <linux/init_task.h>
 377
 378 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 379 {
 380         atomic_set(&mm->mm_users, 1);
 381         atomic_set(&mm->mm_count, 1);
 382         init_rwsem(&mm->mmap_sem);
 383         INIT_LIST_HEAD(&mm->mmlist);
 384         mm->flags = (current->mm) ? current->mm->flags
 385                                   : MMF_DUMP_FILTER_DEFAULT;
 386         mm->core_waiters = 0;
 387         mm->nr_ptes = 0;
 388         set_mm_counter(mm, file_rss, 0);
 389         set_mm_counter(mm, anon_rss, 0);
 390         spin_lock_init(&mm->page_table_lock);
 391         rwlock_init(&mm->ioctx_list_lock);
 392         mm->ioctx_list = NULL;
 393         mm->free_area_cache = TASK_UNMAPPED_BASE;
 394         mm->cached_hole_size = ~0UL;
 395         mm_init_owner(mm, p);
 396
 397         if (likely(!mm_alloc_pgd(mm))) {
 398                 mm->def_flags = 0;
 399                 return mm;
 400         }
 401
 402         free_mm(mm);
 403         return NULL;
 404 }
 405
 406 /*
 407  * Allocate and initialize an mm_struct.
 408  */
 409 struct mm_struct * mm_alloc(void)
 410 {
 411         struct mm_struct * mm;
 412
 413         mm = allocate_mm();
 414         if (mm) {
 415                 memset(mm, 0, sizeof(*mm));
 416                 mm = mm_init(mm, current);
 417         }
 418         return mm;
 419 }
 420
 421 /*
 422  * Called when the last reference to the mm
 423  * is dropped: either by a lazy thread or by
 424  * mmput. Free the page directory and the mm.
 425  */
 426 void __mmdrop(struct mm_struct *mm)
 427 {
 428         BUG_ON(mm == &init_mm);
 429         mm_free_pgd(mm);
 430         destroy_context(mm);
 431         free_mm(mm);
 432 }
 433 EXPORT_SYMBOL_GPL(__mmdrop);
 434
 435 /*
 436  * Decrement the use count and release all resources for an mm.
 437  */
 438 void mmput(struct mm_struct *mm)
 439 {
 440         might_sleep();
 441
 442         if (atomic_dec_and_test(&mm->mm_users)) {
 443                 exit_aio(mm);
 444                 exit_mmap(mm);
 445                 set_mm_exe_file(mm, NULL);
 446                 if (!list_empty(&mm->mmlist)) {
 447                         spin_lock(&mmlist_lock);
 448                         list_del(&mm->mmlist);
 449                         spin_unlock(&mmlist_lock);
 450                 }
 451                 put_swap_token(mm);
 452                 mmdrop(mm);
 453         }
 454 }
 455 EXPORT_SYMBOL_GPL(mmput);
 456
 457 /**
 458  * get_task_mm - acquire a reference to the task's mm
 459  *
 460  * Returns %NULL if the task has no mm.  Checks PF_BORROWED_MM (meaning
 461  * this kernel workthread has transiently adopted a user mm with use_mm,
 462  * to do its AIO) is not set and if so returns a reference to it, after
 463  * bumping up the use count.  User must release the mm via mmput()
 464  * after use.  Typically used by /proc and ptrace.
 465  */
 466 struct mm_struct *get_task_mm(struct task_struct *task)
 467 {
 468         struct mm_struct *mm;
 469
 470         task_lock(task);
 471         mm = task->mm;
 472         if (mm) {
 473                 if (task->flags & PF_BORROWED_MM)
 474                         mm = NULL;
 475                 else
 476                         atomic_inc(&mm->mm_users);
 477         }
 478         task_unlock(task);
 479         return mm;
 480 }
 481 EXPORT_SYMBOL_GPL(get_task_mm);
 482
 483 /* Please note the differences between mmput and mm_release.
 484  * mmput is called whenever we stop holding onto a mm_struct,
 485  * error success whatever.
 486  *
 487  * mm_release is called after a mm_struct has been removed
 488  * from the current process.
 489  *
 490  * This difference is important for error handling, when we
 491  * only half set up a mm_struct for a new process and need to restore
 492  * the old one.  Because we mmput the new mm_struct before
 493  * restoring the old one. . .
 494  * Eric Biederman 10 January 1998
 495  */
 496 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 497 {
 498         struct completion *vfork_done = tsk->vfork_done;
 499
 500         /* Get rid of any cached register state */
 501         deactivate_mm(tsk, mm);
 502
 503         /* notify parent sleeping on vfork() */
 504         if (vfork_done) {
 505                 tsk->vfork_done = NULL;
 506                 complete(vfork_done);
 507         }
 508
 509         /*
 510          * If we're exiting normally, clear a user-space tid field if
 511          * requested.  We leave this alone when dying by signal, to leave
 512          * the value intact in a core dump, and to save the unnecessary
 513          * trouble otherwise.  Userland only wants this done for a sys_exit.
 514          */
 515         if (tsk->clear_child_tid
 516             && !(tsk->flags & PF_SIGNALED)
 517             && atomic_read(&mm->mm_users) > 1) {
 518                 u32 __user * tidptr = tsk->clear_child_tid;
 519                 tsk->clear_child_tid = NULL;
 520
 521                 /*
 522                  * We don't check the error code - if userspace has
 523                  * not set up a proper pointer then tough luck.
 524                  */
 525                 put_user(0, tidptr);
 526                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 527         }
 528 }
 529
 530 /*
 531  * Allocate a new mm structure and copy contents from the
 532  * mm structure of the passed in task structure.
 533  */
 534 struct mm_struct *dup_mm(struct task_struct *tsk)
 535 {
 536         struct mm_struct *mm, *oldmm = current->mm;
 537         int err;
 538
 539         if (!oldmm)
 540                 return NULL;
 541
 542         mm = allocate_mm();
 543         if (!mm)
 544                 goto fail_nomem;
 545
 546         memcpy(mm, oldmm, sizeof(*mm));
 547
 548         /* Initializing for Swap token stuff */
 549         mm->token_priority = 0;
 550         mm->last_interval = 0;
 551
 552         if (!mm_init(mm, tsk))
 553                 goto fail_nomem;
 554
 555         if (init_new_context(tsk, mm))
 556                 goto fail_nocontext;
 557
 558         dup_mm_exe_file(oldmm, mm);
 559
 560         err = dup_mmap(mm, oldmm);
 561         if (err)
 562                 goto free_pt;
 563
 564         mm->hiwater_rss = get_mm_rss(mm);
 565         mm->hiwater_vm = mm->total_vm;
 566
 567         return mm;
 568
 569 free_pt:
 570         mmput(mm);
 571
 572 fail_nomem:
 573         return NULL;
 574
 575 fail_nocontext:
 576         /*
 577          * If init_new_context() failed, we cannot use mmput() to free the mm
 578          * because it calls destroy_context()
 579          */
 580         mm_free_pgd(mm);
 581         free_mm(mm);
 582         return NULL;
 583 }
 584
 585 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 586 {
 587         struct mm_struct * mm, *oldmm;
 588         int retval;
 589
 590         tsk->min_flt = tsk->maj_flt = 0;
 591         tsk->nvcsw = tsk->nivcsw = 0;
 592
 593         tsk->mm = NULL;
 594         tsk->active_mm = NULL;
 595
 596         /*
 597          * Are we cloning a kernel thread?
 598          *
 599          * We need to steal a active VM for that..
 600          */
 601         oldmm = current->mm;
 602         if (!oldmm)
 603                 return 0;
 604
 605         if (clone_flags & CLONE_VM) {
 606                 atomic_inc(&oldmm->mm_users);
 607                 mm = oldmm;
 608                 goto good_mm;
 609         }
 610
 611         retval = -ENOMEM;
 612         mm = dup_mm(tsk);
 613         if (!mm)
 614                 goto fail_nomem;
 615
 616 good_mm:
 617         /* Initializing for Swap token stuff */
 618         mm->token_priority = 0;
 619         mm->last_interval = 0;
 620
 621         tsk->mm = mm;
 622         tsk->active_mm = mm;
 623         return 0;
 624
 625 fail_nomem:
 626         return retval;
 627 }
 628
 629 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 630 {
 631         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 632         /* We don't need to lock fs - think why ;-) */
 633         if (fs) {
 634                 atomic_set(&fs->count, 1);
 635                 rwlock_init(&fs->lock);
 636                 fs->umask = old->umask;
 637                 read_lock(&old->lock);
 638                 fs->root = old->root;
 639                 path_get(&old->root);
 640                 fs->pwd = old->pwd;
 641                 path_get(&old->pwd);
 642                 if (old->altroot.dentry) {
 643                         fs->altroot = old->altroot;
 644                         path_get(&old->altroot);
 645                 } else {
 646                         fs->altroot.mnt = NULL;
 647                         fs->altroot.dentry = NULL;
 648                 }
 649                 read_unlock(&old->lock);
 650         }
 651         return fs;
 652 }
 653
 654 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 655 {
 656         return __copy_fs_struct(old);
 657 }
 658
 659 EXPORT_SYMBOL_GPL(copy_fs_struct);
 660
 661 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 662 {
 663         if (clone_flags & CLONE_FS) {
 664                 atomic_inc(&current->fs->count);
 665                 return 0;
 666         }
 667         tsk->fs = __copy_fs_struct(current->fs);
 668         if (!tsk->fs)
 669                 return -ENOMEM;
 670         return 0;
 671 }
 672
 673 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 674 {
 675         struct files_struct *oldf, *newf;
 676         int error = 0;
 677
 678         /*
 679          * A background process may not have any files ...
 680          */
 681         oldf = current->files;
 682         if (!oldf)
 683                 goto out;
 684
 685         if (clone_flags & CLONE_FILES) {
 686                 atomic_inc(&oldf->count);
 687                 goto out;
 688         }
 689
 690         newf = dup_fd(oldf, &error);
 691         if (!newf)
 692                 goto out;
 693
 694         tsk->files = newf;
 695         error = 0;
 696 out:
 697         return error;
 698 }
 699
 700 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 701 {
 702 #ifdef CONFIG_BLOCK
 703         struct io_context *ioc = current->io_context;
 704
 705         if (!ioc)
 706                 return 0;
 707         /*
 708          * Share io context with parent, if CLONE_IO is set
 709          */
 710         if (clone_flags & CLONE_IO) {
 711                 tsk->io_context = ioc_task_link(ioc);
 712                 if (unlikely(!tsk->io_context))
 713                         return -ENOMEM;
 714         } else if (ioprio_valid(ioc->ioprio)) {
 715                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 716                 if (unlikely(!tsk->io_context))
 717                         return -ENOMEM;
 718
 719                 tsk->io_context->ioprio = ioc->ioprio;
 720         }
 721 #endif
 722         return 0;
 723 }
 724
 725 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 726 {
 727         struct sighand_struct *sig;
 728
 729         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 730                 atomic_inc(&current->sighand->count);
 731                 return 0;
 732         }
 733         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 734         rcu_assign_pointer(tsk->sighand, sig);
 735         if (!sig)
 736                 return -ENOMEM;
 737         atomic_set(&sig->count, 1);
 738         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 739         return 0;
 740 }
 741
 742 void __cleanup_sighand(struct sighand_struct *sighand)
 743 {
 744         if (atomic_dec_and_test(&sighand->count))
 745                 kmem_cache_free(sighand_cachep, sighand);
 746 }
 747
 748 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 749 {
 750         struct signal_struct *sig;
 751         int ret;
 752
 753         if (clone_flags & CLONE_THREAD) {
 754                 atomic_inc(&current->signal->count);
 755                 atomic_inc(&current->signal->live);
 756                 return 0;
 757         }
 758         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 759         tsk->signal = sig;
 760         if (!sig)
 761                 return -ENOMEM;
 762
 763         ret = copy_thread_group_keys(tsk);
 764         if (ret < 0) {
 765                 kmem_cache_free(signal_cachep, sig);
 766                 return ret;
 767         }
 768
 769         atomic_set(&sig->count, 1);
 770         atomic_set(&sig->live, 1);
 771         init_waitqueue_head(&sig->wait_chldexit);
 772         sig->flags = 0;
 773         sig->group_exit_code = 0;
 774         sig->group_exit_task = NULL;
 775         sig->group_stop_count = 0;
 776         sig->curr_target = tsk;
 777         init_sigpending(&sig->shared_pending);
 778         INIT_LIST_HEAD(&sig->posix_timers);
 779
 780         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 781         sig->it_real_incr.tv64 = 0;
 782         sig->real_timer.function = it_real_fn;
 783
 784         sig->it_virt_expires = cputime_zero;
 785         sig->it_virt_incr = cputime_zero;
 786         sig->it_prof_expires = cputime_zero;
 787         sig->it_prof_incr = cputime_zero;
 788
 789         sig->leader = 0;        /* session leadership doesn't inherit */
 790         sig->tty_old_pgrp = NULL;
 791
 792         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 793         sig->gtime = cputime_zero;
 794         sig->cgtime = cputime_zero;
 795         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 796         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 797         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 798         sig->sum_sched_runtime = 0;
 799         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 800         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 801         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 802         taskstats_tgid_init(sig);
 803
 804         task_lock(current->group_leader);
 805         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 806         task_unlock(current->group_leader);
 807
 808         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 809                 /*
 810                  * New sole thread in the process gets an expiry time
 811                  * of the whole CPU time limit.
 812                  */
 813                 tsk->it_prof_expires =
 814                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 815         }
 816         acct_init_pacct(&sig->pacct);
 817
 818         tty_audit_fork(sig);
 819
 820         return 0;
 821 }
 822
 823 void __cleanup_signal(struct signal_struct *sig)
 824 {
 825         exit_thread_group_keys(sig);
 826         kmem_cache_free(signal_cachep, sig);
 827 }
 828
 829 static void cleanup_signal(struct task_struct *tsk)
 830 {
 831         struct signal_struct *sig = tsk->signal;
 832
 833         atomic_dec(&sig->live);
 834
 835         if (atomic_dec_and_test(&sig->count))
 836                 __cleanup_signal(sig);
 837 }
 838
 839 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 840 {
 841         unsigned long new_flags = p->flags;
 842
 843         new_flags &= ~PF_SUPERPRIV;
 844         new_flags |= PF_FORKNOEXEC;
 845         if (!(clone_flags & CLONE_PTRACE))
 846                 p->ptrace = 0;
 847         p->flags = new_flags;
 848         clear_freeze_flag(p);
 849 }
 850
 851 asmlinkage long sys_set_tid_address(int __user *tidptr)
 852 {
 853         current->clear_child_tid = tidptr;
 854
 855         return task_pid_vnr(current);
 856 }
 857
 858 static void rt_mutex_init_task(struct task_struct *p)
 859 {
 860         spin_lock_init(&p->pi_lock);
 861 #ifdef CONFIG_RT_MUTEXES
 862         plist_head_init(&p->pi_waiters, &p->pi_lock);
 863         p->pi_blocked_on = NULL;
 864 #endif
 865 }
 866
 867 #ifdef CONFIG_MM_OWNER
 868 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 869 {
 870         mm->owner = p;
 871 }
 872 #endif /* CONFIG_MM_OWNER */
 873
 874 /*
 875  * This creates a new process as a copy of the old one,
 876  * but does not actually start it yet.
 877  *
 878  * It copies the registers, and all the appropriate
 879  * parts of the process environment (as per the clone
 880  * flags). The actual kick-off is left to the caller.
 881  */
 882 static struct task_struct *copy_process(unsigned long clone_flags,
 883                                         unsigned long stack_start,
 884                                         struct pt_regs *regs,
 885                                         unsigned long stack_size,
 886                                         int __user *child_tidptr,
 887                                         struct pid *pid)
 888 {
 889         int retval;
 890         struct task_struct *p;
 891         int cgroup_callbacks_done = 0;
 892
 893         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 894                 return ERR_PTR(-EINVAL);
 895
 896         /*
 897          * Thread groups must share signals as well, and detached threads
 898          * can only be started up within the thread group.
 899          */
 900         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 901                 return ERR_PTR(-EINVAL);
 902
 903         /*
 904          * Shared signal handlers imply shared VM. By way of the above,
 905          * thread groups also imply shared VM. Blocking this case allows
 906          * for various simplifications in other code.
 907          */
 908         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 909                 return ERR_PTR(-EINVAL);
 910
 911         retval = security_task_create(clone_flags);
 912         if (retval)
 913                 goto fork_out;
 914
 915         retval = -ENOMEM;
 916         p = dup_task_struct(current);
 917         if (!p)
 918                 goto fork_out;
 919
 920         rt_mutex_init_task(p);
 921
 922 #ifdef CONFIG_PROVE_LOCKING
 923         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 924         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 925 #endif
 926         retval = -EAGAIN;
 927         if (atomic_read(&p->user->processes) >=
 928                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 929                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 930                     p->user != current->nsproxy->user_ns->root_user)
 931                         goto bad_fork_free;
 932         }
 933
 934         atomic_inc(&p->user->__count);
 935         atomic_inc(&p->user->processes);
 936         get_group_info(p->group_info);
 937
 938         /*
 939          * If multiple threads are within copy_process(), then this check
 940          * triggers too late. This doesn't hurt, the check is only there
 941          * to stop root fork bombs.
 942          */
 943         if (nr_threads >= max_threads)
 944                 goto bad_fork_cleanup_count;
 945
 946         if (!try_module_get(task_thread_info(p)->exec_domain->module))
 947                 goto bad_fork_cleanup_count;
 948
 949         if (p->binfmt && !try_module_get(p->binfmt->module))
 950                 goto bad_fork_cleanup_put_domain;
 951
 952         p->did_exec = 0;
 953         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
 954         copy_flags(clone_flags, p);
 955         INIT_LIST_HEAD(&p->children);
 956         INIT_LIST_HEAD(&p->sibling);
 957 #ifdef CONFIG_PREEMPT_RCU
 958         p->rcu_read_lock_nesting = 0;
 959         p->rcu_flipctr_idx = 0;
 960 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 961         p->vfork_done = NULL;
 962         spin_lock_init(&p->alloc_lock);
 963
 964         clear_tsk_thread_flag(p, TIF_SIGPENDING);
 965         init_sigpending(&p->pending);
 966
 967         p->utime = cputime_zero;
 968         p->stime = cputime_zero;
 969         p->gtime = cputime_zero;
 970         p->utimescaled = cputime_zero;
 971         p->stimescaled = cputime_zero;
 972         p->prev_utime = cputime_zero;
 973         p->prev_stime = cputime_zero;
 974
 975 #ifdef CONFIG_DETECT_SOFTLOCKUP
 976         p->last_switch_count = 0;
 977         p->last_switch_timestamp = 0;
 978 #endif
 979
 980 #ifdef CONFIG_TASK_XACCT
 981         p->rchar = 0;           /* I/O counter: bytes read */
 982         p->wchar = 0;           /* I/O counter: bytes written */
 983         p->syscr = 0;           /* I/O counter: read syscalls */
 984         p->syscw = 0;           /* I/O counter: write syscalls */
 985 #endif
 986         task_io_accounting_init(p);
 987         acct_clear_integrals(p);
 988
 989         p->it_virt_expires = cputime_zero;
 990         p->it_prof_expires = cputime_zero;
 991         p->it_sched_expires = 0;
 992         INIT_LIST_HEAD(&p->cpu_timers[0]);
 993         INIT_LIST_HEAD(&p->cpu_timers[1]);
 994         INIT_LIST_HEAD(&p->cpu_timers[2]);
 995
 996         p->lock_depth = -1;             /* -1 = no lock */
 997         do_posix_clock_monotonic_gettime(&p->start_time);
 998         p->real_start_time = p->start_time;
 999         monotonic_to_bootbased(&p->real_start_time);
1000 #ifdef CONFIG_SECURITY
1001         p->security = NULL;
1002 #endif
1003         p->cap_bset = current->cap_bset;
1004         p->io_context = NULL;
1005         p->audit_context = NULL;
1006         cgroup_fork(p);
1007 #ifdef CONFIG_NUMA
1008         p->mempolicy = mpol_dup(p->mempolicy);
1009         if (IS_ERR(p->mempolicy)) {
1010                 retval = PTR_ERR(p->mempolicy);
1011                 p->mempolicy = NULL;
1012                 goto bad_fork_cleanup_cgroup;
1013         }
1014         mpol_fix_fork_child_flag(p);
1015 #endif
1016 #ifdef CONFIG_TRACE_IRQFLAGS
1017         p->irq_events = 0;
1018 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1019         p->hardirqs_enabled = 1;
1020 #else
1021         p->hardirqs_enabled = 0;
1022 #endif
1023         p->hardirq_enable_ip = 0;
1024         p->hardirq_enable_event = 0;
1025         p->hardirq_disable_ip = _THIS_IP_;
1026         p->hardirq_disable_event = 0;
1027         p->softirqs_enabled = 1;
1028         p->softirq_enable_ip = _THIS_IP_;
1029         p->softirq_enable_event = 0;
1030         p->softirq_disable_ip = 0;
1031         p->softirq_disable_event = 0;
1032         p->hardirq_context = 0;
1033         p->softirq_context = 0;
1034 #endif
1035 #ifdef CONFIG_LOCKDEP
1036         p->lockdep_depth = 0; /* no locks held yet */
1037         p->curr_chain_key = 0;
1038         p->lockdep_recursion = 0;
1039 #endif
1040
1041 #ifdef CONFIG_DEBUG_MUTEXES
1042         p->blocked_on = NULL; /* not blocked yet */
1043 #endif
1044
1045         /* Perform scheduler related setup. Assign this task to a CPU. */
1046         sched_fork(p, clone_flags);
1047
1048         if ((retval = security_task_alloc(p)))
1049                 goto bad_fork_cleanup_policy;
1050         if ((retval = audit_alloc(p)))
1051                 goto bad_fork_cleanup_security;
1052         /* copy all the process information */
1053         if ((retval = copy_semundo(clone_flags, p)))
1054                 goto bad_fork_cleanup_audit;
1055         if ((retval = copy_files(clone_flags, p)))
1056                 goto bad_fork_cleanup_semundo;
1057         if ((retval = copy_fs(clone_flags, p)))
1058                 goto bad_fork_cleanup_files;
1059         if ((retval = copy_sighand(clone_flags, p)))
1060                 goto bad_fork_cleanup_fs;
1061         if ((retval = copy_signal(clone_flags, p)))
1062                 goto bad_fork_cleanup_sighand;
1063         if ((retval = copy_mm(clone_flags, p)))
1064                 goto bad_fork_cleanup_signal;
1065         if ((retval = copy_keys(clone_flags, p)))
1066                 goto bad_fork_cleanup_mm;
1067         if ((retval = copy_namespaces(clone_flags, p)))
1068                 goto bad_fork_cleanup_keys;
1069         if ((retval = copy_io(clone_flags, p)))
1070                 goto bad_fork_cleanup_namespaces;
1071         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1072         if (retval)
1073                 goto bad_fork_cleanup_io;
1074
1075         if (pid != &init_struct_pid) {
1076                 retval = -ENOMEM;
1077                 pid = alloc_pid(task_active_pid_ns(p));
1078                 if (!pid)
1079                         goto bad_fork_cleanup_io;
1080
1081                 if (clone_flags & CLONE_NEWPID) {
1082                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1083                         if (retval < 0)
1084                                 goto bad_fork_free_pid;
1085                 }
1086         }
1087
1088         p->pid = pid_nr(pid);
1089         p->tgid = p->pid;
1090         if (clone_flags & CLONE_THREAD)
1091                 p->tgid = current->tgid;
1092
1093         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1094         /*
1095          * Clear TID on mm_release()?
1096          */
1097         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1098 #ifdef CONFIG_FUTEX
1099         p->robust_list = NULL;
1100 #ifdef CONFIG_COMPAT
1101         p->compat_robust_list = NULL;
1102 #endif
1103         INIT_LIST_HEAD(&p->pi_state_list);
1104         p->pi_state_cache = NULL;
1105 #endif
1106         /*
1107          * sigaltstack should be cleared when sharing the same VM
1108          */
1109         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1110                 p->sas_ss_sp = p->sas_ss_size = 0;
1111
1112         /*
1113          * Syscall tracing should be turned off in the child regardless
1114          * of CLONE_PTRACE.
1115          */
1116         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1117 #ifdef TIF_SYSCALL_EMU
1118         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1119 #endif
1120         clear_all_latency_tracing(p);
1121
1122         /* Our parent execution domain becomes current domain
1123            These must match for thread signalling to apply */
1124         p->parent_exec_id = p->self_exec_id;
1125
1126         /* ok, now we should be set up.. */
1127         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1128         p->pdeath_signal = 0;
1129         p->exit_state = 0;
1130
1131         /*
1132          * Ok, make it visible to the rest of the system.
1133          * We dont wake it up yet.
1134          */
1135         p->group_leader = p;
1136         INIT_LIST_HEAD(&p->thread_group);
1137         INIT_LIST_HEAD(&p->ptrace_entry);
1138         INIT_LIST_HEAD(&p->ptraced);
1139
1140         /* Now that the task is set up, run cgroup callbacks if
1141          * necessary. We need to run them before the task is visible
1142          * on the tasklist. */
1143         cgroup_fork_callbacks(p);
1144         cgroup_callbacks_done = 1;
1145
1146         /* Need tasklist lock for parent etc handling! */
1147         write_lock_irq(&tasklist_lock);
1148
1149         /*
1150          * The task hasn't been attached yet, so its cpus_allowed mask will
1151          * not be changed, nor will its assigned CPU.
1152          *
1153          * The cpus_allowed mask of the parent may have changed after it was
1154          * copied first time - so re-copy it here, then check the child's CPU
1155          * to ensure it is on a valid CPU (and if not, just force it back to
1156          * parent's CPU). This avoids alot of nasty races.
1157          */
1158         p->cpus_allowed = current->cpus_allowed;
1159         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1160         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1161                         !cpu_online(task_cpu(p))))
1162                 set_task_cpu(p, smp_processor_id());
1163
1164         /* CLONE_PARENT re-uses the old parent */
1165         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1166                 p->real_parent = current->real_parent;
1167         else
1168                 p->real_parent = current;
1169         p->parent = p->real_parent;
1170
1171         spin_lock(&current->sighand->siglock);
1172
1173         /*
1174          * Process group and session signals need to be delivered to just the
1175          * parent before the fork or both the parent and the child after the
1176          * fork. Restart if a signal comes in before we add the new process to
1177          * it's process group.
1178          * A fatal signal pending means that current will exit, so the new
1179          * thread can't slip out of an OOM kill (or normal SIGKILL).
1180          */
1181         recalc_sigpending();
1182         if (signal_pending(current)) {
1183                 spin_unlock(&current->sighand->siglock);
1184                 write_unlock_irq(&tasklist_lock);
1185                 retval = -ERESTARTNOINTR;
1186                 goto bad_fork_free_pid;
1187         }
1188
1189         if (clone_flags & CLONE_THREAD) {
1190                 p->group_leader = current->group_leader;
1191                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1192
1193                 if (!cputime_eq(current->signal->it_virt_expires,
1194                                 cputime_zero) ||
1195                     !cputime_eq(current->signal->it_prof_expires,
1196                                 cputime_zero) ||
1197                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1198                     !list_empty(&current->signal->cpu_timers[0]) ||
1199                     !list_empty(&current->signal->cpu_timers[1]) ||
1200                     !list_empty(&current->signal->cpu_timers[2])) {
1201                         /*
1202                          * Have child wake up on its first tick to check
1203                          * for process CPU timers.
1204                          */
1205                         p->it_prof_expires = jiffies_to_cputime(1);
1206                 }
1207         }
1208
1209         if (likely(p->pid)) {
1210                 list_add_tail(&p->sibling, &p->real_parent->children);
1211                 if (unlikely(p->ptrace & PT_PTRACED))
1212                         __ptrace_link(p, current->parent);
1213
1214                 if (thread_group_leader(p)) {
1215                         if (clone_flags & CLONE_NEWPID)
1216                                 p->nsproxy->pid_ns->child_reaper = p;
1217
1218                         p->signal->leader_pid = pid;
1219                         p->signal->tty = current->signal->tty;
1220                         set_task_pgrp(p, task_pgrp_nr(current));
1221                         set_task_session(p, task_session_nr(current));
1222                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1223                         attach_pid(p, PIDTYPE_SID, task_session(current));
1224                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1225                         __get_cpu_var(process_counts)++;
1226                 }
1227                 attach_pid(p, PIDTYPE_PID, pid);
1228                 nr_threads++;
1229         }
1230
1231         total_forks++;
1232         spin_unlock(&current->sighand->siglock);
1233         write_unlock_irq(&tasklist_lock);
1234         proc_fork_connector(p);
1235         cgroup_post_fork(p);
1236         return p;
1237
1238 bad_fork_free_pid:
1239         if (pid != &init_struct_pid)
1240                 free_pid(pid);
1241 bad_fork_cleanup_io:
1242         put_io_context(p->io_context);
1243 bad_fork_cleanup_namespaces:
1244         exit_task_namespaces(p);
1245 bad_fork_cleanup_keys:
1246         exit_keys(p);
1247 bad_fork_cleanup_mm:
1248         if (p->mm)
1249                 mmput(p->mm);
1250 bad_fork_cleanup_signal:
1251         cleanup_signal(p);
1252 bad_fork_cleanup_sighand:
1253         __cleanup_sighand(p->sighand);
1254 bad_fork_cleanup_fs:
1255         exit_fs(p); /* blocking */
1256 bad_fork_cleanup_files:
1257         exit_files(p); /* blocking */
1258 bad_fork_cleanup_semundo:
1259         exit_sem(p);
1260 bad_fork_cleanup_audit:
1261         audit_free(p);
1262 bad_fork_cleanup_security:
1263         security_task_free(p);
1264 bad_fork_cleanup_policy:
1265 #ifdef CONFIG_NUMA
1266         mpol_put(p->mempolicy);
1267 bad_fork_cleanup_cgroup:
1268 #endif
1269         cgroup_exit(p, cgroup_callbacks_done);
1270         delayacct_tsk_free(p);
1271         if (p->binfmt)
1272                 module_put(p->binfmt->module);
1273 bad_fork_cleanup_put_domain:
1274         module_put(task_thread_info(p)->exec_domain->module);
1275 bad_fork_cleanup_count:
1276         put_group_info(p->group_info);
1277         atomic_dec(&p->user->processes);
1278         free_uid(p->user);
1279 bad_fork_free:
1280         free_task(p);
1281 fork_out:
1282         return ERR_PTR(retval);
1283 }
1284
1285 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1286 {
1287         memset(regs, 0, sizeof(struct pt_regs));
1288         return regs;
1289 }
1290
1291 struct task_struct * __cpuinit fork_idle(int cpu)
1292 {
1293         struct task_struct *task;
1294         struct pt_regs regs;
1295
1296         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1297                                 &init_struct_pid);
1298         if (!IS_ERR(task))
1299                 init_idle(task, cpu);
1300
1301         return task;
1302 }
1303
1304 static int fork_traceflag(unsigned clone_flags)
1305 {
1306         if (clone_flags & CLONE_UNTRACED)
1307                 return 0;
1308         else if (clone_flags & CLONE_VFORK) {
1309                 if (current->ptrace & PT_TRACE_VFORK)
1310                         return PTRACE_EVENT_VFORK;
1311         } else if ((clone_flags & CSIGNAL) != SIGCHLD) {
1312                 if (current->ptrace & PT_TRACE_CLONE)
1313                         return PTRACE_EVENT_CLONE;
1314         } else if (current->ptrace & PT_TRACE_FORK)
1315                 return PTRACE_EVENT_FORK;
1316
1317         return 0;
1318 }
1319
1320 /*
1321  *  Ok, this is the main fork-routine.
1322  *
1323  * It copies the process, and if successful kick-starts
1324  * it and waits for it to finish using the VM if required.
1325  */
1326 long do_fork(unsigned long clone_flags,
1327               unsigned long stack_start,
1328               struct pt_regs *regs,
1329               unsigned long stack_size,
1330               int __user *parent_tidptr,
1331               int __user *child_tidptr)
1332 {
1333         struct task_struct *p;
1334         int trace = 0;
1335         long nr;
1336
1337         /*
1338          * We hope to recycle these flags after 2.6.26
1339          */
1340         if (unlikely(clone_flags & CLONE_STOPPED)) {
1341                 static int __read_mostly count = 100;
1342
1343                 if (count > 0 && printk_ratelimit()) {
1344                         char comm[TASK_COMM_LEN];
1345
1346                         count--;
1347                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1348                                         "clone flags 0x%lx\n",
1349                                 get_task_comm(comm, current),
1350                                 clone_flags & CLONE_STOPPED);
1351                 }
1352         }
1353
1354         if (unlikely(current->ptrace)) {
1355                 trace = fork_traceflag (clone_flags);
1356                 if (trace)
1357                         clone_flags |= CLONE_PTRACE;
1358         }
1359
1360         p = copy_process(clone_flags, stack_start, regs, stack_size,
1361                         child_tidptr, NULL);
1362         /*
1363          * Do this prior waking up the new thread - the thread pointer
1364          * might get invalid after that point, if the thread exits quickly.
1365          */
1366         if (!IS_ERR(p)) {
1367                 struct completion vfork;
1368
1369                 nr = task_pid_vnr(p);
1370
1371                 if (clone_flags & CLONE_PARENT_SETTID)
1372                         put_user(nr, parent_tidptr);
1373
1374                 if (clone_flags & CLONE_VFORK) {
1375                         p->vfork_done = &vfork;
1376                         init_completion(&vfork);
1377                 }
1378
1379                 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) {
1380                         /*
1381                          * We'll start up with an immediate SIGSTOP.
1382                          */
1383                         sigaddset(&p->pending.signal, SIGSTOP);
1384                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1385                 }
1386
1387                 if (!(clone_flags & CLONE_STOPPED))
1388                         wake_up_new_task(p, clone_flags);
1389                 else
1390                         __set_task_state(p, TASK_STOPPED);
1391
1392                 if (unlikely (trace)) {
1393                         current->ptrace_message = nr;
1394                         ptrace_notify ((trace << 8) | SIGTRAP);
1395                 }
1396
1397                 if (clone_flags & CLONE_VFORK) {
1398                         freezer_do_not_count();
1399                         wait_for_completion(&vfork);
1400                         freezer_count();
1401                         if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) {
1402                                 current->ptrace_message = nr;
1403                                 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP);
1404                         }
1405                 }
1406         } else {
1407                 nr = PTR_ERR(p);
1408         }
1409         return nr;
1410 }
1411
1412 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1413 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1414 #endif
1415
1416 static void sighand_ctor(struct kmem_cache *cachep, void *data)
1417 {
1418         struct sighand_struct *sighand = data;
1419
1420         spin_lock_init(&sighand->siglock);
1421         init_waitqueue_head(&sighand->signalfd_wqh);
1422 }
1423
1424 void __init proc_caches_init(void)
1425 {
1426         sighand_cachep = kmem_cache_create("sighand_cache",
1427                         sizeof(struct sighand_struct), 0,
1428                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1429                         sighand_ctor);
1430         signal_cachep = kmem_cache_create("signal_cache",
1431                         sizeof(struct signal_struct), 0,
1432                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1433         files_cachep = kmem_cache_create("files_cache",
1434                         sizeof(struct files_struct), 0,
1435                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1436         fs_cachep = kmem_cache_create("fs_cache",
1437                         sizeof(struct fs_struct), 0,
1438                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1439         vm_area_cachep = kmem_cache_create("vm_area_struct",
1440                         sizeof(struct vm_area_struct), 0,
1441                         SLAB_PANIC, NULL);
1442         mm_cachep = kmem_cache_create("mm_struct",
1443                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1444                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1445 }
1446
1447 /*
1448  * Check constraints on flags passed to the unshare system call and
1449  * force unsharing of additional process context as appropriate.
1450  */
1451 static void check_unshare_flags(unsigned long *flags_ptr)
1452 {
1453         /*
1454          * If unsharing a thread from a thread group, must also
1455          * unshare vm.
1456          */
1457         if (*flags_ptr & CLONE_THREAD)
1458                 *flags_ptr |= CLONE_VM;
1459
1460         /*
1461          * If unsharing vm, must also unshare signal handlers.
1462          */
1463         if (*flags_ptr & CLONE_VM)
1464                 *flags_ptr |= CLONE_SIGHAND;
1465
1466         /*
1467          * If unsharing signal handlers and the task was created
1468          * using CLONE_THREAD, then must unshare the thread
1469          */
1470         if ((*flags_ptr & CLONE_SIGHAND) &&
1471             (atomic_read(&current->signal->count) > 1))
1472                 *flags_ptr |= CLONE_THREAD;
1473
1474         /*
1475          * If unsharing namespace, must also unshare filesystem information.
1476          */
1477         if (*flags_ptr & CLONE_NEWNS)
1478                 *flags_ptr |= CLONE_FS;
1479 }
1480
1481 /*
1482  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1483  */
1484 static int unshare_thread(unsigned long unshare_flags)
1485 {
1486         if (unshare_flags & CLONE_THREAD)
1487                 return -EINVAL;
1488
1489         return 0;
1490 }
1491
1492 /*
1493  * Unshare the filesystem structure if it is being shared
1494  */
1495 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1496 {
1497         struct fs_struct *fs = current->fs;
1498
1499         if ((unshare_flags & CLONE_FS) &&
1500             (fs && atomic_read(&fs->count) > 1)) {
1501                 *new_fsp = __copy_fs_struct(current->fs);
1502                 if (!*new_fsp)
1503                         return -ENOMEM;
1504         }
1505
1506         return 0;
1507 }
1508
1509 /*
1510  * Unsharing of sighand is not supported yet
1511  */
1512 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1513 {
1514         struct sighand_struct *sigh = current->sighand;
1515
1516         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1517                 return -EINVAL;
1518         else
1519                 return 0;
1520 }
1521
1522 /*
1523  * Unshare vm if it is being shared
1524  */
1525 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1526 {
1527         struct mm_struct *mm = current->mm;
1528
1529         if ((unshare_flags & CLONE_VM) &&
1530             (mm && atomic_read(&mm->mm_users) > 1)) {
1531                 return -EINVAL;
1532         }
1533
1534         return 0;
1535 }
1536
1537 /*
1538  * Unshare file descriptor table if it is being shared
1539  */
1540 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1541 {
1542         struct files_struct *fd = current->files;
1543         int error = 0;
1544
1545         if ((unshare_flags & CLONE_FILES) &&
1546             (fd && atomic_read(&fd->count) > 1)) {
1547                 *new_fdp = dup_fd(fd, &error);
1548                 if (!*new_fdp)
1549                         return error;
1550         }
1551
1552         return 0;
1553 }
1554
1555 /*
1556  * unshare allows a process to 'unshare' part of the process
1557  * context which was originally shared using clone.  copy_*
1558  * functions used by do_fork() cannot be used here directly
1559  * because they modify an inactive task_struct that is being
1560  * constructed. Here we are modifying the current, active,
1561  * task_struct.
1562  */
1563 asmlinkage long sys_unshare(unsigned long unshare_flags)
1564 {
1565         int err = 0;
1566         struct fs_struct *fs, *new_fs = NULL;
1567         struct sighand_struct *new_sigh = NULL;
1568         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1569         struct files_struct *fd, *new_fd = NULL;
1570         struct nsproxy *new_nsproxy = NULL;
1571         int do_sysvsem = 0;
1572
1573         check_unshare_flags(&unshare_flags);
1574
1575         /* Return -EINVAL for all unsupported flags */
1576         err = -EINVAL;
1577         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1578                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1579                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1580                                 CLONE_NEWNET))
1581                 goto bad_unshare_out;
1582
1583         /*
1584          * CLONE_NEWIPC must also detach from the undolist: after switching
1585          * to a new ipc namespace, the semaphore arrays from the old
1586          * namespace are unreachable.
1587          */
1588         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1589                 do_sysvsem = 1;
1590         if ((err = unshare_thread(unshare_flags)))
1591                 goto bad_unshare_out;
1592         if ((err = unshare_fs(unshare_flags, &new_fs)))
1593                 goto bad_unshare_cleanup_thread;
1594         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1595                 goto bad_unshare_cleanup_fs;
1596         if ((err = unshare_vm(unshare_flags, &new_mm)))
1597                 goto bad_unshare_cleanup_sigh;
1598         if ((err = unshare_fd(unshare_flags, &new_fd)))
1599                 goto bad_unshare_cleanup_vm;
1600         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1601                         new_fs)))
1602                 goto bad_unshare_cleanup_fd;
1603
1604         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1605                 if (do_sysvsem) {
1606                         /*
1607                          * CLONE_SYSVSEM is equivalent to sys_exit().
1608                          */
1609                         exit_sem(current);
1610                 }
1611
1612                 if (new_nsproxy) {
1613                         switch_task_namespaces(current, new_nsproxy);
1614                         new_nsproxy = NULL;
1615                 }
1616
1617                 task_lock(current);
1618
1619                 if (new_fs) {
1620                         fs = current->fs;
1621                         current->fs = new_fs;
1622                         new_fs = fs;
1623                 }
1624
1625                 if (new_mm) {
1626                         mm = current->mm;
1627                         active_mm = current->active_mm;
1628                         current->mm = new_mm;
1629                         current->active_mm = new_mm;
1630                         activate_mm(active_mm, new_mm);
1631                         new_mm = mm;
1632                 }
1633
1634                 if (new_fd) {
1635                         fd = current->files;
1636                         current->files = new_fd;
1637                         new_fd = fd;
1638                 }
1639
1640                 task_unlock(current);
1641         }
1642
1643         if (new_nsproxy)
1644                 put_nsproxy(new_nsproxy);
1645
1646 bad_unshare_cleanup_fd:
1647         if (new_fd)
1648                 put_files_struct(new_fd);
1649
1650 bad_unshare_cleanup_vm:
1651         if (new_mm)
1652                 mmput(new_mm);
1653
1654 bad_unshare_cleanup_sigh:
1655         if (new_sigh)
1656                 if (atomic_dec_and_test(&new_sigh->count))
1657                         kmem_cache_free(sighand_cachep, new_sigh);
1658
1659 bad_unshare_cleanup_fs:
1660         if (new_fs)
1661                 put_fs_struct(new_fs);
1662
1663 bad_unshare_cleanup_thread:
1664 bad_unshare_out:
1665         return err;
1666 }
1667
1668 /*
1669  *      Helper to unshare the files of the current task.
1670  *      We don't want to expose copy_files internals to
1671  *      the exec layer of the kernel.
1672  */
1673
1674 int unshare_files(struct files_struct **displaced)
1675 {
1676         struct task_struct *task = current;
1677         struct files_struct *copy = NULL;
1678         int error;
1679
1680         error = unshare_fd(CLONE_FILES, &copy);
1681         if (error || !copy) {
1682                 *displaced = NULL;
1683                 return error;
1684         }
1685         *displaced = task->files;
1686         task_lock(task);
1687         task->files = copy;
1688         task_unlock(task);
1689         return 0;
1690 }