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/task_io_accounting_ops.h>
  44 #include <linux/rcupdate.h>
  45 #include <linux/ptrace.h>
  46 #include <linux/mount.h>
  47 #include <linux/audit.h>
  48 #include <linux/memcontrol.h>
  49 #include <linux/profile.h>
  50 #include <linux/rmap.h>
  51 #include <linux/acct.h>
  52 #include <linux/tsacct_kern.h>
  53 #include <linux/cn_proc.h>
  54 #include <linux/freezer.h>
  55 #include <linux/delayacct.h>
  56 #include <linux/taskstats_kern.h>
  57 #include <linux/random.h>
  58 #include <linux/tty.h>
  59 #include <linux/proc_fs.h>
  60 #include <linux/blkdev.h>
  61
  62 #include <asm/pgtable.h>
  63 #include <asm/pgalloc.h>
  64 #include <asm/uaccess.h>
  65 #include <asm/mmu_context.h>
  66 #include <asm/cacheflush.h>
  67 #include <asm/tlbflush.h>
  68
  69 /*
  70  * Protected counters by write_lock_irq(&tasklist_lock)
  71  */
  72 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  73 int nr_threads;                 /* The idle threads do not count.. */
  74
  75 int max_threads;                /* tunable limit on nr_threads */
  76
  77 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  78
  79 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  80
  81 int nr_processes(void)
  82 {
  83         int cpu;
  84         int total = 0;
  85
  86         for_each_online_cpu(cpu)
  87                 total += per_cpu(process_counts, cpu);
  88
  89         return total;
  90 }
  91
  92 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  93 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  94 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  95 static struct kmem_cache *task_struct_cachep;
  96 #endif
  97
  98 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
  99 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 100 {
 101 #ifdef CONFIG_DEBUG_STACK_USAGE
 102         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 103 #else
 104         gfp_t mask = GFP_KERNEL;
 105 #endif
 106         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 107 }
 108
 109 static inline void free_thread_info(struct thread_info *ti)
 110 {
 111         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 112 }
 113 #endif
 114
 115 /* SLAB cache for signal_struct structures (tsk->signal) */
 116 static struct kmem_cache *signal_cachep;
 117
 118 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 119 struct kmem_cache *sighand_cachep;
 120
 121 /* SLAB cache for files_struct structures (tsk->files) */
 122 struct kmem_cache *files_cachep;
 123
 124 /* SLAB cache for fs_struct structures (tsk->fs) */
 125 struct kmem_cache *fs_cachep;
 126
 127 /* SLAB cache for vm_area_struct structures */
 128 struct kmem_cache *vm_area_cachep;
 129
 130 /* SLAB cache for mm_struct structures (tsk->mm) */
 131 static struct kmem_cache *mm_cachep;
 132
 133 void free_task(struct task_struct *tsk)
 134 {
 135         prop_local_destroy_single(&tsk->dirties);
 136         free_thread_info(tsk->stack);
 137         rt_mutex_debug_task_free(tsk);
 138         free_task_struct(tsk);
 139 }
 140 EXPORT_SYMBOL(free_task);
 141
 142 void __put_task_struct(struct task_struct *tsk)
 143 {
 144         WARN_ON(!tsk->exit_state);
 145         WARN_ON(atomic_read(&tsk->usage));
 146         WARN_ON(tsk == current);
 147
 148         security_task_free(tsk);
 149         free_uid(tsk->user);
 150         put_group_info(tsk->group_info);
 151         delayacct_tsk_free(tsk);
 152
 153         if (!profile_handoff_task(tsk))
 154                 free_task(tsk);
 155 }
 156
 157 /*
 158  * macro override instead of weak attribute alias, to workaround
 159  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 160  */
 161 #ifndef arch_task_cache_init
 162 #define arch_task_cache_init()
 163 #endif
 164
 165 void __init fork_init(unsigned long mempages)
 166 {
 167 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 168 #ifndef ARCH_MIN_TASKALIGN
 169 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 170 #endif
 171         /* create a slab on which task_structs can be allocated */
 172         task_struct_cachep =
 173                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 174                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
 175 #endif
 176
 177         /* do the arch specific task caches init */
 178         arch_task_cache_init();
 179
 180         /*
 181          * The default maximum number of threads is set to a safe
 182          * value: the thread structures can take up at most half
 183          * of memory.
 184          */
 185         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 186
 187         /*
 188          * we need to allow at least 20 threads to boot a system
 189          */
 190         if(max_threads < 20)
 191                 max_threads = 20;
 192
 193         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 194         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 195         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 196                 init_task.signal->rlim[RLIMIT_NPROC];
 197 }
 198
 199 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 200                                                struct task_struct *src)
 201 {
 202         *dst = *src;
 203         return 0;
 204 }
 205
 206 static struct task_struct *dup_task_struct(struct task_struct *orig)
 207 {
 208         struct task_struct *tsk;
 209         struct thread_info *ti;
 210         int err;
 211
 212         prepare_to_copy(orig);
 213
 214         tsk = alloc_task_struct();
 215         if (!tsk)
 216                 return NULL;
 217
 218         ti = alloc_thread_info(tsk);
 219         if (!ti) {
 220                 free_task_struct(tsk);
 221                 return NULL;
 222         }
 223
 224         err = arch_dup_task_struct(tsk, orig);
 225         if (err)
 226                 goto out;
 227
 228         tsk->stack = ti;
 229
 230         err = prop_local_init_single(&tsk->dirties);
 231         if (err)
 232                 goto out;
 233
 234         setup_thread_stack(tsk, orig);
 235
 236 #ifdef CONFIG_CC_STACKPROTECTOR
 237         tsk->stack_canary = get_random_int();
 238 #endif
 239
 240         /* One for us, one for whoever does the "release_task()" (usually parent) */
 241         atomic_set(&tsk->usage,2);
 242         atomic_set(&tsk->fs_excl, 0);
 243 #ifdef CONFIG_BLK_DEV_IO_TRACE
 244         tsk->btrace_seq = 0;
 245 #endif
 246         tsk->splice_pipe = NULL;
 247         return tsk;
 248
 249 out:
 250         free_thread_info(ti);
 251         free_task_struct(tsk);
 252         return NULL;
 253 }
 254
 255 #ifdef CONFIG_MMU
 256 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 257 {
 258         struct vm_area_struct *mpnt, *tmp, **pprev;
 259         struct rb_node **rb_link, *rb_parent;
 260         int retval;
 261         unsigned long charge;
 262         struct mempolicy *pol;
 263
 264         down_write(&oldmm->mmap_sem);
 265         flush_cache_dup_mm(oldmm);
 266         /*
 267          * Not linked in yet - no deadlock potential:
 268          */
 269         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 270
 271         mm->locked_vm = 0;
 272         mm->mmap = NULL;
 273         mm->mmap_cache = NULL;
 274         mm->free_area_cache = oldmm->mmap_base;
 275         mm->cached_hole_size = ~0UL;
 276         mm->map_count = 0;
 277         cpus_clear(mm->cpu_vm_mask);
 278         mm->mm_rb = RB_ROOT;
 279         rb_link = &mm->mm_rb.rb_node;
 280         rb_parent = NULL;
 281         pprev = &mm->mmap;
 282
 283         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 284                 struct file *file;
 285
 286                 if (mpnt->vm_flags & VM_DONTCOPY) {
 287                         long pages = vma_pages(mpnt);
 288                         mm->total_vm -= pages;
 289                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 290                                                                 -pages);
 291                         continue;
 292                 }
 293                 charge = 0;
 294                 if (mpnt->vm_flags & VM_ACCOUNT) {
 295                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 296                         if (security_vm_enough_memory(len))
 297                                 goto fail_nomem;
 298                         charge = len;
 299                 }
 300                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 301                 if (!tmp)
 302                         goto fail_nomem;
 303                 *tmp = *mpnt;
 304                 pol = mpol_dup(vma_policy(mpnt));
 305                 retval = PTR_ERR(pol);
 306                 if (IS_ERR(pol))
 307                         goto fail_nomem_policy;
 308                 vma_set_policy(tmp, pol);
 309                 tmp->vm_flags &= ~VM_LOCKED;
 310                 tmp->vm_mm = mm;
 311                 tmp->vm_next = NULL;
 312                 anon_vma_link(tmp);
 313                 file = tmp->vm_file;
 314                 if (file) {
 315                         struct inode *inode = file->f_path.dentry->d_inode;
 316                         get_file(file);
 317                         if (tmp->vm_flags & VM_DENYWRITE)
 318                                 atomic_dec(&inode->i_writecount);
 319
 320                         /* insert tmp into the share list, just after mpnt */
 321                         spin_lock(&file->f_mapping->i_mmap_lock);
 322                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 323                         flush_dcache_mmap_lock(file->f_mapping);
 324                         vma_prio_tree_add(tmp, mpnt);
 325                         flush_dcache_mmap_unlock(file->f_mapping);
 326                         spin_unlock(&file->f_mapping->i_mmap_lock);
 327                 }
 328
 329                 /*
 330                  * Clear hugetlb-related page reserves for children. This only
 331                  * affects MAP_PRIVATE mappings. Faults generated by the child
 332                  * are not guaranteed to succeed, even if read-only
 333                  */
 334                 if (is_vm_hugetlb_page(tmp))
 335                         reset_vma_resv_huge_pages(tmp);
 336
 337                 /*
 338                  * Link in the new vma and copy the page table entries.
 339                  */
 340                 *pprev = tmp;
 341                 pprev = &tmp->vm_next;
 342
 343                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 344                 rb_link = &tmp->vm_rb.rb_right;
 345                 rb_parent = &tmp->vm_rb;
 346
 347                 mm->map_count++;
 348                 retval = copy_page_range(mm, oldmm, mpnt);
 349
 350                 if (tmp->vm_ops && tmp->vm_ops->open)
 351                         tmp->vm_ops->open(tmp);
 352
 353                 if (retval)
 354                         goto out;
 355         }
 356         /* a new mm has just been created */
 357         arch_dup_mmap(oldmm, mm);
 358         retval = 0;
 359 out:
 360         up_write(&mm->mmap_sem);
 361         flush_tlb_mm(oldmm);
 362         up_write(&oldmm->mmap_sem);
 363         return retval;
 364 fail_nomem_policy:
 365         kmem_cache_free(vm_area_cachep, tmp);
 366 fail_nomem:
 367         retval = -ENOMEM;
 368         vm_unacct_memory(charge);
 369         goto out;
 370 }
 371
 372 static inline int mm_alloc_pgd(struct mm_struct * mm)
 373 {
 374         mm->pgd = pgd_alloc(mm);
 375         if (unlikely(!mm->pgd))
 376                 return -ENOMEM;
 377         return 0;
 378 }
 379
 380 static inline void mm_free_pgd(struct mm_struct * mm)
 381 {
 382         pgd_free(mm, mm->pgd);
 383 }
 384 #else
 385 #define dup_mmap(mm, oldmm)     (0)
 386 #define mm_alloc_pgd(mm)        (0)
 387 #define mm_free_pgd(mm)
 388 #endif /* CONFIG_MMU */
 389
 390 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 391
 392 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 393 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 394
 395 #include <linux/init_task.h>
 396
 397 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 398 {
 399         atomic_set(&mm->mm_users, 1);
 400         atomic_set(&mm->mm_count, 1);
 401         init_rwsem(&mm->mmap_sem);
 402         INIT_LIST_HEAD(&mm->mmlist);
 403         mm->flags = (current->mm) ? current->mm->flags
 404                                   : MMF_DUMP_FILTER_DEFAULT;
 405         mm->core_state = NULL;
 406         mm->nr_ptes = 0;
 407         set_mm_counter(mm, file_rss, 0);
 408         set_mm_counter(mm, anon_rss, 0);
 409         spin_lock_init(&mm->page_table_lock);
 410         rwlock_init(&mm->ioctx_list_lock);
 411         mm->ioctx_list = NULL;
 412         mm->free_area_cache = TASK_UNMAPPED_BASE;
 413         mm->cached_hole_size = ~0UL;
 414         mm_init_owner(mm, p);
 415
 416         if (likely(!mm_alloc_pgd(mm))) {
 417                 mm->def_flags = 0;
 418                 mmu_notifier_mm_init(mm);
 419                 return mm;
 420         }
 421
 422         free_mm(mm);
 423         return NULL;
 424 }
 425
 426 /*
 427  * Allocate and initialize an mm_struct.
 428  */
 429 struct mm_struct * mm_alloc(void)
 430 {
 431         struct mm_struct * mm;
 432
 433         mm = allocate_mm();
 434         if (mm) {
 435                 memset(mm, 0, sizeof(*mm));
 436                 mm = mm_init(mm, current);
 437         }
 438         return mm;
 439 }
 440
 441 /*
 442  * Called when the last reference to the mm
 443  * is dropped: either by a lazy thread or by
 444  * mmput. Free the page directory and the mm.
 445  */
 446 void __mmdrop(struct mm_struct *mm)
 447 {
 448         BUG_ON(mm == &init_mm);
 449         mm_free_pgd(mm);
 450         destroy_context(mm);
 451         mmu_notifier_mm_destroy(mm);
 452         free_mm(mm);
 453 }
 454 EXPORT_SYMBOL_GPL(__mmdrop);
 455
 456 /*
 457  * Decrement the use count and release all resources for an mm.
 458  */
 459 void mmput(struct mm_struct *mm)
 460 {
 461         might_sleep();
 462
 463         if (atomic_dec_and_test(&mm->mm_users)) {
 464                 exit_aio(mm);
 465                 exit_mmap(mm);
 466                 set_mm_exe_file(mm, NULL);
 467                 if (!list_empty(&mm->mmlist)) {
 468                         spin_lock(&mmlist_lock);
 469                         list_del(&mm->mmlist);
 470                         spin_unlock(&mmlist_lock);
 471                 }
 472                 put_swap_token(mm);
 473                 mmdrop(mm);
 474         }
 475 }
 476 EXPORT_SYMBOL_GPL(mmput);
 477
 478 /**
 479  * get_task_mm - acquire a reference to the task's mm
 480  *
 481  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 482  * this kernel workthread has transiently adopted a user mm with use_mm,
 483  * to do its AIO) is not set and if so returns a reference to it, after
 484  * bumping up the use count.  User must release the mm via mmput()
 485  * after use.  Typically used by /proc and ptrace.
 486  */
 487 struct mm_struct *get_task_mm(struct task_struct *task)
 488 {
 489         struct mm_struct *mm;
 490
 491         task_lock(task);
 492         mm = task->mm;
 493         if (mm) {
 494                 if (task->flags & PF_KTHREAD)
 495                         mm = NULL;
 496                 else
 497                         atomic_inc(&mm->mm_users);
 498         }
 499         task_unlock(task);
 500         return mm;
 501 }
 502 EXPORT_SYMBOL_GPL(get_task_mm);
 503
 504 /* Please note the differences between mmput and mm_release.
 505  * mmput is called whenever we stop holding onto a mm_struct,
 506  * error success whatever.
 507  *
 508  * mm_release is called after a mm_struct has been removed
 509  * from the current process.
 510  *
 511  * This difference is important for error handling, when we
 512  * only half set up a mm_struct for a new process and need to restore
 513  * the old one.  Because we mmput the new mm_struct before
 514  * restoring the old one. . .
 515  * Eric Biederman 10 January 1998
 516  */
 517 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 518 {
 519         struct completion *vfork_done = tsk->vfork_done;
 520
 521         /* Get rid of any cached register state */
 522         deactivate_mm(tsk, mm);
 523
 524         /* notify parent sleeping on vfork() */
 525         if (vfork_done) {
 526                 tsk->vfork_done = NULL;
 527                 complete(vfork_done);
 528         }
 529
 530         /*
 531          * If we're exiting normally, clear a user-space tid field if
 532          * requested.  We leave this alone when dying by signal, to leave
 533          * the value intact in a core dump, and to save the unnecessary
 534          * trouble otherwise.  Userland only wants this done for a sys_exit.
 535          */
 536         if (tsk->clear_child_tid
 537             && !(tsk->flags & PF_SIGNALED)
 538             && atomic_read(&mm->mm_users) > 1) {
 539                 u32 __user * tidptr = tsk->clear_child_tid;
 540                 tsk->clear_child_tid = NULL;
 541
 542                 /*
 543                  * We don't check the error code - if userspace has
 544                  * not set up a proper pointer then tough luck.
 545                  */
 546                 put_user(0, tidptr);
 547                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 548         }
 549 }
 550
 551 /*
 552  * Allocate a new mm structure and copy contents from the
 553  * mm structure of the passed in task structure.
 554  */
 555 struct mm_struct *dup_mm(struct task_struct *tsk)
 556 {
 557         struct mm_struct *mm, *oldmm = current->mm;
 558         int err;
 559
 560         if (!oldmm)
 561                 return NULL;
 562
 563         mm = allocate_mm();
 564         if (!mm)
 565                 goto fail_nomem;
 566
 567         memcpy(mm, oldmm, sizeof(*mm));
 568
 569         /* Initializing for Swap token stuff */
 570         mm->token_priority = 0;
 571         mm->last_interval = 0;
 572
 573         if (!mm_init(mm, tsk))
 574                 goto fail_nomem;
 575
 576         if (init_new_context(tsk, mm))
 577                 goto fail_nocontext;
 578
 579         dup_mm_exe_file(oldmm, mm);
 580
 581         err = dup_mmap(mm, oldmm);
 582         if (err)
 583                 goto free_pt;
 584
 585         mm->hiwater_rss = get_mm_rss(mm);
 586         mm->hiwater_vm = mm->total_vm;
 587
 588         return mm;
 589
 590 free_pt:
 591         mmput(mm);
 592
 593 fail_nomem:
 594         return NULL;
 595
 596 fail_nocontext:
 597         /*
 598          * If init_new_context() failed, we cannot use mmput() to free the mm
 599          * because it calls destroy_context()
 600          */
 601         mm_free_pgd(mm);
 602         free_mm(mm);
 603         return NULL;
 604 }
 605
 606 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 607 {
 608         struct mm_struct * mm, *oldmm;
 609         int retval;
 610
 611         tsk->min_flt = tsk->maj_flt = 0;
 612         tsk->nvcsw = tsk->nivcsw = 0;
 613
 614         tsk->mm = NULL;
 615         tsk->active_mm = NULL;
 616
 617         /*
 618          * Are we cloning a kernel thread?
 619          *
 620          * We need to steal a active VM for that..
 621          */
 622         oldmm = current->mm;
 623         if (!oldmm)
 624                 return 0;
 625
 626         if (clone_flags & CLONE_VM) {
 627                 atomic_inc(&oldmm->mm_users);
 628                 mm = oldmm;
 629                 goto good_mm;
 630         }
 631
 632         retval = -ENOMEM;
 633         mm = dup_mm(tsk);
 634         if (!mm)
 635                 goto fail_nomem;
 636
 637 good_mm:
 638         /* Initializing for Swap token stuff */
 639         mm->token_priority = 0;
 640         mm->last_interval = 0;
 641
 642         tsk->mm = mm;
 643         tsk->active_mm = mm;
 644         return 0;
 645
 646 fail_nomem:
 647         return retval;
 648 }
 649
 650 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 651 {
 652         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 653         /* We don't need to lock fs - think why ;-) */
 654         if (fs) {
 655                 atomic_set(&fs->count, 1);
 656                 rwlock_init(&fs->lock);
 657                 fs->umask = old->umask;
 658                 read_lock(&old->lock);
 659                 fs->root = old->root;
 660                 path_get(&old->root);
 661                 fs->pwd = old->pwd;
 662                 path_get(&old->pwd);
 663                 read_unlock(&old->lock);
 664         }
 665         return fs;
 666 }
 667
 668 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 669 {
 670         return __copy_fs_struct(old);
 671 }
 672
 673 EXPORT_SYMBOL_GPL(copy_fs_struct);
 674
 675 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 676 {
 677         if (clone_flags & CLONE_FS) {
 678                 atomic_inc(&current->fs->count);
 679                 return 0;
 680         }
 681         tsk->fs = __copy_fs_struct(current->fs);
 682         if (!tsk->fs)
 683                 return -ENOMEM;
 684         return 0;
 685 }
 686
 687 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 688 {
 689         struct files_struct *oldf, *newf;
 690         int error = 0;
 691
 692         /*
 693          * A background process may not have any files ...
 694          */
 695         oldf = current->files;
 696         if (!oldf)
 697                 goto out;
 698
 699         if (clone_flags & CLONE_FILES) {
 700                 atomic_inc(&oldf->count);
 701                 goto out;
 702         }
 703
 704         newf = dup_fd(oldf, &error);
 705         if (!newf)
 706                 goto out;
 707
 708         tsk->files = newf;
 709         error = 0;
 710 out:
 711         return error;
 712 }
 713
 714 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 715 {
 716 #ifdef CONFIG_BLOCK
 717         struct io_context *ioc = current->io_context;
 718
 719         if (!ioc)
 720                 return 0;
 721         /*
 722          * Share io context with parent, if CLONE_IO is set
 723          */
 724         if (clone_flags & CLONE_IO) {
 725                 tsk->io_context = ioc_task_link(ioc);
 726                 if (unlikely(!tsk->io_context))
 727                         return -ENOMEM;
 728         } else if (ioprio_valid(ioc->ioprio)) {
 729                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 730                 if (unlikely(!tsk->io_context))
 731                         return -ENOMEM;
 732
 733                 tsk->io_context->ioprio = ioc->ioprio;
 734         }
 735 #endif
 736         return 0;
 737 }
 738
 739 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 740 {
 741         struct sighand_struct *sig;
 742
 743         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 744                 atomic_inc(&current->sighand->count);
 745                 return 0;
 746         }
 747         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 748         rcu_assign_pointer(tsk->sighand, sig);
 749         if (!sig)
 750                 return -ENOMEM;
 751         atomic_set(&sig->count, 1);
 752         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 753         return 0;
 754 }
 755
 756 void __cleanup_sighand(struct sighand_struct *sighand)
 757 {
 758         if (atomic_dec_and_test(&sighand->count))
 759                 kmem_cache_free(sighand_cachep, sighand);
 760 }
 761
 762 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 763 {
 764         struct signal_struct *sig;
 765         int ret;
 766
 767         if (clone_flags & CLONE_THREAD) {
 768                 atomic_inc(&current->signal->count);
 769                 atomic_inc(&current->signal->live);
 770                 return 0;
 771         }
 772         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 773         tsk->signal = sig;
 774         if (!sig)
 775                 return -ENOMEM;
 776
 777         ret = copy_thread_group_keys(tsk);
 778         if (ret < 0) {
 779                 kmem_cache_free(signal_cachep, sig);
 780                 return ret;
 781         }
 782
 783         atomic_set(&sig->count, 1);
 784         atomic_set(&sig->live, 1);
 785         init_waitqueue_head(&sig->wait_chldexit);
 786         sig->flags = 0;
 787         sig->group_exit_code = 0;
 788         sig->group_exit_task = NULL;
 789         sig->group_stop_count = 0;
 790         sig->curr_target = tsk;
 791         init_sigpending(&sig->shared_pending);
 792         INIT_LIST_HEAD(&sig->posix_timers);
 793
 794         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 795         sig->it_real_incr.tv64 = 0;
 796         sig->real_timer.function = it_real_fn;
 797
 798         sig->it_virt_expires = cputime_zero;
 799         sig->it_virt_incr = cputime_zero;
 800         sig->it_prof_expires = cputime_zero;
 801         sig->it_prof_incr = cputime_zero;
 802
 803         sig->leader = 0;        /* session leadership doesn't inherit */
 804         sig->tty_old_pgrp = NULL;
 805         sig->tty = NULL;
 806
 807         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 808         sig->gtime = cputime_zero;
 809         sig->cgtime = cputime_zero;
 810         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 811         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 812         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 813         task_io_accounting_init(&sig->ioac);
 814         sig->sum_sched_runtime = 0;
 815         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 816         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 817         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 818         taskstats_tgid_init(sig);
 819
 820         task_lock(current->group_leader);
 821         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 822         task_unlock(current->group_leader);
 823
 824         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 825                 /*
 826                  * New sole thread in the process gets an expiry time
 827                  * of the whole CPU time limit.
 828                  */
 829                 tsk->it_prof_expires =
 830                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 831         }
 832         acct_init_pacct(&sig->pacct);
 833
 834         tty_audit_fork(sig);
 835
 836         return 0;
 837 }
 838
 839 void __cleanup_signal(struct signal_struct *sig)
 840 {
 841         exit_thread_group_keys(sig);
 842         tty_kref_put(sig->tty);
 843         kmem_cache_free(signal_cachep, sig);
 844 }
 845
 846 static void cleanup_signal(struct task_struct *tsk)
 847 {
 848         struct signal_struct *sig = tsk->signal;
 849
 850         atomic_dec(&sig->live);
 851
 852         if (atomic_dec_and_test(&sig->count))
 853                 __cleanup_signal(sig);
 854 }
 855
 856 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 857 {
 858         unsigned long new_flags = p->flags;
 859
 860         new_flags &= ~PF_SUPERPRIV;
 861         new_flags |= PF_FORKNOEXEC;
 862         new_flags |= PF_STARTING;
 863         p->flags = new_flags;
 864         clear_freeze_flag(p);
 865 }
 866
 867 asmlinkage long sys_set_tid_address(int __user *tidptr)
 868 {
 869         current->clear_child_tid = tidptr;
 870
 871         return task_pid_vnr(current);
 872 }
 873
 874 static void rt_mutex_init_task(struct task_struct *p)
 875 {
 876         spin_lock_init(&p->pi_lock);
 877 #ifdef CONFIG_RT_MUTEXES
 878         plist_head_init(&p->pi_waiters, &p->pi_lock);
 879         p->pi_blocked_on = NULL;
 880 #endif
 881 }
 882
 883 #ifdef CONFIG_MM_OWNER
 884 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 885 {
 886         mm->owner = p;
 887 }
 888 #endif /* CONFIG_MM_OWNER */
 889
 890 /*
 891  * This creates a new process as a copy of the old one,
 892  * but does not actually start it yet.
 893  *
 894  * It copies the registers, and all the appropriate
 895  * parts of the process environment (as per the clone
 896  * flags). The actual kick-off is left to the caller.
 897  */
 898 static struct task_struct *copy_process(unsigned long clone_flags,
 899                                         unsigned long stack_start,
 900                                         struct pt_regs *regs,
 901                                         unsigned long stack_size,
 902                                         int __user *child_tidptr,
 903                                         struct pid *pid,
 904                                         int trace)
 905 {
 906         int retval;
 907         struct task_struct *p;
 908         int cgroup_callbacks_done = 0;
 909
 910         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 911                 return ERR_PTR(-EINVAL);
 912
 913         /*
 914          * Thread groups must share signals as well, and detached threads
 915          * can only be started up within the thread group.
 916          */
 917         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 918                 return ERR_PTR(-EINVAL);
 919
 920         /*
 921          * Shared signal handlers imply shared VM. By way of the above,
 922          * thread groups also imply shared VM. Blocking this case allows
 923          * for various simplifications in other code.
 924          */
 925         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 926                 return ERR_PTR(-EINVAL);
 927
 928         retval = security_task_create(clone_flags);
 929         if (retval)
 930                 goto fork_out;
 931
 932         retval = -ENOMEM;
 933         p = dup_task_struct(current);
 934         if (!p)
 935                 goto fork_out;
 936
 937         rt_mutex_init_task(p);
 938
 939 #ifdef CONFIG_PROVE_LOCKING
 940         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 941         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 942 #endif
 943         retval = -EAGAIN;
 944         if (atomic_read(&p->user->processes) >=
 945                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 946                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 947                     p->user != current->nsproxy->user_ns->root_user)
 948                         goto bad_fork_free;
 949         }
 950
 951         atomic_inc(&p->user->__count);
 952         atomic_inc(&p->user->processes);
 953         get_group_info(p->group_info);
 954
 955         /*
 956          * If multiple threads are within copy_process(), then this check
 957          * triggers too late. This doesn't hurt, the check is only there
 958          * to stop root fork bombs.
 959          */
 960         if (nr_threads >= max_threads)
 961                 goto bad_fork_cleanup_count;
 962
 963         if (!try_module_get(task_thread_info(p)->exec_domain->module))
 964                 goto bad_fork_cleanup_count;
 965
 966         if (p->binfmt && !try_module_get(p->binfmt->module))
 967                 goto bad_fork_cleanup_put_domain;
 968
 969         p->did_exec = 0;
 970         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
 971         copy_flags(clone_flags, p);
 972         INIT_LIST_HEAD(&p->children);
 973         INIT_LIST_HEAD(&p->sibling);
 974 #ifdef CONFIG_PREEMPT_RCU
 975         p->rcu_read_lock_nesting = 0;
 976         p->rcu_flipctr_idx = 0;
 977 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 978         p->vfork_done = NULL;
 979         spin_lock_init(&p->alloc_lock);
 980
 981         clear_tsk_thread_flag(p, TIF_SIGPENDING);
 982         init_sigpending(&p->pending);
 983
 984         p->utime = cputime_zero;
 985         p->stime = cputime_zero;
 986         p->gtime = cputime_zero;
 987         p->utimescaled = cputime_zero;
 988         p->stimescaled = cputime_zero;
 989         p->prev_utime = cputime_zero;
 990         p->prev_stime = cputime_zero;
 991
 992 #ifdef CONFIG_DETECT_SOFTLOCKUP
 993         p->last_switch_count = 0;
 994         p->last_switch_timestamp = 0;
 995 #endif
 996
 997         task_io_accounting_init(&p->ioac);
 998         acct_clear_integrals(p);
 999
1000         p->it_virt_expires = cputime_zero;
1001         p->it_prof_expires = cputime_zero;
1002         p->it_sched_expires = 0;
1003         INIT_LIST_HEAD(&p->cpu_timers[0]);
1004         INIT_LIST_HEAD(&p->cpu_timers[1]);
1005         INIT_LIST_HEAD(&p->cpu_timers[2]);
1006
1007         p->lock_depth = -1;             /* -1 = no lock */
1008         do_posix_clock_monotonic_gettime(&p->start_time);
1009         p->real_start_time = p->start_time;
1010         monotonic_to_bootbased(&p->real_start_time);
1011 #ifdef CONFIG_SECURITY
1012         p->security = NULL;
1013 #endif
1014         p->cap_bset = current->cap_bset;
1015         p->io_context = NULL;
1016         p->audit_context = NULL;
1017         cgroup_fork(p);
1018 #ifdef CONFIG_NUMA
1019         p->mempolicy = mpol_dup(p->mempolicy);
1020         if (IS_ERR(p->mempolicy)) {
1021                 retval = PTR_ERR(p->mempolicy);
1022                 p->mempolicy = NULL;
1023                 goto bad_fork_cleanup_cgroup;
1024         }
1025         mpol_fix_fork_child_flag(p);
1026 #endif
1027 #ifdef CONFIG_TRACE_IRQFLAGS
1028         p->irq_events = 0;
1029 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1030         p->hardirqs_enabled = 1;
1031 #else
1032         p->hardirqs_enabled = 0;
1033 #endif
1034         p->hardirq_enable_ip = 0;
1035         p->hardirq_enable_event = 0;
1036         p->hardirq_disable_ip = _THIS_IP_;
1037         p->hardirq_disable_event = 0;
1038         p->softirqs_enabled = 1;
1039         p->softirq_enable_ip = _THIS_IP_;
1040         p->softirq_enable_event = 0;
1041         p->softirq_disable_ip = 0;
1042         p->softirq_disable_event = 0;
1043         p->hardirq_context = 0;
1044         p->softirq_context = 0;
1045 #endif
1046 #ifdef CONFIG_LOCKDEP
1047         p->lockdep_depth = 0; /* no locks held yet */
1048         p->curr_chain_key = 0;
1049         p->lockdep_recursion = 0;
1050 #endif
1051
1052 #ifdef CONFIG_DEBUG_MUTEXES
1053         p->blocked_on = NULL; /* not blocked yet */
1054 #endif
1055
1056         /* Perform scheduler related setup. Assign this task to a CPU. */
1057         sched_fork(p, clone_flags);
1058
1059         if ((retval = security_task_alloc(p)))
1060                 goto bad_fork_cleanup_policy;
1061         if ((retval = audit_alloc(p)))
1062                 goto bad_fork_cleanup_security;
1063         /* copy all the process information */
1064         if ((retval = copy_semundo(clone_flags, p)))
1065                 goto bad_fork_cleanup_audit;
1066         if ((retval = copy_files(clone_flags, p)))
1067                 goto bad_fork_cleanup_semundo;
1068         if ((retval = copy_fs(clone_flags, p)))
1069                 goto bad_fork_cleanup_files;
1070         if ((retval = copy_sighand(clone_flags, p)))
1071                 goto bad_fork_cleanup_fs;
1072         if ((retval = copy_signal(clone_flags, p)))
1073                 goto bad_fork_cleanup_sighand;
1074         if ((retval = copy_mm(clone_flags, p)))
1075                 goto bad_fork_cleanup_signal;
1076         if ((retval = copy_keys(clone_flags, p)))
1077                 goto bad_fork_cleanup_mm;
1078         if ((retval = copy_namespaces(clone_flags, p)))
1079                 goto bad_fork_cleanup_keys;
1080         if ((retval = copy_io(clone_flags, p)))
1081                 goto bad_fork_cleanup_namespaces;
1082         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1083         if (retval)
1084                 goto bad_fork_cleanup_io;
1085
1086         if (pid != &init_struct_pid) {
1087                 retval = -ENOMEM;
1088                 pid = alloc_pid(task_active_pid_ns(p));
1089                 if (!pid)
1090                         goto bad_fork_cleanup_io;
1091
1092                 if (clone_flags & CLONE_NEWPID) {
1093                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1094                         if (retval < 0)
1095                                 goto bad_fork_free_pid;
1096                 }
1097         }
1098
1099         p->pid = pid_nr(pid);
1100         p->tgid = p->pid;
1101         if (clone_flags & CLONE_THREAD)
1102                 p->tgid = current->tgid;
1103
1104         if (current->nsproxy != p->nsproxy) {
1105                 retval = ns_cgroup_clone(p, pid);
1106                 if (retval)
1107                         goto bad_fork_free_pid;
1108         }
1109
1110         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1111         /*
1112          * Clear TID on mm_release()?
1113          */
1114         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1115 #ifdef CONFIG_FUTEX
1116         p->robust_list = NULL;
1117 #ifdef CONFIG_COMPAT
1118         p->compat_robust_list = NULL;
1119 #endif
1120         INIT_LIST_HEAD(&p->pi_state_list);
1121         p->pi_state_cache = NULL;
1122 #endif
1123         /*
1124          * sigaltstack should be cleared when sharing the same VM
1125          */
1126         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1127                 p->sas_ss_sp = p->sas_ss_size = 0;
1128
1129         /*
1130          * Syscall tracing should be turned off in the child regardless
1131          * of CLONE_PTRACE.
1132          */
1133         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1134 #ifdef TIF_SYSCALL_EMU
1135         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1136 #endif
1137         clear_all_latency_tracing(p);
1138
1139         /* Our parent execution domain becomes current domain
1140            These must match for thread signalling to apply */
1141         p->parent_exec_id = p->self_exec_id;
1142
1143         /* ok, now we should be set up.. */
1144         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1145         p->pdeath_signal = 0;
1146         p->exit_state = 0;
1147
1148         /*
1149          * Ok, make it visible to the rest of the system.
1150          * We dont wake it up yet.
1151          */
1152         p->group_leader = p;
1153         INIT_LIST_HEAD(&p->thread_group);
1154
1155         /* Now that the task is set up, run cgroup callbacks if
1156          * necessary. We need to run them before the task is visible
1157          * on the tasklist. */
1158         cgroup_fork_callbacks(p);
1159         cgroup_callbacks_done = 1;
1160
1161         /* Need tasklist lock for parent etc handling! */
1162         write_lock_irq(&tasklist_lock);
1163
1164         /*
1165          * The task hasn't been attached yet, so its cpus_allowed mask will
1166          * not be changed, nor will its assigned CPU.
1167          *
1168          * The cpus_allowed mask of the parent may have changed after it was
1169          * copied first time - so re-copy it here, then check the child's CPU
1170          * to ensure it is on a valid CPU (and if not, just force it back to
1171          * parent's CPU). This avoids alot of nasty races.
1172          */
1173         p->cpus_allowed = current->cpus_allowed;
1174         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1175         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1176                         !cpu_online(task_cpu(p))))
1177                 set_task_cpu(p, smp_processor_id());
1178
1179         /* CLONE_PARENT re-uses the old parent */
1180         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1181                 p->real_parent = current->real_parent;
1182         else
1183                 p->real_parent = current;
1184
1185         spin_lock(&current->sighand->siglock);
1186
1187         /*
1188          * Process group and session signals need to be delivered to just the
1189          * parent before the fork or both the parent and the child after the
1190          * fork. Restart if a signal comes in before we add the new process to
1191          * it's process group.
1192          * A fatal signal pending means that current will exit, so the new
1193          * thread can't slip out of an OOM kill (or normal SIGKILL).
1194          */
1195         recalc_sigpending();
1196         if (signal_pending(current)) {
1197                 spin_unlock(&current->sighand->siglock);
1198                 write_unlock_irq(&tasklist_lock);
1199                 retval = -ERESTARTNOINTR;
1200                 goto bad_fork_free_pid;
1201         }
1202
1203         if (clone_flags & CLONE_THREAD) {
1204                 p->group_leader = current->group_leader;
1205                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1206
1207                 if (!cputime_eq(current->signal->it_virt_expires,
1208                                 cputime_zero) ||
1209                     !cputime_eq(current->signal->it_prof_expires,
1210                                 cputime_zero) ||
1211                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1212                     !list_empty(&current->signal->cpu_timers[0]) ||
1213                     !list_empty(&current->signal->cpu_timers[1]) ||
1214                     !list_empty(&current->signal->cpu_timers[2])) {
1215                         /*
1216                          * Have child wake up on its first tick to check
1217                          * for process CPU timers.
1218                          */
1219                         p->it_prof_expires = jiffies_to_cputime(1);
1220                 }
1221         }
1222
1223         if (likely(p->pid)) {
1224                 list_add_tail(&p->sibling, &p->real_parent->children);
1225                 tracehook_finish_clone(p, clone_flags, trace);
1226
1227                 if (thread_group_leader(p)) {
1228                         if (clone_flags & CLONE_NEWPID)
1229                                 p->nsproxy->pid_ns->child_reaper = p;
1230
1231                         p->signal->leader_pid = pid;
1232                         tty_kref_put(p->signal->tty);
1233                         p->signal->tty = tty_kref_get(current->signal->tty);
1234                         set_task_pgrp(p, task_pgrp_nr(current));
1235                         set_task_session(p, task_session_nr(current));
1236                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1237                         attach_pid(p, PIDTYPE_SID, task_session(current));
1238                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1239                         __get_cpu_var(process_counts)++;
1240                 }
1241                 attach_pid(p, PIDTYPE_PID, pid);
1242                 nr_threads++;
1243         }
1244
1245         total_forks++;
1246         spin_unlock(&current->sighand->siglock);
1247         write_unlock_irq(&tasklist_lock);
1248         proc_fork_connector(p);
1249         cgroup_post_fork(p);
1250         return p;
1251
1252 bad_fork_free_pid:
1253         if (pid != &init_struct_pid)
1254                 free_pid(pid);
1255 bad_fork_cleanup_io:
1256         put_io_context(p->io_context);
1257 bad_fork_cleanup_namespaces:
1258         exit_task_namespaces(p);
1259 bad_fork_cleanup_keys:
1260         exit_keys(p);
1261 bad_fork_cleanup_mm:
1262         if (p->mm)
1263                 mmput(p->mm);
1264 bad_fork_cleanup_signal:
1265         cleanup_signal(p);
1266 bad_fork_cleanup_sighand:
1267         __cleanup_sighand(p->sighand);
1268 bad_fork_cleanup_fs:
1269         exit_fs(p); /* blocking */
1270 bad_fork_cleanup_files:
1271         exit_files(p); /* blocking */
1272 bad_fork_cleanup_semundo:
1273         exit_sem(p);
1274 bad_fork_cleanup_audit:
1275         audit_free(p);
1276 bad_fork_cleanup_security:
1277         security_task_free(p);
1278 bad_fork_cleanup_policy:
1279 #ifdef CONFIG_NUMA
1280         mpol_put(p->mempolicy);
1281 bad_fork_cleanup_cgroup:
1282 #endif
1283         cgroup_exit(p, cgroup_callbacks_done);
1284         delayacct_tsk_free(p);
1285         if (p->binfmt)
1286                 module_put(p->binfmt->module);
1287 bad_fork_cleanup_put_domain:
1288         module_put(task_thread_info(p)->exec_domain->module);
1289 bad_fork_cleanup_count:
1290         put_group_info(p->group_info);
1291         atomic_dec(&p->user->processes);
1292         free_uid(p->user);
1293 bad_fork_free:
1294         free_task(p);
1295 fork_out:
1296         return ERR_PTR(retval);
1297 }
1298
1299 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1300 {
1301         memset(regs, 0, sizeof(struct pt_regs));
1302         return regs;
1303 }
1304
1305 struct task_struct * __cpuinit fork_idle(int cpu)
1306 {
1307         struct task_struct *task;
1308         struct pt_regs regs;
1309
1310         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1311                             &init_struct_pid, 0);
1312         if (!IS_ERR(task))
1313                 init_idle(task, cpu);
1314
1315         return task;
1316 }
1317
1318 /*
1319  *  Ok, this is the main fork-routine.
1320  *
1321  * It copies the process, and if successful kick-starts
1322  * it and waits for it to finish using the VM if required.
1323  */
1324 long do_fork(unsigned long clone_flags,
1325               unsigned long stack_start,
1326               struct pt_regs *regs,
1327               unsigned long stack_size,
1328               int __user *parent_tidptr,
1329               int __user *child_tidptr)
1330 {
1331         struct task_struct *p;
1332         int trace = 0;
1333         long nr;
1334
1335         /*
1336          * We hope to recycle these flags after 2.6.26
1337          */
1338         if (unlikely(clone_flags & CLONE_STOPPED)) {
1339                 static int __read_mostly count = 100;
1340
1341                 if (count > 0 && printk_ratelimit()) {
1342                         char comm[TASK_COMM_LEN];
1343
1344                         count--;
1345                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1346                                         "clone flags 0x%lx\n",
1347                                 get_task_comm(comm, current),
1348                                 clone_flags & CLONE_STOPPED);
1349                 }
1350         }
1351
1352         /*
1353          * When called from kernel_thread, don't do user tracing stuff.
1354          */
1355         if (likely(user_mode(regs)))
1356                 trace = tracehook_prepare_clone(clone_flags);
1357
1358         p = copy_process(clone_flags, stack_start, regs, stack_size,
1359                          child_tidptr, NULL, trace);
1360         /*
1361          * Do this prior waking up the new thread - the thread pointer
1362          * might get invalid after that point, if the thread exits quickly.
1363          */
1364         if (!IS_ERR(p)) {
1365                 struct completion vfork;
1366
1367                 nr = task_pid_vnr(p);
1368
1369                 if (clone_flags & CLONE_PARENT_SETTID)
1370                         put_user(nr, parent_tidptr);
1371
1372                 if (clone_flags & CLONE_VFORK) {
1373                         p->vfork_done = &vfork;
1374                         init_completion(&vfork);
1375                 }
1376
1377                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1378
1379                 /*
1380                  * We set PF_STARTING at creation in case tracing wants to
1381                  * use this to distinguish a fully live task from one that
1382                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1383                  * clear it and set the child going.
1384                  */
1385                 p->flags &= ~PF_STARTING;
1386
1387                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1388                         /*
1389                          * We'll start up with an immediate SIGSTOP.
1390                          */
1391                         sigaddset(&p->pending.signal, SIGSTOP);
1392                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1393                         __set_task_state(p, TASK_STOPPED);
1394                 } else {
1395                         wake_up_new_task(p, clone_flags);
1396                 }
1397
1398                 tracehook_report_clone_complete(trace, regs,
1399                                                 clone_flags, nr, p);
1400
1401                 if (clone_flags & CLONE_VFORK) {
1402                         freezer_do_not_count();
1403                         wait_for_completion(&vfork);
1404                         freezer_count();
1405                         tracehook_report_vfork_done(p, nr);
1406                 }
1407         } else {
1408                 nr = PTR_ERR(p);
1409         }
1410         return nr;
1411 }
1412
1413 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1414 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1415 #endif
1416
1417 static void sighand_ctor(void *data)
1418 {
1419         struct sighand_struct *sighand = data;
1420
1421         spin_lock_init(&sighand->siglock);
1422         init_waitqueue_head(&sighand->signalfd_wqh);
1423 }
1424
1425 void __init proc_caches_init(void)
1426 {
1427         sighand_cachep = kmem_cache_create("sighand_cache",
1428                         sizeof(struct sighand_struct), 0,
1429                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1430                         sighand_ctor);
1431         signal_cachep = kmem_cache_create("signal_cache",
1432                         sizeof(struct signal_struct), 0,
1433                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1434         files_cachep = kmem_cache_create("files_cache",
1435                         sizeof(struct files_struct), 0,
1436                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1437         fs_cachep = kmem_cache_create("fs_cache",
1438                         sizeof(struct fs_struct), 0,
1439                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1440         vm_area_cachep = kmem_cache_create("vm_area_struct",
1441                         sizeof(struct vm_area_struct), 0,
1442                         SLAB_PANIC, NULL);
1443         mm_cachep = kmem_cache_create("mm_struct",
1444                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1445                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1446 }
1447
1448 /*
1449  * Check constraints on flags passed to the unshare system call and
1450  * force unsharing of additional process context as appropriate.
1451  */
1452 static void check_unshare_flags(unsigned long *flags_ptr)
1453 {
1454         /*
1455          * If unsharing a thread from a thread group, must also
1456          * unshare vm.
1457          */
1458         if (*flags_ptr & CLONE_THREAD)
1459                 *flags_ptr |= CLONE_VM;
1460
1461         /*
1462          * If unsharing vm, must also unshare signal handlers.
1463          */
1464         if (*flags_ptr & CLONE_VM)
1465                 *flags_ptr |= CLONE_SIGHAND;
1466
1467         /*
1468          * If unsharing signal handlers and the task was created
1469          * using CLONE_THREAD, then must unshare the thread
1470          */
1471         if ((*flags_ptr & CLONE_SIGHAND) &&
1472             (atomic_read(&current->signal->count) > 1))
1473                 *flags_ptr |= CLONE_THREAD;
1474
1475         /*
1476          * If unsharing namespace, must also unshare filesystem information.
1477          */
1478         if (*flags_ptr & CLONE_NEWNS)
1479                 *flags_ptr |= CLONE_FS;
1480 }
1481
1482 /*
1483  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1484  */
1485 static int unshare_thread(unsigned long unshare_flags)
1486 {
1487         if (unshare_flags & CLONE_THREAD)
1488                 return -EINVAL;
1489
1490         return 0;
1491 }
1492
1493 /*
1494  * Unshare the filesystem structure if it is being shared
1495  */
1496 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1497 {
1498         struct fs_struct *fs = current->fs;
1499
1500         if ((unshare_flags & CLONE_FS) &&
1501             (fs && atomic_read(&fs->count) > 1)) {
1502                 *new_fsp = __copy_fs_struct(current->fs);
1503                 if (!*new_fsp)
1504                         return -ENOMEM;
1505         }
1506
1507         return 0;
1508 }
1509
1510 /*
1511  * Unsharing of sighand is not supported yet
1512  */
1513 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1514 {
1515         struct sighand_struct *sigh = current->sighand;
1516
1517         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1518                 return -EINVAL;
1519         else
1520                 return 0;
1521 }
1522
1523 /*
1524  * Unshare vm if it is being shared
1525  */
1526 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1527 {
1528         struct mm_struct *mm = current->mm;
1529
1530         if ((unshare_flags & CLONE_VM) &&
1531             (mm && atomic_read(&mm->mm_users) > 1)) {
1532                 return -EINVAL;
1533         }
1534
1535         return 0;
1536 }
1537
1538 /*
1539  * Unshare file descriptor table if it is being shared
1540  */
1541 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1542 {
1543         struct files_struct *fd = current->files;
1544         int error = 0;
1545
1546         if ((unshare_flags & CLONE_FILES) &&
1547             (fd && atomic_read(&fd->count) > 1)) {
1548                 *new_fdp = dup_fd(fd, &error);
1549                 if (!*new_fdp)
1550                         return error;
1551         }
1552
1553         return 0;
1554 }
1555
1556 /*
1557  * unshare allows a process to 'unshare' part of the process
1558  * context which was originally shared using clone.  copy_*
1559  * functions used by do_fork() cannot be used here directly
1560  * because they modify an inactive task_struct that is being
1561  * constructed. Here we are modifying the current, active,
1562  * task_struct.
1563  */
1564 asmlinkage long sys_unshare(unsigned long unshare_flags)
1565 {
1566         int err = 0;
1567         struct fs_struct *fs, *new_fs = NULL;
1568         struct sighand_struct *new_sigh = NULL;
1569         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1570         struct files_struct *fd, *new_fd = NULL;
1571         struct nsproxy *new_nsproxy = NULL;
1572         int do_sysvsem = 0;
1573
1574         check_unshare_flags(&unshare_flags);
1575
1576         /* Return -EINVAL for all unsupported flags */
1577         err = -EINVAL;
1578         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1579                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1580                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1581                                 CLONE_NEWNET))
1582                 goto bad_unshare_out;
1583
1584         /*
1585          * CLONE_NEWIPC must also detach from the undolist: after switching
1586          * to a new ipc namespace, the semaphore arrays from the old
1587          * namespace are unreachable.
1588          */
1589         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1590                 do_sysvsem = 1;
1591         if ((err = unshare_thread(unshare_flags)))
1592                 goto bad_unshare_out;
1593         if ((err = unshare_fs(unshare_flags, &new_fs)))
1594                 goto bad_unshare_cleanup_thread;
1595         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1596                 goto bad_unshare_cleanup_fs;
1597         if ((err = unshare_vm(unshare_flags, &new_mm)))
1598                 goto bad_unshare_cleanup_sigh;
1599         if ((err = unshare_fd(unshare_flags, &new_fd)))
1600                 goto bad_unshare_cleanup_vm;
1601         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1602                         new_fs)))
1603                 goto bad_unshare_cleanup_fd;
1604
1605         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1606                 if (do_sysvsem) {
1607                         /*
1608                          * CLONE_SYSVSEM is equivalent to sys_exit().
1609                          */
1610                         exit_sem(current);
1611                 }
1612
1613                 if (new_nsproxy) {
1614                         switch_task_namespaces(current, new_nsproxy);
1615                         new_nsproxy = NULL;
1616                 }
1617
1618                 task_lock(current);
1619
1620                 if (new_fs) {
1621                         fs = current->fs;
1622                         current->fs = new_fs;
1623                         new_fs = fs;
1624                 }
1625
1626                 if (new_mm) {
1627                         mm = current->mm;
1628                         active_mm = current->active_mm;
1629                         current->mm = new_mm;
1630                         current->active_mm = new_mm;
1631                         activate_mm(active_mm, new_mm);
1632                         new_mm = mm;
1633                 }
1634
1635                 if (new_fd) {
1636                         fd = current->files;
1637                         current->files = new_fd;
1638                         new_fd = fd;
1639                 }
1640
1641                 task_unlock(current);
1642         }
1643
1644         if (new_nsproxy)
1645                 put_nsproxy(new_nsproxy);
1646
1647 bad_unshare_cleanup_fd:
1648         if (new_fd)
1649                 put_files_struct(new_fd);
1650
1651 bad_unshare_cleanup_vm:
1652         if (new_mm)
1653                 mmput(new_mm);
1654
1655 bad_unshare_cleanup_sigh:
1656         if (new_sigh)
1657                 if (atomic_dec_and_test(&new_sigh->count))
1658                         kmem_cache_free(sighand_cachep, new_sigh);
1659
1660 bad_unshare_cleanup_fs:
1661         if (new_fs)
1662                 put_fs_struct(new_fs);
1663
1664 bad_unshare_cleanup_thread:
1665 bad_unshare_out:
1666         return err;
1667 }
1668
1669 /*
1670  *      Helper to unshare the files of the current task.
1671  *      We don't want to expose copy_files internals to
1672  *      the exec layer of the kernel.
1673  */
1674
1675 int unshare_files(struct files_struct **displaced)
1676 {
1677         struct task_struct *task = current;
1678         struct files_struct *copy = NULL;
1679         int error;
1680
1681         error = unshare_fd(CLONE_FILES, &copy);
1682         if (error || !copy) {
1683                 *displaced = NULL;
1684                 return error;
1685         }
1686         *displaced = task->files;
1687         task_lock(task);
1688         task->files = copy;
1689         task_unlock(task);
1690         return 0;
1691 }