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
 806         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 807         sig->gtime = cputime_zero;
 808         sig->cgtime = cputime_zero;
 809         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 810         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 811         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 812         task_io_accounting_init(&sig->ioac);
 813         sig->sum_sched_runtime = 0;
 814         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 815         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 816         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 817         taskstats_tgid_init(sig);
 818
 819         task_lock(current->group_leader);
 820         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 821         task_unlock(current->group_leader);
 822
 823         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 824                 /*
 825                  * New sole thread in the process gets an expiry time
 826                  * of the whole CPU time limit.
 827                  */
 828                 tsk->it_prof_expires =
 829                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 830         }
 831         acct_init_pacct(&sig->pacct);
 832
 833         tty_audit_fork(sig);
 834
 835         return 0;
 836 }
 837
 838 void __cleanup_signal(struct signal_struct *sig)
 839 {
 840         exit_thread_group_keys(sig);
 841         kmem_cache_free(signal_cachep, sig);
 842 }
 843
 844 static void cleanup_signal(struct task_struct *tsk)
 845 {
 846         struct signal_struct *sig = tsk->signal;
 847
 848         atomic_dec(&sig->live);
 849
 850         if (atomic_dec_and_test(&sig->count))
 851                 __cleanup_signal(sig);
 852 }
 853
 854 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 855 {
 856         unsigned long new_flags = p->flags;
 857
 858         new_flags &= ~PF_SUPERPRIV;
 859         new_flags |= PF_FORKNOEXEC;
 860         new_flags |= PF_STARTING;
 861         p->flags = new_flags;
 862         clear_freeze_flag(p);
 863 }
 864
 865 asmlinkage long sys_set_tid_address(int __user *tidptr)
 866 {
 867         current->clear_child_tid = tidptr;
 868
 869         return task_pid_vnr(current);
 870 }
 871
 872 static void rt_mutex_init_task(struct task_struct *p)
 873 {
 874         spin_lock_init(&p->pi_lock);
 875 #ifdef CONFIG_RT_MUTEXES
 876         plist_head_init(&p->pi_waiters, &p->pi_lock);
 877         p->pi_blocked_on = NULL;
 878 #endif
 879 }
 880
 881 #ifdef CONFIG_MM_OWNER
 882 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 883 {
 884         mm->owner = p;
 885 }
 886 #endif /* CONFIG_MM_OWNER */
 887
 888 /*
 889  * This creates a new process as a copy of the old one,
 890  * but does not actually start it yet.
 891  *
 892  * It copies the registers, and all the appropriate
 893  * parts of the process environment (as per the clone
 894  * flags). The actual kick-off is left to the caller.
 895  */
 896 static struct task_struct *copy_process(unsigned long clone_flags,
 897                                         unsigned long stack_start,
 898                                         struct pt_regs *regs,
 899                                         unsigned long stack_size,
 900                                         int __user *child_tidptr,
 901                                         struct pid *pid,
 902                                         int trace)
 903 {
 904         int retval;
 905         struct task_struct *p;
 906         int cgroup_callbacks_done = 0;
 907
 908         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 909                 return ERR_PTR(-EINVAL);
 910
 911         /*
 912          * Thread groups must share signals as well, and detached threads
 913          * can only be started up within the thread group.
 914          */
 915         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 916                 return ERR_PTR(-EINVAL);
 917
 918         /*
 919          * Shared signal handlers imply shared VM. By way of the above,
 920          * thread groups also imply shared VM. Blocking this case allows
 921          * for various simplifications in other code.
 922          */
 923         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 924                 return ERR_PTR(-EINVAL);
 925
 926         retval = security_task_create(clone_flags);
 927         if (retval)
 928                 goto fork_out;
 929
 930         retval = -ENOMEM;
 931         p = dup_task_struct(current);
 932         if (!p)
 933                 goto fork_out;
 934
 935         rt_mutex_init_task(p);
 936
 937 #ifdef CONFIG_PROVE_LOCKING
 938         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 939         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 940 #endif
 941         retval = -EAGAIN;
 942         if (atomic_read(&p->user->processes) >=
 943                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 944                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 945                     p->user != current->nsproxy->user_ns->root_user)
 946                         goto bad_fork_free;
 947         }
 948
 949         atomic_inc(&p->user->__count);
 950         atomic_inc(&p->user->processes);
 951         get_group_info(p->group_info);
 952
 953         /*
 954          * If multiple threads are within copy_process(), then this check
 955          * triggers too late. This doesn't hurt, the check is only there
 956          * to stop root fork bombs.
 957          */
 958         if (nr_threads >= max_threads)
 959                 goto bad_fork_cleanup_count;
 960
 961         if (!try_module_get(task_thread_info(p)->exec_domain->module))
 962                 goto bad_fork_cleanup_count;
 963
 964         if (p->binfmt && !try_module_get(p->binfmt->module))
 965                 goto bad_fork_cleanup_put_domain;
 966
 967         p->did_exec = 0;
 968         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
 969         copy_flags(clone_flags, p);
 970         INIT_LIST_HEAD(&p->children);
 971         INIT_LIST_HEAD(&p->sibling);
 972 #ifdef CONFIG_PREEMPT_RCU
 973         p->rcu_read_lock_nesting = 0;
 974         p->rcu_flipctr_idx = 0;
 975 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 976         p->vfork_done = NULL;
 977         spin_lock_init(&p->alloc_lock);
 978
 979         clear_tsk_thread_flag(p, TIF_SIGPENDING);
 980         init_sigpending(&p->pending);
 981
 982         p->utime = cputime_zero;
 983         p->stime = cputime_zero;
 984         p->gtime = cputime_zero;
 985         p->utimescaled = cputime_zero;
 986         p->stimescaled = cputime_zero;
 987         p->prev_utime = cputime_zero;
 988         p->prev_stime = cputime_zero;
 989
 990 #ifdef CONFIG_DETECT_SOFTLOCKUP
 991         p->last_switch_count = 0;
 992         p->last_switch_timestamp = 0;
 993 #endif
 994
 995         task_io_accounting_init(&p->ioac);
 996         acct_clear_integrals(p);
 997
 998         p->it_virt_expires = cputime_zero;
 999         p->it_prof_expires = cputime_zero;
1000         p->it_sched_expires = 0;
1001         INIT_LIST_HEAD(&p->cpu_timers[0]);
1002         INIT_LIST_HEAD(&p->cpu_timers[1]);
1003         INIT_LIST_HEAD(&p->cpu_timers[2]);
1004
1005         p->lock_depth = -1;             /* -1 = no lock */
1006         do_posix_clock_monotonic_gettime(&p->start_time);
1007         p->real_start_time = p->start_time;
1008         monotonic_to_bootbased(&p->real_start_time);
1009 #ifdef CONFIG_SECURITY
1010         p->security = NULL;
1011 #endif
1012         p->cap_bset = current->cap_bset;
1013         p->io_context = NULL;
1014         p->audit_context = NULL;
1015         cgroup_fork(p);
1016 #ifdef CONFIG_NUMA
1017         p->mempolicy = mpol_dup(p->mempolicy);
1018         if (IS_ERR(p->mempolicy)) {
1019                 retval = PTR_ERR(p->mempolicy);
1020                 p->mempolicy = NULL;
1021                 goto bad_fork_cleanup_cgroup;
1022         }
1023         mpol_fix_fork_child_flag(p);
1024 #endif
1025 #ifdef CONFIG_TRACE_IRQFLAGS
1026         p->irq_events = 0;
1027 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1028         p->hardirqs_enabled = 1;
1029 #else
1030         p->hardirqs_enabled = 0;
1031 #endif
1032         p->hardirq_enable_ip = 0;
1033         p->hardirq_enable_event = 0;
1034         p->hardirq_disable_ip = _THIS_IP_;
1035         p->hardirq_disable_event = 0;
1036         p->softirqs_enabled = 1;
1037         p->softirq_enable_ip = _THIS_IP_;
1038         p->softirq_enable_event = 0;
1039         p->softirq_disable_ip = 0;
1040         p->softirq_disable_event = 0;
1041         p->hardirq_context = 0;
1042         p->softirq_context = 0;
1043 #endif
1044 #ifdef CONFIG_LOCKDEP
1045         p->lockdep_depth = 0; /* no locks held yet */
1046         p->curr_chain_key = 0;
1047         p->lockdep_recursion = 0;
1048 #endif
1049
1050 #ifdef CONFIG_DEBUG_MUTEXES
1051         p->blocked_on = NULL; /* not blocked yet */
1052 #endif
1053
1054         /* Perform scheduler related setup. Assign this task to a CPU. */
1055         sched_fork(p, clone_flags);
1056
1057         if ((retval = security_task_alloc(p)))
1058                 goto bad_fork_cleanup_policy;
1059         if ((retval = audit_alloc(p)))
1060                 goto bad_fork_cleanup_security;
1061         /* copy all the process information */
1062         if ((retval = copy_semundo(clone_flags, p)))
1063                 goto bad_fork_cleanup_audit;
1064         if ((retval = copy_files(clone_flags, p)))
1065                 goto bad_fork_cleanup_semundo;
1066         if ((retval = copy_fs(clone_flags, p)))
1067                 goto bad_fork_cleanup_files;
1068         if ((retval = copy_sighand(clone_flags, p)))
1069                 goto bad_fork_cleanup_fs;
1070         if ((retval = copy_signal(clone_flags, p)))
1071                 goto bad_fork_cleanup_sighand;
1072         if ((retval = copy_mm(clone_flags, p)))
1073                 goto bad_fork_cleanup_signal;
1074         if ((retval = copy_keys(clone_flags, p)))
1075                 goto bad_fork_cleanup_mm;
1076         if ((retval = copy_namespaces(clone_flags, p)))
1077                 goto bad_fork_cleanup_keys;
1078         if ((retval = copy_io(clone_flags, p)))
1079                 goto bad_fork_cleanup_namespaces;
1080         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1081         if (retval)
1082                 goto bad_fork_cleanup_io;
1083
1084         if (pid != &init_struct_pid) {
1085                 retval = -ENOMEM;
1086                 pid = alloc_pid(task_active_pid_ns(p));
1087                 if (!pid)
1088                         goto bad_fork_cleanup_io;
1089
1090                 if (clone_flags & CLONE_NEWPID) {
1091                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1092                         if (retval < 0)
1093                                 goto bad_fork_free_pid;
1094                 }
1095         }
1096
1097         p->pid = pid_nr(pid);
1098         p->tgid = p->pid;
1099         if (clone_flags & CLONE_THREAD)
1100                 p->tgid = current->tgid;
1101
1102         if (current->nsproxy != p->nsproxy) {
1103                 retval = ns_cgroup_clone(p, pid);
1104                 if (retval)
1105                         goto bad_fork_free_pid;
1106         }
1107
1108         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1109         /*
1110          * Clear TID on mm_release()?
1111          */
1112         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1113 #ifdef CONFIG_FUTEX
1114         p->robust_list = NULL;
1115 #ifdef CONFIG_COMPAT
1116         p->compat_robust_list = NULL;
1117 #endif
1118         INIT_LIST_HEAD(&p->pi_state_list);
1119         p->pi_state_cache = NULL;
1120 #endif
1121         /*
1122          * sigaltstack should be cleared when sharing the same VM
1123          */
1124         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1125                 p->sas_ss_sp = p->sas_ss_size = 0;
1126
1127         /*
1128          * Syscall tracing should be turned off in the child regardless
1129          * of CLONE_PTRACE.
1130          */
1131         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1132 #ifdef TIF_SYSCALL_EMU
1133         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1134 #endif
1135         clear_all_latency_tracing(p);
1136
1137         /* Our parent execution domain becomes current domain
1138            These must match for thread signalling to apply */
1139         p->parent_exec_id = p->self_exec_id;
1140
1141         /* ok, now we should be set up.. */
1142         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1143         p->pdeath_signal = 0;
1144         p->exit_state = 0;
1145
1146         /*
1147          * Ok, make it visible to the rest of the system.
1148          * We dont wake it up yet.
1149          */
1150         p->group_leader = p;
1151         INIT_LIST_HEAD(&p->thread_group);
1152
1153         /* Now that the task is set up, run cgroup callbacks if
1154          * necessary. We need to run them before the task is visible
1155          * on the tasklist. */
1156         cgroup_fork_callbacks(p);
1157         cgroup_callbacks_done = 1;
1158
1159         /* Need tasklist lock for parent etc handling! */
1160         write_lock_irq(&tasklist_lock);
1161
1162         /*
1163          * The task hasn't been attached yet, so its cpus_allowed mask will
1164          * not be changed, nor will its assigned CPU.
1165          *
1166          * The cpus_allowed mask of the parent may have changed after it was
1167          * copied first time - so re-copy it here, then check the child's CPU
1168          * to ensure it is on a valid CPU (and if not, just force it back to
1169          * parent's CPU). This avoids alot of nasty races.
1170          */
1171         p->cpus_allowed = current->cpus_allowed;
1172         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1173         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1174                         !cpu_online(task_cpu(p))))
1175                 set_task_cpu(p, smp_processor_id());
1176
1177         /* CLONE_PARENT re-uses the old parent */
1178         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1179                 p->real_parent = current->real_parent;
1180         else
1181                 p->real_parent = current;
1182
1183         spin_lock(&current->sighand->siglock);
1184
1185         /*
1186          * Process group and session signals need to be delivered to just the
1187          * parent before the fork or both the parent and the child after the
1188          * fork. Restart if a signal comes in before we add the new process to
1189          * it's process group.
1190          * A fatal signal pending means that current will exit, so the new
1191          * thread can't slip out of an OOM kill (or normal SIGKILL).
1192          */
1193         recalc_sigpending();
1194         if (signal_pending(current)) {
1195                 spin_unlock(&current->sighand->siglock);
1196                 write_unlock_irq(&tasklist_lock);
1197                 retval = -ERESTARTNOINTR;
1198                 goto bad_fork_free_pid;
1199         }
1200
1201         if (clone_flags & CLONE_THREAD) {
1202                 p->group_leader = current->group_leader;
1203                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1204
1205                 if (!cputime_eq(current->signal->it_virt_expires,
1206                                 cputime_zero) ||
1207                     !cputime_eq(current->signal->it_prof_expires,
1208                                 cputime_zero) ||
1209                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1210                     !list_empty(&current->signal->cpu_timers[0]) ||
1211                     !list_empty(&current->signal->cpu_timers[1]) ||
1212                     !list_empty(&current->signal->cpu_timers[2])) {
1213                         /*
1214                          * Have child wake up on its first tick to check
1215                          * for process CPU timers.
1216                          */
1217                         p->it_prof_expires = jiffies_to_cputime(1);
1218                 }
1219         }
1220
1221         if (likely(p->pid)) {
1222                 list_add_tail(&p->sibling, &p->real_parent->children);
1223                 tracehook_finish_clone(p, clone_flags, trace);
1224
1225                 if (thread_group_leader(p)) {
1226                         if (clone_flags & CLONE_NEWPID)
1227                                 p->nsproxy->pid_ns->child_reaper = p;
1228
1229                         p->signal->leader_pid = pid;
1230                         p->signal->tty = current->signal->tty;
1231                         set_task_pgrp(p, task_pgrp_nr(current));
1232                         set_task_session(p, task_session_nr(current));
1233                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1234                         attach_pid(p, PIDTYPE_SID, task_session(current));
1235                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1236                         __get_cpu_var(process_counts)++;
1237                 }
1238                 attach_pid(p, PIDTYPE_PID, pid);
1239                 nr_threads++;
1240         }
1241
1242         total_forks++;
1243         spin_unlock(&current->sighand->siglock);
1244         write_unlock_irq(&tasklist_lock);
1245         proc_fork_connector(p);
1246         cgroup_post_fork(p);
1247         return p;
1248
1249 bad_fork_free_pid:
1250         if (pid != &init_struct_pid)
1251                 free_pid(pid);
1252 bad_fork_cleanup_io:
1253         put_io_context(p->io_context);
1254 bad_fork_cleanup_namespaces:
1255         exit_task_namespaces(p);
1256 bad_fork_cleanup_keys:
1257         exit_keys(p);
1258 bad_fork_cleanup_mm:
1259         if (p->mm)
1260                 mmput(p->mm);
1261 bad_fork_cleanup_signal:
1262         cleanup_signal(p);
1263 bad_fork_cleanup_sighand:
1264         __cleanup_sighand(p->sighand);
1265 bad_fork_cleanup_fs:
1266         exit_fs(p); /* blocking */
1267 bad_fork_cleanup_files:
1268         exit_files(p); /* blocking */
1269 bad_fork_cleanup_semundo:
1270         exit_sem(p);
1271 bad_fork_cleanup_audit:
1272         audit_free(p);
1273 bad_fork_cleanup_security:
1274         security_task_free(p);
1275 bad_fork_cleanup_policy:
1276 #ifdef CONFIG_NUMA
1277         mpol_put(p->mempolicy);
1278 bad_fork_cleanup_cgroup:
1279 #endif
1280         cgroup_exit(p, cgroup_callbacks_done);
1281         delayacct_tsk_free(p);
1282         if (p->binfmt)
1283                 module_put(p->binfmt->module);
1284 bad_fork_cleanup_put_domain:
1285         module_put(task_thread_info(p)->exec_domain->module);
1286 bad_fork_cleanup_count:
1287         put_group_info(p->group_info);
1288         atomic_dec(&p->user->processes);
1289         free_uid(p->user);
1290 bad_fork_free:
1291         free_task(p);
1292 fork_out:
1293         return ERR_PTR(retval);
1294 }
1295
1296 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1297 {
1298         memset(regs, 0, sizeof(struct pt_regs));
1299         return regs;
1300 }
1301
1302 struct task_struct * __cpuinit fork_idle(int cpu)
1303 {
1304         struct task_struct *task;
1305         struct pt_regs regs;
1306
1307         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1308                             &init_struct_pid, 0);
1309         if (!IS_ERR(task))
1310                 init_idle(task, cpu);
1311
1312         return task;
1313 }
1314
1315 /*
1316  *  Ok, this is the main fork-routine.
1317  *
1318  * It copies the process, and if successful kick-starts
1319  * it and waits for it to finish using the VM if required.
1320  */
1321 long do_fork(unsigned long clone_flags,
1322               unsigned long stack_start,
1323               struct pt_regs *regs,
1324               unsigned long stack_size,
1325               int __user *parent_tidptr,
1326               int __user *child_tidptr)
1327 {
1328         struct task_struct *p;
1329         int trace = 0;
1330         long nr;
1331
1332         /*
1333          * We hope to recycle these flags after 2.6.26
1334          */
1335         if (unlikely(clone_flags & CLONE_STOPPED)) {
1336                 static int __read_mostly count = 100;
1337
1338                 if (count > 0 && printk_ratelimit()) {
1339                         char comm[TASK_COMM_LEN];
1340
1341                         count--;
1342                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1343                                         "clone flags 0x%lx\n",
1344                                 get_task_comm(comm, current),
1345                                 clone_flags & CLONE_STOPPED);
1346                 }
1347         }
1348
1349         /*
1350          * When called from kernel_thread, don't do user tracing stuff.
1351          */
1352         if (likely(user_mode(regs)))
1353                 trace = tracehook_prepare_clone(clone_flags);
1354
1355         p = copy_process(clone_flags, stack_start, regs, stack_size,
1356                          child_tidptr, NULL, trace);
1357         /*
1358          * Do this prior waking up the new thread - the thread pointer
1359          * might get invalid after that point, if the thread exits quickly.
1360          */
1361         if (!IS_ERR(p)) {
1362                 struct completion vfork;
1363
1364                 nr = task_pid_vnr(p);
1365
1366                 if (clone_flags & CLONE_PARENT_SETTID)
1367                         put_user(nr, parent_tidptr);
1368
1369                 if (clone_flags & CLONE_VFORK) {
1370                         p->vfork_done = &vfork;
1371                         init_completion(&vfork);
1372                 }
1373
1374                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1375
1376                 /*
1377                  * We set PF_STARTING at creation in case tracing wants to
1378                  * use this to distinguish a fully live task from one that
1379                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1380                  * clear it and set the child going.
1381                  */
1382                 p->flags &= ~PF_STARTING;
1383
1384                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1385                         /*
1386                          * We'll start up with an immediate SIGSTOP.
1387                          */
1388                         sigaddset(&p->pending.signal, SIGSTOP);
1389                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1390                         __set_task_state(p, TASK_STOPPED);
1391                 } else {
1392                         wake_up_new_task(p, clone_flags);
1393                 }
1394
1395                 tracehook_report_clone_complete(trace, regs,
1396                                                 clone_flags, nr, p);
1397
1398                 if (clone_flags & CLONE_VFORK) {
1399                         freezer_do_not_count();
1400                         wait_for_completion(&vfork);
1401                         freezer_count();
1402                         tracehook_report_vfork_done(p, nr);
1403                 }
1404         } else {
1405                 nr = PTR_ERR(p);
1406         }
1407         return nr;
1408 }
1409
1410 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1411 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1412 #endif
1413
1414 static void sighand_ctor(void *data)
1415 {
1416         struct sighand_struct *sighand = data;
1417
1418         spin_lock_init(&sighand->siglock);
1419         init_waitqueue_head(&sighand->signalfd_wqh);
1420 }
1421
1422 void __init proc_caches_init(void)
1423 {
1424         sighand_cachep = kmem_cache_create("sighand_cache",
1425                         sizeof(struct sighand_struct), 0,
1426                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1427                         sighand_ctor);
1428         signal_cachep = kmem_cache_create("signal_cache",
1429                         sizeof(struct signal_struct), 0,
1430                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1431         files_cachep = kmem_cache_create("files_cache",
1432                         sizeof(struct files_struct), 0,
1433                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1434         fs_cachep = kmem_cache_create("fs_cache",
1435                         sizeof(struct fs_struct), 0,
1436                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1437         vm_area_cachep = kmem_cache_create("vm_area_struct",
1438                         sizeof(struct vm_area_struct), 0,
1439                         SLAB_PANIC, NULL);
1440         mm_cachep = kmem_cache_create("mm_struct",
1441                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1442                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1443 }
1444
1445 /*
1446  * Check constraints on flags passed to the unshare system call and
1447  * force unsharing of additional process context as appropriate.
1448  */
1449 static void check_unshare_flags(unsigned long *flags_ptr)
1450 {
1451         /*
1452          * If unsharing a thread from a thread group, must also
1453          * unshare vm.
1454          */
1455         if (*flags_ptr & CLONE_THREAD)
1456                 *flags_ptr |= CLONE_VM;
1457
1458         /*
1459          * If unsharing vm, must also unshare signal handlers.
1460          */
1461         if (*flags_ptr & CLONE_VM)
1462                 *flags_ptr |= CLONE_SIGHAND;
1463
1464         /*
1465          * If unsharing signal handlers and the task was created
1466          * using CLONE_THREAD, then must unshare the thread
1467          */
1468         if ((*flags_ptr & CLONE_SIGHAND) &&
1469             (atomic_read(&current->signal->count) > 1))
1470                 *flags_ptr |= CLONE_THREAD;
1471
1472         /*
1473          * If unsharing namespace, must also unshare filesystem information.
1474          */
1475         if (*flags_ptr & CLONE_NEWNS)
1476                 *flags_ptr |= CLONE_FS;
1477 }
1478
1479 /*
1480  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1481  */
1482 static int unshare_thread(unsigned long unshare_flags)
1483 {
1484         if (unshare_flags & CLONE_THREAD)
1485                 return -EINVAL;
1486
1487         return 0;
1488 }
1489
1490 /*
1491  * Unshare the filesystem structure if it is being shared
1492  */
1493 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1494 {
1495         struct fs_struct *fs = current->fs;
1496
1497         if ((unshare_flags & CLONE_FS) &&
1498             (fs && atomic_read(&fs->count) > 1)) {
1499                 *new_fsp = __copy_fs_struct(current->fs);
1500                 if (!*new_fsp)
1501                         return -ENOMEM;
1502         }
1503
1504         return 0;
1505 }
1506
1507 /*
1508  * Unsharing of sighand is not supported yet
1509  */
1510 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1511 {
1512         struct sighand_struct *sigh = current->sighand;
1513
1514         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1515                 return -EINVAL;
1516         else
1517                 return 0;
1518 }
1519
1520 /*
1521  * Unshare vm if it is being shared
1522  */
1523 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1524 {
1525         struct mm_struct *mm = current->mm;
1526
1527         if ((unshare_flags & CLONE_VM) &&
1528             (mm && atomic_read(&mm->mm_users) > 1)) {
1529                 return -EINVAL;
1530         }
1531
1532         return 0;
1533 }
1534
1535 /*
1536  * Unshare file descriptor table if it is being shared
1537  */
1538 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1539 {
1540         struct files_struct *fd = current->files;
1541         int error = 0;
1542
1543         if ((unshare_flags & CLONE_FILES) &&
1544             (fd && atomic_read(&fd->count) > 1)) {
1545                 *new_fdp = dup_fd(fd, &error);
1546                 if (!*new_fdp)
1547                         return error;
1548         }
1549
1550         return 0;
1551 }
1552
1553 /*
1554  * unshare allows a process to 'unshare' part of the process
1555  * context which was originally shared using clone.  copy_*
1556  * functions used by do_fork() cannot be used here directly
1557  * because they modify an inactive task_struct that is being
1558  * constructed. Here we are modifying the current, active,
1559  * task_struct.
1560  */
1561 asmlinkage long sys_unshare(unsigned long unshare_flags)
1562 {
1563         int err = 0;
1564         struct fs_struct *fs, *new_fs = NULL;
1565         struct sighand_struct *new_sigh = NULL;
1566         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1567         struct files_struct *fd, *new_fd = NULL;
1568         struct nsproxy *new_nsproxy = NULL;
1569         int do_sysvsem = 0;
1570
1571         check_unshare_flags(&unshare_flags);
1572
1573         /* Return -EINVAL for all unsupported flags */
1574         err = -EINVAL;
1575         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1576                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1577                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1578                                 CLONE_NEWNET))
1579                 goto bad_unshare_out;
1580
1581         /*
1582          * CLONE_NEWIPC must also detach from the undolist: after switching
1583          * to a new ipc namespace, the semaphore arrays from the old
1584          * namespace are unreachable.
1585          */
1586         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1587                 do_sysvsem = 1;
1588         if ((err = unshare_thread(unshare_flags)))
1589                 goto bad_unshare_out;
1590         if ((err = unshare_fs(unshare_flags, &new_fs)))
1591                 goto bad_unshare_cleanup_thread;
1592         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1593                 goto bad_unshare_cleanup_fs;
1594         if ((err = unshare_vm(unshare_flags, &new_mm)))
1595                 goto bad_unshare_cleanup_sigh;
1596         if ((err = unshare_fd(unshare_flags, &new_fd)))
1597                 goto bad_unshare_cleanup_vm;
1598         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1599                         new_fs)))
1600                 goto bad_unshare_cleanup_fd;
1601
1602         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1603                 if (do_sysvsem) {
1604                         /*
1605                          * CLONE_SYSVSEM is equivalent to sys_exit().
1606                          */
1607                         exit_sem(current);
1608                 }
1609
1610                 if (new_nsproxy) {
1611                         switch_task_namespaces(current, new_nsproxy);
1612                         new_nsproxy = NULL;
1613                 }
1614
1615                 task_lock(current);
1616
1617                 if (new_fs) {
1618                         fs = current->fs;
1619                         current->fs = new_fs;
1620                         new_fs = fs;
1621                 }
1622
1623                 if (new_mm) {
1624                         mm = current->mm;
1625                         active_mm = current->active_mm;
1626                         current->mm = new_mm;
1627                         current->active_mm = new_mm;
1628                         activate_mm(active_mm, new_mm);
1629                         new_mm = mm;
1630                 }
1631
1632                 if (new_fd) {
1633                         fd = current->files;
1634                         current->files = new_fd;
1635                         new_fd = fd;
1636                 }
1637
1638                 task_unlock(current);
1639         }
1640
1641         if (new_nsproxy)
1642                 put_nsproxy(new_nsproxy);
1643
1644 bad_unshare_cleanup_fd:
1645         if (new_fd)
1646                 put_files_struct(new_fd);
1647
1648 bad_unshare_cleanup_vm:
1649         if (new_mm)
1650                 mmput(new_mm);
1651
1652 bad_unshare_cleanup_sigh:
1653         if (new_sigh)
1654                 if (atomic_dec_and_test(&new_sigh->count))
1655                         kmem_cache_free(sighand_cachep, new_sigh);
1656
1657 bad_unshare_cleanup_fs:
1658         if (new_fs)
1659                 put_fs_struct(new_fs);
1660
1661 bad_unshare_cleanup_thread:
1662 bad_unshare_out:
1663         return err;
1664 }
1665
1666 /*
1667  *      Helper to unshare the files of the current task.
1668  *      We don't want to expose copy_files internals to
1669  *      the exec layer of the kernel.
1670  */
1671
1672 int unshare_files(struct files_struct **displaced)
1673 {
1674         struct task_struct *task = current;
1675         struct files_struct *copy = NULL;
1676         int error;
1677
1678         error = unshare_fd(CLONE_FILES, &copy);
1679         if (error || !copy) {
1680                 *displaced = NULL;
1681                 return error;
1682         }
1683         *displaced = task->files;
1684         task_lock(task);
1685         task->files = copy;
1686         task_unlock(task);
1687         return 0;
1688 }