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 #include <trace/sched.h>
  62
  63 #include <asm/pgtable.h>
  64 #include <asm/pgalloc.h>
  65 #include <asm/uaccess.h>
  66 #include <asm/mmu_context.h>
  67 #include <asm/cacheflush.h>
  68 #include <asm/tlbflush.h>
  69
  70 /*
  71  * Protected counters by write_lock_irq(&tasklist_lock)
  72  */
  73 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  74 int nr_threads;                 /* The idle threads do not count.. */
  75
  76 int max_threads;                /* tunable limit on nr_threads */
  77
  78 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  79
  80 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  81
  82 int nr_processes(void)
  83 {
  84         int cpu;
  85         int total = 0;
  86
  87         for_each_online_cpu(cpu)
  88                 total += per_cpu(process_counts, cpu);
  89
  90         return total;
  91 }
  92
  93 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  94 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  95 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  96 static struct kmem_cache *task_struct_cachep;
  97 #endif
  98
  99 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
 100 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
 101 {
 102 #ifdef CONFIG_DEBUG_STACK_USAGE
 103         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 104 #else
 105         gfp_t mask = GFP_KERNEL;
 106 #endif
 107         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 108 }
 109
 110 static inline void free_thread_info(struct thread_info *ti)
 111 {
 112         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 113 }
 114 #endif
 115
 116 /* SLAB cache for signal_struct structures (tsk->signal) */
 117 static struct kmem_cache *signal_cachep;
 118
 119 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 120 struct kmem_cache *sighand_cachep;
 121
 122 /* SLAB cache for files_struct structures (tsk->files) */
 123 struct kmem_cache *files_cachep;
 124
 125 /* SLAB cache for fs_struct structures (tsk->fs) */
 126 struct kmem_cache *fs_cachep;
 127
 128 /* SLAB cache for vm_area_struct structures */
 129 struct kmem_cache *vm_area_cachep;
 130
 131 /* SLAB cache for mm_struct structures (tsk->mm) */
 132 static struct kmem_cache *mm_cachep;
 133
 134 void free_task(struct task_struct *tsk)
 135 {
 136         prop_local_destroy_single(&tsk->dirties);
 137         free_thread_info(tsk->stack);
 138         rt_mutex_debug_task_free(tsk);
 139         free_task_struct(tsk);
 140 }
 141 EXPORT_SYMBOL(free_task);
 142
 143 void __put_task_struct(struct task_struct *tsk)
 144 {
 145         WARN_ON(!tsk->exit_state);
 146         WARN_ON(atomic_read(&tsk->usage));
 147         WARN_ON(tsk == current);
 148
 149         put_cred(tsk->cred);
 150         delayacct_tsk_free(tsk);
 151
 152         if (!profile_handoff_task(tsk))
 153                 free_task(tsk);
 154 }
 155
 156 /*
 157  * macro override instead of weak attribute alias, to workaround
 158  * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions.
 159  */
 160 #ifndef arch_task_cache_init
 161 #define arch_task_cache_init()
 162 #endif
 163
 164 void __init fork_init(unsigned long mempages)
 165 {
 166 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 167 #ifndef ARCH_MIN_TASKALIGN
 168 #define ARCH_MIN_TASKALIGN      L1_CACHE_BYTES
 169 #endif
 170         /* create a slab on which task_structs can be allocated */
 171         task_struct_cachep =
 172                 kmem_cache_create("task_struct", sizeof(struct task_struct),
 173                         ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL);
 174 #endif
 175
 176         /* do the arch specific task caches init */
 177         arch_task_cache_init();
 178
 179         /*
 180          * The default maximum number of threads is set to a safe
 181          * value: the thread structures can take up at most half
 182          * of memory.
 183          */
 184         max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
 185
 186         /*
 187          * we need to allow at least 20 threads to boot a system
 188          */
 189         if(max_threads < 20)
 190                 max_threads = 20;
 191
 192         init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2;
 193         init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2;
 194         init_task.signal->rlim[RLIMIT_SIGPENDING] =
 195                 init_task.signal->rlim[RLIMIT_NPROC];
 196 }
 197
 198 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst,
 199                                                struct task_struct *src)
 200 {
 201         *dst = *src;
 202         return 0;
 203 }
 204
 205 static struct task_struct *dup_task_struct(struct task_struct *orig)
 206 {
 207         struct task_struct *tsk;
 208         struct thread_info *ti;
 209         int err;
 210
 211         prepare_to_copy(orig);
 212
 213         tsk = alloc_task_struct();
 214         if (!tsk)
 215                 return NULL;
 216
 217         ti = alloc_thread_info(tsk);
 218         if (!ti) {
 219                 free_task_struct(tsk);
 220                 return NULL;
 221         }
 222
 223         err = arch_dup_task_struct(tsk, orig);
 224         if (err)
 225                 goto out;
 226
 227         tsk->stack = ti;
 228
 229         err = prop_local_init_single(&tsk->dirties);
 230         if (err)
 231                 goto out;
 232
 233         setup_thread_stack(tsk, orig);
 234
 235 #ifdef CONFIG_CC_STACKPROTECTOR
 236         tsk->stack_canary = get_random_int();
 237 #endif
 238
 239         /* One for us, one for whoever does the "release_task()" (usually parent) */
 240         atomic_set(&tsk->usage,2);
 241         atomic_set(&tsk->fs_excl, 0);
 242 #ifdef CONFIG_BLK_DEV_IO_TRACE
 243         tsk->btrace_seq = 0;
 244 #endif
 245         tsk->splice_pipe = NULL;
 246         return tsk;
 247
 248 out:
 249         free_thread_info(ti);
 250         free_task_struct(tsk);
 251         return NULL;
 252 }
 253
 254 #ifdef CONFIG_MMU
 255 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 256 {
 257         struct vm_area_struct *mpnt, *tmp, **pprev;
 258         struct rb_node **rb_link, *rb_parent;
 259         int retval;
 260         unsigned long charge;
 261         struct mempolicy *pol;
 262
 263         down_write(&oldmm->mmap_sem);
 264         flush_cache_dup_mm(oldmm);
 265         /*
 266          * Not linked in yet - no deadlock potential:
 267          */
 268         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 269
 270         mm->locked_vm = 0;
 271         mm->mmap = NULL;
 272         mm->mmap_cache = NULL;
 273         mm->free_area_cache = oldmm->mmap_base;
 274         mm->cached_hole_size = ~0UL;
 275         mm->map_count = 0;
 276         cpus_clear(mm->cpu_vm_mask);
 277         mm->mm_rb = RB_ROOT;
 278         rb_link = &mm->mm_rb.rb_node;
 279         rb_parent = NULL;
 280         pprev = &mm->mmap;
 281
 282         for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {
 283                 struct file *file;
 284
 285                 if (mpnt->vm_flags & VM_DONTCOPY) {
 286                         long pages = vma_pages(mpnt);
 287                         mm->total_vm -= pages;
 288                         vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file,
 289                                                                 -pages);
 290                         continue;
 291                 }
 292                 charge = 0;
 293                 if (mpnt->vm_flags & VM_ACCOUNT) {
 294                         unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT;
 295                         if (security_vm_enough_memory(len))
 296                                 goto fail_nomem;
 297                         charge = len;
 298                 }
 299                 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
 300                 if (!tmp)
 301                         goto fail_nomem;
 302                 *tmp = *mpnt;
 303                 pol = mpol_dup(vma_policy(mpnt));
 304                 retval = PTR_ERR(pol);
 305                 if (IS_ERR(pol))
 306                         goto fail_nomem_policy;
 307                 vma_set_policy(tmp, pol);
 308                 tmp->vm_flags &= ~VM_LOCKED;
 309                 tmp->vm_mm = mm;
 310                 tmp->vm_next = NULL;
 311                 anon_vma_link(tmp);
 312                 file = tmp->vm_file;
 313                 if (file) {
 314                         struct inode *inode = file->f_path.dentry->d_inode;
 315                         get_file(file);
 316                         if (tmp->vm_flags & VM_DENYWRITE)
 317                                 atomic_dec(&inode->i_writecount);
 318
 319                         /* insert tmp into the share list, just after mpnt */
 320                         spin_lock(&file->f_mapping->i_mmap_lock);
 321                         tmp->vm_truncate_count = mpnt->vm_truncate_count;
 322                         flush_dcache_mmap_lock(file->f_mapping);
 323                         vma_prio_tree_add(tmp, mpnt);
 324                         flush_dcache_mmap_unlock(file->f_mapping);
 325                         spin_unlock(&file->f_mapping->i_mmap_lock);
 326                 }
 327
 328                 /*
 329                  * Clear hugetlb-related page reserves for children. This only
 330                  * affects MAP_PRIVATE mappings. Faults generated by the child
 331                  * are not guaranteed to succeed, even if read-only
 332                  */
 333                 if (is_vm_hugetlb_page(tmp))
 334                         reset_vma_resv_huge_pages(tmp);
 335
 336                 /*
 337                  * Link in the new vma and copy the page table entries.
 338                  */
 339                 *pprev = tmp;
 340                 pprev = &tmp->vm_next;
 341
 342                 __vma_link_rb(mm, tmp, rb_link, rb_parent);
 343                 rb_link = &tmp->vm_rb.rb_right;
 344                 rb_parent = &tmp->vm_rb;
 345
 346                 mm->map_count++;
 347                 retval = copy_page_range(mm, oldmm, mpnt);
 348
 349                 if (tmp->vm_ops && tmp->vm_ops->open)
 350                         tmp->vm_ops->open(tmp);
 351
 352                 if (retval)
 353                         goto out;
 354         }
 355         /* a new mm has just been created */
 356         arch_dup_mmap(oldmm, mm);
 357         retval = 0;
 358 out:
 359         up_write(&mm->mmap_sem);
 360         flush_tlb_mm(oldmm);
 361         up_write(&oldmm->mmap_sem);
 362         return retval;
 363 fail_nomem_policy:
 364         kmem_cache_free(vm_area_cachep, tmp);
 365 fail_nomem:
 366         retval = -ENOMEM;
 367         vm_unacct_memory(charge);
 368         goto out;
 369 }
 370
 371 static inline int mm_alloc_pgd(struct mm_struct * mm)
 372 {
 373         mm->pgd = pgd_alloc(mm);
 374         if (unlikely(!mm->pgd))
 375                 return -ENOMEM;
 376         return 0;
 377 }
 378
 379 static inline void mm_free_pgd(struct mm_struct * mm)
 380 {
 381         pgd_free(mm, mm->pgd);
 382 }
 383 #else
 384 #define dup_mmap(mm, oldmm)     (0)
 385 #define mm_alloc_pgd(mm)        (0)
 386 #define mm_free_pgd(mm)
 387 #endif /* CONFIG_MMU */
 388
 389 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock);
 390
 391 #define allocate_mm()   (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
 392 #define free_mm(mm)     (kmem_cache_free(mm_cachep, (mm)))
 393
 394 #include <linux/init_task.h>
 395
 396 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p)
 397 {
 398         atomic_set(&mm->mm_users, 1);
 399         atomic_set(&mm->mm_count, 1);
 400         init_rwsem(&mm->mmap_sem);
 401         INIT_LIST_HEAD(&mm->mmlist);
 402         mm->flags = (current->mm) ? current->mm->flags
 403                                   : MMF_DUMP_FILTER_DEFAULT;
 404         mm->core_state = NULL;
 405         mm->nr_ptes = 0;
 406         set_mm_counter(mm, file_rss, 0);
 407         set_mm_counter(mm, anon_rss, 0);
 408         spin_lock_init(&mm->page_table_lock);
 409         rwlock_init(&mm->ioctx_list_lock);
 410         mm->ioctx_list = NULL;
 411         mm->free_area_cache = TASK_UNMAPPED_BASE;
 412         mm->cached_hole_size = ~0UL;
 413         mm_init_owner(mm, p);
 414
 415         if (likely(!mm_alloc_pgd(mm))) {
 416                 mm->def_flags = 0;
 417                 mmu_notifier_mm_init(mm);
 418                 return mm;
 419         }
 420
 421         free_mm(mm);
 422         return NULL;
 423 }
 424
 425 /*
 426  * Allocate and initialize an mm_struct.
 427  */
 428 struct mm_struct * mm_alloc(void)
 429 {
 430         struct mm_struct * mm;
 431
 432         mm = allocate_mm();
 433         if (mm) {
 434                 memset(mm, 0, sizeof(*mm));
 435                 mm = mm_init(mm, current);
 436         }
 437         return mm;
 438 }
 439
 440 /*
 441  * Called when the last reference to the mm
 442  * is dropped: either by a lazy thread or by
 443  * mmput. Free the page directory and the mm.
 444  */
 445 void __mmdrop(struct mm_struct *mm)
 446 {
 447         BUG_ON(mm == &init_mm);
 448         mm_free_pgd(mm);
 449         destroy_context(mm);
 450         mmu_notifier_mm_destroy(mm);
 451         free_mm(mm);
 452 }
 453 EXPORT_SYMBOL_GPL(__mmdrop);
 454
 455 /*
 456  * Decrement the use count and release all resources for an mm.
 457  */
 458 void mmput(struct mm_struct *mm)
 459 {
 460         might_sleep();
 461
 462         if (atomic_dec_and_test(&mm->mm_users)) {
 463                 exit_aio(mm);
 464                 exit_mmap(mm);
 465                 set_mm_exe_file(mm, NULL);
 466                 if (!list_empty(&mm->mmlist)) {
 467                         spin_lock(&mmlist_lock);
 468                         list_del(&mm->mmlist);
 469                         spin_unlock(&mmlist_lock);
 470                 }
 471                 put_swap_token(mm);
 472                 mmdrop(mm);
 473         }
 474 }
 475 EXPORT_SYMBOL_GPL(mmput);
 476
 477 /**
 478  * get_task_mm - acquire a reference to the task's mm
 479  *
 480  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 481  * this kernel workthread has transiently adopted a user mm with use_mm,
 482  * to do its AIO) is not set and if so returns a reference to it, after
 483  * bumping up the use count.  User must release the mm via mmput()
 484  * after use.  Typically used by /proc and ptrace.
 485  */
 486 struct mm_struct *get_task_mm(struct task_struct *task)
 487 {
 488         struct mm_struct *mm;
 489
 490         task_lock(task);
 491         mm = task->mm;
 492         if (mm) {
 493                 if (task->flags & PF_KTHREAD)
 494                         mm = NULL;
 495                 else
 496                         atomic_inc(&mm->mm_users);
 497         }
 498         task_unlock(task);
 499         return mm;
 500 }
 501 EXPORT_SYMBOL_GPL(get_task_mm);
 502
 503 /* Please note the differences between mmput and mm_release.
 504  * mmput is called whenever we stop holding onto a mm_struct,
 505  * error success whatever.
 506  *
 507  * mm_release is called after a mm_struct has been removed
 508  * from the current process.
 509  *
 510  * This difference is important for error handling, when we
 511  * only half set up a mm_struct for a new process and need to restore
 512  * the old one.  Because we mmput the new mm_struct before
 513  * restoring the old one. . .
 514  * Eric Biederman 10 January 1998
 515  */
 516 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 517 {
 518         struct completion *vfork_done = tsk->vfork_done;
 519
 520         /* Get rid of any cached register state */
 521         deactivate_mm(tsk, mm);
 522
 523         /* notify parent sleeping on vfork() */
 524         if (vfork_done) {
 525                 tsk->vfork_done = NULL;
 526                 complete(vfork_done);
 527         }
 528
 529         /*
 530          * If we're exiting normally, clear a user-space tid field if
 531          * requested.  We leave this alone when dying by signal, to leave
 532          * the value intact in a core dump, and to save the unnecessary
 533          * trouble otherwise.  Userland only wants this done for a sys_exit.
 534          */
 535         if (tsk->clear_child_tid
 536             && !(tsk->flags & PF_SIGNALED)
 537             && atomic_read(&mm->mm_users) > 1) {
 538                 u32 __user * tidptr = tsk->clear_child_tid;
 539                 tsk->clear_child_tid = NULL;
 540
 541                 /*
 542                  * We don't check the error code - if userspace has
 543                  * not set up a proper pointer then tough luck.
 544                  */
 545                 put_user(0, tidptr);
 546                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 547         }
 548 }
 549
 550 /*
 551  * Allocate a new mm structure and copy contents from the
 552  * mm structure of the passed in task structure.
 553  */
 554 struct mm_struct *dup_mm(struct task_struct *tsk)
 555 {
 556         struct mm_struct *mm, *oldmm = current->mm;
 557         int err;
 558
 559         if (!oldmm)
 560                 return NULL;
 561
 562         mm = allocate_mm();
 563         if (!mm)
 564                 goto fail_nomem;
 565
 566         memcpy(mm, oldmm, sizeof(*mm));
 567
 568         /* Initializing for Swap token stuff */
 569         mm->token_priority = 0;
 570         mm->last_interval = 0;
 571
 572         if (!mm_init(mm, tsk))
 573                 goto fail_nomem;
 574
 575         if (init_new_context(tsk, mm))
 576                 goto fail_nocontext;
 577
 578         dup_mm_exe_file(oldmm, mm);
 579
 580         err = dup_mmap(mm, oldmm);
 581         if (err)
 582                 goto free_pt;
 583
 584         mm->hiwater_rss = get_mm_rss(mm);
 585         mm->hiwater_vm = mm->total_vm;
 586
 587         return mm;
 588
 589 free_pt:
 590         mmput(mm);
 591
 592 fail_nomem:
 593         return NULL;
 594
 595 fail_nocontext:
 596         /*
 597          * If init_new_context() failed, we cannot use mmput() to free the mm
 598          * because it calls destroy_context()
 599          */
 600         mm_free_pgd(mm);
 601         free_mm(mm);
 602         return NULL;
 603 }
 604
 605 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 606 {
 607         struct mm_struct * mm, *oldmm;
 608         int retval;
 609
 610         tsk->min_flt = tsk->maj_flt = 0;
 611         tsk->nvcsw = tsk->nivcsw = 0;
 612
 613         tsk->mm = NULL;
 614         tsk->active_mm = NULL;
 615
 616         /*
 617          * Are we cloning a kernel thread?
 618          *
 619          * We need to steal a active VM for that..
 620          */
 621         oldmm = current->mm;
 622         if (!oldmm)
 623                 return 0;
 624
 625         if (clone_flags & CLONE_VM) {
 626                 atomic_inc(&oldmm->mm_users);
 627                 mm = oldmm;
 628                 goto good_mm;
 629         }
 630
 631         retval = -ENOMEM;
 632         mm = dup_mm(tsk);
 633         if (!mm)
 634                 goto fail_nomem;
 635
 636 good_mm:
 637         /* Initializing for Swap token stuff */
 638         mm->token_priority = 0;
 639         mm->last_interval = 0;
 640
 641         tsk->mm = mm;
 642         tsk->active_mm = mm;
 643         return 0;
 644
 645 fail_nomem:
 646         return retval;
 647 }
 648
 649 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 650 {
 651         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 652         /* We don't need to lock fs - think why ;-) */
 653         if (fs) {
 654                 atomic_set(&fs->count, 1);
 655                 rwlock_init(&fs->lock);
 656                 fs->umask = old->umask;
 657                 read_lock(&old->lock);
 658                 fs->root = old->root;
 659                 path_get(&old->root);
 660                 fs->pwd = old->pwd;
 661                 path_get(&old->pwd);
 662                 read_unlock(&old->lock);
 663         }
 664         return fs;
 665 }
 666
 667 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 668 {
 669         return __copy_fs_struct(old);
 670 }
 671
 672 EXPORT_SYMBOL_GPL(copy_fs_struct);
 673
 674 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 675 {
 676         if (clone_flags & CLONE_FS) {
 677                 atomic_inc(&current->fs->count);
 678                 return 0;
 679         }
 680         tsk->fs = __copy_fs_struct(current->fs);
 681         if (!tsk->fs)
 682                 return -ENOMEM;
 683         return 0;
 684 }
 685
 686 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 687 {
 688         struct files_struct *oldf, *newf;
 689         int error = 0;
 690
 691         /*
 692          * A background process may not have any files ...
 693          */
 694         oldf = current->files;
 695         if (!oldf)
 696                 goto out;
 697
 698         if (clone_flags & CLONE_FILES) {
 699                 atomic_inc(&oldf->count);
 700                 goto out;
 701         }
 702
 703         newf = dup_fd(oldf, &error);
 704         if (!newf)
 705                 goto out;
 706
 707         tsk->files = newf;
 708         error = 0;
 709 out:
 710         return error;
 711 }
 712
 713 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 714 {
 715 #ifdef CONFIG_BLOCK
 716         struct io_context *ioc = current->io_context;
 717
 718         if (!ioc)
 719                 return 0;
 720         /*
 721          * Share io context with parent, if CLONE_IO is set
 722          */
 723         if (clone_flags & CLONE_IO) {
 724                 tsk->io_context = ioc_task_link(ioc);
 725                 if (unlikely(!tsk->io_context))
 726                         return -ENOMEM;
 727         } else if (ioprio_valid(ioc->ioprio)) {
 728                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 729                 if (unlikely(!tsk->io_context))
 730                         return -ENOMEM;
 731
 732                 tsk->io_context->ioprio = ioc->ioprio;
 733         }
 734 #endif
 735         return 0;
 736 }
 737
 738 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 739 {
 740         struct sighand_struct *sig;
 741
 742         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 743                 atomic_inc(&current->sighand->count);
 744                 return 0;
 745         }
 746         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 747         rcu_assign_pointer(tsk->sighand, sig);
 748         if (!sig)
 749                 return -ENOMEM;
 750         atomic_set(&sig->count, 1);
 751         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 752         return 0;
 753 }
 754
 755 void __cleanup_sighand(struct sighand_struct *sighand)
 756 {
 757         if (atomic_dec_and_test(&sighand->count))
 758                 kmem_cache_free(sighand_cachep, sighand);
 759 }
 760
 761
 762 /*
 763  * Initialize POSIX timer handling for a thread group.
 764  */
 765 static void posix_cpu_timers_init_group(struct signal_struct *sig)
 766 {
 767         /* Thread group counters. */
 768         thread_group_cputime_init(sig);
 769
 770         /* Expiration times and increments. */
 771         sig->it_virt_expires = cputime_zero;
 772         sig->it_virt_incr = cputime_zero;
 773         sig->it_prof_expires = cputime_zero;
 774         sig->it_prof_incr = cputime_zero;
 775
 776         /* Cached expiration times. */
 777         sig->cputime_expires.prof_exp = cputime_zero;
 778         sig->cputime_expires.virt_exp = cputime_zero;
 779         sig->cputime_expires.sched_exp = 0;
 780
 781         /* The timer lists. */
 782         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 783         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 784         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 785 }
 786
 787 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 788 {
 789         struct signal_struct *sig;
 790         int ret;
 791
 792         if (clone_flags & CLONE_THREAD) {
 793                 ret = thread_group_cputime_clone_thread(current);
 794                 if (likely(!ret)) {
 795                         atomic_inc(&current->signal->count);
 796                         atomic_inc(&current->signal->live);
 797                 }
 798                 return ret;
 799         }
 800         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 801         tsk->signal = sig;
 802         if (!sig)
 803                 return -ENOMEM;
 804
 805         ret = copy_thread_group_keys(tsk);
 806         if (ret < 0) {
 807                 kmem_cache_free(signal_cachep, sig);
 808                 return ret;
 809         }
 810
 811         atomic_set(&sig->count, 1);
 812         atomic_set(&sig->live, 1);
 813         init_waitqueue_head(&sig->wait_chldexit);
 814         sig->flags = 0;
 815         sig->group_exit_code = 0;
 816         sig->group_exit_task = NULL;
 817         sig->group_stop_count = 0;
 818         sig->curr_target = tsk;
 819         init_sigpending(&sig->shared_pending);
 820         INIT_LIST_HEAD(&sig->posix_timers);
 821
 822         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 823         sig->it_real_incr.tv64 = 0;
 824         sig->real_timer.function = it_real_fn;
 825
 826         sig->leader = 0;        /* session leadership doesn't inherit */
 827         sig->tty_old_pgrp = NULL;
 828         sig->tty = NULL;
 829
 830         sig->cutime = sig->cstime = cputime_zero;
 831         sig->gtime = cputime_zero;
 832         sig->cgtime = cputime_zero;
 833         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 834         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 835         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 836         task_io_accounting_init(&sig->ioac);
 837         taskstats_tgid_init(sig);
 838
 839         task_lock(current->group_leader);
 840         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 841         task_unlock(current->group_leader);
 842
 843         posix_cpu_timers_init_group(sig);
 844
 845         acct_init_pacct(&sig->pacct);
 846
 847         tty_audit_fork(sig);
 848
 849         return 0;
 850 }
 851
 852 void __cleanup_signal(struct signal_struct *sig)
 853 {
 854         thread_group_cputime_free(sig);
 855         exit_thread_group_keys(sig);
 856         tty_kref_put(sig->tty);
 857         kmem_cache_free(signal_cachep, sig);
 858 }
 859
 860 static void cleanup_signal(struct task_struct *tsk)
 861 {
 862         struct signal_struct *sig = tsk->signal;
 863
 864         atomic_dec(&sig->live);
 865
 866         if (atomic_dec_and_test(&sig->count))
 867                 __cleanup_signal(sig);
 868 }
 869
 870 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 871 {
 872         unsigned long new_flags = p->flags;
 873
 874         new_flags &= ~PF_SUPERPRIV;
 875         new_flags |= PF_FORKNOEXEC;
 876         new_flags |= PF_STARTING;
 877         p->flags = new_flags;
 878         clear_freeze_flag(p);
 879 }
 880
 881 asmlinkage long sys_set_tid_address(int __user *tidptr)
 882 {
 883         current->clear_child_tid = tidptr;
 884
 885         return task_pid_vnr(current);
 886 }
 887
 888 static void rt_mutex_init_task(struct task_struct *p)
 889 {
 890         spin_lock_init(&p->pi_lock);
 891 #ifdef CONFIG_RT_MUTEXES
 892         plist_head_init(&p->pi_waiters, &p->pi_lock);
 893         p->pi_blocked_on = NULL;
 894 #endif
 895 }
 896
 897 #ifdef CONFIG_MM_OWNER
 898 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 899 {
 900         mm->owner = p;
 901 }
 902 #endif /* CONFIG_MM_OWNER */
 903
 904 /*
 905  * Initialize POSIX timer handling for a single task.
 906  */
 907 static void posix_cpu_timers_init(struct task_struct *tsk)
 908 {
 909         tsk->cputime_expires.prof_exp = cputime_zero;
 910         tsk->cputime_expires.virt_exp = cputime_zero;
 911         tsk->cputime_expires.sched_exp = 0;
 912         INIT_LIST_HEAD(&tsk->cpu_timers[0]);
 913         INIT_LIST_HEAD(&tsk->cpu_timers[1]);
 914         INIT_LIST_HEAD(&tsk->cpu_timers[2]);
 915 }
 916
 917 /*
 918  * This creates a new process as a copy of the old one,
 919  * but does not actually start it yet.
 920  *
 921  * It copies the registers, and all the appropriate
 922  * parts of the process environment (as per the clone
 923  * flags). The actual kick-off is left to the caller.
 924  */
 925 static struct task_struct *copy_process(unsigned long clone_flags,
 926                                         unsigned long stack_start,
 927                                         struct pt_regs *regs,
 928                                         unsigned long stack_size,
 929                                         int __user *child_tidptr,
 930                                         struct pid *pid,
 931                                         int trace)
 932 {
 933         int retval;
 934         struct task_struct *p;
 935         int cgroup_callbacks_done = 0;
 936
 937         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 938                 return ERR_PTR(-EINVAL);
 939
 940         /*
 941          * Thread groups must share signals as well, and detached threads
 942          * can only be started up within the thread group.
 943          */
 944         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 945                 return ERR_PTR(-EINVAL);
 946
 947         /*
 948          * Shared signal handlers imply shared VM. By way of the above,
 949          * thread groups also imply shared VM. Blocking this case allows
 950          * for various simplifications in other code.
 951          */
 952         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 953                 return ERR_PTR(-EINVAL);
 954
 955         retval = security_task_create(clone_flags);
 956         if (retval)
 957                 goto fork_out;
 958
 959         retval = -ENOMEM;
 960         p = dup_task_struct(current);
 961         if (!p)
 962                 goto fork_out;
 963
 964         rt_mutex_init_task(p);
 965
 966 #ifdef CONFIG_PROVE_LOCKING
 967         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 968         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 969 #endif
 970         retval = -EAGAIN;
 971         if (atomic_read(&p->cred->user->processes) >=
 972                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 973                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 974                     p->cred->user != current->nsproxy->user_ns->root_user)
 975                         goto bad_fork_free;
 976         }
 977
 978         retval = copy_creds(p, clone_flags);
 979         if (retval < 0)
 980                 goto bad_fork_free;
 981
 982         /*
 983          * If multiple threads are within copy_process(), then this check
 984          * triggers too late. This doesn't hurt, the check is only there
 985          * to stop root fork bombs.
 986          */
 987         if (nr_threads >= max_threads)
 988                 goto bad_fork_cleanup_count;
 989
 990         if (!try_module_get(task_thread_info(p)->exec_domain->module))
 991                 goto bad_fork_cleanup_count;
 992
 993         if (p->binfmt && !try_module_get(p->binfmt->module))
 994                 goto bad_fork_cleanup_put_domain;
 995
 996         p->did_exec = 0;
 997         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
 998         copy_flags(clone_flags, p);
 999         INIT_LIST_HEAD(&p->children);
1000         INIT_LIST_HEAD(&p->sibling);
1001 #ifdef CONFIG_PREEMPT_RCU
1002         p->rcu_read_lock_nesting = 0;
1003         p->rcu_flipctr_idx = 0;
1004 #endif /* #ifdef CONFIG_PREEMPT_RCU */
1005         p->vfork_done = NULL;
1006         spin_lock_init(&p->alloc_lock);
1007
1008         clear_tsk_thread_flag(p, TIF_SIGPENDING);
1009         init_sigpending(&p->pending);
1010
1011         p->utime = cputime_zero;
1012         p->stime = cputime_zero;
1013         p->gtime = cputime_zero;
1014         p->utimescaled = cputime_zero;
1015         p->stimescaled = cputime_zero;
1016         p->prev_utime = cputime_zero;
1017         p->prev_stime = cputime_zero;
1018
1019         p->default_timer_slack_ns = current->timer_slack_ns;
1020
1021 #ifdef CONFIG_DETECT_SOFTLOCKUP
1022         p->last_switch_count = 0;
1023         p->last_switch_timestamp = 0;
1024 #endif
1025
1026         task_io_accounting_init(&p->ioac);
1027         acct_clear_integrals(p);
1028
1029         posix_cpu_timers_init(p);
1030
1031         p->lock_depth = -1;             /* -1 = no lock */
1032         do_posix_clock_monotonic_gettime(&p->start_time);
1033         p->real_start_time = p->start_time;
1034         monotonic_to_bootbased(&p->real_start_time);
1035         p->io_context = NULL;
1036         p->audit_context = NULL;
1037         cgroup_fork(p);
1038 #ifdef CONFIG_NUMA
1039         p->mempolicy = mpol_dup(p->mempolicy);
1040         if (IS_ERR(p->mempolicy)) {
1041                 retval = PTR_ERR(p->mempolicy);
1042                 p->mempolicy = NULL;
1043                 goto bad_fork_cleanup_cgroup;
1044         }
1045         mpol_fix_fork_child_flag(p);
1046 #endif
1047 #ifdef CONFIG_TRACE_IRQFLAGS
1048         p->irq_events = 0;
1049 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1050         p->hardirqs_enabled = 1;
1051 #else
1052         p->hardirqs_enabled = 0;
1053 #endif
1054         p->hardirq_enable_ip = 0;
1055         p->hardirq_enable_event = 0;
1056         p->hardirq_disable_ip = _THIS_IP_;
1057         p->hardirq_disable_event = 0;
1058         p->softirqs_enabled = 1;
1059         p->softirq_enable_ip = _THIS_IP_;
1060         p->softirq_enable_event = 0;
1061         p->softirq_disable_ip = 0;
1062         p->softirq_disable_event = 0;
1063         p->hardirq_context = 0;
1064         p->softirq_context = 0;
1065 #endif
1066 #ifdef CONFIG_LOCKDEP
1067         p->lockdep_depth = 0; /* no locks held yet */
1068         p->curr_chain_key = 0;
1069         p->lockdep_recursion = 0;
1070 #endif
1071
1072 #ifdef CONFIG_DEBUG_MUTEXES
1073         p->blocked_on = NULL; /* not blocked yet */
1074 #endif
1075
1076         /* Perform scheduler related setup. Assign this task to a CPU. */
1077         sched_fork(p, clone_flags);
1078
1079         if ((retval = audit_alloc(p)))
1080                 goto bad_fork_cleanup_policy;
1081         /* copy all the process information */
1082         if ((retval = copy_semundo(clone_flags, p)))
1083                 goto bad_fork_cleanup_audit;
1084         if ((retval = copy_files(clone_flags, p)))
1085                 goto bad_fork_cleanup_semundo;
1086         if ((retval = copy_fs(clone_flags, p)))
1087                 goto bad_fork_cleanup_files;
1088         if ((retval = copy_sighand(clone_flags, p)))
1089                 goto bad_fork_cleanup_fs;
1090         if ((retval = copy_signal(clone_flags, p)))
1091                 goto bad_fork_cleanup_sighand;
1092         if ((retval = copy_mm(clone_flags, p)))
1093                 goto bad_fork_cleanup_signal;
1094         if ((retval = copy_keys(clone_flags, p)))
1095                 goto bad_fork_cleanup_mm;
1096         if ((retval = copy_namespaces(clone_flags, p)))
1097                 goto bad_fork_cleanup_keys;
1098         if ((retval = copy_io(clone_flags, p)))
1099                 goto bad_fork_cleanup_namespaces;
1100         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1101         if (retval)
1102                 goto bad_fork_cleanup_io;
1103
1104         if (pid != &init_struct_pid) {
1105                 retval = -ENOMEM;
1106                 pid = alloc_pid(task_active_pid_ns(p));
1107                 if (!pid)
1108                         goto bad_fork_cleanup_io;
1109
1110                 if (clone_flags & CLONE_NEWPID) {
1111                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1112                         if (retval < 0)
1113                                 goto bad_fork_free_pid;
1114                 }
1115         }
1116
1117         p->pid = pid_nr(pid);
1118         p->tgid = p->pid;
1119         if (clone_flags & CLONE_THREAD)
1120                 p->tgid = current->tgid;
1121
1122         if (current->nsproxy != p->nsproxy) {
1123                 retval = ns_cgroup_clone(p, pid);
1124                 if (retval)
1125                         goto bad_fork_free_pid;
1126         }
1127
1128         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1129         /*
1130          * Clear TID on mm_release()?
1131          */
1132         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1133 #ifdef CONFIG_FUTEX
1134         p->robust_list = NULL;
1135 #ifdef CONFIG_COMPAT
1136         p->compat_robust_list = NULL;
1137 #endif
1138         INIT_LIST_HEAD(&p->pi_state_list);
1139         p->pi_state_cache = NULL;
1140 #endif
1141         /*
1142          * sigaltstack should be cleared when sharing the same VM
1143          */
1144         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1145                 p->sas_ss_sp = p->sas_ss_size = 0;
1146
1147         /*
1148          * Syscall tracing should be turned off in the child regardless
1149          * of CLONE_PTRACE.
1150          */
1151         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1152 #ifdef TIF_SYSCALL_EMU
1153         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1154 #endif
1155         clear_all_latency_tracing(p);
1156
1157         /* Our parent execution domain becomes current domain
1158            These must match for thread signalling to apply */
1159         p->parent_exec_id = p->self_exec_id;
1160
1161         /* ok, now we should be set up.. */
1162         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1163         p->pdeath_signal = 0;
1164         p->exit_state = 0;
1165
1166         /*
1167          * Ok, make it visible to the rest of the system.
1168          * We dont wake it up yet.
1169          */
1170         p->group_leader = p;
1171         INIT_LIST_HEAD(&p->thread_group);
1172
1173         /* Now that the task is set up, run cgroup callbacks if
1174          * necessary. We need to run them before the task is visible
1175          * on the tasklist. */
1176         cgroup_fork_callbacks(p);
1177         cgroup_callbacks_done = 1;
1178
1179         /* Need tasklist lock for parent etc handling! */
1180         write_lock_irq(&tasklist_lock);
1181
1182         /*
1183          * The task hasn't been attached yet, so its cpus_allowed mask will
1184          * not be changed, nor will its assigned CPU.
1185          *
1186          * The cpus_allowed mask of the parent may have changed after it was
1187          * copied first time - so re-copy it here, then check the child's CPU
1188          * to ensure it is on a valid CPU (and if not, just force it back to
1189          * parent's CPU). This avoids alot of nasty races.
1190          */
1191         p->cpus_allowed = current->cpus_allowed;
1192         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1193         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1194                         !cpu_online(task_cpu(p))))
1195                 set_task_cpu(p, smp_processor_id());
1196
1197         /* CLONE_PARENT re-uses the old parent */
1198         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1199                 p->real_parent = current->real_parent;
1200         else
1201                 p->real_parent = current;
1202
1203         spin_lock(&current->sighand->siglock);
1204
1205         /*
1206          * Process group and session signals need to be delivered to just the
1207          * parent before the fork or both the parent and the child after the
1208          * fork. Restart if a signal comes in before we add the new process to
1209          * it's process group.
1210          * A fatal signal pending means that current will exit, so the new
1211          * thread can't slip out of an OOM kill (or normal SIGKILL).
1212          */
1213         recalc_sigpending();
1214         if (signal_pending(current)) {
1215                 spin_unlock(&current->sighand->siglock);
1216                 write_unlock_irq(&tasklist_lock);
1217                 retval = -ERESTARTNOINTR;
1218                 goto bad_fork_free_pid;
1219         }
1220
1221         if (clone_flags & CLONE_THREAD) {
1222                 p->group_leader = current->group_leader;
1223                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1224         }
1225
1226         if (likely(p->pid)) {
1227                 list_add_tail(&p->sibling, &p->real_parent->children);
1228                 tracehook_finish_clone(p, clone_flags, trace);
1229
1230                 if (thread_group_leader(p)) {
1231                         if (clone_flags & CLONE_NEWPID)
1232                                 p->nsproxy->pid_ns->child_reaper = p;
1233
1234                         p->signal->leader_pid = pid;
1235                         tty_kref_put(p->signal->tty);
1236                         p->signal->tty = tty_kref_get(current->signal->tty);
1237                         set_task_pgrp(p, task_pgrp_nr(current));
1238                         set_task_session(p, task_session_nr(current));
1239                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1240                         attach_pid(p, PIDTYPE_SID, task_session(current));
1241                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1242                         __get_cpu_var(process_counts)++;
1243                 }
1244                 attach_pid(p, PIDTYPE_PID, pid);
1245                 nr_threads++;
1246         }
1247
1248         total_forks++;
1249         spin_unlock(&current->sighand->siglock);
1250         write_unlock_irq(&tasklist_lock);
1251         proc_fork_connector(p);
1252         cgroup_post_fork(p);
1253         return p;
1254
1255 bad_fork_free_pid:
1256         if (pid != &init_struct_pid)
1257                 free_pid(pid);
1258 bad_fork_cleanup_io:
1259         put_io_context(p->io_context);
1260 bad_fork_cleanup_namespaces:
1261         exit_task_namespaces(p);
1262 bad_fork_cleanup_keys:
1263         exit_keys(p);
1264 bad_fork_cleanup_mm:
1265         if (p->mm)
1266                 mmput(p->mm);
1267 bad_fork_cleanup_signal:
1268         cleanup_signal(p);
1269 bad_fork_cleanup_sighand:
1270         __cleanup_sighand(p->sighand);
1271 bad_fork_cleanup_fs:
1272         exit_fs(p); /* blocking */
1273 bad_fork_cleanup_files:
1274         exit_files(p); /* blocking */
1275 bad_fork_cleanup_semundo:
1276         exit_sem(p);
1277 bad_fork_cleanup_audit:
1278         audit_free(p);
1279 bad_fork_cleanup_policy:
1280 #ifdef CONFIG_NUMA
1281         mpol_put(p->mempolicy);
1282 bad_fork_cleanup_cgroup:
1283 #endif
1284         cgroup_exit(p, cgroup_callbacks_done);
1285         delayacct_tsk_free(p);
1286         if (p->binfmt)
1287                 module_put(p->binfmt->module);
1288 bad_fork_cleanup_put_domain:
1289         module_put(task_thread_info(p)->exec_domain->module);
1290 bad_fork_cleanup_count:
1291         put_cred(p->cred);
1292 bad_fork_free:
1293         free_task(p);
1294 fork_out:
1295         return ERR_PTR(retval);
1296 }
1297
1298 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1299 {
1300         memset(regs, 0, sizeof(struct pt_regs));
1301         return regs;
1302 }
1303
1304 struct task_struct * __cpuinit fork_idle(int cpu)
1305 {
1306         struct task_struct *task;
1307         struct pt_regs regs;
1308
1309         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1310                             &init_struct_pid, 0);
1311         if (!IS_ERR(task))
1312                 init_idle(task, cpu);
1313
1314         return task;
1315 }
1316
1317 /*
1318  *  Ok, this is the main fork-routine.
1319  *
1320  * It copies the process, and if successful kick-starts
1321  * it and waits for it to finish using the VM if required.
1322  */
1323 long do_fork(unsigned long clone_flags,
1324               unsigned long stack_start,
1325               struct pt_regs *regs,
1326               unsigned long stack_size,
1327               int __user *parent_tidptr,
1328               int __user *child_tidptr)
1329 {
1330         struct task_struct *p;
1331         int trace = 0;
1332         long nr;
1333
1334         /*
1335          * We hope to recycle these flags after 2.6.26
1336          */
1337         if (unlikely(clone_flags & CLONE_STOPPED)) {
1338                 static int __read_mostly count = 100;
1339
1340                 if (count > 0 && printk_ratelimit()) {
1341                         char comm[TASK_COMM_LEN];
1342
1343                         count--;
1344                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1345                                         "clone flags 0x%lx\n",
1346                                 get_task_comm(comm, current),
1347                                 clone_flags & CLONE_STOPPED);
1348                 }
1349         }
1350
1351         /*
1352          * When called from kernel_thread, don't do user tracing stuff.
1353          */
1354         if (likely(user_mode(regs)))
1355                 trace = tracehook_prepare_clone(clone_flags);
1356
1357         p = copy_process(clone_flags, stack_start, regs, stack_size,
1358                          child_tidptr, NULL, trace);
1359         /*
1360          * Do this prior waking up the new thread - the thread pointer
1361          * might get invalid after that point, if the thread exits quickly.
1362          */
1363         if (!IS_ERR(p)) {
1364                 struct completion vfork;
1365
1366                 trace_sched_process_fork(current, p);
1367
1368                 nr = task_pid_vnr(p);
1369
1370                 if (clone_flags & CLONE_PARENT_SETTID)
1371                         put_user(nr, parent_tidptr);
1372
1373                 if (clone_flags & CLONE_VFORK) {
1374                         p->vfork_done = &vfork;
1375                         init_completion(&vfork);
1376                 }
1377
1378                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1379
1380                 /*
1381                  * We set PF_STARTING at creation in case tracing wants to
1382                  * use this to distinguish a fully live task from one that
1383                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1384                  * clear it and set the child going.
1385                  */
1386                 p->flags &= ~PF_STARTING;
1387
1388                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1389                         /*
1390                          * We'll start up with an immediate SIGSTOP.
1391                          */
1392                         sigaddset(&p->pending.signal, SIGSTOP);
1393                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1394                         __set_task_state(p, TASK_STOPPED);
1395                 } else {
1396                         wake_up_new_task(p, clone_flags);
1397                 }
1398
1399                 tracehook_report_clone_complete(trace, regs,
1400                                                 clone_flags, nr, p);
1401
1402                 if (clone_flags & CLONE_VFORK) {
1403                         freezer_do_not_count();
1404                         wait_for_completion(&vfork);
1405                         freezer_count();
1406                         tracehook_report_vfork_done(p, nr);
1407                 }
1408         } else {
1409                 nr = PTR_ERR(p);
1410         }
1411         return nr;
1412 }
1413
1414 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1415 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1416 #endif
1417
1418 static void sighand_ctor(void *data)
1419 {
1420         struct sighand_struct *sighand = data;
1421
1422         spin_lock_init(&sighand->siglock);
1423         init_waitqueue_head(&sighand->signalfd_wqh);
1424 }
1425
1426 void __init proc_caches_init(void)
1427 {
1428         sighand_cachep = kmem_cache_create("sighand_cache",
1429                         sizeof(struct sighand_struct), 0,
1430                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1431                         sighand_ctor);
1432         signal_cachep = kmem_cache_create("signal_cache",
1433                         sizeof(struct signal_struct), 0,
1434                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1435         files_cachep = kmem_cache_create("files_cache",
1436                         sizeof(struct files_struct), 0,
1437                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1438         fs_cachep = kmem_cache_create("fs_cache",
1439                         sizeof(struct fs_struct), 0,
1440                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1441         vm_area_cachep = kmem_cache_create("vm_area_struct",
1442                         sizeof(struct vm_area_struct), 0,
1443                         SLAB_PANIC, NULL);
1444         mm_cachep = kmem_cache_create("mm_struct",
1445                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1446                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1447 }
1448
1449 /*
1450  * Check constraints on flags passed to the unshare system call and
1451  * force unsharing of additional process context as appropriate.
1452  */
1453 static void check_unshare_flags(unsigned long *flags_ptr)
1454 {
1455         /*
1456          * If unsharing a thread from a thread group, must also
1457          * unshare vm.
1458          */
1459         if (*flags_ptr & CLONE_THREAD)
1460                 *flags_ptr |= CLONE_VM;
1461
1462         /*
1463          * If unsharing vm, must also unshare signal handlers.
1464          */
1465         if (*flags_ptr & CLONE_VM)
1466                 *flags_ptr |= CLONE_SIGHAND;
1467
1468         /*
1469          * If unsharing signal handlers and the task was created
1470          * using CLONE_THREAD, then must unshare the thread
1471          */
1472         if ((*flags_ptr & CLONE_SIGHAND) &&
1473             (atomic_read(&current->signal->count) > 1))
1474                 *flags_ptr |= CLONE_THREAD;
1475
1476         /*
1477          * If unsharing namespace, must also unshare filesystem information.
1478          */
1479         if (*flags_ptr & CLONE_NEWNS)
1480                 *flags_ptr |= CLONE_FS;
1481 }
1482
1483 /*
1484  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1485  */
1486 static int unshare_thread(unsigned long unshare_flags)
1487 {
1488         if (unshare_flags & CLONE_THREAD)
1489                 return -EINVAL;
1490
1491         return 0;
1492 }
1493
1494 /*
1495  * Unshare the filesystem structure if it is being shared
1496  */
1497 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1498 {
1499         struct fs_struct *fs = current->fs;
1500
1501         if ((unshare_flags & CLONE_FS) &&
1502             (fs && atomic_read(&fs->count) > 1)) {
1503                 *new_fsp = __copy_fs_struct(current->fs);
1504                 if (!*new_fsp)
1505                         return -ENOMEM;
1506         }
1507
1508         return 0;
1509 }
1510
1511 /*
1512  * Unsharing of sighand is not supported yet
1513  */
1514 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1515 {
1516         struct sighand_struct *sigh = current->sighand;
1517
1518         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1519                 return -EINVAL;
1520         else
1521                 return 0;
1522 }
1523
1524 /*
1525  * Unshare vm if it is being shared
1526  */
1527 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1528 {
1529         struct mm_struct *mm = current->mm;
1530
1531         if ((unshare_flags & CLONE_VM) &&
1532             (mm && atomic_read(&mm->mm_users) > 1)) {
1533                 return -EINVAL;
1534         }
1535
1536         return 0;
1537 }
1538
1539 /*
1540  * Unshare file descriptor table if it is being shared
1541  */
1542 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1543 {
1544         struct files_struct *fd = current->files;
1545         int error = 0;
1546
1547         if ((unshare_flags & CLONE_FILES) &&
1548             (fd && atomic_read(&fd->count) > 1)) {
1549                 *new_fdp = dup_fd(fd, &error);
1550                 if (!*new_fdp)
1551                         return error;
1552         }
1553
1554         return 0;
1555 }
1556
1557 /*
1558  * unshare allows a process to 'unshare' part of the process
1559  * context which was originally shared using clone.  copy_*
1560  * functions used by do_fork() cannot be used here directly
1561  * because they modify an inactive task_struct that is being
1562  * constructed. Here we are modifying the current, active,
1563  * task_struct.
1564  */
1565 asmlinkage long sys_unshare(unsigned long unshare_flags)
1566 {
1567         int err = 0;
1568         struct fs_struct *fs, *new_fs = NULL;
1569         struct sighand_struct *new_sigh = NULL;
1570         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1571         struct files_struct *fd, *new_fd = NULL;
1572         struct nsproxy *new_nsproxy = NULL;
1573         int do_sysvsem = 0;
1574
1575         check_unshare_flags(&unshare_flags);
1576
1577         /* Return -EINVAL for all unsupported flags */
1578         err = -EINVAL;
1579         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1580                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1581                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1582                                 CLONE_NEWNET))
1583                 goto bad_unshare_out;
1584
1585         /*
1586          * CLONE_NEWIPC must also detach from the undolist: after switching
1587          * to a new ipc namespace, the semaphore arrays from the old
1588          * namespace are unreachable.
1589          */
1590         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1591                 do_sysvsem = 1;
1592         if ((err = unshare_thread(unshare_flags)))
1593                 goto bad_unshare_out;
1594         if ((err = unshare_fs(unshare_flags, &new_fs)))
1595                 goto bad_unshare_cleanup_thread;
1596         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1597                 goto bad_unshare_cleanup_fs;
1598         if ((err = unshare_vm(unshare_flags, &new_mm)))
1599                 goto bad_unshare_cleanup_sigh;
1600         if ((err = unshare_fd(unshare_flags, &new_fd)))
1601                 goto bad_unshare_cleanup_vm;
1602         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1603                         new_fs)))
1604                 goto bad_unshare_cleanup_fd;
1605
1606         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1607                 if (do_sysvsem) {
1608                         /*
1609                          * CLONE_SYSVSEM is equivalent to sys_exit().
1610                          */
1611                         exit_sem(current);
1612                 }
1613
1614                 if (new_nsproxy) {
1615                         switch_task_namespaces(current, new_nsproxy);
1616                         new_nsproxy = NULL;
1617                 }
1618
1619                 task_lock(current);
1620
1621                 if (new_fs) {
1622                         fs = current->fs;
1623                         current->fs = new_fs;
1624                         new_fs = fs;
1625                 }
1626
1627                 if (new_mm) {
1628                         mm = current->mm;
1629                         active_mm = current->active_mm;
1630                         current->mm = new_mm;
1631                         current->active_mm = new_mm;
1632                         activate_mm(active_mm, new_mm);
1633                         new_mm = mm;
1634                 }
1635
1636                 if (new_fd) {
1637                         fd = current->files;
1638                         current->files = new_fd;
1639                         new_fd = fd;
1640                 }
1641
1642                 task_unlock(current);
1643         }
1644
1645         if (new_nsproxy)
1646                 put_nsproxy(new_nsproxy);
1647
1648 bad_unshare_cleanup_fd:
1649         if (new_fd)
1650                 put_files_struct(new_fd);
1651
1652 bad_unshare_cleanup_vm:
1653         if (new_mm)
1654                 mmput(new_mm);
1655
1656 bad_unshare_cleanup_sigh:
1657         if (new_sigh)
1658                 if (atomic_dec_and_test(&new_sigh->count))
1659                         kmem_cache_free(sighand_cachep, new_sigh);
1660
1661 bad_unshare_cleanup_fs:
1662         if (new_fs)
1663                 put_fs_struct(new_fs);
1664
1665 bad_unshare_cleanup_thread:
1666 bad_unshare_out:
1667         return err;
1668 }
1669
1670 /*
1671  *      Helper to unshare the files of the current task.
1672  *      We don't want to expose copy_files internals to
1673  *      the exec layer of the kernel.
1674  */
1675
1676 int unshare_files(struct files_struct **displaced)
1677 {
1678         struct task_struct *task = current;
1679         struct files_struct *copy = NULL;
1680         int error;
1681
1682         error = unshare_fd(CLONE_FILES, &copy);
1683         if (error || !copy) {
1684                 *displaced = NULL;
1685                 return error;
1686         }
1687         *displaced = task->files;
1688         task_lock(task);
1689         task->files = copy;
1690         task_unlock(task);
1691         return 0;
1692 }