kernel/fork.c

   1 /*
   2  *  linux/kernel/fork.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  *  'fork.c' contains the help-routines for the 'fork' system call
   9  * (see also entry.S and others).
  10  * Fork is rather simple, once you get the hang of it, but the memory
  11  * management can be a bitch. See 'mm/memory.c': 'copy_page_range()'
  12  */
  13
  14 #include <linux/slab.h>
  15 #include <linux/init.h>
  16 #include <linux/unistd.h>
  17 #include <linux/module.h>
  18 #include <linux/vmalloc.h>
  19 #include <linux/completion.h>
  20 #include <linux/mnt_namespace.h>
  21 #include <linux/personality.h>
  22 #include <linux/mempolicy.h>
  23 #include <linux/sem.h>
  24 #include <linux/file.h>
  25 #include <linux/fdtable.h>
  26 #include <linux/iocontext.h>
  27 #include <linux/key.h>
  28 #include <linux/binfmts.h>
  29 #include <linux/mman.h>
  30 #include <linux/fs.h>
  31 #include <linux/nsproxy.h>
  32 #include <linux/capability.h>
  33 #include <linux/cpu.h>
  34 #include <linux/cgroup.h>
  35 #include <linux/security.h>
  36 #include <linux/hugetlb.h>
  37 #include <linux/swap.h>
  38 #include <linux/syscalls.h>
  39 #include <linux/jiffies.h>
  40 #include <linux/tracehook.h>
  41 #include <linux/futex.h>
  42 #include <linux/task_io_accounting_ops.h>
  43 #include <linux/rcupdate.h>
  44 #include <linux/ptrace.h>
  45 #include <linux/mount.h>
  46 #include <linux/audit.h>
  47 #include <linux/memcontrol.h>
  48 #include <linux/profile.h>
  49 #include <linux/rmap.h>
  50 #include <linux/acct.h>
  51 #include <linux/tsacct_kern.h>
  52 #include <linux/cn_proc.h>
  53 #include <linux/freezer.h>
  54 #include <linux/delayacct.h>
  55 #include <linux/taskstats_kern.h>
  56 #include <linux/random.h>
  57 #include <linux/tty.h>
  58 #include <linux/proc_fs.h>
  59 #include <linux/blkdev.h>
  60
  61 #include <asm/pgtable.h>
  62 #include <asm/pgalloc.h>
  63 #include <asm/uaccess.h>
  64 #include <asm/mmu_context.h>
  65 #include <asm/cacheflush.h>
  66 #include <asm/tlbflush.h>
  67
  68 /*
  69  * Protected counters by write_lock_irq(&tasklist_lock)
  70  */
  71 unsigned long total_forks;      /* Handle normal Linux uptimes. */
  72 int nr_threads;                 /* The idle threads do not count.. */
  73
  74 int max_threads;                /* tunable limit on nr_threads */
  75
  76 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
  77
  78 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock);  /* outer */
  79
  80 int nr_processes(void)
  81 {
  82         int cpu;
  83         int total = 0;
  84
  85         for_each_online_cpu(cpu)
  86                 total += per_cpu(process_counts, cpu);
  87
  88         return total;
  89 }
  90
  91 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
  92 # define alloc_task_struct()    kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
  93 # define free_task_struct(tsk)  kmem_cache_free(task_struct_cachep, (tsk))
  94 static struct kmem_cache *task_struct_cachep;
  95 #endif
  96
  97 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR
  98 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk)
  99 {
 100 #ifdef CONFIG_DEBUG_STACK_USAGE
 101         gfp_t mask = GFP_KERNEL | __GFP_ZERO;
 102 #else
 103         gfp_t mask = GFP_KERNEL;
 104 #endif
 105         return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER);
 106 }
 107
 108 static inline void free_thread_info(struct thread_info *ti)
 109 {
 110         free_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 111 }
 112 #endif
 113
 114 /* SLAB cache for signal_struct structures (tsk->signal) */
 115 static struct kmem_cache *signal_cachep;
 116
 117 /* SLAB cache for sighand_struct structures (tsk->sighand) */
 118 struct kmem_cache *sighand_cachep;
 119
 120 /* SLAB cache for files_struct structures (tsk->files) */
 121 struct kmem_cache *files_cachep;
 122
 123 /* SLAB cache for fs_struct structures (tsk->fs) */
 124 struct kmem_cache *fs_cachep;
 125
 126 /* SLAB cache for vm_area_struct structures */
 127 struct kmem_cache *vm_area_cachep;
 128
 129 /* SLAB cache for mm_struct structures (tsk->mm) */
 130 static struct kmem_cache *mm_cachep;
 131
 132 void free_task(struct task_struct *tsk)
 133 {
 134         prop_local_destroy_single(&tsk->dirties);
 135         free_thread_info(tsk->stack);
 136         rt_mutex_debug_task_free(tsk);
 137         free_task_struct(tsk);
 138 }
 139 EXPORT_SYMBOL(free_task);
 140
 141 void __put_task_struct(struct task_struct *tsk)
 142 {
 143         WARN_ON(!tsk->exit_state);
 144         WARN_ON(atomic_read(&tsk->usage));
 145         WARN_ON(tsk == current);
 146
 147         security_task_free(tsk);
 148         free_uid(tsk->user);
 149         put_group_info(tsk->group_info);
 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                 return mm;
 418         }
 419
 420         free_mm(mm);
 421         return NULL;
 422 }
 423
 424 /*
 425  * Allocate and initialize an mm_struct.
 426  */
 427 struct mm_struct * mm_alloc(void)
 428 {
 429         struct mm_struct * mm;
 430
 431         mm = allocate_mm();
 432         if (mm) {
 433                 memset(mm, 0, sizeof(*mm));
 434                 mm = mm_init(mm, current);
 435         }
 436         return mm;
 437 }
 438
 439 /*
 440  * Called when the last reference to the mm
 441  * is dropped: either by a lazy thread or by
 442  * mmput. Free the page directory and the mm.
 443  */
 444 void __mmdrop(struct mm_struct *mm)
 445 {
 446         BUG_ON(mm == &init_mm);
 447         mm_free_pgd(mm);
 448         destroy_context(mm);
 449         free_mm(mm);
 450 }
 451 EXPORT_SYMBOL_GPL(__mmdrop);
 452
 453 /*
 454  * Decrement the use count and release all resources for an mm.
 455  */
 456 void mmput(struct mm_struct *mm)
 457 {
 458         might_sleep();
 459
 460         if (atomic_dec_and_test(&mm->mm_users)) {
 461                 exit_aio(mm);
 462                 exit_mmap(mm);
 463                 set_mm_exe_file(mm, NULL);
 464                 if (!list_empty(&mm->mmlist)) {
 465                         spin_lock(&mmlist_lock);
 466                         list_del(&mm->mmlist);
 467                         spin_unlock(&mmlist_lock);
 468                 }
 469                 put_swap_token(mm);
 470                 mmdrop(mm);
 471         }
 472 }
 473 EXPORT_SYMBOL_GPL(mmput);
 474
 475 /**
 476  * get_task_mm - acquire a reference to the task's mm
 477  *
 478  * Returns %NULL if the task has no mm.  Checks PF_KTHREAD (meaning
 479  * this kernel workthread has transiently adopted a user mm with use_mm,
 480  * to do its AIO) is not set and if so returns a reference to it, after
 481  * bumping up the use count.  User must release the mm via mmput()
 482  * after use.  Typically used by /proc and ptrace.
 483  */
 484 struct mm_struct *get_task_mm(struct task_struct *task)
 485 {
 486         struct mm_struct *mm;
 487
 488         task_lock(task);
 489         mm = task->mm;
 490         if (mm) {
 491                 if (task->flags & PF_KTHREAD)
 492                         mm = NULL;
 493                 else
 494                         atomic_inc(&mm->mm_users);
 495         }
 496         task_unlock(task);
 497         return mm;
 498 }
 499 EXPORT_SYMBOL_GPL(get_task_mm);
 500
 501 /* Please note the differences between mmput and mm_release.
 502  * mmput is called whenever we stop holding onto a mm_struct,
 503  * error success whatever.
 504  *
 505  * mm_release is called after a mm_struct has been removed
 506  * from the current process.
 507  *
 508  * This difference is important for error handling, when we
 509  * only half set up a mm_struct for a new process and need to restore
 510  * the old one.  Because we mmput the new mm_struct before
 511  * restoring the old one. . .
 512  * Eric Biederman 10 January 1998
 513  */
 514 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 515 {
 516         struct completion *vfork_done = tsk->vfork_done;
 517
 518         /* Get rid of any cached register state */
 519         deactivate_mm(tsk, mm);
 520
 521         /* notify parent sleeping on vfork() */
 522         if (vfork_done) {
 523                 tsk->vfork_done = NULL;
 524                 complete(vfork_done);
 525         }
 526
 527         /*
 528          * If we're exiting normally, clear a user-space tid field if
 529          * requested.  We leave this alone when dying by signal, to leave
 530          * the value intact in a core dump, and to save the unnecessary
 531          * trouble otherwise.  Userland only wants this done for a sys_exit.
 532          */
 533         if (tsk->clear_child_tid
 534             && !(tsk->flags & PF_SIGNALED)
 535             && atomic_read(&mm->mm_users) > 1) {
 536                 u32 __user * tidptr = tsk->clear_child_tid;
 537                 tsk->clear_child_tid = NULL;
 538
 539                 /*
 540                  * We don't check the error code - if userspace has
 541                  * not set up a proper pointer then tough luck.
 542                  */
 543                 put_user(0, tidptr);
 544                 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0);
 545         }
 546 }
 547
 548 /*
 549  * Allocate a new mm structure and copy contents from the
 550  * mm structure of the passed in task structure.
 551  */
 552 struct mm_struct *dup_mm(struct task_struct *tsk)
 553 {
 554         struct mm_struct *mm, *oldmm = current->mm;
 555         int err;
 556
 557         if (!oldmm)
 558                 return NULL;
 559
 560         mm = allocate_mm();
 561         if (!mm)
 562                 goto fail_nomem;
 563
 564         memcpy(mm, oldmm, sizeof(*mm));
 565
 566         /* Initializing for Swap token stuff */
 567         mm->token_priority = 0;
 568         mm->last_interval = 0;
 569
 570         if (!mm_init(mm, tsk))
 571                 goto fail_nomem;
 572
 573         if (init_new_context(tsk, mm))
 574                 goto fail_nocontext;
 575
 576         dup_mm_exe_file(oldmm, mm);
 577
 578         err = dup_mmap(mm, oldmm);
 579         if (err)
 580                 goto free_pt;
 581
 582         mm->hiwater_rss = get_mm_rss(mm);
 583         mm->hiwater_vm = mm->total_vm;
 584
 585         return mm;
 586
 587 free_pt:
 588         mmput(mm);
 589
 590 fail_nomem:
 591         return NULL;
 592
 593 fail_nocontext:
 594         /*
 595          * If init_new_context() failed, we cannot use mmput() to free the mm
 596          * because it calls destroy_context()
 597          */
 598         mm_free_pgd(mm);
 599         free_mm(mm);
 600         return NULL;
 601 }
 602
 603 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk)
 604 {
 605         struct mm_struct * mm, *oldmm;
 606         int retval;
 607
 608         tsk->min_flt = tsk->maj_flt = 0;
 609         tsk->nvcsw = tsk->nivcsw = 0;
 610
 611         tsk->mm = NULL;
 612         tsk->active_mm = NULL;
 613
 614         /*
 615          * Are we cloning a kernel thread?
 616          *
 617          * We need to steal a active VM for that..
 618          */
 619         oldmm = current->mm;
 620         if (!oldmm)
 621                 return 0;
 622
 623         if (clone_flags & CLONE_VM) {
 624                 atomic_inc(&oldmm->mm_users);
 625                 mm = oldmm;
 626                 goto good_mm;
 627         }
 628
 629         retval = -ENOMEM;
 630         mm = dup_mm(tsk);
 631         if (!mm)
 632                 goto fail_nomem;
 633
 634 good_mm:
 635         /* Initializing for Swap token stuff */
 636         mm->token_priority = 0;
 637         mm->last_interval = 0;
 638
 639         tsk->mm = mm;
 640         tsk->active_mm = mm;
 641         return 0;
 642
 643 fail_nomem:
 644         return retval;
 645 }
 646
 647 static struct fs_struct *__copy_fs_struct(struct fs_struct *old)
 648 {
 649         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
 650         /* We don't need to lock fs - think why ;-) */
 651         if (fs) {
 652                 atomic_set(&fs->count, 1);
 653                 rwlock_init(&fs->lock);
 654                 fs->umask = old->umask;
 655                 read_lock(&old->lock);
 656                 fs->root = old->root;
 657                 path_get(&old->root);
 658                 fs->pwd = old->pwd;
 659                 path_get(&old->pwd);
 660                 read_unlock(&old->lock);
 661         }
 662         return fs;
 663 }
 664
 665 struct fs_struct *copy_fs_struct(struct fs_struct *old)
 666 {
 667         return __copy_fs_struct(old);
 668 }
 669
 670 EXPORT_SYMBOL_GPL(copy_fs_struct);
 671
 672 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 673 {
 674         if (clone_flags & CLONE_FS) {
 675                 atomic_inc(&current->fs->count);
 676                 return 0;
 677         }
 678         tsk->fs = __copy_fs_struct(current->fs);
 679         if (!tsk->fs)
 680                 return -ENOMEM;
 681         return 0;
 682 }
 683
 684 static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
 685 {
 686         struct files_struct *oldf, *newf;
 687         int error = 0;
 688
 689         /*
 690          * A background process may not have any files ...
 691          */
 692         oldf = current->files;
 693         if (!oldf)
 694                 goto out;
 695
 696         if (clone_flags & CLONE_FILES) {
 697                 atomic_inc(&oldf->count);
 698                 goto out;
 699         }
 700
 701         newf = dup_fd(oldf, &error);
 702         if (!newf)
 703                 goto out;
 704
 705         tsk->files = newf;
 706         error = 0;
 707 out:
 708         return error;
 709 }
 710
 711 static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
 712 {
 713 #ifdef CONFIG_BLOCK
 714         struct io_context *ioc = current->io_context;
 715
 716         if (!ioc)
 717                 return 0;
 718         /*
 719          * Share io context with parent, if CLONE_IO is set
 720          */
 721         if (clone_flags & CLONE_IO) {
 722                 tsk->io_context = ioc_task_link(ioc);
 723                 if (unlikely(!tsk->io_context))
 724                         return -ENOMEM;
 725         } else if (ioprio_valid(ioc->ioprio)) {
 726                 tsk->io_context = alloc_io_context(GFP_KERNEL, -1);
 727                 if (unlikely(!tsk->io_context))
 728                         return -ENOMEM;
 729
 730                 tsk->io_context->ioprio = ioc->ioprio;
 731         }
 732 #endif
 733         return 0;
 734 }
 735
 736 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 737 {
 738         struct sighand_struct *sig;
 739
 740         if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) {
 741                 atomic_inc(&current->sighand->count);
 742                 return 0;
 743         }
 744         sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 745         rcu_assign_pointer(tsk->sighand, sig);
 746         if (!sig)
 747                 return -ENOMEM;
 748         atomic_set(&sig->count, 1);
 749         memcpy(sig->action, current->sighand->action, sizeof(sig->action));
 750         return 0;
 751 }
 752
 753 void __cleanup_sighand(struct sighand_struct *sighand)
 754 {
 755         if (atomic_dec_and_test(&sighand->count))
 756                 kmem_cache_free(sighand_cachep, sighand);
 757 }
 758
 759 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 760 {
 761         struct signal_struct *sig;
 762         int ret;
 763
 764         if (clone_flags & CLONE_THREAD) {
 765                 atomic_inc(&current->signal->count);
 766                 atomic_inc(&current->signal->live);
 767                 return 0;
 768         }
 769         sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL);
 770         tsk->signal = sig;
 771         if (!sig)
 772                 return -ENOMEM;
 773
 774         ret = copy_thread_group_keys(tsk);
 775         if (ret < 0) {
 776                 kmem_cache_free(signal_cachep, sig);
 777                 return ret;
 778         }
 779
 780         atomic_set(&sig->count, 1);
 781         atomic_set(&sig->live, 1);
 782         init_waitqueue_head(&sig->wait_chldexit);
 783         sig->flags = 0;
 784         sig->group_exit_code = 0;
 785         sig->group_exit_task = NULL;
 786         sig->group_stop_count = 0;
 787         sig->curr_target = tsk;
 788         init_sigpending(&sig->shared_pending);
 789         INIT_LIST_HEAD(&sig->posix_timers);
 790
 791         hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 792         sig->it_real_incr.tv64 = 0;
 793         sig->real_timer.function = it_real_fn;
 794
 795         sig->it_virt_expires = cputime_zero;
 796         sig->it_virt_incr = cputime_zero;
 797         sig->it_prof_expires = cputime_zero;
 798         sig->it_prof_incr = cputime_zero;
 799
 800         sig->leader = 0;        /* session leadership doesn't inherit */
 801         sig->tty_old_pgrp = NULL;
 802
 803         sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero;
 804         sig->gtime = cputime_zero;
 805         sig->cgtime = cputime_zero;
 806         sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0;
 807         sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0;
 808         sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0;
 809 #ifdef CONFIG_TASK_XACCT
 810         sig->rchar = sig->wchar = sig->syscr = sig->syscw = 0;
 811 #endif
 812 #ifdef CONFIG_TASK_IO_ACCOUNTING
 813         memset(&sig->ioac, 0, sizeof(sig->ioac));
 814 #endif
 815         sig->sum_sched_runtime = 0;
 816         INIT_LIST_HEAD(&sig->cpu_timers[0]);
 817         INIT_LIST_HEAD(&sig->cpu_timers[1]);
 818         INIT_LIST_HEAD(&sig->cpu_timers[2]);
 819         taskstats_tgid_init(sig);
 820
 821         task_lock(current->group_leader);
 822         memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim);
 823         task_unlock(current->group_leader);
 824
 825         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
 826                 /*
 827                  * New sole thread in the process gets an expiry time
 828                  * of the whole CPU time limit.
 829                  */
 830                 tsk->it_prof_expires =
 831                         secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
 832         }
 833         acct_init_pacct(&sig->pacct);
 834
 835         tty_audit_fork(sig);
 836
 837         return 0;
 838 }
 839
 840 void __cleanup_signal(struct signal_struct *sig)
 841 {
 842         exit_thread_group_keys(sig);
 843         kmem_cache_free(signal_cachep, sig);
 844 }
 845
 846 static void cleanup_signal(struct task_struct *tsk)
 847 {
 848         struct signal_struct *sig = tsk->signal;
 849
 850         atomic_dec(&sig->live);
 851
 852         if (atomic_dec_and_test(&sig->count))
 853                 __cleanup_signal(sig);
 854 }
 855
 856 static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 857 {
 858         unsigned long new_flags = p->flags;
 859
 860         new_flags &= ~PF_SUPERPRIV;
 861         new_flags |= PF_FORKNOEXEC;
 862         new_flags |= PF_STARTING;
 863         p->flags = new_flags;
 864         clear_freeze_flag(p);
 865 }
 866
 867 asmlinkage long sys_set_tid_address(int __user *tidptr)
 868 {
 869         current->clear_child_tid = tidptr;
 870
 871         return task_pid_vnr(current);
 872 }
 873
 874 static void rt_mutex_init_task(struct task_struct *p)
 875 {
 876         spin_lock_init(&p->pi_lock);
 877 #ifdef CONFIG_RT_MUTEXES
 878         plist_head_init(&p->pi_waiters, &p->pi_lock);
 879         p->pi_blocked_on = NULL;
 880 #endif
 881 }
 882
 883 #ifdef CONFIG_MM_OWNER
 884 void mm_init_owner(struct mm_struct *mm, struct task_struct *p)
 885 {
 886         mm->owner = p;
 887 }
 888 #endif /* CONFIG_MM_OWNER */
 889
 890 /*
 891  * This creates a new process as a copy of the old one,
 892  * but does not actually start it yet.
 893  *
 894  * It copies the registers, and all the appropriate
 895  * parts of the process environment (as per the clone
 896  * flags). The actual kick-off is left to the caller.
 897  */
 898 static struct task_struct *copy_process(unsigned long clone_flags,
 899                                         unsigned long stack_start,
 900                                         struct pt_regs *regs,
 901                                         unsigned long stack_size,
 902                                         int __user *child_tidptr,
 903                                         struct pid *pid,
 904                                         int trace)
 905 {
 906         int retval;
 907         struct task_struct *p;
 908         int cgroup_callbacks_done = 0;
 909
 910         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 911                 return ERR_PTR(-EINVAL);
 912
 913         /*
 914          * Thread groups must share signals as well, and detached threads
 915          * can only be started up within the thread group.
 916          */
 917         if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
 918                 return ERR_PTR(-EINVAL);
 919
 920         /*
 921          * Shared signal handlers imply shared VM. By way of the above,
 922          * thread groups also imply shared VM. Blocking this case allows
 923          * for various simplifications in other code.
 924          */
 925         if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
 926                 return ERR_PTR(-EINVAL);
 927
 928         retval = security_task_create(clone_flags);
 929         if (retval)
 930                 goto fork_out;
 931
 932         retval = -ENOMEM;
 933         p = dup_task_struct(current);
 934         if (!p)
 935                 goto fork_out;
 936
 937         rt_mutex_init_task(p);
 938
 939 #ifdef CONFIG_PROVE_LOCKING
 940         DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
 941         DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
 942 #endif
 943         retval = -EAGAIN;
 944         if (atomic_read(&p->user->processes) >=
 945                         p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
 946                 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) &&
 947                     p->user != current->nsproxy->user_ns->root_user)
 948                         goto bad_fork_free;
 949         }
 950
 951         atomic_inc(&p->user->__count);
 952         atomic_inc(&p->user->processes);
 953         get_group_info(p->group_info);
 954
 955         /*
 956          * If multiple threads are within copy_process(), then this check
 957          * triggers too late. This doesn't hurt, the check is only there
 958          * to stop root fork bombs.
 959          */
 960         if (nr_threads >= max_threads)
 961                 goto bad_fork_cleanup_count;
 962
 963         if (!try_module_get(task_thread_info(p)->exec_domain->module))
 964                 goto bad_fork_cleanup_count;
 965
 966         if (p->binfmt && !try_module_get(p->binfmt->module))
 967                 goto bad_fork_cleanup_put_domain;
 968
 969         p->did_exec = 0;
 970         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
 971         copy_flags(clone_flags, p);
 972         INIT_LIST_HEAD(&p->children);
 973         INIT_LIST_HEAD(&p->sibling);
 974 #ifdef CONFIG_PREEMPT_RCU
 975         p->rcu_read_lock_nesting = 0;
 976         p->rcu_flipctr_idx = 0;
 977 #endif /* #ifdef CONFIG_PREEMPT_RCU */
 978         p->vfork_done = NULL;
 979         spin_lock_init(&p->alloc_lock);
 980
 981         clear_tsk_thread_flag(p, TIF_SIGPENDING);
 982         init_sigpending(&p->pending);
 983
 984         p->utime = cputime_zero;
 985         p->stime = cputime_zero;
 986         p->gtime = cputime_zero;
 987         p->utimescaled = cputime_zero;
 988         p->stimescaled = cputime_zero;
 989         p->prev_utime = cputime_zero;
 990         p->prev_stime = cputime_zero;
 991
 992 #ifdef CONFIG_DETECT_SOFTLOCKUP
 993         p->last_switch_count = 0;
 994         p->last_switch_timestamp = 0;
 995 #endif
 996
 997 #ifdef CONFIG_TASK_XACCT
 998         p->rchar = 0;           /* I/O counter: bytes read */
 999         p->wchar = 0;           /* I/O counter: bytes written */
1000         p->syscr = 0;           /* I/O counter: read syscalls */
1001         p->syscw = 0;           /* I/O counter: write syscalls */
1002 #endif
1003         task_io_accounting_init(p);
1004         acct_clear_integrals(p);
1005
1006         p->it_virt_expires = cputime_zero;
1007         p->it_prof_expires = cputime_zero;
1008         p->it_sched_expires = 0;
1009         INIT_LIST_HEAD(&p->cpu_timers[0]);
1010         INIT_LIST_HEAD(&p->cpu_timers[1]);
1011         INIT_LIST_HEAD(&p->cpu_timers[2]);
1012
1013         p->lock_depth = -1;             /* -1 = no lock */
1014         do_posix_clock_monotonic_gettime(&p->start_time);
1015         p->real_start_time = p->start_time;
1016         monotonic_to_bootbased(&p->real_start_time);
1017 #ifdef CONFIG_SECURITY
1018         p->security = NULL;
1019 #endif
1020         p->cap_bset = current->cap_bset;
1021         p->io_context = NULL;
1022         p->audit_context = NULL;
1023         cgroup_fork(p);
1024 #ifdef CONFIG_NUMA
1025         p->mempolicy = mpol_dup(p->mempolicy);
1026         if (IS_ERR(p->mempolicy)) {
1027                 retval = PTR_ERR(p->mempolicy);
1028                 p->mempolicy = NULL;
1029                 goto bad_fork_cleanup_cgroup;
1030         }
1031         mpol_fix_fork_child_flag(p);
1032 #endif
1033 #ifdef CONFIG_TRACE_IRQFLAGS
1034         p->irq_events = 0;
1035 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
1036         p->hardirqs_enabled = 1;
1037 #else
1038         p->hardirqs_enabled = 0;
1039 #endif
1040         p->hardirq_enable_ip = 0;
1041         p->hardirq_enable_event = 0;
1042         p->hardirq_disable_ip = _THIS_IP_;
1043         p->hardirq_disable_event = 0;
1044         p->softirqs_enabled = 1;
1045         p->softirq_enable_ip = _THIS_IP_;
1046         p->softirq_enable_event = 0;
1047         p->softirq_disable_ip = 0;
1048         p->softirq_disable_event = 0;
1049         p->hardirq_context = 0;
1050         p->softirq_context = 0;
1051 #endif
1052 #ifdef CONFIG_LOCKDEP
1053         p->lockdep_depth = 0; /* no locks held yet */
1054         p->curr_chain_key = 0;
1055         p->lockdep_recursion = 0;
1056 #endif
1057
1058 #ifdef CONFIG_DEBUG_MUTEXES
1059         p->blocked_on = NULL; /* not blocked yet */
1060 #endif
1061
1062         /* Perform scheduler related setup. Assign this task to a CPU. */
1063         sched_fork(p, clone_flags);
1064
1065         if ((retval = security_task_alloc(p)))
1066                 goto bad_fork_cleanup_policy;
1067         if ((retval = audit_alloc(p)))
1068                 goto bad_fork_cleanup_security;
1069         /* copy all the process information */
1070         if ((retval = copy_semundo(clone_flags, p)))
1071                 goto bad_fork_cleanup_audit;
1072         if ((retval = copy_files(clone_flags, p)))
1073                 goto bad_fork_cleanup_semundo;
1074         if ((retval = copy_fs(clone_flags, p)))
1075                 goto bad_fork_cleanup_files;
1076         if ((retval = copy_sighand(clone_flags, p)))
1077                 goto bad_fork_cleanup_fs;
1078         if ((retval = copy_signal(clone_flags, p)))
1079                 goto bad_fork_cleanup_sighand;
1080         if ((retval = copy_mm(clone_flags, p)))
1081                 goto bad_fork_cleanup_signal;
1082         if ((retval = copy_keys(clone_flags, p)))
1083                 goto bad_fork_cleanup_mm;
1084         if ((retval = copy_namespaces(clone_flags, p)))
1085                 goto bad_fork_cleanup_keys;
1086         if ((retval = copy_io(clone_flags, p)))
1087                 goto bad_fork_cleanup_namespaces;
1088         retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
1089         if (retval)
1090                 goto bad_fork_cleanup_io;
1091
1092         if (pid != &init_struct_pid) {
1093                 retval = -ENOMEM;
1094                 pid = alloc_pid(task_active_pid_ns(p));
1095                 if (!pid)
1096                         goto bad_fork_cleanup_io;
1097
1098                 if (clone_flags & CLONE_NEWPID) {
1099                         retval = pid_ns_prepare_proc(task_active_pid_ns(p));
1100                         if (retval < 0)
1101                                 goto bad_fork_free_pid;
1102                 }
1103         }
1104
1105         p->pid = pid_nr(pid);
1106         p->tgid = p->pid;
1107         if (clone_flags & CLONE_THREAD)
1108                 p->tgid = current->tgid;
1109
1110         if (current->nsproxy != p->nsproxy) {
1111                 retval = ns_cgroup_clone(p, pid);
1112                 if (retval)
1113                         goto bad_fork_free_pid;
1114         }
1115
1116         p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
1117         /*
1118          * Clear TID on mm_release()?
1119          */
1120         p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
1121 #ifdef CONFIG_FUTEX
1122         p->robust_list = NULL;
1123 #ifdef CONFIG_COMPAT
1124         p->compat_robust_list = NULL;
1125 #endif
1126         INIT_LIST_HEAD(&p->pi_state_list);
1127         p->pi_state_cache = NULL;
1128 #endif
1129         /*
1130          * sigaltstack should be cleared when sharing the same VM
1131          */
1132         if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM)
1133                 p->sas_ss_sp = p->sas_ss_size = 0;
1134
1135         /*
1136          * Syscall tracing should be turned off in the child regardless
1137          * of CLONE_PTRACE.
1138          */
1139         clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
1140 #ifdef TIF_SYSCALL_EMU
1141         clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
1142 #endif
1143         clear_all_latency_tracing(p);
1144
1145         /* Our parent execution domain becomes current domain
1146            These must match for thread signalling to apply */
1147         p->parent_exec_id = p->self_exec_id;
1148
1149         /* ok, now we should be set up.. */
1150         p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
1151         p->pdeath_signal = 0;
1152         p->exit_state = 0;
1153
1154         /*
1155          * Ok, make it visible to the rest of the system.
1156          * We dont wake it up yet.
1157          */
1158         p->group_leader = p;
1159         INIT_LIST_HEAD(&p->thread_group);
1160
1161         /* Now that the task is set up, run cgroup callbacks if
1162          * necessary. We need to run them before the task is visible
1163          * on the tasklist. */
1164         cgroup_fork_callbacks(p);
1165         cgroup_callbacks_done = 1;
1166
1167         /* Need tasklist lock for parent etc handling! */
1168         write_lock_irq(&tasklist_lock);
1169
1170         /*
1171          * The task hasn't been attached yet, so its cpus_allowed mask will
1172          * not be changed, nor will its assigned CPU.
1173          *
1174          * The cpus_allowed mask of the parent may have changed after it was
1175          * copied first time - so re-copy it here, then check the child's CPU
1176          * to ensure it is on a valid CPU (and if not, just force it back to
1177          * parent's CPU). This avoids alot of nasty races.
1178          */
1179         p->cpus_allowed = current->cpus_allowed;
1180         p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed;
1181         if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
1182                         !cpu_online(task_cpu(p))))
1183                 set_task_cpu(p, smp_processor_id());
1184
1185         /* CLONE_PARENT re-uses the old parent */
1186         if (clone_flags & (CLONE_PARENT|CLONE_THREAD))
1187                 p->real_parent = current->real_parent;
1188         else
1189                 p->real_parent = current;
1190
1191         spin_lock(&current->sighand->siglock);
1192
1193         /*
1194          * Process group and session signals need to be delivered to just the
1195          * parent before the fork or both the parent and the child after the
1196          * fork. Restart if a signal comes in before we add the new process to
1197          * it's process group.
1198          * A fatal signal pending means that current will exit, so the new
1199          * thread can't slip out of an OOM kill (or normal SIGKILL).
1200          */
1201         recalc_sigpending();
1202         if (signal_pending(current)) {
1203                 spin_unlock(&current->sighand->siglock);
1204                 write_unlock_irq(&tasklist_lock);
1205                 retval = -ERESTARTNOINTR;
1206                 goto bad_fork_free_pid;
1207         }
1208
1209         if (clone_flags & CLONE_THREAD) {
1210                 p->group_leader = current->group_leader;
1211                 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group);
1212
1213                 if (!cputime_eq(current->signal->it_virt_expires,
1214                                 cputime_zero) ||
1215                     !cputime_eq(current->signal->it_prof_expires,
1216                                 cputime_zero) ||
1217                     current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY ||
1218                     !list_empty(&current->signal->cpu_timers[0]) ||
1219                     !list_empty(&current->signal->cpu_timers[1]) ||
1220                     !list_empty(&current->signal->cpu_timers[2])) {
1221                         /*
1222                          * Have child wake up on its first tick to check
1223                          * for process CPU timers.
1224                          */
1225                         p->it_prof_expires = jiffies_to_cputime(1);
1226                 }
1227         }
1228
1229         if (likely(p->pid)) {
1230                 list_add_tail(&p->sibling, &p->real_parent->children);
1231                 tracehook_finish_clone(p, clone_flags, trace);
1232
1233                 if (thread_group_leader(p)) {
1234                         if (clone_flags & CLONE_NEWPID)
1235                                 p->nsproxy->pid_ns->child_reaper = p;
1236
1237                         p->signal->leader_pid = pid;
1238                         p->signal->tty = current->signal->tty;
1239                         set_task_pgrp(p, task_pgrp_nr(current));
1240                         set_task_session(p, task_session_nr(current));
1241                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
1242                         attach_pid(p, PIDTYPE_SID, task_session(current));
1243                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
1244                         __get_cpu_var(process_counts)++;
1245                 }
1246                 attach_pid(p, PIDTYPE_PID, pid);
1247                 nr_threads++;
1248         }
1249
1250         total_forks++;
1251         spin_unlock(&current->sighand->siglock);
1252         write_unlock_irq(&tasklist_lock);
1253         proc_fork_connector(p);
1254         cgroup_post_fork(p);
1255         return p;
1256
1257 bad_fork_free_pid:
1258         if (pid != &init_struct_pid)
1259                 free_pid(pid);
1260 bad_fork_cleanup_io:
1261         put_io_context(p->io_context);
1262 bad_fork_cleanup_namespaces:
1263         exit_task_namespaces(p);
1264 bad_fork_cleanup_keys:
1265         exit_keys(p);
1266 bad_fork_cleanup_mm:
1267         if (p->mm)
1268                 mmput(p->mm);
1269 bad_fork_cleanup_signal:
1270         cleanup_signal(p);
1271 bad_fork_cleanup_sighand:
1272         __cleanup_sighand(p->sighand);
1273 bad_fork_cleanup_fs:
1274         exit_fs(p); /* blocking */
1275 bad_fork_cleanup_files:
1276         exit_files(p); /* blocking */
1277 bad_fork_cleanup_semundo:
1278         exit_sem(p);
1279 bad_fork_cleanup_audit:
1280         audit_free(p);
1281 bad_fork_cleanup_security:
1282         security_task_free(p);
1283 bad_fork_cleanup_policy:
1284 #ifdef CONFIG_NUMA
1285         mpol_put(p->mempolicy);
1286 bad_fork_cleanup_cgroup:
1287 #endif
1288         cgroup_exit(p, cgroup_callbacks_done);
1289         delayacct_tsk_free(p);
1290         if (p->binfmt)
1291                 module_put(p->binfmt->module);
1292 bad_fork_cleanup_put_domain:
1293         module_put(task_thread_info(p)->exec_domain->module);
1294 bad_fork_cleanup_count:
1295         put_group_info(p->group_info);
1296         atomic_dec(&p->user->processes);
1297         free_uid(p->user);
1298 bad_fork_free:
1299         free_task(p);
1300 fork_out:
1301         return ERR_PTR(retval);
1302 }
1303
1304 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs)
1305 {
1306         memset(regs, 0, sizeof(struct pt_regs));
1307         return regs;
1308 }
1309
1310 struct task_struct * __cpuinit fork_idle(int cpu)
1311 {
1312         struct task_struct *task;
1313         struct pt_regs regs;
1314
1315         task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL,
1316                             &init_struct_pid, 0);
1317         if (!IS_ERR(task))
1318                 init_idle(task, cpu);
1319
1320         return task;
1321 }
1322
1323 /*
1324  *  Ok, this is the main fork-routine.
1325  *
1326  * It copies the process, and if successful kick-starts
1327  * it and waits for it to finish using the VM if required.
1328  */
1329 long do_fork(unsigned long clone_flags,
1330               unsigned long stack_start,
1331               struct pt_regs *regs,
1332               unsigned long stack_size,
1333               int __user *parent_tidptr,
1334               int __user *child_tidptr)
1335 {
1336         struct task_struct *p;
1337         int trace = 0;
1338         long nr;
1339
1340         /*
1341          * We hope to recycle these flags after 2.6.26
1342          */
1343         if (unlikely(clone_flags & CLONE_STOPPED)) {
1344                 static int __read_mostly count = 100;
1345
1346                 if (count > 0 && printk_ratelimit()) {
1347                         char comm[TASK_COMM_LEN];
1348
1349                         count--;
1350                         printk(KERN_INFO "fork(): process `%s' used deprecated "
1351                                         "clone flags 0x%lx\n",
1352                                 get_task_comm(comm, current),
1353                                 clone_flags & CLONE_STOPPED);
1354                 }
1355         }
1356
1357         /*
1358          * When called from kernel_thread, don't do user tracing stuff.
1359          */
1360         if (likely(user_mode(regs)))
1361                 trace = tracehook_prepare_clone(clone_flags);
1362
1363         p = copy_process(clone_flags, stack_start, regs, stack_size,
1364                          child_tidptr, NULL, trace);
1365         /*
1366          * Do this prior waking up the new thread - the thread pointer
1367          * might get invalid after that point, if the thread exits quickly.
1368          */
1369         if (!IS_ERR(p)) {
1370                 struct completion vfork;
1371
1372                 nr = task_pid_vnr(p);
1373
1374                 if (clone_flags & CLONE_PARENT_SETTID)
1375                         put_user(nr, parent_tidptr);
1376
1377                 if (clone_flags & CLONE_VFORK) {
1378                         p->vfork_done = &vfork;
1379                         init_completion(&vfork);
1380                 }
1381
1382                 tracehook_report_clone(trace, regs, clone_flags, nr, p);
1383
1384                 /*
1385                  * We set PF_STARTING at creation in case tracing wants to
1386                  * use this to distinguish a fully live task from one that
1387                  * hasn't gotten to tracehook_report_clone() yet.  Now we
1388                  * clear it and set the child going.
1389                  */
1390                 p->flags &= ~PF_STARTING;
1391
1392                 if (unlikely(clone_flags & CLONE_STOPPED)) {
1393                         /*
1394                          * We'll start up with an immediate SIGSTOP.
1395                          */
1396                         sigaddset(&p->pending.signal, SIGSTOP);
1397                         set_tsk_thread_flag(p, TIF_SIGPENDING);
1398                         __set_task_state(p, TASK_STOPPED);
1399                 } else {
1400                         wake_up_new_task(p, clone_flags);
1401                 }
1402
1403                 tracehook_report_clone_complete(trace, regs,
1404                                                 clone_flags, nr, p);
1405
1406                 if (clone_flags & CLONE_VFORK) {
1407                         freezer_do_not_count();
1408                         wait_for_completion(&vfork);
1409                         freezer_count();
1410                         tracehook_report_vfork_done(p, nr);
1411                 }
1412         } else {
1413                 nr = PTR_ERR(p);
1414         }
1415         return nr;
1416 }
1417
1418 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
1419 #define ARCH_MIN_MMSTRUCT_ALIGN 0
1420 #endif
1421
1422 static void sighand_ctor(void *data)
1423 {
1424         struct sighand_struct *sighand = data;
1425
1426         spin_lock_init(&sighand->siglock);
1427         init_waitqueue_head(&sighand->signalfd_wqh);
1428 }
1429
1430 void __init proc_caches_init(void)
1431 {
1432         sighand_cachep = kmem_cache_create("sighand_cache",
1433                         sizeof(struct sighand_struct), 0,
1434                         SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU,
1435                         sighand_ctor);
1436         signal_cachep = kmem_cache_create("signal_cache",
1437                         sizeof(struct signal_struct), 0,
1438                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1439         files_cachep = kmem_cache_create("files_cache",
1440                         sizeof(struct files_struct), 0,
1441                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1442         fs_cachep = kmem_cache_create("fs_cache",
1443                         sizeof(struct fs_struct), 0,
1444                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1445         vm_area_cachep = kmem_cache_create("vm_area_struct",
1446                         sizeof(struct vm_area_struct), 0,
1447                         SLAB_PANIC, NULL);
1448         mm_cachep = kmem_cache_create("mm_struct",
1449                         sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
1450                         SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
1451 }
1452
1453 /*
1454  * Check constraints on flags passed to the unshare system call and
1455  * force unsharing of additional process context as appropriate.
1456  */
1457 static void check_unshare_flags(unsigned long *flags_ptr)
1458 {
1459         /*
1460          * If unsharing a thread from a thread group, must also
1461          * unshare vm.
1462          */
1463         if (*flags_ptr & CLONE_THREAD)
1464                 *flags_ptr |= CLONE_VM;
1465
1466         /*
1467          * If unsharing vm, must also unshare signal handlers.
1468          */
1469         if (*flags_ptr & CLONE_VM)
1470                 *flags_ptr |= CLONE_SIGHAND;
1471
1472         /*
1473          * If unsharing signal handlers and the task was created
1474          * using CLONE_THREAD, then must unshare the thread
1475          */
1476         if ((*flags_ptr & CLONE_SIGHAND) &&
1477             (atomic_read(&current->signal->count) > 1))
1478                 *flags_ptr |= CLONE_THREAD;
1479
1480         /*
1481          * If unsharing namespace, must also unshare filesystem information.
1482          */
1483         if (*flags_ptr & CLONE_NEWNS)
1484                 *flags_ptr |= CLONE_FS;
1485 }
1486
1487 /*
1488  * Unsharing of tasks created with CLONE_THREAD is not supported yet
1489  */
1490 static int unshare_thread(unsigned long unshare_flags)
1491 {
1492         if (unshare_flags & CLONE_THREAD)
1493                 return -EINVAL;
1494
1495         return 0;
1496 }
1497
1498 /*
1499  * Unshare the filesystem structure if it is being shared
1500  */
1501 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp)
1502 {
1503         struct fs_struct *fs = current->fs;
1504
1505         if ((unshare_flags & CLONE_FS) &&
1506             (fs && atomic_read(&fs->count) > 1)) {
1507                 *new_fsp = __copy_fs_struct(current->fs);
1508                 if (!*new_fsp)
1509                         return -ENOMEM;
1510         }
1511
1512         return 0;
1513 }
1514
1515 /*
1516  * Unsharing of sighand is not supported yet
1517  */
1518 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp)
1519 {
1520         struct sighand_struct *sigh = current->sighand;
1521
1522         if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1)
1523                 return -EINVAL;
1524         else
1525                 return 0;
1526 }
1527
1528 /*
1529  * Unshare vm if it is being shared
1530  */
1531 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp)
1532 {
1533         struct mm_struct *mm = current->mm;
1534
1535         if ((unshare_flags & CLONE_VM) &&
1536             (mm && atomic_read(&mm->mm_users) > 1)) {
1537                 return -EINVAL;
1538         }
1539
1540         return 0;
1541 }
1542
1543 /*
1544  * Unshare file descriptor table if it is being shared
1545  */
1546 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp)
1547 {
1548         struct files_struct *fd = current->files;
1549         int error = 0;
1550
1551         if ((unshare_flags & CLONE_FILES) &&
1552             (fd && atomic_read(&fd->count) > 1)) {
1553                 *new_fdp = dup_fd(fd, &error);
1554                 if (!*new_fdp)
1555                         return error;
1556         }
1557
1558         return 0;
1559 }
1560
1561 /*
1562  * unshare allows a process to 'unshare' part of the process
1563  * context which was originally shared using clone.  copy_*
1564  * functions used by do_fork() cannot be used here directly
1565  * because they modify an inactive task_struct that is being
1566  * constructed. Here we are modifying the current, active,
1567  * task_struct.
1568  */
1569 asmlinkage long sys_unshare(unsigned long unshare_flags)
1570 {
1571         int err = 0;
1572         struct fs_struct *fs, *new_fs = NULL;
1573         struct sighand_struct *new_sigh = NULL;
1574         struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL;
1575         struct files_struct *fd, *new_fd = NULL;
1576         struct nsproxy *new_nsproxy = NULL;
1577         int do_sysvsem = 0;
1578
1579         check_unshare_flags(&unshare_flags);
1580
1581         /* Return -EINVAL for all unsupported flags */
1582         err = -EINVAL;
1583         if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND|
1584                                 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM|
1585                                 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|
1586                                 CLONE_NEWNET))
1587                 goto bad_unshare_out;
1588
1589         /*
1590          * CLONE_NEWIPC must also detach from the undolist: after switching
1591          * to a new ipc namespace, the semaphore arrays from the old
1592          * namespace are unreachable.
1593          */
1594         if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM))
1595                 do_sysvsem = 1;
1596         if ((err = unshare_thread(unshare_flags)))
1597                 goto bad_unshare_out;
1598         if ((err = unshare_fs(unshare_flags, &new_fs)))
1599                 goto bad_unshare_cleanup_thread;
1600         if ((err = unshare_sighand(unshare_flags, &new_sigh)))
1601                 goto bad_unshare_cleanup_fs;
1602         if ((err = unshare_vm(unshare_flags, &new_mm)))
1603                 goto bad_unshare_cleanup_sigh;
1604         if ((err = unshare_fd(unshare_flags, &new_fd)))
1605                 goto bad_unshare_cleanup_vm;
1606         if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy,
1607                         new_fs)))
1608                 goto bad_unshare_cleanup_fd;
1609
1610         if (new_fs ||  new_mm || new_fd || do_sysvsem || new_nsproxy) {
1611                 if (do_sysvsem) {
1612                         /*
1613                          * CLONE_SYSVSEM is equivalent to sys_exit().
1614                          */
1615                         exit_sem(current);
1616                 }
1617
1618                 if (new_nsproxy) {
1619                         switch_task_namespaces(current, new_nsproxy);
1620                         new_nsproxy = NULL;
1621                 }
1622
1623                 task_lock(current);
1624
1625                 if (new_fs) {
1626                         fs = current->fs;
1627                         current->fs = new_fs;
1628                         new_fs = fs;
1629                 }
1630
1631                 if (new_mm) {
1632                         mm = current->mm;
1633                         active_mm = current->active_mm;
1634                         current->mm = new_mm;
1635                         current->active_mm = new_mm;
1636                         activate_mm(active_mm, new_mm);
1637                         new_mm = mm;
1638                 }
1639
1640                 if (new_fd) {
1641                         fd = current->files;
1642                         current->files = new_fd;
1643                         new_fd = fd;
1644                 }
1645
1646                 task_unlock(current);
1647         }
1648
1649         if (new_nsproxy)
1650                 put_nsproxy(new_nsproxy);
1651
1652 bad_unshare_cleanup_fd:
1653         if (new_fd)
1654                 put_files_struct(new_fd);
1655
1656 bad_unshare_cleanup_vm:
1657         if (new_mm)
1658                 mmput(new_mm);
1659
1660 bad_unshare_cleanup_sigh:
1661         if (new_sigh)
1662                 if (atomic_dec_and_test(&new_sigh->count))
1663                         kmem_cache_free(sighand_cachep, new_sigh);
1664
1665 bad_unshare_cleanup_fs:
1666         if (new_fs)
1667                 put_fs_struct(new_fs);
1668
1669 bad_unshare_cleanup_thread:
1670 bad_unshare_out:
1671         return err;
1672 }
1673
1674 /*
1675  *      Helper to unshare the files of the current task.
1676  *      We don't want to expose copy_files internals to
1677  *      the exec layer of the kernel.
1678  */
1679
1680 int unshare_files(struct files_struct **displaced)
1681 {
1682         struct task_struct *task = current;
1683         struct files_struct *copy = NULL;
1684         int error;
1685
1686         error = unshare_fd(CLONE_FILES, &copy);
1687         if (error || !copy) {
1688                 *displaced = NULL;
1689                 return error;
1690         }
1691         *displaced = task->files;
1692         task_lock(task);
1693         task->files = copy;
1694         task_unlock(task);
1695         return 0;
1696 }