1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/slab.h> 15 #include <linux/init.h> 16 #include <linux/unistd.h> 17 #include <linux/module.h> 18 #include <linux/vmalloc.h> 19 #include <linux/completion.h> 20 #include <linux/mnt_namespace.h> 21 #include <linux/personality.h> 22 #include <linux/mempolicy.h> 23 #include <linux/sem.h> 24 #include <linux/file.h> 25 #include <linux/fdtable.h> 26 #include <linux/iocontext.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/mmu_notifier.h> 31 #include <linux/fs.h> 32 #include <linux/nsproxy.h> 33 #include <linux/capability.h> 34 #include <linux/cpu.h> 35 #include <linux/cgroup.h> 36 #include <linux/security.h> 37 #include <linux/hugetlb.h> 38 #include <linux/swap.h> 39 #include <linux/syscalls.h> 40 #include <linux/jiffies.h> 41 #include <linux/tracehook.h> 42 #include <linux/futex.h> 43 #include <linux/task_io_accounting_ops.h> 44 #include <linux/rcupdate.h> 45 #include <linux/ptrace.h> 46 #include <linux/mount.h> 47 #include <linux/audit.h> 48 #include <linux/memcontrol.h> 49 #include <linux/profile.h> 50 #include <linux/rmap.h> 51 #include <linux/acct.h> 52 #include <linux/tsacct_kern.h> 53 #include <linux/cn_proc.h> 54 #include <linux/freezer.h> 55 #include <linux/delayacct.h> 56 #include <linux/taskstats_kern.h> 57 #include <linux/random.h> 58 #include <linux/tty.h> 59 #include <linux/proc_fs.h> 60 #include <linux/blkdev.h> 61 62 #include <asm/pgtable.h> 63 #include <asm/pgalloc.h> 64 #include <asm/uaccess.h> 65 #include <asm/mmu_context.h> 66 #include <asm/cacheflush.h> 67 #include <asm/tlbflush.h> 68 69 /* 70 * Protected counters by write_lock_irq(&tasklist_lock) 71 */ 72 unsigned long total_forks; /* Handle normal Linux uptimes. */ 73 int nr_threads; /* The idle threads do not count.. */ 74 75 int max_threads; /* tunable limit on nr_threads */ 76 77 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 78 79 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 80 81 int nr_processes(void) 82 { 83 int cpu; 84 int total = 0; 85 86 for_each_online_cpu(cpu) 87 total += per_cpu(process_counts, cpu); 88 89 return total; 90 } 91 92 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 93 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 94 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 95 static struct kmem_cache *task_struct_cachep; 96 #endif 97 98 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 99 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 100 { 101 #ifdef CONFIG_DEBUG_STACK_USAGE 102 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 103 #else 104 gfp_t mask = GFP_KERNEL; 105 #endif 106 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 107 } 108 109 static inline void free_thread_info(struct thread_info *ti) 110 { 111 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 112 } 113 #endif 114 115 /* SLAB cache for signal_struct structures (tsk->signal) */ 116 static struct kmem_cache *signal_cachep; 117 118 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 119 struct kmem_cache *sighand_cachep; 120 121 /* SLAB cache for files_struct structures (tsk->files) */ 122 struct kmem_cache *files_cachep; 123 124 /* SLAB cache for fs_struct structures (tsk->fs) */ 125 struct kmem_cache *fs_cachep; 126 127 /* SLAB cache for vm_area_struct structures */ 128 struct kmem_cache *vm_area_cachep; 129 130 /* SLAB cache for mm_struct structures (tsk->mm) */ 131 static struct kmem_cache *mm_cachep; 132 133 void free_task(struct task_struct *tsk) 134 { 135 prop_local_destroy_single(&tsk->dirties); 136 free_thread_info(tsk->stack); 137 rt_mutex_debug_task_free(tsk); 138 free_task_struct(tsk); 139 } 140 EXPORT_SYMBOL(free_task); 141 142 void __put_task_struct(struct task_struct *tsk) 143 { 144 WARN_ON(!tsk->exit_state); 145 WARN_ON(atomic_read(&tsk->usage)); 146 WARN_ON(tsk == current); 147 148 security_task_free(tsk); 149 free_uid(tsk->user); 150 put_group_info(tsk->group_info); 151 delayacct_tsk_free(tsk); 152 153 if (!profile_handoff_task(tsk)) 154 free_task(tsk); 155 } 156 157 /* 158 * macro override instead of weak attribute alias, to workaround 159 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 160 */ 161 #ifndef arch_task_cache_init 162 #define arch_task_cache_init() 163 #endif 164 165 void __init fork_init(unsigned long mempages) 166 { 167 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 168 #ifndef ARCH_MIN_TASKALIGN 169 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 170 #endif 171 /* create a slab on which task_structs can be allocated */ 172 task_struct_cachep = 173 kmem_cache_create("task_struct", sizeof(struct task_struct), 174 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 175 #endif 176 177 /* do the arch specific task caches init */ 178 arch_task_cache_init(); 179 180 /* 181 * The default maximum number of threads is set to a safe 182 * value: the thread structures can take up at most half 183 * of memory. 184 */ 185 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 186 187 /* 188 * we need to allow at least 20 threads to boot a system 189 */ 190 if(max_threads < 20) 191 max_threads = 20; 192 193 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 194 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 195 init_task.signal->rlim[RLIMIT_SIGPENDING] = 196 init_task.signal->rlim[RLIMIT_NPROC]; 197 } 198 199 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 200 struct task_struct *src) 201 { 202 *dst = *src; 203 return 0; 204 } 205 206 static struct task_struct *dup_task_struct(struct task_struct *orig) 207 { 208 struct task_struct *tsk; 209 struct thread_info *ti; 210 int err; 211 212 prepare_to_copy(orig); 213 214 tsk = alloc_task_struct(); 215 if (!tsk) 216 return NULL; 217 218 ti = alloc_thread_info(tsk); 219 if (!ti) { 220 free_task_struct(tsk); 221 return NULL; 222 } 223 224 err = arch_dup_task_struct(tsk, orig); 225 if (err) 226 goto out; 227 228 tsk->stack = ti; 229 230 err = prop_local_init_single(&tsk->dirties); 231 if (err) 232 goto out; 233 234 setup_thread_stack(tsk, orig); 235 236 #ifdef CONFIG_CC_STACKPROTECTOR 237 tsk->stack_canary = get_random_int(); 238 #endif 239 240 /* One for us, one for whoever does the "release_task()" (usually parent) */ 241 atomic_set(&tsk->usage,2); 242 atomic_set(&tsk->fs_excl, 0); 243 #ifdef CONFIG_BLK_DEV_IO_TRACE 244 tsk->btrace_seq = 0; 245 #endif 246 tsk->splice_pipe = NULL; 247 return tsk; 248 249 out: 250 free_thread_info(ti); 251 free_task_struct(tsk); 252 return NULL; 253 } 254 255 #ifdef CONFIG_MMU 256 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 257 { 258 struct vm_area_struct *mpnt, *tmp, **pprev; 259 struct rb_node **rb_link, *rb_parent; 260 int retval; 261 unsigned long charge; 262 struct mempolicy *pol; 263 264 down_write(&oldmm->mmap_sem); 265 flush_cache_dup_mm(oldmm); 266 /* 267 * Not linked in yet - no deadlock potential: 268 */ 269 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 270 271 mm->locked_vm = 0; 272 mm->mmap = NULL; 273 mm->mmap_cache = NULL; 274 mm->free_area_cache = oldmm->mmap_base; 275 mm->cached_hole_size = ~0UL; 276 mm->map_count = 0; 277 cpus_clear(mm->cpu_vm_mask); 278 mm->mm_rb = RB_ROOT; 279 rb_link = &mm->mm_rb.rb_node; 280 rb_parent = NULL; 281 pprev = &mm->mmap; 282 283 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 284 struct file *file; 285 286 if (mpnt->vm_flags & VM_DONTCOPY) { 287 long pages = vma_pages(mpnt); 288 mm->total_vm -= pages; 289 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 290 -pages); 291 continue; 292 } 293 charge = 0; 294 if (mpnt->vm_flags & VM_ACCOUNT) { 295 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 296 if (security_vm_enough_memory(len)) 297 goto fail_nomem; 298 charge = len; 299 } 300 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 301 if (!tmp) 302 goto fail_nomem; 303 *tmp = *mpnt; 304 pol = mpol_dup(vma_policy(mpnt)); 305 retval = PTR_ERR(pol); 306 if (IS_ERR(pol)) 307 goto fail_nomem_policy; 308 vma_set_policy(tmp, pol); 309 tmp->vm_flags &= ~VM_LOCKED; 310 tmp->vm_mm = mm; 311 tmp->vm_next = NULL; 312 anon_vma_link(tmp); 313 file = tmp->vm_file; 314 if (file) { 315 struct inode *inode = file->f_path.dentry->d_inode; 316 get_file(file); 317 if (tmp->vm_flags & VM_DENYWRITE) 318 atomic_dec(&inode->i_writecount); 319 320 /* insert tmp into the share list, just after mpnt */ 321 spin_lock(&file->f_mapping->i_mmap_lock); 322 tmp->vm_truncate_count = mpnt->vm_truncate_count; 323 flush_dcache_mmap_lock(file->f_mapping); 324 vma_prio_tree_add(tmp, mpnt); 325 flush_dcache_mmap_unlock(file->f_mapping); 326 spin_unlock(&file->f_mapping->i_mmap_lock); 327 } 328 329 /* 330 * Clear hugetlb-related page reserves for children. This only 331 * affects MAP_PRIVATE mappings. Faults generated by the child 332 * are not guaranteed to succeed, even if read-only 333 */ 334 if (is_vm_hugetlb_page(tmp)) 335 reset_vma_resv_huge_pages(tmp); 336 337 /* 338 * Link in the new vma and copy the page table entries. 339 */ 340 *pprev = tmp; 341 pprev = &tmp->vm_next; 342 343 __vma_link_rb(mm, tmp, rb_link, rb_parent); 344 rb_link = &tmp->vm_rb.rb_right; 345 rb_parent = &tmp->vm_rb; 346 347 mm->map_count++; 348 retval = copy_page_range(mm, oldmm, mpnt); 349 350 if (tmp->vm_ops && tmp->vm_ops->open) 351 tmp->vm_ops->open(tmp); 352 353 if (retval) 354 goto out; 355 } 356 /* a new mm has just been created */ 357 arch_dup_mmap(oldmm, mm); 358 retval = 0; 359 out: 360 up_write(&mm->mmap_sem); 361 flush_tlb_mm(oldmm); 362 up_write(&oldmm->mmap_sem); 363 return retval; 364 fail_nomem_policy: 365 kmem_cache_free(vm_area_cachep, tmp); 366 fail_nomem: 367 retval = -ENOMEM; 368 vm_unacct_memory(charge); 369 goto out; 370 } 371 372 static inline int mm_alloc_pgd(struct mm_struct * mm) 373 { 374 mm->pgd = pgd_alloc(mm); 375 if (unlikely(!mm->pgd)) 376 return -ENOMEM; 377 return 0; 378 } 379 380 static inline void mm_free_pgd(struct mm_struct * mm) 381 { 382 pgd_free(mm, mm->pgd); 383 } 384 #else 385 #define dup_mmap(mm, oldmm) (0) 386 #define mm_alloc_pgd(mm) (0) 387 #define mm_free_pgd(mm) 388 #endif /* CONFIG_MMU */ 389 390 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 391 392 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 393 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 394 395 #include <linux/init_task.h> 396 397 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 398 { 399 atomic_set(&mm->mm_users, 1); 400 atomic_set(&mm->mm_count, 1); 401 init_rwsem(&mm->mmap_sem); 402 INIT_LIST_HEAD(&mm->mmlist); 403 mm->flags = (current->mm) ? current->mm->flags 404 : MMF_DUMP_FILTER_DEFAULT; 405 mm->core_state = NULL; 406 mm->nr_ptes = 0; 407 set_mm_counter(mm, file_rss, 0); 408 set_mm_counter(mm, anon_rss, 0); 409 spin_lock_init(&mm->page_table_lock); 410 rwlock_init(&mm->ioctx_list_lock); 411 mm->ioctx_list = NULL; 412 mm->free_area_cache = TASK_UNMAPPED_BASE; 413 mm->cached_hole_size = ~0UL; 414 mm_init_owner(mm, p); 415 416 if (likely(!mm_alloc_pgd(mm))) { 417 mm->def_flags = 0; 418 mmu_notifier_mm_init(mm); 419 return mm; 420 } 421 422 free_mm(mm); 423 return NULL; 424 } 425 426 /* 427 * Allocate and initialize an mm_struct. 428 */ 429 struct mm_struct * mm_alloc(void) 430 { 431 struct mm_struct * mm; 432 433 mm = allocate_mm(); 434 if (mm) { 435 memset(mm, 0, sizeof(*mm)); 436 mm = mm_init(mm, current); 437 } 438 return mm; 439 } 440 441 /* 442 * Called when the last reference to the mm 443 * is dropped: either by a lazy thread or by 444 * mmput. Free the page directory and the mm. 445 */ 446 void __mmdrop(struct mm_struct *mm) 447 { 448 BUG_ON(mm == &init_mm); 449 mm_free_pgd(mm); 450 destroy_context(mm); 451 mmu_notifier_mm_destroy(mm); 452 free_mm(mm); 453 } 454 EXPORT_SYMBOL_GPL(__mmdrop); 455 456 /* 457 * Decrement the use count and release all resources for an mm. 458 */ 459 void mmput(struct mm_struct *mm) 460 { 461 might_sleep(); 462 463 if (atomic_dec_and_test(&mm->mm_users)) { 464 exit_aio(mm); 465 exit_mmap(mm); 466 set_mm_exe_file(mm, NULL); 467 if (!list_empty(&mm->mmlist)) { 468 spin_lock(&mmlist_lock); 469 list_del(&mm->mmlist); 470 spin_unlock(&mmlist_lock); 471 } 472 put_swap_token(mm); 473 mmdrop(mm); 474 } 475 } 476 EXPORT_SYMBOL_GPL(mmput); 477 478 /** 479 * get_task_mm - acquire a reference to the task's mm 480 * 481 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 482 * this kernel workthread has transiently adopted a user mm with use_mm, 483 * to do its AIO) is not set and if so returns a reference to it, after 484 * bumping up the use count. User must release the mm via mmput() 485 * after use. Typically used by /proc and ptrace. 486 */ 487 struct mm_struct *get_task_mm(struct task_struct *task) 488 { 489 struct mm_struct *mm; 490 491 task_lock(task); 492 mm = task->mm; 493 if (mm) { 494 if (task->flags & PF_KTHREAD) 495 mm = NULL; 496 else 497 atomic_inc(&mm->mm_users); 498 } 499 task_unlock(task); 500 return mm; 501 } 502 EXPORT_SYMBOL_GPL(get_task_mm); 503 504 /* Please note the differences between mmput and mm_release. 505 * mmput is called whenever we stop holding onto a mm_struct, 506 * error success whatever. 507 * 508 * mm_release is called after a mm_struct has been removed 509 * from the current process. 510 * 511 * This difference is important for error handling, when we 512 * only half set up a mm_struct for a new process and need to restore 513 * the old one. Because we mmput the new mm_struct before 514 * restoring the old one. . . 515 * Eric Biederman 10 January 1998 516 */ 517 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 518 { 519 struct completion *vfork_done = tsk->vfork_done; 520 521 /* Get rid of any cached register state */ 522 deactivate_mm(tsk, mm); 523 524 /* notify parent sleeping on vfork() */ 525 if (vfork_done) { 526 tsk->vfork_done = NULL; 527 complete(vfork_done); 528 } 529 530 /* 531 * If we're exiting normally, clear a user-space tid field if 532 * requested. We leave this alone when dying by signal, to leave 533 * the value intact in a core dump, and to save the unnecessary 534 * trouble otherwise. Userland only wants this done for a sys_exit. 535 */ 536 if (tsk->clear_child_tid 537 && !(tsk->flags & PF_SIGNALED) 538 && atomic_read(&mm->mm_users) > 1) { 539 u32 __user * tidptr = tsk->clear_child_tid; 540 tsk->clear_child_tid = NULL; 541 542 /* 543 * We don't check the error code - if userspace has 544 * not set up a proper pointer then tough luck. 545 */ 546 put_user(0, tidptr); 547 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 548 } 549 } 550 551 /* 552 * Allocate a new mm structure and copy contents from the 553 * mm structure of the passed in task structure. 554 */ 555 struct mm_struct *dup_mm(struct task_struct *tsk) 556 { 557 struct mm_struct *mm, *oldmm = current->mm; 558 int err; 559 560 if (!oldmm) 561 return NULL; 562 563 mm = allocate_mm(); 564 if (!mm) 565 goto fail_nomem; 566 567 memcpy(mm, oldmm, sizeof(*mm)); 568 569 /* Initializing for Swap token stuff */ 570 mm->token_priority = 0; 571 mm->last_interval = 0; 572 573 if (!mm_init(mm, tsk)) 574 goto fail_nomem; 575 576 if (init_new_context(tsk, mm)) 577 goto fail_nocontext; 578 579 dup_mm_exe_file(oldmm, mm); 580 581 err = dup_mmap(mm, oldmm); 582 if (err) 583 goto free_pt; 584 585 mm->hiwater_rss = get_mm_rss(mm); 586 mm->hiwater_vm = mm->total_vm; 587 588 return mm; 589 590 free_pt: 591 mmput(mm); 592 593 fail_nomem: 594 return NULL; 595 596 fail_nocontext: 597 /* 598 * If init_new_context() failed, we cannot use mmput() to free the mm 599 * because it calls destroy_context() 600 */ 601 mm_free_pgd(mm); 602 free_mm(mm); 603 return NULL; 604 } 605 606 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 607 { 608 struct mm_struct * mm, *oldmm; 609 int retval; 610 611 tsk->min_flt = tsk->maj_flt = 0; 612 tsk->nvcsw = tsk->nivcsw = 0; 613 614 tsk->mm = NULL; 615 tsk->active_mm = NULL; 616 617 /* 618 * Are we cloning a kernel thread? 619 * 620 * We need to steal a active VM for that.. 621 */ 622 oldmm = current->mm; 623 if (!oldmm) 624 return 0; 625 626 if (clone_flags & CLONE_VM) { 627 atomic_inc(&oldmm->mm_users); 628 mm = oldmm; 629 goto good_mm; 630 } 631 632 retval = -ENOMEM; 633 mm = dup_mm(tsk); 634 if (!mm) 635 goto fail_nomem; 636 637 good_mm: 638 /* Initializing for Swap token stuff */ 639 mm->token_priority = 0; 640 mm->last_interval = 0; 641 642 tsk->mm = mm; 643 tsk->active_mm = mm; 644 return 0; 645 646 fail_nomem: 647 return retval; 648 } 649 650 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 651 { 652 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 653 /* We don't need to lock fs - think why ;-) */ 654 if (fs) { 655 atomic_set(&fs->count, 1); 656 rwlock_init(&fs->lock); 657 fs->umask = old->umask; 658 read_lock(&old->lock); 659 fs->root = old->root; 660 path_get(&old->root); 661 fs->pwd = old->pwd; 662 path_get(&old->pwd); 663 read_unlock(&old->lock); 664 } 665 return fs; 666 } 667 668 struct fs_struct *copy_fs_struct(struct fs_struct *old) 669 { 670 return __copy_fs_struct(old); 671 } 672 673 EXPORT_SYMBOL_GPL(copy_fs_struct); 674 675 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 676 { 677 if (clone_flags & CLONE_FS) { 678 atomic_inc(¤t->fs->count); 679 return 0; 680 } 681 tsk->fs = __copy_fs_struct(current->fs); 682 if (!tsk->fs) 683 return -ENOMEM; 684 return 0; 685 } 686 687 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 688 { 689 struct files_struct *oldf, *newf; 690 int error = 0; 691 692 /* 693 * A background process may not have any files ... 694 */ 695 oldf = current->files; 696 if (!oldf) 697 goto out; 698 699 if (clone_flags & CLONE_FILES) { 700 atomic_inc(&oldf->count); 701 goto out; 702 } 703 704 newf = dup_fd(oldf, &error); 705 if (!newf) 706 goto out; 707 708 tsk->files = newf; 709 error = 0; 710 out: 711 return error; 712 } 713 714 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 715 { 716 #ifdef CONFIG_BLOCK 717 struct io_context *ioc = current->io_context; 718 719 if (!ioc) 720 return 0; 721 /* 722 * Share io context with parent, if CLONE_IO is set 723 */ 724 if (clone_flags & CLONE_IO) { 725 tsk->io_context = ioc_task_link(ioc); 726 if (unlikely(!tsk->io_context)) 727 return -ENOMEM; 728 } else if (ioprio_valid(ioc->ioprio)) { 729 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 730 if (unlikely(!tsk->io_context)) 731 return -ENOMEM; 732 733 tsk->io_context->ioprio = ioc->ioprio; 734 } 735 #endif 736 return 0; 737 } 738 739 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 740 { 741 struct sighand_struct *sig; 742 743 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 744 atomic_inc(¤t->sighand->count); 745 return 0; 746 } 747 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 748 rcu_assign_pointer(tsk->sighand, sig); 749 if (!sig) 750 return -ENOMEM; 751 atomic_set(&sig->count, 1); 752 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 753 return 0; 754 } 755 756 void __cleanup_sighand(struct sighand_struct *sighand) 757 { 758 if (atomic_dec_and_test(&sighand->count)) 759 kmem_cache_free(sighand_cachep, sighand); 760 } 761 762 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 763 { 764 struct signal_struct *sig; 765 int ret; 766 767 if (clone_flags & CLONE_THREAD) { 768 atomic_inc(¤t->signal->count); 769 atomic_inc(¤t->signal->live); 770 return 0; 771 } 772 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 773 tsk->signal = sig; 774 if (!sig) 775 return -ENOMEM; 776 777 ret = copy_thread_group_keys(tsk); 778 if (ret < 0) { 779 kmem_cache_free(signal_cachep, sig); 780 return ret; 781 } 782 783 atomic_set(&sig->count, 1); 784 atomic_set(&sig->live, 1); 785 init_waitqueue_head(&sig->wait_chldexit); 786 sig->flags = 0; 787 sig->group_exit_code = 0; 788 sig->group_exit_task = NULL; 789 sig->group_stop_count = 0; 790 sig->curr_target = tsk; 791 init_sigpending(&sig->shared_pending); 792 INIT_LIST_HEAD(&sig->posix_timers); 793 794 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 795 sig->it_real_incr.tv64 = 0; 796 sig->real_timer.function = it_real_fn; 797 798 sig->it_virt_expires = cputime_zero; 799 sig->it_virt_incr = cputime_zero; 800 sig->it_prof_expires = cputime_zero; 801 sig->it_prof_incr = cputime_zero; 802 803 sig->leader = 0; /* session leadership doesn't inherit */ 804 sig->tty_old_pgrp = NULL; 805 806 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 807 sig->gtime = cputime_zero; 808 sig->cgtime = cputime_zero; 809 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 810 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 811 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 812 task_io_accounting_init(&sig->ioac); 813 sig->sum_sched_runtime = 0; 814 INIT_LIST_HEAD(&sig->cpu_timers[0]); 815 INIT_LIST_HEAD(&sig->cpu_timers[1]); 816 INIT_LIST_HEAD(&sig->cpu_timers[2]); 817 taskstats_tgid_init(sig); 818 819 task_lock(current->group_leader); 820 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 821 task_unlock(current->group_leader); 822 823 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 824 /* 825 * New sole thread in the process gets an expiry time 826 * of the whole CPU time limit. 827 */ 828 tsk->it_prof_expires = 829 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 830 } 831 acct_init_pacct(&sig->pacct); 832 833 tty_audit_fork(sig); 834 835 return 0; 836 } 837 838 void __cleanup_signal(struct signal_struct *sig) 839 { 840 exit_thread_group_keys(sig); 841 kmem_cache_free(signal_cachep, sig); 842 } 843 844 static void cleanup_signal(struct task_struct *tsk) 845 { 846 struct signal_struct *sig = tsk->signal; 847 848 atomic_dec(&sig->live); 849 850 if (atomic_dec_and_test(&sig->count)) 851 __cleanup_signal(sig); 852 } 853 854 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 855 { 856 unsigned long new_flags = p->flags; 857 858 new_flags &= ~PF_SUPERPRIV; 859 new_flags |= PF_FORKNOEXEC; 860 new_flags |= PF_STARTING; 861 p->flags = new_flags; 862 clear_freeze_flag(p); 863 } 864 865 asmlinkage long sys_set_tid_address(int __user *tidptr) 866 { 867 current->clear_child_tid = tidptr; 868 869 return task_pid_vnr(current); 870 } 871 872 static void rt_mutex_init_task(struct task_struct *p) 873 { 874 spin_lock_init(&p->pi_lock); 875 #ifdef CONFIG_RT_MUTEXES 876 plist_head_init(&p->pi_waiters, &p->pi_lock); 877 p->pi_blocked_on = NULL; 878 #endif 879 } 880 881 #ifdef CONFIG_MM_OWNER 882 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 883 { 884 mm->owner = p; 885 } 886 #endif /* CONFIG_MM_OWNER */ 887 888 /* 889 * This creates a new process as a copy of the old one, 890 * but does not actually start it yet. 891 * 892 * It copies the registers, and all the appropriate 893 * parts of the process environment (as per the clone 894 * flags). The actual kick-off is left to the caller. 895 */ 896 static struct task_struct *copy_process(unsigned long clone_flags, 897 unsigned long stack_start, 898 struct pt_regs *regs, 899 unsigned long stack_size, 900 int __user *child_tidptr, 901 struct pid *pid, 902 int trace) 903 { 904 int retval; 905 struct task_struct *p; 906 int cgroup_callbacks_done = 0; 907 908 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 909 return ERR_PTR(-EINVAL); 910 911 /* 912 * Thread groups must share signals as well, and detached threads 913 * can only be started up within the thread group. 914 */ 915 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 916 return ERR_PTR(-EINVAL); 917 918 /* 919 * Shared signal handlers imply shared VM. By way of the above, 920 * thread groups also imply shared VM. Blocking this case allows 921 * for various simplifications in other code. 922 */ 923 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 924 return ERR_PTR(-EINVAL); 925 926 retval = security_task_create(clone_flags); 927 if (retval) 928 goto fork_out; 929 930 retval = -ENOMEM; 931 p = dup_task_struct(current); 932 if (!p) 933 goto fork_out; 934 935 rt_mutex_init_task(p); 936 937 #ifdef CONFIG_PROVE_LOCKING 938 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 939 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 940 #endif 941 retval = -EAGAIN; 942 if (atomic_read(&p->user->processes) >= 943 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 944 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 945 p->user != current->nsproxy->user_ns->root_user) 946 goto bad_fork_free; 947 } 948 949 atomic_inc(&p->user->__count); 950 atomic_inc(&p->user->processes); 951 get_group_info(p->group_info); 952 953 /* 954 * If multiple threads are within copy_process(), then this check 955 * triggers too late. This doesn't hurt, the check is only there 956 * to stop root fork bombs. 957 */ 958 if (nr_threads >= max_threads) 959 goto bad_fork_cleanup_count; 960 961 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 962 goto bad_fork_cleanup_count; 963 964 if (p->binfmt && !try_module_get(p->binfmt->module)) 965 goto bad_fork_cleanup_put_domain; 966 967 p->did_exec = 0; 968 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 969 copy_flags(clone_flags, p); 970 INIT_LIST_HEAD(&p->children); 971 INIT_LIST_HEAD(&p->sibling); 972 #ifdef CONFIG_PREEMPT_RCU 973 p->rcu_read_lock_nesting = 0; 974 p->rcu_flipctr_idx = 0; 975 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 976 p->vfork_done = NULL; 977 spin_lock_init(&p->alloc_lock); 978 979 clear_tsk_thread_flag(p, TIF_SIGPENDING); 980 init_sigpending(&p->pending); 981 982 p->utime = cputime_zero; 983 p->stime = cputime_zero; 984 p->gtime = cputime_zero; 985 p->utimescaled = cputime_zero; 986 p->stimescaled = cputime_zero; 987 p->prev_utime = cputime_zero; 988 p->prev_stime = cputime_zero; 989 990 #ifdef CONFIG_DETECT_SOFTLOCKUP 991 p->last_switch_count = 0; 992 p->last_switch_timestamp = 0; 993 #endif 994 995 task_io_accounting_init(&p->ioac); 996 acct_clear_integrals(p); 997 998 p->it_virt_expires = cputime_zero; 999 p->it_prof_expires = cputime_zero; 1000 p->it_sched_expires = 0; 1001 INIT_LIST_HEAD(&p->cpu_timers[0]); 1002 INIT_LIST_HEAD(&p->cpu_timers[1]); 1003 INIT_LIST_HEAD(&p->cpu_timers[2]); 1004 1005 p->lock_depth = -1; /* -1 = no lock */ 1006 do_posix_clock_monotonic_gettime(&p->start_time); 1007 p->real_start_time = p->start_time; 1008 monotonic_to_bootbased(&p->real_start_time); 1009 #ifdef CONFIG_SECURITY 1010 p->security = NULL; 1011 #endif 1012 p->cap_bset = current->cap_bset; 1013 p->io_context = NULL; 1014 p->audit_context = NULL; 1015 cgroup_fork(p); 1016 #ifdef CONFIG_NUMA 1017 p->mempolicy = mpol_dup(p->mempolicy); 1018 if (IS_ERR(p->mempolicy)) { 1019 retval = PTR_ERR(p->mempolicy); 1020 p->mempolicy = NULL; 1021 goto bad_fork_cleanup_cgroup; 1022 } 1023 mpol_fix_fork_child_flag(p); 1024 #endif 1025 #ifdef CONFIG_TRACE_IRQFLAGS 1026 p->irq_events = 0; 1027 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1028 p->hardirqs_enabled = 1; 1029 #else 1030 p->hardirqs_enabled = 0; 1031 #endif 1032 p->hardirq_enable_ip = 0; 1033 p->hardirq_enable_event = 0; 1034 p->hardirq_disable_ip = _THIS_IP_; 1035 p->hardirq_disable_event = 0; 1036 p->softirqs_enabled = 1; 1037 p->softirq_enable_ip = _THIS_IP_; 1038 p->softirq_enable_event = 0; 1039 p->softirq_disable_ip = 0; 1040 p->softirq_disable_event = 0; 1041 p->hardirq_context = 0; 1042 p->softirq_context = 0; 1043 #endif 1044 #ifdef CONFIG_LOCKDEP 1045 p->lockdep_depth = 0; /* no locks held yet */ 1046 p->curr_chain_key = 0; 1047 p->lockdep_recursion = 0; 1048 #endif 1049 1050 #ifdef CONFIG_DEBUG_MUTEXES 1051 p->blocked_on = NULL; /* not blocked yet */ 1052 #endif 1053 1054 /* Perform scheduler related setup. Assign this task to a CPU. */ 1055 sched_fork(p, clone_flags); 1056 1057 if ((retval = security_task_alloc(p))) 1058 goto bad_fork_cleanup_policy; 1059 if ((retval = audit_alloc(p))) 1060 goto bad_fork_cleanup_security; 1061 /* copy all the process information */ 1062 if ((retval = copy_semundo(clone_flags, p))) 1063 goto bad_fork_cleanup_audit; 1064 if ((retval = copy_files(clone_flags, p))) 1065 goto bad_fork_cleanup_semundo; 1066 if ((retval = copy_fs(clone_flags, p))) 1067 goto bad_fork_cleanup_files; 1068 if ((retval = copy_sighand(clone_flags, p))) 1069 goto bad_fork_cleanup_fs; 1070 if ((retval = copy_signal(clone_flags, p))) 1071 goto bad_fork_cleanup_sighand; 1072 if ((retval = copy_mm(clone_flags, p))) 1073 goto bad_fork_cleanup_signal; 1074 if ((retval = copy_keys(clone_flags, p))) 1075 goto bad_fork_cleanup_mm; 1076 if ((retval = copy_namespaces(clone_flags, p))) 1077 goto bad_fork_cleanup_keys; 1078 if ((retval = copy_io(clone_flags, p))) 1079 goto bad_fork_cleanup_namespaces; 1080 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1081 if (retval) 1082 goto bad_fork_cleanup_io; 1083 1084 if (pid != &init_struct_pid) { 1085 retval = -ENOMEM; 1086 pid = alloc_pid(task_active_pid_ns(p)); 1087 if (!pid) 1088 goto bad_fork_cleanup_io; 1089 1090 if (clone_flags & CLONE_NEWPID) { 1091 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1092 if (retval < 0) 1093 goto bad_fork_free_pid; 1094 } 1095 } 1096 1097 p->pid = pid_nr(pid); 1098 p->tgid = p->pid; 1099 if (clone_flags & CLONE_THREAD) 1100 p->tgid = current->tgid; 1101 1102 if (current->nsproxy != p->nsproxy) { 1103 retval = ns_cgroup_clone(p, pid); 1104 if (retval) 1105 goto bad_fork_free_pid; 1106 } 1107 1108 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1109 /* 1110 * Clear TID on mm_release()? 1111 */ 1112 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1113 #ifdef CONFIG_FUTEX 1114 p->robust_list = NULL; 1115 #ifdef CONFIG_COMPAT 1116 p->compat_robust_list = NULL; 1117 #endif 1118 INIT_LIST_HEAD(&p->pi_state_list); 1119 p->pi_state_cache = NULL; 1120 #endif 1121 /* 1122 * sigaltstack should be cleared when sharing the same VM 1123 */ 1124 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1125 p->sas_ss_sp = p->sas_ss_size = 0; 1126 1127 /* 1128 * Syscall tracing should be turned off in the child regardless 1129 * of CLONE_PTRACE. 1130 */ 1131 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1132 #ifdef TIF_SYSCALL_EMU 1133 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1134 #endif 1135 clear_all_latency_tracing(p); 1136 1137 /* Our parent execution domain becomes current domain 1138 These must match for thread signalling to apply */ 1139 p->parent_exec_id = p->self_exec_id; 1140 1141 /* ok, now we should be set up.. */ 1142 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1143 p->pdeath_signal = 0; 1144 p->exit_state = 0; 1145 1146 /* 1147 * Ok, make it visible to the rest of the system. 1148 * We dont wake it up yet. 1149 */ 1150 p->group_leader = p; 1151 INIT_LIST_HEAD(&p->thread_group); 1152 1153 /* Now that the task is set up, run cgroup callbacks if 1154 * necessary. We need to run them before the task is visible 1155 * on the tasklist. */ 1156 cgroup_fork_callbacks(p); 1157 cgroup_callbacks_done = 1; 1158 1159 /* Need tasklist lock for parent etc handling! */ 1160 write_lock_irq(&tasklist_lock); 1161 1162 /* 1163 * The task hasn't been attached yet, so its cpus_allowed mask will 1164 * not be changed, nor will its assigned CPU. 1165 * 1166 * The cpus_allowed mask of the parent may have changed after it was 1167 * copied first time - so re-copy it here, then check the child's CPU 1168 * to ensure it is on a valid CPU (and if not, just force it back to 1169 * parent's CPU). This avoids alot of nasty races. 1170 */ 1171 p->cpus_allowed = current->cpus_allowed; 1172 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1173 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1174 !cpu_online(task_cpu(p)))) 1175 set_task_cpu(p, smp_processor_id()); 1176 1177 /* CLONE_PARENT re-uses the old parent */ 1178 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1179 p->real_parent = current->real_parent; 1180 else 1181 p->real_parent = current; 1182 1183 spin_lock(¤t->sighand->siglock); 1184 1185 /* 1186 * Process group and session signals need to be delivered to just the 1187 * parent before the fork or both the parent and the child after the 1188 * fork. Restart if a signal comes in before we add the new process to 1189 * it's process group. 1190 * A fatal signal pending means that current will exit, so the new 1191 * thread can't slip out of an OOM kill (or normal SIGKILL). 1192 */ 1193 recalc_sigpending(); 1194 if (signal_pending(current)) { 1195 spin_unlock(¤t->sighand->siglock); 1196 write_unlock_irq(&tasklist_lock); 1197 retval = -ERESTARTNOINTR; 1198 goto bad_fork_free_pid; 1199 } 1200 1201 if (clone_flags & CLONE_THREAD) { 1202 p->group_leader = current->group_leader; 1203 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1204 1205 if (!cputime_eq(current->signal->it_virt_expires, 1206 cputime_zero) || 1207 !cputime_eq(current->signal->it_prof_expires, 1208 cputime_zero) || 1209 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1210 !list_empty(¤t->signal->cpu_timers[0]) || 1211 !list_empty(¤t->signal->cpu_timers[1]) || 1212 !list_empty(¤t->signal->cpu_timers[2])) { 1213 /* 1214 * Have child wake up on its first tick to check 1215 * for process CPU timers. 1216 */ 1217 p->it_prof_expires = jiffies_to_cputime(1); 1218 } 1219 } 1220 1221 if (likely(p->pid)) { 1222 list_add_tail(&p->sibling, &p->real_parent->children); 1223 tracehook_finish_clone(p, clone_flags, trace); 1224 1225 if (thread_group_leader(p)) { 1226 if (clone_flags & CLONE_NEWPID) 1227 p->nsproxy->pid_ns->child_reaper = p; 1228 1229 p->signal->leader_pid = pid; 1230 p->signal->tty = current->signal->tty; 1231 set_task_pgrp(p, task_pgrp_nr(current)); 1232 set_task_session(p, task_session_nr(current)); 1233 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1234 attach_pid(p, PIDTYPE_SID, task_session(current)); 1235 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1236 __get_cpu_var(process_counts)++; 1237 } 1238 attach_pid(p, PIDTYPE_PID, pid); 1239 nr_threads++; 1240 } 1241 1242 total_forks++; 1243 spin_unlock(¤t->sighand->siglock); 1244 write_unlock_irq(&tasklist_lock); 1245 proc_fork_connector(p); 1246 cgroup_post_fork(p); 1247 return p; 1248 1249 bad_fork_free_pid: 1250 if (pid != &init_struct_pid) 1251 free_pid(pid); 1252 bad_fork_cleanup_io: 1253 put_io_context(p->io_context); 1254 bad_fork_cleanup_namespaces: 1255 exit_task_namespaces(p); 1256 bad_fork_cleanup_keys: 1257 exit_keys(p); 1258 bad_fork_cleanup_mm: 1259 if (p->mm) 1260 mmput(p->mm); 1261 bad_fork_cleanup_signal: 1262 cleanup_signal(p); 1263 bad_fork_cleanup_sighand: 1264 __cleanup_sighand(p->sighand); 1265 bad_fork_cleanup_fs: 1266 exit_fs(p); /* blocking */ 1267 bad_fork_cleanup_files: 1268 exit_files(p); /* blocking */ 1269 bad_fork_cleanup_semundo: 1270 exit_sem(p); 1271 bad_fork_cleanup_audit: 1272 audit_free(p); 1273 bad_fork_cleanup_security: 1274 security_task_free(p); 1275 bad_fork_cleanup_policy: 1276 #ifdef CONFIG_NUMA 1277 mpol_put(p->mempolicy); 1278 bad_fork_cleanup_cgroup: 1279 #endif 1280 cgroup_exit(p, cgroup_callbacks_done); 1281 delayacct_tsk_free(p); 1282 if (p->binfmt) 1283 module_put(p->binfmt->module); 1284 bad_fork_cleanup_put_domain: 1285 module_put(task_thread_info(p)->exec_domain->module); 1286 bad_fork_cleanup_count: 1287 put_group_info(p->group_info); 1288 atomic_dec(&p->user->processes); 1289 free_uid(p->user); 1290 bad_fork_free: 1291 free_task(p); 1292 fork_out: 1293 return ERR_PTR(retval); 1294 } 1295 1296 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1297 { 1298 memset(regs, 0, sizeof(struct pt_regs)); 1299 return regs; 1300 } 1301 1302 struct task_struct * __cpuinit fork_idle(int cpu) 1303 { 1304 struct task_struct *task; 1305 struct pt_regs regs; 1306 1307 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1308 &init_struct_pid, 0); 1309 if (!IS_ERR(task)) 1310 init_idle(task, cpu); 1311 1312 return task; 1313 } 1314 1315 /* 1316 * Ok, this is the main fork-routine. 1317 * 1318 * It copies the process, and if successful kick-starts 1319 * it and waits for it to finish using the VM if required. 1320 */ 1321 long do_fork(unsigned long clone_flags, 1322 unsigned long stack_start, 1323 struct pt_regs *regs, 1324 unsigned long stack_size, 1325 int __user *parent_tidptr, 1326 int __user *child_tidptr) 1327 { 1328 struct task_struct *p; 1329 int trace = 0; 1330 long nr; 1331 1332 /* 1333 * We hope to recycle these flags after 2.6.26 1334 */ 1335 if (unlikely(clone_flags & CLONE_STOPPED)) { 1336 static int __read_mostly count = 100; 1337 1338 if (count > 0 && printk_ratelimit()) { 1339 char comm[TASK_COMM_LEN]; 1340 1341 count--; 1342 printk(KERN_INFO "fork(): process `%s' used deprecated " 1343 "clone flags 0x%lx\n", 1344 get_task_comm(comm, current), 1345 clone_flags & CLONE_STOPPED); 1346 } 1347 } 1348 1349 /* 1350 * When called from kernel_thread, don't do user tracing stuff. 1351 */ 1352 if (likely(user_mode(regs))) 1353 trace = tracehook_prepare_clone(clone_flags); 1354 1355 p = copy_process(clone_flags, stack_start, regs, stack_size, 1356 child_tidptr, NULL, trace); 1357 /* 1358 * Do this prior waking up the new thread - the thread pointer 1359 * might get invalid after that point, if the thread exits quickly. 1360 */ 1361 if (!IS_ERR(p)) { 1362 struct completion vfork; 1363 1364 nr = task_pid_vnr(p); 1365 1366 if (clone_flags & CLONE_PARENT_SETTID) 1367 put_user(nr, parent_tidptr); 1368 1369 if (clone_flags & CLONE_VFORK) { 1370 p->vfork_done = &vfork; 1371 init_completion(&vfork); 1372 } 1373 1374 tracehook_report_clone(trace, regs, clone_flags, nr, p); 1375 1376 /* 1377 * We set PF_STARTING at creation in case tracing wants to 1378 * use this to distinguish a fully live task from one that 1379 * hasn't gotten to tracehook_report_clone() yet. Now we 1380 * clear it and set the child going. 1381 */ 1382 p->flags &= ~PF_STARTING; 1383 1384 if (unlikely(clone_flags & CLONE_STOPPED)) { 1385 /* 1386 * We'll start up with an immediate SIGSTOP. 1387 */ 1388 sigaddset(&p->pending.signal, SIGSTOP); 1389 set_tsk_thread_flag(p, TIF_SIGPENDING); 1390 __set_task_state(p, TASK_STOPPED); 1391 } else { 1392 wake_up_new_task(p, clone_flags); 1393 } 1394 1395 tracehook_report_clone_complete(trace, regs, 1396 clone_flags, nr, p); 1397 1398 if (clone_flags & CLONE_VFORK) { 1399 freezer_do_not_count(); 1400 wait_for_completion(&vfork); 1401 freezer_count(); 1402 tracehook_report_vfork_done(p, nr); 1403 } 1404 } else { 1405 nr = PTR_ERR(p); 1406 } 1407 return nr; 1408 } 1409 1410 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1411 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1412 #endif 1413 1414 static void sighand_ctor(void *data) 1415 { 1416 struct sighand_struct *sighand = data; 1417 1418 spin_lock_init(&sighand->siglock); 1419 init_waitqueue_head(&sighand->signalfd_wqh); 1420 } 1421 1422 void __init proc_caches_init(void) 1423 { 1424 sighand_cachep = kmem_cache_create("sighand_cache", 1425 sizeof(struct sighand_struct), 0, 1426 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1427 sighand_ctor); 1428 signal_cachep = kmem_cache_create("signal_cache", 1429 sizeof(struct signal_struct), 0, 1430 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1431 files_cachep = kmem_cache_create("files_cache", 1432 sizeof(struct files_struct), 0, 1433 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1434 fs_cachep = kmem_cache_create("fs_cache", 1435 sizeof(struct fs_struct), 0, 1436 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1437 vm_area_cachep = kmem_cache_create("vm_area_struct", 1438 sizeof(struct vm_area_struct), 0, 1439 SLAB_PANIC, NULL); 1440 mm_cachep = kmem_cache_create("mm_struct", 1441 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1442 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1443 } 1444 1445 /* 1446 * Check constraints on flags passed to the unshare system call and 1447 * force unsharing of additional process context as appropriate. 1448 */ 1449 static void check_unshare_flags(unsigned long *flags_ptr) 1450 { 1451 /* 1452 * If unsharing a thread from a thread group, must also 1453 * unshare vm. 1454 */ 1455 if (*flags_ptr & CLONE_THREAD) 1456 *flags_ptr |= CLONE_VM; 1457 1458 /* 1459 * If unsharing vm, must also unshare signal handlers. 1460 */ 1461 if (*flags_ptr & CLONE_VM) 1462 *flags_ptr |= CLONE_SIGHAND; 1463 1464 /* 1465 * If unsharing signal handlers and the task was created 1466 * using CLONE_THREAD, then must unshare the thread 1467 */ 1468 if ((*flags_ptr & CLONE_SIGHAND) && 1469 (atomic_read(¤t->signal->count) > 1)) 1470 *flags_ptr |= CLONE_THREAD; 1471 1472 /* 1473 * If unsharing namespace, must also unshare filesystem information. 1474 */ 1475 if (*flags_ptr & CLONE_NEWNS) 1476 *flags_ptr |= CLONE_FS; 1477 } 1478 1479 /* 1480 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1481 */ 1482 static int unshare_thread(unsigned long unshare_flags) 1483 { 1484 if (unshare_flags & CLONE_THREAD) 1485 return -EINVAL; 1486 1487 return 0; 1488 } 1489 1490 /* 1491 * Unshare the filesystem structure if it is being shared 1492 */ 1493 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1494 { 1495 struct fs_struct *fs = current->fs; 1496 1497 if ((unshare_flags & CLONE_FS) && 1498 (fs && atomic_read(&fs->count) > 1)) { 1499 *new_fsp = __copy_fs_struct(current->fs); 1500 if (!*new_fsp) 1501 return -ENOMEM; 1502 } 1503 1504 return 0; 1505 } 1506 1507 /* 1508 * Unsharing of sighand is not supported yet 1509 */ 1510 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1511 { 1512 struct sighand_struct *sigh = current->sighand; 1513 1514 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1515 return -EINVAL; 1516 else 1517 return 0; 1518 } 1519 1520 /* 1521 * Unshare vm if it is being shared 1522 */ 1523 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1524 { 1525 struct mm_struct *mm = current->mm; 1526 1527 if ((unshare_flags & CLONE_VM) && 1528 (mm && atomic_read(&mm->mm_users) > 1)) { 1529 return -EINVAL; 1530 } 1531 1532 return 0; 1533 } 1534 1535 /* 1536 * Unshare file descriptor table if it is being shared 1537 */ 1538 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1539 { 1540 struct files_struct *fd = current->files; 1541 int error = 0; 1542 1543 if ((unshare_flags & CLONE_FILES) && 1544 (fd && atomic_read(&fd->count) > 1)) { 1545 *new_fdp = dup_fd(fd, &error); 1546 if (!*new_fdp) 1547 return error; 1548 } 1549 1550 return 0; 1551 } 1552 1553 /* 1554 * unshare allows a process to 'unshare' part of the process 1555 * context which was originally shared using clone. copy_* 1556 * functions used by do_fork() cannot be used here directly 1557 * because they modify an inactive task_struct that is being 1558 * constructed. Here we are modifying the current, active, 1559 * task_struct. 1560 */ 1561 asmlinkage long sys_unshare(unsigned long unshare_flags) 1562 { 1563 int err = 0; 1564 struct fs_struct *fs, *new_fs = NULL; 1565 struct sighand_struct *new_sigh = NULL; 1566 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1567 struct files_struct *fd, *new_fd = NULL; 1568 struct nsproxy *new_nsproxy = NULL; 1569 int do_sysvsem = 0; 1570 1571 check_unshare_flags(&unshare_flags); 1572 1573 /* Return -EINVAL for all unsupported flags */ 1574 err = -EINVAL; 1575 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1576 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1577 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1578 CLONE_NEWNET)) 1579 goto bad_unshare_out; 1580 1581 /* 1582 * CLONE_NEWIPC must also detach from the undolist: after switching 1583 * to a new ipc namespace, the semaphore arrays from the old 1584 * namespace are unreachable. 1585 */ 1586 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1587 do_sysvsem = 1; 1588 if ((err = unshare_thread(unshare_flags))) 1589 goto bad_unshare_out; 1590 if ((err = unshare_fs(unshare_flags, &new_fs))) 1591 goto bad_unshare_cleanup_thread; 1592 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1593 goto bad_unshare_cleanup_fs; 1594 if ((err = unshare_vm(unshare_flags, &new_mm))) 1595 goto bad_unshare_cleanup_sigh; 1596 if ((err = unshare_fd(unshare_flags, &new_fd))) 1597 goto bad_unshare_cleanup_vm; 1598 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1599 new_fs))) 1600 goto bad_unshare_cleanup_fd; 1601 1602 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1603 if (do_sysvsem) { 1604 /* 1605 * CLONE_SYSVSEM is equivalent to sys_exit(). 1606 */ 1607 exit_sem(current); 1608 } 1609 1610 if (new_nsproxy) { 1611 switch_task_namespaces(current, new_nsproxy); 1612 new_nsproxy = NULL; 1613 } 1614 1615 task_lock(current); 1616 1617 if (new_fs) { 1618 fs = current->fs; 1619 current->fs = new_fs; 1620 new_fs = fs; 1621 } 1622 1623 if (new_mm) { 1624 mm = current->mm; 1625 active_mm = current->active_mm; 1626 current->mm = new_mm; 1627 current->active_mm = new_mm; 1628 activate_mm(active_mm, new_mm); 1629 new_mm = mm; 1630 } 1631 1632 if (new_fd) { 1633 fd = current->files; 1634 current->files = new_fd; 1635 new_fd = fd; 1636 } 1637 1638 task_unlock(current); 1639 } 1640 1641 if (new_nsproxy) 1642 put_nsproxy(new_nsproxy); 1643 1644 bad_unshare_cleanup_fd: 1645 if (new_fd) 1646 put_files_struct(new_fd); 1647 1648 bad_unshare_cleanup_vm: 1649 if (new_mm) 1650 mmput(new_mm); 1651 1652 bad_unshare_cleanup_sigh: 1653 if (new_sigh) 1654 if (atomic_dec_and_test(&new_sigh->count)) 1655 kmem_cache_free(sighand_cachep, new_sigh); 1656 1657 bad_unshare_cleanup_fs: 1658 if (new_fs) 1659 put_fs_struct(new_fs); 1660 1661 bad_unshare_cleanup_thread: 1662 bad_unshare_out: 1663 return err; 1664 } 1665 1666 /* 1667 * Helper to unshare the files of the current task. 1668 * We don't want to expose copy_files internals to 1669 * the exec layer of the kernel. 1670 */ 1671 1672 int unshare_files(struct files_struct **displaced) 1673 { 1674 struct task_struct *task = current; 1675 struct files_struct *copy = NULL; 1676 int error; 1677 1678 error = unshare_fd(CLONE_FILES, ©); 1679 if (error || !copy) { 1680 *displaced = NULL; 1681 return error; 1682 } 1683 *displaced = task->files; 1684 task_lock(task); 1685 task->files = copy; 1686 task_unlock(task); 1687 return 0; 1688 } 1689