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/personality.h> 21 #include <linux/mempolicy.h> 22 #include <linux/sem.h> 23 #include <linux/file.h> 24 #include <linux/fdtable.h> 25 #include <linux/iocontext.h> 26 #include <linux/key.h> 27 #include <linux/binfmts.h> 28 #include <linux/mman.h> 29 #include <linux/mmu_notifier.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/compat.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/ftrace.h> 50 #include <linux/profile.h> 51 #include <linux/rmap.h> 52 #include <linux/acct.h> 53 #include <linux/tsacct_kern.h> 54 #include <linux/cn_proc.h> 55 #include <linux/freezer.h> 56 #include <linux/delayacct.h> 57 #include <linux/taskstats_kern.h> 58 #include <linux/random.h> 59 #include <linux/tty.h> 60 #include <linux/proc_fs.h> 61 #include <linux/blkdev.h> 62 #include <linux/fs_struct.h> 63 #include <linux/magic.h> 64 #include <linux/perf_counter.h> 65 66 #include <asm/pgtable.h> 67 #include <asm/pgalloc.h> 68 #include <asm/uaccess.h> 69 #include <asm/mmu_context.h> 70 #include <asm/cacheflush.h> 71 #include <asm/tlbflush.h> 72 73 #include <trace/events/sched.h> 74 75 /* 76 * Protected counters by write_lock_irq(&tasklist_lock) 77 */ 78 unsigned long total_forks; /* Handle normal Linux uptimes. */ 79 int nr_threads; /* The idle threads do not count.. */ 80 81 int max_threads; /* tunable limit on nr_threads */ 82 83 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 84 85 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 86 87 int nr_processes(void) 88 { 89 int cpu; 90 int total = 0; 91 92 for_each_online_cpu(cpu) 93 total += per_cpu(process_counts, cpu); 94 95 return total; 96 } 97 98 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 99 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 100 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 101 static struct kmem_cache *task_struct_cachep; 102 #endif 103 104 #ifndef __HAVE_ARCH_THREAD_INFO_ALLOCATOR 105 static inline struct thread_info *alloc_thread_info(struct task_struct *tsk) 106 { 107 #ifdef CONFIG_DEBUG_STACK_USAGE 108 gfp_t mask = GFP_KERNEL | __GFP_ZERO; 109 #else 110 gfp_t mask = GFP_KERNEL; 111 #endif 112 return (struct thread_info *)__get_free_pages(mask, THREAD_SIZE_ORDER); 113 } 114 115 static inline void free_thread_info(struct thread_info *ti) 116 { 117 free_pages((unsigned long)ti, THREAD_SIZE_ORDER); 118 } 119 #endif 120 121 /* SLAB cache for signal_struct structures (tsk->signal) */ 122 static struct kmem_cache *signal_cachep; 123 124 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 125 struct kmem_cache *sighand_cachep; 126 127 /* SLAB cache for files_struct structures (tsk->files) */ 128 struct kmem_cache *files_cachep; 129 130 /* SLAB cache for fs_struct structures (tsk->fs) */ 131 struct kmem_cache *fs_cachep; 132 133 /* SLAB cache for vm_area_struct structures */ 134 struct kmem_cache *vm_area_cachep; 135 136 /* SLAB cache for mm_struct structures (tsk->mm) */ 137 static struct kmem_cache *mm_cachep; 138 139 void free_task(struct task_struct *tsk) 140 { 141 prop_local_destroy_single(&tsk->dirties); 142 free_thread_info(tsk->stack); 143 rt_mutex_debug_task_free(tsk); 144 ftrace_graph_exit_task(tsk); 145 free_task_struct(tsk); 146 } 147 EXPORT_SYMBOL(free_task); 148 149 void __put_task_struct(struct task_struct *tsk) 150 { 151 WARN_ON(!tsk->exit_state); 152 WARN_ON(atomic_read(&tsk->usage)); 153 WARN_ON(tsk == current); 154 155 put_cred(tsk->real_cred); 156 put_cred(tsk->cred); 157 delayacct_tsk_free(tsk); 158 159 if (!profile_handoff_task(tsk)) 160 free_task(tsk); 161 } 162 163 /* 164 * macro override instead of weak attribute alias, to workaround 165 * gcc 4.1.0 and 4.1.1 bugs with weak attribute and empty functions. 166 */ 167 #ifndef arch_task_cache_init 168 #define arch_task_cache_init() 169 #endif 170 171 void __init fork_init(unsigned long mempages) 172 { 173 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 174 #ifndef ARCH_MIN_TASKALIGN 175 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 176 #endif 177 /* create a slab on which task_structs can be allocated */ 178 task_struct_cachep = 179 kmem_cache_create("task_struct", sizeof(struct task_struct), 180 ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); 181 #endif 182 183 /* do the arch specific task caches init */ 184 arch_task_cache_init(); 185 186 /* 187 * The default maximum number of threads is set to a safe 188 * value: the thread structures can take up at most half 189 * of memory. 190 */ 191 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 192 193 /* 194 * we need to allow at least 20 threads to boot a system 195 */ 196 if(max_threads < 20) 197 max_threads = 20; 198 199 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 200 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 201 init_task.signal->rlim[RLIMIT_SIGPENDING] = 202 init_task.signal->rlim[RLIMIT_NPROC]; 203 } 204 205 int __attribute__((weak)) arch_dup_task_struct(struct task_struct *dst, 206 struct task_struct *src) 207 { 208 *dst = *src; 209 return 0; 210 } 211 212 static struct task_struct *dup_task_struct(struct task_struct *orig) 213 { 214 struct task_struct *tsk; 215 struct thread_info *ti; 216 unsigned long *stackend; 217 218 int err; 219 220 prepare_to_copy(orig); 221 222 tsk = alloc_task_struct(); 223 if (!tsk) 224 return NULL; 225 226 ti = alloc_thread_info(tsk); 227 if (!ti) { 228 free_task_struct(tsk); 229 return NULL; 230 } 231 232 err = arch_dup_task_struct(tsk, orig); 233 if (err) 234 goto out; 235 236 tsk->stack = ti; 237 238 err = prop_local_init_single(&tsk->dirties); 239 if (err) 240 goto out; 241 242 setup_thread_stack(tsk, orig); 243 stackend = end_of_stack(tsk); 244 *stackend = STACK_END_MAGIC; /* for overflow detection */ 245 246 #ifdef CONFIG_CC_STACKPROTECTOR 247 tsk->stack_canary = get_random_int(); 248 #endif 249 250 /* One for us, one for whoever does the "release_task()" (usually parent) */ 251 atomic_set(&tsk->usage,2); 252 atomic_set(&tsk->fs_excl, 0); 253 #ifdef CONFIG_BLK_DEV_IO_TRACE 254 tsk->btrace_seq = 0; 255 #endif 256 tsk->splice_pipe = NULL; 257 return tsk; 258 259 out: 260 free_thread_info(ti); 261 free_task_struct(tsk); 262 return NULL; 263 } 264 265 #ifdef CONFIG_MMU 266 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 267 { 268 struct vm_area_struct *mpnt, *tmp, **pprev; 269 struct rb_node **rb_link, *rb_parent; 270 int retval; 271 unsigned long charge; 272 struct mempolicy *pol; 273 274 down_write(&oldmm->mmap_sem); 275 flush_cache_dup_mm(oldmm); 276 /* 277 * Not linked in yet - no deadlock potential: 278 */ 279 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 280 281 mm->locked_vm = 0; 282 mm->mmap = NULL; 283 mm->mmap_cache = NULL; 284 mm->free_area_cache = oldmm->mmap_base; 285 mm->cached_hole_size = ~0UL; 286 mm->map_count = 0; 287 cpumask_clear(mm_cpumask(mm)); 288 mm->mm_rb = RB_ROOT; 289 rb_link = &mm->mm_rb.rb_node; 290 rb_parent = NULL; 291 pprev = &mm->mmap; 292 293 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 294 struct file *file; 295 296 if (mpnt->vm_flags & VM_DONTCOPY) { 297 long pages = vma_pages(mpnt); 298 mm->total_vm -= pages; 299 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 300 -pages); 301 continue; 302 } 303 charge = 0; 304 if (mpnt->vm_flags & VM_ACCOUNT) { 305 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 306 if (security_vm_enough_memory(len)) 307 goto fail_nomem; 308 charge = len; 309 } 310 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 311 if (!tmp) 312 goto fail_nomem; 313 *tmp = *mpnt; 314 pol = mpol_dup(vma_policy(mpnt)); 315 retval = PTR_ERR(pol); 316 if (IS_ERR(pol)) 317 goto fail_nomem_policy; 318 vma_set_policy(tmp, pol); 319 tmp->vm_flags &= ~VM_LOCKED; 320 tmp->vm_mm = mm; 321 tmp->vm_next = NULL; 322 anon_vma_link(tmp); 323 file = tmp->vm_file; 324 if (file) { 325 struct inode *inode = file->f_path.dentry->d_inode; 326 struct address_space *mapping = file->f_mapping; 327 328 get_file(file); 329 if (tmp->vm_flags & VM_DENYWRITE) 330 atomic_dec(&inode->i_writecount); 331 spin_lock(&mapping->i_mmap_lock); 332 if (tmp->vm_flags & VM_SHARED) 333 mapping->i_mmap_writable++; 334 tmp->vm_truncate_count = mpnt->vm_truncate_count; 335 flush_dcache_mmap_lock(mapping); 336 /* insert tmp into the share list, just after mpnt */ 337 vma_prio_tree_add(tmp, mpnt); 338 flush_dcache_mmap_unlock(mapping); 339 spin_unlock(&mapping->i_mmap_lock); 340 } 341 342 /* 343 * Clear hugetlb-related page reserves for children. This only 344 * affects MAP_PRIVATE mappings. Faults generated by the child 345 * are not guaranteed to succeed, even if read-only 346 */ 347 if (is_vm_hugetlb_page(tmp)) 348 reset_vma_resv_huge_pages(tmp); 349 350 /* 351 * Link in the new vma and copy the page table entries. 352 */ 353 *pprev = tmp; 354 pprev = &tmp->vm_next; 355 356 __vma_link_rb(mm, tmp, rb_link, rb_parent); 357 rb_link = &tmp->vm_rb.rb_right; 358 rb_parent = &tmp->vm_rb; 359 360 mm->map_count++; 361 retval = copy_page_range(mm, oldmm, mpnt); 362 363 if (tmp->vm_ops && tmp->vm_ops->open) 364 tmp->vm_ops->open(tmp); 365 366 if (retval) 367 goto out; 368 } 369 /* a new mm has just been created */ 370 arch_dup_mmap(oldmm, mm); 371 retval = 0; 372 out: 373 up_write(&mm->mmap_sem); 374 flush_tlb_mm(oldmm); 375 up_write(&oldmm->mmap_sem); 376 return retval; 377 fail_nomem_policy: 378 kmem_cache_free(vm_area_cachep, tmp); 379 fail_nomem: 380 retval = -ENOMEM; 381 vm_unacct_memory(charge); 382 goto out; 383 } 384 385 static inline int mm_alloc_pgd(struct mm_struct * mm) 386 { 387 mm->pgd = pgd_alloc(mm); 388 if (unlikely(!mm->pgd)) 389 return -ENOMEM; 390 return 0; 391 } 392 393 static inline void mm_free_pgd(struct mm_struct * mm) 394 { 395 pgd_free(mm, mm->pgd); 396 } 397 #else 398 #define dup_mmap(mm, oldmm) (0) 399 #define mm_alloc_pgd(mm) (0) 400 #define mm_free_pgd(mm) 401 #endif /* CONFIG_MMU */ 402 403 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 404 405 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 406 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 407 408 static unsigned long default_dump_filter = MMF_DUMP_FILTER_DEFAULT; 409 410 static int __init coredump_filter_setup(char *s) 411 { 412 default_dump_filter = 413 (simple_strtoul(s, NULL, 0) << MMF_DUMP_FILTER_SHIFT) & 414 MMF_DUMP_FILTER_MASK; 415 return 1; 416 } 417 418 __setup("coredump_filter=", coredump_filter_setup); 419 420 #include <linux/init_task.h> 421 422 static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 423 { 424 atomic_set(&mm->mm_users, 1); 425 atomic_set(&mm->mm_count, 1); 426 init_rwsem(&mm->mmap_sem); 427 INIT_LIST_HEAD(&mm->mmlist); 428 mm->flags = (current->mm) ? current->mm->flags : default_dump_filter; 429 mm->oom_adj = (current->mm) ? current->mm->oom_adj : 0; 430 mm->core_state = NULL; 431 mm->nr_ptes = 0; 432 set_mm_counter(mm, file_rss, 0); 433 set_mm_counter(mm, anon_rss, 0); 434 spin_lock_init(&mm->page_table_lock); 435 spin_lock_init(&mm->ioctx_lock); 436 INIT_HLIST_HEAD(&mm->ioctx_list); 437 mm->free_area_cache = TASK_UNMAPPED_BASE; 438 mm->cached_hole_size = ~0UL; 439 mm_init_owner(mm, p); 440 441 if (likely(!mm_alloc_pgd(mm))) { 442 mm->def_flags = 0; 443 mmu_notifier_mm_init(mm); 444 return mm; 445 } 446 447 free_mm(mm); 448 return NULL; 449 } 450 451 /* 452 * Allocate and initialize an mm_struct. 453 */ 454 struct mm_struct * mm_alloc(void) 455 { 456 struct mm_struct * mm; 457 458 mm = allocate_mm(); 459 if (mm) { 460 memset(mm, 0, sizeof(*mm)); 461 mm = mm_init(mm, current); 462 } 463 return mm; 464 } 465 466 /* 467 * Called when the last reference to the mm 468 * is dropped: either by a lazy thread or by 469 * mmput. Free the page directory and the mm. 470 */ 471 void __mmdrop(struct mm_struct *mm) 472 { 473 BUG_ON(mm == &init_mm); 474 mm_free_pgd(mm); 475 destroy_context(mm); 476 mmu_notifier_mm_destroy(mm); 477 free_mm(mm); 478 } 479 EXPORT_SYMBOL_GPL(__mmdrop); 480 481 /* 482 * Decrement the use count and release all resources for an mm. 483 */ 484 void mmput(struct mm_struct *mm) 485 { 486 might_sleep(); 487 488 if (atomic_dec_and_test(&mm->mm_users)) { 489 exit_aio(mm); 490 exit_mmap(mm); 491 set_mm_exe_file(mm, NULL); 492 if (!list_empty(&mm->mmlist)) { 493 spin_lock(&mmlist_lock); 494 list_del(&mm->mmlist); 495 spin_unlock(&mmlist_lock); 496 } 497 put_swap_token(mm); 498 mmdrop(mm); 499 } 500 } 501 EXPORT_SYMBOL_GPL(mmput); 502 503 /** 504 * get_task_mm - acquire a reference to the task's mm 505 * 506 * Returns %NULL if the task has no mm. Checks PF_KTHREAD (meaning 507 * this kernel workthread has transiently adopted a user mm with use_mm, 508 * to do its AIO) is not set and if so returns a reference to it, after 509 * bumping up the use count. User must release the mm via mmput() 510 * after use. Typically used by /proc and ptrace. 511 */ 512 struct mm_struct *get_task_mm(struct task_struct *task) 513 { 514 struct mm_struct *mm; 515 516 task_lock(task); 517 mm = task->mm; 518 if (mm) { 519 if (task->flags & PF_KTHREAD) 520 mm = NULL; 521 else 522 atomic_inc(&mm->mm_users); 523 } 524 task_unlock(task); 525 return mm; 526 } 527 EXPORT_SYMBOL_GPL(get_task_mm); 528 529 /* Please note the differences between mmput and mm_release. 530 * mmput is called whenever we stop holding onto a mm_struct, 531 * error success whatever. 532 * 533 * mm_release is called after a mm_struct has been removed 534 * from the current process. 535 * 536 * This difference is important for error handling, when we 537 * only half set up a mm_struct for a new process and need to restore 538 * the old one. Because we mmput the new mm_struct before 539 * restoring the old one. . . 540 * Eric Biederman 10 January 1998 541 */ 542 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 543 { 544 struct completion *vfork_done = tsk->vfork_done; 545 546 /* Get rid of any futexes when releasing the mm */ 547 #ifdef CONFIG_FUTEX 548 if (unlikely(tsk->robust_list)) 549 exit_robust_list(tsk); 550 #ifdef CONFIG_COMPAT 551 if (unlikely(tsk->compat_robust_list)) 552 compat_exit_robust_list(tsk); 553 #endif 554 #endif 555 556 /* Get rid of any cached register state */ 557 deactivate_mm(tsk, mm); 558 559 /* notify parent sleeping on vfork() */ 560 if (vfork_done) { 561 tsk->vfork_done = NULL; 562 complete(vfork_done); 563 } 564 565 /* 566 * If we're exiting normally, clear a user-space tid field if 567 * requested. We leave this alone when dying by signal, to leave 568 * the value intact in a core dump, and to save the unnecessary 569 * trouble otherwise. Userland only wants this done for a sys_exit. 570 */ 571 if (tsk->clear_child_tid) { 572 if (!(tsk->flags & PF_SIGNALED) && 573 atomic_read(&mm->mm_users) > 1) { 574 /* 575 * We don't check the error code - if userspace has 576 * not set up a proper pointer then tough luck. 577 */ 578 put_user(0, tsk->clear_child_tid); 579 sys_futex(tsk->clear_child_tid, FUTEX_WAKE, 580 1, NULL, NULL, 0); 581 } 582 tsk->clear_child_tid = NULL; 583 } 584 } 585 586 /* 587 * Allocate a new mm structure and copy contents from the 588 * mm structure of the passed in task structure. 589 */ 590 struct mm_struct *dup_mm(struct task_struct *tsk) 591 { 592 struct mm_struct *mm, *oldmm = current->mm; 593 int err; 594 595 if (!oldmm) 596 return NULL; 597 598 mm = allocate_mm(); 599 if (!mm) 600 goto fail_nomem; 601 602 memcpy(mm, oldmm, sizeof(*mm)); 603 604 /* Initializing for Swap token stuff */ 605 mm->token_priority = 0; 606 mm->last_interval = 0; 607 608 if (!mm_init(mm, tsk)) 609 goto fail_nomem; 610 611 if (init_new_context(tsk, mm)) 612 goto fail_nocontext; 613 614 dup_mm_exe_file(oldmm, mm); 615 616 err = dup_mmap(mm, oldmm); 617 if (err) 618 goto free_pt; 619 620 mm->hiwater_rss = get_mm_rss(mm); 621 mm->hiwater_vm = mm->total_vm; 622 623 return mm; 624 625 free_pt: 626 mmput(mm); 627 628 fail_nomem: 629 return NULL; 630 631 fail_nocontext: 632 /* 633 * If init_new_context() failed, we cannot use mmput() to free the mm 634 * because it calls destroy_context() 635 */ 636 mm_free_pgd(mm); 637 free_mm(mm); 638 return NULL; 639 } 640 641 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 642 { 643 struct mm_struct * mm, *oldmm; 644 int retval; 645 646 tsk->min_flt = tsk->maj_flt = 0; 647 tsk->nvcsw = tsk->nivcsw = 0; 648 #ifdef CONFIG_DETECT_HUNG_TASK 649 tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw; 650 #endif 651 652 tsk->mm = NULL; 653 tsk->active_mm = NULL; 654 655 /* 656 * Are we cloning a kernel thread? 657 * 658 * We need to steal a active VM for that.. 659 */ 660 oldmm = current->mm; 661 if (!oldmm) 662 return 0; 663 664 if (clone_flags & CLONE_VM) { 665 atomic_inc(&oldmm->mm_users); 666 mm = oldmm; 667 goto good_mm; 668 } 669 670 retval = -ENOMEM; 671 mm = dup_mm(tsk); 672 if (!mm) 673 goto fail_nomem; 674 675 good_mm: 676 /* Initializing for Swap token stuff */ 677 mm->token_priority = 0; 678 mm->last_interval = 0; 679 680 tsk->mm = mm; 681 tsk->active_mm = mm; 682 return 0; 683 684 fail_nomem: 685 return retval; 686 } 687 688 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 689 { 690 struct fs_struct *fs = current->fs; 691 if (clone_flags & CLONE_FS) { 692 /* tsk->fs is already what we want */ 693 write_lock(&fs->lock); 694 if (fs->in_exec) { 695 write_unlock(&fs->lock); 696 return -EAGAIN; 697 } 698 fs->users++; 699 write_unlock(&fs->lock); 700 return 0; 701 } 702 tsk->fs = copy_fs_struct(fs); 703 if (!tsk->fs) 704 return -ENOMEM; 705 return 0; 706 } 707 708 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 709 { 710 struct files_struct *oldf, *newf; 711 int error = 0; 712 713 /* 714 * A background process may not have any files ... 715 */ 716 oldf = current->files; 717 if (!oldf) 718 goto out; 719 720 if (clone_flags & CLONE_FILES) { 721 atomic_inc(&oldf->count); 722 goto out; 723 } 724 725 newf = dup_fd(oldf, &error); 726 if (!newf) 727 goto out; 728 729 tsk->files = newf; 730 error = 0; 731 out: 732 return error; 733 } 734 735 static int copy_io(unsigned long clone_flags, struct task_struct *tsk) 736 { 737 #ifdef CONFIG_BLOCK 738 struct io_context *ioc = current->io_context; 739 740 if (!ioc) 741 return 0; 742 /* 743 * Share io context with parent, if CLONE_IO is set 744 */ 745 if (clone_flags & CLONE_IO) { 746 tsk->io_context = ioc_task_link(ioc); 747 if (unlikely(!tsk->io_context)) 748 return -ENOMEM; 749 } else if (ioprio_valid(ioc->ioprio)) { 750 tsk->io_context = alloc_io_context(GFP_KERNEL, -1); 751 if (unlikely(!tsk->io_context)) 752 return -ENOMEM; 753 754 tsk->io_context->ioprio = ioc->ioprio; 755 } 756 #endif 757 return 0; 758 } 759 760 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 761 { 762 struct sighand_struct *sig; 763 764 if (clone_flags & CLONE_SIGHAND) { 765 atomic_inc(¤t->sighand->count); 766 return 0; 767 } 768 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 769 rcu_assign_pointer(tsk->sighand, sig); 770 if (!sig) 771 return -ENOMEM; 772 atomic_set(&sig->count, 1); 773 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 774 return 0; 775 } 776 777 void __cleanup_sighand(struct sighand_struct *sighand) 778 { 779 if (atomic_dec_and_test(&sighand->count)) 780 kmem_cache_free(sighand_cachep, sighand); 781 } 782 783 784 /* 785 * Initialize POSIX timer handling for a thread group. 786 */ 787 static void posix_cpu_timers_init_group(struct signal_struct *sig) 788 { 789 /* Thread group counters. */ 790 thread_group_cputime_init(sig); 791 792 /* Expiration times and increments. */ 793 sig->it_virt_expires = cputime_zero; 794 sig->it_virt_incr = cputime_zero; 795 sig->it_prof_expires = cputime_zero; 796 sig->it_prof_incr = cputime_zero; 797 798 /* Cached expiration times. */ 799 sig->cputime_expires.prof_exp = cputime_zero; 800 sig->cputime_expires.virt_exp = cputime_zero; 801 sig->cputime_expires.sched_exp = 0; 802 803 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 804 sig->cputime_expires.prof_exp = 805 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 806 sig->cputimer.running = 1; 807 } 808 809 /* The timer lists. */ 810 INIT_LIST_HEAD(&sig->cpu_timers[0]); 811 INIT_LIST_HEAD(&sig->cpu_timers[1]); 812 INIT_LIST_HEAD(&sig->cpu_timers[2]); 813 } 814 815 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 816 { 817 struct signal_struct *sig; 818 819 if (clone_flags & CLONE_THREAD) { 820 atomic_inc(¤t->signal->count); 821 atomic_inc(¤t->signal->live); 822 return 0; 823 } 824 825 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 826 tsk->signal = sig; 827 if (!sig) 828 return -ENOMEM; 829 830 atomic_set(&sig->count, 1); 831 atomic_set(&sig->live, 1); 832 init_waitqueue_head(&sig->wait_chldexit); 833 sig->flags = 0; 834 if (clone_flags & CLONE_NEWPID) 835 sig->flags |= SIGNAL_UNKILLABLE; 836 sig->group_exit_code = 0; 837 sig->group_exit_task = NULL; 838 sig->group_stop_count = 0; 839 sig->curr_target = tsk; 840 init_sigpending(&sig->shared_pending); 841 INIT_LIST_HEAD(&sig->posix_timers); 842 843 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 844 sig->it_real_incr.tv64 = 0; 845 sig->real_timer.function = it_real_fn; 846 847 sig->leader = 0; /* session leadership doesn't inherit */ 848 sig->tty_old_pgrp = NULL; 849 sig->tty = NULL; 850 851 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 852 sig->gtime = cputime_zero; 853 sig->cgtime = cputime_zero; 854 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 855 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 856 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 857 task_io_accounting_init(&sig->ioac); 858 sig->sum_sched_runtime = 0; 859 taskstats_tgid_init(sig); 860 861 task_lock(current->group_leader); 862 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 863 task_unlock(current->group_leader); 864 865 posix_cpu_timers_init_group(sig); 866 867 acct_init_pacct(&sig->pacct); 868 869 tty_audit_fork(sig); 870 871 return 0; 872 } 873 874 void __cleanup_signal(struct signal_struct *sig) 875 { 876 thread_group_cputime_free(sig); 877 tty_kref_put(sig->tty); 878 kmem_cache_free(signal_cachep, sig); 879 } 880 881 static void cleanup_signal(struct task_struct *tsk) 882 { 883 struct signal_struct *sig = tsk->signal; 884 885 atomic_dec(&sig->live); 886 887 if (atomic_dec_and_test(&sig->count)) 888 __cleanup_signal(sig); 889 } 890 891 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 892 { 893 unsigned long new_flags = p->flags; 894 895 new_flags &= ~PF_SUPERPRIV; 896 new_flags |= PF_FORKNOEXEC; 897 new_flags |= PF_STARTING; 898 p->flags = new_flags; 899 clear_freeze_flag(p); 900 } 901 902 SYSCALL_DEFINE1(set_tid_address, int __user *, tidptr) 903 { 904 current->clear_child_tid = tidptr; 905 906 return task_pid_vnr(current); 907 } 908 909 static void rt_mutex_init_task(struct task_struct *p) 910 { 911 spin_lock_init(&p->pi_lock); 912 #ifdef CONFIG_RT_MUTEXES 913 plist_head_init(&p->pi_waiters, &p->pi_lock); 914 p->pi_blocked_on = NULL; 915 #endif 916 } 917 918 #ifdef CONFIG_MM_OWNER 919 void mm_init_owner(struct mm_struct *mm, struct task_struct *p) 920 { 921 mm->owner = p; 922 } 923 #endif /* CONFIG_MM_OWNER */ 924 925 /* 926 * Initialize POSIX timer handling for a single task. 927 */ 928 static void posix_cpu_timers_init(struct task_struct *tsk) 929 { 930 tsk->cputime_expires.prof_exp = cputime_zero; 931 tsk->cputime_expires.virt_exp = cputime_zero; 932 tsk->cputime_expires.sched_exp = 0; 933 INIT_LIST_HEAD(&tsk->cpu_timers[0]); 934 INIT_LIST_HEAD(&tsk->cpu_timers[1]); 935 INIT_LIST_HEAD(&tsk->cpu_timers[2]); 936 } 937 938 /* 939 * This creates a new process as a copy of the old one, 940 * but does not actually start it yet. 941 * 942 * It copies the registers, and all the appropriate 943 * parts of the process environment (as per the clone 944 * flags). The actual kick-off is left to the caller. 945 */ 946 static struct task_struct *copy_process(unsigned long clone_flags, 947 unsigned long stack_start, 948 struct pt_regs *regs, 949 unsigned long stack_size, 950 int __user *child_tidptr, 951 struct pid *pid, 952 int trace) 953 { 954 int retval; 955 struct task_struct *p; 956 int cgroup_callbacks_done = 0; 957 958 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 959 return ERR_PTR(-EINVAL); 960 961 /* 962 * Thread groups must share signals as well, and detached threads 963 * can only be started up within the thread group. 964 */ 965 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 966 return ERR_PTR(-EINVAL); 967 968 /* 969 * Shared signal handlers imply shared VM. By way of the above, 970 * thread groups also imply shared VM. Blocking this case allows 971 * for various simplifications in other code. 972 */ 973 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 974 return ERR_PTR(-EINVAL); 975 976 retval = security_task_create(clone_flags); 977 if (retval) 978 goto fork_out; 979 980 retval = -ENOMEM; 981 p = dup_task_struct(current); 982 if (!p) 983 goto fork_out; 984 985 ftrace_graph_init_task(p); 986 987 rt_mutex_init_task(p); 988 989 #ifdef CONFIG_PROVE_LOCKING 990 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 991 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 992 #endif 993 retval = -EAGAIN; 994 if (atomic_read(&p->real_cred->user->processes) >= 995 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 996 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 997 p->real_cred->user != INIT_USER) 998 goto bad_fork_free; 999 } 1000 1001 retval = copy_creds(p, clone_flags); 1002 if (retval < 0) 1003 goto bad_fork_free; 1004 1005 /* 1006 * If multiple threads are within copy_process(), then this check 1007 * triggers too late. This doesn't hurt, the check is only there 1008 * to stop root fork bombs. 1009 */ 1010 retval = -EAGAIN; 1011 if (nr_threads >= max_threads) 1012 goto bad_fork_cleanup_count; 1013 1014 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1015 goto bad_fork_cleanup_count; 1016 1017 if (p->binfmt && !try_module_get(p->binfmt->module)) 1018 goto bad_fork_cleanup_put_domain; 1019 1020 p->did_exec = 0; 1021 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1022 copy_flags(clone_flags, p); 1023 INIT_LIST_HEAD(&p->children); 1024 INIT_LIST_HEAD(&p->sibling); 1025 #ifdef CONFIG_PREEMPT_RCU 1026 p->rcu_read_lock_nesting = 0; 1027 p->rcu_flipctr_idx = 0; 1028 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1029 p->vfork_done = NULL; 1030 spin_lock_init(&p->alloc_lock); 1031 1032 init_sigpending(&p->pending); 1033 1034 p->utime = cputime_zero; 1035 p->stime = cputime_zero; 1036 p->gtime = cputime_zero; 1037 p->utimescaled = cputime_zero; 1038 p->stimescaled = cputime_zero; 1039 p->prev_utime = cputime_zero; 1040 p->prev_stime = cputime_zero; 1041 1042 p->default_timer_slack_ns = current->timer_slack_ns; 1043 1044 task_io_accounting_init(&p->ioac); 1045 acct_clear_integrals(p); 1046 1047 posix_cpu_timers_init(p); 1048 1049 p->lock_depth = -1; /* -1 = no lock */ 1050 do_posix_clock_monotonic_gettime(&p->start_time); 1051 p->real_start_time = p->start_time; 1052 monotonic_to_bootbased(&p->real_start_time); 1053 p->io_context = NULL; 1054 p->audit_context = NULL; 1055 cgroup_fork(p); 1056 #ifdef CONFIG_NUMA 1057 p->mempolicy = mpol_dup(p->mempolicy); 1058 if (IS_ERR(p->mempolicy)) { 1059 retval = PTR_ERR(p->mempolicy); 1060 p->mempolicy = NULL; 1061 goto bad_fork_cleanup_cgroup; 1062 } 1063 mpol_fix_fork_child_flag(p); 1064 #endif 1065 #ifdef CONFIG_TRACE_IRQFLAGS 1066 p->irq_events = 0; 1067 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1068 p->hardirqs_enabled = 1; 1069 #else 1070 p->hardirqs_enabled = 0; 1071 #endif 1072 p->hardirq_enable_ip = 0; 1073 p->hardirq_enable_event = 0; 1074 p->hardirq_disable_ip = _THIS_IP_; 1075 p->hardirq_disable_event = 0; 1076 p->softirqs_enabled = 1; 1077 p->softirq_enable_ip = _THIS_IP_; 1078 p->softirq_enable_event = 0; 1079 p->softirq_disable_ip = 0; 1080 p->softirq_disable_event = 0; 1081 p->hardirq_context = 0; 1082 p->softirq_context = 0; 1083 #endif 1084 #ifdef CONFIG_LOCKDEP 1085 p->lockdep_depth = 0; /* no locks held yet */ 1086 p->curr_chain_key = 0; 1087 p->lockdep_recursion = 0; 1088 #endif 1089 1090 #ifdef CONFIG_DEBUG_MUTEXES 1091 p->blocked_on = NULL; /* not blocked yet */ 1092 #endif 1093 1094 p->bts = NULL; 1095 1096 /* Perform scheduler related setup. Assign this task to a CPU. */ 1097 sched_fork(p, clone_flags); 1098 1099 retval = perf_counter_init_task(p); 1100 if (retval) 1101 goto bad_fork_cleanup_policy; 1102 1103 if ((retval = audit_alloc(p))) 1104 goto bad_fork_cleanup_policy; 1105 /* copy all the process information */ 1106 if ((retval = copy_semundo(clone_flags, p))) 1107 goto bad_fork_cleanup_audit; 1108 if ((retval = copy_files(clone_flags, p))) 1109 goto bad_fork_cleanup_semundo; 1110 if ((retval = copy_fs(clone_flags, p))) 1111 goto bad_fork_cleanup_files; 1112 if ((retval = copy_sighand(clone_flags, p))) 1113 goto bad_fork_cleanup_fs; 1114 if ((retval = copy_signal(clone_flags, p))) 1115 goto bad_fork_cleanup_sighand; 1116 if ((retval = copy_mm(clone_flags, p))) 1117 goto bad_fork_cleanup_signal; 1118 if ((retval = copy_namespaces(clone_flags, p))) 1119 goto bad_fork_cleanup_mm; 1120 if ((retval = copy_io(clone_flags, p))) 1121 goto bad_fork_cleanup_namespaces; 1122 retval = copy_thread(clone_flags, stack_start, stack_size, p, regs); 1123 if (retval) 1124 goto bad_fork_cleanup_io; 1125 1126 if (pid != &init_struct_pid) { 1127 retval = -ENOMEM; 1128 pid = alloc_pid(p->nsproxy->pid_ns); 1129 if (!pid) 1130 goto bad_fork_cleanup_io; 1131 1132 if (clone_flags & CLONE_NEWPID) { 1133 retval = pid_ns_prepare_proc(p->nsproxy->pid_ns); 1134 if (retval < 0) 1135 goto bad_fork_free_pid; 1136 } 1137 } 1138 1139 p->pid = pid_nr(pid); 1140 p->tgid = p->pid; 1141 if (clone_flags & CLONE_THREAD) 1142 p->tgid = current->tgid; 1143 1144 if (current->nsproxy != p->nsproxy) { 1145 retval = ns_cgroup_clone(p, pid); 1146 if (retval) 1147 goto bad_fork_free_pid; 1148 } 1149 1150 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1151 /* 1152 * Clear TID on mm_release()? 1153 */ 1154 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1155 #ifdef CONFIG_FUTEX 1156 p->robust_list = NULL; 1157 #ifdef CONFIG_COMPAT 1158 p->compat_robust_list = NULL; 1159 #endif 1160 INIT_LIST_HEAD(&p->pi_state_list); 1161 p->pi_state_cache = NULL; 1162 #endif 1163 /* 1164 * sigaltstack should be cleared when sharing the same VM 1165 */ 1166 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1167 p->sas_ss_sp = p->sas_ss_size = 0; 1168 1169 /* 1170 * Syscall tracing should be turned off in the child regardless 1171 * of CLONE_PTRACE. 1172 */ 1173 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1174 #ifdef TIF_SYSCALL_EMU 1175 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1176 #endif 1177 clear_all_latency_tracing(p); 1178 1179 /* ok, now we should be set up.. */ 1180 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1181 p->pdeath_signal = 0; 1182 p->exit_state = 0; 1183 1184 /* 1185 * Ok, make it visible to the rest of the system. 1186 * We dont wake it up yet. 1187 */ 1188 p->group_leader = p; 1189 INIT_LIST_HEAD(&p->thread_group); 1190 1191 /* Now that the task is set up, run cgroup callbacks if 1192 * necessary. We need to run them before the task is visible 1193 * on the tasklist. */ 1194 cgroup_fork_callbacks(p); 1195 cgroup_callbacks_done = 1; 1196 1197 /* Need tasklist lock for parent etc handling! */ 1198 write_lock_irq(&tasklist_lock); 1199 1200 /* 1201 * The task hasn't been attached yet, so its cpus_allowed mask will 1202 * not be changed, nor will its assigned CPU. 1203 * 1204 * The cpus_allowed mask of the parent may have changed after it was 1205 * copied first time - so re-copy it here, then check the child's CPU 1206 * to ensure it is on a valid CPU (and if not, just force it back to 1207 * parent's CPU). This avoids alot of nasty races. 1208 */ 1209 p->cpus_allowed = current->cpus_allowed; 1210 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1211 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1212 !cpu_online(task_cpu(p)))) 1213 set_task_cpu(p, smp_processor_id()); 1214 1215 /* CLONE_PARENT re-uses the old parent */ 1216 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) { 1217 p->real_parent = current->real_parent; 1218 p->parent_exec_id = current->parent_exec_id; 1219 } else { 1220 p->real_parent = current; 1221 p->parent_exec_id = current->self_exec_id; 1222 } 1223 1224 spin_lock(¤t->sighand->siglock); 1225 1226 /* 1227 * Process group and session signals need to be delivered to just the 1228 * parent before the fork or both the parent and the child after the 1229 * fork. Restart if a signal comes in before we add the new process to 1230 * it's process group. 1231 * A fatal signal pending means that current will exit, so the new 1232 * thread can't slip out of an OOM kill (or normal SIGKILL). 1233 */ 1234 recalc_sigpending(); 1235 if (signal_pending(current)) { 1236 spin_unlock(¤t->sighand->siglock); 1237 write_unlock_irq(&tasklist_lock); 1238 retval = -ERESTARTNOINTR; 1239 goto bad_fork_free_pid; 1240 } 1241 1242 if (clone_flags & CLONE_THREAD) { 1243 p->group_leader = current->group_leader; 1244 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1245 } 1246 1247 if (likely(p->pid)) { 1248 list_add_tail(&p->sibling, &p->real_parent->children); 1249 tracehook_finish_clone(p, clone_flags, trace); 1250 1251 if (thread_group_leader(p)) { 1252 if (clone_flags & CLONE_NEWPID) 1253 p->nsproxy->pid_ns->child_reaper = p; 1254 1255 p->signal->leader_pid = pid; 1256 tty_kref_put(p->signal->tty); 1257 p->signal->tty = tty_kref_get(current->signal->tty); 1258 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1259 attach_pid(p, PIDTYPE_SID, task_session(current)); 1260 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1261 __get_cpu_var(process_counts)++; 1262 } 1263 attach_pid(p, PIDTYPE_PID, pid); 1264 nr_threads++; 1265 } 1266 1267 total_forks++; 1268 spin_unlock(¤t->sighand->siglock); 1269 write_unlock_irq(&tasklist_lock); 1270 proc_fork_connector(p); 1271 cgroup_post_fork(p); 1272 perf_counter_fork(p); 1273 return p; 1274 1275 bad_fork_free_pid: 1276 if (pid != &init_struct_pid) 1277 free_pid(pid); 1278 bad_fork_cleanup_io: 1279 put_io_context(p->io_context); 1280 bad_fork_cleanup_namespaces: 1281 exit_task_namespaces(p); 1282 bad_fork_cleanup_mm: 1283 if (p->mm) 1284 mmput(p->mm); 1285 bad_fork_cleanup_signal: 1286 cleanup_signal(p); 1287 bad_fork_cleanup_sighand: 1288 __cleanup_sighand(p->sighand); 1289 bad_fork_cleanup_fs: 1290 exit_fs(p); /* blocking */ 1291 bad_fork_cleanup_files: 1292 exit_files(p); /* blocking */ 1293 bad_fork_cleanup_semundo: 1294 exit_sem(p); 1295 bad_fork_cleanup_audit: 1296 audit_free(p); 1297 bad_fork_cleanup_policy: 1298 perf_counter_free_task(p); 1299 #ifdef CONFIG_NUMA 1300 mpol_put(p->mempolicy); 1301 bad_fork_cleanup_cgroup: 1302 #endif 1303 cgroup_exit(p, cgroup_callbacks_done); 1304 delayacct_tsk_free(p); 1305 if (p->binfmt) 1306 module_put(p->binfmt->module); 1307 bad_fork_cleanup_put_domain: 1308 module_put(task_thread_info(p)->exec_domain->module); 1309 bad_fork_cleanup_count: 1310 atomic_dec(&p->cred->user->processes); 1311 put_cred(p->real_cred); 1312 put_cred(p->cred); 1313 bad_fork_free: 1314 free_task(p); 1315 fork_out: 1316 return ERR_PTR(retval); 1317 } 1318 1319 noinline struct pt_regs * __cpuinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1320 { 1321 memset(regs, 0, sizeof(struct pt_regs)); 1322 return regs; 1323 } 1324 1325 struct task_struct * __cpuinit fork_idle(int cpu) 1326 { 1327 struct task_struct *task; 1328 struct pt_regs regs; 1329 1330 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1331 &init_struct_pid, 0); 1332 if (!IS_ERR(task)) 1333 init_idle(task, cpu); 1334 1335 return task; 1336 } 1337 1338 /* 1339 * Ok, this is the main fork-routine. 1340 * 1341 * It copies the process, and if successful kick-starts 1342 * it and waits for it to finish using the VM if required. 1343 */ 1344 long do_fork(unsigned long clone_flags, 1345 unsigned long stack_start, 1346 struct pt_regs *regs, 1347 unsigned long stack_size, 1348 int __user *parent_tidptr, 1349 int __user *child_tidptr) 1350 { 1351 struct task_struct *p; 1352 int trace = 0; 1353 long nr; 1354 1355 /* 1356 * Do some preliminary argument and permissions checking before we 1357 * actually start allocating stuff 1358 */ 1359 if (clone_flags & CLONE_NEWUSER) { 1360 if (clone_flags & CLONE_THREAD) 1361 return -EINVAL; 1362 /* hopefully this check will go away when userns support is 1363 * complete 1364 */ 1365 if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SETUID) || 1366 !capable(CAP_SETGID)) 1367 return -EPERM; 1368 } 1369 1370 /* 1371 * We hope to recycle these flags after 2.6.26 1372 */ 1373 if (unlikely(clone_flags & CLONE_STOPPED)) { 1374 static int __read_mostly count = 100; 1375 1376 if (count > 0 && printk_ratelimit()) { 1377 char comm[TASK_COMM_LEN]; 1378 1379 count--; 1380 printk(KERN_INFO "fork(): process `%s' used deprecated " 1381 "clone flags 0x%lx\n", 1382 get_task_comm(comm, current), 1383 clone_flags & CLONE_STOPPED); 1384 } 1385 } 1386 1387 /* 1388 * When called from kernel_thread, don't do user tracing stuff. 1389 */ 1390 if (likely(user_mode(regs))) 1391 trace = tracehook_prepare_clone(clone_flags); 1392 1393 p = copy_process(clone_flags, stack_start, regs, stack_size, 1394 child_tidptr, NULL, trace); 1395 /* 1396 * Do this prior waking up the new thread - the thread pointer 1397 * might get invalid after that point, if the thread exits quickly. 1398 */ 1399 if (!IS_ERR(p)) { 1400 struct completion vfork; 1401 1402 trace_sched_process_fork(current, p); 1403 1404 nr = task_pid_vnr(p); 1405 1406 if (clone_flags & CLONE_PARENT_SETTID) 1407 put_user(nr, parent_tidptr); 1408 1409 if (clone_flags & CLONE_VFORK) { 1410 p->vfork_done = &vfork; 1411 init_completion(&vfork); 1412 } 1413 1414 audit_finish_fork(p); 1415 tracehook_report_clone(regs, clone_flags, nr, p); 1416 1417 /* 1418 * We set PF_STARTING at creation in case tracing wants to 1419 * use this to distinguish a fully live task from one that 1420 * hasn't gotten to tracehook_report_clone() yet. Now we 1421 * clear it and set the child going. 1422 */ 1423 p->flags &= ~PF_STARTING; 1424 1425 if (unlikely(clone_flags & CLONE_STOPPED)) { 1426 /* 1427 * We'll start up with an immediate SIGSTOP. 1428 */ 1429 sigaddset(&p->pending.signal, SIGSTOP); 1430 set_tsk_thread_flag(p, TIF_SIGPENDING); 1431 __set_task_state(p, TASK_STOPPED); 1432 } else { 1433 wake_up_new_task(p, clone_flags); 1434 } 1435 1436 tracehook_report_clone_complete(trace, regs, 1437 clone_flags, nr, p); 1438 1439 if (clone_flags & CLONE_VFORK) { 1440 freezer_do_not_count(); 1441 wait_for_completion(&vfork); 1442 freezer_count(); 1443 tracehook_report_vfork_done(p, nr); 1444 } 1445 } else { 1446 nr = PTR_ERR(p); 1447 } 1448 return nr; 1449 } 1450 1451 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1452 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1453 #endif 1454 1455 static void sighand_ctor(void *data) 1456 { 1457 struct sighand_struct *sighand = data; 1458 1459 spin_lock_init(&sighand->siglock); 1460 init_waitqueue_head(&sighand->signalfd_wqh); 1461 } 1462 1463 void __init proc_caches_init(void) 1464 { 1465 sighand_cachep = kmem_cache_create("sighand_cache", 1466 sizeof(struct sighand_struct), 0, 1467 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU| 1468 SLAB_NOTRACK, sighand_ctor); 1469 signal_cachep = kmem_cache_create("signal_cache", 1470 sizeof(struct signal_struct), 0, 1471 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1472 files_cachep = kmem_cache_create("files_cache", 1473 sizeof(struct files_struct), 0, 1474 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1475 fs_cachep = kmem_cache_create("fs_cache", 1476 sizeof(struct fs_struct), 0, 1477 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1478 mm_cachep = kmem_cache_create("mm_struct", 1479 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1480 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL); 1481 vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC); 1482 mmap_init(); 1483 } 1484 1485 /* 1486 * Check constraints on flags passed to the unshare system call and 1487 * force unsharing of additional process context as appropriate. 1488 */ 1489 static void check_unshare_flags(unsigned long *flags_ptr) 1490 { 1491 /* 1492 * If unsharing a thread from a thread group, must also 1493 * unshare vm. 1494 */ 1495 if (*flags_ptr & CLONE_THREAD) 1496 *flags_ptr |= CLONE_VM; 1497 1498 /* 1499 * If unsharing vm, must also unshare signal handlers. 1500 */ 1501 if (*flags_ptr & CLONE_VM) 1502 *flags_ptr |= CLONE_SIGHAND; 1503 1504 /* 1505 * If unsharing signal handlers and the task was created 1506 * using CLONE_THREAD, then must unshare the thread 1507 */ 1508 if ((*flags_ptr & CLONE_SIGHAND) && 1509 (atomic_read(¤t->signal->count) > 1)) 1510 *flags_ptr |= CLONE_THREAD; 1511 1512 /* 1513 * If unsharing namespace, must also unshare filesystem information. 1514 */ 1515 if (*flags_ptr & CLONE_NEWNS) 1516 *flags_ptr |= CLONE_FS; 1517 } 1518 1519 /* 1520 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1521 */ 1522 static int unshare_thread(unsigned long unshare_flags) 1523 { 1524 if (unshare_flags & CLONE_THREAD) 1525 return -EINVAL; 1526 1527 return 0; 1528 } 1529 1530 /* 1531 * Unshare the filesystem structure if it is being shared 1532 */ 1533 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1534 { 1535 struct fs_struct *fs = current->fs; 1536 1537 if (!(unshare_flags & CLONE_FS) || !fs) 1538 return 0; 1539 1540 /* don't need lock here; in the worst case we'll do useless copy */ 1541 if (fs->users == 1) 1542 return 0; 1543 1544 *new_fsp = copy_fs_struct(fs); 1545 if (!*new_fsp) 1546 return -ENOMEM; 1547 1548 return 0; 1549 } 1550 1551 /* 1552 * Unsharing of sighand is not supported yet 1553 */ 1554 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1555 { 1556 struct sighand_struct *sigh = current->sighand; 1557 1558 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1559 return -EINVAL; 1560 else 1561 return 0; 1562 } 1563 1564 /* 1565 * Unshare vm if it is being shared 1566 */ 1567 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1568 { 1569 struct mm_struct *mm = current->mm; 1570 1571 if ((unshare_flags & CLONE_VM) && 1572 (mm && atomic_read(&mm->mm_users) > 1)) { 1573 return -EINVAL; 1574 } 1575 1576 return 0; 1577 } 1578 1579 /* 1580 * Unshare file descriptor table if it is being shared 1581 */ 1582 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1583 { 1584 struct files_struct *fd = current->files; 1585 int error = 0; 1586 1587 if ((unshare_flags & CLONE_FILES) && 1588 (fd && atomic_read(&fd->count) > 1)) { 1589 *new_fdp = dup_fd(fd, &error); 1590 if (!*new_fdp) 1591 return error; 1592 } 1593 1594 return 0; 1595 } 1596 1597 /* 1598 * unshare allows a process to 'unshare' part of the process 1599 * context which was originally shared using clone. copy_* 1600 * functions used by do_fork() cannot be used here directly 1601 * because they modify an inactive task_struct that is being 1602 * constructed. Here we are modifying the current, active, 1603 * task_struct. 1604 */ 1605 SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) 1606 { 1607 int err = 0; 1608 struct fs_struct *fs, *new_fs = NULL; 1609 struct sighand_struct *new_sigh = NULL; 1610 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1611 struct files_struct *fd, *new_fd = NULL; 1612 struct nsproxy *new_nsproxy = NULL; 1613 int do_sysvsem = 0; 1614 1615 check_unshare_flags(&unshare_flags); 1616 1617 /* Return -EINVAL for all unsupported flags */ 1618 err = -EINVAL; 1619 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1620 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1621 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWNET)) 1622 goto bad_unshare_out; 1623 1624 /* 1625 * CLONE_NEWIPC must also detach from the undolist: after switching 1626 * to a new ipc namespace, the semaphore arrays from the old 1627 * namespace are unreachable. 1628 */ 1629 if (unshare_flags & (CLONE_NEWIPC|CLONE_SYSVSEM)) 1630 do_sysvsem = 1; 1631 if ((err = unshare_thread(unshare_flags))) 1632 goto bad_unshare_out; 1633 if ((err = unshare_fs(unshare_flags, &new_fs))) 1634 goto bad_unshare_cleanup_thread; 1635 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1636 goto bad_unshare_cleanup_fs; 1637 if ((err = unshare_vm(unshare_flags, &new_mm))) 1638 goto bad_unshare_cleanup_sigh; 1639 if ((err = unshare_fd(unshare_flags, &new_fd))) 1640 goto bad_unshare_cleanup_vm; 1641 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1642 new_fs))) 1643 goto bad_unshare_cleanup_fd; 1644 1645 if (new_fs || new_mm || new_fd || do_sysvsem || new_nsproxy) { 1646 if (do_sysvsem) { 1647 /* 1648 * CLONE_SYSVSEM is equivalent to sys_exit(). 1649 */ 1650 exit_sem(current); 1651 } 1652 1653 if (new_nsproxy) { 1654 switch_task_namespaces(current, new_nsproxy); 1655 new_nsproxy = NULL; 1656 } 1657 1658 task_lock(current); 1659 1660 if (new_fs) { 1661 fs = current->fs; 1662 write_lock(&fs->lock); 1663 current->fs = new_fs; 1664 if (--fs->users) 1665 new_fs = NULL; 1666 else 1667 new_fs = fs; 1668 write_unlock(&fs->lock); 1669 } 1670 1671 if (new_mm) { 1672 mm = current->mm; 1673 active_mm = current->active_mm; 1674 current->mm = new_mm; 1675 current->active_mm = new_mm; 1676 activate_mm(active_mm, new_mm); 1677 new_mm = mm; 1678 } 1679 1680 if (new_fd) { 1681 fd = current->files; 1682 current->files = new_fd; 1683 new_fd = fd; 1684 } 1685 1686 task_unlock(current); 1687 } 1688 1689 if (new_nsproxy) 1690 put_nsproxy(new_nsproxy); 1691 1692 bad_unshare_cleanup_fd: 1693 if (new_fd) 1694 put_files_struct(new_fd); 1695 1696 bad_unshare_cleanup_vm: 1697 if (new_mm) 1698 mmput(new_mm); 1699 1700 bad_unshare_cleanup_sigh: 1701 if (new_sigh) 1702 if (atomic_dec_and_test(&new_sigh->count)) 1703 kmem_cache_free(sighand_cachep, new_sigh); 1704 1705 bad_unshare_cleanup_fs: 1706 if (new_fs) 1707 free_fs_struct(new_fs); 1708 1709 bad_unshare_cleanup_thread: 1710 bad_unshare_out: 1711 return err; 1712 } 1713 1714 /* 1715 * Helper to unshare the files of the current task. 1716 * We don't want to expose copy_files internals to 1717 * the exec layer of the kernel. 1718 */ 1719 1720 int unshare_files(struct files_struct **displaced) 1721 { 1722 struct task_struct *task = current; 1723 struct files_struct *copy = NULL; 1724 int error; 1725 1726 error = unshare_fd(CLONE_FILES, ©); 1727 if (error || !copy) { 1728 *displaced = NULL; 1729 return error; 1730 } 1731 *displaced = task->files; 1732 task_lock(task); 1733 task->files = copy; 1734 task_unlock(task); 1735 return 0; 1736 } 1737