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/key.h> 26 #include <linux/binfmts.h> 27 #include <linux/mman.h> 28 #include <linux/fs.h> 29 #include <linux/nsproxy.h> 30 #include <linux/capability.h> 31 #include <linux/cpu.h> 32 #include <linux/cgroup.h> 33 #include <linux/security.h> 34 #include <linux/swap.h> 35 #include <linux/syscalls.h> 36 #include <linux/jiffies.h> 37 #include <linux/futex.h> 38 #include <linux/task_io_accounting_ops.h> 39 #include <linux/rcupdate.h> 40 #include <linux/ptrace.h> 41 #include <linux/mount.h> 42 #include <linux/audit.h> 43 #include <linux/profile.h> 44 #include <linux/rmap.h> 45 #include <linux/acct.h> 46 #include <linux/tsacct_kern.h> 47 #include <linux/cn_proc.h> 48 #include <linux/freezer.h> 49 #include <linux/delayacct.h> 50 #include <linux/taskstats_kern.h> 51 #include <linux/random.h> 52 #include <linux/tty.h> 53 #include <linux/proc_fs.h> 54 55 #include <asm/pgtable.h> 56 #include <asm/pgalloc.h> 57 #include <asm/uaccess.h> 58 #include <asm/mmu_context.h> 59 #include <asm/cacheflush.h> 60 #include <asm/tlbflush.h> 61 62 /* 63 * Protected counters by write_lock_irq(&tasklist_lock) 64 */ 65 unsigned long total_forks; /* Handle normal Linux uptimes. */ 66 int nr_threads; /* The idle threads do not count.. */ 67 68 int max_threads; /* tunable limit on nr_threads */ 69 70 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 71 72 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 73 74 int nr_processes(void) 75 { 76 int cpu; 77 int total = 0; 78 79 for_each_online_cpu(cpu) 80 total += per_cpu(process_counts, cpu); 81 82 return total; 83 } 84 85 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 86 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 87 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 88 static struct kmem_cache *task_struct_cachep; 89 #endif 90 91 /* SLAB cache for signal_struct structures (tsk->signal) */ 92 static struct kmem_cache *signal_cachep; 93 94 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 95 struct kmem_cache *sighand_cachep; 96 97 /* SLAB cache for files_struct structures (tsk->files) */ 98 struct kmem_cache *files_cachep; 99 100 /* SLAB cache for fs_struct structures (tsk->fs) */ 101 struct kmem_cache *fs_cachep; 102 103 /* SLAB cache for vm_area_struct structures */ 104 struct kmem_cache *vm_area_cachep; 105 106 /* SLAB cache for mm_struct structures (tsk->mm) */ 107 static struct kmem_cache *mm_cachep; 108 109 void free_task(struct task_struct *tsk) 110 { 111 prop_local_destroy_single(&tsk->dirties); 112 free_thread_info(tsk->stack); 113 rt_mutex_debug_task_free(tsk); 114 free_task_struct(tsk); 115 } 116 EXPORT_SYMBOL(free_task); 117 118 void __put_task_struct(struct task_struct *tsk) 119 { 120 WARN_ON(!tsk->exit_state); 121 WARN_ON(atomic_read(&tsk->usage)); 122 WARN_ON(tsk == current); 123 124 security_task_free(tsk); 125 free_uid(tsk->user); 126 put_group_info(tsk->group_info); 127 delayacct_tsk_free(tsk); 128 129 if (!profile_handoff_task(tsk)) 130 free_task(tsk); 131 } 132 133 void __init fork_init(unsigned long mempages) 134 { 135 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 136 #ifndef ARCH_MIN_TASKALIGN 137 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 138 #endif 139 /* create a slab on which task_structs can be allocated */ 140 task_struct_cachep = 141 kmem_cache_create("task_struct", sizeof(struct task_struct), 142 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL); 143 #endif 144 145 /* 146 * The default maximum number of threads is set to a safe 147 * value: the thread structures can take up at most half 148 * of memory. 149 */ 150 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 151 152 /* 153 * we need to allow at least 20 threads to boot a system 154 */ 155 if(max_threads < 20) 156 max_threads = 20; 157 158 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 159 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 160 init_task.signal->rlim[RLIMIT_SIGPENDING] = 161 init_task.signal->rlim[RLIMIT_NPROC]; 162 } 163 164 static struct task_struct *dup_task_struct(struct task_struct *orig) 165 { 166 struct task_struct *tsk; 167 struct thread_info *ti; 168 int err; 169 170 prepare_to_copy(orig); 171 172 tsk = alloc_task_struct(); 173 if (!tsk) 174 return NULL; 175 176 ti = alloc_thread_info(tsk); 177 if (!ti) { 178 free_task_struct(tsk); 179 return NULL; 180 } 181 182 *tsk = *orig; 183 tsk->stack = ti; 184 185 err = prop_local_init_single(&tsk->dirties); 186 if (err) { 187 free_thread_info(ti); 188 free_task_struct(tsk); 189 return NULL; 190 } 191 192 setup_thread_stack(tsk, orig); 193 194 #ifdef CONFIG_CC_STACKPROTECTOR 195 tsk->stack_canary = get_random_int(); 196 #endif 197 198 /* One for us, one for whoever does the "release_task()" (usually parent) */ 199 atomic_set(&tsk->usage,2); 200 atomic_set(&tsk->fs_excl, 0); 201 #ifdef CONFIG_BLK_DEV_IO_TRACE 202 tsk->btrace_seq = 0; 203 #endif 204 tsk->splice_pipe = NULL; 205 return tsk; 206 } 207 208 #ifdef CONFIG_MMU 209 static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 210 { 211 struct vm_area_struct *mpnt, *tmp, **pprev; 212 struct rb_node **rb_link, *rb_parent; 213 int retval; 214 unsigned long charge; 215 struct mempolicy *pol; 216 217 down_write(&oldmm->mmap_sem); 218 flush_cache_dup_mm(oldmm); 219 /* 220 * Not linked in yet - no deadlock potential: 221 */ 222 down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING); 223 224 mm->locked_vm = 0; 225 mm->mmap = NULL; 226 mm->mmap_cache = NULL; 227 mm->free_area_cache = oldmm->mmap_base; 228 mm->cached_hole_size = ~0UL; 229 mm->map_count = 0; 230 cpus_clear(mm->cpu_vm_mask); 231 mm->mm_rb = RB_ROOT; 232 rb_link = &mm->mm_rb.rb_node; 233 rb_parent = NULL; 234 pprev = &mm->mmap; 235 236 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 237 struct file *file; 238 239 if (mpnt->vm_flags & VM_DONTCOPY) { 240 long pages = vma_pages(mpnt); 241 mm->total_vm -= pages; 242 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 243 -pages); 244 continue; 245 } 246 charge = 0; 247 if (mpnt->vm_flags & VM_ACCOUNT) { 248 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 249 if (security_vm_enough_memory(len)) 250 goto fail_nomem; 251 charge = len; 252 } 253 tmp = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 254 if (!tmp) 255 goto fail_nomem; 256 *tmp = *mpnt; 257 pol = mpol_copy(vma_policy(mpnt)); 258 retval = PTR_ERR(pol); 259 if (IS_ERR(pol)) 260 goto fail_nomem_policy; 261 vma_set_policy(tmp, pol); 262 tmp->vm_flags &= ~VM_LOCKED; 263 tmp->vm_mm = mm; 264 tmp->vm_next = NULL; 265 anon_vma_link(tmp); 266 file = tmp->vm_file; 267 if (file) { 268 struct inode *inode = file->f_path.dentry->d_inode; 269 get_file(file); 270 if (tmp->vm_flags & VM_DENYWRITE) 271 atomic_dec(&inode->i_writecount); 272 273 /* insert tmp into the share list, just after mpnt */ 274 spin_lock(&file->f_mapping->i_mmap_lock); 275 tmp->vm_truncate_count = mpnt->vm_truncate_count; 276 flush_dcache_mmap_lock(file->f_mapping); 277 vma_prio_tree_add(tmp, mpnt); 278 flush_dcache_mmap_unlock(file->f_mapping); 279 spin_unlock(&file->f_mapping->i_mmap_lock); 280 } 281 282 /* 283 * Link in the new vma and copy the page table entries. 284 */ 285 *pprev = tmp; 286 pprev = &tmp->vm_next; 287 288 __vma_link_rb(mm, tmp, rb_link, rb_parent); 289 rb_link = &tmp->vm_rb.rb_right; 290 rb_parent = &tmp->vm_rb; 291 292 mm->map_count++; 293 retval = copy_page_range(mm, oldmm, mpnt); 294 295 if (tmp->vm_ops && tmp->vm_ops->open) 296 tmp->vm_ops->open(tmp); 297 298 if (retval) 299 goto out; 300 } 301 /* a new mm has just been created */ 302 arch_dup_mmap(oldmm, mm); 303 retval = 0; 304 out: 305 up_write(&mm->mmap_sem); 306 flush_tlb_mm(oldmm); 307 up_write(&oldmm->mmap_sem); 308 return retval; 309 fail_nomem_policy: 310 kmem_cache_free(vm_area_cachep, tmp); 311 fail_nomem: 312 retval = -ENOMEM; 313 vm_unacct_memory(charge); 314 goto out; 315 } 316 317 static inline int mm_alloc_pgd(struct mm_struct * mm) 318 { 319 mm->pgd = pgd_alloc(mm); 320 if (unlikely(!mm->pgd)) 321 return -ENOMEM; 322 return 0; 323 } 324 325 static inline void mm_free_pgd(struct mm_struct * mm) 326 { 327 pgd_free(mm->pgd); 328 } 329 #else 330 #define dup_mmap(mm, oldmm) (0) 331 #define mm_alloc_pgd(mm) (0) 332 #define mm_free_pgd(mm) 333 #endif /* CONFIG_MMU */ 334 335 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 336 337 #define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL)) 338 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 339 340 #include <linux/init_task.h> 341 342 static struct mm_struct * mm_init(struct mm_struct * mm) 343 { 344 atomic_set(&mm->mm_users, 1); 345 atomic_set(&mm->mm_count, 1); 346 init_rwsem(&mm->mmap_sem); 347 INIT_LIST_HEAD(&mm->mmlist); 348 mm->flags = (current->mm) ? current->mm->flags 349 : MMF_DUMP_FILTER_DEFAULT; 350 mm->core_waiters = 0; 351 mm->nr_ptes = 0; 352 set_mm_counter(mm, file_rss, 0); 353 set_mm_counter(mm, anon_rss, 0); 354 spin_lock_init(&mm->page_table_lock); 355 rwlock_init(&mm->ioctx_list_lock); 356 mm->ioctx_list = NULL; 357 mm->free_area_cache = TASK_UNMAPPED_BASE; 358 mm->cached_hole_size = ~0UL; 359 360 if (likely(!mm_alloc_pgd(mm))) { 361 mm->def_flags = 0; 362 return mm; 363 } 364 free_mm(mm); 365 return NULL; 366 } 367 368 /* 369 * Allocate and initialize an mm_struct. 370 */ 371 struct mm_struct * mm_alloc(void) 372 { 373 struct mm_struct * mm; 374 375 mm = allocate_mm(); 376 if (mm) { 377 memset(mm, 0, sizeof(*mm)); 378 mm = mm_init(mm); 379 } 380 return mm; 381 } 382 383 /* 384 * Called when the last reference to the mm 385 * is dropped: either by a lazy thread or by 386 * mmput. Free the page directory and the mm. 387 */ 388 void fastcall __mmdrop(struct mm_struct *mm) 389 { 390 BUG_ON(mm == &init_mm); 391 mm_free_pgd(mm); 392 destroy_context(mm); 393 free_mm(mm); 394 } 395 396 /* 397 * Decrement the use count and release all resources for an mm. 398 */ 399 void mmput(struct mm_struct *mm) 400 { 401 might_sleep(); 402 403 if (atomic_dec_and_test(&mm->mm_users)) { 404 exit_aio(mm); 405 exit_mmap(mm); 406 if (!list_empty(&mm->mmlist)) { 407 spin_lock(&mmlist_lock); 408 list_del(&mm->mmlist); 409 spin_unlock(&mmlist_lock); 410 } 411 put_swap_token(mm); 412 mmdrop(mm); 413 } 414 } 415 EXPORT_SYMBOL_GPL(mmput); 416 417 /** 418 * get_task_mm - acquire a reference to the task's mm 419 * 420 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 421 * this kernel workthread has transiently adopted a user mm with use_mm, 422 * to do its AIO) is not set and if so returns a reference to it, after 423 * bumping up the use count. User must release the mm via mmput() 424 * after use. Typically used by /proc and ptrace. 425 */ 426 struct mm_struct *get_task_mm(struct task_struct *task) 427 { 428 struct mm_struct *mm; 429 430 task_lock(task); 431 mm = task->mm; 432 if (mm) { 433 if (task->flags & PF_BORROWED_MM) 434 mm = NULL; 435 else 436 atomic_inc(&mm->mm_users); 437 } 438 task_unlock(task); 439 return mm; 440 } 441 EXPORT_SYMBOL_GPL(get_task_mm); 442 443 /* Please note the differences between mmput and mm_release. 444 * mmput is called whenever we stop holding onto a mm_struct, 445 * error success whatever. 446 * 447 * mm_release is called after a mm_struct has been removed 448 * from the current process. 449 * 450 * This difference is important for error handling, when we 451 * only half set up a mm_struct for a new process and need to restore 452 * the old one. Because we mmput the new mm_struct before 453 * restoring the old one. . . 454 * Eric Biederman 10 January 1998 455 */ 456 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 457 { 458 struct completion *vfork_done = tsk->vfork_done; 459 460 /* Get rid of any cached register state */ 461 deactivate_mm(tsk, mm); 462 463 /* notify parent sleeping on vfork() */ 464 if (vfork_done) { 465 tsk->vfork_done = NULL; 466 complete(vfork_done); 467 } 468 469 /* 470 * If we're exiting normally, clear a user-space tid field if 471 * requested. We leave this alone when dying by signal, to leave 472 * the value intact in a core dump, and to save the unnecessary 473 * trouble otherwise. Userland only wants this done for a sys_exit. 474 */ 475 if (tsk->clear_child_tid 476 && !(tsk->flags & PF_SIGNALED) 477 && atomic_read(&mm->mm_users) > 1) { 478 u32 __user * tidptr = tsk->clear_child_tid; 479 tsk->clear_child_tid = NULL; 480 481 /* 482 * We don't check the error code - if userspace has 483 * not set up a proper pointer then tough luck. 484 */ 485 put_user(0, tidptr); 486 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 487 } 488 } 489 490 /* 491 * Allocate a new mm structure and copy contents from the 492 * mm structure of the passed in task structure. 493 */ 494 static struct mm_struct *dup_mm(struct task_struct *tsk) 495 { 496 struct mm_struct *mm, *oldmm = current->mm; 497 int err; 498 499 if (!oldmm) 500 return NULL; 501 502 mm = allocate_mm(); 503 if (!mm) 504 goto fail_nomem; 505 506 memcpy(mm, oldmm, sizeof(*mm)); 507 508 /* Initializing for Swap token stuff */ 509 mm->token_priority = 0; 510 mm->last_interval = 0; 511 512 if (!mm_init(mm)) 513 goto fail_nomem; 514 515 if (init_new_context(tsk, mm)) 516 goto fail_nocontext; 517 518 err = dup_mmap(mm, oldmm); 519 if (err) 520 goto free_pt; 521 522 mm->hiwater_rss = get_mm_rss(mm); 523 mm->hiwater_vm = mm->total_vm; 524 525 return mm; 526 527 free_pt: 528 mmput(mm); 529 530 fail_nomem: 531 return NULL; 532 533 fail_nocontext: 534 /* 535 * If init_new_context() failed, we cannot use mmput() to free the mm 536 * because it calls destroy_context() 537 */ 538 mm_free_pgd(mm); 539 free_mm(mm); 540 return NULL; 541 } 542 543 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 544 { 545 struct mm_struct * mm, *oldmm; 546 int retval; 547 548 tsk->min_flt = tsk->maj_flt = 0; 549 tsk->nvcsw = tsk->nivcsw = 0; 550 551 tsk->mm = NULL; 552 tsk->active_mm = NULL; 553 554 /* 555 * Are we cloning a kernel thread? 556 * 557 * We need to steal a active VM for that.. 558 */ 559 oldmm = current->mm; 560 if (!oldmm) 561 return 0; 562 563 if (clone_flags & CLONE_VM) { 564 atomic_inc(&oldmm->mm_users); 565 mm = oldmm; 566 goto good_mm; 567 } 568 569 retval = -ENOMEM; 570 mm = dup_mm(tsk); 571 if (!mm) 572 goto fail_nomem; 573 574 good_mm: 575 /* Initializing for Swap token stuff */ 576 mm->token_priority = 0; 577 mm->last_interval = 0; 578 579 tsk->mm = mm; 580 tsk->active_mm = mm; 581 return 0; 582 583 fail_nomem: 584 return retval; 585 } 586 587 static struct fs_struct *__copy_fs_struct(struct fs_struct *old) 588 { 589 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 590 /* We don't need to lock fs - think why ;-) */ 591 if (fs) { 592 atomic_set(&fs->count, 1); 593 rwlock_init(&fs->lock); 594 fs->umask = old->umask; 595 read_lock(&old->lock); 596 fs->rootmnt = mntget(old->rootmnt); 597 fs->root = dget(old->root); 598 fs->pwdmnt = mntget(old->pwdmnt); 599 fs->pwd = dget(old->pwd); 600 if (old->altroot) { 601 fs->altrootmnt = mntget(old->altrootmnt); 602 fs->altroot = dget(old->altroot); 603 } else { 604 fs->altrootmnt = NULL; 605 fs->altroot = NULL; 606 } 607 read_unlock(&old->lock); 608 } 609 return fs; 610 } 611 612 struct fs_struct *copy_fs_struct(struct fs_struct *old) 613 { 614 return __copy_fs_struct(old); 615 } 616 617 EXPORT_SYMBOL_GPL(copy_fs_struct); 618 619 static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) 620 { 621 if (clone_flags & CLONE_FS) { 622 atomic_inc(¤t->fs->count); 623 return 0; 624 } 625 tsk->fs = __copy_fs_struct(current->fs); 626 if (!tsk->fs) 627 return -ENOMEM; 628 return 0; 629 } 630 631 static int count_open_files(struct fdtable *fdt) 632 { 633 int size = fdt->max_fds; 634 int i; 635 636 /* Find the last open fd */ 637 for (i = size/(8*sizeof(long)); i > 0; ) { 638 if (fdt->open_fds->fds_bits[--i]) 639 break; 640 } 641 i = (i+1) * 8 * sizeof(long); 642 return i; 643 } 644 645 static struct files_struct *alloc_files(void) 646 { 647 struct files_struct *newf; 648 struct fdtable *fdt; 649 650 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); 651 if (!newf) 652 goto out; 653 654 atomic_set(&newf->count, 1); 655 656 spin_lock_init(&newf->file_lock); 657 newf->next_fd = 0; 658 fdt = &newf->fdtab; 659 fdt->max_fds = NR_OPEN_DEFAULT; 660 fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; 661 fdt->open_fds = (fd_set *)&newf->open_fds_init; 662 fdt->fd = &newf->fd_array[0]; 663 INIT_RCU_HEAD(&fdt->rcu); 664 fdt->next = NULL; 665 rcu_assign_pointer(newf->fdt, fdt); 666 out: 667 return newf; 668 } 669 670 /* 671 * Allocate a new files structure and copy contents from the 672 * passed in files structure. 673 * errorp will be valid only when the returned files_struct is NULL. 674 */ 675 static struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) 676 { 677 struct files_struct *newf; 678 struct file **old_fds, **new_fds; 679 int open_files, size, i; 680 struct fdtable *old_fdt, *new_fdt; 681 682 *errorp = -ENOMEM; 683 newf = alloc_files(); 684 if (!newf) 685 goto out; 686 687 spin_lock(&oldf->file_lock); 688 old_fdt = files_fdtable(oldf); 689 new_fdt = files_fdtable(newf); 690 open_files = count_open_files(old_fdt); 691 692 /* 693 * Check whether we need to allocate a larger fd array and fd set. 694 * Note: we're not a clone task, so the open count won't change. 695 */ 696 if (open_files > new_fdt->max_fds) { 697 new_fdt->max_fds = 0; 698 spin_unlock(&oldf->file_lock); 699 spin_lock(&newf->file_lock); 700 *errorp = expand_files(newf, open_files-1); 701 spin_unlock(&newf->file_lock); 702 if (*errorp < 0) 703 goto out_release; 704 new_fdt = files_fdtable(newf); 705 /* 706 * Reacquire the oldf lock and a pointer to its fd table 707 * who knows it may have a new bigger fd table. We need 708 * the latest pointer. 709 */ 710 spin_lock(&oldf->file_lock); 711 old_fdt = files_fdtable(oldf); 712 } 713 714 old_fds = old_fdt->fd; 715 new_fds = new_fdt->fd; 716 717 memcpy(new_fdt->open_fds->fds_bits, 718 old_fdt->open_fds->fds_bits, open_files/8); 719 memcpy(new_fdt->close_on_exec->fds_bits, 720 old_fdt->close_on_exec->fds_bits, open_files/8); 721 722 for (i = open_files; i != 0; i--) { 723 struct file *f = *old_fds++; 724 if (f) { 725 get_file(f); 726 } else { 727 /* 728 * The fd may be claimed in the fd bitmap but not yet 729 * instantiated in the files array if a sibling thread 730 * is partway through open(). So make sure that this 731 * fd is available to the new process. 732 */ 733 FD_CLR(open_files - i, new_fdt->open_fds); 734 } 735 rcu_assign_pointer(*new_fds++, f); 736 } 737 spin_unlock(&oldf->file_lock); 738 739 /* compute the remainder to be cleared */ 740 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 741 742 /* This is long word aligned thus could use a optimized version */ 743 memset(new_fds, 0, size); 744 745 if (new_fdt->max_fds > open_files) { 746 int left = (new_fdt->max_fds-open_files)/8; 747 int start = open_files / (8 * sizeof(unsigned long)); 748 749 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 750 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 751 } 752 753 return newf; 754 755 out_release: 756 kmem_cache_free(files_cachep, newf); 757 out: 758 return NULL; 759 } 760 761 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 762 { 763 struct files_struct *oldf, *newf; 764 int error = 0; 765 766 /* 767 * A background process may not have any files ... 768 */ 769 oldf = current->files; 770 if (!oldf) 771 goto out; 772 773 if (clone_flags & CLONE_FILES) { 774 atomic_inc(&oldf->count); 775 goto out; 776 } 777 778 /* 779 * Note: we may be using current for both targets (See exec.c) 780 * This works because we cache current->files (old) as oldf. Don't 781 * break this. 782 */ 783 tsk->files = NULL; 784 newf = dup_fd(oldf, &error); 785 if (!newf) 786 goto out; 787 788 tsk->files = newf; 789 error = 0; 790 out: 791 return error; 792 } 793 794 /* 795 * Helper to unshare the files of the current task. 796 * We don't want to expose copy_files internals to 797 * the exec layer of the kernel. 798 */ 799 800 int unshare_files(void) 801 { 802 struct files_struct *files = current->files; 803 int rc; 804 805 BUG_ON(!files); 806 807 /* This can race but the race causes us to copy when we don't 808 need to and drop the copy */ 809 if(atomic_read(&files->count) == 1) 810 { 811 atomic_inc(&files->count); 812 return 0; 813 } 814 rc = copy_files(0, current); 815 if(rc) 816 current->files = files; 817 return rc; 818 } 819 820 EXPORT_SYMBOL(unshare_files); 821 822 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) 823 { 824 struct sighand_struct *sig; 825 826 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 827 atomic_inc(¤t->sighand->count); 828 return 0; 829 } 830 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 831 rcu_assign_pointer(tsk->sighand, sig); 832 if (!sig) 833 return -ENOMEM; 834 atomic_set(&sig->count, 1); 835 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 836 return 0; 837 } 838 839 void __cleanup_sighand(struct sighand_struct *sighand) 840 { 841 if (atomic_dec_and_test(&sighand->count)) 842 kmem_cache_free(sighand_cachep, sighand); 843 } 844 845 static int copy_signal(unsigned long clone_flags, struct task_struct *tsk) 846 { 847 struct signal_struct *sig; 848 int ret; 849 850 if (clone_flags & CLONE_THREAD) { 851 atomic_inc(¤t->signal->count); 852 atomic_inc(¤t->signal->live); 853 return 0; 854 } 855 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 856 tsk->signal = sig; 857 if (!sig) 858 return -ENOMEM; 859 860 ret = copy_thread_group_keys(tsk); 861 if (ret < 0) { 862 kmem_cache_free(signal_cachep, sig); 863 return ret; 864 } 865 866 atomic_set(&sig->count, 1); 867 atomic_set(&sig->live, 1); 868 init_waitqueue_head(&sig->wait_chldexit); 869 sig->flags = 0; 870 sig->group_exit_code = 0; 871 sig->group_exit_task = NULL; 872 sig->group_stop_count = 0; 873 sig->curr_target = NULL; 874 init_sigpending(&sig->shared_pending); 875 INIT_LIST_HEAD(&sig->posix_timers); 876 877 hrtimer_init(&sig->real_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 878 sig->it_real_incr.tv64 = 0; 879 sig->real_timer.function = it_real_fn; 880 sig->tsk = tsk; 881 882 sig->it_virt_expires = cputime_zero; 883 sig->it_virt_incr = cputime_zero; 884 sig->it_prof_expires = cputime_zero; 885 sig->it_prof_incr = cputime_zero; 886 887 sig->leader = 0; /* session leadership doesn't inherit */ 888 sig->tty_old_pgrp = NULL; 889 890 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 891 sig->gtime = cputime_zero; 892 sig->cgtime = cputime_zero; 893 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 894 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 895 sig->inblock = sig->oublock = sig->cinblock = sig->coublock = 0; 896 sig->sum_sched_runtime = 0; 897 INIT_LIST_HEAD(&sig->cpu_timers[0]); 898 INIT_LIST_HEAD(&sig->cpu_timers[1]); 899 INIT_LIST_HEAD(&sig->cpu_timers[2]); 900 taskstats_tgid_init(sig); 901 902 task_lock(current->group_leader); 903 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 904 task_unlock(current->group_leader); 905 906 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 907 /* 908 * New sole thread in the process gets an expiry time 909 * of the whole CPU time limit. 910 */ 911 tsk->it_prof_expires = 912 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 913 } 914 acct_init_pacct(&sig->pacct); 915 916 tty_audit_fork(sig); 917 918 return 0; 919 } 920 921 void __cleanup_signal(struct signal_struct *sig) 922 { 923 exit_thread_group_keys(sig); 924 kmem_cache_free(signal_cachep, sig); 925 } 926 927 static void cleanup_signal(struct task_struct *tsk) 928 { 929 struct signal_struct *sig = tsk->signal; 930 931 atomic_dec(&sig->live); 932 933 if (atomic_dec_and_test(&sig->count)) 934 __cleanup_signal(sig); 935 } 936 937 static void copy_flags(unsigned long clone_flags, struct task_struct *p) 938 { 939 unsigned long new_flags = p->flags; 940 941 new_flags &= ~PF_SUPERPRIV; 942 new_flags |= PF_FORKNOEXEC; 943 if (!(clone_flags & CLONE_PTRACE)) 944 p->ptrace = 0; 945 p->flags = new_flags; 946 clear_freeze_flag(p); 947 } 948 949 asmlinkage long sys_set_tid_address(int __user *tidptr) 950 { 951 current->clear_child_tid = tidptr; 952 953 return task_pid_vnr(current); 954 } 955 956 static void rt_mutex_init_task(struct task_struct *p) 957 { 958 spin_lock_init(&p->pi_lock); 959 #ifdef CONFIG_RT_MUTEXES 960 plist_head_init(&p->pi_waiters, &p->pi_lock); 961 p->pi_blocked_on = NULL; 962 #endif 963 } 964 965 /* 966 * This creates a new process as a copy of the old one, 967 * but does not actually start it yet. 968 * 969 * It copies the registers, and all the appropriate 970 * parts of the process environment (as per the clone 971 * flags). The actual kick-off is left to the caller. 972 */ 973 static struct task_struct *copy_process(unsigned long clone_flags, 974 unsigned long stack_start, 975 struct pt_regs *regs, 976 unsigned long stack_size, 977 int __user *child_tidptr, 978 struct pid *pid) 979 { 980 int retval; 981 struct task_struct *p; 982 int cgroup_callbacks_done = 0; 983 984 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 985 return ERR_PTR(-EINVAL); 986 987 /* 988 * Thread groups must share signals as well, and detached threads 989 * can only be started up within the thread group. 990 */ 991 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 992 return ERR_PTR(-EINVAL); 993 994 /* 995 * Shared signal handlers imply shared VM. By way of the above, 996 * thread groups also imply shared VM. Blocking this case allows 997 * for various simplifications in other code. 998 */ 999 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 1000 return ERR_PTR(-EINVAL); 1001 1002 retval = security_task_create(clone_flags); 1003 if (retval) 1004 goto fork_out; 1005 1006 retval = -ENOMEM; 1007 p = dup_task_struct(current); 1008 if (!p) 1009 goto fork_out; 1010 1011 rt_mutex_init_task(p); 1012 1013 #ifdef CONFIG_TRACE_IRQFLAGS 1014 DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled); 1015 DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled); 1016 #endif 1017 retval = -EAGAIN; 1018 if (atomic_read(&p->user->processes) >= 1019 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 1020 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 1021 p->user != current->nsproxy->user_ns->root_user) 1022 goto bad_fork_free; 1023 } 1024 1025 atomic_inc(&p->user->__count); 1026 atomic_inc(&p->user->processes); 1027 get_group_info(p->group_info); 1028 1029 /* 1030 * If multiple threads are within copy_process(), then this check 1031 * triggers too late. This doesn't hurt, the check is only there 1032 * to stop root fork bombs. 1033 */ 1034 if (nr_threads >= max_threads) 1035 goto bad_fork_cleanup_count; 1036 1037 if (!try_module_get(task_thread_info(p)->exec_domain->module)) 1038 goto bad_fork_cleanup_count; 1039 1040 if (p->binfmt && !try_module_get(p->binfmt->module)) 1041 goto bad_fork_cleanup_put_domain; 1042 1043 p->did_exec = 0; 1044 delayacct_tsk_init(p); /* Must remain after dup_task_struct() */ 1045 copy_flags(clone_flags, p); 1046 INIT_LIST_HEAD(&p->children); 1047 INIT_LIST_HEAD(&p->sibling); 1048 #ifdef CONFIG_PREEMPT_RCU 1049 p->rcu_read_lock_nesting = 0; 1050 p->rcu_flipctr_idx = 0; 1051 #endif /* #ifdef CONFIG_PREEMPT_RCU */ 1052 p->vfork_done = NULL; 1053 spin_lock_init(&p->alloc_lock); 1054 1055 clear_tsk_thread_flag(p, TIF_SIGPENDING); 1056 init_sigpending(&p->pending); 1057 1058 p->utime = cputime_zero; 1059 p->stime = cputime_zero; 1060 p->gtime = cputime_zero; 1061 p->utimescaled = cputime_zero; 1062 p->stimescaled = cputime_zero; 1063 p->prev_utime = cputime_zero; 1064 p->prev_stime = cputime_zero; 1065 1066 #ifdef CONFIG_DETECT_SOFTLOCKUP 1067 p->last_switch_count = 0; 1068 p->last_switch_timestamp = 0; 1069 #endif 1070 1071 #ifdef CONFIG_TASK_XACCT 1072 p->rchar = 0; /* I/O counter: bytes read */ 1073 p->wchar = 0; /* I/O counter: bytes written */ 1074 p->syscr = 0; /* I/O counter: read syscalls */ 1075 p->syscw = 0; /* I/O counter: write syscalls */ 1076 #endif 1077 task_io_accounting_init(p); 1078 acct_clear_integrals(p); 1079 1080 p->it_virt_expires = cputime_zero; 1081 p->it_prof_expires = cputime_zero; 1082 p->it_sched_expires = 0; 1083 INIT_LIST_HEAD(&p->cpu_timers[0]); 1084 INIT_LIST_HEAD(&p->cpu_timers[1]); 1085 INIT_LIST_HEAD(&p->cpu_timers[2]); 1086 1087 p->lock_depth = -1; /* -1 = no lock */ 1088 do_posix_clock_monotonic_gettime(&p->start_time); 1089 p->real_start_time = p->start_time; 1090 monotonic_to_bootbased(&p->real_start_time); 1091 #ifdef CONFIG_SECURITY 1092 p->security = NULL; 1093 #endif 1094 p->io_context = NULL; 1095 p->audit_context = NULL; 1096 cgroup_fork(p); 1097 #ifdef CONFIG_NUMA 1098 p->mempolicy = mpol_copy(p->mempolicy); 1099 if (IS_ERR(p->mempolicy)) { 1100 retval = PTR_ERR(p->mempolicy); 1101 p->mempolicy = NULL; 1102 goto bad_fork_cleanup_cgroup; 1103 } 1104 mpol_fix_fork_child_flag(p); 1105 #endif 1106 #ifdef CONFIG_TRACE_IRQFLAGS 1107 p->irq_events = 0; 1108 #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW 1109 p->hardirqs_enabled = 1; 1110 #else 1111 p->hardirqs_enabled = 0; 1112 #endif 1113 p->hardirq_enable_ip = 0; 1114 p->hardirq_enable_event = 0; 1115 p->hardirq_disable_ip = _THIS_IP_; 1116 p->hardirq_disable_event = 0; 1117 p->softirqs_enabled = 1; 1118 p->softirq_enable_ip = _THIS_IP_; 1119 p->softirq_enable_event = 0; 1120 p->softirq_disable_ip = 0; 1121 p->softirq_disable_event = 0; 1122 p->hardirq_context = 0; 1123 p->softirq_context = 0; 1124 #endif 1125 #ifdef CONFIG_LOCKDEP 1126 p->lockdep_depth = 0; /* no locks held yet */ 1127 p->curr_chain_key = 0; 1128 p->lockdep_recursion = 0; 1129 #endif 1130 1131 #ifdef CONFIG_DEBUG_MUTEXES 1132 p->blocked_on = NULL; /* not blocked yet */ 1133 #endif 1134 1135 /* Perform scheduler related setup. Assign this task to a CPU. */ 1136 sched_fork(p, clone_flags); 1137 1138 if ((retval = security_task_alloc(p))) 1139 goto bad_fork_cleanup_policy; 1140 if ((retval = audit_alloc(p))) 1141 goto bad_fork_cleanup_security; 1142 /* copy all the process information */ 1143 if ((retval = copy_semundo(clone_flags, p))) 1144 goto bad_fork_cleanup_audit; 1145 if ((retval = copy_files(clone_flags, p))) 1146 goto bad_fork_cleanup_semundo; 1147 if ((retval = copy_fs(clone_flags, p))) 1148 goto bad_fork_cleanup_files; 1149 if ((retval = copy_sighand(clone_flags, p))) 1150 goto bad_fork_cleanup_fs; 1151 if ((retval = copy_signal(clone_flags, p))) 1152 goto bad_fork_cleanup_sighand; 1153 if ((retval = copy_mm(clone_flags, p))) 1154 goto bad_fork_cleanup_signal; 1155 if ((retval = copy_keys(clone_flags, p))) 1156 goto bad_fork_cleanup_mm; 1157 if ((retval = copy_namespaces(clone_flags, p))) 1158 goto bad_fork_cleanup_keys; 1159 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1160 if (retval) 1161 goto bad_fork_cleanup_namespaces; 1162 1163 if (pid != &init_struct_pid) { 1164 retval = -ENOMEM; 1165 pid = alloc_pid(task_active_pid_ns(p)); 1166 if (!pid) 1167 goto bad_fork_cleanup_namespaces; 1168 1169 if (clone_flags & CLONE_NEWPID) { 1170 retval = pid_ns_prepare_proc(task_active_pid_ns(p)); 1171 if (retval < 0) 1172 goto bad_fork_free_pid; 1173 } 1174 } 1175 1176 p->pid = pid_nr(pid); 1177 p->tgid = p->pid; 1178 if (clone_flags & CLONE_THREAD) 1179 p->tgid = current->tgid; 1180 1181 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1182 /* 1183 * Clear TID on mm_release()? 1184 */ 1185 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1186 #ifdef CONFIG_FUTEX 1187 p->robust_list = NULL; 1188 #ifdef CONFIG_COMPAT 1189 p->compat_robust_list = NULL; 1190 #endif 1191 INIT_LIST_HEAD(&p->pi_state_list); 1192 p->pi_state_cache = NULL; 1193 #endif 1194 /* 1195 * sigaltstack should be cleared when sharing the same VM 1196 */ 1197 if ((clone_flags & (CLONE_VM|CLONE_VFORK)) == CLONE_VM) 1198 p->sas_ss_sp = p->sas_ss_size = 0; 1199 1200 /* 1201 * Syscall tracing should be turned off in the child regardless 1202 * of CLONE_PTRACE. 1203 */ 1204 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1205 #ifdef TIF_SYSCALL_EMU 1206 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1207 #endif 1208 clear_all_latency_tracing(p); 1209 1210 /* Our parent execution domain becomes current domain 1211 These must match for thread signalling to apply */ 1212 p->parent_exec_id = p->self_exec_id; 1213 1214 /* ok, now we should be set up.. */ 1215 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1216 p->pdeath_signal = 0; 1217 p->exit_state = 0; 1218 1219 /* 1220 * Ok, make it visible to the rest of the system. 1221 * We dont wake it up yet. 1222 */ 1223 p->group_leader = p; 1224 INIT_LIST_HEAD(&p->thread_group); 1225 INIT_LIST_HEAD(&p->ptrace_children); 1226 INIT_LIST_HEAD(&p->ptrace_list); 1227 1228 /* Now that the task is set up, run cgroup callbacks if 1229 * necessary. We need to run them before the task is visible 1230 * on the tasklist. */ 1231 cgroup_fork_callbacks(p); 1232 cgroup_callbacks_done = 1; 1233 1234 /* Need tasklist lock for parent etc handling! */ 1235 write_lock_irq(&tasklist_lock); 1236 1237 /* for sys_ioprio_set(IOPRIO_WHO_PGRP) */ 1238 p->ioprio = current->ioprio; 1239 1240 /* 1241 * The task hasn't been attached yet, so its cpus_allowed mask will 1242 * not be changed, nor will its assigned CPU. 1243 * 1244 * The cpus_allowed mask of the parent may have changed after it was 1245 * copied first time - so re-copy it here, then check the child's CPU 1246 * to ensure it is on a valid CPU (and if not, just force it back to 1247 * parent's CPU). This avoids alot of nasty races. 1248 */ 1249 p->cpus_allowed = current->cpus_allowed; 1250 p->rt.nr_cpus_allowed = current->rt.nr_cpus_allowed; 1251 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1252 !cpu_online(task_cpu(p)))) 1253 set_task_cpu(p, smp_processor_id()); 1254 1255 /* CLONE_PARENT re-uses the old parent */ 1256 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1257 p->real_parent = current->real_parent; 1258 else 1259 p->real_parent = current; 1260 p->parent = p->real_parent; 1261 1262 spin_lock(¤t->sighand->siglock); 1263 1264 /* 1265 * Process group and session signals need to be delivered to just the 1266 * parent before the fork or both the parent and the child after the 1267 * fork. Restart if a signal comes in before we add the new process to 1268 * it's process group. 1269 * A fatal signal pending means that current will exit, so the new 1270 * thread can't slip out of an OOM kill (or normal SIGKILL). 1271 */ 1272 recalc_sigpending(); 1273 if (signal_pending(current)) { 1274 spin_unlock(¤t->sighand->siglock); 1275 write_unlock_irq(&tasklist_lock); 1276 retval = -ERESTARTNOINTR; 1277 goto bad_fork_free_pid; 1278 } 1279 1280 if (clone_flags & CLONE_THREAD) { 1281 p->group_leader = current->group_leader; 1282 list_add_tail_rcu(&p->thread_group, &p->group_leader->thread_group); 1283 1284 if (!cputime_eq(current->signal->it_virt_expires, 1285 cputime_zero) || 1286 !cputime_eq(current->signal->it_prof_expires, 1287 cputime_zero) || 1288 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1289 !list_empty(¤t->signal->cpu_timers[0]) || 1290 !list_empty(¤t->signal->cpu_timers[1]) || 1291 !list_empty(¤t->signal->cpu_timers[2])) { 1292 /* 1293 * Have child wake up on its first tick to check 1294 * for process CPU timers. 1295 */ 1296 p->it_prof_expires = jiffies_to_cputime(1); 1297 } 1298 } 1299 1300 if (likely(p->pid)) { 1301 add_parent(p); 1302 if (unlikely(p->ptrace & PT_PTRACED)) 1303 __ptrace_link(p, current->parent); 1304 1305 if (thread_group_leader(p)) { 1306 if (clone_flags & CLONE_NEWPID) 1307 p->nsproxy->pid_ns->child_reaper = p; 1308 1309 p->signal->tty = current->signal->tty; 1310 set_task_pgrp(p, task_pgrp_nr(current)); 1311 set_task_session(p, task_session_nr(current)); 1312 attach_pid(p, PIDTYPE_PGID, task_pgrp(current)); 1313 attach_pid(p, PIDTYPE_SID, task_session(current)); 1314 list_add_tail_rcu(&p->tasks, &init_task.tasks); 1315 __get_cpu_var(process_counts)++; 1316 } 1317 attach_pid(p, PIDTYPE_PID, pid); 1318 nr_threads++; 1319 } 1320 1321 total_forks++; 1322 spin_unlock(¤t->sighand->siglock); 1323 write_unlock_irq(&tasklist_lock); 1324 proc_fork_connector(p); 1325 cgroup_post_fork(p); 1326 return p; 1327 1328 bad_fork_free_pid: 1329 if (pid != &init_struct_pid) 1330 free_pid(pid); 1331 bad_fork_cleanup_namespaces: 1332 exit_task_namespaces(p); 1333 bad_fork_cleanup_keys: 1334 exit_keys(p); 1335 bad_fork_cleanup_mm: 1336 if (p->mm) 1337 mmput(p->mm); 1338 bad_fork_cleanup_signal: 1339 cleanup_signal(p); 1340 bad_fork_cleanup_sighand: 1341 __cleanup_sighand(p->sighand); 1342 bad_fork_cleanup_fs: 1343 exit_fs(p); /* blocking */ 1344 bad_fork_cleanup_files: 1345 exit_files(p); /* blocking */ 1346 bad_fork_cleanup_semundo: 1347 exit_sem(p); 1348 bad_fork_cleanup_audit: 1349 audit_free(p); 1350 bad_fork_cleanup_security: 1351 security_task_free(p); 1352 bad_fork_cleanup_policy: 1353 #ifdef CONFIG_NUMA 1354 mpol_free(p->mempolicy); 1355 bad_fork_cleanup_cgroup: 1356 #endif 1357 cgroup_exit(p, cgroup_callbacks_done); 1358 delayacct_tsk_free(p); 1359 if (p->binfmt) 1360 module_put(p->binfmt->module); 1361 bad_fork_cleanup_put_domain: 1362 module_put(task_thread_info(p)->exec_domain->module); 1363 bad_fork_cleanup_count: 1364 put_group_info(p->group_info); 1365 atomic_dec(&p->user->processes); 1366 free_uid(p->user); 1367 bad_fork_free: 1368 free_task(p); 1369 fork_out: 1370 return ERR_PTR(retval); 1371 } 1372 1373 noinline struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1374 { 1375 memset(regs, 0, sizeof(struct pt_regs)); 1376 return regs; 1377 } 1378 1379 struct task_struct * __cpuinit fork_idle(int cpu) 1380 { 1381 struct task_struct *task; 1382 struct pt_regs regs; 1383 1384 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, 1385 &init_struct_pid); 1386 if (!IS_ERR(task)) 1387 init_idle(task, cpu); 1388 1389 return task; 1390 } 1391 1392 static int fork_traceflag(unsigned clone_flags) 1393 { 1394 if (clone_flags & CLONE_UNTRACED) 1395 return 0; 1396 else if (clone_flags & CLONE_VFORK) { 1397 if (current->ptrace & PT_TRACE_VFORK) 1398 return PTRACE_EVENT_VFORK; 1399 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1400 if (current->ptrace & PT_TRACE_CLONE) 1401 return PTRACE_EVENT_CLONE; 1402 } else if (current->ptrace & PT_TRACE_FORK) 1403 return PTRACE_EVENT_FORK; 1404 1405 return 0; 1406 } 1407 1408 /* 1409 * Ok, this is the main fork-routine. 1410 * 1411 * It copies the process, and if successful kick-starts 1412 * it and waits for it to finish using the VM if required. 1413 */ 1414 long do_fork(unsigned long clone_flags, 1415 unsigned long stack_start, 1416 struct pt_regs *regs, 1417 unsigned long stack_size, 1418 int __user *parent_tidptr, 1419 int __user *child_tidptr) 1420 { 1421 struct task_struct *p; 1422 int trace = 0; 1423 long nr; 1424 1425 if (unlikely(current->ptrace)) { 1426 trace = fork_traceflag (clone_flags); 1427 if (trace) 1428 clone_flags |= CLONE_PTRACE; 1429 } 1430 1431 p = copy_process(clone_flags, stack_start, regs, stack_size, 1432 child_tidptr, NULL); 1433 /* 1434 * Do this prior waking up the new thread - the thread pointer 1435 * might get invalid after that point, if the thread exits quickly. 1436 */ 1437 if (!IS_ERR(p)) { 1438 struct completion vfork; 1439 1440 /* 1441 * this is enough to call pid_nr_ns here, but this if 1442 * improves optimisation of regular fork() 1443 */ 1444 nr = (clone_flags & CLONE_NEWPID) ? 1445 task_pid_nr_ns(p, current->nsproxy->pid_ns) : 1446 task_pid_vnr(p); 1447 1448 if (clone_flags & CLONE_PARENT_SETTID) 1449 put_user(nr, parent_tidptr); 1450 1451 if (clone_flags & CLONE_VFORK) { 1452 p->vfork_done = &vfork; 1453 init_completion(&vfork); 1454 } 1455 1456 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1457 /* 1458 * We'll start up with an immediate SIGSTOP. 1459 */ 1460 sigaddset(&p->pending.signal, SIGSTOP); 1461 set_tsk_thread_flag(p, TIF_SIGPENDING); 1462 } 1463 1464 if (!(clone_flags & CLONE_STOPPED)) 1465 wake_up_new_task(p, clone_flags); 1466 else 1467 p->state = TASK_STOPPED; 1468 1469 if (unlikely (trace)) { 1470 current->ptrace_message = nr; 1471 ptrace_notify ((trace << 8) | SIGTRAP); 1472 } 1473 1474 if (clone_flags & CLONE_VFORK) { 1475 freezer_do_not_count(); 1476 wait_for_completion(&vfork); 1477 freezer_count(); 1478 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) { 1479 current->ptrace_message = nr; 1480 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1481 } 1482 } 1483 } else { 1484 nr = PTR_ERR(p); 1485 } 1486 return nr; 1487 } 1488 1489 #ifndef ARCH_MIN_MMSTRUCT_ALIGN 1490 #define ARCH_MIN_MMSTRUCT_ALIGN 0 1491 #endif 1492 1493 static void sighand_ctor(struct kmem_cache *cachep, void *data) 1494 { 1495 struct sighand_struct *sighand = data; 1496 1497 spin_lock_init(&sighand->siglock); 1498 init_waitqueue_head(&sighand->signalfd_wqh); 1499 } 1500 1501 void __init proc_caches_init(void) 1502 { 1503 sighand_cachep = kmem_cache_create("sighand_cache", 1504 sizeof(struct sighand_struct), 0, 1505 SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_DESTROY_BY_RCU, 1506 sighand_ctor); 1507 signal_cachep = kmem_cache_create("signal_cache", 1508 sizeof(struct signal_struct), 0, 1509 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1510 files_cachep = kmem_cache_create("files_cache", 1511 sizeof(struct files_struct), 0, 1512 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1513 fs_cachep = kmem_cache_create("fs_cache", 1514 sizeof(struct fs_struct), 0, 1515 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1516 vm_area_cachep = kmem_cache_create("vm_area_struct", 1517 sizeof(struct vm_area_struct), 0, 1518 SLAB_PANIC, NULL); 1519 mm_cachep = kmem_cache_create("mm_struct", 1520 sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, 1521 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); 1522 } 1523 1524 /* 1525 * Check constraints on flags passed to the unshare system call and 1526 * force unsharing of additional process context as appropriate. 1527 */ 1528 static void check_unshare_flags(unsigned long *flags_ptr) 1529 { 1530 /* 1531 * If unsharing a thread from a thread group, must also 1532 * unshare vm. 1533 */ 1534 if (*flags_ptr & CLONE_THREAD) 1535 *flags_ptr |= CLONE_VM; 1536 1537 /* 1538 * If unsharing vm, must also unshare signal handlers. 1539 */ 1540 if (*flags_ptr & CLONE_VM) 1541 *flags_ptr |= CLONE_SIGHAND; 1542 1543 /* 1544 * If unsharing signal handlers and the task was created 1545 * using CLONE_THREAD, then must unshare the thread 1546 */ 1547 if ((*flags_ptr & CLONE_SIGHAND) && 1548 (atomic_read(¤t->signal->count) > 1)) 1549 *flags_ptr |= CLONE_THREAD; 1550 1551 /* 1552 * If unsharing namespace, must also unshare filesystem information. 1553 */ 1554 if (*flags_ptr & CLONE_NEWNS) 1555 *flags_ptr |= CLONE_FS; 1556 } 1557 1558 /* 1559 * Unsharing of tasks created with CLONE_THREAD is not supported yet 1560 */ 1561 static int unshare_thread(unsigned long unshare_flags) 1562 { 1563 if (unshare_flags & CLONE_THREAD) 1564 return -EINVAL; 1565 1566 return 0; 1567 } 1568 1569 /* 1570 * Unshare the filesystem structure if it is being shared 1571 */ 1572 static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) 1573 { 1574 struct fs_struct *fs = current->fs; 1575 1576 if ((unshare_flags & CLONE_FS) && 1577 (fs && atomic_read(&fs->count) > 1)) { 1578 *new_fsp = __copy_fs_struct(current->fs); 1579 if (!*new_fsp) 1580 return -ENOMEM; 1581 } 1582 1583 return 0; 1584 } 1585 1586 /* 1587 * Unsharing of sighand is not supported yet 1588 */ 1589 static int unshare_sighand(unsigned long unshare_flags, struct sighand_struct **new_sighp) 1590 { 1591 struct sighand_struct *sigh = current->sighand; 1592 1593 if ((unshare_flags & CLONE_SIGHAND) && atomic_read(&sigh->count) > 1) 1594 return -EINVAL; 1595 else 1596 return 0; 1597 } 1598 1599 /* 1600 * Unshare vm if it is being shared 1601 */ 1602 static int unshare_vm(unsigned long unshare_flags, struct mm_struct **new_mmp) 1603 { 1604 struct mm_struct *mm = current->mm; 1605 1606 if ((unshare_flags & CLONE_VM) && 1607 (mm && atomic_read(&mm->mm_users) > 1)) { 1608 return -EINVAL; 1609 } 1610 1611 return 0; 1612 } 1613 1614 /* 1615 * Unshare file descriptor table if it is being shared 1616 */ 1617 static int unshare_fd(unsigned long unshare_flags, struct files_struct **new_fdp) 1618 { 1619 struct files_struct *fd = current->files; 1620 int error = 0; 1621 1622 if ((unshare_flags & CLONE_FILES) && 1623 (fd && atomic_read(&fd->count) > 1)) { 1624 *new_fdp = dup_fd(fd, &error); 1625 if (!*new_fdp) 1626 return error; 1627 } 1628 1629 return 0; 1630 } 1631 1632 /* 1633 * Unsharing of semundo for tasks created with CLONE_SYSVSEM is not 1634 * supported yet 1635 */ 1636 static int unshare_semundo(unsigned long unshare_flags, struct sem_undo_list **new_ulistp) 1637 { 1638 if (unshare_flags & CLONE_SYSVSEM) 1639 return -EINVAL; 1640 1641 return 0; 1642 } 1643 1644 /* 1645 * unshare allows a process to 'unshare' part of the process 1646 * context which was originally shared using clone. copy_* 1647 * functions used by do_fork() cannot be used here directly 1648 * because they modify an inactive task_struct that is being 1649 * constructed. Here we are modifying the current, active, 1650 * task_struct. 1651 */ 1652 asmlinkage long sys_unshare(unsigned long unshare_flags) 1653 { 1654 int err = 0; 1655 struct fs_struct *fs, *new_fs = NULL; 1656 struct sighand_struct *new_sigh = NULL; 1657 struct mm_struct *mm, *new_mm = NULL, *active_mm = NULL; 1658 struct files_struct *fd, *new_fd = NULL; 1659 struct sem_undo_list *new_ulist = NULL; 1660 struct nsproxy *new_nsproxy = NULL; 1661 1662 check_unshare_flags(&unshare_flags); 1663 1664 /* Return -EINVAL for all unsupported flags */ 1665 err = -EINVAL; 1666 if (unshare_flags & ~(CLONE_THREAD|CLONE_FS|CLONE_NEWNS|CLONE_SIGHAND| 1667 CLONE_VM|CLONE_FILES|CLONE_SYSVSEM| 1668 CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER| 1669 CLONE_NEWNET)) 1670 goto bad_unshare_out; 1671 1672 if ((err = unshare_thread(unshare_flags))) 1673 goto bad_unshare_out; 1674 if ((err = unshare_fs(unshare_flags, &new_fs))) 1675 goto bad_unshare_cleanup_thread; 1676 if ((err = unshare_sighand(unshare_flags, &new_sigh))) 1677 goto bad_unshare_cleanup_fs; 1678 if ((err = unshare_vm(unshare_flags, &new_mm))) 1679 goto bad_unshare_cleanup_sigh; 1680 if ((err = unshare_fd(unshare_flags, &new_fd))) 1681 goto bad_unshare_cleanup_vm; 1682 if ((err = unshare_semundo(unshare_flags, &new_ulist))) 1683 goto bad_unshare_cleanup_fd; 1684 if ((err = unshare_nsproxy_namespaces(unshare_flags, &new_nsproxy, 1685 new_fs))) 1686 goto bad_unshare_cleanup_semundo; 1687 1688 if (new_fs || new_mm || new_fd || new_ulist || new_nsproxy) { 1689 1690 if (new_nsproxy) { 1691 switch_task_namespaces(current, new_nsproxy); 1692 new_nsproxy = NULL; 1693 } 1694 1695 task_lock(current); 1696 1697 if (new_fs) { 1698 fs = current->fs; 1699 current->fs = new_fs; 1700 new_fs = fs; 1701 } 1702 1703 if (new_mm) { 1704 mm = current->mm; 1705 active_mm = current->active_mm; 1706 current->mm = new_mm; 1707 current->active_mm = new_mm; 1708 activate_mm(active_mm, new_mm); 1709 new_mm = mm; 1710 } 1711 1712 if (new_fd) { 1713 fd = current->files; 1714 current->files = new_fd; 1715 new_fd = fd; 1716 } 1717 1718 task_unlock(current); 1719 } 1720 1721 if (new_nsproxy) 1722 put_nsproxy(new_nsproxy); 1723 1724 bad_unshare_cleanup_semundo: 1725 bad_unshare_cleanup_fd: 1726 if (new_fd) 1727 put_files_struct(new_fd); 1728 1729 bad_unshare_cleanup_vm: 1730 if (new_mm) 1731 mmput(new_mm); 1732 1733 bad_unshare_cleanup_sigh: 1734 if (new_sigh) 1735 if (atomic_dec_and_test(&new_sigh->count)) 1736 kmem_cache_free(sighand_cachep, new_sigh); 1737 1738 bad_unshare_cleanup_fs: 1739 if (new_fs) 1740 put_fs_struct(new_fs); 1741 1742 bad_unshare_cleanup_thread: 1743 bad_unshare_out: 1744 return err; 1745 } 1746