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/config.h> 15 #include <linux/slab.h> 16 #include <linux/init.h> 17 #include <linux/unistd.h> 18 #include <linux/smp_lock.h> 19 #include <linux/module.h> 20 #include <linux/vmalloc.h> 21 #include <linux/completion.h> 22 #include <linux/namespace.h> 23 #include <linux/personality.h> 24 #include <linux/mempolicy.h> 25 #include <linux/sem.h> 26 #include <linux/file.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/fs.h> 31 #include <linux/cpu.h> 32 #include <linux/cpuset.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/ptrace.h> 39 #include <linux/mount.h> 40 #include <linux/audit.h> 41 #include <linux/profile.h> 42 #include <linux/rmap.h> 43 #include <linux/acct.h> 44 45 #include <asm/pgtable.h> 46 #include <asm/pgalloc.h> 47 #include <asm/uaccess.h> 48 #include <asm/mmu_context.h> 49 #include <asm/cacheflush.h> 50 #include <asm/tlbflush.h> 51 52 /* 53 * Protected counters by write_lock_irq(&tasklist_lock) 54 */ 55 unsigned long total_forks; /* Handle normal Linux uptimes. */ 56 int nr_threads; /* The idle threads do not count.. */ 57 58 int max_threads; /* tunable limit on nr_threads */ 59 60 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 61 62 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 63 64 EXPORT_SYMBOL(tasklist_lock); 65 66 int nr_processes(void) 67 { 68 int cpu; 69 int total = 0; 70 71 for_each_online_cpu(cpu) 72 total += per_cpu(process_counts, cpu); 73 74 return total; 75 } 76 77 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 78 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 79 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 80 static kmem_cache_t *task_struct_cachep; 81 #endif 82 83 /* SLAB cache for signal_struct structures (tsk->signal) */ 84 kmem_cache_t *signal_cachep; 85 86 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 87 kmem_cache_t *sighand_cachep; 88 89 /* SLAB cache for files_struct structures (tsk->files) */ 90 kmem_cache_t *files_cachep; 91 92 /* SLAB cache for fs_struct structures (tsk->fs) */ 93 kmem_cache_t *fs_cachep; 94 95 /* SLAB cache for vm_area_struct structures */ 96 kmem_cache_t *vm_area_cachep; 97 98 /* SLAB cache for mm_struct structures (tsk->mm) */ 99 static kmem_cache_t *mm_cachep; 100 101 void free_task(struct task_struct *tsk) 102 { 103 free_thread_info(tsk->thread_info); 104 free_task_struct(tsk); 105 } 106 EXPORT_SYMBOL(free_task); 107 108 void __put_task_struct(struct task_struct *tsk) 109 { 110 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 111 WARN_ON(atomic_read(&tsk->usage)); 112 WARN_ON(tsk == current); 113 114 if (unlikely(tsk->audit_context)) 115 audit_free(tsk); 116 security_task_free(tsk); 117 free_uid(tsk->user); 118 put_group_info(tsk->group_info); 119 120 if (!profile_handoff_task(tsk)) 121 free_task(tsk); 122 } 123 124 void __init fork_init(unsigned long mempages) 125 { 126 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 127 #ifndef ARCH_MIN_TASKALIGN 128 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 129 #endif 130 /* create a slab on which task_structs can be allocated */ 131 task_struct_cachep = 132 kmem_cache_create("task_struct", sizeof(struct task_struct), 133 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL); 134 #endif 135 136 /* 137 * The default maximum number of threads is set to a safe 138 * value: the thread structures can take up at most half 139 * of memory. 140 */ 141 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 142 143 /* 144 * we need to allow at least 20 threads to boot a system 145 */ 146 if(max_threads < 20) 147 max_threads = 20; 148 149 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 150 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 151 init_task.signal->rlim[RLIMIT_SIGPENDING] = 152 init_task.signal->rlim[RLIMIT_NPROC]; 153 } 154 155 static struct task_struct *dup_task_struct(struct task_struct *orig) 156 { 157 struct task_struct *tsk; 158 struct thread_info *ti; 159 160 prepare_to_copy(orig); 161 162 tsk = alloc_task_struct(); 163 if (!tsk) 164 return NULL; 165 166 ti = alloc_thread_info(tsk); 167 if (!ti) { 168 free_task_struct(tsk); 169 return NULL; 170 } 171 172 *ti = *orig->thread_info; 173 *tsk = *orig; 174 tsk->thread_info = ti; 175 ti->task = tsk; 176 177 /* One for us, one for whoever does the "release_task()" (usually parent) */ 178 atomic_set(&tsk->usage,2); 179 return tsk; 180 } 181 182 #ifdef CONFIG_MMU 183 static inline int dup_mmap(struct mm_struct * mm, struct mm_struct * oldmm) 184 { 185 struct vm_area_struct * mpnt, *tmp, **pprev; 186 struct rb_node **rb_link, *rb_parent; 187 int retval; 188 unsigned long charge; 189 struct mempolicy *pol; 190 191 down_write(&oldmm->mmap_sem); 192 flush_cache_mm(current->mm); 193 mm->locked_vm = 0; 194 mm->mmap = NULL; 195 mm->mmap_cache = NULL; 196 mm->free_area_cache = oldmm->mmap_base; 197 mm->cached_hole_size = ~0UL; 198 mm->map_count = 0; 199 set_mm_counter(mm, rss, 0); 200 set_mm_counter(mm, anon_rss, 0); 201 cpus_clear(mm->cpu_vm_mask); 202 mm->mm_rb = RB_ROOT; 203 rb_link = &mm->mm_rb.rb_node; 204 rb_parent = NULL; 205 pprev = &mm->mmap; 206 207 for (mpnt = current->mm->mmap ; mpnt ; mpnt = mpnt->vm_next) { 208 struct file *file; 209 210 if (mpnt->vm_flags & VM_DONTCOPY) { 211 __vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 212 -vma_pages(mpnt)); 213 continue; 214 } 215 charge = 0; 216 if (mpnt->vm_flags & VM_ACCOUNT) { 217 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 218 if (security_vm_enough_memory(len)) 219 goto fail_nomem; 220 charge = len; 221 } 222 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 223 if (!tmp) 224 goto fail_nomem; 225 *tmp = *mpnt; 226 pol = mpol_copy(vma_policy(mpnt)); 227 retval = PTR_ERR(pol); 228 if (IS_ERR(pol)) 229 goto fail_nomem_policy; 230 vma_set_policy(tmp, pol); 231 tmp->vm_flags &= ~VM_LOCKED; 232 tmp->vm_mm = mm; 233 tmp->vm_next = NULL; 234 anon_vma_link(tmp); 235 file = tmp->vm_file; 236 if (file) { 237 struct inode *inode = file->f_dentry->d_inode; 238 get_file(file); 239 if (tmp->vm_flags & VM_DENYWRITE) 240 atomic_dec(&inode->i_writecount); 241 242 /* insert tmp into the share list, just after mpnt */ 243 spin_lock(&file->f_mapping->i_mmap_lock); 244 tmp->vm_truncate_count = mpnt->vm_truncate_count; 245 flush_dcache_mmap_lock(file->f_mapping); 246 vma_prio_tree_add(tmp, mpnt); 247 flush_dcache_mmap_unlock(file->f_mapping); 248 spin_unlock(&file->f_mapping->i_mmap_lock); 249 } 250 251 /* 252 * Link in the new vma and copy the page table entries: 253 * link in first so that swapoff can see swap entries. 254 * Note that, exceptionally, here the vma is inserted 255 * without holding mm->mmap_sem. 256 */ 257 spin_lock(&mm->page_table_lock); 258 *pprev = tmp; 259 pprev = &tmp->vm_next; 260 261 __vma_link_rb(mm, tmp, rb_link, rb_parent); 262 rb_link = &tmp->vm_rb.rb_right; 263 rb_parent = &tmp->vm_rb; 264 265 mm->map_count++; 266 retval = copy_page_range(mm, current->mm, tmp); 267 spin_unlock(&mm->page_table_lock); 268 269 if (tmp->vm_ops && tmp->vm_ops->open) 270 tmp->vm_ops->open(tmp); 271 272 if (retval) 273 goto out; 274 } 275 retval = 0; 276 277 out: 278 flush_tlb_mm(current->mm); 279 up_write(&oldmm->mmap_sem); 280 return retval; 281 fail_nomem_policy: 282 kmem_cache_free(vm_area_cachep, tmp); 283 fail_nomem: 284 retval = -ENOMEM; 285 vm_unacct_memory(charge); 286 goto out; 287 } 288 289 static inline int mm_alloc_pgd(struct mm_struct * mm) 290 { 291 mm->pgd = pgd_alloc(mm); 292 if (unlikely(!mm->pgd)) 293 return -ENOMEM; 294 return 0; 295 } 296 297 static inline void mm_free_pgd(struct mm_struct * mm) 298 { 299 pgd_free(mm->pgd); 300 } 301 #else 302 #define dup_mmap(mm, oldmm) (0) 303 #define mm_alloc_pgd(mm) (0) 304 #define mm_free_pgd(mm) 305 #endif /* CONFIG_MMU */ 306 307 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 308 309 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 310 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 311 312 #include <linux/init_task.h> 313 314 static struct mm_struct * mm_init(struct mm_struct * mm) 315 { 316 atomic_set(&mm->mm_users, 1); 317 atomic_set(&mm->mm_count, 1); 318 init_rwsem(&mm->mmap_sem); 319 INIT_LIST_HEAD(&mm->mmlist); 320 mm->core_waiters = 0; 321 mm->nr_ptes = 0; 322 spin_lock_init(&mm->page_table_lock); 323 rwlock_init(&mm->ioctx_list_lock); 324 mm->ioctx_list = NULL; 325 mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm); 326 mm->free_area_cache = TASK_UNMAPPED_BASE; 327 mm->cached_hole_size = ~0UL; 328 329 if (likely(!mm_alloc_pgd(mm))) { 330 mm->def_flags = 0; 331 return mm; 332 } 333 free_mm(mm); 334 return NULL; 335 } 336 337 /* 338 * Allocate and initialize an mm_struct. 339 */ 340 struct mm_struct * mm_alloc(void) 341 { 342 struct mm_struct * mm; 343 344 mm = allocate_mm(); 345 if (mm) { 346 memset(mm, 0, sizeof(*mm)); 347 mm = mm_init(mm); 348 } 349 return mm; 350 } 351 352 /* 353 * Called when the last reference to the mm 354 * is dropped: either by a lazy thread or by 355 * mmput. Free the page directory and the mm. 356 */ 357 void fastcall __mmdrop(struct mm_struct *mm) 358 { 359 BUG_ON(mm == &init_mm); 360 mm_free_pgd(mm); 361 destroy_context(mm); 362 free_mm(mm); 363 } 364 365 /* 366 * Decrement the use count and release all resources for an mm. 367 */ 368 void mmput(struct mm_struct *mm) 369 { 370 if (atomic_dec_and_test(&mm->mm_users)) { 371 exit_aio(mm); 372 exit_mmap(mm); 373 if (!list_empty(&mm->mmlist)) { 374 spin_lock(&mmlist_lock); 375 list_del(&mm->mmlist); 376 spin_unlock(&mmlist_lock); 377 } 378 put_swap_token(mm); 379 mmdrop(mm); 380 } 381 } 382 EXPORT_SYMBOL_GPL(mmput); 383 384 /** 385 * get_task_mm - acquire a reference to the task's mm 386 * 387 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 388 * this kernel workthread has transiently adopted a user mm with use_mm, 389 * to do its AIO) is not set and if so returns a reference to it, after 390 * bumping up the use count. User must release the mm via mmput() 391 * after use. Typically used by /proc and ptrace. 392 */ 393 struct mm_struct *get_task_mm(struct task_struct *task) 394 { 395 struct mm_struct *mm; 396 397 task_lock(task); 398 mm = task->mm; 399 if (mm) { 400 if (task->flags & PF_BORROWED_MM) 401 mm = NULL; 402 else 403 atomic_inc(&mm->mm_users); 404 } 405 task_unlock(task); 406 return mm; 407 } 408 EXPORT_SYMBOL_GPL(get_task_mm); 409 410 /* Please note the differences between mmput and mm_release. 411 * mmput is called whenever we stop holding onto a mm_struct, 412 * error success whatever. 413 * 414 * mm_release is called after a mm_struct has been removed 415 * from the current process. 416 * 417 * This difference is important for error handling, when we 418 * only half set up a mm_struct for a new process and need to restore 419 * the old one. Because we mmput the new mm_struct before 420 * restoring the old one. . . 421 * Eric Biederman 10 January 1998 422 */ 423 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 424 { 425 struct completion *vfork_done = tsk->vfork_done; 426 427 /* Get rid of any cached register state */ 428 deactivate_mm(tsk, mm); 429 430 /* notify parent sleeping on vfork() */ 431 if (vfork_done) { 432 tsk->vfork_done = NULL; 433 complete(vfork_done); 434 } 435 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { 436 u32 __user * tidptr = tsk->clear_child_tid; 437 tsk->clear_child_tid = NULL; 438 439 /* 440 * We don't check the error code - if userspace has 441 * not set up a proper pointer then tough luck. 442 */ 443 put_user(0, tidptr); 444 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 445 } 446 } 447 448 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 449 { 450 struct mm_struct * mm, *oldmm; 451 int retval; 452 453 tsk->min_flt = tsk->maj_flt = 0; 454 tsk->nvcsw = tsk->nivcsw = 0; 455 456 tsk->mm = NULL; 457 tsk->active_mm = NULL; 458 459 /* 460 * Are we cloning a kernel thread? 461 * 462 * We need to steal a active VM for that.. 463 */ 464 oldmm = current->mm; 465 if (!oldmm) 466 return 0; 467 468 if (clone_flags & CLONE_VM) { 469 atomic_inc(&oldmm->mm_users); 470 mm = oldmm; 471 /* 472 * There are cases where the PTL is held to ensure no 473 * new threads start up in user mode using an mm, which 474 * allows optimizing out ipis; the tlb_gather_mmu code 475 * is an example. 476 */ 477 spin_unlock_wait(&oldmm->page_table_lock); 478 goto good_mm; 479 } 480 481 retval = -ENOMEM; 482 mm = allocate_mm(); 483 if (!mm) 484 goto fail_nomem; 485 486 /* Copy the current MM stuff.. */ 487 memcpy(mm, oldmm, sizeof(*mm)); 488 if (!mm_init(mm)) 489 goto fail_nomem; 490 491 if (init_new_context(tsk,mm)) 492 goto fail_nocontext; 493 494 retval = dup_mmap(mm, oldmm); 495 if (retval) 496 goto free_pt; 497 498 mm->hiwater_rss = get_mm_counter(mm,rss); 499 mm->hiwater_vm = mm->total_vm; 500 501 good_mm: 502 tsk->mm = mm; 503 tsk->active_mm = mm; 504 return 0; 505 506 free_pt: 507 mmput(mm); 508 fail_nomem: 509 return retval; 510 511 fail_nocontext: 512 /* 513 * If init_new_context() failed, we cannot use mmput() to free the mm 514 * because it calls destroy_context() 515 */ 516 mm_free_pgd(mm); 517 free_mm(mm); 518 return retval; 519 } 520 521 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 522 { 523 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 524 /* We don't need to lock fs - think why ;-) */ 525 if (fs) { 526 atomic_set(&fs->count, 1); 527 rwlock_init(&fs->lock); 528 fs->umask = old->umask; 529 read_lock(&old->lock); 530 fs->rootmnt = mntget(old->rootmnt); 531 fs->root = dget(old->root); 532 fs->pwdmnt = mntget(old->pwdmnt); 533 fs->pwd = dget(old->pwd); 534 if (old->altroot) { 535 fs->altrootmnt = mntget(old->altrootmnt); 536 fs->altroot = dget(old->altroot); 537 } else { 538 fs->altrootmnt = NULL; 539 fs->altroot = NULL; 540 } 541 read_unlock(&old->lock); 542 } 543 return fs; 544 } 545 546 struct fs_struct *copy_fs_struct(struct fs_struct *old) 547 { 548 return __copy_fs_struct(old); 549 } 550 551 EXPORT_SYMBOL_GPL(copy_fs_struct); 552 553 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 554 { 555 if (clone_flags & CLONE_FS) { 556 atomic_inc(¤t->fs->count); 557 return 0; 558 } 559 tsk->fs = __copy_fs_struct(current->fs); 560 if (!tsk->fs) 561 return -ENOMEM; 562 return 0; 563 } 564 565 static int count_open_files(struct files_struct *files, int size) 566 { 567 int i; 568 569 /* Find the last open fd */ 570 for (i = size/(8*sizeof(long)); i > 0; ) { 571 if (files->open_fds->fds_bits[--i]) 572 break; 573 } 574 i = (i+1) * 8 * sizeof(long); 575 return i; 576 } 577 578 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 579 { 580 struct files_struct *oldf, *newf; 581 struct file **old_fds, **new_fds; 582 int open_files, size, i, error = 0, expand; 583 584 /* 585 * A background process may not have any files ... 586 */ 587 oldf = current->files; 588 if (!oldf) 589 goto out; 590 591 if (clone_flags & CLONE_FILES) { 592 atomic_inc(&oldf->count); 593 goto out; 594 } 595 596 /* 597 * Note: we may be using current for both targets (See exec.c) 598 * This works because we cache current->files (old) as oldf. Don't 599 * break this. 600 */ 601 tsk->files = NULL; 602 error = -ENOMEM; 603 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); 604 if (!newf) 605 goto out; 606 607 atomic_set(&newf->count, 1); 608 609 spin_lock_init(&newf->file_lock); 610 newf->next_fd = 0; 611 newf->max_fds = NR_OPEN_DEFAULT; 612 newf->max_fdset = __FD_SETSIZE; 613 newf->close_on_exec = &newf->close_on_exec_init; 614 newf->open_fds = &newf->open_fds_init; 615 newf->fd = &newf->fd_array[0]; 616 617 spin_lock(&oldf->file_lock); 618 619 open_files = count_open_files(oldf, oldf->max_fdset); 620 expand = 0; 621 622 /* 623 * Check whether we need to allocate a larger fd array or fd set. 624 * Note: we're not a clone task, so the open count won't change. 625 */ 626 if (open_files > newf->max_fdset) { 627 newf->max_fdset = 0; 628 expand = 1; 629 } 630 if (open_files > newf->max_fds) { 631 newf->max_fds = 0; 632 expand = 1; 633 } 634 635 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 636 if (expand) { 637 spin_unlock(&oldf->file_lock); 638 spin_lock(&newf->file_lock); 639 error = expand_files(newf, open_files-1); 640 spin_unlock(&newf->file_lock); 641 if (error < 0) 642 goto out_release; 643 spin_lock(&oldf->file_lock); 644 } 645 646 old_fds = oldf->fd; 647 new_fds = newf->fd; 648 649 memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8); 650 memcpy(newf->close_on_exec->fds_bits, oldf->close_on_exec->fds_bits, open_files/8); 651 652 for (i = open_files; i != 0; i--) { 653 struct file *f = *old_fds++; 654 if (f) { 655 get_file(f); 656 } else { 657 /* 658 * The fd may be claimed in the fd bitmap but not yet 659 * instantiated in the files array if a sibling thread 660 * is partway through open(). So make sure that this 661 * fd is available to the new process. 662 */ 663 FD_CLR(open_files - i, newf->open_fds); 664 } 665 *new_fds++ = f; 666 } 667 spin_unlock(&oldf->file_lock); 668 669 /* compute the remainder to be cleared */ 670 size = (newf->max_fds - open_files) * sizeof(struct file *); 671 672 /* This is long word aligned thus could use a optimized version */ 673 memset(new_fds, 0, size); 674 675 if (newf->max_fdset > open_files) { 676 int left = (newf->max_fdset-open_files)/8; 677 int start = open_files / (8 * sizeof(unsigned long)); 678 679 memset(&newf->open_fds->fds_bits[start], 0, left); 680 memset(&newf->close_on_exec->fds_bits[start], 0, left); 681 } 682 683 tsk->files = newf; 684 error = 0; 685 out: 686 return error; 687 688 out_release: 689 free_fdset (newf->close_on_exec, newf->max_fdset); 690 free_fdset (newf->open_fds, newf->max_fdset); 691 free_fd_array(newf->fd, newf->max_fds); 692 kmem_cache_free(files_cachep, newf); 693 goto out; 694 } 695 696 /* 697 * Helper to unshare the files of the current task. 698 * We don't want to expose copy_files internals to 699 * the exec layer of the kernel. 700 */ 701 702 int unshare_files(void) 703 { 704 struct files_struct *files = current->files; 705 int rc; 706 707 if(!files) 708 BUG(); 709 710 /* This can race but the race causes us to copy when we don't 711 need to and drop the copy */ 712 if(atomic_read(&files->count) == 1) 713 { 714 atomic_inc(&files->count); 715 return 0; 716 } 717 rc = copy_files(0, current); 718 if(rc) 719 current->files = files; 720 return rc; 721 } 722 723 EXPORT_SYMBOL(unshare_files); 724 725 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 726 { 727 struct sighand_struct *sig; 728 729 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 730 atomic_inc(¤t->sighand->count); 731 return 0; 732 } 733 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 734 tsk->sighand = sig; 735 if (!sig) 736 return -ENOMEM; 737 spin_lock_init(&sig->siglock); 738 atomic_set(&sig->count, 1); 739 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 740 return 0; 741 } 742 743 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 744 { 745 struct signal_struct *sig; 746 int ret; 747 748 if (clone_flags & CLONE_THREAD) { 749 atomic_inc(¤t->signal->count); 750 atomic_inc(¤t->signal->live); 751 return 0; 752 } 753 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 754 tsk->signal = sig; 755 if (!sig) 756 return -ENOMEM; 757 758 ret = copy_thread_group_keys(tsk); 759 if (ret < 0) { 760 kmem_cache_free(signal_cachep, sig); 761 return ret; 762 } 763 764 atomic_set(&sig->count, 1); 765 atomic_set(&sig->live, 1); 766 init_waitqueue_head(&sig->wait_chldexit); 767 sig->flags = 0; 768 sig->group_exit_code = 0; 769 sig->group_exit_task = NULL; 770 sig->group_stop_count = 0; 771 sig->curr_target = NULL; 772 init_sigpending(&sig->shared_pending); 773 INIT_LIST_HEAD(&sig->posix_timers); 774 775 sig->it_real_value = sig->it_real_incr = 0; 776 sig->real_timer.function = it_real_fn; 777 sig->real_timer.data = (unsigned long) tsk; 778 init_timer(&sig->real_timer); 779 780 sig->it_virt_expires = cputime_zero; 781 sig->it_virt_incr = cputime_zero; 782 sig->it_prof_expires = cputime_zero; 783 sig->it_prof_incr = cputime_zero; 784 785 sig->tty = current->signal->tty; 786 sig->pgrp = process_group(current); 787 sig->session = current->signal->session; 788 sig->leader = 0; /* session leadership doesn't inherit */ 789 sig->tty_old_pgrp = 0; 790 791 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 792 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 793 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 794 sig->sched_time = 0; 795 INIT_LIST_HEAD(&sig->cpu_timers[0]); 796 INIT_LIST_HEAD(&sig->cpu_timers[1]); 797 INIT_LIST_HEAD(&sig->cpu_timers[2]); 798 799 task_lock(current->group_leader); 800 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 801 task_unlock(current->group_leader); 802 803 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 804 /* 805 * New sole thread in the process gets an expiry time 806 * of the whole CPU time limit. 807 */ 808 tsk->it_prof_expires = 809 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 810 } 811 812 return 0; 813 } 814 815 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 816 { 817 unsigned long new_flags = p->flags; 818 819 new_flags &= ~PF_SUPERPRIV; 820 new_flags |= PF_FORKNOEXEC; 821 if (!(clone_flags & CLONE_PTRACE)) 822 p->ptrace = 0; 823 p->flags = new_flags; 824 } 825 826 asmlinkage long sys_set_tid_address(int __user *tidptr) 827 { 828 current->clear_child_tid = tidptr; 829 830 return current->pid; 831 } 832 833 /* 834 * This creates a new process as a copy of the old one, 835 * but does not actually start it yet. 836 * 837 * It copies the registers, and all the appropriate 838 * parts of the process environment (as per the clone 839 * flags). The actual kick-off is left to the caller. 840 */ 841 static task_t *copy_process(unsigned long clone_flags, 842 unsigned long stack_start, 843 struct pt_regs *regs, 844 unsigned long stack_size, 845 int __user *parent_tidptr, 846 int __user *child_tidptr, 847 int pid) 848 { 849 int retval; 850 struct task_struct *p = NULL; 851 852 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 853 return ERR_PTR(-EINVAL); 854 855 /* 856 * Thread groups must share signals as well, and detached threads 857 * can only be started up within the thread group. 858 */ 859 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 860 return ERR_PTR(-EINVAL); 861 862 /* 863 * Shared signal handlers imply shared VM. By way of the above, 864 * thread groups also imply shared VM. Blocking this case allows 865 * for various simplifications in other code. 866 */ 867 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 868 return ERR_PTR(-EINVAL); 869 870 retval = security_task_create(clone_flags); 871 if (retval) 872 goto fork_out; 873 874 retval = -ENOMEM; 875 p = dup_task_struct(current); 876 if (!p) 877 goto fork_out; 878 879 retval = -EAGAIN; 880 if (atomic_read(&p->user->processes) >= 881 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 882 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 883 p->user != &root_user) 884 goto bad_fork_free; 885 } 886 887 atomic_inc(&p->user->__count); 888 atomic_inc(&p->user->processes); 889 get_group_info(p->group_info); 890 891 /* 892 * If multiple threads are within copy_process(), then this check 893 * triggers too late. This doesn't hurt, the check is only there 894 * to stop root fork bombs. 895 */ 896 if (nr_threads >= max_threads) 897 goto bad_fork_cleanup_count; 898 899 if (!try_module_get(p->thread_info->exec_domain->module)) 900 goto bad_fork_cleanup_count; 901 902 if (p->binfmt && !try_module_get(p->binfmt->module)) 903 goto bad_fork_cleanup_put_domain; 904 905 p->did_exec = 0; 906 copy_flags(clone_flags, p); 907 p->pid = pid; 908 retval = -EFAULT; 909 if (clone_flags & CLONE_PARENT_SETTID) 910 if (put_user(p->pid, parent_tidptr)) 911 goto bad_fork_cleanup; 912 913 p->proc_dentry = NULL; 914 915 INIT_LIST_HEAD(&p->children); 916 INIT_LIST_HEAD(&p->sibling); 917 p->vfork_done = NULL; 918 spin_lock_init(&p->alloc_lock); 919 spin_lock_init(&p->proc_lock); 920 921 clear_tsk_thread_flag(p, TIF_SIGPENDING); 922 init_sigpending(&p->pending); 923 924 p->utime = cputime_zero; 925 p->stime = cputime_zero; 926 p->sched_time = 0; 927 p->rchar = 0; /* I/O counter: bytes read */ 928 p->wchar = 0; /* I/O counter: bytes written */ 929 p->syscr = 0; /* I/O counter: read syscalls */ 930 p->syscw = 0; /* I/O counter: write syscalls */ 931 acct_clear_integrals(p); 932 933 p->it_virt_expires = cputime_zero; 934 p->it_prof_expires = cputime_zero; 935 p->it_sched_expires = 0; 936 INIT_LIST_HEAD(&p->cpu_timers[0]); 937 INIT_LIST_HEAD(&p->cpu_timers[1]); 938 INIT_LIST_HEAD(&p->cpu_timers[2]); 939 940 p->lock_depth = -1; /* -1 = no lock */ 941 do_posix_clock_monotonic_gettime(&p->start_time); 942 p->security = NULL; 943 p->io_context = NULL; 944 p->io_wait = NULL; 945 p->audit_context = NULL; 946 #ifdef CONFIG_NUMA 947 p->mempolicy = mpol_copy(p->mempolicy); 948 if (IS_ERR(p->mempolicy)) { 949 retval = PTR_ERR(p->mempolicy); 950 p->mempolicy = NULL; 951 goto bad_fork_cleanup; 952 } 953 #endif 954 955 p->tgid = p->pid; 956 if (clone_flags & CLONE_THREAD) 957 p->tgid = current->tgid; 958 959 if ((retval = security_task_alloc(p))) 960 goto bad_fork_cleanup_policy; 961 if ((retval = audit_alloc(p))) 962 goto bad_fork_cleanup_security; 963 /* copy all the process information */ 964 if ((retval = copy_semundo(clone_flags, p))) 965 goto bad_fork_cleanup_audit; 966 if ((retval = copy_files(clone_flags, p))) 967 goto bad_fork_cleanup_semundo; 968 if ((retval = copy_fs(clone_flags, p))) 969 goto bad_fork_cleanup_files; 970 if ((retval = copy_sighand(clone_flags, p))) 971 goto bad_fork_cleanup_fs; 972 if ((retval = copy_signal(clone_flags, p))) 973 goto bad_fork_cleanup_sighand; 974 if ((retval = copy_mm(clone_flags, p))) 975 goto bad_fork_cleanup_signal; 976 if ((retval = copy_keys(clone_flags, p))) 977 goto bad_fork_cleanup_mm; 978 if ((retval = copy_namespace(clone_flags, p))) 979 goto bad_fork_cleanup_keys; 980 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 981 if (retval) 982 goto bad_fork_cleanup_namespace; 983 984 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 985 /* 986 * Clear TID on mm_release()? 987 */ 988 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 989 990 /* 991 * Syscall tracing should be turned off in the child regardless 992 * of CLONE_PTRACE. 993 */ 994 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 995 996 /* Our parent execution domain becomes current domain 997 These must match for thread signalling to apply */ 998 999 p->parent_exec_id = p->self_exec_id; 1000 1001 /* ok, now we should be set up.. */ 1002 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1003 p->pdeath_signal = 0; 1004 p->exit_state = 0; 1005 1006 /* 1007 * Ok, make it visible to the rest of the system. 1008 * We dont wake it up yet. 1009 */ 1010 p->group_leader = p; 1011 INIT_LIST_HEAD(&p->ptrace_children); 1012 INIT_LIST_HEAD(&p->ptrace_list); 1013 1014 /* Perform scheduler related setup. Assign this task to a CPU. */ 1015 sched_fork(p, clone_flags); 1016 1017 /* Need tasklist lock for parent etc handling! */ 1018 write_lock_irq(&tasklist_lock); 1019 1020 /* 1021 * The task hasn't been attached yet, so its cpus_allowed mask will 1022 * not be changed, nor will its assigned CPU. 1023 * 1024 * The cpus_allowed mask of the parent may have changed after it was 1025 * copied first time - so re-copy it here, then check the child's CPU 1026 * to ensure it is on a valid CPU (and if not, just force it back to 1027 * parent's CPU). This avoids alot of nasty races. 1028 */ 1029 p->cpus_allowed = current->cpus_allowed; 1030 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed))) 1031 set_task_cpu(p, smp_processor_id()); 1032 1033 /* 1034 * Check for pending SIGKILL! The new thread should not be allowed 1035 * to slip out of an OOM kill. (or normal SIGKILL.) 1036 */ 1037 if (sigismember(¤t->pending.signal, SIGKILL)) { 1038 write_unlock_irq(&tasklist_lock); 1039 retval = -EINTR; 1040 goto bad_fork_cleanup_namespace; 1041 } 1042 1043 /* CLONE_PARENT re-uses the old parent */ 1044 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1045 p->real_parent = current->real_parent; 1046 else 1047 p->real_parent = current; 1048 p->parent = p->real_parent; 1049 1050 if (clone_flags & CLONE_THREAD) { 1051 spin_lock(¤t->sighand->siglock); 1052 /* 1053 * Important: if an exit-all has been started then 1054 * do not create this new thread - the whole thread 1055 * group is supposed to exit anyway. 1056 */ 1057 if (current->signal->flags & SIGNAL_GROUP_EXIT) { 1058 spin_unlock(¤t->sighand->siglock); 1059 write_unlock_irq(&tasklist_lock); 1060 retval = -EAGAIN; 1061 goto bad_fork_cleanup_namespace; 1062 } 1063 p->group_leader = current->group_leader; 1064 1065 if (current->signal->group_stop_count > 0) { 1066 /* 1067 * There is an all-stop in progress for the group. 1068 * We ourselves will stop as soon as we check signals. 1069 * Make the new thread part of that group stop too. 1070 */ 1071 current->signal->group_stop_count++; 1072 set_tsk_thread_flag(p, TIF_SIGPENDING); 1073 } 1074 1075 if (!cputime_eq(current->signal->it_virt_expires, 1076 cputime_zero) || 1077 !cputime_eq(current->signal->it_prof_expires, 1078 cputime_zero) || 1079 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1080 !list_empty(¤t->signal->cpu_timers[0]) || 1081 !list_empty(¤t->signal->cpu_timers[1]) || 1082 !list_empty(¤t->signal->cpu_timers[2])) { 1083 /* 1084 * Have child wake up on its first tick to check 1085 * for process CPU timers. 1086 */ 1087 p->it_prof_expires = jiffies_to_cputime(1); 1088 } 1089 1090 spin_unlock(¤t->sighand->siglock); 1091 } 1092 1093 /* 1094 * inherit ioprio 1095 */ 1096 p->ioprio = current->ioprio; 1097 1098 SET_LINKS(p); 1099 if (unlikely(p->ptrace & PT_PTRACED)) 1100 __ptrace_link(p, current->parent); 1101 1102 cpuset_fork(p); 1103 1104 attach_pid(p, PIDTYPE_PID, p->pid); 1105 attach_pid(p, PIDTYPE_TGID, p->tgid); 1106 if (thread_group_leader(p)) { 1107 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1108 attach_pid(p, PIDTYPE_SID, p->signal->session); 1109 if (p->pid) 1110 __get_cpu_var(process_counts)++; 1111 } 1112 1113 nr_threads++; 1114 total_forks++; 1115 write_unlock_irq(&tasklist_lock); 1116 retval = 0; 1117 1118 fork_out: 1119 if (retval) 1120 return ERR_PTR(retval); 1121 return p; 1122 1123 bad_fork_cleanup_namespace: 1124 exit_namespace(p); 1125 bad_fork_cleanup_keys: 1126 exit_keys(p); 1127 bad_fork_cleanup_mm: 1128 if (p->mm) 1129 mmput(p->mm); 1130 bad_fork_cleanup_signal: 1131 exit_signal(p); 1132 bad_fork_cleanup_sighand: 1133 exit_sighand(p); 1134 bad_fork_cleanup_fs: 1135 exit_fs(p); /* blocking */ 1136 bad_fork_cleanup_files: 1137 exit_files(p); /* blocking */ 1138 bad_fork_cleanup_semundo: 1139 exit_sem(p); 1140 bad_fork_cleanup_audit: 1141 audit_free(p); 1142 bad_fork_cleanup_security: 1143 security_task_free(p); 1144 bad_fork_cleanup_policy: 1145 #ifdef CONFIG_NUMA 1146 mpol_free(p->mempolicy); 1147 #endif 1148 bad_fork_cleanup: 1149 if (p->binfmt) 1150 module_put(p->binfmt->module); 1151 bad_fork_cleanup_put_domain: 1152 module_put(p->thread_info->exec_domain->module); 1153 bad_fork_cleanup_count: 1154 put_group_info(p->group_info); 1155 atomic_dec(&p->user->processes); 1156 free_uid(p->user); 1157 bad_fork_free: 1158 free_task(p); 1159 goto fork_out; 1160 } 1161 1162 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1163 { 1164 memset(regs, 0, sizeof(struct pt_regs)); 1165 return regs; 1166 } 1167 1168 task_t * __devinit fork_idle(int cpu) 1169 { 1170 task_t *task; 1171 struct pt_regs regs; 1172 1173 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1174 if (!task) 1175 return ERR_PTR(-ENOMEM); 1176 init_idle(task, cpu); 1177 unhash_process(task); 1178 return task; 1179 } 1180 1181 static inline int fork_traceflag (unsigned clone_flags) 1182 { 1183 if (clone_flags & CLONE_UNTRACED) 1184 return 0; 1185 else if (clone_flags & CLONE_VFORK) { 1186 if (current->ptrace & PT_TRACE_VFORK) 1187 return PTRACE_EVENT_VFORK; 1188 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1189 if (current->ptrace & PT_TRACE_CLONE) 1190 return PTRACE_EVENT_CLONE; 1191 } else if (current->ptrace & PT_TRACE_FORK) 1192 return PTRACE_EVENT_FORK; 1193 1194 return 0; 1195 } 1196 1197 /* 1198 * Ok, this is the main fork-routine. 1199 * 1200 * It copies the process, and if successful kick-starts 1201 * it and waits for it to finish using the VM if required. 1202 */ 1203 long do_fork(unsigned long clone_flags, 1204 unsigned long stack_start, 1205 struct pt_regs *regs, 1206 unsigned long stack_size, 1207 int __user *parent_tidptr, 1208 int __user *child_tidptr) 1209 { 1210 struct task_struct *p; 1211 int trace = 0; 1212 long pid = alloc_pidmap(); 1213 1214 if (pid < 0) 1215 return -EAGAIN; 1216 if (unlikely(current->ptrace)) { 1217 trace = fork_traceflag (clone_flags); 1218 if (trace) 1219 clone_flags |= CLONE_PTRACE; 1220 } 1221 1222 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid); 1223 /* 1224 * Do this prior waking up the new thread - the thread pointer 1225 * might get invalid after that point, if the thread exits quickly. 1226 */ 1227 if (!IS_ERR(p)) { 1228 struct completion vfork; 1229 1230 if (clone_flags & CLONE_VFORK) { 1231 p->vfork_done = &vfork; 1232 init_completion(&vfork); 1233 } 1234 1235 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1236 /* 1237 * We'll start up with an immediate SIGSTOP. 1238 */ 1239 sigaddset(&p->pending.signal, SIGSTOP); 1240 set_tsk_thread_flag(p, TIF_SIGPENDING); 1241 } 1242 1243 if (!(clone_flags & CLONE_STOPPED)) 1244 wake_up_new_task(p, clone_flags); 1245 else 1246 p->state = TASK_STOPPED; 1247 1248 if (unlikely (trace)) { 1249 current->ptrace_message = pid; 1250 ptrace_notify ((trace << 8) | SIGTRAP); 1251 } 1252 1253 if (clone_flags & CLONE_VFORK) { 1254 wait_for_completion(&vfork); 1255 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1256 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1257 } 1258 } else { 1259 free_pidmap(pid); 1260 pid = PTR_ERR(p); 1261 } 1262 return pid; 1263 } 1264 1265 void __init proc_caches_init(void) 1266 { 1267 sighand_cachep = kmem_cache_create("sighand_cache", 1268 sizeof(struct sighand_struct), 0, 1269 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1270 signal_cachep = kmem_cache_create("signal_cache", 1271 sizeof(struct signal_struct), 0, 1272 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1273 files_cachep = kmem_cache_create("files_cache", 1274 sizeof(struct files_struct), 0, 1275 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1276 fs_cachep = kmem_cache_create("fs_cache", 1277 sizeof(struct fs_struct), 0, 1278 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1279 vm_area_cachep = kmem_cache_create("vm_area_struct", 1280 sizeof(struct vm_area_struct), 0, 1281 SLAB_PANIC, NULL, NULL); 1282 mm_cachep = kmem_cache_create("mm_struct", 1283 sizeof(struct mm_struct), 0, 1284 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1285 } 1286