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 long pages = vma_pages(mpnt); 212 mm->total_vm -= pages; 213 __vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 214 -pages); 215 continue; 216 } 217 charge = 0; 218 if (mpnt->vm_flags & VM_ACCOUNT) { 219 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 220 if (security_vm_enough_memory(len)) 221 goto fail_nomem; 222 charge = len; 223 } 224 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 225 if (!tmp) 226 goto fail_nomem; 227 *tmp = *mpnt; 228 pol = mpol_copy(vma_policy(mpnt)); 229 retval = PTR_ERR(pol); 230 if (IS_ERR(pol)) 231 goto fail_nomem_policy; 232 vma_set_policy(tmp, pol); 233 tmp->vm_flags &= ~VM_LOCKED; 234 tmp->vm_mm = mm; 235 tmp->vm_next = NULL; 236 anon_vma_link(tmp); 237 file = tmp->vm_file; 238 if (file) { 239 struct inode *inode = file->f_dentry->d_inode; 240 get_file(file); 241 if (tmp->vm_flags & VM_DENYWRITE) 242 atomic_dec(&inode->i_writecount); 243 244 /* insert tmp into the share list, just after mpnt */ 245 spin_lock(&file->f_mapping->i_mmap_lock); 246 tmp->vm_truncate_count = mpnt->vm_truncate_count; 247 flush_dcache_mmap_lock(file->f_mapping); 248 vma_prio_tree_add(tmp, mpnt); 249 flush_dcache_mmap_unlock(file->f_mapping); 250 spin_unlock(&file->f_mapping->i_mmap_lock); 251 } 252 253 /* 254 * Link in the new vma and copy the page table entries: 255 * link in first so that swapoff can see swap entries. 256 * Note that, exceptionally, here the vma is inserted 257 * without holding mm->mmap_sem. 258 */ 259 spin_lock(&mm->page_table_lock); 260 *pprev = tmp; 261 pprev = &tmp->vm_next; 262 263 __vma_link_rb(mm, tmp, rb_link, rb_parent); 264 rb_link = &tmp->vm_rb.rb_right; 265 rb_parent = &tmp->vm_rb; 266 267 mm->map_count++; 268 retval = copy_page_range(mm, current->mm, tmp); 269 spin_unlock(&mm->page_table_lock); 270 271 if (tmp->vm_ops && tmp->vm_ops->open) 272 tmp->vm_ops->open(tmp); 273 274 if (retval) 275 goto out; 276 } 277 retval = 0; 278 279 out: 280 flush_tlb_mm(current->mm); 281 up_write(&oldmm->mmap_sem); 282 return retval; 283 fail_nomem_policy: 284 kmem_cache_free(vm_area_cachep, tmp); 285 fail_nomem: 286 retval = -ENOMEM; 287 vm_unacct_memory(charge); 288 goto out; 289 } 290 291 static inline int mm_alloc_pgd(struct mm_struct * mm) 292 { 293 mm->pgd = pgd_alloc(mm); 294 if (unlikely(!mm->pgd)) 295 return -ENOMEM; 296 return 0; 297 } 298 299 static inline void mm_free_pgd(struct mm_struct * mm) 300 { 301 pgd_free(mm->pgd); 302 } 303 #else 304 #define dup_mmap(mm, oldmm) (0) 305 #define mm_alloc_pgd(mm) (0) 306 #define mm_free_pgd(mm) 307 #endif /* CONFIG_MMU */ 308 309 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 310 311 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 312 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 313 314 #include <linux/init_task.h> 315 316 static struct mm_struct * mm_init(struct mm_struct * mm) 317 { 318 atomic_set(&mm->mm_users, 1); 319 atomic_set(&mm->mm_count, 1); 320 init_rwsem(&mm->mmap_sem); 321 INIT_LIST_HEAD(&mm->mmlist); 322 mm->core_waiters = 0; 323 mm->nr_ptes = 0; 324 spin_lock_init(&mm->page_table_lock); 325 rwlock_init(&mm->ioctx_list_lock); 326 mm->ioctx_list = NULL; 327 mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm); 328 mm->free_area_cache = TASK_UNMAPPED_BASE; 329 mm->cached_hole_size = ~0UL; 330 331 if (likely(!mm_alloc_pgd(mm))) { 332 mm->def_flags = 0; 333 return mm; 334 } 335 free_mm(mm); 336 return NULL; 337 } 338 339 /* 340 * Allocate and initialize an mm_struct. 341 */ 342 struct mm_struct * mm_alloc(void) 343 { 344 struct mm_struct * mm; 345 346 mm = allocate_mm(); 347 if (mm) { 348 memset(mm, 0, sizeof(*mm)); 349 mm = mm_init(mm); 350 } 351 return mm; 352 } 353 354 /* 355 * Called when the last reference to the mm 356 * is dropped: either by a lazy thread or by 357 * mmput. Free the page directory and the mm. 358 */ 359 void fastcall __mmdrop(struct mm_struct *mm) 360 { 361 BUG_ON(mm == &init_mm); 362 mm_free_pgd(mm); 363 destroy_context(mm); 364 free_mm(mm); 365 } 366 367 /* 368 * Decrement the use count and release all resources for an mm. 369 */ 370 void mmput(struct mm_struct *mm) 371 { 372 if (atomic_dec_and_test(&mm->mm_users)) { 373 exit_aio(mm); 374 exit_mmap(mm); 375 if (!list_empty(&mm->mmlist)) { 376 spin_lock(&mmlist_lock); 377 list_del(&mm->mmlist); 378 spin_unlock(&mmlist_lock); 379 } 380 put_swap_token(mm); 381 mmdrop(mm); 382 } 383 } 384 EXPORT_SYMBOL_GPL(mmput); 385 386 /** 387 * get_task_mm - acquire a reference to the task's mm 388 * 389 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 390 * this kernel workthread has transiently adopted a user mm with use_mm, 391 * to do its AIO) is not set and if so returns a reference to it, after 392 * bumping up the use count. User must release the mm via mmput() 393 * after use. Typically used by /proc and ptrace. 394 */ 395 struct mm_struct *get_task_mm(struct task_struct *task) 396 { 397 struct mm_struct *mm; 398 399 task_lock(task); 400 mm = task->mm; 401 if (mm) { 402 if (task->flags & PF_BORROWED_MM) 403 mm = NULL; 404 else 405 atomic_inc(&mm->mm_users); 406 } 407 task_unlock(task); 408 return mm; 409 } 410 EXPORT_SYMBOL_GPL(get_task_mm); 411 412 /* Please note the differences between mmput and mm_release. 413 * mmput is called whenever we stop holding onto a mm_struct, 414 * error success whatever. 415 * 416 * mm_release is called after a mm_struct has been removed 417 * from the current process. 418 * 419 * This difference is important for error handling, when we 420 * only half set up a mm_struct for a new process and need to restore 421 * the old one. Because we mmput the new mm_struct before 422 * restoring the old one. . . 423 * Eric Biederman 10 January 1998 424 */ 425 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 426 { 427 struct completion *vfork_done = tsk->vfork_done; 428 429 /* Get rid of any cached register state */ 430 deactivate_mm(tsk, mm); 431 432 /* notify parent sleeping on vfork() */ 433 if (vfork_done) { 434 tsk->vfork_done = NULL; 435 complete(vfork_done); 436 } 437 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { 438 u32 __user * tidptr = tsk->clear_child_tid; 439 tsk->clear_child_tid = NULL; 440 441 /* 442 * We don't check the error code - if userspace has 443 * not set up a proper pointer then tough luck. 444 */ 445 put_user(0, tidptr); 446 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 447 } 448 } 449 450 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 451 { 452 struct mm_struct * mm, *oldmm; 453 int retval; 454 455 tsk->min_flt = tsk->maj_flt = 0; 456 tsk->nvcsw = tsk->nivcsw = 0; 457 458 tsk->mm = NULL; 459 tsk->active_mm = NULL; 460 461 /* 462 * Are we cloning a kernel thread? 463 * 464 * We need to steal a active VM for that.. 465 */ 466 oldmm = current->mm; 467 if (!oldmm) 468 return 0; 469 470 if (clone_flags & CLONE_VM) { 471 atomic_inc(&oldmm->mm_users); 472 mm = oldmm; 473 /* 474 * There are cases where the PTL is held to ensure no 475 * new threads start up in user mode using an mm, which 476 * allows optimizing out ipis; the tlb_gather_mmu code 477 * is an example. 478 */ 479 spin_unlock_wait(&oldmm->page_table_lock); 480 goto good_mm; 481 } 482 483 retval = -ENOMEM; 484 mm = allocate_mm(); 485 if (!mm) 486 goto fail_nomem; 487 488 /* Copy the current MM stuff.. */ 489 memcpy(mm, oldmm, sizeof(*mm)); 490 if (!mm_init(mm)) 491 goto fail_nomem; 492 493 if (init_new_context(tsk,mm)) 494 goto fail_nocontext; 495 496 retval = dup_mmap(mm, oldmm); 497 if (retval) 498 goto free_pt; 499 500 mm->hiwater_rss = get_mm_counter(mm,rss); 501 mm->hiwater_vm = mm->total_vm; 502 503 good_mm: 504 tsk->mm = mm; 505 tsk->active_mm = mm; 506 return 0; 507 508 free_pt: 509 mmput(mm); 510 fail_nomem: 511 return retval; 512 513 fail_nocontext: 514 /* 515 * If init_new_context() failed, we cannot use mmput() to free the mm 516 * because it calls destroy_context() 517 */ 518 mm_free_pgd(mm); 519 free_mm(mm); 520 return retval; 521 } 522 523 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 524 { 525 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 526 /* We don't need to lock fs - think why ;-) */ 527 if (fs) { 528 atomic_set(&fs->count, 1); 529 rwlock_init(&fs->lock); 530 fs->umask = old->umask; 531 read_lock(&old->lock); 532 fs->rootmnt = mntget(old->rootmnt); 533 fs->root = dget(old->root); 534 fs->pwdmnt = mntget(old->pwdmnt); 535 fs->pwd = dget(old->pwd); 536 if (old->altroot) { 537 fs->altrootmnt = mntget(old->altrootmnt); 538 fs->altroot = dget(old->altroot); 539 } else { 540 fs->altrootmnt = NULL; 541 fs->altroot = NULL; 542 } 543 read_unlock(&old->lock); 544 } 545 return fs; 546 } 547 548 struct fs_struct *copy_fs_struct(struct fs_struct *old) 549 { 550 return __copy_fs_struct(old); 551 } 552 553 EXPORT_SYMBOL_GPL(copy_fs_struct); 554 555 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 556 { 557 if (clone_flags & CLONE_FS) { 558 atomic_inc(¤t->fs->count); 559 return 0; 560 } 561 tsk->fs = __copy_fs_struct(current->fs); 562 if (!tsk->fs) 563 return -ENOMEM; 564 return 0; 565 } 566 567 static int count_open_files(struct files_struct *files, int size) 568 { 569 int i; 570 571 /* Find the last open fd */ 572 for (i = size/(8*sizeof(long)); i > 0; ) { 573 if (files->open_fds->fds_bits[--i]) 574 break; 575 } 576 i = (i+1) * 8 * sizeof(long); 577 return i; 578 } 579 580 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 581 { 582 struct files_struct *oldf, *newf; 583 struct file **old_fds, **new_fds; 584 int open_files, size, i, error = 0, expand; 585 586 /* 587 * A background process may not have any files ... 588 */ 589 oldf = current->files; 590 if (!oldf) 591 goto out; 592 593 if (clone_flags & CLONE_FILES) { 594 atomic_inc(&oldf->count); 595 goto out; 596 } 597 598 /* 599 * Note: we may be using current for both targets (See exec.c) 600 * This works because we cache current->files (old) as oldf. Don't 601 * break this. 602 */ 603 tsk->files = NULL; 604 error = -ENOMEM; 605 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); 606 if (!newf) 607 goto out; 608 609 atomic_set(&newf->count, 1); 610 611 spin_lock_init(&newf->file_lock); 612 newf->next_fd = 0; 613 newf->max_fds = NR_OPEN_DEFAULT; 614 newf->max_fdset = __FD_SETSIZE; 615 newf->close_on_exec = &newf->close_on_exec_init; 616 newf->open_fds = &newf->open_fds_init; 617 newf->fd = &newf->fd_array[0]; 618 619 spin_lock(&oldf->file_lock); 620 621 open_files = count_open_files(oldf, oldf->max_fdset); 622 expand = 0; 623 624 /* 625 * Check whether we need to allocate a larger fd array or fd set. 626 * Note: we're not a clone task, so the open count won't change. 627 */ 628 if (open_files > newf->max_fdset) { 629 newf->max_fdset = 0; 630 expand = 1; 631 } 632 if (open_files > newf->max_fds) { 633 newf->max_fds = 0; 634 expand = 1; 635 } 636 637 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 638 if (expand) { 639 spin_unlock(&oldf->file_lock); 640 spin_lock(&newf->file_lock); 641 error = expand_files(newf, open_files-1); 642 spin_unlock(&newf->file_lock); 643 if (error < 0) 644 goto out_release; 645 spin_lock(&oldf->file_lock); 646 } 647 648 old_fds = oldf->fd; 649 new_fds = newf->fd; 650 651 memcpy(newf->open_fds->fds_bits, oldf->open_fds->fds_bits, open_files/8); 652 memcpy(newf->close_on_exec->fds_bits, oldf->close_on_exec->fds_bits, open_files/8); 653 654 for (i = open_files; i != 0; i--) { 655 struct file *f = *old_fds++; 656 if (f) { 657 get_file(f); 658 } else { 659 /* 660 * The fd may be claimed in the fd bitmap but not yet 661 * instantiated in the files array if a sibling thread 662 * is partway through open(). So make sure that this 663 * fd is available to the new process. 664 */ 665 FD_CLR(open_files - i, newf->open_fds); 666 } 667 *new_fds++ = f; 668 } 669 spin_unlock(&oldf->file_lock); 670 671 /* compute the remainder to be cleared */ 672 size = (newf->max_fds - open_files) * sizeof(struct file *); 673 674 /* This is long word aligned thus could use a optimized version */ 675 memset(new_fds, 0, size); 676 677 if (newf->max_fdset > open_files) { 678 int left = (newf->max_fdset-open_files)/8; 679 int start = open_files / (8 * sizeof(unsigned long)); 680 681 memset(&newf->open_fds->fds_bits[start], 0, left); 682 memset(&newf->close_on_exec->fds_bits[start], 0, left); 683 } 684 685 tsk->files = newf; 686 error = 0; 687 out: 688 return error; 689 690 out_release: 691 free_fdset (newf->close_on_exec, newf->max_fdset); 692 free_fdset (newf->open_fds, newf->max_fdset); 693 free_fd_array(newf->fd, newf->max_fds); 694 kmem_cache_free(files_cachep, newf); 695 goto out; 696 } 697 698 /* 699 * Helper to unshare the files of the current task. 700 * We don't want to expose copy_files internals to 701 * the exec layer of the kernel. 702 */ 703 704 int unshare_files(void) 705 { 706 struct files_struct *files = current->files; 707 int rc; 708 709 if(!files) 710 BUG(); 711 712 /* This can race but the race causes us to copy when we don't 713 need to and drop the copy */ 714 if(atomic_read(&files->count) == 1) 715 { 716 atomic_inc(&files->count); 717 return 0; 718 } 719 rc = copy_files(0, current); 720 if(rc) 721 current->files = files; 722 return rc; 723 } 724 725 EXPORT_SYMBOL(unshare_files); 726 727 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 728 { 729 struct sighand_struct *sig; 730 731 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 732 atomic_inc(¤t->sighand->count); 733 return 0; 734 } 735 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 736 tsk->sighand = sig; 737 if (!sig) 738 return -ENOMEM; 739 spin_lock_init(&sig->siglock); 740 atomic_set(&sig->count, 1); 741 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 742 return 0; 743 } 744 745 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 746 { 747 struct signal_struct *sig; 748 int ret; 749 750 if (clone_flags & CLONE_THREAD) { 751 atomic_inc(¤t->signal->count); 752 atomic_inc(¤t->signal->live); 753 return 0; 754 } 755 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 756 tsk->signal = sig; 757 if (!sig) 758 return -ENOMEM; 759 760 ret = copy_thread_group_keys(tsk); 761 if (ret < 0) { 762 kmem_cache_free(signal_cachep, sig); 763 return ret; 764 } 765 766 atomic_set(&sig->count, 1); 767 atomic_set(&sig->live, 1); 768 init_waitqueue_head(&sig->wait_chldexit); 769 sig->flags = 0; 770 sig->group_exit_code = 0; 771 sig->group_exit_task = NULL; 772 sig->group_stop_count = 0; 773 sig->curr_target = NULL; 774 init_sigpending(&sig->shared_pending); 775 INIT_LIST_HEAD(&sig->posix_timers); 776 777 sig->it_real_value = sig->it_real_incr = 0; 778 sig->real_timer.function = it_real_fn; 779 sig->real_timer.data = (unsigned long) tsk; 780 init_timer(&sig->real_timer); 781 782 sig->it_virt_expires = cputime_zero; 783 sig->it_virt_incr = cputime_zero; 784 sig->it_prof_expires = cputime_zero; 785 sig->it_prof_incr = cputime_zero; 786 787 sig->tty = current->signal->tty; 788 sig->pgrp = process_group(current); 789 sig->session = current->signal->session; 790 sig->leader = 0; /* session leadership doesn't inherit */ 791 sig->tty_old_pgrp = 0; 792 793 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 794 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 795 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 796 sig->sched_time = 0; 797 INIT_LIST_HEAD(&sig->cpu_timers[0]); 798 INIT_LIST_HEAD(&sig->cpu_timers[1]); 799 INIT_LIST_HEAD(&sig->cpu_timers[2]); 800 801 task_lock(current->group_leader); 802 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 803 task_unlock(current->group_leader); 804 805 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 806 /* 807 * New sole thread in the process gets an expiry time 808 * of the whole CPU time limit. 809 */ 810 tsk->it_prof_expires = 811 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 812 } 813 814 return 0; 815 } 816 817 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 818 { 819 unsigned long new_flags = p->flags; 820 821 new_flags &= ~PF_SUPERPRIV; 822 new_flags |= PF_FORKNOEXEC; 823 if (!(clone_flags & CLONE_PTRACE)) 824 p->ptrace = 0; 825 p->flags = new_flags; 826 } 827 828 asmlinkage long sys_set_tid_address(int __user *tidptr) 829 { 830 current->clear_child_tid = tidptr; 831 832 return current->pid; 833 } 834 835 /* 836 * This creates a new process as a copy of the old one, 837 * but does not actually start it yet. 838 * 839 * It copies the registers, and all the appropriate 840 * parts of the process environment (as per the clone 841 * flags). The actual kick-off is left to the caller. 842 */ 843 static task_t *copy_process(unsigned long clone_flags, 844 unsigned long stack_start, 845 struct pt_regs *regs, 846 unsigned long stack_size, 847 int __user *parent_tidptr, 848 int __user *child_tidptr, 849 int pid) 850 { 851 int retval; 852 struct task_struct *p = NULL; 853 854 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 855 return ERR_PTR(-EINVAL); 856 857 /* 858 * Thread groups must share signals as well, and detached threads 859 * can only be started up within the thread group. 860 */ 861 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 862 return ERR_PTR(-EINVAL); 863 864 /* 865 * Shared signal handlers imply shared VM. By way of the above, 866 * thread groups also imply shared VM. Blocking this case allows 867 * for various simplifications in other code. 868 */ 869 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 870 return ERR_PTR(-EINVAL); 871 872 retval = security_task_create(clone_flags); 873 if (retval) 874 goto fork_out; 875 876 retval = -ENOMEM; 877 p = dup_task_struct(current); 878 if (!p) 879 goto fork_out; 880 881 retval = -EAGAIN; 882 if (atomic_read(&p->user->processes) >= 883 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 884 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 885 p->user != &root_user) 886 goto bad_fork_free; 887 } 888 889 atomic_inc(&p->user->__count); 890 atomic_inc(&p->user->processes); 891 get_group_info(p->group_info); 892 893 /* 894 * If multiple threads are within copy_process(), then this check 895 * triggers too late. This doesn't hurt, the check is only there 896 * to stop root fork bombs. 897 */ 898 if (nr_threads >= max_threads) 899 goto bad_fork_cleanup_count; 900 901 if (!try_module_get(p->thread_info->exec_domain->module)) 902 goto bad_fork_cleanup_count; 903 904 if (p->binfmt && !try_module_get(p->binfmt->module)) 905 goto bad_fork_cleanup_put_domain; 906 907 p->did_exec = 0; 908 copy_flags(clone_flags, p); 909 p->pid = pid; 910 retval = -EFAULT; 911 if (clone_flags & CLONE_PARENT_SETTID) 912 if (put_user(p->pid, parent_tidptr)) 913 goto bad_fork_cleanup; 914 915 p->proc_dentry = NULL; 916 917 INIT_LIST_HEAD(&p->children); 918 INIT_LIST_HEAD(&p->sibling); 919 p->vfork_done = NULL; 920 spin_lock_init(&p->alloc_lock); 921 spin_lock_init(&p->proc_lock); 922 923 clear_tsk_thread_flag(p, TIF_SIGPENDING); 924 init_sigpending(&p->pending); 925 926 p->utime = cputime_zero; 927 p->stime = cputime_zero; 928 p->sched_time = 0; 929 p->rchar = 0; /* I/O counter: bytes read */ 930 p->wchar = 0; /* I/O counter: bytes written */ 931 p->syscr = 0; /* I/O counter: read syscalls */ 932 p->syscw = 0; /* I/O counter: write syscalls */ 933 acct_clear_integrals(p); 934 935 p->it_virt_expires = cputime_zero; 936 p->it_prof_expires = cputime_zero; 937 p->it_sched_expires = 0; 938 INIT_LIST_HEAD(&p->cpu_timers[0]); 939 INIT_LIST_HEAD(&p->cpu_timers[1]); 940 INIT_LIST_HEAD(&p->cpu_timers[2]); 941 942 p->lock_depth = -1; /* -1 = no lock */ 943 do_posix_clock_monotonic_gettime(&p->start_time); 944 p->security = NULL; 945 p->io_context = NULL; 946 p->io_wait = NULL; 947 p->audit_context = NULL; 948 #ifdef CONFIG_NUMA 949 p->mempolicy = mpol_copy(p->mempolicy); 950 if (IS_ERR(p->mempolicy)) { 951 retval = PTR_ERR(p->mempolicy); 952 p->mempolicy = NULL; 953 goto bad_fork_cleanup; 954 } 955 #endif 956 957 p->tgid = p->pid; 958 if (clone_flags & CLONE_THREAD) 959 p->tgid = current->tgid; 960 961 if ((retval = security_task_alloc(p))) 962 goto bad_fork_cleanup_policy; 963 if ((retval = audit_alloc(p))) 964 goto bad_fork_cleanup_security; 965 /* copy all the process information */ 966 if ((retval = copy_semundo(clone_flags, p))) 967 goto bad_fork_cleanup_audit; 968 if ((retval = copy_files(clone_flags, p))) 969 goto bad_fork_cleanup_semundo; 970 if ((retval = copy_fs(clone_flags, p))) 971 goto bad_fork_cleanup_files; 972 if ((retval = copy_sighand(clone_flags, p))) 973 goto bad_fork_cleanup_fs; 974 if ((retval = copy_signal(clone_flags, p))) 975 goto bad_fork_cleanup_sighand; 976 if ((retval = copy_mm(clone_flags, p))) 977 goto bad_fork_cleanup_signal; 978 if ((retval = copy_keys(clone_flags, p))) 979 goto bad_fork_cleanup_mm; 980 if ((retval = copy_namespace(clone_flags, p))) 981 goto bad_fork_cleanup_keys; 982 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 983 if (retval) 984 goto bad_fork_cleanup_namespace; 985 986 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 987 /* 988 * Clear TID on mm_release()? 989 */ 990 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 991 992 /* 993 * Syscall tracing should be turned off in the child regardless 994 * of CLONE_PTRACE. 995 */ 996 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 997 #ifdef TIF_SYSCALL_EMU 998 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 999 #endif 1000 1001 /* Our parent execution domain becomes current domain 1002 These must match for thread signalling to apply */ 1003 1004 p->parent_exec_id = p->self_exec_id; 1005 1006 /* ok, now we should be set up.. */ 1007 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1008 p->pdeath_signal = 0; 1009 p->exit_state = 0; 1010 1011 /* 1012 * Ok, make it visible to the rest of the system. 1013 * We dont wake it up yet. 1014 */ 1015 p->group_leader = p; 1016 INIT_LIST_HEAD(&p->ptrace_children); 1017 INIT_LIST_HEAD(&p->ptrace_list); 1018 1019 /* Perform scheduler related setup. Assign this task to a CPU. */ 1020 sched_fork(p, clone_flags); 1021 1022 /* Need tasklist lock for parent etc handling! */ 1023 write_lock_irq(&tasklist_lock); 1024 1025 /* 1026 * The task hasn't been attached yet, so its cpus_allowed mask will 1027 * not be changed, nor will its assigned CPU. 1028 * 1029 * The cpus_allowed mask of the parent may have changed after it was 1030 * copied first time - so re-copy it here, then check the child's CPU 1031 * to ensure it is on a valid CPU (and if not, just force it back to 1032 * parent's CPU). This avoids alot of nasty races. 1033 */ 1034 p->cpus_allowed = current->cpus_allowed; 1035 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed))) 1036 set_task_cpu(p, smp_processor_id()); 1037 1038 /* 1039 * Check for pending SIGKILL! The new thread should not be allowed 1040 * to slip out of an OOM kill. (or normal SIGKILL.) 1041 */ 1042 if (sigismember(¤t->pending.signal, SIGKILL)) { 1043 write_unlock_irq(&tasklist_lock); 1044 retval = -EINTR; 1045 goto bad_fork_cleanup_namespace; 1046 } 1047 1048 /* CLONE_PARENT re-uses the old parent */ 1049 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1050 p->real_parent = current->real_parent; 1051 else 1052 p->real_parent = current; 1053 p->parent = p->real_parent; 1054 1055 if (clone_flags & CLONE_THREAD) { 1056 spin_lock(¤t->sighand->siglock); 1057 /* 1058 * Important: if an exit-all has been started then 1059 * do not create this new thread - the whole thread 1060 * group is supposed to exit anyway. 1061 */ 1062 if (current->signal->flags & SIGNAL_GROUP_EXIT) { 1063 spin_unlock(¤t->sighand->siglock); 1064 write_unlock_irq(&tasklist_lock); 1065 retval = -EAGAIN; 1066 goto bad_fork_cleanup_namespace; 1067 } 1068 p->group_leader = current->group_leader; 1069 1070 if (current->signal->group_stop_count > 0) { 1071 /* 1072 * There is an all-stop in progress for the group. 1073 * We ourselves will stop as soon as we check signals. 1074 * Make the new thread part of that group stop too. 1075 */ 1076 current->signal->group_stop_count++; 1077 set_tsk_thread_flag(p, TIF_SIGPENDING); 1078 } 1079 1080 if (!cputime_eq(current->signal->it_virt_expires, 1081 cputime_zero) || 1082 !cputime_eq(current->signal->it_prof_expires, 1083 cputime_zero) || 1084 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1085 !list_empty(¤t->signal->cpu_timers[0]) || 1086 !list_empty(¤t->signal->cpu_timers[1]) || 1087 !list_empty(¤t->signal->cpu_timers[2])) { 1088 /* 1089 * Have child wake up on its first tick to check 1090 * for process CPU timers. 1091 */ 1092 p->it_prof_expires = jiffies_to_cputime(1); 1093 } 1094 1095 spin_unlock(¤t->sighand->siglock); 1096 } 1097 1098 /* 1099 * inherit ioprio 1100 */ 1101 p->ioprio = current->ioprio; 1102 1103 SET_LINKS(p); 1104 if (unlikely(p->ptrace & PT_PTRACED)) 1105 __ptrace_link(p, current->parent); 1106 1107 cpuset_fork(p); 1108 1109 attach_pid(p, PIDTYPE_PID, p->pid); 1110 attach_pid(p, PIDTYPE_TGID, p->tgid); 1111 if (thread_group_leader(p)) { 1112 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1113 attach_pid(p, PIDTYPE_SID, p->signal->session); 1114 if (p->pid) 1115 __get_cpu_var(process_counts)++; 1116 } 1117 1118 nr_threads++; 1119 total_forks++; 1120 write_unlock_irq(&tasklist_lock); 1121 retval = 0; 1122 1123 fork_out: 1124 if (retval) 1125 return ERR_PTR(retval); 1126 return p; 1127 1128 bad_fork_cleanup_namespace: 1129 exit_namespace(p); 1130 bad_fork_cleanup_keys: 1131 exit_keys(p); 1132 bad_fork_cleanup_mm: 1133 if (p->mm) 1134 mmput(p->mm); 1135 bad_fork_cleanup_signal: 1136 exit_signal(p); 1137 bad_fork_cleanup_sighand: 1138 exit_sighand(p); 1139 bad_fork_cleanup_fs: 1140 exit_fs(p); /* blocking */ 1141 bad_fork_cleanup_files: 1142 exit_files(p); /* blocking */ 1143 bad_fork_cleanup_semundo: 1144 exit_sem(p); 1145 bad_fork_cleanup_audit: 1146 audit_free(p); 1147 bad_fork_cleanup_security: 1148 security_task_free(p); 1149 bad_fork_cleanup_policy: 1150 #ifdef CONFIG_NUMA 1151 mpol_free(p->mempolicy); 1152 #endif 1153 bad_fork_cleanup: 1154 if (p->binfmt) 1155 module_put(p->binfmt->module); 1156 bad_fork_cleanup_put_domain: 1157 module_put(p->thread_info->exec_domain->module); 1158 bad_fork_cleanup_count: 1159 put_group_info(p->group_info); 1160 atomic_dec(&p->user->processes); 1161 free_uid(p->user); 1162 bad_fork_free: 1163 free_task(p); 1164 goto fork_out; 1165 } 1166 1167 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1168 { 1169 memset(regs, 0, sizeof(struct pt_regs)); 1170 return regs; 1171 } 1172 1173 task_t * __devinit fork_idle(int cpu) 1174 { 1175 task_t *task; 1176 struct pt_regs regs; 1177 1178 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1179 if (!task) 1180 return ERR_PTR(-ENOMEM); 1181 init_idle(task, cpu); 1182 unhash_process(task); 1183 return task; 1184 } 1185 1186 static inline int fork_traceflag (unsigned clone_flags) 1187 { 1188 if (clone_flags & CLONE_UNTRACED) 1189 return 0; 1190 else if (clone_flags & CLONE_VFORK) { 1191 if (current->ptrace & PT_TRACE_VFORK) 1192 return PTRACE_EVENT_VFORK; 1193 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1194 if (current->ptrace & PT_TRACE_CLONE) 1195 return PTRACE_EVENT_CLONE; 1196 } else if (current->ptrace & PT_TRACE_FORK) 1197 return PTRACE_EVENT_FORK; 1198 1199 return 0; 1200 } 1201 1202 /* 1203 * Ok, this is the main fork-routine. 1204 * 1205 * It copies the process, and if successful kick-starts 1206 * it and waits for it to finish using the VM if required. 1207 */ 1208 long do_fork(unsigned long clone_flags, 1209 unsigned long stack_start, 1210 struct pt_regs *regs, 1211 unsigned long stack_size, 1212 int __user *parent_tidptr, 1213 int __user *child_tidptr) 1214 { 1215 struct task_struct *p; 1216 int trace = 0; 1217 long pid = alloc_pidmap(); 1218 1219 if (pid < 0) 1220 return -EAGAIN; 1221 if (unlikely(current->ptrace)) { 1222 trace = fork_traceflag (clone_flags); 1223 if (trace) 1224 clone_flags |= CLONE_PTRACE; 1225 } 1226 1227 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid); 1228 /* 1229 * Do this prior waking up the new thread - the thread pointer 1230 * might get invalid after that point, if the thread exits quickly. 1231 */ 1232 if (!IS_ERR(p)) { 1233 struct completion vfork; 1234 1235 if (clone_flags & CLONE_VFORK) { 1236 p->vfork_done = &vfork; 1237 init_completion(&vfork); 1238 } 1239 1240 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1241 /* 1242 * We'll start up with an immediate SIGSTOP. 1243 */ 1244 sigaddset(&p->pending.signal, SIGSTOP); 1245 set_tsk_thread_flag(p, TIF_SIGPENDING); 1246 } 1247 1248 if (!(clone_flags & CLONE_STOPPED)) 1249 wake_up_new_task(p, clone_flags); 1250 else 1251 p->state = TASK_STOPPED; 1252 1253 if (unlikely (trace)) { 1254 current->ptrace_message = pid; 1255 ptrace_notify ((trace << 8) | SIGTRAP); 1256 } 1257 1258 if (clone_flags & CLONE_VFORK) { 1259 wait_for_completion(&vfork); 1260 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1261 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1262 } 1263 } else { 1264 free_pidmap(pid); 1265 pid = PTR_ERR(p); 1266 } 1267 return pid; 1268 } 1269 1270 void __init proc_caches_init(void) 1271 { 1272 sighand_cachep = kmem_cache_create("sighand_cache", 1273 sizeof(struct sighand_struct), 0, 1274 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1275 signal_cachep = kmem_cache_create("signal_cache", 1276 sizeof(struct signal_struct), 0, 1277 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1278 files_cachep = kmem_cache_create("files_cache", 1279 sizeof(struct files_struct), 0, 1280 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1281 fs_cachep = kmem_cache_create("fs_cache", 1282 sizeof(struct fs_struct), 0, 1283 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1284 vm_area_cachep = kmem_cache_create("vm_area_struct", 1285 sizeof(struct vm_area_struct), 0, 1286 SLAB_PANIC, NULL, NULL); 1287 mm_cachep = kmem_cache_create("mm_struct", 1288 sizeof(struct mm_struct), 0, 1289 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1290 } 1291