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/rcupdate.h> 39 #include <linux/ptrace.h> 40 #include <linux/mount.h> 41 #include <linux/audit.h> 42 #include <linux/profile.h> 43 #include <linux/rmap.h> 44 #include <linux/acct.h> 45 46 #include <asm/pgtable.h> 47 #include <asm/pgalloc.h> 48 #include <asm/uaccess.h> 49 #include <asm/mmu_context.h> 50 #include <asm/cacheflush.h> 51 #include <asm/tlbflush.h> 52 53 /* 54 * Protected counters by write_lock_irq(&tasklist_lock) 55 */ 56 unsigned long total_forks; /* Handle normal Linux uptimes. */ 57 int nr_threads; /* The idle threads do not count.. */ 58 59 int max_threads; /* tunable limit on nr_threads */ 60 61 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 62 63 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 64 65 EXPORT_SYMBOL(tasklist_lock); 66 67 int nr_processes(void) 68 { 69 int cpu; 70 int total = 0; 71 72 for_each_online_cpu(cpu) 73 total += per_cpu(process_counts, cpu); 74 75 return total; 76 } 77 78 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 79 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 80 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 81 static kmem_cache_t *task_struct_cachep; 82 #endif 83 84 /* SLAB cache for signal_struct structures (tsk->signal) */ 85 kmem_cache_t *signal_cachep; 86 87 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 88 kmem_cache_t *sighand_cachep; 89 90 /* SLAB cache for files_struct structures (tsk->files) */ 91 kmem_cache_t *files_cachep; 92 93 /* SLAB cache for fs_struct structures (tsk->fs) */ 94 kmem_cache_t *fs_cachep; 95 96 /* SLAB cache for vm_area_struct structures */ 97 kmem_cache_t *vm_area_cachep; 98 99 /* SLAB cache for mm_struct structures (tsk->mm) */ 100 static kmem_cache_t *mm_cachep; 101 102 void free_task(struct task_struct *tsk) 103 { 104 free_thread_info(tsk->thread_info); 105 free_task_struct(tsk); 106 } 107 EXPORT_SYMBOL(free_task); 108 109 void __put_task_struct(struct task_struct *tsk) 110 { 111 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 112 WARN_ON(atomic_read(&tsk->usage)); 113 WARN_ON(tsk == current); 114 115 if (unlikely(tsk->audit_context)) 116 audit_free(tsk); 117 security_task_free(tsk); 118 free_uid(tsk->user); 119 put_group_info(tsk->group_info); 120 121 if (!profile_handoff_task(tsk)) 122 free_task(tsk); 123 } 124 125 void __init fork_init(unsigned long mempages) 126 { 127 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 128 #ifndef ARCH_MIN_TASKALIGN 129 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 130 #endif 131 /* create a slab on which task_structs can be allocated */ 132 task_struct_cachep = 133 kmem_cache_create("task_struct", sizeof(struct task_struct), 134 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL); 135 #endif 136 137 /* 138 * The default maximum number of threads is set to a safe 139 * value: the thread structures can take up at most half 140 * of memory. 141 */ 142 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 143 144 /* 145 * we need to allow at least 20 threads to boot a system 146 */ 147 if(max_threads < 20) 148 max_threads = 20; 149 150 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 151 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 152 init_task.signal->rlim[RLIMIT_SIGPENDING] = 153 init_task.signal->rlim[RLIMIT_NPROC]; 154 } 155 156 static struct task_struct *dup_task_struct(struct task_struct *orig) 157 { 158 struct task_struct *tsk; 159 struct thread_info *ti; 160 161 prepare_to_copy(orig); 162 163 tsk = alloc_task_struct(); 164 if (!tsk) 165 return NULL; 166 167 ti = alloc_thread_info(tsk); 168 if (!ti) { 169 free_task_struct(tsk); 170 return NULL; 171 } 172 173 *ti = *orig->thread_info; 174 *tsk = *orig; 175 tsk->thread_info = ti; 176 ti->task = tsk; 177 178 /* One for us, one for whoever does the "release_task()" (usually parent) */ 179 atomic_set(&tsk->usage,2); 180 atomic_set(&tsk->fs_excl, 0); 181 return tsk; 182 } 183 184 #ifdef CONFIG_MMU 185 static inline int dup_mmap(struct mm_struct * mm, struct mm_struct * oldmm) 186 { 187 struct vm_area_struct * mpnt, *tmp, **pprev; 188 struct rb_node **rb_link, *rb_parent; 189 int retval; 190 unsigned long charge; 191 struct mempolicy *pol; 192 193 down_write(&oldmm->mmap_sem); 194 flush_cache_mm(current->mm); 195 mm->locked_vm = 0; 196 mm->mmap = NULL; 197 mm->mmap_cache = NULL; 198 mm->free_area_cache = oldmm->mmap_base; 199 mm->cached_hole_size = ~0UL; 200 mm->map_count = 0; 201 set_mm_counter(mm, rss, 0); 202 set_mm_counter(mm, anon_rss, 0); 203 cpus_clear(mm->cpu_vm_mask); 204 mm->mm_rb = RB_ROOT; 205 rb_link = &mm->mm_rb.rb_node; 206 rb_parent = NULL; 207 pprev = &mm->mmap; 208 209 for (mpnt = current->mm->mmap ; mpnt ; mpnt = mpnt->vm_next) { 210 struct file *file; 211 212 if (mpnt->vm_flags & VM_DONTCOPY) { 213 long pages = vma_pages(mpnt); 214 mm->total_vm -= pages; 215 __vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 216 -pages); 217 continue; 218 } 219 charge = 0; 220 if (mpnt->vm_flags & VM_ACCOUNT) { 221 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 222 if (security_vm_enough_memory(len)) 223 goto fail_nomem; 224 charge = len; 225 } 226 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 227 if (!tmp) 228 goto fail_nomem; 229 *tmp = *mpnt; 230 pol = mpol_copy(vma_policy(mpnt)); 231 retval = PTR_ERR(pol); 232 if (IS_ERR(pol)) 233 goto fail_nomem_policy; 234 vma_set_policy(tmp, pol); 235 tmp->vm_flags &= ~VM_LOCKED; 236 tmp->vm_mm = mm; 237 tmp->vm_next = NULL; 238 anon_vma_link(tmp); 239 file = tmp->vm_file; 240 if (file) { 241 struct inode *inode = file->f_dentry->d_inode; 242 get_file(file); 243 if (tmp->vm_flags & VM_DENYWRITE) 244 atomic_dec(&inode->i_writecount); 245 246 /* insert tmp into the share list, just after mpnt */ 247 spin_lock(&file->f_mapping->i_mmap_lock); 248 tmp->vm_truncate_count = mpnt->vm_truncate_count; 249 flush_dcache_mmap_lock(file->f_mapping); 250 vma_prio_tree_add(tmp, mpnt); 251 flush_dcache_mmap_unlock(file->f_mapping); 252 spin_unlock(&file->f_mapping->i_mmap_lock); 253 } 254 255 /* 256 * Link in the new vma and copy the page table entries: 257 * link in first so that swapoff can see swap entries. 258 * Note that, exceptionally, here the vma is inserted 259 * without holding mm->mmap_sem. 260 */ 261 spin_lock(&mm->page_table_lock); 262 *pprev = tmp; 263 pprev = &tmp->vm_next; 264 265 __vma_link_rb(mm, tmp, rb_link, rb_parent); 266 rb_link = &tmp->vm_rb.rb_right; 267 rb_parent = &tmp->vm_rb; 268 269 mm->map_count++; 270 retval = copy_page_range(mm, current->mm, tmp); 271 spin_unlock(&mm->page_table_lock); 272 273 if (tmp->vm_ops && tmp->vm_ops->open) 274 tmp->vm_ops->open(tmp); 275 276 if (retval) 277 goto out; 278 } 279 retval = 0; 280 281 out: 282 flush_tlb_mm(current->mm); 283 up_write(&oldmm->mmap_sem); 284 return retval; 285 fail_nomem_policy: 286 kmem_cache_free(vm_area_cachep, tmp); 287 fail_nomem: 288 retval = -ENOMEM; 289 vm_unacct_memory(charge); 290 goto out; 291 } 292 293 static inline int mm_alloc_pgd(struct mm_struct * mm) 294 { 295 mm->pgd = pgd_alloc(mm); 296 if (unlikely(!mm->pgd)) 297 return -ENOMEM; 298 return 0; 299 } 300 301 static inline void mm_free_pgd(struct mm_struct * mm) 302 { 303 pgd_free(mm->pgd); 304 } 305 #else 306 #define dup_mmap(mm, oldmm) (0) 307 #define mm_alloc_pgd(mm) (0) 308 #define mm_free_pgd(mm) 309 #endif /* CONFIG_MMU */ 310 311 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 312 313 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 314 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 315 316 #include <linux/init_task.h> 317 318 static struct mm_struct * mm_init(struct mm_struct * mm) 319 { 320 atomic_set(&mm->mm_users, 1); 321 atomic_set(&mm->mm_count, 1); 322 init_rwsem(&mm->mmap_sem); 323 INIT_LIST_HEAD(&mm->mmlist); 324 mm->core_waiters = 0; 325 mm->nr_ptes = 0; 326 spin_lock_init(&mm->page_table_lock); 327 rwlock_init(&mm->ioctx_list_lock); 328 mm->ioctx_list = NULL; 329 mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm); 330 mm->free_area_cache = TASK_UNMAPPED_BASE; 331 mm->cached_hole_size = ~0UL; 332 333 if (likely(!mm_alloc_pgd(mm))) { 334 mm->def_flags = 0; 335 return mm; 336 } 337 free_mm(mm); 338 return NULL; 339 } 340 341 /* 342 * Allocate and initialize an mm_struct. 343 */ 344 struct mm_struct * mm_alloc(void) 345 { 346 struct mm_struct * mm; 347 348 mm = allocate_mm(); 349 if (mm) { 350 memset(mm, 0, sizeof(*mm)); 351 mm = mm_init(mm); 352 } 353 return mm; 354 } 355 356 /* 357 * Called when the last reference to the mm 358 * is dropped: either by a lazy thread or by 359 * mmput. Free the page directory and the mm. 360 */ 361 void fastcall __mmdrop(struct mm_struct *mm) 362 { 363 BUG_ON(mm == &init_mm); 364 mm_free_pgd(mm); 365 destroy_context(mm); 366 free_mm(mm); 367 } 368 369 /* 370 * Decrement the use count and release all resources for an mm. 371 */ 372 void mmput(struct mm_struct *mm) 373 { 374 if (atomic_dec_and_test(&mm->mm_users)) { 375 exit_aio(mm); 376 exit_mmap(mm); 377 if (!list_empty(&mm->mmlist)) { 378 spin_lock(&mmlist_lock); 379 list_del(&mm->mmlist); 380 spin_unlock(&mmlist_lock); 381 } 382 put_swap_token(mm); 383 mmdrop(mm); 384 } 385 } 386 EXPORT_SYMBOL_GPL(mmput); 387 388 /** 389 * get_task_mm - acquire a reference to the task's mm 390 * 391 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 392 * this kernel workthread has transiently adopted a user mm with use_mm, 393 * to do its AIO) is not set and if so returns a reference to it, after 394 * bumping up the use count. User must release the mm via mmput() 395 * after use. Typically used by /proc and ptrace. 396 */ 397 struct mm_struct *get_task_mm(struct task_struct *task) 398 { 399 struct mm_struct *mm; 400 401 task_lock(task); 402 mm = task->mm; 403 if (mm) { 404 if (task->flags & PF_BORROWED_MM) 405 mm = NULL; 406 else 407 atomic_inc(&mm->mm_users); 408 } 409 task_unlock(task); 410 return mm; 411 } 412 EXPORT_SYMBOL_GPL(get_task_mm); 413 414 /* Please note the differences between mmput and mm_release. 415 * mmput is called whenever we stop holding onto a mm_struct, 416 * error success whatever. 417 * 418 * mm_release is called after a mm_struct has been removed 419 * from the current process. 420 * 421 * This difference is important for error handling, when we 422 * only half set up a mm_struct for a new process and need to restore 423 * the old one. Because we mmput the new mm_struct before 424 * restoring the old one. . . 425 * Eric Biederman 10 January 1998 426 */ 427 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 428 { 429 struct completion *vfork_done = tsk->vfork_done; 430 431 /* Get rid of any cached register state */ 432 deactivate_mm(tsk, mm); 433 434 /* notify parent sleeping on vfork() */ 435 if (vfork_done) { 436 tsk->vfork_done = NULL; 437 complete(vfork_done); 438 } 439 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { 440 u32 __user * tidptr = tsk->clear_child_tid; 441 tsk->clear_child_tid = NULL; 442 443 /* 444 * We don't check the error code - if userspace has 445 * not set up a proper pointer then tough luck. 446 */ 447 put_user(0, tidptr); 448 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 449 } 450 } 451 452 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 453 { 454 struct mm_struct * mm, *oldmm; 455 int retval; 456 457 tsk->min_flt = tsk->maj_flt = 0; 458 tsk->nvcsw = tsk->nivcsw = 0; 459 460 tsk->mm = NULL; 461 tsk->active_mm = NULL; 462 463 /* 464 * Are we cloning a kernel thread? 465 * 466 * We need to steal a active VM for that.. 467 */ 468 oldmm = current->mm; 469 if (!oldmm) 470 return 0; 471 472 if (clone_flags & CLONE_VM) { 473 atomic_inc(&oldmm->mm_users); 474 mm = oldmm; 475 /* 476 * There are cases where the PTL is held to ensure no 477 * new threads start up in user mode using an mm, which 478 * allows optimizing out ipis; the tlb_gather_mmu code 479 * is an example. 480 */ 481 spin_unlock_wait(&oldmm->page_table_lock); 482 goto good_mm; 483 } 484 485 retval = -ENOMEM; 486 mm = allocate_mm(); 487 if (!mm) 488 goto fail_nomem; 489 490 /* Copy the current MM stuff.. */ 491 memcpy(mm, oldmm, sizeof(*mm)); 492 if (!mm_init(mm)) 493 goto fail_nomem; 494 495 if (init_new_context(tsk,mm)) 496 goto fail_nocontext; 497 498 retval = dup_mmap(mm, oldmm); 499 if (retval) 500 goto free_pt; 501 502 mm->hiwater_rss = get_mm_counter(mm,rss); 503 mm->hiwater_vm = mm->total_vm; 504 505 good_mm: 506 tsk->mm = mm; 507 tsk->active_mm = mm; 508 return 0; 509 510 free_pt: 511 mmput(mm); 512 fail_nomem: 513 return retval; 514 515 fail_nocontext: 516 /* 517 * If init_new_context() failed, we cannot use mmput() to free the mm 518 * because it calls destroy_context() 519 */ 520 mm_free_pgd(mm); 521 free_mm(mm); 522 return retval; 523 } 524 525 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 526 { 527 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 528 /* We don't need to lock fs - think why ;-) */ 529 if (fs) { 530 atomic_set(&fs->count, 1); 531 rwlock_init(&fs->lock); 532 fs->umask = old->umask; 533 read_lock(&old->lock); 534 fs->rootmnt = mntget(old->rootmnt); 535 fs->root = dget(old->root); 536 fs->pwdmnt = mntget(old->pwdmnt); 537 fs->pwd = dget(old->pwd); 538 if (old->altroot) { 539 fs->altrootmnt = mntget(old->altrootmnt); 540 fs->altroot = dget(old->altroot); 541 } else { 542 fs->altrootmnt = NULL; 543 fs->altroot = NULL; 544 } 545 read_unlock(&old->lock); 546 } 547 return fs; 548 } 549 550 struct fs_struct *copy_fs_struct(struct fs_struct *old) 551 { 552 return __copy_fs_struct(old); 553 } 554 555 EXPORT_SYMBOL_GPL(copy_fs_struct); 556 557 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 558 { 559 if (clone_flags & CLONE_FS) { 560 atomic_inc(¤t->fs->count); 561 return 0; 562 } 563 tsk->fs = __copy_fs_struct(current->fs); 564 if (!tsk->fs) 565 return -ENOMEM; 566 return 0; 567 } 568 569 static int count_open_files(struct fdtable *fdt) 570 { 571 int size = fdt->max_fdset; 572 int i; 573 574 /* Find the last open fd */ 575 for (i = size/(8*sizeof(long)); i > 0; ) { 576 if (fdt->open_fds->fds_bits[--i]) 577 break; 578 } 579 i = (i+1) * 8 * sizeof(long); 580 return i; 581 } 582 583 static struct files_struct *alloc_files(void) 584 { 585 struct files_struct *newf; 586 struct fdtable *fdt; 587 588 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); 589 if (!newf) 590 goto out; 591 592 atomic_set(&newf->count, 1); 593 594 spin_lock_init(&newf->file_lock); 595 fdt = &newf->fdtab; 596 fdt->next_fd = 0; 597 fdt->max_fds = NR_OPEN_DEFAULT; 598 fdt->max_fdset = __FD_SETSIZE; 599 fdt->close_on_exec = &newf->close_on_exec_init; 600 fdt->open_fds = &newf->open_fds_init; 601 fdt->fd = &newf->fd_array[0]; 602 INIT_RCU_HEAD(&fdt->rcu); 603 fdt->free_files = NULL; 604 fdt->next = NULL; 605 rcu_assign_pointer(newf->fdt, fdt); 606 out: 607 return newf; 608 } 609 610 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 611 { 612 struct files_struct *oldf, *newf; 613 struct file **old_fds, **new_fds; 614 int open_files, size, i, error = 0, expand; 615 struct fdtable *old_fdt, *new_fdt; 616 617 /* 618 * A background process may not have any files ... 619 */ 620 oldf = current->files; 621 if (!oldf) 622 goto out; 623 624 if (clone_flags & CLONE_FILES) { 625 atomic_inc(&oldf->count); 626 goto out; 627 } 628 629 /* 630 * Note: we may be using current for both targets (See exec.c) 631 * This works because we cache current->files (old) as oldf. Don't 632 * break this. 633 */ 634 tsk->files = NULL; 635 error = -ENOMEM; 636 newf = alloc_files(); 637 if (!newf) 638 goto out; 639 640 spin_lock(&oldf->file_lock); 641 old_fdt = files_fdtable(oldf); 642 new_fdt = files_fdtable(newf); 643 size = old_fdt->max_fdset; 644 open_files = count_open_files(old_fdt); 645 expand = 0; 646 647 /* 648 * Check whether we need to allocate a larger fd array or fd set. 649 * Note: we're not a clone task, so the open count won't change. 650 */ 651 if (open_files > new_fdt->max_fdset) { 652 new_fdt->max_fdset = 0; 653 expand = 1; 654 } 655 if (open_files > new_fdt->max_fds) { 656 new_fdt->max_fds = 0; 657 expand = 1; 658 } 659 660 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 661 if (expand) { 662 spin_unlock(&oldf->file_lock); 663 spin_lock(&newf->file_lock); 664 error = expand_files(newf, open_files-1); 665 spin_unlock(&newf->file_lock); 666 if (error < 0) 667 goto out_release; 668 new_fdt = files_fdtable(newf); 669 /* 670 * Reacquire the oldf lock and a pointer to its fd table 671 * who knows it may have a new bigger fd table. We need 672 * the latest pointer. 673 */ 674 spin_lock(&oldf->file_lock); 675 old_fdt = files_fdtable(oldf); 676 } 677 678 old_fds = old_fdt->fd; 679 new_fds = new_fdt->fd; 680 681 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); 682 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); 683 684 for (i = open_files; i != 0; i--) { 685 struct file *f = *old_fds++; 686 if (f) { 687 get_file(f); 688 } else { 689 /* 690 * The fd may be claimed in the fd bitmap but not yet 691 * instantiated in the files array if a sibling thread 692 * is partway through open(). So make sure that this 693 * fd is available to the new process. 694 */ 695 FD_CLR(open_files - i, new_fdt->open_fds); 696 } 697 rcu_assign_pointer(*new_fds++, f); 698 } 699 spin_unlock(&oldf->file_lock); 700 701 /* compute the remainder to be cleared */ 702 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 703 704 /* This is long word aligned thus could use a optimized version */ 705 memset(new_fds, 0, size); 706 707 if (new_fdt->max_fdset > open_files) { 708 int left = (new_fdt->max_fdset-open_files)/8; 709 int start = open_files / (8 * sizeof(unsigned long)); 710 711 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 712 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 713 } 714 715 tsk->files = newf; 716 error = 0; 717 out: 718 return error; 719 720 out_release: 721 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); 722 free_fdset (new_fdt->open_fds, new_fdt->max_fdset); 723 free_fd_array(new_fdt->fd, new_fdt->max_fds); 724 kmem_cache_free(files_cachep, newf); 725 goto out; 726 } 727 728 /* 729 * Helper to unshare the files of the current task. 730 * We don't want to expose copy_files internals to 731 * the exec layer of the kernel. 732 */ 733 734 int unshare_files(void) 735 { 736 struct files_struct *files = current->files; 737 int rc; 738 739 if(!files) 740 BUG(); 741 742 /* This can race but the race causes us to copy when we don't 743 need to and drop the copy */ 744 if(atomic_read(&files->count) == 1) 745 { 746 atomic_inc(&files->count); 747 return 0; 748 } 749 rc = copy_files(0, current); 750 if(rc) 751 current->files = files; 752 return rc; 753 } 754 755 EXPORT_SYMBOL(unshare_files); 756 757 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 758 { 759 struct sighand_struct *sig; 760 761 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 762 atomic_inc(¤t->sighand->count); 763 return 0; 764 } 765 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 766 tsk->sighand = sig; 767 if (!sig) 768 return -ENOMEM; 769 spin_lock_init(&sig->siglock); 770 atomic_set(&sig->count, 1); 771 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 772 return 0; 773 } 774 775 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 776 { 777 struct signal_struct *sig; 778 int ret; 779 780 if (clone_flags & CLONE_THREAD) { 781 atomic_inc(¤t->signal->count); 782 atomic_inc(¤t->signal->live); 783 return 0; 784 } 785 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 786 tsk->signal = sig; 787 if (!sig) 788 return -ENOMEM; 789 790 ret = copy_thread_group_keys(tsk); 791 if (ret < 0) { 792 kmem_cache_free(signal_cachep, sig); 793 return ret; 794 } 795 796 atomic_set(&sig->count, 1); 797 atomic_set(&sig->live, 1); 798 init_waitqueue_head(&sig->wait_chldexit); 799 sig->flags = 0; 800 sig->group_exit_code = 0; 801 sig->group_exit_task = NULL; 802 sig->group_stop_count = 0; 803 sig->curr_target = NULL; 804 init_sigpending(&sig->shared_pending); 805 INIT_LIST_HEAD(&sig->posix_timers); 806 807 sig->it_real_value = sig->it_real_incr = 0; 808 sig->real_timer.function = it_real_fn; 809 sig->real_timer.data = (unsigned long) tsk; 810 init_timer(&sig->real_timer); 811 812 sig->it_virt_expires = cputime_zero; 813 sig->it_virt_incr = cputime_zero; 814 sig->it_prof_expires = cputime_zero; 815 sig->it_prof_incr = cputime_zero; 816 817 sig->tty = current->signal->tty; 818 sig->pgrp = process_group(current); 819 sig->session = current->signal->session; 820 sig->leader = 0; /* session leadership doesn't inherit */ 821 sig->tty_old_pgrp = 0; 822 823 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 824 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 825 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 826 sig->sched_time = 0; 827 INIT_LIST_HEAD(&sig->cpu_timers[0]); 828 INIT_LIST_HEAD(&sig->cpu_timers[1]); 829 INIT_LIST_HEAD(&sig->cpu_timers[2]); 830 831 task_lock(current->group_leader); 832 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 833 task_unlock(current->group_leader); 834 835 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 836 /* 837 * New sole thread in the process gets an expiry time 838 * of the whole CPU time limit. 839 */ 840 tsk->it_prof_expires = 841 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 842 } 843 844 return 0; 845 } 846 847 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 848 { 849 unsigned long new_flags = p->flags; 850 851 new_flags &= ~PF_SUPERPRIV; 852 new_flags |= PF_FORKNOEXEC; 853 if (!(clone_flags & CLONE_PTRACE)) 854 p->ptrace = 0; 855 p->flags = new_flags; 856 } 857 858 asmlinkage long sys_set_tid_address(int __user *tidptr) 859 { 860 current->clear_child_tid = tidptr; 861 862 return current->pid; 863 } 864 865 /* 866 * This creates a new process as a copy of the old one, 867 * but does not actually start it yet. 868 * 869 * It copies the registers, and all the appropriate 870 * parts of the process environment (as per the clone 871 * flags). The actual kick-off is left to the caller. 872 */ 873 static task_t *copy_process(unsigned long clone_flags, 874 unsigned long stack_start, 875 struct pt_regs *regs, 876 unsigned long stack_size, 877 int __user *parent_tidptr, 878 int __user *child_tidptr, 879 int pid) 880 { 881 int retval; 882 struct task_struct *p = NULL; 883 884 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 885 return ERR_PTR(-EINVAL); 886 887 /* 888 * Thread groups must share signals as well, and detached threads 889 * can only be started up within the thread group. 890 */ 891 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 892 return ERR_PTR(-EINVAL); 893 894 /* 895 * Shared signal handlers imply shared VM. By way of the above, 896 * thread groups also imply shared VM. Blocking this case allows 897 * for various simplifications in other code. 898 */ 899 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 900 return ERR_PTR(-EINVAL); 901 902 retval = security_task_create(clone_flags); 903 if (retval) 904 goto fork_out; 905 906 retval = -ENOMEM; 907 p = dup_task_struct(current); 908 if (!p) 909 goto fork_out; 910 911 retval = -EAGAIN; 912 if (atomic_read(&p->user->processes) >= 913 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 914 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 915 p->user != &root_user) 916 goto bad_fork_free; 917 } 918 919 atomic_inc(&p->user->__count); 920 atomic_inc(&p->user->processes); 921 get_group_info(p->group_info); 922 923 /* 924 * If multiple threads are within copy_process(), then this check 925 * triggers too late. This doesn't hurt, the check is only there 926 * to stop root fork bombs. 927 */ 928 if (nr_threads >= max_threads) 929 goto bad_fork_cleanup_count; 930 931 if (!try_module_get(p->thread_info->exec_domain->module)) 932 goto bad_fork_cleanup_count; 933 934 if (p->binfmt && !try_module_get(p->binfmt->module)) 935 goto bad_fork_cleanup_put_domain; 936 937 p->did_exec = 0; 938 copy_flags(clone_flags, p); 939 p->pid = pid; 940 retval = -EFAULT; 941 if (clone_flags & CLONE_PARENT_SETTID) 942 if (put_user(p->pid, parent_tidptr)) 943 goto bad_fork_cleanup; 944 945 p->proc_dentry = NULL; 946 947 INIT_LIST_HEAD(&p->children); 948 INIT_LIST_HEAD(&p->sibling); 949 p->vfork_done = NULL; 950 spin_lock_init(&p->alloc_lock); 951 spin_lock_init(&p->proc_lock); 952 953 clear_tsk_thread_flag(p, TIF_SIGPENDING); 954 init_sigpending(&p->pending); 955 956 p->utime = cputime_zero; 957 p->stime = cputime_zero; 958 p->sched_time = 0; 959 p->rchar = 0; /* I/O counter: bytes read */ 960 p->wchar = 0; /* I/O counter: bytes written */ 961 p->syscr = 0; /* I/O counter: read syscalls */ 962 p->syscw = 0; /* I/O counter: write syscalls */ 963 acct_clear_integrals(p); 964 965 p->it_virt_expires = cputime_zero; 966 p->it_prof_expires = cputime_zero; 967 p->it_sched_expires = 0; 968 INIT_LIST_HEAD(&p->cpu_timers[0]); 969 INIT_LIST_HEAD(&p->cpu_timers[1]); 970 INIT_LIST_HEAD(&p->cpu_timers[2]); 971 972 p->lock_depth = -1; /* -1 = no lock */ 973 do_posix_clock_monotonic_gettime(&p->start_time); 974 p->security = NULL; 975 p->io_context = NULL; 976 p->io_wait = NULL; 977 p->audit_context = NULL; 978 #ifdef CONFIG_NUMA 979 p->mempolicy = mpol_copy(p->mempolicy); 980 if (IS_ERR(p->mempolicy)) { 981 retval = PTR_ERR(p->mempolicy); 982 p->mempolicy = NULL; 983 goto bad_fork_cleanup; 984 } 985 #endif 986 987 p->tgid = p->pid; 988 if (clone_flags & CLONE_THREAD) 989 p->tgid = current->tgid; 990 991 if ((retval = security_task_alloc(p))) 992 goto bad_fork_cleanup_policy; 993 if ((retval = audit_alloc(p))) 994 goto bad_fork_cleanup_security; 995 /* copy all the process information */ 996 if ((retval = copy_semundo(clone_flags, p))) 997 goto bad_fork_cleanup_audit; 998 if ((retval = copy_files(clone_flags, p))) 999 goto bad_fork_cleanup_semundo; 1000 if ((retval = copy_fs(clone_flags, p))) 1001 goto bad_fork_cleanup_files; 1002 if ((retval = copy_sighand(clone_flags, p))) 1003 goto bad_fork_cleanup_fs; 1004 if ((retval = copy_signal(clone_flags, p))) 1005 goto bad_fork_cleanup_sighand; 1006 if ((retval = copy_mm(clone_flags, p))) 1007 goto bad_fork_cleanup_signal; 1008 if ((retval = copy_keys(clone_flags, p))) 1009 goto bad_fork_cleanup_mm; 1010 if ((retval = copy_namespace(clone_flags, p))) 1011 goto bad_fork_cleanup_keys; 1012 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1013 if (retval) 1014 goto bad_fork_cleanup_namespace; 1015 1016 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1017 /* 1018 * Clear TID on mm_release()? 1019 */ 1020 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1021 1022 /* 1023 * Syscall tracing should be turned off in the child regardless 1024 * of CLONE_PTRACE. 1025 */ 1026 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1027 #ifdef TIF_SYSCALL_EMU 1028 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1029 #endif 1030 1031 /* Our parent execution domain becomes current domain 1032 These must match for thread signalling to apply */ 1033 1034 p->parent_exec_id = p->self_exec_id; 1035 1036 /* ok, now we should be set up.. */ 1037 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1038 p->pdeath_signal = 0; 1039 p->exit_state = 0; 1040 1041 /* 1042 * Ok, make it visible to the rest of the system. 1043 * We dont wake it up yet. 1044 */ 1045 p->group_leader = p; 1046 INIT_LIST_HEAD(&p->ptrace_children); 1047 INIT_LIST_HEAD(&p->ptrace_list); 1048 1049 /* Perform scheduler related setup. Assign this task to a CPU. */ 1050 sched_fork(p, clone_flags); 1051 1052 /* Need tasklist lock for parent etc handling! */ 1053 write_lock_irq(&tasklist_lock); 1054 1055 /* 1056 * The task hasn't been attached yet, so its cpus_allowed mask will 1057 * not be changed, nor will its assigned CPU. 1058 * 1059 * The cpus_allowed mask of the parent may have changed after it was 1060 * copied first time - so re-copy it here, then check the child's CPU 1061 * to ensure it is on a valid CPU (and if not, just force it back to 1062 * parent's CPU). This avoids alot of nasty races. 1063 */ 1064 p->cpus_allowed = current->cpus_allowed; 1065 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1066 !cpu_online(task_cpu(p)))) 1067 set_task_cpu(p, smp_processor_id()); 1068 1069 /* 1070 * Check for pending SIGKILL! The new thread should not be allowed 1071 * to slip out of an OOM kill. (or normal SIGKILL.) 1072 */ 1073 if (sigismember(¤t->pending.signal, SIGKILL)) { 1074 write_unlock_irq(&tasklist_lock); 1075 retval = -EINTR; 1076 goto bad_fork_cleanup_namespace; 1077 } 1078 1079 /* CLONE_PARENT re-uses the old parent */ 1080 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1081 p->real_parent = current->real_parent; 1082 else 1083 p->real_parent = current; 1084 p->parent = p->real_parent; 1085 1086 if (clone_flags & CLONE_THREAD) { 1087 spin_lock(¤t->sighand->siglock); 1088 /* 1089 * Important: if an exit-all has been started then 1090 * do not create this new thread - the whole thread 1091 * group is supposed to exit anyway. 1092 */ 1093 if (current->signal->flags & SIGNAL_GROUP_EXIT) { 1094 spin_unlock(¤t->sighand->siglock); 1095 write_unlock_irq(&tasklist_lock); 1096 retval = -EAGAIN; 1097 goto bad_fork_cleanup_namespace; 1098 } 1099 p->group_leader = current->group_leader; 1100 1101 if (current->signal->group_stop_count > 0) { 1102 /* 1103 * There is an all-stop in progress for the group. 1104 * We ourselves will stop as soon as we check signals. 1105 * Make the new thread part of that group stop too. 1106 */ 1107 current->signal->group_stop_count++; 1108 set_tsk_thread_flag(p, TIF_SIGPENDING); 1109 } 1110 1111 if (!cputime_eq(current->signal->it_virt_expires, 1112 cputime_zero) || 1113 !cputime_eq(current->signal->it_prof_expires, 1114 cputime_zero) || 1115 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1116 !list_empty(¤t->signal->cpu_timers[0]) || 1117 !list_empty(¤t->signal->cpu_timers[1]) || 1118 !list_empty(¤t->signal->cpu_timers[2])) { 1119 /* 1120 * Have child wake up on its first tick to check 1121 * for process CPU timers. 1122 */ 1123 p->it_prof_expires = jiffies_to_cputime(1); 1124 } 1125 1126 spin_unlock(¤t->sighand->siglock); 1127 } 1128 1129 /* 1130 * inherit ioprio 1131 */ 1132 p->ioprio = current->ioprio; 1133 1134 SET_LINKS(p); 1135 if (unlikely(p->ptrace & PT_PTRACED)) 1136 __ptrace_link(p, current->parent); 1137 1138 cpuset_fork(p); 1139 1140 attach_pid(p, PIDTYPE_PID, p->pid); 1141 attach_pid(p, PIDTYPE_TGID, p->tgid); 1142 if (thread_group_leader(p)) { 1143 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1144 attach_pid(p, PIDTYPE_SID, p->signal->session); 1145 if (p->pid) 1146 __get_cpu_var(process_counts)++; 1147 } 1148 1149 if (!current->signal->tty && p->signal->tty) 1150 p->signal->tty = NULL; 1151 1152 nr_threads++; 1153 total_forks++; 1154 write_unlock_irq(&tasklist_lock); 1155 retval = 0; 1156 1157 fork_out: 1158 if (retval) 1159 return ERR_PTR(retval); 1160 return p; 1161 1162 bad_fork_cleanup_namespace: 1163 exit_namespace(p); 1164 bad_fork_cleanup_keys: 1165 exit_keys(p); 1166 bad_fork_cleanup_mm: 1167 if (p->mm) 1168 mmput(p->mm); 1169 bad_fork_cleanup_signal: 1170 exit_signal(p); 1171 bad_fork_cleanup_sighand: 1172 exit_sighand(p); 1173 bad_fork_cleanup_fs: 1174 exit_fs(p); /* blocking */ 1175 bad_fork_cleanup_files: 1176 exit_files(p); /* blocking */ 1177 bad_fork_cleanup_semundo: 1178 exit_sem(p); 1179 bad_fork_cleanup_audit: 1180 audit_free(p); 1181 bad_fork_cleanup_security: 1182 security_task_free(p); 1183 bad_fork_cleanup_policy: 1184 #ifdef CONFIG_NUMA 1185 mpol_free(p->mempolicy); 1186 #endif 1187 bad_fork_cleanup: 1188 if (p->binfmt) 1189 module_put(p->binfmt->module); 1190 bad_fork_cleanup_put_domain: 1191 module_put(p->thread_info->exec_domain->module); 1192 bad_fork_cleanup_count: 1193 put_group_info(p->group_info); 1194 atomic_dec(&p->user->processes); 1195 free_uid(p->user); 1196 bad_fork_free: 1197 free_task(p); 1198 goto fork_out; 1199 } 1200 1201 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1202 { 1203 memset(regs, 0, sizeof(struct pt_regs)); 1204 return regs; 1205 } 1206 1207 task_t * __devinit fork_idle(int cpu) 1208 { 1209 task_t *task; 1210 struct pt_regs regs; 1211 1212 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1213 if (!task) 1214 return ERR_PTR(-ENOMEM); 1215 init_idle(task, cpu); 1216 unhash_process(task); 1217 return task; 1218 } 1219 1220 static inline int fork_traceflag (unsigned clone_flags) 1221 { 1222 if (clone_flags & CLONE_UNTRACED) 1223 return 0; 1224 else if (clone_flags & CLONE_VFORK) { 1225 if (current->ptrace & PT_TRACE_VFORK) 1226 return PTRACE_EVENT_VFORK; 1227 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1228 if (current->ptrace & PT_TRACE_CLONE) 1229 return PTRACE_EVENT_CLONE; 1230 } else if (current->ptrace & PT_TRACE_FORK) 1231 return PTRACE_EVENT_FORK; 1232 1233 return 0; 1234 } 1235 1236 /* 1237 * Ok, this is the main fork-routine. 1238 * 1239 * It copies the process, and if successful kick-starts 1240 * it and waits for it to finish using the VM if required. 1241 */ 1242 long do_fork(unsigned long clone_flags, 1243 unsigned long stack_start, 1244 struct pt_regs *regs, 1245 unsigned long stack_size, 1246 int __user *parent_tidptr, 1247 int __user *child_tidptr) 1248 { 1249 struct task_struct *p; 1250 int trace = 0; 1251 long pid = alloc_pidmap(); 1252 1253 if (pid < 0) 1254 return -EAGAIN; 1255 if (unlikely(current->ptrace)) { 1256 trace = fork_traceflag (clone_flags); 1257 if (trace) 1258 clone_flags |= CLONE_PTRACE; 1259 } 1260 1261 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid); 1262 /* 1263 * Do this prior waking up the new thread - the thread pointer 1264 * might get invalid after that point, if the thread exits quickly. 1265 */ 1266 if (!IS_ERR(p)) { 1267 struct completion vfork; 1268 1269 if (clone_flags & CLONE_VFORK) { 1270 p->vfork_done = &vfork; 1271 init_completion(&vfork); 1272 } 1273 1274 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1275 /* 1276 * We'll start up with an immediate SIGSTOP. 1277 */ 1278 sigaddset(&p->pending.signal, SIGSTOP); 1279 set_tsk_thread_flag(p, TIF_SIGPENDING); 1280 } 1281 1282 if (!(clone_flags & CLONE_STOPPED)) 1283 wake_up_new_task(p, clone_flags); 1284 else 1285 p->state = TASK_STOPPED; 1286 1287 if (unlikely (trace)) { 1288 current->ptrace_message = pid; 1289 ptrace_notify ((trace << 8) | SIGTRAP); 1290 } 1291 1292 if (clone_flags & CLONE_VFORK) { 1293 wait_for_completion(&vfork); 1294 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1295 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1296 } 1297 } else { 1298 free_pidmap(pid); 1299 pid = PTR_ERR(p); 1300 } 1301 return pid; 1302 } 1303 1304 void __init proc_caches_init(void) 1305 { 1306 sighand_cachep = kmem_cache_create("sighand_cache", 1307 sizeof(struct sighand_struct), 0, 1308 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1309 signal_cachep = kmem_cache_create("signal_cache", 1310 sizeof(struct signal_struct), 0, 1311 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1312 files_cachep = kmem_cache_create("files_cache", 1313 sizeof(struct files_struct), 0, 1314 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1315 fs_cachep = kmem_cache_create("fs_cache", 1316 sizeof(struct fs_struct), 0, 1317 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1318 vm_area_cachep = kmem_cache_create("vm_area_struct", 1319 sizeof(struct vm_area_struct), 0, 1320 SLAB_PANIC, NULL, NULL); 1321 mm_cachep = kmem_cache_create("mm_struct", 1322 sizeof(struct mm_struct), 0, 1323 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1324 } 1325