1 /* 2 * mm/mmap.c 3 * 4 * Written by obz. 5 * 6 * Address space accounting code <alan@lxorguk.ukuu.org.uk> 7 */ 8 9 #include <linux/slab.h> 10 #include <linux/backing-dev.h> 11 #include <linux/mm.h> 12 #include <linux/shm.h> 13 #include <linux/mman.h> 14 #include <linux/pagemap.h> 15 #include <linux/swap.h> 16 #include <linux/syscalls.h> 17 #include <linux/capability.h> 18 #include <linux/init.h> 19 #include <linux/file.h> 20 #include <linux/fs.h> 21 #include <linux/personality.h> 22 #include <linux/security.h> 23 #include <linux/hugetlb.h> 24 #include <linux/profile.h> 25 #include <linux/module.h> 26 #include <linux/mount.h> 27 #include <linux/mempolicy.h> 28 #include <linux/rmap.h> 29 #include <linux/mmu_notifier.h> 30 #include <linux/perf_event.h> 31 32 #include <asm/uaccess.h> 33 #include <asm/cacheflush.h> 34 #include <asm/tlb.h> 35 #include <asm/mmu_context.h> 36 37 #include "internal.h" 38 39 #ifndef arch_mmap_check 40 #define arch_mmap_check(addr, len, flags) (0) 41 #endif 42 43 #ifndef arch_rebalance_pgtables 44 #define arch_rebalance_pgtables(addr, len) (addr) 45 #endif 46 47 static void unmap_region(struct mm_struct *mm, 48 struct vm_area_struct *vma, struct vm_area_struct *prev, 49 unsigned long start, unsigned long end); 50 51 /* 52 * WARNING: the debugging will use recursive algorithms so never enable this 53 * unless you know what you are doing. 54 */ 55 #undef DEBUG_MM_RB 56 57 /* description of effects of mapping type and prot in current implementation. 58 * this is due to the limited x86 page protection hardware. The expected 59 * behavior is in parens: 60 * 61 * map_type prot 62 * PROT_NONE PROT_READ PROT_WRITE PROT_EXEC 63 * MAP_SHARED r: (no) no r: (yes) yes r: (no) yes r: (no) yes 64 * w: (no) no w: (no) no w: (yes) yes w: (no) no 65 * x: (no) no x: (no) yes x: (no) yes x: (yes) yes 66 * 67 * MAP_PRIVATE r: (no) no r: (yes) yes r: (no) yes r: (no) yes 68 * w: (no) no w: (no) no w: (copy) copy w: (no) no 69 * x: (no) no x: (no) yes x: (no) yes x: (yes) yes 70 * 71 */ 72 pgprot_t protection_map[16] = { 73 __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111, 74 __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111 75 }; 76 77 pgprot_t vm_get_page_prot(unsigned long vm_flags) 78 { 79 return __pgprot(pgprot_val(protection_map[vm_flags & 80 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) | 81 pgprot_val(arch_vm_get_page_prot(vm_flags))); 82 } 83 EXPORT_SYMBOL(vm_get_page_prot); 84 85 int sysctl_overcommit_memory = OVERCOMMIT_GUESS; /* heuristic overcommit */ 86 int sysctl_overcommit_ratio = 50; /* default is 50% */ 87 int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT; 88 struct percpu_counter vm_committed_as; 89 90 /* 91 * Check that a process has enough memory to allocate a new virtual 92 * mapping. 0 means there is enough memory for the allocation to 93 * succeed and -ENOMEM implies there is not. 94 * 95 * We currently support three overcommit policies, which are set via the 96 * vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting 97 * 98 * Strict overcommit modes added 2002 Feb 26 by Alan Cox. 99 * Additional code 2002 Jul 20 by Robert Love. 100 * 101 * cap_sys_admin is 1 if the process has admin privileges, 0 otherwise. 102 * 103 * Note this is a helper function intended to be used by LSMs which 104 * wish to use this logic. 105 */ 106 int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) 107 { 108 unsigned long free, allowed; 109 110 vm_acct_memory(pages); 111 112 /* 113 * Sometimes we want to use more memory than we have 114 */ 115 if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS) 116 return 0; 117 118 if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) { 119 unsigned long n; 120 121 free = global_page_state(NR_FILE_PAGES); 122 free += nr_swap_pages; 123 124 /* 125 * Any slabs which are created with the 126 * SLAB_RECLAIM_ACCOUNT flag claim to have contents 127 * which are reclaimable, under pressure. The dentry 128 * cache and most inode caches should fall into this 129 */ 130 free += global_page_state(NR_SLAB_RECLAIMABLE); 131 132 /* 133 * Leave the last 3% for root 134 */ 135 if (!cap_sys_admin) 136 free -= free / 32; 137 138 if (free > pages) 139 return 0; 140 141 /* 142 * nr_free_pages() is very expensive on large systems, 143 * only call if we're about to fail. 144 */ 145 n = nr_free_pages(); 146 147 /* 148 * Leave reserved pages. The pages are not for anonymous pages. 149 */ 150 if (n <= totalreserve_pages) 151 goto error; 152 else 153 n -= totalreserve_pages; 154 155 /* 156 * Leave the last 3% for root 157 */ 158 if (!cap_sys_admin) 159 n -= n / 32; 160 free += n; 161 162 if (free > pages) 163 return 0; 164 165 goto error; 166 } 167 168 allowed = (totalram_pages - hugetlb_total_pages()) 169 * sysctl_overcommit_ratio / 100; 170 /* 171 * Leave the last 3% for root 172 */ 173 if (!cap_sys_admin) 174 allowed -= allowed / 32; 175 allowed += total_swap_pages; 176 177 /* Don't let a single process grow too big: 178 leave 3% of the size of this process for other processes */ 179 if (mm) 180 allowed -= mm->total_vm / 32; 181 182 if (percpu_counter_read_positive(&vm_committed_as) < allowed) 183 return 0; 184 error: 185 vm_unacct_memory(pages); 186 187 return -ENOMEM; 188 } 189 190 /* 191 * Requires inode->i_mapping->i_mmap_lock 192 */ 193 static void __remove_shared_vm_struct(struct vm_area_struct *vma, 194 struct file *file, struct address_space *mapping) 195 { 196 if (vma->vm_flags & VM_DENYWRITE) 197 atomic_inc(&file->f_path.dentry->d_inode->i_writecount); 198 if (vma->vm_flags & VM_SHARED) 199 mapping->i_mmap_writable--; 200 201 flush_dcache_mmap_lock(mapping); 202 if (unlikely(vma->vm_flags & VM_NONLINEAR)) 203 list_del_init(&vma->shared.vm_set.list); 204 else 205 vma_prio_tree_remove(vma, &mapping->i_mmap); 206 flush_dcache_mmap_unlock(mapping); 207 } 208 209 /* 210 * Unlink a file-based vm structure from its prio_tree, to hide 211 * vma from rmap and vmtruncate before freeing its page tables. 212 */ 213 void unlink_file_vma(struct vm_area_struct *vma) 214 { 215 struct file *file = vma->vm_file; 216 217 if (file) { 218 struct address_space *mapping = file->f_mapping; 219 spin_lock(&mapping->i_mmap_lock); 220 __remove_shared_vm_struct(vma, file, mapping); 221 spin_unlock(&mapping->i_mmap_lock); 222 } 223 } 224 225 /* 226 * Close a vm structure and free it, returning the next. 227 */ 228 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma) 229 { 230 struct vm_area_struct *next = vma->vm_next; 231 232 might_sleep(); 233 if (vma->vm_ops && vma->vm_ops->close) 234 vma->vm_ops->close(vma); 235 if (vma->vm_file) { 236 fput(vma->vm_file); 237 if (vma->vm_flags & VM_EXECUTABLE) 238 removed_exe_file_vma(vma->vm_mm); 239 } 240 mpol_put(vma_policy(vma)); 241 kmem_cache_free(vm_area_cachep, vma); 242 return next; 243 } 244 245 SYSCALL_DEFINE1(brk, unsigned long, brk) 246 { 247 unsigned long rlim, retval; 248 unsigned long newbrk, oldbrk; 249 struct mm_struct *mm = current->mm; 250 unsigned long min_brk; 251 252 down_write(&mm->mmap_sem); 253 254 #ifdef CONFIG_COMPAT_BRK 255 min_brk = mm->end_code; 256 #else 257 min_brk = mm->start_brk; 258 #endif 259 if (brk < min_brk) 260 goto out; 261 262 /* 263 * Check against rlimit here. If this check is done later after the test 264 * of oldbrk with newbrk then it can escape the test and let the data 265 * segment grow beyond its set limit the in case where the limit is 266 * not page aligned -Ram Gupta 267 */ 268 rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur; 269 if (rlim < RLIM_INFINITY && (brk - mm->start_brk) + 270 (mm->end_data - mm->start_data) > rlim) 271 goto out; 272 273 newbrk = PAGE_ALIGN(brk); 274 oldbrk = PAGE_ALIGN(mm->brk); 275 if (oldbrk == newbrk) 276 goto set_brk; 277 278 /* Always allow shrinking brk. */ 279 if (brk <= mm->brk) { 280 if (!do_munmap(mm, newbrk, oldbrk-newbrk)) 281 goto set_brk; 282 goto out; 283 } 284 285 /* Check against existing mmap mappings. */ 286 if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE)) 287 goto out; 288 289 /* Ok, looks good - let it rip. */ 290 if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk) 291 goto out; 292 set_brk: 293 mm->brk = brk; 294 out: 295 retval = mm->brk; 296 up_write(&mm->mmap_sem); 297 return retval; 298 } 299 300 #ifdef DEBUG_MM_RB 301 static int browse_rb(struct rb_root *root) 302 { 303 int i = 0, j; 304 struct rb_node *nd, *pn = NULL; 305 unsigned long prev = 0, pend = 0; 306 307 for (nd = rb_first(root); nd; nd = rb_next(nd)) { 308 struct vm_area_struct *vma; 309 vma = rb_entry(nd, struct vm_area_struct, vm_rb); 310 if (vma->vm_start < prev) 311 printk("vm_start %lx prev %lx\n", vma->vm_start, prev), i = -1; 312 if (vma->vm_start < pend) 313 printk("vm_start %lx pend %lx\n", vma->vm_start, pend); 314 if (vma->vm_start > vma->vm_end) 315 printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start); 316 i++; 317 pn = nd; 318 prev = vma->vm_start; 319 pend = vma->vm_end; 320 } 321 j = 0; 322 for (nd = pn; nd; nd = rb_prev(nd)) { 323 j++; 324 } 325 if (i != j) 326 printk("backwards %d, forwards %d\n", j, i), i = 0; 327 return i; 328 } 329 330 void validate_mm(struct mm_struct *mm) 331 { 332 int bug = 0; 333 int i = 0; 334 struct vm_area_struct *tmp = mm->mmap; 335 while (tmp) { 336 tmp = tmp->vm_next; 337 i++; 338 } 339 if (i != mm->map_count) 340 printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1; 341 i = browse_rb(&mm->mm_rb); 342 if (i != mm->map_count) 343 printk("map_count %d rb %d\n", mm->map_count, i), bug = 1; 344 BUG_ON(bug); 345 } 346 #else 347 #define validate_mm(mm) do { } while (0) 348 #endif 349 350 static struct vm_area_struct * 351 find_vma_prepare(struct mm_struct *mm, unsigned long addr, 352 struct vm_area_struct **pprev, struct rb_node ***rb_link, 353 struct rb_node ** rb_parent) 354 { 355 struct vm_area_struct * vma; 356 struct rb_node ** __rb_link, * __rb_parent, * rb_prev; 357 358 __rb_link = &mm->mm_rb.rb_node; 359 rb_prev = __rb_parent = NULL; 360 vma = NULL; 361 362 while (*__rb_link) { 363 struct vm_area_struct *vma_tmp; 364 365 __rb_parent = *__rb_link; 366 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb); 367 368 if (vma_tmp->vm_end > addr) { 369 vma = vma_tmp; 370 if (vma_tmp->vm_start <= addr) 371 break; 372 __rb_link = &__rb_parent->rb_left; 373 } else { 374 rb_prev = __rb_parent; 375 __rb_link = &__rb_parent->rb_right; 376 } 377 } 378 379 *pprev = NULL; 380 if (rb_prev) 381 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb); 382 *rb_link = __rb_link; 383 *rb_parent = __rb_parent; 384 return vma; 385 } 386 387 static inline void 388 __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma, 389 struct vm_area_struct *prev, struct rb_node *rb_parent) 390 { 391 if (prev) { 392 vma->vm_next = prev->vm_next; 393 prev->vm_next = vma; 394 } else { 395 mm->mmap = vma; 396 if (rb_parent) 397 vma->vm_next = rb_entry(rb_parent, 398 struct vm_area_struct, vm_rb); 399 else 400 vma->vm_next = NULL; 401 } 402 } 403 404 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma, 405 struct rb_node **rb_link, struct rb_node *rb_parent) 406 { 407 rb_link_node(&vma->vm_rb, rb_parent, rb_link); 408 rb_insert_color(&vma->vm_rb, &mm->mm_rb); 409 } 410 411 static void __vma_link_file(struct vm_area_struct *vma) 412 { 413 struct file *file; 414 415 file = vma->vm_file; 416 if (file) { 417 struct address_space *mapping = file->f_mapping; 418 419 if (vma->vm_flags & VM_DENYWRITE) 420 atomic_dec(&file->f_path.dentry->d_inode->i_writecount); 421 if (vma->vm_flags & VM_SHARED) 422 mapping->i_mmap_writable++; 423 424 flush_dcache_mmap_lock(mapping); 425 if (unlikely(vma->vm_flags & VM_NONLINEAR)) 426 vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear); 427 else 428 vma_prio_tree_insert(vma, &mapping->i_mmap); 429 flush_dcache_mmap_unlock(mapping); 430 } 431 } 432 433 static void 434 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma, 435 struct vm_area_struct *prev, struct rb_node **rb_link, 436 struct rb_node *rb_parent) 437 { 438 __vma_link_list(mm, vma, prev, rb_parent); 439 __vma_link_rb(mm, vma, rb_link, rb_parent); 440 __anon_vma_link(vma); 441 } 442 443 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma, 444 struct vm_area_struct *prev, struct rb_node **rb_link, 445 struct rb_node *rb_parent) 446 { 447 struct address_space *mapping = NULL; 448 449 if (vma->vm_file) 450 mapping = vma->vm_file->f_mapping; 451 452 if (mapping) { 453 spin_lock(&mapping->i_mmap_lock); 454 vma->vm_truncate_count = mapping->truncate_count; 455 } 456 anon_vma_lock(vma); 457 458 __vma_link(mm, vma, prev, rb_link, rb_parent); 459 __vma_link_file(vma); 460 461 anon_vma_unlock(vma); 462 if (mapping) 463 spin_unlock(&mapping->i_mmap_lock); 464 465 mm->map_count++; 466 validate_mm(mm); 467 } 468 469 /* 470 * Helper for vma_adjust in the split_vma insert case: 471 * insert vm structure into list and rbtree and anon_vma, 472 * but it has already been inserted into prio_tree earlier. 473 */ 474 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma) 475 { 476 struct vm_area_struct *__vma, *prev; 477 struct rb_node **rb_link, *rb_parent; 478 479 __vma = find_vma_prepare(mm, vma->vm_start,&prev, &rb_link, &rb_parent); 480 BUG_ON(__vma && __vma->vm_start < vma->vm_end); 481 __vma_link(mm, vma, prev, rb_link, rb_parent); 482 mm->map_count++; 483 } 484 485 static inline void 486 __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma, 487 struct vm_area_struct *prev) 488 { 489 prev->vm_next = vma->vm_next; 490 rb_erase(&vma->vm_rb, &mm->mm_rb); 491 if (mm->mmap_cache == vma) 492 mm->mmap_cache = prev; 493 } 494 495 /* 496 * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that 497 * is already present in an i_mmap tree without adjusting the tree. 498 * The following helper function should be used when such adjustments 499 * are necessary. The "insert" vma (if any) is to be inserted 500 * before we drop the necessary locks. 501 */ 502 void vma_adjust(struct vm_area_struct *vma, unsigned long start, 503 unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert) 504 { 505 struct mm_struct *mm = vma->vm_mm; 506 struct vm_area_struct *next = vma->vm_next; 507 struct vm_area_struct *importer = NULL; 508 struct address_space *mapping = NULL; 509 struct prio_tree_root *root = NULL; 510 struct file *file = vma->vm_file; 511 struct anon_vma *anon_vma = NULL; 512 long adjust_next = 0; 513 int remove_next = 0; 514 515 if (next && !insert) { 516 if (end >= next->vm_end) { 517 /* 518 * vma expands, overlapping all the next, and 519 * perhaps the one after too (mprotect case 6). 520 */ 521 again: remove_next = 1 + (end > next->vm_end); 522 end = next->vm_end; 523 anon_vma = next->anon_vma; 524 importer = vma; 525 } else if (end > next->vm_start) { 526 /* 527 * vma expands, overlapping part of the next: 528 * mprotect case 5 shifting the boundary up. 529 */ 530 adjust_next = (end - next->vm_start) >> PAGE_SHIFT; 531 anon_vma = next->anon_vma; 532 importer = vma; 533 } else if (end < vma->vm_end) { 534 /* 535 * vma shrinks, and !insert tells it's not 536 * split_vma inserting another: so it must be 537 * mprotect case 4 shifting the boundary down. 538 */ 539 adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT); 540 anon_vma = next->anon_vma; 541 importer = next; 542 } 543 } 544 545 if (file) { 546 mapping = file->f_mapping; 547 if (!(vma->vm_flags & VM_NONLINEAR)) 548 root = &mapping->i_mmap; 549 spin_lock(&mapping->i_mmap_lock); 550 if (importer && 551 vma->vm_truncate_count != next->vm_truncate_count) { 552 /* 553 * unmap_mapping_range might be in progress: 554 * ensure that the expanding vma is rescanned. 555 */ 556 importer->vm_truncate_count = 0; 557 } 558 if (insert) { 559 insert->vm_truncate_count = vma->vm_truncate_count; 560 /* 561 * Put into prio_tree now, so instantiated pages 562 * are visible to arm/parisc __flush_dcache_page 563 * throughout; but we cannot insert into address 564 * space until vma start or end is updated. 565 */ 566 __vma_link_file(insert); 567 } 568 } 569 570 /* 571 * When changing only vma->vm_end, we don't really need 572 * anon_vma lock. 573 */ 574 if (vma->anon_vma && (insert || importer || start != vma->vm_start)) 575 anon_vma = vma->anon_vma; 576 if (anon_vma) { 577 spin_lock(&anon_vma->lock); 578 /* 579 * Easily overlooked: when mprotect shifts the boundary, 580 * make sure the expanding vma has anon_vma set if the 581 * shrinking vma had, to cover any anon pages imported. 582 */ 583 if (importer && !importer->anon_vma) { 584 importer->anon_vma = anon_vma; 585 __anon_vma_link(importer); 586 } 587 } 588 589 if (root) { 590 flush_dcache_mmap_lock(mapping); 591 vma_prio_tree_remove(vma, root); 592 if (adjust_next) 593 vma_prio_tree_remove(next, root); 594 } 595 596 vma->vm_start = start; 597 vma->vm_end = end; 598 vma->vm_pgoff = pgoff; 599 if (adjust_next) { 600 next->vm_start += adjust_next << PAGE_SHIFT; 601 next->vm_pgoff += adjust_next; 602 } 603 604 if (root) { 605 if (adjust_next) 606 vma_prio_tree_insert(next, root); 607 vma_prio_tree_insert(vma, root); 608 flush_dcache_mmap_unlock(mapping); 609 } 610 611 if (remove_next) { 612 /* 613 * vma_merge has merged next into vma, and needs 614 * us to remove next before dropping the locks. 615 */ 616 __vma_unlink(mm, next, vma); 617 if (file) 618 __remove_shared_vm_struct(next, file, mapping); 619 if (next->anon_vma) 620 __anon_vma_merge(vma, next); 621 } else if (insert) { 622 /* 623 * split_vma has split insert from vma, and needs 624 * us to insert it before dropping the locks 625 * (it may either follow vma or precede it). 626 */ 627 __insert_vm_struct(mm, insert); 628 } 629 630 if (anon_vma) 631 spin_unlock(&anon_vma->lock); 632 if (mapping) 633 spin_unlock(&mapping->i_mmap_lock); 634 635 if (remove_next) { 636 if (file) { 637 fput(file); 638 if (next->vm_flags & VM_EXECUTABLE) 639 removed_exe_file_vma(mm); 640 } 641 mm->map_count--; 642 mpol_put(vma_policy(next)); 643 kmem_cache_free(vm_area_cachep, next); 644 /* 645 * In mprotect's case 6 (see comments on vma_merge), 646 * we must remove another next too. It would clutter 647 * up the code too much to do both in one go. 648 */ 649 if (remove_next == 2) { 650 next = vma->vm_next; 651 goto again; 652 } 653 } 654 655 validate_mm(mm); 656 } 657 658 /* 659 * If the vma has a ->close operation then the driver probably needs to release 660 * per-vma resources, so we don't attempt to merge those. 661 */ 662 static inline int is_mergeable_vma(struct vm_area_struct *vma, 663 struct file *file, unsigned long vm_flags) 664 { 665 /* VM_CAN_NONLINEAR may get set later by f_op->mmap() */ 666 if ((vma->vm_flags ^ vm_flags) & ~VM_CAN_NONLINEAR) 667 return 0; 668 if (vma->vm_file != file) 669 return 0; 670 if (vma->vm_ops && vma->vm_ops->close) 671 return 0; 672 return 1; 673 } 674 675 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1, 676 struct anon_vma *anon_vma2) 677 { 678 return !anon_vma1 || !anon_vma2 || (anon_vma1 == anon_vma2); 679 } 680 681 /* 682 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff) 683 * in front of (at a lower virtual address and file offset than) the vma. 684 * 685 * We cannot merge two vmas if they have differently assigned (non-NULL) 686 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible. 687 * 688 * We don't check here for the merged mmap wrapping around the end of pagecache 689 * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which 690 * wrap, nor mmaps which cover the final page at index -1UL. 691 */ 692 static int 693 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags, 694 struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff) 695 { 696 if (is_mergeable_vma(vma, file, vm_flags) && 697 is_mergeable_anon_vma(anon_vma, vma->anon_vma)) { 698 if (vma->vm_pgoff == vm_pgoff) 699 return 1; 700 } 701 return 0; 702 } 703 704 /* 705 * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff) 706 * beyond (at a higher virtual address and file offset than) the vma. 707 * 708 * We cannot merge two vmas if they have differently assigned (non-NULL) 709 * anon_vmas, nor if same anon_vma is assigned but offsets incompatible. 710 */ 711 static int 712 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags, 713 struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff) 714 { 715 if (is_mergeable_vma(vma, file, vm_flags) && 716 is_mergeable_anon_vma(anon_vma, vma->anon_vma)) { 717 pgoff_t vm_pglen; 718 vm_pglen = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; 719 if (vma->vm_pgoff + vm_pglen == vm_pgoff) 720 return 1; 721 } 722 return 0; 723 } 724 725 /* 726 * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out 727 * whether that can be merged with its predecessor or its successor. 728 * Or both (it neatly fills a hole). 729 * 730 * In most cases - when called for mmap, brk or mremap - [addr,end) is 731 * certain not to be mapped by the time vma_merge is called; but when 732 * called for mprotect, it is certain to be already mapped (either at 733 * an offset within prev, or at the start of next), and the flags of 734 * this area are about to be changed to vm_flags - and the no-change 735 * case has already been eliminated. 736 * 737 * The following mprotect cases have to be considered, where AAAA is 738 * the area passed down from mprotect_fixup, never extending beyond one 739 * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after: 740 * 741 * AAAA AAAA AAAA AAAA 742 * PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPNNNNNN PPPPNNNNXXXX 743 * cannot merge might become might become might become 744 * PPNNNNNNNNNN PPPPPPPPPPNN PPPPPPPPPPPP 6 or 745 * mmap, brk or case 4 below case 5 below PPPPPPPPXXXX 7 or 746 * mremap move: PPPPNNNNNNNN 8 747 * AAAA 748 * PPPP NNNN PPPPPPPPPPPP PPPPPPPPNNNN PPPPNNNNNNNN 749 * might become case 1 below case 2 below case 3 below 750 * 751 * Odd one out? Case 8, because it extends NNNN but needs flags of XXXX: 752 * mprotect_fixup updates vm_flags & vm_page_prot on successful return. 753 */ 754 struct vm_area_struct *vma_merge(struct mm_struct *mm, 755 struct vm_area_struct *prev, unsigned long addr, 756 unsigned long end, unsigned long vm_flags, 757 struct anon_vma *anon_vma, struct file *file, 758 pgoff_t pgoff, struct mempolicy *policy) 759 { 760 pgoff_t pglen = (end - addr) >> PAGE_SHIFT; 761 struct vm_area_struct *area, *next; 762 763 /* 764 * We later require that vma->vm_flags == vm_flags, 765 * so this tests vma->vm_flags & VM_SPECIAL, too. 766 */ 767 if (vm_flags & VM_SPECIAL) 768 return NULL; 769 770 if (prev) 771 next = prev->vm_next; 772 else 773 next = mm->mmap; 774 area = next; 775 if (next && next->vm_end == end) /* cases 6, 7, 8 */ 776 next = next->vm_next; 777 778 /* 779 * Can it merge with the predecessor? 780 */ 781 if (prev && prev->vm_end == addr && 782 mpol_equal(vma_policy(prev), policy) && 783 can_vma_merge_after(prev, vm_flags, 784 anon_vma, file, pgoff)) { 785 /* 786 * OK, it can. Can we now merge in the successor as well? 787 */ 788 if (next && end == next->vm_start && 789 mpol_equal(policy, vma_policy(next)) && 790 can_vma_merge_before(next, vm_flags, 791 anon_vma, file, pgoff+pglen) && 792 is_mergeable_anon_vma(prev->anon_vma, 793 next->anon_vma)) { 794 /* cases 1, 6 */ 795 vma_adjust(prev, prev->vm_start, 796 next->vm_end, prev->vm_pgoff, NULL); 797 } else /* cases 2, 5, 7 */ 798 vma_adjust(prev, prev->vm_start, 799 end, prev->vm_pgoff, NULL); 800 return prev; 801 } 802 803 /* 804 * Can this new request be merged in front of next? 805 */ 806 if (next && end == next->vm_start && 807 mpol_equal(policy, vma_policy(next)) && 808 can_vma_merge_before(next, vm_flags, 809 anon_vma, file, pgoff+pglen)) { 810 if (prev && addr < prev->vm_end) /* case 4 */ 811 vma_adjust(prev, prev->vm_start, 812 addr, prev->vm_pgoff, NULL); 813 else /* cases 3, 8 */ 814 vma_adjust(area, addr, next->vm_end, 815 next->vm_pgoff - pglen, NULL); 816 return area; 817 } 818 819 return NULL; 820 } 821 822 /* 823 * find_mergeable_anon_vma is used by anon_vma_prepare, to check 824 * neighbouring vmas for a suitable anon_vma, before it goes off 825 * to allocate a new anon_vma. It checks because a repetitive 826 * sequence of mprotects and faults may otherwise lead to distinct 827 * anon_vmas being allocated, preventing vma merge in subsequent 828 * mprotect. 829 */ 830 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma) 831 { 832 struct vm_area_struct *near; 833 unsigned long vm_flags; 834 835 near = vma->vm_next; 836 if (!near) 837 goto try_prev; 838 839 /* 840 * Since only mprotect tries to remerge vmas, match flags 841 * which might be mprotected into each other later on. 842 * Neither mlock nor madvise tries to remerge at present, 843 * so leave their flags as obstructing a merge. 844 */ 845 vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC); 846 vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC); 847 848 if (near->anon_vma && vma->vm_end == near->vm_start && 849 mpol_equal(vma_policy(vma), vma_policy(near)) && 850 can_vma_merge_before(near, vm_flags, 851 NULL, vma->vm_file, vma->vm_pgoff + 852 ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT))) 853 return near->anon_vma; 854 try_prev: 855 /* 856 * It is potentially slow to have to call find_vma_prev here. 857 * But it's only on the first write fault on the vma, not 858 * every time, and we could devise a way to avoid it later 859 * (e.g. stash info in next's anon_vma_node when assigning 860 * an anon_vma, or when trying vma_merge). Another time. 861 */ 862 BUG_ON(find_vma_prev(vma->vm_mm, vma->vm_start, &near) != vma); 863 if (!near) 864 goto none; 865 866 vm_flags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC); 867 vm_flags |= near->vm_flags & (VM_READ|VM_WRITE|VM_EXEC); 868 869 if (near->anon_vma && near->vm_end == vma->vm_start && 870 mpol_equal(vma_policy(near), vma_policy(vma)) && 871 can_vma_merge_after(near, vm_flags, 872 NULL, vma->vm_file, vma->vm_pgoff)) 873 return near->anon_vma; 874 none: 875 /* 876 * There's no absolute need to look only at touching neighbours: 877 * we could search further afield for "compatible" anon_vmas. 878 * But it would probably just be a waste of time searching, 879 * or lead to too many vmas hanging off the same anon_vma. 880 * We're trying to allow mprotect remerging later on, 881 * not trying to minimize memory used for anon_vmas. 882 */ 883 return NULL; 884 } 885 886 #ifdef CONFIG_PROC_FS 887 void vm_stat_account(struct mm_struct *mm, unsigned long flags, 888 struct file *file, long pages) 889 { 890 const unsigned long stack_flags 891 = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN); 892 893 if (file) { 894 mm->shared_vm += pages; 895 if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC) 896 mm->exec_vm += pages; 897 } else if (flags & stack_flags) 898 mm->stack_vm += pages; 899 if (flags & (VM_RESERVED|VM_IO)) 900 mm->reserved_vm += pages; 901 } 902 #endif /* CONFIG_PROC_FS */ 903 904 /* 905 * The caller must hold down_write(¤t->mm->mmap_sem). 906 */ 907 908 unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, 909 unsigned long len, unsigned long prot, 910 unsigned long flags, unsigned long pgoff) 911 { 912 struct mm_struct * mm = current->mm; 913 struct inode *inode; 914 unsigned int vm_flags; 915 int error; 916 unsigned long reqprot = prot; 917 918 /* 919 * Does the application expect PROT_READ to imply PROT_EXEC? 920 * 921 * (the exception is when the underlying filesystem is noexec 922 * mounted, in which case we dont add PROT_EXEC.) 923 */ 924 if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC)) 925 if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC))) 926 prot |= PROT_EXEC; 927 928 if (!len) 929 return -EINVAL; 930 931 if (!(flags & MAP_FIXED)) 932 addr = round_hint_to_min(addr); 933 934 /* Careful about overflows.. */ 935 len = PAGE_ALIGN(len); 936 if (!len) 937 return -ENOMEM; 938 939 /* offset overflow? */ 940 if ((pgoff + (len >> PAGE_SHIFT)) < pgoff) 941 return -EOVERFLOW; 942 943 /* Too many mappings? */ 944 if (mm->map_count > sysctl_max_map_count) 945 return -ENOMEM; 946 947 /* Obtain the address to map to. we verify (or select) it and ensure 948 * that it represents a valid section of the address space. 949 */ 950 addr = get_unmapped_area(file, addr, len, pgoff, flags); 951 if (addr & ~PAGE_MASK) 952 return addr; 953 954 /* Do simple checking here so the lower-level routines won't have 955 * to. we assume access permissions have been handled by the open 956 * of the memory object, so we don't do any here. 957 */ 958 vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) | 959 mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC; 960 961 if (flags & MAP_LOCKED) 962 if (!can_do_mlock()) 963 return -EPERM; 964 965 /* mlock MCL_FUTURE? */ 966 if (vm_flags & VM_LOCKED) { 967 unsigned long locked, lock_limit; 968 locked = len >> PAGE_SHIFT; 969 locked += mm->locked_vm; 970 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 971 lock_limit >>= PAGE_SHIFT; 972 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 973 return -EAGAIN; 974 } 975 976 inode = file ? file->f_path.dentry->d_inode : NULL; 977 978 if (file) { 979 switch (flags & MAP_TYPE) { 980 case MAP_SHARED: 981 if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE)) 982 return -EACCES; 983 984 /* 985 * Make sure we don't allow writing to an append-only 986 * file.. 987 */ 988 if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE)) 989 return -EACCES; 990 991 /* 992 * Make sure there are no mandatory locks on the file. 993 */ 994 if (locks_verify_locked(inode)) 995 return -EAGAIN; 996 997 vm_flags |= VM_SHARED | VM_MAYSHARE; 998 if (!(file->f_mode & FMODE_WRITE)) 999 vm_flags &= ~(VM_MAYWRITE | VM_SHARED); 1000 1001 /* fall through */ 1002 case MAP_PRIVATE: 1003 if (!(file->f_mode & FMODE_READ)) 1004 return -EACCES; 1005 if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) { 1006 if (vm_flags & VM_EXEC) 1007 return -EPERM; 1008 vm_flags &= ~VM_MAYEXEC; 1009 } 1010 1011 if (!file->f_op || !file->f_op->mmap) 1012 return -ENODEV; 1013 break; 1014 1015 default: 1016 return -EINVAL; 1017 } 1018 } else { 1019 switch (flags & MAP_TYPE) { 1020 case MAP_SHARED: 1021 /* 1022 * Ignore pgoff. 1023 */ 1024 pgoff = 0; 1025 vm_flags |= VM_SHARED | VM_MAYSHARE; 1026 break; 1027 case MAP_PRIVATE: 1028 /* 1029 * Set pgoff according to addr for anon_vma. 1030 */ 1031 pgoff = addr >> PAGE_SHIFT; 1032 break; 1033 default: 1034 return -EINVAL; 1035 } 1036 } 1037 1038 error = security_file_mmap(file, reqprot, prot, flags, addr, 0); 1039 if (error) 1040 return error; 1041 1042 return mmap_region(file, addr, len, flags, vm_flags, pgoff); 1043 } 1044 EXPORT_SYMBOL(do_mmap_pgoff); 1045 1046 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len, 1047 unsigned long, prot, unsigned long, flags, 1048 unsigned long, fd, unsigned long, pgoff) 1049 { 1050 struct file *file = NULL; 1051 unsigned long retval = -EBADF; 1052 1053 if (!(flags & MAP_ANONYMOUS)) { 1054 if (unlikely(flags & MAP_HUGETLB)) 1055 return -EINVAL; 1056 file = fget(fd); 1057 if (!file) 1058 goto out; 1059 } else if (flags & MAP_HUGETLB) { 1060 struct user_struct *user = NULL; 1061 /* 1062 * VM_NORESERVE is used because the reservations will be 1063 * taken when vm_ops->mmap() is called 1064 * A dummy user value is used because we are not locking 1065 * memory so no accounting is necessary 1066 */ 1067 len = ALIGN(len, huge_page_size(&default_hstate)); 1068 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len, VM_NORESERVE, 1069 &user, HUGETLB_ANONHUGE_INODE); 1070 if (IS_ERR(file)) 1071 return PTR_ERR(file); 1072 } 1073 1074 flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE); 1075 1076 down_write(¤t->mm->mmap_sem); 1077 retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff); 1078 up_write(¤t->mm->mmap_sem); 1079 1080 if (file) 1081 fput(file); 1082 out: 1083 return retval; 1084 } 1085 1086 /* 1087 * Some shared mappigns will want the pages marked read-only 1088 * to track write events. If so, we'll downgrade vm_page_prot 1089 * to the private version (using protection_map[] without the 1090 * VM_SHARED bit). 1091 */ 1092 int vma_wants_writenotify(struct vm_area_struct *vma) 1093 { 1094 unsigned int vm_flags = vma->vm_flags; 1095 1096 /* If it was private or non-writable, the write bit is already clear */ 1097 if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED))) 1098 return 0; 1099 1100 /* The backer wishes to know when pages are first written to? */ 1101 if (vma->vm_ops && vma->vm_ops->page_mkwrite) 1102 return 1; 1103 1104 /* The open routine did something to the protections already? */ 1105 if (pgprot_val(vma->vm_page_prot) != 1106 pgprot_val(vm_get_page_prot(vm_flags))) 1107 return 0; 1108 1109 /* Specialty mapping? */ 1110 if (vm_flags & (VM_PFNMAP|VM_INSERTPAGE)) 1111 return 0; 1112 1113 /* Can the mapping track the dirty pages? */ 1114 return vma->vm_file && vma->vm_file->f_mapping && 1115 mapping_cap_account_dirty(vma->vm_file->f_mapping); 1116 } 1117 1118 /* 1119 * We account for memory if it's a private writeable mapping, 1120 * not hugepages and VM_NORESERVE wasn't set. 1121 */ 1122 static inline int accountable_mapping(struct file *file, unsigned int vm_flags) 1123 { 1124 /* 1125 * hugetlb has its own accounting separate from the core VM 1126 * VM_HUGETLB may not be set yet so we cannot check for that flag. 1127 */ 1128 if (file && is_file_hugepages(file)) 1129 return 0; 1130 1131 return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE; 1132 } 1133 1134 unsigned long mmap_region(struct file *file, unsigned long addr, 1135 unsigned long len, unsigned long flags, 1136 unsigned int vm_flags, unsigned long pgoff) 1137 { 1138 struct mm_struct *mm = current->mm; 1139 struct vm_area_struct *vma, *prev; 1140 int correct_wcount = 0; 1141 int error; 1142 struct rb_node **rb_link, *rb_parent; 1143 unsigned long charged = 0; 1144 struct inode *inode = file ? file->f_path.dentry->d_inode : NULL; 1145 1146 /* Clear old maps */ 1147 error = -ENOMEM; 1148 munmap_back: 1149 vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent); 1150 if (vma && vma->vm_start < addr + len) { 1151 if (do_munmap(mm, addr, len)) 1152 return -ENOMEM; 1153 goto munmap_back; 1154 } 1155 1156 /* Check against address space limit. */ 1157 if (!may_expand_vm(mm, len >> PAGE_SHIFT)) 1158 return -ENOMEM; 1159 1160 /* 1161 * Set 'VM_NORESERVE' if we should not account for the 1162 * memory use of this mapping. 1163 */ 1164 if ((flags & MAP_NORESERVE)) { 1165 /* We honor MAP_NORESERVE if allowed to overcommit */ 1166 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER) 1167 vm_flags |= VM_NORESERVE; 1168 1169 /* hugetlb applies strict overcommit unless MAP_NORESERVE */ 1170 if (file && is_file_hugepages(file)) 1171 vm_flags |= VM_NORESERVE; 1172 } 1173 1174 /* 1175 * Private writable mapping: check memory availability 1176 */ 1177 if (accountable_mapping(file, vm_flags)) { 1178 charged = len >> PAGE_SHIFT; 1179 if (security_vm_enough_memory(charged)) 1180 return -ENOMEM; 1181 vm_flags |= VM_ACCOUNT; 1182 } 1183 1184 /* 1185 * Can we just expand an old mapping? 1186 */ 1187 vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL); 1188 if (vma) 1189 goto out; 1190 1191 /* 1192 * Determine the object being mapped and call the appropriate 1193 * specific mapper. the address has already been validated, but 1194 * not unmapped, but the maps are removed from the list. 1195 */ 1196 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 1197 if (!vma) { 1198 error = -ENOMEM; 1199 goto unacct_error; 1200 } 1201 1202 vma->vm_mm = mm; 1203 vma->vm_start = addr; 1204 vma->vm_end = addr + len; 1205 vma->vm_flags = vm_flags; 1206 vma->vm_page_prot = vm_get_page_prot(vm_flags); 1207 vma->vm_pgoff = pgoff; 1208 1209 if (file) { 1210 error = -EINVAL; 1211 if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP)) 1212 goto free_vma; 1213 if (vm_flags & VM_DENYWRITE) { 1214 error = deny_write_access(file); 1215 if (error) 1216 goto free_vma; 1217 correct_wcount = 1; 1218 } 1219 vma->vm_file = file; 1220 get_file(file); 1221 error = file->f_op->mmap(file, vma); 1222 if (error) 1223 goto unmap_and_free_vma; 1224 if (vm_flags & VM_EXECUTABLE) 1225 added_exe_file_vma(mm); 1226 1227 /* Can addr have changed?? 1228 * 1229 * Answer: Yes, several device drivers can do it in their 1230 * f_op->mmap method. -DaveM 1231 */ 1232 addr = vma->vm_start; 1233 pgoff = vma->vm_pgoff; 1234 vm_flags = vma->vm_flags; 1235 } else if (vm_flags & VM_SHARED) { 1236 error = shmem_zero_setup(vma); 1237 if (error) 1238 goto free_vma; 1239 } 1240 1241 if (vma_wants_writenotify(vma)) { 1242 pgprot_t pprot = vma->vm_page_prot; 1243 1244 /* Can vma->vm_page_prot have changed?? 1245 * 1246 * Answer: Yes, drivers may have changed it in their 1247 * f_op->mmap method. 1248 * 1249 * Ensures that vmas marked as uncached stay that way. 1250 */ 1251 vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED); 1252 if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot))) 1253 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); 1254 } 1255 1256 vma_link(mm, vma, prev, rb_link, rb_parent); 1257 file = vma->vm_file; 1258 1259 /* Once vma denies write, undo our temporary denial count */ 1260 if (correct_wcount) 1261 atomic_inc(&inode->i_writecount); 1262 out: 1263 perf_event_mmap(vma); 1264 1265 mm->total_vm += len >> PAGE_SHIFT; 1266 vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT); 1267 if (vm_flags & VM_LOCKED) { 1268 /* 1269 * makes pages present; downgrades, drops, reacquires mmap_sem 1270 */ 1271 long nr_pages = mlock_vma_pages_range(vma, addr, addr + len); 1272 if (nr_pages < 0) 1273 return nr_pages; /* vma gone! */ 1274 mm->locked_vm += (len >> PAGE_SHIFT) - nr_pages; 1275 } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK)) 1276 make_pages_present(addr, addr + len); 1277 return addr; 1278 1279 unmap_and_free_vma: 1280 if (correct_wcount) 1281 atomic_inc(&inode->i_writecount); 1282 vma->vm_file = NULL; 1283 fput(file); 1284 1285 /* Undo any partial mapping done by a device driver. */ 1286 unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end); 1287 charged = 0; 1288 free_vma: 1289 kmem_cache_free(vm_area_cachep, vma); 1290 unacct_error: 1291 if (charged) 1292 vm_unacct_memory(charged); 1293 return error; 1294 } 1295 1296 /* Get an address range which is currently unmapped. 1297 * For shmat() with addr=0. 1298 * 1299 * Ugly calling convention alert: 1300 * Return value with the low bits set means error value, 1301 * ie 1302 * if (ret & ~PAGE_MASK) 1303 * error = ret; 1304 * 1305 * This function "knows" that -ENOMEM has the bits set. 1306 */ 1307 #ifndef HAVE_ARCH_UNMAPPED_AREA 1308 unsigned long 1309 arch_get_unmapped_area(struct file *filp, unsigned long addr, 1310 unsigned long len, unsigned long pgoff, unsigned long flags) 1311 { 1312 struct mm_struct *mm = current->mm; 1313 struct vm_area_struct *vma; 1314 unsigned long start_addr; 1315 1316 if (len > TASK_SIZE) 1317 return -ENOMEM; 1318 1319 if (flags & MAP_FIXED) 1320 return addr; 1321 1322 if (addr) { 1323 addr = PAGE_ALIGN(addr); 1324 vma = find_vma(mm, addr); 1325 if (TASK_SIZE - len >= addr && 1326 (!vma || addr + len <= vma->vm_start)) 1327 return addr; 1328 } 1329 if (len > mm->cached_hole_size) { 1330 start_addr = addr = mm->free_area_cache; 1331 } else { 1332 start_addr = addr = TASK_UNMAPPED_BASE; 1333 mm->cached_hole_size = 0; 1334 } 1335 1336 full_search: 1337 for (vma = find_vma(mm, addr); ; vma = vma->vm_next) { 1338 /* At this point: (!vma || addr < vma->vm_end). */ 1339 if (TASK_SIZE - len < addr) { 1340 /* 1341 * Start a new search - just in case we missed 1342 * some holes. 1343 */ 1344 if (start_addr != TASK_UNMAPPED_BASE) { 1345 addr = TASK_UNMAPPED_BASE; 1346 start_addr = addr; 1347 mm->cached_hole_size = 0; 1348 goto full_search; 1349 } 1350 return -ENOMEM; 1351 } 1352 if (!vma || addr + len <= vma->vm_start) { 1353 /* 1354 * Remember the place where we stopped the search: 1355 */ 1356 mm->free_area_cache = addr + len; 1357 return addr; 1358 } 1359 if (addr + mm->cached_hole_size < vma->vm_start) 1360 mm->cached_hole_size = vma->vm_start - addr; 1361 addr = vma->vm_end; 1362 } 1363 } 1364 #endif 1365 1366 void arch_unmap_area(struct mm_struct *mm, unsigned long addr) 1367 { 1368 /* 1369 * Is this a new hole at the lowest possible address? 1370 */ 1371 if (addr >= TASK_UNMAPPED_BASE && addr < mm->free_area_cache) { 1372 mm->free_area_cache = addr; 1373 mm->cached_hole_size = ~0UL; 1374 } 1375 } 1376 1377 /* 1378 * This mmap-allocator allocates new areas top-down from below the 1379 * stack's low limit (the base): 1380 */ 1381 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN 1382 unsigned long 1383 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 1384 const unsigned long len, const unsigned long pgoff, 1385 const unsigned long flags) 1386 { 1387 struct vm_area_struct *vma; 1388 struct mm_struct *mm = current->mm; 1389 unsigned long addr = addr0; 1390 1391 /* requested length too big for entire address space */ 1392 if (len > TASK_SIZE) 1393 return -ENOMEM; 1394 1395 if (flags & MAP_FIXED) 1396 return addr; 1397 1398 /* requesting a specific address */ 1399 if (addr) { 1400 addr = PAGE_ALIGN(addr); 1401 vma = find_vma(mm, addr); 1402 if (TASK_SIZE - len >= addr && 1403 (!vma || addr + len <= vma->vm_start)) 1404 return addr; 1405 } 1406 1407 /* check if free_area_cache is useful for us */ 1408 if (len <= mm->cached_hole_size) { 1409 mm->cached_hole_size = 0; 1410 mm->free_area_cache = mm->mmap_base; 1411 } 1412 1413 /* either no address requested or can't fit in requested address hole */ 1414 addr = mm->free_area_cache; 1415 1416 /* make sure it can fit in the remaining address space */ 1417 if (addr > len) { 1418 vma = find_vma(mm, addr-len); 1419 if (!vma || addr <= vma->vm_start) 1420 /* remember the address as a hint for next time */ 1421 return (mm->free_area_cache = addr-len); 1422 } 1423 1424 if (mm->mmap_base < len) 1425 goto bottomup; 1426 1427 addr = mm->mmap_base-len; 1428 1429 do { 1430 /* 1431 * Lookup failure means no vma is above this address, 1432 * else if new region fits below vma->vm_start, 1433 * return with success: 1434 */ 1435 vma = find_vma(mm, addr); 1436 if (!vma || addr+len <= vma->vm_start) 1437 /* remember the address as a hint for next time */ 1438 return (mm->free_area_cache = addr); 1439 1440 /* remember the largest hole we saw so far */ 1441 if (addr + mm->cached_hole_size < vma->vm_start) 1442 mm->cached_hole_size = vma->vm_start - addr; 1443 1444 /* try just below the current vma->vm_start */ 1445 addr = vma->vm_start-len; 1446 } while (len < vma->vm_start); 1447 1448 bottomup: 1449 /* 1450 * A failed mmap() very likely causes application failure, 1451 * so fall back to the bottom-up function here. This scenario 1452 * can happen with large stack limits and large mmap() 1453 * allocations. 1454 */ 1455 mm->cached_hole_size = ~0UL; 1456 mm->free_area_cache = TASK_UNMAPPED_BASE; 1457 addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags); 1458 /* 1459 * Restore the topdown base: 1460 */ 1461 mm->free_area_cache = mm->mmap_base; 1462 mm->cached_hole_size = ~0UL; 1463 1464 return addr; 1465 } 1466 #endif 1467 1468 void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr) 1469 { 1470 /* 1471 * Is this a new hole at the highest possible address? 1472 */ 1473 if (addr > mm->free_area_cache) 1474 mm->free_area_cache = addr; 1475 1476 /* dont allow allocations above current base */ 1477 if (mm->free_area_cache > mm->mmap_base) 1478 mm->free_area_cache = mm->mmap_base; 1479 } 1480 1481 unsigned long 1482 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, 1483 unsigned long pgoff, unsigned long flags) 1484 { 1485 unsigned long (*get_area)(struct file *, unsigned long, 1486 unsigned long, unsigned long, unsigned long); 1487 1488 unsigned long error = arch_mmap_check(addr, len, flags); 1489 if (error) 1490 return error; 1491 1492 /* Careful about overflows.. */ 1493 if (len > TASK_SIZE) 1494 return -ENOMEM; 1495 1496 get_area = current->mm->get_unmapped_area; 1497 if (file && file->f_op && file->f_op->get_unmapped_area) 1498 get_area = file->f_op->get_unmapped_area; 1499 addr = get_area(file, addr, len, pgoff, flags); 1500 if (IS_ERR_VALUE(addr)) 1501 return addr; 1502 1503 if (addr > TASK_SIZE - len) 1504 return -ENOMEM; 1505 if (addr & ~PAGE_MASK) 1506 return -EINVAL; 1507 1508 return arch_rebalance_pgtables(addr, len); 1509 } 1510 1511 EXPORT_SYMBOL(get_unmapped_area); 1512 1513 /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */ 1514 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) 1515 { 1516 struct vm_area_struct *vma = NULL; 1517 1518 if (mm) { 1519 /* Check the cache first. */ 1520 /* (Cache hit rate is typically around 35%.) */ 1521 vma = mm->mmap_cache; 1522 if (!(vma && vma->vm_end > addr && vma->vm_start <= addr)) { 1523 struct rb_node * rb_node; 1524 1525 rb_node = mm->mm_rb.rb_node; 1526 vma = NULL; 1527 1528 while (rb_node) { 1529 struct vm_area_struct * vma_tmp; 1530 1531 vma_tmp = rb_entry(rb_node, 1532 struct vm_area_struct, vm_rb); 1533 1534 if (vma_tmp->vm_end > addr) { 1535 vma = vma_tmp; 1536 if (vma_tmp->vm_start <= addr) 1537 break; 1538 rb_node = rb_node->rb_left; 1539 } else 1540 rb_node = rb_node->rb_right; 1541 } 1542 if (vma) 1543 mm->mmap_cache = vma; 1544 } 1545 } 1546 return vma; 1547 } 1548 1549 EXPORT_SYMBOL(find_vma); 1550 1551 /* Same as find_vma, but also return a pointer to the previous VMA in *pprev. */ 1552 struct vm_area_struct * 1553 find_vma_prev(struct mm_struct *mm, unsigned long addr, 1554 struct vm_area_struct **pprev) 1555 { 1556 struct vm_area_struct *vma = NULL, *prev = NULL; 1557 struct rb_node *rb_node; 1558 if (!mm) 1559 goto out; 1560 1561 /* Guard against addr being lower than the first VMA */ 1562 vma = mm->mmap; 1563 1564 /* Go through the RB tree quickly. */ 1565 rb_node = mm->mm_rb.rb_node; 1566 1567 while (rb_node) { 1568 struct vm_area_struct *vma_tmp; 1569 vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb); 1570 1571 if (addr < vma_tmp->vm_end) { 1572 rb_node = rb_node->rb_left; 1573 } else { 1574 prev = vma_tmp; 1575 if (!prev->vm_next || (addr < prev->vm_next->vm_end)) 1576 break; 1577 rb_node = rb_node->rb_right; 1578 } 1579 } 1580 1581 out: 1582 *pprev = prev; 1583 return prev ? prev->vm_next : vma; 1584 } 1585 1586 /* 1587 * Verify that the stack growth is acceptable and 1588 * update accounting. This is shared with both the 1589 * grow-up and grow-down cases. 1590 */ 1591 static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow) 1592 { 1593 struct mm_struct *mm = vma->vm_mm; 1594 struct rlimit *rlim = current->signal->rlim; 1595 unsigned long new_start; 1596 1597 /* address space limit tests */ 1598 if (!may_expand_vm(mm, grow)) 1599 return -ENOMEM; 1600 1601 /* Stack limit test */ 1602 if (size > rlim[RLIMIT_STACK].rlim_cur) 1603 return -ENOMEM; 1604 1605 /* mlock limit tests */ 1606 if (vma->vm_flags & VM_LOCKED) { 1607 unsigned long locked; 1608 unsigned long limit; 1609 locked = mm->locked_vm + grow; 1610 limit = rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT; 1611 if (locked > limit && !capable(CAP_IPC_LOCK)) 1612 return -ENOMEM; 1613 } 1614 1615 /* Check to ensure the stack will not grow into a hugetlb-only region */ 1616 new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start : 1617 vma->vm_end - size; 1618 if (is_hugepage_only_range(vma->vm_mm, new_start, size)) 1619 return -EFAULT; 1620 1621 /* 1622 * Overcommit.. This must be the final test, as it will 1623 * update security statistics. 1624 */ 1625 if (security_vm_enough_memory_mm(mm, grow)) 1626 return -ENOMEM; 1627 1628 /* Ok, everything looks good - let it rip */ 1629 mm->total_vm += grow; 1630 if (vma->vm_flags & VM_LOCKED) 1631 mm->locked_vm += grow; 1632 vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow); 1633 return 0; 1634 } 1635 1636 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64) 1637 /* 1638 * PA-RISC uses this for its stack; IA64 for its Register Backing Store. 1639 * vma is the last one with address > vma->vm_end. Have to extend vma. 1640 */ 1641 #ifndef CONFIG_IA64 1642 static 1643 #endif 1644 int expand_upwards(struct vm_area_struct *vma, unsigned long address) 1645 { 1646 int error; 1647 1648 if (!(vma->vm_flags & VM_GROWSUP)) 1649 return -EFAULT; 1650 1651 /* 1652 * We must make sure the anon_vma is allocated 1653 * so that the anon_vma locking is not a noop. 1654 */ 1655 if (unlikely(anon_vma_prepare(vma))) 1656 return -ENOMEM; 1657 anon_vma_lock(vma); 1658 1659 /* 1660 * vma->vm_start/vm_end cannot change under us because the caller 1661 * is required to hold the mmap_sem in read mode. We need the 1662 * anon_vma lock to serialize against concurrent expand_stacks. 1663 * Also guard against wrapping around to address 0. 1664 */ 1665 if (address < PAGE_ALIGN(address+4)) 1666 address = PAGE_ALIGN(address+4); 1667 else { 1668 anon_vma_unlock(vma); 1669 return -ENOMEM; 1670 } 1671 error = 0; 1672 1673 /* Somebody else might have raced and expanded it already */ 1674 if (address > vma->vm_end) { 1675 unsigned long size, grow; 1676 1677 size = address - vma->vm_start; 1678 grow = (address - vma->vm_end) >> PAGE_SHIFT; 1679 1680 error = acct_stack_growth(vma, size, grow); 1681 if (!error) 1682 vma->vm_end = address; 1683 } 1684 anon_vma_unlock(vma); 1685 return error; 1686 } 1687 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */ 1688 1689 /* 1690 * vma is the first one with address < vma->vm_start. Have to extend vma. 1691 */ 1692 static int expand_downwards(struct vm_area_struct *vma, 1693 unsigned long address) 1694 { 1695 int error; 1696 1697 /* 1698 * We must make sure the anon_vma is allocated 1699 * so that the anon_vma locking is not a noop. 1700 */ 1701 if (unlikely(anon_vma_prepare(vma))) 1702 return -ENOMEM; 1703 1704 address &= PAGE_MASK; 1705 error = security_file_mmap(NULL, 0, 0, 0, address, 1); 1706 if (error) 1707 return error; 1708 1709 anon_vma_lock(vma); 1710 1711 /* 1712 * vma->vm_start/vm_end cannot change under us because the caller 1713 * is required to hold the mmap_sem in read mode. We need the 1714 * anon_vma lock to serialize against concurrent expand_stacks. 1715 */ 1716 1717 /* Somebody else might have raced and expanded it already */ 1718 if (address < vma->vm_start) { 1719 unsigned long size, grow; 1720 1721 size = vma->vm_end - address; 1722 grow = (vma->vm_start - address) >> PAGE_SHIFT; 1723 1724 error = acct_stack_growth(vma, size, grow); 1725 if (!error) { 1726 vma->vm_start = address; 1727 vma->vm_pgoff -= grow; 1728 } 1729 } 1730 anon_vma_unlock(vma); 1731 return error; 1732 } 1733 1734 int expand_stack_downwards(struct vm_area_struct *vma, unsigned long address) 1735 { 1736 return expand_downwards(vma, address); 1737 } 1738 1739 #ifdef CONFIG_STACK_GROWSUP 1740 int expand_stack(struct vm_area_struct *vma, unsigned long address) 1741 { 1742 return expand_upwards(vma, address); 1743 } 1744 1745 struct vm_area_struct * 1746 find_extend_vma(struct mm_struct *mm, unsigned long addr) 1747 { 1748 struct vm_area_struct *vma, *prev; 1749 1750 addr &= PAGE_MASK; 1751 vma = find_vma_prev(mm, addr, &prev); 1752 if (vma && (vma->vm_start <= addr)) 1753 return vma; 1754 if (!prev || expand_stack(prev, addr)) 1755 return NULL; 1756 if (prev->vm_flags & VM_LOCKED) { 1757 if (mlock_vma_pages_range(prev, addr, prev->vm_end) < 0) 1758 return NULL; /* vma gone! */ 1759 } 1760 return prev; 1761 } 1762 #else 1763 int expand_stack(struct vm_area_struct *vma, unsigned long address) 1764 { 1765 return expand_downwards(vma, address); 1766 } 1767 1768 struct vm_area_struct * 1769 find_extend_vma(struct mm_struct * mm, unsigned long addr) 1770 { 1771 struct vm_area_struct * vma; 1772 unsigned long start; 1773 1774 addr &= PAGE_MASK; 1775 vma = find_vma(mm,addr); 1776 if (!vma) 1777 return NULL; 1778 if (vma->vm_start <= addr) 1779 return vma; 1780 if (!(vma->vm_flags & VM_GROWSDOWN)) 1781 return NULL; 1782 start = vma->vm_start; 1783 if (expand_stack(vma, addr)) 1784 return NULL; 1785 if (vma->vm_flags & VM_LOCKED) { 1786 if (mlock_vma_pages_range(vma, addr, start) < 0) 1787 return NULL; /* vma gone! */ 1788 } 1789 return vma; 1790 } 1791 #endif 1792 1793 /* 1794 * Ok - we have the memory areas we should free on the vma list, 1795 * so release them, and do the vma updates. 1796 * 1797 * Called with the mm semaphore held. 1798 */ 1799 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma) 1800 { 1801 /* Update high watermark before we lower total_vm */ 1802 update_hiwater_vm(mm); 1803 do { 1804 long nrpages = vma_pages(vma); 1805 1806 mm->total_vm -= nrpages; 1807 vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages); 1808 vma = remove_vma(vma); 1809 } while (vma); 1810 validate_mm(mm); 1811 } 1812 1813 /* 1814 * Get rid of page table information in the indicated region. 1815 * 1816 * Called with the mm semaphore held. 1817 */ 1818 static void unmap_region(struct mm_struct *mm, 1819 struct vm_area_struct *vma, struct vm_area_struct *prev, 1820 unsigned long start, unsigned long end) 1821 { 1822 struct vm_area_struct *next = prev? prev->vm_next: mm->mmap; 1823 struct mmu_gather *tlb; 1824 unsigned long nr_accounted = 0; 1825 1826 lru_add_drain(); 1827 tlb = tlb_gather_mmu(mm, 0); 1828 update_hiwater_rss(mm); 1829 unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL); 1830 vm_unacct_memory(nr_accounted); 1831 free_pgtables(tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS, 1832 next? next->vm_start: 0); 1833 tlb_finish_mmu(tlb, start, end); 1834 } 1835 1836 /* 1837 * Create a list of vma's touched by the unmap, removing them from the mm's 1838 * vma list as we go.. 1839 */ 1840 static void 1841 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma, 1842 struct vm_area_struct *prev, unsigned long end) 1843 { 1844 struct vm_area_struct **insertion_point; 1845 struct vm_area_struct *tail_vma = NULL; 1846 unsigned long addr; 1847 1848 insertion_point = (prev ? &prev->vm_next : &mm->mmap); 1849 do { 1850 rb_erase(&vma->vm_rb, &mm->mm_rb); 1851 mm->map_count--; 1852 tail_vma = vma; 1853 vma = vma->vm_next; 1854 } while (vma && vma->vm_start < end); 1855 *insertion_point = vma; 1856 tail_vma->vm_next = NULL; 1857 if (mm->unmap_area == arch_unmap_area) 1858 addr = prev ? prev->vm_end : mm->mmap_base; 1859 else 1860 addr = vma ? vma->vm_start : mm->mmap_base; 1861 mm->unmap_area(mm, addr); 1862 mm->mmap_cache = NULL; /* Kill the cache. */ 1863 } 1864 1865 /* 1866 * __split_vma() bypasses sysctl_max_map_count checking. We use this on the 1867 * munmap path where it doesn't make sense to fail. 1868 */ 1869 static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma, 1870 unsigned long addr, int new_below) 1871 { 1872 struct mempolicy *pol; 1873 struct vm_area_struct *new; 1874 1875 if (is_vm_hugetlb_page(vma) && (addr & 1876 ~(huge_page_mask(hstate_vma(vma))))) 1877 return -EINVAL; 1878 1879 new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 1880 if (!new) 1881 return -ENOMEM; 1882 1883 /* most fields are the same, copy all, and then fixup */ 1884 *new = *vma; 1885 1886 if (new_below) 1887 new->vm_end = addr; 1888 else { 1889 new->vm_start = addr; 1890 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT); 1891 } 1892 1893 pol = mpol_dup(vma_policy(vma)); 1894 if (IS_ERR(pol)) { 1895 kmem_cache_free(vm_area_cachep, new); 1896 return PTR_ERR(pol); 1897 } 1898 vma_set_policy(new, pol); 1899 1900 if (new->vm_file) { 1901 get_file(new->vm_file); 1902 if (vma->vm_flags & VM_EXECUTABLE) 1903 added_exe_file_vma(mm); 1904 } 1905 1906 if (new->vm_ops && new->vm_ops->open) 1907 new->vm_ops->open(new); 1908 1909 if (new_below) 1910 vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff + 1911 ((addr - new->vm_start) >> PAGE_SHIFT), new); 1912 else 1913 vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new); 1914 1915 return 0; 1916 } 1917 1918 /* 1919 * Split a vma into two pieces at address 'addr', a new vma is allocated 1920 * either for the first part or the tail. 1921 */ 1922 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, 1923 unsigned long addr, int new_below) 1924 { 1925 if (mm->map_count >= sysctl_max_map_count) 1926 return -ENOMEM; 1927 1928 return __split_vma(mm, vma, addr, new_below); 1929 } 1930 1931 /* Munmap is split into 2 main parts -- this part which finds 1932 * what needs doing, and the areas themselves, which do the 1933 * work. This now handles partial unmappings. 1934 * Jeremy Fitzhardinge <jeremy@goop.org> 1935 */ 1936 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) 1937 { 1938 unsigned long end; 1939 struct vm_area_struct *vma, *prev, *last; 1940 1941 if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start) 1942 return -EINVAL; 1943 1944 if ((len = PAGE_ALIGN(len)) == 0) 1945 return -EINVAL; 1946 1947 /* Find the first overlapping VMA */ 1948 vma = find_vma_prev(mm, start, &prev); 1949 if (!vma) 1950 return 0; 1951 /* we have start < vma->vm_end */ 1952 1953 /* if it doesn't overlap, we have nothing.. */ 1954 end = start + len; 1955 if (vma->vm_start >= end) 1956 return 0; 1957 1958 /* 1959 * If we need to split any vma, do it now to save pain later. 1960 * 1961 * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially 1962 * unmapped vm_area_struct will remain in use: so lower split_vma 1963 * places tmp vma above, and higher split_vma places tmp vma below. 1964 */ 1965 if (start > vma->vm_start) { 1966 int error; 1967 1968 /* 1969 * Make sure that map_count on return from munmap() will 1970 * not exceed its limit; but let map_count go just above 1971 * its limit temporarily, to help free resources as expected. 1972 */ 1973 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count) 1974 return -ENOMEM; 1975 1976 error = __split_vma(mm, vma, start, 0); 1977 if (error) 1978 return error; 1979 prev = vma; 1980 } 1981 1982 /* Does it split the last one? */ 1983 last = find_vma(mm, end); 1984 if (last && end > last->vm_start) { 1985 int error = __split_vma(mm, last, end, 1); 1986 if (error) 1987 return error; 1988 } 1989 vma = prev? prev->vm_next: mm->mmap; 1990 1991 /* 1992 * unlock any mlock()ed ranges before detaching vmas 1993 */ 1994 if (mm->locked_vm) { 1995 struct vm_area_struct *tmp = vma; 1996 while (tmp && tmp->vm_start < end) { 1997 if (tmp->vm_flags & VM_LOCKED) { 1998 mm->locked_vm -= vma_pages(tmp); 1999 munlock_vma_pages_all(tmp); 2000 } 2001 tmp = tmp->vm_next; 2002 } 2003 } 2004 2005 /* 2006 * Remove the vma's, and unmap the actual pages 2007 */ 2008 detach_vmas_to_be_unmapped(mm, vma, prev, end); 2009 unmap_region(mm, vma, prev, start, end); 2010 2011 /* Fix up all other VM information */ 2012 remove_vma_list(mm, vma); 2013 2014 return 0; 2015 } 2016 2017 EXPORT_SYMBOL(do_munmap); 2018 2019 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len) 2020 { 2021 int ret; 2022 struct mm_struct *mm = current->mm; 2023 2024 profile_munmap(addr); 2025 2026 down_write(&mm->mmap_sem); 2027 ret = do_munmap(mm, addr, len); 2028 up_write(&mm->mmap_sem); 2029 return ret; 2030 } 2031 2032 static inline void verify_mm_writelocked(struct mm_struct *mm) 2033 { 2034 #ifdef CONFIG_DEBUG_VM 2035 if (unlikely(down_read_trylock(&mm->mmap_sem))) { 2036 WARN_ON(1); 2037 up_read(&mm->mmap_sem); 2038 } 2039 #endif 2040 } 2041 2042 /* 2043 * this is really a simplified "do_mmap". it only handles 2044 * anonymous maps. eventually we may be able to do some 2045 * brk-specific accounting here. 2046 */ 2047 unsigned long do_brk(unsigned long addr, unsigned long len) 2048 { 2049 struct mm_struct * mm = current->mm; 2050 struct vm_area_struct * vma, * prev; 2051 unsigned long flags; 2052 struct rb_node ** rb_link, * rb_parent; 2053 pgoff_t pgoff = addr >> PAGE_SHIFT; 2054 int error; 2055 2056 len = PAGE_ALIGN(len); 2057 if (!len) 2058 return addr; 2059 2060 error = security_file_mmap(NULL, 0, 0, 0, addr, 1); 2061 if (error) 2062 return error; 2063 2064 flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags; 2065 2066 error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED); 2067 if (error & ~PAGE_MASK) 2068 return error; 2069 2070 /* 2071 * mlock MCL_FUTURE? 2072 */ 2073 if (mm->def_flags & VM_LOCKED) { 2074 unsigned long locked, lock_limit; 2075 locked = len >> PAGE_SHIFT; 2076 locked += mm->locked_vm; 2077 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 2078 lock_limit >>= PAGE_SHIFT; 2079 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 2080 return -EAGAIN; 2081 } 2082 2083 /* 2084 * mm->mmap_sem is required to protect against another thread 2085 * changing the mappings in case we sleep. 2086 */ 2087 verify_mm_writelocked(mm); 2088 2089 /* 2090 * Clear old maps. this also does some error checking for us 2091 */ 2092 munmap_back: 2093 vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent); 2094 if (vma && vma->vm_start < addr + len) { 2095 if (do_munmap(mm, addr, len)) 2096 return -ENOMEM; 2097 goto munmap_back; 2098 } 2099 2100 /* Check against address space limits *after* clearing old maps... */ 2101 if (!may_expand_vm(mm, len >> PAGE_SHIFT)) 2102 return -ENOMEM; 2103 2104 if (mm->map_count > sysctl_max_map_count) 2105 return -ENOMEM; 2106 2107 if (security_vm_enough_memory(len >> PAGE_SHIFT)) 2108 return -ENOMEM; 2109 2110 /* Can we just expand an old private anonymous mapping? */ 2111 vma = vma_merge(mm, prev, addr, addr + len, flags, 2112 NULL, NULL, pgoff, NULL); 2113 if (vma) 2114 goto out; 2115 2116 /* 2117 * create a vma struct for an anonymous mapping 2118 */ 2119 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 2120 if (!vma) { 2121 vm_unacct_memory(len >> PAGE_SHIFT); 2122 return -ENOMEM; 2123 } 2124 2125 vma->vm_mm = mm; 2126 vma->vm_start = addr; 2127 vma->vm_end = addr + len; 2128 vma->vm_pgoff = pgoff; 2129 vma->vm_flags = flags; 2130 vma->vm_page_prot = vm_get_page_prot(flags); 2131 vma_link(mm, vma, prev, rb_link, rb_parent); 2132 out: 2133 mm->total_vm += len >> PAGE_SHIFT; 2134 if (flags & VM_LOCKED) { 2135 if (!mlock_vma_pages_range(vma, addr, addr + len)) 2136 mm->locked_vm += (len >> PAGE_SHIFT); 2137 } 2138 return addr; 2139 } 2140 2141 EXPORT_SYMBOL(do_brk); 2142 2143 /* Release all mmaps. */ 2144 void exit_mmap(struct mm_struct *mm) 2145 { 2146 struct mmu_gather *tlb; 2147 struct vm_area_struct *vma; 2148 unsigned long nr_accounted = 0; 2149 unsigned long end; 2150 2151 /* mm's last user has gone, and its about to be pulled down */ 2152 mmu_notifier_release(mm); 2153 2154 if (mm->locked_vm) { 2155 vma = mm->mmap; 2156 while (vma) { 2157 if (vma->vm_flags & VM_LOCKED) 2158 munlock_vma_pages_all(vma); 2159 vma = vma->vm_next; 2160 } 2161 } 2162 2163 arch_exit_mmap(mm); 2164 2165 vma = mm->mmap; 2166 if (!vma) /* Can happen if dup_mmap() received an OOM */ 2167 return; 2168 2169 lru_add_drain(); 2170 flush_cache_mm(mm); 2171 tlb = tlb_gather_mmu(mm, 1); 2172 /* update_hiwater_rss(mm) here? but nobody should be looking */ 2173 /* Use -1 here to ensure all VMAs in the mm are unmapped */ 2174 end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL); 2175 vm_unacct_memory(nr_accounted); 2176 2177 free_pgtables(tlb, vma, FIRST_USER_ADDRESS, 0); 2178 tlb_finish_mmu(tlb, 0, end); 2179 2180 /* 2181 * Walk the list again, actually closing and freeing it, 2182 * with preemption enabled, without holding any MM locks. 2183 */ 2184 while (vma) 2185 vma = remove_vma(vma); 2186 2187 BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT); 2188 } 2189 2190 /* Insert vm structure into process list sorted by address 2191 * and into the inode's i_mmap tree. If vm_file is non-NULL 2192 * then i_mmap_lock is taken here. 2193 */ 2194 int insert_vm_struct(struct mm_struct * mm, struct vm_area_struct * vma) 2195 { 2196 struct vm_area_struct * __vma, * prev; 2197 struct rb_node ** rb_link, * rb_parent; 2198 2199 /* 2200 * The vm_pgoff of a purely anonymous vma should be irrelevant 2201 * until its first write fault, when page's anon_vma and index 2202 * are set. But now set the vm_pgoff it will almost certainly 2203 * end up with (unless mremap moves it elsewhere before that 2204 * first wfault), so /proc/pid/maps tells a consistent story. 2205 * 2206 * By setting it to reflect the virtual start address of the 2207 * vma, merges and splits can happen in a seamless way, just 2208 * using the existing file pgoff checks and manipulations. 2209 * Similarly in do_mmap_pgoff and in do_brk. 2210 */ 2211 if (!vma->vm_file) { 2212 BUG_ON(vma->anon_vma); 2213 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT; 2214 } 2215 __vma = find_vma_prepare(mm,vma->vm_start,&prev,&rb_link,&rb_parent); 2216 if (__vma && __vma->vm_start < vma->vm_end) 2217 return -ENOMEM; 2218 if ((vma->vm_flags & VM_ACCOUNT) && 2219 security_vm_enough_memory_mm(mm, vma_pages(vma))) 2220 return -ENOMEM; 2221 vma_link(mm, vma, prev, rb_link, rb_parent); 2222 return 0; 2223 } 2224 2225 /* 2226 * Copy the vma structure to a new location in the same mm, 2227 * prior to moving page table entries, to effect an mremap move. 2228 */ 2229 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, 2230 unsigned long addr, unsigned long len, pgoff_t pgoff) 2231 { 2232 struct vm_area_struct *vma = *vmap; 2233 unsigned long vma_start = vma->vm_start; 2234 struct mm_struct *mm = vma->vm_mm; 2235 struct vm_area_struct *new_vma, *prev; 2236 struct rb_node **rb_link, *rb_parent; 2237 struct mempolicy *pol; 2238 2239 /* 2240 * If anonymous vma has not yet been faulted, update new pgoff 2241 * to match new location, to increase its chance of merging. 2242 */ 2243 if (!vma->vm_file && !vma->anon_vma) 2244 pgoff = addr >> PAGE_SHIFT; 2245 2246 find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent); 2247 new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags, 2248 vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma)); 2249 if (new_vma) { 2250 /* 2251 * Source vma may have been merged into new_vma 2252 */ 2253 if (vma_start >= new_vma->vm_start && 2254 vma_start < new_vma->vm_end) 2255 *vmap = new_vma; 2256 } else { 2257 new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); 2258 if (new_vma) { 2259 *new_vma = *vma; 2260 pol = mpol_dup(vma_policy(vma)); 2261 if (IS_ERR(pol)) { 2262 kmem_cache_free(vm_area_cachep, new_vma); 2263 return NULL; 2264 } 2265 vma_set_policy(new_vma, pol); 2266 new_vma->vm_start = addr; 2267 new_vma->vm_end = addr + len; 2268 new_vma->vm_pgoff = pgoff; 2269 if (new_vma->vm_file) { 2270 get_file(new_vma->vm_file); 2271 if (vma->vm_flags & VM_EXECUTABLE) 2272 added_exe_file_vma(mm); 2273 } 2274 if (new_vma->vm_ops && new_vma->vm_ops->open) 2275 new_vma->vm_ops->open(new_vma); 2276 vma_link(mm, new_vma, prev, rb_link, rb_parent); 2277 } 2278 } 2279 return new_vma; 2280 } 2281 2282 /* 2283 * Return true if the calling process may expand its vm space by the passed 2284 * number of pages 2285 */ 2286 int may_expand_vm(struct mm_struct *mm, unsigned long npages) 2287 { 2288 unsigned long cur = mm->total_vm; /* pages */ 2289 unsigned long lim; 2290 2291 lim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT; 2292 2293 if (cur + npages > lim) 2294 return 0; 2295 return 1; 2296 } 2297 2298 2299 static int special_mapping_fault(struct vm_area_struct *vma, 2300 struct vm_fault *vmf) 2301 { 2302 pgoff_t pgoff; 2303 struct page **pages; 2304 2305 /* 2306 * special mappings have no vm_file, and in that case, the mm 2307 * uses vm_pgoff internally. So we have to subtract it from here. 2308 * We are allowed to do this because we are the mm; do not copy 2309 * this code into drivers! 2310 */ 2311 pgoff = vmf->pgoff - vma->vm_pgoff; 2312 2313 for (pages = vma->vm_private_data; pgoff && *pages; ++pages) 2314 pgoff--; 2315 2316 if (*pages) { 2317 struct page *page = *pages; 2318 get_page(page); 2319 vmf->page = page; 2320 return 0; 2321 } 2322 2323 return VM_FAULT_SIGBUS; 2324 } 2325 2326 /* 2327 * Having a close hook prevents vma merging regardless of flags. 2328 */ 2329 static void special_mapping_close(struct vm_area_struct *vma) 2330 { 2331 } 2332 2333 static const struct vm_operations_struct special_mapping_vmops = { 2334 .close = special_mapping_close, 2335 .fault = special_mapping_fault, 2336 }; 2337 2338 /* 2339 * Called with mm->mmap_sem held for writing. 2340 * Insert a new vma covering the given region, with the given flags. 2341 * Its pages are supplied by the given array of struct page *. 2342 * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated. 2343 * The region past the last page supplied will always produce SIGBUS. 2344 * The array pointer and the pages it points to are assumed to stay alive 2345 * for as long as this mapping might exist. 2346 */ 2347 int install_special_mapping(struct mm_struct *mm, 2348 unsigned long addr, unsigned long len, 2349 unsigned long vm_flags, struct page **pages) 2350 { 2351 struct vm_area_struct *vma; 2352 2353 vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); 2354 if (unlikely(vma == NULL)) 2355 return -ENOMEM; 2356 2357 vma->vm_mm = mm; 2358 vma->vm_start = addr; 2359 vma->vm_end = addr + len; 2360 2361 vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND; 2362 vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); 2363 2364 vma->vm_ops = &special_mapping_vmops; 2365 vma->vm_private_data = pages; 2366 2367 if (unlikely(insert_vm_struct(mm, vma))) { 2368 kmem_cache_free(vm_area_cachep, vma); 2369 return -ENOMEM; 2370 } 2371 2372 mm->total_vm += len >> PAGE_SHIFT; 2373 2374 perf_event_mmap(vma); 2375 2376 return 0; 2377 } 2378 2379 static DEFINE_MUTEX(mm_all_locks_mutex); 2380 2381 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma) 2382 { 2383 if (!test_bit(0, (unsigned long *) &anon_vma->head.next)) { 2384 /* 2385 * The LSB of head.next can't change from under us 2386 * because we hold the mm_all_locks_mutex. 2387 */ 2388 spin_lock_nest_lock(&anon_vma->lock, &mm->mmap_sem); 2389 /* 2390 * We can safely modify head.next after taking the 2391 * anon_vma->lock. If some other vma in this mm shares 2392 * the same anon_vma we won't take it again. 2393 * 2394 * No need of atomic instructions here, head.next 2395 * can't change from under us thanks to the 2396 * anon_vma->lock. 2397 */ 2398 if (__test_and_set_bit(0, (unsigned long *) 2399 &anon_vma->head.next)) 2400 BUG(); 2401 } 2402 } 2403 2404 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping) 2405 { 2406 if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) { 2407 /* 2408 * AS_MM_ALL_LOCKS can't change from under us because 2409 * we hold the mm_all_locks_mutex. 2410 * 2411 * Operations on ->flags have to be atomic because 2412 * even if AS_MM_ALL_LOCKS is stable thanks to the 2413 * mm_all_locks_mutex, there may be other cpus 2414 * changing other bitflags in parallel to us. 2415 */ 2416 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags)) 2417 BUG(); 2418 spin_lock_nest_lock(&mapping->i_mmap_lock, &mm->mmap_sem); 2419 } 2420 } 2421 2422 /* 2423 * This operation locks against the VM for all pte/vma/mm related 2424 * operations that could ever happen on a certain mm. This includes 2425 * vmtruncate, try_to_unmap, and all page faults. 2426 * 2427 * The caller must take the mmap_sem in write mode before calling 2428 * mm_take_all_locks(). The caller isn't allowed to release the 2429 * mmap_sem until mm_drop_all_locks() returns. 2430 * 2431 * mmap_sem in write mode is required in order to block all operations 2432 * that could modify pagetables and free pages without need of 2433 * altering the vma layout (for example populate_range() with 2434 * nonlinear vmas). It's also needed in write mode to avoid new 2435 * anon_vmas to be associated with existing vmas. 2436 * 2437 * A single task can't take more than one mm_take_all_locks() in a row 2438 * or it would deadlock. 2439 * 2440 * The LSB in anon_vma->head.next and the AS_MM_ALL_LOCKS bitflag in 2441 * mapping->flags avoid to take the same lock twice, if more than one 2442 * vma in this mm is backed by the same anon_vma or address_space. 2443 * 2444 * We can take all the locks in random order because the VM code 2445 * taking i_mmap_lock or anon_vma->lock outside the mmap_sem never 2446 * takes more than one of them in a row. Secondly we're protected 2447 * against a concurrent mm_take_all_locks() by the mm_all_locks_mutex. 2448 * 2449 * mm_take_all_locks() and mm_drop_all_locks are expensive operations 2450 * that may have to take thousand of locks. 2451 * 2452 * mm_take_all_locks() can fail if it's interrupted by signals. 2453 */ 2454 int mm_take_all_locks(struct mm_struct *mm) 2455 { 2456 struct vm_area_struct *vma; 2457 int ret = -EINTR; 2458 2459 BUG_ON(down_read_trylock(&mm->mmap_sem)); 2460 2461 mutex_lock(&mm_all_locks_mutex); 2462 2463 for (vma = mm->mmap; vma; vma = vma->vm_next) { 2464 if (signal_pending(current)) 2465 goto out_unlock; 2466 if (vma->vm_file && vma->vm_file->f_mapping) 2467 vm_lock_mapping(mm, vma->vm_file->f_mapping); 2468 } 2469 2470 for (vma = mm->mmap; vma; vma = vma->vm_next) { 2471 if (signal_pending(current)) 2472 goto out_unlock; 2473 if (vma->anon_vma) 2474 vm_lock_anon_vma(mm, vma->anon_vma); 2475 } 2476 2477 ret = 0; 2478 2479 out_unlock: 2480 if (ret) 2481 mm_drop_all_locks(mm); 2482 2483 return ret; 2484 } 2485 2486 static void vm_unlock_anon_vma(struct anon_vma *anon_vma) 2487 { 2488 if (test_bit(0, (unsigned long *) &anon_vma->head.next)) { 2489 /* 2490 * The LSB of head.next can't change to 0 from under 2491 * us because we hold the mm_all_locks_mutex. 2492 * 2493 * We must however clear the bitflag before unlocking 2494 * the vma so the users using the anon_vma->head will 2495 * never see our bitflag. 2496 * 2497 * No need of atomic instructions here, head.next 2498 * can't change from under us until we release the 2499 * anon_vma->lock. 2500 */ 2501 if (!__test_and_clear_bit(0, (unsigned long *) 2502 &anon_vma->head.next)) 2503 BUG(); 2504 spin_unlock(&anon_vma->lock); 2505 } 2506 } 2507 2508 static void vm_unlock_mapping(struct address_space *mapping) 2509 { 2510 if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) { 2511 /* 2512 * AS_MM_ALL_LOCKS can't change to 0 from under us 2513 * because we hold the mm_all_locks_mutex. 2514 */ 2515 spin_unlock(&mapping->i_mmap_lock); 2516 if (!test_and_clear_bit(AS_MM_ALL_LOCKS, 2517 &mapping->flags)) 2518 BUG(); 2519 } 2520 } 2521 2522 /* 2523 * The mmap_sem cannot be released by the caller until 2524 * mm_drop_all_locks() returns. 2525 */ 2526 void mm_drop_all_locks(struct mm_struct *mm) 2527 { 2528 struct vm_area_struct *vma; 2529 2530 BUG_ON(down_read_trylock(&mm->mmap_sem)); 2531 BUG_ON(!mutex_is_locked(&mm_all_locks_mutex)); 2532 2533 for (vma = mm->mmap; vma; vma = vma->vm_next) { 2534 if (vma->anon_vma) 2535 vm_unlock_anon_vma(vma->anon_vma); 2536 if (vma->vm_file && vma->vm_file->f_mapping) 2537 vm_unlock_mapping(vma->vm_file->f_mapping); 2538 } 2539 2540 mutex_unlock(&mm_all_locks_mutex); 2541 } 2542 2543 /* 2544 * initialise the VMA slab 2545 */ 2546 void __init mmap_init(void) 2547 { 2548 int ret; 2549 2550 ret = percpu_counter_init(&vm_committed_as, 0); 2551 VM_BUG_ON(ret); 2552 } 2553