1 /* 2 * mm/mremap.c 3 * 4 * (C) Copyright 1996 Linus Torvalds 5 * 6 * Address space accounting code <alan@lxorguk.ukuu.org.uk> 7 * (C) Copyright 2002 Red Hat Inc, All Rights Reserved 8 */ 9 10 #include <linux/mm.h> 11 #include <linux/hugetlb.h> 12 #include <linux/shm.h> 13 #include <linux/ksm.h> 14 #include <linux/mman.h> 15 #include <linux/swap.h> 16 #include <linux/capability.h> 17 #include <linux/fs.h> 18 #include <linux/swapops.h> 19 #include <linux/highmem.h> 20 #include <linux/security.h> 21 #include <linux/syscalls.h> 22 #include <linux/mmu_notifier.h> 23 #include <linux/uaccess.h> 24 #include <linux/mm-arch-hooks.h> 25 26 #include <asm/cacheflush.h> 27 #include <asm/tlbflush.h> 28 29 #include "internal.h" 30 31 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) 32 { 33 pgd_t *pgd; 34 pud_t *pud; 35 pmd_t *pmd; 36 37 pgd = pgd_offset(mm, addr); 38 if (pgd_none_or_clear_bad(pgd)) 39 return NULL; 40 41 pud = pud_offset(pgd, addr); 42 if (pud_none_or_clear_bad(pud)) 43 return NULL; 44 45 pmd = pmd_offset(pud, addr); 46 if (pmd_none(*pmd)) 47 return NULL; 48 49 return pmd; 50 } 51 52 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma, 53 unsigned long addr) 54 { 55 pgd_t *pgd; 56 pud_t *pud; 57 pmd_t *pmd; 58 59 pgd = pgd_offset(mm, addr); 60 pud = pud_alloc(mm, pgd, addr); 61 if (!pud) 62 return NULL; 63 64 pmd = pmd_alloc(mm, pud, addr); 65 if (!pmd) 66 return NULL; 67 68 VM_BUG_ON(pmd_trans_huge(*pmd)); 69 70 return pmd; 71 } 72 73 static void take_rmap_locks(struct vm_area_struct *vma) 74 { 75 if (vma->vm_file) 76 i_mmap_lock_write(vma->vm_file->f_mapping); 77 if (vma->anon_vma) 78 anon_vma_lock_write(vma->anon_vma); 79 } 80 81 static void drop_rmap_locks(struct vm_area_struct *vma) 82 { 83 if (vma->anon_vma) 84 anon_vma_unlock_write(vma->anon_vma); 85 if (vma->vm_file) 86 i_mmap_unlock_write(vma->vm_file->f_mapping); 87 } 88 89 static pte_t move_soft_dirty_pte(pte_t pte) 90 { 91 /* 92 * Set soft dirty bit so we can notice 93 * in userspace the ptes were moved. 94 */ 95 #ifdef CONFIG_MEM_SOFT_DIRTY 96 if (pte_present(pte)) 97 pte = pte_mksoft_dirty(pte); 98 else if (is_swap_pte(pte)) 99 pte = pte_swp_mksoft_dirty(pte); 100 #endif 101 return pte; 102 } 103 104 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, 105 unsigned long old_addr, unsigned long old_end, 106 struct vm_area_struct *new_vma, pmd_t *new_pmd, 107 unsigned long new_addr, bool need_rmap_locks, bool *need_flush) 108 { 109 struct mm_struct *mm = vma->vm_mm; 110 pte_t *old_pte, *new_pte, pte; 111 spinlock_t *old_ptl, *new_ptl; 112 bool force_flush = false; 113 unsigned long len = old_end - old_addr; 114 115 /* 116 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma 117 * locks to ensure that rmap will always observe either the old or the 118 * new ptes. This is the easiest way to avoid races with 119 * truncate_pagecache(), page migration, etc... 120 * 121 * When need_rmap_locks is false, we use other ways to avoid 122 * such races: 123 * 124 * - During exec() shift_arg_pages(), we use a specially tagged vma 125 * which rmap call sites look for using is_vma_temporary_stack(). 126 * 127 * - During mremap(), new_vma is often known to be placed after vma 128 * in rmap traversal order. This ensures rmap will always observe 129 * either the old pte, or the new pte, or both (the page table locks 130 * serialize access to individual ptes, but only rmap traversal 131 * order guarantees that we won't miss both the old and new ptes). 132 */ 133 if (need_rmap_locks) 134 take_rmap_locks(vma); 135 136 /* 137 * We don't have to worry about the ordering of src and dst 138 * pte locks because exclusive mmap_sem prevents deadlock. 139 */ 140 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); 141 new_pte = pte_offset_map(new_pmd, new_addr); 142 new_ptl = pte_lockptr(mm, new_pmd); 143 if (new_ptl != old_ptl) 144 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 145 arch_enter_lazy_mmu_mode(); 146 147 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, 148 new_pte++, new_addr += PAGE_SIZE) { 149 if (pte_none(*old_pte)) 150 continue; 151 152 /* 153 * We are remapping a dirty PTE, make sure to 154 * flush TLB before we drop the PTL for the 155 * old PTE or we may race with page_mkclean(). 156 */ 157 if (pte_present(*old_pte) && pte_dirty(*old_pte)) 158 force_flush = true; 159 pte = ptep_get_and_clear(mm, old_addr, old_pte); 160 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); 161 pte = move_soft_dirty_pte(pte); 162 set_pte_at(mm, new_addr, new_pte, pte); 163 } 164 165 arch_leave_lazy_mmu_mode(); 166 if (new_ptl != old_ptl) 167 spin_unlock(new_ptl); 168 pte_unmap(new_pte - 1); 169 if (force_flush) 170 flush_tlb_range(vma, old_end - len, old_end); 171 else 172 *need_flush = true; 173 pte_unmap_unlock(old_pte - 1, old_ptl); 174 if (need_rmap_locks) 175 drop_rmap_locks(vma); 176 } 177 178 #define LATENCY_LIMIT (64 * PAGE_SIZE) 179 180 unsigned long move_page_tables(struct vm_area_struct *vma, 181 unsigned long old_addr, struct vm_area_struct *new_vma, 182 unsigned long new_addr, unsigned long len, 183 bool need_rmap_locks) 184 { 185 unsigned long extent, next, old_end; 186 pmd_t *old_pmd, *new_pmd; 187 bool need_flush = false; 188 unsigned long mmun_start; /* For mmu_notifiers */ 189 unsigned long mmun_end; /* For mmu_notifiers */ 190 191 old_end = old_addr + len; 192 flush_cache_range(vma, old_addr, old_end); 193 194 mmun_start = old_addr; 195 mmun_end = old_end; 196 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); 197 198 for (; old_addr < old_end; old_addr += extent, new_addr += extent) { 199 cond_resched(); 200 next = (old_addr + PMD_SIZE) & PMD_MASK; 201 /* even if next overflowed, extent below will be ok */ 202 extent = next - old_addr; 203 if (extent > old_end - old_addr) 204 extent = old_end - old_addr; 205 old_pmd = get_old_pmd(vma->vm_mm, old_addr); 206 if (!old_pmd) 207 continue; 208 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); 209 if (!new_pmd) 210 break; 211 if (pmd_trans_huge(*old_pmd)) { 212 if (extent == HPAGE_PMD_SIZE) { 213 bool moved; 214 /* See comment in move_ptes() */ 215 if (need_rmap_locks) 216 take_rmap_locks(vma); 217 moved = move_huge_pmd(vma, old_addr, new_addr, 218 old_end, old_pmd, new_pmd, 219 &need_flush); 220 if (need_rmap_locks) 221 drop_rmap_locks(vma); 222 if (moved) 223 continue; 224 } 225 split_huge_pmd(vma, old_pmd, old_addr); 226 if (pmd_trans_unstable(old_pmd)) 227 continue; 228 } 229 if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr)) 230 break; 231 next = (new_addr + PMD_SIZE) & PMD_MASK; 232 if (extent > next - new_addr) 233 extent = next - new_addr; 234 if (extent > LATENCY_LIMIT) 235 extent = LATENCY_LIMIT; 236 move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, 237 new_pmd, new_addr, need_rmap_locks, &need_flush); 238 } 239 if (need_flush) 240 flush_tlb_range(vma, old_end-len, old_addr); 241 242 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); 243 244 return len + old_addr - old_end; /* how much done */ 245 } 246 247 static unsigned long move_vma(struct vm_area_struct *vma, 248 unsigned long old_addr, unsigned long old_len, 249 unsigned long new_len, unsigned long new_addr, bool *locked) 250 { 251 struct mm_struct *mm = vma->vm_mm; 252 struct vm_area_struct *new_vma; 253 unsigned long vm_flags = vma->vm_flags; 254 unsigned long new_pgoff; 255 unsigned long moved_len; 256 unsigned long excess = 0; 257 unsigned long hiwater_vm; 258 int split = 0; 259 int err; 260 bool need_rmap_locks; 261 262 /* 263 * We'd prefer to avoid failure later on in do_munmap: 264 * which may split one vma into three before unmapping. 265 */ 266 if (mm->map_count >= sysctl_max_map_count - 3) 267 return -ENOMEM; 268 269 /* 270 * Advise KSM to break any KSM pages in the area to be moved: 271 * it would be confusing if they were to turn up at the new 272 * location, where they happen to coincide with different KSM 273 * pages recently unmapped. But leave vma->vm_flags as it was, 274 * so KSM can come around to merge on vma and new_vma afterwards. 275 */ 276 err = ksm_madvise(vma, old_addr, old_addr + old_len, 277 MADV_UNMERGEABLE, &vm_flags); 278 if (err) 279 return err; 280 281 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); 282 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, 283 &need_rmap_locks); 284 if (!new_vma) 285 return -ENOMEM; 286 287 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, 288 need_rmap_locks); 289 if (moved_len < old_len) { 290 err = -ENOMEM; 291 } else if (vma->vm_ops && vma->vm_ops->mremap) { 292 err = vma->vm_ops->mremap(new_vma); 293 } 294 295 if (unlikely(err)) { 296 /* 297 * On error, move entries back from new area to old, 298 * which will succeed since page tables still there, 299 * and then proceed to unmap new area instead of old. 300 */ 301 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, 302 true); 303 vma = new_vma; 304 old_len = new_len; 305 old_addr = new_addr; 306 new_addr = err; 307 } else { 308 arch_remap(mm, old_addr, old_addr + old_len, 309 new_addr, new_addr + new_len); 310 } 311 312 /* Conceal VM_ACCOUNT so old reservation is not undone */ 313 if (vm_flags & VM_ACCOUNT) { 314 vma->vm_flags &= ~VM_ACCOUNT; 315 excess = vma->vm_end - vma->vm_start - old_len; 316 if (old_addr > vma->vm_start && 317 old_addr + old_len < vma->vm_end) 318 split = 1; 319 } 320 321 /* 322 * If we failed to move page tables we still do total_vm increment 323 * since do_munmap() will decrement it by old_len == new_len. 324 * 325 * Since total_vm is about to be raised artificially high for a 326 * moment, we need to restore high watermark afterwards: if stats 327 * are taken meanwhile, total_vm and hiwater_vm appear too high. 328 * If this were a serious issue, we'd add a flag to do_munmap(). 329 */ 330 hiwater_vm = mm->hiwater_vm; 331 vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT); 332 333 /* Tell pfnmap has moved from this vma */ 334 if (unlikely(vma->vm_flags & VM_PFNMAP)) 335 untrack_pfn_moved(vma); 336 337 if (do_munmap(mm, old_addr, old_len) < 0) { 338 /* OOM: unable to split vma, just get accounts right */ 339 vm_unacct_memory(excess >> PAGE_SHIFT); 340 excess = 0; 341 } 342 mm->hiwater_vm = hiwater_vm; 343 344 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 345 if (excess) { 346 vma->vm_flags |= VM_ACCOUNT; 347 if (split) 348 vma->vm_next->vm_flags |= VM_ACCOUNT; 349 } 350 351 if (vm_flags & VM_LOCKED) { 352 mm->locked_vm += new_len >> PAGE_SHIFT; 353 *locked = true; 354 } 355 356 return new_addr; 357 } 358 359 static struct vm_area_struct *vma_to_resize(unsigned long addr, 360 unsigned long old_len, unsigned long new_len, unsigned long *p) 361 { 362 struct mm_struct *mm = current->mm; 363 struct vm_area_struct *vma = find_vma(mm, addr); 364 unsigned long pgoff; 365 366 if (!vma || vma->vm_start > addr) 367 return ERR_PTR(-EFAULT); 368 369 if (is_vm_hugetlb_page(vma)) 370 return ERR_PTR(-EINVAL); 371 372 /* We can't remap across vm area boundaries */ 373 if (old_len > vma->vm_end - addr) 374 return ERR_PTR(-EFAULT); 375 376 if (new_len == old_len) 377 return vma; 378 379 /* Need to be careful about a growing mapping */ 380 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; 381 pgoff += vma->vm_pgoff; 382 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) 383 return ERR_PTR(-EINVAL); 384 385 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) 386 return ERR_PTR(-EFAULT); 387 388 if (vma->vm_flags & VM_LOCKED) { 389 unsigned long locked, lock_limit; 390 locked = mm->locked_vm << PAGE_SHIFT; 391 lock_limit = rlimit(RLIMIT_MEMLOCK); 392 locked += new_len - old_len; 393 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 394 return ERR_PTR(-EAGAIN); 395 } 396 397 if (!may_expand_vm(mm, vma->vm_flags, 398 (new_len - old_len) >> PAGE_SHIFT)) 399 return ERR_PTR(-ENOMEM); 400 401 if (vma->vm_flags & VM_ACCOUNT) { 402 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; 403 if (security_vm_enough_memory_mm(mm, charged)) 404 return ERR_PTR(-ENOMEM); 405 *p = charged; 406 } 407 408 return vma; 409 } 410 411 static unsigned long mremap_to(unsigned long addr, unsigned long old_len, 412 unsigned long new_addr, unsigned long new_len, bool *locked) 413 { 414 struct mm_struct *mm = current->mm; 415 struct vm_area_struct *vma; 416 unsigned long ret = -EINVAL; 417 unsigned long charged = 0; 418 unsigned long map_flags; 419 420 if (offset_in_page(new_addr)) 421 goto out; 422 423 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 424 goto out; 425 426 /* Ensure the old/new locations do not overlap */ 427 if (addr + old_len > new_addr && new_addr + new_len > addr) 428 goto out; 429 430 ret = do_munmap(mm, new_addr, new_len); 431 if (ret) 432 goto out; 433 434 if (old_len >= new_len) { 435 ret = do_munmap(mm, addr+new_len, old_len - new_len); 436 if (ret && old_len != new_len) 437 goto out; 438 old_len = new_len; 439 } 440 441 vma = vma_to_resize(addr, old_len, new_len, &charged); 442 if (IS_ERR(vma)) { 443 ret = PTR_ERR(vma); 444 goto out; 445 } 446 447 map_flags = MAP_FIXED; 448 if (vma->vm_flags & VM_MAYSHARE) 449 map_flags |= MAP_SHARED; 450 451 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + 452 ((addr - vma->vm_start) >> PAGE_SHIFT), 453 map_flags); 454 if (offset_in_page(ret)) 455 goto out1; 456 457 ret = move_vma(vma, addr, old_len, new_len, new_addr, locked); 458 if (!(offset_in_page(ret))) 459 goto out; 460 out1: 461 vm_unacct_memory(charged); 462 463 out: 464 return ret; 465 } 466 467 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) 468 { 469 unsigned long end = vma->vm_end + delta; 470 if (end < vma->vm_end) /* overflow */ 471 return 0; 472 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ 473 return 0; 474 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, 475 0, MAP_FIXED) & ~PAGE_MASK) 476 return 0; 477 return 1; 478 } 479 480 /* 481 * Expand (or shrink) an existing mapping, potentially moving it at the 482 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 483 * 484 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 485 * This option implies MREMAP_MAYMOVE. 486 */ 487 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, 488 unsigned long, new_len, unsigned long, flags, 489 unsigned long, new_addr) 490 { 491 struct mm_struct *mm = current->mm; 492 struct vm_area_struct *vma; 493 unsigned long ret = -EINVAL; 494 unsigned long charged = 0; 495 bool locked = false; 496 497 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 498 return ret; 499 500 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) 501 return ret; 502 503 if (offset_in_page(addr)) 504 return ret; 505 506 old_len = PAGE_ALIGN(old_len); 507 new_len = PAGE_ALIGN(new_len); 508 509 /* 510 * We allow a zero old-len as a special case 511 * for DOS-emu "duplicate shm area" thing. But 512 * a zero new-len is nonsensical. 513 */ 514 if (!new_len) 515 return ret; 516 517 if (down_write_killable(¤t->mm->mmap_sem)) 518 return -EINTR; 519 520 if (flags & MREMAP_FIXED) { 521 ret = mremap_to(addr, old_len, new_addr, new_len, 522 &locked); 523 goto out; 524 } 525 526 /* 527 * Always allow a shrinking remap: that just unmaps 528 * the unnecessary pages.. 529 * do_munmap does all the needed commit accounting 530 */ 531 if (old_len >= new_len) { 532 ret = do_munmap(mm, addr+new_len, old_len - new_len); 533 if (ret && old_len != new_len) 534 goto out; 535 ret = addr; 536 goto out; 537 } 538 539 /* 540 * Ok, we need to grow.. 541 */ 542 vma = vma_to_resize(addr, old_len, new_len, &charged); 543 if (IS_ERR(vma)) { 544 ret = PTR_ERR(vma); 545 goto out; 546 } 547 548 /* old_len exactly to the end of the area.. 549 */ 550 if (old_len == vma->vm_end - addr) { 551 /* can we just expand the current mapping? */ 552 if (vma_expandable(vma, new_len - old_len)) { 553 int pages = (new_len - old_len) >> PAGE_SHIFT; 554 555 if (vma_adjust(vma, vma->vm_start, addr + new_len, 556 vma->vm_pgoff, NULL)) { 557 ret = -ENOMEM; 558 goto out; 559 } 560 561 vm_stat_account(mm, vma->vm_flags, pages); 562 if (vma->vm_flags & VM_LOCKED) { 563 mm->locked_vm += pages; 564 locked = true; 565 new_addr = addr; 566 } 567 ret = addr; 568 goto out; 569 } 570 } 571 572 /* 573 * We weren't able to just expand or shrink the area, 574 * we need to create a new one and move it.. 575 */ 576 ret = -ENOMEM; 577 if (flags & MREMAP_MAYMOVE) { 578 unsigned long map_flags = 0; 579 if (vma->vm_flags & VM_MAYSHARE) 580 map_flags |= MAP_SHARED; 581 582 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 583 vma->vm_pgoff + 584 ((addr - vma->vm_start) >> PAGE_SHIFT), 585 map_flags); 586 if (offset_in_page(new_addr)) { 587 ret = new_addr; 588 goto out; 589 } 590 591 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked); 592 } 593 out: 594 if (offset_in_page(ret)) { 595 vm_unacct_memory(charged); 596 locked = 0; 597 } 598 up_write(¤t->mm->mmap_sem); 599 if (locked && new_len > old_len) 600 mm_populate(new_addr + old_len, new_len - old_len); 601 return ret; 602 } 603