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 pte = ptep_get_and_clear(mm, old_addr, old_pte); 153 /* 154 * If we are remapping a dirty PTE, make sure 155 * to flush TLB before we drop the PTL for the 156 * old PTE or we may race with page_mkclean(). 157 * 158 * This check has to be done after we removed the 159 * old PTE from page tables or another thread may 160 * dirty it after the check and before the removal. 161 */ 162 if (pte_present(pte) && pte_dirty(pte)) 163 force_flush = true; 164 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); 165 pte = move_soft_dirty_pte(pte); 166 set_pte_at(mm, new_addr, new_pte, pte); 167 } 168 169 arch_leave_lazy_mmu_mode(); 170 if (new_ptl != old_ptl) 171 spin_unlock(new_ptl); 172 pte_unmap(new_pte - 1); 173 if (force_flush) 174 flush_tlb_range(vma, old_end - len, old_end); 175 else 176 *need_flush = true; 177 pte_unmap_unlock(old_pte - 1, old_ptl); 178 if (need_rmap_locks) 179 drop_rmap_locks(vma); 180 } 181 182 #define LATENCY_LIMIT (64 * PAGE_SIZE) 183 184 unsigned long move_page_tables(struct vm_area_struct *vma, 185 unsigned long old_addr, struct vm_area_struct *new_vma, 186 unsigned long new_addr, unsigned long len, 187 bool need_rmap_locks) 188 { 189 unsigned long extent, next, old_end; 190 pmd_t *old_pmd, *new_pmd; 191 bool need_flush = false; 192 unsigned long mmun_start; /* For mmu_notifiers */ 193 unsigned long mmun_end; /* For mmu_notifiers */ 194 195 old_end = old_addr + len; 196 flush_cache_range(vma, old_addr, old_end); 197 198 mmun_start = old_addr; 199 mmun_end = old_end; 200 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); 201 202 for (; old_addr < old_end; old_addr += extent, new_addr += extent) { 203 cond_resched(); 204 next = (old_addr + PMD_SIZE) & PMD_MASK; 205 /* even if next overflowed, extent below will be ok */ 206 extent = next - old_addr; 207 if (extent > old_end - old_addr) 208 extent = old_end - old_addr; 209 old_pmd = get_old_pmd(vma->vm_mm, old_addr); 210 if (!old_pmd) 211 continue; 212 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); 213 if (!new_pmd) 214 break; 215 if (pmd_trans_huge(*old_pmd)) { 216 if (extent == HPAGE_PMD_SIZE) { 217 bool moved; 218 /* See comment in move_ptes() */ 219 if (need_rmap_locks) 220 take_rmap_locks(vma); 221 moved = move_huge_pmd(vma, old_addr, new_addr, 222 old_end, old_pmd, new_pmd, 223 &need_flush); 224 if (need_rmap_locks) 225 drop_rmap_locks(vma); 226 if (moved) 227 continue; 228 } 229 split_huge_pmd(vma, old_pmd, old_addr); 230 if (pmd_trans_unstable(old_pmd)) 231 continue; 232 } 233 if (pte_alloc(new_vma->vm_mm, new_pmd, new_addr)) 234 break; 235 next = (new_addr + PMD_SIZE) & PMD_MASK; 236 if (extent > next - new_addr) 237 extent = next - new_addr; 238 if (extent > LATENCY_LIMIT) 239 extent = LATENCY_LIMIT; 240 move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma, 241 new_pmd, new_addr, need_rmap_locks, &need_flush); 242 } 243 if (need_flush) 244 flush_tlb_range(vma, old_end-len, old_addr); 245 246 mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end); 247 248 return len + old_addr - old_end; /* how much done */ 249 } 250 251 static unsigned long move_vma(struct vm_area_struct *vma, 252 unsigned long old_addr, unsigned long old_len, 253 unsigned long new_len, unsigned long new_addr, bool *locked) 254 { 255 struct mm_struct *mm = vma->vm_mm; 256 struct vm_area_struct *new_vma; 257 unsigned long vm_flags = vma->vm_flags; 258 unsigned long new_pgoff; 259 unsigned long moved_len; 260 unsigned long excess = 0; 261 unsigned long hiwater_vm; 262 int split = 0; 263 int err; 264 bool need_rmap_locks; 265 266 /* 267 * We'd prefer to avoid failure later on in do_munmap: 268 * which may split one vma into three before unmapping. 269 */ 270 if (mm->map_count >= sysctl_max_map_count - 3) 271 return -ENOMEM; 272 273 /* 274 * Advise KSM to break any KSM pages in the area to be moved: 275 * it would be confusing if they were to turn up at the new 276 * location, where they happen to coincide with different KSM 277 * pages recently unmapped. But leave vma->vm_flags as it was, 278 * so KSM can come around to merge on vma and new_vma afterwards. 279 */ 280 err = ksm_madvise(vma, old_addr, old_addr + old_len, 281 MADV_UNMERGEABLE, &vm_flags); 282 if (err) 283 return err; 284 285 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); 286 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, 287 &need_rmap_locks); 288 if (!new_vma) 289 return -ENOMEM; 290 291 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len, 292 need_rmap_locks); 293 if (moved_len < old_len) { 294 err = -ENOMEM; 295 } else if (vma->vm_ops && vma->vm_ops->mremap) { 296 err = vma->vm_ops->mremap(new_vma); 297 } 298 299 if (unlikely(err)) { 300 /* 301 * On error, move entries back from new area to old, 302 * which will succeed since page tables still there, 303 * and then proceed to unmap new area instead of old. 304 */ 305 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, 306 true); 307 vma = new_vma; 308 old_len = new_len; 309 old_addr = new_addr; 310 new_addr = err; 311 } else { 312 arch_remap(mm, old_addr, old_addr + old_len, 313 new_addr, new_addr + new_len); 314 } 315 316 /* Conceal VM_ACCOUNT so old reservation is not undone */ 317 if (vm_flags & VM_ACCOUNT) { 318 vma->vm_flags &= ~VM_ACCOUNT; 319 excess = vma->vm_end - vma->vm_start - old_len; 320 if (old_addr > vma->vm_start && 321 old_addr + old_len < vma->vm_end) 322 split = 1; 323 } 324 325 /* 326 * If we failed to move page tables we still do total_vm increment 327 * since do_munmap() will decrement it by old_len == new_len. 328 * 329 * Since total_vm is about to be raised artificially high for a 330 * moment, we need to restore high watermark afterwards: if stats 331 * are taken meanwhile, total_vm and hiwater_vm appear too high. 332 * If this were a serious issue, we'd add a flag to do_munmap(). 333 */ 334 hiwater_vm = mm->hiwater_vm; 335 vm_stat_account(mm, vma->vm_flags, new_len >> PAGE_SHIFT); 336 337 /* Tell pfnmap has moved from this vma */ 338 if (unlikely(vma->vm_flags & VM_PFNMAP)) 339 untrack_pfn_moved(vma); 340 341 if (do_munmap(mm, old_addr, old_len) < 0) { 342 /* OOM: unable to split vma, just get accounts right */ 343 vm_unacct_memory(excess >> PAGE_SHIFT); 344 excess = 0; 345 } 346 mm->hiwater_vm = hiwater_vm; 347 348 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 349 if (excess) { 350 vma->vm_flags |= VM_ACCOUNT; 351 if (split) 352 vma->vm_next->vm_flags |= VM_ACCOUNT; 353 } 354 355 if (vm_flags & VM_LOCKED) { 356 mm->locked_vm += new_len >> PAGE_SHIFT; 357 *locked = true; 358 } 359 360 return new_addr; 361 } 362 363 static struct vm_area_struct *vma_to_resize(unsigned long addr, 364 unsigned long old_len, unsigned long new_len, unsigned long *p) 365 { 366 struct mm_struct *mm = current->mm; 367 struct vm_area_struct *vma = find_vma(mm, addr); 368 unsigned long pgoff; 369 370 if (!vma || vma->vm_start > addr) 371 return ERR_PTR(-EFAULT); 372 373 if (is_vm_hugetlb_page(vma)) 374 return ERR_PTR(-EINVAL); 375 376 /* We can't remap across vm area boundaries */ 377 if (old_len > vma->vm_end - addr) 378 return ERR_PTR(-EFAULT); 379 380 if (new_len == old_len) 381 return vma; 382 383 /* Need to be careful about a growing mapping */ 384 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; 385 pgoff += vma->vm_pgoff; 386 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) 387 return ERR_PTR(-EINVAL); 388 389 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) 390 return ERR_PTR(-EFAULT); 391 392 if (vma->vm_flags & VM_LOCKED) { 393 unsigned long locked, lock_limit; 394 locked = mm->locked_vm << PAGE_SHIFT; 395 lock_limit = rlimit(RLIMIT_MEMLOCK); 396 locked += new_len - old_len; 397 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 398 return ERR_PTR(-EAGAIN); 399 } 400 401 if (!may_expand_vm(mm, vma->vm_flags, 402 (new_len - old_len) >> PAGE_SHIFT)) 403 return ERR_PTR(-ENOMEM); 404 405 if (vma->vm_flags & VM_ACCOUNT) { 406 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; 407 if (security_vm_enough_memory_mm(mm, charged)) 408 return ERR_PTR(-ENOMEM); 409 *p = charged; 410 } 411 412 return vma; 413 } 414 415 static unsigned long mremap_to(unsigned long addr, unsigned long old_len, 416 unsigned long new_addr, unsigned long new_len, bool *locked) 417 { 418 struct mm_struct *mm = current->mm; 419 struct vm_area_struct *vma; 420 unsigned long ret = -EINVAL; 421 unsigned long charged = 0; 422 unsigned long map_flags; 423 424 if (offset_in_page(new_addr)) 425 goto out; 426 427 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 428 goto out; 429 430 /* Ensure the old/new locations do not overlap */ 431 if (addr + old_len > new_addr && new_addr + new_len > addr) 432 goto out; 433 434 ret = do_munmap(mm, new_addr, new_len); 435 if (ret) 436 goto out; 437 438 if (old_len >= new_len) { 439 ret = do_munmap(mm, addr+new_len, old_len - new_len); 440 if (ret && old_len != new_len) 441 goto out; 442 old_len = new_len; 443 } 444 445 vma = vma_to_resize(addr, old_len, new_len, &charged); 446 if (IS_ERR(vma)) { 447 ret = PTR_ERR(vma); 448 goto out; 449 } 450 451 map_flags = MAP_FIXED; 452 if (vma->vm_flags & VM_MAYSHARE) 453 map_flags |= MAP_SHARED; 454 455 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + 456 ((addr - vma->vm_start) >> PAGE_SHIFT), 457 map_flags); 458 if (offset_in_page(ret)) 459 goto out1; 460 461 ret = move_vma(vma, addr, old_len, new_len, new_addr, locked); 462 if (!(offset_in_page(ret))) 463 goto out; 464 out1: 465 vm_unacct_memory(charged); 466 467 out: 468 return ret; 469 } 470 471 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) 472 { 473 unsigned long end = vma->vm_end + delta; 474 if (end < vma->vm_end) /* overflow */ 475 return 0; 476 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ 477 return 0; 478 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, 479 0, MAP_FIXED) & ~PAGE_MASK) 480 return 0; 481 return 1; 482 } 483 484 /* 485 * Expand (or shrink) an existing mapping, potentially moving it at the 486 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 487 * 488 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 489 * This option implies MREMAP_MAYMOVE. 490 */ 491 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, 492 unsigned long, new_len, unsigned long, flags, 493 unsigned long, new_addr) 494 { 495 struct mm_struct *mm = current->mm; 496 struct vm_area_struct *vma; 497 unsigned long ret = -EINVAL; 498 unsigned long charged = 0; 499 bool locked = false; 500 501 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 502 return ret; 503 504 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) 505 return ret; 506 507 if (offset_in_page(addr)) 508 return ret; 509 510 old_len = PAGE_ALIGN(old_len); 511 new_len = PAGE_ALIGN(new_len); 512 513 /* 514 * We allow a zero old-len as a special case 515 * for DOS-emu "duplicate shm area" thing. But 516 * a zero new-len is nonsensical. 517 */ 518 if (!new_len) 519 return ret; 520 521 if (down_write_killable(¤t->mm->mmap_sem)) 522 return -EINTR; 523 524 if (flags & MREMAP_FIXED) { 525 ret = mremap_to(addr, old_len, new_addr, new_len, 526 &locked); 527 goto out; 528 } 529 530 /* 531 * Always allow a shrinking remap: that just unmaps 532 * the unnecessary pages.. 533 * do_munmap does all the needed commit accounting 534 */ 535 if (old_len >= new_len) { 536 ret = do_munmap(mm, addr+new_len, old_len - new_len); 537 if (ret && old_len != new_len) 538 goto out; 539 ret = addr; 540 goto out; 541 } 542 543 /* 544 * Ok, we need to grow.. 545 */ 546 vma = vma_to_resize(addr, old_len, new_len, &charged); 547 if (IS_ERR(vma)) { 548 ret = PTR_ERR(vma); 549 goto out; 550 } 551 552 /* old_len exactly to the end of the area.. 553 */ 554 if (old_len == vma->vm_end - addr) { 555 /* can we just expand the current mapping? */ 556 if (vma_expandable(vma, new_len - old_len)) { 557 int pages = (new_len - old_len) >> PAGE_SHIFT; 558 559 if (vma_adjust(vma, vma->vm_start, addr + new_len, 560 vma->vm_pgoff, NULL)) { 561 ret = -ENOMEM; 562 goto out; 563 } 564 565 vm_stat_account(mm, vma->vm_flags, pages); 566 if (vma->vm_flags & VM_LOCKED) { 567 mm->locked_vm += pages; 568 locked = true; 569 new_addr = addr; 570 } 571 ret = addr; 572 goto out; 573 } 574 } 575 576 /* 577 * We weren't able to just expand or shrink the area, 578 * we need to create a new one and move it.. 579 */ 580 ret = -ENOMEM; 581 if (flags & MREMAP_MAYMOVE) { 582 unsigned long map_flags = 0; 583 if (vma->vm_flags & VM_MAYSHARE) 584 map_flags |= MAP_SHARED; 585 586 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 587 vma->vm_pgoff + 588 ((addr - vma->vm_start) >> PAGE_SHIFT), 589 map_flags); 590 if (offset_in_page(new_addr)) { 591 ret = new_addr; 592 goto out; 593 } 594 595 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked); 596 } 597 out: 598 if (offset_in_page(ret)) { 599 vm_unacct_memory(charged); 600 locked = 0; 601 } 602 up_write(¤t->mm->mmap_sem); 603 if (locked && new_len > old_len) 604 mm_populate(new_addr + old_len, new_len - old_len); 605 return ret; 606 } 607