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