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/sched/sysctl.h> 24 #include <linux/uaccess.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 pte_t move_soft_dirty_pte(pte_t pte) 74 { 75 /* 76 * Set soft dirty bit so we can notice 77 * in userspace the ptes were moved. 78 */ 79 #ifdef CONFIG_MEM_SOFT_DIRTY 80 if (pte_present(pte)) 81 pte = pte_mksoft_dirty(pte); 82 else if (is_swap_pte(pte)) 83 pte = pte_swp_mksoft_dirty(pte); 84 #endif 85 return pte; 86 } 87 88 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, 89 unsigned long old_addr, unsigned long old_end, 90 struct vm_area_struct *new_vma, pmd_t *new_pmd, 91 unsigned long new_addr, bool need_rmap_locks) 92 { 93 struct address_space *mapping = NULL; 94 struct anon_vma *anon_vma = NULL; 95 struct mm_struct *mm = vma->vm_mm; 96 pte_t *old_pte, *new_pte, pte; 97 spinlock_t *old_ptl, *new_ptl; 98 99 /* 100 * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma 101 * locks to ensure that rmap will always observe either the old or the 102 * new ptes. This is the easiest way to avoid races with 103 * truncate_pagecache(), page migration, etc... 104 * 105 * When need_rmap_locks is false, we use other ways to avoid 106 * such races: 107 * 108 * - During exec() shift_arg_pages(), we use a specially tagged vma 109 * which rmap call sites look for using is_vma_temporary_stack(). 110 * 111 * - During mremap(), new_vma is often known to be placed after vma 112 * in rmap traversal order. This ensures rmap will always observe 113 * either the old pte, or the new pte, or both (the page table locks 114 * serialize access to individual ptes, but only rmap traversal 115 * order guarantees that we won't miss both the old and new ptes). 116 */ 117 if (need_rmap_locks) { 118 if (vma->vm_file) { 119 mapping = vma->vm_file->f_mapping; 120 i_mmap_lock_write(mapping); 121 } 122 if (vma->anon_vma) { 123 anon_vma = vma->anon_vma; 124 anon_vma_lock_write(anon_vma); 125 } 126 } 127 128 /* 129 * We don't have to worry about the ordering of src and dst 130 * pte locks because exclusive mmap_sem prevents deadlock. 131 */ 132 old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl); 133 new_pte = pte_offset_map(new_pmd, new_addr); 134 new_ptl = pte_lockptr(mm, new_pmd); 135 if (new_ptl != old_ptl) 136 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); 137 arch_enter_lazy_mmu_mode(); 138 139 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, 140 new_pte++, new_addr += PAGE_SIZE) { 141 if (pte_none(*old_pte)) 142 continue; 143 pte = ptep_get_and_clear(mm, old_addr, old_pte); 144 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr); 145 pte = move_soft_dirty_pte(pte); 146 set_pte_at(mm, new_addr, new_pte, pte); 147 } 148 149 arch_leave_lazy_mmu_mode(); 150 if (new_ptl != old_ptl) 151 spin_unlock(new_ptl); 152 pte_unmap(new_pte - 1); 153 pte_unmap_unlock(old_pte - 1, old_ptl); 154 if (anon_vma) 155 anon_vma_unlock_write(anon_vma); 156 if (mapping) 157 i_mmap_unlock_write(mapping); 158 } 159 160 #define LATENCY_LIMIT (64 * PAGE_SIZE) 161 162 unsigned long move_page_tables(struct vm_area_struct *vma, 163 unsigned long old_addr, struct vm_area_struct *new_vma, 164 unsigned long new_addr, unsigned long len, 165 bool need_rmap_locks) 166 { 167 unsigned long extent, next, old_end; 168 pmd_t *old_pmd, *new_pmd; 169 bool need_flush = false; 170 unsigned long mmun_start; /* For mmu_notifiers */ 171 unsigned long mmun_end; /* For mmu_notifiers */ 172 173 old_end = old_addr + len; 174 flush_cache_range(vma, old_addr, old_end); 175 176 mmun_start = old_addr; 177 mmun_end = old_end; 178 mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end); 179 180 for (; old_addr < old_end; old_addr += extent, new_addr += extent) { 181 cond_resched(); 182 next = (old_addr + PMD_SIZE) & PMD_MASK; 183 /* even if next overflowed, extent below will be ok */ 184 extent = next - old_addr; 185 if (extent > old_end - old_addr) 186 extent = old_end - old_addr; 187 old_pmd = get_old_pmd(vma->vm_mm, old_addr); 188 if (!old_pmd) 189 continue; 190 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); 191 if (!new_pmd) 192 break; 193 if (pmd_trans_huge(*old_pmd)) { 194 int err = 0; 195 if (extent == HPAGE_PMD_SIZE) { 196 VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma, 197 vma); 198 /* See comment in move_ptes() */ 199 if (need_rmap_locks) 200 anon_vma_lock_write(vma->anon_vma); 201 err = move_huge_pmd(vma, new_vma, old_addr, 202 new_addr, old_end, 203 old_pmd, new_pmd); 204 if (need_rmap_locks) 205 anon_vma_unlock_write(vma->anon_vma); 206 } 207 if (err > 0) { 208 need_flush = true; 209 continue; 210 } else if (!err) { 211 split_huge_page_pmd(vma, old_addr, old_pmd); 212 } 213 VM_BUG_ON(pmd_trans_huge(*old_pmd)); 214 } 215 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma, 216 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 /* 279 * On error, move entries back from new area to old, 280 * which will succeed since page tables still there, 281 * and then proceed to unmap new area instead of old. 282 */ 283 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len, 284 true); 285 vma = new_vma; 286 old_len = new_len; 287 old_addr = new_addr; 288 new_addr = -ENOMEM; 289 } else if (vma->vm_file && vma->vm_file->f_op->mremap) { 290 err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma); 291 if (err < 0) { 292 move_page_tables(new_vma, new_addr, vma, old_addr, 293 moved_len, true); 294 return err; 295 } 296 } 297 298 /* Conceal VM_ACCOUNT so old reservation is not undone */ 299 if (vm_flags & VM_ACCOUNT) { 300 vma->vm_flags &= ~VM_ACCOUNT; 301 excess = vma->vm_end - vma->vm_start - old_len; 302 if (old_addr > vma->vm_start && 303 old_addr + old_len < vma->vm_end) 304 split = 1; 305 } 306 307 /* 308 * If we failed to move page tables we still do total_vm increment 309 * since do_munmap() will decrement it by old_len == new_len. 310 * 311 * Since total_vm is about to be raised artificially high for a 312 * moment, we need to restore high watermark afterwards: if stats 313 * are taken meanwhile, total_vm and hiwater_vm appear too high. 314 * If this were a serious issue, we'd add a flag to do_munmap(). 315 */ 316 hiwater_vm = mm->hiwater_vm; 317 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); 318 319 if (do_munmap(mm, old_addr, old_len) < 0) { 320 /* OOM: unable to split vma, just get accounts right */ 321 vm_unacct_memory(excess >> PAGE_SHIFT); 322 excess = 0; 323 } 324 mm->hiwater_vm = hiwater_vm; 325 326 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 327 if (excess) { 328 vma->vm_flags |= VM_ACCOUNT; 329 if (split) 330 vma->vm_next->vm_flags |= VM_ACCOUNT; 331 } 332 333 if (vm_flags & VM_LOCKED) { 334 mm->locked_vm += new_len >> PAGE_SHIFT; 335 *locked = true; 336 } 337 338 return new_addr; 339 } 340 341 static struct vm_area_struct *vma_to_resize(unsigned long addr, 342 unsigned long old_len, unsigned long new_len, unsigned long *p) 343 { 344 struct mm_struct *mm = current->mm; 345 struct vm_area_struct *vma = find_vma(mm, addr); 346 347 if (!vma || vma->vm_start > addr) 348 goto Efault; 349 350 if (is_vm_hugetlb_page(vma)) 351 goto Einval; 352 353 /* We can't remap across vm area boundaries */ 354 if (old_len > vma->vm_end - addr) 355 goto Efault; 356 357 /* Need to be careful about a growing mapping */ 358 if (new_len > old_len) { 359 unsigned long pgoff; 360 361 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) 362 goto Efault; 363 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; 364 pgoff += vma->vm_pgoff; 365 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) 366 goto Einval; 367 } 368 369 if (vma->vm_flags & VM_LOCKED) { 370 unsigned long locked, lock_limit; 371 locked = mm->locked_vm << PAGE_SHIFT; 372 lock_limit = rlimit(RLIMIT_MEMLOCK); 373 locked += new_len - old_len; 374 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 375 goto Eagain; 376 } 377 378 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) 379 goto Enomem; 380 381 if (vma->vm_flags & VM_ACCOUNT) { 382 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; 383 if (security_vm_enough_memory_mm(mm, charged)) 384 goto Efault; 385 *p = charged; 386 } 387 388 return vma; 389 390 Efault: /* very odd choice for most of the cases, but... */ 391 return ERR_PTR(-EFAULT); 392 Einval: 393 return ERR_PTR(-EINVAL); 394 Enomem: 395 return ERR_PTR(-ENOMEM); 396 Eagain: 397 return ERR_PTR(-EAGAIN); 398 } 399 400 static unsigned long mremap_to(unsigned long addr, unsigned long old_len, 401 unsigned long new_addr, unsigned long new_len, bool *locked) 402 { 403 struct mm_struct *mm = current->mm; 404 struct vm_area_struct *vma; 405 unsigned long ret = -EINVAL; 406 unsigned long charged = 0; 407 unsigned long map_flags; 408 409 if (new_addr & ~PAGE_MASK) 410 goto out; 411 412 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 413 goto out; 414 415 /* Check if the location we're moving into overlaps the 416 * old location at all, and fail if it does. 417 */ 418 if ((new_addr <= addr) && (new_addr+new_len) > addr) 419 goto out; 420 421 if ((addr <= new_addr) && (addr+old_len) > new_addr) 422 goto out; 423 424 ret = do_munmap(mm, new_addr, new_len); 425 if (ret) 426 goto out; 427 428 if (old_len >= new_len) { 429 ret = do_munmap(mm, addr+new_len, old_len - new_len); 430 if (ret && old_len != new_len) 431 goto out; 432 old_len = new_len; 433 } 434 435 vma = vma_to_resize(addr, old_len, new_len, &charged); 436 if (IS_ERR(vma)) { 437 ret = PTR_ERR(vma); 438 goto out; 439 } 440 441 map_flags = MAP_FIXED; 442 if (vma->vm_flags & VM_MAYSHARE) 443 map_flags |= MAP_SHARED; 444 445 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + 446 ((addr - vma->vm_start) >> PAGE_SHIFT), 447 map_flags); 448 if (ret & ~PAGE_MASK) 449 goto out1; 450 451 ret = move_vma(vma, addr, old_len, new_len, new_addr, locked); 452 if (!(ret & ~PAGE_MASK)) 453 goto out; 454 out1: 455 vm_unacct_memory(charged); 456 457 out: 458 return ret; 459 } 460 461 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) 462 { 463 unsigned long end = vma->vm_end + delta; 464 if (end < vma->vm_end) /* overflow */ 465 return 0; 466 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ 467 return 0; 468 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, 469 0, MAP_FIXED) & ~PAGE_MASK) 470 return 0; 471 return 1; 472 } 473 474 /* 475 * Expand (or shrink) an existing mapping, potentially moving it at the 476 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 477 * 478 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 479 * This option implies MREMAP_MAYMOVE. 480 */ 481 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, 482 unsigned long, new_len, unsigned long, flags, 483 unsigned long, new_addr) 484 { 485 struct mm_struct *mm = current->mm; 486 struct vm_area_struct *vma; 487 unsigned long ret = -EINVAL; 488 unsigned long charged = 0; 489 bool locked = false; 490 491 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 492 return ret; 493 494 if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE)) 495 return ret; 496 497 if (addr & ~PAGE_MASK) 498 return ret; 499 500 old_len = PAGE_ALIGN(old_len); 501 new_len = PAGE_ALIGN(new_len); 502 503 /* 504 * We allow a zero old-len as a special case 505 * for DOS-emu "duplicate shm area" thing. But 506 * a zero new-len is nonsensical. 507 */ 508 if (!new_len) 509 return ret; 510 511 down_write(¤t->mm->mmap_sem); 512 513 if (flags & MREMAP_FIXED) { 514 ret = mremap_to(addr, old_len, new_addr, new_len, 515 &locked); 516 goto out; 517 } 518 519 /* 520 * Always allow a shrinking remap: that just unmaps 521 * the unnecessary pages.. 522 * do_munmap does all the needed commit accounting 523 */ 524 if (old_len >= new_len) { 525 ret = do_munmap(mm, addr+new_len, old_len - new_len); 526 if (ret && old_len != new_len) 527 goto out; 528 ret = addr; 529 goto out; 530 } 531 532 /* 533 * Ok, we need to grow.. 534 */ 535 vma = vma_to_resize(addr, old_len, new_len, &charged); 536 if (IS_ERR(vma)) { 537 ret = PTR_ERR(vma); 538 goto out; 539 } 540 541 /* old_len exactly to the end of the area.. 542 */ 543 if (old_len == vma->vm_end - addr) { 544 /* can we just expand the current mapping? */ 545 if (vma_expandable(vma, new_len - old_len)) { 546 int pages = (new_len - old_len) >> PAGE_SHIFT; 547 548 if (vma_adjust(vma, vma->vm_start, addr + new_len, 549 vma->vm_pgoff, NULL)) { 550 ret = -ENOMEM; 551 goto out; 552 } 553 554 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); 555 if (vma->vm_flags & VM_LOCKED) { 556 mm->locked_vm += pages; 557 locked = true; 558 new_addr = addr; 559 } 560 ret = addr; 561 goto out; 562 } 563 } 564 565 /* 566 * We weren't able to just expand or shrink the area, 567 * we need to create a new one and move it.. 568 */ 569 ret = -ENOMEM; 570 if (flags & MREMAP_MAYMOVE) { 571 unsigned long map_flags = 0; 572 if (vma->vm_flags & VM_MAYSHARE) 573 map_flags |= MAP_SHARED; 574 575 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 576 vma->vm_pgoff + 577 ((addr - vma->vm_start) >> PAGE_SHIFT), 578 map_flags); 579 if (new_addr & ~PAGE_MASK) { 580 ret = new_addr; 581 goto out; 582 } 583 584 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked); 585 } 586 out: 587 if (ret & ~PAGE_MASK) 588 vm_unacct_memory(charged); 589 up_write(¤t->mm->mmap_sem); 590 if (locked && new_len > old_len) 591 mm_populate(new_addr + old_len, new_len - old_len); 592 return ret; 593 } 594