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