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