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