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 * Before moving the page tables from the new vma to 225 * the old vma, we need to be sure the old vma is 226 * queued after new vma in the same_anon_vma list to 227 * prevent SMP races with rmap_walk (that could lead 228 * rmap_walk to miss some page table). 229 */ 230 anon_vma_moveto_tail(vma); 231 232 /* 233 * On error, move entries back from new area to old, 234 * which will succeed since page tables still there, 235 * and then proceed to unmap new area instead of old. 236 */ 237 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len); 238 vma = new_vma; 239 old_len = new_len; 240 old_addr = new_addr; 241 new_addr = -ENOMEM; 242 } 243 244 /* Conceal VM_ACCOUNT so old reservation is not undone */ 245 if (vm_flags & VM_ACCOUNT) { 246 vma->vm_flags &= ~VM_ACCOUNT; 247 excess = vma->vm_end - vma->vm_start - old_len; 248 if (old_addr > vma->vm_start && 249 old_addr + old_len < vma->vm_end) 250 split = 1; 251 } 252 253 /* 254 * If we failed to move page tables we still do total_vm increment 255 * since do_munmap() will decrement it by old_len == new_len. 256 * 257 * Since total_vm is about to be raised artificially high for a 258 * moment, we need to restore high watermark afterwards: if stats 259 * are taken meanwhile, total_vm and hiwater_vm appear too high. 260 * If this were a serious issue, we'd add a flag to do_munmap(). 261 */ 262 hiwater_vm = mm->hiwater_vm; 263 mm->total_vm += new_len >> PAGE_SHIFT; 264 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); 265 266 if (do_munmap(mm, old_addr, old_len) < 0) { 267 /* OOM: unable to split vma, just get accounts right */ 268 vm_unacct_memory(excess >> PAGE_SHIFT); 269 excess = 0; 270 } 271 mm->hiwater_vm = hiwater_vm; 272 273 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 274 if (excess) { 275 vma->vm_flags |= VM_ACCOUNT; 276 if (split) 277 vma->vm_next->vm_flags |= VM_ACCOUNT; 278 } 279 280 if (vm_flags & VM_LOCKED) { 281 mm->locked_vm += new_len >> PAGE_SHIFT; 282 if (new_len > old_len) 283 mlock_vma_pages_range(new_vma, new_addr + old_len, 284 new_addr + new_len); 285 } 286 287 return new_addr; 288 } 289 290 static struct vm_area_struct *vma_to_resize(unsigned long addr, 291 unsigned long old_len, unsigned long new_len, unsigned long *p) 292 { 293 struct mm_struct *mm = current->mm; 294 struct vm_area_struct *vma = find_vma(mm, addr); 295 296 if (!vma || vma->vm_start > addr) 297 goto Efault; 298 299 if (is_vm_hugetlb_page(vma)) 300 goto Einval; 301 302 /* We can't remap across vm area boundaries */ 303 if (old_len > vma->vm_end - addr) 304 goto Efault; 305 306 /* Need to be careful about a growing mapping */ 307 if (new_len > old_len) { 308 unsigned long pgoff; 309 310 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) 311 goto Efault; 312 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; 313 pgoff += vma->vm_pgoff; 314 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) 315 goto Einval; 316 } 317 318 if (vma->vm_flags & VM_LOCKED) { 319 unsigned long locked, lock_limit; 320 locked = mm->locked_vm << PAGE_SHIFT; 321 lock_limit = rlimit(RLIMIT_MEMLOCK); 322 locked += new_len - old_len; 323 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 324 goto Eagain; 325 } 326 327 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) 328 goto Enomem; 329 330 if (vma->vm_flags & VM_ACCOUNT) { 331 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; 332 if (security_vm_enough_memory_mm(mm, charged)) 333 goto Efault; 334 *p = charged; 335 } 336 337 return vma; 338 339 Efault: /* very odd choice for most of the cases, but... */ 340 return ERR_PTR(-EFAULT); 341 Einval: 342 return ERR_PTR(-EINVAL); 343 Enomem: 344 return ERR_PTR(-ENOMEM); 345 Eagain: 346 return ERR_PTR(-EAGAIN); 347 } 348 349 static unsigned long mremap_to(unsigned long addr, 350 unsigned long old_len, unsigned long new_addr, 351 unsigned long new_len) 352 { 353 struct mm_struct *mm = current->mm; 354 struct vm_area_struct *vma; 355 unsigned long ret = -EINVAL; 356 unsigned long charged = 0; 357 unsigned long map_flags; 358 359 if (new_addr & ~PAGE_MASK) 360 goto out; 361 362 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 363 goto out; 364 365 /* Check if the location we're moving into overlaps the 366 * old location at all, and fail if it does. 367 */ 368 if ((new_addr <= addr) && (new_addr+new_len) > addr) 369 goto out; 370 371 if ((addr <= new_addr) && (addr+old_len) > new_addr) 372 goto out; 373 374 ret = do_munmap(mm, new_addr, new_len); 375 if (ret) 376 goto out; 377 378 if (old_len >= new_len) { 379 ret = do_munmap(mm, addr+new_len, old_len - new_len); 380 if (ret && old_len != new_len) 381 goto out; 382 old_len = new_len; 383 } 384 385 vma = vma_to_resize(addr, old_len, new_len, &charged); 386 if (IS_ERR(vma)) { 387 ret = PTR_ERR(vma); 388 goto out; 389 } 390 391 map_flags = MAP_FIXED; 392 if (vma->vm_flags & VM_MAYSHARE) 393 map_flags |= MAP_SHARED; 394 395 ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff + 396 ((addr - vma->vm_start) >> PAGE_SHIFT), 397 map_flags); 398 if (ret & ~PAGE_MASK) 399 goto out1; 400 401 ret = move_vma(vma, addr, old_len, new_len, new_addr); 402 if (!(ret & ~PAGE_MASK)) 403 goto out; 404 out1: 405 vm_unacct_memory(charged); 406 407 out: 408 return ret; 409 } 410 411 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta) 412 { 413 unsigned long end = vma->vm_end + delta; 414 if (end < vma->vm_end) /* overflow */ 415 return 0; 416 if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */ 417 return 0; 418 if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start, 419 0, MAP_FIXED) & ~PAGE_MASK) 420 return 0; 421 return 1; 422 } 423 424 /* 425 * Expand (or shrink) an existing mapping, potentially moving it at the 426 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 427 * 428 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 429 * This option implies MREMAP_MAYMOVE. 430 */ 431 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, 432 unsigned long, new_len, unsigned long, flags, 433 unsigned long, new_addr) 434 { 435 struct mm_struct *mm = current->mm; 436 struct vm_area_struct *vma; 437 unsigned long ret = -EINVAL; 438 unsigned long charged = 0; 439 440 down_write(¤t->mm->mmap_sem); 441 442 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 443 goto out; 444 445 if (addr & ~PAGE_MASK) 446 goto out; 447 448 old_len = PAGE_ALIGN(old_len); 449 new_len = PAGE_ALIGN(new_len); 450 451 /* 452 * We allow a zero old-len as a special case 453 * for DOS-emu "duplicate shm area" thing. But 454 * a zero new-len is nonsensical. 455 */ 456 if (!new_len) 457 goto out; 458 459 if (flags & MREMAP_FIXED) { 460 if (flags & MREMAP_MAYMOVE) 461 ret = mremap_to(addr, old_len, new_addr, new_len); 462 goto out; 463 } 464 465 /* 466 * Always allow a shrinking remap: that just unmaps 467 * the unnecessary pages.. 468 * do_munmap does all the needed commit accounting 469 */ 470 if (old_len >= new_len) { 471 ret = do_munmap(mm, addr+new_len, old_len - new_len); 472 if (ret && old_len != new_len) 473 goto out; 474 ret = addr; 475 goto out; 476 } 477 478 /* 479 * Ok, we need to grow.. 480 */ 481 vma = vma_to_resize(addr, old_len, new_len, &charged); 482 if (IS_ERR(vma)) { 483 ret = PTR_ERR(vma); 484 goto out; 485 } 486 487 /* old_len exactly to the end of the area.. 488 */ 489 if (old_len == vma->vm_end - addr) { 490 /* can we just expand the current mapping? */ 491 if (vma_expandable(vma, new_len - old_len)) { 492 int pages = (new_len - old_len) >> PAGE_SHIFT; 493 494 if (vma_adjust(vma, vma->vm_start, addr + new_len, 495 vma->vm_pgoff, NULL)) { 496 ret = -ENOMEM; 497 goto out; 498 } 499 500 mm->total_vm += pages; 501 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); 502 if (vma->vm_flags & VM_LOCKED) { 503 mm->locked_vm += pages; 504 mlock_vma_pages_range(vma, addr + old_len, 505 addr + new_len); 506 } 507 ret = addr; 508 goto out; 509 } 510 } 511 512 /* 513 * We weren't able to just expand or shrink the area, 514 * we need to create a new one and move it.. 515 */ 516 ret = -ENOMEM; 517 if (flags & MREMAP_MAYMOVE) { 518 unsigned long map_flags = 0; 519 if (vma->vm_flags & VM_MAYSHARE) 520 map_flags |= MAP_SHARED; 521 522 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 523 vma->vm_pgoff + 524 ((addr - vma->vm_start) >> PAGE_SHIFT), 525 map_flags); 526 if (new_addr & ~PAGE_MASK) { 527 ret = new_addr; 528 goto out; 529 } 530 531 ret = move_vma(vma, addr, old_len, new_len, new_addr); 532 } 533 out: 534 if (ret & ~PAGE_MASK) 535 vm_unacct_memory(charged); 536 up_write(¤t->mm->mmap_sem); 537 return ret; 538 } 539