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