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