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