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/slab.h> 13 #include <linux/shm.h> 14 #include <linux/ksm.h> 15 #include <linux/mman.h> 16 #include <linux/swap.h> 17 #include <linux/capability.h> 18 #include <linux/fs.h> 19 #include <linux/highmem.h> 20 #include <linux/security.h> 21 #include <linux/syscalls.h> 22 #include <linux/mmu_notifier.h> 23 24 #include <asm/uaccess.h> 25 #include <asm/cacheflush.h> 26 #include <asm/tlbflush.h> 27 28 #include "internal.h" 29 30 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr) 31 { 32 pgd_t *pgd; 33 pud_t *pud; 34 pmd_t *pmd; 35 36 pgd = pgd_offset(mm, addr); 37 if (pgd_none_or_clear_bad(pgd)) 38 return NULL; 39 40 pud = pud_offset(pgd, addr); 41 if (pud_none_or_clear_bad(pud)) 42 return NULL; 43 44 pmd = pmd_offset(pud, addr); 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, 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 if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr)) 67 return NULL; 68 69 return pmd; 70 } 71 72 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd, 73 unsigned long old_addr, unsigned long old_end, 74 struct vm_area_struct *new_vma, pmd_t *new_pmd, 75 unsigned long new_addr) 76 { 77 struct address_space *mapping = NULL; 78 struct mm_struct *mm = vma->vm_mm; 79 pte_t *old_pte, *new_pte, pte; 80 spinlock_t *old_ptl, *new_ptl; 81 unsigned long old_start; 82 83 old_start = old_addr; 84 mmu_notifier_invalidate_range_start(vma->vm_mm, 85 old_start, old_end); 86 if (vma->vm_file) { 87 /* 88 * Subtle point from Rajesh Venkatasubramanian: before 89 * moving file-based ptes, we must lock truncate_pagecache 90 * out, since it might clean the dst vma before the src vma, 91 * and we propagate stale pages into the dst afterward. 92 */ 93 mapping = vma->vm_file->f_mapping; 94 spin_lock(&mapping->i_mmap_lock); 95 if (new_vma->vm_truncate_count && 96 new_vma->vm_truncate_count != vma->vm_truncate_count) 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_nested(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_nested(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, 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 /* 265 * Expand (or shrink) an existing mapping, potentially moving it at the 266 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 267 * 268 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 269 * This option implies MREMAP_MAYMOVE. 270 */ 271 unsigned long do_mremap(unsigned long addr, 272 unsigned long old_len, unsigned long new_len, 273 unsigned long flags, unsigned long new_addr) 274 { 275 struct mm_struct *mm = current->mm; 276 struct vm_area_struct *vma; 277 unsigned long ret = -EINVAL; 278 unsigned long charged = 0; 279 280 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 281 goto out; 282 283 if (addr & ~PAGE_MASK) 284 goto out; 285 286 old_len = PAGE_ALIGN(old_len); 287 new_len = PAGE_ALIGN(new_len); 288 289 /* 290 * We allow a zero old-len as a special case 291 * for DOS-emu "duplicate shm area" thing. But 292 * a zero new-len is nonsensical. 293 */ 294 if (!new_len) 295 goto out; 296 297 /* new_addr is only valid if MREMAP_FIXED is specified */ 298 if (flags & MREMAP_FIXED) { 299 if (new_addr & ~PAGE_MASK) 300 goto out; 301 if (!(flags & MREMAP_MAYMOVE)) 302 goto out; 303 304 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 305 goto out; 306 307 /* Check if the location we're moving into overlaps the 308 * old location at all, and fail if it does. 309 */ 310 if ((new_addr <= addr) && (new_addr+new_len) > addr) 311 goto out; 312 313 if ((addr <= new_addr) && (addr+old_len) > new_addr) 314 goto out; 315 316 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); 317 if (ret) 318 goto out; 319 320 ret = do_munmap(mm, new_addr, new_len); 321 if (ret) 322 goto out; 323 } 324 325 /* 326 * Always allow a shrinking remap: that just unmaps 327 * the unnecessary pages.. 328 * do_munmap does all the needed commit accounting 329 */ 330 if (old_len >= new_len) { 331 ret = do_munmap(mm, addr+new_len, old_len - new_len); 332 if (ret && old_len != new_len) 333 goto out; 334 ret = addr; 335 if (!(flags & MREMAP_FIXED) || (new_addr == addr)) 336 goto out; 337 old_len = new_len; 338 } 339 340 /* 341 * Ok, we need to grow.. or relocate. 342 */ 343 ret = -EFAULT; 344 vma = find_vma(mm, addr); 345 if (!vma || vma->vm_start > addr) 346 goto out; 347 if (is_vm_hugetlb_page(vma)) { 348 ret = -EINVAL; 349 goto out; 350 } 351 /* We can't remap across vm area boundaries */ 352 if (old_len > vma->vm_end - addr) 353 goto out; 354 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) { 355 if (new_len > old_len) 356 goto out; 357 } 358 if (vma->vm_flags & VM_LOCKED) { 359 unsigned long locked, lock_limit; 360 locked = mm->locked_vm << PAGE_SHIFT; 361 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 362 locked += new_len - old_len; 363 ret = -EAGAIN; 364 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 365 goto out; 366 } 367 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) { 368 ret = -ENOMEM; 369 goto out; 370 } 371 372 if (vma->vm_flags & VM_ACCOUNT) { 373 charged = (new_len - old_len) >> PAGE_SHIFT; 374 if (security_vm_enough_memory(charged)) 375 goto out_nc; 376 } 377 378 /* old_len exactly to the end of the area.. 379 * And we're not relocating the area. 380 */ 381 if (old_len == vma->vm_end - addr && 382 !((flags & MREMAP_FIXED) && (addr != new_addr)) && 383 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) { 384 unsigned long max_addr = TASK_SIZE; 385 if (vma->vm_next) 386 max_addr = vma->vm_next->vm_start; 387 /* can we just expand the current mapping? */ 388 if (max_addr - addr >= new_len) { 389 int pages = (new_len - old_len) >> PAGE_SHIFT; 390 391 vma_adjust(vma, vma->vm_start, 392 addr + new_len, vma->vm_pgoff, NULL); 393 394 mm->total_vm += pages; 395 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); 396 if (vma->vm_flags & VM_LOCKED) { 397 mm->locked_vm += pages; 398 mlock_vma_pages_range(vma, addr + old_len, 399 addr + new_len); 400 } 401 ret = addr; 402 goto out; 403 } 404 } 405 406 /* 407 * We weren't able to just expand or shrink the area, 408 * we need to create a new one and move it.. 409 */ 410 ret = -ENOMEM; 411 if (flags & MREMAP_MAYMOVE) { 412 if (!(flags & MREMAP_FIXED)) { 413 unsigned long map_flags = 0; 414 if (vma->vm_flags & VM_MAYSHARE) 415 map_flags |= MAP_SHARED; 416 417 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 418 vma->vm_pgoff, map_flags); 419 if (new_addr & ~PAGE_MASK) { 420 ret = new_addr; 421 goto out; 422 } 423 424 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); 425 if (ret) 426 goto out; 427 } 428 ret = move_vma(vma, addr, old_len, new_len, new_addr); 429 } 430 out: 431 if (ret & ~PAGE_MASK) 432 vm_unacct_memory(charged); 433 out_nc: 434 return ret; 435 } 436 437 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, 438 unsigned long, new_len, unsigned long, flags, 439 unsigned long, new_addr) 440 { 441 unsigned long ret; 442 443 down_write(¤t->mm->mmap_sem); 444 ret = do_mremap(addr, old_len, new_len, flags, new_addr); 445 up_write(¤t->mm->mmap_sem); 446 return ret; 447 } 448