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/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 vmtruncate out, 89 * 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_nested(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_nested(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; 177 178 /* 179 * We'd prefer to avoid failure later on in do_munmap: 180 * which may split one vma into three before unmapping. 181 */ 182 if (mm->map_count >= sysctl_max_map_count - 3) 183 return -ENOMEM; 184 185 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); 186 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff); 187 if (!new_vma) 188 return -ENOMEM; 189 190 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len); 191 if (moved_len < old_len) { 192 /* 193 * On error, move entries back from new area to old, 194 * which will succeed since page tables still there, 195 * and then proceed to unmap new area instead of old. 196 */ 197 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len); 198 vma = new_vma; 199 old_len = new_len; 200 old_addr = new_addr; 201 new_addr = -ENOMEM; 202 } 203 204 /* Conceal VM_ACCOUNT so old reservation is not undone */ 205 if (vm_flags & VM_ACCOUNT) { 206 vma->vm_flags &= ~VM_ACCOUNT; 207 excess = vma->vm_end - vma->vm_start - old_len; 208 if (old_addr > vma->vm_start && 209 old_addr + old_len < vma->vm_end) 210 split = 1; 211 } 212 213 /* 214 * If we failed to move page tables we still do total_vm increment 215 * since do_munmap() will decrement it by old_len == new_len. 216 * 217 * Since total_vm is about to be raised artificially high for a 218 * moment, we need to restore high watermark afterwards: if stats 219 * are taken meanwhile, total_vm and hiwater_vm appear too high. 220 * If this were a serious issue, we'd add a flag to do_munmap(). 221 */ 222 hiwater_vm = mm->hiwater_vm; 223 mm->total_vm += new_len >> PAGE_SHIFT; 224 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); 225 226 if (do_munmap(mm, old_addr, old_len) < 0) { 227 /* OOM: unable to split vma, just get accounts right */ 228 vm_unacct_memory(excess >> PAGE_SHIFT); 229 excess = 0; 230 } 231 mm->hiwater_vm = hiwater_vm; 232 233 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 234 if (excess) { 235 vma->vm_flags |= VM_ACCOUNT; 236 if (split) 237 vma->vm_next->vm_flags |= VM_ACCOUNT; 238 } 239 240 if (vm_flags & VM_LOCKED) { 241 mm->locked_vm += new_len >> PAGE_SHIFT; 242 if (new_len > old_len) 243 mlock_vma_pages_range(new_vma, new_addr + old_len, 244 new_addr + new_len); 245 } 246 247 return new_addr; 248 } 249 250 /* 251 * Expand (or shrink) an existing mapping, potentially moving it at the 252 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 253 * 254 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 255 * This option implies MREMAP_MAYMOVE. 256 */ 257 unsigned long do_mremap(unsigned long addr, 258 unsigned long old_len, unsigned long new_len, 259 unsigned long flags, unsigned long new_addr) 260 { 261 struct mm_struct *mm = current->mm; 262 struct vm_area_struct *vma; 263 unsigned long ret = -EINVAL; 264 unsigned long charged = 0; 265 266 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 267 goto out; 268 269 if (addr & ~PAGE_MASK) 270 goto out; 271 272 old_len = PAGE_ALIGN(old_len); 273 new_len = PAGE_ALIGN(new_len); 274 275 /* 276 * We allow a zero old-len as a special case 277 * for DOS-emu "duplicate shm area" thing. But 278 * a zero new-len is nonsensical. 279 */ 280 if (!new_len) 281 goto out; 282 283 /* new_addr is only valid if MREMAP_FIXED is specified */ 284 if (flags & MREMAP_FIXED) { 285 if (new_addr & ~PAGE_MASK) 286 goto out; 287 if (!(flags & MREMAP_MAYMOVE)) 288 goto out; 289 290 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 291 goto out; 292 293 /* Check if the location we're moving into overlaps the 294 * old location at all, and fail if it does. 295 */ 296 if ((new_addr <= addr) && (new_addr+new_len) > addr) 297 goto out; 298 299 if ((addr <= new_addr) && (addr+old_len) > new_addr) 300 goto out; 301 302 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); 303 if (ret) 304 goto out; 305 306 ret = do_munmap(mm, new_addr, new_len); 307 if (ret) 308 goto out; 309 } 310 311 /* 312 * Always allow a shrinking remap: that just unmaps 313 * the unnecessary pages.. 314 * do_munmap does all the needed commit accounting 315 */ 316 if (old_len >= new_len) { 317 ret = do_munmap(mm, addr+new_len, old_len - new_len); 318 if (ret && old_len != new_len) 319 goto out; 320 ret = addr; 321 if (!(flags & MREMAP_FIXED) || (new_addr == addr)) 322 goto out; 323 old_len = new_len; 324 } 325 326 /* 327 * Ok, we need to grow.. or relocate. 328 */ 329 ret = -EFAULT; 330 vma = find_vma(mm, addr); 331 if (!vma || vma->vm_start > addr) 332 goto out; 333 if (is_vm_hugetlb_page(vma)) { 334 ret = -EINVAL; 335 goto out; 336 } 337 /* We can't remap across vm area boundaries */ 338 if (old_len > vma->vm_end - addr) 339 goto out; 340 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) { 341 if (new_len > old_len) 342 goto out; 343 } 344 if (vma->vm_flags & VM_LOCKED) { 345 unsigned long locked, lock_limit; 346 locked = mm->locked_vm << PAGE_SHIFT; 347 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 348 locked += new_len - old_len; 349 ret = -EAGAIN; 350 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 351 goto out; 352 } 353 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) { 354 ret = -ENOMEM; 355 goto out; 356 } 357 358 if (vma->vm_flags & VM_ACCOUNT) { 359 charged = (new_len - old_len) >> PAGE_SHIFT; 360 if (security_vm_enough_memory(charged)) 361 goto out_nc; 362 } 363 364 /* old_len exactly to the end of the area.. 365 * And we're not relocating the area. 366 */ 367 if (old_len == vma->vm_end - addr && 368 !((flags & MREMAP_FIXED) && (addr != new_addr)) && 369 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) { 370 unsigned long max_addr = TASK_SIZE; 371 if (vma->vm_next) 372 max_addr = vma->vm_next->vm_start; 373 /* can we just expand the current mapping? */ 374 if (max_addr - addr >= new_len) { 375 int pages = (new_len - old_len) >> PAGE_SHIFT; 376 377 vma_adjust(vma, vma->vm_start, 378 addr + new_len, vma->vm_pgoff, NULL); 379 380 mm->total_vm += pages; 381 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); 382 if (vma->vm_flags & VM_LOCKED) { 383 mm->locked_vm += pages; 384 mlock_vma_pages_range(vma, addr + old_len, 385 addr + new_len); 386 } 387 ret = addr; 388 goto out; 389 } 390 } 391 392 /* 393 * We weren't able to just expand or shrink the area, 394 * we need to create a new one and move it.. 395 */ 396 ret = -ENOMEM; 397 if (flags & MREMAP_MAYMOVE) { 398 if (!(flags & MREMAP_FIXED)) { 399 unsigned long map_flags = 0; 400 if (vma->vm_flags & VM_MAYSHARE) 401 map_flags |= MAP_SHARED; 402 403 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 404 vma->vm_pgoff, map_flags); 405 if (new_addr & ~PAGE_MASK) { 406 ret = new_addr; 407 goto out; 408 } 409 410 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1); 411 if (ret) 412 goto out; 413 } 414 ret = move_vma(vma, addr, old_len, new_len, new_addr); 415 } 416 out: 417 if (ret & ~PAGE_MASK) 418 vm_unacct_memory(charged); 419 out_nc: 420 return ret; 421 } 422 423 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, 424 unsigned long, new_len, unsigned long, flags, 425 unsigned long, new_addr) 426 { 427 unsigned long ret; 428 429 down_write(¤t->mm->mmap_sem); 430 ret = do_mremap(addr, old_len, new_len, flags, new_addr); 431 up_write(¤t->mm->mmap_sem); 432 return ret; 433 } 434