1 /* 2 * mm/mremap.c 3 * 4 * (C) Copyright 1996 Linus Torvalds 5 * 6 * Address space accounting code <alan@redhat.com> 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/fs.h> 17 #include <linux/highmem.h> 18 #include <linux/security.h> 19 #include <linux/syscalls.h> 20 21 #include <asm/uaccess.h> 22 #include <asm/cacheflush.h> 23 #include <asm/tlbflush.h> 24 25 static pte_t *get_one_pte_map_nested(struct mm_struct *mm, unsigned long addr) 26 { 27 pgd_t *pgd; 28 pud_t *pud; 29 pmd_t *pmd; 30 pte_t *pte = NULL; 31 32 pgd = pgd_offset(mm, addr); 33 if (pgd_none_or_clear_bad(pgd)) 34 goto end; 35 36 pud = pud_offset(pgd, addr); 37 if (pud_none_or_clear_bad(pud)) 38 goto end; 39 40 pmd = pmd_offset(pud, addr); 41 if (pmd_none_or_clear_bad(pmd)) 42 goto end; 43 44 pte = pte_offset_map_nested(pmd, addr); 45 if (pte_none(*pte)) { 46 pte_unmap_nested(pte); 47 pte = NULL; 48 } 49 end: 50 return pte; 51 } 52 53 static pte_t *get_one_pte_map(struct mm_struct *mm, unsigned long addr) 54 { 55 pgd_t *pgd; 56 pud_t *pud; 57 pmd_t *pmd; 58 59 pgd = pgd_offset(mm, addr); 60 if (pgd_none_or_clear_bad(pgd)) 61 return NULL; 62 63 pud = pud_offset(pgd, addr); 64 if (pud_none_or_clear_bad(pud)) 65 return NULL; 66 67 pmd = pmd_offset(pud, addr); 68 if (pmd_none_or_clear_bad(pmd)) 69 return NULL; 70 71 return pte_offset_map(pmd, addr); 72 } 73 74 static inline pte_t *alloc_one_pte_map(struct mm_struct *mm, unsigned long addr) 75 { 76 pgd_t *pgd; 77 pud_t *pud; 78 pmd_t *pmd; 79 pte_t *pte = NULL; 80 81 pgd = pgd_offset(mm, addr); 82 83 pud = pud_alloc(mm, pgd, addr); 84 if (!pud) 85 return NULL; 86 pmd = pmd_alloc(mm, pud, addr); 87 if (pmd) 88 pte = pte_alloc_map(mm, pmd, addr); 89 return pte; 90 } 91 92 static int 93 move_one_page(struct vm_area_struct *vma, unsigned long old_addr, 94 struct vm_area_struct *new_vma, unsigned long new_addr) 95 { 96 struct address_space *mapping = NULL; 97 struct mm_struct *mm = vma->vm_mm; 98 int error = 0; 99 pte_t *src, *dst; 100 101 if (vma->vm_file) { 102 /* 103 * Subtle point from Rajesh Venkatasubramanian: before 104 * moving file-based ptes, we must lock vmtruncate out, 105 * since it might clean the dst vma before the src vma, 106 * and we propagate stale pages into the dst afterward. 107 */ 108 mapping = vma->vm_file->f_mapping; 109 spin_lock(&mapping->i_mmap_lock); 110 if (new_vma->vm_truncate_count && 111 new_vma->vm_truncate_count != vma->vm_truncate_count) 112 new_vma->vm_truncate_count = 0; 113 } 114 spin_lock(&mm->page_table_lock); 115 116 src = get_one_pte_map_nested(mm, old_addr); 117 if (src) { 118 /* 119 * Look to see whether alloc_one_pte_map needs to perform a 120 * memory allocation. If it does then we need to drop the 121 * atomic kmap 122 */ 123 dst = get_one_pte_map(mm, new_addr); 124 if (unlikely(!dst)) { 125 pte_unmap_nested(src); 126 if (mapping) 127 spin_unlock(&mapping->i_mmap_lock); 128 dst = alloc_one_pte_map(mm, new_addr); 129 if (mapping && !spin_trylock(&mapping->i_mmap_lock)) { 130 spin_unlock(&mm->page_table_lock); 131 spin_lock(&mapping->i_mmap_lock); 132 spin_lock(&mm->page_table_lock); 133 } 134 src = get_one_pte_map_nested(mm, old_addr); 135 } 136 /* 137 * Since alloc_one_pte_map can drop and re-acquire 138 * page_table_lock, we should re-check the src entry... 139 */ 140 if (src) { 141 if (dst) { 142 pte_t pte; 143 pte = ptep_clear_flush(vma, old_addr, src); 144 145 /* ZERO_PAGE can be dependant on virtual addr */ 146 pte = move_pte(pte, new_vma->vm_page_prot, 147 old_addr, new_addr); 148 set_pte_at(mm, new_addr, dst, pte); 149 } else 150 error = -ENOMEM; 151 pte_unmap_nested(src); 152 } 153 if (dst) 154 pte_unmap(dst); 155 } 156 spin_unlock(&mm->page_table_lock); 157 if (mapping) 158 spin_unlock(&mapping->i_mmap_lock); 159 return error; 160 } 161 162 static unsigned long move_page_tables(struct vm_area_struct *vma, 163 unsigned long old_addr, struct vm_area_struct *new_vma, 164 unsigned long new_addr, unsigned long len) 165 { 166 unsigned long offset; 167 168 flush_cache_range(vma, old_addr, old_addr + len); 169 170 /* 171 * This is not the clever way to do this, but we're taking the 172 * easy way out on the assumption that most remappings will be 173 * only a few pages.. This also makes error recovery easier. 174 */ 175 for (offset = 0; offset < len; offset += PAGE_SIZE) { 176 if (move_one_page(vma, old_addr + offset, 177 new_vma, new_addr + offset) < 0) 178 break; 179 cond_resched(); 180 } 181 return offset; 182 } 183 184 static unsigned long move_vma(struct vm_area_struct *vma, 185 unsigned long old_addr, unsigned long old_len, 186 unsigned long new_len, unsigned long new_addr) 187 { 188 struct mm_struct *mm = vma->vm_mm; 189 struct vm_area_struct *new_vma; 190 unsigned long vm_flags = vma->vm_flags; 191 unsigned long new_pgoff; 192 unsigned long moved_len; 193 unsigned long excess = 0; 194 int split = 0; 195 196 /* 197 * We'd prefer to avoid failure later on in do_munmap: 198 * which may split one vma into three before unmapping. 199 */ 200 if (mm->map_count >= sysctl_max_map_count - 3) 201 return -ENOMEM; 202 203 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); 204 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff); 205 if (!new_vma) 206 return -ENOMEM; 207 208 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len); 209 if (moved_len < old_len) { 210 /* 211 * On error, move entries back from new area to old, 212 * which will succeed since page tables still there, 213 * and then proceed to unmap new area instead of old. 214 */ 215 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len); 216 vma = new_vma; 217 old_len = new_len; 218 old_addr = new_addr; 219 new_addr = -ENOMEM; 220 } 221 222 /* Conceal VM_ACCOUNT so old reservation is not undone */ 223 if (vm_flags & VM_ACCOUNT) { 224 vma->vm_flags &= ~VM_ACCOUNT; 225 excess = vma->vm_end - vma->vm_start - old_len; 226 if (old_addr > vma->vm_start && 227 old_addr + old_len < vma->vm_end) 228 split = 1; 229 } 230 231 /* 232 * if we failed to move page tables we still do total_vm increment 233 * since do_munmap() will decrement it by old_len == new_len 234 */ 235 mm->total_vm += new_len >> PAGE_SHIFT; 236 __vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); 237 238 if (do_munmap(mm, old_addr, old_len) < 0) { 239 /* OOM: unable to split vma, just get accounts right */ 240 vm_unacct_memory(excess >> PAGE_SHIFT); 241 excess = 0; 242 } 243 244 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 245 if (excess) { 246 vma->vm_flags |= VM_ACCOUNT; 247 if (split) 248 vma->vm_next->vm_flags |= VM_ACCOUNT; 249 } 250 251 if (vm_flags & VM_LOCKED) { 252 mm->locked_vm += new_len >> PAGE_SHIFT; 253 if (new_len > old_len) 254 make_pages_present(new_addr + old_len, 255 new_addr + new_len); 256 } 257 258 return new_addr; 259 } 260 261 /* 262 * Expand (or shrink) an existing mapping, potentially moving it at the 263 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 264 * 265 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 266 * This option implies MREMAP_MAYMOVE. 267 */ 268 unsigned long do_mremap(unsigned long addr, 269 unsigned long old_len, unsigned long new_len, 270 unsigned long flags, unsigned long new_addr) 271 { 272 struct vm_area_struct *vma; 273 unsigned long ret = -EINVAL; 274 unsigned long charged = 0; 275 276 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 277 goto out; 278 279 if (addr & ~PAGE_MASK) 280 goto out; 281 282 old_len = PAGE_ALIGN(old_len); 283 new_len = PAGE_ALIGN(new_len); 284 285 /* 286 * We allow a zero old-len as a special case 287 * for DOS-emu "duplicate shm area" thing. But 288 * a zero new-len is nonsensical. 289 */ 290 if (!new_len) 291 goto out; 292 293 /* new_addr is only valid if MREMAP_FIXED is specified */ 294 if (flags & MREMAP_FIXED) { 295 if (new_addr & ~PAGE_MASK) 296 goto out; 297 if (!(flags & MREMAP_MAYMOVE)) 298 goto out; 299 300 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 301 goto out; 302 303 /* Check if the location we're moving into overlaps the 304 * old location at all, and fail if it does. 305 */ 306 if ((new_addr <= addr) && (new_addr+new_len) > addr) 307 goto out; 308 309 if ((addr <= new_addr) && (addr+old_len) > new_addr) 310 goto out; 311 312 ret = do_munmap(current->mm, new_addr, new_len); 313 if (ret) 314 goto out; 315 } 316 317 /* 318 * Always allow a shrinking remap: that just unmaps 319 * the unnecessary pages.. 320 * do_munmap does all the needed commit accounting 321 */ 322 if (old_len >= new_len) { 323 ret = do_munmap(current->mm, addr+new_len, old_len - new_len); 324 if (ret && old_len != new_len) 325 goto out; 326 ret = addr; 327 if (!(flags & MREMAP_FIXED) || (new_addr == addr)) 328 goto out; 329 old_len = new_len; 330 } 331 332 /* 333 * Ok, we need to grow.. or relocate. 334 */ 335 ret = -EFAULT; 336 vma = find_vma(current->mm, addr); 337 if (!vma || vma->vm_start > addr) 338 goto out; 339 if (is_vm_hugetlb_page(vma)) { 340 ret = -EINVAL; 341 goto out; 342 } 343 /* We can't remap across vm area boundaries */ 344 if (old_len > vma->vm_end - addr) 345 goto out; 346 if (vma->vm_flags & VM_DONTEXPAND) { 347 if (new_len > old_len) 348 goto out; 349 } 350 if (vma->vm_flags & VM_LOCKED) { 351 unsigned long locked, lock_limit; 352 locked = current->mm->locked_vm << PAGE_SHIFT; 353 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 354 locked += new_len - old_len; 355 ret = -EAGAIN; 356 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 357 goto out; 358 } 359 if (!may_expand_vm(current->mm, (new_len - old_len) >> PAGE_SHIFT)) { 360 ret = -ENOMEM; 361 goto out; 362 } 363 364 if (vma->vm_flags & VM_ACCOUNT) { 365 charged = (new_len - old_len) >> PAGE_SHIFT; 366 if (security_vm_enough_memory(charged)) 367 goto out_nc; 368 } 369 370 /* old_len exactly to the end of the area.. 371 * And we're not relocating the area. 372 */ 373 if (old_len == vma->vm_end - addr && 374 !((flags & MREMAP_FIXED) && (addr != new_addr)) && 375 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) { 376 unsigned long max_addr = TASK_SIZE; 377 if (vma->vm_next) 378 max_addr = vma->vm_next->vm_start; 379 /* can we just expand the current mapping? */ 380 if (max_addr - addr >= new_len) { 381 int pages = (new_len - old_len) >> PAGE_SHIFT; 382 383 vma_adjust(vma, vma->vm_start, 384 addr + new_len, vma->vm_pgoff, NULL); 385 386 current->mm->total_vm += pages; 387 __vm_stat_account(vma->vm_mm, vma->vm_flags, 388 vma->vm_file, pages); 389 if (vma->vm_flags & VM_LOCKED) { 390 current->mm->locked_vm += pages; 391 make_pages_present(addr + old_len, 392 addr + new_len); 393 } 394 ret = addr; 395 goto out; 396 } 397 } 398 399 /* 400 * We weren't able to just expand or shrink the area, 401 * we need to create a new one and move it.. 402 */ 403 ret = -ENOMEM; 404 if (flags & MREMAP_MAYMOVE) { 405 if (!(flags & MREMAP_FIXED)) { 406 unsigned long map_flags = 0; 407 if (vma->vm_flags & VM_MAYSHARE) 408 map_flags |= MAP_SHARED; 409 410 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 411 vma->vm_pgoff, map_flags); 412 ret = new_addr; 413 if (new_addr & ~PAGE_MASK) 414 goto out; 415 } 416 ret = move_vma(vma, addr, old_len, new_len, new_addr); 417 } 418 out: 419 if (ret & ~PAGE_MASK) 420 vm_unacct_memory(charged); 421 out_nc: 422 return ret; 423 } 424 425 asmlinkage unsigned long sys_mremap(unsigned long addr, 426 unsigned long old_len, unsigned long new_len, 427 unsigned long flags, unsigned long new_addr) 428 { 429 unsigned long ret; 430 431 down_write(¤t->mm->mmap_sem); 432 ret = do_mremap(addr, old_len, new_len, flags, new_addr); 433 up_write(¤t->mm->mmap_sem); 434 return ret; 435 } 436