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 set_pte_at(mm, new_addr, dst, pte); 145 } else 146 error = -ENOMEM; 147 pte_unmap_nested(src); 148 } 149 if (dst) 150 pte_unmap(dst); 151 } 152 spin_unlock(&mm->page_table_lock); 153 if (mapping) 154 spin_unlock(&mapping->i_mmap_lock); 155 return error; 156 } 157 158 static unsigned long move_page_tables(struct vm_area_struct *vma, 159 unsigned long old_addr, struct vm_area_struct *new_vma, 160 unsigned long new_addr, unsigned long len) 161 { 162 unsigned long offset; 163 164 flush_cache_range(vma, old_addr, old_addr + len); 165 166 /* 167 * This is not the clever way to do this, but we're taking the 168 * easy way out on the assumption that most remappings will be 169 * only a few pages.. This also makes error recovery easier. 170 */ 171 for (offset = 0; offset < len; offset += PAGE_SIZE) { 172 if (move_one_page(vma, old_addr + offset, 173 new_vma, new_addr + offset) < 0) 174 break; 175 cond_resched(); 176 } 177 return offset; 178 } 179 180 static unsigned long move_vma(struct vm_area_struct *vma, 181 unsigned long old_addr, unsigned long old_len, 182 unsigned long new_len, unsigned long new_addr) 183 { 184 struct mm_struct *mm = vma->vm_mm; 185 struct vm_area_struct *new_vma; 186 unsigned long vm_flags = vma->vm_flags; 187 unsigned long new_pgoff; 188 unsigned long moved_len; 189 unsigned long excess = 0; 190 int split = 0; 191 192 /* 193 * We'd prefer to avoid failure later on in do_munmap: 194 * which may split one vma into three before unmapping. 195 */ 196 if (mm->map_count >= sysctl_max_map_count - 3) 197 return -ENOMEM; 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 if (do_munmap(mm, old_addr, old_len) < 0) { 228 /* OOM: unable to split vma, just get accounts right */ 229 vm_unacct_memory(excess >> PAGE_SHIFT); 230 excess = 0; 231 } 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 mm->total_vm += new_len >> PAGE_SHIFT; 241 __vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); 242 if (vm_flags & VM_LOCKED) { 243 mm->locked_vm += new_len >> PAGE_SHIFT; 244 if (new_len > old_len) 245 make_pages_present(new_addr + old_len, 246 new_addr + new_len); 247 } 248 249 return new_addr; 250 } 251 252 /* 253 * Expand (or shrink) an existing mapping, potentially moving it at the 254 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 255 * 256 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 257 * This option implies MREMAP_MAYMOVE. 258 */ 259 unsigned long do_mremap(unsigned long addr, 260 unsigned long old_len, unsigned long new_len, 261 unsigned long flags, unsigned long new_addr) 262 { 263 struct vm_area_struct *vma; 264 unsigned long ret = -EINVAL; 265 unsigned long charged = 0; 266 267 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 268 goto out; 269 270 if (addr & ~PAGE_MASK) 271 goto out; 272 273 old_len = PAGE_ALIGN(old_len); 274 new_len = PAGE_ALIGN(new_len); 275 276 /* 277 * We allow a zero old-len as a special case 278 * for DOS-emu "duplicate shm area" thing. But 279 * a zero new-len is nonsensical. 280 */ 281 if (!new_len) 282 goto out; 283 284 /* new_addr is only valid if MREMAP_FIXED is specified */ 285 if (flags & MREMAP_FIXED) { 286 if (new_addr & ~PAGE_MASK) 287 goto out; 288 if (!(flags & MREMAP_MAYMOVE)) 289 goto out; 290 291 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 292 goto out; 293 294 /* Check if the location we're moving into overlaps the 295 * old location at all, and fail if it does. 296 */ 297 if ((new_addr <= addr) && (new_addr+new_len) > addr) 298 goto out; 299 300 if ((addr <= new_addr) && (addr+old_len) > new_addr) 301 goto out; 302 303 ret = do_munmap(current->mm, new_addr, new_len); 304 if (ret) 305 goto out; 306 } 307 308 /* 309 * Always allow a shrinking remap: that just unmaps 310 * the unnecessary pages.. 311 * do_munmap does all the needed commit accounting 312 */ 313 if (old_len >= new_len) { 314 ret = do_munmap(current->mm, addr+new_len, old_len - new_len); 315 if (ret && old_len != new_len) 316 goto out; 317 ret = addr; 318 if (!(flags & MREMAP_FIXED) || (new_addr == addr)) 319 goto out; 320 old_len = new_len; 321 } 322 323 /* 324 * Ok, we need to grow.. or relocate. 325 */ 326 ret = -EFAULT; 327 vma = find_vma(current->mm, addr); 328 if (!vma || vma->vm_start > addr) 329 goto out; 330 if (is_vm_hugetlb_page(vma)) { 331 ret = -EINVAL; 332 goto out; 333 } 334 /* We can't remap across vm area boundaries */ 335 if (old_len > vma->vm_end - addr) 336 goto out; 337 if (vma->vm_flags & VM_DONTEXPAND) { 338 if (new_len > old_len) 339 goto out; 340 } 341 if (vma->vm_flags & VM_LOCKED) { 342 unsigned long locked, lock_limit; 343 locked = current->mm->locked_vm << PAGE_SHIFT; 344 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 345 locked += new_len - old_len; 346 ret = -EAGAIN; 347 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 348 goto out; 349 } 350 if (!may_expand_vm(current->mm, (new_len - old_len) >> PAGE_SHIFT)) { 351 ret = -ENOMEM; 352 goto out; 353 } 354 355 if (vma->vm_flags & VM_ACCOUNT) { 356 charged = (new_len - old_len) >> PAGE_SHIFT; 357 if (security_vm_enough_memory(charged)) 358 goto out_nc; 359 } 360 361 /* old_len exactly to the end of the area.. 362 * And we're not relocating the area. 363 */ 364 if (old_len == vma->vm_end - addr && 365 !((flags & MREMAP_FIXED) && (addr != new_addr)) && 366 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) { 367 unsigned long max_addr = TASK_SIZE; 368 if (vma->vm_next) 369 max_addr = vma->vm_next->vm_start; 370 /* can we just expand the current mapping? */ 371 if (max_addr - addr >= new_len) { 372 int pages = (new_len - old_len) >> PAGE_SHIFT; 373 374 vma_adjust(vma, vma->vm_start, 375 addr + new_len, vma->vm_pgoff, NULL); 376 377 current->mm->total_vm += pages; 378 __vm_stat_account(vma->vm_mm, vma->vm_flags, 379 vma->vm_file, pages); 380 if (vma->vm_flags & VM_LOCKED) { 381 current->mm->locked_vm += pages; 382 make_pages_present(addr + old_len, 383 addr + new_len); 384 } 385 ret = addr; 386 goto out; 387 } 388 } 389 390 /* 391 * We weren't able to just expand or shrink the area, 392 * we need to create a new one and move it.. 393 */ 394 ret = -ENOMEM; 395 if (flags & MREMAP_MAYMOVE) { 396 if (!(flags & MREMAP_FIXED)) { 397 unsigned long map_flags = 0; 398 if (vma->vm_flags & VM_MAYSHARE) 399 map_flags |= MAP_SHARED; 400 401 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 402 vma->vm_pgoff, map_flags); 403 ret = new_addr; 404 if (new_addr & ~PAGE_MASK) 405 goto out; 406 } 407 ret = move_vma(vma, addr, old_len, new_len, new_addr); 408 } 409 out: 410 if (ret & ~PAGE_MASK) 411 vm_unacct_memory(charged); 412 out_nc: 413 return ret; 414 } 415 416 asmlinkage unsigned long sys_mremap(unsigned long addr, 417 unsigned long old_len, unsigned long new_len, 418 unsigned long flags, unsigned long new_addr) 419 { 420 unsigned long ret; 421 422 down_write(¤t->mm->mmap_sem); 423 ret = do_mremap(addr, old_len, new_len, flags, new_addr); 424 up_write(¤t->mm->mmap_sem); 425 return ret; 426 } 427