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