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