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); 101 102 for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE, 103 new_pte++, new_addr += PAGE_SIZE) { 104 if (pte_none(*old_pte)) 105 continue; 106 pte = ptep_clear_flush(vma, old_addr, old_pte); 107 /* ZERO_PAGE can be dependant on virtual addr */ 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 if (new_ptl != old_ptl) 113 spin_unlock(new_ptl); 114 pte_unmap_nested(new_pte - 1); 115 pte_unmap_unlock(old_pte - 1, old_ptl); 116 if (mapping) 117 spin_unlock(&mapping->i_mmap_lock); 118 } 119 120 #define LATENCY_LIMIT (64 * PAGE_SIZE) 121 122 static unsigned long move_page_tables(struct vm_area_struct *vma, 123 unsigned long old_addr, struct vm_area_struct *new_vma, 124 unsigned long new_addr, unsigned long len) 125 { 126 unsigned long extent, next, old_end; 127 pmd_t *old_pmd, *new_pmd; 128 129 old_end = old_addr + len; 130 flush_cache_range(vma, old_addr, old_end); 131 132 for (; old_addr < old_end; old_addr += extent, new_addr += extent) { 133 cond_resched(); 134 next = (old_addr + PMD_SIZE) & PMD_MASK; 135 if (next - 1 > old_end) 136 next = old_end; 137 extent = next - old_addr; 138 old_pmd = get_old_pmd(vma->vm_mm, old_addr); 139 if (!old_pmd) 140 continue; 141 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr); 142 if (!new_pmd) 143 break; 144 next = (new_addr + PMD_SIZE) & PMD_MASK; 145 if (extent > next - new_addr) 146 extent = next - new_addr; 147 if (extent > LATENCY_LIMIT) 148 extent = LATENCY_LIMIT; 149 move_ptes(vma, old_pmd, old_addr, old_addr + extent, 150 new_vma, new_pmd, new_addr); 151 } 152 153 return len + old_addr - old_end; /* how much done */ 154 } 155 156 static unsigned long move_vma(struct vm_area_struct *vma, 157 unsigned long old_addr, unsigned long old_len, 158 unsigned long new_len, unsigned long new_addr) 159 { 160 struct mm_struct *mm = vma->vm_mm; 161 struct vm_area_struct *new_vma; 162 unsigned long vm_flags = vma->vm_flags; 163 unsigned long new_pgoff; 164 unsigned long moved_len; 165 unsigned long excess = 0; 166 unsigned long hiwater_vm; 167 int split = 0; 168 169 /* 170 * We'd prefer to avoid failure later on in do_munmap: 171 * which may split one vma into three before unmapping. 172 */ 173 if (mm->map_count >= sysctl_max_map_count - 3) 174 return -ENOMEM; 175 176 new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT); 177 new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff); 178 if (!new_vma) 179 return -ENOMEM; 180 181 moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len); 182 if (moved_len < old_len) { 183 /* 184 * On error, move entries back from new area to old, 185 * which will succeed since page tables still there, 186 * and then proceed to unmap new area instead of old. 187 */ 188 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len); 189 vma = new_vma; 190 old_len = new_len; 191 old_addr = new_addr; 192 new_addr = -ENOMEM; 193 } 194 195 /* Conceal VM_ACCOUNT so old reservation is not undone */ 196 if (vm_flags & VM_ACCOUNT) { 197 vma->vm_flags &= ~VM_ACCOUNT; 198 excess = vma->vm_end - vma->vm_start - old_len; 199 if (old_addr > vma->vm_start && 200 old_addr + old_len < vma->vm_end) 201 split = 1; 202 } 203 204 /* 205 * If we failed to move page tables we still do total_vm increment 206 * since do_munmap() will decrement it by old_len == new_len. 207 * 208 * Since total_vm is about to be raised artificially high for a 209 * moment, we need to restore high watermark afterwards: if stats 210 * are taken meanwhile, total_vm and hiwater_vm appear too high. 211 * If this were a serious issue, we'd add a flag to do_munmap(). 212 */ 213 hiwater_vm = mm->hiwater_vm; 214 mm->total_vm += new_len >> PAGE_SHIFT; 215 vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT); 216 217 if (do_munmap(mm, old_addr, old_len) < 0) { 218 /* OOM: unable to split vma, just get accounts right */ 219 vm_unacct_memory(excess >> PAGE_SHIFT); 220 excess = 0; 221 } 222 mm->hiwater_vm = hiwater_vm; 223 224 /* Restore VM_ACCOUNT if one or two pieces of vma left */ 225 if (excess) { 226 vma->vm_flags |= VM_ACCOUNT; 227 if (split) 228 vma->vm_next->vm_flags |= VM_ACCOUNT; 229 } 230 231 if (vm_flags & VM_LOCKED) { 232 mm->locked_vm += new_len >> PAGE_SHIFT; 233 if (new_len > old_len) 234 make_pages_present(new_addr + old_len, 235 new_addr + new_len); 236 } 237 238 return new_addr; 239 } 240 241 /* 242 * Expand (or shrink) an existing mapping, potentially moving it at the 243 * same time (controlled by the MREMAP_MAYMOVE flag and available VM space) 244 * 245 * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise 246 * This option implies MREMAP_MAYMOVE. 247 */ 248 unsigned long do_mremap(unsigned long addr, 249 unsigned long old_len, unsigned long new_len, 250 unsigned long flags, unsigned long new_addr) 251 { 252 struct mm_struct *mm = current->mm; 253 struct vm_area_struct *vma; 254 unsigned long ret = -EINVAL; 255 unsigned long charged = 0; 256 257 if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE)) 258 goto out; 259 260 if (addr & ~PAGE_MASK) 261 goto out; 262 263 old_len = PAGE_ALIGN(old_len); 264 new_len = PAGE_ALIGN(new_len); 265 266 /* 267 * We allow a zero old-len as a special case 268 * for DOS-emu "duplicate shm area" thing. But 269 * a zero new-len is nonsensical. 270 */ 271 if (!new_len) 272 goto out; 273 274 /* new_addr is only valid if MREMAP_FIXED is specified */ 275 if (flags & MREMAP_FIXED) { 276 if (new_addr & ~PAGE_MASK) 277 goto out; 278 if (!(flags & MREMAP_MAYMOVE)) 279 goto out; 280 281 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len) 282 goto out; 283 284 /* Check if the location we're moving into overlaps the 285 * old location at all, and fail if it does. 286 */ 287 if ((new_addr <= addr) && (new_addr+new_len) > addr) 288 goto out; 289 290 if ((addr <= new_addr) && (addr+old_len) > new_addr) 291 goto out; 292 293 ret = do_munmap(mm, new_addr, new_len); 294 if (ret) 295 goto out; 296 } 297 298 /* 299 * Always allow a shrinking remap: that just unmaps 300 * the unnecessary pages.. 301 * do_munmap does all the needed commit accounting 302 */ 303 if (old_len >= new_len) { 304 ret = do_munmap(mm, addr+new_len, old_len - new_len); 305 if (ret && old_len != new_len) 306 goto out; 307 ret = addr; 308 if (!(flags & MREMAP_FIXED) || (new_addr == addr)) 309 goto out; 310 old_len = new_len; 311 } 312 313 /* 314 * Ok, we need to grow.. or relocate. 315 */ 316 ret = -EFAULT; 317 vma = find_vma(mm, addr); 318 if (!vma || vma->vm_start > addr) 319 goto out; 320 if (is_vm_hugetlb_page(vma)) { 321 ret = -EINVAL; 322 goto out; 323 } 324 /* We can't remap across vm area boundaries */ 325 if (old_len > vma->vm_end - addr) 326 goto out; 327 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) { 328 if (new_len > old_len) 329 goto out; 330 } 331 if (vma->vm_flags & VM_LOCKED) { 332 unsigned long locked, lock_limit; 333 locked = mm->locked_vm << PAGE_SHIFT; 334 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur; 335 locked += new_len - old_len; 336 ret = -EAGAIN; 337 if (locked > lock_limit && !capable(CAP_IPC_LOCK)) 338 goto out; 339 } 340 if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) { 341 ret = -ENOMEM; 342 goto out; 343 } 344 345 if (vma->vm_flags & VM_ACCOUNT) { 346 charged = (new_len - old_len) >> PAGE_SHIFT; 347 if (security_vm_enough_memory(charged)) 348 goto out_nc; 349 } 350 351 /* old_len exactly to the end of the area.. 352 * And we're not relocating the area. 353 */ 354 if (old_len == vma->vm_end - addr && 355 !((flags & MREMAP_FIXED) && (addr != new_addr)) && 356 (old_len != new_len || !(flags & MREMAP_MAYMOVE))) { 357 unsigned long max_addr = TASK_SIZE; 358 if (vma->vm_next) 359 max_addr = vma->vm_next->vm_start; 360 /* can we just expand the current mapping? */ 361 if (max_addr - addr >= new_len) { 362 int pages = (new_len - old_len) >> PAGE_SHIFT; 363 364 vma_adjust(vma, vma->vm_start, 365 addr + new_len, vma->vm_pgoff, NULL); 366 367 mm->total_vm += pages; 368 vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages); 369 if (vma->vm_flags & VM_LOCKED) { 370 mm->locked_vm += pages; 371 make_pages_present(addr + old_len, 372 addr + new_len); 373 } 374 ret = addr; 375 goto out; 376 } 377 } 378 379 /* 380 * We weren't able to just expand or shrink the area, 381 * we need to create a new one and move it.. 382 */ 383 ret = -ENOMEM; 384 if (flags & MREMAP_MAYMOVE) { 385 if (!(flags & MREMAP_FIXED)) { 386 unsigned long map_flags = 0; 387 if (vma->vm_flags & VM_MAYSHARE) 388 map_flags |= MAP_SHARED; 389 390 new_addr = get_unmapped_area(vma->vm_file, 0, new_len, 391 vma->vm_pgoff, map_flags); 392 ret = new_addr; 393 if (new_addr & ~PAGE_MASK) 394 goto out; 395 } 396 ret = move_vma(vma, addr, old_len, new_len, new_addr); 397 } 398 out: 399 if (ret & ~PAGE_MASK) 400 vm_unacct_memory(charged); 401 out_nc: 402 return ret; 403 } 404 405 asmlinkage unsigned long sys_mremap(unsigned long addr, 406 unsigned long old_len, unsigned long new_len, 407 unsigned long flags, unsigned long new_addr) 408 { 409 unsigned long ret; 410 411 down_write(¤t->mm->mmap_sem); 412 ret = do_mremap(addr, old_len, new_len, flags, new_addr); 413 up_write(¤t->mm->mmap_sem); 414 return ret; 415 } 416