1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/fs/adfs/map.c 4 * 5 * Copyright (C) 1997-2002 Russell King 6 */ 7 #include <linux/slab.h> 8 #include <linux/statfs.h> 9 #include <asm/unaligned.h> 10 #include "adfs.h" 11 12 /* 13 * The ADFS map is basically a set of sectors. Each sector is called a 14 * zone which contains a bitstream made up of variable sized fragments. 15 * Each bit refers to a set of bytes in the filesystem, defined by 16 * log2bpmb. This may be larger or smaller than the sector size, but 17 * the overall size it describes will always be a round number of 18 * sectors. A fragment id is always idlen bits long. 19 * 20 * < idlen > < n > <1> 21 * +---------+-------//---------+---+ 22 * | frag id | 0000....000000 | 1 | 23 * +---------+-------//---------+---+ 24 * 25 * The physical disk space used by a fragment is taken from the start of 26 * the fragment id up to and including the '1' bit - ie, idlen + n + 1 27 * bits. 28 * 29 * A fragment id can be repeated multiple times in the whole map for 30 * large or fragmented files. The first map zone a fragment starts in 31 * is given by fragment id / ids_per_zone - this allows objects to start 32 * from any zone on the disk. 33 * 34 * Free space is described by a linked list of fragments. Each free 35 * fragment describes free space in the same way as the other fragments, 36 * however, the frag id specifies an offset (in map bits) from the end 37 * of this fragment to the start of the next free fragment. 38 * 39 * Objects stored on the disk are allocated object ids (we use these as 40 * our inode numbers.) Object ids contain a fragment id and an optional 41 * offset. This allows a directory fragment to contain small files 42 * associated with that directory. 43 */ 44 45 /* 46 * For the future... 47 */ 48 static DEFINE_RWLOCK(adfs_map_lock); 49 50 /* 51 * This is fun. We need to load up to 19 bits from the map at an 52 * arbitrary bit alignment. (We're limited to 19 bits by F+ version 2). 53 */ 54 #define GET_FRAG_ID(_map,_start,_idmask) \ 55 ({ \ 56 unsigned char *_m = _map + (_start >> 3); \ 57 u32 _frag = get_unaligned_le32(_m); \ 58 _frag >>= (_start & 7); \ 59 _frag & _idmask; \ 60 }) 61 62 /* 63 * return the map bit offset of the fragment frag_id in the zone dm. 64 * Note that the loop is optimised for best asm code - look at the 65 * output of: 66 * gcc -D__KERNEL__ -O2 -I../../include -o - -S map.c 67 */ 68 static int lookup_zone(const struct adfs_discmap *dm, const unsigned int idlen, 69 const u32 frag_id, unsigned int *offset) 70 { 71 const unsigned int endbit = dm->dm_endbit; 72 const u32 idmask = (1 << idlen) - 1; 73 unsigned char *map = dm->dm_bh->b_data; 74 unsigned int start = dm->dm_startbit; 75 unsigned int freelink, fragend; 76 u32 frag; 77 78 frag = GET_FRAG_ID(map, 8, idmask & 0x7fff); 79 freelink = frag ? 8 + frag : 0; 80 81 do { 82 frag = GET_FRAG_ID(map, start, idmask); 83 84 fragend = find_next_bit_le(map, endbit, start + idlen); 85 if (fragend >= endbit) 86 goto error; 87 88 if (start == freelink) { 89 freelink += frag & 0x7fff; 90 } else if (frag == frag_id) { 91 unsigned int length = fragend + 1 - start; 92 93 if (*offset < length) 94 return start + *offset; 95 *offset -= length; 96 } 97 98 start = fragend + 1; 99 } while (start < endbit); 100 return -1; 101 102 error: 103 printk(KERN_ERR "adfs: oversized fragment 0x%x at 0x%x-0x%x\n", 104 frag, start, fragend); 105 return -1; 106 } 107 108 /* 109 * Scan the free space map, for this zone, calculating the total 110 * number of map bits in each free space fragment. 111 * 112 * Note: idmask is limited to 15 bits [3.2] 113 */ 114 static unsigned int 115 scan_free_map(struct adfs_sb_info *asb, struct adfs_discmap *dm) 116 { 117 const unsigned int endbit = dm->dm_endbit; 118 const unsigned int idlen = asb->s_idlen; 119 const unsigned int frag_idlen = idlen <= 15 ? idlen : 15; 120 const u32 idmask = (1 << frag_idlen) - 1; 121 unsigned char *map = dm->dm_bh->b_data; 122 unsigned int start = 8, fragend; 123 u32 frag; 124 unsigned long total = 0; 125 126 /* 127 * get fragment id 128 */ 129 frag = GET_FRAG_ID(map, start, idmask); 130 131 /* 132 * If the freelink is null, then no free fragments 133 * exist in this zone. 134 */ 135 if (frag == 0) 136 return 0; 137 138 do { 139 start += frag; 140 141 frag = GET_FRAG_ID(map, start, idmask); 142 143 fragend = find_next_bit_le(map, endbit, start + idlen); 144 if (fragend >= endbit) 145 goto error; 146 147 total += fragend + 1 - start; 148 } while (frag >= idlen + 1); 149 150 if (frag != 0) 151 printk(KERN_ERR "adfs: undersized free fragment\n"); 152 153 return total; 154 error: 155 printk(KERN_ERR "adfs: oversized free fragment\n"); 156 return 0; 157 } 158 159 static int scan_map(struct adfs_sb_info *asb, unsigned int zone, 160 const u32 frag_id, unsigned int mapoff) 161 { 162 const unsigned int idlen = asb->s_idlen; 163 struct adfs_discmap *dm, *dm_end; 164 int result; 165 166 dm = asb->s_map + zone; 167 zone = asb->s_map_size; 168 dm_end = asb->s_map + zone; 169 170 do { 171 result = lookup_zone(dm, idlen, frag_id, &mapoff); 172 173 if (result != -1) 174 goto found; 175 176 dm ++; 177 if (dm == dm_end) 178 dm = asb->s_map; 179 } while (--zone > 0); 180 181 return -1; 182 found: 183 result -= dm->dm_startbit; 184 result += dm->dm_startblk; 185 186 return result; 187 } 188 189 /* 190 * calculate the amount of free blocks in the map. 191 * 192 * n=1 193 * total_free = E(free_in_zone_n) 194 * nzones 195 */ 196 void adfs_map_statfs(struct super_block *sb, struct kstatfs *buf) 197 { 198 struct adfs_sb_info *asb = ADFS_SB(sb); 199 struct adfs_discrecord *dr = adfs_map_discrecord(asb->s_map); 200 struct adfs_discmap *dm; 201 unsigned int total = 0; 202 unsigned int zone; 203 204 dm = asb->s_map; 205 zone = asb->s_map_size; 206 207 do { 208 total += scan_free_map(asb, dm++); 209 } while (--zone > 0); 210 211 buf->f_blocks = adfs_disc_size(dr) >> sb->s_blocksize_bits; 212 buf->f_files = asb->s_ids_per_zone * asb->s_map_size; 213 buf->f_bavail = 214 buf->f_bfree = signed_asl(total, asb->s_map2blk); 215 } 216 217 int adfs_map_lookup(struct super_block *sb, u32 frag_id, unsigned int offset) 218 { 219 struct adfs_sb_info *asb = ADFS_SB(sb); 220 unsigned int zone, mapoff; 221 int result; 222 223 /* 224 * map & root fragment is special - it starts in the center of the 225 * disk. The other fragments start at zone (frag / ids_per_zone) 226 */ 227 if (frag_id == ADFS_ROOT_FRAG) 228 zone = asb->s_map_size >> 1; 229 else 230 zone = frag_id / asb->s_ids_per_zone; 231 232 if (zone >= asb->s_map_size) 233 goto bad_fragment; 234 235 /* Convert sector offset to map offset */ 236 mapoff = signed_asl(offset, -asb->s_map2blk); 237 238 read_lock(&adfs_map_lock); 239 result = scan_map(asb, zone, frag_id, mapoff); 240 read_unlock(&adfs_map_lock); 241 242 if (result > 0) { 243 unsigned int secoff; 244 245 /* Calculate sector offset into map block */ 246 secoff = offset - signed_asl(mapoff, asb->s_map2blk); 247 return secoff + signed_asl(result, asb->s_map2blk); 248 } 249 250 adfs_error(sb, "fragment 0x%04x at offset %d not found in map", 251 frag_id, offset); 252 return 0; 253 254 bad_fragment: 255 adfs_error(sb, "invalid fragment 0x%04x (zone = %d, max = %d)", 256 frag_id, zone, asb->s_map_size); 257 return 0; 258 } 259 260 static unsigned char adfs_calczonecheck(struct super_block *sb, unsigned char *map) 261 { 262 unsigned int v0, v1, v2, v3; 263 int i; 264 265 v0 = v1 = v2 = v3 = 0; 266 for (i = sb->s_blocksize - 4; i; i -= 4) { 267 v0 += map[i] + (v3 >> 8); 268 v3 &= 0xff; 269 v1 += map[i + 1] + (v0 >> 8); 270 v0 &= 0xff; 271 v2 += map[i + 2] + (v1 >> 8); 272 v1 &= 0xff; 273 v3 += map[i + 3] + (v2 >> 8); 274 v2 &= 0xff; 275 } 276 v0 += v3 >> 8; 277 v1 += map[1] + (v0 >> 8); 278 v2 += map[2] + (v1 >> 8); 279 v3 += map[3] + (v2 >> 8); 280 281 return v0 ^ v1 ^ v2 ^ v3; 282 } 283 284 static int adfs_checkmap(struct super_block *sb, struct adfs_discmap *dm) 285 { 286 unsigned char crosscheck = 0, zonecheck = 1; 287 int i; 288 289 for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) { 290 unsigned char *map; 291 292 map = dm[i].dm_bh->b_data; 293 294 if (adfs_calczonecheck(sb, map) != map[0]) { 295 adfs_error(sb, "zone %d fails zonecheck", i); 296 zonecheck = 0; 297 } 298 crosscheck ^= map[3]; 299 } 300 if (crosscheck != 0xff) 301 adfs_error(sb, "crosscheck != 0xff"); 302 return crosscheck == 0xff && zonecheck; 303 } 304 305 /* 306 * Layout the map - the first zone contains a copy of the disc record, 307 * and the last zone must be limited to the size of the filesystem. 308 */ 309 static void adfs_map_layout(struct adfs_discmap *dm, unsigned int nzones, 310 struct adfs_discrecord *dr) 311 { 312 unsigned int zone, zone_size; 313 u64 size; 314 315 zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare); 316 317 dm[0].dm_bh = NULL; 318 dm[0].dm_startblk = 0; 319 dm[0].dm_startbit = 32 + ADFS_DR_SIZE_BITS; 320 dm[0].dm_endbit = 32 + zone_size; 321 322 for (zone = 1; zone < nzones; zone++) { 323 dm[zone].dm_bh = NULL; 324 dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS; 325 dm[zone].dm_startbit = 32; 326 dm[zone].dm_endbit = 32 + zone_size; 327 } 328 329 size = adfs_disc_size(dr) >> dr->log2bpmb; 330 size -= (nzones - 1) * zone_size - ADFS_DR_SIZE_BITS; 331 dm[nzones - 1].dm_endbit = 32 + size; 332 } 333 334 static int adfs_map_read(struct adfs_discmap *dm, struct super_block *sb, 335 unsigned int map_addr, unsigned int nzones) 336 { 337 unsigned int zone; 338 339 for (zone = 0; zone < nzones; zone++) { 340 dm[zone].dm_bh = sb_bread(sb, map_addr + zone); 341 if (!dm[zone].dm_bh) 342 return -EIO; 343 } 344 345 return 0; 346 } 347 348 static void adfs_map_relse(struct adfs_discmap *dm, unsigned int nzones) 349 { 350 unsigned int zone; 351 352 for (zone = 0; zone < nzones; zone++) 353 brelse(dm[zone].dm_bh); 354 } 355 356 struct adfs_discmap *adfs_read_map(struct super_block *sb, struct adfs_discrecord *dr) 357 { 358 struct adfs_sb_info *asb = ADFS_SB(sb); 359 struct adfs_discmap *dm; 360 unsigned int map_addr, zone_size, nzones; 361 int ret; 362 363 nzones = dr->nzones | dr->nzones_high << 8; 364 zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare); 365 366 asb->s_idlen = dr->idlen; 367 asb->s_map_size = nzones; 368 asb->s_map2blk = dr->log2bpmb - dr->log2secsize; 369 asb->s_log2sharesize = dr->log2sharesize; 370 asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1); 371 372 map_addr = (nzones >> 1) * zone_size - 373 ((nzones > 1) ? ADFS_DR_SIZE_BITS : 0); 374 map_addr = signed_asl(map_addr, asb->s_map2blk); 375 376 dm = kmalloc_array(nzones, sizeof(*dm), GFP_KERNEL); 377 if (dm == NULL) { 378 adfs_error(sb, "not enough memory"); 379 return ERR_PTR(-ENOMEM); 380 } 381 382 adfs_map_layout(dm, nzones, dr); 383 384 ret = adfs_map_read(dm, sb, map_addr, nzones); 385 if (ret) { 386 adfs_error(sb, "unable to read map"); 387 goto error_free; 388 } 389 390 if (adfs_checkmap(sb, dm)) 391 return dm; 392 393 adfs_error(sb, "map corrupted"); 394 395 error_free: 396 adfs_map_relse(dm, nzones); 397 kfree(dm); 398 return ERR_PTR(-EIO); 399 } 400 401 void adfs_free_map(struct super_block *sb) 402 { 403 struct adfs_sb_info *asb = ADFS_SB(sb); 404 405 adfs_map_relse(asb->s_map, asb->s_map_size); 406 kfree(asb->s_map); 407 } 408