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 fragend; 76 u32 frag; 77 78 do { 79 frag = GET_FRAG_ID(map, start, idmask); 80 81 fragend = find_next_bit_le(map, endbit, start + idlen); 82 if (fragend >= endbit) 83 goto error; 84 85 if (frag == frag_id) { 86 unsigned int length = fragend + 1 - start; 87 88 if (*offset < length) 89 return start + *offset; 90 *offset -= length; 91 } 92 93 start = fragend + 1; 94 } while (start < endbit); 95 return -1; 96 97 error: 98 printk(KERN_ERR "adfs: oversized fragment 0x%x at 0x%x-0x%x\n", 99 frag, start, fragend); 100 return -1; 101 } 102 103 /* 104 * Scan the free space map, for this zone, calculating the total 105 * number of map bits in each free space fragment. 106 * 107 * Note: idmask is limited to 15 bits [3.2] 108 */ 109 static unsigned int 110 scan_free_map(struct adfs_sb_info *asb, struct adfs_discmap *dm) 111 { 112 const unsigned int endbit = dm->dm_endbit; 113 const unsigned int idlen = asb->s_idlen; 114 const unsigned int frag_idlen = idlen <= 15 ? idlen : 15; 115 const u32 idmask = (1 << frag_idlen) - 1; 116 unsigned char *map = dm->dm_bh->b_data; 117 unsigned int start = 8, fragend; 118 u32 frag; 119 unsigned long total = 0; 120 121 /* 122 * get fragment id 123 */ 124 frag = GET_FRAG_ID(map, start, idmask); 125 126 /* 127 * If the freelink is null, then no free fragments 128 * exist in this zone. 129 */ 130 if (frag == 0) 131 return 0; 132 133 do { 134 start += frag; 135 136 frag = GET_FRAG_ID(map, start, idmask); 137 138 fragend = find_next_bit_le(map, endbit, start + idlen); 139 if (fragend >= endbit) 140 goto error; 141 142 total += fragend + 1 - start; 143 } while (frag >= idlen + 1); 144 145 if (frag != 0) 146 printk(KERN_ERR "adfs: undersized free fragment\n"); 147 148 return total; 149 error: 150 printk(KERN_ERR "adfs: oversized free fragment\n"); 151 return 0; 152 } 153 154 static int scan_map(struct adfs_sb_info *asb, unsigned int zone, 155 const u32 frag_id, unsigned int mapoff) 156 { 157 const unsigned int idlen = asb->s_idlen; 158 struct adfs_discmap *dm, *dm_end; 159 int result; 160 161 dm = asb->s_map + zone; 162 zone = asb->s_map_size; 163 dm_end = asb->s_map + zone; 164 165 do { 166 result = lookup_zone(dm, idlen, frag_id, &mapoff); 167 168 if (result != -1) 169 goto found; 170 171 dm ++; 172 if (dm == dm_end) 173 dm = asb->s_map; 174 } while (--zone > 0); 175 176 return -1; 177 found: 178 result -= dm->dm_startbit; 179 result += dm->dm_startblk; 180 181 return result; 182 } 183 184 /* 185 * calculate the amount of free blocks in the map. 186 * 187 * n=1 188 * total_free = E(free_in_zone_n) 189 * nzones 190 */ 191 void adfs_map_statfs(struct super_block *sb, struct kstatfs *buf) 192 { 193 struct adfs_sb_info *asb = ADFS_SB(sb); 194 struct adfs_discrecord *dr = adfs_map_discrecord(asb->s_map); 195 struct adfs_discmap *dm; 196 unsigned int total = 0; 197 unsigned int zone; 198 199 dm = asb->s_map; 200 zone = asb->s_map_size; 201 202 do { 203 total += scan_free_map(asb, dm++); 204 } while (--zone > 0); 205 206 buf->f_blocks = adfs_disc_size(dr) >> sb->s_blocksize_bits; 207 buf->f_files = asb->s_ids_per_zone * asb->s_map_size; 208 buf->f_bavail = 209 buf->f_bfree = signed_asl(total, asb->s_map2blk); 210 } 211 212 int adfs_map_lookup(struct super_block *sb, u32 frag_id, unsigned int offset) 213 { 214 struct adfs_sb_info *asb = ADFS_SB(sb); 215 unsigned int zone, mapoff; 216 int result; 217 218 /* 219 * map & root fragment is special - it starts in the center of the 220 * disk. The other fragments start at zone (frag / ids_per_zone) 221 */ 222 if (frag_id == ADFS_ROOT_FRAG) 223 zone = asb->s_map_size >> 1; 224 else 225 zone = frag_id / asb->s_ids_per_zone; 226 227 if (zone >= asb->s_map_size) 228 goto bad_fragment; 229 230 /* Convert sector offset to map offset */ 231 mapoff = signed_asl(offset, -asb->s_map2blk); 232 233 read_lock(&adfs_map_lock); 234 result = scan_map(asb, zone, frag_id, mapoff); 235 read_unlock(&adfs_map_lock); 236 237 if (result > 0) { 238 unsigned int secoff; 239 240 /* Calculate sector offset into map block */ 241 secoff = offset - signed_asl(mapoff, asb->s_map2blk); 242 return secoff + signed_asl(result, asb->s_map2blk); 243 } 244 245 adfs_error(sb, "fragment 0x%04x at offset %d not found in map", 246 frag_id, offset); 247 return 0; 248 249 bad_fragment: 250 adfs_error(sb, "invalid fragment 0x%04x (zone = %d, max = %d)", 251 frag_id, zone, asb->s_map_size); 252 return 0; 253 } 254 255 static unsigned char adfs_calczonecheck(struct super_block *sb, unsigned char *map) 256 { 257 unsigned int v0, v1, v2, v3; 258 int i; 259 260 v0 = v1 = v2 = v3 = 0; 261 for (i = sb->s_blocksize - 4; i; i -= 4) { 262 v0 += map[i] + (v3 >> 8); 263 v3 &= 0xff; 264 v1 += map[i + 1] + (v0 >> 8); 265 v0 &= 0xff; 266 v2 += map[i + 2] + (v1 >> 8); 267 v1 &= 0xff; 268 v3 += map[i + 3] + (v2 >> 8); 269 v2 &= 0xff; 270 } 271 v0 += v3 >> 8; 272 v1 += map[1] + (v0 >> 8); 273 v2 += map[2] + (v1 >> 8); 274 v3 += map[3] + (v2 >> 8); 275 276 return v0 ^ v1 ^ v2 ^ v3; 277 } 278 279 static int adfs_checkmap(struct super_block *sb, struct adfs_discmap *dm) 280 { 281 unsigned char crosscheck = 0, zonecheck = 1; 282 int i; 283 284 for (i = 0; i < ADFS_SB(sb)->s_map_size; i++) { 285 unsigned char *map; 286 287 map = dm[i].dm_bh->b_data; 288 289 if (adfs_calczonecheck(sb, map) != map[0]) { 290 adfs_error(sb, "zone %d fails zonecheck", i); 291 zonecheck = 0; 292 } 293 crosscheck ^= map[3]; 294 } 295 if (crosscheck != 0xff) 296 adfs_error(sb, "crosscheck != 0xff"); 297 return crosscheck == 0xff && zonecheck; 298 } 299 300 /* 301 * Layout the map - the first zone contains a copy of the disc record, 302 * and the last zone must be limited to the size of the filesystem. 303 */ 304 static void adfs_map_layout(struct adfs_discmap *dm, unsigned int nzones, 305 struct adfs_discrecord *dr) 306 { 307 unsigned int zone, zone_size; 308 u64 size; 309 310 zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare); 311 312 dm[0].dm_bh = NULL; 313 dm[0].dm_startblk = 0; 314 dm[0].dm_startbit = 32 + ADFS_DR_SIZE_BITS; 315 dm[0].dm_endbit = 32 + zone_size; 316 317 for (zone = 1; zone < nzones; zone++) { 318 dm[zone].dm_bh = NULL; 319 dm[zone].dm_startblk = zone * zone_size - ADFS_DR_SIZE_BITS; 320 dm[zone].dm_startbit = 32; 321 dm[zone].dm_endbit = 32 + zone_size; 322 } 323 324 size = adfs_disc_size(dr) >> dr->log2bpmb; 325 size -= (nzones - 1) * zone_size - ADFS_DR_SIZE_BITS; 326 dm[nzones - 1].dm_endbit = 32 + size; 327 } 328 329 static int adfs_map_read(struct adfs_discmap *dm, struct super_block *sb, 330 unsigned int map_addr, unsigned int nzones) 331 { 332 unsigned int zone; 333 334 for (zone = 0; zone < nzones; zone++) { 335 dm[zone].dm_bh = sb_bread(sb, map_addr + zone); 336 if (!dm[zone].dm_bh) 337 return -EIO; 338 } 339 340 return 0; 341 } 342 343 static void adfs_map_relse(struct adfs_discmap *dm, unsigned int nzones) 344 { 345 unsigned int zone; 346 347 for (zone = 0; zone < nzones; zone++) 348 brelse(dm[zone].dm_bh); 349 } 350 351 struct adfs_discmap *adfs_read_map(struct super_block *sb, struct adfs_discrecord *dr) 352 { 353 struct adfs_sb_info *asb = ADFS_SB(sb); 354 struct adfs_discmap *dm; 355 unsigned int map_addr, zone_size, nzones; 356 int ret; 357 358 nzones = asb->s_map_size; 359 zone_size = (8 << dr->log2secsize) - le16_to_cpu(dr->zone_spare); 360 map_addr = (nzones >> 1) * zone_size - 361 ((nzones > 1) ? ADFS_DR_SIZE_BITS : 0); 362 map_addr = signed_asl(map_addr, asb->s_map2blk); 363 364 asb->s_ids_per_zone = zone_size / (asb->s_idlen + 1); 365 366 dm = kmalloc_array(nzones, sizeof(*dm), GFP_KERNEL); 367 if (dm == NULL) { 368 adfs_error(sb, "not enough memory"); 369 return ERR_PTR(-ENOMEM); 370 } 371 372 adfs_map_layout(dm, nzones, dr); 373 374 ret = adfs_map_read(dm, sb, map_addr, nzones); 375 if (ret) { 376 adfs_error(sb, "unable to read map"); 377 goto error_free; 378 } 379 380 if (adfs_checkmap(sb, dm)) 381 return dm; 382 383 adfs_error(sb, "map corrupted"); 384 385 error_free: 386 adfs_map_relse(dm, nzones); 387 kfree(dm); 388 return ERR_PTR(-EIO); 389 } 390 391 void adfs_free_map(struct super_block *sb) 392 { 393 struct adfs_sb_info *asb = ADFS_SB(sb); 394 395 adfs_map_relse(asb->s_map, asb->s_map_size); 396 kfree(asb->s_map); 397 } 398