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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 <linux/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 */
48static 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 */
68static 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
102error:
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 */
114static unsigned int
115scan_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;
154error:
155 printk(KERN_ERR "adfs: oversized free fragment\n");
156 return 0;
157}
158
159static 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;
182found:
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 */
196void 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
217int 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
254bad_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
260static 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
284static 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 */
309static 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
334static 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
348static 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
356struct 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_objs(*dm, nzones);
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
395error_free:
396 adfs_map_relse(dm, nzones);
397 kfree(dm);
398 return ERR_PTR(-EIO);
399}
400
401void 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}