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 */
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_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
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}
408