xref: /openbmc/linux/fs/adfs/map.c (revision f93793fd)
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  */
lookup_zone(const struct adfs_discmap * dm,const unsigned int idlen,const u32 frag_id,unsigned int * offset)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
scan_free_map(struct adfs_sb_info * asb,struct adfs_discmap * dm)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 
scan_map(struct adfs_sb_info * asb,unsigned int zone,const u32 frag_id,unsigned int mapoff)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  */
adfs_map_statfs(struct super_block * sb,struct kstatfs * buf)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 
adfs_map_lookup(struct super_block * sb,u32 frag_id,unsigned int offset)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 
adfs_calczonecheck(struct super_block * sb,unsigned char * map)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 
adfs_checkmap(struct super_block * sb,struct adfs_discmap * dm)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  */
adfs_map_layout(struct adfs_discmap * dm,unsigned int nzones,struct adfs_discrecord * dr)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 
adfs_map_read(struct adfs_discmap * dm,struct super_block * sb,unsigned int map_addr,unsigned int nzones)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 
adfs_map_relse(struct adfs_discmap * dm,unsigned int nzones)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 
adfs_read_map(struct super_block * sb,struct adfs_discrecord * dr)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 
adfs_free_map(struct super_block * sb)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