1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * linux/fs/adfs/dir_f.c
4 *
5 * Copyright (C) 1997-1999 Russell King
6 *
7 * E and F format directory handling
8 */
9 #include "adfs.h"
10 #include "dir_f.h"
11
12 /*
13 * Read an (unaligned) value of length 1..4 bytes
14 */
15 static inline unsigned int adfs_readval(unsigned char *p, int len)
16 {
17 unsigned int val = 0;
18
19 switch (len) {
20 case 4: val |= p[3] << 24;
21 fallthrough;
22 case 3: val |= p[2] << 16;
23 fallthrough;
24 case 2: val |= p[1] << 8;
25 fallthrough;
26 default: val |= p[0];
27 }
28 return val;
29 }
30
31 static inline void adfs_writeval(unsigned char *p, int len, unsigned int val)
32 {
33 switch (len) {
34 case 4: p[3] = val >> 24;
35 fallthrough;
36 case 3: p[2] = val >> 16;
37 fallthrough;
38 case 2: p[1] = val >> 8;
39 fallthrough;
40 default: p[0] = val;
41 }
42 }
43
44 #define ror13(v) ((v >> 13) | (v << 19))
45
46 #define dir_u8(idx) \
47 ({ int _buf = idx >> blocksize_bits; \
48 int _off = idx - (_buf << blocksize_bits);\
49 *(u8 *)(bh[_buf]->b_data + _off); \
50 })
51
52 #define dir_u32(idx) \
53 ({ int _buf = idx >> blocksize_bits; \
54 int _off = idx - (_buf << blocksize_bits);\
55 *(__le32 *)(bh[_buf]->b_data + _off); \
56 })
57
58 #define bufoff(_bh,_idx) \
59 ({ int _buf = _idx >> blocksize_bits; \
60 int _off = _idx - (_buf << blocksize_bits);\
61 (void *)(_bh[_buf]->b_data + _off); \
62 })
63
64 /*
65 * There are some algorithms that are nice in
66 * assembler, but a bitch in C... This is one
67 * of them.
68 */
69 static u8
70 adfs_dir_checkbyte(const struct adfs_dir *dir)
71 {
72 struct buffer_head * const *bh = dir->bh;
73 const int blocksize_bits = dir->sb->s_blocksize_bits;
74 union { __le32 *ptr32; u8 *ptr8; } ptr, end;
75 u32 dircheck = 0;
76 int last = 5 - 26;
77 int i = 0;
78
79 /*
80 * Accumulate each word up to the last whole
81 * word of the last directory entry. This
82 * can spread across several buffer heads.
83 */
84 do {
85 last += 26;
86 do {
87 dircheck = le32_to_cpu(dir_u32(i)) ^ ror13(dircheck);
88
89 i += sizeof(u32);
90 } while (i < (last & ~3));
91 } while (dir_u8(last) != 0);
92
93 /*
94 * Accumulate the last few bytes. These
95 * bytes will be within the same bh.
96 */
97 if (i != last) {
98 ptr.ptr8 = bufoff(bh, i);
99 end.ptr8 = ptr.ptr8 + last - i;
100
101 do {
102 dircheck = *ptr.ptr8++ ^ ror13(dircheck);
103 } while (ptr.ptr8 < end.ptr8);
104 }
105
106 /*
107 * The directory tail is in the final bh
108 * Note that contary to the RISC OS PRMs,
109 * the first few bytes are NOT included
110 * in the check. All bytes are in the
111 * same bh.
112 */
113 ptr.ptr8 = bufoff(bh, 2008);
114 end.ptr8 = ptr.ptr8 + 36;
115
116 do {
117 __le32 v = *ptr.ptr32++;
118 dircheck = le32_to_cpu(v) ^ ror13(dircheck);
119 } while (ptr.ptr32 < end.ptr32);
120
121 return (dircheck ^ (dircheck >> 8) ^ (dircheck >> 16) ^ (dircheck >> 24)) & 0xff;
122 }
123
124 static int adfs_f_validate(struct adfs_dir *dir)
125 {
126 struct adfs_dirheader *head = dir->dirhead;
127 struct adfs_newdirtail *tail = dir->newtail;
128
129 if (head->startmasseq != tail->endmasseq ||
130 tail->dirlastmask || tail->reserved[0] || tail->reserved[1] ||
131 (memcmp(&head->startname, "Nick", 4) &&
132 memcmp(&head->startname, "Hugo", 4)) ||
133 memcmp(&head->startname, &tail->endname, 4) ||
134 adfs_dir_checkbyte(dir) != tail->dircheckbyte)
135 return -EIO;
136
137 return 0;
138 }
139
140 /* Read and check that a directory is valid */
141 static int adfs_f_read(struct super_block *sb, u32 indaddr, unsigned int size,
142 struct adfs_dir *dir)
143 {
144 const unsigned int blocksize_bits = sb->s_blocksize_bits;
145 int ret;
146
147 if (size && size != ADFS_NEWDIR_SIZE)
148 return -EIO;
149
150 ret = adfs_dir_read_buffers(sb, indaddr, ADFS_NEWDIR_SIZE, dir);
151 if (ret)
152 return ret;
153
154 dir->dirhead = bufoff(dir->bh, 0);
155 dir->newtail = bufoff(dir->bh, 2007);
156
157 if (adfs_f_validate(dir))
158 goto bad_dir;
159
160 dir->parent_id = adfs_readval(dir->newtail->dirparent, 3);
161
162 return 0;
163
164 bad_dir:
165 adfs_error(sb, "dir %06x is corrupted", indaddr);
166 adfs_dir_relse(dir);
167
168 return -EIO;
169 }
170
171 /*
172 * convert a disk-based directory entry to a Linux ADFS directory entry
173 */
174 static inline void
175 adfs_dir2obj(struct adfs_dir *dir, struct object_info *obj,
176 struct adfs_direntry *de)
177 {
178 unsigned int name_len;
179
180 for (name_len = 0; name_len < ADFS_F_NAME_LEN; name_len++) {
181 if (de->dirobname[name_len] < ' ')
182 break;
183
184 obj->name[name_len] = de->dirobname[name_len];
185 }
186
187 obj->name_len = name_len;
188 obj->indaddr = adfs_readval(de->dirinddiscadd, 3);
189 obj->loadaddr = adfs_readval(de->dirload, 4);
190 obj->execaddr = adfs_readval(de->direxec, 4);
191 obj->size = adfs_readval(de->dirlen, 4);
192 obj->attr = de->newdiratts;
193
194 adfs_object_fixup(dir, obj);
195 }
196
197 /*
198 * convert a Linux ADFS directory entry to a disk-based directory entry
199 */
200 static inline void
201 adfs_obj2dir(struct adfs_direntry *de, struct object_info *obj)
202 {
203 adfs_writeval(de->dirinddiscadd, 3, obj->indaddr);
204 adfs_writeval(de->dirload, 4, obj->loadaddr);
205 adfs_writeval(de->direxec, 4, obj->execaddr);
206 adfs_writeval(de->dirlen, 4, obj->size);
207 de->newdiratts = obj->attr;
208 }
209
210 /*
211 * get a directory entry. Note that the caller is responsible
212 * for holding the relevant locks.
213 */
214 static int
215 __adfs_dir_get(struct adfs_dir *dir, int pos, struct object_info *obj)
216 {
217 struct adfs_direntry de;
218 int ret;
219
220 ret = adfs_dir_copyfrom(&de, dir, pos, 26);
221 if (ret)
222 return ret;
223
224 if (!de.dirobname[0])
225 return -ENOENT;
226
227 adfs_dir2obj(dir, obj, &de);
228
229 return 0;
230 }
231
232 static int
233 adfs_f_setpos(struct adfs_dir *dir, unsigned int fpos)
234 {
235 if (fpos >= ADFS_NUM_DIR_ENTRIES)
236 return -ENOENT;
237
238 dir->pos = 5 + fpos * 26;
239 return 0;
240 }
241
242 static int
243 adfs_f_getnext(struct adfs_dir *dir, struct object_info *obj)
244 {
245 unsigned int ret;
246
247 ret = __adfs_dir_get(dir, dir->pos, obj);
248 if (ret == 0)
249 dir->pos += 26;
250
251 return ret;
252 }
253
254 static int adfs_f_iterate(struct adfs_dir *dir, struct dir_context *ctx)
255 {
256 struct object_info obj;
257 int pos = 5 + (ctx->pos - 2) * 26;
258
259 while (ctx->pos < 2 + ADFS_NUM_DIR_ENTRIES) {
260 if (__adfs_dir_get(dir, pos, &obj))
261 break;
262 if (!dir_emit(ctx, obj.name, obj.name_len,
263 obj.indaddr, DT_UNKNOWN))
264 break;
265 pos += 26;
266 ctx->pos++;
267 }
268 return 0;
269 }
270
271 static int adfs_f_update(struct adfs_dir *dir, struct object_info *obj)
272 {
273 struct adfs_direntry de;
274 int offset, ret;
275
276 offset = 5 - (int)sizeof(de);
277
278 do {
279 offset += sizeof(de);
280 ret = adfs_dir_copyfrom(&de, dir, offset, sizeof(de));
281 if (ret) {
282 adfs_error(dir->sb, "error reading directory entry");
283 return -ENOENT;
284 }
285 if (!de.dirobname[0]) {
286 adfs_error(dir->sb, "unable to locate entry to update");
287 return -ENOENT;
288 }
289 } while (adfs_readval(de.dirinddiscadd, 3) != obj->indaddr);
290
291 /* Update the directory entry with the new object state */
292 adfs_obj2dir(&de, obj);
293
294 /* Write the directory entry back to the directory */
295 return adfs_dir_copyto(dir, offset, &de, 26);
296 }
297
298 static int adfs_f_commit(struct adfs_dir *dir)
299 {
300 int ret;
301
302 /* Increment directory sequence number */
303 dir->dirhead->startmasseq += 1;
304 dir->newtail->endmasseq += 1;
305
306 /* Update directory check byte */
307 dir->newtail->dircheckbyte = adfs_dir_checkbyte(dir);
308
309 /* Make sure the directory still validates correctly */
310 ret = adfs_f_validate(dir);
311 if (ret)
312 adfs_msg(dir->sb, KERN_ERR, "error: update broke directory");
313
314 return ret;
315 }
316
317 const struct adfs_dir_ops adfs_f_dir_ops = {
318 .read = adfs_f_read,
319 .iterate = adfs_f_iterate,
320 .setpos = adfs_f_setpos,
321 .getnext = adfs_f_getnext,
322 .update = adfs_f_update,
323 .commit = adfs_f_commit,
324 };
325
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