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(p: &head->startname, q: "Nick" , size: 4) && |
132 | memcmp(p: &head->startname, q: "Hugo" , size: 4)) || |
133 | memcmp(p: &head->startname, q: &tail->endname, size: 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(p: dir->newtail->dirparent, len: 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(p: de->dirinddiscadd, len: 3); |
189 | obj->loadaddr = adfs_readval(p: de->dirload, len: 4); |
190 | obj->execaddr = adfs_readval(p: de->direxec, len: 4); |
191 | obj->size = adfs_readval(p: de->dirlen, len: 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(p: de->dirinddiscadd, len: 3, val: obj->indaddr); |
204 | adfs_writeval(p: de->dirload, len: 4, val: obj->loadaddr); |
205 | adfs_writeval(p: de->direxec, len: 4, val: obj->execaddr); |
206 | adfs_writeval(p: de->dirlen, len: 4, val: 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(dst: &de, dir, offset: pos, len: 26); |
221 | if (ret) |
222 | return ret; |
223 | |
224 | if (!de.dirobname[0]) |
225 | return -ENOENT; |
226 | |
227 | adfs_dir2obj(dir, obj, de: &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, pos: 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: &obj)) |
261 | break; |
262 | if (!dir_emit(ctx, name: obj.name, namelen: obj.name_len, |
263 | ino: 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(dst: &de, dir, offset, len: 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(p: de.dirinddiscadd, len: 3) != obj->indaddr); |
290 | |
291 | /* Update the directory entry with the new object state */ |
292 | adfs_obj2dir(de: &de, obj); |
293 | |
294 | /* Write the directory entry back to the directory */ |
295 | return adfs_dir_copyto(dir, offset, src: &de, len: 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(sb: dir->sb, KERN_ERR, fmt: "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 | |