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 */
15static 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
31static 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 */
69static u8
70adfs_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
124static 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 */
141static 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
164bad_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 */
174static inline void
175adfs_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 */
200static inline void
201adfs_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 */
214static 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
232static int
233adfs_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
242static int
243adfs_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
254static 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
271static 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
298static 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
317const 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