1 /*-
2 * Copyright (c) 2013, Joseph Koshy
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer
10 * in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 #include <sys/param.h>
28 #include <sys/queue.h>
29
30 #include <assert.h>
31 #include <errno.h>
32 #include <gelf.h>
33 #include <stdlib.h>
34 #include <string.h>
35
36 #include "libelftc.h"
37 #include "_libelftc.h"
38
39 ELFTC_VCSID("$Id: elftc_string_table.c 2869 2013-01-06 13:29:18Z jkoshy $");
40
41 #define ELFTC_STRING_TABLE_DEFAULT_SIZE (4*1024)
42 #define ELFTC_STRING_TABLE_EXPECTED_STRING_SIZE 16
43 #define ELFTC_STRING_TABLE_EXPECTED_CHAIN_LENGTH 8
44 #define ELFTC_STRING_TABLE_POOL_SIZE_INCREMENT (4*1024)
45
46 struct _Elftc_String_Table_Entry {
47 int ste_idx;
48 SLIST_ENTRY(_Elftc_String_Table_Entry) ste_next;
49 };
50
51 #define ELFTC_STRING_TABLE_COMPACTION_FLAG 0x1
52 #define ELFTC_STRING_TABLE_LENGTH(st) ((st)->st_len >> 1)
53 #define ELFTC_STRING_TABLE_CLEAR_COMPACTION_FLAG(st) do { \
54 (st)->st_len &= ~ELFTC_STRING_TABLE_COMPACTION_FLAG; \
55 } while (0)
56 #define ELFTC_STRING_TABLE_SET_COMPACTION_FLAG(st) do { \
57 (st)->st_len |= ELFTC_STRING_TABLE_COMPACTION_FLAG; \
58 } while (0)
59 #define ELFTC_STRING_TABLE_UPDATE_LENGTH(st, len) do { \
60 (st)->st_len = \
61 ((st)->st_len & \
62 ELFTC_STRING_TABLE_COMPACTION_FLAG) | \
63 ((len) << 1); \
64 } while (0)
65
66 struct _Elftc_String_Table {
67 unsigned int st_len; /* length and flags */
68 int st_nbuckets;
69 int st_string_pool_size;
70 char *st_string_pool;
71 SLIST_HEAD(_Elftc_String_Table_Bucket,
72 _Elftc_String_Table_Entry) st_buckets[];
73 };
74
75 static struct _Elftc_String_Table_Entry *
elftc_string_table_find_hash_entry(Elftc_String_Table * st,const char * string,int * rhashindex)76 elftc_string_table_find_hash_entry(Elftc_String_Table *st, const char *string,
77 int *rhashindex)
78 {
79 struct _Elftc_String_Table_Entry *ste;
80 int hashindex;
81 char *s;
82
83 hashindex = libelftc_hash_string(string) % st->st_nbuckets;
84
85 if (rhashindex)
86 *rhashindex = hashindex;
87
88 SLIST_FOREACH(ste, &st->st_buckets[hashindex], ste_next) {
89 s = st->st_string_pool + abs(ste->ste_idx);
90
91 assert(s > st->st_string_pool &&
92 s < st->st_string_pool + st->st_string_pool_size);
93
94 if (strcmp(s, string) == 0)
95 return (ste);
96 }
97
98 return (NULL);
99 }
100
101 static int
elftc_string_table_add_to_pool(Elftc_String_Table * st,const char * string)102 elftc_string_table_add_to_pool(Elftc_String_Table *st, const char *string)
103 {
104 char *newpool;
105 int len, newsize, stlen;
106
107 len = strlen(string) + 1; /* length, including the trailing NUL */
108 stlen = ELFTC_STRING_TABLE_LENGTH(st);
109
110 /* Resize the pool, if needed. */
111 if (stlen + len >= st->st_string_pool_size) {
112 newsize = roundup(st->st_string_pool_size +
113 ELFTC_STRING_TABLE_POOL_SIZE_INCREMENT,
114 ELFTC_STRING_TABLE_POOL_SIZE_INCREMENT);
115 if ((newpool = realloc(st->st_string_pool, newsize)) ==
116 NULL)
117 return (0);
118 st->st_string_pool = newpool;
119 st->st_string_pool_size = newsize;
120 }
121
122 strcpy(st->st_string_pool + stlen, string);
123 ELFTC_STRING_TABLE_UPDATE_LENGTH(st, stlen + len);
124
125 return (stlen);
126 }
127
128 Elftc_String_Table *
elftc_string_table_create(int sizehint)129 elftc_string_table_create(int sizehint)
130 {
131 int n, nbuckets, tablesize;
132 struct _Elftc_String_Table *st;
133
134 if (sizehint < ELFTC_STRING_TABLE_DEFAULT_SIZE)
135 sizehint = ELFTC_STRING_TABLE_DEFAULT_SIZE;
136
137 nbuckets = sizehint / (ELFTC_STRING_TABLE_EXPECTED_CHAIN_LENGTH *
138 ELFTC_STRING_TABLE_EXPECTED_STRING_SIZE);
139
140 tablesize = sizeof(struct _Elftc_String_Table) +
141 nbuckets * sizeof(struct _Elftc_String_Table_Bucket);
142
143 if ((st = malloc(tablesize)) == NULL)
144 return (NULL);
145 if ((st->st_string_pool = malloc(sizehint)) == NULL) {
146 free(st);
147 return (NULL);
148 }
149
150 for (n = 0; n < nbuckets; n++)
151 SLIST_INIT(&st->st_buckets[n]);
152
153 st->st_len = 0;
154 st->st_nbuckets = nbuckets;
155 st->st_string_pool_size = sizehint;
156 *st->st_string_pool = '\0';
157 ELFTC_STRING_TABLE_UPDATE_LENGTH(st, 1);
158
159 return (st);
160 }
161
162 void
elftc_string_table_destroy(Elftc_String_Table * st)163 elftc_string_table_destroy(Elftc_String_Table *st)
164 {
165 int n;
166 struct _Elftc_String_Table_Entry *s, *t;
167
168 for (n = 0; n < st->st_nbuckets; n++)
169 SLIST_FOREACH_SAFE(s, &st->st_buckets[n], ste_next, t)
170 free(s);
171 free(st->st_string_pool);
172 free(st);
173
174 return;
175 }
176
177 Elftc_String_Table *
elftc_string_table_from_section(Elf_Scn * scn,int sizehint)178 elftc_string_table_from_section(Elf_Scn *scn, int sizehint)
179 {
180 int len;
181 Elf_Data *d;
182 GElf_Shdr sh;
183 const char *s, *end;
184 Elftc_String_Table *st;
185
186 /* Verify the type of the section passed in. */
187 if (gelf_getshdr(scn, &sh) == NULL ||
188 sh.sh_type != SHT_STRTAB) {
189 errno = EINVAL;
190 return (NULL);
191 }
192
193 if ((d = elf_getdata(scn, NULL)) == NULL ||
194 d->d_size == 0) {
195 errno = EINVAL;
196 return (NULL);
197 }
198
199 if ((st = elftc_string_table_create(sizehint)) == NULL)
200 return (NULL);
201
202 s = d->d_buf;
203
204 /*
205 * Verify that the first byte of the data buffer is '\0'.
206 */
207 if (*s != '\0') {
208 errno = EINVAL;
209 goto fail;
210 }
211
212 end = s + d->d_size;
213
214 /*
215 * Skip the first '\0' and insert the strings in the buffer,
216 * in order.
217 */
218 for (s += 1; s < end; s += len) {
219 if (elftc_string_table_insert(st, s) == 0)
220 goto fail;
221
222 len = strlen(s) + 1; /* Include space for the trailing NUL. */
223 }
224
225 return (st);
226
227 fail:
228 if (st)
229 (void) elftc_string_table_destroy(st);
230
231 return (NULL);
232 }
233
234 const char *
elftc_string_table_image(Elftc_String_Table * st,size_t * size)235 elftc_string_table_image(Elftc_String_Table *st, size_t *size)
236 {
237 char *r, *s, *end;
238 struct _Elftc_String_Table_Entry *ste;
239 struct _Elftc_String_Table_Bucket *head;
240 int copied, hashindex, offset, length, newsize;
241
242 /*
243 * For the common case of a string table has not seen
244 * a string deletion, we can just export the current
245 * pool.
246 */
247 if ((st->st_len & ELFTC_STRING_TABLE_COMPACTION_FLAG) == 0) {
248 if (size)
249 *size = ELFTC_STRING_TABLE_LENGTH(st);
250 return (st->st_string_pool);
251 }
252
253 /*
254 * Otherwise, compact the string table in-place.
255 */
256 assert(*st->st_string_pool == '\0');
257
258 newsize = 1;
259 end = st->st_string_pool + ELFTC_STRING_TABLE_LENGTH(st);
260
261 for (r = s = st->st_string_pool + 1;
262 s < end;
263 s += length, r += copied) {
264
265 copied = 0;
266 length = strlen(s) + 1;
267
268 ste = elftc_string_table_find_hash_entry(st, s,
269 &hashindex);
270 head = &st->st_buckets[hashindex];
271
272 assert(ste != NULL);
273
274 /* Ignore deleted strings. */
275 if (ste->ste_idx < 0) {
276 SLIST_REMOVE(head, ste, _Elftc_String_Table_Entry,
277 ste_next);
278 free(ste);
279 continue;
280 }
281
282 /* Move 'live' strings up. */
283 offset = newsize;
284 newsize += length;
285 copied = length;
286
287 if (r == s) /* Nothing removed yet. */
288 continue;
289
290 memmove(r, s, copied);
291
292 /* Update the index for this entry. */
293 ste->ste_idx = offset;
294 }
295
296 ELFTC_STRING_TABLE_CLEAR_COMPACTION_FLAG(st);
297 ELFTC_STRING_TABLE_UPDATE_LENGTH(st, newsize);
298
299 if (size)
300 *size = newsize;
301
302 return (st->st_string_pool);
303 }
304
305 size_t
elftc_string_table_insert(Elftc_String_Table * st,const char * string)306 elftc_string_table_insert(Elftc_String_Table *st, const char *string)
307 {
308 int hashindex, idx;
309 struct _Elftc_String_Table_Entry *ste;
310
311 hashindex = 0;
312
313 ste = elftc_string_table_find_hash_entry(st, string, &hashindex);
314
315 assert(hashindex >= 0 && hashindex < st->st_nbuckets);
316
317 if (ste == NULL) {
318 if ((ste = malloc(sizeof(*ste))) == NULL)
319 return (0);
320 if ((ste->ste_idx = elftc_string_table_add_to_pool(st,
321 string)) == 0) {
322 free(ste);
323 return (0);
324 }
325
326 SLIST_INSERT_HEAD(&st->st_buckets[hashindex], ste, ste_next);
327 }
328
329 idx = ste->ste_idx;
330 if (idx < 0) /* Undelete. */
331 ste->ste_idx = idx = (- idx);
332
333 return (idx);
334 }
335
336 size_t
elftc_string_table_lookup(Elftc_String_Table * st,const char * string)337 elftc_string_table_lookup(Elftc_String_Table *st, const char *string)
338 {
339 int hashindex, idx;
340 struct _Elftc_String_Table_Entry *ste;
341
342 ste = elftc_string_table_find_hash_entry(st, string, &hashindex);
343
344 assert(hashindex >= 0 && hashindex < st->st_nbuckets);
345
346 if (ste == NULL || (idx = ste->ste_idx) < 0)
347 return (0);
348
349 return (idx);
350 }
351
352 int
elftc_string_table_remove(Elftc_String_Table * st,const char * string)353 elftc_string_table_remove(Elftc_String_Table *st, const char *string)
354 {
355 int idx;
356 struct _Elftc_String_Table_Entry *ste;
357
358 ste = elftc_string_table_find_hash_entry(st, string, NULL);
359
360 if (ste == NULL || (idx = ste->ste_idx) < 0)
361 return (ELFTC_FAILURE);
362
363 assert(idx > 0 && idx < (int) ELFTC_STRING_TABLE_LENGTH(st));
364
365 ste->ste_idx = (- idx);
366
367 ELFTC_STRING_TABLE_SET_COMPACTION_FLAG(st);
368
369 return (ELFTC_SUCCESS);
370 }
371
372 const char *
elftc_string_table_to_string(Elftc_String_Table * st,size_t offset)373 elftc_string_table_to_string(Elftc_String_Table *st, size_t offset)
374 {
375 const char *s;
376
377 s = st->st_string_pool + offset;
378
379 /*
380 * Check for:
381 * - An offset value within pool bounds.
382 * - A non-NUL byte at the specified offset.
383 * - The end of the prior string at offset - 1.
384 */
385 if (offset == 0 || offset >= ELFTC_STRING_TABLE_LENGTH(st) ||
386 *s == '\0' || *(s - 1) != '\0') {
387 errno = EINVAL;
388 return (NULL);
389 }
390
391 return (s);
392 }
393