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22#include <sys/types.h>
23#include <sys/stat.h>
24#include <fcntl.h>
25#include <stdio.h>
26#include <stdlib.h>
27#include <string.h>
28#include <unistd.h>
29
30#include "elf.h"
31#include "warn.h"
32
33struct section *find_section_by_name(struct elf *elf, const char *name)
34{
35 struct section *sec;
36
37 list_for_each_entry(sec, &elf->sections, list)
38 if (!strcmp(sec->name, name))
39 return sec;
40
41 return NULL;
42}
43
44static struct section *find_section_by_index(struct elf *elf,
45 unsigned int idx)
46{
47 struct section *sec;
48
49 list_for_each_entry(sec, &elf->sections, list)
50 if (sec->idx == idx)
51 return sec;
52
53 return NULL;
54}
55
56static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
57{
58 struct section *sec;
59 struct symbol *sym;
60
61 list_for_each_entry(sec, &elf->sections, list)
62 hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
63 if (sym->idx == idx)
64 return sym;
65
66 return NULL;
67}
68
69struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
70{
71 struct symbol *sym;
72
73 list_for_each_entry(sym, &sec->symbol_list, list)
74 if (sym->type != STT_SECTION &&
75 sym->offset == offset)
76 return sym;
77
78 return NULL;
79}
80
81struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
82 unsigned int len)
83{
84 struct rela *rela;
85 unsigned long o;
86
87 if (!sec->rela)
88 return NULL;
89
90 for (o = offset; o < offset + len; o++)
91 hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
92 if (rela->offset == o)
93 return rela;
94
95 return NULL;
96}
97
98struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)
99{
100 return find_rela_by_dest_range(sec, offset, 1);
101}
102
103struct symbol *find_containing_func(struct section *sec, unsigned long offset)
104{
105 struct symbol *func;
106
107 list_for_each_entry(func, &sec->symbol_list, list)
108 if (func->type == STT_FUNC && offset >= func->offset &&
109 offset < func->offset + func->len)
110 return func;
111
112 return NULL;
113}
114
115static int read_sections(struct elf *elf)
116{
117 Elf_Scn *s = NULL;
118 struct section *sec;
119 size_t shstrndx, sections_nr;
120 int i;
121
122 if (elf_getshdrnum(elf->elf, §ions_nr)) {
123 perror("elf_getshdrnum");
124 return -1;
125 }
126
127 if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
128 perror("elf_getshdrstrndx");
129 return -1;
130 }
131
132 for (i = 0; i < sections_nr; i++) {
133 sec = malloc(sizeof(*sec));
134 if (!sec) {
135 perror("malloc");
136 return -1;
137 }
138 memset(sec, 0, sizeof(*sec));
139
140 INIT_LIST_HEAD(&sec->symbol_list);
141 INIT_LIST_HEAD(&sec->rela_list);
142 hash_init(sec->rela_hash);
143 hash_init(sec->symbol_hash);
144
145 list_add_tail(&sec->list, &elf->sections);
146
147 s = elf_getscn(elf->elf, i);
148 if (!s) {
149 perror("elf_getscn");
150 return -1;
151 }
152
153 sec->idx = elf_ndxscn(s);
154
155 if (!gelf_getshdr(s, &sec->sh)) {
156 perror("gelf_getshdr");
157 return -1;
158 }
159
160 sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
161 if (!sec->name) {
162 perror("elf_strptr");
163 return -1;
164 }
165
166 sec->elf_data = elf_getdata(s, NULL);
167 if (!sec->elf_data) {
168 perror("elf_getdata");
169 return -1;
170 }
171
172 if (sec->elf_data->d_off != 0 ||
173 sec->elf_data->d_size != sec->sh.sh_size) {
174 WARN("unexpected data attributes for %s", sec->name);
175 return -1;
176 }
177
178 sec->data = (unsigned long)sec->elf_data->d_buf;
179 sec->len = sec->elf_data->d_size;
180 }
181
182
183 if (elf_nextscn(elf->elf, s)) {
184 WARN("section entry mismatch");
185 return -1;
186 }
187
188 return 0;
189}
190
191static int read_symbols(struct elf *elf)
192{
193 struct section *symtab;
194 struct symbol *sym;
195 struct list_head *entry, *tmp;
196 int symbols_nr, i;
197
198 symtab = find_section_by_name(elf, ".symtab");
199 if (!symtab) {
200 WARN("missing symbol table");
201 return -1;
202 }
203
204 symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
205
206 for (i = 0; i < symbols_nr; i++) {
207 sym = malloc(sizeof(*sym));
208 if (!sym) {
209 perror("malloc");
210 return -1;
211 }
212 memset(sym, 0, sizeof(*sym));
213
214 sym->idx = i;
215
216 if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
217 perror("gelf_getsym");
218 goto err;
219 }
220
221 sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
222 sym->sym.st_name);
223 if (!sym->name) {
224 perror("elf_strptr");
225 goto err;
226 }
227
228 sym->type = GELF_ST_TYPE(sym->sym.st_info);
229 sym->bind = GELF_ST_BIND(sym->sym.st_info);
230
231 if (sym->sym.st_shndx > SHN_UNDEF &&
232 sym->sym.st_shndx < SHN_LORESERVE) {
233 sym->sec = find_section_by_index(elf,
234 sym->sym.st_shndx);
235 if (!sym->sec) {
236 WARN("couldn't find section for symbol %s",
237 sym->name);
238 goto err;
239 }
240 if (sym->type == STT_SECTION) {
241 sym->name = sym->sec->name;
242 sym->sec->sym = sym;
243 }
244 } else
245 sym->sec = find_section_by_index(elf, 0);
246
247 sym->offset = sym->sym.st_value;
248 sym->len = sym->sym.st_size;
249
250
251 entry = &sym->sec->symbol_list;
252 list_for_each_prev(tmp, &sym->sec->symbol_list) {
253 struct symbol *s;
254
255 s = list_entry(tmp, struct symbol, list);
256
257 if (sym->offset > s->offset) {
258 entry = tmp;
259 break;
260 }
261
262 if (sym->offset == s->offset && sym->len >= s->len) {
263 entry = tmp;
264 break;
265 }
266 }
267 list_add(&sym->list, entry);
268 hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
269 }
270
271 return 0;
272
273err:
274 free(sym);
275 return -1;
276}
277
278static int read_relas(struct elf *elf)
279{
280 struct section *sec;
281 struct rela *rela;
282 int i;
283 unsigned int symndx;
284
285 list_for_each_entry(sec, &elf->sections, list) {
286 if (sec->sh.sh_type != SHT_RELA)
287 continue;
288
289 sec->base = find_section_by_name(elf, sec->name + 5);
290 if (!sec->base) {
291 WARN("can't find base section for rela section %s",
292 sec->name);
293 return -1;
294 }
295
296 sec->base->rela = sec;
297
298 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
299 rela = malloc(sizeof(*rela));
300 if (!rela) {
301 perror("malloc");
302 return -1;
303 }
304 memset(rela, 0, sizeof(*rela));
305
306 if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
307 perror("gelf_getrela");
308 return -1;
309 }
310
311 rela->type = GELF_R_TYPE(rela->rela.r_info);
312 rela->addend = rela->rela.r_addend;
313 rela->offset = rela->rela.r_offset;
314 symndx = GELF_R_SYM(rela->rela.r_info);
315 rela->sym = find_symbol_by_index(elf, symndx);
316 if (!rela->sym) {
317 WARN("can't find rela entry symbol %d for %s",
318 symndx, sec->name);
319 return -1;
320 }
321
322 list_add_tail(&rela->list, &sec->rela_list);
323 hash_add(sec->rela_hash, &rela->hash, rela->offset);
324
325 }
326 }
327
328 return 0;
329}
330
331struct elf *elf_open(const char *name)
332{
333 struct elf *elf;
334
335 elf_version(EV_CURRENT);
336
337 elf = malloc(sizeof(*elf));
338 if (!elf) {
339 perror("malloc");
340 return NULL;
341 }
342 memset(elf, 0, sizeof(*elf));
343
344 INIT_LIST_HEAD(&elf->sections);
345
346 elf->name = strdup(name);
347 if (!elf->name) {
348 perror("strdup");
349 goto err;
350 }
351
352 elf->fd = open(name, O_RDONLY);
353 if (elf->fd == -1) {
354 perror("open");
355 goto err;
356 }
357
358 elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
359 if (!elf->elf) {
360 perror("elf_begin");
361 goto err;
362 }
363
364 if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
365 perror("gelf_getehdr");
366 goto err;
367 }
368
369 if (read_sections(elf))
370 goto err;
371
372 if (read_symbols(elf))
373 goto err;
374
375 if (read_relas(elf))
376 goto err;
377
378 return elf;
379
380err:
381 elf_close(elf);
382 return NULL;
383}
384
385void elf_close(struct elf *elf)
386{
387 struct section *sec, *tmpsec;
388 struct symbol *sym, *tmpsym;
389 struct rela *rela, *tmprela;
390
391 list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
392 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
393 list_del(&sym->list);
394 hash_del(&sym->hash);
395 free(sym);
396 }
397 list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
398 list_del(&rela->list);
399 hash_del(&rela->hash);
400 free(rela);
401 }
402 list_del(&sec->list);
403 free(sec);
404 }
405 if (elf->name)
406 free(elf->name);
407 if (elf->fd > 0)
408 close(elf->fd);
409 if (elf->elf)
410 elf_end(elf->elf);
411 free(elf);
412}
413
