2 * elf.c - ELF access library
4 * Adapted from kpatch (https://github.com/dynup/kpatch):
5 * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
6 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; either version 2
11 * of the License, or (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, see <http://www.gnu.org/licenses/>.
22 #include <sys/types.h>
34 * Fallback for systems without this "read, mmaping if possible" cmd.
36 #ifndef ELF_C_READ_MMAP
37 #define ELF_C_READ_MMAP ELF_C_READ
40 #define WARN_ELF(format, ...) \
41 WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))
43 struct section *find_section_by_name(struct elf *elf, const char *name)
47 list_for_each_entry(sec, &elf->sections, list)
48 if (!strcmp(sec->name, name))
54 static struct section *find_section_by_index(struct elf *elf,
59 list_for_each_entry(sec, &elf->sections, list)
66 static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
71 list_for_each_entry(sec, &elf->sections, list)
72 hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
79 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
83 list_for_each_entry(sym, &sec->symbol_list, list)
84 if (sym->type != STT_SECTION &&
85 sym->offset == offset)
91 struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
95 list_for_each_entry(sym, &sec->symbol_list, list)
96 if (sym->type != STT_SECTION &&
97 offset >= sym->offset && offset < sym->offset + sym->len)
103 struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
112 for (o = offset; o < offset + len; o++)
113 hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
114 if (rela->offset == o)
120 struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)
122 return find_rela_by_dest_range(sec, offset, 1);
125 struct symbol *find_containing_func(struct section *sec, unsigned long offset)
129 list_for_each_entry(func, &sec->symbol_list, list)
130 if (func->type == STT_FUNC && offset >= func->offset &&
131 offset < func->offset + func->len)
137 static int read_sections(struct elf *elf)
141 size_t shstrndx, sections_nr;
144 if (elf_getshdrnum(elf->elf, §ions_nr)) {
145 WARN_ELF("elf_getshdrnum");
149 if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
150 WARN_ELF("elf_getshdrstrndx");
154 for (i = 0; i < sections_nr; i++) {
155 sec = malloc(sizeof(*sec));
160 memset(sec, 0, sizeof(*sec));
162 INIT_LIST_HEAD(&sec->symbol_list);
163 INIT_LIST_HEAD(&sec->rela_list);
164 hash_init(sec->rela_hash);
165 hash_init(sec->symbol_hash);
167 list_add_tail(&sec->list, &elf->sections);
169 s = elf_getscn(elf->elf, i);
171 WARN_ELF("elf_getscn");
175 sec->idx = elf_ndxscn(s);
177 if (!gelf_getshdr(s, &sec->sh)) {
178 WARN_ELF("gelf_getshdr");
182 sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
184 WARN_ELF("elf_strptr");
188 sec->data = elf_getdata(s, NULL);
190 WARN_ELF("elf_getdata");
194 if (sec->data->d_off != 0 ||
195 sec->data->d_size != sec->sh.sh_size) {
196 WARN("unexpected data attributes for %s", sec->name);
200 sec->len = sec->data->d_size;
203 /* sanity check, one more call to elf_nextscn() should return NULL */
204 if (elf_nextscn(elf->elf, s)) {
205 WARN("section entry mismatch");
212 static int read_symbols(struct elf *elf)
214 struct section *symtab;
216 struct list_head *entry, *tmp;
219 symtab = find_section_by_name(elf, ".symtab");
221 WARN("missing symbol table");
225 symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
227 for (i = 0; i < symbols_nr; i++) {
228 sym = malloc(sizeof(*sym));
233 memset(sym, 0, sizeof(*sym));
237 if (!gelf_getsym(symtab->data, i, &sym->sym)) {
238 WARN_ELF("gelf_getsym");
242 sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
245 WARN_ELF("elf_strptr");
249 sym->type = GELF_ST_TYPE(sym->sym.st_info);
250 sym->bind = GELF_ST_BIND(sym->sym.st_info);
252 if (sym->sym.st_shndx > SHN_UNDEF &&
253 sym->sym.st_shndx < SHN_LORESERVE) {
254 sym->sec = find_section_by_index(elf,
257 WARN("couldn't find section for symbol %s",
261 if (sym->type == STT_SECTION) {
262 sym->name = sym->sec->name;
266 sym->sec = find_section_by_index(elf, 0);
268 sym->offset = sym->sym.st_value;
269 sym->len = sym->sym.st_size;
271 /* sorted insert into a per-section list */
272 entry = &sym->sec->symbol_list;
273 list_for_each_prev(tmp, &sym->sec->symbol_list) {
276 s = list_entry(tmp, struct symbol, list);
278 if (sym->offset > s->offset) {
283 if (sym->offset == s->offset && sym->len >= s->len) {
288 list_add(&sym->list, entry);
289 hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
299 static int read_relas(struct elf *elf)
306 list_for_each_entry(sec, &elf->sections, list) {
307 if (sec->sh.sh_type != SHT_RELA)
310 sec->base = find_section_by_name(elf, sec->name + 5);
312 WARN("can't find base section for rela section %s",
317 sec->base->rela = sec;
319 for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
320 rela = malloc(sizeof(*rela));
325 memset(rela, 0, sizeof(*rela));
327 if (!gelf_getrela(sec->data, i, &rela->rela)) {
328 WARN_ELF("gelf_getrela");
332 rela->type = GELF_R_TYPE(rela->rela.r_info);
333 rela->addend = rela->rela.r_addend;
334 rela->offset = rela->rela.r_offset;
335 symndx = GELF_R_SYM(rela->rela.r_info);
336 rela->sym = find_symbol_by_index(elf, symndx);
338 WARN("can't find rela entry symbol %d for %s",
343 list_add_tail(&rela->list, &sec->rela_list);
344 hash_add(sec->rela_hash, &rela->hash, rela->offset);
352 struct elf *elf_open(const char *name)
356 elf_version(EV_CURRENT);
358 elf = malloc(sizeof(*elf));
363 memset(elf, 0, sizeof(*elf));
365 INIT_LIST_HEAD(&elf->sections);
367 elf->fd = open(name, O_RDONLY);
373 elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
375 WARN_ELF("elf_begin");
379 if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
380 WARN_ELF("gelf_getehdr");
384 if (read_sections(elf))
387 if (read_symbols(elf))
400 void elf_close(struct elf *elf)
402 struct section *sec, *tmpsec;
403 struct symbol *sym, *tmpsym;
404 struct rela *rela, *tmprela;
412 list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
413 list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
414 list_del(&sym->list);
415 hash_del(&sym->hash);
418 list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
419 list_del(&rela->list);
420 hash_del(&rela->hash);
423 list_del(&sec->list);