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>
33 struct section
*find_section_by_name(struct elf
*elf
, const char *name
)
37 list_for_each_entry(sec
, &elf
->sections
, list
)
38 if (!strcmp(sec
->name
, name
))
44 static struct section
*find_section_by_index(struct elf
*elf
,
49 list_for_each_entry(sec
, &elf
->sections
, list
)
56 static struct symbol
*find_symbol_by_index(struct elf
*elf
, unsigned int idx
)
61 list_for_each_entry(sec
, &elf
->sections
, list
)
62 list_for_each_entry(sym
, &sec
->symbols
, list
)
69 struct symbol
*find_symbol_by_offset(struct section
*sec
, unsigned long offset
)
73 list_for_each_entry(sym
, &sec
->symbols
, list
)
74 if (sym
->type
!= STT_SECTION
&&
75 sym
->offset
== offset
)
81 struct rela
*find_rela_by_dest_range(struct section
*sec
, unsigned long offset
,
89 list_for_each_entry(rela
, &sec
->rela
->relas
, list
)
90 if (rela
->offset
>= offset
&& rela
->offset
< offset
+ len
)
96 struct rela
*find_rela_by_dest(struct section
*sec
, unsigned long offset
)
98 return find_rela_by_dest_range(sec
, offset
, 1);
101 struct symbol
*find_containing_func(struct section
*sec
, unsigned long offset
)
105 list_for_each_entry(func
, &sec
->symbols
, list
)
106 if (func
->type
== STT_FUNC
&& offset
>= func
->offset
&&
107 offset
< func
->offset
+ func
->len
)
113 static int read_sections(struct elf
*elf
)
117 size_t shstrndx
, sections_nr
;
120 if (elf_getshdrnum(elf
->elf
, §ions_nr
)) {
121 perror("elf_getshdrnum");
125 if (elf_getshdrstrndx(elf
->elf
, &shstrndx
)) {
126 perror("elf_getshdrstrndx");
130 for (i
= 0; i
< sections_nr
; i
++) {
131 sec
= malloc(sizeof(*sec
));
136 memset(sec
, 0, sizeof(*sec
));
138 INIT_LIST_HEAD(&sec
->symbols
);
139 INIT_LIST_HEAD(&sec
->relas
);
141 list_add_tail(&sec
->list
, &elf
->sections
);
143 s
= elf_getscn(elf
->elf
, i
);
145 perror("elf_getscn");
149 sec
->idx
= elf_ndxscn(s
);
151 if (!gelf_getshdr(s
, &sec
->sh
)) {
152 perror("gelf_getshdr");
156 sec
->name
= elf_strptr(elf
->elf
, shstrndx
, sec
->sh
.sh_name
);
158 perror("elf_strptr");
162 sec
->elf_data
= elf_getdata(s
, NULL
);
163 if (!sec
->elf_data
) {
164 perror("elf_getdata");
168 if (sec
->elf_data
->d_off
!= 0 ||
169 sec
->elf_data
->d_size
!= sec
->sh
.sh_size
) {
170 WARN("unexpected data attributes for %s", sec
->name
);
174 sec
->data
= (unsigned long)sec
->elf_data
->d_buf
;
175 sec
->len
= sec
->elf_data
->d_size
;
178 /* sanity check, one more call to elf_nextscn() should return NULL */
179 if (elf_nextscn(elf
->elf
, s
)) {
180 WARN("section entry mismatch");
187 static int read_symbols(struct elf
*elf
)
189 struct section
*symtab
;
191 struct list_head
*entry
, *tmp
;
194 symtab
= find_section_by_name(elf
, ".symtab");
196 WARN("missing symbol table");
200 symbols_nr
= symtab
->sh
.sh_size
/ symtab
->sh
.sh_entsize
;
202 for (i
= 0; i
< symbols_nr
; i
++) {
203 sym
= malloc(sizeof(*sym
));
208 memset(sym
, 0, sizeof(*sym
));
212 if (!gelf_getsym(symtab
->elf_data
, i
, &sym
->sym
)) {
213 perror("gelf_getsym");
217 sym
->name
= elf_strptr(elf
->elf
, symtab
->sh
.sh_link
,
220 perror("elf_strptr");
224 sym
->type
= GELF_ST_TYPE(sym
->sym
.st_info
);
225 sym
->bind
= GELF_ST_BIND(sym
->sym
.st_info
);
227 if (sym
->sym
.st_shndx
> SHN_UNDEF
&&
228 sym
->sym
.st_shndx
< SHN_LORESERVE
) {
229 sym
->sec
= find_section_by_index(elf
,
232 WARN("couldn't find section for symbol %s",
236 if (sym
->type
== STT_SECTION
) {
237 sym
->name
= sym
->sec
->name
;
241 sym
->sec
= find_section_by_index(elf
, 0);
243 sym
->offset
= sym
->sym
.st_value
;
244 sym
->len
= sym
->sym
.st_size
;
246 /* sorted insert into a per-section list */
247 entry
= &sym
->sec
->symbols
;
248 list_for_each_prev(tmp
, &sym
->sec
->symbols
) {
251 s
= list_entry(tmp
, struct symbol
, list
);
253 if (sym
->offset
> s
->offset
) {
258 if (sym
->offset
== s
->offset
&& sym
->len
>= s
->len
) {
263 list_add(&sym
->list
, entry
);
273 static int read_relas(struct elf
*elf
)
280 list_for_each_entry(sec
, &elf
->sections
, list
) {
281 if (sec
->sh
.sh_type
!= SHT_RELA
)
284 sec
->base
= find_section_by_name(elf
, sec
->name
+ 5);
286 WARN("can't find base section for rela section %s",
291 sec
->base
->rela
= sec
;
293 for (i
= 0; i
< sec
->sh
.sh_size
/ sec
->sh
.sh_entsize
; i
++) {
294 rela
= malloc(sizeof(*rela
));
299 memset(rela
, 0, sizeof(*rela
));
301 list_add_tail(&rela
->list
, &sec
->relas
);
303 if (!gelf_getrela(sec
->elf_data
, i
, &rela
->rela
)) {
304 perror("gelf_getrela");
308 rela
->type
= GELF_R_TYPE(rela
->rela
.r_info
);
309 rela
->addend
= rela
->rela
.r_addend
;
310 rela
->offset
= rela
->rela
.r_offset
;
311 symndx
= GELF_R_SYM(rela
->rela
.r_info
);
312 rela
->sym
= find_symbol_by_index(elf
, symndx
);
314 WARN("can't find rela entry symbol %d for %s",
324 struct elf
*elf_open(const char *name
)
328 elf_version(EV_CURRENT
);
330 elf
= malloc(sizeof(*elf
));
335 memset(elf
, 0, sizeof(*elf
));
337 INIT_LIST_HEAD(&elf
->sections
);
339 elf
->name
= strdup(name
);
345 elf
->fd
= open(name
, O_RDONLY
);
351 elf
->elf
= elf_begin(elf
->fd
, ELF_C_READ_MMAP
, NULL
);
357 if (!gelf_getehdr(elf
->elf
, &elf
->ehdr
)) {
358 perror("gelf_getehdr");
362 if (read_sections(elf
))
365 if (read_symbols(elf
))
378 void elf_close(struct elf
*elf
)
380 struct section
*sec
, *tmpsec
;
381 struct symbol
*sym
, *tmpsym
;
382 struct rela
*rela
, *tmprela
;
384 list_for_each_entry_safe(sec
, tmpsec
, &elf
->sections
, list
) {
385 list_for_each_entry_safe(sym
, tmpsym
, &sec
->symbols
, list
) {
386 list_del(&sym
->list
);
389 list_for_each_entry_safe(rela
, tmprela
, &sec
->relas
, list
) {
390 list_del(&rela
->list
);
393 list_del(&sec
->list
);
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