[linux-2.6-block.git] / tools / objtool / elf.c

/*
 * elf.c - ELF access library
 *
 * Adapted from kpatch (https://github.com/dynup/kpatch):
 * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
 * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "elf.h"
#include "warn.h"

struct section *find_section_by_name(struct elf *elf, const char *name)
{
	struct section *sec;

	list_for_each_entry(sec, &elf->sections, list)
		if (!strcmp(sec->name, name))
			return sec;

	return NULL;
}

static struct section *find_section_by_index(struct elf *elf,
					     unsigned int idx)
{
	struct section *sec;

	list_for_each_entry(sec, &elf->sections, list)
		if (sec->idx == idx)
			return sec;

	return NULL;
}

static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
{
	struct section *sec;
	struct symbol *sym;

	list_for_each_entry(sec, &elf->sections, list)
		hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
			if (sym->idx == idx)
				return sym;

	return NULL;
}

struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
{
	struct symbol *sym;

	list_for_each_entry(sym, &sec->symbol_list, list)
		if (sym->type != STT_SECTION &&
		    sym->offset == offset)
			return sym;

	return NULL;
}

struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
				     unsigned int len)
{
	struct rela *rela;
	unsigned long o;

	if (!sec->rela)
		return NULL;

	for (o = offset; o < offset + len; o++)
		hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
			if (rela->offset == o)
				return rela;

	return NULL;
}

struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)
{
	return find_rela_by_dest_range(sec, offset, 1);
}

struct symbol *find_containing_func(struct section *sec, unsigned long offset)
{
	struct symbol *func;

	list_for_each_entry(func, &sec->symbol_list, list)
		if (func->type == STT_FUNC && offset >= func->offset &&
		    offset < func->offset + func->len)
			return func;

	return NULL;
}

static int read_sections(struct elf *elf)
{
	Elf_Scn *s = NULL;
	struct section *sec;
	size_t shstrndx, sections_nr;
	int i;

	if (elf_getshdrnum(elf->elf, &sections_nr)) {
		perror("elf_getshdrnum");
		return -1;
	}

	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
		perror("elf_getshdrstrndx");
		return -1;
	}

	for (i = 0; i < sections_nr; i++) {
		sec = malloc(sizeof(*sec));
		if (!sec) {
			perror("malloc");
			return -1;
		}
		memset(sec, 0, sizeof(*sec));

		INIT_LIST_HEAD(&sec->symbol_list);
		INIT_LIST_HEAD(&sec->rela_list);
		hash_init(sec->rela_hash);
		hash_init(sec->symbol_hash);

		list_add_tail(&sec->list, &elf->sections);

		s = elf_getscn(elf->elf, i);
		if (!s) {
			perror("elf_getscn");
			return -1;
		}

		sec->idx = elf_ndxscn(s);

		if (!gelf_getshdr(s, &sec->sh)) {
			perror("gelf_getshdr");
			return -1;
		}

		sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
		if (!sec->name) {
			perror("elf_strptr");
			return -1;
		}

		sec->elf_data = elf_getdata(s, NULL);
		if (!sec->elf_data) {
			perror("elf_getdata");
			return -1;
		}

		if (sec->elf_data->d_off != 0 ||
		    sec->elf_data->d_size != sec->sh.sh_size) {
			WARN("unexpected data attributes for %s", sec->name);
			return -1;
		}

		sec->data = (unsigned long)sec->elf_data->d_buf;
		sec->len = sec->elf_data->d_size;
	}

	/* sanity check, one more call to elf_nextscn() should return NULL */
	if (elf_nextscn(elf->elf, s)) {
		WARN("section entry mismatch");
		return -1;
	}

	return 0;
}

static int read_symbols(struct elf *elf)
{
	struct section *symtab;
	struct symbol *sym;
	struct list_head *entry, *tmp;
	int symbols_nr, i;

	symtab = find_section_by_name(elf, ".symtab");
	if (!symtab) {
		WARN("missing symbol table");
		return -1;
	}

	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;

	for (i = 0; i < symbols_nr; i++) {
		sym = malloc(sizeof(*sym));
		if (!sym) {
			perror("malloc");
			return -1;
		}
		memset(sym, 0, sizeof(*sym));

		sym->idx = i;

		if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
			perror("gelf_getsym");
			goto err;
		}

		sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
				       sym->sym.st_name);
		if (!sym->name) {
			perror("elf_strptr");
			goto err;
		}

		sym->type = GELF_ST_TYPE(sym->sym.st_info);
		sym->bind = GELF_ST_BIND(sym->sym.st_info);

		if (sym->sym.st_shndx > SHN_UNDEF &&
		    sym->sym.st_shndx < SHN_LORESERVE) {
			sym->sec = find_section_by_index(elf,
							 sym->sym.st_shndx);
			if (!sym->sec) {
				WARN("couldn't find section for symbol %s",
				     sym->name);
				goto err;
			}
			if (sym->type == STT_SECTION) {
				sym->name = sym->sec->name;
				sym->sec->sym = sym;
			}
		} else
			sym->sec = find_section_by_index(elf, 0);

		sym->offset = sym->sym.st_value;
		sym->len = sym->sym.st_size;

		/* sorted insert into a per-section list */
		entry = &sym->sec->symbol_list;
		list_for_each_prev(tmp, &sym->sec->symbol_list) {
			struct symbol *s;

			s = list_entry(tmp, struct symbol, list);

			if (sym->offset > s->offset) {
				entry = tmp;
				break;
			}

			if (sym->offset == s->offset && sym->len >= s->len) {
				entry = tmp;
				break;
			}
		}
		list_add(&sym->list, entry);
		hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
	}

	return 0;

err:
	free(sym);
	return -1;
}

static int read_relas(struct elf *elf)
{
	struct section *sec;
	struct rela *rela;
	int i;
	unsigned int symndx;

	list_for_each_entry(sec, &elf->sections, list) {
		if (sec->sh.sh_type != SHT_RELA)
			continue;

		sec->base = find_section_by_name(elf, sec->name + 5);
		if (!sec->base) {
			WARN("can't find base section for rela section %s",
			     sec->name);
			return -1;
		}

		sec->base->rela = sec;

		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
			rela = malloc(sizeof(*rela));
			if (!rela) {
				perror("malloc");
				return -1;
			}
			memset(rela, 0, sizeof(*rela));

			if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
				perror("gelf_getrela");
				return -1;
			}

			rela->type = GELF_R_TYPE(rela->rela.r_info);
			rela->addend = rela->rela.r_addend;
			rela->offset = rela->rela.r_offset;
			symndx = GELF_R_SYM(rela->rela.r_info);
			rela->sym = find_symbol_by_index(elf, symndx);
			if (!rela->sym) {
				WARN("can't find rela entry symbol %d for %s",
				     symndx, sec->name);
				return -1;
			}

			list_add_tail(&rela->list, &sec->rela_list);
			hash_add(sec->rela_hash, &rela->hash, rela->offset);

		}
	}

	return 0;
}

struct elf *elf_open(const char *name)
{
	struct elf *elf;

	elf_version(EV_CURRENT);

	elf = malloc(sizeof(*elf));
	if (!elf) {
		perror("malloc");
		return NULL;
	}
	memset(elf, 0, sizeof(*elf));

	INIT_LIST_HEAD(&elf->sections);

	elf->name = strdup(name);
	if (!elf->name) {
		perror("strdup");
		goto err;
	}

	elf->fd = open(name, O_RDONLY);
	if (elf->fd == -1) {
		perror("open");
		goto err;
	}

	elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
	if (!elf->elf) {
		perror("elf_begin");
		goto err;
	}

	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
		perror("gelf_getehdr");
		goto err;
	}

	if (read_sections(elf))
		goto err;

	if (read_symbols(elf))
		goto err;

	if (read_relas(elf))
		goto err;

	return elf;

err:
	elf_close(elf);
	return NULL;
}

void elf_close(struct elf *elf)
{
	struct section *sec, *tmpsec;
	struct symbol *sym, *tmpsym;
	struct rela *rela, *tmprela;

	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
		list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
			list_del(&sym->list);
			hash_del(&sym->hash);
			free(sym);
		}
		list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
			list_del(&rela->list);
			hash_del(&rela->hash);
			free(rela);
		}
		list_del(&sec->list);
		free(sec);
	}
	if (elf->name)
		free(elf->name);
	if (elf->fd > 0)
		close(elf->fd);
	if (elf->elf)
		elf_end(elf->elf);
	free(elf);
}
Commit	Line	Data
442f04c3 JP	1	/*
	2	* elf.c - ELF access library
	3	*
	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>
	7	*
	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.
	12	*
	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.
	17	*
	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/>.
	20	*/
	21
	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
	33	struct 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
	44	static 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
	56	static 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)
042ba73f	62	hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
442f04c3 JP	63	if (sym->idx == idx)
	64	return sym;
	65
	66	return NULL;
	67	}
	68
	69	struct symbol find_symbol_by_offset(struct section sec, unsigned long offset)
	70	{
	71	struct symbol *sym;
	72
a196e171	73	list_for_each_entry(sym, &sec->symbol_list, list)
442f04c3 JP	74	if (sym->type != STT_SECTION &&
	75	sym->offset == offset)
	76	return sym;
	77
	78	return NULL;
	79	}
	80
	81	struct rela find_rela_by_dest_range(struct section sec, unsigned long offset,
	82	unsigned int len)
	83	{
	84	struct rela *rela;
042ba73f	85	unsigned long o;
442f04c3 JP	86
	87	if (!sec->rela)
	88	return NULL;
	89
042ba73f JP	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;
442f04c3 JP	94
	95	return NULL;
	96	}
	97
	98	struct rela find_rela_by_dest(struct section sec, unsigned long offset)
	99	{
	100	return find_rela_by_dest_range(sec, offset, 1);
	101	}
	102
	103	struct symbol find_containing_func(struct section sec, unsigned long offset)
	104	{
	105	struct symbol *func;
	106
a196e171	107	list_for_each_entry(func, &sec->symbol_list, list)
442f04c3 JP	108	if (func->type == STT_FUNC && offset >= func->offset &&
	109	offset < func->offset + func->len)
	110	return func;
	111
	112	return NULL;
	113	}
	114
	115	static 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, &sections_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
a196e171 JP	140	INIT_LIST_HEAD(&sec->symbol_list);
a196e171 JP	141	INIT_LIST_HEAD(&sec->rela_list);
042ba73f JP	142	hash_init(sec->rela_hash);
042ba73f JP	143	hash_init(sec->symbol_hash);
442f04c3 JP	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	/* sanity check, one more call to elf_nextscn() should return NULL */
	183	if (elf_nextscn(elf->elf, s)) {
	184	WARN("section entry mismatch");
	185	return -1;
	186	}
	187
	188	return 0;
	189	}
	190
	191	static 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	/* sorted insert into a per-section list */
a196e171 JP	251	entry = &sym->sec->symbol_list;
a196e171 JP	252	list_for_each_prev(tmp, &sym->sec->symbol_list) {
442f04c3 JP	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);
042ba73f	268	hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
442f04c3 JP	269	}
	270
	271	return 0;
	272
	273	err:
	274	free(sym);
	275	return -1;
	276	}
	277
	278	static 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
442f04c3 JP	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	}
042ba73f JP	321
	322	list_add_tail(&rela->list, &sec->rela_list);
	323	hash_add(sec->rela_hash, &rela->hash, rela->offset);
	324
442f04c3 JP	325	}
	326	}
	327
	328	return 0;
	329	}
	330
	331	struct 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
	380	err:
	381	elf_close(elf);
	382	return NULL;
	383	}
	384
	385	void 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) {
a196e171	392	list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
442f04c3	393	list_del(&sym->list);
042ba73f	394	hash_del(&sym->hash);
442f04c3 JP	395	free(sym);
442f04c3 JP	396	}
a196e171	397	list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
442f04c3	398	list_del(&rela->list);
042ba73f	399	hash_del(&rela->hash);
442f04c3 JP	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	}