[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"

/*
 * Fallback for systems without this "read, mmaping if possible" cmd.
 */
#ifndef ELF_C_READ_MMAP
#define ELF_C_READ_MMAP ELF_C_READ
#endif

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
774bec3f ACM	33	/*
	34	* Fallback for systems without this "read, mmaping if possible" cmd.
	35	*/
	36	#ifndef ELF_C_READ_MMAP
	37	#define ELF_C_READ_MMAP ELF_C_READ
	38	#endif
	39
442f04c3 JP	40	struct section find_section_by_name(struct elf elf, const char *name)
	41	{
	42	struct section *sec;
	43
	44	list_for_each_entry(sec, &elf->sections, list)
	45	if (!strcmp(sec->name, name))
	46	return sec;
	47
	48	return NULL;
	49	}
	50
	51	static struct section find_section_by_index(struct elf elf,
	52	unsigned int idx)
	53	{
	54	struct section *sec;
	55
	56	list_for_each_entry(sec, &elf->sections, list)
	57	if (sec->idx == idx)
	58	return sec;
	59
	60	return NULL;
	61	}
	62
	63	static struct symbol find_symbol_by_index(struct elf elf, unsigned int idx)
	64	{
	65	struct section *sec;
	66	struct symbol *sym;
	67
	68	list_for_each_entry(sec, &elf->sections, list)
042ba73f	69	hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
442f04c3 JP	70	if (sym->idx == idx)
	71	return sym;
	72
	73	return NULL;
	74	}
	75
	76	struct symbol find_symbol_by_offset(struct section sec, unsigned long offset)
	77	{
	78	struct symbol *sym;
	79
a196e171	80	list_for_each_entry(sym, &sec->symbol_list, list)
442f04c3 JP	81	if (sym->type != STT_SECTION &&
	82	sym->offset == offset)
	83	return sym;
	84
	85	return NULL;
	86	}
	87
	88	struct rela find_rela_by_dest_range(struct section sec, unsigned long offset,
	89	unsigned int len)
	90	{
	91	struct rela *rela;
042ba73f	92	unsigned long o;
442f04c3 JP	93
	94	if (!sec->rela)
	95	return NULL;
	96
042ba73f JP	97	for (o = offset; o < offset + len; o++)
	98	hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
	99	if (rela->offset == o)
	100	return rela;
442f04c3 JP	101
	102	return NULL;
	103	}
	104
	105	struct rela find_rela_by_dest(struct section sec, unsigned long offset)
	106	{
	107	return find_rela_by_dest_range(sec, offset, 1);
	108	}
	109
	110	struct symbol find_containing_func(struct section sec, unsigned long offset)
	111	{
	112	struct symbol *func;
	113
a196e171	114	list_for_each_entry(func, &sec->symbol_list, list)
442f04c3 JP	115	if (func->type == STT_FUNC && offset >= func->offset &&
	116	offset < func->offset + func->len)
	117	return func;
	118
	119	return NULL;
	120	}
	121
	122	static int read_sections(struct elf *elf)
	123	{
	124	Elf_Scn *s = NULL;
	125	struct section *sec;
	126	size_t shstrndx, sections_nr;
	127	int i;
	128
	129	if (elf_getshdrnum(elf->elf, &sections_nr)) {
	130	perror("elf_getshdrnum");
	131	return -1;
	132	}
	133
	134	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
	135	perror("elf_getshdrstrndx");
	136	return -1;
	137	}
	138
	139	for (i = 0; i < sections_nr; i++) {
	140	sec = malloc(sizeof(*sec));
	141	if (!sec) {
	142	perror("malloc");
	143	return -1;
	144	}
	145	memset(sec, 0, sizeof(*sec));
	146
a196e171 JP	147	INIT_LIST_HEAD(&sec->symbol_list);
a196e171 JP	148	INIT_LIST_HEAD(&sec->rela_list);
042ba73f JP	149	hash_init(sec->rela_hash);
042ba73f JP	150	hash_init(sec->symbol_hash);
442f04c3 JP	151
	152	list_add_tail(&sec->list, &elf->sections);
	153
	154	s = elf_getscn(elf->elf, i);
	155	if (!s) {
	156	perror("elf_getscn");
	157	return -1;
	158	}
	159
	160	sec->idx = elf_ndxscn(s);
	161
	162	if (!gelf_getshdr(s, &sec->sh)) {
	163	perror("gelf_getshdr");
	164	return -1;
	165	}
	166
	167	sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
	168	if (!sec->name) {
	169	perror("elf_strptr");
	170	return -1;
	171	}
	172
	173	sec->elf_data = elf_getdata(s, NULL);
	174	if (!sec->elf_data) {
	175	perror("elf_getdata");
	176	return -1;
	177	}
	178
	179	if (sec->elf_data->d_off != 0 \|\|
	180	sec->elf_data->d_size != sec->sh.sh_size) {
	181	WARN("unexpected data attributes for %s", sec->name);
	182	return -1;
	183	}
	184
	185	sec->data = (unsigned long)sec->elf_data->d_buf;
	186	sec->len = sec->elf_data->d_size;
	187	}
	188
	189	/* sanity check, one more call to elf_nextscn() should return NULL */
	190	if (elf_nextscn(elf->elf, s)) {
	191	WARN("section entry mismatch");
	192	return -1;
	193	}
	194
	195	return 0;
	196	}
	197
	198	static int read_symbols(struct elf *elf)
	199	{
	200	struct section *symtab;
	201	struct symbol *sym;
	202	struct list_head entry, tmp;
	203	int symbols_nr, i;
	204
	205	symtab = find_section_by_name(elf, ".symtab");
	206	if (!symtab) {
	207	WARN("missing symbol table");
	208	return -1;
	209	}
	210
	211	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
	212
	213	for (i = 0; i < symbols_nr; i++) {
	214	sym = malloc(sizeof(*sym));
215	if (!sym) {
216	perror("malloc");
217	return -1;
218	}
219	memset(sym, 0, sizeof(*sym));
220
221	sym->idx = i;
222
223	if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
224	perror("gelf_getsym");
225	goto err;
226	}
227
228	sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
229	sym->sym.st_name);
230	if (!sym->name) {
231	perror("elf_strptr");
232	goto err;
233	}
234
235	sym->type = GELF_ST_TYPE(sym->sym.st_info);
236	sym->bind = GELF_ST_BIND(sym->sym.st_info);
237
238	if (sym->sym.st_shndx > SHN_UNDEF &&
239	sym->sym.st_shndx < SHN_LORESERVE) {
240	sym->sec = find_section_by_index(elf,
241	sym->sym.st_shndx);
242	if (!sym->sec) {
243	WARN("couldn't find section for symbol %s",
244	sym->name);
245	goto err;
246	}
247	if (sym->type == STT_SECTION) {
248	sym->name = sym->sec->name;
249	sym->sec->sym = sym;
250	}
251	} else
252	sym->sec = find_section_by_index(elf, 0);
253
254	sym->offset = sym->sym.st_value;
255	sym->len = sym->sym.st_size;
256
257	/* sorted insert into a per-section list */
a196e171 JP	258	entry = &sym->sec->symbol_list;
a196e171 JP	259	list_for_each_prev(tmp, &sym->sec->symbol_list) {
442f04c3 JP	260	struct symbol *s;
	261
	262	s = list_entry(tmp, struct symbol, list);
	263
	264	if (sym->offset > s->offset) {
	265	entry = tmp;
	266	break;
	267	}
	268
	269	if (sym->offset == s->offset && sym->len >= s->len) {
	270	entry = tmp;
	271	break;
	272	}
	273	}
	274	list_add(&sym->list, entry);
042ba73f	275	hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
442f04c3 JP	276	}
	277
	278	return 0;
	279
	280	err:
	281	free(sym);
	282	return -1;
	283	}
	284
	285	static int read_relas(struct elf *elf)
	286	{
	287	struct section *sec;
	288	struct rela *rela;
	289	int i;
	290	unsigned int symndx;
	291
	292	list_for_each_entry(sec, &elf->sections, list) {
	293	if (sec->sh.sh_type != SHT_RELA)
	294	continue;
	295
	296	sec->base = find_section_by_name(elf, sec->name + 5);
	297	if (!sec->base) {
	298	WARN("can't find base section for rela section %s",
	299	sec->name);
	300	return -1;
	301	}
	302
	303	sec->base->rela = sec;
	304
	305	for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
	306	rela = malloc(sizeof(*rela));
	307	if (!rela) {
	308	perror("malloc");
	309	return -1;
	310	}
	311	memset(rela, 0, sizeof(*rela));
	312
442f04c3 JP	313	if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
	314	perror("gelf_getrela");
	315	return -1;
	316	}
	317
	318	rela->type = GELF_R_TYPE(rela->rela.r_info);
	319	rela->addend = rela->rela.r_addend;
	320	rela->offset = rela->rela.r_offset;
	321	symndx = GELF_R_SYM(rela->rela.r_info);
	322	rela->sym = find_symbol_by_index(elf, symndx);
	323	if (!rela->sym) {
	324	WARN("can't find rela entry symbol %d for %s",
	325	symndx, sec->name);
	326	return -1;
	327	}
042ba73f JP	328
	329	list_add_tail(&rela->list, &sec->rela_list);
	330	hash_add(sec->rela_hash, &rela->hash, rela->offset);
	331
442f04c3 JP	332	}
	333	}
	334
	335	return 0;
	336	}
	337
	338	struct elf elf_open(const char name)
	339	{
	340	struct elf *elf;
	341
	342	elf_version(EV_CURRENT);
	343
	344	elf = malloc(sizeof(*elf));
	345	if (!elf) {
	346	perror("malloc");
	347	return NULL;
	348	}
	349	memset(elf, 0, sizeof(*elf));
	350
	351	INIT_LIST_HEAD(&elf->sections);
	352
	353	elf->name = strdup(name);
	354	if (!elf->name) {
	355	perror("strdup");
	356	goto err;
	357	}
	358
	359	elf->fd = open(name, O_RDONLY);
	360	if (elf->fd == -1) {
	361	perror("open");
	362	goto err;
	363	}
	364
	365	elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
	366	if (!elf->elf) {
	367	perror("elf_begin");
	368	goto err;
	369	}
	370
	371	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
	372	perror("gelf_getehdr");
	373	goto err;
	374	}
	375
	376	if (read_sections(elf))
	377	goto err;
	378
	379	if (read_symbols(elf))
	380	goto err;
	381
	382	if (read_relas(elf))
	383	goto err;
	384
	385	return elf;
	386
	387	err:
	388	elf_close(elf);
	389	return NULL;
	390	}
	391
	392	void elf_close(struct elf *elf)
	393	{
	394	struct section sec, tmpsec;
	395	struct symbol sym, tmpsym;
396	struct rela rela, tmprela;
397
398	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
a196e171	399	list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
442f04c3	400	list_del(&sym->list);
042ba73f	401	hash_del(&sym->hash);
442f04c3 JP	402	free(sym);
442f04c3 JP	403	}
a196e171	404	list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
442f04c3	405	list_del(&rela->list);
042ba73f	406	hash_del(&rela->hash);
442f04c3 JP	407	free(rela);
	408	}
	409	list_del(&sec->list);
	410	free(sec);
	411	}
	412	if (elf->name)
	413	free(elf->name);
	414	if (elf->fd > 0)
	415	close(elf->fd);
	416	if (elf->elf)
	417	elf_end(elf->elf);
	418	free(elf);
	419	}