[linux.git] / tools / objtool / elf.c

/*
 * elf.c - ELF access library
 *
 * Adapted from kpatch (https://github.com/dynup/kpatch):
 * Copyright (C) 2013-2015 Josh Poimboeuf <[email protected]>
 * Copyright (C) 2014 Seth Jennings <[email protected]>
 *
 * 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 <errno.h>

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

#define MAX_NAME_LEN 128

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 symbol *find_symbol_by_name(struct elf *elf, const char *name)
{
	struct section *sec;
	struct symbol *sym;

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

	return NULL;
}

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

	list_for_each_entry(sym, &sec->symbol_list, list)
		if (sym->type != STT_SECTION &&
		    offset >= sym->offset && offset < sym->offset + sym->len)
			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)) {
		WARN_ELF("elf_getshdrnum");
		return -1;
	}

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

		sec->idx = elf_ndxscn(s);

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

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

		if (sec->sh.sh_size != 0) {
			sec->data = elf_getdata(s, NULL);
			if (!sec->data) {
				WARN_ELF("elf_getdata");
				return -1;
			}
			if (sec->data->d_off != 0 ||
			    sec->data->d_size != sec->sh.sh_size) {
				WARN("unexpected data attributes for %s",
				     sec->name);
				return -1;
			}
		}
		sec->len = sec->sh.sh_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, *sec;
	struct symbol *sym, *pfunc;
	struct list_head *entry, *tmp;
	int symbols_nr, i;
	char *coldstr;

	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->data, i, &sym->sym)) {
			WARN_ELF("gelf_getsym");
			goto err;
		}

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

	/* Create parent/child links for any cold subfunctions */
	list_for_each_entry(sec, &elf->sections, list) {
		list_for_each_entry(sym, &sec->symbol_list, list) {
			char pname[MAX_NAME_LEN + 1];
			size_t pnamelen;
			if (sym->type != STT_FUNC)
				continue;
			sym->pfunc = sym->cfunc = sym;
			coldstr = strstr(sym->name, ".cold");
			if (!coldstr)
				continue;

			pnamelen = coldstr - sym->name;
			if (pnamelen > MAX_NAME_LEN) {
				WARN("%s(): parent function name exceeds maximum length of %d characters",
				     sym->name, MAX_NAME_LEN);
				return -1;
			}

			strncpy(pname, sym->name, pnamelen);
			pname[pnamelen] = '\0';
			pfunc = find_symbol_by_name(elf, pname);

			if (!pfunc) {
				WARN("%s(): can't find parent function",
				     sym->name);
				return -1;
			}

			sym->pfunc = pfunc;
			pfunc->cfunc = sym;

			/*
			 * Unfortunately, -fnoreorder-functions puts the child
			 * inside the parent.  Remove the overlap so we can
			 * have sane assumptions.
			 *
			 * Note that pfunc->len now no longer matches
			 * pfunc->sym.st_size.
			 */
			if (sym->sec == pfunc->sec &&
			    sym->offset >= pfunc->offset &&
			    sym->offset + sym->len == pfunc->offset + pfunc->len) {
				pfunc->len -= sym->len;
			}
		}
	}

	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->data, i, &rela->rela)) {
				WARN_ELF("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);
			rela->rela_sec = sec;
			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, int flags)
{
	struct elf *elf;
	Elf_Cmd cmd;

	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->fd = open(name, flags);
	if (elf->fd == -1) {
		fprintf(stderr, "objtool: Can't open '%s': %s\n",
			name, strerror(errno));
		goto err;
	}

	if ((flags & O_ACCMODE) == O_RDONLY)
		cmd = ELF_C_READ_MMAP;
	else if ((flags & O_ACCMODE) == O_RDWR)
		cmd = ELF_C_RDWR;
	else /* O_WRONLY */
		cmd = ELF_C_WRITE;

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

	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
		WARN_ELF("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;
}

struct section *elf_create_section(struct elf *elf, const char *name,
				   size_t entsize, int nr)
{
	struct section *sec, *shstrtab;
	size_t size = entsize * nr;
	struct Elf_Scn *s;
	Elf_Data *data;

	sec = malloc(sizeof(*sec));
	if (!sec) {
		perror("malloc");
		return NULL;
	}
	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_newscn(elf->elf);
	if (!s) {
		WARN_ELF("elf_newscn");
		return NULL;
	}

	sec->name = strdup(name);
	if (!sec->name) {
		perror("strdup");
		return NULL;
	}

	sec->idx = elf_ndxscn(s);
	sec->len = size;
	sec->changed = true;

	sec->data = elf_newdata(s);
	if (!sec->data) {
		WARN_ELF("elf_newdata");
		return NULL;
	}

	sec->data->d_size = size;
	sec->data->d_align = 1;

	if (size) {
		sec->data->d_buf = malloc(size);
		if (!sec->data->d_buf) {
			perror("malloc");
			return NULL;
		}
		memset(sec->data->d_buf, 0, size);
	}

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

	sec->sh.sh_size = size;
	sec->sh.sh_entsize = entsize;
	sec->sh.sh_type = SHT_PROGBITS;
	sec->sh.sh_addralign = 1;
	sec->sh.sh_flags = SHF_ALLOC;


	/* Add section name to .shstrtab (or .strtab for Clang) */
	shstrtab = find_section_by_name(elf, ".shstrtab");
	if (!shstrtab)
		shstrtab = find_section_by_name(elf, ".strtab");
	if (!shstrtab) {
		WARN("can't find .shstrtab or .strtab section");
		return NULL;
	}

	s = elf_getscn(elf->elf, shstrtab->idx);
	if (!s) {
		WARN_ELF("elf_getscn");
		return NULL;
	}

	data = elf_newdata(s);
	if (!data) {
		WARN_ELF("elf_newdata");
		return NULL;
	}

	data->d_buf = sec->name;
	data->d_size = strlen(name) + 1;
	data->d_align = 1;

	sec->sh.sh_name = shstrtab->len;

	shstrtab->len += strlen(name) + 1;
	shstrtab->changed = true;

	return sec;
}

struct section *elf_create_rela_section(struct elf *elf, struct section *base)
{
	char *relaname;
	struct section *sec;

	relaname = malloc(strlen(base->name) + strlen(".rela") + 1);
	if (!relaname) {
		perror("malloc");
		return NULL;
	}
	strcpy(relaname, ".rela");
	strcat(relaname, base->name);

	sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0);
	free(relaname);
	if (!sec)
		return NULL;

	base->rela = sec;
	sec->base = base;

	sec->sh.sh_type = SHT_RELA;
	sec->sh.sh_addralign = 8;
	sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
	sec->sh.sh_info = base->idx;
	sec->sh.sh_flags = SHF_INFO_LINK;

	return sec;
}

int elf_rebuild_rela_section(struct section *sec)
{
	struct rela *rela;
	int nr, idx = 0, size;
	GElf_Rela *relas;

	nr = 0;
	list_for_each_entry(rela, &sec->rela_list, list)
		nr++;

	size = nr * sizeof(*relas);
	relas = malloc(size);
	if (!relas) {
		perror("malloc");
		return -1;
	}

	sec->data->d_buf = relas;
	sec->data->d_size = size;

	sec->sh.sh_size = size;

	idx = 0;
	list_for_each_entry(rela, &sec->rela_list, list) {
		relas[idx].r_offset = rela->offset;
		relas[idx].r_addend = rela->addend;
		relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type);
		idx++;
	}

	return 0;
}

int elf_write(struct elf *elf)
{
	struct section *sec;
	Elf_Scn *s;

	/* Update section headers for changed sections: */
	list_for_each_entry(sec, &elf->sections, list) {
		if (sec->changed) {
			s = elf_getscn(elf->elf, sec->idx);
			if (!s) {
				WARN_ELF("elf_getscn");
				return -1;
			}
			if (!gelf_update_shdr(s, &sec->sh)) {
				WARN_ELF("gelf_update_shdr");
				return -1;
			}
		}
	}

	/* Make sure the new section header entries get updated properly. */
	elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);

	/* Write all changes to the file. */
	if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
		WARN_ELF("elf_update");
		return -1;
	}

	return 0;
}

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

	if (elf->elf)
		elf_end(elf->elf);

	if (elf->fd > 0)
		close(elf->fd);

	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);
	}

	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 <[email protected]>
	6	* Copyright (C) 2014 Seth Jennings <[email protected]>
	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>
385d11b1	29	#include <errno.h>
442f04c3 JP	30
	31	#include "elf.h"
	32	#include "warn.h"
	33
22566c16 AS	34	#define MAX_NAME_LEN 128
22566c16 AS	35
442f04c3 JP	36	struct section find_section_by_name(struct elf elf, const char *name)
	37	{
	38	struct section *sec;
	39
	40	list_for_each_entry(sec, &elf->sections, list)
	41	if (!strcmp(sec->name, name))
	42	return sec;
	43
	44	return NULL;
	45	}
	46
	47	static struct section find_section_by_index(struct elf elf,
	48	unsigned int idx)
	49	{
	50	struct section *sec;
	51
	52	list_for_each_entry(sec, &elf->sections, list)
	53	if (sec->idx == idx)
	54	return sec;
	55
	56	return NULL;
	57	}
	58
	59	static struct symbol find_symbol_by_index(struct elf elf, unsigned int idx)
	60	{
	61	struct section *sec;
	62	struct symbol *sym;
	63
	64	list_for_each_entry(sec, &elf->sections, list)
042ba73f	65	hash_for_each_possible(sec->symbol_hash, sym, hash, idx)
442f04c3 JP	66	if (sym->idx == idx)
	67	return sym;
	68
	69	return NULL;
	70	}
	71
	72	struct symbol find_symbol_by_offset(struct section sec, unsigned long offset)
	73	{
	74	struct symbol *sym;
	75
a196e171	76	list_for_each_entry(sym, &sec->symbol_list, list)
442f04c3 JP	77	if (sym->type != STT_SECTION &&
	78	sym->offset == offset)
	79	return sym;
	80
	81	return NULL;
	82	}
	83
13810435 JP	84	struct symbol find_symbol_by_name(struct elf elf, const char *name)
	85	{
	86	struct section *sec;
	87	struct symbol *sym;
	88
	89	list_for_each_entry(sec, &elf->sections, list)
	90	list_for_each_entry(sym, &sec->symbol_list, list)
	91	if (!strcmp(sym->name, name))
	92	return sym;
	93
	94	return NULL;
	95	}
	96
5c51f4ae JP	97	struct symbol find_symbol_containing(struct section sec, unsigned long offset)
	98	{
	99	struct symbol *sym;
	100
	101	list_for_each_entry(sym, &sec->symbol_list, list)
	102	if (sym->type != STT_SECTION &&
	103	offset >= sym->offset && offset < sym->offset + sym->len)
	104	return sym;
	105
	106	return NULL;
	107	}
	108
442f04c3 JP	109	struct rela find_rela_by_dest_range(struct section sec, unsigned long offset,
	110	unsigned int len)
	111	{
	112	struct rela *rela;
042ba73f	113	unsigned long o;
442f04c3 JP	114
	115	if (!sec->rela)
	116	return NULL;
	117
042ba73f JP	118	for (o = offset; o < offset + len; o++)
	119	hash_for_each_possible(sec->rela->rela_hash, rela, hash, o)
	120	if (rela->offset == o)
	121	return rela;
442f04c3 JP	122
	123	return NULL;
	124	}
	125
	126	struct rela find_rela_by_dest(struct section sec, unsigned long offset)
	127	{
	128	return find_rela_by_dest_range(sec, offset, 1);
	129	}
	130
	131	struct symbol find_containing_func(struct section sec, unsigned long offset)
	132	{
	133	struct symbol *func;
	134
a196e171	135	list_for_each_entry(func, &sec->symbol_list, list)
442f04c3 JP	136	if (func->type == STT_FUNC && offset >= func->offset &&
	137	offset < func->offset + func->len)
	138	return func;
	139
	140	return NULL;
	141	}
	142
	143	static int read_sections(struct elf *elf)
	144	{
	145	Elf_Scn *s = NULL;
	146	struct section *sec;
	147	size_t shstrndx, sections_nr;
	148	int i;
	149
	150	if (elf_getshdrnum(elf->elf, &sections_nr)) {
baa41469	151	WARN_ELF("elf_getshdrnum");
442f04c3 JP	152	return -1;
	153	}
	154
	155	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
baa41469	156	WARN_ELF("elf_getshdrstrndx");
442f04c3 JP	157	return -1;
	158	}
	159
	160	for (i = 0; i < sections_nr; i++) {
	161	sec = malloc(sizeof(*sec));
	162	if (!sec) {
	163	perror("malloc");
	164	return -1;
	165	}
	166	memset(sec, 0, sizeof(*sec));
	167
a196e171 JP	168	INIT_LIST_HEAD(&sec->symbol_list);
a196e171 JP	169	INIT_LIST_HEAD(&sec->rela_list);
042ba73f JP	170	hash_init(sec->rela_hash);
042ba73f JP	171	hash_init(sec->symbol_hash);
442f04c3 JP	172
	173	list_add_tail(&sec->list, &elf->sections);
	174
	175	s = elf_getscn(elf->elf, i);
	176	if (!s) {
baa41469	177	WARN_ELF("elf_getscn");
442f04c3 JP	178	return -1;
	179	}
	180
	181	sec->idx = elf_ndxscn(s);
	182
	183	if (!gelf_getshdr(s, &sec->sh)) {
baa41469	184	WARN_ELF("gelf_getshdr");
442f04c3 JP	185	return -1;
	186	}
	187
	188	sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
	189	if (!sec->name) {
baa41469	190	WARN_ELF("elf_strptr");
442f04c3 JP	191	return -1;
	192	}
	193
df968c93 PV	194	if (sec->sh.sh_size != 0) {
	195	sec->data = elf_getdata(s, NULL);
	196	if (!sec->data) {
	197	WARN_ELF("elf_getdata");
	198	return -1;
	199	}
	200	if (sec->data->d_off != 0 \|\|
	201	sec->data->d_size != sec->sh.sh_size) {
	202	WARN("unexpected data attributes for %s",
	203	sec->name);
	204	return -1;
	205	}
442f04c3	206	}
df968c93	207	sec->len = sec->sh.sh_size;
442f04c3 JP	208	}
	209
	210	/* sanity check, one more call to elf_nextscn() should return NULL */
	211	if (elf_nextscn(elf->elf, s)) {
	212	WARN("section entry mismatch");
	213	return -1;
	214	}
	215
	216	return 0;
	217	}
	218
	219	static int read_symbols(struct elf *elf)
	220	{
13810435 JP	221	struct section symtab, sec;
13810435 JP	222	struct symbol sym, pfunc;
442f04c3 JP	223	struct list_head entry, tmp;
442f04c3 JP	224	int symbols_nr, i;
13810435	225	char *coldstr;
442f04c3 JP	226
	227	symtab = find_section_by_name(elf, ".symtab");
	228	if (!symtab) {
	229	WARN("missing symbol table");
	230	return -1;
	231	}
	232
	233	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
	234
	235	for (i = 0; i < symbols_nr; i++) {
	236	sym = malloc(sizeof(*sym));
	237	if (!sym) {
	238	perror("malloc");
	239	return -1;
	240	}
	241	memset(sym, 0, sizeof(*sym));
	242
	243	sym->idx = i;
	244
baa41469 JP	245	if (!gelf_getsym(symtab->data, i, &sym->sym)) {
baa41469 JP	246	WARN_ELF("gelf_getsym");
442f04c3 JP	247	goto err;
	248	}
	249
	250	sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
	251	sym->sym.st_name);
	252	if (!sym->name) {
baa41469	253	WARN_ELF("elf_strptr");
442f04c3 JP	254	goto err;
	255	}
	256
	257	sym->type = GELF_ST_TYPE(sym->sym.st_info);
	258	sym->bind = GELF_ST_BIND(sym->sym.st_info);
	259
	260	if (sym->sym.st_shndx > SHN_UNDEF &&
	261	sym->sym.st_shndx < SHN_LORESERVE) {
	262	sym->sec = find_section_by_index(elf,
	263	sym->sym.st_shndx);
	264	if (!sym->sec) {
	265	WARN("couldn't find section for symbol %s",
	266	sym->name);
	267	goto err;
	268	}
	269	if (sym->type == STT_SECTION) {
	270	sym->name = sym->sec->name;
	271	sym->sec->sym = sym;
	272	}
	273	} else
	274	sym->sec = find_section_by_index(elf, 0);
	275
	276	sym->offset = sym->sym.st_value;
	277	sym->len = sym->sym.st_size;
	278
	279	/* sorted insert into a per-section list */
a196e171 JP	280	entry = &sym->sec->symbol_list;
a196e171 JP	281	list_for_each_prev(tmp, &sym->sec->symbol_list) {
442f04c3 JP	282	struct symbol *s;
	283
	284	s = list_entry(tmp, struct symbol, list);
	285
	286	if (sym->offset > s->offset) {
	287	entry = tmp;
	288	break;
	289	}
	290
	291	if (sym->offset == s->offset && sym->len >= s->len) {
	292	entry = tmp;
	293	break;
	294	}
	295	}
	296	list_add(&sym->list, entry);
042ba73f	297	hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
442f04c3 JP	298	}
442f04c3 JP	299
13810435 JP	300	/* Create parent/child links for any cold subfunctions */
	301	list_for_each_entry(sec, &elf->sections, list) {
	302	list_for_each_entry(sym, &sec->symbol_list, list) {
22566c16 AS	303	char pname[MAX_NAME_LEN + 1];
22566c16 AS	304	size_t pnamelen;
13810435 JP	305	if (sym->type != STT_FUNC)
	306	continue;
	307	sym->pfunc = sym->cfunc = sym;
bcb6fb5d	308	coldstr = strstr(sym->name, ".cold");
08b393d0 JP	309	if (!coldstr)
	310	continue;
	311
22566c16 AS	312	pnamelen = coldstr - sym->name;
	313	if (pnamelen > MAX_NAME_LEN) {
	314	WARN("%s(): parent function name exceeds maximum length of %d characters",
	315	sym->name, MAX_NAME_LEN);
	316	return -1;
	317	}
	318
	319	strncpy(pname, sym->name, pnamelen);
	320	pname[pnamelen] = '\0';
	321	pfunc = find_symbol_by_name(elf, pname);
08b393d0 JP	322
	323	if (!pfunc) {
	324	WARN("%s(): can't find parent function",
	325	sym->name);
0b9301fb	326	return -1;
08b393d0 JP	327	}
	328
	329	sym->pfunc = pfunc;
	330	pfunc->cfunc = sym;
	331
	332	/*
	333	* Unfortunately, -fnoreorder-functions puts the child
	334	* inside the parent. Remove the overlap so we can
	335	* have sane assumptions.
	336	*
	337	* Note that pfunc->len now no longer matches
	338	* pfunc->sym.st_size.
	339	*/
	340	if (sym->sec == pfunc->sec &&
	341	sym->offset >= pfunc->offset &&
	342	sym->offset + sym->len == pfunc->offset + pfunc->len) {
	343	pfunc->len -= sym->len;
13810435 JP	344	}
	345	}
	346	}
	347
442f04c3 JP	348	return 0;
	349
	350	err:
	351	free(sym);
	352	return -1;
	353	}
	354
	355	static int read_relas(struct elf *elf)
	356	{
	357	struct section *sec;
	358	struct rela *rela;
	359	int i;
	360	unsigned int symndx;
	361
	362	list_for_each_entry(sec, &elf->sections, list) {
	363	if (sec->sh.sh_type != SHT_RELA)
	364	continue;
	365
	366	sec->base = find_section_by_name(elf, sec->name + 5);
	367	if (!sec->base) {
	368	WARN("can't find base section for rela section %s",
	369	sec->name);
	370	return -1;
	371	}
	372
	373	sec->base->rela = sec;
	374
	375	for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
	376	rela = malloc(sizeof(*rela));
	377	if (!rela) {
	378	perror("malloc");
	379	return -1;
	380	}
	381	memset(rela, 0, sizeof(*rela));
	382
baa41469 JP	383	if (!gelf_getrela(sec->data, i, &rela->rela)) {
baa41469 JP	384	WARN_ELF("gelf_getrela");
442f04c3 JP	385	return -1;
	386	}
	387
	388	rela->type = GELF_R_TYPE(rela->rela.r_info);
	389	rela->addend = rela->rela.r_addend;
	390	rela->offset = rela->rela.r_offset;
	391	symndx = GELF_R_SYM(rela->rela.r_info);
	392	rela->sym = find_symbol_by_index(elf, symndx);
4a60aa05	393	rela->rela_sec = sec;
442f04c3 JP	394	if (!rela->sym) {
	395	WARN("can't find rela entry symbol %d for %s",
	396	symndx, sec->name);
	397	return -1;
	398	}
042ba73f JP	399
	400	list_add_tail(&rela->list, &sec->rela_list);
	401	hash_add(sec->rela_hash, &rela->hash, rela->offset);
	402
442f04c3 JP	403	}
	404	}
	405
	406	return 0;
	407	}
	408
627fce14	409	struct elf elf_open(const char name, int flags)
442f04c3 JP	410	{
442f04c3 JP	411	struct elf *elf;
627fce14	412	Elf_Cmd cmd;
442f04c3 JP	413
	414	elf_version(EV_CURRENT);
	415
	416	elf = malloc(sizeof(*elf));
	417	if (!elf) {
	418	perror("malloc");
	419	return NULL;
	420	}
	421	memset(elf, 0, sizeof(*elf));
	422
	423	INIT_LIST_HEAD(&elf->sections);
	424
627fce14	425	elf->fd = open(name, flags);
442f04c3	426	if (elf->fd == -1) {
385d11b1 JP	427	fprintf(stderr, "objtool: Can't open '%s': %s\n",
385d11b1 JP	428	name, strerror(errno));
442f04c3 JP	429	goto err;
	430	}
	431
627fce14 JP	432	if ((flags & O_ACCMODE) == O_RDONLY)
	433	cmd = ELF_C_READ_MMAP;
	434	else if ((flags & O_ACCMODE) == O_RDWR)
	435	cmd = ELF_C_RDWR;
	436	else /* O_WRONLY */
	437	cmd = ELF_C_WRITE;
	438
	439	elf->elf = elf_begin(elf->fd, cmd, NULL);
442f04c3	440	if (!elf->elf) {
baa41469	441	WARN_ELF("elf_begin");
442f04c3 JP	442	goto err;
	443	}
	444
	445	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
baa41469	446	WARN_ELF("gelf_getehdr");
442f04c3 JP	447	goto err;
	448	}
	449
	450	if (read_sections(elf))
	451	goto err;
	452
	453	if (read_symbols(elf))
	454	goto err;
	455
	456	if (read_relas(elf))
	457	goto err;
	458
	459	return elf;
	460
	461	err:
	462	elf_close(elf);
	463	return NULL;
	464	}
	465
627fce14 JP	466	struct section elf_create_section(struct elf elf, const char *name,
	467	size_t entsize, int nr)
	468	{
	469	struct section sec, shstrtab;
	470	size_t size = entsize * nr;
	471	struct Elf_Scn *s;
	472	Elf_Data *data;
	473
	474	sec = malloc(sizeof(*sec));
	475	if (!sec) {
	476	perror("malloc");
	477	return NULL;
	478	}
	479	memset(sec, 0, sizeof(*sec));
	480
	481	INIT_LIST_HEAD(&sec->symbol_list);
	482	INIT_LIST_HEAD(&sec->rela_list);
	483	hash_init(sec->rela_hash);
	484	hash_init(sec->symbol_hash);
	485
	486	list_add_tail(&sec->list, &elf->sections);
	487
	488	s = elf_newscn(elf->elf);
	489	if (!s) {
	490	WARN_ELF("elf_newscn");
	491	return NULL;
	492	}
	493
	494	sec->name = strdup(name);
	495	if (!sec->name) {
	496	perror("strdup");
	497	return NULL;
	498	}
	499
	500	sec->idx = elf_ndxscn(s);
	501	sec->len = size;
	502	sec->changed = true;
	503
	504	sec->data = elf_newdata(s);
	505	if (!sec->data) {
	506	WARN_ELF("elf_newdata");
	507	return NULL;
	508	}
	509
	510	sec->data->d_size = size;
	511	sec->data->d_align = 1;
	512
	513	if (size) {
	514	sec->data->d_buf = malloc(size);
	515	if (!sec->data->d_buf) {
	516	perror("malloc");
	517	return NULL;
	518	}
	519	memset(sec->data->d_buf, 0, size);
	520	}
	521
	522	if (!gelf_getshdr(s, &sec->sh)) {
	523	WARN_ELF("gelf_getshdr");
	524	return NULL;
	525	}
	526
	527	sec->sh.sh_size = size;
	528	sec->sh.sh_entsize = entsize;
	529	sec->sh.sh_type = SHT_PROGBITS;
530	sec->sh.sh_addralign = 1;
531	sec->sh.sh_flags = SHF_ALLOC;
532
533
6d77d3b4	534	/* Add section name to .shstrtab (or .strtab for Clang) */
627fce14	535	shstrtab = find_section_by_name(elf, ".shstrtab");
6d77d3b4 SS	536	if (!shstrtab)
6d77d3b4 SS	537	shstrtab = find_section_by_name(elf, ".strtab");
627fce14	538	if (!shstrtab) {
6d77d3b4	539	WARN("can't find .shstrtab or .strtab section");
627fce14 JP	540	return NULL;
	541	}
	542
	543	s = elf_getscn(elf->elf, shstrtab->idx);
	544	if (!s) {
	545	WARN_ELF("elf_getscn");
	546	return NULL;
	547	}
	548
	549	data = elf_newdata(s);
	550	if (!data) {
	551	WARN_ELF("elf_newdata");
	552	return NULL;
	553	}
	554
	555	data->d_buf = sec->name;
	556	data->d_size = strlen(name) + 1;
	557	data->d_align = 1;
	558
	559	sec->sh.sh_name = shstrtab->len;
	560
	561	shstrtab->len += strlen(name) + 1;
	562	shstrtab->changed = true;
	563
	564	return sec;
	565	}
	566
	567	struct section elf_create_rela_section(struct elf elf, struct section *base)
	568	{
	569	char *relaname;
	570	struct section *sec;
	571
	572	relaname = malloc(strlen(base->name) + strlen(".rela") + 1);
	573	if (!relaname) {
	574	perror("malloc");
	575	return NULL;
	576	}
	577	strcpy(relaname, ".rela");
	578	strcat(relaname, base->name);
	579
	580	sec = elf_create_section(elf, relaname, sizeof(GElf_Rela), 0);
0998b7a0	581	free(relaname);
627fce14 JP	582	if (!sec)
	583	return NULL;
	584
	585	base->rela = sec;
	586	sec->base = base;
	587
	588	sec->sh.sh_type = SHT_RELA;
	589	sec->sh.sh_addralign = 8;
	590	sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;
	591	sec->sh.sh_info = base->idx;
	592	sec->sh.sh_flags = SHF_INFO_LINK;
	593
	594	return sec;
	595	}
	596
	597	int elf_rebuild_rela_section(struct section *sec)
	598	{
	599	struct rela *rela;
	600	int nr, idx = 0, size;
	601	GElf_Rela *relas;
	602
	603	nr = 0;
	604	list_for_each_entry(rela, &sec->rela_list, list)
	605	nr++;
	606
	607	size = nr * sizeof(*relas);
	608	relas = malloc(size);
	609	if (!relas) {
	610	perror("malloc");
	611	return -1;
	612	}
	613
	614	sec->data->d_buf = relas;
	615	sec->data->d_size = size;
	616
	617	sec->sh.sh_size = size;
	618
	619	idx = 0;
	620	list_for_each_entry(rela, &sec->rela_list, list) {
	621	relas[idx].r_offset = rela->offset;
	622	relas[idx].r_addend = rela->addend;
	623	relas[idx].r_info = GELF_R_INFO(rela->sym->idx, rela->type);
	624	idx++;
	625	}
	626
	627	return 0;
	628	}
	629
	630	int elf_write(struct elf *elf)
	631	{
	632	struct section *sec;
	633	Elf_Scn *s;
	634
97dab2ae	635	/* Update section headers for changed sections: */
627fce14 JP	636	list_for_each_entry(sec, &elf->sections, list) {
	637	if (sec->changed) {
	638	s = elf_getscn(elf->elf, sec->idx);
	639	if (!s) {
	640	WARN_ELF("elf_getscn");
	641	return -1;
	642	}
97dab2ae	643	if (!gelf_update_shdr(s, &sec->sh)) {
627fce14 JP	644	WARN_ELF("gelf_update_shdr");
	645	return -1;
	646	}
	647	}
	648	}
	649
97dab2ae JP	650	/* Make sure the new section header entries get updated properly. */
	651	elf_flagelf(elf->elf, ELF_C_SET, ELF_F_DIRTY);
	652
	653	/* Write all changes to the file. */
627fce14 JP	654	if (elf_update(elf->elf, ELF_C_WRITE) < 0) {
	655	WARN_ELF("elf_update");
	656	return -1;
	657	}
	658
	659	return 0;
	660	}
	661
442f04c3 JP	662	void elf_close(struct elf *elf)
	663	{
	664	struct section sec, tmpsec;
	665	struct symbol sym, tmpsym;
	666	struct rela rela, tmprela;
	667
baa41469 JP	668	if (elf->elf)
	669	elf_end(elf->elf);
	670
	671	if (elf->fd > 0)
	672	close(elf->fd);
	673
442f04c3	674	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
a196e171	675	list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
442f04c3	676	list_del(&sym->list);
042ba73f	677	hash_del(&sym->hash);
442f04c3 JP	678	free(sym);
442f04c3 JP	679	}
a196e171	680	list_for_each_entry_safe(rela, tmprela, &sec->rela_list, list) {
442f04c3	681	list_del(&rela->list);
042ba73f	682	hash_del(&rela->hash);
442f04c3 JP	683	free(rela);
	684	}
	685	list_del(&sec->list);
	686	free(sec);
	687	}
baa41469	688
442f04c3 JP	689	free(elf);
442f04c3 JP	690	}