tools/objtool/elf.c - LeafOS-Devices/android_kernel_samsung_gta4xl - Gitiles

 /*
  * 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 <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) {
 		/*
 		 * A missing symbol table is actually possible if it's an empty
 		 * .o file.  This can happen for thunk_64.o.
 		 */
 		return 0;
 	}

 	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 */
 	shstrtab = find_section_by_name(elf, ".shstrtab");
 	if (!shstrtab) {
 		WARN("can't find .shstrtab 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);
 }
	/*
	* 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 <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) {
	/*
	* A missing symbol table is actually possible if it's an empty
	* .o file. This can happen for thunk_64.o.
	*/
	return 0;
	}

	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 */
	shstrtab = find_section_by_name(elf, ".shstrtab");
	if (!shstrtab) {
	WARN("can't find .shstrtab 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);
	}