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/*
* Copyright 2003-2006 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*
*/
#include "salibelf.h"
#include <stdlib.h>
#include <unistd.h>
extern void print_debug(const char*,...);
// ELF file parsing helpers. Note that we do *not* use libelf here.
int read_elf_header(int fd, ELF_EHDR* ehdr) {
if (pread(fd, ehdr, sizeof (ELF_EHDR), 0) != sizeof (ELF_EHDR) ||
memcmp(&ehdr->e_ident[EI_MAG0], ELFMAG, SELFMAG) != 0 ||
ehdr->e_version != EV_CURRENT) {
return 0;
}
return 1;
}
bool is_elf_file(int fd) {
ELF_EHDR ehdr;
return read_elf_header(fd, &ehdr);
}
// read program header table of an ELF file
ELF_PHDR* read_program_header_table(int fd, ELF_EHDR* hdr) {
ELF_PHDR* phbuf = 0;
// allocate memory for program header table
size_t nbytes = hdr->e_phnum * hdr->e_phentsize;
if ((phbuf = (ELF_PHDR*) malloc(nbytes)) == NULL) {
print_debug("can't allocate memory for reading program header table\n");
return NULL;
}
if (pread(fd, phbuf, nbytes, hdr->e_phoff) != nbytes) {
print_debug("ELF file is truncated! can't read program header table\n");
free(phbuf);
return NULL;
}
return phbuf;
}
// read section header table of an ELF file
ELF_SHDR* read_section_header_table(int fd, ELF_EHDR* hdr) {
ELF_SHDR* shbuf = 0;
// allocate memory for section header table
size_t nbytes = hdr->e_shnum * hdr->e_shentsize;
if ((shbuf = (ELF_SHDR*) malloc(nbytes)) == NULL) {
print_debug("can't allocate memory for reading section header table\n");
return NULL;
}
if (pread(fd, shbuf, nbytes, hdr->e_shoff) != nbytes) {
print_debug("ELF file is truncated! can't read section header table\n");
free(shbuf);
return NULL;
}
return shbuf;
}
// read a particular section's data
void* read_section_data(int fd, ELF_EHDR* ehdr, ELF_SHDR* shdr) {
void *buf = NULL;
if (shdr->sh_type == SHT_NOBITS || shdr->sh_size == 0) {
return buf;
}
if ((buf = calloc(shdr->sh_size, 1)) == NULL) {
print_debug("can't allocate memory for reading section data\n");
return NULL;
}
if (pread(fd, buf, shdr->sh_size, shdr->sh_offset) != shdr->sh_size) {
free(buf);
print_debug("section data read failed\n");
return NULL;
}
return buf;
}
uintptr_t find_base_address(int fd, ELF_EHDR* ehdr) {
uintptr_t baseaddr = (uintptr_t)-1;
int cnt;
ELF_PHDR *phbuf, *phdr;
// read program header table
if ((phbuf = read_program_header_table(fd, ehdr)) == NULL) {
goto quit;
}
// the base address of a shared object is the lowest vaddr of
// its loadable segments (PT_LOAD)
for (phdr = phbuf, cnt = 0; cnt < ehdr->e_phnum; cnt++, phdr++) {
if (phdr->p_type == PT_LOAD && phdr->p_vaddr < baseaddr) {
baseaddr = phdr->p_vaddr;
}
}
quit:
if (phbuf) free(phbuf);
return baseaddr;
}
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