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/*
* Fix up the permission bits for the program load section containing the
* .got section of a PPC ELF binary.
*/
#include <stdio.h>
#include <err.h>
#define ELFSIZE 32
#include <sys/exec_elf.h>
#include <sys/endian.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
void xlseek(int, off_t, int);
void xread(int, void *, size_t);
void xwrite(int, void *, size_t);
void *xmalloc(size_t);
void
xlseek(int fd, off_t off, int whence)
{
int rv;
rv = lseek(fd, off, whence);
if (rv < 0) {
err(1, "lseek");
}
}
void
xread(int fd, void *buf, size_t size)
{
int rv;
rv = read(fd, buf, size);
if (rv < 0) {
err(1, "read");
}
if (rv != size) {
errx(1, "short read %d vs. %d", rv, size);
}
}
void
xwrite(int fd, void *buf, size_t size)
{
int rv;
rv = write(fd, buf, size);
if (rv < 0) {
err(1, "write");
}
if (rv != size) {
errx(1, "short write %d vs. %d", rv, size);
}
}
void *
xmalloc(size_t size)
{
void *buf;
buf = malloc(size);
if (buf == NULL) {
err(1, "malloc");
}
return buf;
}
int
main(int argc, char **argv)
{
Elf32_Ehdr eh;
Elf32_Phdr *ph;
Elf32_Shdr *sh;
Elf32_Addr gotaddr;
size_t phsize, shsize, strsize;
char *strbuf;
int fd, i, idx;
/*
* Check arguments and open the file.
*/
if (argc != 2) {
errx(1, "usage: %s <file>", getprogname());
}
fd = open(argv[1], O_RDWR);
if (fd < 0) {
err(1, "open %s", argv[1]);
}
/*
* Read and validate the ELF header.
*/
xread(fd, &eh, sizeof (eh));
if (memcmp(eh.e_ident, ELFMAG, SELFMAG) != 0 ||
eh.e_ident[EI_CLASS] != ELFCLASS) {
errx(1, "not an ELF file");
}
if (be16toh(eh.e_machine) != EM_PPC) {
errx(1, "ELF file is wrong architecture");
}
if (be16toh(eh.e_type) != ET_EXEC) {
errx(1, "ELF file is not an executable");
}
if (be16toh(eh.e_shnum) > 512 || be16toh(eh.e_phnum) > 128) {
errx(1, "ELF file has too many sections");
}
if (be16toh(eh.e_shstrndx) >= be16toh(eh.e_shnum)) {
errx(1, "string table index out of range");
}
/*
* Read the program headers, section headers and string table.
*/
phsize = be16toh(eh.e_phnum) * sizeof(Elf_Phdr);
ph = xmalloc(phsize);
xlseek(fd, (off_t)be32toh(eh.e_phoff), SEEK_SET);
xread(fd, ph, phsize);
shsize = be16toh(eh.e_shnum) * sizeof(Elf_Shdr);
sh = xmalloc(shsize);
xlseek(fd, (off_t)be32toh(eh.e_shoff), SEEK_SET);
xread(fd, sh, shsize);
idx = be16toh(eh.e_shstrndx);
strsize = be32toh(sh[idx].sh_size);
strbuf = xmalloc(strsize);
xlseek(fd, (off_t)be32toh(sh[idx].sh_offset), SEEK_SET);
xread(fd, strbuf, strsize);
/*
* Find the .got section.
*/
gotaddr = 0;
for (i = 0; i < be16toh(eh.e_shnum); i++) {
if (strcmp(&strbuf[be32toh(sh[i].sh_name)], ".got") == 0) {
gotaddr = be32toh(sh[i].sh_addr);
break;
}
}
if (gotaddr == 0) {
errx(1, "couldn't find the .got section");
}
/*
* Find the program header load section containing the .got section.
*/
idx = -1;
for (i = 0; i < be16toh(eh.e_phnum); i++) {
if (be32toh(ph[i].p_type) == PT_LOAD &&
gotaddr >= be32toh(ph[i].p_vaddr) &&
gotaddr < be32toh(ph[i].p_vaddr) + be32toh(ph[i].p_memsz)) {
idx = i;
}
}
if (idx == -1) {
errx(1, "couldn't find program header for .got");
}
if (be32toh(ph[idx].p_flags) & PF_X) {
errx(1, "permission bits already include execute");
}
/*
* Add execute permission and write back the entry.
*/
ph[idx].p_flags |= be32toh(PF_X);
xlseek(fd, (off_t)be32toh(eh.e_phoff), SEEK_SET);
xwrite(fd, ph, phsize);
errx(0, "execute permission added");
exit(0);
}
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