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// SPDX-License-Identifier: GPL-2.0
#include <byteswap.h>
#include <elf.h>
#include <endian.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef be32toh
/* If libc provides [bl]e{32,64}toh() then we'll use them */
#elif BYTE_ORDER == LITTLE_ENDIAN
# define be32toh(x) bswap_32(x)
# define le32toh(x) (x)
# define be64toh(x) bswap_64(x)
# define le64toh(x) (x)
#elif BYTE_ORDER == BIG_ENDIAN
# define be32toh(x) (x)
# define le32toh(x) bswap_32(x)
# define be64toh(x) (x)
# define le64toh(x) bswap_64(x)
#endif
__attribute__((noreturn))
static void die(const char *msg)
{
fputs(msg, stderr);
exit(EXIT_FAILURE);
}
int main(int argc, const char *argv[])
{
uint64_t entry;
size_t nread;
FILE *file;
union {
Elf32_Ehdr ehdr32;
Elf64_Ehdr ehdr64;
} hdr;
if (argc != 2)
die("Usage: elf-entry <elf-file>\n");
file = fopen(argv[1], "r");
if (!file) {
perror("Unable to open input file");
return EXIT_FAILURE;
}
nread = fread(&hdr, 1, sizeof(hdr), file);
if (nread != sizeof(hdr)) {
perror("Unable to read input file");
fclose(file);
return EXIT_FAILURE;
}
if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) {
fclose(file);
die("Input is not an ELF\n");
}
switch (hdr.ehdr32.e_ident[EI_CLASS]) {
case ELFCLASS32:
switch (hdr.ehdr32.e_ident[EI_DATA]) {
case ELFDATA2LSB:
entry = le32toh(hdr.ehdr32.e_entry);
break;
case ELFDATA2MSB:
entry = be32toh(hdr.ehdr32.e_entry);
break;
default:
fclose(file);
die("Invalid ELF encoding\n");
}
/* Sign extend to form a canonical address */
entry = (int64_t)(int32_t)entry;
break;
case ELFCLASS64:
switch (hdr.ehdr32.e_ident[EI_DATA]) {
case ELFDATA2LSB:
entry = le64toh(hdr.ehdr64.e_entry);
break;
case ELFDATA2MSB:
entry = be64toh(hdr.ehdr64.e_entry);
break;
default:
fclose(file);
die("Invalid ELF encoding\n");
}
break;
default:
fclose(file);
die("Invalid ELF class\n");
}
printf("0x%016" PRIx64 "\n", entry);
fclose(file);
return EXIT_SUCCESS;
}
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