1 // SPDX-License-Identifier: GPL-2.0
2 #include <elf.h>
3 #include <inttypes.h>
4 #include <stdint.h>
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <string.h>
8
9 __attribute__((noreturn))
die(const char *msg)10 static void die(const char *msg)
11 {
12 fputs(msg, stderr);
13 exit(EXIT_FAILURE);
14 }
15
main(int argc, const char *argv[])16 int main(int argc, const char *argv[])
17 {
18 uint64_t entry;
19 size_t nread;
20 FILE *file;
21 union {
22 Elf32_Ehdr ehdr32;
23 Elf64_Ehdr ehdr64;
24 } hdr;
25
26 if (argc != 2)
27 die("Usage: elf-entry <elf-file>\n");
28
29 file = fopen(argv[1], "r");
30 if (!file) {
31 perror("Unable to open input file");
32 return EXIT_FAILURE;
33 }
34
35 nread = fread(&hdr, 1, sizeof(hdr), file);
36 if (nread != sizeof(hdr)) {
37 fclose(file);
38 perror("Unable to read input file");
39 return EXIT_FAILURE;
40 }
41
42 if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) {
43 fclose(file);
44 die("Input is not an ELF\n");
45 }
46
47 switch (hdr.ehdr32.e_ident[EI_CLASS]) {
48 case ELFCLASS32:
49 /* Sign extend to form a canonical address */
50 entry = (int64_t)(int32_t)hdr.ehdr32.e_entry;
51 break;
52
53 case ELFCLASS64:
54 entry = hdr.ehdr64.e_entry;
55 break;
56
57 default:
58 fclose(file);
59 die("Invalid ELF class\n");
60 }
61
62 fclose(file);
63 printf("0x%016" PRIx64 "\n", entry);
64
65 return EXIT_SUCCESS;
66 }
67