1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun #include <byteswap.h>
3*4882a593Smuzhiyun #include <elf.h>
4*4882a593Smuzhiyun #include <endian.h>
5*4882a593Smuzhiyun #include <inttypes.h>
6*4882a593Smuzhiyun #include <stdint.h>
7*4882a593Smuzhiyun #include <stdio.h>
8*4882a593Smuzhiyun #include <stdlib.h>
9*4882a593Smuzhiyun #include <string.h>
10*4882a593Smuzhiyun
11*4882a593Smuzhiyun #ifdef be32toh
12*4882a593Smuzhiyun /* If libc provides [bl]e{32,64}toh() then we'll use them */
13*4882a593Smuzhiyun #elif BYTE_ORDER == LITTLE_ENDIAN
14*4882a593Smuzhiyun # define be32toh(x) bswap_32(x)
15*4882a593Smuzhiyun # define le32toh(x) (x)
16*4882a593Smuzhiyun # define be64toh(x) bswap_64(x)
17*4882a593Smuzhiyun # define le64toh(x) (x)
18*4882a593Smuzhiyun #elif BYTE_ORDER == BIG_ENDIAN
19*4882a593Smuzhiyun # define be32toh(x) (x)
20*4882a593Smuzhiyun # define le32toh(x) bswap_32(x)
21*4882a593Smuzhiyun # define be64toh(x) (x)
22*4882a593Smuzhiyun # define le64toh(x) bswap_64(x)
23*4882a593Smuzhiyun #endif
24*4882a593Smuzhiyun
25*4882a593Smuzhiyun __attribute__((noreturn))
die(const char * msg)26*4882a593Smuzhiyun static void die(const char *msg)
27*4882a593Smuzhiyun {
28*4882a593Smuzhiyun fputs(msg, stderr);
29*4882a593Smuzhiyun exit(EXIT_FAILURE);
30*4882a593Smuzhiyun }
31*4882a593Smuzhiyun
main(int argc,const char * argv[])32*4882a593Smuzhiyun int main(int argc, const char *argv[])
33*4882a593Smuzhiyun {
34*4882a593Smuzhiyun uint64_t entry;
35*4882a593Smuzhiyun size_t nread;
36*4882a593Smuzhiyun FILE *file;
37*4882a593Smuzhiyun union {
38*4882a593Smuzhiyun Elf32_Ehdr ehdr32;
39*4882a593Smuzhiyun Elf64_Ehdr ehdr64;
40*4882a593Smuzhiyun } hdr;
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun if (argc != 2)
43*4882a593Smuzhiyun die("Usage: elf-entry <elf-file>\n");
44*4882a593Smuzhiyun
45*4882a593Smuzhiyun file = fopen(argv[1], "r");
46*4882a593Smuzhiyun if (!file) {
47*4882a593Smuzhiyun perror("Unable to open input file");
48*4882a593Smuzhiyun return EXIT_FAILURE;
49*4882a593Smuzhiyun }
50*4882a593Smuzhiyun
51*4882a593Smuzhiyun nread = fread(&hdr, 1, sizeof(hdr), file);
52*4882a593Smuzhiyun if (nread != sizeof(hdr)) {
53*4882a593Smuzhiyun perror("Unable to read input file");
54*4882a593Smuzhiyun fclose(file);
55*4882a593Smuzhiyun return EXIT_FAILURE;
56*4882a593Smuzhiyun }
57*4882a593Smuzhiyun
58*4882a593Smuzhiyun if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) {
59*4882a593Smuzhiyun fclose(file);
60*4882a593Smuzhiyun die("Input is not an ELF\n");
61*4882a593Smuzhiyun }
62*4882a593Smuzhiyun
63*4882a593Smuzhiyun switch (hdr.ehdr32.e_ident[EI_CLASS]) {
64*4882a593Smuzhiyun case ELFCLASS32:
65*4882a593Smuzhiyun switch (hdr.ehdr32.e_ident[EI_DATA]) {
66*4882a593Smuzhiyun case ELFDATA2LSB:
67*4882a593Smuzhiyun entry = le32toh(hdr.ehdr32.e_entry);
68*4882a593Smuzhiyun break;
69*4882a593Smuzhiyun case ELFDATA2MSB:
70*4882a593Smuzhiyun entry = be32toh(hdr.ehdr32.e_entry);
71*4882a593Smuzhiyun break;
72*4882a593Smuzhiyun default:
73*4882a593Smuzhiyun fclose(file);
74*4882a593Smuzhiyun die("Invalid ELF encoding\n");
75*4882a593Smuzhiyun }
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun /* Sign extend to form a canonical address */
78*4882a593Smuzhiyun entry = (int64_t)(int32_t)entry;
79*4882a593Smuzhiyun break;
80*4882a593Smuzhiyun
81*4882a593Smuzhiyun case ELFCLASS64:
82*4882a593Smuzhiyun switch (hdr.ehdr32.e_ident[EI_DATA]) {
83*4882a593Smuzhiyun case ELFDATA2LSB:
84*4882a593Smuzhiyun entry = le64toh(hdr.ehdr64.e_entry);
85*4882a593Smuzhiyun break;
86*4882a593Smuzhiyun case ELFDATA2MSB:
87*4882a593Smuzhiyun entry = be64toh(hdr.ehdr64.e_entry);
88*4882a593Smuzhiyun break;
89*4882a593Smuzhiyun default:
90*4882a593Smuzhiyun fclose(file);
91*4882a593Smuzhiyun die("Invalid ELF encoding\n");
92*4882a593Smuzhiyun }
93*4882a593Smuzhiyun break;
94*4882a593Smuzhiyun
95*4882a593Smuzhiyun default:
96*4882a593Smuzhiyun fclose(file);
97*4882a593Smuzhiyun die("Invalid ELF class\n");
98*4882a593Smuzhiyun }
99*4882a593Smuzhiyun
100*4882a593Smuzhiyun printf("0x%016" PRIx64 "\n", entry);
101*4882a593Smuzhiyun fclose(file);
102*4882a593Smuzhiyun return EXIT_SUCCESS;
103*4882a593Smuzhiyun }
104