1// SPDX-License-Identifier: GPL-2.0
2#include <byteswap.h>
3#include <elf.h>
4#include <endian.h>
5#include <inttypes.h>
6#include <stdint.h>
7#include <stdio.h>
8#include <stdlib.h>
9#include <string.h>
10
11#ifdef be32toh
12/* If libc provides [bl]e{32,64}toh() then we'll use them */
13#elif BYTE_ORDER == LITTLE_ENDIAN
14# define be32toh(x) bswap_32(x)
15# define le32toh(x) (x)
16# define be64toh(x) bswap_64(x)
17# define le64toh(x) (x)
18#elif BYTE_ORDER == BIG_ENDIAN
19# define be32toh(x) (x)
20# define le32toh(x) bswap_32(x)
21# define be64toh(x) (x)
22# define le64toh(x) bswap_64(x)
23#endif
24
25__attribute__((noreturn))
26static void die(const char *msg)
27{
28 fputs(s: msg, stderr);
29 exit(EXIT_FAILURE);
30}
31
32int main(int argc, const char *argv[])
33{
34 uint64_t entry;
35 size_t nread;
36 FILE *file;
37 union {
38 Elf32_Ehdr ehdr32;
39 Elf64_Ehdr ehdr64;
40 } hdr;
41
42 if (argc != 2)
43 die(msg: "Usage: elf-entry <elf-file>\n");
44
45 file = fopen(filename: argv[1], modes: "r");
46 if (!file) {
47 perror(s: "Unable to open input file");
48 return EXIT_FAILURE;
49 }
50
51 nread = fread(ptr: &hdr, size: 1, n: sizeof(hdr), stream: file);
52 if (nread != sizeof(hdr)) {
53 perror(s: "Unable to read input file");
54 fclose(stream: file);
55 return EXIT_FAILURE;
56 }
57
58 if (memcmp(s1: hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) {
59 fclose(stream: file);
60 die(msg: "Input is not an ELF\n");
61 }
62
63 switch (hdr.ehdr32.e_ident[EI_CLASS]) {
64 case ELFCLASS32:
65 switch (hdr.ehdr32.e_ident[EI_DATA]) {
66 case ELFDATA2LSB:
67 entry = le32toh(hdr.ehdr32.e_entry);
68 break;
69 case ELFDATA2MSB:
70 entry = be32toh(hdr.ehdr32.e_entry);
71 break;
72 default:
73 fclose(stream: file);
74 die(msg: "Invalid ELF encoding\n");
75 }
76
77 /* Sign extend to form a canonical address */
78 entry = (int64_t)(int32_t)entry;
79 break;
80
81 case ELFCLASS64:
82 switch (hdr.ehdr32.e_ident[EI_DATA]) {
83 case ELFDATA2LSB:
84 entry = le64toh(hdr.ehdr64.e_entry);
85 break;
86 case ELFDATA2MSB:
87 entry = be64toh(hdr.ehdr64.e_entry);
88 break;
89 default:
90 fclose(stream: file);
91 die(msg: "Invalid ELF encoding\n");
92 }
93 break;
94
95 default:
96 fclose(stream: file);
97 die(msg: "Invalid ELF class\n");
98 }
99
100 printf(format: "0x%016" PRIx64 "\n", entry);
101 fclose(stream: file);
102 return EXIT_SUCCESS;
103}
104

source code of linux/arch/mips/tools/elf-entry.c