Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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(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("Usage: elf-entry <elf-file>\n");
44
45 file = fopen(argv[1], "r");
46 if (!file) {
47 perror("Unable to open input file");
48 return EXIT_FAILURE;
49 }
50
51 nread = fread(&hdr, 1, sizeof(hdr), file);
52 if (nread != sizeof(hdr)) {
53 perror("Unable to read input file");
54 return EXIT_FAILURE;
55 }
56
57 if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG))
58 die("Input is not an ELF\n");
59
60 switch (hdr.ehdr32.e_ident[EI_CLASS]) {
61 case ELFCLASS32:
62 switch (hdr.ehdr32.e_ident[EI_DATA]) {
63 case ELFDATA2LSB:
64 entry = le32toh(hdr.ehdr32.e_entry);
65 break;
66 case ELFDATA2MSB:
67 entry = be32toh(hdr.ehdr32.e_entry);
68 break;
69 default:
70 die("Invalid ELF encoding\n");
71 }
72
73 /* Sign extend to form a canonical address */
74 entry = (int64_t)(int32_t)entry;
75 break;
76
77 case ELFCLASS64:
78 switch (hdr.ehdr32.e_ident[EI_DATA]) {
79 case ELFDATA2LSB:
80 entry = le64toh(hdr.ehdr64.e_entry);
81 break;
82 case ELFDATA2MSB:
83 entry = be64toh(hdr.ehdr64.e_entry);
84 break;
85 default:
86 die("Invalid ELF encoding\n");
87 }
88 break;
89
90 default:
91 die("Invalid ELF class\n");
92 }
93
94 printf("0x%016" PRIx64 "\n", entry);
95 return EXIT_SUCCESS;
96}