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))
die(const char * msg)26 static void die(const char *msg)
27 {
28 fputs(msg, stderr);
29 exit(EXIT_FAILURE);
30 }
31
main(int argc,const char * argv[])32 int 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 fclose(file);
55 return EXIT_FAILURE;
56 }
57
58 if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) {
59 fclose(file);
60 die("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(file);
74 die("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(file);
91 die("Invalid ELF encoding\n");
92 }
93 break;
94
95 default:
96 fclose(file);
97 die("Invalid ELF class\n");
98 }
99
100 printf("0x%016" PRIx64 "\n", entry);
101 fclose(file);
102 return EXIT_SUCCESS;
103 }
104