mips/tools/elf-entry.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <byteswap.h>
0003 #include <elf.h>
0004 #include <endian.h>
0005 #include <inttypes.h>
0006 #include <stdint.h>
0007 #include <stdio.h>
0008 #include <stdlib.h>
0009 #include <string.h>
0010
0011 #ifdef be32toh
0012 /* If libc provides [bl]e{32,64}toh() then we'll use them */
0013 #elif BYTE_ORDER == LITTLE_ENDIAN
0014 # define be32toh(x) bswap_32(x)
0015 # define le32toh(x) (x)
0016 # define be64toh(x) bswap_64(x)
0017 # define le64toh(x) (x)
0018 #elif BYTE_ORDER == BIG_ENDIAN
0019 # define be32toh(x) (x)
0020 # define le32toh(x) bswap_32(x)
0021 # define be64toh(x) (x)
0022 # define le64toh(x) bswap_64(x)
0023 #endif
0024
0025 __attribute__((noreturn))
0026 static void die(const char *msg)
0027 {
0028     fputs(msg, stderr);
0029     exit(EXIT_FAILURE);
0030 }
0031
0032 int main(int argc, const char *argv[])
0033 {
0034     uint64_t entry;
0035     size_t nread;
0036     FILE *file;
0037     union {
0038         Elf32_Ehdr ehdr32;
0039         Elf64_Ehdr ehdr64;
0040     } hdr;
0041
0042     if (argc != 2)
0043         die("Usage: elf-entry <elf-file>\n");
0044
0045     file = fopen(argv[1], "r");
0046     if (!file) {
0047         perror("Unable to open input file");
0048         return EXIT_FAILURE;
0049     }
0050
0051     nread = fread(&hdr, 1, sizeof(hdr), file);
0052     if (nread != sizeof(hdr)) {
0053         perror("Unable to read input file");
0054         fclose(file);
0055         return EXIT_FAILURE;
0056     }
0057
0058     if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) {
0059         fclose(file);
0060         die("Input is not an ELF\n");
0061     }
0062
0063     switch (hdr.ehdr32.e_ident[EI_CLASS]) {
0064     case ELFCLASS32:
0065         switch (hdr.ehdr32.e_ident[EI_DATA]) {
0066         case ELFDATA2LSB:
0067             entry = le32toh(hdr.ehdr32.e_entry);
0068             break;
0069         case ELFDATA2MSB:
0070             entry = be32toh(hdr.ehdr32.e_entry);
0071             break;
0072         default:
0073             fclose(file);
0074             die("Invalid ELF encoding\n");
0075         }
0076
0077         /* Sign extend to form a canonical address */
0078         entry = (int64_t)(int32_t)entry;
0079         break;
0080
0081     case ELFCLASS64:
0082         switch (hdr.ehdr32.e_ident[EI_DATA]) {
0083         case ELFDATA2LSB:
0084             entry = le64toh(hdr.ehdr64.e_entry);
0085             break;
0086         case ELFDATA2MSB:
0087             entry = be64toh(hdr.ehdr64.e_entry);
0088             break;
0089         default:
0090             fclose(file);
0091             die("Invalid ELF encoding\n");
0092         }
0093         break;
0094
0095     default:
0096         fclose(file);
0097         die("Invalid ELF class\n");
0098     }
0099
0100     printf("0x%016" PRIx64 "\n", entry);
0101     fclose(file);
0102     return EXIT_SUCCESS;
0103 }