// SPDX-License-Identifier: GPL-2.0 #include <byteswap.h> #include <elf.h> #include <endian.h> #include <inttypes.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #ifdef be32toh /* If libc provides [bl]e{32,64}toh() then we'll use them */ #elif BYTE_ORDER == LITTLE_ENDIAN # define be32toh(x) bswap_32(x) # define le32toh(x) (x) # define be64toh(x) bswap_64(x) # define le64toh(x) (x) #elif BYTE_ORDER == BIG_ENDIAN # define be32toh(x) (x) # define le32toh(x) bswap_32(x) # define be64toh(x) (x) # define le64toh(x) bswap_64(x) #endif __attribute__((noreturn)) static void die(const char *msg) { fputs(msg, stderr); exit(EXIT_FAILURE); } int main(int argc, const char *argv[]) { uint64_t entry; size_t nread; FILE *file; union { Elf32_Ehdr ehdr32; Elf64_Ehdr ehdr64; } hdr; if (argc != 2) die("Usage: elf-entry <elf-file>\n"); file = fopen(argv[1], "r"); if (!file) { perror("Unable to open input file"); return EXIT_FAILURE; } nread = fread(&hdr, 1, sizeof(hdr), file); if (nread != sizeof(hdr)) { perror("Unable to read input file"); fclose(file); return EXIT_FAILURE; } if (memcmp(hdr.ehdr32.e_ident, ELFMAG, SELFMAG)) { fclose(file); die("Input is not an ELF\n"); } switch (hdr.ehdr32.e_ident[EI_CLASS]) { case ELFCLASS32: switch (hdr.ehdr32.e_ident[EI_DATA]) { case ELFDATA2LSB: entry = le32toh(hdr.ehdr32.e_entry); break; case ELFDATA2MSB: entry = be32toh(hdr.ehdr32.e_entry); break; default: fclose(file); die("Invalid ELF encoding\n"); } /* Sign extend to form a canonical address */ entry = (int64_t)(int32_t)entry; break; case ELFCLASS64: switch (hdr.ehdr32.e_ident[EI_DATA]) { case ELFDATA2LSB: entry = le64toh(hdr.ehdr64.e_entry); break; case ELFDATA2MSB: entry = be64toh(hdr.ehdr64.e_entry); break; default: fclose(file); die("Invalid ELF encoding\n"); } break; default: fclose(file); die("Invalid ELF class\n"); } printf("0x%016" PRIx64 "\n", entry); fclose(file); return EXIT_SUCCESS; }