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