uint32_t read_id_isar5(void) {
    uint32_t value;
    asm volatile("mrc p15, 0, %0, c0, c2, 5" : "=r"(value));
    return value;
}

void check_crypto_extension(void) {
    uint32_t id_isar5 = read_id_isar5();
    
    uint32_t aes  = (id_isar5 >> 4) & 0xF;
    uint32_t sha1 = (id_isar5 >> 8) & 0xF;
    uint32_t sha2 = (id_isar5 >> 12) & 0xF;
    
    printf("Cryptography Extension サポート状況:\n");
    printf("  AES:  %s\n", aes  ? "あり" : "なし");
    printf("  SHA1: %s\n", sha1 ? "あり" : "なし");
    printf("  SHA2: %s\n", sha2 ? "あり" : "なし");
}