windows_id_aa64isar0_el1.c

/*
this is undocumented, to be confirmed
read id_aa64isar0_el1 from registry HKLM\HARDWARE\DESCRIPTION\System\CentralProcessor\x\CP 4030
*/
uint64_t getaa64isar0() {
    const WCHAR cpus_key[] = L"HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\";
    HKEY cpus_handle;
    if (ERROR_SUCCESS != RegOpenKeyExW(HKEY_LOCAL_MACHINE, cpus_key, 0, KEY_ENUMERATE_SUB_KEYS, &cpus_handle)) {
        printf("failed open reg\n");
        return 0;
    }
    DWORD cpu_index = 0;
    WCHAR cpu_num[256] = { 0 };
    uint64_t CP4030 = 0;
    WCHAR cpu_key[(sizeof(cpus_key) / sizeof(*cpus_key)) + 256] = L"HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\";
    while (ERROR_SUCCESS == RegEnumKeyW(cpus_handle, cpu_index++, cpu_num, 255)) {
        if (0 != wcscpy_s(&cpu_key[sizeof(cpus_key) / sizeof(*cpus_key) - 1], 256, cpu_num)) {
        	break;
        }
        wprintf(L"checking %s\n", cpu_key);
        HKEY cpu_handle;
        if (ERROR_SUCCESS != RegOpenKeyExW(HKEY_LOCAL_MACHINE, cpu_key, 0, KEY_READ, &cpu_handle)) {
            printf("failed open reg\n");
            break;
        }
        DWORD value_type;
        uint64_t value;
        DWORD value_size = sizeof(value);
        if (ERROR_SUCCESS != RegQueryValueExW(cpu_handle, L"CP 4030", NULL, &value_type, (LPBYTE)&value, &value_size)) {
            RegCloseKey(cpu_handle);
            printf("failed read cp4030\n");
        	break;
        }

        if (value_type != REG_QWORD) {
            RegCloseKey(cpu_handle);
            printf("failed cp4030 is not qword\n");
        	break;
        }
        wprintf(L"cp4030 for cpu[%d] \"%s\" is %016zx\n", cpu_index-1, cpu_num, value);
        CP4030 = value;

        RegCloseKey(cpu_handle);
        break;
    }
    RegCloseKey(cpus_handle);
    return CP4030;
}