#define ull unsigned long long

struct EFI_SYSTEM_TABLE {
    char _buf[60];
    struct EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL {
        ull _buf;
        ull (*OutputString)(
            struct EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL *This,
            unsigned short *String);
        ull _buf2[4];
        ull (*ClearScreen)(
             struct EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL *This);
    } *ConOut;
};
  
void efi_main(void *ImageHandle __attribute__ ((unused)), struct EFI_SYSTEM_TABLE *SystemTable)
{
    SystemTable->ConOut->ClearScreen(SystemTable->ConOut);
    SystemTable->ConOut->OutputString(SystemTable->ConOut, L"Hello UEFI!\n");
    while (1);
}