Note: Read/Write UEFI variables under Windows 7 and later

test.c

#include "stdafx.h"

void RasiePrivileges(void)
{
	HANDLE hToken;
	TOKEN_PRIVILEGES tkp;

	if (!OpenProcessToken(GetCurrentProcess(), 
			TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, 
			&hToken)) {
				printf("Failed OpenProcessToken\r\n");
				return;
	}

	LookupPrivilegeValue(NULL, SE_SYSTEM_ENVIRONMENT_NAME,
		&tkp.Privileges[0].Luid);
	tkp.PrivilegeCount = 1;
	tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
	
	DWORD len;
	AdjustTokenPrivileges(hToken, FALSE, &tkp, 0, NULL, &len);

	if (GetLastError() != ERROR_SUCCESS) {
		printf("Failed RasiePrivileges()\r\n");
		return;
	}
}

int _tmain(int argc, _TCHAR* argv[])
{
	BYTE Val[4096];
	DWORD dwLen = 0;
	const TCHAR name[] = TEXT("BootOrder");
	const TCHAR guid[] = TEXT("{8BE4DF61-93CA-11D2-AA0D-00E098032B8C}");
	const TCHAR system[] = TEXT("System");
	const TCHAR sys_guid[] = TEXT("{E947FCf9-DD01-4965-B808-32A7B6815657}");
	const unsigned int offset_TPM = 11; // TPM On/Off offset

#if 0
	const TCHAR name[] = TEXT("");
	const TCHAR guid[] = TEXT("{00000000-0000-0000-0000-000000000000}");
#endif

	printf("Change Boot Order\r\n");
	RasiePrivileges();

	dwLen = GetFirmwareEnvironmentVariable(
		name, guid, Val, 4096);

	if (dwLen == 0)
	{
		DWORD dwErr = GetLastError();
		printf("Failed, GetFirmwareEnvironmentVariable(), GetLastError return %d(0x%08x)\r\n",
			dwErr, dwErr);
		return 1;
	}

	printf("Dump BootOrder variable, Len:%d(0x%02x)\r\n", dwLen, dwLen);
	for(UINT32 i = 0; i < dwLen; i++) {
		printf("%02x", Val[i]);
		if (i%16 == 0 && i != 0) {
			printf("\r\n");
		} else {
			putchar(' ');
		}
	}

	printf("\r\nExchange BootOrder Item1 & Item2\r\n");
	BYTE Tmp[2];
	Tmp[0] = Val[0];
	Tmp[1] = Val[1];
	
	Val[0] = Val[2];
	Val[1] = Val[3];
	
	Val[2] = Tmp[0];
	Val[3] = Tmp[1];

	if (SetFirmwareEnvironmentVariable(name, guid, Val, dwLen) == TRUE) {
		printf("Success!! SetFirmwareEnvironmentVariable\r\n");
	} else {
		printf("Failed!! SetFirmwareEnvironmentVariable\r\n");
	}

	printf("Read TPM Support state\r\n");
	dwLen = GetFirmwareEnvironmentVariable(
		system, sys_guid, Val, 4096);

	if (dwLen == 0)
	{
		DWORD dwErr = GetLastError();
		printf("Failed, GetFirmwareEnvironmentVariable(), GetLastError return %d(0x%08x)\r\n",
			dwErr, dwErr);
		return 2;
	}
	
	if (Val[offset_TPM]) {
		printf("TPM Support is Enabled, will change to Disable\r\n");
	} else {
		printf("TPM Support is Disabled, will change to Enable\r\n");
	}
	Val[offset_TPM] = (Val[offset_TPM]) ? 0 : 1;

	if (SetFirmwareEnvironmentVariable(system, sys_guid, Val, dwLen) == TRUE) {
		printf("Success!! Change TPM Support Setting\r\n");
	} else {
		printf("Failed!! Can't change TPM Support Setting\r\n");
	}
	return 0;
}