TEE-Watchdog: Mitigating Unauthorized Activities within Trusted Execution Environments in ARM-Based Low-Power IoT Devices

Algorithm 3

Enabling MPU protection using the Procedure Set_Protection

	Input:             ⊳ Address of the region and permissions
	Output:
	Procedure Set_Protection
	Set bit 0 of MPU_CTRL to 0           ⊳ Disables MPU
	Set bits [31 : 5] of MPU_RBAR to    ⊳ Sets region address to be protected
	if AP == ReadWritePriv then
	Set bits [2 : 1] of MPU_RBAR to 00  ⊳ Sets Access Permission of to be Read/Write by privileged code only
	else if AP = = ReadWrite then
	Set bits [2 : 1] of MPU_RBAR to 01 ⊳ Sets Access Permission of to be Read/Write by any code
	else if AP = = ReadOnlyPriv then
	Set bits [2 : 1] of MPU_RBAR to 10 ⊳ Sets Access Permission of to be Read Only by privileged code only
	else if AP = = ReadOnly then
	Set bits [2 : 1] of MPU_RBAR to 11   ⊳ Sets Access Permission of to be Read Only by any code
	else
	Set bit 0 of MPU_CTRL to 1      ⊳ Enables MPU protection for the region
	return
	end
	Set bit 0 of MPU_CTRL to 1                    ⊳ Enables MPU protection for the region
	⊳ The procedure is successful
	return;
	End Procedure