0001 =============================================
0002 Firmware TPM Driver
0003 =============================================
0004
0005 This document describes the firmware Trusted Platform Module (fTPM)
0006 device driver.
0007
0008 Introduction
0009 ============
0010
0011 This driver is a shim for firmware implemented in ARM's TrustZone
0012 environment. The driver allows programs to interact with the TPM in the same
0013 way they would interact with a hardware TPM.
0014
0015 Design
0016 ======
0017
0018 The driver acts as a thin layer that passes commands to and from a TPM
0019 implemented in firmware. The driver itself doesn't contain much logic and is
0020 used more like a dumb pipe between firmware and kernel/userspace.
0021
0022 The firmware itself is based on the following paper:
0023 https://www.microsoft.com/en-us/research/wp-content/uploads/2017/06/ftpm1.pdf
0024
0025 When the driver is loaded it will expose ``/dev/tpmX`` character devices to
0026 userspace which will enable userspace to communicate with the firmware TPM
0027 through this device.
