On Tue, 24 Oct 2023 at 18:44, Eddie James wrote:
>
> Briefly describe the feature and specify the requirements.
>
> Signed-off-by: Eddie James
> Reviewed-by: Simon Glass
> ---
> Changes since v12:
> - Add a bit of detail about OS usage and what pieces are measured
>
> doc/usage/index.rst | 1 +
> doc/usage/measured_boot.rst | 31 +++
> 2 files changed, 32 insertions(+)
> create mode 100644 doc/usage/measured_boot.rst
>
> diff --git a/doc/usage/index.rst b/doc/usage/index.rst
> index 98b4719c40..bf53bb6bda 100644
> --- a/doc/usage/index.rst
> +++ b/doc/usage/index.rst
> @@ -14,6 +14,7 @@ Use U-Boot
> partitions
> cmdline
> semihosting
> + measured_boot
>
> Shell commands
> --
> diff --git a/doc/usage/measured_boot.rst b/doc/usage/measured_boot.rst
> new file mode 100644
> index 00..0aad590859
> --- /dev/null
> +++ b/doc/usage/measured_boot.rst
> @@ -0,0 +1,31 @@
> +.. SPDX-License-Identifier: GPL-2.0+
> +
> +Measured Boot
> +=
> +
> +U-Boot can perform a measured boot, the process of hashing various components
> +of the boot process, extending the results in the TPM and logging the
> +component's measurement in memory for the operating system to consume.
> +
> +By default, U-Boot will measure the operating system (linux) image, the
> +initrd image, and the "bootargs" environment variable. By enabling
> +CONFIG_MEASURE_DEVICETREE, U-Boot will also measure the devicetree image.
> +
> +The operating system typically would verify that the hashes found in the
> +TPM PCRs match the contents of the event log. This can further be checked
> +against the hash results of previous boots.
> +
> +Requirements
> +-
> +
> +* A hardware TPM 2.0 supported by the U-Boot drivers
> +* CONFIG_TPM=y
> +* CONFIG_MEASURED_BOOT=y
> +* Device-tree configuration of the TPM device to specify the memory area
> + for event logging. The TPM device node must either contain a phandle to
> + a reserved memory region or "linux,sml-base" and "linux,sml-size"
> + indicating the address and size of the memory region. An example can be
> + found in arch/sandbox/dts/test.dts
> +* The operating system must also be configured to use the memory regions
> + specified in the U-Boot device-tree in order to make use of the event
> + log.
> --
> 2.39.3
>
I will extend this for UEFI since measured boot was already supported
there for a couple of years
Reviewed-by: Ilias Apalodimas
