[PATCH v2] doc: describe UEFI measured boot
Ilias Apalodimas
ilias.apalodimas at linaro.org
Fri Jun 14 14:14:03 CEST 2024
We currently only describe the process to enable measured boot using
bootm. Describe the UEFI requirements as well which predate bootm.
Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
---
Changes since v1:
- fixed remarks from Heinrich on titling and DTB measured PCR
doc/usage/measured_boot.rst | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/doc/usage/measured_boot.rst b/doc/usage/measured_boot.rst
index 9691904a9d8a..b5f7b05aeb02 100644
--- a/doc/usage/measured_boot.rst
+++ b/doc/usage/measured_boot.rst
@@ -7,19 +7,39 @@ 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.
+The functionality is available when booting via the EFI subsystem or 'bootm'
+command.
+
+UEFI measured boot
+------------------
+The EFI subsystem implements the `EFI TCG protocol
+<https://trustedcomputinggroup.org/resource/tcg-efi-protocol-specification/>`_
+and the `TCG PC Client Specific Platform Firmware Profile Specification
+<https://trustedcomputinggroup.org/resource/pc-client-specific-platform-firmware-profile-specification/>`_
+which defines the binaries to be measured and the corresponding PCRs to be used.
+
+Requirements
+~~~~~~~~~~~~
+* A hardware TPM 2.0 supported by an enabled U-Boot driver
+* CONFIG_EFI_TCG2_PROTOCOL=y
+* CONFIG_EFI_TCG2_PROTOCOL_EVENTLOG_SIZE=y
+* optional CONFIG_EFI_TCG2_PROTOCOL_MEASURE_DTB=y will measure the loaded DTB in PCR 1
+
+Measured legacy boot with bootm command
+----------------------------------------
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.
+CONFIG_MEASURE_DEVICETREE, U-Boot will also measure the devicetree image in PCR1.
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
+* A hardware TPM 2.0 supported by an enabled U-Boot driver
+* CONFIG_TPMv2=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
--
2.45.1
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