Hi Heinrich On Thu, 19 Oct 2023 at 21:22, Heinrich Schuchardt <xypron.g...@gmx.de> wrote: > > On 10/19/23 18:21, Eddie James wrote: > > Briefly describe the feature and specify the requirements. > > > > Signed-off-by: Eddie James <eaja...@linux.ibm.com> > > Reviewed-by: Simon Glass <s...@chromium.org> > > --- > > 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 0000000000..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 > > The OS image would mean the root file system? I guess you mean the > loaded EFI binary here. Measured boot is not Linux specific. > > We should consider different scenarios: > > * U-Boot loading kernel, initrd, device-tree > * U-Boot loading GRUB (or another boot manager), device-tree, > GRUB loading initrd > * U-Boot loading GRUB and passing a device-tree to GRUB, > GRUB loading initrd and a new device-tree > > With the documentation the user should be enabled to understand what > U-Boot measures in each of these cases. Please, observe that upstream > GRUB uses LoadImage() while distros (e.g. Debian and Ubuntu) tend to > bypass LoadImage(). > > Arent't there some other objects measured? > > - SMBIOS table > - ACPI tables (still to be implemented) > - EFI variables
Eddie's part is trying to describe how 'bootm' would measure binaries. I'll update it with the EFI part once we merge this. Regards /Ilias > > Best regards > > Heinrich > > > +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. >
