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man: reword the list of PE sections in systemd-stub

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Let's put the section name at the beginning of each sentence. This way we
can avoid awkward constructs like "kernel is looked for in the .linux section".
Also, since the paragraph above says that this is a list of "PE sections", we
can just say "section". In other places, it is often useful to say "PE section"
to avoid ambiguity.

Also fix the off-by-one in the count of sections.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2023-11-24 15:19:50 +01:00
parent ed272a9ff5
commit 963ea30a5d
1 changed files with 36 additions and 38 deletions
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74
man/systemd-stub.xml
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@ -55,38 +55,37 @@
<!-- Let's keep this in the canonical order we also measure the sections by, i.e. as in
src/fundamental/uki.h's UnifiedSection enum -->
<listitem><para>The ELF Linux kernel images will be looked for in the <literal>.linux</literal> PE
section of the executed image.</para></listitem>
<listitem><para>A <literal>.linux</literal> section with the ELF Linux kernel image.</para></listitem>
<listitem><para>OS release information, i.e. the
<citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> file of
the OS the kernel belongs to, in the <literal>.osrel</literal> PE section.</para></listitem>
<listitem><para>An <literal>.osrel</literal> section with OS release information, i.e. the contents of
the <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> file
of the OS the kernel belongs to.</para></listitem>
<listitem><para>The kernel command line to pass to the invoked kernel will be looked for in the
<literal>.cmdline</literal> PE section.</para></listitem>
<listitem><para>A <literal>.cmdline</literal> section with the kernel command line to pass to the
invoked kernel.</para></listitem>
<listitem><para>The initrd will be loaded from the <literal>.initrd</literal> PE
<listitem><para>An <literal>.initrd</literal> section with the initrd.</para></listitem>
<listitem><para>A <literal>.splash</literal> section with an image (in the Windows
<filename>.BMP</filename> format) to show on screen before invoking the kernel.</para></listitem>
<listitem><para>A <literal>.dtb</literal> section with a compiled binary DeviceTree.</para></listitem>
<listitem><para>A <literal>.uname</literal> section with the kernel version information, i.e. the
output of <command>uname -r</command> for the kernel included in the <literal>.linux</literal>
section.</para></listitem>
<listitem><para>A boot splash (in Windows <filename>.BMP</filename> format) to show on screen before
invoking the kernel will be looked for in the <literal>.splash</literal> PE section.</para></listitem>
<listitem><para>An <literal>.sbat</literal> section with
<ulink url="https://github.com/rhboot/shim/blob/main/SBAT.md">SBAT</ulink> revocation
metadata.</para></listitem>
<listitem><para>A compiled binary DeviceTree will be looked for in the <literal>.dtb</literal> PE
section.</para></listitem>
<listitem><para>A <literal>.pcrsig</literal> section with a set of cryptographic signatures for the
expected TPM2 PCR values after the kernel has been booted, in JSON format. This is useful for
implementing TPM2 policies that bind disk encryption and similar to kernels that are signed by a
specific key.</para></listitem>
<listitem><para>Kernel version information, i.e. the output of <command>uname -r</command> for the
kernel included in the UKI, in the <literal>.uname</literal> PE section.</para></listitem>
<listitem><para><ulink url="https://github.com/rhboot/shim/blob/main/SBAT.md">SBAT</ulink> revocation
metadata, in the <literal>.sbat</literal> PE section.</para></listitem>
<listitem><para>A set of cryptographic signatures for expected TPM2 PCR values when this kernel is
booted, in JSON format, in the <literal>.pcrsig</literal> section. This is useful for implementing TPM2
policies that bind disk encryption and similar to kernels that are signed by a specific
key.</para></listitem>
<listitem><para>A public key in PEM format matching this TPM2 PCR signature data in the
<literal>.pcrpkey</literal> section.</para></listitem>
<listitem><para>A <literal>.pcrpkey</literal> section with a public key in the PEM format matching the
signature data in the the <literal>.pcrsig</literal> section.</para></listitem>
</itemizedlist>
<para>If UEFI SecureBoot is enabled and the <literal>.cmdline</literal> section is present in the executed
@ -100,15 +99,14 @@
DeviceTree in the corresponding EFI configuration table. systemd-stub will ask the firmware via the
<literal>EFI_DT_FIXUP_PROTOCOL</literal> for hardware specific fixups to the DeviceTree.</para>
<para>The contents of seven of these eight PE sections are measured into TPM PCR 11, that is otherwise
not used. Thus, it can be pre-calculated without too much effort. The <literal>.pcrsig</literal> section
is not included in this PCR measurement, since it's supposed to contain signatures for the expected
results for these measurements, i.e. of the outputs of the measurement operation, and thus cannot also be
input to it.</para>
<para>The contents of eight of these nine sections are measured into TPM PCR 11. It is otherwise not used
and thus the result can be pre-calculated without too much effort. The <literal>.pcrsig</literal> section
is not included in this PCR measurement, since it is supposed to contain signatures for the output of the
measurement operation, and thus cannot also be input to it.</para>
<para>When <literal>.pcrsig</literal> and/or <literal>.pcrpkey</literal> are present in a unified kernel
image their contents are passed to the booted kernel in an synthetic initrd cpio archive that places them in the
<filename>/.extra/tpm2-pcr-signature.json</filename> and
<para>When <literal>.pcrsig</literal> and/or <literal>.pcrpkey</literal> sections are present in a
unified kernel image their contents are passed to the booted kernel in an synthetic initrd cpio archive
that places them in the <filename>/.extra/tpm2-pcr-signature.json</filename> and
<filename>/.extra/tpm2-pcr-public-key.pem</filename> files. Typically, a
<citerefentry><refentrytitle>tmpfiles.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> line then
ensures they are copied into <filename>/run/systemd/tpm2-pcr-signature.json</filename> and
@ -395,7 +393,8 @@
<varlistentry>
<term><filename>/</filename></term>
<listitem><para>The main initrd from the <literal>.initrd</literal> PE section of the unified kernel image.</para>
<listitem><para>The main initrd from the <literal>.initrd</literal> PE section of the unified kernel
image.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
</varlistentry>
@ -412,8 +411,8 @@
<varlistentry>
<term><filename>/.extra/global_credentials/*.cred</filename></term>
<listitem><para>Similar, credential files in the <filename>/loader/credentials/</filename> directory
in the file system the unified kernel image is placed in are copied into the
<listitem><para>Similarly, credential files in the <filename>/loader/credentials/</filename>
directory in the file system the unified kernel image is placed in are copied into the
<filename>/.extra/global_credentials/</filename> directory in the initrd execution
environment.</para>
@ -433,8 +432,7 @@
<term><filename>/.extra/tpm2-pcr-signature.json</filename></term>
<listitem><para>The TPM2 PCR signature JSON object included in the <literal>.pcrsig</literal> PE
section of the unified kernel image is copied into the
<filename>/.extra/tpm2-pcr-signature.json</filename> file in the initrd execution
environment.</para>
<filename>/.extra/tpm2-pcr-signature.json</filename> file in the initrd execution environment.</para>
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
</varlistentry>