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4e1f0037b8
Distributions apparently only compile a subset of TPM2 drivers into the kernel. For those not compiled it but provided as kmod we need a synchronization point: we must wait before the first TPM2 interaction until the driver is available and accessible. This adds a tpm2.target unit as such a synchronization point. It's ordered after /dev/tpmrm0, and is pulled in by a generator whenever we detect that the kernel reported a TPM2 to exist but we have no device for it yet. This should solve the issue, but might create problems: if there are TPM devices supported by firmware that we don't have Linux drivers for we'll hang for a bit. Hence let's add a kernel cmdline switch to disable (or alternatively force) this logic. Fixes: #30164
61 lines
2.7 KiB
XML
61 lines
2.7 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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<!ENTITY % entities SYSTEM "custom-entities.ent" >
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%entities;
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]>
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-tpm2-generator">
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<refentryinfo>
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<title>systemd-tpm2-generator</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-tpm2-generator</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-tpm2-generator</refname>
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<refpurpose>Generator for inserting TPM2 synchronization point in the boot process</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/usr/lib/systemd/system-generators/systemd-tpm2-generator</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-tpm2-generator</filename> is a generator that adds a <varname>Wants=</varname>
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dependency from <filename>sysinit.target</filename> to <filename>tpm2.target</filename> when it detects
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that the firmware discovered a TPM2 device but the OS kernel so far did
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not. <filename>tpm2.target</filename> is supposed to act as synchronization point for all services that
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require TPM2 device access. See
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<citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
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details.</para>
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<para>The <option>systemd.tpm2_wait=</option> kernel command line option may be used to override
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behaviour of the generator. It accepts a boolean value: if true then <filename>tpm2.target</filename>
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will be added as synchronization point even if the firmware has not detected a TPM2 device. If false, the
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target will not be inserted even if firmware reported a device but the OS kernel doesn't expose a device
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for it yet. The latter might be useful in environments where a suitable TPM2 driver for the available
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hardware is not available.</para>
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<para><filename>systemd-tpm2-generator</filename> implements
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<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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