From: Michael Ellerman <mpe@ellerman•id.au>
To: Jarkko Sakkinen <jarkko@kernel•org>,
Stefan Berger <stefanb@linux•ibm.com>
Cc: eajames@linux•ibm.com, jgg@ziepe•ca, yangyingliang@huawei•com,
linux-integrity@vger•kernel.org, linuxppc-dev@lists•ozlabs.org,
peterhuewe@gmx•de
Subject: Re: [PATCH 1/2] powerpc/tpm: Create linux,sml-base/size as big endian
Date: Tue, 28 Feb 2023 22:21:36 +1100 [thread overview]
Message-ID: <87r0uaujb3.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <Y/1wm3kmsto5tzeB@kernel.org>
Jarkko Sakkinen <jarkko@kernel•org> writes:
> On Mon, Feb 27, 2023 at 06:08:31PM -0500, Stefan Berger wrote:
>> On 2/23/23 22:25, Michael Ellerman wrote:
>> > There's code in prom_instantiate_sml() to do a "SML handover" (Stored
>> > Measurement Log) from OF to Linux, before Linux shuts down Open
>> > Firmware.
>> >
>> > This involves creating a buffer to hold the SML, and creating two device
>> > tree properties to record its base address and size. The kernel then
>> > later reads those properties from the device tree to find the SML.
>> >
>> > When the code was initially added in commit 4a727429abec ("PPC64: Add
>> > support for instantiating SML from Open Firmware") the powerpc kernel
>> > was always built big endian, so the properties were created big endian
>> > by default.
>> >
>> > However since then little endian support was added to powerpc, and now
>> > the code lacks conversions to big endian when creating the properties.
>> >
>> > This means on little endian kernels the device tree properties are
>> > little endian, which is contrary to the device tree spec, and in
>> > contrast to all other device tree properties.
>> >
>> > To cope with that a workaround was added in tpm_read_log_of() to skip
>> > the endian conversion if the properties were created via the SML
>> > handover.
>> >
>> > A better solution is to encode the properties as big endian as they
>> > should be, and remove the workaround.
>> >
>> > Typically changing the encoding of a property like this would present
>> > problems for kexec. However the SML is not propagated across kexec, so
>> > changing the encoding of the properties is a non-issue.
>> >
>> > Fixes: e46e22f12b19 ("tpm: enhance read_log_of() to support Physical TPM event log")
>> > Signed-off-by: Michael Ellerman <mpe@ellerman•id.au>
>>
>> Reviewed-by: Stefan Berger <stefanb@linux•ibm.com>
>
> 2/2 does not have a fixes tag.
True. Arguably the bug goes back to the introduction of
kexec_file_load() support, although the patch won't backport that far
due to code refactoring. So that would be:
Fixes: a0458284f062 ("powerpc: Add support code for kexec_file_load()")
cheers
next prev parent reply other threads:[~2023-02-28 11:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-24 3:25 [PATCH 1/2] powerpc/tpm: Create linux,sml-base/size as big endian Michael Ellerman
2023-02-24 3:25 ` [PATCH 2/2] powerpc/tpm: Reserve SML log when kexec'ing Michael Ellerman
2023-02-28 19:18 ` Stefan Berger
2023-03-02 22:05 ` Michael Ellerman
2023-02-27 23:08 ` [PATCH 1/2] powerpc/tpm: Create linux,sml-base/size as big endian Stefan Berger
2023-02-28 3:10 ` Jarkko Sakkinen
2023-02-28 11:21 ` Michael Ellerman [this message]
2023-03-01 23:09 ` Jarkko Sakkinen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87r0uaujb3.fsf@mpe.ellerman.id.au \
--to=mpe@ellerman$(echo .)id.au \
--cc=eajames@linux$(echo .)ibm.com \
--cc=jarkko@kernel$(echo .)org \
--cc=jgg@ziepe$(echo .)ca \
--cc=linux-integrity@vger$(echo .)kernel.org \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=peterhuewe@gmx$(echo .)de \
--cc=stefanb@linux$(echo .)ibm.com \
--cc=yangyingliang@huawei$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox