linux-kernel - Re: [PATCH v2] drivers: gpu: drm: msm: registers: improve reproducibility

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Message-ID: <858dea80-1bd6-4bbc-9b98-9f959c00b304@ti.com>
Date: Mon, 8 Sep 2025 12:59:37 -0500
From: Ryan Eatmon <reatmon@...com>
To: <rob.clark@....qualcomm.com>
CC: Rob Clark <robdclark@...il.com>,
        Dmitry Baryshkov
	<dmitry.baryshkov@....qualcomm.com>,
        Viswanath Kraleti
	<viswanath.kraleti@....qualcomm.com>,
        Abhinav Kumar
	<quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        Bruce Ashfield <bruce.ashfield@...il.com>
Subject: Re: [PATCH v2] drivers: gpu: drm: msm: registers: improve
 reproducibility



On 9/8/2025 9:19 AM, Rob Clark wrote:
> On Mon, Sep 8, 2025 at 6:39 AM Ryan Eatmon <reatmon@...com> wrote:
>>
>>
>>
>> On 9/6/2025 6:24 PM, Rob Clark wrote:
>>> On Sat, May 24, 2025 at 10:15 AM Dmitry Baryshkov
>>> <dmitry.baryshkov@....qualcomm.com> wrote:
>>>>
>>>> On Sat, May 24, 2025 at 09:25:37PM +0530, Viswanath Kraleti wrote:
>>>>> From: Ryan Eatmon <reatmon@...com>
>>>>>
>>>>> The files generated by gen_header.py capture the source path to the
>>>>> input files and the date.  While that can be informative, it varies
>>>>> based on where and when the kernel was built as the full path is
>>>>> captured.
>>>>>
>>>>> Since all of the files that this tool is run on is under the drivers
>>>>> directory, this modifies the application to strip all of the path before
>>>>> drivers.  Additionally it prints <stripped> instead of the date.
>>>>>
>>>>> Signed-off-by: Ryan Eatmon <reatmon@...com>
>>>>> Signed-off-by: Bruce Ashfield <bruce.ashfield@...il.com>
>>>>> Signed-off-by: Viswanath Kraleti <viswanath.kraleti@....qualcomm.com>
>>>>> ---
>>>>> The files generated by gen_header.py include the source path to the
>>>>> input files and the build date. While this information can be useful,
>>>>> it inadvertently exposes build system configuration details in the
>>>>> binaries. This hinders binary reproducibility, as the output will
>>>>> vary if the build environment changes.
>>>>>
>>>>> This change was originally submitted to the linux-yocto-dev kernel [1]
>>>>> to address binary reproducibility QA errors. However, the fix is generic
>>>>> enough to be applicable to the mainline kernel and would benefit other
>>>>> distributions as well. So proposing it here for broader inclusion.
>>>>>
>>>>> [1] https://git.yoctoproject.org/linux-yocto-dev/commit/?id=f36faf0f9f8d8f5b4c43a68e5c6bd83a62253140
>>>>> ---
>>>>> Changes in v2:
>>>>> - Corrected author id
>>>>> - Link to v1: https://lore.kernel.org/r/20250523-binrep-v1-1-c3a446518847@oss.qualcomm.com
>>>>> ---
>>>>>    drivers/gpu/drm/msm/registers/gen_header.py | 8 +++++---
>>>>>    1 file changed, 5 insertions(+), 3 deletions(-)
>>>>>
>>>>
>>>> Acked-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>>>>
>>>> Rob, WDYT?
>>>
>>> I'm revisiting this one, in the context of trying to re-sync
>>> gen_header.py with mesa.. but it is only changing the contents of
>>> comments, so it's not quite clear to me how this ends up mattering for
>>> binary reproducibility.
>>
>> The reason it matters is that for Yocto, the generated header file is
>> identified as a file that needs to be installed into the sysroot.  All
>> files going into the sysroot are checked to make sure they do not
>> contain dates and/or paths to the build directory contained within.
>> Since this is a generated header file that is included in the sysroot we
>> needed to strip out the path and date.
>>
>> The idea for the reproducible builds are that the same files on a
>> different a machine at a different time should produce 100% identical
>> files.  Including paths and dates violates that tenet.
>>
>> Hope that helps explain why we needed this.  So long as the
>> gen_header.py is being called to generate header files then we need to
>> maintain the reproducible aspect.
>>
> 
> My plan is (was?) to just replace the entire comment header with simply:
> 
>    /* Autogenerated file, DO NOT EDIT manually! */
> 
> That said, I'm not entirely sure why these files should get installed
> into the sysroot?  I'm not super hands-on familiar with Yocto, so
> maybe there is a good reason.. but if there is, maybe the plan to
> remove the license/etc from the comment header isn't such a good idea
> after all?

The generated header files would be part of a linux-headers package that 
would be needed to build other packages as part of the distro.  And so 
the header files are all checked against the rules.  A linux-headers 
type package is common for distros to have available.


> BR,
> -R
> 
>>
>>> That said, since the generated files are no longer checked in to mesa
>>> or the kernel, we could probably just drop all of this if it mattered.
>>>
>>> BR,
>>> -R
>>
>> --
>> Ryan Eatmon                reatmon@...com
>> -----------------------------------------
>> Texas Instruments, Inc.  -  LCPD  -  MGTS
>>
>>

-- 
Ryan Eatmon                reatmon@...com
-----------------------------------------
Texas Instruments, Inc.  -  LCPD  -  MGTS