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

[Ryan Eatmon <reatmon@ti.com>]

On 9/6/2025 6:24 PM, Rob Clark wrote:
> On Sat, May 24, 2025 at 10:15 AM Dmitry Baryshkov
> <dmitry.baryshkov@oss.qualcomm.com> wrote:
>>
>> On Sat, May 24, 2025 at 09:25:37PM +0530, Viswanath Kraleti wrote:
>>> From: Ryan Eatmon <reatmon@ti.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@ti.com>
>>> Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
>>> Signed-off-by: Viswanath Kraleti <viswanath.kraleti@oss.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@oss.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.


> 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@ti.com
-----------------------------------------
Texas Instruments, Inc.  -  LCPD  -  MGTS