Subject: Re: [PATCH 00/34] Make kernel build deterministic

From: Michal Marek <[email-masked]>
Date: Wed, 06 Apr 2011 11:07:34 +0200

On 5.4.2011 21:24, Artem Bityutskiy wrote:
> On Tue, 2011-04-05 at 08:49 -0700, Greg KH wrote:
>> On Tue, Apr 05, 2011 at 04:58:47PM +0200, Michal Marek wrote:
>>>
>>> Hi,
>>>
>>> this series makes it possible to build bit-identical kernel image and
>>> modules from identical sources. Of course the build is already
>>> deterministic in terms of behavior of the code, but the various
>>> timestamps embedded in the object files make it hard to compare two
>>> builds, for instance to verify that a makefile cleanup didn't
>>> accidentally change something. A prime example is /proc/config.gz, which
>>> has both a timestamp in the gzip header and a timestamp in the payload
>>> data. With this series applied, a script like this will produce
>>> identical kernels each time:
>>
>> Very nice stuff.  Do you want to take the individual patches through one
>> of your trees, or do you mind if the subsystem maintainers take them
>> through theirs?
> 
> But unfortunately, it is very easy to break this and for sure it'll be
> broken very soon.

I'm not so pessimistic. 34 patches and 57 files might sound like a lot,
but given that this has been accumulating since day one, the cleanup
should last for some time.

> So additionally, I'd suggest:
> 1. Instrument checkpatch.pl and make it err or warn on timestamps.

This is patch 34/34 in this series: https://lkml.org/lkml/2011/4/5/198

> 2. Probably instrument linux-next to rise a warning when people break
>    this.

I'm not sure if Stephen has that much spare time, and I don't think it
is necessary. I think the checkpatch check is sufficient and I'll check
myself occasionally.

Michal