#70943 linux-libre is not reproducible (regression)

Message #5 received at submit@debbugs.gnu.org (full text, mbox, reply):

From: Maxim Cournoyer <maxim.cournoyer@gmail.com>

To: bug-guix <bug-guix@gnu.org>

Subject: linux-libre is not reproducible (regression)

Date: Tue, 14 May 2024 11:40:35 -0400

Hello,

I've investigated non-determinism in our linux-libre package, which
sadly appears to have regressed in that regard since I last looked into
it 3 years ago (see commit 01ea70a29c5c1ded31c37ce8c43192bc1956b2ca
("gnu: linux-libre: Make build reproducible.")).

I'm currently seeing these differing files:

--8<---------------cut here---------------start------------->8---
$ diff -ql /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9{,-check}
Files /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/bzImage and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/bzImage differ
Common subdirectories: /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/lib and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/lib
Common subdirectories: /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/share and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/share
Files /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/System.map and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/System.map differ
--8<---------------cut here---------------end--------------->8---

I'll take a look at what Yocto does differently, if anything.

-- 
Thanks,
Maxim

Message #8 received at 70943@debbugs.gnu.org (full text, mbox, reply):

From: Maxim Cournoyer <maxim.cournoyer@gmail.com>

To: 70943@debbugs.gnu.org

Subject: Re: bug#70943: linux-libre is not reproducible (regression)

Date: Sun, 26 May 2024 14:15:59 -0400

Hi,

Maxim Cournoyer <maxim.cournoyer@gmail.com> writes:

> Hello,
>
> I've investigated non-determinism in our linux-libre package, which
> sadly appears to have regressed in that regard since I last looked into
> it 3 years ago (see commit 01ea70a29c5c1ded31c37ce8c43192bc1956b2ca
> ("gnu: linux-libre: Make build reproducible.")).
>
> I'm currently seeing these differing files:
>
> $ diff -ql /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9{,-check}
> Files /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/bzImage and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/bzImage differ
> Common subdirectories: /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/lib and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/lib
> Common subdirectories: /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/share and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/share
> Files /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9/System.map and /gnu/store/6vx6vkranmggv690ggm79zhdhwvmbji9-linux-libre-6.8.9-check/System.map differ
>
> I'll take a look at what Yocto does differently, if anything.

I didn't see anything special, although some BPF switches got turned on
in the kernel by default in newer 6.X releases, and BPF appears to
introduce non-determinism, accordingy to the Reproducible Builds website
which says this [0]:

   Several distributions noticed recent versions of the Linux Kernel are
   no longer reproducible because the BPF Type Format (BTF) metadata is
   not generated in a deterministic way. This was discussed on the
   #reproducible-builds IRC channel, but no solution appears to be in
   sight for now.

[0]  https://reproducible-builds.org/reports/2023-04/

So it seems there'll need to be some reproducibility work for that
feature in the kernel before it can be resolved (we could also disable
all BPF features, but that seems counter-current at this point in time).

-- 
Thanks,
Maxim

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