When patching a kernel git repository, in a recipe inheriting
kernel-yocto.bbclass,
the resulting commit hash will become different every time the source is
unpacked and patched.
This is a problem that causes non-reproducible builds, when the commit hash is
built
into the kernel (CONFIG_LOCALVERSION_AUTO=y).
Currently it is not a problem in linux-yocto, since an empty .scmversion is
created in kernel_do_configure [1]. This is preventing the kernel build from
generating its own .scmversion.
If removing this commit, setting CONFIG_LOCALVERSION_AUTO=y and applying any
patch in the linux-yocto recipe, this will result in a non-reproducible build.
However, there are other kernel recipes where this is already a problem;
meta-freescale [2] and meta-tegra [3].
Currently we solve this problem by using the --committer-date-is-author-date
"git am" option, when applying patches with kgit-s2q:
From f2b6cdb745e7a7965497efccff415ec81207f4d7 Mon Sep 17 00:00:00 2001
From: Jimmy Assarsson <ex...@kvaser.com>
Date: Fri, 4 Feb 2022 17:58:29 +0100
Subject: [PATCH] kgit-s2q: call "git am" with --committer-date-is-author-date
Produce deterministic commit hashes, by passing the
"--committer-date-is-author-date" option when applying patches with "git am".
Signed-off-by: Jimmy Assarsson <jimmyassars...@gmail.com>
---
tools/kgit-s2q | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/kgit-s2q b/tools/kgit-s2q
index 706783e..b46a138 100755
--- a/tools/kgit-s2q
+++ b/tools/kgit-s2q
@@ -558,7 +558,7 @@ do
echo "($APPLIED/$COUNT) `basename $i`"
fi
- git am --keep-non-patch $DIR/$i > /dev/null 2>&1
+ git am --keep-non-patch --committer-date-is-author-date $DIR/$i > /dev/null
2>&1
if [ $? != 0 ];then
git am --abort > /dev/null 2>&1
echo "[INFO]: check of $DIR/$i with \"git am\" did not pass, trying
reduced context."
I'm not sure if this is a proper solution to fix the problem or what side
effects it may introduce?
[1]
https://git.yoctoproject.org/poky/tree/meta/classes/kernel.bbclass?h=honister#n589
[2]
https://git.yoctoproject.org/meta-freescale/tree/classes/fsl-kernel-localversion.bbclass?h=honister
[3]
https://github.com/OE4T/meta-tegra/blob/honister/recipes-kernel/linux/linux-tegra_4.9.bb
Best regards,
jimmy
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