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Message-Id: <20210714194723.55677-23-sashal@kernel.org>
Date: Wed, 14 Jul 2021 15:47:18 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Matthias Maennich <maennich@...gle.com>,
Masahiro Yamada <masahiroy@...nel.org>,
Sasha Levin <sashal@...nel.org>, linux-kbuild@...r.kernel.org
Subject: [PATCH AUTOSEL 4.14 23/28] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set
From: Matthias Maennich <maennich@...gle.com>
[ Upstream commit a979522a1a88556e42a22ce61bccc58e304cb361 ]
To avoid unnecessary recompilations, mkcompile_h does not regenerate
compile.h if just the timestamp changed.
Though, if KBUILD_BUILD_TIMESTAMP is set, an explicit timestamp for the
build was requested, in which case we should not ignore it.
If a user follows the documentation for reproducible builds [1] and
defines KBUILD_BUILD_TIMESTAMP as the git commit timestamp, a clean
build will have the correct timestamp. A subsequent cherry-pick (or
amend) changes the commit timestamp and if an incremental build is done
with a different KBUILD_BUILD_TIMESTAMP now, that new value is not taken
into consideration. But it should for reproducibility.
Hence, whenever KBUILD_BUILD_TIMESTAMP is explicitly set, do not ignore
UTS_VERSION when making a decision about whether the regenerated version
of compile.h should be moved into place.
[1] https://www.kernel.org/doc/html/latest/kbuild/reproducible-builds.html
Signed-off-by: Matthias Maennich <maennich@...gle.com>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
scripts/mkcompile_h | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
index 959199c3147e..49f92fffa098 100755
--- a/scripts/mkcompile_h
+++ b/scripts/mkcompile_h
@@ -83,15 +83,23 @@ UTS_TRUNCATE="cut -b -$UTS_LEN"
# Only replace the real compile.h if the new one is different,
# in order to preserve the timestamp and avoid unnecessary
# recompilations.
-# We don't consider the file changed if only the date/time changed.
+# We don't consider the file changed if only the date/time changed,
+# unless KBUILD_BUILD_TIMESTAMP was explicitly set (e.g. for
+# reproducible builds with that value referring to a commit timestamp).
# A kernel config change will increase the generation number, thus
# causing compile.h to be updated (including date/time) due to the
# changed comment in the
# first line.
+if [ -z "$KBUILD_BUILD_TIMESTAMP" ]; then
+ IGNORE_PATTERN="UTS_VERSION"
+else
+ IGNORE_PATTERN="NOT_A_PATTERN_TO_BE_MATCHED"
+fi
+
if [ -r $TARGET ] && \
- grep -v 'UTS_VERSION' $TARGET > .tmpver.1 && \
- grep -v 'UTS_VERSION' .tmpcompile > .tmpver.2 && \
+ grep -v $IGNORE_PATTERN $TARGET > .tmpver.1 && \
+ grep -v $IGNORE_PATTERN .tmpcompile > .tmpver.2 && \
cmp -s .tmpver.1 .tmpver.2; then
rm -f .tmpcompile
else
--
2.30.2
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