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authorMatthias Maennich <maennich@google.com>2021-06-12 17:18:38 +0300
committerMasahiro Yamada <masahiroy@kernel.org>2021-06-17 04:01:12 +0300
commita979522a1a88556e42a22ce61bccc58e304cb361 (patch)
treeb614804f871ab8b5cbbd5e1eed311bcc347f2b77
parent4a6795933a890d41504c6df04527d1e093a4cbe6 (diff)
downloadlinux-a979522a1a88556e42a22ce61bccc58e304cb361.tar.xz
kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set
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@google.com> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
-rwxr-xr-xscripts/mkcompile_h14
1 files changed, 11 insertions, 3 deletions
diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
index 06bbf4c2c66c..6a2a04d92f42 100755
--- a/scripts/mkcompile_h
+++ b/scripts/mkcompile_h
@@ -68,15 +68,23 @@ UTS_VERSION="$(echo $UTS_VERSION $CONFIG_FLAGS $TIMESTAMP | cut -b -$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