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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Matthias Maennich <maennich@google.com>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Sasha Levin <sashal@kernel.org>,
	linux-kbuild@vger.kernel.org
Subject: [PATCH AUTOSEL 4.9 14/18] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set
Date: Wed, 14 Jul 2021 15:48:02 -0400	[thread overview]
Message-ID: <20210714194806.55962-14-sashal@kernel.org> (raw)
In-Reply-To: <20210714194806.55962-1-sashal@kernel.org>

From: Matthias Maennich <maennich@google.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@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 scripts/mkcompile_h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
index 6fdc97ef6023..cb73747002ed 100755
--- a/scripts/mkcompile_h
+++ b/scripts/mkcompile_h
@@ -82,15 +82,23 @@ 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


  parent reply	other threads:[~2021-07-14 20:02 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14 19:47 [PATCH AUTOSEL 4.9 01/18] ARM: dts: rockchip: fix pinctrl sleep nodename for rk3036-kylin and rk3288 Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 02/18] ARM: dts: rockchip: Fix power-controller node names for rk3288 Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 03/18] reset: ti-syscon: fix to_ti_syscon_reset_data macro Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 04/18] ARM: brcmstb: dts: fix NAND nodes names Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 05/18] ARM: dts: BCM63xx: Fix " Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 06/18] ARM: dts: imx25-pinfunc: Fix gpio function name for pads GPIO_[A-F] Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 07/18] ARM: dts: imx6: phyFLEX: Fix UART hardware flow control Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 08/18] ARM: imx: pm-imx5: Fix references to imx5_cpu_suspend_info Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 09/18] ARM: dts: am437x: align gpio hog names with dt-schema Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 10/18] ARM: dts: omap5-board-common: " Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 11/18] ARM: dts: stm32: fix RCC node name on stm32f429 MCU Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 12/18] arm64: dts: juno: Update SCPI nodes as per the YAML schema Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 13/18] thermal/core: Correct function name thermal_zone_device_unregister() Sasha Levin
2021-07-14 19:48 ` Sasha Levin [this message]
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 15/18] rtc: max77686: Do not enforce (incorrect) interrupt trigger type Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 16/18] scsi: aic7xxx: Fix unintentional sign extension issue on left shift of u8 Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 17/18] scsi: be2iscsi: Fix some missing space in some messages Sasha Levin
2021-07-16 19:22   ` Marion & Christophe JAILLET
2021-07-21 10:42     ` Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 18/18] sched/fair: Fix CFS bandwidth hrtimer expiry type Sasha Levin

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