From patchwork Sat Jun 12 14:18:38 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Maennich X-Patchwork-Id: 12317101 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F36DC48BE5 for ; Sat, 12 Jun 2021 14:18:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E330E611CA for ; Sat, 12 Jun 2021 14:18:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230225AbhFLOUu (ORCPT ); Sat, 12 Jun 2021 10:20:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53968 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230191AbhFLOUu (ORCPT ); Sat, 12 Jun 2021 10:20:50 -0400 Received: from mail-ed1-x549.google.com (mail-ed1-x549.google.com [IPv6:2a00:1450:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58D1EC061767 for ; Sat, 12 Jun 2021 07:18:50 -0700 (PDT) Received: by mail-ed1-x549.google.com with SMTP id y16-20020a0564024410b0290394293f6816so299eda.20 for ; Sat, 12 Jun 2021 07:18:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=xb2QAx7zepAh/lQE/CJVc+d/CGuwmfQ6M6AYYspdx1I=; b=Pn1g/j4Q/Ps8hO/Wv4OvCFaicBjrttTarkv+9pOFkNnWNh42V8bddGeTBrO7Vlw5cg 4Re/hLQOA9OFtL8OPulFNerctA3fi6rLZzfhwueqHLWuSSMio0KiWvt527JC1LgSqsb2 0BGa8BtMC9LNQROvUh4K4i3i8r4C1wLe3tGLLQZbGZvaVLEyjSIUSe0t+qtRBffeeF7d kfctmL+xofvpBMsrn7fJkFCk7I4CIOn2L3ofNk9TRXWSYNS8is69W9dcKsEkIRQAK7FU 5Nr9P35dYmK7LOYSRj8fb1RokC30zVaHTZQ5vy0hjLOghItjI4u9ECqBDv2AxmgW5+3h +T0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=xb2QAx7zepAh/lQE/CJVc+d/CGuwmfQ6M6AYYspdx1I=; b=KQ120h8ffN+9NKpNuFRRiay5E0yLj1FUdro6JCxRR7LmnIcKx1ODfQBBjOSesMJ4mo QcazvZDwocP0Ma/wgZYjGw6zl7WIsKOyFbQ4MlYwG56mfskhRxCosCfP+/+ez5CoKLFu /Ads6ez3k+p2X6GxhlwXWzUXfJPaZNFb+jmnHB6HuL1zDPF1hEEmKN9pyg0lWZv3W5ao 2WJG4AV16dcDpWuk+Ml5DUIvLk+nXgXlBWntbl1dBXPu2gjU+7ytXEUyVn5IVH3O28gW djnwBug97OEK+vgwk9id+HtQtqII8UDB2SMpBP4K5UKxcsDb3GtGje+KpHMH525QKHCS fu2Q== X-Gm-Message-State: AOAM5305+tBGoGaWd3yRd4DLmTPE6s7/tOYEoFDF6VBy+yPDaEi3XW8F g61D8hOAhBT/xj0kW/ba4yFk1pwthx0tqg== X-Google-Smtp-Source: ABdhPJxV4Tljny9btCWJBH1v2SI+ztKhUT2tTQK+HNQFAwxoBsiqTJfeNy9EcbO/TEDFQfbxpoi5va0A06egsA== X-Received: from lux.lon.corp.google.com ([2a00:79e0:d:210:f276:1917:882e:b90d]) (user=maennich job=sendgmr) by 2002:a05:6402:1458:: with SMTP id d24mr8742698edx.85.1623507525727; Sat, 12 Jun 2021 07:18:45 -0700 (PDT) Date: Sat, 12 Jun 2021 15:18:38 +0100 Message-Id: <20210612141838.1073085-1-maennich@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.32.0.272.g935e593368-goog Subject: [PATCH] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set From: Matthias Maennich To: linux-kernel@vger.kernel.org Cc: kernel-team@android.com, maennich@google.com, Masahiro Yamada , linux-kbuild@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org 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 Cc: Masahiro Yamada Cc: linux-kbuild@vger.kernel.org Signed-off-by: Matthias Maennich --- scripts/mkcompile_h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h index 4ae735039daf..a72b154de7b0 100755 --- a/scripts/mkcompile_h +++ b/scripts/mkcompile_h @@ -70,15 +70,23 @@ 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