From mboxrd@z Thu Jan 1 00:00:00 1970 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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=unavailable 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 CB45BC2B9F4 for ; Thu, 17 Jun 2021 09:18:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1B63613C1 for ; Thu, 17 Jun 2021 09:18:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231555AbhFQJU4 (ORCPT ); Thu, 17 Jun 2021 05:20:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231490AbhFQJU2 (ORCPT ); Thu, 17 Jun 2021 05:20:28 -0400 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 996E9C06175F for ; Thu, 17 Jun 2021 02:18:19 -0700 (PDT) Received: by mail-wm1-x329.google.com with SMTP id l9so2951520wms.1 for ; Thu, 17 Jun 2021 02:18:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=9BepfpuI4gTK3FDci2Lw1qhlFFFZ3rGxYCCkc+cXF5A=; b=rEJJW1nGT5ylLY1WRR4sbUmeZ+p69uWBzd918Tu6NWXyw8VSh+KQa6pYyJAWoYqaLQ SzDs7ugq8o7Y//fBT9oADwN+jcDPoRyabCUpBKHewMC+2S0XY++dYKEhC/EUtMecou+N jV5e/igrVRQ2jSRPsXRaS8Y2MAU/20IcwzZR7EGTuGshicwMsn4hYr18RP7cOeZgLJoE 7zt7Awhz2L2OnsrCfo+uIBsAfgeX0mhS6hCbr/e8VfL6oURjdrApFJaLIsOOlHMpIuT4 6KOtpNt1NwQWzzMRqiPE8/L6tP4x5/gf0J+y32KCqGHNmyGojBowXqx6hPaLukvnOqzh hD2A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9BepfpuI4gTK3FDci2Lw1qhlFFFZ3rGxYCCkc+cXF5A=; b=nnoEEKxqHoE0JkJyuO+1bQwz4YtmjJyC/ud7jWNJLWqlgqVS5b/BR6xT/BVNrbVM9G wBu/3eH3oTRsOp2LHfQgtooYQpS72J9aPZGuHHvi6ZXGXZe016qe7pGk78ZpUejmEMkk GzIvK4986YJhGqfosrASsDPjImq3yynZi75dei4gEKilW8k/FJH9SRmxuXszwPeOKg8h CW9aScSg64iJa2sOfTNnygKwa8KCDMuhidyoI2Hj8PRMadE2F/ds2nTxjJBgcyKMg1MT pJ5jbmLvyIm2dFFF0joMphSgqLcIoOX1SZG5+friQUYXBgLOIiC/i5I6UYM65Alr8PcG Dn2g== X-Gm-Message-State: AOAM530DfLf49AjEySvgDfMUvbAuBhiZ61gDgBfGNvEwfOZjg6Mb0liA Zsea3yirkB6iVLh5FmVsLcbtkw== X-Google-Smtp-Source: ABdhPJxTg0xGDQpF89VezzMjDxw0WHX0T5a/cJf/rozDCBGUj8PS8Tt5YHO54OPysoA+ej/KVYtqrg== X-Received: by 2002:a1c:5418:: with SMTP id i24mr3926482wmb.1.1623921497930; Thu, 17 Jun 2021 02:18:17 -0700 (PDT) Received: from google.com ([2a00:79e0:d:210:dde2:86fa:532c:18b9]) by smtp.gmail.com with ESMTPSA id p13sm3711248wrt.89.2021.06.17.02.18.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Jun 2021 02:18:16 -0700 (PDT) Date: Thu, 17 Jun 2021 10:18:16 +0100 From: Matthias Maennich To: Masahiro Yamada Cc: Linux Kernel Mailing List , "Cc: Android Kernel" , Linux Kbuild mailing list Subject: Re: [PATCH] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set Message-ID: References: <20210612141838.1073085-1-maennich@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 17, 2021 at 10:43:19AM +0900, Masahiro Yamada wrote: >On Thu, Jun 17, 2021 at 10:05 AM Masahiro Yamada wrote: >> >> On Sat, Jun 12, 2021 at 11:18 PM Matthias Maennich wrote: >> > >> > 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 >> > --- >> >> >> Applied to linux-kbuild. Thanks. Thanks! >> > >This may not be a big deal, but when KBUILD_BUILD_TIMESTAMP is unset, >the timestamp is not updated. It still has a user-specified string. I think treating this like any other 'random' prior timestamp is ok. So, I agree: not a big deal. Cheers, Matthias > > > > >-- >Best Regards >Masahiro Yamada