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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BD551C433E2 for ; Thu, 17 Sep 2020 13:08:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 858B921734 for ; Thu, 17 Sep 2020 13:08:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726850AbgIQMbe (ORCPT ); Thu, 17 Sep 2020 08:31:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726799AbgIQM3B (ORCPT ); Thu, 17 Sep 2020 08:29:01 -0400 X-Greylist: delayed 370 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Thu, 17 Sep 2020 05:28:59 PDT Received: from smtp.ungleich.ch (smtp.ungleich.ch [IPv6:2a0a:e5c0:0:2:400:b3ff:fe39:7956]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9418C06178A for ; Thu, 17 Sep 2020 05:28:59 -0700 (PDT) Received: from bridge.localdomain (localhost [IPv6:::1]) by smtp.ungleich.ch (Postfix) with ESMTP id E27731FD7E; Thu, 17 Sep 2020 14:22:42 +0200 (CEST) Received: by bridge.localdomain (Postfix, from userid 1000) id 0C6E01A60327; Thu, 17 Sep 2020 14:22:57 +0200 (CEST) References: <20200910112701.13853-1-linux@rasmusvillemoes.dk> <20200917065615.18843-1-linux@rasmusvillemoes.dk> User-agent: mu4e 1.4.13; emacs 27.1 From: Nico Schottelius To: Rasmus Villemoes Cc: Masahiro Yamada , Randy Dunlap , Brian Norris , Bhaskar Chowdhury , Nico Schottelius , Guenter Roeck , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] scripts/setlocalversion: make git describe output more reliable In-reply-to: <20200917065615.18843-1-linux@rasmusvillemoes.dk> Date: Thu, 17 Sep 2020 14:22:57 +0200 Message-ID: <87pn6k384e.fsf@ungleich.ch> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks for the patch Rasmus. Overall it looks good to me, be aligned to the stable patch submission rules makes sense. A tiny thing though: I did not calculate the exact collision probability with 12 characters and it does not make sense to even discuss this, if this is a current rule for stable patches. However we have a couple of 12's scattered in the code. And if the submission rule changes in the future, we should have a single location to update it. So I suggest you introduce something on the line of: ... num_chars=12 ... --abbrev=$num_chars ... I guess you get the picture. Greetings from the sunny mountains, Nico Rasmus Villemoes writes: > When building for an embedded target using Yocto, we're sometimes > observing that the version string that gets built into vmlinux (and > thus what uname -a reports) differs from the path under /lib/modules/ > where modules get installed in the rootfs, but only in the length of > the -gabc123def suffix. Hence modprobe always fails. > > The problem is that Yocto has the concept of "sstate" (shared state), > which allows different developers/buildbots/etc. to share build > artifacts, based on a hash of all the metadata that went into building > that artifact - and that metadata includes all dependencies (e.g. the > compiler used etc.). That normally works quite well; usually a clean > build (without using any sstate cache) done by one developer ends up > being binary identical to a build done on another host. However, one > thing that can cause two developers to end up with different builds > [and thus make one's vmlinux package incompatible with the other's > kernel-dev package], which is not captured by the metadata hashing, is > this `git describe`: The output of that can be affected by > > (1) git version: before 2.11 git defaulted to a minimum of 7, since > 2.11 (git.git commit e6c587) the default is dynamic based on the > number of objects in the repo > (2) hence even if both run the same git version, the output can differ > based on how many remotes are being tracked (or just lots of local > development branches or plain old garbage) > (3) and of course somebody could have a core.abbrev config setting in > ~/.gitconfig > > So in order to avoid `uname -a` output relying on such random details > of the build environment which are rather hard to ensure are > consistent between developers and buildbots, make sure the abbreviated > sha1 always consists of exactly 12 hex characters. That is consistent > with the current rule for -stable patches, and is almost always enough > to identify the head commit unambigously - in the few cases where it > does not, the v5.4.3-00021- prefix would certainly nail it down. > > Signed-off-by: Rasmus Villemoes > --- > v2: use 12 instead of 15, and ensure that the result does have exactly > 12 hex chars. > > scripts/setlocalversion | 21 ++++++++++++++++----- > 1 file changed, 16 insertions(+), 5 deletions(-) > > diff --git a/scripts/setlocalversion b/scripts/setlocalversion > index 20f2efd57b11..bb709eda96cd 100755 > --- a/scripts/setlocalversion > +++ b/scripts/setlocalversion > @@ -45,7 +45,7 @@ scm_version() > > # Check for git and a git repo. > if test -z "$(git rev-parse --show-cdup 2>/dev/null)" && > - head=$(git rev-parse --verify --short HEAD 2>/dev/null); then > + head=$(git rev-parse --verify HEAD 2>/dev/null); then > > # If we are at a tagged commit (like "v2.6.30-rc6"), we ignore > # it, because this version is defined in the top level Makefile. > @@ -59,11 +59,22 @@ scm_version() > fi > # If we are past a tagged commit (like > # "v2.6.30-rc5-302-g72357d5"), we pretty print it. > - if atag="$(git describe 2>/dev/null)"; then > - echo "$atag" | awk -F- '{printf("-%05d-%s", $(NF-1),$(NF))}' > - > - # If we don't have a tag at all we print -g{commitish}. > + # > + # Ensure the abbreviated sha1 has exactly 12 > + # hex characters, to make the output > + # independent of git version, local > + # core.abbrev settings and/or total number of > + # objects in the current repository - passing > + # --abbrev=12 ensures a minimum of 12, and the > + # awk substr() then picks the 'g' and first 12 > + # hex chars. > + if atag="$(git describe --abbrev=12 2>/dev/null)"; then > + echo "$atag" | awk -F- '{printf("-%05d-%s", $(NF-1),substr($(NF),0,13))}' > + > + # If we don't have a tag at all we print -g{commitish}, > + # again using exactly 12 hex chars. > else > + head="$(echo $head | cut -c1-12)" > printf '%s%s' -g $head > fi > fi -- Modern, affordable, Swiss Virtual Machines. Visit www.datacenterlight.ch