From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm1-f65.google.com ([209.85.128.65]:35075 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727392AbgBFQRb (ORCPT ); Thu, 6 Feb 2020 11:17:31 -0500 Received: by mail-wm1-f65.google.com with SMTP id b17so706437wmb.0 for ; Thu, 06 Feb 2020 08:17:30 -0800 (PST) Date: Thu, 6 Feb 2020 16:17:25 +0000 From: Quentin Perret Subject: Re: [PATCH v2] kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS Message-ID: <20200206161725.GA235676@google.com> References: <20200129181541.105335-1-qperret@google.com> <20200206155651.GC16783@linux-8ccs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200206155651.GC16783@linux-8ccs> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Jessica Yu Cc: masahiroy@kernel.org, nico@fluxnic.net, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, maennich@google.com, kernel-team@android.com Hi Jessica, On Thursday 06 Feb 2020 at 16:56:51 (+0100), Jessica Yu wrote: > +++ Quentin Perret [29/01/20 18:15 +0000]: > > +config UNUSED_KSYMS_WHITELIST > > + string "Whitelist of symbols to keep in ksymtab" > > + depends on TRIM_UNUSED_KSYMS > > + help > > + By default, all unused exported symbols will be trimmed from the > > + build when TRIM_UNUSED_KSYMS is selected. > > Hm, I thought TRIM_UNUSED_KSYMS just *unexports* unused symbols, no? Right. > "Trimmed from the build" sounds like the symbols are not compiled in > or dropped completely. Please correct me if I misunderstood. Good point. I tried to re-use the wording from the help text of TRIM_UNUSED_KSYMS ("This option allows for unused exported symbols to be dropped from the build"), but I agree this is a bit confusing. I'll re-write the help text in v3. > > > + UNUSED_KSYMS_WHITELIST allows to whitelist symbols that must be kept > > + exported at all times, even in absence of in-tree users. The value to > > + set here is the path to a text file containing the list of symbols, > > + one per line. > > + > > endif # MODULES > > > > config MODULES_TREE_LOOKUP > > diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh > > index a904bf1f5e67..8e1b7f70e800 100755 > > --- a/scripts/adjust_autoksyms.sh > > +++ b/scripts/adjust_autoksyms.sh > > @@ -48,6 +48,7 @@ cat > "$new_ksyms_file" << EOT > > EOT > > sed 's/ko$/mod/' modules.order | > > xargs -n1 sed -n -e '2{s/ /\n/g;/^$/!p;}' -- | > > +cat - "${CONFIG_UNUSED_KSYMS_WHITELIST:-/dev/null}" | > > sort -u | > > sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$new_ksyms_file" > > In general, I agree with the motivation behind this patch, even though > we try not to provide too much support for out-of-tree modules. > However, in this particular case, I think it's fair to provide some > mechanism to keep some exported symbols around that we know will have > users, despite having no in-tree users for a particular > configuration/build. For example, livepatch exports symbols that have > no in-tree users (except for the sample livepatch module, but you'd > have to enable SAMPLES), and all livepatch users will always be out of > tree. > > I also agree with Matthias' feedback, so assuming that gets > incorporated into v3: > > Acked-by: Jessica Yu Thanks for the review! Quentin