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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 520A8C04EB5 for ; Sat, 8 Feb 2020 05:05:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18DAE21741 for ; Sat, 8 Feb 2020 05:05:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581138357; bh=mUWhAbWt8lrtPN4liulN5va6T88Z/Zmj1F9ISdTM2iA=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=Sdq2ty/r4Sz6uICutGSHF+KfC6RXXr8BEL5fQK7RyWexooCcjh8N5spPTAtLoEdX6 xjoE6hkBBY+K027Gf8ZFlJEjNcPzYyN+gGLCeAoKN5LoJLFoVjPuwZfsBzO46ONIsM pdcyhn2viIMPQlPFjqCJbkp5vvoFp+6x2HnFTYmM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726876AbgBHFF4 (ORCPT ); Sat, 8 Feb 2020 00:05:56 -0500 Received: from conssluserg-05.nifty.com ([210.131.2.90]:31875 "EHLO conssluserg-05.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725789AbgBHFFz (ORCPT ); Sat, 8 Feb 2020 00:05:55 -0500 Received: from mail-vs1-f53.google.com (mail-vs1-f53.google.com [209.85.217.53]) (authenticated) by conssluserg-05.nifty.com with ESMTP id 01855cV8011501; Sat, 8 Feb 2020 14:05:39 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-05.nifty.com 01855cV8011501 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1581138339; bh=xfUarjL/4ttWXwZmf+E7cmkD+z3pYKifJ+1FXUZBOd4=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=p+pP5BWuh6eY4h4B7Uqb17+o64tPtJRMrqtRePHYbor6cES5e+HIJrXW3VFYiIPpa UPbziR9jkRhAo04T1Jjjrn9pM8e7Qs8UDY07GPm4EUgmDJNrzGSKV47lms35konP2L ZXZ7s5PRVrpVtmVUi0aSBtE7LDZHHk8rI9jhqedbBGj+n4pks4ml5Oa+moMRnh5ImB T2MmDh6YxT3qSFrFUw1gJDfzZ/FadeMk5+UYcx34ABjj6Haaz4C/B5sSQqSGE9K1H8 W3uV27lkLwZ7EQj1NG2HbY4GbmoB1wlybWIeJ094ef7EG/yYiSjzRo3Nx+gI4ZiZ/6 mfRG/RhlTEZlg== X-Nifty-SrcIP: [209.85.217.53] Received: by mail-vs1-f53.google.com with SMTP id g15so1017892vsf.1; Fri, 07 Feb 2020 21:05:39 -0800 (PST) X-Gm-Message-State: APjAAAVqEQXOtRuKKHvc98si0lyMDf/HyZzTEx8tUb+lPFNTSSGoQa1i 1tjF0CHxEYfTf465ddOWtCS2CAhdYQBCWMyUtWQ= X-Google-Smtp-Source: APXvYqzuJPmPD4c8u/4HoEoZbf4Rvm7VGU+szn3HrfAvLVT0ccCAjc+VWktkYW8xrxc2aIREO4VKePYTnpYF8+lvAUk= X-Received: by 2002:a05:6102:1174:: with SMTP id k20mr1077279vsg.155.1581138338276; Fri, 07 Feb 2020 21:05:38 -0800 (PST) MIME-Version: 1.0 References: <20200207180755.100561-1-qperret@google.com> <20200207180755.100561-2-qperret@google.com> In-Reply-To: <20200207180755.100561-2-qperret@google.com> From: Masahiro Yamada Date: Sat, 8 Feb 2020 06:05:02 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 1/3] kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS To: Quentin Perret Cc: Nicolas Pitre , Linux Kernel Mailing List , Linux Kbuild mailing list , Matthias Maennich , "Cc: Android Kernel" , Jessica Yu , Christoph Hellwig Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi. On Fri, Feb 7, 2020 at 7:08 PM Quentin Perret wrote: > > CONFIG_TRIM_UNUSED_KSYMS currently removes all unused exported symbols > from ksymtab. This works really well when using in-tree drivers, but > cannot be used in its current form if some of them are out-of-tree. > > Indeed, even if the list of symbols required by out-of-tree drivers is > known at compile time, the only solution today to guarantee these don't > get trimmed is to set CONFIG_TRIM_UNUSED_KSYMS=n. This not only wastes > space, but also makes it difficult to control the ABI usable by vendor > modules in distribution kernels such as Android. Being able to control > the kernel ABI surface is particularly useful to ship a unique Generic > Kernel Image (GKI) for all vendors, which is a first step in the > direction of getting all vendors to contribute their code upstream. > > As such, attempt to improve the situation by enabling users to specify a > symbol 'whitelist' at compile time. Any symbol specified in this > whitelist will be kept exported when CONFIG_TRIM_UNUSED_KSYMS is set, > even if it has no in-tree user. The whitelist is defined as a simple > text file, listing symbols, one per line. > > Acked-by: Jessica Yu > Signed-off-by: Quentin Perret > --- > @Nicolas: I left your Reviewed-by behind as the code has changed a bit > but let me know what you think > --- > init/Kconfig | 13 +++++++++++++ > scripts/adjust_autoksyms.sh | 5 +++++ > 2 files changed, 18 insertions(+) > > diff --git a/init/Kconfig b/init/Kconfig > index a34064a031a5..79fd976ce031 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -2180,6 +2180,19 @@ config TRIM_UNUSED_KSYMS > > If unsure, or if you need to build out-of-tree modules, say N. > > +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 un-exported from the > + build when TRIM_UNUSED_KSYMS is selected. > + > + 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. The path can be absolute, or relative to the kernel > + source tree. > + > endif # MODULES > > config MODULES_TREE_LOOKUP > diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh > index a904bf1f5e67..58335eee4b38 100755 > --- a/scripts/adjust_autoksyms.sh > +++ b/scripts/adjust_autoksyms.sh > @@ -38,6 +38,10 @@ esac > # We need access to CONFIG_ symbols > . include/config/auto.conf > > +# The symbol whitelist, relative to the source tree > +eval ksym_wl="${CONFIG_UNUSED_KSYMS_WHITELIST:-/dev/null}" What is this 'eval' needed for? This worked for me without it. > +[[ "$ksym_wl" =~ ^/ ]] || ksym_wl="$abs_srctree/$ksym_wl" > + > # Generate a new ksym list file with symbols needed by the current > # set of modules. > cat > "$new_ksyms_file" << EOT > @@ -48,6 +52,7 @@ cat > "$new_ksyms_file" << EOT > EOT > sed 's/ko$/mod/' modules.order | > xargs -n1 sed -n -e '2{s/ /\n/g;/^$/!p;}' -- | > +cat - "$ksym_wl" | > sort -u | > sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$new_ksyms_file" > > -- > 2.25.0.341.g760bfbb309-goog > -- Best Regards Masahiro Yamada