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=-17.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 86917C3F2D2 for ; Fri, 28 Feb 2020 17:20:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C046246A3 for ; Fri, 28 Feb 2020 17:20:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="XjXoCgsS" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726809AbgB1RUY (ORCPT ); Fri, 28 Feb 2020 12:20:24 -0500 Received: from mail-wr1-f73.google.com ([209.85.221.73]:50025 "EHLO mail-wr1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725730AbgB1RUW (ORCPT ); Fri, 28 Feb 2020 12:20:22 -0500 Received: by mail-wr1-f73.google.com with SMTP id w6so1608870wrm.16 for ; Fri, 28 Feb 2020 09:20:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=J1M2XLrXGsvQG61qq/obE84N3dNLneXy1mWEldFInts=; b=XjXoCgsSfTy56ylcFST9gATMRLMhYF0GKahSkShnMyatFoxxMU/XQxPH1YTnDZpgY+ QQ8OInypLFfEbaDDEB/ck/FIv/Vz5CNguqofPFvj6mqxPdfHgStaloNzO/dEuhllDYx0 Kn7njdap21Msp/7C6w4k65UtboxxwqjD6p3ostzCq1TrUsz/p2tphkQe5wDjxbyazucn kQ2Y2bvXg+WNQtvQKadNEtZNZos5PObEWnuVxbSHUZtdYoWGFzgf8rWFZRnyK8iqwwAJ GA7hr78UihFSoz2hgUDEbbTrTdF8/9prdgZQq0gp7xwOpjfkceTSeMTJpS528SvT6qxd KOfg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=J1M2XLrXGsvQG61qq/obE84N3dNLneXy1mWEldFInts=; b=pYbkgdvt2rpzsZDZsKJdkh7YgV5ENiFZxsI9jFD64YNq2+nR4086W1bWF4KZqBvnj6 5tM3GfmAw14gMbim2ipNfBPFmub4IpdFr2pPPNr2ubv3jvfucY+iiRX+moSzNPlLXC2u ijIKuagpEyur5KUPli19piRsjFY89/n6b7LWPzwdRabZM7ZNERWkkZBbM2KKyP9ZZ5e7 7ia6JHgLsr9aBqszgvlT0xzCdp87/yJ7uJR2ZHjRusLxxpX7rN7fYBeLK15W7OP9BAz3 33M/V4uz9jU2bwOE4XpLb4hhqhctavKrvptvjnp8EOat6qRb7rv1/8wwpUVeVZhprj1S 6H7g== X-Gm-Message-State: APjAAAWQnsmGbVJnEkHKjh/3752QE0POCoDhLZR/FSKJ9pJYkIbomYXA pQhjqyJJszSEZXJHHUB4Rp++R03lLTIZ X-Google-Smtp-Source: APXvYqzWUjmgAs0gWTsax0UACPwKiN2Y7zcwmRJ6s2bwdkhcpeunlwMy6aapGtHYdi90TFWX4H24ZE9m4Z/V X-Received: by 2002:adf:ee03:: with SMTP id y3mr5915285wrn.5.1582910420967; Fri, 28 Feb 2020 09:20:20 -0800 (PST) Date: Fri, 28 Feb 2020 17:20:13 +0000 In-Reply-To: <20200228172015.44369-1-qperret@google.com> Message-Id: <20200228172015.44369-2-qperret@google.com> Mime-Version: 1.0 References: <20200228172015.44369-1-qperret@google.com> X-Mailer: git-send-email 2.25.1.481.gfbce0eb801-goog Subject: [PATCH v6 1/3] kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS From: Quentin Perret To: masahiroy@kernel.org, nico@fluxnic.net Cc: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, maennich@google.com, kernel-team@android.com, jeyu@kernel.org, hch@infradead.org, qperret@google.com 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 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 Acked-by: Nicolas Pitre Tested-by: Matthias Maennich Reviewed-by: Matthias Maennich Signed-off-by: Quentin Perret --- init/Kconfig | 13 +++++++++++++ scripts/adjust_autoksyms.sh | 12 ++++++++++++ 2 files changed, 25 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index 20a6ac33761c..873256bdbea5 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2208,6 +2208,19 @@ 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..212ba45595d3 100755 --- a/scripts/adjust_autoksyms.sh +++ b/scripts/adjust_autoksyms.sh @@ -38,6 +38,17 @@ esac # We need access to CONFIG_ symbols . include/config/auto.conf +ksym_wl=/dev/null +if [ -n "$CONFIG_UNUSED_KSYMS_WHITELIST" ]; then + # Use 'eval' to expand the whitelist path and check if it is relative + eval ksym_wl="$CONFIG_UNUSED_KSYMS_WHITELIST" + [ "${ksym_wl}" != "${ksym_wl#/}" ] || ksym_wl="$abs_srctree/$ksym_wl" + if [ ! -f "$ksym_wl" ] || [ ! -r "$ksym_wl" ]; then + echo "ERROR: '$ksym_wl' whitelist file not found" >&2 + exit 1 + fi +fi + # Generate a new ksym list file with symbols needed by the current # set of modules. cat > "$new_ksyms_file" << EOT @@ -48,6 +59,7 @@ 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" -- 2.25.1.481.gfbce0eb801-goog