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 5741CC2D0DB for ; Wed, 29 Jan 2020 18:15:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 31D052064C for ; Wed, 29 Jan 2020 18:15:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="b89C2vjA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727299AbgA2SPp (ORCPT ); Wed, 29 Jan 2020 13:15:45 -0500 Received: from mail-qv1-f74.google.com ([209.85.219.74]:51932 "EHLO mail-qv1-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726245AbgA2SPp (ORCPT ); Wed, 29 Jan 2020 13:15:45 -0500 Received: by mail-qv1-f74.google.com with SMTP id e10so347991qvq.18 for ; Wed, 29 Jan 2020 10:15:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=8OmDOl+HzY7kcK871zVejMIspdUpfLqTD5KCeutuWtI=; b=b89C2vjAvi8rn6ke4cMrbzWhPNxthh3YpogsX2uEkpXypteStYFa0eHE/vbKpyKJ7c kWBwggD5XvuNwYUWI3HuS2xE8BtlawGJaAre2+1dfgETw9jFkKK6veUMfpnsJgwGEvS2 ewiUCzMI+c7/iBJZ8k++QCDfVxrlW41Rxy71EifgoDosJUOQnNzS2Qu5dfJHfZYldD3U kqYxC9hGbFd+k+7wkbuxYBxMxuFdnt0siR959H1OQ2ZgvBwY85FaMSAPHb0mkKviUm+V jooaRPM1l29+Kfwou3Aigf5v39axWr8UVxi1lWm5JGeUFN4uv0P8fFv+4VJOQHiVLxhF xZLg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=8OmDOl+HzY7kcK871zVejMIspdUpfLqTD5KCeutuWtI=; b=keN2owWw5yGJKCvq3YS0pTUYhgCYe7cHYUz0CAv0hKaEpO71vJcQsYZosv2v3UIuS6 jLqlo4+DBI85PSPMa/6r/ar/ZBHzXpjiaM6hNPxKwUDEqN3xc8/fQKuaRX7RTaZsFhpn mh2gjFYOG/Jdi6YKZih1IDmrxQtfgG570KBoFaOvKF8bhrcjONqGLDmpmPtiZCcGPawa s/k0T5xqj5oHMYzKOLnyGWSpd/GwCMZHtMFoBmjhXsDF5q95gmuisTs/vnFvyzq3xxA6 5yySUKF5wj6x21P58so/+vXcMC2XKXFL/E/8jctm67uH7uGKxLHaFmkKL2ztBdFuwkQe cCLA== X-Gm-Message-State: APjAAAXfT8TznNnzF7+SSw+hWLJICS816b4K6ktmfqw6i943+UddKszS gn0lJC+qNWZPjBJ4KDc2mUrBsmmnBihb X-Google-Smtp-Source: APXvYqwN3ACQ2noJKaiSC9xLyVQkZaRwlbZlPfvTuolBVWN/pWc4or7pdoyNb13qvrWpG7kKbhq6JsmksPdy X-Received: by 2002:ac8:1385:: with SMTP id h5mr461391qtj.59.1580321744050; Wed, 29 Jan 2020 10:15:44 -0800 (PST) Date: Wed, 29 Jan 2020 18:15:41 +0000 Message-Id: <20200129181541.105335-1-qperret@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.25.0.341.g760bfbb309-goog Subject: [PATCH v2] 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, qperret@google.com, jeyu@kernel.org 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. 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. Signed-off-by: Quentin Perret --- v2: make sure to quote the whitelist path properly (Nicolas) --- init/Kconfig | 12 ++++++++++++ scripts/adjust_autoksyms.sh | 1 + 2 files changed, 13 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index a34064a031a5..d9c977ef7de5 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2180,6 +2180,18 @@ 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 trimmed 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. + 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" -- 2.25.0.341.g760bfbb309-goog