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[209.132.180.67]) by mx.google.com with ESMTP id h18si349356otk.227.2020.02.17.07.25.40; Mon, 17 Feb 2020 07:25:53 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=vmX0bhk8; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728696AbgBQPWG (ORCPT + 99 others); Mon, 17 Feb 2020 10:22:06 -0500 Received: from mail-wr1-f66.google.com ([209.85.221.66]:38101 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727533AbgBQPWG (ORCPT ); Mon, 17 Feb 2020 10:22:06 -0500 Received: by mail-wr1-f66.google.com with SMTP id y17so20193811wrh.5 for ; Mon, 17 Feb 2020 07:22:03 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=IUWp4SkyLItoviNWg0X5RFOhBbayzqtWbjEcxmFScDY=; b=vmX0bhk8RT87WRMMTfXKylvEUBqgF04aBWw4VMbFI/Px/MCSycqwFBu1CXnE1S9/gE u1vgJMC7Fk5fSbEJvfaQgTj/vXCxMRSrMLw2uKJOhpJNdWBPiXijg9zLzOTShMAgFoUV oOunjY3RY/XW20FVT6FE5vx6ZeNfouB/57K4eC3V89k8T+HRybbT2o3YoYhP2jyMxGgf AkouZDCiFULTKy/OyyT0C9x20vc2CQ2s4G67U8Jhtl7ifDkGG1OsD+7HyXnrnhfpVEo8 c+ntfhUWjUlq6ijf1rL2rfcE+V/V1pPaIZf1MA0M46ntz202XOWUsu3tLznGiqWKlaEV NQ+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=IUWp4SkyLItoviNWg0X5RFOhBbayzqtWbjEcxmFScDY=; b=ZmadNg3mIEEv8FUQyC35BX8RM8ZdP9o4VW+6sNzYganUQiB+FeBcQnkvpzWw1jQFb4 YKw6/ABO5b1ccWdW7PrAV4/B8ftP0N//Xaa7DoeBdKiWWd4katQldYu+aAReDXoyQ03e vQVo5ybhO9mGstz9eiquK1zj/gPNANVSX63jl0fcwuMAhFYeWqatukaiq51OpCNtcE+P EDXm8aHbGeyZYsj94Zqp+gCM7s9D67MTFQlZ3+peCGSEUQrc0pasbJMJluSkXLsE4GPc zGsD+Ky46PvxM7FH+3Pxl12v6brtAzEuT8P53OHR0sxk1wq4hjNMYpb6vZB+Q9hk91++ JNpQ== X-Gm-Message-State: APjAAAUqdRnkQwCXngYQGyR3+Sez8QijKNNfllafnc8UVgQ9R4/REW8t U3YQsjhqrC3tjR4iFZ4qpQyC0g== X-Received: by 2002:adf:ecd0:: with SMTP id s16mr22245577wro.325.1581952922518; Mon, 17 Feb 2020 07:22:02 -0800 (PST) Received: from google.com ([2a00:79e0:d:210:e8f7:125b:61e9:733d]) by smtp.gmail.com with ESMTPSA id q1sm1491719wrw.5.2020.02.17.07.22.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Feb 2020 07:22:01 -0800 (PST) Date: Mon, 17 Feb 2020 15:22:01 +0000 From: Matthias Maennich To: Quentin Perret Cc: masahiroy@kernel.org, nico@fluxnic.net, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, kernel-team@android.com, jeyu@kernel.org, hch@infradead.org Subject: Re: [PATCH v4 1/3] kbuild: allow symbol whitelisting with TRIM_UNUSED_KSYMS Message-ID: <20200217152201.GA48466@google.com> References: <20200212202140.138092-1-qperret@google.com> <20200212202140.138092-2-qperret@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200212202140.138092-2-qperret@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 12, 2020 at 08:21:38PM +0000, 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 >--- > init/Kconfig | 13 +++++++++++++ > scripts/adjust_autoksyms.sh | 5 +++++ > 2 files changed, 18 insertions(+) > >diff --git a/init/Kconfig b/init/Kconfig >index cfee56c151f1..58b672afceb2 100644 >--- a/init/Kconfig >+++ b/init/Kconfig >@@ -2210,6 +2210,19 @@ 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..93f4d10e66e6 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 > >+# Use 'eval' to expand the whitelist path and check if it is relative >+eval ksym_wl="${CONFIG_UNUSED_KSYMS_WHITELIST:-/dev/null}" >+[ "${ksym_wl:0:1}" = "/" ] || 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" | In case the whitelist file can't be found, the error message is cat: path/to/file: file not found I wonder whether we can make this error message a bit more specific by telling the user that the KSYMS_WHITELIST is missing. With the above addressed (and your amend for the absolute path test), please feel free to add Tested-by: Matthias Maennich Reviewed-by: Matthias Maennich Cheers, Matthias > sort -u | > sed -e 's/\(.*\)/#define __KSYM_\1 1/' >> "$new_ksyms_file" > >-- >2.25.0.225.g125e21ebc7-goog >