From patchwork Mon Jan 25 20:42:10 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josh Poimboeuf X-Patchwork-Id: 12044351 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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 6C0E3C433E0 for ; Mon, 25 Jan 2021 20:53:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1996822582 for ; Mon, 25 Jan 2021 20:53:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732148AbhAYUxa (ORCPT ); Mon, 25 Jan 2021 15:53:30 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:28708 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726648AbhAYUns (ORCPT ); Mon, 25 Jan 2021 15:43:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611607341; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=ZgDCZSeGhmRWWHT5vzy2jb80PxnR6l3Ybnpj6nBPRRM=; b=Tspy7zkrs7mBKrZOOHw8cC/HRAeL4eFq40ciOPeYRyFFOSprOfSA3jtFpdHZ7SycgoOwWE dlJkK3SZXqx2PW4DTHMWE5N+f77MNc2XLgvbs5/Ix8wqX2BtD1dvljsIm5WPYk5+Vc/qQI FmlBzI+Gss283+bkZKTS1J6sAXG/0RQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-504-9rCtESvLMP-ekps1qOjHfQ-1; Mon, 25 Jan 2021 15:42:19 -0500 X-MC-Unique: 9rCtESvLMP-ekps1qOjHfQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6F3EB800592; Mon, 25 Jan 2021 20:42:18 +0000 (UTC) Received: from treble.redhat.com (ovpn-120-118.rdu2.redhat.com [10.10.120.118]) by smtp.corp.redhat.com (Postfix) with ESMTP id F39576F44E; Mon, 25 Jan 2021 20:42:16 +0000 (UTC) From: Josh Poimboeuf To: Kees Cook Cc: linux-kernel@vger.kernel.org, Masahiro Yamada , Michal Marek , linux-hardening@vger.kernel.org, linux-kbuild@vger.kernel.org, Peter Zijlstra , Justin Forbes , Ondrej Mosnacek Subject: [PATCH RFC] gcc-plugins: Handle GCC version mismatch for OOT modules Date: Mon, 25 Jan 2021 14:42:10 -0600 Message-Id: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org When building out-of-tree kernel modules, the build system doesn't require the GCC version to match the version used to build the original kernel. That's probably [1] fine. In fact, for many distros, the version of GCC used to build the latest kernel doesn't necessarily match the latest released GCC, so a GCC mismatch turns out to be pretty common. And with CONFIG_MODVERSIONS it's probably more common. So a lot of users have come to rely on being able to use a different version of GCC when building OOT modules. But with GCC plugins enabled, that's no longer allowed: cc1: error: incompatible gcc/plugin versions cc1: error: failed to initialize plugin ./scripts/gcc-plugins/structleak_plugin.so That error comes from the plugin's call to plugin_default_version_check(), which strictly enforces the GCC version. The strict check makes sense, because there's nothing to prevent the GCC plugin ABI from changing -- and it often does. But failing the build isn't necessary. For most plugins, OOT modules will otherwise work just fine without the plugin instrumentation. When a GCC version mismatch is detected, print a warning and disable the plugin. The only exception is the RANDSTRUCT plugin which needs all code to see the same struct layouts. In that case print an error. [1] Ignoring, for the moment, that the kernel now has toolchain-dependent kconfig options, which can silently disable features and cause havoc when compiler versions differ, or even when certain libraries are missing. This is a separate problem which also needs to be addressed. Reported-by: Ondrej Mosnacek Signed-off-by: Josh Poimboeuf --- scripts/Makefile.gcc-plugins | 19 +++++++++++++++++++ scripts/Makefile.kcov | 11 +++++++++++ 2 files changed, 30 insertions(+) diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 952e46876329..7227692fba59 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -51,6 +51,25 @@ export DISABLE_ARM_SSP_PER_TASK_PLUGIN GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) # The sancov_plugin.so is included via CFLAGS_KCOV, so it is removed here. GCC_PLUGINS_CFLAGS := $(filter-out %/sancov_plugin.so, $(GCC_PLUGINS_CFLAGS)) + +# Out-of-tree module check: If there's a GCC version mismatch, disable plugins +# and print a warning. Otherwise the OOT module build will fail due to +# plugin_default_version_check(). +ifneq ($(GCC_PLUGINS_CFLAGS),) + ifneq ($(KBUILD_EXTMOD),) + ifneq ($(CONFIG_GCC_VERSION), $(shell $(srctree)/scripts/gcc-version.sh $(HOSTCXX))) + + ifdef CONFIG_GCC_PLUGIN_RANDSTRUCT + $(error error: CONFIG_GCC_PLUGIN_RANDSTRUCT requires out-of-tree modules to be built using the same GCC version as the kernel.) + endif + + $(warning warning: Disabling GCC plugins for out-of-tree modules due to GCC version mismatch.) + $(warning warning: The following plugins have been disabled: $(gcc-plugin-y)) + GCC_PLUGINS_CFLAGS := + endif + endif +endif + export GCC_PLUGINS_CFLAGS # Add the flags to the build! diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov index 67e8cfe3474b..63a2bc2aabb2 100644 --- a/scripts/Makefile.kcov +++ b/scripts/Makefile.kcov @@ -3,4 +3,15 @@ kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC) += -fsanitize-coverage=trace-pc kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS) += -fsanitize-coverage=trace-cmp kcov-flags-$(CONFIG_GCC_PLUGIN_SANCOV) += -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so +# Out-of-tree module check for GCC version mismatch. +# See the similar check in scripts/Makefile.gcc-plugins +ifneq ($(CONFIG_GCC_PLUGIN_SANCOV),) + ifneq ($(KBUILD_EXTMOD),) + ifneq ($(CONFIG_GCC_VERSION), $(shell $(srctree)/scripts/gcc-version.sh $(HOSTCXX))) + $(warning warning: Disabling CONFIG_GCC_PLUGIN_SANCOV for out-of-tree modules due to GCC version mismatch.) + kcov-flags-y := $(filter-out %/sancov_plugin.so, $(kcov-flags-y)) + endif + endif +endif + export CFLAGS_KCOV := $(kcov-flags-y)