From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on gnuweeb.org X-Spam-Level: X-Spam-Status: No, score=-6.2 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.6 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by gnuweeb.org (Postfix) with ESMTPS id 12D327FD23 for ; Thu, 16 Jun 2022 16:44:18 +0000 (UTC) Authentication-Results: gnuweeb.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=t/4p6pGt; dkim-atps=neutral Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id CA877615B5; Thu, 16 Jun 2022 16:44:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A1E6C34114; Thu, 16 Jun 2022 16:44:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655397856; bh=EolkjpCPZI2MjBzt62Su7lhjjW4xiamLc2eTna4D4RY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=t/4p6pGthRLYB+t18wzKMBvG8YhBSmOj9OtlHdRZkkzCg6TPbfVT8Ym9er2q+OG/T eU5+83JXJEKYQUx/QfhsWf37Dp7FF1iKXdivRNJra/69Vw+popfCVdqFGw90ruWGPR dZTvPbCQ7oUJXojmCDmvO1AOOW2IKp1m5X9pbW2IYE10EWjb7spFHlCFQI9H23suvy 9LNu+aVdWeUD7Mi9cjocgqhLlSEMBpqZoT6Qp0r6r7DaA+HCQbNR4s+qfLMezv5Tf5 oN/ocqb4jVxWj1pdBu8t2496S3rgRAm/yaldO+WHgA735SDWRM/MIkHZsEsv7UXoIa uTsl0FD9FSzQw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 1DDD05C0546; Thu, 16 Jun 2022 09:44:16 -0700 (PDT) Date: Thu, 16 Jun 2022 09:44:16 -0700 From: "Paul E. McKenney" To: Marco Elver Cc: kernel test robot , Frederic Weisbecker , kbuild-all@lists.01.org, GNU/Weeb Mailing List , linux-kernel@vger.kernel.org, dvyukov@google.com Subject: Re: [ammarfaizi2-block:paulmck/linux-rcu/pmladek.2022.06.15a 133/140] vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section Message-ID: <20220616164416.GA2130702@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <202206160411.v3iL3YC0-lkp@intel.com> <20220615204039.GI1790663@paulmck-ThinkPad-P17-Gen-1> <20220615211717.GA972937@paulmck-ThinkPad-P17-Gen-1> <20220616134021.GP1790663@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220616134021.GP1790663@paulmck-ThinkPad-P17-Gen-1> List-Id: On Thu, Jun 16, 2022 at 06:40:21AM -0700, Paul E. McKenney wrote: > On Thu, Jun 16, 2022 at 10:19:18AM +0200, Marco Elver wrote: > > On Wed, 15 Jun 2022 at 23:17, Paul E. McKenney wrote: > > > > > > On Wed, Jun 15, 2022 at 01:40:39PM -0700, Paul E. McKenney wrote: > > > > On Thu, Jun 16, 2022 at 04:26:16AM +0800, kernel test robot wrote: > > > > > tree: https://github.com/ammarfaizi2/linux-block paulmck/linux-rcu/pmladek.2022.06.15a > > > > > head: 0ba7324b44282870af740a5a121add62c7f5f730 > > > > > commit: db21b02f8044e812f8a5e3811f602409290e3ede [133/140] context_tracking: Convert state to atomic_t > > > > > config: x86_64-randconfig-r003-20220516 (https://download.01.org/0day-ci/archive/20220616/202206160411.v3iL3YC0-lkp@intel.com/config) > > > > > compiler: gcc-11 (Debian 11.3.0-3) 11.3.0 > > > > > reproduce (this is a W=1 build): > > > > > # https://github.com/ammarfaizi2/linux-block/commit/db21b02f8044e812f8a5e3811f602409290e3ede > > > > > git remote add ammarfaizi2-block https://github.com/ammarfaizi2/linux-block > > > > > git fetch --no-tags ammarfaizi2-block paulmck/linux-rcu/pmladek.2022.06.15a > > > > > git checkout db21b02f8044e812f8a5e3811f602409290e3ede > > > > > # save the config file > > > > > mkdir build_dir && cp config build_dir/.config > > > > > make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash > > > > > > > > > > If you fix the issue, kindly add following tag where applicable > > > > > Reported-by: kernel test robot > > > > > > > > > > All warnings (new ones prefixed by >>): > > > > > > > > > > >> vmlinux.o: warning: objtool: __ct_user_exit+0x41: call to __kasan_check_read() leaves .noinstr.text section > > > > > >> vmlinux.o: warning: objtool: __ct_user_enter+0x7f: call to __kasan_check_read() leaves .noinstr.text section > > > > > > > > Marco, Dmitry, my guess is that this is due to the ct->active check in > > > > both functions. Are we supposed to do something to make this sort of > > > > thing safe for KASAN? > > > > > > This time actually CCing Marco and Dmitry... > > > > It's due to the atomic_read()s within the noinstr function. Within > > noinstr you can use arch_atomic_read() to avoid the instrumentation. > > Thank you, will fix! And please see below for an alleged fix. Thanx, Paul ------------------------------------------------------------------------ commit 81e24ca26ee9933bcacf67a61e3f6ae41a025442 Author: Paul E. McKenney Date: Thu Jun 16 09:30:37 2022 -0700 context_tracking: Use arch_atomic_read() in __ct_state for KASAN Context tracking's __ct_state() function can be invoked from noinstr state where RCU is not watching. This means that its use of atomic_read() causes KASAN to invoke the non-noinstr __kasan_check_read() function from the noinstr function __ct_state(). This is problematic because someone tracing the __kasan_check_read() function could get a nasty surprise because of RCU not watching. This commit therefore replaces the __ct_state() function's use of atomic_read() with arch_atomic_read(), which KASAN does not attempt to add instrumention to. Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Marco Elver diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h index 0aecc07fb4f50..81c51e5f03143 100644 --- a/include/linux/context_tracking_state.h +++ b/include/linux/context_tracking_state.h @@ -49,7 +49,7 @@ DECLARE_PER_CPU(struct context_tracking, context_tracking); static __always_inline int __ct_state(void) { - return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK; + return arch_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK; } #endif