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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 878E3C10F25 for ; Mon, 9 Mar 2020 20:27:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6274520828 for ; Mon, 9 Mar 2020 20:27:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583785637; bh=Cp2OSP+6393xKUwgxAT6OGHAr/9fHNhb62H4ClztTX8=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=FKQnrD2fVBvOtpd63DYgjT04jsCcP+fO+vNF4FqOluI/+vS/+w0wp3ADUyv2kL7RO nU5Nb6g5xUDWvisVeriMT/aPV/DFs0Qwdb/+yoo8qJFciV/B2wXO77jOkd7A4eOnkm ApiyLMQzoMQ2JKCTtIemktTbAgIdQFybTVRRmmds= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726307AbgCIU1Q (ORCPT ); Mon, 9 Mar 2020 16:27:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:51476 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725992AbgCIU1Q (ORCPT ); Mon, 9 Mar 2020 16:27:16 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2675620409; Mon, 9 Mar 2020 20:27:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583785635; bh=Cp2OSP+6393xKUwgxAT6OGHAr/9fHNhb62H4ClztTX8=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=wKWOOwaEs7ml5tl0PLrde2wyBO0l8WOs6GCqSpiDv0Aq14wakbNp25Y0Hn0MFW2Nx osCbeJkh/eNAAvRDA3k098kq5lRApEBb9lMfioQKyS6mddhlx8eB0mWTgRRaBzmFpL EW/OI6UcUFaELfFoNFy8LQ6Wm0MndX2RcOrZgsI4= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id EB47E3522730; Mon, 9 Mar 2020 13:27:14 -0700 (PDT) Date: Mon, 9 Mar 2020 13:27:14 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, kernel-team@fb.com, mingo@kernel.org, elver@google.com, andreyknvl@google.com, glider@google.com, dvyukov@google.com, cai@lca.pw, boqun.feng@gmail.com Subject: Re: [PATCH kcsan 26/32] kcsan, trace: Make KCSAN compatible with tracing Message-ID: <20200309202714.GT2935@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200309190359.GA5822@paulmck-ThinkPad-P72> <20200309190420.6100-26-paulmck@kernel.org> <20200309155722.49d6bb93@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200309155722.49d6bb93@gandalf.local.home> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 09, 2020 at 03:57:22PM -0400, Steven Rostedt wrote: > On Mon, 9 Mar 2020 12:04:14 -0700 > paulmck@kernel.org wrote: > > > From: Marco Elver > > > > Previously the system would lock up if ftrace was enabled together with > > KCSAN. This is due to recursion on reporting if the tracer code is > > instrumented with KCSAN. > > > > To avoid this for all types of tracing, disable KCSAN instrumentation > > for all of kernel/trace. > > > > Furthermore, since KCSAN relies on udelay() to introduce delay, we have > > to disable ftrace for udelay() (currently done for x86) in case KCSAN is > > used together with lockdep and ftrace. The reason is that it may corrupt > > lockdep IRQ flags tracing state due to a peculiar case of recursion > > (details in Makefile comment). > > > > Signed-off-by: Marco Elver > > Reported-by: Qian Cai > > Cc: Paul E. McKenney > > Cc: Steven Rostedt > > Acked-by: Steven Rostedt (VMware) Applied, thank you! Thanx, Paul > -- Steve > > > Signed-off-by: Paul E. McKenney > > Tested-by: Qian Cai > > --- > > arch/x86/lib/Makefile | 5 +++++ > > kernel/kcsan/Makefile | 2 ++ > > kernel/trace/Makefile | 3 +++ > > 3 files changed, 10 insertions(+) > > > > diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile > > index 432a077..6110bce7 100644 > > --- a/arch/x86/lib/Makefile > > +++ b/arch/x86/lib/Makefile > > @@ -8,6 +8,11 @@ KCOV_INSTRUMENT_delay.o := n > > > > # KCSAN uses udelay for introducing watchpoint delay; avoid recursion. > > KCSAN_SANITIZE_delay.o := n > > +ifdef CONFIG_KCSAN > > +# In case KCSAN+lockdep+ftrace are enabled, disable ftrace for delay.o to avoid > > +# lockdep -> [other libs] -> KCSAN -> udelay -> ftrace -> lockdep recursion. > > +CFLAGS_REMOVE_delay.o = $(CC_FLAGS_FTRACE) > > +endif > > > > # Early boot use of cmdline; don't instrument it > > ifdef CONFIG_AMD_MEM_ENCRYPT > > diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile > > index df6b779..d4999b3 100644 > > --- a/kernel/kcsan/Makefile > > +++ b/kernel/kcsan/Makefile > > @@ -4,6 +4,8 @@ KCOV_INSTRUMENT := n > > UBSAN_SANITIZE := n > > > > CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE) > > +CFLAGS_REMOVE_debugfs.o = $(CC_FLAGS_FTRACE) > > +CFLAGS_REMOVE_report.o = $(CC_FLAGS_FTRACE) > > > > CFLAGS_core.o := $(call cc-option,-fno-conserve-stack,) \ > > $(call cc-option,-fno-stack-protector,) > > diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile > > index 0e63db6..9072486 100644 > > --- a/kernel/trace/Makefile > > +++ b/kernel/trace/Makefile > > @@ -6,6 +6,9 @@ ifdef CONFIG_FUNCTION_TRACER > > ORIG_CFLAGS := $(KBUILD_CFLAGS) > > KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS)) > > > > +# Avoid recursion due to instrumentation. > > +KCSAN_SANITIZE := n > > + > > ifdef CONFIG_FTRACE_SELFTEST > > # selftest needs instrumentation > > CFLAGS_trace_selftest_dynamic.o = $(CC_FLAGS_FTRACE) >