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=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 54FB3C433DF for ; Wed, 3 Jun 2020 11:42:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3525920738 for ; Wed, 3 Jun 2020 11:42:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="SlUqS3YP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725922AbgFCLmc (ORCPT ); Wed, 3 Jun 2020 07:42:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726016AbgFCLm3 (ORCPT ); Wed, 3 Jun 2020 07:42:29 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB72EC08C5C1 for ; Wed, 3 Jun 2020 04:42:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=YtDsltKEuKDuBSNGU0EYICMCiPeDra4uCaDiVXYzdZw=; b=SlUqS3YPzG753zLpAc4q4lUSXN qW+qjOX9itDRedsa+mjuLMfrLn+XHhB/1Y64UqITi8iGlLB9JfJfTWZZ0i6k38Ty+wIYtEnvdxAv4 7rehbBxfczByXcqzv0HrElYxuR7t28FaTWv9M9Q8ZmVOOzNKnXgtTBnllXtbxH583m/9RpN5cKCCj yXuCqmHIEZn+RfdT4c62vV9JIZgxxETGtmi0KwBssAeeS485mLXyhgqp29yd1Y2hC0hVskIWzOsYm /bT/JG7w96dG6tg/L7T7A/0Cif9YXaHwU5nbNMAPIbqGDZt7bptMyAIREsgIFe4pU0n7ewwA1yUp/ rS8bWXBg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jgRmr-0005jm-RH; Wed, 03 Jun 2020 11:42:26 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 0342C306E4A; Wed, 3 Jun 2020 13:42:24 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id B6147209DB0CC; Wed, 3 Jun 2020 13:42:23 +0200 (CEST) Message-ID: <20200603114052.127756554@infradead.org> User-Agent: quilt/0.66 Date: Wed, 03 Jun 2020 13:40:20 +0200 From: Peter Zijlstra To: tglx@linutronix.de Cc: x86@kernel.org, elver@google.com, paulmck@kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, peterz@infradead.org, will@kernel.org, dvyukov@google.com, glider@google.com, andreyknvl@google.com Subject: [PATCH 6/9] x86/entry: Re-order #DB handler to avoid *SAN instrumentation References: <20200603114014.152292216@infradead.org> MIME-Version: 1.0 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 vmlinux.o: warning: objtool: exc_debug()+0xbb: call to clear_ti_thread_flag.constprop.0() leaves .noinstr.text section vmlinux.o: warning: objtool: noist_exc_debug()+0x55: call to clear_ti_thread_flag.constprop.0() leaves .noinstr.text section Rework things so that handle_debug() looses the noinstr and move the clear_thread_flag() into that. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/traps.c | 55 +++++++++++++++++++++++------------------------- 1 file changed, 27 insertions(+), 28 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -775,26 +775,44 @@ static __always_inline void debug_exit(u * * May run on IST stack. */ -static void noinstr handle_debug(struct pt_regs *regs, unsigned long dr6, - bool user_icebp) +static void handle_debug(struct pt_regs *regs, unsigned long dr6, bool user) { struct task_struct *tsk = current; + bool user_icebp; int si_code; + /* + * The SDM says "The processor clears the BTF flag when it + * generates a debug exception." Clear TIF_BLOCKSTEP to keep + * TIF_BLOCKSTEP in sync with the hardware BTF flag. + */ + clear_thread_flag(TIF_BLOCKSTEP); + + /* + * If DR6 is zero, no point in trying to handle it. The kernel is + * not using INT1. + */ + if (!user && !dr6) + return; + + /* + * If dr6 has no reason to give us about the origin of this trap, + * then it's very likely the result of an icebp/int01 trap. + * User wants a sigtrap for that. + */ + user_icebp = user && !dr6; + /* Store the virtualized DR6 value */ tsk->thread.debugreg6 = dr6; - instrumentation_begin(); #ifdef CONFIG_KPROBES if (kprobe_debug_handler(regs)) { - instrumentation_end(); return; } #endif if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0, SIGTRAP) == NOTIFY_STOP) { - instrumentation_end(); return; } @@ -825,7 +843,6 @@ static void noinstr handle_debug(struct out: cond_local_irq_disable(regs); - instrumentation_end(); } static __always_inline void exc_debug_kernel(struct pt_regs *regs, @@ -834,14 +851,6 @@ static __always_inline void exc_debug_ke nmi_enter(); instrumentation_begin(); trace_hardirqs_off_finish(); - instrumentation_end(); - - /* - * The SDM says "The processor clears the BTF flag when it - * generates a debug exception." Clear TIF_BLOCKSTEP to keep - * TIF_BLOCKSTEP in sync with the hardware BTF flag. - */ - clear_thread_flag(TIF_BLOCKSTEP); /* * Catch SYSENTER with TF set and clear DR_STEP. If this hit a @@ -850,14 +859,8 @@ static __always_inline void exc_debug_ke if ((dr6 & DR_STEP) && is_sysenter_singlestep(regs)) dr6 &= ~DR_STEP; - /* - * If DR6 is zero, no point in trying to handle it. The kernel is - * not using INT1. - */ - if (dr6) - handle_debug(regs, dr6, false); + handle_debug(regs, dr6, false); - instrumentation_begin(); if (regs->flags & X86_EFLAGS_IF) trace_hardirqs_on_prepare(); instrumentation_end(); @@ -868,14 +871,10 @@ static __always_inline void exc_debug_us unsigned long dr6) { idtentry_enter_user(regs); - clear_thread_flag(TIF_BLOCKSTEP); + instrumentation_begin(); - /* - * If dr6 has no reason to give us about the origin of this trap, - * then it's very likely the result of an icebp/int01 trap. - * User wants a sigtrap for that. - */ - handle_debug(regs, dr6, !dr6); + handle_debug(regs, dr6, true); + instrumentation_end(); idtentry_exit_user(regs); }