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=-6.5 required=3.0 tests=BAYES_00,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 4CDD7C433DF for ; Fri, 21 Aug 2020 10:22:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 20E46207BB for ; Fri, 21 Aug 2020 10:22:00 +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="nkteX0mG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728556AbgHUKVr (ORCPT ); Fri, 21 Aug 2020 06:21:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728004AbgHUKVo (ORCPT ); Fri, 21 Aug 2020 06:21:44 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1BC46C061385 for ; Fri, 21 Aug 2020 03:21:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=89BOS8Xfm6MesTdxPgzj6ElZtckhCmB4aelY19U2HWU=; b=nkteX0mGbgnag6vGtkcrTJwkSZ 6PKiPxiC1zTu+9elSmVm3S6802HORn7HVcV/kUZ9qdsFJEJVr/BGAFfp3tE0Pgj8tY7ZKTCo+3MNG Bd4m7ErGf1XYauxuvXIgZR1NFQ6yTKXBaoEPr5qmTeupJtzpHLAfDd+v1AlRmlrjhdPtb6xzaAUgL qhHvcj7Yns8Y4LJYED1da4Jc6wi6rrfb6sOnD4Gwuyn1McQ67shhKfeB/6eNXoQ7mk+71xRSUlwgJ BBbX27fRUEE4l8kgL24nHEaMLwHnRI+aJNdv106mEZeRzqe2673eUFnzhsfmZhwyylpxYIdhBT31F sjPJNjsQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k94An-0003G2-2v; Fri, 21 Aug 2020 10:21:25 +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 8CE34306099; Fri, 21 Aug 2020 12:21:24 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 6281E2C8FF36A; Fri, 21 Aug 2020 12:21:24 +0200 (CEST) Message-ID: <20200821102053.102084073@infradead.org> User-Agent: quilt/0.66 Date: Fri, 21 Aug 2020 11:39:18 +0200 From: Peter Zijlstra To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Kyle Huey , Alexandre Chartre , Robert O'Callahan , "Paul E. McKenney" , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Andy Lutomirski , Josh Poimboeuf , Daniel Thompson , Peter Zijlstra Subject: [PATCH v2 6/8] x86/debug: Move historical SYSENTER junk into exc_debug_kernel() References: <20200821093912.815135402@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 The historical SYSENTER junk is explicitly for from-kernel, so move it to the #DB-from-kernel handler. It is ordered after the notifier, this is important for KGDB which uses TF single-step and needs to consume the event before we get here. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/traps.c | 47 ++++++++++++++++++++++++----------------------- 1 file changed, 24 insertions(+), 23 deletions(-) --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -783,17 +783,15 @@ static __always_inline unsigned long deb * * May run on IST stack. */ -static void handle_debug(struct pt_regs *regs, unsigned long dr6) +static bool handle_debug(struct pt_regs *regs, unsigned long *dr6) { struct task_struct *tsk = current; /* Store the virtualized DR6 value */ - tsk->thread.debugreg6 = dr6; + tsk->thread.debugreg6 = *dr6; - if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, 0, - SIGTRAP) == NOTIFY_STOP) { - return; - } + if (notify_die(DIE_DEBUG, "debug", regs, (long)dr6, 0, SIGTRAP) == NOTIFY_STOP) + return true; /* It's safe to allow irq's after DR6 has been saved */ cond_local_irq_enable(regs); @@ -807,30 +805,20 @@ static void handle_debug(struct pt_regs /* * Reload dr6, the notifier might have changed it. */ - dr6 = tsk->thread.debugreg6; - - if (WARN_ON_ONCE((dr6 & DR_STEP) && !user_mode(regs))) { - /* - * Historical junk that used to handle SYSENTER single-stepping. - * This should be unreachable now. If we survive for a while - * without anyone hitting this warning, we'll turn this into - * an oops. - */ - tsk->thread.debugreg6 &= ~DR_STEP; - set_tsk_thread_flag(tsk, TIF_SINGLESTEP); - regs->flags &= ~X86_EFLAGS_TF; - } + *dr6 = tsk->thread.debugreg6; /* * 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. */ - if (dr6 & (DR_STEP | DR_TRAP_BITS) || !dr6) - send_sigtrap(regs, 0, get_si_code(dr6)); + if (*dr6 & (DR_STEP | DR_TRAP_BITS) || !*dr6) + send_sigtrap(regs, 0, get_si_code(*dr6)); out: cond_local_irq_disable(regs); + + return false; } static __always_inline void exc_debug_kernel(struct pt_regs *regs, @@ -873,7 +861,20 @@ static __always_inline void exc_debug_ke if (!dr6) goto out; - handle_debug(regs, dr6); + if (handle_debug(regs, &dr6)) + goto out; + + if (WARN_ON_ONCE(dr6 & DR_STEP)) { + /* + * Historical junk that used to handle SYSENTER single-stepping. + * This should be unreachable now. If we survive for a while + * without anyone hitting this warning, we'll turn this into + * an oops. + */ + dr6 &= ~DR_STEP; + set_thread_flag(TIF_SINGLESTEP); + regs->flags &= ~X86_EFLAGS_TF; + } out: instrumentation_end(); @@ -903,7 +904,7 @@ static __always_inline void exc_debug_us irqentry_enter_from_user_mode(regs); instrumentation_begin(); - handle_debug(regs, dr6); + handle_debug(regs, &dr6); instrumentation_end(); irqentry_exit_to_user_mode(regs);