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=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 EF8F3C4363A for ; Tue, 27 Oct 2020 09:44:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4BDA622265 for ; Tue, 27 Oct 2020 09:44:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="vz+ye3AB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2895837AbgJ0Joc (ORCPT ); Tue, 27 Oct 2020 05:44:32 -0400 Received: from merlin.infradead.org ([205.233.59.134]:38470 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2895821AbgJ0Job (ORCPT ); Tue, 27 Oct 2020 05:44:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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=XdIEkBr7sDLhWAZDeKeH5tPyKdV7Qd0PyKAPdl+F/ws=; b=vz+ye3AB3ljYu7T2htIgHyltRP JSuhty7SBzj8kWU/udRTfSJZFWpCzJebklLyHxzgrtPA0OU8E+iCEemJI2Xd5CJrKNVbS5B6jcZtK b5sdcfmCjupVoiU5KsyPu72xArCsG4YaOXfgIS7nVkaovm+1FS7nq8oWHzvdyCwOSqoFA+B4ruxks 8B0Bdk9G0GacdjWwVDJNBMeMFEbnfgdy8NoaBoeRN+RtGF9wQ364jnbk0mPvKdJ8Sguxtadi+G5ry sxeIhCqpQ3ehob4MO1Z5Cfy2FCtrWZMQe3U3yRT+TBcECHQxXnLJY8QrX+ZxRxZQ+xG+Xogke0oS7 2IFA/7wg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kXLWF-0005AL-Mp; Tue, 27 Oct 2020 09:43:55 +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 46DB630411F; Tue, 27 Oct 2020 10:43:53 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 307B82B7AC14F; Tue, 27 Oct 2020 10:43:53 +0100 (CET) Message-ID: <20201027093608.096535386@infradead.org> User-Agent: quilt/0.66 Date: Tue, 27 Oct 2020 10:15:07 +0100 From: Peter Zijlstra To: tglx@linutronix.de, luto@kernel.org, me@kylehuey.com Cc: x86@kernel.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, rocallahan@gmail.com, alexandre.chartre@oracle.com, paulmck@kernel.org, frederic@kernel.org, pbonzini@redhat.com, sean.j.christopherson@intel.com, mhiramat@kernel.org, pmladek@suse.com, joel@joelfernandes.org, rostedt@goodmis.org, boris.ostrovsky@oracle.com, jgross@suse.com, brgerst@gmail.com, jpoimboe@redhat.com, daniel.thompson@linaro.org, julliard@winehq.org, pgofman@codeweavers.com, peterz@infradead.org Subject: [PATCH 3/3] x86/debug: Fix PTRACE_{BLOCK,SINGLE}STEP vs ptrace_get_debugreg(6) References: <20201027091504.712183781@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit d53d9bc0cf78 ("x86/debug: Change thread.debugreg6 to thread.virtual_dr6") changed the semantics of the variable from random collection of bits, to exactly only those bits that ptrace() needs. Unfortunately we lost DR_STEP for PTRACE_{BLOCK,SINGLE}STEP. Fixes: d53d9bc0cf78 ("x86/debug: Change thread.debugreg6 to thread.virtual_dr6") Reported-by: Kyle Huey Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/ptrace.h | 2 ++ arch/x86/kernel/step.c | 9 +++++++++ arch/x86/kernel/traps.c | 2 +- 3 files changed, 12 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -355,6 +355,8 @@ static inline unsigned long regs_get_ker #define arch_has_block_step() (boot_cpu_data.x86 >= 6) #endif +extern unsigned long user_dr_step(unsigned long dr6); + #define ARCH_HAS_USER_SINGLE_STEP_REPORT struct user_desc; --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -235,3 +235,12 @@ void user_disable_single_step(struct tas if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF)) task_pt_regs(child)->flags &= ~X86_EFLAGS_TF; } + +unsigned long user_dr_step(unsigned long dr6) +{ + if (test_thread_flag(TIF_BLOCKSTEP) || + test_thread_flag(TIF_SINGLESTEP)) + return dr6 & DR_STEP; + + return 0; +} --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -940,7 +940,7 @@ static __always_inline void exc_debug_us * Clear the virtual DR6 value, ptrace() routines will set bits here * for things it wants signals for. */ - current->thread.virtual_dr6 = 0; + current->thread.virtual_dr6 = user_dr_step(dr6); /* * The SDM says "The processor clears the BTF flag when it