From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965787AbcCJLDn (ORCPT ); Thu, 10 Mar 2016 06:03:43 -0500 Received: from torg.zytor.com ([198.137.202.12]:38040 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965588AbcCJLDZ (ORCPT ); Thu, 10 Mar 2016 06:03:25 -0500 Date: Thu, 10 Mar 2016 03:02:17 -0800 From: tip-bot for Andy Lutomirski Message-ID: Cc: dvlasenk@redhat.com, brgerst@gmail.com, oleg@redhat.com, luto@amacapital.net, andrew.cooper3@citrix.com, hpa@zytor.com, torvalds@linux-foundation.org, peterz@infradead.org, mingo@kernel.org, luto@kernel.org, linux-kernel@vger.kernel.org, bp@alien8.de, tglx@linutronix.de Reply-To: luto@kernel.org, linux-kernel@vger.kernel.org, bp@alien8.de, tglx@linutronix.de, torvalds@linux-foundation.org, peterz@infradead.org, mingo@kernel.org, luto@amacapital.net, hpa@zytor.com, andrew.cooper3@citrix.com, brgerst@gmail.com, dvlasenk@redhat.com, oleg@redhat.com In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/asm] x86/entry/traps: Clear TIF_BLOCKSTEP on all debug exceptions Git-Commit-ID: 81edd9f69a6fd214fdbe66b43de6aa1610c84c63 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 81edd9f69a6fd214fdbe66b43de6aa1610c84c63 Gitweb: http://git.kernel.org/tip/81edd9f69a6fd214fdbe66b43de6aa1610c84c63 Author: Andy Lutomirski AuthorDate: Wed, 9 Mar 2016 19:00:28 -0800 Committer: Ingo Molnar CommitDate: Thu, 10 Mar 2016 09:48:13 +0100 x86/entry/traps: Clear TIF_BLOCKSTEP on all debug exceptions The SDM says that debug exceptions clear BTF, and we need to keep TIF_BLOCKSTEP in sync with BTF. Clear it unconditionally and improve the comment. I suspect that the fact that kmemcheck could cause TIF_BLOCKSTEP not to be cleared was just an oversight. Signed-off-by: Andy Lutomirski Cc: Andrew Cooper Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/fa86e55d196e6dde5b38839595bde2a292c52fdc.1457578375.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/traps.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 410e8e2..1af5621 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -598,6 +598,13 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) dr6 &= ~DR6_RESERVED; /* + * 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_tsk_thread_flag(tsk, TIF_BLOCKSTEP); + + /* * 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. @@ -612,11 +619,6 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code) /* DR6 may or may not be cleared by the CPU */ set_debugreg(0, 6); - /* - * The processor cleared BTF, so don't mark that we need it set. - */ - clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP); - /* Store the virtualized DR6 value */ tsk->thread.debugreg6 = dr6;