From patchwork Sun Feb 5 19:20:48 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Willy Tarreau X-Patchwork-Id: 93380 Delivered-To: patch@linaro.org Received: by 10.182.3.34 with SMTP id 2csp1527933obz; Sun, 5 Feb 2017 12:30:47 -0800 (PST) X-Received: by 10.98.200.207 with SMTP id i76mr9269911pfk.38.1486326647578; Sun, 05 Feb 2017 12:30:47 -0800 (PST) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id n5si26959657pgh.185.2017.02.05.12.30.47; Sun, 05 Feb 2017 12:30:47 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754858AbdBEUak (ORCPT + 25 others); Sun, 5 Feb 2017 15:30:40 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:27410 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752120AbdBETWg (ORCPT ); Sun, 5 Feb 2017 14:22:36 -0500 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id v15JLiia008166; Sun, 5 Feb 2017 20:21:44 +0100 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Will Deacon , Willy Tarreau Subject: [PATCH 3.10 061/319] arm64: debug: avoid resetting stepping state machine when TIF_SINGLESTEP Date: Sun, 5 Feb 2017 20:20:48 +0100 Message-Id: <1486322486-8024-32-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1486322486-8024-1-git-send-email-w@1wt.eu> References: <1486322486-8024-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Will Deacon commit 3a402a709500c5a3faca2111668c33d96555e35a upstream. When TIF_SINGLESTEP is set for a task, the single-step state machine is enabled and we must take care not to reset it to the active-not-pending state if it is already in the active-pending state. Unfortunately, that's exactly what user_enable_single_step does, by unconditionally setting the SS bit in the SPSR for the current task. This causes failures in the GDB testsuite, where GDB ends up missing expected step traps if the instruction being stepped generates another trap, e.g. PTRACE_EVENT_FORK from an SVC instruction. This patch fixes the problem by preserving the current state of the stepping state machine when TIF_SINGLESTEP is set on the current thread. Cc: Reported-by: Yao Qi Signed-off-by: Will Deacon Signed-off-by: Willy Tarreau --- arch/arm64/kernel/debug-monitors.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) -- 2.8.0.rc2.1.gbe9624a diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index f4726dc..49e6e30 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -276,8 +276,10 @@ int kernel_active_single_step(void) /* ptrace API */ void user_enable_single_step(struct task_struct *task) { - set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP); - set_regs_spsr_ss(task_pt_regs(task)); + struct thread_info *ti = task_thread_info(task); + + if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP)) + set_regs_spsr_ss(task_pt_regs(task)); } void user_disable_single_step(struct task_struct *task)