From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759401AbbJIASz (ORCPT ); Thu, 8 Oct 2015 20:18:55 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35348 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758952AbbJIARb (ORCPT ); Thu, 8 Oct 2015 20:17:31 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "T.J. Purtell" , "Russell King" Date: Fri, 09 Oct 2015 01:12:28 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 075/107] ARM: 7880/1: Clear the IT state independent of the Thumb-2 mode In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.247 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.72-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: "T.J. Purtell" commit 6ecf830e5029598732e04067e325d946097519cb upstream. The ARM architecture reference specifies that the IT state bits in the PSR must be all zeros in ARM mode or behavior is unspecified. On the Qualcomm Snapdragon S4/Krait architecture CPUs the processor continues to consider the IT state bits while in ARM mode. This makes it so that some instructions are skipped by the CPU. Signed-off-by: T.J. Purtell [rmk+kernel@arm.linux.org.uk: fixed whitespace formatting in patch] Signed-off-by: Russell King Signed-off-by: Ben Hutchings --- arch/arm/kernel/signal.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -486,12 +486,18 @@ setup_return(struct pt_regs *regs, struc */ thumb = handler & 1; - if (thumb) { - cpsr |= PSR_T_BIT; #if __LINUX_ARM_ARCH__ >= 7 - /* clear the If-Then Thumb-2 execution state */ - cpsr &= ~PSR_IT_MASK; + /* + * Clear the If-Then Thumb-2 execution state + * ARM spec requires this to be all 000s in ARM mode + * Snapdragon S4/Krait misbehaves on a Thumb=>ARM + * signal transition without this. + */ + cpsr &= ~PSR_IT_MASK; #endif + + if (thumb) { + cpsr |= PSR_T_BIT; } else cpsr &= ~PSR_T_BIT; }