From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759344AbbJIASt (ORCPT ); Thu, 8 Oct 2015 20:18:49 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35336 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758945AbbJIARb (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, "Tony Lindgren" , "Russell King" , "Grazvydas Ignotas" , "H. Nikolaus Schaller" Date: Fri, 09 Oct 2015 01:12:28 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 076/107] ARM: fix Thumb2 signal handling when ARMv6 is enabled 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: Russell King commit 9b55613f42e8d40d5c9ccb8970bde6af4764b2ab upstream. When a kernel is built covering ARMv6 to ARMv7, we omit to clear the IT state when entering a signal handler. This can cause the first few instructions to be conditionally executed depending on the parent context. In any case, the original test for >= ARMv7 is broken - ARMv6 can have Thumb-2 support as well, and an ARMv6T2 specific build would omit this code too. Relax the test back to ARMv6 or greater. This results in us always clearing the IT state bits in the PSR, even on CPUs where these bits are reserved. However, they're reserved for the IT state, so this should cause no harm. Fixes: d71e1352e240 ("Clear the IT state when invoking a Thumb-2 signal handler") Acked-by: Tony Lindgren Tested-by: H. Nikolaus Schaller Tested-by: Grazvydas Ignotas Signed-off-by: Russell King Signed-off-by: Ben Hutchings --- arch/arm/kernel/signal.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -486,12 +486,17 @@ setup_return(struct pt_regs *regs, struc */ thumb = handler & 1; -#if __LINUX_ARM_ARCH__ >= 7 +#if __LINUX_ARM_ARCH__ >= 6 /* - * 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. + * 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. + * + * We must do this whenever we are running on a Thumb-2 + * capable CPU, which includes ARMv6T2. However, we elect + * to do this whenever we're on an ARMv6 or later CPU for + * simplicity. */ cpsr &= ~PSR_IT_MASK; #endif