From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:43782 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753373AbdFSPap (ORCPT ); Mon, 19 Jun 2017 11:30:45 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Paul Burton , linux-mips@linux-mips.org, Ralf Baechle Subject: [PATCH 4.9 55/60] MIPS: Fix bnezc/jialc return address calculation Date: Mon, 19 Jun 2017 23:17:49 +0800 Message-Id: <20170619151646.735443999@linuxfoundation.org> In-Reply-To: <20170619151644.680979056@linuxfoundation.org> References: <20170619151644.680979056@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paul Burton commit 1a73d9310e093fc3adffba4d0a67b9fab2ee3f63 upstream. The code handling the pop76 opcode (ie. bnezc & jialc instructions) in __compute_return_epc_for_insn() needs to set the value of $31 in the jialc case, which is encoded with rs = 0. However its check to differentiate bnezc (rs != 0) from jialc (rs = 0) was unfortunately backwards, meaning that if we emulate a bnezc instruction we clobber $31 & if we emulate a jialc instruction it actually behaves like a jic instruction. Fix this by inverting the check of rs to match the way the instructions are actually encoded. Signed-off-by: Paul Burton Fixes: 28d6f93d201d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC instructions") Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16178/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/branch.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/arch/mips/kernel/branch.c +++ b/arch/mips/kernel/branch.c @@ -804,8 +804,10 @@ int __compute_return_epc_for_insn(struct break; } /* Compact branch: BNEZC || JIALC */ - if (insn.i_format.rs) + if (!insn.i_format.rs) { + /* JIALC: set $31/ra */ regs->regs[31] = epc + 4; + } regs->cp0_epc += 8; break; #endif