From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752357AbcEIUG2 (ORCPT ); Mon, 9 May 2016 16:06:28 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54865 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752136AbcEIT5S (ORCPT ); Mon, 9 May 2016 15:57:18 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Anton Blanchard , Michael Ellerman , Kamal Mostafa Subject: [PATCH 4.2.y-ckt 33/59] powerpc: Fix bad inline asm constraint in create_zero_mask() Date: Mon, 9 May 2016 12:55:51 -0700 Message-Id: <1462823777-8384-34-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1462823777-8384-1-git-send-email-kamal@canonical.com> References: <1462823777-8384-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 4.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.2.8-ckt10 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Anton Blanchard commit b4c112114aab9aff5ed4568ca5e662bb02cdfe74 upstream. In create_zero_mask() we have: addi %1,%2,-1 andc %1,%1,%2 popcntd %0,%1 using the "r" constraint for %2. r0 is a valid register in the "r" set, but addi X,r0,X turns it into an li: li r7,-1 andc r7,r7,r0 popcntd r4,r7 Fix this by using the "b" constraint, for which r0 is not a valid register. This was found with a kernel build using gcc trunk, narrowed down to when -frename-registers was enabled at -O2. It is just luck however that we aren't seeing this on older toolchains. Thanks to Segher for working with me to find this issue. Fixes: d0cebfa650a0 ("powerpc: word-at-a-time optimization for 64-bit Little Endian") Signed-off-by: Anton Blanchard Signed-off-by: Michael Ellerman Signed-off-by: Kamal Mostafa --- arch/powerpc/include/asm/word-at-a-time.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/word-at-a-time.h b/arch/powerpc/include/asm/word-at-a-time.h index 5b3a903..7043539 100644 --- a/arch/powerpc/include/asm/word-at-a-time.h +++ b/arch/powerpc/include/asm/word-at-a-time.h @@ -77,7 +77,7 @@ static inline unsigned long create_zero_mask(unsigned long bits) "andc %1,%1,%2\n\t" "popcntd %0,%1" : "=r" (leading_zero_bits), "=&r" (trailing_zero_bit_mask) - : "r" (bits)); + : "b" (bits)); return leading_zero_bits; } -- 2.7.4