From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:33996 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933372AbeDKSxw (ORCPT ); Wed, 11 Apr 2018 14:53:52 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Matthias Kaehlcke , Grant Grundler , Greg Hackmann , Kees Cook , Linus Torvalds , Michael Davidson , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH 4.9 006/310] x86/mm/kaslr: Use the _ASM_MUL macro for multiplication to work around Clang incompatibility Date: Wed, 11 Apr 2018 20:32:25 +0200 Message-Id: <20180411183622.563621237@linuxfoundation.org> In-Reply-To: <20180411183622.305902791@linuxfoundation.org> References: <20180411183622.305902791@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: Matthias Kaehlcke [ Upstream commit 121843eb02a6e2fa30aefab64bfe183c97230c75 ] The constraint "rm" allows the compiler to put mix_const into memory. When the input operand is a memory location then MUL needs an operand size suffix, since Clang can't infer the multiplication width from the operand. Add and use the _ASM_MUL macro which determines the operand size and resolves to the NUL instruction with the corresponding suffix. This fixes the following error when building with clang: CC arch/x86/lib/kaslr.o /tmp/kaslr-dfe1ad.s: Assembler messages: /tmp/kaslr-dfe1ad.s:182: Error: no instruction mnemonic suffix given and no register operands; can't size instruction Signed-off-by: Matthias Kaehlcke Cc: Grant Grundler Cc: Greg Hackmann Cc: Kees Cook Cc: Linus Torvalds Cc: Michael Davidson Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170501224741.133938-1-mka@chromium.org Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/asm.h | 1 + arch/x86/lib/kaslr.c | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-) --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -34,6 +34,7 @@ #define _ASM_ADD __ASM_SIZE(add) #define _ASM_SUB __ASM_SIZE(sub) #define _ASM_XADD __ASM_SIZE(xadd) +#define _ASM_MUL __ASM_SIZE(mul) #define _ASM_AX __ASM_REG(ax) #define _ASM_BX __ASM_REG(bx) --- a/arch/x86/lib/kaslr.c +++ b/arch/x86/lib/kaslr.c @@ -5,6 +5,7 @@ * kernel starts. This file is included in the compressed kernel and * normally linked in the regular. */ +#include #include #include #include @@ -79,7 +80,7 @@ unsigned long kaslr_get_random_long(cons } /* Circular multiply for better bit diffusion */ - asm("mul %3" + asm(_ASM_MUL "%3" : "=a" (random), "=d" (raw) : "a" (random), "rm" (mix_const)); random += raw;