From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752395AbeBBO4F (ORCPT ); Fri, 2 Feb 2018 09:56:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:53296 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751643AbeBBOz6 (ORCPT ); Fri, 2 Feb 2018 09:55:58 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 406392178E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=acme@kernel.org Date: Fri, 2 Feb 2018 11:55:56 -0300 From: Arnaldo Carvalho de Melo To: Borislav Petkov Cc: Matthew Whitehead , peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/perf : Add check for CPUID instruction before using Message-ID: <20180202145556.GE26905@kernel.org> References: <1517581851-6600-1-git-send-email-tedheadster@gmail.com> <20180202143731.ohtpa4kh4twtj7yo@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180202143731.ohtpa4kh4twtj7yo@pd.tnic> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Fri, Feb 02, 2018 at 03:37:31PM +0100, Borislav Petkov escreveu: > On Fri, Feb 02, 2018 at 09:30:51AM -0500, Matthew Whitehead wrote: > > We still officially support the ancient i486 cpu. First generation > > versions of this processor do not have the CPUID instruction, though > > later versions do. Therefore you must check that the cpu supports > > it before using it. At present it fails with an "Illegal Instruction" > > signal on the early processors. > > > > This code was based on similar code in the gcc package. > > > > Signed-off-by: Matthew Whitehead > > --- > > tools/perf/arch/x86/util/header.c | 51 +++++++++++++++++++++++++++++++++++++++ > > tools/perf/util/header.h | 2 ++ > > 2 files changed, 53 insertions(+) > > > > diff --git a/tools/perf/arch/x86/util/header.c b/tools/perf/arch/x86/util/header.c > > index fb0d71afee8b..d4d12894c64d 100644 > > --- a/tools/perf/arch/x86/util/header.c > > +++ b/tools/perf/arch/x86/util/header.c > > @@ -7,6 +7,54 @@ > > > > #include "../../util/header.h" > > > > +/* This code based on gcc cpuid.h __get_cpuid_max() */ > > +unsigned int have_cpuid(void) > > You could've copied have_cpuid_p() from arch/x86/kernel/cpu/common.c > > > +{ > > + unsigned int __eax, __ebx; > > + > > +#ifndef __x86_64__ > > +/* See if we can use cpuid. On AMD64 we always can. */ > > +#if __GNUC__ >= 3 > > + __asm__ ("pushf{l|d}\n\t" > > + "pushf{l|d}\n\t" > > + "pop{l}\t%0\n\t" > > + "mov{l}\t{%0, %1|%1, %0}\n\t" > > + "xor{l}\t{%2, %0|%0, %2}\n\t" > > + "push{l}\t%0\n\t" > > + "popf{l|d}\n\t" > > + "pushf{l|d}\n\t" > > + "pop{l}\t%0\n\t" > > + "popf{l|d}\n\t" > > + : "=&r" (__eax), "=&r" (__ebx) > > + : "i" (0x00200000)); > > +#else > > +/* Host GCCs older than 3.0 weren't supporting Intel asm syntax > > + * nor alternatives in i386 code. > > We don't support gcc < 3 > > #if GCC_VERSION < 30200 > # error Sorry, your compiler is too old - please upgrade it. > #endif > > There's even talk currently to raise the minimum version to 4.9 or so. But this is for the kernel build process, right? If we don't have a strict reason to forbid archeology... 8-) - Arnaldo