From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F26C2C0650F for ; Tue, 30 Jul 2019 07:54:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CEDF2206A2 for ; Tue, 30 Jul 2019 07:54:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730694AbfG3Hyn (ORCPT ); Tue, 30 Jul 2019 03:54:43 -0400 Received: from mga05.intel.com ([192.55.52.43]:55879 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726432AbfG3Hyn (ORCPT ); Tue, 30 Jul 2019 03:54:43 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Jul 2019 00:54:42 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,326,1559545200"; d="scan'208";a="171845359" Received: from ahunter-desktop.fi.intel.com (HELO [10.237.72.122]) ([10.237.72.122]) by fmsmga008.fm.intel.com with ESMTP; 30 Jul 2019 00:54:39 -0700 Subject: Re: [PATCH 3/3] Fix insn.c misaligned address error To: Masami Hiramatsu Cc: Arnaldo Carvalho de Melo , Numfor Mbiziwo-Tiapo , peterz@infradead.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, songliubraving@fb.com, mbd@fb.com, linux-kernel@vger.kernel.org, irogers@google.com, eranian@google.com References: <20190724184512.162887-1-nums@google.com> <20190724184512.162887-4-nums@google.com> <20190726193806.GB24867@kernel.org> <20190727184638.3263eb76c3cbde95f9896210@kernel.org> <2bc0fcc6-0477-ba1d-7418-5497efa7d571@intel.com> <20190730094745.f5d6e7fa062e09d70b643801@kernel.org> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: Date: Tue, 30 Jul 2019 10:53:19 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190730094745.f5d6e7fa062e09d70b643801@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/07/19 3:47 AM, Masami Hiramatsu wrote: > On Mon, 29 Jul 2019 11:22:34 +0300 > Adrian Hunter wrote: > >> On 27/07/19 12:46 PM, Masami Hiramatsu wrote: >>> On Fri, 26 Jul 2019 16:38:06 -0300 >>> Arnaldo Carvalho de Melo wrote: >>> >>>> Em Wed, Jul 24, 2019 at 11:45:12AM -0700, Numfor Mbiziwo-Tiapo escreveu: >>>>> The ubsan (undefined behavior sanitizer) version of perf throws an >>>>> error on the 'x86 instruction decoder - new instructions' function >>>>> of perf test. >>>>> >>>>> To reproduce this run: >>>>> make -C tools/perf USE_CLANG=1 EXTRA_CFLAGS="-fsanitize=undefined" >>>>> >>>>> then run: tools/perf/perf test 62 -v >>>>> >>>>> The error occurs in the __get_next macro (line 34) where an int is >>>>> read from a potentially unaligned address. Using memcpy instead of >>>>> assignment from an unaligned pointer. >>>> >>>> Since this came from the kernel, don't we have to fix it there as well? >>>> Masami, Adrian? >>> >>> I guess we don't need it, since x86 can access "unaligned address" and >>> x86 insn decoder in kernel runs only on x86. I'm not sure about perf's >>> that part. Maybe if we run it on other arch as cross-arch application, >>> it may cause unaligned pointer issue. >> >> Yes, theoretically Intel PT decoding can be done on any arch. >> >> But the memcpy is probably sub-optimal for x86, so the patch as it stands >> does not seem suitable. I notice the kernel has get_unaligned() and >> put_unaligned(). >> >> Obviously it would be better for a patch to be accepted to >> arch/x86/lib/insn.c also. > > Hmm, then I rather like memcpy() for arch/x86/lib/insn.c, because it runs only > on x86. Yes, I was wrong about memcpy, and it is simpler for perf tools than dragging out get_unaligned().