Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753731AbbEKMDA (ORCPT ); Mon, 11 May 2015 08:03:00 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:59941 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753094AbbEKMCy (ORCPT ); Mon, 11 May 2015 08:02:54 -0400 Message-ID: <55509A67.1040704@hitachi.com> Date: Mon, 11 May 2015 21:02:47 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: He Kuang , Ingo Molnar CC: a.p.zijlstra@chello.nl, acme@kernel.org, jolsa@kernel.org, mingo@redhat.com, wangnan0@huawei.com, linux-kernel@vger.kernel.org Subject: Re: Re: [PATCH v3 3/3] perf probe: Show better error message when failed to find variable References: <1431336304-16863-1-git-send-email-hekuang@huawei.com> <1431336304-16863-3-git-send-email-hekuang@huawei.com> <20150511093010.GA31869@gmail.com> <555079CF.40701@huawei.com> <20150511095052.GA7441@gmail.com> <55508149.8040404@huawei.com> In-Reply-To: <55508149.8040404@huawei.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2708 Lines: 82 On 2015/05/11 19:15, He Kuang wrote: > > > On 2015/5/11 17:50, Ingo Molnar wrote: >> * He Kuang wrote: >> >>> Hi, Ingo >>> >>> On 2015/5/11 17:30, Ingo Molnar wrote: >>>> * He Kuang wrote: >>>> >>>>> Indicate to check variable location range in error message when we got >>>>> failed to find the variable. >>>>> >>>>> Before this patch: >>>>> >>>>> $ perf probe --add 'generic_perform_write+118 bytes' >>>>> Failed to find the location of bytes at this address. >>>>> Perhaps, it has been optimized out. >>>>> Error: Failed to add events. >>>>> >>>>> After this patch: >>>>> $ perf probe --add 'generic_perform_write+118 bytes' >>>>> Failed to find the location of bytes at this address. >>>> What does this sentence mean? I thought 'address' means 'location of >>>> bytes'. So the address identifies the location and obviously we know >>>> that. So this message wants to say something else. >>> 'generic_perform_write' is a function name, while 'bytes' is a local >>> variable in this function. Maybe the variable I chose make you confused. >>> >>> This maybe clear: >>> Failed to find the location of 'bytes' at this address. >> Yeah, absolutely! This highlights the importance of putting >> user-supplied symbols into quotes and such. >> >> Maybe even write: >> >> Failed to find the location of the 'bytes' variable at this address. OK, He, could you also include this fix? Thank you, >> >> Another question: what does 'generic_perform_write+118' mean here? Why >> the offset? > > This is for setting a kprobe at the location has an offset of 118 > bytes to the entry of the function 'generic_perform_write'. > > In the previous patch: https://lkml.org/lkml/2015/5/11/170, > we show a valid byte offset range of variables in scope, 118 is > an invalid address which can be read from the result, this offset > is just for showing the error message. > >> >> Thanks, >> >> Ingo >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ >> > > > -- Masami HIRAMATSU Linux Technology Research Center, System Productivity Research Dept. Center for Technology Innovation - Systems Engineering Hitachi, Ltd., Research & Development Group E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/