From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757249Ab3LWKuS (ORCPT ); Mon, 23 Dec 2013 05:50:18 -0500 Received: from mail4.hitachi.co.jp ([133.145.228.5]:58640 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755151Ab3LWKuR (ORCPT ); Mon, 23 Dec 2013 05:50:17 -0500 Message-ID: <52B81562.5000607@hitachi.com> Date: Mon, 23 Dec 2013 19:50:10 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Namhyung Kim Cc: Arnaldo Carvalho de Melo , Ingo Molnar , Srikar Dronamraju , David Ahern , lkml , "Steven Rostedt (Red Hat)" , Oleg Nesterov , "David A. Long" , systemtap@sourceware.org, yrl.pp-manager.tt@hitachi.com Subject: Re: [PATCH -tip 3/3] perf-probe: Use the actual address as a hint for uprobes References: <20131220100255.7169.19384.stgit@kbuild-fedora.novalocal> <20131220100302.7169.96318.stgit@kbuild-fedora.novalocal> <20131220180351.GC28878@ghostprotocols.net> <52B75F9E.7000802@hitachi.com> <87wqiwc8ly.fsf@sejong.aot.lge.com> In-Reply-To: <87wqiwc8ly.fsf@sejong.aot.lge.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2013/12/23 16:46), Namhyung Kim wrote: > On Mon, 23 Dec 2013 06:54:38 +0900, Masami Hiramatsu wrote: >> (2013/12/21 3:03), Arnaldo Carvalho de Melo wrote: >>> Em Fri, Dec 20, 2013 at 10:03:02AM +0000, Masami Hiramatsu escreveu: >> BTW, I'm not sure why debuginfo and nm shows symbol address + 0x400000, >> and why the perf's map/symbol can remove this offset. Could you tell me >> how it works? >> If I can get the offset (0x400000) from binary, I don't need this kind >> of ugly hacks... > > AFAIK the actual symbol address is what nm (and debuginfo) shows. But > perf adjusts symbol address to have a relative address from the start of > mapping (i.e. file offset) like below: > > sym.st_value -= shdr.sh_addr - shdr.sh_offset; Thanks! this is what I really need! > This way, we can handle mmap and symbol address almost uniformly > (i.e. ip = map->start + symbol->address). But this requires the mmap > event during perf record. For perf probe, we might need to synthesize > mapping info from the section/segment header since it doesn't have the > mmap event. Currently, the dso__new_map() just creates a map starts > from 0. I think the uprobe requires only the relative address, doesn't that? Thank you, -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com