From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753401AbbFQIw5 (ORCPT ); Wed, 17 Jun 2015 04:52:57 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:33809 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751526AbbFQIww (ORCPT ); Wed, 17 Jun 2015 04:52:52 -0400 Message-ID: <5581355B.3010906@hitachi.com> Date: Wed, 17 Jun 2015 17:52:43 +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: hekuang , Arnaldo Carvalho de Melo , He Kuang CC: a.p.zijlstra@chello.nl, mingo@redhat.com, namhyung@kernel.org, wangnan0@huawei.com, linux-kernel@vger.kernel.org Subject: Re: Re: [PATCH] perf probe: Fix failure to probe events on arm References: <1434355613-110216-1-git-send-email-hekuang@huawei.com> <20150615144911.GA5845@kernel.org> <55804023.1080409@zoho.com> In-Reply-To: <55804023.1080409@zoho.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 On 2015/06/17 0:26, hekuang wrote: > hi, Arnaldo > > On 06/15/2015 10:49 PM, Arnaldo Carvalho de Melo wrote: >> Em Mon, Jun 15, 2015 at 08:06:53AM +0000, He Kuang escreveu: >>> Fix failure to probe events on arm, problem is introduced by commit >>> 5a51fcd1f30c ("perf probe: Skip kernel symbols which is out of >>> .text"). For some architectures, label '_etext' is not in the .text >>> section(in .notes section for arm/arm64). Label out of .text section is >>> not loaded as symbols and we got a zero value when look up its address, >>> which causes all events be wrongly skiped. >>> >>> This patch uses kernel map->end when failed to get the address of >>> '_etext' and fixes the problem. >> Masami, can't we always use map->end then? Can you please take a look at >> this patch and ack/nack it? >> >> - Arnaldo > > I think _etext is more accurate than kernel map->end, because > __map_groups__fixup_end() is called at the end of > dso__load_sym(), which fixes map->end to next_map->start. > > Comparative result as this: > etext_addr=ffffffff819a1b85, map->end=ffffffff81ff1000. > > So if possible, we should use _etext. Hmm, this seems to have another problem. If etext_addr != map->end, we can't relay on that. Is there any good way to get the ".text" address range from symbol map? Until we find it, I'd rather like to skip checking text address range on arm, because it looks meaningless :( Thank you, > > Thanks. >> >>> Problem can be reproduced on arm as following: >>> >>> # perf probe --add='generic_perform_write' >>> generic_perform_write+0 is out of .text, skip it. >>> Probe point 'generic_perform_write' not found. >>> Error: Failed to add events. Reason: No such file or directory (Code: -2) >>> >>> After this patch: >>> >>> # perf probe --add='generic_perform_write' >>> Added new event: >>> probe:generic_perform_write (on generic_perform_write) >>> >>> You can now use it in all perf tools, such as: >>> >>> perf record -e probe:generic_perform_write -aR sleep 1 >>> >>> Signed-off-by: He Kuang >>> --- >>> tools/perf/util/probe-event.c | 16 +++++++++++++++- >>> 1 file changed, 15 insertions(+), 1 deletion(-) >>> >>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c >>> index daa24a2..ee26961 100644 >>> --- a/tools/perf/util/probe-event.c >>> +++ b/tools/perf/util/probe-event.c >>> @@ -575,8 +575,22 @@ static int post_process_probe_trace_events(struct probe_trace_event *tevs, >>> pr_warning("Relocated base symbol is not found!\n"); >>> return -EINVAL; >>> } >>> - /* Get the address of _etext for checking non-probable text symbol */ >>> + /* Get the address of _etext for checking non-probable text symbol, >>> + for some architectures (e.g. arm, arm64), _etext is out of .text >>> + section and not loaded as symbols, use kernel map->end instead. >>> + */ >>> etext_addr = kernel_get_symbol_address_by_name("_etext", false); >>> + if (etext_addr == 0) { >>> + struct map *map; >>> + >>> + map = kernel_get_module_map(NULL); >>> + if (!map) { >>> + pr_err("Failed to get a map for kernel\n"); >>> + return -EINVAL; >>> + } >>> + >>> + etext_addr = map->end; >>> + } >>> >>> for (i = 0; i < ntevs; i++) { >>> if (tevs[i].point.address && !tevs[i].point.retprobe) { >>> -- >>> 1.8.5.2 >> -- >> 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/ >> > > > -- > 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