From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756826AbbFPP1d (ORCPT ); Tue, 16 Jun 2015 11:27:33 -0400 Received: from sender1.zohomail.com ([74.201.84.158]:21486 "EHLO sender153-mail.zoho.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756305AbbFPP1Z (ORCPT ); Tue, 16 Jun 2015 11:27:25 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=zapps768; d=zoho.com; h=subject:to:references:cc:from:message-id:date:user-agent:mime-version:in-reply-to:content-type; b=RvvSpS5UY54b0Zmd/jos3SVvVg2WKnnVPynFZHVWTMcqWYEp3SBs02WArQNaJ2MAI3nTs0rPPUIe dBV2fo3dizEmMhWw6xAD3kLnCi9I76DxhXae4jkbDwRmCUowF+Fw Subject: Re: [PATCH] perf probe: Fix failure to probe events on arm To: Arnaldo Carvalho de Melo , He Kuang , Masami Hiramatsu References: <1434355613-110216-1-git-send-email-hekuang@huawei.com> <20150615144911.GA5845@kernel.org> Cc: a.p.zijlstra@chello.nl, mingo@redhat.com, namhyung@kernel.org, wangnan0@huawei.com, linux-kernel@vger.kernel.org From: hekuang Message-ID: <55804023.1080409@zoho.com> Date: Tue, 16 Jun 2015 23:26:27 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 MIME-Version: 1.0 In-Reply-To: <20150615144911.GA5845@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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/ >