From mboxrd@z Thu Jan 1 00:00:00 1970 From: Milian Wolff Subject: Re: perf trace: Problems initializing symbol libraries! Date: Tue, 17 May 2016 09:51:44 +0200 Message-ID: <27102286.6frB0TEpAH@milian-kdab2> References: <2323271.hRPH2PSKxc@milian-kdab2> <1849423.FYp0BrzLMo@agathebauer> <20160516201359.GB3455@kernel.org> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart6447973.oYRdr1UEkZ"; micalg="sha1"; protocol="application/pkcs7-signature" Return-path: Received: from mail.kdab.com ([176.9.126.58]:41652 "EHLO mail.kdab.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932222AbcEQHvv (ORCPT ); Tue, 17 May 2016 03:51:51 -0400 In-Reply-To: <20160516201359.GB3455@kernel.org> Sender: linux-perf-users-owner@vger.kernel.org List-ID: To: Arnaldo Carvalho de Melo Cc: linux-perf-users@vger.kernel.org --nextPart6447973.oYRdr1UEkZ Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Monday, May 16, 2016 5:13:59 PM CEST Arnaldo Carvalho de Melo wrote: > Em Mon, May 16, 2016 at 01:31:48PM +0200, Milian Wolff escreveu: > > On Donnerstag, 12. Mai 2016 15:10:44 CEST Arnaldo Carvalho de Melo wrote: > > > Em Thu, May 12, 2016 at 02:05:35PM +0200, Milian Wolff escreveu: > > > > I'm getting the following error when trying to run `perf trace` built > > > > from > > > > acme's perf/core branch on an Ubuntu 16.04 machine: > > > > > > > > $ perf trace > > > > Problems initializing symbol libraries! > > Ok, so with the perf tool that comes with ubuntu 16.04 I get: > > acme@ubuntu:~$ perf record ls > WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted, > check /proc/sys/kernel/kptr_restrict. > > Samples in kernel functions may not be resolved if a suitable vmlinux > file is not found in the buildid cache or in the vmlinux path. > > Samples in kernel modules won't be resolved at all. > > If some relocation was applied (e.g. kexec) symbols may be misresolved > even with a suitable vmlinux or kallsyms file. > > Cannot read kernel map > Couldn't record kernel reference relocation symbol > Symbol resolution may be skewed if relocation was used (e.g. kexec). > Check /proc/kallsyms permission or run as root. > git perf.data > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.002 MB perf.data (14 samples) ] > acme@ubuntu:~$ > > Which is a better message than: > > acme@ubuntu:~$ perf trace > Error: No permissions to read > /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit) Hint: Try > 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing' > > acme@ubuntu:~$ sudo mount -o remount,mode=755 /sys/kernel/debug/tracing > acme@ubuntu:~$ perf trace > Error: No permissions to read > /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit) Hint: Try > 'sudo mount -o remount,mode=755 /sys/kernel/debug/tracing' > > acme@ubuntu:~$ sudo mount -o remount,mode=755 /sys/kernel/debug > acme@ubuntu:~$ perf trace > Problems initializing symbol libraries! > acme@ubuntu:~$ > > So, if I follow the instructions given in the 'perf record ls' case: > > acme@ubuntu:~$ sudo sh -c "echo 0 > /proc/sys/kernel/kptr_restrict" > acme@ubuntu:~$ perf trace > Error: Operation not permitted. > Hint: Check /proc/sys/kernel/perf_event_paranoid setting. > Hint: For system wide tracing it needs to be set to -1. > Hint: Try: 'sudo sh -c "echo -1 > /proc/sys/kernel/ perf_event_paranoid"' > Hint: The current value is 1. > acme@ubuntu:~$ > > It gets a bit better, then, one more step... > > acme@ubuntu:~$ perf trace --ev sched:sched_switch -e nanosleep sleep 1 > 0.938 ( 0.025 ms): sleep/7461 nanosleep(rqtp: 0x7ffc77ca6310 > ) ... 0.938 ( ): > sched:sched_switch:prev_comm=sleep prev_pid=7461 prev_prio=120 prev_state=S > ==> next_comm=swapper/1 next_pid=0 next_prio=120) 1001.076 (1000.163 ms): > sleep/7461 ... [continued]: nanosleep()) = 0 acme@ubuntu:~$ > > So, the problem is not with what is in my perf/core branch, its that ubuntu > 16.04's kernel comes with kptr_restrict defaulting to 1, I have to get that > warning emitted by 'perf record' into 'perf trace'. Thanks a lot Arnaldo, that makes it work for me. I'll include the line to set kptr_restrict to 0 into my "perf init" script that elevates the restrictions. Thanks again -- Milian Wolff | milian.wolff@kdab.com | Software Engineer KDAB (Deutschland) GmbH&Co KG, a KDAB Group company Tel: +49-30-521325470 KDAB - The Qt Experts --nextPart6447973.oYRdr1UEkZ Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIUdzCCBGYw ggNOoAMCAQICEFEmCpMc4n+cw6VfeeByroIwDQYJKoZIhvcNAQEFBQAwgZMxCzAJBgNVBAYTAlVT MQswCQYDVQQIEwJVVDEXMBUGA1UEBxMOU2FsdCBMYWtlIENpdHkxHjAcBgNVBAoTFVRoZSBVU0VS VFJVU1QgTmV0d29yazEhMB8GA1UECxMYaHR0cDovL3d3dy51c2VydHJ1c3QuY29tMRswGQYDVQQD ExJVVE4gLSBEQVRBQ29ycCBTR0MwHhcNMDUwNjA3MDgwOTEwWhcNMTkwNjI0MTkwNjMwWjBvMQsw CQYDVQQGEwJTRTEUMBIGA1UEChMLQWRkVHJ1c3QgQUIxJjAkBgNVBAsTHUFkZFRydXN0IEV4dGVy bmFsIFRUUCBOZXR3b3JrMSIwIAYDVQQDExlBZGRUcnVzdCBFeHRlcm5hbCBDQSBSb290MIIBIjAN BgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAt/caM+byAAQtOeBOW+0fvGwPzbX6I7bO3psRM5ek 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