linux-kernel - Re: perf test BPF failing on f24: fix

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Date:	Thu, 4 Aug 2016 08:08:00 +0900
From:	Masami Hiramatsu <mhiramat@...nel.org>
To:	Masami Hiramatsu <mhiramat@...nel.org>
Cc:	"Wangnan (F)" <wangnan0@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: perf test BPF failing on f24: fix

On Wed, 3 Aug 2016 23:45:57 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> > > [root@...et ~]# perf probe sys_epoll_wait
> > > Failed to find debug information for address ffffffffbd295b50
> > > Probe point 'sys_epoll_wait' not found.
> > >    Error: Failed to add events.
> 
> So, at least I should investigate it.

FYI, on ubuntu16.04, I can put probes on sys_epoll_wait as below

mhiramat@...note:~/ksrc/linux/tools/perf$ sudo ./perf probe -vnf sys_epoll_wait
probe-definition(0): sys_epoll_wait 
symbol:sys_epoll_wait file:(null) line:0 offset:0 return:0 lazy:(null)
0 arguments
Looking at the vmlinux_path (8 entries long)
Using /usr/lib/debug/boot/vmlinux-4.4.0-31-generic for symbols
Open Debuginfo file: /usr/lib/debug/boot/vmlinux-4.4.0-31-generic
Try to find probe point from debuginfo.
Symbol sys_epoll_wait address found : ffffffff81257410
Matched function: SyS_epoll_wait
found inline addr: 0xffffffff81257410
Probe point found: SyS_epoll_wait+0
found inline addr: 0xffffffff8125756d
Probe point found: SyS_epoll_pwait+141
found inline addr: 0xffffffff81257793
Probe point found: compat_SyS_epoll_pwait+147
Found 3 probe_trace_events.
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: p:probe/sys_epoll_wait _text+2454544
Writing event: p:probe/sys_epoll_wait_1 _text+2454893
Writing event: p:probe/sys_epoll_wait_2 _text+2455443
Added new events:
  probe:sys_epoll_wait (on sys_epoll_wait)
  probe:sys_epoll_wait_1 (on sys_epoll_wait)
  probe:sys_epoll_wait_2 (on sys_epoll_wait)

You can now use it in all perf tools, such as:

	perf record -e probe:sys_epoll_wait_2 -aR sleep 1

-- 
Masami Hiramatsu <mhiramat@...nel.org>