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

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Date:	Thu, 4 Aug 2016 09:50:25 +0800
From:	"Wangnan (F)" <wangnan0@...wei.com>
To:	Masami Hiramatsu <mhiramat@...nel.org>
CC:	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 2016/8/4 7:08, Masami Hiramatsu wrote:
> 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
>


Have you checked 'readelf -wi'? I guess you wouldn't find
sys_epoll_wait.

Thank you.