linux-kernel - Re: perf probe -L on ubuntu 16.04

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Date:	Thu, 19 May 2016 11:00:39 +0900
From:	Masami Hiramatsu <mhiramat@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: perf probe -L on ubuntu 16.04

On Mon, 16 May 2016 22:56:36 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Hi Masami,
> 
> 	Have you ever tried using 'perf probe' on ubuntu?
> 
> acme@...ntu:~/git/linux$ sudo apt-cache search linux-image-$(uname -r)
> linux-image-4.4.0-21-generic - Linux kernel image for version 4.4.0 on
> 64 bit x86 SMP
> linux-image-4.4.0-21-generic-dbgsym - Linux kernel debug image for
> version 4.4.0 on 64 bit x86 SMP
> acme@...ntu:~/git/linux$ 
> acme@...ntu:~/git/linux$ 
> 
> So those are installed, but then I try:
> 
> 
> root@...ntu:~# perf probe -vvv -L getname_flags
> Looking at the vmlinux_path (8 entries long)
> Using /usr/lib/debug/boot/vmlinux-4.4.0-21-generic for symbols
> Open Debuginfo file: /usr/lib/debug/boot/vmlinux-4.4.0-21-generic
> fname: /build/linux-Ay7j_C/linux-4.4.0/fs/namei.c, lineno:125
> New line range: 125 to 2147483647
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> Get 3665 lines from this CU
> path: /build/linux-Ay7j_C/linux-4.4.0/fs/namei.c
> Failed to find source file path.
>   Error: Failed to show lines. Reason: No such file or directory (Code: -2)
> root@...ntu:~# 
> 
> Couldn't find the source code files, which is the case:
> 
> acme@...ntu:~/git/linux$ dpkg -L linux-image-$(uname -r)-dbgsym | grep
> '\.c'
> acme@...ntu:~/git/linux$ dpkg -L linux-image-$(uname -r)-dbgsym | grep
> '\.ko' | tail -2
> /usr/lib/debug/lib/modules/4.4.0-21-generic/kernel/crypto/pcbc.ko
> /usr/lib/debug/lib/modules/4.4.0-21-generic/kernel/crypto/crc32.ko
> acme@...ntu:~/git/linux$ 
> 
> Have to dig deeper to see where the source code is, ideas?

It shows the "path" is ;
> path: /build/linux-Ay7j_C/linux-4.4.0/fs/namei.c

So, would you have the source code under this temporary directory?
(yeah, I guess No)
Anyway, ubuntu has "linux-source" package, or apt source linux-image-`uname -r`
will give you the source tree in current dir.

After you get a proper kernel source code, you can use -s to show source code.

    -s, --source <directory>
                          path to kernel source

I ensured it is working correctly by below command.
$ perf probe -s ./linux-4.4.0 -L getname_flags

Enjoy! :)



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