Re: Systemtap user space probing issue - Unknown symbol in module

[David Smith <dsmith at redhat dot com>]

On 07/18/2016 05:58 AM, buddhika chamith wrote:
> Hi All,
> 
> Not sure if this has been addressed before. Checked the archive and
> couldn't find a solution there. I tried user space probing with
> Systemtap 3.0. But it gives me the following error.
> 
> $ sudo stap -e 'probe process("./h264ref").function("*") { printf("hello\n"); }'
> ERROR: Couldn't insert module
> '/tmp/stapsPVPF2/stap_b964ab648506800b700ce82c4e1cf5cd_167937.ko':
> Unknown symbol in module
> WARNING: /usr/bin/staprun exited with status: 1
> Pass 5: run failed.  [man error::pass5]
> Tip: /usr/share/doc/systemtap/README.Debian should help you get started.

... stuff deleted ...

> What do I need to do in order to fix this?

The first thing to try would be to see if your systemtap installation
can run simple systemtap scripts. The error you see of "Unknown symbol
in module" makes me doubt that it can. Can you look in your kernel logs
to see if the unknown symbol is actually listed?

Let's try the most basic systemtap script possible:

# stap -ve 'probe begin { printf("hello world\n"); exit() }'

Let's try a bit more challenging script:

# stap -ve 'probe nd_syscall.read { printf("hello world\n"); exit() }'

If those 2 scripts work, then we'll look at your executable you are
trying to probe. Was your 'h264ref' executable compiled with debugging
info (-g)?

Try the following:

# stap -vL 'process("./h264ref").function("*")'

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
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