Re: Listing probe alias resolution failures

[David Smith <dsmith at redhat dot com>]

patm@pdx.edu wrote:
> With (version 0.5.14 built 2007-04-30) of systemtap and kernel 2.6.19.7 
> (i386), there are a lot (~220) of failures in the tapset like the 
> following:
>
> semantic error: no match for probe point while resolving probe point 
> vm.write_shared_copy
>
> To get a list of all of these, I pulled out some code from the systemtap 
> GUI and made a quick standalone java program "listprobes", it works like 
> the following:

I'm not a java programmer, but it appears like you might be expecting 
every function listed in the tapsets to be resolvable on a particular 
kernel.  This isn't the case.  Let's take an easy example - the probe 
alias syscall.open (in tapset/syscalls2.stp):

=============
probe syscall.open =
		kernel.function("sys_open") ?,
		kernel.function("compat_sys_open") ?,
		kernel.function("sys32_open") ?
{
...
}
=============

This probe alias looks for "sys_open" first, then if it doesn't exist 
looks for "compat_sys_open", then looks for "sys32_open".  If "sys_open" 
exists in your kernel, it isn't an error that "compat_sys_open" and 
"sys32_open" do not exist.

In actual use, if you've gotten "no match for probe point" errors let us 
know and we'll try to fix them.

--
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)