Re: user-space tracing on Debian... or..?

[Lukas Berk <lberk at redhat dot com>]

Hey,

[...]
> Error:
> Pass 1: parsed user script and 97 library script(s) using
> 216852virt/35972res/2972shr/33668data kb, in 230usr/50sys/507real ms.
> semantic error: while resolving probe point: identifier 'process' at
> test.stp:2:7
>         source: probe process("./test").function("main").return
>                       ^
> 
> semantic error: process return probes not available [man
> error::inode-uprobes]
> Pass 2: analyzed script: 0 probe(s), 0 function(s), 0 embed(s), 0 global(s)
> using 217908virt/37272res/3116shr/34724data kb, in 10usr/10sys/27real ms.
> Pass 2: analysis failed.  [man error::pass2]
> 
> From what I understand is that it has something to do with the fact that
> Systemtap uses Uprobes instead of Utrace in newer kernels. Is there any way
> I can run probes of this type? Or is there a workaround to be able to run a
> probe with the same effect?

Taken from the error::inode-uprobes man page;
function.return probes
  process.function().return probes require "return-probes" or "uretprobes"
functionality, that has not been implemented yet in the kernel.  Until  it
is re-added, consider using process.statement() probes placed on source
line numbers at the function's return statements.

It may also be possible to use the --runtime=dyninst option to use
function.return style probes, however I'm not sure on the state of
dyninst on debian.  So for script portability it might be worth using the
process.statement approach.

Please let us know if any of the error:: man page entries are unclear
and we'll do our best to make them more precise and/or readable.

Cheers,

Lukas

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