[Bug runtime/28378] semantic error: process return probes not available [man error::inode-uprobes]

["mark at klomp dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28378

--- Comment #6 from Mark Wielaard <mark at klomp dot org> ---
(In reply to Nylon Chen from comment #5)
> but my stap has other error
> "semantic error: while processing probe tp_syscall.read.return from:
> nd_syscall.read.return from: syscall.read.return from: syscall.read.return"

Right, but that seems a totally other issue than you originally reported.
If you were using syscall probes then you really should have added that to the
original report. I suspect other issues you are seeing might also come from not
providing the full script you are using.

Might I again suggest you upgrade your system to something more modern and/or
contact Ubuntu support about the kernel/systemtap combination they are shipping
to make sure they are compatible.

> I try to reduce this stap script
> 
> ```
> ...
> 
> probe syscall.write { write_fds[tid()] = fd }
> 
> probe syscall.write.return {
>   p = pid()
>   // Get fd even if non-dwarf syscall return probe.
>   fd = write_fds[tid()]
>   delete write_fds[tid()]
>   bytes = retval
>   time = gettimeofday_us() - @entry(gettimeofday_us())
>   if (bytes > 0)
>     filewrite[p, fd] <<< bytes
>   time_io[p, fd] <<< time
> }
> 
> ...
> ```
> 
> the error message point out the problem is "syscall.xxx.return"
> 
> I try to comment (/**/) it, and the compiler's result is ok
> 
> I just curious about this result.

Right, since your systemtap/kernel doesn't support return probes you cannot use
@entry in your script. Since you already have an syscall entry probe I suggest
to record the time in the same way you record the write_fds.

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