problem tracing open syscalls

[Martin Hunt]

On Sun, 2007-02-25 at 21:18 +0100, Andreas Kostyrka wrote:
> One additional thing are the skipped probes, however one wants to
> interpret it:
> open 4485 <unknown>
> open 4485 <unknown>
> open 4485 <unknown>
> WARNING: Number of errors: 0, skipped probes: 2073
> Pass 5: run completed in 60usr/110sys/34870real ms.

If you are only seeing <unknown>, it is likely that a gcc bug is putting
the wrong address for filename in the kernel debuginfo.  Attempting to
access that address is causing a page fault, which systemtap handles.
Because it is not safe to sleep, systemtap returns an error for the
attempted userspace copy. Somehow that error is also getting counted as
a "skipped probe", which is a bug.

Martin