Re: your fault handler is faulty

["Frank Ch. Eigler" <fche at redhat dot com>]

Hi -

On Tue, Sep 06, 2005 at 12:16:05AM -0700, Martin Hunt wrote:
> [...]
> Most everything I have that does user_string() is now faulting.
> >stap -e 'probe kernel.function("sys_open") {warn("in sys_open");log(user_string($filename))}'
> WARNING: in sys_open
> ERROR: probe faulted near embedded-code at /usr/share/systemtap/tapset/logging.stp:16:28
> [...]

FWIW, I see similar faults during a bunch of other tests, like this one:

global b , a
probe kernel.function("sys_read")
{
  a[b++] = (execname() . " " . pp())
  if (b>100) exit()
}
probe end {
  foreach (aa in a) log(a[aa])
}

> Reverting your latest changes fixes this. WARNING lines alternate
> with valid filenames, so I don't think it is a case where faults
> were simply being ignored before.

Given that the new code is only associated with the kprobes
fault_handler hook, there really should no way the new code can
introduce a regression.  I suspect that there are real problems that
we haven't seen before for some reason.  Perhaps we need a plain C
kprobes equivalents to demonstrate the problem.

- FChE