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Re: kernel read fault when accessing context variables
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: tonyg362 <tonyg3622 at yahoo dot com>
- Cc: systemtap at sourceware dot org
- Date: Thu, 08 Jul 2010 11:01:31 -0400
- Subject: Re: kernel read fault when accessing context variables
- References: <29099754.post@talk.nabble.com>
tonyg362 <tonyg3622@yahoo.com> writes:
> [...]
> I am able access $npid->tgid just fine and it prints the correct npid,
> however whenever I try to access $prev->tgid the entire probe is skipped and
> I get a kernel read fault:
>
> SystemTap translator/driver (version 0.9.8/0.141 non-git sources)
> [...]
> ERROR: kernel read fault at 0x000000000000029d (addr) near identifier
> '$prev' at test.stp:2:9
There are a couple of possible workarounds and fixes for the cause,
most likely incorrect debugging data.
1) run your script with --skip-badvars
2) with modern systemtap, wrap your $var accessing code in try {} catch {}
3) try building your kernel with gcc 4.5 or Red Hat's 4.4.4
VTA-enabled backports
- FChE