Re: trace_printk() support in trace-cmd

[Avi Kivity <avi@redhat.com>]

On 12/12/2010 07:43 PM, Arnaldo Carvalho de Melo wrote:
> Em Sun, Dec 12, 2010 at 07:42:06PM +0200, Avi Kivity escreveu:
> >  On 12/12/2010 07:36 PM, Arnaldo Carvalho de Melo wrote:
> >  >Em Sun, Dec 12, 2010 at 06:35:24PM +0200, Avi Kivity escreveu:
> >  >>   On 11/23/2010 05:45 PM, Steven Rostedt wrote:
> >  >>   >Again, the work around is to replace your trace_printks() with
> >  >>   >__trace_printk(_THIS_IP_, ...) or just modify the trace_printk() macro
> >  >>   >in include/linux/kernel.h to always use the __trace_printk() version.
> >  >>
> >  >>   This works; I'm using it for now (I tried to use 'perf probe', but I
> >  >>   get unpredictable results, like null pointer derefs).
> >  >
> >  >Can you tell us which functions, environment, etc?
> >
> >  Something around 2.6.27-rc4; example functions are FNAME(fetch) in
> >  arch/x86/kvm/paging_tmpl.h; compiled modular (which was Steven's
> >  guess as to why it fails).
> >
> >  (note, the failure is with trace-cmd, not /sys/kernel/debug/tracing).
>
> I mean the "I tried to use 'perf probe'" part.

Well, same, more or less.

   perf probe -m kvm --add 'fetch_access=paging64_fetch 
pt_access=gw->pt_access pte_access=gw->pte_access dirty'

would return garbage for gw->*, and the log would show the exception 
handler called.  gw is most certainly valid.

-- 
error compiling committee.c: too many arguments to function