Re: trace_printk() support in trace-cmd
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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.
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