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Re: stap error: no match while resolving probe point kernel.function("do_mmap_pgoff@mm/mmap.c:901")
2010/2/22 PrzemysÅaw PaweÅczyk <przemyslaw@pawelczyk.it>:
> Not all local variables are accessible in stap scripts. It depends on
> many things:
> - what compiler really does with them,
> - how good debuginfo compiler generates,
> - is elfutils able to fully (and correctly) recognize this debuginfo,
> - maybe even something more I don't remember now.
The consequence of the first point is that it depends also on a probe
location, i.e. some variables are available only in specific parts of
functions.
> OTOH you obviously aren't interested in the initial value of the
> variable, which is already known, so e.g.
> 'kernel.function("do_mmap_pgoff@mm/mmap.c+205")' would be more
> interesting assuming correct_wcount availability.
I (and you before) made a mistake using kernel.function for
line-oriented probing. Mark has already posted an explanation.
On Mon, Feb 22, 2010 at 13:13, Mark Wielaard <mjw@redhat.com> wrote:
> If you need to try at a specific line, instead of at the function start,
> then you might also try a kernel.statement probe instead of a
> kernel.function probe.
Therefore there is a hope that:
stap -L 'kernel.statement("do_mmap_pgoff@mm/mmap.c+205")'
will show you correct_wcount.
Regards.
--
PrzemysÅaw PaweÅczyk