decoding of multi-byte nops in dtrace
Fabian Keil
freebsd-listen at fabiankeil.de
Sun Jun 10 13:34:11 UTC 2012
Andriy Gapon <avg at FreeBSD.org> wrote:
> It seems that the $subj is missing :-)
> In my environment that causes many functions to not have fbt return probe,
> because function body decoding fails before 'ret' is found.
>
> Here is my attempt at fixing the problem:
> http://people.freebsd.org/~avg/fbt-nop.patch
> Reviews and suggestions are welcome.
The patch seems to reduce the number of missing
fbt return probes by about 50% for me.
Without the patch:
fk at r500 /usr/src $sudo dtrace -ln fbt::: | grep -c entry
23395
fk at r500 /usr/src $sudo dtrace -ln fbt::: | grep -c return
16739
With the patch (and updated kernel sources):
fk at r500 ~ $sudo dtrace -ln fbt::: | grep -c entry
23409
fk at r500 ~ $sudo dtrace -ln fbt::: | grep -c return
19879
Thanks
Fabian
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