decoding of multi-byte nops in dtrace

[Fabian Keil]

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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