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Re: nd_syscalls for ARM


On 03/14/2011 12:19 PM, Turgis, Frederic wrote:
> Hi,
> 
> Registers.stp is not defined for ARM therefore we can't use int_arg(), pointer_arg()
> definitions for ARM, especially we can't use nd_syscall.
> - has anyone proposed to port it ?
> 
> - if I had to set a priority on this work (and convince Linaro), how useful would you
> rate it, from past experience on your own architecture ?

Fred,

If you've got some spare time, defining registers.stp for ARM would be
useful.

Having said that...

The nd_syscall probes haven't really gotten a whole lot of attention
lately, since there are some broken things there that can't be easily
fixed.  See pr11424
(<http://sourceware.org/bugzilla/show_bug.cgi?id=11424>) for details,
but basically the '?' (optional) and '!' (optional and sufficient) probe
operators don't work for kprobe.function probes.  I'm unsure of how much
the kprobe.function stuff is used these days.

When possible, I try to keep the syscall tapset and the nd_syscall
tapset in sync.  But, sometimes it just isn't possible.

Bug pr11424 causes several nd_syscall failures (the syscall tapset and
the nd_syscall tapset should have the same number of passes/failures,
but the nd_syscall tapset has several more failures).

There are probably some spots in the tapsets that could use some arm
attention, one being target_set.stp.  For this to work for arm, you'll
need to either define register.stp or add some conditionals to let it
use the syscall probes (instead of the nd_syscall probes).  It would
probably be a good idea to make a pass through all of the '%(arch' code
and see what needs doing for ARM.

-- 
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)


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