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Thread: IA64 trap code 16 bytes atomic copy on montecito, take 2




IA64 trap code 16 bytes atomic copy on montecito, take 2
user name
2006-11-03 01:55:49
Keshavamurthy, Anil wrote on Thursday, November 02, 2006
5:32 PM
> > > But I can't see how you plan to *remove* the
breakpoint and restore the
> > > original instruction.
> 
> Restoring the break is very simple, just restore back
the
> upper 23 bits in the upper 8 byte boundary( since we
have not
> touched the bits 0:17 which is present in the lower 8
byte boundary)


Sure. If you go with that route, make sure it is documented
that kprobe will
fire only if the original instruction gets executed.

A quick grep of kprobes.[ch] shows that the probe
instruction always fire
independent of what the original "qp" field is.
Above will change probing
behavior.  The former make a lot of sense that one should
get a kprobe
trap only When probing instruction gets executed. The latter
can equally
argue that unconditional trap in the execution stream has
its beauty. I
suppose the jury is all in the hands of usage model.

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