RE: [PATCH]IA64 trap code 16 bytes atomic copy on montecito, take 2

From: Chen, Kenneth W <kenneth.w.chen_at_intel.com>
Date: 2006-11-03 12:55:49
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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Received on Fri Nov 03 12:56:22 2006

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