Messages in this thread | | | Date | Wed, 23 Oct 2002 12:21:05 -0400 | From | Karim Yaghmour <> | Subject | Re: 2.4 Ready list - Kernel Hooks |
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Werner Almesberger wrote: > Richard J Moore wrote: > > This is nothing more than a call-back mechanism such as could be used by > > LSM or LTT. > > Hmm, Greg has already voiced some violent disagreement regarding > LSM :-) That leaves LTT. Given the more exploratory nature of LTT, > I wonder if [dk]probes wouldn't be quite sufficient there, too.
The whole point of tracing is that the system's behavior should not be modified but only recorded. Generating int3 won't do.
> Oh, you could probably have some "fast" probes by just checking > for a certain "anchor" pattern (e.g. a sequence of 5 nops on > i386), which could then be replaced with a direct call. This > optimization would have to be optional, in case some code yields > the anchor pattern such that it isn't also a basic block.
If I remember correctly, the optimized arch-dependent code in kernel hooks uses "compare immediate" and the value of the immediate is edited to enable/disable hooking. Given modern branch-prediction the cost should be quite close to an unconditional jump.
Karim
=================================================== Karim Yaghmour karim@opersys.com Embedded and Real-Time Linux Expert =================================================== - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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