From: Karim Yaghmour <karim@opersys.com>
To: Werner Almesberger <wa@almesberger.net>
Cc: Richard J Moore <richardj_moore@uk.ibm.com>,
Rob Landley <landley@trommello.org>,
linux-kernel@vger.kernel.org,
S Vamsikrishna <vamsi_krishna@in.ibm.com>
Subject: Re: 2.4 Ready list - Kernel Hooks
Date: Wed, 23 Oct 2002 12:21:05 -0400 [thread overview]
Message-ID: <3DB6CC71.9DA9A543@opersys.com> (raw)
In-Reply-To: <20021023122841.G1421@almesberger.net>
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
===================================================
next prev parent reply other threads:[~2002-10-23 16:10 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-10-22 23:09 Richard J Moore
2002-10-22 23:54 ` Greg KH
2002-10-23 15:28 ` Werner Almesberger
2002-10-23 16:21 ` Karim Yaghmour [this message]
-- strict thread matches above, loose matches on Subject: below --
2002-10-24 16:38 Richard J Moore
2002-10-24 17:02 ` Greg KH
2002-10-23 16:47 Richard J Moore
2002-10-23 19:50 ` Werner Almesberger
2002-10-24 7:38 ` Vamsi Krishna S .
2002-10-24 17:22 ` Werner Almesberger
2002-10-23 8:10 Richard J Moore
2002-10-23 17:09 ` Greg KH
2002-10-21 12:24 Richard J Moore
2002-10-22 21:02 ` Werner Almesberger
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