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 2.4 Ready list - Kernel Hooks 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3DB6CC71.9DA9A543@opersys.com \
--to=karim@opersys.com \
--cc=landley@trommello.org \
--cc=linux-kernel@vger.kernel.org \
--cc=richardj_moore@uk.ibm.com \
--cc=vamsi_krishna@in.ibm.com \
--cc=wa@almesberger.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.