Re: [ANNOUNCE] Generalised Kernel Hooks Interface (GKHI)

From: Matti Aarnio (matti.aarnio@zmailer.org)
Date: Fri Nov 10 2000 - 10:07:54 EST


  I have been wondering what all of the furor has been about...

        Initially I thought that it is "a way to load in a module which
        defines its own syscalls, etc.." and/or "we want to sell binary
        images which can activate some hooks" but having just read the
        GKHI README, that thing is far away from its intentions.
        (Well, it doesn't preclude those, but neither it mentions them
         as objectives. And giving a license stating use of GNU GPL
         also doesn't quite fit "proprietary binary hook" image..)

On Wed, Nov 08, 2000 at 04:35:33PM -0500, Michael Rothwell wrote:
> Sounds great; unfortunately, the core group has spoken out against a
> modular kernel.

        Really ?

$ /sbin/lsmod
Module Size Used by
parport_pc 23184 1 (autoclean)
lp 5072 0 (autoclean) (unused)
parport 30048 1 (autoclean) [parport_pc lp]
8021q 10032 2
3c59x 24304 2 (autoclean)
ipv6 152816 -1 (autoclean)
autofs 11536 1 (autoclean)
usb-uhci 23408 0 (autoclean) (unused)
usbcore 49504 1 (autoclean) [usb-uhci]
es1371 29920 0
ac97_codec 7824 0 [es1371]
soundcore 4336 4 [es1371]

> -M
>
> richardj_moore@uk.ibm.com wrote:
> >
> > We've just release version 0.6 of Generalised Kernel Hooks Interface (GKHI)
> > see the IBM Linux Technology Centre's web page DProbes link:
> > http://oss.software.ibm.com/developerworks/opensource/linux

... (reordered, cut away..)

> > Here's the abstract for this facility. With this intend to modularise our
> > RAS offerings, in particular DProbes, so that they can be applied
> > dynamically without having to be carried as excess baggage.

        Richard,

        Please educate me, what does "our RAS offerings" mean here ?
        (I didn't find "RAS" at your signature-URL site, but I didn't
         poke around very much..)

        I do know that when IBM suits speak with phrases like that,
        they are selling me something which costs $$$.

        Which definitely gives proprietary, binary only, hook image...
        But GKHI, and DProbes are neither. Thus I am confused, but can
        understand the furor...

> > Some folks expressed an interest in this type of facility recently in
> > discussions concerning making call-backs from the kernel to kernel modules.

        Indeed, one such mechanism could be a way to register IOCTL
        call chains, which now (for sockets) are quite ugly.
        Lots and lots of subsystems do ioctl()s via /proc/ objects
        just because other methods are way too messy.

        [ ioctl's go via the protocol family of the control socket to
          family-specific subset, but then the "fun" begins for things
          which aren't quite of any specific protocol family -- see
          DLCI support hooks at ipv4, and bridge ioctls at both ipv4
          and at packet.

          Grep the kernel source for "_hook", and you see a lot of
          things.. Mostly varying mouses, and bridging, it seems.
          Netfilter calls its managed coherent interface "hook", but
          it is way better. ]

        Also the bridging system is less than desirable looking with
        its pervasive hooks, but that can be solved by making layer2
        devices fully stackable. (Something for 2.5)

> > Richard Moore - RAS Project Lead - Linux Technology Centre (PISC).
> > http://oss.software.ibm.com/developerworks/opensource/linux
> > Office: (+44) (0)1962-817072, Mobile: (+44) (0)7768-298183
> > IBM UK Ltd, MP135 Galileo Centre, Hursley Park, Winchester, SO21 2JN, UK

/Matti Aarnio
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