From: Andi Kleen <ak@suse.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-kernel@vger.kernel.org, bgerst@didntduck.org, haba@pdc.kth.se
Subject: Re: Size of pointers in sys_call_table?
Date: 28 Aug 2001 18:54:06 +0200 [thread overview]
Message-ID: <oupd75gjfbl.fsf@pigdrop.muc.suse.de> (raw)
In-Reply-To: <3B8B9C00.4842710D@didntduck.org.suse.lists.linux.kernel> <E15blYK-0006Fb-00@the-village.bc.nu.suse.lists.linux.kernel>
In-Reply-To: Alan Cox's message of "28 Aug 2001 18:19:47 +0200"
Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
> > The layout of the sys_call_table is totally architecture dependant. The
> > question to ask here is why do you need to use it? Modifying it to hook
> > into syscalls is frowned upon.
>
> And potentially unsafe (think about caching, and non atomic writes on
> some platforms)
It is ATM impossible to make a module that patches sys_call_table safe against
module unload races. The only way is to put a stub into the main kernel
that manages the module counters and calls a separate hook (i.e. as done
by nfsd's syscall)
[Introducing quiescent states in module unloading would probably fix that,
as it has been discussed for a long time now, but I lost hope that it'll ever
get implemented in the main kernel]
Other than that on some weird architectures like IA64 it can get quite
complicated to patch the syscall table.
-Andi
next parent reply other threads:[~2001-08-28 16:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3B8B9C00.4842710D@didntduck.org.suse.lists.linux.kernel>
[not found] ` <E15blYK-0006Fb-00@the-village.bc.nu.suse.lists.linux.kernel>
2001-08-28 16:54 ` Andi Kleen [this message]
2001-08-29 1:00 ` Size of pointers in sys_call_table? Keith Owens
2001-08-28 12:53 Harald Barth
2001-08-28 13:26 ` Brian Gerst
2001-08-28 14:30 ` Harald Barth
2001-08-28 16:17 ` Alan Cox
2001-08-29 0:49 ` Keith Owens
2001-08-29 23:26 ` Ralf Baechle
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