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Subject: Re: export of sys_call_table
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: bidulock@openss7.org
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: 03 Oct 2002 23:02:40 +0100
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On Thu, 2002-10-03 at 22:39, Brian F. G. Bidulock wrote:
> I see that RH, in their infinite wisdom, have seen fit to remove
> the export of sys_call_table in 8.0 kernels breaking any loadable
> modules that wish to implement non-implemented system calls such
> as LiS's or iBCS implementation of putmsg/getmsg.

Overwriting syscall table entries is not safe. Its not safe because
there is no locking mechanism, and its not safe because of the pentium
III errata.

> Until now, loadable modules have been able to just overwrite
> the non implemented point in the sys_call_table when they load
> and putting it back when they unload.  There is no mechanism
> for registering system calls.

Not actually safely implementable. The right way to do this is a
relevant 2.5 question. In general however you shouldnt need to register
syscalls because the upper layer interfaces already exist (the LiS stuff
is an example otherwise I grant). 

Alan

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