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Date: Tue, 16 Jan 2007 08:53:19 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH 0/59] Cleanup sysctl
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Cc: Andrew Morton <akpm@osdl.org>, linux-mips@linux-mips.org,
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Eric W. Biederman wrote:
> 
> - Removal of sys_sysctl support where people had used conflicting sysctl
>   numbers. Trying to break glibc or other applications by changing the
>   ABI is not cool.  9 instances of this in the kernel seems a little
>   extreme.
> 

It would be highly advantageous if we could have a file that acts as a 
central registry of architectural sysctl numbers *and have the numbers 
in the kernel derived from there*.  As I've said before, I don't really 
think sys_sysctl is any worse than ad hoc system calls (sys_mips and the 
like), but the real problem is that there are architectural and 
non-archtectural numbers, and they're mixed in all over the place.

I think it would be fair to say that if they're not in <linux/sysctl.h> 
they're not architectural, but that doesn't resolve the counterpositive 
(are there sysctls in <linux/sysctl.h> which aren't architectural?  From 
the looks of it, I would say yes.)  Non-architectural sysctl numbers 
should not be exported to userspace, and should eventually be rejected 
by sys_sysctl.

	-hpa