linux-kernel - Re: [REGRESSION][PATCH V4 3/3] bpf jit: Let the powerpc jit handle negative offsets

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Message-ID: <1335831987.20866.93.camel@pasglop>
Date:	Tue, 01 May 2012 10:26:27 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Jan Seiffert <kaffeemonster@...glemail.com>
Cc:	David Miller <davem@...emloft.net>, eric.dumazet@...il.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [REGRESSION][PATCH V4 3/3] bpf jit: Let the powerpc jit handle
 negative offsets

On Tue, 2012-05-01 at 00:32 +0200, Jan Seiffert wrote:

> *shudder*
> Link to another lib for only one function because....
> 
> http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/net/bpf.h?rev=1.59&content-type=text/x-cvsweb-markup&only_with_tag=MAIN
> The "Original" says it's an u_int.
> 
> But i guess it is unfixable without breaking something, except with ugly code.
> Should the padding at least be made explicit in the in-kernel struct?
> Did anyone ever tested the 32bit on 64bit compat code (different padding)?

Haven't tested no. A quick google pointed to 2 web pages telling people
to do the wrong thing and 4 broken programs out there, interestingly in
different ways :-) (somebody's doing a reinterpret_cast of one struct
into another, somebody does his/her own local redefinition of the
struct ... using a ulong !, etc....)

I don't see a good way to sort that out other than introducing a new
kernel-side structure, change the sockopt number, and support the old
one as backward binary compat, but that's gross.

Cheers,
Ben.

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