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

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Message-ID: <4F9F31E0.5020308@googlemail.com>
Date:	Tue, 1 May 2012 02:44:16 +0200
From:	Jan Seiffert <kaffeemonster@...glemail.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
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

Benjamin Herrenschmidt schrieb:
> 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....)
> 

Ouch!

> 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.
> 

But a sane way forward?

BTW, has anyone checked the new syscall filter code for these ... misfortunes?
I mean before the ABI is set in stone...

> Cheers,
> Ben.
> 
> 
> 

Greetings
	Jan

-- 
😉 
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