linux-kernel - Re: [PATCH] Remove v850 from linux/elf-em.h

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Date:	Mon, 21 Mar 2016 09:39:32 -0700
From:	David Daney <ddaney.cavm@...il.com>
To:	Rob Landley <rob@...dley.net>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Ungerer <gerg@...pgear.com>
Subject: Re: [PATCH] Remove v850 from linux/elf-em.h

On 03/18/2016 06:15 PM, Rob Landley wrote:
> On 03/18/2016 12:46 PM, David Daney wrote:
>> I am not going to comment on it any more, but [commenting more]
>
> Yes you are. (And did then too.)
>
>> On 03/17/2016 07:32 PM, Rob Landley wrote:
>> [...]
>>>
>>> As I explained last email, userspace uses the libc header, not the linux
>>> header,
>>
>> The fallacy in this argument is the assertion that we know what
>> userspace does.
>
> Userspace programs that did that already broke on earlier symbol removals.
>
>> Userspace could easily do:
>>
>> #include <linux/elf-em.h>
>> .
>>     case SYMBOL_YOU_WANT_TO_REMOVE:
>>
>>   ¡BOOM!  it is broken.
>
> So you're assuming I don't know how headers get used by userspace.

Yes, exactly.  Don't feel bad about it though, because nobody else knows 
either.

> That's nice. Clearly, I never would have thought of that.
>
> Once again, "As I explained last email", symbols have been removed from
> this particular header before.

Since you know, a priori, that symbols in that file are never used by 
userspace, why not send a patch that moves it to include/linux/elf-em.h 
so that userspace doesn't see it?  Then you could remove as many symbols 
as you like.

David Daney

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