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

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Message-ID: <56E90733.4010805@landley.net>
Date:	Wed, 16 Mar 2016 02:11:47 -0500
From:	Rob Landley <rob@...dley.net>
To:	David Daney <ddaney.cavm@...il.com>
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 03/15/2016 06:22 PM, David Daney wrote:
> On 03/15/2016 02:10 PM, Rob Landley wrote:
>> From: Rob Landley <rob@...dley.net>
>>
>> The v850 port was removed by commits f606ddf42fd4 and 07a887d399b8 in
>> 2008.
>> These #defines are not used in the current kernel.
>>
>> Signed-off-by: Rob Landley <rob@...dley.net>
>> ---
>>   include/uapi/linux/elf-em.h |    3 ---
>>   1 file changed, 3 deletions(-)
>>
>> diff --git a/include/uapi/linux/elf-em.h b/include/uapi/linux/elf-em.h
>> index b56dfcf..c3fdfe7 100644
>> --- a/include/uapi/linux/elf-em.h
>> +++ b/include/uapi/linux/elf-em.h
>> @@ -30,7 +30,6 @@
>>   #define EM_X86_64    62    /* AMD x86-64 */
>>   #define EM_S390        22    /* IBM S/390 */
>>   #define EM_CRIS        76    /* Axis Communications 32-bit embedded
>> processor */
>> -#define EM_V850        87    /* NEC v850 */
> 
> Can you do this to userspace visible files?

Commit 6f6f467eaaa0 did and nobody seemed to mind?

> I thought only additions and obvious corrections were allowed.  Removing
> symbols could cause build breakage for something.

There's a /usr/include/elf.h in glibc with 3 times as many EM_BLAH
symbols as this one defines. Something that cares about identifying
architectures Linux doesn't actually support would presumably use that
header instead of this one.

This is the only architecture included in this file that isn't currently
supported by Linux (except the mips symbols with the comment about them
not being used, which have been there since the first version of the file).

I found this while auditing toybox's "file" command. (We just copied the
constant values into our own table, but when making the table I was
checking which values the actual Linux ELF loaders in the various arch
directories would bind to.)

Rob