linux-kernel - Re: [PATCH] prctl: implement PR_GET

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Message-Id: <20170201140322.b469641861861caf8cf6da48@linux-foundation.org>
Date:   Wed, 1 Feb 2017 14:03:22 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Helge Deller <deller@....de>
Cc:     linux-kernel@...r.kernel.org, linux-parisc@...r.kernel.org,
        Michael Kerrisk <mtk.manpages@...glemail.com>,
        linux-api@...r.kernel.org
Subject: Re: [PATCH] prctl: implement PR_GET_ENDIAN for all architectures

On Wed, 1 Feb 2017 20:47:06 +0100 Helge Deller <deller@....de> wrote:

> Hi Andrew,
> 
> On 01.02.2017 01:26, Andrew Morton wrote:
> > On Sat, 28 Jan 2017 12:13:10 +0100 Helge Deller <deller@....de> wrote:
> > 
> >> The prctl(PR_GET_ENDIAN) syscall was added to Kernel 2.6.18, but
> >> implemented for PowerPC only.
> >> This trivial patch adds support for this syscall for all other architectures.
> > 
> > Seems reasonable.  I guess.
> 
> Heck, I did forgot but I submitted a similar patch 8 years ago:
> http://www.serverphorums.com/read.php?12,51902
> 
> > Why is this needed?
> 
> It's not actually needed beside the trivial reason of providing an interface
> not just for one single architecture.
> 
> After reading the discussion from 2009 again, I'm fine if 
> you would simply drop the patch. The decision up to you.

Can't decide.  I guess that moving it into the kernel will, over time,
eliminate some irritating ifdefs from userspace code.

The implementation itself is a bit half-assed.  The put_user() in
arch/powerpc/kernel/process.c:get_endian() should be moved into
kernel/sys.c.  So the arch code only does the "what endianness am I"
function and common code copies that out to userspace.