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

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Date:   Wed, 1 Feb 2017 21:08:06 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     James Bottomley <James.Bottomley@...senpartnership.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Helge Deller <deller@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-parisc@...r.kernel.org,
        Michael Kerrisk <mtk.manpages@...glemail.com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH] prctl: implement PR_GET_ENDIAN for all architectures

On Wed, Feb 1, 2017 at 3:12 PM, James Bottomley
<James.Bottomley@...senpartnership.com> wrote:
> On Tue, 2017-01-31 at 16:26 -0800, 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.  Why is this needed?
>
> I don't think it is other than for PPC.  If you're not variable endian
> (which is only PPC to date), then you should know a priori what endian
> you are from the #defines in userspace.

I find it vaguely odd even on PPC.  Surely you can tell what your
endianness is directly.  (An API to query the endianness of another
task would be useful, though.)