linux-kernel - Re: [PATCH 2/5] nolibc: add support for s390

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Message-ID: <yt9dedsdjn6z.fsf@linux.ibm.com>
Date:   Mon, 02 Jan 2023 10:33:08 +0100
From:   Sven Schnelle <svens@...ux.ibm.com>
To:     Willy Tarreau <w@....eu>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kernel@...r.kernel.org, hca@...ux.ibm.com
Subject: Re: [PATCH 2/5] nolibc: add support for s390

Willy Tarreau <w@....eu> writes:

> On Mon, Jan 02, 2023 at 09:17:04AM +0100, Sven Schnelle wrote:
>> The kernel compiles with z10 as minimum architecture, so
>> i'm leaning towards enforcing the same arch for nolibc. What do you think?
>
> Sure, as long as this works for most users, that's likely fine.
> Alternately, are there equivalent sequences of instructions that achieve
> the same on older architectures, and would that be relevant ?

Well, it's only one instruction that needs to be changed - we could also
use aghi to do the same thing. Maybe that's better.

Also i will add -m64 to the testing Makefile, it shouldn't hurt.

> One future improvement I'll need will be to store the envp value into a
> global "environ" variable, and run over it to catch the pointer that
> follows the NULL and save it into the "_auxv" variable. I've done it for
> all other archs here already:
>
>   https://git.kernel.org/pub/scm/linux/kernel/git/wtarreau/nolibc.git/log/?h=20221227-nolibc-weak-4
>
> I'll give it a try once I'm able to build and test your code, and may
> ask you for some help if I don't succeed in doing it. If you want to do
> it yourself, please have a look at the last commits adding environ and
> auxv to any arch of your choice, such as x86_64.

Ok, thanks for the Heads-Up. I'll take a look. I think i would send this
as a separate Patch, so we get the initial support done first if that's ok.