linux-kernel - Re: [PATCH] riscv: add S and U modes to ISA string

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Date:   Sun, 11 Nov 2018 14:14:12 -0800 (PST)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     me@...ki.ch
CC:     david.abdurachmanov@...il.com, aou@...s.berkeley.edu,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject:     Re: [PATCH] riscv: add S and U modes to ISA string

On Sat, 10 Nov 2018 00:35:15 PST (-0800), me@...ki.ch wrote:
> On 10.11.18 07:45, David Abdurachmanov wrote:
>>
>> The patch adds the missing S and U modes.
>
> This is the same patch I submitted earlier (see v2 here [1], based on
> Palmer's feedback). Palmer stated that the "S" extension should not be
> exposed to usermode.
>
> Since two people arrived at the same solution, I wonder if the
> supervisor mode should really be hidden from userspace, as it's about
> the CPU information, not about the environment the calling code is
> running as.
>
> [1] https://lkml.org/lkml/2018/11/10/96

I still think S should be hidden from applications.  This patch was fairly 
mechanical, so it probably just wasn't though about twice -- that's the problem 
with user ABI stuff, lots of times the obvious answer isn't the correct one :).

I'll take your second patch, I just haven't gotten around to actually fully 
reviewing patches yet as I'm still in my email triage phase.

Thanks!