linux-kernel - Re: [RFC][CFT] signal handling fixes

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Message-ID: <CAMuHMdVMbo5868XxW5Lk6tiX3qY0drevfjv9TjMNmbrLrbAPig@mail.gmail.com>
Date:   Thu, 23 Sep 2021 16:43:39 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Finn Thain <fthain@...ux-m68k.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][CFT] signal handling fixes

Hi Finn,

On Thu, Sep 16, 2021 at 11:03 AM Finn Thain <fthain@...ux-m68k.org> wrote:
> On Sun, 25 Jul 2021, Al Viro wrote:
> > ...
> >
> > PS:  FWIW, ifdefs in arch/m68k/kernel/signal.c are wrong - it's not !MMU
> > vs. coldfire/MMU vs. classic/MMU.  It's actually 68000 vs. coldfire vs.
> > everything else.  These days it's nearly correct, but only because on
> > MMU variants of coldfire we never see exception stack frames with type
> > other than 4 - it's controlled by alignment of kernel stack pointer on
> > those, and it's under the kernel control, so it's always 32bit-aligned.
> > It used to be more serious back when we had 68360 support - that's !MMU
> > and exception stack frames are like those on 68020, unless I'm
> > misreading their manual...
> >
>
> I don't claim to understand this code but CPU32 cores appear to be
> unsupported on either #ifdef branch: the MMU branch due to CACR and CAAR
> used in push_cache(), and the !MMU branch due to frame format $4 used in
> adjust_format().
>
> The CPU32 Reference Manual appendix says these chips only supports control
> registers SFC, DFC, VBR and stack frame formats $0, $2, $C.
> https://www.nxp.com/files-static/microcontrollers/doc/ref_manual/CPU32RM.pdf

As of commit a3595962d82495f5 ("m68knommu: remove obsolete 68360
support"), nothing selects MCPU32 anymore.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds