Re: [PATCH] m68knommu: remove set_fs()

Hi Christoph,

On Mon, Jul 5, 2021 at 10:56 AM Christoph Hellwig <[email protected]> wrote:
> On Mon, Jul 05, 2021 at 10:44:51AM +0200, Geert Uytterhoeven wrote:
> > > --- a/arch/m68k/Kconfig
> > > +++ b/arch/m68k/Kconfig
> > > @@ -32,7 +32,7 @@ config M68K
> > >         select NO_DMA if !MMU && !COLDFIRE
> > >         select OLD_SIGACTION
> > >         select OLD_SIGSUSPEND3
> > > -       select SET_FS
> > > +       select SET_FS if MMU
> >
> > Probably this should be
> >
> >     select SET_FS if CPU_HAS_ADDRESS_SPACES
> >
> > instead.  Classic m68k (except for good old 68000) has address spaces,
> > Coldfire has not.
>
> No, at least not yet.  Coldfire and co still rely on set_fs for various
> things in the m68k arch code, and also don't provide
> __{get,put}_kernel_nofault yet.  So wile m68k with CPU_HAS_ADDRESS_SPACES
> will probably one of the hardest ports to get rid of set_fs() for,
> m68k/mmu without CPU_HAS_ADDRESS_SPACES would be a logical next step.
> I could try to whiteboard code some of it, but I'd need help from dedicated

M68k/mmu with CPU_HAS_ADDRESS_SPACES needs to use the address spaces
to access user space from kernel space using the "moves" instruction.
Coldfire doesn't.

See arch/m68k/include/asm/uaccess.h.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

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