Re: [PATCH] m68knommu: remove set_fs()

[Christoph Hellwig <hch@lst.de>]

On Tue, Jul 06, 2021 at 11:36:26AM -0700, Linus Torvalds wrote:
> On Mon, Jul 5, 2021 at 9:13 PM Christoph Hellwig <hch@lst.de> wrote:
> >
> > It still needs "real" kernel-style set_fs for the mm/maccess.c routines,
> > but adding __{get,put}_kernel_nofault should not be too hard.
> 
> Yeah, it's not that it wants set-fs(), it's that I missed that m68k
> doesn't have HAVE_GET_KERNEL_NOFAULT.
> 
> Implementing __get/put_kernel_nofault() should be fairly
> straightforward: they are basically the same thing as the
> __get/put_user() functions, except they should just use "move" instead
> of "moves".
> 
> The m68k uaccess.h file already kind of has support for that, but it's
> hardcoded to the CONFIG_CPU_HAS_ADDRESS_SPACES config, rather than
> being available as two different versions.

So I've come up with a whole (compile tested only) series.  We don't
really need the preempt_disable either given the m68k saves and restores
the SFC/DFC registers on context switch:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/m68k-set_fs