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Date:   Tue, 15 Feb 2022 07:13:42 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Christoph Hellwig <hch@lst.de>
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Subject: Re: [PATCH 09/14] m68k: drop custom __access_ok()
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On Tue, Feb 15, 2022 at 07:29:42AM +0100, Christoph Hellwig wrote:
> On Tue, Feb 15, 2022 at 12:37:41AM +0000, Al Viro wrote:
> > Perhaps simply wrap that sucker into #ifdef CONFIG_CPU_HAS_ADDRESS_SPACES
> > (and trim the comment down to "coldfire and 68000 will pick generic
> > variant")?
> 
> I wonder if we should invert CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE,
> select the separate address space config for s390, sparc64, non-coldfire
> m68k and mips with EVA and then just have one single access_ok for
> overlapping address space (as added by Arnd) and non-overlapping ones
> (always return true).

parisc is also such...  How about

	select ALTERNATE_SPACE_USERLAND

for that bunch?  While we are at it, how many unusual access_ok() instances are
left after this series?  arm64, itanic, um, anything else?

FWIW, sparc32 has a slightly unusual instance (see uaccess_32.h there); it's
obviously cheaper than generic and I wonder if the trick is legitimate (and
applicable elsewhere, perhaps)...