linux-kernel - Re: [PATCH 09/14] m68k: drop custom __access

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Date:   Tue, 15 Feb 2022 07:13:42 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Arnd Bergmann <arnd@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-api@...r.kernel.org, arnd@...db.de,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk,
        will@...nel.org, guoren@...nel.org, bcain@...eaurora.org,
        geert@...ux-m68k.org, monstr@...str.eu, tsbogend@...ha.franken.de,
        nickhu@...estech.com, green.hu@...il.com, dinguyen@...nel.org,
        shorne@...il.com, deller@....de, mpe@...erman.id.au,
        peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        hca@...ux.ibm.com, dalias@...c.org, davem@...emloft.net,
        richard@....at, x86@...nel.org, jcmvbkbc@...il.com,
        ebiederm@...ssion.com, akpm@...ux-foundation.org, ardb@...nel.org,
        linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-um@...ts.infradead.org,
        linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH 09/14] m68k: drop custom __access_ok()

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)...