linux-kernel - Re: Can we drop upstream Linux x32 support?

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Message-ID: <Pine.BSM.4.64L.1812112155170.21176@herc.mirbsd.org>
Date:   Tue, 11 Dec 2018 21:59:48 +0000 (UTC)
From:   Thorsten Glaser <tg@...bsd.de>
To:     John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
cc:     Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Florian Weimer <fweimer@...hat.com>,
        Mike Frysinger <vapier@...too.org>,
        "H. J. Lu" <hjl.tools@...il.com>, Rich Felker <dalias@...c.org>,
        x32@...ldd.debian.org, Arnd Bergmann <arnd@...db.de>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Can we drop upstream Linux x32 support?

John Paul Adrian Glaubitz dixit:

>I can't say anything about the syscall interface. However, what I do know
>is that the weird combination of a 32-bit userland with a 64-bit kernel
>interface is sometimes causing issues. For example, application code usually

Yes, but more and more ${foo}64ilp32 architectures are popping up.

>Additionally, x32 support in many applications is either rudimentary

If a signal is sent that this kind of architectures will stay, some
people might be convinced to fix that.

>It's also that the performance benefits of x32 are often eaten up by
>the fact that none of the scripted languages that I know of provide

Non-JITted languages like yours truly’s shell do benefit from it,
though. (mksh works just fine on LP64 but its internal structures
pack massively better on ILP32, for example.)

>If x32 is eventually to be removed, we should also take care of removing
>x32 support from userland code. From the top of my head, this would at least

I don’t think so. The patches also contain
– stuff to support 64-bit time_t on 32-bit architectures, e.g:
- bugfixes like printf("%lld", (long long)timet_value) instead
  of assuming time_t fits into a long (also important for other
  operating systems…)
- generally switching from generic types like long to specific
  types like size_t, ptrdiff_t, etc.
- there was one more but after having written two eMails I forgot it
- oh and, of course, they lay the base for e.g. amd64ilp32 support

bye,
//mirabilos
-- 
FWIW, I'm quite impressed with mksh interactively. I thought it was much
*much* more bare bones. But it turns out it beats the living hell out of
ksh93 in that respect. I'd even consider it for my daily use if I hadn't
wasted half my life on my zsh setup. :-) -- Frank Terbeck in #!/bin/mksh