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

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Message-ID: <3143388.E8mgBzaflP@blindfold>
Date:   Fri, 14 Dec 2018 16:17:59 +0100
From:   Richard Weinberger <richard@....at>
To:     David Laight <David.Laight@...lab.com>
Cc:     'Richard Weinberger' <richard.weinberger@...il.com>,
        "kevin@...rana.org" <kevin@...rana.org>,
        "glaubitz@...sik.fu-berlin.de" <glaubitz@...sik.fu-berlin.de>,
        Andy Lutomirski <luto@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:ABI/API" <linux-api@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        "fweimer@...hat.com" <fweimer@...hat.com>,
        Mike Frysinger <vapier@...too.org>,
        "H.J. Lu" <hjl.tools@...il.com>,
        "dalias@...c.org" <dalias@...c.org>,
        "x32@...ldd.debian.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?

Am Freitag, 14. Dezember 2018, 15:38:53 CET schrieb David Laight:
> From: Richard Weinberger
> > Sent: 13 December 2018 09:05
> > On Thu, Dec 13, 2018 at 6:03 AM Kevin Easton <kevin@...rana.org> wrote:
> > >
> > > On Tue, Dec 11, 2018 at 11:29:14AM +0100, John Paul Adrian Glaubitz wrote:
> > > ...
> > > > 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
> > > > expects things like time_t to be 32-bit on a 32-bit system. However, this
> > > > isn't the case for x32 which is why code fails to build.
> > >
> > > OpenBSD and NetBSD both have 64-bit time_t on 32-bit systems and have
> > > had for four or five years at this point.
> > 
> > They can also do flag-day changes and break existing applications, Linux not.
> 
> Not true at all.
> The binary compatibility in NetBSD is probably better than that in Linux
> and goes back a long way.
> 
> For the time_t changes new system calls numbers were assigned where needed.
> The system headers and libc were updated so that recompiled code would
> use the new system calls.
> 
> The only real advantage that NetBSD has is that its libc (and standard
> utilities) are released with the kernel making it much easier to get
> applications to use the new features.
> 
> This was also done a very long time ago when file offsets were extended
> to 64 bits.
> 
> Some of the system calls have quite a few 'compatibility' versions.
> As well as the ones for emulations of other operating systems.
> It has been possible to run copies of firefox compiled for Linux
> under NetBSD.

I stand corrected, I was under the impression that NetBSD went the same
path as OpenBSD did. Thanks for pointing this out.

Thanks,
//richard