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

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Message-ID: <Pine.BSM.4.64L.1812150450500.18185@herc.mirbsd.org>
Date:   Sat, 15 Dec 2018 04:53:48 +0000 (UTC)
From:   Thorsten Glaser <tg@...bsd.de>
To:     Andy Lutomirski <luto@...nel.org>
cc:     Linus Torvalds <torvalds@...ux-foundation.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>
Subject: Re: Can we drop upstream Linux x32 support?

Andy Lutomirski dixit:

>x32 is not this at all.  The kernel ABI part of x32 isn't ILP32.  It's
>IP32, 32-bit size_t, and *64-bit* long.  The core kernel doesn't

Yeah, I was looking at this from userspace PoV, as I said I’m not
a Linux kernel programmer.

In BSD we have register_t which is probably the equivalent to your
__kernel_long_t? Maybe removing the “long” from the name helps.

But yes, x32 is just a (second to i386) ILP32 userspace API in an
amd64 kernel. This does imply mapping on the userspace (x32) to
kernel (amd64) boundary and back. I would have thought full struct
member mapping, as dalias described, to be the most robust.

>something similar to work using the normal x86_64 syscalls.  And I'm

But those would require the longer structs etc. and therefore
lose all the benefits of x32…

bye,
//mirabilos
-- 
„Cool, /usr/share/doc/mksh/examples/uhr.gz ist ja ein Grund,
mksh auf jedem System zu installieren.“
	-- XTaran auf der OpenRheinRuhr, ganz begeistert
(EN: “[…]uhr.gz is a reason to install mksh on every system.”)