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Date:   Sat, 15 Dec 2018 04:53:48 +0000 (UTC)
From:   Thorsten Glaser <tg@mirbsd.de>
To:     Andy Lutomirski <luto@kernel.org>
cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@alien8.de>,
        Florian Weimer <fweimer@redhat.com>,
        Mike Frysinger <vapier@gentoo.org>,
        "H. J. Lu" <hjl.tools@gmail.com>, Rich Felker <dalias@libc.org>,
        x32@buildd.debian.org, Arnd Bergmann <arnd@arndb.de>,
        Will Deacon <will.deacon@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: Can we drop upstream Linux x32 support?
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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.”)