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

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Date:   Wed, 12 Dec 2018 18:14:00 +0000
From:   Joseph Myers <joseph@...esourcery.com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     <tg@...bsd.de>, Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <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>, <vapier@...too.org>,
        "H.J. Lu" <hjl.tools@...il.com>, Rich Felker <dalias@...c.org>,
        <x32@...ldd.debian.org>, Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: Can we drop upstream Linux x32 support?

On Wed, 12 Dec 2018, Arnd Bergmann wrote:

> > MIPS had o32, n32, n64 since like forever.
> 
> o32 and n32 are practically the same, the only difference on the
> syscall ABI that I can see are the actual syscall numbers, and
> the 'struct sigcontext' definition.

And for syscalls that have 64-bit arguments, n32 generally passes those in 
a single register (like n64), not pairs of registers (like o32).  But, 
yes, userspace structure layout for n32 is generally much closer to o32 
than to n64.

-- 
Joseph S. Myers
joseph@...esourcery.com