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Date:   Wed, 12 Dec 2018 18:14:00 +0000
From:   Joseph Myers <joseph@codesourcery.com>
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To:     Arnd Bergmann <arnd@arndb.de>
CC:     <tg@mirbsd.de>, Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        "H.J. Lu" <hjl.tools@gmail.com>, Rich Felker <dalias@libc.org>,
        <x32@buildd.debian.org>, 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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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@codesourcery.com