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Date: Fri, 26 Jan 2018 07:57:35 -0800
From: Andy Lutomirski <>
To: Alan Cox <>
Cc: David Laight <>, Andy Lutomirski <>, 
	Linus Torvalds <>, "the arch/x86 maintainers" <>, 
	LKML <>, 
	Greg Kroah-Hartman <>, Jann Horn <>, 
	Samuel Neves <>, Dan Williams <>, 
	Kernel Hardening <>, Borislav Petkov <>
Subject: Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast
 path with retpolines on

On Fri, Jan 26, 2018 at 6:24 AM, Alan Cox <> wrote:
>> NetBSD (and the other BSD?) defines a structure for the arguments to
>> each syscall.
> Goes back to v7 or so but they put the syscall arguments into the uarea
> so that no pointers were needed (uarea being a per process mapping at a
> fixed address) in order to also reduce pointer dereferencing costs (not
> that those matter much on modern processors)

I gave the rearrangement like this a try yesterday and it's a bit of a
mess.  Part of the problem is that there are a bunch of pieces of code
that expect sys_xyz() to be actual callable functions.  The best way
to deal with that is probably to switch to calling normal functions.

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