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From: Alan Cox <alan@linux.intel.com>
Date: Fri, 26 Jan 2018 14:24:07 +0000
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Subject: [kernel-hardening] Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast
 path with retpolines on
To: David Laight <David.Laight@ACULAB.COM>, 'Andy Lutomirski' <luto@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>
Cc: the arch/x86 maintainers <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Jann Horn <jannh@google.com>, Samuel Neves <samuel.c.p.neves@gmail.com>, Dan Williams <dan.j.williams@intel.com>, Kernel Hardening <kernel-hardening@lists.openwall.com>, Borislav Petkov <bp@alien8.de>
List-ID: <kernel-hardening.lists.openwall.com>

> 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)

Alan.