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Subject: Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast
 path with retpolines on
From:   Alan Cox <alan@linux.intel.com>
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>,
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        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>
Date:   Fri, 26 Jan 2018 14:24:07 +0000
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> 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.