Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
In-Reply-To: <20180126180722.GA13338@ZenIV.linux.org.uk>
References: <CA+55aFyONQeyHit6LcQz_JM5+C9pr61fcWFSpdn=7K_2mZN+oA@mail.gmail.com>
 <CALCETrVUY9p9jMNhuBgM3mWATsr1Fc_ZWc=bjidBkLw7bq5Vdg@mail.gmail.com>
 <CA+55aFwUn7+WiHxL7PBWxNrGB0--HETqUjdRwxi+DkMvCP_CaA@mail.gmail.com>
 <CALCETrV1JHK1ovjjD1vbs08K1an6tq6nbRoAj9uyrY2GUYJJBA@mail.gmail.com>
 <CA+55aFzTXVRPo7OBPMo2OB26GisY8-dg6NaC8ackVJgS9M0+4w@mail.gmail.com>
 <CALCETrU42C1S3nvSuLuamXtp2-s1xBG3q5cSNVOfGThncHxBZA@mail.gmail.com>
 <b8ea504729db4073abf82ebd5d8a53c6@AcuMS.aculab.com> <1516976647.5438.6.camel@linux.intel.com>
 <CALCETrXaARjGa+fCmxDDYNQCgv0ZSm+DaUFoXFmRxU9J245HxQ@mail.gmail.com>
 <CA+55aFzr_tvdjsq1B+N1zrprNe-qfwo0At+r8uKiS=BGN_92vQ@mail.gmail.com> <20180126180722.GA13338@ZenIV.linux.org.uk>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 26 Jan 2018 10:13:38 -0800
Message-ID: <CA+55aFydRUyNWz5M2nWWMsLk5dW5JjRRNcFjP62yecAJ_bSDpQ@mail.gmail.com>
Subject: Re: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast
 path with retpolines on
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Andy Lutomirski <luto@kernel.org>, Alan Cox <alan@linux.intel.com>,
        David Laight <David.Laight@aculab.com>,
        "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>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, Jan 26, 2018 at 10:07 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Umm...  What about other architectures?  Or do you want SYSCALL_DEFINE...
> to be per-arch?  I wonder how much would that "go through pt_regs" hurt
> on something like sparc...

No, but I just talked to Will Deacon about register clearing on entry,
and so I suspect that arm64 might want something similar too.

So I think some opt-in for letting architectures add their own
function would be good. Because it wouldn't be all architectures, but
it probably _would_ be more than just x86.

You need to add architecture-specific "load argX from ptregs" macros anyway.

             Linus