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From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>,
	Borislav Petkov <bp@alien8.de>
Subject: [kernel-hardening] Re: [PATCH 1/3] x86/entry/64: Remove the SYSCALL64 fast path
Date: Sun, 28 Jan 2018 20:00:35 +0100	[thread overview]
Message-ID: <20180128190035.q2bqchwhc2fww6io@gmail.com> (raw)
In-Reply-To: <462dff8d4d64dfbfc851fbf3130641809d980ecd.1517164461.git.luto@kernel.org>


* Andy Lutomirski <luto@kernel.org> wrote:

> The SYCALLL64 fast path was a nice, if small, optimization back in
> the good old days when syscalls were actually reasonably fast.  Now
> we have PTI to slow everything down, and indirect branches are
> verboten, making everything messier.  The retpoline code in the fast
> path was particularly nasty.
> 
> Just get rid of the fast path.  The slow path is barely slower.
> 
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> 
> This isn't quite identical to Linus' patch.  I cleaned up the
> SYSCALL64 entry code to use all pushes rather than pushing all but 6
> regs and moving the rest.

Hm, could we please have this in two parts please, out of general paranoia?

One patch doing the easy fast path removal, the other doing the mov/push 
conversion?

Bisectability, reviewability and all that.

Exact same patch result.

Thanks,

	Ingo

  reply	other threads:[~2018-01-28 19:00 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-28 18:38 [kernel-hardening] [PATCH 0/3] x86/pti-ish syscall cleanups Andy Lutomirski
2018-01-28 18:38 ` [kernel-hardening] [PATCH 1/3] x86/entry/64: Remove the SYSCALL64 fast path Andy Lutomirski
2018-01-28 19:00   ` Ingo Molnar [this message]
2018-01-30 14:49   ` [tip:x86/pti] " tip-bot for Andy Lutomirski
2018-01-30 14:50   ` [tip:x86/pti] x86/entry/64: Push extra regs right away tip-bot for Andy Lutomirski
2018-01-28 18:38 ` [kernel-hardening] [PATCH 2/3] x86/asm: Move 'status' from thread_struct to thread_info Andy Lutomirski
2018-01-28 19:02   ` [kernel-hardening] " Ingo Molnar
2018-01-28 19:19   ` Linus Torvalds
2018-01-30 14:50   ` [tip:x86/pti] " tip-bot for Andy Lutomirski
2018-01-28 18:38 ` [kernel-hardening] [PATCH 3/3] syscalls: Add a bit of documentation to __SYSCALL_DEFINE Andy Lutomirski
2018-01-28 19:15   ` [kernel-hardening] " Linus Torvalds
2018-01-28 20:21     ` Al Viro
2018-01-28 20:42       ` Linus Torvalds
2018-01-28 22:50         ` Al Viro
2018-01-29  6:22           ` Al Viro
2018-01-28 19:21   ` Ingo Molnar

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