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From: "Woodhouse, David" <dwmw@amazon.co.uk>
To: Paul Turner <pjt@google.com>, LKML <linux-kernel@vger.kernel.org>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linux-foundation.org>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	"Dave Hansen" <dave.hansen@intel.com>, <tglx@linuxtronix.de>,
	Kees Cook <keescook@google.com>, Rik van Riel <riel@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Jiri Kosina <jikos@kernel.org>, <gnomes@lxorguk.ukuu.org.uk>
Subject: Re: [RFC] Retpoline: Binary mitigation for branch-target-injection (aka "Spectre")
Date: Thu, 4 Jan 2018 09:30:13 +0000	[thread overview]
Message-ID: <1515058213.12987.89.camel@amazon.co.uk> (raw)
In-Reply-To: <CAPM31RLaz7OuO_rm45_he=S0OZqPWY7zp-O6uevD25Br+YXwJA@mail.gmail.com>

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On Thu, 2018-01-04 at 01:10 -0800, Paul Turner wrote:
> Apologies for the discombobulation around today's disclosure.  Obviously the
> original goal was to communicate this a little more coherently, but the
> unscheduled advances in the disclosure disrupted the efforts to pull this
> together more cleanly.
> 
> I wanted to open discussion the "retpoline" approach and and define its
> requirements so that we can separate the core
> details from questions regarding any particular implementation thereof.
> 
> As a starting point, a full write-up describing the approach is available at:
>   https://support.google.com/faqs/answer/7625886

Note that (ab)using 'ret' in this way is incompatible with CET on
upcoming processors. HJ added a -mno-indirect-branch-register option to
the latest round of GCC patches, which puts the branch target in a
register instead of on the stack. My kernel patches (which I'm about to
reconcile with Andi's tweaks and post) do the same.

That means that in the cases where at runtime we want to ALTERNATIVE
out the retpoline, it just turns back into a bare 'jmp *\reg'.


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  parent reply	other threads:[~2018-01-04  9:35 UTC|newest]

Thread overview: 79+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-04  9:10 [RFC] Retpoline: Binary mitigation for branch-target-injection (aka "Spectre") Paul Turner
2018-01-04  9:12 ` Paul Turner
2018-01-04  9:24 ` Paul Turner
2018-01-04  9:48   ` Greg Kroah-Hartman
2018-01-04  9:56     ` Woodhouse, David
2018-01-04  9:30 ` Woodhouse, David [this message]
2018-01-04 14:36   ` [PATCH v3 01/13] x86/retpoline: Add initial retpoline support David Woodhouse
2018-01-04 18:03     ` Linus Torvalds
2018-01-04 19:32       ` Woodhouse, David
2018-01-04 18:17     ` Alexei Starovoitov
2018-01-04 18:25       ` Linus Torvalds
2018-01-04 18:36         ` Alexei Starovoitov
2018-01-04 19:27           ` David Woodhouse
2018-01-05 10:28             ` Paul Turner
2018-01-05 10:55               ` David Woodhouse
2018-01-05 11:19                 ` Paul Turner
2018-01-05 11:25                 ` Paul Turner
2018-01-05 11:26               ` Paolo Bonzini
2018-01-05 12:20                 ` Paul Turner
2018-01-05 10:40         ` Paul Turner
2018-01-04 18:40       ` Andi Kleen
2018-01-05 10:32         ` Paul Turner
2018-01-05 12:54     ` Thomas Gleixner
2018-01-05 13:01       ` Juergen Gross
2018-01-05 13:03         ` Thomas Gleixner
2018-01-05 13:56       ` Woodhouse, David
2018-01-05 16:41         ` Woodhouse, David
2018-01-05 16:45           ` Borislav Petkov
2018-01-05 17:08             ` Josh Poimboeuf
2018-01-06  0:30               ` Borislav Petkov
2018-01-06  8:23                 ` David Woodhouse
2018-01-06 17:02                   ` Borislav Petkov
2018-01-07  9:40                     ` David Woodhouse
2018-01-07 11:46                       ` Borislav Petkov
2018-01-07 12:21                         ` David Woodhouse
2018-01-07 14:03                           ` Borislav Petkov
2018-01-08 21:50                             ` David Woodhouse
2018-01-08  5:06                 ` Josh Poimboeuf
2018-01-08  7:55                   ` Woodhouse, David
2018-01-05 17:12             ` Woodhouse, David
2018-01-05 17:28               ` Linus Torvalds
2018-01-05 17:48                 ` David Woodhouse
2018-01-05 18:05                 ` Andi Kleen
2018-01-05 20:32                 ` Woodhouse, David
2018-01-05 21:11                   ` Brian Gerst
2018-01-05 22:16                     ` Woodhouse, David
2018-01-05 22:43                       ` Borislav Petkov
2018-01-05 22:00                 ` Woodhouse, David
2018-01-05 22:06                   ` Borislav Petkov
2018-01-05 23:50                   ` Linus Torvalds
2018-01-06 10:53                     ` Woodhouse, David
2018-01-04 14:36   ` [PATCH v3 02/13] x86/retpoline/crypto: Convert crypto assembler indirect jumps David Woodhouse
2018-01-04 14:37   ` [PATCH v3 03/13] x86/retpoline/entry: Convert entry " David Woodhouse
2018-01-04 14:46     ` Dave Hansen
2018-01-04 14:49       ` Woodhouse, David
2018-01-04 14:37   ` [PATCH v3 04/13] x86/retpoline/ftrace: Convert ftrace " David Woodhouse
2018-01-04 14:37   ` [PATCH v3 05/13] x86/retpoline/hyperv: Convert " David Woodhouse
2018-01-04 14:37   ` [PATCH v3 06/13] x86/retpoline/xen: Convert Xen hypercall " David Woodhouse
2018-01-04 15:10     ` Juergen Gross
2018-01-04 15:18       ` David Woodhouse
2018-01-04 15:54     ` Juergen Gross
2018-01-04 14:37   ` [PATCH v3 07/13] x86/retpoline/checksum32: Convert assembler " David Woodhouse
2018-01-04 14:37   ` [PATCH v3 08/13] x86/alternatives: Add missing \n at end of ALTERNATIVE inline asm David Woodhouse
2018-01-05 13:04     ` [tip:x86/pti] x86/alternatives: Add missing '\n' " tip-bot for David Woodhouse
2018-01-04 14:37   ` [PATCH v3 09/13] x86/retpoline/irq32: Convert assembler indirect jumps David Woodhouse
2018-01-04 14:37   ` [PATCH v3 10/13] x86/retpoline/pvops: " David Woodhouse
2018-01-04 15:02     ` Juergen Gross
2018-01-04 15:12       ` Woodhouse, David
2018-01-04 15:18       ` Andrew Cooper
2018-01-04 16:04         ` Juergen Gross
2018-01-04 16:37       ` Andi Kleen
2018-01-04 14:37   ` [PATCH v3 11/13] retpoline/taint: Taint kernel for missing retpoline in compiler David Woodhouse
2018-01-04 22:06     ` Justin Forbes
2018-01-04 14:37   ` [PATCH v3 12/13] retpoline/objtool: Disable some objtool warnings David Woodhouse
2018-01-04 14:37   ` [PATCH v3 13/13] retpoline: Attempt to quiten objtool warning for unreachable code David Woodhouse
2018-01-04 16:18   ` [RFC] Retpoline: Binary mitigation for branch-target-injection (aka "Spectre") Andy Lutomirski
2018-01-04 16:24     ` David Woodhouse
2018-01-05 10:49     ` Paul Turner
2018-01-05 11:43       ` Woodhouse, David

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