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From: Nick Desaulniers <ndesaulniers@google.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Will Deacon <will@kernel.org>
Cc: linux-toolchains@vger.kernel.org,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Jose E. Marchesi" <jemarch@gnu.org>,
	Kees Cook <keescook@chromium.org>,
	Florian Weimer <fweimer@redhat.com>,
	Christian Brauner <christian.brauner@canonical.com>,
	nick.alcock@oracle.com,
	Segher Boessenkool <segher@kernel.crashing.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Jian Cai <jiancai@google.com>, Luis Lozano <llozano@google.com>,
	Kristof Beyls <Kristof.Beyls@arm.com>
Subject: Re: Plumbers CF MCs
Date: Tue, 23 Mar 2021 15:26:29 -0700	[thread overview]
Message-ID: <CAKwvOdkk6bwJh22L51F0DAMuFXJYKUTjbzQV+STD2h35Z7_vQA@mail.gmail.com> (raw)
In-Reply-To: <a60f83d2-75da-d147-ae92-47a5b474e162@citrix.com>

On Tue, Mar 23, 2021 at 12:29 PM Andrew Cooper
<andrew.cooper3@citrix.com> wrote:
>
> On 23/03/2021 08:35, Peter Zijlstra wrote:
> > There also is talk about straight line speculation mitigations. for x86
> > we should probably emit an INT3 after every JMP and RET. Although this
> > might not be controversial and be sorted by the time Plumbers happens.
>
> I guess this one is levied at me.
>
> Hopefully it isn't controversial in any way.  I have just had sufficient
> tuits to get around to making an x86 straight line speculation feature
> request to the GCC and Clang communities yet.
>
> For the compiler folk here, the tl;dr is that indirect CALL/JMP (i.e.
> function pointers, jump tables) and RET instructions may speculatively
> execute the next sequential instruction(s) before taking the control
> flow change into account.  Having some toolchain support to deal with
> this would be great, and preferable to some of the asm hackary currently
> under suggestion.

There is some prior art here, for ARM in -fharden-sls=*.
https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/downloads/straight-line-speculation

It's not clear from the kernel thread that the existing compiler
mitigations are amenable with live patching in/out mitigations for
hardware that is affected or not, respectively.
https://lore.kernel.org/lkml/20210305095256.GA22536@willie-the-truck/

Perhaps worth a discussion on the mailing list in
https://www.kernel.org/doc/html/latest/admin-guide/security-bugs.html ?
-- 
Thanks,
~Nick Desaulniers

  parent reply	other threads:[~2021-03-23 22:29 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-22 20:23 Plumbers CF MCs Nick Desaulniers
2021-03-22 20:39 ` Jose E. Marchesi
2021-03-31 19:34   ` Elena Zannoni
2021-03-31 20:36     ` Nick Desaulniers
2021-04-01  7:59       ` Jose E. Marchesi
2021-04-01 20:01         ` Nick Desaulniers
2021-04-01 13:29       ` Steven Rostedt
2021-04-01 13:31         ` Steven Rostedt
2021-04-01 13:49         ` Elena Zannoni
2021-04-01 15:11           ` Miguel Ojeda
2021-04-01 20:11           ` Nick Desaulniers
2021-04-01 13:25     ` Steven Rostedt
2021-04-01 13:25       ` Steven Rostedt
2021-03-23  8:35 ` Peter Zijlstra
2021-03-23  8:45   ` Peter Zijlstra
2021-03-23 19:29   ` Andrew Cooper
2021-03-23 19:53     ` Peter Zijlstra
2021-03-23 22:12       ` Peter Zijlstra
2021-03-24  0:36         ` Steven Rostedt
2021-03-24  8:15           ` Peter Zijlstra
2021-03-23 22:23       ` Andrew Cooper
2021-03-24  8:08         ` Peter Zijlstra
2021-03-24 11:30           ` Andrew Cooper
2021-04-02 12:40       ` Segher Boessenkool
2021-03-23 22:26     ` Nick Desaulniers [this message]
2021-03-24  7:52       ` Peter Zijlstra
2021-03-24  8:47   ` Christian Brauner
2021-03-30 14:13   ` Will Deacon
2021-04-01  7:17     ` Kees Cook
2021-04-02 12:33   ` Segher Boessenkool

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