From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-toolchains@vger.kernel.org,
clang-built-linux <clang-built-linux@googlegroups.com>,
"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>,
Will Deacon <will@kernel.org>
Subject: Re: Plumbers CF MCs
Date: Tue, 23 Mar 2021 20:36:12 -0400 [thread overview]
Message-ID: <20210323203612.02a5b29d@oasis.local.home> (raw)
In-Reply-To: <20210323221246.GB5208@worktop.programming.kicks-ass.net>
On Tue, 23 Mar 2021 23:12:46 +0100
Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Mar 23, 2021 at 08:53:58PM +0100, Peter Zijlstra wrote:
>
> > Another utterly disguisting option is to align all CALL instructions on
> > 8 bytes and have it followed by 3 INT3s to make it 8 bytes long. Then
> > have every function prologue round up the return address. This should
> > work with tail-call optimizations because the round-up is NOP when
> > repeated. The obvious down-side is that it will utterly wreck the RSB
>
> Slightly less horrible: "CALL func; INT3" + "INC (%RSP); RET; INT3".
> It still completely wrecks RSB, but isn't nearly as wasteful.
I'm confused. Why is speculation after a CALL dangerous? That code will
be executed on the return of the call anyway. That is, it's not
speculating something that wont execute in the future, whereas code
after RET and JMP wont be executed.
-- Steve
next prev parent reply other threads:[~2021-03-24 0:37 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 [this message]
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
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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