From: Peter Zijlstra <peterz@infradead.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
llvm@lists.linux.dev
Subject: Re: [PATCH] x86/build: Move '-mindirect-branch-cs-prefix' out of GCC-only block
Date: Thu, 18 Aug 2022 10:00:59 +0200 [thread overview]
Message-ID: <Yv3xu7f3NDC1is6o@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <Yv3uI/MoJVctmBCh@worktop.programming.kicks-ass.net>
On Thu, Aug 18, 2022 at 09:45:39AM +0200, Peter Zijlstra wrote:
> The thing to do is boot with (warning, *very* verbose):
>
> "spectre_v2=retpoline,lfence debug-alternative"
>
> and observe that the retpoline sites all replace:
>
> "cs call __x86_indirect_thunk_r11" (6 bytes)
>
> with:
>
> "lfence; jmp *%r11" (6 bytes)
^^ call, ofc, unless the original was jmp then jmp...
/me goes get more morning juice in an attempt to wake up.
>
>
> This being clang, you'll ofcourse still have a few weird:
>
> "Jcc.d32 __x86_indirect_thunk_r11"
>
> sites that will not be able to be replaced, but there's nothing I can do
> about that other than to continue to encourage y'all to stop emitting
> them ;-)
next prev parent reply other threads:[~2022-08-18 8:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-17 18:54 [PATCH] x86/build: Move '-mindirect-branch-cs-prefix' out of GCC-only block Nathan Chancellor
2022-08-17 22:08 ` Nick Desaulniers
2022-08-18 7:45 ` Peter Zijlstra
2022-08-18 8:00 ` Peter Zijlstra [this message]
2022-09-30 18:10 ` Nick Desaulniers
2022-10-04 21:27 ` Nick Desaulniers
2022-10-06 17:56 ` Nick Desaulniers
2022-08-18 7:49 ` Peter Zijlstra
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