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Message-ID: <20230814174810.GGZNpo2sjkpFiJLjif@fat_crate.local>
Date: Mon, 14 Aug 2023 19:48:10 +0200
From: Borislav Petkov <bp@...en8.de>
To: Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, David.Kaplan@....com,
Andrew.Cooper3@...rix.com, jpoimboe@...nel.org,
gregkh@...uxfoundation.org, nik.borisov@...e.com
Subject: Re: [PATCH v2 05/11] x86/cpu: Clean up SRSO return thunk mess
On Mon, Aug 14, 2023 at 01:44:31PM +0200, Peter Zijlstra wrote:
> Where Zen1/2 flush the BTB entry using the instruction decoder trick
> (test,movabs) Zen3/4 use instruction aliasing. SRSO adds RSB (RAP in
I'll change that "instruction aliasing" to "BTB aliasing".
> AMD speak) stuffing to force speculation into a trap an cause a
> mis-predict.
I'll change that to the much more precise:
"SRSO adds a return sequence (srso_safe_ret()) which forces the function
return instruction to speculate into a trap (UD2). This RET will then
mispredict and execution will continue at the return site read from the
top of the stack."
--
Regards/Gruss,
Boris.
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