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Message-ID: <20230814195733.GIZNqHLQw79BvfjsXd@fat_crate.local>
Date: Mon, 14 Aug 2023 21:57:33 +0200
From: Borislav Petkov <bp@...en8.de>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
linux-kernel@...r.kernel.org, David.Kaplan@....com,
Andrew.Cooper3@...rix.com, gregkh@...uxfoundation.org,
nik.borisov@...e.com
Subject: Re: [PATCH v2 00/11] Fix up SRSO stuff
On Mon, Aug 14, 2023 at 12:51:53PM -0700, Josh Poimboeuf wrote:
> > * Regarding alignment - the instructions which need to be untrained,
> > * must all start at a cacheline boundary for Zen1/2 generations. That
> > * is, both the ret in zen_untrain_ret() and srso_safe_ret() in the
> > * srso_untrain_ret() must both be placed at the beginning of
> > * a cacheline.
> > */
>
> It's a good comment, but RET in srso_safe_ret() is still misaligned.
> Don't we need something like so?
Well, I guess that comment is still not good enough. Not the RET must be
cacheline-aligned but the function return sequences must be.
IOW, we need this:
<--- cacheline begin
SYM_INNER_LABEL(retbleed_return_thunk, SYM_L_GLOBAL)
ret
int3
and
<--- cacheline begin
SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
lea 8(%_ASM_SP), %_ASM_SP
ret
int3
I'll improve on it before I apply it.
Thx.
--
Regards/Gruss,
Boris.
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