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Message-ID: <2ba33fe385b7043830e1a8d428047e53@overdrivepizza.com>
Date: Thu, 21 Jul 2022 13:22:12 -0700
From: Joao Moreira <joao@...rdrivepizza.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Sami Tolvanen <samitolvanen@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Josh Poimboeuf <jpoimboe@...nel.org>,
"Cooper, Andrew" <andrew.cooper3@...rix.com>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
Johannes Wikner <kwikner@...z.ch>,
Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
"Moreira, Joao" <joao.moreira@...el.com>,
"Nuzman, Joseph" <joseph.nuzman@...el.com>,
Steven Rostedt <rostedt@...dmis.org>,
"Gross, Jurgen" <jgross@...e.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Peter Collingbourne <pcc@...gle.com>,
Kees Cook <keescook@...omium.org>
Subject: Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation
> Ok. I don't know the context, but I was thinking along the lines of
> the same hash value perhaps being used multiple times because it has
> the same function type. Then using the "addl" trick means that the
> hash value in %r10 will be changing and cannot be re-used.
Fwiiw, even if %r10 value was not being destroyed by the "addl", the
call right after the check implies that you cannot trust the contents of
%r10 anymore (it may have been messed up within the called function).
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