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Date:   Thu, 21 Jul 2022 13:22:12 -0700
From:   Joao Moreira <joao@overdrivepizza.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Sami Tolvanen <samitolvanen@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
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        the arch/x86 maintainers <x86@kernel.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        "Cooper, Andrew" <andrew.cooper3@citrix.com>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
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        Alyssa Milburn <alyssa.milburn@linux.intel.com>,
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        "Moreira, Joao" <joao.moreira@intel.com>,
        "Nuzman, Joseph" <joseph.nuzman@intel.com>,
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        "Gross, Jurgen" <jgross@suse.com>,
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        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Peter Collingbourne <pcc@google.com>,
        Kees Cook <keescook@chromium.org>
Subject: Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation
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> 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).