linux-kernel - Re: [RFC][PATCH] x86,ibt: Use UDB instead of 0xEA

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Message-ID: <78bd985a-a59e-4469-a84d-a0eb7faa20c3@zytor.com>
Date: Fri, 15 Aug 2025 10:14:57 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Andrew Cooper <andrew.cooper3@...rix.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, kees@...nel.org, alyssa.milburn@...el.com,
        scott.d.constable@...el.com, joao@...rdrivepizza.com,
        samitolvanen@...gle.com, nathan@...nel.org,
        alexei.starovoitov@...il.com, mhiramat@...nel.org, ojeda@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] x86,ibt: Use UDB instead of 0xEA

On 2025-08-15 04:19, Andrew Cooper wrote:
>>
>> CS Jcc, decodes to Jcc,pn for non-taken
>> DS Jcc, decodes to Jcc,pt for taken
> 
> Ah, thanks.  I was looking at the hex in one of the comments and still
> couldn't figure it out.
> 
> So with this notation, we also have the dual meaning of ,pt between the
> P4 and LNC.  At least the encoding is the same.
> 

What "dual meaning?"

	-hpa