linux-kernel - Re: [RFC PATCH v2 00/17] objtool: Function validation tracing

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Message-ID: <90abf24a-326a-4215-8e13-2e1a2e3194ea@oracle.com>
Date: Wed, 24 Sep 2025 12:52:35 +0200
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: alexandre.chartre@...cle.com, linux-kernel@...r.kernel.org,
        mingo@...nel.org, jpoimboe@...nel.org
Subject: Re: [RFC PATCH v2 00/17] objtool: Function validation tracing


On 9/24/25 12:10, Peter Zijlstra wrote:
> On Wed, Sep 24, 2025 at 12:08:47PM +0200, Peter Zijlstra wrote:
>> On Wed, Sep 24, 2025 at 09:42:06AM +0200, Peter Zijlstra wrote:
>>
>>>>>    d051:  perf_get_x86_pmu_capability+0x51    | xchg   %ax,%ax
>>
>> That libopcode is 'funny', isn't that typically spelled "nop" ?
> 
> Ooh, I see, it is "osp nop" and yeah binutils also seems to do that as
> "xchg %ax,%ax".

Yes, "xchg %ax,%ax" is NOP2 (opcodes: 0x66 0x90), "nop" is NOP1 (0x90).

That's one more improvement we can do: identify NOP instructions and
display them as NOP<n>

alex.