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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <5ffadb49-57ea-49e8-892a-5adf17ba3a2c@oracle.com>
Date: Wed, 24 Sep 2025 13:57:34 +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 13:45, Peter Zijlstra wrote:
> On Wed, Sep 24, 2025 at 12:58:13PM +0200, Peter Zijlstra wrote:
>> On Wed, Sep 24, 2025 at 12:52:35PM +0200, Alexandre Chartre wrote:
>>>
>>> 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>
>>
>> Right, I have just the function for that. Let me do a patch for you.
> 
> Bah, I'm having trouble with the makefiles, but we sorta already detect
> nops, and the below should sorta work. I'll improve decode.c a bit.
> 
> --- a/tools/objtool/disas.c
> +++ b/tools/objtool/disas.c
> @@ -273,6 +273,9 @@ static size_t disas_insn(struct disas_co
>   	dctx->insn = insn;
>   	dctx->result[0] = '\0';
>   
> +	if (insn->type == INSN_NOP)
> +		return snprintf(dctx->result, DISAS_RESULT_SIZE, "NOP%d", insn->len);
> +
>   	/*
>   	 * Set the disassembler buffer to read data from the section
>   	 * containing the instruction to disassemble.

Cool, an easy change :) Thanks.

alex.