linux-kernel - Re: [PATCH] scripts/decodecode: Make objdump always use operand-size suffix

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Message-ID: <93a60cc2-52df-878e-6b07-dd80d5d3f149@gnuweeb.org>
Date:   Tue, 1 Mar 2022 16:16:47 +0700
From:   Ammar Faizi <ammarfaizi2@...weeb.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     weidonghui <weidonghui@...winnertech.com>, tools@...ux.kernel.org,
        linux-kernel@...r.kernel.org, gwml@...r.gnuweeb.org,
        x86@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] scripts/decodecode: Make objdump always use operand-size
 suffix

On 3/1/22 3:41 PM, Borislav Petkov wrote:
> On Tue, Mar 01, 2022 at 11:11:19AM +0700, Ammar Faizi wrote:
>> For better reading, always use operand-size suffix for the generated
> 
> What does "better reading" mean here exactly?
> 
> See, there's a reason why -M suffix is not default in objdump. And in
> my experience, I've never looked at objdump output and thought, "hm, so
> the operand size insn mnemonic suffix is missing here". And if at all,
> one usually wants to know the operand size of a single instruction - not
> the whole bunch - and for that we tend to look at the vendor manuals
> directly...
> 
> So I don't think this brings any improvement to the output but hey, I
> could be missing a reason.
> 

I am aware that for particular cases, we can deduce the operand-size from its
operand. So using operand-size is not always mandatory.

I would say always using operand-size is our habit in writing Assembly code.
Especially for the Linux kernel. Looking at entry_64.S, entry_32.S and many
Assembly files here, we always use the operand-size. It also helps to determine
the size quickly. It gives us extra information about the operand size when
sometimes it can be vague.

For me (and probably other people who always take care of the operand-size),
it is a convenience to have them in the objdump as well :)

I don't think it's that urgent to have, but having it should not bother people
who don't care with the operand-size suffix anyway.

-- 
Ammar Faizi