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

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Date:   Tue, 1 Mar 2022 11:44:31 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Ammar Faizi <ammarfaizi2@...weeb.org>
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 Tue, Mar 01, 2022 at 04:16:47PM +0700, Ammar Faizi wrote:
> I would say always using operand-size is our habit in writing Assembly code.

"our" is who?

> 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.

When do you ever need to determine the operand size quickly?

> It gives us extra information about the operand size when
> sometimes it can be vague.

So I'm looking at output of

objdump -d arch/x86/entry/entry_64.o

and it does by default add suffixes when it is not perfectly clear what
the operand size is, for example:

	6a 2b                   pushq  $0x2b

vs

	41 51                   push   %r9

so I think the default of not explicitly adding suffixes when it is
clear what size it is, is the most optimal one.

> 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.

So I'd prefer if this were a command line option which turns this on
only for whoever absolutely needs it.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette