linux-kernel - Re: [PATCH 2/3] objtool: Ignore retpoline alternatives

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Message-ID: <1515693428.22302.388.camel@infradead.org>
Date:   Thu, 11 Jan 2018 17:57:08 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/3] objtool: Ignore retpoline alternatives

On Thu, 2018-01-11 at 09:29 -0800, Linus Torvalds wrote:
> 
> That, btw, is also why it's pointless to make the small numbers
> "bigger". Using "1122" as a label is actively worse than just using
> "1".

Actually in macros I don't think that's entirely true (depending on the
assembler/preprocessor behaviour, which is often surprising).

You want to use labels in macros which are not going to conflict with
what the human has typed into their .S file. If they have code along
the lines of

 	jnz 1f
	INVOKE_MACRO
1:

... then you surely don't want to be using the label '1' in your macro.

I'm fairly sure that's true if you're using CPP macros (which we seem
to do most of the time even in .S files). It might actually DTRT if you
are using .macro; I'm not sure.

So I will go back to numeric labels, as I said. But not '1:'. :)
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