linux-kernel - Re: [PATCH 01/10] x86: assembly, ENTRY for fn, GLOBAL for data

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Date:   Wed, 1 Mar 2017 11:27:54 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Slaby <jslaby@...e.cz>, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, jpoimboe@...hat.com, linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel@...ts.xenproject.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        linux-pm@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 01/10] x86: assembly, ENTRY for fn, GLOBAL for data


* Thomas Gleixner <tglx@...utronix.de> wrote:

> On Wed, 1 Mar 2017, Ingo Molnar wrote:
> > 
> > * Jiri Slaby <jslaby@...e.cz> wrote:
> > 
> > > This is a start of series to unify use of ENTRY, ENDPROC, GLOBAL, END,
> > > and other macros across x86. When we have all this sorted out, this will
> > > help to inject DWARF unwinding info by objtool later.
> > > 
> > > So, let us use the macros this way:
> > > * ENTRY -- start of a global function
> > > * ENDPROC -- end of a local/global function
> > > * GLOBAL -- start of a globally visible data symbol
> > > * END -- end of local/global data symbol
> > 
> > So how about using macro names that actually show the purpose, instead of 
> > importing all the crappy, historic, essentially randomly chosen debug symbol macro 
> > names from the binutils and older kernels?
> > 
> > Something sane, like:
> > 
> > 	SYM__FUNCTION_START
> 
> Sane would be:
> 
>      	SYM_FUNCTION_START
> 
> The double underscore is just not giving any value.

So the double underscore (at least in my view) has two advantages:

1) it helps separate the prefix from the postfix.

I.e. it's a 'symbols' namespace, and a 'function start', not the 'start' of a 
'symbol function'.

2) It also helps easy greppability.

Try this in latest -tip:

  git grep e820__

To see all the E820 API calls - with no false positives!

'git grep e820_' on the other hand is a lot less reliable...

But no strong feelings either way, I just try to sneak in these small namespace 
structure tricks when nobody's looking! ;-)

Thanks,

	Ingo