linux-kernel - Re: [PATCH] compiler: remove stringification from __ADDRESSABLE

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Message-ID: <20250212234112.3i54fmgthakuxghf@jpoimboe>
Date: Wed, 12 Feb 2025 15:41:12 -0800
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: Jan Beulich <jbeulich@...e.com>
Cc: lkml <linux-kernel@...r.kernel.org>, Juergen Gross <jgross@...e.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Luc Van Oostenryck <luc.vanoostenryck@...il.com>
Subject: Re: [PATCH] compiler: remove stringification from __ADDRESSABLE_ASM()

On Wed, Feb 12, 2025 at 03:32:44PM -0800, Josh Poimboeuf wrote:
> > I think that __ADDRESSABLE_ASM{,_STR}() better would have a separate
> > comment, as that presently kind of shared with {_,}__ADDRESSABLE() isn't
> > really applicable to assembly code.
> > 
> > Is data allocation actually necessary in __ADDRESSABLE_ASM()? Aiui the
> > sole goal is to have sym in the symbol table. That could be achieved by
> > a simple .global (or e.g. .hidden) directive.
> 
> Hm, yes, but isn't that a bug?  It shouldn't be defining the symbol, as
> that will already be defined elsewhere.  So it would link to the local
> symbol instead of the actual static key defined in another object.
> 
> Even worse, the local symbol gets discarded during linking?  Not sure
> how that works without a linker error...

Oh, I forgot how my patch worked.  __ADDRESSABLE_ASM is defining a
pointer to the symbol, not defining the symbol itself.  So forget all
that :-)

But yes, using .global with STATIC_CALL_KEY() sounds like a much easier
way.

-- 
Josh