linux-kernel - Re: PROC macro to annotate functions in assembly files

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Message-Id: <1229603702.27623.1290725827@webmail.messagingengine.com>
Date:	Thu, 18 Dec 2008 13:35:02 +0100
From:	"Alexander van Heukelum" <heukelum@...tmail.fm>
To:	"Russell King" <rmk+lkml@....linux.org.uk>,
	"Alexander van Heukelum" <heukelum@...lshack.com>
Cc:	"David Howells" <dhowells@...hat.com>, linux-arch@...r.kernel.org,
	"Ingo Molnar" <mingo@...e.hu>,
	"LKML" <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Sam Ravnborg" <sam@...nborg.org>,
	"Cyrill Gorcunov" <gorcunov@...il.com>
Subject: Re: PROC macro to annotate functions in assembly files

On Thu, 18 Dec 2008 11:44:27 +0000, "Russell King"
<rmk+lkml@....linux.org.uk> said:
> On Wed, Dec 17, 2008 at 12:12:14PM +0100, Alexander van Heukelum wrote:
> > Yeah, assembly files contain some interesting nesting. In this
> > particular case I think the solution is simple... Just use PROC
> > and ENDPROC around the complete functions, and leave the explicit
> > .global's for the additional entry points.
> 
> I'm sorry, that doesn't work in all cases.
> 
> On ARM with later toolchains, there's additional metadata associated with
> every symbol, and it's beginning to matter getting this right.  That
> metadata includes whether it's a function, and more importantly whether
> the code pointed to by the symbol is Thumb or ARM.
> 
> This leads to:
> 
> ENTRY(__ashldi3)
> ENTRY(__aeabi_llsl)
> 
> ...
> 
> ENDPROC(__ashldi3)
> ENDPROC(__aeabi_llsl)
> 
> and we want both of those symbols to have exactly the same attributes.
> 
> Merely adding a .globl for the second name doesn't do that.  It needs
> .globl, .size, and .type.
> 
> So what you're actually talking about using your approach is enforcing
> the pairing of the existing ENTRY/ENDPROC and open coding everything
> else.

Note that enforcing the pairing will be enabled by ARCH code. Is the
construct you show here (two symbols covering identical code) the only
problem you forsee? I don't want to introduce too many macro's to
handle special cases, but this one should be solved.

> Forgive me if I think this is a backward step.  It certainly seems to
> add some insane restrictions.

Some restrictions are introduced, indeed. And I agree that evading the
checking framework by doing things manually should be avoided.

Greetings,
    Alexander

> -- 
> Russell King
>  Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
>  maintainer of:
-- 
  Alexander van Heukelum
  heukelum@...tmail.fm

-- 
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