linux-kernel - Re: [PATCH v5 01/10] x86/asm: Add FP

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Message-ID: <20150611141804.GA12084@treble.redhat.com>
Date:	Thu, 11 Jun 2015 09:18:04 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Jiri Kosina <jkosina@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 01/10] x86/asm: Add FP_SAVE/RESTORE frame pointer
 macros

On Thu, Jun 11, 2015 at 08:46:33AM +0200, Pavel Machek wrote:
> On Thu 2015-06-11 06:22:49, Jiri Kosina wrote:
> > On Wed, 10 Jun 2015, Pavel Machek wrote:
> > 
> > > > diff --git a/arch/x86/include/asm/func.h b/arch/x86/include/asm/func.h
> > > > new file mode 100644
> > > > index 0000000..4d62782
> > > > --- /dev/null
> > > > +++ b/arch/x86/include/asm/func.h
> > > > @@ -0,0 +1,24 @@
> > > > +#ifndef _ASM_X86_FUNC_H
> > > > +#define _ASM_X86_FUNC_H
> > > > +
> > > > +#include <linux/linkage.h>
> > > > +#include <asm/asm.h>
> > > > +
> > > > +/*
> > > > + * These are frame pointer save and restore macros.  They should be used by
> > > > + * every callable non-leaf asm function.
> > > > + */
> > > > +.macro FP_SAVE name
> > > > +	.if CONFIG_FRAME_POINTER
> > > > +		push %_ASM_BP
> > > > +		_ASM_MOV %_ASM_SP, %_ASM_BP
> > > > +	.endif
> > > > +.endm
> > > 
> > > Hmm. This will not compile when included into .c file. Should it have
> > > other extension than .h? (Or can the macros be done in different way?
> > 
> > We have quite a few of .h headers in the kernel already which are supposed 
> > to be included only by .S files, so what exactly is the problem you are 
> > seeing here?
> 
> Such as...? Can this be merged into one of them so that we don't have
> a separate file? For example "frame.h"?
> 
> (I thought asm includes traditionally had different extension, but I
> may be mistaken).
> 
> And at the very least, dwarf2.h includes
> 
> #ifndef __ASSEMBLY__
> #warning "asm/dwarf2.h should be only included in pure assembly files"
> #endif
> 
> and guards stuff that would not compile in C with
> 
> #ifdef __ASSEMBLY__
> ....

Ok, I'll move the FP_SAVE/RESTORE stuff into frame.h (which seems to be
completely unused).  And I'll make sure to use "#ifdef __ASSEMBLY__".

-- 
Josh
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