linux-kernel - Re: [PATCH 01/11] ftrace: handle generic arch calls

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Date:	Wed, 29 Oct 2008 20:49:56 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Abhishek Sagar <sagar.abhishek@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <srostedt@...hat.com>,
	Adrian Bunk <bunk@...nel.org>
Subject: Re: [PATCH 01/11] ftrace: handle generic arch calls

On Wed, Oct 29, 2008 at 03:24:19PM -0400, Steven Rostedt wrote:
> 
> On Wed, 29 Oct 2008, Sam Ravnborg wrote:
> > >  
> > > +if ($arch eq "x86") {
> > > +    if ($bits == 64) {
> > > +	$arch = "x86_64";
> > > +    } else {
> > > +	$arch = "i386";
> > > +    }
> > > +}
> > > +
> > >  if ($arch eq "x86_64") {
> > >      $section_regex = "Disassembly of section";
> > >      $function_regex = "^([0-9a-fA-F]+)\\s+<(.*?)>:";
> > > 
> > 
> > This looks strange to my eyes.
> > Why not do the more obvious:
> > if ($arch eq "x86" && $bits == 64) {
> > 
> > The change above is like trying to stick to the old i386/x86_64
> > notation.
> 
> Trying to fix it tells me my answer to why I did it his way ;-)
> 
> I have queued patches that will support other archs so x86 is not the
> only arch that can be used here. But x86 is special, it seems to be the 
> only arch (that I know of, correct me if I'm wrong) that can compile with
> multiple archs defined: make ARCH=x86_64, make ARCH=i386, or
> make ARCH=x86. All are legit.
> 
> Now how do we handle this. I've been fine for all my testing to do just 
> x86_64 and i386 because a normal make of x86 will use automatically set
> ARCH to i386 or x86_64 depending on the build.
> 
> But then Adrian Bunk pointed out that "make ARCH=x86" fails. Now I need to 
> add a case for x86, but still allow for x86_64 or i386 being passed in.
> 
> Since x86 is the ambiguous case, I made it the one that would be converted 
> to i386 or x86_64 since those could be passed in directly.
The trick is usually to replace use of ARCH with SRCARCH.

	Sam
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