linux-kernel - Re: "N" symbols and System.map

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Message-ID: <20090504193336.GA10453@uranus.ravnborg.org>
Date:	Mon, 4 May 2009 21:33:36 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Andreas Schwab <schwab@...ux-m68k.org>
Cc:	Andreas Schwab <schwab@...ux-m68k.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org
Subject: Re: "N" symbols and System.map

On Fri, May 01, 2009 at 05:00:39PM -0700, H. Peter Anvin wrote:
> Sam Ravnborg wrote:
> >On Sat, May 02, 2009 at 01:10:18AM +0200, Andreas Schwab wrote:
> >>"H. Peter Anvin" <hpa@...ux.intel.com> writes:
> >>
> >>>right now, we filter out symbols that nm tag N, meaning "debugging
> >>>symbols", from System.map.  However, at least on x86, the 
> >>>linker-generated
> >>>symbol _end is tagged N, and in fact is the only N in the entire image.
> >>>
> >>>Are there other architectures which would suffer if N were included in
> >>>System.map, or would that be a reasonable thing to do?
> >>There should not be any N symbols unless you are using stabs debugging.
> >
> >We have in vmlinux:
> >        .end : AT(ADDR(.end) - LOAD_OFFSET) {
> >                _end = .;
> >        }
> >
> >
> >And I see:
> >c1834000 N _end
> >
> >This is the _only_ 'N' symbol in my vmlinux.
> >
> 
> Yup, this is what happens.  I don't know why the linker does this, and 
> if there is a way around it.

Andreas - can you explain what is happning here?
I can include 'N' symbols in System.map - but I have not yet reached
a level of understanding that make me go and do it.

	Sam
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