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Date: Wed, 28 May 2008 21:09:07 +0200
From: Sam Ravnborg <sam@ravnborg.org>
Subject: Re: kbuild variable $(src) broken in 2.6.23-rc3?
Message-ID: <20080528190907.GA6466@uranus.ravnborg.org>
References: <20080521144211.902CD37652C@pmx1.sophos.com> <20080521190453.GA12638@uranus.ravnborg.org> <20080521194806.GJ22488@duo.random>
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To: Andrea Arcangeli <andrea@qumranet.com>
Cc: tvrtko.ursulin@sophos.com, linux-kbuild@vger.kernel.org

On Wed, May 21, 2008 at 09:48:08PM +0200, Andrea Arcangeli wrote:
> On Wed, May 21, 2008 at 09:04:53PM +0200, Sam Ravnborg wrote:
> > Andrea Arcangeli <andrea@qumranet.com> reported a similar issue.
> > I have not gotten around to look at it yet.
> > I minimal Makefile that exhibits the problem
> > would be helpfull!
> 
> I don't have the minimal but I can easily provide you a way to
> reproduce:
> 
> git clone git://git.kernel.org/pub/scm/virt/kvm/kvm-userspace.git
> cd kvm-userspace
> patch -p1 -R <../belowinlinedworkaround
> ./configure --kerneldir=/usr/src/anykernel
> cd kernel
> make
> 
> The below has the benefit of making more robust and higher prio the
> inclusion of external-module-compat so it may not to be backed out
> after this 2.6.26-rc regression is fixed.
> 
> The problem is that the $(src) in the EXTRA_CFLAGS below is expanded
> to "".

I have now tried to reproduce this bug with no luck.
- I tried to clone the git tree and follow your instructions.
  But it failed to build due to some files missing in the
  kernel directory so I gace up on that.
- Then I tried to create a few Makefiles for an external
  module. I used a copy of the ext-2 filesystem and modifided
  the Makefile like below:
#
# Makefile for the linux ext2-filesystem routines.
#

obj-m += ext2.o

ext2-y := balloc.o dir.o file.o fsync.o ialloc.o inode.o \
          ioctl.o namei.o super.o symlink.o

EXTRA_CFLAGS := -I$(src)


Manually inspecting the command lines to gcc told me that $(src) was
properly expanded.

So something more subtle is going on.

Can I ask you to in an empty directory to create
a Makefile like this:
obj-m := foo.o
ccflags-y := -I$(src)

Another question. Do you use a -mm or -next kernel.
Or do you use a vanlla -linus kernel?

Because Andrew has some patches in -mm that may impact
how we handle -I but I do not have -mm available on this box.

	Sam