Subject: Re: architectures with ARCH_SUPPORTS_AOUT but no binfmt_aout
From: David Woodhouse <dwmw2@infradead.org>
To: Adrian Bunk <bunk@kernel.org>
Cc: Peter Korsgaard <jacmet@sunsite.dk>, linux-kernel@vger.kernel.org,
       sam@ravnborg.org, dhowells@redhat.com, andi@firstfloor.org,
       "Kirill A. Shutemov" <k.shutemov@gmail.com>, ysato@users.sourceforge.jp,
       takata@linux-m32r.org, linux-m32r@ml.linux-m32r.org, kyle@mcmartin.ca,
       matthew@wil.cx, grundler@parisc-linux.org, linux-parisc@vger.kernel.org,
       lethal@linux-sh.org, linux-sh@vger.kernel.org,
       linux-arch@vger.kernel.org
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Date: Tue, 17 Jun 2008 11:18:45 +0100
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On Tue, 2008-06-17 at 13:11 +0300, Adrian Bunk wrote:
> On Tue, Jun 17, 2008 at 10:46:44AM +0100, David Woodhouse wrote:
> > On Tue, 2008-06-17 at 11:42 +0300, Adrian Bunk wrote:
> > > 
> > > > Why _are_ there architectures which define ARCH_SUPPORTS_AOUT and have
> > > > <asm/a.out.h> but don't support binfmt_aout, anyway? How does that make
> > > > sense?
> > > 
> > > My guess would be that binfmt_aout isn't actually used there.
> > > 
> > > The affected architectures are:
> > > - h8300
> > > - m32r
> > > - parisc
> > > - sh
> > > - v850
> > > 
> > > v850 is broken beyond repair, and I hope my patch to remove the 
> > > architecture will make it into 2.6.27.
> > > 
> > > For the other 4 architectures I have Cc'ed the architecture maintainers.
> > 
> > There's another set of architectures which have <asm/a.out.h> but don't
> > define ARCH_SUPPORTS_AOUT. Including PowerPC.
> > 
> > I think we can probably get away with removing <asm/a.out.h> from every
> > architecture other than Alpha, ARM, m68k and x86, and killing
> > ARCH_SUPPORTS_AOUT completely.
> 
> include/linux/a.out.h contains an #include <asm/a.out.h> and is exported 
> to userspace...

Actually, it isn't -- but it _should_ be. But we can do it conditionally.
See http://git.infradead.org/users/dwmw2/aout-2.6.git?a=commitdiff;h=5939c6a41

> > Or maybe, as dhowells suggests, re-defining ARCH_SUPPORTS_AOUT to be set
> > only on Alpha, ARM, m68k and x86 (so BINFMT_AOUT can depend on it).
> 
> The pattern for this stuff is to provide a HAVE_AOUT kconfig variable 
> that gets select'ed by these architectures.

Or that; it doesn't really matter. I was about to remove
ARCH_SUPPORTS_AOUT completely, but David suggested that it could be used
to kill that hard-coded '(X86_32 || ALPHA || ARM || M68K)' in
fs/Kconfig.binfmt.


-- 
dwmw2

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