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Date: Wed, 22 May 2013 13:00:16 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20130522100016.GC24931@redhat.com>
References: <20130521214645.GA8863@redhat.com>
	<20130522094854.GD30148@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Blue Swirl <blauwirbel@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>

On Wed, May 22, 2013 at 11:48:54AM +0200, Stefan Hajnoczi wrote:
> On Wed, May 22, 2013 at 12:46:45AM +0300, Michael S. Tsirkin wrote:
> > Once in a while make gets killed and doesn't
> > clean up partial object files after it.
> > Result is nasty errors from link.
> > This hack checks object is well formed before linking,
> > and rebuilds it if not.
> > 
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> > 
> > Is below useful for others?
> > 
> >  Makefile.target | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/Makefile.target b/Makefile.target
> > index ce4391f..4dddee5 100644
> > --- a/Makefile.target
> > +++ b/Makefile.target
> > @@ -191,3 +191,10 @@ endif
> >  
> >  GENERATED_HEADERS += config-target.h
> >  Makefile: $(GENERATED_HEADERS)
> > +
> > +.SECONDEXPANSION:
> > +
> > +.PHONY: CORRUPTBINARY
> > +
> > +$(all-obj-y): % : $$(if $$(shell size %), , CORRUPTBINARY)
> 
> How does size(1) establish the validity of the ELF file?
>  Is it possible
> to sneak past a truncated file (which I think is the only type of
> corruption you're trying to protect against)?
> 
> Stefan

It just parses the header, so of course it is.
But it does seem to catch the common failure
scenarios for me.

-- 
MST