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Date: Wed, 22 May 2013 11:48:54 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130522094854.GD30148@stefanha-thinkpad.redhat.com>
References: <20130521214645.GA8863@redhat.com>
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In-Reply-To: <20130521214645.GA8863@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files
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To: "Michael S. Tsirkin" <mst@redhat.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 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