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Date: Fri, 5 Apr 2013 14:59:41 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130405125941.GD15818@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2] hw/i386/pc: reject to boot a wrong
 header magic kernel
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To: liguang <lig.fnst@cn.fujitsu.com>
Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org

On Mon, Apr 01, 2013 at 09:21:57AM +0800, liguang wrote:
> if head magic is missing or wrong unexpectedly, we'd
> better to reject booting.
> e.g.
> I make a mistake to boot a vmlinuz for MIPS(which
> I think it's for x86) like this:
> qemu-system-x86_64 -kernel vmlinuz -initrd demord
> then qemu report:
> "qemu: linux kernel too old to load a ram disk"
> that's misleading.
> 
> Signed-off-by: liguang <lig.fnst@cn.fujitsu.com>
> ---
>  hw/i386/pc.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index b1e06fa..bfbb5fe 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -683,6 +683,9 @@ static void load_linux(void *fw_cfg,
>          if (load_multiboot(fw_cfg, f, kernel_filename, initrd_filename,
>                             kernel_cmdline, kernel_size, header)) {
>              return;
> +        } else {
> +            fprintf(stderr, "not a valid multiboot image!\n");
> +            exit(1);
>          }
>          protocol = 0;

The point of protocol = 0 is to support old Linux kernels.  If we exit
when probing load_multiboot() fails then QEMU will no longer load old
Linux kernels!

I suggest just:
fprintf(stderr, "warning: not a valid multiboot or modern kernel image\n");

Stefan