Re: [Xen-devel] [PATCH 4/4] x86: check for multiboot{1, 2} header presence

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 19.06.19 at 13:02, <roger.pau@xxxxxxxxxx> wrote:
> After building the hypervisor binary. Note that the check is performed
> by searching for the magic header value at the start of the binary.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> ---
>  xen/arch/x86/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
> index 8a8d8f060f..9bb3bf6e6c 100644
> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -102,6 +102,9 @@ 
> syms-warn-dup-$(CONFIG_SUPPRESS_DUPLICATE_SYMBOL_WARNINGS) :=
>  $(TARGET): $(TARGET)-syms $(efi-y) boot/mkelf32
>       ./boot/mkelf32 $(notes_phdrs) $(TARGET)-syms $(TARGET) 
> $(XEN_IMG_OFFSET) \
>                      `$(NM) $(TARGET)-syms | sed -ne 's/^\([^ ]*\) . 
> __2M_rwdata_end$$/0x\1/p'`
> +     # Check for multiboot{1,2} headers
> +     od -t x4 -N 8192 $(TARGET) | grep 1badb002 > /dev/null
> +     od -t x4 -N 32768 $(TARGET) | grep e85250d6 > /dev/null

What's the behavior when a signature is _not _ found? Will
$(TARGET) get deleted (by make)? I don't think it would (as we
don't specific .DELETE_ON_ERROR anywhere), so a subsequent
rebuild may not even execute this rule, and hence may look to be
successful despite it not actually having been.

Jan


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