Re: [Xen-devel] [PATCH v2 2/3] x86: check for multiboot{1, 2} header presence

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Jun 21, 2019 at 06:20:54PM +0100, Andrew Cooper wrote:
> On 21/06/2019 17:38, Roger Pau Monne 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>
> 
> While the change is ok, won't this break the gitlab CI which is
> currently using the llvm-8 toolchain?

Yes, that's right. It's also going to break the FreeBSD Xen build on
osstest (this is not part of the xen- flights however).

ATM the gitlab llvm-8 builds don't seem to correctly pick up the LD
env variable, so they still pass with this change applied.

> > ---
> > Changes since v1:
> >  - Use an intermediate file to perform the header checks.
> > ---
> >  xen/arch/x86/Makefile | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
> > index 8a8d8f060f..5c908c49e3 100644
> > --- a/xen/arch/x86/Makefile
> > +++ b/xen/arch/x86/Makefile
> > @@ -100,8 +100,12 @@ syms-warn-dup-y := --warn-dup
> >  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) \
> > +   ./boot/mkelf32 $(notes_phdrs) $(TARGET)-syms $(@D)/.$(@F) 
> > $(XEN_IMG_OFFSET) \
> >                    `$(NM) $(TARGET)-syms | sed -ne 's/^\([^ ]*\) . 
> > __2M_rwdata_end$$/0x\1/p'`
> > +   # Check for multiboot{1,2} headers
> > +   od -t x4 -N 8192 $(@D)/.$(@F) | grep 1badb002 > /dev/null
> > +   od -t x4 -N 32768 $(@D)/.$(@F) | grep e85250d6 > /dev/null
> > +   mv $(@D)/.$(@F) $(TARGET)
> 
> This might be a bit cleaner to read as
> 
> $(TARGET): tmp=$(@D)/.$(@F)
> $(TARGET): $(TARGET)-syms $(efi-y) boot/mkelf32
> 
> rather than having $(@D)/.$(@F) spread throughout the rule.

Ack, Thanks!

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