Re: [PATCH] xen: Fix EFI buildid alignment

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Thu, Nov 20, 2025 at 12:43:57AM +0000, Andrew Cooper wrote:
> On 19/11/2025 7:12 pm, Marek Marczykowski-Górecki wrote:
> > Old binutils get confused about .buildid overlapping (in VA space) with
> > earlier section. That confusion results in weird errors down the road,
> > like this one:
> >
> >     objcopy: xen.efi: Data Directory size (1c) exceeds space left in 
> > section (8)
> >
> > While the bug is fixed in later binutils version, force alignment of the
> > buildid to avoid overlapping and make it work with older versions too.
> > This can be reverted once toolchain base is raised at or above binutils
> > 2.36.
> >
> > Details at:
> > https://lore.kernel.org/all/3TMd7J2u5gCA8ouIG_Xfcw7s5JKMG06XsDIesEB3Fi9htUJ43Lfl057wXohlpCHcszqoCmicpIlneEDO26ZqT8QfC2Y39VxBuqD3nS1j5Q4=@trmm.net/
> >
> > Signed-off-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > Fixes: eee5909e9d1e ("x86/EFI: use less crude a way of generating the build 
> > ID")
> 
> We typically put these tags in the other order.  I can fix on commit.
> 
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, although...
> 
> > ---
> > While the actual bug apparently is in binutils, the commit mentioned in
> > Fixes: tag introduced part that triggers that bug.
> > ---
> >  xen/arch/x86/xen.lds.S | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> > index 5d02f83a409c..967f9167f757 100644
> > --- a/xen/arch/x86/xen.lds.S
> > +++ b/xen/arch/x86/xen.lds.S
> > @@ -171,6 +171,8 @@ SECTIONS
> >         __note_gnu_build_id_end = .;
> >    } PHDR(note) PHDR(text)
> >  #elif defined(BUILD_ID_EFI)
> > +  /* Workaround bug in binutils < 2.38 */
> 
> ... this says 2.38, but the commit message says 2.36.  Which one is it?

2.36

> ~Andrew
> 
> > +  . = ALIGN(32);
> >    DECL_SECTION(.buildid) {
> >         __note_gnu_build_id_start = .;
> >         *(.buildid)
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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