Re: [Xen-devel] [PATCH] xen/x86: fix linker script to work with lld

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Wed, Jul 11, 2018 at 02:48:25AM -0600, Jan Beulich wrote:
> >>> On 11.07.18 at 10:29, <roger.pau@xxxxxxxxxx> wrote:
> > On Wed, Jul 11, 2018 at 01:09:30AM -0600, Jan Beulich wrote:
> >> Another possible thing to try might be to make the extern declaration
> >> of the symbol weak, and drop the offending line altogether.
> >
> > Oh, that didn't occur to me, and does seem to work. Below is what I've
> > successfully tested:
> >
> > diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> > index 5f2392621d..d84704745e 100644
> > --- a/xen/arch/x86/xen.lds.S
> > +++ b/xen/arch/x86/xen.lds.S
> > @@ -297,8 +297,6 @@ SECTIONS
> >    } :text
> >  #endif
> >
> > -  efi = DEFINED(efi) ? efi : .;
> > -
> >    /* Sections to be discarded */
> >    /DISCARD/ : {
> >         *(.exit.text)
> > diff --git a/xen/include/xen/efi.h b/xen/include/xen/efi.h
> > index 44b7d3ec3a..8e25bfaebb 100644
> > --- a/xen/include/xen/efi.h
> > +++ b/xen/include/xen/efi.h
> > @@ -21,7 +21,7 @@ struct efi {
> >      unsigned long smbios3;      /* SMBIOS v3 table */
> >  };
> >
> > -extern struct efi efi;
> > +extern struct efi efi __attribute__((weak));
> >
> >  #ifndef __ASSEMBLY__
> >
> >
> > If that's acceptable I will refresh and resend the patch.
>
> Let's see what Daniel and maybe others say. If you go that route,
> could I talk you into adding __weak to compiler.h (I dislike to suggest
> the leading double underscores, but not using them there would just
> be too inconsistent with the rest of this header)?

If this works in all cases (build with tools with and without PE support,
xen.efi and xen.gz via Multiboot2 proto boot correctly on EFI platforms,
etc.) then I am OK with that.

Daniel

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