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

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Wed, Jul 11, 2018 at 10:59:20AM +0200, Roger Pau Monné wrote:
> On Wed, Jul 11, 2018 at 10:55:56AM +0200, Daniel Kiper wrote:
> > 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.
>
> Yes, I've tested it with both linkers (PE capable and incapable) and
> it works.

Great! What about boot on EFI platforms? Probably it works but I would
like to be sure.

Daniel

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