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

[Roger Pau Monné <roger.pau@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)?

Hm, the header is kind of mixed on the usage of underscores. inline,
always_inline or noreturn for example don't have them, so if you
prefer I think it should be fine to add weak without underscores.

There's an existing case of __attribute__((weak)) in
livepatch_payload.h which I will replace in the same patch if that's
fine.

Thanks, Roger.

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