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

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

On Tue, Jul 03, 2018 at 06:02:27PM +0200, Daniel Kiper wrote:
> On Thu, Jun 28, 2018 at 11:35:24PM -0600, Jan Beulich wrote:
> > >>> Roger Pau Monne <roger.pau@xxxxxxxxxx> 06/28/18 5:38 PM >>>
> > >lld (the llvm linker) has some issues with Xen linker script. It
> > >doesn't understand '||' in assert expressions:
> > >
> > >ld    -melf_x86_64_fbsd  -T xen.lds -N prelink.o --build-id=sha1 \
> > >/root/src/xen/xen/common/symbols-dummy.o -o /root/src/xen/xen/.xen-syms.0
> > >ld: error: xen.lds:260: malformed number: |
> > >>>> ASSERT(__image_base__ > (((((((((261 >> 8) * 0xffff000000000000) | 
> > >>>> (261 << 39))) + ((1 << 39) / 2)) + (64 << 30)) + (1 << 30)) + (1 << 
> > >>>> 30))) ||
> > >>>>                                                                        
> > >>>>                                                                        
> > >>>> ^
> > >
> > >And doesn't work properly with the 'DEFINED(foo) ? foo : ...'
> > >expression:
> > >
> > >ld    -melf_x86_64_fbsd  -T xen.lds -N prelink.o --build-id=sha1 \
> > >/root/src/xen/xen/common/symbols-dummy.o -o /root/src/xen/xen/.xen-syms.0
> > >ld: error: xen.lds:233: symbol not found: efi
> 
> This smells like lld bug. efi symbol is clearly undefined in prelink.o
> (lld does not support i386pep emulation):
> 
>  11147: 0000000000000000     0 NOTYPE  GLOBAL HIDDEN   UND efi
> 
> However, surprisingly DEFINED() states that it is and ternary operator
> fires address calculation from undefined symbol. So, I think that lld
> have to be fixed instead of Xen. It should be noted that binutils ld
> works without any issue.

Yes, I know it's a bug in llvm ld. The '||' issue has already been
fixed upstream, and I hope the DEFINED one won't take long to get
fixed also.

Thanks, Roger.

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