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

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

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.

Daniel

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