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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 03.07.18 at 18:02, <daniel.kiper@xxxxxxxxxx> 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.

Right, but if we can make Xen build nevertheless, this would be better.
So what we need here is a (re-)explanation of why you've needed to
do the very change Roger is suggesting to revert.

Jan



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