Re: [Xen-devel] Clang/LLVM version requirements

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.09.12 at 12:11, Tim Deegan <tim@xxxxxxx> wrote:
> At 11:04 +0100 on 07 Sep (1347015863), Jan Beulich wrote:
>> >>> On 07.09.12 at 10:50, Tim Deegan <tim@xxxxxxx> wrote:
>> > In any case we probably ought to check for stray .data symbols too.
>> 
>> Not really, no. Those would still be present in reloc.bin, and
>> hence make it into reloc.S.
> 
> But they would break the test, because the magic alignment happens in
> .text, right?  Anyway, compile-time failure seems more useful.  How
> about this, based on the similar checks for init-only files?

Yes, it's happening in .text currently. The problem, iirc, really was
that _end and __bss_start didn't always match (depending on
compiler version), apparently because at the linking stage _end
got aligned more strictly than __bss_start.

So the patch is fine by me if it covers that misalignment case.
But it seems a little heavy handed - I'd think that instead of the
sub-section, we could just create an arbitrary other section, or
even allow uninitialized variable (it's unclear to me why Paolo
wrote the comment - in c/s 25479:61dfb3da56b - regarding BSS
the way it is now) - after all we only need to make sure that
- the space gets properly allocated in trampoline.S, i.e. also in
  reloc.bin
- all accesses are PC-relative
Neither has anything to do with use of uninitialized variables.

Jan


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