Spectre V1 diagnostic / mitigation

[Peter Bergner]

On 12/19/18 7:59 AM, Florian Weimer wrote:
> * Richard Biener:
> 
>> Sure, if we'd ever deploy this in production placing this in the
>> TCB for glibc targets might be beneifical.  But as said the
>> current implementation was just an experiment intended to be
>> maximum portable.  I suppose the dynamic loader takes care
>> of initializing the TCB data?
> 
> Yes, the dynamic linker will initialize it.  If you need 100% reliable
> initialization with something that is not zero, it's going to be tricky
> though.  Initial-exec TLS memory has this covered, but in the TCB, we
> only have zeroed-out reservations today.

We have non-zero initialized TCB entries on powerpc*-linux which are used
for the GCC __builtin_cpu_is() and __builtin_cpu_supports() builtin
functions.  Tulio would know the magic that was used to get them setup.

Peter