aarch64 TLS optimizations?

Andrew Haley aph@redhat.com
Fri May 17 14:59:00 GMT 2019


On 5/17/19 2:51 PM, Tom Horsley wrote:
> I'm trying (for reason too complex to go into) to
> locate the TLS offset of the tcache_shutting_down
> variable from malloc in the ubuntu provided
> glibc on aarch64 ubuntu 18.04.
> 
> Various "normal" TLS variables appear to operate
> much like x86_64 with a GOT table entry where the
> TLS offset of the variable gets stashed.
> 
> But in the ubuntu glibc there is no GOT entry for
> that variable, and disassembly of the code shows
> that it seems to "just know" the offset to use.
> 
> Is there some kind of magic TLS optimization that
> can happen for certain variables on aarch64? I'm trying
> to understand how it could know the offset like
> it appears to do in the code.

https://www.fsfla.org/~lxoliva/writeups/TLS/paper-lk2006.pdf



-- 
Andrew Haley
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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