ldso_tls: Refetch dtv from memory if THREAD_DTV has changed

ldso_tls: Refetch dtv from memory if THREAD_DTV has changed

_dl_update_slotinfo might change THREAD_DTV () (if it needs to reallocate it),
but the caller (__tls_get_addr) doesn't refetch dtv from memory, it uses its
cached copy. This may crash (if dtv[GET_ADDR_MODULE] is off the cliff, or
might read uninitialized memory and return it.
Typically dtv[GET_ADDR_MODULE].pointer.val is NULL and so __tls_get_addr
returns NULL + offset_within_PT_TLS. The next time __tls_get_addr is called
for the same library it will return correct address as _dl_update_slotinfo
won't need to be called.

Signed-off-by: Jakub Jelinek <jakub@redhat.com>
Signed-off-by: Filippo Arcidiacono <filippo.arcidiacono@st.com>
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>