[scudo][standalone] Introduce the thread specific data structures
This CL adds the structures dealing with thread specific data for the
allocator. This includes the thread specific data structure itself and
two registries for said structures: an exclusive one, where each thread
will have its own TSD struct, and a shared one, where a pool of TSD
structs will be shared by all threads, with dynamic reassignment at
runtime based on contention.
This departs from the current Scudo implementation: we intend to make
the Registry a template parameter of the allocator (as opposed to a
single global entity), allowing various allocators to coexist with
different TSD registry models. As a result, TSD registry and Allocator
are tightly coupled.
This also corrects a couple of things in other files that I noticed
while adding this.
Reviewers: eugenis, vitalybuka, morehouse, hctim
Reviewed By: morehouse
Subscribers: srhines, mgorny, delcypher, jfb, #sanitizers, llvm-commits
Tags: #llvm, #sanitizers
Differential Revision: https://reviews.llvm.org/D62258