Summary:
Some of glibc's own thread local data is destroyed after a user's thread local
destructors are called, via __libc_thread_freeres. This might involve calling
free, as is the case for strerror_thread_freeres.
If there is no prior heap operation in the thread, this free would end up
initializing some thread specific data that would never be destroyed properly
(as user's pthread destructors have already been called), while still being
deallocated when the TLS goes away. As a result, a program could SEGV, usually
in __sanitizer::AllocatorGlobalStats::Unregister, where one of the doubly linked
list links would refer to a now unmapped memory area.

To prevent this from happening, we will not do a full initialization from the
deallocation path. This means that the fallback cache & quarantine will be used
if no other heap operation has been called, and we effectively prevent the TSD
being initialized and never destroyed. The TSD will be fully initialized for all
other paths.

In the event of a thread doing only frees and nothing else, a TSD would never
be initialized for that thread, but this situation is unlikely and we can live
with that.

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D37697

llvm-svn: 312939

Summary:
We were not following the `man` documented behaviors for invalid arguments to
`memalign` and associated functions. Using `CHECK` for those was a bit extreme,
so we relax the behavior to return null pointers as expected when this happens.
Adapt the associated test.

I am using this change also to change a few more minor performance improvements:
- mark as `UNLIKELY` a bunch of unlikely conditions;
- the current `CHECK` in `__sanitizer::RoundUpTo` is redundant for us in *all*
  calls. So I am introducing our own version without said `CHECK`.
- change our combined allocator `GetActuallyAllocatedSize`. We already know if
  the pointer is from the Primary or Secondary, so the `PointerIsMine` check is
  redundant as well, and costly for the 32-bit Primary. So we get the size by
  directly using the available Primary functions.

Finally, change a `int` to `uptr` to avoid a warning/error when compiling on
Android.

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D34782

llvm-svn: 306698

Summary:
This change adds Android support to the allocator (but doesn't yet enable it in
the cmake config), and should be the last fragment of the rewritten change
D31947.

Android has more memory constraints than other platforms, so the idea of a
unique context per thread would not have worked. The alternative chosen is to
allocate a set of contexts based on the number of cores on the machine, and
share those contexts within the threads. Contexts can be dynamically reassigned
to threads to prevent contention, based on a scheme suggested by @dvyuokv in
the initial review.

Additionally, given that Android doesn't support ELF TLS (only emutls for now),
we use the TSan TLS slot to make things faster: Scudo is mutually exclusive
with other sanitizers so this shouldn't cause any problem.

An additional change made here, is replacing `thread_local` by `THREADLOCAL`
and using the initial-exec thread model in the non-Android version to prevent
extraneous weak definition and checks on the relevant variables.

Reviewers: kcc, dvyukov, alekseyshl

Reviewed By: alekseyshl

Subscribers: srhines, mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D32649

llvm-svn: 302300