Re: [PATCH] aarch64: Remove ld.so __tls_get_addr plt usage

[Florian Weimer <fweimer@redhat.com>]

> bionic implemented
> https://sourceware.org/glibc/wiki/ThreadPropertiesAPI in
> https://android.googlesource.com/platform/bionic/+/refs/heads/main/libc/include/sys/thread_properties.h
> but tbh i'm not sure that the sanitizer folks moved over to the new
> api?

I think I wrote about this before: The APIs are underspecified.  I think
we want to be able to change the boundaries of static TLS eventually
(allocating more backing storage before the start or the end, using
address space that previously was only reserved with PROT_NONE).

Maybe I should put it into the wiki page.

> (i don't think we could just use malloc() because jemalloc -- which we
> still haven't fully removed for very low-end users in favor of scudo
> -- was itself using TLS thread locals? scudo has its own reserved
> constant slot in bionic, so that should be fine, i think, but we're
> not there yet.)

Yes, that's the TCB bootstrap problem I mentioned.  It's only relevant
to the initial thread.  There is no functional requirement to allocate
TCBs directly on the thread they are used for.  So once we solve the TCB
issue for the main thread (and have a mode that uses malloc otherwise),
I think we are done.

Thanks,
Florian