Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC: r231618, r233231 (partial)

Add thread-local storage support for ARM to rtld-elf

Reviewed by: cognet
Obtained from: NetBSD

MFC r232831:
Add support for preinit, init and fini arrays to rtld.
Only binaries marked with proper ABI note gets array ctr/dtrs called.

MFC r232856:
When iterating over the dso program headers, the object is not initialized
yet, and object segments are not yet mapped. Only parse the notes that
appear in the first page of the dso (as it should be anyway), and use
the preloaded page content.

MFC r232857 (by dim):
Fix a warning/error with clang.

MFC r232859 (by dim):
Amend r232857, now dropping the casts entirely, as they were not
necessary at all.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

When loading dso without PT_GNU_STACK phdr, only call
__pthread_map_stacks_exec() on architectures that allow executable
stacks.

Reported and tested by: marcel (ia64)

Now that the kernel defines CACHE_LINE_SIZE in machine/param.h, use
that definition in the custom locking code for the run-time linker
rather than local definitions.

Pointed out by: tinderbox
MFC after: 2 weeks

No need to provide atomic_cmpset_32() anymore.

Only provide the dummy, non-atomic atomic_cmpset_32() if
ARM_HAS_ATOMIC_CMPSET_32 isn't defined.

Implement a dummy atomic_cmpset_32(). It should be safe to use it in rtld as
the signals are masked anyway.

Add stubs for TLS.
Arbitraly choose the 2nd variant until I figure out which one I should use.

Import arm bits for rtld-elf.

Obtained from: NetBSD