aarch64: add unimplemented errors and aborts in arch-cpu.hh

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: save the tcb to tpidr_el0 for now

we will have to readdress this long term,
but for now this brings us forward.
The compiler is generating code that loads from there
when trying to reach for TLS.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: add initialization steps in boot.S

add the missing FPU initialization (which is required very early,
because of C++/libboost),
and since we are at it, also disable monitoring debug.
Add for debugging purposes a symbol that points to the bottom
of the stack as well.
elf.hh: add AArch64 dynamic relocation types

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
aarch64: improve atomic.h a bit

It's still not stellar, but a bit better.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>
loader.cc: a small step forward for AArch64

We reach the call to ELF's init_array constructors
(and we die in there because of lack of memory allocation).
mempool: show out of memory with debug_early

abort() cannot be relied on to display successfully early on,
because it uses C++ features which need initialization.

Signed-off-by: Claudio Fontana <claudio.fontana@huawei.com>