Change powerpc64le's long double from 64-bit double to IEEE 754
binary128 (quad, 113-bit mantissa), matching aarch64 and riscv64.

Gated on FreeBSD 16 and powerpc64le only.

Differential Revision: https://reviews.freebsd.org/D57388
Reviewed by:	adrian
Relnotes:	yes

On PowerPC platforms a valid link to the Table of Contents (TOC) is
required for PLT lookups to function.  This TOC pointer is stored in
a dedicated register, and is used along with the stack pointer by both
C prologue and PLT lookup code.

When calling swapcontext() with uc_link != NULL, a PLT lookup to
setcontext(3) is attempted from within the _ctx_done context.  The
exiting process has usually trashed both r1 and r2 at this point,
leading to a crash within the PLT lookup before setcontext(2) is
reached to restore the linked context.

Save and restore r2 as in a regular function.  This ensures the
subsequent PLT lookup to setcontext(3) succeeds.

Signed-off-by: Timothy Pearson <tpearson@raptorengineering.com>

MFC after:	1 week
Pull Request:	https://github.com/freebsd/freebsd-src/pull/1759

_libc_get_static_tls_base() is just _tcb_get() followed by adding (for
Variant I) or subtracting (for Variant II) the offset, so just inline
that as the implementation (like we do in rtld-elf) rather than having
another copy (or equivalent) of _tcb_get()'s assembly.

_get_static_tls_base() doesn't even have any MD assembly as it's
reading thr->tcb, the only difference is whether to add or subtract, so
again just inline that.

Whilst here add some missing blank lines to comply with style(9) for
elf_utils.c's includes, and use a pointer type rather than uintptr_t to
reduce the need to cast, as is done in rtld-elf.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D50592

This is a residual of the $FreeBSD$ removal.

MFC After: 3 days (though I'll just run the command on the branches)
Sponsored by: Netflix

Remove attempts to use NetBSD __weak_alias macros to export _-prefixed
versions of various fp[sg]et* symbols under softfloat.  __weak_alias
isn't defined so we didn't export them and thus the Symbol.map entries
were wrong.

Reviewed by:	jhibbits
Differential Revision:	https://reviews.freebsd.org/D44327

These provide standard APIs, but are implemented using another system
call (e.g., pipe implemented in terms of pipe2) or are interposed by the
threading library to support cancelation.

After discussion with kib (see D44111), I've concluded that it is
better to keep most public interfaces in libc with as little
as possible in libsys.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D44241

Historically we exposed _getlogin as a private symbol on a per-arch basis
(except on aarch64 and riscv) for no obvious reason.  We now need to
expose it for libc's use so remove the special case from
makesyscalls.lua and expose it in the generated syscalls.map.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D44116

This is a mix genuine MD interfaces and compat symbols like _getlogin.

Reviewed by:	kib, emaste, imp
Pull Request:	https://github.com/freebsd/freebsd-src/pull/908

libc/<arch>/sys/Makefile.inc -> libsys/<arch>/Makefile.sys.

Require that libsys/<arch>/Makefile.sys exist.  At least for current
archtiectures, it's not possible for an architecture to not have and MD
syscall bits.

powerpcspe/Makefile.sys's structure means it had to be modified when moved
so rename detection won't work, but it has trivial contents so the
history is unimportant.

Reviewed by:	kib, emaste, imp
Pull Request:	https://github.com/freebsd/freebsd-src/pull/908

Reviewed by:	kib, emaste, imp
Pull Request:	https://github.com/freebsd/freebsd-src/pull/908