Add the Branch Target Identification (BTI) note to libc assembly
sources and Pointer Authentication Code (PAC) instructions to _init and
_fini.
_init and _fini may be called indirectly so need a BTI landing pad. As
they are non-leaf functions use the appropriate PAC instruction that
also guards against changing the link register.
As all object files need the note for any binary using these object files
we need to insert it in all asm files.
Reviewed by: markj
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D42227
(cherry picked from commit 522126fea72419fae344fbcb897b41588909308a)
The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.
Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix
Split the ELF feature note into a separate file that is linked into
*crt1.o the same as crtbrand.S was before. crtbrand.o is now linked
into crti.o on all platforms in addition to *crt1.o.
Reviewed by: kib
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D25304
