We don't always know the size of the register set at compile time,
e.g. on arm64 the size of the SVE registers need to be queried on boot.
To support register sets that needs to be calculated at run time
query the correct size when it is zero.

Reviewed by:	markj, kib (earlier version)
Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D41302

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

If a debugger detaches from a process that has a new thread that has
not yet executed, the new thread will raise a SIGTRAP signal to report
it's thread birth event even after the detach.  With the debugger
detached, this results in a SIGTRAP sent to the process and typically
a core dump.  Fix this by clearing TDB_BORN from any new threads
during detach.

Bump __FreeBSD_version for debuggers to notice when the fix is
present.

Reported by:	GDB's testsuite
Reviewed by:	kib, markj (previous version)
Differential Revision:	https://reviews.freebsd.org/D39856

Reviewed by:	markj
Discussed with:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D37590

and TDB_COREDUMPRQ to TDB_COREDUMPREQ

Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D37590

Make most AST handlers dynamically registered.  This allows to have
subsystem-specific handler source located in the subsystem files,
instead of making subr_trap.c aware of it.  For instance, signal
delivery code on return to userspace is now moved to kern_sig.c.

Also, it allows to have some handlers designated as the cleanup (kclear)
type, which are called both at AST and on thread/process exit.  For
instance, ast(), exit1(), and NFS server no longer need to be aware
about UFS softdep processing.

The dynamic registration also allows third-party modules to register AST
handlers if needed.  There is one caveat with loadable modules: the
code does not make any effort to ensure that the module is not unloaded
before all threads processed through AST handler in it.  In fact, this
is already present behavior for hwpmc.ko and ufs.ko.  I do not think it
is worth the efforts and the runtime overhead to try to fix it.

Reviewed by:	markj
Tested by:	emaste (arm64), pho
Discussed with:	jhb
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D35888

This more clearly differentiates system call arguments from integer
registers and return values. On current architectures it has no effect,
but on architectures where pointers are not integers (CHERI) and may
not even share registers (CHERI-MIPS) it is necessiary to differentiate
between system call arguments (syscallarg_t) and integer register values
(register_t).

Obtained from:	CheriBSD

Reviewed by:	imp, kib
Differential Revision:	https://reviews.freebsd.org/D33780

exit1() sets P_WEXIT before waiting for holding threads to finish,
rather than after, so this assertion is racy.

Fixes:	12fb39ec3e6b ("proc: Relax proc_rwmem()'s assertion on the process hold count")
Reported by:	Jenkins

This reference ensures that the process and its associated vmspace will
not be destroyed while proc_rwmem() is executing.  If, however, the
calling thread belongs to the target process, then it is unnecessary to
hold the process.  In particular, fasttrap - a module which enables
userspace dtrace - may frequently call proc_rwmem(), and we'd prefer to
avoid the overhead of locking and bumping the hold count when possible.

Thus, make the assertion conditional on "p != curproc".  Also assert
that the process is not already exiting.  No functional change intended.

MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation

Reviewed by:	andrew, emaste
Differential Revision:	https://reviews.freebsd.org/D34177