sys: Remove $FreeBSD$: one-line .c pattern

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

riscv: fix VM_MAXUSER_ADDRESS checks in asm routines

There are two issues with the checks against VM_MAXUSER_ADDRESS. First,
the comparison should consider the values as unsigned, otherwise
addresses with the high bit set will fail to branch. Second, the value
of VM_MAXUSER_ADDRESS is, by convention, one larger than the maximum
mappable user address and invalid itself. Thus, use the bgeu instruction
for these comparisons.

Add a regression test case for copyin(9).

PR: 257193
Reported by: Robert Morris <rtm@lcs.mit.edu>
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D31209

Use unsigned loads in fubyte, fuword16, generic_bs_r_1, generic_bs_r_2
as these functions should do zero-extend.

Discovered by running pci_read_cap(), and by hint from James Clarke.

Reviewed by: James Clarke <jrtc27@jrtc27.com>
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D23236

Provide protection against starvation of the ll/sc loops when accessing userpace.

Casueword(9) on ll/sc architectures must be prepared for userspace
constantly modifying the same cache line as containing the CAS word,
and not loop infinitely. Otherwise, rogue userspace livelocks the
kernel.

To fix the issue, change casueword(9) interface to return new value 1
indicating that either comparision or store failed, instead of relying
on the oldval == *oldvalp comparison. The primitive no longer retries
the operation if it failed spuriously. Modify callers of
casueword(9), all in kern_umtx.c, to handle retries, and react to
stops and requests to terminate between retries.

On x86, despite cmpxchg should not return spurious failures, we can
take advantage of the new interface and just return PSL.ZF.

Reviewed by: andrew (arm64, previous version), markj
Tested by: pho
Reported by: https://xenbits.xen.org/xsa/advisory-295.txt
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D20772

Permit supervisor to access user VA space for certain functions only.

This is done by setting SUM (permit Supervisor User Memory access)
bit in sstatus register.

The functions we allow access for are routines in assembly that
explicitly handle crossing the user kernel boundary.

Approved by: re (kib)
Sponsored by: DARPA, AFRL

Remove the unused fuwintr() and suiwintr() functions.

Half of implementations always failed (returned (-1)) and they were
previously used in only one place.

Reviewed by: kib, andrew
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D15102

Rename assym.s to assym.inc

assym is only to be included by other .s files, and should never
actually be assembled by itself.

Reviewed by: imp, bdrewery (earlier)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D14180

Welcome the RISC-V 64-bit kernel.

This is the final step required allowing to compile and to run RISC-V
kernel and userland from HEAD.

RISC-V is a completely open ISA that is freely available to academia
and industry.

Thanks to all the people involved! Special thanks to Andrew Turner,
David Chisnall, Ed Maste, Konstantin Belousov, John Baldwin and
Arun Thomas for their help.
Thanks to Robert Watson for organizing this project.

This project sponsored by UK Higher Education Innovation Fund (HEIF5) and
DARPA CTSRD project at the University of Cambridge Computer Laboratory.

FreeBSD/RISC-V project home: https://wiki.freebsd.org/riscv

Reviewed by: andrew, emaste, kib
Relnotes: Yes
Sponsored by: DARPA, AFRL
Sponsored by: HEIF5
Differential Revision: https://reviews.freebsd.org/D4982