sys: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

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

Remove /^\s*\*+\s*\$FreeBSD\$.*$\n/

arm64 lib32: prepare arm64 headers to redirect to arm

In order to compile lib32 libraries and other 32-bit code on arm64,
<machine/foo.h> needs to be redirected to an arm header rather
than arm64 when building with -m32. Ifdef the arm64 headers that
are installed in /usr/include/machine and used by user-level software
(including references from /usr/include/*.h) so that if __arm__ is
defined when including the arm64 version, <arm/foo.h> is included
rather than using the rest of the file's contents. Some arm headers
had no arm64 equivalent; headers were added just to do the redirection.
These files use #error if __arm__ is not defined to guard against
confusion. Also add an include/arm Makefile, and modify Makefiles
as needed to install everything, including the arm files in
/usr/include/arm. fenv.h comes from lib/msun/arm/fenv.h.

The new arm64 headers are:
acle-compat.h
cpuinfo.h
sysreg.h

Reviewed by: jrtc27, imp
Differential Revision: https://reviews.freebsd.org/D40944

Add padding for future use on arm64

Allow new features to be supported without changing the size of
existing structures.

Reviewed by: kib
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D39777

Move kstack_contains() and GET_STACK_USAGE() to MD machine/stack.h

Reviewed by: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D38320

Add arm64 pointer authentication support

Pointer authentication allows userspace to add instructions to insert
a Pointer Authentication Code (PAC) into a register based on an address
and modifier and check if the PAC is correct. If the check fails it will
either return an invalid address or fault to the kernel.

As many of these instructions are a NOP when disabled and in earlier
revisions of the architecture this can be used, for example, to sign
the return address before pushing it to the stack making Return-oriented
programming (ROP) attack more difficult on hardware that supports them.

The kernel manages five 128 bit signing keys: 2 instruction keys, 2 data
keys, and a generic key. The instructions then use one of these when
signing the registers. Instructions that use the first four store the
PAC in the register being signed, however the instructions that use the
generic key store the PAC in a separate register.

Currently all userspace threads share all the keys within a process
with a new set of userspace keys being generated when executing a new
process. This means a forked child will share its keys with its parent
until it calls an appropriate exec system call.

In the kernel we allow the use of one of the instruction keys, the ia
key. This will be used to sign return addresses in function calls.
Unlike userspace each kernel thread has its own randomly generated.

Thread0 has a static key as does the early code on secondary CPUs.
This should be safe as there is minimal user interaction with these
threads, however we could generate random keys when the Armv8.5
Random number generation instructions are present.

Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D31261

Make struct syscall_args machine independent

After a round of cleanups in late 2020, all definitions are
functionally identical.

This removes a rotted __aligned(8) on arm. It was added in
b7112ead32bc50ef9744099bdbb1cfbd6e906b2a and was intended to align the
args member so that 64-bit types (off_t, etc) could be safely read on
armeb compiled with clang. With the removal of armev, this is no
longer needed (armv7 requires that 32-bit aligned reads of 64-bit
values be supported and we enable such support on armv6). As further
evidence this is unnecessary, cleanups to struct syscall_args have
resulted in args being 32-bit aligned on 32-bit systems. The sole
effect is to bloat the struct by 4 bytes.

Reviewed by: kib, jhb, imp
Differential Revision: https://reviews.freebsd.org/D33308

arm64, powerpc: fix calculation of 'used' in GET_STACK_USAGE

We do not consider the space reserved for the pcb to be part of the
total kstack size, so it should not be included in the calculation of
the used stack size.

MFC after: 1 week
Sponsored by: The FreeBSD Foundation

Per-thread stack canary on arm64

With the update to llvm 13 we are able to tell the compiler it can find
the SSP canary relative to the register that holds the userspace stack
pointer. As this is unused in most of the kernel it can be used here
to point to a per-thread SSP canary.

As the kernel could be built with an old toolchain, e.g. when upgrading
from 13, add a warning that the options was enabled but the compiler
doesn't support it to both the build and kernel boot.

Discussed with: emaste
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33079

Pass the syscall number to capsicum permission-denied signals

The syscall number is stored in the same register as the syscall return
on amd64 (and possibly other architectures) and so it is impossible to
recover in the signal handler after the call has returned. This small
tweak delivers it in the `si_value` field of the signal, which is
sufficient to catch capability violations and emulate them with a call
to a more-privileged process in the signal handler.

This reapplies 3a522ba1bc852c3d4660a4fa32e4a94999d09a47 with a fix for
the static assertion failure on i386.

Approved by: markj (mentor)

Reviewed by: kib, bcr (manpages)

Differential Revision: https://reviews.freebsd.org/D29185

Revert "Pass the syscall number to capsicum permission-denied signals"

This broke the i386 build.

This reverts commit 3a522ba1bc852c3d4660a4fa32e4a94999d09a47.

Pass the syscall number to capsicum permission-denied signals

The syscall number is stored in the same register as the syscall return
on amd64 (and possibly other architectures) and so it is impossible to
recover in the signal handler after the call has returned. This small
tweak delivers it in the `si_value` field of the signal, which is
sufficient to catch capability violations and emulate them with a call
to a more-privileged process in the signal handler.

Approved by: markj (mentor)

Reviewed by: kib, bcr (manpages)

Differential Revision: https://reviews.freebsd.org/D29185

Get rid of sa->narg. It serves no purpose; use sa->callp->sy_narg instead.

Reviewed by: kib
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D26458

Utilize ASIDs to reduce both the direct and indirect costs of context
switching. The indirect costs being unnecessary TLB misses that are
incurred when ASIDs are not used. In fact, currently, when we perform a
context switch on one processor, we issue a broadcast TLB invalidation that
flushes the TLB contents on every processor.

Mark all user-space ("ttbr0") page table entries with the non-global flag so
that they are cached in the TLB under their ASID.

Correct an error in pmap_pinit0(). The pointer to the root of the page
table was being initialized to the root of the kernel-space page table
rather than a user-space page table. However, the root of the page table
that was being cached in process 0's md_l0addr field correctly pointed to a
user-space page table. As long as ASIDs weren't being used, this was
harmless, except that it led to some unnecessary page table switches in
pmap_switch(). Specifically, other kernel processes besides process 0 would
have their md_l0addr field set to the root of the kernel-space page table,
and so pmap_switch() would actually change page tables when switching
between process 0 and other kernel processes.

Implement a workaround for Cavium erratum 27456 affecting ThunderX machines.
(I would like to thank andrew@ for providing the code to detect the affected
machines.)

Address integer overflow in the definition of TCR_ASID_16.

Setup TCR according to the PARange and ASIDBits fields from
ID_AA64MMFR0_EL1. Previously, TCR_ASID_16 was unconditionally set.

Modify build_l1_block_pagetable so that lower attributes, such as ATTR_nG,
can be specified as a parameter.

Eliminate some unused code.

Earlier versions were tested to varying degrees by: andrew, emaste, markj

MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D21922

Add GET_STACK_USAGE() for arm64.

Its absence meant that GEOM direct dispatch was disabled (the service
routines check the current thread's stack usage to determine whether
to hand off the request to a dedicated thread), and this change is
sufficient to enable direct dispatch by default.

Reviewed by: allanjude
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D15527

Add rudimentary support for building FreeBSD/arm64 with COMPAT_FREEBSD32.

Right now I'm using two Raspberry Pi's (2 and 3) to test CloudABI
support for armv6, armv7 and aarch64. It would be nice if I could
restrict this to just a single instance when testing smaller changes.
This is why I'd like to get COMPAT_CLOUDABI32 to work on arm64.

As COMPAT_CLOUDABI32 depends on COMPAT_FREEBSD32, at least for the ELF
loading, this change adds all of the bits necessary to at least build a
kernel with COMPAT_FREEBSD32. All of the machine dependent system calls
are still stubbed out, for the reason that implementations for these are
only useful if actual support for running FreeBSD binaries is added.
This is outside the scope of this work.

Reviewed by: andrew
Differential Revision: https://reviews.freebsd.org/D13144

Move the l0 pagetable address to struct mdproc. It is a property of the
whole process so should live there.

Sponsored by: DARPA, AFRL

Make struct syscall_args visible to userspace compilation environment
from machine/proc.h, consistently on all architectures.

Reviewed by: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 3 weeks
X-Differential revision: https://reviews.freebsd.org/D11080

Renumber clauses to avoid missing 3

Add the start of the arm64 machine headers. This is the subset needed to
start getting userland libraries building.

Reviewed by: imp
Sponsored by: The FreeBSD Foundation