sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

syscalls: fix missing SIGSYS for several ENOSYS errors

In particular, when the syscall number is too large, or when syscall is
dynamic. For that, add nosys_sysent structure to pass fake sysent to
syscall top code.

Reviewed by: dchagin, markj
Discussed with: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D41976

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

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

modules: bzero the modspecific_t

Per https://reviews.llvm.org/D68115, only the first field is
zero-initialized, meanwhile other fields are undef.

The pattern can be observed on clang as well, that when
-ftrivial-auto-var-init=pattern is specified 0xaa is filled for
non-active fields, otherwise they are zero-initialized.
Technically both are acceptable when using clang. However it
would be good to simply bzero the modspecific_t in such case to
be strict to the standard.

MFC with: 2cab2d43b83b
MFC after: 1 day
Sponsored by: Juniper Networks, Inc.
Reviewed by: delphij
Differential Revision: https://reviews.freebsd.org/D40830

syscalls: fix modspecific_t stack content leak

Zero-initialize the whole modspecific_t so that there would
not be kernel stack content leak in the unused part.

Sponsored by: Juniper Networks, Inc.
MFC after: 1 days
Differential Revision: https://reviews.freebsd.org/D40815

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

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

sys/kern: Use C99 fixed-width integer types.

No functional change.

Reviewed by: imp, kib
Differential Revision: https://reviews.freebsd.org/D33630

Move syscall_thread_{enter,exit}() into the slow path. This is only
needed for syscalls from unloadable modules.

Reviewed by: kib
MFC after: 2 weeks
Sponsored by: EPSRC
Differential Revision: https://reviews.freebsd.org/D26988

add a sanity check to the system call registration code

A system call number should be at least reserved.
We do not expect an attempt to register a fixed number system call
when nothing at all is known about it.

MFC after: 3 weeks
Sponsored by: Panzura

fix a typo resulting in a wrong variable in kern_syscall_deregister

The difference is between sysent, a global, and sysents, a function
parameter.

Avoid calls to syscall_thread_enter/exit for statically defined syscalls

The entire mechanism is rarely used and is quite not performant due to
atomci ops on the syscall table. It also has added overhead for completely
unrelated syscalls.

Reduce it by avoiding the func calls if possible (which consistutes vast
majority of cases).

Provides about 3% syscall rate speed up for getuid on Broadwell.

Reduce duplication in dynamic syscall registration code.

Remove the unused syscall_(de)register() functions in favor of the
better documented and easier to use syscall_helper_(un)register(9)
functions.

The default and freebsd32 versions differed in which array of struct
sysents they used and a few missing updates to the 32-bit code as
features were added to the main code.

Reviewed by: cem
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D14337

sys/kern: adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Implement lockless resource limits.

Use the same scheme implemented to manage credentials.

Code needing to look at process's credentials (as opposed to thred's) is
provided with *_proc variants of relevant functions.

Places which possibly had to take the proc lock anyway still use the proc
pointer to access limits.

Generalised support for copy-on-write structures shared by threads.

Thread credentials are maintained as follows: each thread has a pointer to
creds and a reference on them. The pointer is compared with proc's creds on
userspace<->kernel boundary and updated if needed.

This patch introduces a counter which can be compared instead, so that more
structures can use this scheme without adding more comparisons on the boundary.

Fix up module unload for syscall_module_handler consumers.

After r273707 it was registering syscalls as static.

This fixes hwpmc module unload.

Reported by: markj

Avoid dynamic syscall overhead for statically compiled modules.

The kernel tracks syscall users so that modules can safely unregister them.

But if the module is not unloadable or was compiled into the kernel, there is
no need to do this.

Achieve this by adding SY_THR_STATIC_KLD macro which expands to SY_THR_STATIC
during kernel build and 0 otherwise.

Reviewed by: kib (previous version)
MFC after: 2 weeks

Call chainevh callback when we are invoked with neither MOD_LOAD nor
MOD_UNLOAD. This makes it possible to add custom hooks for other module
events.

Return EOPNOTSUPP when there is no callback available.

Pointed out by: jhb
Reviewed by: jhb
MFC after: 1 month

In syscall_module_handler(): all switch branches return, remove
unreached code as pointed out in a Chinese forum [1].

[1] http://www.freebsdchina.org/forum/viewtopic.php?t=50619

Pointed out by: btw616 <btw s qq com>
MFC after: 1 month

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Count number of threads that enter and leave dynamically registered
syscalls. On the dynamic syscall deregistration, wait until all
threads leave the syscall code. This somewhat increases the safety
of the loadable modules unloading.

Reviewed by: jhb
Tested by: pho
MFC after: 1 month

MFC r205321:
Introduce SYSCALL_INIT_HELPER and SYSCALL32_INIT_HELPER macros and
neccessary support functions to allow registering dynamically loaded
syscalls from the MOD_LOAD handlers. Helpers handle registration
failures semi-automatically.

Introduce SYSCALL_INIT_HELPER and SYSCALL32_INIT_HELPER macros and
neccessary support functions to allow registering dynamically loaded
syscalls from the MOD_LOAD handlers. Helpers handle registration
failures semi-automatically.

Reviewed by: jhb
MFC after: 2 weeks

- Import the HEAD csup code which is the basis for the cvsmode work.

Various style fixes. 7 space indent is just odd.

Make system call modules a bit more robust:
- If we fail to register the system call during MOD_LOAD, then note that
so that we don't try to deregister it or invoke the chained event handler
during the subsequent MOD_UNLOAD event. Doing the deregister when the
register failed could result in trashing system call entries.
- Add a SI_SUB_SYSCALLS just before starting up init and use that to
register syscall modules instead of SI_SUB_DRIVERS. Registering system
calls as late as possible increases the chances that any other module
event handlers or SYSINITs in a module are executed to initialize the
data in a kld before a syscall dependent on that data is able to be
invoked.

MFC after: 3 days

Do a pass over all modules in the kernel and make them return EOPNOTSUPP
for unknown events.

A number of modules return EINVAL in this instance, and I have left
those alone for now and instead taught MOD_QUIESCE to accept this
as "didn't do anything".

Use __FBSDID().

- Lock down the ``module'' structure by adding an SX lock that is used by
all the global bits of ``module'' data. This commit adds a few generic
macros, MOD_SLOCK, MOD_XLOCK, etc., that are meant to be used as ways
of accessing the SX lock. It is also the first step in helping to lock
down the kernel linker and module systems.

Reviewed by: jhb, jake, smp@

KSE Milestone 2
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.

Sorry john! (your next MFC will be a doosie!)

Reviewed by: peter@freebsd.org, dillon@freebsd.org

X-MFC after: ha ha ha ha

sysvipc loadable.

new syscall entry lkmressys - "reserved loadable syscall"

Make syscall_register allow overwriting of such entries (lkmressys).

Trim unused options (or #ifdef for undoc options).

Submitted by: phk

$Id$ -> $FreeBSD$

Call the chained module handler before unregistering the syscall so that
errors can be detected.

Submitted by: "A.Yu.Isupov" <isupov@moonhe.jinr.ru>
PR: kern/12239

Move lkmnosys() from kern_lkm.c to here.

Implement a mechanism for a module to report a small amount of module
specific data back to the user via kldstat(2). Use that mechanism in
the syscall handler to report the syscall number used.

Implement support for adding syscalls in KLD modules.

Submitted by: Assar Westerlund <assar@sics.se>