Replace random sbuf_printf() with cheaper cat/putc.

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

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

tty: Default to printing kernel stack traceback only on INVARIANT kernels

Change the default from printing a breif kernel thread stack informaton
back to omitting it for non-invariant kernels in response to
SIGINFO/^T. Full and brief stack support can be selected with the
kern.tty_info_kstacks sysctl.

MFC After: 2 weeks
Sponsored by: Netflix
Reviewed by: grembo, jhb
Differential Revision: https://reviews.freebsd.org/D35576

Correctly measure system load averages > 1024

The old fixed-point arithmetic used for calculating load averages had an
overflow at 1024. So on systems with extremely high load, the observed
load average would actually fall back to 0 and shoot up again, creating
a kind of sawtooth graph.

Fix this by using 64-bit math internally, while still reporting the load
average to userspace as a 32-bit number.

Sponsored by: Axcient
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D35134

tty_info: Avoid warning by using logical instead of bitwise operators

Since TD_IS_RUNNING() and TS_ON_RUNQ() are defined as logical
expressions involving '==', clang 14 warns about them being checked with
a bitwise operator instead of a logical one:

```
sys/kern/tty_info.c:124:9: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
runa = TD_IS_RUNNING(td) | TD_ON_RUNQ(td);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
||
sys/sys/proc.h:562:27: note: expanded from macro 'TD_IS_RUNNING'
^
sys/kern/tty_info.c:124:9: note: cast one or both operands to int to silence this warning
sys/sys/proc.h:562:27: note: expanded from macro 'TD_IS_RUNNING'
^
sys/kern/tty_info.c:129:9: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]
runb = TD_IS_RUNNING(td2) | TD_ON_RUNQ(td2);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
||
sys/sys/proc.h:562:27: note: expanded from macro 'TD_IS_RUNNING'
^
sys/kern/tty_info.c:129:9: note: cast one or both operands to int to silence this warning
sys/sys/proc.h:562:27: note: expanded from macro 'TD_IS_RUNNING'
^
```

Fix this by using logical operators instead. No functional change
intended.

Reviewed by: cem, emaste, kevans, markj
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D34186

kern.tty_info_kstacks: set compact format as default

kern.tty_info_kstacks: add a compact format

Add a more compact display format for kern.tty_info_kstacks inspired by
procstat -kk. Set it as a default one.

# sysctl kern.tty_info_kstacks=1
kern.tty_info_kstacks: 0 -> 1
# sleep 2
^T
load: 0.17 cmd: sleep 623 [nanslp] 0.72r 0.00u 0.00s 0% 2124k
#0 0xffffffff80c4443e at mi_switch+0xbe
#1 0xffffffff80c98044 at sleepq_catch_signals+0x494
#2 0xffffffff80c982c2 at sleepq_timedwait_sig+0x12
#3 0xffffffff80c43af3 at _sleep+0x193
#4 0xffffffff80c50e31 at kern_clock_nanosleep+0x1a1
#5 0xffffffff80c5119b at sys_nanosleep+0x3b
#6 0xffffffff810ffc69 at amd64_syscall+0x119
#7 0xffffffff810d5520 at fast_syscall_common+0x101
sleep: about 1 second(s) left out of the original 2
^C
# sysctl kern.tty_info_kstacks=2
kern.tty_info_kstacks: 1 -> 2
# sleep 2
^T
load: 0.24 cmd: sleep 625 [nanslp] 0.81r 0.00u 0.00s 0% 2124k
mi_switch+0xbe sleepq_catch_signals+0x494 sleepq_timedwait_sig+0x12
sleep+0x193 kern_clock_nanosleep+0x1a1 sys_nanosleep+0x3b
amd64_syscall+0x119 fast_syscall_common+0x101
sleep: about 1 second(s) left out of the original 2
^C

Suggested by: avg
Reviewed by: mjg
Relnotes: yes
Sponsored by: Mysterious Code Ltd.
Differential Revision: https://reviews.freebsd.org/D25487

Flip kern.tty_info_kstacks on by default

It's a useful debug aid for anyone using Ctrl-T today, and doesn't seem to be
widely known. So, enable it out of the box to help people find it.

It's a tunable and sysctl, so if you don't like it, it's easy to disable
locally.

If people really hate it, we can always flip it back.

Reported by: Daniel O'Connor

tty: convert tty_lock_assert to tty_assert_locked to hide lock type

A later change, currently being iterated on in D24459, will in-fact change
the lock type to an sx so that TTY drivers can sleep on it if they need to.
Committing this ahead of time to make the review in question a little more
palatable.

tty_lock_assert() is unfortunately still needed for now in two places to
make sure that the tty lock has not been recursed upon, for those scenarios
where it's supplied by the TTY driver and possibly a mutex that is allowed
to recurse.

Suggested by: markj

Reimplement stack capture of running threads on i386 and amd64.

After r355784 the td_oncpu field is no longer synchronized by the thread
lock, so the stack capture interrupt cannot be delievered precisely.
Fix this using a loop which drops the thread lock and restarts if the
wrong thread was sampled from the stack capture interrupt handler.

Change the implementation to use a regular interrupt instead of an NMI.
Now that we drop the thread lock, there is no advantage to the latter.

Simplify the KPIs. Remove stack_save_td_running() and add a return
value to stack_save_td(). On platforms that do not support stack
capture of running threads, stack_save_td() returns EOPNOTSUPP. If the
target thread is running in user mode, stack_save_td() returns EBUSY.

Reviewed by: kib
Reported by: mjg, pho
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D23355

Add KERNEL_PANICKED macro for use in place of direct panicstr tests

Fix SIGINFO stack collection to ignore threads with swapped-out stacks.

We by definition cannot trace the stack of such a thread. Also remove a
redundant stack_zero() call in the SIGINFO handler, the stack structure
is cleared by the MD stack_capture().

Sponsored by: The FreeBSD Foundation

Avoid fixing the tty_info() buffer size in tty.h.

Different compilation units may otherwise get a different view of the
layout of struct tty depending on whether they include opt_printf.h.
This caused a blowup in the number of types defined in the kernel's
CTF file after r339468; thanks to dim@ for bisecting down to that
revision.

PR: 232675
Reported by: dim
Reviewed by: cem (previous version)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17877

We need opt_stack.h after r339605.

Reviewed by: cem
Sponsored by: The FreeBSD Foundation

Conditionalize kern.tty_info_kstacks feature on STACKS option

Fix tinderbox (mips XLPN32) after r339471.

Reported by: tinderbox
X-MFC-With: r339471
Sponsored by: Dell EMC Isilon

tty info (^T): Add optional kernel stack(9) traces

It is often useful for developers and administrators to determine a running
thread's stack for debugging purposes. With this feature, using ^T will
print that information

For now, the feature is disabled by default. Enable with sysctl
kern.tty_info_kstacks=1.

Discussed with: markj
Reviewed by: oshogbo
Relnotes: yes
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D17621

Replace ttyprintf with sbuf_printf and tty drain routine

Add string variants of cnputc and tty_putchar, and use them from the tty
sbuf drain routine.

Suggested by: ed@
Sponsored by: Dell EMC Isilon

sys: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

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.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Renumber license clauses in sys/kern to avoid skipping #3

Fix whitespace inconsistencies in TTY code.

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

Print an extra newline when not at the first column already.

This makes siginfo output look a lot better when pressing it the first
time when in sh(1), for example:

$ load: 0.00 cmd: sh 1945 [ttyin] 3.94r 0.00u 0.00s 0% 1960k
load: 0.00 cmd: sh 1945 [ttyin] 4.19r 0.00u 0.00s 0% 1960k

will now become:

$
load: 0.00 cmd: sh 1945 [ttyin] 3.94r 0.00u 0.00s 0% 1960k
load: 0.00 cmd: sh 1945 [ttyin] 4.19r 0.00u 0.00s 0% 1960k

Several cleanups to tty_info(), better known as Ctrl-T.

- Only pick up PROC_LOCK once, which means we can drop the PGRP_LOCK
right after picking up PROC_LOCK for the first time.

- Print the process real time, making it consistent with tools like
time(1).

- Use `p' and `td' to reference the process/thread we are going to
print. Only use pick-variables inside the loops. We already did this
for the threads, but not the processes.

Replace bcopy() calls inside the TTY layer with memcpy()/strlcpy().

In all these cases the buffers never overlap. Program names are also
likely to be shorter, so use a regular strlcpy() to copy p_comm.

Remove even more unneeded variable assignments.

kern_time.c:
- Unused variable `p'.

kern_thr.c:
- Variable `error' is always caught immediately, so no reason to
initialize it. There is no way that error != 0 at the end of
create_thread().

kern_sig.c:
- Unused variable `code'.

kern_synch.c:
- `rval' is always assigned in all different cases.

kern_rwlock.c:
- `v' is always overwritten with RW_UNLOCKED further on.

kern_malloc.c:
- `size' is always initialized with the proper value before being used.

kern_exit.c:
- `error' is always caught and returned immediately. abort2() never
returns a non-zero value.

kern_exec.c:
- `len' is always assigned inside the if-statement right below it.

tty_info.c:
- `td' is always overwritten by FOREACH_THREAD_IN_PROC().

Found by: LLVM's scan-build

Silence compiler warning inside our ^T handler.

It turns out we're casting fixpt_t* to int*.

Spotted by: clang

If a process is a zombie and we couldn't identify another useful state,
print out the state as "zombine" in preference to "unknown" when ^T is
pressed.

MFC after: 3 days
Sponsored by: Google, Inc.

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

Integrate the new MPSAFE TTY layer to the FreeBSD operating system.

The last half year I've been working on a replacement TTY layer for the
FreeBSD kernel. The new TTY layer was designed to improve the following:

- Improved driver model:

The old TTY layer has a driver model that is not abstract enough to
make it friendly to use. A good example is the output path, where the
device drivers directly access the output buffers. This means that an
in-kernel PPP implementation must always convert network buffers into
TTY buffers.

If a PPP implementation would be built on top of the new TTY layer
(still needs a hooks layer, though), it would allow the PPP
implementation to directly hand the data to the TTY driver.

- Improved hotplugging:

With the old TTY layer, it isn't entirely safe to destroy TTY's from
the system. This implementation has a two-step destructing design,
where the driver first abandons the TTY. After all threads have left
the TTY, the TTY layer calls a routine in the driver, which can be
used to free resources (unit numbers, etc).

The pts(4) driver also implements this feature, which means
posix_openpt() will now return PTY's that are created on the fly.

- Improved performance:

One of the major improvements is the per-TTY mutex, which is expected
to improve scalability when compared to the old Giant locking.
Another change is the unbuffered copying to userspace, which is both
used on TTY device nodes and PTY masters.

Upgrading should be quite straightforward. Unlike previous versions,
existing kernel configuration files do not need to be changed, except
when they reference device drivers that are listed in UPDATING.

Obtained from: //depot/projects/mpsafetty/...
Approved by: philip (ex-mentor)
Discussed: on the lists, at BSDCan, at the DevSummit
Sponsored by: Snow B.V., the Netherlands
dcons(4) fixed by: kan

Move ttyinfo() into its own C file.

The ttyinfo() routine generates the fancy output when pressing ^T. Right
now it is stored in tty.c. In the MPSAFE TTY code it is already stored
in tty_info.c. To make integration of the MPSAFE TTY code a little
easier, take the same approach.

This makes the TTY code a little bit more readable, because having the
proc_*/thread_* routines in tty.c is very distractful.

Approved by: philip (mentor)