r360033:
tests: kqueue: use a more precise timer for the NOTE_ABSTIME test

Originally noticed while attempting to run the kqueue tests under
qemu-user-static, this apparently just happens sometimes when running in a
jail in general -- the timer will fire off "too early," but it's really just
the result of imprecise measurements (noted by cem).

Kicking this over to NOTE_USECONDS still tests the correct thing while
allowing it to work more consistently; a basic sanity test reveals that we
often end up coming in just less than 200 microseconds after the timer
fired off.

r360108:
tests: kqueue: fix some issues with now() on ILP32 platforms

There were ultimately two separate problems here:
- a 32-bit long cannot represent microseconds since 1970 (noted by ian)
- time_t is 32-bit on i386, so now() was wrong anyways even with the correct
  return type.

For the first, just explicitly use a uint64_t for now() and all of the
callers. For the second, we need to explicitly cast tv_sec to uint64_t
before it gets multiplied in the SEC_TO_US macro. Casting this instance
rather than generally in the macro was arbitrarily chosen simply because all
other uses are converting small relative time values.

The tests now pass on i386, at least; presumably other ILP32 will be fine
now as well.

r359406, r359413-r359416, r359424-r359425, r359427, r359432-r359433,
r359443, r359675-r359678

Note: this is not necessarily a complete fix to get these programs to build
with -fno-common applied; further work may be needed in this branch.

r359389:
config(8): fixes for -fno-common

Move this handful of definitions into main.c, properly declare these as
extern in config.h. This fixes the config(8) build with -fno-common.

Unexplained in my previous commit to gas, -fno-common will become the
default in GCC10 and LLVM11, so it's worth addressing these in advance.

r359394:
MFV r359393: tcsh: import 6974bc35a5cd

This removes an extra variable definition that causes the -fno-common build
to fail, which will be a new default in GCC10/LLVM11.

r359397:
zfs: fix -fno-common issues

A similar (or identical?) fix has already landed in OpenZFS.

-fno-common will become the default in GCC10/LLVM11.

r359398:
sh: remove duplicate el definition

el is declared extern in myhistedit.h and defined in histedit.c. Remove the
duplicate definition in input.c to appease the -fno-common build.

-fno-common will become the default in GCC10/LLVM11.

r359399:
telnet: remove some duplicate definitions, mark terminaltype extern

Most of these were already properly declared and defined elsewhere, this is
effectively just a minor cleanup that fixes the -fno-common build.

-fno-common will become the default in GCC10/LLVM11.

r359403:
Revert 359399: telnet -fno-common bits

There was a large misfire from my local diff that I need to investigate, and
this version committed did not build.

r359404:
Re-apply r359399: telnet -fno-common fix

line and auth_level's redefinitions are just extraneous

telnetd will #define extern and then include ext.h to allocate storage for
all of these extern'd vars; however, two of them are actually defined in
libtelnet instead. Instead of doing an #ifdef extern dance around those
function pointers, just add an EXTERN macro to make it easier to
differentiate by sight which ones will get allocated in globals.c and which
ones are defined elsewhere.

r359406:
telnet: kill off remaining duplicate definition

r359413:
ipfilter: remove duplicate definition of 'thishost'

thishost is already defined in lib/initparse.c; no need for this one. This
fixes the ipfilter build with -fno-common.

-fno-common will become the default in GCC10/LLVM11.

r359414:
iscontrol: move definition of vflag/iscsidev to iscontrol.c

Mark the declaration extern as these are used elsewhere; this fixes the
build with -fno-common.

r359415:
userboot: mark host_fsops as extern

This is already defined elsewhere; mark this declaration extern to the fix
the -fno-common build.

r359416:
systat: remove redundant definition of kd

kd is already properly declared in extern.h and defined in main.c, rendering
this definition useless. This fixes the -fno-common build.

r359424:
openssh: -fno-common fix from upstream f47d72ddad

This is currently staged in vendor/ as part of the 8.0p1 import, which isn't
quite ready to land. Given that this is a simple one-line fix, apply it now
as the fallout will be pretty minimal.

-fno-common will become the default in GCC10/LLVM11.

r359425:
locate: fix -fno-common build

Just a single variable declaration to extern and define elsewhere here,
myctype.

-fno-common will become a default in GCC10/LLVM11.

r359427:
fsck_ffs/fsdb: fix -fno-common build

This one is also a small list:

- 3x duplicate definition (ufs2_zino, returntosingle, nflag)
- 5x 'needs extern', 3/5 of which are referenced in fsdb

-fno-common will become the default in GCC10/LLVM11.

r359432:
gdb: compile with -fcommon explicitly

As described in the comment, gdb relies on some of the linker magic that
happens with -fcommon. I suspect the life expectancy of gdb-in-base is low
enough that this isn't worth spending much time addressing, especially given
the vintage. Hit it with the -fcommon hammer so that it continues to just
work.

r359433:
bmake: fix -fno-common build

debug was declared extern, but debug_file was not; correct this and define
debug_file in main.c (as debug is) to fix the -fno-common build.

-fno-common will become the default with GCC10/LLVM11.

r359443:
MFV r359442: bmake: import -fno-common fix build back from upstream

sjg@ committed the local patch previously committed upstream; pull it in to
vendor/ to ease any potential stress of future imports.

r359675:
kqueue tests: fix -fno-common build

vnode_fd and kqfd are both shared among multiple CU; define them exactly
once.

In the case of vnode_fd, it was simply the declaration that needed
correction.

-fno-common will become the default in GCC10/LLVM11.

r359676:
ntpd: fix build with -fno-common

Only a small nit here: psl should be declared extern and defined exactly
once.

-fno-common will become the default in GCC10/LLVM11.

r359677:
yp*: fix -fno-common build

This is mostly two problems spread out far and wide:
- ypldap_process should be declared properly
- debug is defined differently in many programs

For the latter, just extern it and define it everywhere that actually needs
it. This mostly works out nicely for ^/libexec/ypxfr, which can remove the
assignment at the beginning of main in favor of defining it properly.

-fno-common will become the default in GCC10/LLVM11.

r359678:
indent: fix the -fno-common build

Spread the globals far and wide, hopefully to the files that make the most
sense.

-fno-common will become the default in GCC10/LLVM11.

Make whitespace more consistent in libkqueue tests.

After r337820, which "corrected" some spaces-instead-of-tab whitespace
issues in the libkqueue tests, jmg@ pointed out that these files were
originally space-based, not tab-spaced, and so the correction should
have been to get rid of the tabs that had been introduced in previous
changes, not the spaces. This change does that. This is a whitespace
only change; no functional change is intended.

Reported by:	jmg@
Sponsored by:	Dell EMC Isilon

Reported by:	Renato Botelho <garga.bsd@gmail.com>
MFC after:	3 days
X-MFC-with:	r337814
Sponsored by:	Dell EMC

A follow-up to r337812 to catch a couple more memory leaks that should
have been included in that change.

Reported by:	Coverity
CID:		1296064, 1296067 (for real this time)
MFC after:	3 days
X-MFC-with:	r337812
Sponsored by:	Dell EMC

The libkqueue tests have several places that leak memory by using an
idiom like:

puts(kevent_to_str(kevp));

Rework to save the pointer returned from kevent_to_str() and then
free() it after it has been used.

Reported by:	asomers (pointer to Coverity), Coverity
CID:		1296063, 1296064, 1296065, 1296066, 1296067, 1350287, 1394960
Sponsored by:	Dell EMC

ian@ pointed out that in the test_abstime() function time(NULL) is
used twice; once in an "if" test and again in the enclosed error
message. If the true branch was taken and the process got preempted
before the second time(NULL) call, by the time the error message was
generated enough time could have elapsed that the message could claim
that the event came "too early" but print an event time that was after
the expected timeout. Correct by making the time(NULL) call only once
and using that returned time in both the "if" test and the error
message.

Reported by:	ian@
MFC after:	4 days
X-MFC-with:	r336761, r336781, r336802
Sponsored by:	Dell EMC

Another cast for printing an intmax_t was needed in a kqueue test for
some arches.

Pointy-hat:	me (twice)
MFC after:	1 week
X-MFC-with:	r336761, r336781
Sponsored by:	Dell EMC

A cast for printing an intmax_t was needed in a kqueue test for some
arches.

MFC after:	1 week
X-MFC-with:	r336761
Sponsored by:	Dell EMC

If a timer is updated (re-added) with a different time period
(specified in the .data field of the kevent), the new time period has
no effect; the timer will not expire until the original time has
elapsed. This violates the documented behavior as the kqueue(2) man
page says (in part) "Re-adding an existing event will modify the
parameters of the original event, and not result in a duplicate
entry."

This modification, adapted from a patch submitted by cem@ to PR214987,
fixes the kqueue system to allow updating a timer entry. The
kevent timer behavior is changed to:

  * When a timer is re-added, update the timer parameters to and
    re-start the timer using the new parameters.
  * Allow updating both active and already expired timers.
  * When the timer has already expired, dequeue any undelivered events
    and clear the count of expirations.

All of these changes address the original PR and also bring the
FreeBSD and macOS kevent timer behaviors into agreement.

A few other changes were made along the way:

  * Update the kqueue(2) man page to reflect the new timer behavior.
  * Fix man page style issues in kqueue(2) diagnosed by igor.
  * Update the timer libkqueue system test to test for the updated
    timer behavior.
  * Fix the (test) libkqueue common.h file so that it includes
    config.h which defines various HAVE_* feature defines, before the
    #if tests for such variables in common.h. This enables the use of
    the actual err(3) family of functions.
  * Fix the usages of the err(3) functions in the tests for incorrect
    type of variables. Those were formerly undiagnosed due to the
    disablement of the err(3) functions (see previous bullet point).

PR:		214987
Reported by:	Brian Wellington <bwelling@xbill.org>
Reviewed by:	kib
MFC after:	1 week
Relnotes:	yes
Sponsored by:	Dell EMC
Differential Revision:	https://reviews.freebsd.org/D15778