select: replace reference counting with memory barriers in selfd

Refcounting was added to combat a race between selfdfree and doselwakup,
but it adds avoidable overhead.

selfdfree detects it can fr

select: replace reference counting with memory barriers in selfd

Refcounting was added to combat a race between selfdfree and doselwakup,
but it adds avoidable overhead.

selfdfree detects it can free the object by ->sf_si == NULL, thus we can
ensure that the condition only holds after all accesses are completed.

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poll/select: change selfd_zone into a malloc type

On a sample box vmstat -z shows:

ITEM SIZE LIMIT USED FREE REQ
64: 64, 0, 1043784, 436753

poll/select: change selfd_zone into a malloc type

On a sample box vmstat -z shows:

ITEM SIZE LIMIT USED FREE REQ
64: 64, 0, 1043784, 4367538,3698187229
selfd: 64, 0, 1520, 13726,182729008

But at the same time:
vm.uma.selfd.keg.domain.1.pages: 121
vm.uma.selfd.keg.domain.0.pages: 121

Thus 242 pages got pulled even though the malloc zone would likely accomodate
the load without using extra memory.

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kern: clean up empty lines in .c and .h files

MFH

Sponsored by: Rubicon Communications, LLC (netgate.com)

poll: factor fd lookup out of scan and rescan

fd: remove fd_lastfile

It keeps recalculated way more often than it is needed.

Provide a routine (fdlastfile) to get it if necessary.

Consumers may be better off with a bitmap iterator instead.

Cast all ioctl command arguments through uint32_t internally.

Hide debug print showing use of sign extended ioctl command argument
under INVARIANTS. The print is available to all and can easily fill

Cast all ioctl command arguments through uint32_t internally.

Hide debug print showing use of sign extended ioctl command argument
under INVARIANTS. The print is available to all and can easily fill
up the logs.

No functional change intended.

MFC after: 1 week
Sponsored by: Mellanox Technologies

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Merge ^/head r357408 through r357661.

fd: remove the seq argument from fget_unlocked

It is almost always NULL.

Merge ^/head r357270 through r357349.

Remove duplicated empty lines from kern/*.c

No functional changes.

posix_fallocate: push vnop implementation into the fileop layer

This opens the door for other descriptor types to implement
posix_fallocate(2) as needed.

Reviewed by: kib, bcr (manpages)
Differenti

posix_fallocate: push vnop implementation into the fileop layer

This opens the door for other descriptor types to implement
posix_fallocate(2) as needed.

Reviewed by: kib, bcr (manpages)
Differential Revision: https://reviews.freebsd.org/D23042

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Merge ^/head r352764 through r353315.

devfs: plug redundant bwillwrite avoidance

vn_write already checks for vnode type to see if bwillwrite should be called.

This effectively reverts r244643.

Reviewed by: kib
Sponsored by: The FreeBS

devfs: plug redundant bwillwrite avoidance

vn_write already checks for vnode type to see if bwillwrite should be called.

This effectively reverts r244643.

Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D21905

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MFHead @r350386

Sponsored by: The FreeBSD Foundation

Check and avoid overflow when incrementing fp->f_count in
fget_unlocked() and fhold().

On sufficiently large machine, f_count can be legitimately very large,
e.g. malicious code can dup same fd up t

Check and avoid overflow when incrementing fp->f_count in
fget_unlocked() and fhold().

On sufficiently large machine, f_count can be legitimately very large,
e.g. malicious code can dup same fd up to the per-process
filedescriptors limit, and then fork as much as it can.
On some smaller machine, I see
kern.maxfilesperproc: 939132
kern.maxprocperuid: 34203
which already overflows u_int. More, the malicious code can create
transient references by sending fds over unix sockets.

I realized that this check is missed after reading
https://secfault-security.com/blog/FreeBSD-SA-1902.fd.html

Reviewed by: markj (previous version), mjg
Tested by: pho (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D20947

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Merge ^/head r339813 through r340125.

kern_poll: Restore explanatory comment removed in r177374

The comment isn't stale. The check is bogus in the sense that poll(2)
does not require pollfd entries to be unique in fd space, so there is

kern_poll: Restore explanatory comment removed in r177374

The comment isn't stale. The check is bogus in the sense that poll(2)
does not require pollfd entries to be unique in fd space, so there is no
reason there cannot be more pollfd entries than open or even allowed
fds. The check is mostly a seatbelt against accidental misuse or
abuse. FD_SETSIZE, while usually unrelated to poll, is used as an
arbitrary floor for systems with very low kern.maxfilesperproc.

Additionally, document this possible EINVAL condition in the poll.2
manual.

No functional change.

Reviewed by: markj
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D17671

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Merge ^/head r339670 through r339812.

poll: Unify userspace pollfd pointer name

Some of the poll code used 'fds' and some used 'ufds' to refer to the
uap->fds userspace pointer that was passed around to subroutines. Some of
the poll co

poll: Unify userspace pollfd pointer name

Some of the poll code used 'fds' and some used 'ufds' to refer to the
uap->fds userspace pointer that was passed around to subroutines. Some of
the poll code used 'fds' to refer to the kernel memory pollfd arrays, which
seemed unnecessarily confusing.

Unify on 'ufds' to refer to the userspace pollfd array.

Additionally, 'bits' is not an accurate description of the kernel pollfd
array in kern_poll, so rename that to 'kfds'. Finally, clean up some logic
with mallocarray() and nitems().

No functional change.

Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D17670

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MFH r338661 through r339200.

Sponsored by: The FreeBSD Foundation

Merge ^/head r338731 through r338987.

select: stop doing zero-sized memsets

Approved by: re (kib)

Fix the build after r333457

In r333457, the arguments to kern_pwritev() were accidentally
re-ordered as part of ANSIfication, breaking the build.

ANSIfy sys_generic.c