diff --git a/lib/libpmc/pmc.3 b/lib/libpmc/pmc.3
index 83f555a5a770..83906a8d9e44 100644
--- a/lib/libpmc/pmc.3
+++ b/lib/libpmc/pmc.3
@@ -1,595 +1,591 @@
 .\" Copyright (c) 2003-2008 Joseph Koshy.  All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 5, 2023
+.Dd June 16, 2023
 .Dt PMC 3
 .Os
 .Sh NAME
 .Nm pmc
 .Nd library for accessing hardware performance monitoring counters
 .Sh LIBRARY
 .Lb libpmc
 .Sh SYNOPSIS
 .In pmc.h
 .Sh DESCRIPTION
 The
 .Lb libpmc
 provides a programming interface that allows applications to use
 hardware performance counters to gather performance data about
 specific processes or for the system as a whole.
 The library is implemented using the lower-level facilities offered by
 the
 .Xr hwpmc 4
 driver.
 .Ss Key Concepts
 Performance monitoring counters (PMCs) are represented by the library
 using a software abstraction.
 These
 .Dq abstract
 PMCs can have two scopes:
 .Bl -bullet
 .It
 System scope.
 These PMCs measure events in a whole-system manner, i.e., independent
 of the currently executing thread.
 System scope PMCs are allocated on specific CPUs and do not
 migrate between CPUs.
 Non-privileged process are allowed to allocate system scope PMCs if the
 .Xr hwpmc 4
 sysctl tunable:
 .Va security.bsd.unprivileged_syspmcs
 is non-zero.
 .It
 Process scope.
 These PMCs only measure hardware events when the processes they are
 attached to are executing on a CPU.
 In an SMP system, process scope PMCs migrate between CPUs along with
 their target processes.
 .El
 .Pp
 Orthogonal to PMC scope, PMCs may be allocated in one of two
 operational modes:
 .Bl -bullet
 .It
 Counting PMCs measure events according to their scope
 (system or process).
 The application needs to explicitly read these counters
 to retrieve their value.
 .It
 Sampling PMCs cause the CPU to be periodically interrupted
 and information about its state of execution to be collected.
 Sampling PMCs are used to profile specific processes and kernel
 threads or to profile the system as a whole.
 .El
 .Pp
 The scope and operational mode for a software PMC are specified at
 PMC allocation time.
 An application is allowed to allocate multiple PMCs subject
 to availability of hardware resources.
 .Pp
 The library uses human-readable strings to name the event being
 measured by hardware.
 The syntax used for specifying a hardware event along with additional
 event specific qualifiers (if any) is described in detail in section
 .Sx "EVENT SPECIFIERS"
 below.
 .Pp
 PMCs are associated with the process that allocated them and
 will be automatically reclaimed by the system when the process exits.
 Additionally, process-scope PMCs have to be attached to one or more
 target processes before they can perform measurements.
 A process-scope PMC may be attached to those target processes
 that its owner process would otherwise be permitted to debug.
 An owner process may attach PMCs to itself allowing
 it to measure its own behavior.
 Additionally, on some machine architectures, such self-attached PMCs
 may be read cheaply using specialized instructions supported by the
 processor.
 .Pp
 Certain kinds of PMCs require that a log file be configured before
 they may be started.
 These include:
 .Bl -bullet
 .It
 System scope sampling PMCs.
 .It
 Process scope sampling PMCs.
 .It
 Process scope counting PMCs that have been configured to report PMC
 readings on process context switches or process exits.
 .El
 .Pp
 Up to one log file may be configured per owner process.
 Events logged to a log file may be subsequently analyzed using the
 .Xr pmclog 3
 family of functions.
 .Ss Supported CPUs
 The CPUs known to the PMC library are named by the
 .Vt "enum pmc_cputype"
 enumeration.
 Supported CPUs include:
 .Pp
 .Bl -tag -width "Li PMC_CPU_ARMV7_CORTEX_A15" -compact
 .It Li PMC_CPU_AMD_K7
 .Tn "AMD Athlon"
 CPUs.
 .It Li PMC_CPU_AMD_K8
 .Tn "AMD Athlon64"
 CPUs.
 .It Li PMC_CPU_ARMV7_CORTEX_A5
 .Tn ARMv7
 .Tn Cortex A5
 CPUs.
 .It Li PMC_CPU_ARMV7_CORTEX_A7
 .Tn ARMv7
 .Tn Cortex A7
 CPUs.
 .It Li PMC_CPU_ARMV7_CORTEX_A8
 .Tn ARMv7
 .Tn Cortex A8
 CPUs.
 .It Li PMC_CPU_ARMV7_CORTEX_A9
 .Tn ARMv7
 .Tn Cortex A9
 CPUs.
 .It Li PMC_CPU_ARMV7_CORTEX_A15
 .Tn ARMv7 Cortex A15
 CPUs.
 .It Li PMC_CPU_ARMV7_CORTEX_A17
 .Tn ARMv7
 .Tn Cortex A17
 CPUs.
 .It Li PMC_CPU_ARMV8_CORTEX_A53
 ARMv8
 .Tn Cortex A53
 CPUs.
 .It Li PMC_CPU_ARMV8_CORTEX_A57
 ARMv8
 .Tn Cortex A57
 CPUs.
 .It Li PMC_CPU_ARMV8_CORTEX_A76
 ARMv8
 .Tn Cortex A76
 CPUs.
 .It Li GENERIC
 Generic
 .It Li PMC_CPU_INTEL_ATOM
 .Tn Intel
 .Tn Atom
 CPUs and other CPUs conforming to version 3 of the
 .Tn Intel
 performance measurement architecture.
 .It Li PMC_CPU_INTEL_CORE
 .Tn Intel
 .Tn Core Solo
 and
 .Tn Core Duo
 CPUs, and other CPUs conforming to version 1 of the
 .Tn Intel
 performance measurement architecture.
 .It Li PMC_CPU_INTEL_CORE2
 .Tn Intel
 .Tn "Core2 Solo" ,
 .Tn "Core2 Duo"
 and
 .Tn "Core2 Extreme"
 CPUs, and other CPUs conforming to version 2 of the
 .Tn Intel
 performance measurement architecture.
 .It Li PMC_CPU_PPC_7450
 .Tn PowerPC
 MPC7450 CPUs.
 .It Li PMC_CPU_PPC_970
 .Tn IBM
 .Tn PowerPC
 970 CPUs.
 .It Li PMC_CPU_PPC_E500
 .Tn PowerPC
 e500 Core CPUs.
 .It Li PMC_CPU_PPC_POWER8
 .Tn IBM
 .Tn POWER8 and
 .Tn POWER9
 CPUs.
 .El
 .Ss Supported PMCs
 PMCs supported by this library are named by the
 .Vt enum pmc_class
 enumeration.
 Supported PMC classes include:
 .Pp
 .Bl -tag -width "Li PMC_CLASS_POWER8" -compact
 .It Li PMC_CLASS_IAF
 Fixed function hardware counters presents in CPUs conforming to the
 .Tn Intel
 performance measurement architecture version 2 and later.
 .It Li PMC_CLASS_IAP
 Programmable hardware counters present in CPUs conforming to the
 .Tn Intel
 performance measurement architecture version 1 and later.
 .It Li PMC_CLASS_K7
 Programmable hardware counters present in
 .Tn "AMD Athlon"
 CPUs.
 .It Li PMC_CLASS_K8
 Programmable hardware counters present in
 .Tn "AMD Athlon64"
 CPUs.
 .It Li PMC_CLASS_TSC
 The timestamp counter on i386 and amd64 architecture CPUs.
 .It Li PMC_CLASS_ARMV7
 .Tn ARMv7
 .It Li PMC_CLASS_ARMV8
 .Tn ARMv8
 .It Li PMC_CLASS_PPC970
 .Tn IBM
 .Tn PowerPC
 970 class.
 .It Li PMC_CLASS_POWER8
 .Tn IBM
 .Tn POWER8
 class.
 .It Li PMC_CLASS_SOFT
 Software events.
 .El
 .Ss PMC Capabilities
 Capabilities of performance monitoring hardware are denoted using
 the
 .Vt "enum pmc_caps"
 enumeration.
 Supported capabilities include:
 .Pp
 .Bl -tag -width "Li PMC_CAP_INTERRUPT" -compact
 .It Li PMC_CAP_CASCADE
 The ability to cascade counters.
 .It Li PMC_CAP_DOMWIDE
 Separate counters tied to each NUMA domain.
 .It Li PMC_CAP_EDGE
 The ability to count negated to asserted transitions of the hardware
 conditions being probed for.
 .It Li PMC_CAP_INTERRUPT
 The ability to interrupt the CPU.
 .It Li PMC_CAP_INVERT
 The ability to invert the sense of the hardware conditions being
 measured.
 .It Li PMC_CAP_PRECISE
 The ability to perform precise sampling.
 .It Li PMC_CAP_QUALIFIER
 The hardware allows monitored to be further qualified in some
 system dependent way.
 .It Li PMC_CAP_READ
 The ability to read from performance counters.
 .It Li PMC_CAP_SYSTEM
 The ability to restrict counting of hardware events to when the CPU is
 running privileged code.
 .It Li PMC_CAP_SYSWIDE
 A single counter aggregating events for the whole system.
 .It Li PMC_CAP_THRESHOLD
 The ability to ignore simultaneous hardware events below a
 programmable threshold.
 .It Li PMC_CAP_USER
 The ability to restrict counting of hardware events to those when the
 CPU is running unprivileged code.
 .It Li PMC_CAP_WRITE
 The ability to write to performance counters.
 .El
 .Ss CPU Naming Conventions
 CPUs are named using small integers from zero up to, but
 excluding, the value returned by function
 .Fn pmc_ncpu .
 On platforms supporting sparsely numbered CPUs not all the numbers in
 this range will denote valid CPUs.
 Operations on non-existent CPUs will return an error.
 .Ss Functional Grouping of the API
 This section contains a brief overview of the available functionality
 in the PMC library.
 Each function listed here is described further in its own manual page.
 .Bl -tag -width 2n
 .It Administration
 .Bl -tag -width 6n -compact
 .It Fn pmc_disable , Fn pmc_enable
 Administratively disable (enable) specific performance monitoring
 counter hardware.
 Counters that are disabled will not be available to applications to
 use.
 .El
 .It "Convenience Functions"
 .Bl -tag -width 6n -compact
 .It Fn pmc_event_names_of_class
 Returns a list of event names supported by a given PMC type.
 .It Fn pmc_name_of_capability
 Convert a
 .Dv PMC_CAP_*
 flag to a human-readable string.
 .It Fn pmc_name_of_class
 Convert a
 .Dv PMC_CLASS_*
 constant to a human-readable string.
 .It Fn pmc_name_of_cputype
 Return a human-readable name for a CPU type.
 .It Fn pmc_name_of_disposition
 Return a human-readable string describing a PMC's disposition.
 .It Fn pmc_name_of_event
 Convert a numeric event code to a human-readable string.
 .It Fn pmc_name_of_mode
 Convert a
 .Dv PMC_MODE_*
 constant to a human-readable name.
 .It Fn pmc_name_of_state
 Return a human-readable string describing a PMC's current state.
 .El
 .It "Library Initialization"
 .Bl -tag -width 6n -compact
 .It Fn pmc_init
 Initialize the library.
 This function must be called before any other library function.
 .El
 .It "Log File Handling"
 .Bl -tag -width 6n -compact
 .It Fn pmc_configure_logfile
 Configure a log file for
 .Xr hwpmc 4
 to write logged events to.
 .It Fn pmc_flush_logfile
 Flush all pending log data in
 .Xr hwpmc 4 Ns Ap s
 buffers.
 .It Fn pmc_close_logfile
 Flush all pending log data and close
 .Xr hwpmc 4 Ns Ap s
 side of the stream.
 .It Fn pmc_writelog
 Append arbitrary user data to the current log file.
 .El
 .It "PMC Management"
 .Bl -tag -width 6n -compact
 .It Fn pmc_allocate , Fn pmc_release
 Allocate (free) a PMC.
 .It Fn pmc_attach , Fn pmc_detach
 Attach (detach) a process scope PMC to a target.
 .It Fn pmc_read , Fn pmc_write , Fn pmc_rw
 Read (write) a value from (to) a PMC.
 .It Fn pmc_start , Fn pmc_stop
 Start (stop) a software PMC.
 .It Fn pmc_set
 Set the reload value for a sampling PMC.
 .El
 .It "Queries"
 .Bl -tag -width 6n -compact
 .It Fn pmc_capabilities
 Retrieve the capabilities for a given PMC.
 .It Fn pmc_cpuinfo
 Retrieve information about the CPUs and PMC hardware present in the
 system.
 .It Fn pmc_get_driver_stats
 Retrieve statistics maintained by
 .Xr hwpmc 4 .
 .It Fn pmc_ncpu
 Determine the greatest possible CPU number on the system.
 .It Fn pmc_npmc
 Return the number of hardware PMCs present in a given CPU.
 .It Fn pmc_pmcinfo
 Return information about the state of a given CPU's PMCs.
 .It Fn pmc_width
 Determine the width of a hardware counter in bits.
 .El
 .It "x86 Architecture Specific API"
 .Bl -tag -width 6n -compact
 .It Fn pmc_get_msr
 Returns the processor model specific register number
 associated with
 .Fa pmc .
 Applications may then use the x86
 .Ic RDPMC
 instruction to directly read the contents of the PMC.
 .El
 .El
 .Ss Signal Handling Requirements
 Applications using PMCs are required to handle the following signals:
 .Bl -tag -width ".Dv SIGBUS"
 .It Dv SIGBUS
 When the
 .Xr hwpmc 4
 module is unloaded using
 .Xr kldunload 8 ,
 processes that have PMCs allocated to them will be sent a
 .Dv SIGBUS
 signal.
 .It Dv SIGIO
 The
 .Xr hwpmc 4
 driver will send a PMC owning process a
 .Dv SIGIO
 signal if:
 .Bl -bullet
 .It
 any process-mode PMC allocated by it loses all its
 target processes.
 .It
 the driver encounters an error when writing log data to a
 configured log file.
 This error may be retrieved by a subsequent call to
 .Fn pmc_flush_logfile .
 .El
 .El
 .Ss Typical Program Flow
 .Bl -enum
 .It
 An application would first invoke function
 .Fn pmc_init
 to allow the library to initialize itself.
 .It
 Signal handling would then be set up.
 .It
 Next the application would allocate the PMCs it desires using function
 .Fn pmc_allocate .
 .It
 Initial values for PMCs may be set using function
 .Fn pmc_set .
 .It
 If a log file is necessary for the PMCs to work, it would
 be configured using function
 .Fn pmc_configure_logfile .
 .It
 Process scope PMCs would then be attached to their target processes
 using function
 .Fn pmc_attach .
 .It
 The PMCs would then be started using function
 .Fn pmc_start .
 .It
 Once started, the values of counting PMCs may be read using function
 .Fn pmc_read .
 For PMCs that write events to the log file, this logged data would be
 read and parsed using the
 .Xr pmclog 3
 family of functions.
 .It
 PMCs are stopped using function
 .Fn pmc_stop ,
 and process scope PMCs are detached from their targets using
 function
 .Fn pmc_detach .
 .It
 Before the process exits, it may release its PMCs using function
 .Fn pmc_release .
 Any configured log file may be closed using function
 .Fn pmc_configure_logfile .
 .El
 .Sh EVENT SPECIFIERS
 Event specifiers are strings comprising of an event name, followed by
 optional parameters modifying the semantics of the hardware event
 being probed.
 Event names are PMC architecture dependent, but the PMC library defines
 machine independent aliases for commonly used events.
 .Pp
 Event specifiers spellings are case-insensitive and space characters,
 periods, underscores and hyphens are considered equivalent to each other.
 Thus the event specifiers
 .Qq "Example Event" ,
 .Qq "example-event" ,
 and
 .Qq "EXAMPLE_EVENT"
 are equivalent.
 .Ss PMC Architecture Dependent Events
 PMC architecture dependent event specifiers are described in the
 following manual pages:
 .Bl -column " PMC_CLASS_TSC " "MANUAL PAGE "
 .It Em "PMC Class"      Ta Em "Manual Page"
 .It Li PMC_CLASS_IAF    Ta Xr pmc.iaf 3
 .It Li PMC_CLASS_IAP    Ta Xr pmc.atom 3 , Xr pmc.core 3 , Xr pmc.core2 3
 .It Li PMC_CLASS_K7     Ta Xr pmc.k7 3
 .It Li PMC_CLASS_K8     Ta Xr pmc.k8 3
 .It Li PMC_CLASS_TSC    Ta Xr pmc.tsc 3
 .El
 .Ss Event Name Aliases
 Event name aliases are PMC-independent names for commonly used events.
 The following aliases are known to this version of the
 .Nm pmc
 library:
 .Bl -tag -width indent
 .It Li branches
 Measure the number of branches retired.
 .It Li branch-mispredicts
 Measure the number of retired branches that were mispredicted.
 .It Li cycles
 Measure processor cycles.
 This event is implemented using the processor's Time Stamp Counter
 register.
 .It Li dc-misses
 Measure the number of data cache misses.
 .It Li ic-misses
 Measure the number of instruction cache misses.
 .It Li instructions
 Measure the number of instructions retired.
 .It Li interrupts
 Measure the number of interrupts seen.
 .It Li unhalted-cycles
 Measure the number of cycles the processor is not in a halted
 or sleep state.
 .El
 .Sh COMPATIBILITY
 The interface between the
 .Nm pmc
 library and the
 .Xr hwpmc 4
 driver is intended to be private to the implementation and may
 change.
 In order to ease forward compatibility with future versions of the
 .Xr hwpmc 4
 driver, applications are urged to dynamically link with the
 .Nm pmc
 library.
-.Pp
-The
-.Nm pmc
-API is
-.Ud
+Doing otherwise is unsupported.
 .Sh SEE ALSO
 .Xr pmc.atom 3 ,
 .Xr pmc.core 3 ,
 .Xr pmc.core2 3 ,
 .Xr pmc.haswell 3 ,
 .Xr pmc.haswelluc 3 ,
 .Xr pmc.haswellxeon 3 ,
 .Xr pmc.iaf 3 ,
 .Xr pmc.ivybridge 3 ,
 .Xr pmc.ivybridgexeon 3 ,
 .Xr pmc.k7 3 ,
 .Xr pmc.k8 3 ,
 .Xr pmc.sandybridge 3 ,
 .Xr pmc.sandybridgeuc 3 ,
 .Xr pmc.sandybridgexeon 3 ,
 .Xr pmc.soft 3 ,
 .Xr pmc.tsc 3 ,
 .Xr pmc.westmere 3 ,
 .Xr pmc.westmereuc 3 ,
 .Xr pmc_allocate 3 ,
 .Xr pmc_attach 3 ,
 .Xr pmc_capabilities 3 ,
 .Xr pmc_configure_logfile 3 ,
 .Xr pmc_disable 3 ,
 .Xr pmc_event_names_of_class 3 ,
 .Xr pmc_get_driver_stats 3 ,
 .Xr pmc_get_msr 3 ,
 .Xr pmc_init 3 ,
 .Xr pmc_name_of_capability 3 ,
 .Xr pmc_read 3 ,
 .Xr pmc_set 3 ,
 .Xr pmc_start 3 ,
 .Xr pmclog 3 ,
 .Xr hwpmc 4 ,
 .Xr pmccontrol 8 ,
 .Xr pmcstat 8
 .Sh HISTORY
 The
 .Nm pmc
 library first appeared in
 .Fx 6.0 .
 .Sh AUTHORS
 The
 .Lb libpmc
 library was written by
 .An Joseph Koshy Aq Mt jkoshy@FreeBSD.org .
diff --git a/share/man/man4/hwpmc.4 b/share/man/man4/hwpmc.4
index 6c9e90b36c2d..c394af90cd8d 100644
--- a/share/man/man4/hwpmc.4
+++ b/share/man/man4/hwpmc.4
@@ -1,827 +1,818 @@
 .\" Copyright (c) 2003-2008 Joseph Koshy
 .\" Copyright (c) 2007 The FreeBSD Foundation
 .\" All rights reserved.
 .\"
 .\" Portions of this software were developed by A. Joseph Koshy under
 .\" sponsorship from the FreeBSD Foundation and Google, Inc.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 31, 2023
+.Dd June 16, 2023
 .Dt HWPMC 4
 .Os
 .Sh NAME
 .Nm hwpmc
 .Nd "Hardware Performance Monitoring Counter support"
 .Sh SYNOPSIS
 The following option must be present in the kernel configuration file:
 .Bd -ragged -offset indent
 .Cd "options HWPMC_HOOKS"
 .Ed
 .Pp
 Additionally, for i386 systems:
 .Bd -ragged -offset indent
 .Cd "device apic"
 .Ed
 .Pp
 To load the driver as a module at boot time, place the
 following line in
 .Xr rc.conf 5 :
 .Bd -literal -offset indent
 kld_list="${kld_list} hwpmc"
 .Ed
 .Pp
 Alternatively, to compile this driver into the kernel:
 .Bd -ragged -offset indent
 .Cd "device hwpmc"
 .Ed
 .Sh DESCRIPTION
 The
 .Nm
 driver virtualizes the hardware performance monitoring facilities in
 modern CPUs and provides support for using these facilities from
 user level processes.
 .Pp
 The driver supports multi-processor systems.
 .Pp
 PMCs are allocated using the
 .Dv PMC_OP_PMCALLOCATE
 request.
 A successful
 .Dv PMC_OP_PMCALLOCATE
 request will return a handle to the requesting process.
 Subsequent operations on the allocated PMC use this handle to denote
 the specific PMC.
 A process that has successfully allocated a PMC is termed an
 .Dq "owner process" .
 .Pp
 PMCs may be allocated with process or system scope.
 .Bl -tag -width ".Em Process-scope"
 .It Em "Process-scope"
 The PMC is active only when a thread belonging
 to a process it is attached to is scheduled on a CPU.
 .It Em "System-scope"
 The PMC operates independently of processes and
 measures hardware events for the system as a whole.
 .El
 .Pp
 PMCs may be allocated for counting or for sampling:
 .Bl -tag -width ".Em Counting"
 .It Em Counting
 In counting modes, the PMCs count hardware events.
 These counts are retrievable using the
 .Dv PMC_OP_PMCREAD
 system call on all architectures.
 Some architectures offer faster methods of reading these counts.
 .It Em Sampling
 In sampling modes, the PMCs are configured to sample the CPU
 instruction pointer (and optionally to capture the call chain leading
 up to the sampled instruction pointer) after a configurable number of
 hardware events have been observed.
 Instruction pointer samples and call chain records are usually
 directed to a log file for subsequent analysis.
 .El
 .Pp
 Scope and operational mode are orthogonal; a PMC may thus be
 configured to operate in one of the following four modes:
 .Bl -tag -width indent
 .It Process-scope, counting
 These PMCs count hardware events whenever a thread in their attached process is
 scheduled on a CPU.
 These PMCs normally count from zero, but the initial count may be
 set using the
 .Dv PMC_OP_SETCOUNT
 operation.
 Applications can read the value of the PMC anytime using the
 .Dv PMC_OP_PMCRW
 operation.
 .It Process-scope, sampling
 These PMCs sample the target processes instruction pointer after they
 have seen the configured number of hardware events.
 The PMCs only count events when a thread belonging to their attached
 process is active.
 The desired frequency of sampling is set using the
 .Dv PMC_OP_SETCOUNT
 operation prior to starting the PMC.
 Log files are configured using the
 .Dv PMC_OP_CONFIGURELOG
 operation.
 .It System-scope, counting
 These PMCs count hardware events seen by them independent of the
 processes that are executing.
 The current count on these PMCs can be read using the
 .Dv PMC_OP_PMCRW
 request.
 These PMCs normally count from zero, but the initial count may be
 set using the
 .Dv PMC_OP_SETCOUNT
 operation.
 .It System-scope, sampling
 These PMCs will periodically sample the instruction pointer of the CPU
 they are allocated on, and will write the sample to a log for further
 processing.
 The desired frequency of sampling is set using the
 .Dv PMC_OP_SETCOUNT
 operation prior to starting the PMC.
 Log files are configured using the
 .Dv PMC_OP_CONFIGURELOG
 operation.
 .Pp
 System-wide statistical sampling can only be enabled by a process with
 super-user privileges.
 .El
 .Pp
 Processes are allowed to allocate as many PMCs as the hardware and
 current operating conditions permit.
 Processes may mix allocations of system-wide and process-private
 PMCs.
 Multiple processes may be using PMCs simultaneously.
 .Pp
 Allocated PMCs are started using the
 .Dv PMC_OP_PMCSTART
 operation, and stopped using the
 .Dv PMC_OP_PMCSTOP
 operation.
 Stopping and starting a PMC is permitted at any time the owner process
 has a valid handle to the PMC.
 .Pp
 Process-private PMCs need to be attached to a target process before
 they can be used.
 Attaching a process to a PMC is done using the
 .Dv PMC_OP_PMCATTACH
 operation.
 An already attached PMC may be detached from its target process
 using the converse
 .Dv PMC_OP_PMCDETACH
 operation.
 Issuing a
 .Dv PMC_OP_PMCSTART
 operation on an as yet unattached PMC will cause it to be attached
 to its owner process.
 The following rules determine whether a given process may attach
 a PMC to another target process:
 .Bl -bullet -compact
 .It
 A non-jailed process with super-user privileges is allowed to attach
 to any other process in the system.
 .It
 Other processes are only allowed to attach to targets that they would
 be able to attach to for debugging (as determined by
 .Xr p_candebug 9 ) .
 .El
 .Pp
 PMCs are released using
 .Dv PMC_OP_PMCRELEASE .
 After a successful
 .Dv PMC_OP_PMCRELEASE
 operation the handle to the PMC will become invalid.
 .Ss Modifier Flags
 The
 .Dv PMC_OP_PMCALLOCATE
 operation supports the following flags that modify the behavior
 of an allocated PMC:
 .Bl -tag -width indent
 .It Dv PMC_F_CALLCHAIN
 This modifier informs sampling PMCs to record a callchain when
 capturing a sample.
 The maximum depth to which call chains are recorded is specified
 by the
 .Va "kern.hwpmc.callchaindepth"
 kernel tunable.
 .It Dv PMC_F_DESCENDANTS
 This modifier is valid only for a PMC being allocated in process-private
 mode.
 It signifies that the PMC will track hardware events for its
 target process and the target's current and future descendants.
 .It Dv PMC_F_LOG_PROCCSW
 This modifier is valid only for a PMC being allocated in process-private
 mode.
 When this modifier is present, at every context switch,
 .Nm
 will log a record containing the number of hardware events
 seen by the target process when it was scheduled on the CPU.
 .It Dv PMC_F_LOG_PROCEXIT
 This modifier is valid only for a PMC being allocated in process-private
 mode.
 With this modifier present,
 .Nm
 will maintain per-process counts for each target process attached to
 a PMC.
 At process exit time, a record containing the target process' PID and
 the accumulated per-process count for that process will be written to the
 configured log file.
 .El
 .Pp
 Modifiers
 .Dv PMC_F_LOG_PROCEXIT
 and
 .Dv PMC_F_LOG_PROCCSW
 may be used in combination with modifier
 .Dv PMC_F_DESCENDANTS
 to track the behavior of complex pipelines of processes.
 PMCs with modifiers
 .Dv PMC_F_LOG_PROCEXIT
 and
 .Dv PMC_F_LOG_PROCCSW
 cannot be started until their owner process has configured a log file.
 .Ss Signals
 The
 .Nm
 driver may deliver signals to processes that have allocated PMCs:
 .Bl -tag -width ".Dv SIGBUS"
 .It Dv SIGIO
 A
 .Dv PMC_OP_PMCRW
 operation was attempted on a process-private PMC that does not have
 attached target processes.
 .It Dv SIGBUS
 The
 .Nm
 driver is being unloaded from the kernel.
 .El
 .Ss PMC ROW DISPOSITIONS
 A PMC row is defined as the set of PMC resources at the same hardware
 address in the CPUs in a system.
 Since process scope PMCs need to move between CPUs following their
 target threads, allocation of a process scope PMC reserves all PMCs in
 a PMC row for use only with process scope PMCs.
 Accordingly a PMC row will be in one of the following dispositions:
 .Bl -tag -width ".Dv PMC_DISP_STANDALONE" -compact
 .It Dv PMC_DISP_FREE
 Hardware counters in this row are free and may be use to satisfy
 either of system scope or process scope allocation requests.
 .It Dv PMC_DISP_THREAD
 Hardware counters in this row are in use by process scope PMCs
 and are only available for process scope allocation requests.
 .It Dv PMC_DISP_STANDALONE
 Some hardware counters in this row have been administratively
 disabled or are in use by system scope PMCs.
 Non-disabled hardware counters in such a row may be used
 for satisfying system scope allocation requests.
 No process scope PMCs will use hardware counters in this row.
 .El
-.Sh PROGRAMMING API
-The recommended way for application programs to use the facilities of
-the
-.Nm
-driver is using the API provided by the
+.Sh COMPATIBILITY
+The API and ABI documented in this manual page may change in the future.
+This interface is intended to be consumed by the
 .Xr pmc 3
-library.
-.Pp
+library; other consumers are unsupported.
+Applications targeting PMCs should use the
+.Xr pmc 3
+library API.
+.Sh PROGRAMMING API
 The
 .Nm
 driver operates using a system call number that is dynamically
 allotted to it when it is loaded into the kernel.
 .Pp
 The
 .Nm
 driver supports the following operations:
 .Bl -tag -width indent
 .It Dv PMC_OP_CONFIGURELOG
 Configure a log file for PMCs that require a log file.
 The
 .Nm
 driver will write log data to this file asynchronously.
 If it encounters an error, logging will be stopped and the error code
 encountered will be saved for subsequent retrieval by a
 .Dv PMC_OP_FLUSHLOG
 request.
 .It Dv PMC_OP_FLUSHLOG
 Transfer buffered log data inside
 .Nm
 to a configured output file.
 This operation returns to the caller after the write operation
 has returned.
 The returned error code reflects any pending error state inside
 .Nm .
 .It Dv PMC_OP_GETCPUINFO
 Retrieve information about the highest possible CPU number for the system,
 and the number of hardware performance monitoring counters available per CPU.
 .It Dv PMC_OP_GETDRIVERSTATS
 Retrieve module statistics (for analyzing the behavior of
 .Nm
 itself).
 .It Dv PMC_OP_GETMODULEVERSION
 Retrieve the version number of API.
 .It Dv PMC_OP_GETPMCINFO
 Retrieve information about the current state of the PMCs on a
 given CPU.
 .It Dv PMC_OP_PMCADMIN
 Set the administrative state (i.e., whether enabled or disabled) for
 the hardware PMCs managed by the
 .Nm
 driver.
 The invoking process needs to possess the
 .Dv PRIV_PMC_MANAGE
 privilege.
 .It Dv PMC_OP_PMCALLOCATE
 Allocate and configure a PMC.
 On successful allocation, a handle to the PMC (a 32 bit value)
 is returned.
 .It Dv PMC_OP_PMCATTACH
 Attach a process mode PMC to a target process.
 The PMC will be active whenever a thread in the target process is
 scheduled on a CPU.
 .Pp
 If the
 .Dv PMC_F_DESCENDANTS
 flag had been specified at PMC allocation time, then the PMC is
 attached to all current and future descendants of the target process.
 .It Dv PMC_OP_PMCDETACH
 Detach a PMC from its target process.
 .It Dv PMC_OP_PMCRELEASE
 Release a PMC.
 .It Dv PMC_OP_PMCRW
 Read and write a PMC.
 This operation is valid only for PMCs configured in counting modes.
 .It Dv PMC_OP_SETCOUNT
 Set the initial count (for counting mode PMCs) or the desired sampling
 rate (for sampling mode PMCs).
 .It Dv PMC_OP_PMCSTART
 Start a PMC.
 .It Dv PMC_OP_PMCSTOP
 Stop a PMC.
 .It Dv PMC_OP_WRITELOG
 Insert a timestamped user record into the log file.
 .El
 .Ss i386 Specific API
 Some i386 family CPUs support the RDPMC instruction which allows a
 user process to read a PMC value without needing to invoke a
 .Dv PMC_OP_PMCRW
 operation.
 On such CPUs, the machine address associated with an allocated PMC is
 retrievable using the
 .Dv PMC_OP_PMCX86GETMSR
 system call.
 .Bl -tag -width indent
 .It Dv PMC_OP_PMCX86GETMSR
 Retrieve the MSR (machine specific register) number associated with
 the given PMC handle.
 .Pp
 The PMC needs to be in process-private mode and allocated without the
 .Dv PMC_F_DESCENDANTS
 modifier flag, and should be attached only to its owner process at the
 time of the call.
 .El
 .Ss amd64 Specific API
 AMD64 CPUs support the RDPMC instruction which allows a
 user process to read a PMC value without needing to invoke a
 .Dv PMC_OP_PMCRW
 operation.
 The machine address associated with an allocated PMC is
 retrievable using the
 .Dv PMC_OP_PMCX86GETMSR
 system call.
 .Bl -tag -width indent
 .It Dv PMC_OP_PMCX86GETMSR
 Retrieve the MSR (machine specific register) number associated with
 the given PMC handle.
 .Pp
 The PMC needs to be in process-private mode and allocated without the
 .Dv PMC_F_DESCENDANTS
 modifier flag, and should be attached only to its owner process at the
 time of the call.
 .El
 .Sh SYSCTL VARIABLES AND LOADER TUNABLES
 The behavior of
 .Nm
 is influenced by the following
 .Xr sysctl 8
 and
 .Xr loader 8
 tunables:
 .Bl -tag -width indent
 .It Va kern.hwpmc.callchaindepth Pq integer, read-only
 The maximum number of call chain records to capture per sample.
 The default is 8.
 .It Va kern.hwpmc.debugflags Pq string, read-write
 (Only available if the
 .Nm
 driver was compiled with
 .Fl DDEBUG . )
 Control the verbosity of debug messages from the
 .Nm
 driver.
 .It Va kern.hwpmc.hashsize Pq integer, read-only
 The number of rows in the hash tables used to keep track of owner and
 target processes.
 The default is 16.
 .It Va kern.hwpmc.logbuffersize Pq integer, read-only
 The size in kilobytes of each log buffer used by
 .Nm Ns 's
 logging function.
 The default buffer size is 4KB.
 .It Va kern.hwpmc.mincount Pq integer, read-write
 The minimum sampling rate for sampling mode PMCs.
 The default count is 1000 events.
 .It Va kern.hwpmc.mtxpoolsize Pq integer, read-only
 The size of the spin mutex pool used by the PMC driver.
 The default is 32.
 .It Va kern.hwpmc.nbuffers_pcpu Pq integer, read-only
 The number of log buffers used by
 .Nm
 for logging.
 The default is 64.
 .It Va kern.hwpmc.nsamples Pq integer, read-only
 The number of entries in the per-CPU ring buffer used during sampling.
 The default is 512.
 .It Va security.bsd.unprivileged_syspmcs Pq boolean, read-write
 If set to non-zero, allow unprivileged processes to allocate system-wide
 PMCs.
 The default value is 0.
 .It Va security.bsd.unprivileged_proc_debug Pq boolean, read-write
 If set to 0, the
 .Nm
 driver will only allow privileged processes to attach PMCs to other
 processes.
 .El
 .Pp
 These variables may be set in the kernel environment using
 .Xr kenv 1
 before
 .Nm
 is loaded.
 .Sh IMPLEMENTATION NOTES
 .Ss SMP Symmetry
 The kernel driver requires all physical CPUs in an SMP system to have
 identical performance monitoring counter hardware.
 .Ss Sparse CPU Numbering
 On platforms that sparsely number CPUs and which support hot-plugging
 of CPUs, requests that specify non-existent or disabled CPUs will fail
 with an error.
 Applications allocating system-scope PMCs need to be aware of
 the possibility of such transient failures.
 .Ss x86 TSC Handling
 Historically, on the x86 architecture,
 .Fx
 has permitted user processes running at a processor CPL of 3 to
 read the TSC using the RDTSC instruction.
 The
 .Nm
 driver preserves this behavior.
 .Ss Intel P4/HTT Handling
 On CPUs with HTT support, Intel P4 PMCs are capable of qualifying
 only a subset of hardware events on a per-logical CPU basis.
 Consequently, if HTT is enabled on a system with Intel Pentium P4
 PMCs, then the
 .Nm
 driver will reject allocation requests for process-private PMCs that
 request counting of hardware events that cannot be counted separately
 for each logical CPU.
 .Sh DIAGNOSTICS
 .Bl -diag
 .It "hwpmc: [class/npmc/capabilities]..."
 Announce the presence of
 .Va npmc
 PMCs of class
 .Va class ,
 with capabilities described by bit string
 .Va capabilities .
 .It "hwpmc: kernel version (0x%x) does not match module version (0x%x)."
 The module loading process failed because a version mismatch was detected
 between the currently executing kernel and the module being loaded.
 .It "hwpmc: this kernel has not been compiled with 'options HWPMC_HOOKS'."
 The module loading process failed because the currently executing kernel
 was not configured with the required configuration option
 .Dv HWPMC_HOOKS .
 .It "hwpmc: tunable hashsize=%d must be greater than zero."
 A negative value was supplied for tunable
 .Va kern.hwpmc.hashsize .
 .It "hwpmc: tunable logbuffersize=%d must be greater than zero."
 A negative value was supplied for tunable
 .Va kern.hwpmc.logbuffersize .
 .It "hwpmc: tunable nlogbuffers=%d must be greater than zero."
 A negative value was supplied for tunable
 .Va kern.hwpmc.nlogbuffers .
 .It "hwpmc: tunable nsamples=%d out of range."
 The value for tunable
 .Va kern.hwpmc.nsamples
 was negative or greater than 65535.
 .El
-.Sh COMPATIBILITY
-The
-.Nm
-driver is
-.Ud
-The API and ABI documented in this manual page may change in
-the future.
-The recommended method of accessing this driver is using the
-.Xr pmc 3
-API.
 .Sh ERRORS
 A command issued to the
 .Nm
 driver may fail with the following errors:
 .Bl -tag -width Er
 .It Bq Er EAGAIN
 Helper process creation failed for a
 .Dv PMC_OP_CONFIGURELOG
 request due to a temporary resource shortage in the kernel.
 .It Bq Er EBUSY
 A
 .Dv PMC_OP_CONFIGURELOG
 operation was requested while an existing log was active.
 .It Bq Er EBUSY
 A DISABLE operation was requested using the
 .Dv PMC_OP_PMCADMIN
 request for a set of hardware resources currently in use for
 process-private PMCs.
 .It Bq Er EBUSY
 A
 .Dv PMC_OP_PMCADMIN
 operation was requested on an active system mode PMC.
 .It Bq Er EBUSY
 A
 .Dv PMC_OP_PMCATTACH
 operation was requested for a target process that already had another
 PMC using the same hardware resources attached to it.
 .It Bq Er EBUSY
 A
 .Dv PMC_OP_PMCRW
 request writing a new value was issued on a PMC that was active.
 .It Bq Er EBUSY
 A
 .Dv PMC_OP_PMCSETCOUNT
 request was issued on a PMC that was active.
 .It Bq Er EDOOFUS
 A
 .Dv PMC_OP_PMCSTART
 operation was requested without a log file being configured for a
 PMC allocated with
 .Dv PMC_F_LOG_PROCCSW
 and
 .Dv PMC_F_LOG_PROCEXIT
 modifiers.
 .It Bq Er EDOOFUS
 A
 .Dv PMC_OP_PMCSTART
 operation was requested on a system-wide sampling PMC without a log
 file being configured.
 .It Bq Er EEXIST
 A
 .Dv PMC_OP_PMCATTACH
 request was reissued for a target process that already is the target
 of this PMC.
 .It Bq Er EFAULT
 A bad address was passed in to the driver.
 .It Bq Er EINVAL
 An invalid PMC handle was specified.
 .It Bq Er EINVAL
 An invalid CPU number was passed in for a
 .Dv PMC_OP_GETPMCINFO
 operation.
 .It Bq Er EINVAL
 The
 .Ar pm_flags
 argument to a
 .Dv PMC_OP_CONFIGURELOG
 request contained unknown flags.
 .It Bq Er EINVAL
 A
 .Dv PMC_OP_CONFIGURELOG
 request to de-configure a log file was issued without a log file
 being configured.
 .It Bq Er EINVAL
 A
 .Dv PMC_OP_FLUSHLOG
 request was issued without a log file being configured.
 .It Bq Er EINVAL
 An invalid CPU number was passed in for a
 .Dv PMC_OP_PMCADMIN
 operation.
 .It Bq Er EINVAL
 An invalid operation request was passed in for a
 .Dv PMC_OP_PMCADMIN
 operation.
 .It Bq Er EINVAL
 An invalid PMC ID was passed in for a
 .Dv PMC_OP_PMCADMIN
 operation.
 .It Bq Er EINVAL
 A suitable PMC matching the parameters passed in to a
 .Dv PMC_OP_PMCALLOCATE
 request could not be allocated.
 .It Bq Er EINVAL
 An invalid PMC mode was requested during a
 .Dv PMC_OP_PMCALLOCATE
 request.
 .It Bq Er EINVAL
 An invalid CPU number was specified during a
 .Dv PMC_OP_PMCALLOCATE
 request.
 .It Bq Er EINVAL
 A CPU other than
 .Dv PMC_CPU_ANY
 was specified in a
 .Dv PMC_OP_PMCALLOCATE
 request for a process-private PMC.
 .It Bq Er EINVAL
 A CPU number of
 .Dv PMC_CPU_ANY
 was specified in a
 .Dv PMC_OP_PMCALLOCATE
 request for a system-wide PMC.
 .It Bq Er EINVAL
 The
 .Ar pm_flags
 argument to an
 .Dv PMC_OP_PMCALLOCATE
 request contained unknown flags.
 .It Bq Er EINVAL
 (On Intel Pentium 4 CPUs with HTT support)
 A
 .Dv PMC_OP_PMCALLOCATE
 request for a process-private PMC was issued for an event that does
 not support counting on a per-logical CPU basis.
 .It Bq Er EINVAL
 A PMC allocated for system-wide operation was specified with a
 .Dv PMC_OP_PMCATTACH
 or
 .Dv PMC_OP_PMCDETACH
 request.
 .It Bq Er EINVAL
 The
 .Ar pm_pid
 argument to a
 .Dv PMC_OP_PMCATTACH
 or
 .Dv PMC_OP_PMCDETACH
 request specified an illegal process ID.
 .It Bq Er EINVAL
 A
 .Dv PMC_OP_PMCDETACH
 request was issued for a PMC not attached to the target process.
 .It Bq Er EINVAL
 Argument
 .Ar pm_flags
 to a
 .Dv PMC_OP_PMCRW
 request contained illegal flags.
 .It Bq Er EINVAL
 A
 .Dv PMC_OP_PMCX86GETMSR
 operation was requested for a PMC not in process-virtual mode, or
 for a PMC that is not solely attached to its owner process, or for
 a PMC that was allocated with flag
 .Dv PMC_F_DESCENDANTS .
 .It Bq Er EINVAL
 A
 .Dv PMC_OP_WRITELOG
 request was issued for an owner process without a log file
 configured.
 .It Bq Er ENOMEM
 The system was not able to allocate kernel memory.
 .It Bq Er ENOSYS
 (On i386 and amd64 architectures)
 A
 .Dv PMC_OP_PMCX86GETMSR
 operation was requested for hardware that does not support reading
 PMCs directly with the RDPMC instruction.
 .It Bq Er ENXIO
 A
 .Dv PMC_OP_GETPMCINFO
 operation was requested for an absent or disabled CPU.
 .It Bq Er ENXIO
 A
 .Dv PMC_OP_PMCALLOCATE
 operation specified allocation of a system-wide PMC on an absent or
 disabled CPU.
 .It Bq Er ENXIO
 A
 .Dv PMC_OP_PMCSTART
 or
 .Dv PMC_OP_PMCSTOP
 request was issued for a system-wide PMC that was allocated on a CPU
 that is currently absent or disabled.
 .It Bq Er EOPNOTSUPP
 A
 .Dv PMC_OP_PMCALLOCATE
 request was issued for PMC capabilities not supported
 by the specified PMC class.
 .It Bq Er EOPNOTSUPP
 (i386 architectures)
 A sampling mode PMC was requested on a CPU lacking an APIC.
 .It Bq Er EPERM
 A
 .Dv PMC_OP_PMCADMIN
 request was issued by a process without super-user
 privilege or by a jailed super-user process.
 .It Bq Er EPERM
 A
 .Dv PMC_OP_PMCATTACH
 operation was issued for a target process that the current process
 does not have permission to attach to.
 .It Bq Er EPERM
 (i386 and amd64 architectures)
 A
 .Dv PMC_OP_PMCATTACH
 operation was issued on a PMC whose MSR has been retrieved using
 .Dv PMC_OP_PMCX86GETMSR .
 .It Bq Er ESRCH
 A process issued a PMC operation request without having allocated any
 PMCs.
 .It Bq Er ESRCH
 A process issued a PMC operation request after the PMC was detached
 from all of its target processes.
 .It Bq Er ESRCH
 A
 .Dv PMC_OP_PMCATTACH
 or
 .Dv PMC_OP_PMCDETACH
 request specified a non-existent process ID.
 .It Bq Er ESRCH
 The target process for a
 .Dv PMC_OP_PMCDETACH
 operation is not being monitored by
 .Nm .
 .El
 .Sh SEE ALSO
 .Xr kenv 1 ,
 .Xr pmc 3 ,
 .Xr pmclog 3 ,
 .Xr kldload 8 ,
 .Xr pmccontrol 8 ,
 .Xr pmcstat 8 ,
 .Xr sysctl 8 ,
 .Xr kproc_create 9 ,
 .Xr p_candebug 9
 .Sh HISTORY
 The
 .Nm
 driver first appeared in
 .Fx 6.0 .
 .Sh AUTHORS
 The
 .Nm
 driver was written by
 .An Joseph Koshy Aq Mt jkoshy@FreeBSD.org .
 .Sh BUGS
 The driver samples the state of the kernel's logical processor support
 at the time of initialization (i.e., at module load time).
 On CPUs supporting logical processors, the driver could misbehave if
 logical processors are subsequently enabled or disabled while the
 driver is active.
 .Pp
 On the i386 architecture, the driver requires that the local APIC on the
 CPU be enabled for sampling mode to be supported.
 Many single-processor motherboards keep the APIC disabled in BIOS; on
 such systems
 .Nm
 will not support sampling PMCs.
 .Sh SECURITY CONSIDERATIONS
 PMCs may be used to monitor the actual behavior of the system on hardware.
 In situations where this constitutes an undesirable information leak,
 the following options are available:
 .Bl -enum
 .It
 Set the
 .Xr sysctl 8
 tunable
 .Va security.bsd.unprivileged_syspmcs
 to 0.
 This ensures that unprivileged processes cannot allocate system-wide
 PMCs and thus cannot observe the hardware behavior of the system
 as a whole.
 This tunable may also be set at boot time using
 .Xr loader 8 ,
 or with
 .Xr kenv 1
 prior to loading the
 .Nm
 driver into the kernel.
 .It
 Set the
 .Xr sysctl 8
 tunable
 .Va security.bsd.unprivileged_proc_debug
 to 0.
 This will ensure that an unprivileged process cannot attach a PMC
 to any process other than itself and thus cannot observe the hardware
 behavior of other processes with the same credentials.
 .El
 .Pp
 System administrators should note that on IA-32 platforms
 .Fx
 makes the content of the IA-32 TSC counter available to all processes
 via the RDTSC instruction.