Also track the CPU Spin time for OpenBSD systems.

Use the non-cgo version for all openbsd architectures.
The old code only pulled some defines from header files. Just add them
as enumerations in native go. Also be careful at what the SysctlRaw returns.

Implement a way that supports both recent and old pre-6.4 OpenBSD systems.
With go-1.16 OpenBSD binaries will link to libc and because of this binaries
built on OpenBSD 6.9-current do not run on OpenBSD 6.3. OpenBSD 6.3 is also
not supported for more then 2 years. So maybe the compat code is not needed.
Still validation object length before doing an unsafe pointer conversion
is probably reasonable but I'm no golang expert.

Signed-off-by: Claudio Jeker <claudio@openbsd.org>

collector/cpu_openbsd.go

@@ -1,4 +1,4 @@
-// Copyright 2018 The Prometheus Authors
+// Copyright 2020 The Prometheus Authors
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -11,8 +11,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build openbsd && !amd64 && !nocpu
-// +build openbsd,!amd64,!nocpu
+//go:build !nocpu
+// +build !nocpu
 
 package collector
 
@@ -25,11 +25,31 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-/*
-#include <sys/param.h>
-#include <sys/sched.h>
-*/
-import "C"
+type clockinfo struct {
+	hz      int32
+	tick    int32
+	tickadj int32
+	stathz  int32
+	profhz  int32
+}
+
+const (
+	CP_USER = iota
+	CP_NICE
+	CP_SYS
+	CP_SPIN
+	CP_INTR
+	CP_IDLE
+	CPUSTATES
+)
+const (
+	CP_USER_O63 = iota
+	CP_NICE_O63
+	CP_SYS_O63
+	CP_INTR_O63
+	CP_IDLE_O63
+	CPUSTATES_O63
+)
 
 type cpuCollector struct {
 	cpu    typedDesc
@@ -52,32 +72,41 @@ func (c *cpuCollector) Update(ch chan<- prometheus.Metric) (err error) {
 	if err != nil {
 		return err
 	}
-	clock := *(*C.struct_clockinfo)(unsafe.Pointer(&clockb[0]))
+	clock := *(*clockinfo)(unsafe.Pointer(&clockb[0]))
 	hz := float64(clock.stathz)
 
 	ncpus, err := unix.SysctlUint32("hw.ncpu")
 	if err != nil {
 		return err
 	}
 
-	var cpTime [][C.CPUSTATES]C.int64_t
+	var cpTime [][CPUSTATES]uint64
 	for i := 0; i < int(ncpus); i++ {
 		cpb, err := unix.SysctlRaw("kern.cp_time2", i)
 		if err != nil && err != unix.ENODEV {
 			return err
 		}
 		if err != unix.ENODEV {
-			cpTime = append(cpTime, *(*[C.CPUSTATES]C.int64_t)(unsafe.Pointer(&cpb[0])))
+			var times [CPUSTATES]uint64
+			for n := 0; n < len(cpb); n += 8 {
+				times[n/8] = *(*uint64)(unsafe.Pointer(&cpb[n]))
+			}
+			if len(cpb)/8 == CPUSTATES_O63 {
+				copy(times[CP_INTR:], times[CP_INTR_O63:])
+				times[CP_SPIN] = 0
+			}
+			cpTime = append(cpTime, times)
 		}
 	}
 
 	for cpu, time := range cpTime {
 		lcpu := strconv.Itoa(cpu)
-		ch <- c.cpu.mustNewConstMetric(float64(time[C.CP_USER])/hz, lcpu, "user")
-		ch <- c.cpu.mustNewConstMetric(float64(time[C.CP_NICE])/hz, lcpu, "nice")
-		ch <- c.cpu.mustNewConstMetric(float64(time[C.CP_SYS])/hz, lcpu, "system")
-		ch <- c.cpu.mustNewConstMetric(float64(time[C.CP_INTR])/hz, lcpu, "interrupt")
-		ch <- c.cpu.mustNewConstMetric(float64(time[C.CP_IDLE])/hz, lcpu, "idle")
+		ch <- c.cpu.mustNewConstMetric(float64(time[CP_USER])/hz, lcpu, "user")
+		ch <- c.cpu.mustNewConstMetric(float64(time[CP_NICE])/hz, lcpu, "nice")
+		ch <- c.cpu.mustNewConstMetric(float64(time[CP_SYS])/hz, lcpu, "system")
+		ch <- c.cpu.mustNewConstMetric(float64(time[CP_SPIN])/hz, lcpu, "spin")
+		ch <- c.cpu.mustNewConstMetric(float64(time[CP_INTR])/hz, lcpu, "interrupt")
+		ch <- c.cpu.mustNewConstMetric(float64(time[CP_IDLE])/hz, lcpu, "idle")
 	}
 	return err
 }