- While we are spreading the counter(9) across network stack, more userland

tools would need to know about the counter_u64_t type. Allow to include
sys/counter.h from userspace.
- Utilize now defined type in kvm_counter_u64_fetch().

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.

lib/libkvm/kvm_pcpu.c

@@ -42,6 +42,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/param.h>
 #include <sys/pcpu.h>
 #include <sys/sysctl.h>
+#include <sys/counter.h>
 #include <kvm.h>
 #include <limits.h>
 #include <stdlib.h>
@@ -319,7 +320,8 @@ kvm_read_zpcpu(kvm_t *kd, void *buf, u_long base, size_t size, int cpu)
 uint64_t
 kvm_counter_u64_fetch(kvm_t *kd, u_long base)
 {
-	uint64_t r, c;
+	counter_u64_t c;
+	uint64_t r;
 
 	if (mp_ncpus == 0)
 		if (_kvm_pcpu_init(kd) < 0)

sys/sys/counter.h

@@ -31,6 +31,7 @@
 
 typedef uint64_t *counter_u64_t;
 
+#ifdef _KERNEL
 #include <machine/counter.h>
 
 counter_u64_t	counter_u64_alloc(int);
@@ -58,4 +59,5 @@ uint64_t	counter_u64_fetch(counter_u64_t);
 	for (int i = 0; i < (n); i++)				\
 		counter_u64_zero((a)[i]);			\
 } while (0)
+#endif	/* _KERNEL */
 #endif	/* ! __SYS_COUNTER_H__ */