Add MSR support for FreeBSD

Tested on GhostBSD (based on FreeBSD)
It should work on DragonFlyBSD (the cpuctl driver has been ported from FreeBSD)
The situation for OpenBSD and NetBSD is not clear ; not supported

libcpuid/rdmsr.c

@@ -97,6 +97,75 @@ int cpu_msr_driver_close(struct msr_driver_t* drv)
 
 /* #endif defined (__linux__) || defined (__gnu_linux__) */
 
+#elif defined (__FreeBSD__) || defined (__DragonFly__)
+/* Assuming FreeBSD with /dev/cpuctlX */
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/ioctl.h>
+#include <sys/cpuctl.h>
+
+struct msr_driver_t { int fd; };
+static int rdmsr_supported(void);
+struct msr_driver_t* cpu_msr_driver_open(void)
+{
+	return cpu_msr_driver_open_core(0);
+}
+
+struct msr_driver_t* cpu_msr_driver_open_core(int core_num)
+{
+	char msr[32];
+	struct msr_driver_t* handle;
+	if(core_num < 0 && cpuid_get_total_cpus() <= core_num)
+	{
+		set_error(ERR_INVCNB);
+		return NULL;
+	}
+	if (!rdmsr_supported()) {
+		set_error(ERR_NO_RDMSR);
+		return NULL;
+	}
+	sprintf(msr, "/dev/cpuctl%i", core_num);
+	int fd = open(msr, O_RDONLY);
+	if (fd < 0) {
+		if (errno == EIO) {
+			set_error(ERR_NO_RDMSR);
+			return NULL;
+		}
+		set_error(ERR_NO_DRIVER);
+		return NULL;
+	}
+	handle = (struct msr_driver_t*) malloc(sizeof(struct msr_driver_t));
+	handle->fd = fd;
+	return handle;
+}
+
+int cpu_rdmsr(struct msr_driver_t* driver, uint32_t msr_index, uint64_t* result)
+{
+	cpuctl_msr_args_t args;
+	args.msr = msr_index;
+
+	if (!driver || driver->fd < 0)
+		return set_error(ERR_HANDLE);
+
+	if(ioctl(driver->fd, CPUCTL_RDMSR, &args))
+		return set_error(ERR_INVMSR);
+
+	*result = args.data; 
+	return 0;
+}
+
+int cpu_msr_driver_close(struct msr_driver_t* drv)
+{
+	if (drv && drv->fd >= 0) {
+		close(drv->fd);
+		free(drv);
+	}
+	return 0;
+}
+
+/* #endif defined (__FreeBSD__) || defined (__DragonFly__) */
+
 #elif defined (_WIN32)
 #include <windows.h>
 #include <winioctl.h>