syscalls: implement clock_getres

kernel-src/sys/syscalls/clockgetres.c

@@ -0,0 +1,34 @@
+#include <kernel/syscalls.h>
+#include <time.h>
+#include <kernel/usercopy.h>
+
+#define CLOCK_REALTIME 0
+#define CLOCK_MONOTONIC 1
+#define CLOCK_BOOTTIME 7
+
+syscallret_t syscall_clock_getres(context_t *, int clockid, timespec_t *res) {
+	syscallret_t ret;
+
+	switch (clockid) {
+		case CLOCK_REALTIME:
+		case CLOCK_MONOTONIC:
+		case CLOCK_BOOTTIME:
+			if (res) {
+				timespec_t ts = {
+					.s = 0,
+					.ns = 1
+				};
+
+				ret.errno = usercopy_touser(res, &ts, sizeof(timespec_t));
+			} else {
+				ret.errno = 0;
+			}
+			break;
+		default:
+			ret.errno = EINVAL;
+			break;
+	}
+
+	ret.ret = ret.errno ? -1 : 0;
+	return ret;
+}