improved uart character printing and poweroff/restart

src/drivers/uart.c

@@ -0,0 +1,27 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <drivers/uart.h>
+
+void uart_put(size_t base_addr, uint8_t data) {
+	*(volatile uint8_t *)base_addr = data;
+}
+
+int kputchar(int ch) {
+	uart_put(UART_ADDRESS, ch);
+	return ch;
+}
+
+void kprint(const char *str) {
+	while (*str) {
+		kputchar(*str++);
+	}
+}
+
+void knewline(void) {
+	kputchar('\n');
+}
+
+void kputs(const char *str) {
+	kprint(str);
+	knewline();
+}