diff --git a/tests/Makefile b/tests/Makefile
index 000856ac..94d7d434 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -12,7 +12,7 @@ dumps: $(addsuffix .dump,$(PROGRAMS))
 %.o: %.S
 	$(GCC) $(CFLAGS) -D__ASSEMBLY__=1 -c $< -o $@
 
-%.o: %.c
+%.o: %.c mmio.h
 	$(GCC) $(CFLAGS) -c $< -o $@
 
 %.riscv: %.o crt.o syscalls.o
diff --git a/tests/mmio.h b/tests/mmio.h
new file mode 100644
index 00000000..3fb791c6
--- /dev/null
+++ b/tests/mmio.h
@@ -0,0 +1,16 @@
+#ifndef __MMIO_H__
+#define __MMIO_H__
+
+static inline void write_reg(unsigned long addr, unsigned int data)
+{
+	volatile unsigned int *ptr = (volatile unsigned int *) addr;
+	*ptr = data;
+}
+
+static inline unsigned long read_reg(unsigned long addr)
+{
+	volatile unsigned int *ptr = (volatile unsigned int *) addr;
+	return *ptr;
+}
+
+#endif
diff --git a/tests/pwm.c b/tests/pwm.c
index 5b99bfff..77c56424 100644
--- a/tests/pwm.c
+++ b/tests/pwm.c
@@ -2,17 +2,7 @@
 #define PWM_DUTY 0x2004
 #define PWM_ENABLE 0x2008
 
-static inline void write_reg(unsigned long addr, unsigned int data)
-{
-	volatile unsigned int *ptr = (volatile unsigned int *) addr;
-	*ptr = data;
-}
-
-static inline unsigned long read_reg(unsigned long addr)
-{
-	volatile unsigned int *ptr = (volatile unsigned int *) addr;
-	return *ptr;
-}
+#include "mmio.h"
 
 int main(void)
 {