1 files changed, 34 insertions, 0 deletions
diff --git a/PL0_test.c b/PL0_test.c
new file mode 100644
index 0000000..7609294
--- /dev/null
+++ b/PL0_test.c
@@ -0,0 +1,34 @@
+#include "uart.h"
+#include "psr.h"
+
+void PL0_main(void)
+{
+  uart_puts("hello PL0! Switching to user mode!\n\r");
+
+  asm("cps #0b10000\n\r"
+      "isb" ::: "memory");
+
+  // if all went correct, Success! gets printed
+  uart_puts("Success!\n\r");
+
+  // if we're indeed i PL0, we should crash now, when trying to access
+  // memory we're not allowed to
+  char first_kernel_byte[2];
+
+  first_kernel_byte[0] = *(char*) ((uint32_t) 0x8000);
+  first_kernel_byte[1] = '\0';
+  
+  uart_puts(first_kernel_byte);
+    
+  while (1)
+    {
+      char c;
+      switch(c = uart_getc())
+	{
+	case '\r':
+	  uart_putc('\n');
+	default:
+	  uart_putc(c);
+	}
+    }
+}