Add priv.h/c to allow switching to user mode. Change some things with the MPU in main() to actually work.

1 files changed, 24 insertions, 0 deletions

diff --git a/src/kern/priv.c b/src/kern/priv.c
new file mode 100644
index 0000000..9d64005
--- /dev/null
+++ b/src/kern/priv.c
@@ -0,0 +1,24 @@
+#include "kern/priv.h"
+
+void set_control_register(uint32_t reg)
+{
+  asm volatile("msr control, %0" : "=r"(reg) :);
+}
+
+uint32_t get_control_register()
+{
+  uint32_t control;
+  asm volatile("mrs %0, control" : "=r"(control) :);
+  return control;
+}
+
+void enter_user_mode()
+{
+  asm volatile (
+      "mov r0, #1\n\t"
+      "msr control, r0\n\t"
+    );
+
+  // uint32_t creg = get_control_register();
+  // set_control_register(creg | 1);
+}