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

2 files changed, 59 insertions, 2 deletions

diff --git a/src/kern/main.c b/src/kern/main.c
index e3995b1..df2f0bf 100644
--- a/src/kern/main.c
+++ b/src/kern/main.c
@@ -7,6 +7,7 @@
 #include "kern/mem.h"
 #include "kern/mpu/mpu_manager.h"
 #include "kern/panic.h"
+#include "kern/priv.h"
 
 void on_hard_fault()
 {
@@ -60,7 +61,7 @@ int main()
   memopts.sharable = 0;
   memopts.tex = 0;
   memopts.size = REGION_SIZE_256Kb;
-  memopts.perms = ACCESS_PERMS_BOTH_RO;
+  memopts.perms = ACCESS_PERMS_ONLY_PRIV_RO;
   memopts.subregion_disable = 0;
   memopts.executable = 1;
   memopts.enable = 1;
@@ -72,7 +73,7 @@ int main()
   memopts.cacheable = 1;
   memopts.sharable = 0;
   memopts.tex = 0;
-  memopts.size = REGION_SIZE_32Kb;
+  memopts.size = REGION_SIZE_64Kb;
   memopts.perms = ACCESS_PERMS_FULL;
   memopts.subregion_disable = 0;
   memopts.executable = 1;
@@ -93,6 +94,19 @@ int main()
 
   mpu_configure_region(2, &memopts);
 
+  memopts.region = (void*) 0x40000000 /* Peripheral base. */;
+  memopts.bufferable = 1;
+  memopts.cacheable = 0;
+  memopts.sharable = 1;
+  memopts.tex = 0;
+  memopts.size = REGION_SIZE_512Mb;
+  memopts.perms = ACCESS_PERMS_ONLY_PRIV;
+  memopts.subregion_disable = 0;
+  memopts.executable = 0;
+  memopts.enable = 1;
+
+  mpu_configure_region(3, &memopts);
+
   for (uint32_t i = 0; i < 8; ++ i) {
     MPU.rn_r = i;
     klogf("--- %d ---\n", i);
@@ -112,8 +126,27 @@ int main()
   // memopts.size = REGION_SIZE_16Kb;
   // memopts.perms = ACCESS_PERMS_NO_ACCESS;
 
+  klogf("CONTROL: %p\n", get_control_register());
+  klogf("CONTROL: %p\n", get_control_register());
   klogf("MPU not enabled\n");
+
+  volatile int x;
+  klogf("x location: %p\n", &x);
+
   mpu_set_enabled(1);
+
+  x = 5;
+  klogf("Still alive?\n");
+
+  klogf("Entering User Mode\n");
+  enter_user_mode();
+
+  asm volatile (
+      "svc #4\n"
+      );
+
+  klogf("Should Kernel Panic\n");
+
   for(;;);
   // klogf("MPU enabled\n");
 
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);
+}