enter and exit supervisor call (+ fixed jumping to PL0 for the first time - setting sp was broken there)

1 files changed, 11 insertions, 4 deletions

diff --git a/PL0_test.c b/PL0_test.c
index 32addf8..2e008a2 100644
--- a/PL0_test.c
+++ b/PL0_test.c
@@ -1,18 +1,25 @@
 #include "uart.h"
 #include "psr.h"
 
+// entry point - must remain the only function in the file!
 void PL0_main(void)
 {
-  // if all went correct, Success! gets printed
+  // 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
+  uart_puts("calling supervisor\n\r");
+  
+  asm volatile("svc #0");
+
+  uart_puts("back from supervisor call\n\r");
+  
+  // if we're indeed in 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[0] = *(char*) ((uint32_t) 0x0);
   first_kernel_byte[1] = '\0';
-  
+
   uart_puts(first_kernel_byte);
     
   while (1)