Syscalls work !

simulator/syscall.ml

@@ -8,11 +8,11 @@ let sys_input_int () = Scanf.scanf "%d " (fun x -> x)
 
 (** Prints the string starting at start_addr in RAM on stdout.
     The string must end with \000. *)
-let sys_print_str rom start_addr =
+let sys_print_str ram start_addr =
   let addr = ref start_addr in
   let current_char = ref 0 in
   let read_char () =
-    let c = Ram.int_of_bits @@ Ram.get_byte rom !addr in
+    let c = Ram.int_of_bits @@ Ram.get_byte ram !addr in
     current_char := c;
     incr addr in    
   while (read_char () ; !current_char <> 0) do
@@ -40,7 +40,7 @@ let syscall ram rom =
   match v0 with
     | 0  -> 0 (* a dummy syscall *)
     | 1  -> reset ram ; sys_print_int a0
-    | 4  -> reset ram ; sys_print_str rom a0
+    | 4  -> reset ram ; sys_print_str ram a0
     | 5  -> reset ram ; sys_input_int ()
     | 10 -> reset ram ; sys_exit ()
     | n  -> failwith @@

test/asm/syscall.s

 .text
 main:
-    addi $a0,$zero,21
-    addi $a0,$a0,21
+    addi $a0, $zero, 42
     addi $v0,$zero,1
     syscall
-    nop
-    addi $v0,$zero, 10
+
+    la $a0, hello
+    addi $v0,$zero, 4
+    syscall
+
+    addi $v0, $zero, 10
     syscall
 .data
+  hello: .asciiz "\nHello, world\n"