Ignore the pushed value in interrupts and exceptions

Also handle more types of exceptions.
*** First commit compatible with the C rewrite!! ***

audio.asm

@@ -158,6 +158,7 @@ stop_audio:
     ret
 
 refill_buffer_0:
+    add rsp, 4
     push r0
     push r1
     push r31
@@ -181,6 +182,7 @@ refill_buffer_0_loop:
     reti
 
 refill_buffer_1:
+    add rsp, 4
     push r0
     push r1
     push r31
@@ -204,6 +206,7 @@ refill_buffer_1_loop:
     reti
 
 refill_buffer_2:
+    add rsp, 4
     push r0
     push r1
     push r31
@@ -227,6 +230,7 @@ refill_buffer_2_loop:
     reti
 
 refill_buffer_3:
+    add rsp, 4
     push r0
     push r1
     push r31

exception.asm

@@ -1,5 +1,19 @@
 ; exception handling routines
 
+; called if a divide by zero occurs
+; does not return, calls panic
+system_div_zero_handler:
+    mov r0, system_div_zero_str
+    jmp panic
+system_div_zero_str: data.str "Divide by zero" data.8 10 data.8 0
+
+; called if an invalid opcode is executed
+; does not return, calls panic
+system_invalid_op_handler:
+    mov r0, system_invalid_op_str
+    jmp panic
+system_invalid_op_str: data.str "Invalid opcode" data.8 10 data.8 0
+
 ; called if a page fault occurs
 ; does not return, calls panic
 system_page_fault_handler:
@@ -7,3 +21,15 @@ system_page_fault_handler:
     pop r1
     jmp panic
 system_page_fault_str: data.str "Page fault at virtual address r1" data.8 10 data.8 0
+
+; called upon execution of a `brk` instruction
+system_breakpoint_handler:
+    add rsp, 4
+    push r0
+
+    mov r0, system_breakpoint_str
+    call debug_print
+
+    pop r0
+    reti
+system_breakpoint_str: data.str "Breakpoint reached!" data.8 10 data.8 0

main.asm

@@ -4,7 +4,7 @@
 
 const FOX32ROM_VERSION_MAJOR: 0
 const FOX32ROM_VERSION_MINOR: 5
-const FOX32ROM_VERSION_PATCH: 0
+const FOX32ROM_VERSION_PATCH: 2
 
 const SYSTEM_STACK:     0x01FFF800
 const BACKGROUND_COLOR: 0xFF674764
@@ -39,12 +39,21 @@ entry_seed_done:
     ; set the interrupt vector for interrupt 0xFF - vsync
     mov [0x000003FC], system_vsync_handler
 
+    ; set the exception vector for exception 0x00 - divide by zero
+    mov [0x00000400], system_div_zero_handler
+
+    ; set the exception vector for exception 0x01 - invalid opcode
+    mov [0x00000404], system_invalid_op_handler
+
     ; set the exception vector for exception 0x02 - page fault read
     mov [0x00000408], system_page_fault_handler
 
     ; set the exception vector for exception 0x03 - page fault write
     mov [0x0000040C], system_page_fault_handler
 
+    ; set the exception vector for exception 0x04 - breakpoint
+    mov [0x0000040C], system_breakpoint_handler
+
     ; enable interrupts
     ise
 

monitor/vsync.asm

@@ -1,6 +1,7 @@
 ; debug monitor vsync routine
 
 monitor_vsync_handler:
+    add rsp, 4
     push r0
     push r1
     push r2

panic.asm

@@ -6,7 +6,6 @@
 ; outputs:
 ; none, does not return
 panic:
-    brk
     cmp r0, 0
     ifz mov r0, panic_string
     call debug_print

vsync.asm

@@ -1,6 +1,7 @@
 ; vsync interrupt routine
 
 system_vsync_handler:
+    add rsp, 4
     push r0
     push r1
     push r2