Provide all exception handlers.

Otherwise unexpected roll-over onto the next handler will happen.

target/lm32/crt0.S

@@ -90,9 +90,10 @@
         .global	_start  
 _start: 
         .weak _debug_unit
-_debug_unit:	   
         .global _reset_handler
         .type 	_reset_handler, @function
+        .align  256
+_debug_unit:
 _reset_handler:
     xor r0, r0, r0
     wcsr    IE, r0
@@ -103,11 +104,46 @@ _reset_handler:
     calli   _crt0
     nop
         .size	_reset_handler, .-_reset_handler
-	
+
+.extern _breakpoint_handler
+        .global _breakpoint_handler
+        .type 	_breakpoint_handler, @function
+        .align  32
+_breakpoint_handler:
+    bret
+
+.extern _instruction_bus_error_handler
+        .global _instruction_bus_error_handler
+        .type   _instruction_bus_error_handler, @function
+        .align  32
+_instruction_bus_error_handler:
+    eret
+
+.extern _watchpoint_handler
+        .global _watchpoint_handler
+        .type   _watchpoint_handler, @function
+        .align  32
+_watchpoint_handler:
+    bret
+
+.extern _data_bus_error_handler
+        .global _data_bus_error_handler
+        .type   _data_bus_error_handler, @function
+        .align  32
+_data_bus_error_handler:
+    eret
+
+.extern _divide_by_zero_handler
+        .global _divide_by_zero_handler
+        .type   _divide_by_zero_handler, @function
+        .align  32
+_divide_by_zero_handler:
+    eret
+
 .extern _irq_entry
-.org 0xc0
         .global _interrupt_handler
         .type 	_interrupt_handler, @function
+        .align  32
 _interrupt_handler:
     sw      (sp+0), ra
     calli   _save_all
@@ -121,7 +157,14 @@ _interrupt_handler:
     nop
     nop
     nop
-
+
+.extern _system_call_handler
+        .global _system_call_handler
+        .type   _system_call_handler, @function
+        .align  32
+_system_call_handler:
+    eret
+
 .org 0x100
         .global _crt0
         .type 	_crt0, @function