Add uvm32_useBreak(uvmst, bool) function to enable ebreak handling.

This is used in host-gdbstub to enable the functionality.

This allows the stackoverflow test to continue working. Meter test modified to handle new evt type.

hosts/host-gdbstub/host-gdbstub.c

@@ -58,6 +58,7 @@ int main(int argc, char *argv[]) {
   }
 
   uvm32_init(&vmst);
+  uvm32_useBreak(&vmst, true); // enable ebreak
 
   if (!uvm32_load(&vmst, rom, romlen)) {
     fprintf(stderr, "load failed!\n");

test/meter/test/tests.c

@@ -40,6 +40,8 @@ uint32_t metered_run(uint32_t num_instr) {
             case UVM32_EVT_END:
                 TEST_ASSERT_EQUAL(0, 1);    // trigger an assert, we didn't get to 100000 yet
             break;
+            case UVM32_EVT_BREAK:
+            break;
         }
     }
 

uvm32/uvm32.c

@@ -313,14 +313,15 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
                 setStatusErr(vmst, UVM32_ERR_MEM_WR);
                 setup_err_evt(vmst, evt);
             break;
-            case 3: // ebreak
+            default:
+                if (vmst->useBreak && ret == 3) {   // ebreak
                     vmst->_ioevt.typ = UVM32_EVT_BREAK;
                     setStatus(vmst, UVM32_STATUS_PAUSED);
-            break;
+                } else {
-            default:
                     // unhandled exception
                     setStatusErr(vmst, UVM32_ERR_INTERNAL_CORE);
                     setup_err_evt(vmst, evt);
+                }
             break;
         }
 
@@ -351,6 +352,10 @@ uint32_t uvm32_run(uvm32_state_t *vmst, uvm32_evt_t *evt, uint32_t instr_meter)
     }
 }
 
+void uvm32_useBreak(uvm32_state_t *vmst, bool enabled) {
+    vmst->useBreak = enabled;
+}
+
 bool uvm32_hasEnded(const uvm32_state_t *vmst) {
     return vmst->_status == UVM32_STATUS_ENDED;
 }

uvm32/uvm32.h

@@ -151,6 +151,7 @@ typedef struct {
     uint32_t _extramLen;                    /*! Length of external RAM */
     bool _extramDirty;                      /*! Flag to indicate VM code has modified extram since last run */
     uint32_t garbage;                       /*! Used for returning valid pointer when operations fail */
+    bool useBreak;                          /*! produce UVM32_EVT_BREAK */
 } uvm32_state_t;
 
 /*! Initialise a VM instance */
@@ -196,6 +197,8 @@ uvm32_slice_t uvm32_arg_getslice(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_ar
 /*! Read a syscall argument pointer as a slice of known length */
 uvm32_slice_t uvm32_arg_getslice_fixed(uvm32_state_t *vmst, uvm32_evt_t *evt, uvm32_arg_t arg, uint32_t len);
 
+/*! Allow ebreak in code, will generate UVM32_EVT_BREAK */
+void uvm32_useBreak(uvm32_state_t *vmst, bool enabled);
 
 /*! Setup a block of memory to act as external RAM, it will be available on in VM code at address `UVM32_EXTRAM_BASE`. The memory is not copied, so the caller must ensure it remains available until `uvm32_extram()` is called to setup a different region or the VM is ended. */
 void uvm32_extram(uvm32_state_t *vmst, uint8_t *extram, uint32_t len);