src/emulator/shrooms_vb_core.rs

@@ -210,7 +210,7 @@ extern "C" fn on_execute(sim: *mut VB, address: u32, code: *const u16, length: c
         }
     }
 
-    let mut stopped = data.stop_reason.is_some();
+    let mut stopped = data.stop_reason.is_some() || data.monitor.event.is_some();
     if data.step_from.is_some_and(|s| s != address) {
         data.step_from = None;
         data.stop_reason = Some(StopReason::Stepped);
@@ -247,7 +247,13 @@ extern "C" fn on_exception(sim: *mut VB, cause: *mut u16) -> c_int {
     // There is no way for the userdata to be null or otherwise invalid.
     let data: &mut VBState = unsafe { &mut *vb_get_user_data(sim).cast() };
     data.monitor.event = data.monitor.queued_event.take();
-    data.monitor.queued_event = Some(SimEvent::Interrupt(unsafe { *cause }));
+    let cause = unsafe { *cause };
+    let pc = if cause == 0xff70 {
+        0xffffff60
+    } else {
+        (cause & 0xfff0) as u32 | 0xffff0000
+    };
+    data.monitor.queued_event = Some(SimEvent::Interrupt(cause, pc));
     unsafe { vb_set_exception_callback(sim, None) };
     unsafe { vb_set_fetch_callback(sim, Some(on_fetch)) };
     if data.monitor.event.is_some() { 1 } else { 0 }
@@ -319,7 +325,8 @@ extern "C" fn on_write(
 pub enum SimEvent {
     Call(u32),
     Return,
-    Interrupt(u16),
+    Halt,
+    Interrupt(u16, u32),
     Reti,
 }
 
@@ -327,6 +334,7 @@ struct EventMonitor {
     enabled: bool,
     event: Option<SimEvent>,
     queued_event: Option<SimEvent>,
+    just_halted: bool,
 }
 
 impl EventMonitor {
@@ -335,6 +343,7 @@ impl EventMonitor {
             enabled: false,
             event: None,
             queued_event: None,
+            just_halted: false,
         }
     }
 
@@ -343,7 +352,8 @@ impl EventMonitor {
         self.queued_event.is_some()
     }
 
-    fn do_detect_event(&self, sim: *mut VB, address: u32, code: &[u16]) -> Option<SimEvent> {
+    fn do_detect_event(&mut self, sim: *mut VB, address: u32, code: &[u16]) -> Option<SimEvent> {
+        const HALT_OPCODE: u16 = 0b011010;
         const JAL_OPCODE: u16 = 0b101011;
         const JMP_OPCODE: u16 = 0b000110;
         const RETI_OPCODE: u16 = 0b011001;
@@ -359,6 +369,18 @@ impl EventMonitor {
 
         let opcode = code[0] >> 10;
 
+        if opcode == HALT_OPCODE {
+            if !self.just_halted {
+                self.just_halted = true;
+                self.event = Some(SimEvent::Halt);
+            } else {
+                self.just_halted = false;
+            }
+            // Don't _return_ an event, we want to emit this right away.
+            // If the CPU is halting, no other callbacks will run for a long time.
+            return None;
+        }
+
         if opcode == JAL_OPCODE {
             let disp = format_iv_disp(code);
             if disp != 4 {

src/profiler.rs

@@ -96,10 +96,11 @@ struct ProfileSession {
 
 struct StackFrame {
     #[expect(dead_code)]
-    address: Option<u32>,
+    address: u32,
     cycles: u64,
 }
 
+const RESET_CODE: u16 = 0xfff0;
 impl ProfileSession {
     async fn new(file_path: PathBuf) -> Self {
         let symbol_manager = SymbolManager::with_config(Default::default());
@@ -109,22 +110,24 @@ impl ProfileSession {
             .expect("cannae load symbols");
         let mut call_stacks = HashMap::new();
         call_stacks.insert(
-            0,
+            RESET_CODE,
             vec![StackFrame {
-                address: None,
+                address: 0xfffffff0,
                 cycles: 0,
             }],
         );
         Self {
             symbol_map,
             call_stacks,
-            context_stack: vec![],
+            context_stack: vec![RESET_CODE],
         }
     }
 
     fn track_elapsed_cycles(&mut self, cycles: u32) {
-        let code = self.context_stack.last().copied().unwrap_or(0);
-        let Some(stack) = self.call_stacks.get_mut(&code) else {
+        let Some(code) = self.context_stack.last() else {
+            return; // program is halted, CPU is idle
+        };
+        let Some(stack) = self.call_stacks.get_mut(code) else {
             panic!("missing stack {code:04x}");
         };
         for frame in stack {
@@ -134,42 +137,63 @@ impl ProfileSession {
 
     fn track_event(&mut self, event: SimEvent) {
         match event {
-            SimEvent::Interrupt(code) => {
-                self.context_stack.push(code);
-                if self.call_stacks.insert(code, vec![]).is_some() {
-                    panic!("{code:04x} fired twice");
-                }
-            }
-            SimEvent::Reti => {
-                let Some(code) = self.context_stack.pop() else {
-                    panic!("reti when not in interrupt");
+            SimEvent::Call(address) => {
+                let Some(code) = self.context_stack.last() else {
+                    panic!("How did we call anything when we're halted?");
                 };
-                if self.call_stacks.remove(&code).is_none() {
-                    panic!("{code:04x} popped but never called")
-                }
-            }
-            SimEvent::Call(addr) => {
-                let code = self.context_stack.last().copied().unwrap_or(0);
-                let Some(stack) = self.call_stacks.get_mut(&code) else {
+                let Some(stack) = self.call_stacks.get_mut(code) else {
                     panic!("missing stack {code:04x}");
                 };
                 let name = self
                     .symbol_map
-                    .lookup_sync(wholesym::LookupAddress::Svma(addr as u64));
-                println!("depth {}: {:?}", stack.len(), name);
-                stack.push(StackFrame {
-                    address: Some(addr),
-                    cycles: 0,
-                });
+                    .lookup_sync(wholesym::LookupAddress::Svma(address as u64));
+                println!("depth {}: {:x?}", stack.len(), name);
+                stack.push(StackFrame { address, cycles: 0 });
             }
             SimEvent::Return => {
-                let code = self.context_stack.last().copied().unwrap_or(0);
-                let Some(stack) = self.call_stacks.get_mut(&code) else {
+                let Some(code) = self.context_stack.last() else {
+                    panic!("how did we return when we're halted?");
+                };
+                let Some(stack) = self.call_stacks.get_mut(code) else {
                     panic!("missing stack {code:04x}");
                 };
                 if stack.pop().is_none() {
                     panic!("returned from {code:04x} but stack was empty");
                 }
+                if stack.is_empty() {
+                    panic!("returned to oblivion");
+                }
+            }
+            SimEvent::Halt => {
+                let Some(RESET_CODE) = self.context_stack.pop() else {
+                    panic!("halted when not in an interrupt");
+                };
+            }
+            SimEvent::Interrupt(code, address) => {
+                // if the CPU was halted before, wake it up now
+                if self.context_stack.is_empty() {
+                    self.context_stack.push(RESET_CODE);
+                }
+
+                self.context_stack.push(code);
+                if self
+                    .call_stacks
+                    .insert(code, vec![StackFrame { address, cycles: 0 }])
+                    .is_some()
+                {
+                    panic!("{code:04x} fired twice");
+                }
+            }
+            SimEvent::Reti => {
+                let Some(code) = self.context_stack.pop() else {
+                    panic!("RETI when halted");
+                };
+                if code == RESET_CODE {
+                    panic!("RETI when not in interrupt");
+                }
+                if self.call_stacks.remove(&code).is_none() {
+                    panic!("{code:04x} popped but never called");
+                }
             }
         }
     }