src/emulator.rs

@@ -15,8 +15,8 @@ use anyhow::Result;
 use egui_toast::{Toast, ToastKind, ToastOptions};
 
 use crate::{audio::Audio, graphics::TextureSink};
-pub use shrooms_vb_core::VBKey;
 use shrooms_vb_core::{Sim, EXPECTED_FRAME_SIZE};
+pub use shrooms_vb_core::{VBKey, VBRegister};
 
 mod shrooms_vb_core;
 
@@ -390,6 +390,13 @@ impl Emulator {
                     }
                 }
             }
+            EmulatorCommand::ReadRegister(sim_id, register, done) => {
+                let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
+                    return;
+                };
+                let value = sim.read_register(register);
+                let _ = done.send(value);
+            }
             EmulatorCommand::SetAudioEnabled(p1, p2) => {
                 self.audio_on[SimId::Player1.to_index()].store(p1, Ordering::Release);
                 self.audio_on[SimId::Player2.to_index()].store(p2, Ordering::Release);
@@ -447,6 +454,7 @@ pub enum EmulatorCommand {
     StopSecondSim,
     Pause,
     Resume,
+    ReadRegister(SimId, VBRegister, oneshot::Sender<u32>),
     SetAudioEnabled(bool, bool),
     Link,
     Unlink,

src/emulator/shrooms_vb_core.rs

@@ -55,6 +55,13 @@ bitflags! {
     }
 }
 
+#[derive(Clone, Copy, Debug)]
+pub enum VBRegister {
+    Program(u32),
+    System(u32),
+    PC,
+}
+
 type OnFrame = extern "C" fn(sim: *mut VB) -> c_int;
 
 #[link(name = "vb")]
@@ -77,6 +84,10 @@ extern "C" {
         right_stride_x: c_int,
         right_stride_y: c_int,
     );
+    #[link_name = "vbGetProgramCounter"]
+    fn vb_get_program_counter(sim: *mut VB) -> u32;
+    #[link_name = "vbGetProgramRegister"]
+    fn vb_get_program_register(sim: *mut VB, index: c_uint) -> i32;
     #[link_name = "vbGetSamples"]
     fn vb_get_samples(
         sim: *mut VB,
@@ -84,6 +95,8 @@ extern "C" {
         capacity: *mut c_uint,
         position: *mut c_uint,
     ) -> *mut c_void;
+    #[link_name = "vbGetSystemRegister"]
+    fn vb_get_system_register(sim: *mut VB, index: c_uint) -> i32;
     #[link_name = "vbGetUserData"]
     fn vb_get_user_data(sim: *mut VB) -> *mut c_void;
     #[link_name = "vbInit"]
@@ -291,6 +304,16 @@ impl Sim {
     pub fn set_keys(&mut self, keys: VBKey) {
         unsafe { vb_set_keys(self.sim, keys.bits()) };
     }
+
+    pub fn read_register(&mut self, register: VBRegister) -> u32 {
+        match register {
+            VBRegister::Program(index) => unsafe {
+                vb_get_program_register(self.sim, index) as u32
+            },
+            VBRegister::System(index) => unsafe { vb_get_system_register(self.sim, index) as u32 },
+            VBRegister::PC => unsafe { vb_get_program_counter(self.sim) },
+        }
+    }
 }
 
 impl Drop for Sim {

src/gdbserver.rs

@@ -227,12 +227,23 @@ impl GdbConnection {
                 self.client.send_command(EmulatorCommand::Resume);
                 // Don't send a response until we hit a breakpoint or get interrupted
             } else if req.match_str("p") {
-                let Some(register) = req.match_hex::<u32>() else {
+                let mut read_register = || {
+                    let register_index = req.match_hex::<usize>()?;
+                    let register = REGISTERS.get(register_index)?.to_vb_register();
+                    let (tx, rx) = ::oneshot::channel();
+                    self.client.send_command(EmulatorCommand::ReadRegister(
+                        self.sim_id,
+                        register,
+                        tx,
+                    ));
+                    rx.recv().ok()
+                };
+                let Some(value) = read_register() else {
                     let res = self.response();
                     self.send(res).await?;
                     continue;
                 };
-                let res = self.response().write_hex(register);
+                let res = self.response().write_hex(value);
                 self.send(res).await?;
             } else if req.match_str("m") {
                 let mut read_params = || {

src/gdbserver/registers.rs

@@ -1,5 +1,7 @@
+use crate::emulator::VBRegister;
+
 pub struct RegisterInfo {
-    index: usize,
+    dwarf: u32,
     name: &'static str,
     set: &'static str,
     alt_name: Option<&'static str>,
@@ -14,48 +16,59 @@ impl RegisterInfo {
         }
         string.push_str(&format!(
             ";bitsize:32;offset:{};encoding:uint;format:hex;set:{};dwarf:{}",
-            self.index * 4,
+            self.dwarf * 4,
             self.set,
-            self.index
+            self.dwarf
         ));
         if let Some(generic) = self.generic {
             string.push_str(&format!(";generic:{}", generic));
         }
         string
     }
+
+    pub fn to_vb_register(&self) -> VBRegister {
+        match self.dwarf {
+            0..32 => VBRegister::Program(self.dwarf),
+            32..40 => VBRegister::System(self.dwarf - 32),
+            40..42 => VBRegister::System(self.dwarf - 16),
+            42..45 => VBRegister::System(self.dwarf - 13),
+            45 => VBRegister::PC,
+            other => panic!("unexpected DWARF register {other}"),
+        }
+    }
 }
 
 macro_rules! register {
-    ($set:expr, $index:expr, $name:expr) => {
+    ($set:expr, $dwarf:expr, $name:expr) => {
         RegisterInfo {
-            index: $index,
+            dwarf: $dwarf,
             name: $name,
             set: $set,
             alt_name: None,
             generic: None,
         }
     };
-    ($set:expr, $index:expr, $name:expr, alt: $alt:expr) => {
+    ($set:expr, $dwarf:expr, $name:expr, alt: $alt:expr) => {
         RegisterInfo {
-            index: $index,
+            dwarf: $dwarf,
             name: $name,
             set: $set,
             alt_name: Some($alt),
             generic: None,
         }
     };
-    ($set:expr, $index:expr, $name:expr, generic: $generic:expr) => {
+    ($set:expr, $dwarf:expr, $name:expr, generic: $generic:expr) => {
         RegisterInfo {
-            index: $index,
+            dwarf: $dwarf,
             name: $name,
             set: $set,
             alt_name: None,
             generic: Some($generic),
         }
     };
-    ($set:expr, $index:expr, $name:expr, alt: $alt:expr, generic: $generic:expr) => {
+    ($set:expr, $dwarf:expr, $name:expr, alt: $alt:expr, generic: $generic:expr) => {
         RegisterInfo {
-            index: $index,
+            dwarf: $dwarf,
             name: $name,
             set: $set,
             alt_name: Some($alt),