chore: Release lemur version 0.3.2

Reviewed-on: #3

Cargo.lock

@@ -1755,9 +1755,15 @@ version = "3.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2db585e1d738fc771bf08a151420d3ed193d9d895a36df7f6f8a9456b911ddc"
 
+[[package]]
+name = "lazy_static"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
+
 [[package]]
 name = "lemur"
-version = "0.2.7"
+version = "0.3.2"
 dependencies = [
  "anyhow",
  "atoi",
@@ -1788,6 +1794,8 @@ dependencies = [
  "serde_json",
  "thread-priority",
  "tokio",
+ "tracing",
+ "tracing-subscriber",
  "wgpu",
  "windows 0.58.0",
  "winit",
@@ -1883,6 +1891,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "matchers"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8263075bb86c5a1b1427b5ae862e8889656f126e9f77c484496e8b47cf5c5558"
+dependencies = [
+ "regex-automata 0.1.10",
+]
+
 [[package]]
 name = "memchr"
 version = "2.7.4"
@@ -2068,6 +2085,16 @@ dependencies = [
  "minimal-lexical",
 ]
 
+[[package]]
+name = "nu-ansi-term"
+version = "0.46.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77a8165726e8236064dbb45459242600304b42a5ea24ee2948e18e023bf7ba84"
+dependencies = [
+ "overload",
+ "winapi",
+]
+
 [[package]]
 name = "num-complex"
 version = "0.4.6"
@@ -2408,6 +2435,12 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "overload"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b15813163c1d831bf4a13c3610c05c0d03b39feb07f7e09fa234dac9b15aaf39"
+
 [[package]]
 name = "owned_ttf_parser"
 version = "0.25.0"
@@ -2701,8 +2734,17 @@ checksum = "b544ef1b4eac5dc2db33ea63606ae9ffcfac26c1416a2806ae0bf5f56b201191"
 dependencies = [
  "aho-corasick",
  "memchr",
- "regex-automata",
+ "regex-automata 0.4.9",
- "regex-syntax",
+ "regex-syntax 0.8.5",
+]
+
+[[package]]
+name = "regex-automata"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c230d73fb8d8c1b9c0b3135c5142a8acee3a0558fb8db5cf1cb65f8d7862132"
+dependencies = [
+ "regex-syntax 0.6.29",
 ]
 
 [[package]]
@@ -2713,9 +2755,15 @@ checksum = "809e8dc61f6de73b46c85f4c96486310fe304c434cfa43669d7b40f711150908"
 dependencies = [
  "aho-corasick",
  "memchr",
- "regex-syntax",
+ "regex-syntax 0.8.5",
 ]
 
+[[package]]
+name = "regex-syntax"
+version = "0.6.29"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f162c6dd7b008981e4d40210aca20b4bd0f9b60ca9271061b07f78537722f2e1"
+
 [[package]]
 name = "regex-syntax"
 version = "0.8.5"
@@ -2906,6 +2954,15 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "sharded-slab"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f40ca3c46823713e0d4209592e8d6e826aa57e928f09752619fc696c499637f6"
+dependencies = [
+ "lazy_static",
+]
+
 [[package]]
 name = "shlex"
 version = "1.3.0"
@@ -3123,6 +3180,16 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "thread_local"
+version = "1.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b9ef9bad013ada3808854ceac7b46812a6465ba368859a37e2100283d2d719c"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+]
+
 [[package]]
 name = "tiny-skia"
 version = "0.11.4"
@@ -3248,6 +3315,36 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e672c95779cf947c5311f83787af4fa8fffd12fb27e4993211a84bdfd9610f9c"
 dependencies = [
  "once_cell",
+ "valuable",
+]
+
+[[package]]
+name = "tracing-log"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee855f1f400bd0e5c02d150ae5de3840039a3f54b025156404e34c23c03f47c3"
+dependencies = [
+ "log",
+ "once_cell",
+ "tracing-core",
+]
+
+[[package]]
+name = "tracing-subscriber"
+version = "0.3.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e8189decb5ac0fa7bc8b96b7cb9b2701d60d48805aca84a238004d665fcc4008"
+dependencies = [
+ "matchers",
+ "nu-ansi-term",
+ "once_cell",
+ "regex",
+ "sharded-slab",
+ "smallvec",
+ "thread_local",
+ "tracing",
+ "tracing-core",
+ "tracing-log",
 ]
 
 [[package]]
@@ -3358,6 +3455,12 @@ version = "1.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f8c5f0a0af699448548ad1a2fbf920fb4bee257eae39953ba95cb84891a0446a"
 
+[[package]]
+name = "valuable"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "830b7e5d4d90034032940e4ace0d9a9a057e7a45cd94e6c007832e39edb82f6d"
+
 [[package]]
 name = "vec_map"
 version = "0.8.2"

Cargo.toml

@@ -4,7 +4,7 @@ description = "An emulator for the Virtual Boy."
 repository = "https://git.virtual-boy.com/PVB/lemur"
 publish = false
 license = "MIT"
-version = "0.2.7"
+version = "0.3.2"
 edition = "2021"
 
 [dependencies]
@@ -36,6 +36,8 @@ serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 thread-priority = "1"
 tokio = { version = "1", features = ["io-util", "macros", "net", "rt", "sync"] }
+tracing = { version = "0.1", features = ["release_max_level_info"] }
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 wgpu = "23"
 winit = { version = "0.30", features = ["serde"] }
 

README.md

@@ -5,7 +5,7 @@ A Virtual Boy emulator built around the shrooms-vb core. Written in Rust, using
 ## Setup
 
 Install the following dependencies:
- - `cargo`
+ - `cargo` (via [rustup](https://rustup.rs/), the version from your package manager is too old)
 
 Run
 ```sh

build.Dockerfile

@@ -23,6 +23,10 @@ ENV PATH="/osxcross/bin:$PATH" \
     CXX_x86_64-apple-darwin="o64-clang++" \
     CC_aarch64-apple-darwin="oa64-clang" \
     CXX_aarch64-apple-darwin="o6a4-clang++" \
+    SHROOMS_CFLAGS_x86_64-unknown-linux-gnu="-flto" \
+    CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUSTFLAGS="-Clinker-plugin-lto -Clinker=clang -Clink-arg=-fuse-ld=lld" \
+    SHROOMS_CFLAGS_x86_64-pc-windows-msvc="-flto" \
+    CARGO_TARGET_X86_64_PC_WINDOWS_MSVC_RUSTFLAGS="-Lnative=/xwin/crt/lib/x86_64 -Lnative=/xwin/sdk/lib/um/x86_64 -Lnative=/xwin/sdk/lib/ucrt/x86_64 -Clinker-plugin-lto -Clink-arg=-fuse-ld=lld" \
     CARGO_TARGET_X86_64_PC_WINDOWS_MSVC_LINKER="lld-link-19" \
     CARGO_TARGET_X86_64_APPLE_DARWIN_LINKER="o64-clang" \
     CARGO_TARGET_X86_64_APPLE_DARWIN_AR="llvm-ar-19" \
@@ -30,5 +34,4 @@ ENV PATH="/osxcross/bin:$PATH" \
     CARGO_TARGET_AARCH64_APPLE_DARWIN_AR="llvm-ar-19" \
     CROSS_COMPILE="setting-this-to-silence-a-warning-" \
     RC_PATH="llvm-rc-19" \
-    RUSTFLAGS="-Lnative=/xwin/crt/lib/x86_64 -Lnative=/xwin/sdk/lib/um/x86_64 -Lnative=/xwin/sdk/lib/ucrt/x86_64" \
     MACOSX_DEPLOYMENT_TARGET="14.5"

build.rs

@@ -8,13 +8,25 @@ fn main() -> Result<(), Box<dyn Error>> {
     }
 
     println!("cargo::rerun-if-changed=shrooms-vb-core");
-    cc::Build::new()
+
+    let mut builder = cc::Build::new();
+    let _ = builder.try_flags_from_environment("SHROOMS_CFLAGS");
+    let opt_level = if builder.get_compiler().is_like_msvc() {
+        2
+    } else {
+        3
+    };
+    builder
         .include(Path::new("shrooms-vb-core/core"))
-        .opt_level(2)
+        .opt_level(opt_level)
         .flag_if_supported("-fno-strict-aliasing")
         .define("VB_LITTLE_ENDIAN", None)
         .define("VB_SIGNED_PROPAGATE", None)
         .define("VB_DIV_GENERIC", None)
+        .define("VB_DIRECT_EXECUTE", "on_execute")
+        .define("VB_DIRECT_FRAME", "on_frame")
+        .define("VB_DIRECT_READ", "on_read")
+        .define("VB_DIRECT_WRITE", "on_write")
         .file(Path::new("shrooms-vb-core/core/vb.c"))
         .compile("vb");
 

src/app.rs

@@ -6,6 +6,7 @@ use egui::{
     ViewportCommand, ViewportId, ViewportInfo,
 };
 use gilrs::{EventType, Gilrs};
+use tracing::{error, warn};
 use winit::{
     application::ApplicationHandler,
     event::WindowEvent,
@@ -34,6 +35,7 @@ fn load_icon() -> anyhow::Result<IconData> {
 
 pub struct Application {
     icon: Option<Arc<IconData>>,
+    wgpu: WgpuState,
     client: EmulatorClient,
     proxy: EventLoopProxy<UserEvent>,
     mappings: MappingProvider,
@@ -50,6 +52,7 @@ impl Application {
         proxy: EventLoopProxy<UserEvent>,
         debug_port: Option<u16>,
     ) -> Self {
+        let wgpu = WgpuState::new();
         let icon = load_icon().ok().map(Arc::new);
         let persistence = Persistence::new();
         let mappings = MappingProvider::new(persistence.clone());
@@ -61,6 +64,7 @@ impl Application {
         }
         Self {
             icon,
+            wgpu,
             client,
             proxy,
             mappings,
@@ -79,7 +83,7 @@ impl Application {
         }
         self.viewports.insert(
             viewport_id,
-            Viewport::new(event_loop, self.icon.clone(), window),
+            Viewport::new(event_loop, &self.wgpu, self.icon.clone(), window),
         );
     }
 }
@@ -230,13 +234,65 @@ impl ApplicationHandler<UserEvent> for Application {
     fn exiting(&mut self, _event_loop: &ActiveEventLoop) {
         let (sender, receiver) = oneshot::channel();
         if self.client.send_command(EmulatorCommand::Exit(sender)) {
-            if let Err(err) = receiver.recv_timeout(Duration::from_secs(5)) {
+            if let Err(error) = receiver.recv_timeout(Duration::from_secs(5)) {
-                eprintln!("could not gracefully exit: {}", err);
+                error!(%error, "could not gracefully exit.");
             }
         }
     }
 }
 
+struct WgpuState {
+    instance: Arc<wgpu::Instance>,
+    adapter: Arc<wgpu::Adapter>,
+    device: Arc<wgpu::Device>,
+    queue: Arc<wgpu::Queue>,
+}
+
+impl WgpuState {
+    fn new() -> Self {
+        let egui_wgpu::WgpuConfiguration {
+            wgpu_setup:
+                egui_wgpu::WgpuSetup::CreateNew {
+                    #[allow(unused)]
+                    supported_backends,
+                    device_descriptor,
+                    ..
+                },
+            ..
+        } = egui_wgpu::WgpuConfiguration::default()
+        else {
+            panic!("required fields not found")
+        };
+        #[cfg(windows)]
+        let supported_backends = wgpu::util::backend_bits_from_env()
+            .unwrap_or((wgpu::Backends::PRIMARY | wgpu::Backends::GL) - wgpu::Backends::VULKAN);
+        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
+            backends: supported_backends,
+            ..wgpu::InstanceDescriptor::default()
+        });
+
+        let adapter = pollster::block_on(instance.request_adapter(&wgpu::RequestAdapterOptions {
+            power_preference: wgpu::PowerPreference::HighPerformance,
+            compatible_surface: None,
+            force_fallback_adapter: false,
+        }))
+        .expect("could not create adapter");
+
+        let trace_path = std::env::var("WGPU_TRACE");
+        let (device, queue) = pollster::block_on(adapter.request_device(
+            &(*device_descriptor)(&adapter),
+            trace_path.ok().as_ref().map(std::path::Path::new),
+        ))
+        .expect("could not request device");
+        Self {
+            instance: Arc::new(instance),
+            adapter: Arc::new(adapter),
+            device: Arc::new(device),
+            queue: Arc::new(queue),
+        }
+    }
+}
+
 struct Viewport {
     painter: egui_wgpu::winit::Painter,
     ctx: Context,
@@ -250,6 +306,7 @@ struct Viewport {
 impl Viewport {
     pub fn new(
         event_loop: &ActiveEventLoop,
+        wgpu: &WgpuState,
         icon: Option<Arc<IconData>>,
         mut app: Box<dyn AppWindow>,
     ) -> Self {
@@ -273,20 +330,16 @@ impl Viewport {
         });
         egui_extras::install_image_loaders(&ctx);
 
-        #[allow(unused_mut)]
+        let wgpu_config = egui_wgpu::WgpuConfiguration {
-        let mut wgpu_config = egui_wgpu::WgpuConfiguration {
             present_mode: wgpu::PresentMode::AutoNoVsync,
+            wgpu_setup: egui_wgpu::WgpuSetup::Existing {
+                instance: wgpu.instance.clone(),
+                adapter: wgpu.adapter.clone(),
+                device: wgpu.device.clone(),
+                queue: wgpu.queue.clone(),
+            },
             ..egui_wgpu::WgpuConfiguration::default()
         };
-        #[cfg(windows)]
-        {
-            if let egui_wgpu::WgpuSetup::CreateNew {
-                supported_backends, ..
-            } = &mut wgpu_config.wgpu_setup
-            {
-                *supported_backends -= wgpu::Backends::VULKAN;
-            }
-        }
 
         let mut painter =
             egui_wgpu::winit::Painter::new(ctx.clone(), wgpu_config, 1, None, false, true);
@@ -434,9 +487,12 @@ fn create_window_and_state(
 }
 
 fn process_gamepad_input(mappings: MappingProvider, proxy: EventLoopProxy<UserEvent>) {
-    let Ok(mut gilrs) = Gilrs::new() else {
+    let mut gilrs = match Gilrs::new() {
-        eprintln!("could not connect gamepad listener");
+        Ok(gilrs) => gilrs,
-        return;
+        Err(error) => {
+            warn!(%error, "could not connect gamepad listener");
+            return;
+        }
     };
     while let Some(event) = gilrs.next_event_blocking(None) {
         if event.event == EventType::Connected {

src/audio.rs

@@ -4,6 +4,7 @@ use anyhow::{bail, Result};
 use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
 use itertools::Itertools;
 use rubato::{FftFixedInOut, Resampler};
+use tracing::error;
 
 pub struct Audio {
     #[allow(unused)]
@@ -54,7 +55,7 @@ impl Audio {
                 }
                 chunk.commit_all();
             },
-            move |err| eprintln!("stream error: {err}"),
+            move |error| error!(%error, "stream error"),
             None,
         )?;
         stream.play()?;

src/emulator.rs

@@ -15,11 +15,13 @@ use anyhow::Result;
 use atomic::Atomic;
 use bytemuck::NoUninit;
 use egui_toast::{Toast, ToastKind, ToastOptions};
+use tracing::{error, warn};
 
 use crate::{audio::Audio, graphics::TextureSink};
 use shrooms_vb_core::{Sim, StopReason, EXPECTED_FRAME_SIZE};
-pub use shrooms_vb_core::{VBKey, VBRegister};
+pub use shrooms_vb_core::{VBKey, VBRegister, VBWatchpointType};
 
+mod address_set;
 mod shrooms_vb_core;
 
 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
@@ -303,9 +305,13 @@ impl Emulator {
     }
 
     fn start_debugging(&mut self, sim_id: SimId, sender: DebugSender) {
+        if self.sim_state[sim_id.to_index()].load(Ordering::Acquire) != SimState::Ready {
+            // Can't debug unless a game is connected
+            return;
+        }
         let debug = DebugInfo {
             sender,
-            stop_reason: Some(DebugStopReason::Trapped),
+            stop_reason: Some(DebugStopReason::Paused),
         };
         self.debuggers.insert(sim_id, debug);
         self.state
@@ -328,7 +334,7 @@ impl Emulator {
     }
 
     fn debug_interrupt(&mut self, sim_id: SimId) {
-        self.debug_stop(sim_id, DebugStopReason::Trapped);
+        self.debug_stop(sim_id, DebugStopReason::Paused);
     }
 
     fn debug_stop(&mut self, sim_id: SimId, reason: DebugStopReason) {
@@ -421,6 +427,9 @@ impl Emulator {
                 if let Some(reason) = sim.stop_reason() {
                     let stop_reason = match reason {
                         StopReason::Stepped => DebugStopReason::Trace,
+                        StopReason::Watchpoint(watch, address) => {
+                            DebugStopReason::Watchpoint(watch, address)
+                        }
                         StopReason::Breakpoint => DebugStopReason::Breakpoint,
                     };
                     self.debug_stop(sim_id, stop_reason);
@@ -528,6 +537,12 @@ impl Emulator {
                 let value = sim.read_register(register);
                 let _ = done.send(value);
             }
+            EmulatorCommand::WriteRegister(sim_id, register, value) => {
+                let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
+                    return;
+                };
+                sim.write_register(register, value);
+            }
             EmulatorCommand::ReadMemory(sim_id, start, length, mut buffer, done) => {
                 let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
                     return;
@@ -535,6 +550,13 @@ impl Emulator {
                 sim.read_memory(start, length, &mut buffer);
                 let _ = done.send(buffer);
             }
+            EmulatorCommand::WriteMemory(sim_id, start, buffer, done) => {
+                let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
+                    return;
+                };
+                sim.write_memory(start, &buffer);
+                let _ = done.send(buffer);
+            }
             EmulatorCommand::AddBreakpoint(sim_id, address) => {
                 let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
                     return;
@@ -547,6 +569,18 @@ impl Emulator {
                 };
                 sim.remove_breakpoint(address);
             }
+            EmulatorCommand::AddWatchpoint(sim_id, address, length, watch) => {
+                let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
+                    return;
+                };
+                sim.add_watchpoint(address, length, watch);
+            }
+            EmulatorCommand::RemoveWatchpoint(sim_id, address, length, watch) => {
+                let Some(sim) = self.sims.get_mut(sim_id.to_index()) else {
+                    return;
+                };
+                sim.remove_watchpoint(address, length, watch);
+            }
             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);
@@ -592,7 +626,7 @@ impl Emulator {
                 return;
             }
         }
-        eprintln!("{}", message);
+        error!("{}", message);
     }
 }
 
@@ -610,9 +644,13 @@ pub enum EmulatorCommand {
     DebugContinue(SimId),
     DebugStep(SimId),
     ReadRegister(SimId, VBRegister, oneshot::Sender<u32>),
+    WriteRegister(SimId, VBRegister, u32),
     ReadMemory(SimId, u32, usize, Vec<u8>, oneshot::Sender<Vec<u8>>),
+    WriteMemory(SimId, u32, Vec<u8>, oneshot::Sender<Vec<u8>>),
     AddBreakpoint(SimId, u32),
     RemoveBreakpoint(SimId, u32),
+    AddWatchpoint(SimId, u32, usize, VBWatchpointType),
+    RemoveWatchpoint(SimId, u32, usize, VBWatchpointType),
     SetAudioEnabled(bool, bool),
     Link,
     Unlink,
@@ -645,8 +683,10 @@ pub enum DebugStopReason {
     Trace,
     // We hit a breakpoint
     Breakpoint,
+    // We hit a watchpoint
+    Watchpoint(VBWatchpointType, u32),
     // The debugger told us to pause
-    Trapped,
+    Paused,
 }
 
 struct DebugInfo {
@@ -684,7 +724,7 @@ impl EmulatorClient {
         match self.queue.send(command) {
             Ok(()) => true,
             Err(err) => {
-                eprintln!(
+                warn!(
                     "could not send command {:?} as emulator is shut down",
                     err.0
                 );

src/emulator/address_set.rs

@@ -0,0 +1,270 @@
+use std::{
+    collections::{BTreeMap, BTreeSet},
+    ops::Bound,
+};
+
+#[derive(Debug, Default)]
+pub struct AddressSet {
+    ranges: BTreeSet<(u32, usize)>,
+    bounds: BTreeMap<u32, usize>,
+}
+
+impl AddressSet {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn add(&mut self, address: u32, length: usize) {
+        if length == 0 || !self.ranges.insert((address, length)) {
+            return;
+        }
+        let end = (address as usize)
+            .checked_add(length)
+            .and_then(|e| u32::try_from(e).ok());
+
+        if let Some(end) = end {
+            let val_before = self.bounds.range(..=end).next_back().map_or(0, |(_, &v)| v);
+            self.bounds.insert(end, val_before);
+        }
+
+        let val_before = self
+            .bounds
+            .range(..address)
+            .next_back()
+            .map_or(0, |(_, &v)| v);
+        if let Some(&val_at) = self.bounds.get(&address) {
+            if val_before == val_at + 1 {
+                self.bounds.remove(&address);
+            }
+        } else {
+            self.bounds.insert(address, val_before);
+        }
+
+        let start_bound = Bound::Included(address);
+        let end_bound = match end {
+            Some(e) => Bound::Excluded(e),
+            None => Bound::Unbounded,
+        };
+
+        for (_, val) in self.bounds.range_mut((start_bound, end_bound)) {
+            *val += 1;
+        }
+    }
+
+    pub fn remove(&mut self, address: u32, length: usize) {
+        if !self.ranges.remove(&(address, length)) {
+            return;
+        }
+        let end = (address as usize)
+            .checked_add(length)
+            .and_then(|e| u32::try_from(e).ok());
+
+        if let Some(end) = end {
+            let val_before = self.bounds.range(..end).next_back().map_or(0, |(_, &v)| v);
+            if let Some(&val_at) = self.bounds.get(&end) {
+                if val_at + 1 == val_before {
+                    self.bounds.remove(&end);
+                }
+            } else {
+                self.bounds.insert(end, val_before);
+            }
+        }
+
+        let val_before = self
+            .bounds
+            .range(..address)
+            .next_back()
+            .map_or(0, |(_, &v)| v);
+        if let Some(&val_at) = self.bounds.get(&address) {
+            if val_before + 1 == val_at {
+                self.bounds.remove(&address);
+            }
+        } else {
+            self.bounds.insert(address, val_before);
+        }
+
+        let start_bound = Bound::Included(address);
+        let end_bound = match end {
+            Some(e) => Bound::Excluded(e),
+            None => Bound::Unbounded,
+        };
+
+        for (_, val) in self.bounds.range_mut((start_bound, end_bound)) {
+            *val -= 1;
+        }
+    }
+
+    pub fn clear(&mut self) {
+        self.ranges.clear();
+        self.bounds.clear();
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.bounds.is_empty()
+    }
+
+    pub fn contains(&self, address: u32) -> bool {
+        self.bounds
+            .range(..=address)
+            .next_back()
+            .is_some_and(|(_, &val)| val > 0)
+    }
+
+    pub fn start_of_range_containing(&self, address: u32) -> Option<u32> {
+        if !self.contains(address) {
+            return None;
+        }
+        self.ranges
+            .range(..=(address, usize::MAX))
+            .rev()
+            .find_map(|&(start, length)| {
+                let contains = start <= address
+                    && (start as usize)
+                        .checked_add(length)
+                        .is_none_or(|end| end > address as usize);
+                contains.then_some(start)
+            })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::AddressSet;
+
+    #[test]
+    fn should_not_include_addresses_when_empty() {
+        let set = AddressSet::new();
+        assert!(set.is_empty());
+        assert!(!set.contains(0x13374200));
+        assert_eq!(set.start_of_range_containing(0x13374200), None);
+    }
+
+    #[test]
+    fn should_include_addresses_when_full() {
+        let mut set = AddressSet::new();
+        set.add(0x00000000, 0x100000000);
+        assert!(set.contains(0x13374200));
+        assert_eq!(set.start_of_range_containing(0x13374200), Some(0x00000000));
+    }
+
+    #[test]
+    fn should_ignore_empty_address_ranges() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 0);
+        assert!(set.is_empty());
+        assert!(!set.contains(0x13374200));
+    }
+
+    #[test]
+    fn should_add_addresses_idempotently() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 1);
+        set.add(0x13374200, 1);
+        set.remove(0x13374200, 1);
+        assert!(set.is_empty());
+        assert!(!set.contains(0x13374200));
+    }
+
+    #[test]
+    fn should_remove_addresses_idempotently() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 1);
+        set.remove(0x13374200, 1);
+        set.remove(0x13374200, 1);
+        assert!(set.is_empty());
+        assert!(!set.contains(0x13374200));
+    }
+
+    #[test]
+    fn should_report_address_in_range() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 4);
+        assert!(!set.contains(0x133741ff));
+        for address in 0x13374200..0x13374204 {
+            assert!(set.contains(address));
+        }
+        assert!(!set.contains(0x13374204));
+    }
+
+    #[test]
+    fn should_allow_overlapping_addresses() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 4);
+        set.add(0x13374201, 1);
+        set.add(0x13374202, 2);
+
+        assert!(!set.contains(0x133741ff));
+        for address in 0x13374200..0x13374204 {
+            assert!(set.contains(address));
+        }
+        assert!(!set.contains(0x13374204));
+
+        set.remove(0x13374200, 4);
+        assert!(!set.contains(0x13374200));
+        for address in 0x13374201..0x13374204 {
+            assert!(set.contains(address));
+        }
+        assert!(!set.contains(0x13374204));
+    }
+
+    #[test]
+    fn should_allow_removing_overlapped_address_ranges() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 8);
+        set.add(0x13374204, 8);
+        set.remove(0x13374204, 8);
+
+        for address in 0x13374200..0x13374208 {
+            assert!(set.contains(address));
+        }
+        for address in 0x13374208..0x1337420c {
+            assert!(!set.contains(address));
+        }
+    }
+
+    #[test]
+    fn should_merge_adjacent_ranges() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 4);
+        set.add(0x13374204, 4);
+        set.add(0x13374208, 4);
+        set.add(0x1337420c, 4);
+
+        assert!(!set.contains(0x133741ff));
+        for address in 0x13374200..0x13374210 {
+            assert!(set.contains(address));
+        }
+        assert!(!set.contains(0x13374210));
+
+        set.remove(0x13374200, 4);
+        set.remove(0x13374204, 4);
+        set.remove(0x13374208, 4);
+        set.remove(0x1337420c, 4);
+
+        assert!(set.is_empty());
+        for address in 0x133741ff..=0x13374210 {
+            assert!(!set.contains(address));
+        }
+    }
+
+    #[test]
+    fn should_find_start_of_range() {
+        let mut set = AddressSet::new();
+        set.add(0x13374200, 4);
+        assert_eq!(set.start_of_range_containing(0x133741ff), None);
+        for address in 0x13374200..0x13374204 {
+            assert_eq!(set.start_of_range_containing(address), Some(0x13374200));
+        }
+        assert_eq!(set.start_of_range_containing(0x13374204), None);
+    }
+
+    #[test]
+    fn should_ignore_ranges_not_containing_address() {
+        let mut set = AddressSet::new();
+        set.add(0x10000000, 1024);
+        set.add(0x30000000, 1024);
+
+        assert!(!set.contains(0x20000000));
+        assert_eq!(set.start_of_range_containing(0x20000000), None);
+    }
+}

src/emulator/shrooms_vb_core.rs

@@ -5,6 +5,8 @@ use bitflags::bitflags;
 use num_derive::{FromPrimitive, ToPrimitive};
 use serde::{Deserialize, Serialize};
 
+use super::address_set::AddressSet;
+
 #[repr(C)]
 struct VB {
     _data: [u8; 0],
@@ -62,9 +64,31 @@ pub enum VBRegister {
     PC,
 }
 
-type OnFrame = extern "C" fn(sim: *mut VB) -> c_int;
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum VBWatchpointType {
+    Read,
+    Write,
+    Access,
+}
+
 type OnExecute =
     extern "C" fn(sim: *mut VB, address: u32, code: *const u16, length: c_int) -> c_int;
+type OnFrame = extern "C" fn(sim: *mut VB) -> c_int;
+type OnRead = extern "C" fn(
+    sim: *mut VB,
+    address: u32,
+    type_: VBDataType,
+    value: *mut i32,
+    cycles: *mut u32,
+) -> c_int;
+type OnWrite = extern "C" fn(
+    sim: *mut VB,
+    address: u32,
+    type_: VBDataType,
+    value: *mut i32,
+    cycles: *mut u32,
+    cancel: *mut c_int,
+) -> c_int;
 
 #[link(name = "vb")]
 extern "C" {
@@ -112,15 +136,21 @@ extern "C" {
     #[link_name = "vbSetCartROM"]
     fn vb_set_cart_rom(sim: *mut VB, rom: *mut c_void, size: u32) -> c_int;
     #[link_name = "vbSetExecuteCallback"]
-    fn vb_set_execute_callback(sim: *mut VB, callback: Option<OnExecute>);
+    fn vb_set_execute_callback(sim: *mut VB, callback: Option<OnExecute>) -> Option<OnExecute>;
     #[link_name = "vbSetFrameCallback"]
-    fn vb_set_frame_callback(sim: *mut VB, callback: Option<OnFrame>);
+    fn vb_set_frame_callback(sim: *mut VB, callback: Option<OnFrame>) -> Option<OnFrame>;
     #[link_name = "vbSetKeys"]
     fn vb_set_keys(sim: *mut VB, keys: u16) -> u16;
     #[link_name = "vbSetOption"]
     fn vb_set_option(sim: *mut VB, key: VBOption, value: c_int);
     #[link_name = "vbSetPeer"]
     fn vb_set_peer(sim: *mut VB, peer: *mut VB);
+    #[link_name = "vbSetProgramCounter"]
+    fn vb_set_program_counter(sim: *mut VB, value: u32) -> u32;
+    #[link_name = "vbSetProgramRegister"]
+    fn vb_set_program_register(sim: *mut VB, index: c_uint, value: i32) -> i32;
+    #[link_name = "vbSetReadCallback"]
+    fn vb_set_read_callback(sim: *mut VB, callback: Option<OnRead>) -> Option<OnRead>;
     #[link_name = "vbSetSamples"]
     fn vb_set_samples(
         sim: *mut VB,
@@ -128,12 +158,19 @@ extern "C" {
         typ_: VBDataType,
         capacity: c_uint,
     ) -> c_int;
+    #[link_name = "vbSetSystemRegister"]
+    fn vb_set_system_register(sim: *mut VB, index: c_uint, value: u32) -> u32;
     #[link_name = "vbSetUserData"]
     fn vb_set_user_data(sim: *mut VB, tag: *mut c_void);
+    #[link_name = "vbSetWriteCallback"]
+    fn vb_set_write_callback(sim: *mut VB, callback: Option<OnWrite>) -> Option<OnWrite>;
     #[link_name = "vbSizeOf"]
     fn vb_size_of() -> usize;
+    #[link_name = "vbWrite"]
+    fn vb_write(sim: *mut VB, address: u32, _type: VBDataType, value: i32) -> i32;
 }
 
+#[no_mangle]
 extern "C" fn on_frame(sim: *mut VB) -> c_int {
     // SAFETY: the *mut VB owns its userdata.
     // There is no way for the userdata to be null or otherwise invalid.
@@ -142,23 +179,81 @@ extern "C" fn on_frame(sim: *mut VB) -> c_int {
     1
 }
 
+#[no_mangle]
 extern "C" fn on_execute(sim: *mut VB, address: u32, _code: *const u16, _length: c_int) -> c_int {
     // SAFETY: the *mut VB owns its userdata.
     // 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() };
 
-    let mut stopped = 0;
+    let mut stopped = data.stop_reason.is_some();
     if data.step_from.is_some_and(|s| s != address) {
         data.step_from = None;
         data.stop_reason = Some(StopReason::Stepped);
-        stopped = 1;
+        stopped = true;
     }
     if data.breakpoints.binary_search(&address).is_ok() {
         data.stop_reason = Some(StopReason::Breakpoint);
-        stopped = 1;
+        stopped = true;
     }
 
-    stopped
+    if stopped {
+        1
+    } else {
+        0
+    }
+}
+
+#[no_mangle]
+extern "C" fn on_read(
+    sim: *mut VB,
+    address: u32,
+    _type: VBDataType,
+    _value: *mut i32,
+    _cycles: *mut u32,
+) -> c_int {
+    // SAFETY: the *mut VB owns its userdata.
+    // 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() };
+
+    if let Some(start) = data.read_watchpoints.start_of_range_containing(address) {
+        let watch = if data.write_watchpoints.contains(address) {
+            VBWatchpointType::Access
+        } else {
+            VBWatchpointType::Read
+        };
+        data.stop_reason = Some(StopReason::Watchpoint(watch, start));
+    }
+
+    // Don't stop here, the debugger expects us to break after the memory access.
+    // We'll stop in on_execute instead.
+    0
+}
+
+#[no_mangle]
+extern "C" fn on_write(
+    sim: *mut VB,
+    address: u32,
+    _type: VBDataType,
+    _value: *mut i32,
+    _cycles: *mut u32,
+    _cancel: *mut c_int,
+) -> c_int {
+    // SAFETY: the *mut VB owns its userdata.
+    // 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() };
+
+    if let Some(start) = data.write_watchpoints.start_of_range_containing(address) {
+        let watch = if data.read_watchpoints.contains(address) {
+            VBWatchpointType::Access
+        } else {
+            VBWatchpointType::Write
+        };
+        data.stop_reason = Some(StopReason::Watchpoint(watch, start));
+    }
+
+    // Don't stop here, the debugger expects us to break after the memory access.
+    // We'll stop in on_execute instead.
+    0
 }
 
 const AUDIO_CAPACITY_SAMPLES: usize = 834 * 4;
@@ -170,6 +265,23 @@ struct VBState {
     stop_reason: Option<StopReason>,
     step_from: Option<u32>,
     breakpoints: Vec<u32>,
+    read_watchpoints: AddressSet,
+    write_watchpoints: AddressSet,
+}
+
+impl VBState {
+    fn needs_execute_callback(&self) -> bool {
+        self.step_from.is_some()
+            || !self.breakpoints.is_empty()
+            || !self.read_watchpoints.is_empty()
+            || !self.write_watchpoints.is_empty()
+    }
+}
+
+pub enum StopReason {
+    Breakpoint,
+    Watchpoint(VBWatchpointType, u32),
+    Stepped,
 }
 
 #[repr(transparent)]
@@ -177,11 +289,6 @@ pub struct Sim {
     sim: *mut VB,
 }
 
-pub enum StopReason {
-    Breakpoint,
-    Stepped,
-}
-
 impl Sim {
     pub fn new() -> Self {
         // init the VB instance itself
@@ -201,6 +308,8 @@ impl Sim {
             stop_reason: None,
             step_from: None,
             breakpoints: vec![],
+            read_watchpoints: AddressSet::new(),
+            write_watchpoints: AddressSet::new(),
         };
         unsafe { vb_set_user_data(sim, Box::into_raw(Box::new(state)).cast()) };
         unsafe { vb_set_frame_callback(sim, Some(on_frame)) };
@@ -350,6 +459,20 @@ impl Sim {
         }
     }
 
+    pub fn write_register(&mut self, register: VBRegister, value: u32) {
+        match register {
+            VBRegister::Program(index) => unsafe {
+                vb_set_program_register(self.sim, index, value as i32);
+            },
+            VBRegister::System(index) => unsafe {
+                vb_set_system_register(self.sim, index, value);
+            },
+            VBRegister::PC => unsafe {
+                vb_set_program_counter(self.sim, value);
+            },
+        }
+    }
+
     pub fn read_memory(&mut self, start: u32, length: usize, into: &mut Vec<u8>) {
         let mut address = start;
         for _ in 0..length {
@@ -359,6 +482,14 @@ impl Sim {
         }
     }
 
+    pub fn write_memory(&mut self, start: u32, buffer: &[u8]) {
+        let mut address = start;
+        for byte in buffer {
+            unsafe { vb_write(self.sim, address, VBDataType::U8, *byte as i32) };
+            address = address.wrapping_add(1);
+        }
+    }
+
     pub fn add_breakpoint(&mut self, address: u32) {
         let data = self.get_state();
         if let Err(index) = data.breakpoints.binary_search(&address) {
@@ -374,7 +505,71 @@ impl Sim {
         let data = self.get_state();
         if let Ok(index) = data.breakpoints.binary_search(&address) {
             data.breakpoints.remove(index);
-            if data.step_from.is_none() && data.breakpoints.is_empty() {
+            if !data.needs_execute_callback() {
+                unsafe { vb_set_execute_callback(self.sim, None) };
+            }
+        }
+    }
+
+    pub fn add_watchpoint(&mut self, address: u32, length: usize, watch: VBWatchpointType) {
+        match watch {
+            VBWatchpointType::Read => self.add_read_watchpoint(address, length),
+            VBWatchpointType::Write => self.add_write_watchpoint(address, length),
+            VBWatchpointType::Access => {
+                self.add_read_watchpoint(address, length);
+                self.add_write_watchpoint(address, length);
+            }
+        }
+    }
+
+    fn add_read_watchpoint(&mut self, address: u32, length: usize) {
+        let state = self.get_state();
+        state.read_watchpoints.add(address, length);
+        if !state.read_watchpoints.is_empty() {
+            unsafe { vb_set_read_callback(self.sim, Some(on_read)) };
+            unsafe { vb_set_execute_callback(self.sim, Some(on_execute)) };
+        }
+    }
+
+    fn add_write_watchpoint(&mut self, address: u32, length: usize) {
+        let state = self.get_state();
+        state.write_watchpoints.add(address, length);
+        if !state.write_watchpoints.is_empty() {
+            unsafe { vb_set_write_callback(self.sim, Some(on_write)) };
+            unsafe { vb_set_execute_callback(self.sim, Some(on_execute)) };
+        }
+    }
+
+    pub fn remove_watchpoint(&mut self, address: u32, length: usize, watch: VBWatchpointType) {
+        match watch {
+            VBWatchpointType::Read => self.remove_read_watchpoint(address, length),
+            VBWatchpointType::Write => self.remove_write_watchpoint(address, length),
+            VBWatchpointType::Access => {
+                self.remove_read_watchpoint(address, length);
+                self.remove_write_watchpoint(address, length);
+            }
+        }
+    }
+
+    fn remove_read_watchpoint(&mut self, address: u32, length: usize) {
+        let state = self.get_state();
+        state.read_watchpoints.remove(address, length);
+        let needs_execute = state.needs_execute_callback();
+        if state.read_watchpoints.is_empty() {
+            unsafe { vb_set_read_callback(self.sim, None) };
+            if !needs_execute {
+                unsafe { vb_set_execute_callback(self.sim, None) };
+            }
+        }
+    }
+
+    fn remove_write_watchpoint(&mut self, address: u32, length: usize) {
+        let state = self.get_state();
+        state.write_watchpoints.remove(address, length);
+        let needs_execute = state.needs_execute_callback();
+        if state.write_watchpoints.is_empty() {
+            unsafe { vb_set_write_callback(self.sim, None) };
+            if !needs_execute {
                 unsafe { vb_set_execute_callback(self.sim, None) };
             }
         }
@@ -393,13 +588,17 @@ impl Sim {
         let data = self.get_state();
         data.step_from = None;
         data.breakpoints.clear();
+        data.read_watchpoints.clear();
+        data.write_watchpoints.clear();
+        unsafe { vb_set_read_callback(self.sim, None) };
+        unsafe { vb_set_write_callback(self.sim, None) };
         unsafe { vb_set_execute_callback(self.sim, None) };
     }
 
     pub fn stop_reason(&mut self) -> Option<StopReason> {
         let data = self.get_state();
         let reason = data.stop_reason.take();
-        if data.step_from.is_none() && data.breakpoints.is_empty() {
+        if !data.needs_execute_callback() {
             unsafe { vb_set_execute_callback(self.sim, None) };
         }
         reason

src/gdbserver.rs

@@ -9,11 +9,14 @@ use std::{
 use tokio::{
     io::{AsyncWriteExt as _, BufReader},
     net::{TcpListener, TcpStream},
-    select,
+    pin, select,
     sync::{mpsc, oneshot},
 };
+use tracing::{debug, enabled, error, info, Level};
 
-use crate::emulator::{DebugEvent, DebugStopReason, EmulatorClient, EmulatorCommand, SimId};
+use crate::emulator::{
+    DebugEvent, DebugStopReason, EmulatorClient, EmulatorCommand, SimId, VBWatchpointType,
+};
 
 mod registers;
 mod request;
@@ -54,8 +57,9 @@ impl GdbServer {
                 .unwrap()
                 .block_on(async move {
                     select! {
-                        _ = run_server(sim_id, client, port, &status) => {}
+                        _ = run_server(sim_id, client.clone(), port, &status) => {}
                         _ = rx => {
+                            client.send_command(EmulatorCommand::StopDebugging(sim_id));
                             *status.lock().unwrap() = GdbServerStatus::Stopped;
                         }
                     }
@@ -70,21 +74,52 @@ impl GdbServer {
     }
 }
 
+impl Drop for GdbServer {
+    fn drop(&mut self) {
+        self.stop();
+    }
+}
+
 async fn run_server(
     sim_id: SimId,
     client: EmulatorClient,
     port: u16,
     status: &Mutex<GdbServerStatus>,
 ) {
-    let Some(stream) = try_connect(port, status).await else {
+    let (debug_sink, mut debug_source) = mpsc::unbounded_channel();
-        return;
+    client.send_command(EmulatorCommand::StartDebugging(sim_id, debug_sink));
+
+    info!("Connecting to debugger on port {port}...");
+    let connect_future = try_connect(port, status);
+    pin!(connect_future);
+
+    let stream = loop {
+        select! {
+            stream = &mut connect_future => {
+                if let Some(stream) = stream {
+                    break stream;
+                } else {
+                    return;
+                }
+            }
+            event = debug_source.recv() => {
+                if event.is_none() {
+                    // The sim has stopped (or was never started)
+                    *status.lock().unwrap() = GdbServerStatus::Stopped;
+                    return;
+                }
+            }
+        }
     };
+    info!("Connected!");
     let mut connection = GdbConnection::new(sim_id, client);
-    match connection.run(stream).await {
+    match connection.run(stream, debug_source).await {
         Ok(()) => {
+            info!("Finished debugging.");
             *status.lock().unwrap() = GdbServerStatus::Stopped;
         }
         Err(error) => {
+            error!(%error, "Error from debugger.");
             *status.lock().unwrap() = GdbServerStatus::Error(error.to_string());
         }
     }
@@ -95,6 +130,7 @@ async fn try_connect(port: u16, status: &Mutex<GdbServerStatus>) -> Option<TcpSt
     let listener = match TcpListener::bind(("127.0.0.1", port)).await {
         Ok(l) => l,
         Err(err) => {
+            error!(%err, "Could not open port.");
             *status.lock().unwrap() = GdbServerStatus::Error(err.to_string());
             return None;
         }
@@ -105,6 +141,7 @@ async fn try_connect(port: u16, status: &Mutex<GdbServerStatus>) -> Option<TcpSt
             Some(stream)
         }
         Err(err) => {
+            error!(%err, "Could not connect to debugger.");
             *status.lock().unwrap() = GdbServerStatus::Error(err.to_string());
             None
         }
@@ -145,12 +182,13 @@ impl GdbConnection {
             memory_buf: None,
         }
     }
-    async fn run(&mut self, stream: TcpStream) -> Result<()> {
+    async fn run(
-        let (debug_sink, mut debug_source) = mpsc::unbounded_channel();
+        &mut self,
+        stream: TcpStream,
+        mut debug_source: mpsc::UnboundedReceiver<DebugEvent>,
+    ) -> Result<()> {
         let (rx, mut tx) = stream.into_split();
         let mut request_source = RequestSource::new(BufReader::new(rx));
-        self.client
-            .send_command(EmulatorCommand::StartDebugging(self.sim_id, debug_sink));
         loop {
             let response = select! {
                 maybe_event = debug_source.recv() => {
@@ -167,9 +205,11 @@ impl GdbConnection {
             };
             if let Some(res) = response {
                 let buffer = res.finish();
-                match std::str::from_utf8(&buffer) {
+                if enabled!(Level::DEBUG) {
-                    Ok(text) => println!("response: {text}"),
+                    match std::str::from_utf8(&buffer) {
-                    Err(_) => println!("response: {buffer:02x?}"),
+                        Ok(text) => debug!("response: {text}"),
+                        Err(_) => debug!("response: {buffer:02x?}"),
+                    }
                 }
                 tx.write_all(&buffer).await?;
                 self.response_buf = Some(buffer);
@@ -187,14 +227,14 @@ impl GdbConnection {
                 }
                 self.stop_reason = Some(reason);
                 self.response()
-                    .write_str(debug_stop_reason_string(self.stop_reason))
+                    .write_str(&debug_stop_reason_string(self.stop_reason))
             }
         };
         Some(res)
     }
 
     fn handle_request(&mut self, mut req: Request<'_>) -> Result<Option<Response>> {
-        println!("received {:02x?}", req);
+        debug!("received {:02x?}", req);
 
         if req.kind == RequestKind::Signal {
             self.client
@@ -208,7 +248,7 @@ impl GdbConnection {
             res
         } else if req.match_str("qSupported:") {
             self.response()
-                .write_str("multiprocess+;swbreak+;vContSupported+;PacketSize=10000")
+                .write_str("multiprocess+;swbreak+;vContSupported+;PacketSize=10000;SupportedWatchpointTypes=x86_64,aarch64-bas,aarch64-mask")
         } else if req
             .match_some_str([
                 "QThreadSuffixSupported",
@@ -251,7 +291,7 @@ impl GdbConnection {
             bail!("debug process was killed");
         } else if req.match_str("?") {
             self.response()
-                .write_str(debug_stop_reason_string(self.stop_reason))
+                .write_str(&debug_stop_reason_string(self.stop_reason))
         } else if req.match_some_str(["c", "vCont;c:"]).is_some() {
             self.client
                 .send_command(EmulatorCommand::DebugContinue(self.sim_id));
@@ -278,24 +318,37 @@ impl GdbConnection {
             } else {
                 self.response()
             }
+        } else if req.match_str("P") {
+            let mut write_register = || {
+                let register_index = req.match_hex::<usize>()?;
+                let register = REGISTERS.get(register_index)?.to_vb_register();
+                if !req.match_str("=") {
+                    return None;
+                }
+                let value = {
+                    let mut buffer = [0; 4];
+                    if !req.match_hex_bytes(&mut buffer) {
+                        return None;
+                    }
+                    u32::from_le_bytes(buffer)
+                };
+                self.client.send_command(EmulatorCommand::WriteRegister(
+                    self.sim_id,
+                    register,
+                    value,
+                ));
+                Some(())
+            };
+            if let Some(()) = write_register() {
+                self.response().write_str("OK")
+            } else {
+                self.response()
+            }
         } else if let Some(op) = req.match_some_str(["m", "x"]) {
             let mut read_memory = || {
-                let start = req.match_hex::<u64>()?;
+                let (start, length) = parse_memory_range(&mut req)?;
-                if !req.match_str(",") {
-                    return None;
-                };
-                let length = req.match_hex::<usize>()?;
-
                 let mut buf = self.memory_buf.take().unwrap_or_default();
                 buf.clear();
-
-                // The v810 has a 32-bit address space.
-                // Addresses wrap within that space, but we don't need to implement that for 64-bit addresses.
-                // Just refuse to return any info for addresses above 0xffffffff.
-                let Ok(start) = u32::try_from(start) else {
-                    return Some(buf);
-                };
-                let length = length.min((u32::MAX - start) as usize + 1);
                 if length == 0 {
                     return Some(buf);
                 }
@@ -329,18 +382,100 @@ impl GdbConnection {
             } else {
                 self.response()
             }
-        } else if req.match_str("Z0,") {
+        } else if let Some(op) = req.match_some_str(["M", "X"]) {
-            if let Some(address) = req.match_hex() {
+            let mut write_memory = || {
+                let (start, length) = parse_memory_range(&mut req)?;
+                if length == 0 {
+                    return Some(());
+                }
+                if !req.match_str(":") {
+                    return None;
+                }
+                let mut buf = self.memory_buf.take().unwrap_or_default();
+                buf.resize(length, 0);
+                let successful_read = if op == "M" {
+                    req.match_hex_bytes(&mut buf)
+                } else {
+                    req.match_bytes(&mut buf)
+                };
+                if !successful_read {
+                    self.memory_buf = Some(buf);
+                    return None;
+                }
+                let (tx, rx) = ::oneshot::channel();
                 self.client
-                    .send_command(EmulatorCommand::AddBreakpoint(self.sim_id, address));
+                    .send_command(EmulatorCommand::WriteMemory(self.sim_id, start, buf, tx));
+                let buf = rx.recv().ok()?;
+                self.memory_buf = Some(buf);
+                Some(())
+            };
+            if write_memory().is_some() {
                 self.response().write_str("OK")
             } else {
                 self.response()
             }
-        } else if req.match_str("z0,") {
+        } else if req.match_str("Z") {
-            if let Some(address) = req.match_hex() {
+            let mut parse_request = || {
-                self.client
+                let type_ = req.match_hex::<u8>()?;
-                    .send_command(EmulatorCommand::RemoveBreakpoint(self.sim_id, address));
+                if !req.match_str(",") {
+                    return None;
+                }
+                let address = req.match_hex()?;
+                if type_ == 0 || type_ == 1 {
+                    return Some(EmulatorCommand::AddBreakpoint(self.sim_id, address));
+                }
+                if !req.match_str(",") {
+                    return None;
+                }
+                let length = req.match_hex()?;
+                let watch = match type_ {
+                    2 => VBWatchpointType::Write,
+                    3 => VBWatchpointType::Read,
+                    4 => VBWatchpointType::Access,
+                    _ => return None,
+                };
+                Some(EmulatorCommand::AddWatchpoint(
+                    self.sim_id,
+                    address,
+                    length,
+                    watch,
+                ))
+            };
+            if let Some(command) = parse_request() {
+                self.client.send_command(command);
+                self.response().write_str("OK")
+            } else {
+                self.response()
+            }
+        } else if req.match_str("z") {
+            let mut parse_request = || {
+                let type_ = req.match_hex::<u8>()?;
+                if !req.match_str(",") {
+                    return None;
+                }
+                let address = req.match_hex()?;
+                if type_ == 0 || type_ == 1 {
+                    return Some(EmulatorCommand::RemoveBreakpoint(self.sim_id, address));
+                }
+                if !req.match_str(",") {
+                    return None;
+                }
+                let length = req.match_hex()?;
+                let watch = match type_ {
+                    2 => VBWatchpointType::Write,
+                    3 => VBWatchpointType::Read,
+                    4 => VBWatchpointType::Access,
+                    _ => return None,
+                };
+                Some(EmulatorCommand::RemoveWatchpoint(
+                    self.sim_id,
+                    address,
+                    length,
+                    watch,
+                ))
+            };
+            if let Some(command) = parse_request() {
+                self.client.send_command(command);
                 self.response().write_str("OK")
             } else {
                 self.response()
@@ -367,11 +502,59 @@ impl Drop for GdbConnection {
     }
 }
 
-fn debug_stop_reason_string(reason: Option<DebugStopReason>) -> &'static str {
+// parse a memory range into a start and a length.
-    match reason {
+fn parse_memory_range(req: &mut Request<'_>) -> Option<(u32, usize)> {
-        Some(DebugStopReason::Trace) => "T05;thread:p1.t1;threads:p1.t1;reason:trace;",
+    let start = req.match_hex::<u64>()?;
-        Some(DebugStopReason::Breakpoint) => "T05;thread:p1.t1;threads:p1.t1;reason:breakpoint;",
+    if !req.match_str(",") {
-        Some(DebugStopReason::Trapped) => "T05;swbreak;thread:p1.t1;threads:p1.t1;reason:trap;",
+        return None;
-        None => "T00;thread:p1.t1;threads:p1.t1;",
+    };
+    let length = req.match_hex::<usize>()?;
+    let Ok(start) = u32::try_from(start) else {
+        // The v810 has a 32-bit address space.
+        // Addresses wrap within that space, but we don't need to implement that for 64-bit addresses.
+        // Just refuse to return any info for addresses above 0xffffffff.
+        return Some((0, 0));
+    };
+    let length = length.min((u32::MAX - start) as usize + 1);
+    Some((start, length))
+}
+
+fn debug_stop_reason_string(reason: Option<DebugStopReason>) -> String {
+    let mut result = String::new();
+    result += if reason.is_some_and(|r| r != DebugStopReason::Paused) {
+        "T05;"
+    } else {
+        "T00;"
+    };
+    if let Some(DebugStopReason::Breakpoint) = reason {
+        result += "swbreak;";
     }
+    if let Some(DebugStopReason::Watchpoint(watch, address)) = reason {
+        result += match watch {
+            VBWatchpointType::Write => "watch:",
+            VBWatchpointType::Read => "rwatch:",
+            VBWatchpointType::Access => "awatch:",
+        };
+        result += &format!("{address:08x};");
+    }
+
+    result += "thread:p1.t1;threads:p1.t1;";
+
+    if let Some(reason) = reason {
+        result += "reason:";
+        result += match reason {
+            DebugStopReason::Trace => "trace;",
+            DebugStopReason::Breakpoint => "breakpoint;",
+            DebugStopReason::Watchpoint(_, _) => "watchpoint;",
+            DebugStopReason::Paused => "trap;",
+        };
+    }
+
+    if let Some(DebugStopReason::Watchpoint(_, address)) = reason {
+        result += "description:";
+        result += &hex::encode(address.to_string());
+        result += ";";
+    }
+
+    result
 }

src/gdbserver/request.rs

@@ -60,6 +60,29 @@ impl Request<'_> {
             }
         }
     }
+
+    pub fn match_hex_bytes(&mut self, buffer: &mut [u8]) -> bool {
+        if self.buffer.len() < buffer.len() * 2 {
+            return false;
+        }
+        for (i, item) in buffer.iter_mut().enumerate() {
+            match u8::from_radix_16(&self.buffer[(i * 2)..(i * 2) + 2]) {
+                (byte, 2) => *item = byte,
+                _ => return false,
+            };
+        }
+        self.buffer = self.buffer.split_at(buffer.len()).1;
+        true
+    }
+
+    pub fn match_bytes(&mut self, buffer: &mut [u8]) -> bool {
+        if self.buffer.len() < buffer.len() {
+            return false;
+        }
+        buffer.copy_from_slice(&self.buffer[0..buffer.len()]);
+        self.buffer = self.buffer.split_at(buffer.len()).1;
+        true
+    }
 }
 
 pub struct RequestSource<R> {

src/main.rs

@@ -3,11 +3,13 @@
 
 use std::{path::PathBuf, process, time::SystemTime};
 
-use anyhow::Result;
+use anyhow::{bail, Result};
 use app::Application;
 use clap::Parser;
 use emulator::EmulatorBuilder;
 use thread_priority::{ThreadBuilder, ThreadPriority};
+use tracing::error;
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt, EnvFilter, Layer};
 use winit::event_loop::{ControlFlow, EventLoop};
 
 mod app;
@@ -29,6 +31,13 @@ struct Args {
     debug_port: Option<u16>,
 }
 
+fn init_logger() {
+    let directives = std::env::var("RUST_LOG").unwrap_or("error,lemur=info".into());
+    let filter = EnvFilter::builder().parse_lossy(directives);
+    let layer = tracing_subscriber::fmt::layer().with_filter(filter);
+    tracing_subscriber::registry().with(layer).init();
+}
+
 fn set_panic_handler() {
     std::panic::set_hook(Box::new(|info| {
         let mut message = String::new();
@@ -76,6 +85,8 @@ fn set_process_priority_to_high() -> Result<()> {
 }
 
 fn main() -> Result<()> {
+    init_logger();
+
     set_panic_handler();
 
     #[cfg(windows)]
@@ -84,10 +95,13 @@ fn main() -> Result<()> {
     let args = Args::parse();
 
     let (mut builder, client) = EmulatorBuilder::new();
-    if let Some(path) = args.rom {
+    if let Some(path) = &args.rom {
-        builder = builder.with_rom(&path);
+        builder = builder.with_rom(path);
     }
     if args.debug_port.is_some() {
+        if args.rom.is_none() {
+            bail!("to start debugging, please select a game.");
+        }
         builder = builder.start_paused(true);
     }
 
@@ -97,8 +111,8 @@ fn main() -> Result<()> {
         .spawn_careless(move || {
             let mut emulator = match builder.build() {
                 Ok(e) => e,
-                Err(err) => {
+                Err(error) => {
-                    eprintln!("Error initializing emulator: {err}");
+                    error!(%error, "Error initializing emulator");
                     process::exit(1);
                 }
             };

src/window/game.rs

@@ -142,8 +142,7 @@ impl GameWindow {
     fn show_options_menu(&mut self, ctx: &Context, ui: &mut Ui) {
         ui.menu_button("Video", |ui| {
             ui.menu_button("Screen Size", |ui| {
-                let current_dims = ctx.input(|i| i.viewport().inner_rect.unwrap());
+                let current_dims = self.config.dimensions;
-                let current_dims = current_dims.max - current_dims.min;
 
                 for scale in 1..=4 {
                     let label = format!("x{scale}");
@@ -183,10 +182,7 @@ impl GameWindow {
                     return;
                 }
 
-                let current_dims = {
+                let current_dims = self.config.dimensions;
-                    let viewport = ctx.input(|i| i.viewport().inner_rect.unwrap());
-                    viewport.max - viewport.min
-                };
                 let new_proportions = display_mode.proportions();
                 let scale = new_proportions / old_proportions;
                 if scale != Vec2::new(1.0, 1.0) {
@@ -330,7 +326,7 @@ impl AppWindow for GameWindow {
 
     fn show(&mut self, ctx: &Context) {
         let dimensions = {
-            let bounds = ctx.input(|i| i.viewport().inner_rect.unwrap());
+            let bounds = ctx.available_rect();
             bounds.max - bounds.min
         };
         self.update_config(|c| c.dimensions = dimensions);

src/window/gdb.rs

@@ -3,7 +3,7 @@ use winit::event_loop::EventLoopProxy;
 
 use crate::{
     app::UserEvent,
-    emulator::{EmulatorClient, SimId},
+    emulator::{EmulatorClient, SimId, SimState},
     gdbserver::{GdbServer, GdbServerStatus},
 };
 
@@ -11,6 +11,7 @@ use super::AppWindow;
 
 pub struct GdbServerWindow {
     sim_id: SimId,
+    client: EmulatorClient,
     port_str: String,
     connected: bool,
     quit_on_disconnect: bool,
@@ -22,6 +23,7 @@ impl GdbServerWindow {
     pub fn new(sim_id: SimId, client: EmulatorClient, proxy: EventLoopProxy<UserEvent>) -> Self {
         Self {
             sim_id,
+            client: client.clone(),
             port_str: (8080 + sim_id.to_index()).to_string(),
             connected: false,
             quit_on_disconnect: false,
@@ -78,7 +80,9 @@ impl AppWindow for GdbServerWindow {
                     self.connected = false;
                 }
                 let start_button = Button::new("Start");
-                if ui.add_enabled(port_num.is_some(), start_button).clicked() {
+                let can_start =
+                    port_num.is_some() && self.client.sim_state(self.sim_id) == SimState::Ready;
+                if ui.add_enabled(can_start, start_button).clicked() {
                     let port = port_num.unwrap();
                     self.server.start(port);
                     self.connected = true;