Add live debugger frontend and mutex stall recovery (#383)

src/SharpEmu.Debugger/Breakpoints/Breakpoint.cs

@@ -0,0 +1,48 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.Debugger.Breakpoints;
+
+/// <summary>
+/// A single breakpoint or watchpoint. Instances are immutable; the owning
+/// <see cref="BreakpointStore"/> replaces an entry to change its enabled state.
+/// </summary>
+public sealed class Breakpoint
+{
+    public Breakpoint(int id, BreakpointKind kind, ulong address, ulong length = 1, bool enabled = true)
+    {
+        if (length == 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(length), "Breakpoint length must be at least one byte.");
+        }
+
+        Id = id;
+        Kind = kind;
+        Address = address;
+        Length = length;
+        Enabled = enabled;
+    }
+
+    /// <summary>The store-assigned identifier used by clients to reference it.</summary>
+    public int Id { get; }
+
+    public BreakpointKind Kind { get; }
+
+    /// <summary>The first guest address the breakpoint covers.</summary>
+    public ulong Address { get; }
+
+    /// <summary>
+    /// The number of bytes the breakpoint covers. Always one for
+    /// <see cref="BreakpointKind.Execute"/>; the watch kinds may span a range.
+    /// </summary>
+    public ulong Length { get; }
+
+    public bool Enabled { get; }
+
+    /// <summary>True when <paramref name="address"/> falls within this breakpoint.</summary>
+    public bool Covers(ulong address) => address >= Address && address < Address + Length;
+
+    /// <summary>Returns a copy with a different enabled state.</summary>
+    public Breakpoint WithEnabled(bool enabled)
+        => enabled == Enabled ? this : new Breakpoint(Id, Kind, Address, Length, enabled);
+}

src/SharpEmu.Debugger/Breakpoints/BreakpointKind.cs

@@ -0,0 +1,26 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.Debugger.Breakpoints;
+
+/// <summary>
+/// The kind of stop a breakpoint requests. Execution breakpoints are honoured
+/// at the frame-boundary seam that exists today; the data-watch kinds are part
+/// of the surface so client protocols and tooling can be built against them,
+/// and are armed once the execution backend can report the corresponding
+/// accesses.
+/// </summary>
+public enum BreakpointKind
+{
+    /// <summary>Stop when the instruction pointer reaches the address.</summary>
+    Execute,
+
+    /// <summary>Stop when the guest reads from the address range.</summary>
+    ReadWatch,
+
+    /// <summary>Stop when the guest writes to the address range.</summary>
+    WriteWatch,
+
+    /// <summary>Stop when the guest reads from or writes to the address range.</summary>
+    AccessWatch,
+}

src/SharpEmu.Debugger/Breakpoints/BreakpointStore.cs

@@ -0,0 +1,90 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+namespace SharpEmu.Debugger.Breakpoints;
+
+/// <summary>
+/// A thread-safe registry of breakpoints. The debug server mutates it from
+/// client-servicing threads while the emulation thread queries it at frame
+/// boundaries, so every operation takes the same lock.
+/// </summary>
+public sealed class BreakpointStore
+{
+    private readonly object _sync = new();
+    private readonly Dictionary<int, Breakpoint> _breakpoints = new();
+    private int _nextId = 1;
+
+    /// <summary>Adds a breakpoint and returns the created entry with its id.</summary>
+    public Breakpoint Add(BreakpointKind kind, ulong address, ulong length = 1)
+    {
+        lock (_sync)
+        {
+            var effectiveLength = kind == BreakpointKind.Execute ? 1UL : Math.Max(1UL, length);
+            var breakpoint = new Breakpoint(_nextId++, kind, address, effectiveLength);
+            _breakpoints[breakpoint.Id] = breakpoint;
+            return breakpoint;
+        }
+    }
+
+    /// <summary>Removes a breakpoint by id. Returns false when it did not exist.</summary>
+    public bool Remove(int id)
+    {
+        lock (_sync)
+        {
+            return _breakpoints.Remove(id);
+        }
+    }
+
+    /// <summary>Enables or disables a breakpoint by id.</summary>
+    public bool SetEnabled(int id, bool enabled)
+    {
+        lock (_sync)
+        {
+            if (!_breakpoints.TryGetValue(id, out var breakpoint))
+            {
+                return false;
+            }
+
+            _breakpoints[id] = breakpoint.WithEnabled(enabled);
+            return true;
+        }
+    }
+
+    /// <summary>Removes every breakpoint.</summary>
+    public void Clear()
+    {
+        lock (_sync)
+        {
+            _breakpoints.Clear();
+        }
+    }
+
+    /// <summary>Returns a point-in-time copy of all breakpoints.</summary>
+    public IReadOnlyList<Breakpoint> Snapshot()
+    {
+        lock (_sync)
+        {
+            return _breakpoints.Values.ToArray();
+        }
+    }
+
+    /// <summary>
+    /// Finds the first enabled execution breakpoint covering <paramref name="address"/>,
+    /// or null when none applies.
+    /// </summary>
+    public Breakpoint? FindExecuteHit(ulong address)
+    {
+        lock (_sync)
+        {
+            foreach (var breakpoint in _breakpoints.Values)
+            {
+                if (breakpoint.Enabled && breakpoint.Kind == BreakpointKind.Execute && breakpoint.Covers(address))
+                {
+                    return breakpoint;
+                }
+            }
+
+            return null;
+        }
+    }
+}