3 files changed, 286 insertions, 0 deletions
diff --git a/src/Ryujinx.Cpu/Signal/NativeSignalHandler.cs b/src/Ryujinx.Cpu/Signal/NativeSignalHandler.cs
new file mode 100644
index 00000000..5a9d92cc
--- /dev/null
+++ b/src/Ryujinx.Cpu/Signal/NativeSignalHandler.cs
@@ -0,0 +1,179 @@
+using ARMeilleure.Signal;
+using Ryujinx.Common;
+using Ryujinx.Memory;
+using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Cpu.Signal
+{
+    [StructLayout(LayoutKind.Sequential, Pack = 1)]
+    struct SignalHandlerRange
+    {
+        public int IsActive;
+        public nuint RangeAddress;
+        public nuint RangeEndAddress;
+        public IntPtr ActionPointer;
+    }
+
+    [InlineArray(NativeSignalHandlerGenerator.MaxTrackedRanges)]
+    struct SignalHandlerRangeArray
+    {
+        public SignalHandlerRange Range0;
+    }
+
+    [StructLayout(LayoutKind.Sequential, Pack = 1)]
+    struct SignalHandlerConfig
+    {
+        /// <summary>
+        /// The byte offset of the faulting address in the SigInfo or ExceptionRecord struct.
+        /// </summary>
+        public int StructAddressOffset;
+
+        /// <summary>
+        /// The byte offset of the write flag in the SigInfo or ExceptionRecord struct.
+        /// </summary>
+        public int StructWriteOffset;
+
+        /// <summary>
+        /// The sigaction handler that was registered before this one. (unix only)
+        /// </summary>
+        public nuint UnixOldSigaction;
+
+        /// <summary>
+        /// The type of the previous sigaction. True for the 3 argument variant. (unix only)
+        /// </summary>
+        public int UnixOldSigaction3Arg;
+
+        /// <summary>
+        /// Fixed size array of tracked ranges.
+        /// </summary>
+        public SignalHandlerRangeArray Ranges;
+    }
+
+    static class NativeSignalHandler
+    {
+        private static readonly IntPtr _handlerConfig;
+        private static IntPtr _signalHandlerPtr;
+
+        private static MemoryBlock _codeBlock;
+
+        private static readonly object _lock = new();
+        private static bool _initialized;
+
+        static NativeSignalHandler()
+        {
+            _handlerConfig = Marshal.AllocHGlobal(Unsafe.SizeOf<SignalHandlerConfig>());
+            ref SignalHandlerConfig config = ref GetConfigRef();
+
+            config = new SignalHandlerConfig();
+        }
+
+        public static void InitializeSignalHandler(ulong pageSize, Func<IntPtr, IntPtr, IntPtr> customSignalHandlerFactory = null)
+        {
+            if (_initialized)
+            {
+                return;
+            }
+
+            lock (_lock)
+            {
+                if (_initialized)
+                {
+                    return;
+                }
+
+                int rangeStructSize = Unsafe.SizeOf<SignalHandlerRange>();
+
+                ref SignalHandlerConfig config = ref GetConfigRef();
+
+                if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
+                {
+                    _signalHandlerPtr = MapCode(NativeSignalHandlerGenerator.GenerateUnixSignalHandler(_handlerConfig, rangeStructSize, pageSize));
+
+                    if (customSignalHandlerFactory != null)
+                    {
+                        _signalHandlerPtr = customSignalHandlerFactory(UnixSignalHandlerRegistration.GetSegfaultExceptionHandler().sa_handler, _signalHandlerPtr);
+                    }
+
+                    var old = UnixSignalHandlerRegistration.RegisterExceptionHandler(_signalHandlerPtr);
+
+                    config.UnixOldSigaction = (nuint)(ulong)old.sa_handler;
+                    config.UnixOldSigaction3Arg = old.sa_flags & 4;
+                }
+                else
+                {
+                    config.StructAddressOffset = 40; // ExceptionInformation1
+                    config.StructWriteOffset = 32; // ExceptionInformation0
+
+                    _signalHandlerPtr = MapCode(NativeSignalHandlerGenerator.GenerateWindowsSignalHandler(_handlerConfig, rangeStructSize, pageSize));
+
+                    if (customSignalHandlerFactory != null)
+                    {
+                        _signalHandlerPtr = customSignalHandlerFactory(IntPtr.Zero, _signalHandlerPtr);
+                    }
+
+                    WindowsSignalHandlerRegistration.RegisterExceptionHandler(_signalHandlerPtr);
+                }
+
+                _initialized = true;
+            }
+        }
+
+        private static IntPtr MapCode(ReadOnlySpan<byte> code)
+        {
+            Debug.Assert(_codeBlock == null);
+
+            ulong codeSizeAligned = BitUtils.AlignUp((ulong)code.Length, MemoryBlock.GetPageSize());
+
+            _codeBlock = new MemoryBlock(codeSizeAligned);
+            _codeBlock.Write(0, code);
+            _codeBlock.Reprotect(0, codeSizeAligned, MemoryPermission.ReadAndExecute);
+
+            return _codeBlock.Pointer;
+        }
+
+        private static unsafe ref SignalHandlerConfig GetConfigRef()
+        {
+            return ref Unsafe.AsRef<SignalHandlerConfig>((void*)_handlerConfig);
+        }
+
+        public static bool AddTrackedRegion(nuint address, nuint endAddress, IntPtr action)
+        {
+            Span<SignalHandlerRange> ranges = GetConfigRef().Ranges;
+
+            for (int i = 0; i < NativeSignalHandlerGenerator.MaxTrackedRanges; i++)
+            {
+                if (ranges[i].IsActive == 0)
+                {
+                    ranges[i].RangeAddress = address;
+                    ranges[i].RangeEndAddress = endAddress;
+                    ranges[i].ActionPointer = action;
+                    ranges[i].IsActive = 1;
+
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        public static bool RemoveTrackedRegion(nuint address)
+        {
+            Span<SignalHandlerRange> ranges = GetConfigRef().Ranges;
+
+            for (int i = 0; i < NativeSignalHandlerGenerator.MaxTrackedRanges; i++)
+            {
+                if (ranges[i].IsActive == 1 && ranges[i].RangeAddress == address)
+                {
+                    ranges[i].IsActive = 0;
+
+                    return true;
+                }
+            }
+
+            return false;
+        }
+    }
+}
diff --git a/src/Ryujinx.Cpu/Signal/UnixSignalHandlerRegistration.cs b/src/Ryujinx.Cpu/Signal/UnixSignalHandlerRegistration.cs
new file mode 100644
index 00000000..e88a6c0f
--- /dev/null
+++ b/src/Ryujinx.Cpu/Signal/UnixSignalHandlerRegistration.cs
@@ -0,0 +1,83 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Cpu.Signal
+{
+    static partial class UnixSignalHandlerRegistration
+    {
+        [StructLayout(LayoutKind.Sequential, Pack = 1)]
+        public unsafe struct SigSet
+        {
+            fixed long sa_mask[16];
+        }
+
+        [StructLayout(LayoutKind.Sequential, Pack = 1)]
+        public struct SigAction
+        {
+            public IntPtr sa_handler;
+            public SigSet sa_mask;
+            public int sa_flags;
+            public IntPtr sa_restorer;
+        }
+
+        private const int SIGSEGV = 11;
+        private const int SIGBUS = 10;
+        private const int SA_SIGINFO = 0x00000004;
+
+        [LibraryImport("libc", SetLastError = true)]
+        private static partial int sigaction(int signum, ref SigAction sigAction, out SigAction oldAction);
+
+        [LibraryImport("libc", SetLastError = true)]
+        private static partial int sigaction(int signum, IntPtr sigAction, out SigAction oldAction);
+
+        [LibraryImport("libc", SetLastError = true)]
+        private static partial int sigemptyset(ref SigSet set);
+
+        public static SigAction GetSegfaultExceptionHandler()
+        {
+            int result = sigaction(SIGSEGV, IntPtr.Zero, out SigAction old);
+
+            if (result != 0)
+            {
+                throw new InvalidOperationException($"Could not get SIGSEGV sigaction. Error: {result}");
+            }
+
+            return old;
+        }
+
+        public static SigAction RegisterExceptionHandler(IntPtr action)
+        {
+            SigAction sig = new()
+            {
+                sa_handler = action,
+                sa_flags = SA_SIGINFO,
+            };
+
+            sigemptyset(ref sig.sa_mask);
+
+            int result = sigaction(SIGSEGV, ref sig, out SigAction old);
+
+            if (result != 0)
+            {
+                throw new InvalidOperationException($"Could not register SIGSEGV sigaction. Error: {result}");
+            }
+
+            if (OperatingSystem.IsMacOS())
+            {
+                result = sigaction(SIGBUS, ref sig, out _);
+
+                if (result != 0)
+                {
+                    throw new InvalidOperationException($"Could not register SIGBUS sigaction. Error: {result}");
+                }
+            }
+
+            return old;
+        }
+
+        public static bool RestoreExceptionHandler(SigAction oldAction)
+        {
+            return sigaction(SIGSEGV, ref oldAction, out SigAction _) == 0 && (!OperatingSystem.IsMacOS() || sigaction(SIGBUS, ref oldAction, out SigAction _) == 0);
+        }
+    }
+}
diff --git a/src/Ryujinx.Cpu/Signal/WindowsSignalHandlerRegistration.cs b/src/Ryujinx.Cpu/Signal/WindowsSignalHandlerRegistration.cs
new file mode 100644
index 00000000..1fbce0f7
--- /dev/null
+++ b/src/Ryujinx.Cpu/Signal/WindowsSignalHandlerRegistration.cs
@@ -0,0 +1,24 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Cpu.Signal
+{
+    static partial class WindowsSignalHandlerRegistration
+    {
+        [LibraryImport("kernel32.dll")]
+        private static partial IntPtr AddVectoredExceptionHandler(uint first, IntPtr handler);
+
+        [LibraryImport("kernel32.dll")]
+        private static partial ulong RemoveVectoredExceptionHandler(IntPtr handle);
+
+        public static IntPtr RegisterExceptionHandler(IntPtr action)
+        {
+            return AddVectoredExceptionHandler(1, action);
+        }
+
+        public static bool RemoveExceptionHandler(IntPtr handle)
+        {
+            return RemoveVectoredExceptionHandler(handle) != 0;
+        }
+    }
+}