Use alternate stack for the segfault handler too

src/Ryujinx.Cpu/Nce/NceCpuContext.cs

@@ -117,9 +117,8 @@ namespace Ryujinx.Cpu.Nce
             int tableIndex = NceThreadTable.Register(_getTpidrEl0(), nec.NativeContextPtr);
 
             nec.SetStartAddress(address);
-            nec.RegisterAlternateStack();
             _threadStart(nec.NativeContextPtr);
-            nec.UnregisterAlternateStack();
+            nec.Exit();
 
             NceThreadTable.Unregister(tableIndex);
         }

src/Ryujinx.Cpu/Nce/NceExecutionContext.cs

@@ -102,9 +102,18 @@ namespace Ryujinx.Cpu.Nce
             ref var storage = ref _context.GetStorage();
             storage.X[30] = address;
             storage.HostThreadHandle = NceThreadPal.GetCurrentThreadHandle();
+
+            RegisterAlternateStack();
         }
 
-        public void RegisterAlternateStack()
+        public void Exit()
+        {
+            _context.GetStorage().HostThreadHandle = IntPtr.Zero;
+
+            UnregisterAlternateStack();
+        }
+
+        private void RegisterAlternateStack()
         {
             // We need to use an alternate stack to handle the suspend signal,
             // as the guest stack may be in a state that is not suitable for the signal handlers.
@@ -113,7 +122,7 @@ namespace Ryujinx.Cpu.Nce
             NativeSignalHandler.InstallUnixAlternateStackForCurrentThread(_alternateStackMemory.GetPointer(0UL, AlternateStackSize), AlternateStackSize);
         }
 
-        public void UnregisterAlternateStack()
+        private void UnregisterAlternateStack()
         {
             NativeSignalHandler.UninstallUnixAlternateStackForCurrentThread();
             _alternateStackMemory.Dispose();

src/Ryujinx.Cpu/Signal/AndroidSignalHandlerRegistration.cs

@@ -1,87 +0,0 @@
-using System;
-using System.Runtime.InteropServices;
-
-namespace Ryujinx.Cpu.Signal
-{
-    static class AndroidSignalHandlerRegistration
-    {
-        [StructLayout(LayoutKind.Sequential, Pack = 8)]
-        public unsafe struct SigSet
-        {
-            fixed long sa_mask[16];
-        }
-
-        [StructLayout(LayoutKind.Sequential, Pack = 8)]
-        public struct SigAction
-        {
-            public int sa_flags;
-            public IntPtr sa_handler;
-            public SigSet sa_mask;
-            public IntPtr sa_restorer;
-        }
-
-        private const int SIGSEGV = 11;
-        private const int SA_SIGINFO = 0x00000004;
-
-        [DllImport("libc", SetLastError = true)]
-        private static extern int sigaction(int signum, ref SigAction sigAction, out SigAction oldAction);
-
-        [DllImport("libc", SetLastError = true)]
-        private static extern int sigaction(int signum, IntPtr sigAction, out SigAction oldAction);
-
-        [DllImport("libc", SetLastError = true)]
-        private static extern int sigemptyset(ref SigSet set);
-
-        public static SigAction GetSegfaultExceptionHandler()
-        {
-            int result = sigaction(SIGSEGV, IntPtr.Zero, out SigAction old);
-
-            if (result != 0)
-            {
-                throw new InvalidOperationException($"Could not get SIGSEGV sigaction. Error: {result}");
-            }
-
-            return old;
-        }
-
-        public static SigAction RegisterExceptionHandler(IntPtr action, int userSignal = -1)
-        {
-            SigAction sig = new SigAction
-            {
-                sa_handler = action,
-                sa_flags = SA_SIGINFO
-            };
-
-            sigemptyset(ref sig.sa_mask);
-
-            int result = sigaction(SIGSEGV, ref sig, out SigAction old);
-
-            if (result != 0)
-            {
-                throw new InvalidOperationException($"Could not register SIGSEGV sigaction. Error: {result}");
-            }
-
-            if (userSignal != -1)
-            {
-                result = sigaction(userSignal, ref sig, out SigAction oldu);
-
-                if (oldu.sa_handler != IntPtr.Zero)
-                {
-                    throw new InvalidOperationException($"SIG{userSignal} is already in use.");
-                }
-
-                if (result != 0)
-                {
-                    throw new InvalidOperationException($"Could not register SIG{userSignal} sigaction. Error: {result}");
-                }
-            }
-
-            return old;
-        }
-
-        public static bool RestoreExceptionHandler(SigAction oldAction)
-        {
-            return sigaction(SIGSEGV, ref oldAction, out SigAction _) == 0;
-        }
-    }
-}

src/Ryujinx.Cpu/Signal/NativeSignalHandler.cs

@@ -100,25 +100,13 @@ namespace Ryujinx.Cpu.Signal
 
                     if (customSignalHandlerFactory != null)
                     {
-                        _signalHandlerPtr = customSignalHandlerFactory(Ryujinx.Common.SystemInfo.SystemInfo.IsAndroid() ?
+                        _signalHandlerPtr = customSignalHandlerFactory(UnixSignalHandlerRegistration.GetSegfaultExceptionHandler().sa_handler, _signalHandlerPtr);
-                            AndroidSignalHandlerRegistration.GetSegfaultExceptionHandler().sa_handler :
-                            UnixSignalHandlerRegistration.GetSegfaultExceptionHandler().sa_handler, _signalHandlerPtr);
                     }
 
-                    if (Ryujinx.Common.SystemInfo.SystemInfo.IsAndroid())
+                    var old = UnixSignalHandlerRegistration.RegisterExceptionHandler(_signalHandlerPtr);
-                    {
-                        var old = AndroidSignalHandlerRegistration.RegisterExceptionHandler(_signalHandlerPtr);
 
-                        config.UnixOldSigaction = (nuint)(ulong)old.sa_handler;
+                    config.UnixOldSigaction = (nuint)(ulong)old.sa_handler;
-                        config.UnixOldSigaction3Arg = old.sa_flags & 4;
+                    config.UnixOldSigaction3Arg = old.sa_flags & 4;
-                    }
-                    else
-                    {
-                        var old = UnixSignalHandlerRegistration.RegisterExceptionHandler(_signalHandlerPtr);
-
-                        config.UnixOldSigaction = (nuint)(ulong)old.sa_handler;
-                        config.UnixOldSigaction3Arg = old.sa_flags & 4;
-                    }
                 }
                 else
                 {

src/Ryujinx.Cpu/Signal/UnixSignalHandlerRegistration.cs

@@ -43,6 +43,7 @@ namespace Ryujinx.Cpu.Signal
         private const int SA_SIGINFO = 0x00000004;
         private const int SA_ONSTACK = 0x08000000;
         private const int SS_DISABLE = 2;
+        private const int SS_AUTODISARM = 1 << 31;
 
         [LibraryImport("libc", SetLastError = true)]
         private static partial int sigaction(int signum, ref SigAction sigAction, out SigAction oldAction);
@@ -102,7 +103,7 @@ namespace Ryujinx.Cpu.Signal
                 SigActionBionic sig = new()
                 {
                     sa_handler = action,
-                    sa_flags = SA_SIGINFO
+                    sa_flags = SA_SIGINFO | SA_ONSTACK,
                 };
 
                 sigemptyset(ref sig.sa_mask);
@@ -122,7 +123,7 @@ namespace Ryujinx.Cpu.Signal
                 SigAction sig = new SigAction
                 {
                     sa_handler = action,
-                    sa_flags = SA_SIGINFO
+                    sa_flags = SA_SIGINFO | SA_ONSTACK,
                 };
 
                 sigemptyset(ref sig.sa_mask);
@@ -153,6 +154,7 @@ namespace Ryujinx.Cpu.Signal
             Stack stack = new()
             {
                 ss_sp = stackPtr,
+                ss_flags = SS_AUTODISARM,
                 ss_size = (IntPtr)stackSize
             };
 
@@ -197,7 +199,7 @@ namespace Ryujinx.Cpu.Signal
 
                 if (oldu.sa_handler != IntPtr.Zero)
                 {
-                    throw new SystemException($"SIG{sigNum} is already in use.");
+                    throw new InvalidOperationException($"SIG{sigNum} is already in use.");
                 }
 
                 if (result != 0)
@@ -219,7 +221,7 @@ namespace Ryujinx.Cpu.Signal
 
                 if (oldu.sa_handler != IntPtr.Zero)
                 {
-                    throw new SystemException($"SIG{sigNum} is already in use.");
+                    throw new InvalidOperationException($"SIG{sigNum} is already in use.");
                 }
 
                 if (result != 0)