1 files changed, 260 insertions, 0 deletions
diff --git a/src/ARMeilleure/Signal/NativeSignalHandlerGenerator.cs b/src/ARMeilleure/Signal/NativeSignalHandlerGenerator.cs
new file mode 100644
index 00000000..c5e708e1
--- /dev/null
+++ b/src/ARMeilleure/Signal/NativeSignalHandlerGenerator.cs
@@ -0,0 +1,260 @@
+using ARMeilleure.IntermediateRepresentation;
+using ARMeilleure.Translation;
+using System;
+using System.Runtime.InteropServices;
+using static ARMeilleure.IntermediateRepresentation.Operand.Factory;
+
+namespace ARMeilleure.Signal
+{
+    public static class NativeSignalHandlerGenerator
+    {
+        public const int MaxTrackedRanges = 8;
+
+        private const int StructAddressOffset = 0;
+        private const int StructWriteOffset = 4;
+        private const int UnixOldSigaction = 8;
+        private const int UnixOldSigaction3Arg = 16;
+        private const int RangeOffset = 20;
+
+        private const int EXCEPTION_CONTINUE_SEARCH = 0;
+        private const int EXCEPTION_CONTINUE_EXECUTION = -1;
+
+        private const uint EXCEPTION_ACCESS_VIOLATION = 0xc0000005;
+
+        private static Operand EmitGenericRegionCheck(EmitterContext context, IntPtr signalStructPtr, Operand faultAddress, Operand isWrite, int rangeStructSize, ulong pageSize)
+        {
+            ulong pageMask = pageSize - 1;
+
+            Operand inRegionLocal = context.AllocateLocal(OperandType.I32);
+            context.Copy(inRegionLocal, Const(0));
+
+            Operand endLabel = Label();
+
+            for (int i = 0; i < MaxTrackedRanges; i++)
+            {
+                ulong rangeBaseOffset = (ulong)(RangeOffset + i * rangeStructSize);
+
+                Operand nextLabel = Label();
+
+                Operand isActive = context.Load(OperandType.I32, Const((ulong)signalStructPtr + rangeBaseOffset));
+
+                context.BranchIfFalse(nextLabel, isActive);
+
+                Operand rangeAddress = context.Load(OperandType.I64, Const((ulong)signalStructPtr + rangeBaseOffset + 4));
+                Operand rangeEndAddress = context.Load(OperandType.I64, Const((ulong)signalStructPtr + rangeBaseOffset + 12));
+
+                // Is the fault address within this tracked region?
+                Operand inRange = context.BitwiseAnd(
+                    context.ICompare(faultAddress, rangeAddress, Comparison.GreaterOrEqualUI),
+                    context.ICompare(faultAddress, rangeEndAddress, Comparison.LessUI));
+
+                // Only call tracking if in range.
+                context.BranchIfFalse(nextLabel, inRange, BasicBlockFrequency.Cold);
+
+                Operand offset = context.BitwiseAnd(context.Subtract(faultAddress, rangeAddress), Const(~pageMask));
+
+                // Call the tracking action, with the pointer's relative offset to the base address.
+                Operand trackingActionPtr = context.Load(OperandType.I64, Const((ulong)signalStructPtr + rangeBaseOffset + 20));
+
+                context.Copy(inRegionLocal, Const(0));
+
+                Operand skipActionLabel = Label();
+
+                // Tracking action should be non-null to call it, otherwise assume false return.
+                context.BranchIfFalse(skipActionLabel, trackingActionPtr);
+                Operand result = context.Call(trackingActionPtr, OperandType.I32, offset, Const(pageSize), isWrite);
+                context.Copy(inRegionLocal, result);
+
+                context.MarkLabel(skipActionLabel);
+
+                // If the tracking action returns false or does not exist, it might be an invalid access due to a partial overlap on Windows.
+                if (OperatingSystem.IsWindows())
+                {
+                    context.BranchIfTrue(endLabel, inRegionLocal);
+
+                    context.Copy(inRegionLocal, WindowsPartialUnmapHandler.EmitRetryFromAccessViolation(context));
+                }
+
+                context.Branch(endLabel);
+
+                context.MarkLabel(nextLabel);
+            }
+
+            context.MarkLabel(endLabel);
+
+            return context.Copy(inRegionLocal);
+        }
+
+        private static Operand GenerateUnixFaultAddress(EmitterContext context, Operand sigInfoPtr)
+        {
+            ulong structAddressOffset = OperatingSystem.IsMacOS() ? 24ul : 16ul; // si_addr
+            return context.Load(OperandType.I64, context.Add(sigInfoPtr, Const(structAddressOffset)));
+        }
+
+        private static Operand GenerateUnixWriteFlag(EmitterContext context, Operand ucontextPtr)
+        {
+            if (OperatingSystem.IsMacOS())
+            {
+                const ulong McontextOffset = 48; // uc_mcontext
+                Operand ctxPtr = context.Load(OperandType.I64, context.Add(ucontextPtr, Const(McontextOffset)));
+
+                if (RuntimeInformation.ProcessArchitecture == Architecture.Arm64)
+                {
+                    const ulong EsrOffset = 8; // __es.__esr
+                    Operand esr = context.Load(OperandType.I64, context.Add(ctxPtr, Const(EsrOffset)));
+                    return context.BitwiseAnd(esr, Const(0x40ul));
+                }
+                else if (RuntimeInformation.ProcessArchitecture == Architecture.X64)
+                {
+                    const ulong ErrOffset = 4; // __es.__err
+                    Operand err = context.Load(OperandType.I64, context.Add(ctxPtr, Const(ErrOffset)));
+                    return context.BitwiseAnd(err, Const(2ul));
+                }
+            }
+            else if (OperatingSystem.IsLinux())
+            {
+                if (RuntimeInformation.ProcessArchitecture == Architecture.Arm64)
+                {
+                    Operand auxPtr = context.AllocateLocal(OperandType.I64);
+
+                    Operand loopLabel = Label();
+                    Operand successLabel = Label();
+
+                    const ulong AuxOffset = 464; // uc_mcontext.__reserved
+                    const uint EsrMagic = 0x45535201;
+
+                    context.Copy(auxPtr, context.Add(ucontextPtr, Const(AuxOffset)));
+
+                    context.MarkLabel(loopLabel);
+
+                    // _aarch64_ctx::magic
+                    Operand magic = context.Load(OperandType.I32, auxPtr);
+                    // _aarch64_ctx::size
+                    Operand size = context.Load(OperandType.I32, context.Add(auxPtr, Const(4ul)));
+
+                    context.BranchIf(successLabel, magic, Const(EsrMagic), Comparison.Equal);
+
+                    context.Copy(auxPtr, context.Add(auxPtr, context.ZeroExtend32(OperandType.I64, size)));
+
+                    context.Branch(loopLabel);
+
+                    context.MarkLabel(successLabel);
+
+                    // esr_context::esr
+                    Operand esr = context.Load(OperandType.I64, context.Add(auxPtr, Const(8ul)));
+                    return context.BitwiseAnd(esr, Const(0x40ul));
+                }
+                else if (RuntimeInformation.ProcessArchitecture == Architecture.X64)
+                {
+                    const int ErrOffset = 192; // uc_mcontext.gregs[REG_ERR]
+                    Operand err = context.Load(OperandType.I64, context.Add(ucontextPtr, Const(ErrOffset)));
+                    return context.BitwiseAnd(err, Const(2ul));
+                }
+            }
+
+            throw new PlatformNotSupportedException();
+        }
+
+        public static byte[] GenerateUnixSignalHandler(IntPtr signalStructPtr, int rangeStructSize, ulong pageSize)
+        {
+            EmitterContext context = new();
+
+            // (int sig, SigInfo* sigInfo, void* ucontext)
+            Operand sigInfoPtr = context.LoadArgument(OperandType.I64, 1);
+            Operand ucontextPtr = context.LoadArgument(OperandType.I64, 2);
+
+            Operand faultAddress = GenerateUnixFaultAddress(context, sigInfoPtr);
+            Operand writeFlag = GenerateUnixWriteFlag(context, ucontextPtr);
+
+            Operand isWrite = context.ICompareNotEqual(writeFlag, Const(0L)); // Normalize to 0/1.
+
+            Operand isInRegion = EmitGenericRegionCheck(context, signalStructPtr, faultAddress, isWrite, rangeStructSize, pageSize);
+
+            Operand endLabel = Label();
+
+            context.BranchIfTrue(endLabel, isInRegion);
+
+            Operand unixOldSigaction = context.Load(OperandType.I64, Const((ulong)signalStructPtr + UnixOldSigaction));
+            Operand unixOldSigaction3Arg = context.Load(OperandType.I64, Const((ulong)signalStructPtr + UnixOldSigaction3Arg));
+            Operand threeArgLabel = Label();
+
+            context.BranchIfTrue(threeArgLabel, unixOldSigaction3Arg);
+
+            context.Call(unixOldSigaction, OperandType.None, context.LoadArgument(OperandType.I32, 0));
+            context.Branch(endLabel);
+
+            context.MarkLabel(threeArgLabel);
+
+            context.Call(unixOldSigaction,
+                OperandType.None,
+                context.LoadArgument(OperandType.I32, 0),
+                sigInfoPtr,
+                context.LoadArgument(OperandType.I64, 2)
+                );
+
+            context.MarkLabel(endLabel);
+
+            context.Return();
+
+            ControlFlowGraph cfg = context.GetControlFlowGraph();
+
+            OperandType[] argTypes = new OperandType[] { OperandType.I32, OperandType.I64, OperandType.I64 };
+
+            return Compiler.Compile(cfg, argTypes, OperandType.None, CompilerOptions.HighCq, RuntimeInformation.ProcessArchitecture).Code;
+        }
+
+        public static byte[] GenerateWindowsSignalHandler(IntPtr signalStructPtr, int rangeStructSize, ulong pageSize)
+        {
+            EmitterContext context = new();
+
+            // (ExceptionPointers* exceptionInfo)
+            Operand exceptionInfoPtr = context.LoadArgument(OperandType.I64, 0);
+            Operand exceptionRecordPtr = context.Load(OperandType.I64, exceptionInfoPtr);
+
+            // First thing's first - this catches a number of exceptions, but we only want access violations.
+            Operand validExceptionLabel = Label();
+
+            Operand exceptionCode = context.Load(OperandType.I32, exceptionRecordPtr);
+
+            context.BranchIf(validExceptionLabel, exceptionCode, Const(EXCEPTION_ACCESS_VIOLATION), Comparison.Equal);
+
+            context.Return(Const(EXCEPTION_CONTINUE_SEARCH)); // Don't handle this one.
+
+            context.MarkLabel(validExceptionLabel);
+
+            // Next, read the address of the invalid access, and whether it is a write or not.
+
+            Operand structAddressOffset = context.Load(OperandType.I32, Const((ulong)signalStructPtr + StructAddressOffset));
+            Operand structWriteOffset = context.Load(OperandType.I32, Const((ulong)signalStructPtr + StructWriteOffset));
+
+            Operand faultAddress = context.Load(OperandType.I64, context.Add(exceptionRecordPtr, context.ZeroExtend32(OperandType.I64, structAddressOffset)));
+            Operand writeFlag = context.Load(OperandType.I64, context.Add(exceptionRecordPtr, context.ZeroExtend32(OperandType.I64, structWriteOffset)));
+
+            Operand isWrite = context.ICompareNotEqual(writeFlag, Const(0L)); // Normalize to 0/1.
+
+            Operand isInRegion = EmitGenericRegionCheck(context, signalStructPtr, faultAddress, isWrite, rangeStructSize, pageSize);
+
+            Operand endLabel = Label();
+
+            // If the region check result is false, then run the next vectored exception handler.
+
+            context.BranchIfTrue(endLabel, isInRegion);
+
+            context.Return(Const(EXCEPTION_CONTINUE_SEARCH));
+
+            context.MarkLabel(endLabel);
+
+            // Otherwise, return to execution.
+
+            context.Return(Const(EXCEPTION_CONTINUE_EXECUTION));
+
+            // Compile and return the function.
+
+            ControlFlowGraph cfg = context.GetControlFlowGraph();
+
+            OperandType[] argTypes = new OperandType[] { OperandType.I64 };
+
+            return Compiler.Compile(cfg, argTypes, OperandType.I32, CompilerOptions.HighCq, RuntimeInformation.ProcessArchitecture).Code;
+        }
+    }
+}