Fix Massive Bug Preventing UE5 Titles From Booting (#406)

* Fix cross platform memcpy bug
2026-07-22 19:06:15 +08:00 · 2026-07-18 12:50:59 -06:00
parent 94153955b0
commit daaeb6213e
4 changed files with 173 additions and 6 deletions
@@ -0,0 +1,153 @@
+// Copyright (C) 2026 SharpEmu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+using SharpEmu.Core.Cpu.Native;
+using SharpEmu.HLE;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Xunit;
+
+namespace SharpEmu.Libs.Tests.Cpu;
+
+public sealed class MemcpyHleRoutingTests
+{
+    private const string MemcpyNid = "Q3VBxCXhUHs";
+    private const string MemsetNid = "QrZZdJ8XsX0";
+    private const string RdtscNid = "-2IRUCO--PM";
+
+    [Fact]
+    public void IsHlePreferredNid_PrefersHleForMemcpy_OnEveryPlatform()
+    {
+        Assert.True(
+            InvokeIsHlePreferredNid(MemcpyNid),
+            $"memcpy ({MemcpyNid}) must route through HLE on every platform. It was previously " +
+            "gated behind OperatingSystem.IsWindows(), which left Linux and macOS on the LLE " +
+            "intrinsic stub and faulted in guest code. Do not reintroduce an OS condition here.");
+    }
+
+    [Fact]
+    public void IsHlePreferredNid_PrefersHleForMemset()
+    {
+        Assert.True(
+            InvokeIsHlePreferredNid(MemsetNid),
+            $"memset ({MemsetNid}) must route through HLE on every platform.");
+    }
+
+    [Fact]
+    public void TryCreateNativeImportIntrinsic_DoesNotClaimMemcpy()
+    {
+        if (RuntimeInformation.ProcessArchitecture != Architecture.X64)
+        {
+            return;
+        }
+
+        var claimed = InvokeTryCreateNativeImportIntrinsic(MemcpyNid, out var address);
+
+        Assert.False(
+            claimed,
+            $"memcpy ({MemcpyNid}) must fall through to the HLE trampoline. SetupImportStubs tries " +
+            "the intrinsic stub before the trampoline, so without an IsHlePreferredNid guard here " +
+            "the intrinsic claims memcpy and the HLE routing never takes effect.");
+        Assert.Equal(0, address);
+    }
+
+    [Fact]
+    public void TryCreateNativeImportIntrinsic_StillClaimsNonHleNids()
+    {
+        if (RuntimeInformation.ProcessArchitecture != Architecture.X64)
+        {
+            return;
+        }
+
+        var claimed = InvokeTryCreateNativeImportIntrinsic(RdtscNid, out var address);
+
+        Assert.True(
+            claimed,
+            $"rdtsc ({RdtscNid}) has no HLE handler and must still receive an intrinsic stub. If " +
+            "this fails the memcpy assertions above may be passing vacuously.");
+        Assert.NotEqual(0, address);
+
+        unsafe
+        {
+            Assert.True(HostMemory.Free((void*)address, 0, HostMemory.MEM_RELEASE));
+        }
+    }
+
+    [Fact]
+    public void IsHlePreferredNid_DoesNotBranchOnHostOperatingSystem()
+    {
+        var method = typeof(DirectExecutionBackend).GetMethod(
+            "IsHlePreferredNid",
+            BindingFlags.Static | BindingFlags.NonPublic);
+        Assert.NotNull(method);
+
+        var callees = ResolveCallees(method);
+
+        Assert.DoesNotContain(callees, static name =>
+            name is "IsWindows" or "IsLinux" or "IsMacOS" or "IsOSPlatform" or "IsFreeBSD");
+    }
+
+    private static HashSet<string> ResolveCallees(MethodBase method)
+    {
+        var il = method.GetMethodBody()?.GetILAsByteArray();
+        Assert.NotNull(il);
+
+        var module = method.Module;
+        var generic = method.DeclaringType?.GetGenericArguments();
+        var callees = new HashSet<string>(StringComparer.Ordinal);
+
+        for (var i = 0; i + 4 < il.Length; i++)
+        {
+            if (il[i] is not (0x28 or 0x6F))
+            {
+                continue;
+            }
+
+            var token = BitConverter.ToInt32(il, i + 1);
+            try
+            {
+                var callee = module.ResolveMethod(token, generic, null);
+                if (callee?.Name is { } name)
+                {
+                    callees.Add(name);
+                }
+            }
+            catch (ArgumentException)
+            {
+            }
+        }
+
+        return callees;
+    }
+
+    private static bool InvokeIsHlePreferredNid(string nid)
+    {
+        var method = typeof(DirectExecutionBackend).GetMethod(
+            "IsHlePreferredNid",
+            BindingFlags.Static | BindingFlags.NonPublic);
+        Assert.NotNull(method);
+        return (bool)method.Invoke(null, [nid])!;
+    }
+
+    private static bool InvokeTryCreateNativeImportIntrinsic(string nid, out nint address)
+    {
+        var backend = (DirectExecutionBackend)RuntimeHelpers.GetUninitializedObject(
+            typeof(DirectExecutionBackend));
+        var trampolineList = typeof(DirectExecutionBackend).GetField(
+            "_importHandlerTrampolines",
+            BindingFlags.Instance | BindingFlags.NonPublic);
+        Assert.NotNull(trampolineList);
+        trampolineList.SetValue(backend, new List<nint>());
+
+        var method = typeof(DirectExecutionBackend).GetMethod(
+            "TryCreateNativeImportIntrinsic",
+            BindingFlags.Instance | BindingFlags.NonPublic);
+        Assert.NotNull(method);
+
+        object?[] args = [nid, null];
+        var claimed = (bool)method.Invoke(backend, args)!;
+        address = (nint)args[1]!;
+        return claimed;
+    }
+}