[cDAC] Implement GetModuleForAssembly for cDAC

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs

@@ -283,7 +283,32 @@ public int GetAssemblyInfo(ulong vmAssembly, DacDbiAssemblyInfo* pData)
         => LegacyFallbackHelper.CanFallback() && _legacy is not null ? _legacy.GetAssemblyInfo(vmAssembly, pData) : HResults.E_NOTIMPL;
 
     public int GetModuleForAssembly(ulong vmAssembly, ulong* pModule)
-        => LegacyFallbackHelper.CanFallback() && _legacy is not null ? _legacy.GetModuleForAssembly(vmAssembly, pModule) : HResults.E_NOTIMPL;
+    {
+        *pModule = 0;
+        int hr = HResults.S_OK;
+        try
+        {
+            Contracts.ILoader loader = _target.Contracts.Loader;
+            Contracts.ModuleHandle handle = loader.GetModuleHandleFromAssemblyPtr(new TargetPointer(vmAssembly));
+            TargetPointer modulePtr = loader.GetModule(handle);
+            *pModule = modulePtr.Value;
+        }
+        catch (System.Exception ex)
+        {
+            hr = ex.HResult;
+        }
+#if DEBUG
+        if (_legacy is not null)
+        {
+            ulong moduleLocal;
+            int hrLocal = _legacy.GetModuleForAssembly(vmAssembly, &moduleLocal);
+            Debug.ValidateHResult(hr, hrLocal);
+            if (hr == HResults.S_OK)
+                Debug.Assert(*pModule == moduleLocal, $"cDAC: {*pModule:x}, DAC: {moduleLocal:x}");
+        }
+#endif
+        return hr;
+    }
 
     public int GetAddressType(ulong address, int* pRetVal)
         => LegacyFallbackHelper.CanFallback() && _legacy is not null ? _legacy.GetAddressType(address, pRetVal) : HResults.E_NOTIMPL;

src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiLoaderDumpTests.cs

@@ -44,6 +44,43 @@ public void GetAppDomainFullName_ReturnsNonEmpty(TestConfiguration config)
         Assert.False(string.IsNullOrEmpty(holder.Value), "AppDomain name should not be empty");
     }
 
+    [ConditionalTheory]
+    [MemberData(nameof(TestConfigurations))]
+    public unsafe void GetModuleForAssembly_ReturnsExpectedModule(TestConfiguration config)
+    {
+        InitializeDumpTest(config);
+        DacDbiImpl dbi = CreateDacDbi();
+        ILoader loader = Target.Contracts.Loader;
+
+        bool testedAtLeastOne = false;
+        foreach (ModuleHandle module in GetAllModules())
+        {
+            TargetPointer assemblyPtr = loader.GetAssembly(module);
+            TargetPointer expectedModulePtr = loader.GetModule(module);
+
+            ulong resultModule;
+            int hr = dbi.GetModuleForAssembly(assemblyPtr.Value, &resultModule);
+            Assert.Equal(System.HResults.S_OK, hr);
+            Assert.NotEqual(0UL, resultModule);
+            Assert.Equal(expectedModulePtr.Value, resultModule);
+            testedAtLeastOne = true;
+        }
+        Assert.True(testedAtLeastOne, "Expected at least one module in the dump");
+    }
+
+    [ConditionalTheory]
+    [MemberData(nameof(TestConfigurations))]
+    public unsafe void GetModuleForAssembly_InvalidAssembly(TestConfiguration config)
+    {
+        InitializeDumpTest(config);
+        DacDbiImpl dbi = CreateDacDbi();
+
+        ulong resultModule = ulong.MaxValue;
+        int hr = dbi.GetModuleForAssembly(0, &resultModule);
+        Assert.NotEqual(System.HResults.S_OK, hr);
+        Assert.Equal(0UL, resultModule);
+    }
+
     [ConditionalTheory]
     [MemberData(nameof(TestConfigurations))]
     public unsafe void GetTypeHandle_ReturnsMethodTableForTypeDef(TestConfiguration config)