[cDAC] Implement GetMetadata for cDAC

docs/design/datacontracts/EcmaMetadata.md

@@ -6,6 +6,7 @@ This contract provides methods to get a view of the ECMA-335 metadata for a give
 
 ```csharp
 TargetSpan GetReadOnlyMetadataAddress(ModuleHandle handle);
+TargetSpan GetReadWriteSavedMetadataAddress(ModuleHandle handle);
 System.Reflection.Metadata.MetadataReader? GetMetadata(ModuleHandle handle);
 ```
 

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IEcmaMetadata.cs

@@ -10,6 +10,8 @@ public interface IEcmaMetadata : IContract
 {
     static string IContract.Name { get; } = nameof(EcmaMetadata);
     TargetSpan GetReadOnlyMetadataAddress(ModuleHandle handle) => throw new NotImplementedException();
+    TargetSpan GetReadWriteSavedMetadataAddress(ModuleHandle handle) => throw new NotImplementedException();
+
     MetadataReader? GetMetadata(ModuleHandle module) => throw new NotImplementedException();
 }
 

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/CorDbHResults.cs

@@ -17,4 +17,5 @@ public static class CorDbgHResults
     public const int CORDBG_E_UNSUPPORTED_DELEGATE = unchecked((int)0x80131c68);
     public const int CORDBG_E_ENC_HANGING_FIELD = unchecked((int)0x80131342);
     public const int CLDB_E_FILE_CORRUPT = unchecked((int)0x8013110e);
+    public const int CORDBG_E_MISSING_METADATA = unchecked((int)0x80131c35);
 }

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/EcmaMetadata_1.cs

@@ -393,7 +393,7 @@ private uint GetMetadataGeneration(ModuleHandle handle)
         return module.MetadataGeneration;
     }
 
-    private TargetSpan GetReadWriteSavedMetadataAddress(ModuleHandle handle)
+    public TargetSpan GetReadWriteSavedMetadataAddress(ModuleHandle handle)
     {
         Data.Module module = target.ProcessedData.GetOrAdd<Data.Module>(handle.Address);
         Data.DynamicMetadata dynamicMetadata = target.ProcessedData.GetOrAdd<Data.DynamicMetadata>(module.DynamicMetadata);

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

@@ -348,7 +348,48 @@ public int GetModulePath(ulong vmModule, nint pStrFilename, Interop.BOOL* pResul
     }
 
     public int GetMetadata(ulong vmModule, DacDbiTargetBuffer* pTargetBuffer)
-        => LegacyFallbackHelper.CanFallback() && _legacy is not null ? _legacy.GetMetadata(vmModule, pTargetBuffer) : HResults.E_NOTIMPL;
+    {
+        int hr = HResults.S_OK;
+        try
+        {
+            *pTargetBuffer = default;
+            Contracts.ILoader loader = _target.Contracts.Loader;
+            Contracts.ModuleHandle handle = loader.GetModuleHandleFromModulePtr(new TargetPointer(vmModule));
+            Contracts.ModuleFlags flags = loader.GetFlags(handle);
+            Contracts.IEcmaMetadata ecmaMetadata = _target.Contracts.EcmaMetadata;
+
+            // Dynamic modules keep an eagerly-serialized metadata buffer, while non-dynamic modules read metadata from the loaded PE image.
+            TargetSpan targetSpan = flags.HasFlag(Contracts.ModuleFlags.ReflectionEmit)
+                ? ecmaMetadata.GetReadWriteSavedMetadataAddress(handle)
+                : ecmaMetadata.GetReadOnlyMetadataAddress(handle);
+
+            pTargetBuffer->pAddress = targetSpan.Address.Value;
+            pTargetBuffer->cbSize = checked((uint)targetSpan.Size);
+
+            if (pTargetBuffer->cbSize == 0)
+            {
+                throw Marshal.GetExceptionForHR(CorDbgHResults.CORDBG_E_MISSING_METADATA)!;
+            }
+        }
+        catch (System.Exception ex)
+        {
+            hr = ex.HResult;
+        }
+#if DEBUG
+        if (_legacy is not null)
+        {
+            DacDbiTargetBuffer pTargetBufferLocal = default;
+            int hrLocal = _legacy.GetMetadata(vmModule, pTargetBuffer == null ? null : &pTargetBufferLocal);
+            Debug.ValidateHResult(hr, hrLocal);
+            if (hr == HResults.S_OK)
+            {
+                Debug.Assert(pTargetBuffer->pAddress == pTargetBufferLocal.pAddress, $"pAddress: cDAC: {pTargetBuffer->pAddress:x}, DAC: {pTargetBufferLocal.pAddress:x}");
+                Debug.Assert(pTargetBuffer->cbSize == pTargetBufferLocal.cbSize, $"cbSize: cDAC: {pTargetBuffer->cbSize}, DAC: {pTargetBufferLocal.cbSize}");
+            }
+        }
+#endif
+        return hr;
+    }
 
     public int GetSymbolsBuffer(ulong vmModule, DacDbiTargetBuffer* pTargetBuffer, SymbolFormat* pSymbolFormat)
     {

src/native/managed/cdac/tests/UnitTests/DacDbiImplTests.cs

@@ -1415,4 +1415,103 @@ public void ConvertToNativeVarInfo_MapsAllFields()
         Assert.Equal(5u, nvi.loc.vlsBaseReg);
         Assert.Equal(-0x28, nvi.loc.vlsOffset);
     }
+
+    private static DacDbiImpl CreateDacDbiForModule(
+        MockTarget.Architecture arch,
+        ulong vmModule,
+        Contracts.ModuleHandle handle,
+        ModuleFlags flags,
+        Mock<IEcmaMetadata> mockEcmaMetadata)
+    {
+        var mockLoader = new Mock<ILoader>();
+        mockLoader.Setup(l => l.GetModuleHandleFromModulePtr(new TargetPointer(vmModule))).Returns(handle);
+        mockLoader.Setup(l => l.GetFlags(handle)).Returns(flags);
+
+        var target = new TestPlaceholderTarget.Builder(arch)
+            .UseReader((_, _) => -1)
+            .AddMockContract(mockLoader)
+            .AddMockContract(mockEcmaMetadata)
+            .Build();
+        return new DacDbiImpl(target, legacyObj: null);
+    }
+
+    [Theory]
+    [ClassData(typeof(MockTarget.StdArch))]
+    public void GetMetadata_NonDynamicModule(MockTarget.Architecture arch)
+    {
+        ulong vmModule = 0x1000;
+        TargetPointer moduleAddr = new(0x1000);
+        TargetPointer metadataAddr = new(0xabc0);
+        uint metadataSize = 0x200;
+
+        Contracts.ModuleHandle handle = new(moduleAddr);
+        var mockEcmaMetadata = new Mock<IEcmaMetadata>();
+        mockEcmaMetadata.Setup(e => e.GetReadOnlyMetadataAddress(handle)).Returns(new TargetSpan(metadataAddr, metadataSize));
+
+        DacDbiImpl dacDbi = CreateDacDbiForModule(arch, vmModule, handle, (ModuleFlags)0, mockEcmaMetadata);
+
+        DacDbiTargetBuffer buffer;
+        int hr = dacDbi.GetMetadata(vmModule, &buffer);
+
+        Assert.Equal(System.HResults.S_OK, hr);
+        Assert.Equal(metadataAddr.Value, buffer.pAddress);
+        Assert.Equal(metadataSize, buffer.cbSize);
+        mockEcmaMetadata.Verify(e => e.GetReadWriteSavedMetadataAddress(It.IsAny<Contracts.ModuleHandle>()), Times.Never);
+    }
+
+    [Theory]
+    [ClassData(typeof(MockTarget.StdArch))]
+    public void GetMetadata_DynamicModule(MockTarget.Architecture arch)
+    {
+        ulong vmModule = 0x1000;
+        TargetPointer moduleAddr = new(0x1000);
+        TargetPointer metadataAddr = new(0xdef0);
+        uint metadataSize = 0x80;
+
+        Contracts.ModuleHandle handle = new(moduleAddr);
+        var mockEcmaMetadata = new Mock<IEcmaMetadata>();
+        mockEcmaMetadata.Setup(e => e.GetReadWriteSavedMetadataAddress(handle)).Returns(new TargetSpan(metadataAddr, metadataSize));
+
+        DacDbiImpl dacDbi = CreateDacDbiForModule(arch, vmModule, handle, ModuleFlags.ReflectionEmit, mockEcmaMetadata);
+
+        DacDbiTargetBuffer buffer;
+        int hr = dacDbi.GetMetadata(vmModule, &buffer);
+
+        Assert.Equal(System.HResults.S_OK, hr);
+        Assert.Equal(metadataAddr.Value, buffer.pAddress);
+        Assert.Equal(metadataSize, buffer.cbSize);
+        mockEcmaMetadata.Verify(e => e.GetReadOnlyMetadataAddress(It.IsAny<Contracts.ModuleHandle>()), Times.Never);
+    }
+
+    [Theory]
+    [ClassData(typeof(MockTarget.StdArch))]
+    public void GetMetadata_EmptyMetadata(MockTarget.Architecture arch)
+    {
+        ulong vmModule = 0x1000;
+        TargetPointer moduleAddr = new(0x1000);
+
+        Contracts.ModuleHandle handle = new(moduleAddr);
+        var mockEcmaMetadata = new Mock<IEcmaMetadata>();
+        mockEcmaMetadata.Setup(e => e.GetReadOnlyMetadataAddress(handle)).Returns(new TargetSpan(TargetPointer.Null, 0));
+
+        DacDbiImpl dacDbi = CreateDacDbiForModule(arch, vmModule, handle, (ModuleFlags)0, mockEcmaMetadata);
+
+        DacDbiTargetBuffer buffer;
+        int hr = dacDbi.GetMetadata(vmModule, &buffer);
+
+        Assert.Equal(CorDbgHResults.CORDBG_E_MISSING_METADATA, hr);
+    }
+
+    [Theory]
+    [ClassData(typeof(MockTarget.StdArch))]
+    public void GetMetadata_NullBuffer(MockTarget.Architecture arch)
+    {
+        ulong vmModule = 0x1000;
+        Contracts.ModuleHandle handle = new(new TargetPointer(vmModule));
+        var mockEcmaMetadata = new Mock<IEcmaMetadata>();
+        DacDbiImpl dacDbi = CreateDacDbiForModule(arch, vmModule, handle, (ModuleFlags)0, mockEcmaMetadata);
+
+        int hr = dacDbi.GetMetadata(vmModule, null);
+        Assert.Equal(System.HResults.E_POINTER, hr);
+    }
 }