[release/6.0] Add alignment to mapped field stream

src/libraries/System.Reflection.Metadata/src/System.Reflection.Metadata.csproj

@@ -6,6 +6,8 @@
     <TargetFrameworks>$(NetCoreAppCurrent);netstandard2.0;net461</TargetFrameworks>
     <Nullable>enable</Nullable>
     <IsPackable>true</IsPackable>
+    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+    <ServicingVersion>1</ServicingVersion>
     <PackageDescription>This packages provides a low-level .NET (ECMA-335) metadata reader and writer. It's geared for performance and is the ideal choice for building higher-level libraries that intend to provide their own object model, such as compilers.
 
 Commonly Used Types:

src/libraries/System.Reflection.Metadata/src/System/Reflection/PortableExecutable/ManagedTextSection.cs

@@ -121,7 +121,7 @@ public ManagedTextSection(
 
         public const int MappedFieldDataAlignment = 8;
 
-        public int CalculateOffsetToMappedFieldDataStream()
+        internal int CalculateOffsetToMappedFieldDataStreamUnaligned()
         {
             int result = ComputeOffsetToImportTable();
 
@@ -135,6 +135,16 @@ public int CalculateOffsetToMappedFieldDataStream()
             return result;
         }
 
+        public int CalculateOffsetToMappedFieldDataStream()
+        {
+             int result = CalculateOffsetToMappedFieldDataStreamUnaligned();
+             if (MappedFieldDataSize != 0)
+             {
+                 result = BitArithmetic.Align(result, MappedFieldDataAlignment);
+             }
+             return result;
+        }
+
         internal int ComputeOffsetToDebugDirectory()
         {
             Debug.Assert(MetadataSize % 4 == 0);
@@ -185,7 +195,7 @@ public int GetEntryPointAddress(int rva)
         {
             // TODO: constants
             return RequiresStartupStub ?
-                rva + CalculateOffsetToMappedFieldDataStream() - (Is32Bit ? 6 : 10) :
+                rva + CalculateOffsetToMappedFieldDataStreamUnaligned() - (Is32Bit ? 6 : 10) :
                 0;
         }
 
@@ -293,6 +303,8 @@ public void Serialize(
             // mapped field data:
             if (mappedFieldDataBuilderOpt != null)
             {
+                if (mappedFieldDataBuilderOpt.Count != 0)
+                    builder.Align(MappedFieldDataAlignment);
                 builder.LinkSuffix(mappedFieldDataBuilderOpt);
             }
 

src/libraries/System.Reflection.Metadata/tests/PortableExecutable/PEBuilderTests.cs

@@ -64,7 +64,8 @@ private static void WritePEImage(
             Blob mvidFixup = default(Blob),
             byte[] privateKeyOpt = null,
             bool publicSigned = false,
-            Machine machine = 0)
+            Machine machine = 0,
+            BlobBuilder? mappedFieldData = null)
         {
             var peHeaderBuilder = new PEHeaderBuilder(imageCharacteristics: entryPointHandle.IsNil ? Characteristics.Dll : Characteristics.ExecutableImage,
                                                       machine: machine);
@@ -75,7 +76,8 @@ private static void WritePEImage(
                 ilBuilder,
                 entryPoint: entryPointHandle,
                 flags: CorFlags.ILOnly | (privateKeyOpt != null || publicSigned ? CorFlags.StrongNameSigned : 0),
-                deterministicIdProvider: content => s_contentId);
+                deterministicIdProvider: content => s_contentId,
+                mappedFieldData: mappedFieldData);
 
             var peBlob = new BlobBuilder();
 
@@ -487,6 +489,98 @@ private static MethodDefinitionHandle ComplexEmit(MetadataBuilder metadata, Blob
             return default(MethodDefinitionHandle);
         }
 
+        [Theory] // Validate FieldRVA alignment on common machine types
+        [MemberData(nameof(AllMachineTypes))]
+        public void FieldRVAAlignmentVerify(Machine machine)
+        {
+            using (var peStream = new MemoryStream())
+            {
+                var ilBuilder = new BlobBuilder();
+                var mappedRVADataBuilder = new BlobBuilder();
+                var metadataBuilder = new MetadataBuilder();
+                double validationNumber = 0.100001;
+                var fieldDef = FieldRVAValidationEmit(metadataBuilder, mappedRVADataBuilder, validationNumber);
+
+                WritePEImage(peStream, metadataBuilder, ilBuilder, default(MethodDefinitionHandle),
+                    mappedFieldData: mappedRVADataBuilder,
+                    machine: machine);
+
+                // Validate FieldRVA is aligned as ManagedPEBuilder.MappedFieldDataAlignemnt
+                peStream.Position = 0;
+                using (var peReader = new PEReader(peStream, PEStreamOptions.LeaveOpen))
+                {
+                    var mdReader = peReader.GetMetadataReader();
+
+                    // Validate that there is only 1 field rva entry
+                    Assert.Equal(1, mdReader.FieldRvaTable.NumberOfRows);
+
+                    // Validate that the RVA is aligned properly (which should be at least an 8 byte alignment
+                    Assert.Equal(0, mdReader.FieldRvaTable.GetRva(1) % ManagedPEBuilder.MappedFieldDataAlignment);
+
+                    // Validate that the correct data is at the RVA
+                    var fieldRVAData = peReader.GetSectionData(mdReader.FieldRvaTable.GetRva(1));
+                    Assert.Equal(validationNumber, fieldRVAData.GetReader().ReadDouble());
+                }
+
+                VerifyPE(peStream, machine);
+            }
+        }
+
+        private static FieldDefinitionHandle FieldRVAValidationEmit(MetadataBuilder metadata, BlobBuilder mappedRVAData, double doubleToWriteAsData)
+        {
+            metadata.AddModule(
+                0,
+                metadata.GetOrAddString("ConsoleApplication.exe"),
+                metadata.GetOrAddGuid(s_guid),
+                default(GuidHandle),
+                default(GuidHandle));
+
+            metadata.AddAssembly(
+                metadata.GetOrAddString("ConsoleApplication"),
+                version: new Version(1, 0, 0, 0),
+                culture: default(StringHandle),
+                publicKey: metadata.GetOrAddBlob(ImmutableArray.Create(Misc.KeyPair_PublicKey)),
+                flags: AssemblyFlags.PublicKey,
+                hashAlgorithm: AssemblyHashAlgorithm.Sha1);
+
+            var mscorlibAssemblyRef = metadata.AddAssemblyReference(
+                name: metadata.GetOrAddString("mscorlib"),
+                version: new Version(4, 0, 0, 0),
+                culture: default(StringHandle),
+                publicKeyOrToken: metadata.GetOrAddBlob(ImmutableArray.Create<byte>(0xB7, 0x7A, 0x5C, 0x56, 0x19, 0x34, 0xE0, 0x89)),
+                flags: default(AssemblyFlags),
+                hashValue: default(BlobHandle));
+
+            var systemObjectTypeRef = metadata.AddTypeReference(
+                mscorlibAssemblyRef,
+                metadata.GetOrAddString("System"),
+                metadata.GetOrAddString("Object"));
+
+            mappedRVAData.WriteDouble(doubleToWriteAsData);
+
+            var rvaFieldSignature = new BlobBuilder();
+
+            new BlobEncoder(rvaFieldSignature).
+                FieldSignature().Double();
+
+            var fieldRVADef = metadata.AddFieldDefinition(
+            FieldAttributes.Public | FieldAttributes.Static | FieldAttributes.HasFieldRVA,
+            metadata.GetOrAddString("RvaField"),
+            metadata.GetOrAddBlob(rvaFieldSignature));
+
+            metadata.AddFieldRelativeVirtualAddress(fieldRVADef, 0);
+
+            metadata.AddTypeDefinition(
+                TypeAttributes.Class | TypeAttributes.Public | TypeAttributes.AutoLayout | TypeAttributes.BeforeFieldInit,
+                metadata.GetOrAddString("ConsoleApplication"),
+                metadata.GetOrAddString("Program"),
+                systemObjectTypeRef,
+                fieldList: fieldRVADef,
+                methodList: MetadataTokens.MethodDefinitionHandle(1));
+
+            return fieldRVADef;
+        }
+
         private class TestResourceSectionBuilder : ResourceSectionBuilder
         {
             public TestResourceSectionBuilder()