Add ILStrip task to trim method bodies (#57359)

This is used for iOS when assemblies are FullAOT compiled since the method body IL is unnecessary there.

3 files changed, 310 insertions, 1 deletions

diff --git a/src/tasks/ILStripTask/ILStrip.cs b/src/tasks/ILStripTask/ILStrip.cs
new file mode 100644
index 00000000000..7ce5a5ecc07
--- /dev/null
+++ b/src/tasks/ILStripTask/ILStrip.cs
@@ -0,0 +1,277 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.IO;
+using System.Collections;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Microsoft.Build.Framework;
+using Microsoft.Build.Utilities;
+using Mono.Cecil;
+using Mono.Cecil.Binary;
+using Mono.Cecil.Cil;
+using Mono.Cecil.Metadata;
+
+public class ILStrip : Microsoft.Build.Utilities.Task
+{
+    /// <summary>
+    /// Assemblies to be stripped.
+    /// The assemblies will be modified in place if OutputPath metadata is not set.
+    /// </summary>
+    [Required]
+    public ITaskItem[] Assemblies { get; set; } = Array.Empty<ITaskItem>();
+
+    /// <summary>
+    /// Disable parallel stripping
+    /// </summary>
+    public bool DisableParallelStripping { get; set; }
+
+    public override bool Execute()
+    {
+        if (Assemblies.Length == 0)
+        {
+            throw new ArgumentException($"'{nameof(Assemblies)}' is required.", nameof(Assemblies));
+        }
+
+        if (DisableParallelStripping)
+        {
+            foreach (var assemblyItem in Assemblies)
+            {
+                if (!StripAssembly(assemblyItem))
+                    return !Log.HasLoggedErrors;
+            }
+        }
+        else
+        {
+            Parallel.ForEach(Assemblies,
+                new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount },
+                assemblyItem => StripAssembly(assemblyItem));
+        }
+
+        return !Log.HasLoggedErrors;
+    }
+
+    private bool StripAssembly(ITaskItem assemblyItem)
+    {
+        string assemblyFile = assemblyItem.ItemSpec;
+        var outputPath = assemblyItem.GetMetadata("OutputPath");
+        if (String.IsNullOrWhiteSpace(outputPath))
+        {
+            outputPath = assemblyFile;
+        	Log.LogMessage(MessageImportance.Low, $"[ILStrip] {assemblyFile}");
+        }
+		else
+		{
+        	Log.LogMessage(MessageImportance.Low, $"[ILStrip] {assemblyFile} to {outputPath}");
+		}
+
+        try
+        {
+            AssemblyDefinition assembly = AssemblyFactory.GetAssembly(assemblyFile);
+            AssemblyStripper.StripAssembly(assembly, outputPath);
+        }
+        catch (Exception ex)
+        {
+            Log.LogMessage(MessageImportance.Low, ex.ToString());
+            Log.LogError($"ILStrip failed for {assemblyFile}: {ex.Message}");
+            return false;
+        }
+
+        return true;
+    }
+
+    private class AssemblyStripper
+    {
+        AssemblyDefinition assembly;
+        BinaryWriter writer;
+
+        Image original;
+        Image stripped;
+
+        ReflectionWriter reflection_writer;
+        MetadataWriter metadata_writer;
+
+        TablesHeap original_tables;
+        TablesHeap stripped_tables;
+
+        AssemblyStripper(AssemblyDefinition assembly, BinaryWriter writer)
+        {
+            this.assembly = assembly;
+            this.writer = writer;
+        }
+
+        void Strip()
+        {
+            FullLoad();
+            ClearMethodBodies();
+            CopyOriginalImage();
+            PatchMethods();
+            PatchFields();
+            PatchResources();
+            Write();
+        }
+
+        void FullLoad()
+        {
+            assembly.MainModule.FullLoad();
+        }
+
+        void ClearMethodBodies()
+        {
+            foreach (TypeDefinition type in assembly.MainModule.Types)
+            {
+                ClearMethodBodies(type.Constructors);
+                ClearMethodBodies(type.Methods);
+            }
+        }
+
+        static void ClearMethodBodies(ICollection methods)
+        {
+            foreach (MethodDefinition method in methods)
+            {
+                if (!method.HasBody)
+                    continue;
+
+                MethodBody body = new MethodBody(method);
+                body.CilWorker.Emit(OpCodes.Ret);
+
+                method.Body = body;
+            }
+        }
+
+        void CopyOriginalImage()
+        {
+            original = assembly.MainModule.Image;
+            stripped = Image.CreateImage();
+
+            stripped.Accept(new CopyImageVisitor(original));
+
+            assembly.MainModule.Image = stripped;
+
+            original_tables = original.MetadataRoot.Streams.TablesHeap;
+            stripped_tables = stripped.MetadataRoot.Streams.TablesHeap;
+
+            TableCollection tables = original_tables.Tables;
+            foreach (IMetadataTable table in tables)
+                stripped_tables.Tables.Add(table);
+
+            stripped_tables.Valid = original_tables.Valid;
+            stripped_tables.Sorted = original_tables.Sorted;
+
+            reflection_writer = new ReflectionWriter(assembly.MainModule);
+            reflection_writer.StructureWriter = new StructureWriter(assembly, writer);
+            reflection_writer.CodeWriter.Stripped = true;
+
+            metadata_writer = reflection_writer.MetadataWriter;
+
+            PatchHeap(metadata_writer.StringWriter, original.MetadataRoot.Streams.StringsHeap);
+            PatchHeap(metadata_writer.GuidWriter, original.MetadataRoot.Streams.GuidHeap);
+            PatchHeap(metadata_writer.UserStringWriter, original.MetadataRoot.Streams.UserStringsHeap);
+            PatchHeap(metadata_writer.BlobWriter, original.MetadataRoot.Streams.BlobHeap);
+
+            if (assembly.EntryPoint != null)
+                metadata_writer.EntryPointToken = assembly.EntryPoint.MetadataToken.ToUInt();
+        }
+
+        static void PatchHeap(MemoryBinaryWriter heap_writer, MetadataHeap heap)
+        {
+            if (heap == null)
+                return;
+
+            heap_writer.BaseStream.Position = 0;
+            heap_writer.Write(heap.Data);
+        }
+
+        void PatchMethods()
+        {
+            MethodTable methodTable = (MethodTable)stripped_tables[MethodTable.RId];
+            if (methodTable == null)
+                return;
+
+            RVA method_rva = RVA.Zero;
+
+            for (int i = 0; i < methodTable.Rows.Count; i++)
+            {
+                MethodRow methodRow = methodTable[i];
+
+                methodRow.ImplFlags |= MethodImplAttributes.NoInlining;
+
+                MetadataToken methodToken = MetadataToken.FromMetadataRow(TokenType.Method, i);
+
+                MethodDefinition method = (MethodDefinition)assembly.MainModule.LookupByToken(methodToken);
+
+                if (method.HasBody)
+                {
+                    method_rva = method_rva != RVA.Zero
+                        ? method_rva
+                        : reflection_writer.CodeWriter.WriteMethodBody(method);
+
+                    methodRow.RVA = method_rva;
+                }
+                else
+                    methodRow.RVA = RVA.Zero;
+            }
+        }
+
+        void PatchFields()
+        {
+            FieldRVATable fieldRvaTable = (FieldRVATable)stripped_tables[FieldRVATable.RId];
+            if (fieldRvaTable == null)
+                return;
+
+            for (int i = 0; i < fieldRvaTable.Rows.Count; i++)
+            {
+                FieldRVARow fieldRvaRow = fieldRvaTable[i];
+
+                MetadataToken fieldToken = new MetadataToken(TokenType.Field, fieldRvaRow.Field);
+
+                FieldDefinition field = (FieldDefinition)assembly.MainModule.LookupByToken(fieldToken);
+
+                fieldRvaRow.RVA = metadata_writer.GetDataCursor();
+                metadata_writer.AddData(field.InitialValue.Length + 3 & (~3));
+                metadata_writer.AddFieldInitData(field.InitialValue);
+            }
+        }
+
+        void PatchResources()
+        {
+            ManifestResourceTable resourceTable = (ManifestResourceTable)stripped_tables[ManifestResourceTable.RId];
+            if (resourceTable == null)
+                return;
+
+            for (int i = 0; i < resourceTable.Rows.Count; i++)
+            {
+                ManifestResourceRow resourceRow = resourceTable[i];
+
+                if (resourceRow.Implementation.RID != 0)
+                    continue;
+
+                foreach (Resource resource in assembly.MainModule.Resources)
+                {
+                    EmbeddedResource er = resource as EmbeddedResource;
+                    if (er == null)
+                        continue;
+
+                    if (resource.Name != original.MetadataRoot.Streams.StringsHeap[resourceRow.Name])
+                        continue;
+
+                    resourceRow.Offset = metadata_writer.AddResource(er.Data);
+                }
+            }
+        }
+
+        void Write()
+        {
+            stripped.MetadataRoot.Accept(metadata_writer);
+        }
+
+        public static void StripAssembly(AssemblyDefinition assembly, string file)
+        {
+            using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write, FileShare.None))
+            {
+                new AssemblyStripper(assembly, new BinaryWriter(fs)).Strip();
+            }
+        }
+    }
+}
diff --git a/src/tasks/ILStripTask/ILStrip.csproj b/src/tasks/ILStripTask/ILStrip.csproj
new file mode 100644
index 00000000000..879c56f26ae
--- /dev/null
+++ b/src/tasks/ILStripTask/ILStrip.csproj
@@ -0,0 +1,32 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFrameworks>$(TargetFrameworkForNETCoreTasks);$(TargetFrameworkForNETFrameworkTasks)</TargetFrameworks>
+    <OutputType>Library</OutputType>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <EnableDefaultCompileItems>false</EnableDefaultCompileItems>
+    <NoWarn>$(NoWarn),CA1050,CS0618,CS0649,CS8604,CS8602,CS8632,SYSLIB0003</NoWarn>
+    <RunAnalyzers>false</RunAnalyzers>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Build" Version="$(RefOnlyMicrosoftBuildVersion)" />
+    <PackageReference Include="Microsoft.Build.Framework" Version="$(RefOnlyMicrosoftBuildFrameworkVersion)" />
+    <PackageReference Include="Microsoft.Build.Tasks.Core" Version="$(RefOnlyMicrosoftBuildTasksCoreVersion)" />
+    <PackageReference Include="Microsoft.Build.Utilities.Core" Version="$(RefOnlyMicrosoftBuildUtilitiesCoreVersion)" />
+    <PackageReference Include="Microsoft.DotNet.CilStrip.Sources" Version="$(MicrosoftDotNetCilStripSourcesVersion)" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="ILStrip.cs" />
+    <Compile Include="..\Common\Utils.cs" />
+    <Compile Include="$(RepoRoot)src\libraries\System.Private.CoreLib\src\System\Diagnostics\CodeAnalysis\NullableAttributes.cs" Condition="'$(TargetFrameworkIdentifier)' == '.NETFramework'" />
+  </ItemGroup>
+
+  <!-- GetFilesToPackage assists to place `ILStrip.dll` in a NuGet package in Microsoft.NET.Runtime.MonoTargets.Sdk.pkgproj for external use -->
+  <Target Name="GetFilesToPackage" Returns="@(FilesToPackage)">
+    <ItemGroup>
+      <_PublishFramework Remove="@(_PublishFramework)" />
+      <_PublishFramework Include="$(TargetFrameworks)" />
+
+      <FilesToPackage Include="$(OutputPath)%(_PublishFramework.Identity)\$(AssemblyName).dll" TargetPath="tasks\%(_PublishFramework.Identity)" />
+    </ItemGroup>
+  </Target>
+</Project>
diff --git a/src/tasks/RuntimeConfigParser/RuntimeConfigParser.csproj b/src/tasks/RuntimeConfigParser/RuntimeConfigParser.csproj
index c19669c373c..2fb35e649ee 100644
--- a/src/tasks/RuntimeConfigParser/RuntimeConfigParser.csproj
+++ b/src/tasks/RuntimeConfigParser/RuntimeConfigParser.csproj
@@ -26,7 +26,7 @@
     <Compile Include="$(RepoRoot)src\libraries\System.Private.CoreLib\src\System\Diagnostics\CodeAnalysis\NullableAttributes.cs" Condition="'$(TargetFrameworkIdentifier)' == '.NETFramework'" />
   </ItemGroup>
 
-  <!-- GetFilesToPackage assists to place `RuntimeConfigParser.dll` in a NuGet package in Microsoft.NET.Runtime.RuntimeConfigParser.Task.pkgproj for external use -->
+  <!-- GetFilesToPackage assists to place `RuntimeConfigParser.dll` in a NuGet package in Microsoft.NET.Runtime.MonoTargets.Sdk.pkgproj for external use -->
   <Target Name="GetFilesToPackage" Returns="@(FilesToPackage)">
     <ItemGroup>
       <_PublishFramework Remove="@(_PublishFramework)" />