[native] Runtime linking at app build time

NativeLinkingTODO.md

@@ -0,0 +1,30 @@
+# Problems to solve
+
+  * `libSystem.Security.Cryptography.Native.Android.a` contains the `JNI_OnLoad` function
+    which initializes the whole crypto support library, but we can't use it as it would
+    conflict with our own.  Potential solution is to modify the above library's source code
+    to add an init function that we will call from our own `JNI_OnLoad` and make the library's
+    init function do the same. The `JNI_OnLoad` object file would have to be omitted from the
+    library's `.a`
+  * `p/invoke usage`.
+    Currently, all the BCL archives (with exception of the above crypto one) are
+    linked into the unified runtime using `--whole-archive` - that is, they become part of the
+    runtime in their entirety.  This is wasteful, but necessary, so that `p/invokes` into those
+    libraries work correctly.  Instead, we should scan the application DLLs for p/invokes from
+    those libraries and generate code to reference the required functions, so that the linker
+    can do its job and remove code not used by the application.  Likely needed is a linker step.
+  * `p/invoke` handling mechanism.  Right now, we `dlopen` the relevant `.so` library and look
+    up the required symbol in there.  With the unified runtime the `.so` disappears, so we either
+    need to look it up in our own library or, better, call the function directly.  The latter is
+    a bit more complicated to implement but would give us much faster code, thus it's the preferred
+    solution.
+
+# Helpers
+
+  * linker can output a list of pinvokes, see https://github.com/dotnet/android/issues/7114
+
+# Ideas
+
+  * Use [mold](https://github.com/rui314/mold) which has recently been re-licensed under `MIT/X11`
+    (and contains components licensed under a mixture of `BSD*` and `Apache 2.0` licenses), so we
+    can easily redistribute it instead of the LLVM's `lld`.  The advantage is `mold`'s [speed](https://github.com/rui314/mold?tab=readme-ov-file#mold-a-modern-linker)

build-tools/create-packs/Microsoft.Android.Runtime.proj

@@ -42,7 +42,20 @@ projects that use the Microsoft.Android framework in .NET 6+.
       <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libmono-android.release.so" />
       <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libxamarin-debug-app-helper.so" />
       <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libxamarin-native-tracing.so" />
-      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libunwind_xamarin.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libunwind_xamarin-release.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libruntime-base-release.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libxa-java-interop-release.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libxa-lz4-release.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libxa-shared-bits-release.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libmono-android.release-static-release.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libpinvoke-override-dynamic-release.a" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\crtbegin_so.o" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\crtend_so.o" />
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libclang_rt.builtins-*-android.a" />
+
+      <!-- Remove once https://github.com/dotnet/runtime/pull/107615 is merged and released -->
+      <_AndroidRuntimePackAssets Include="$(MicrosoftAndroidSdkOutDir)lib\$(AndroidRID)\libunwind.a" />
+
       <FrameworkListFileClass Include="@(_AndroidRuntimePackAssemblies->'%(Filename)%(Extension)')" Profile="Android" />
       <FrameworkListFileClass Include="@(_AndroidRuntimePackAssets->'%(Filename)%(Extension)')" Profile="Android" />
     </ItemGroup>

build-tools/installers/create-installers.targets

@@ -180,17 +180,29 @@
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)ELFSharp.dll" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)ManifestOverlays\Timing.xml" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm64\libc.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm64\libdl.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm64\liblog.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm64\libm.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm64\libz.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm\libc.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm\libdl.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm\liblog.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm\libm.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-arm\libz.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x64\libc.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x64\libdl.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x64\liblog.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x64\libm.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x64\libz.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x86\libc.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x86\libdl.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x86\liblog.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x86\libm.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)dsostubs\android-arm64\libarchive-dso-stub.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)dsostubs\android-arm\libarchive-dso-stub.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)dsostubs\android-x64\libarchive-dso-stub.so" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)dsostubs\android-x86\libarchive-dso-stub.so" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)libstubs\android-x86\libz.so" />
   </ItemGroup>
   <ItemGroup>
     <_MSBuildTargetsSrcFiles Include="$(MSBuildTargetsSrcDir)\Xamarin.Android.AvailableItems.targets" />

build-tools/xaprepare/xaprepare/ConfigAndData/Configurables.cs

@@ -146,6 +146,37 @@ public static partial class Defaults
 				{ "x86_64",         "x86_64-linux-android" },
 			};
 
+			public static readonly Dictionary<string, string> AbiToRID = new (StringComparer.Ordinal) {
+				{ "armeabi-v7a",    "android-arm" },
+				{ "arm64-v8a",      "android-arm64" },
+				{ "x86",            "android-x86" },
+				{ "x86_64",         "android-x64" },
+			};
+
+			public static readonly Dictionary<string, string> AbiToClangArch = new (StringComparer.Ordinal) {
+				{ "armeabi-v7a",    "arm" },
+				{ "arm64-v8a",      "aarch64" },
+				{ "x86",            "i686" },
+				{ "x86_64",         "x86_64" },
+			};
+
+			/// <summary>
+			///   Used in rules.mk generator. Files to include in the XA bundle archives.
+			/// </summary>
+			public static readonly List <string> BundleZipsInclude = new List <string> {
+				"$(ZIP_OUTPUT_BASENAME)/THIRD-PARTY-NOTICES.TXT",
+				"$(ZIP_OUTPUT_BASENAME)/bin/Debug",
+				"$(ZIP_OUTPUT_BASENAME)/bin/Release",
+			};
+
+			/// <summary>
+			///   Used in rules.mk generator. Files to exclude from the XA bundle archives. Must be syntactically
+			///   correct for GNU Make.
+			/// </summary>
+			public static readonly List <string> BundleZipsExclude = new List <string> {
+				"$(ZIP_OUTPUT_BASENAME)/bin/*/bundle-*.zip"
+			};
+
 			public static readonly List <NDKTool> NDKTools = new List<NDKTool> {
 				// Tools prefixed with architecture triple
 				new NDKTool (name: "as", prefixed: true),
@@ -220,6 +251,7 @@ public static partial class Paths
 			// Other
 			public static string AndroidNdkDirectory                 => ctx.Properties.GetRequiredValue (KnownProperties.AndroidNdkDirectory);
 			public static string AndroidToolchainRootDirectory       => GetCachedPath (ref androidToolchainRootDirectory,       () => Path.Combine (AndroidNdkDirectory, "toolchains", "llvm", "prebuilt", NdkToolchainOSTag));
+			public static string AndroidClangRootDirectory           => GetCachedPath (ref androidClangRootDirectory,           () => Path.Combine (AndroidToolchainRootDirectory, "lib", "clang"));
 			public static string AndroidToolchainBinDirectory        => GetCachedPath (ref androidToolchainBinDirectory,        () => Path.Combine (AndroidToolchainRootDirectory, "bin"));
 			public static string AndroidToolchainSysrootLibDirectory => GetCachedPath (ref androidToolchainSysrootLibDirectory, () => Path.Combine (AndroidToolchainRootDirectory, "sysroot", "usr", "lib"));
 			public static string WindowsBinutilsInstallDir           => GetCachedPath (ref windowsBinutilsInstallDir,           () => Path.Combine (InstallMSBuildDir, "binutils"));
@@ -264,6 +296,7 @@ static string GetCachedPath (ref string? variable, Func<string> creator)
 			static string? buildBinDir;
 			static string? binDir;
 			static string? androidToolchainRootDirectory;
+			static string? androidClangRootDirectory;
 			static string? androidToolchainBinDirectory;
 			static string? androidToolchainSysrootLibDirectory;
 			static string? installMSBuildDir;

build-tools/xaprepare/xaprepare/Steps/Step_Android_SDK_NDK.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
@@ -151,13 +152,82 @@ bool AcceptLicenses (Context context, string sdkRoot)
 
 		bool GatherNDKInfo (Context context)
 		{
+			if (!CopyRedistributableFiles (context)) {
+				return false;
+			}
+
 			// Ignore NDK property setting if not installing the NDK
 			if (!DependencyTypeToInstall.HasFlag (AndroidToolchainComponentType.BuildDependency))
 				return true;
 			else
 				return context.BuildInfo.GatherNDKInfo (context);
 		}
 
+		bool CopyRedistributableFiles (Context context)
+		{
+			string androidVersionPath = Path.Combine (Configurables.Paths.AndroidToolchainRootDirectory, "AndroidVersion.txt");
+			if (!File.Exists (androidVersionPath)) {
+				throw new InvalidOperationException ($"Android version file '{androidVersionPath}' not found");
+			}
+
+			string[]? lines = File.ReadAllLines (androidVersionPath);
+			if (lines == null || lines.Length < 1) {
+				throw new InvalidOperationException ($"Unknown format of Android version file '{androidVersionPath}'");
+			}
+
+			// First line is (should be) the LLVM version, we need just the main release number
+			string[] llvmVersion = lines[0].Split ('.');
+			if (llvmVersion.Length < 3) {
+				throw new InvalidOperationException ($"Unknown LLVM version format for '{lines[0]}'");
+			}
+
+			string clangLibPath = Path.Combine (
+				Configurables.Paths.AndroidClangRootDirectory,
+				llvmVersion[0],
+				"lib",
+				"linux"
+			);
+
+			foreach (var kvp in Configurables.Defaults.AndroidToolchainPrefixes) {
+				string abi = kvp.Key;
+
+				string crtFilesPath = Path.Combine (
+					Configurables.Paths.AndroidToolchainSysrootLibDirectory,
+					kvp.Value,
+					BuildAndroidPlatforms.NdkMinimumAPI.ToString (CultureInfo.InvariantCulture)
+				);
+
+				string clangArch = Configurables.Defaults.AbiToClangArch[abi];
+				CopyFile (abi, crtFilesPath, "crtbegin_so.o");
+				CopyFile (abi, crtFilesPath, "crtend_so.o");
+				CopyFile (abi, clangLibPath, $"libclang_rt.builtins-{clangArch}-android.a");
+
+				// Yay, consistency
+				if (String.Compare (clangArch, "i686", StringComparison.Ordinal) == 0) {
+					clangArch = "i386";
+				}
+
+				// Remove once https://github.com/dotnet/runtime/pull/107615 is merged and released
+				CopyFile (abi, Path.Combine (clangLibPath, clangArch), "libunwind.a");
+			}
+
+			return true;
+
+			void CopyFile (string abi, string sourceDir, string fileName)
+			{
+				Log.StatusLine ($"  {context.Characters.Bullet} Copying NDK redistributable: ", $"{fileName} ({abi})", tailColor: ConsoleColor.White);
+				string rid = Configurables.Defaults.AbiToRID [abi];
+				string outputDir = Path.Combine (
+					context.Properties.GetRequiredValue (KnownProperties.MicrosoftAndroidSdkOutDir),
+					"lib",
+					rid
+				);
+
+				string sourceFile = Path.Combine (sourceDir, fileName);
+				Utilities.CopyFileToDir (sourceFile, outputDir);
+			}
+		}
+
 		void CheckPackageStatus (Context context, string packageCacheDir, AndroidPackage pkg, List <AndroidPackage> toDownload)
 		{
 			Log.StatusLine ($"  {context.Characters.Bullet} Installing ", pkg.Component.Name, tailColor: ConsoleColor.White);

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.After.targets

@@ -24,6 +24,9 @@ This file is imported *after* the Microsoft.NET.Sdk/Sdk.targets.
   <Import Project="Microsoft.Android.Sdk.Aot.targets"         Condition=" '$(AndroidApplication)' == 'true' " />
   <Import Project="Microsoft.Android.Sdk.Application.targets" Condition=" '$(AndroidApplication)' == 'true' " />
   <Import Project="Microsoft.Android.Sdk.AssemblyResolution.targets" />
+
+  <!-- This one must be imported after `Microsoft.Android.Sdk.AssemblyResolution.targets` -->
+  <Import Project="Microsoft.Android.Sdk.NativeRuntime.targets" Condition=" '$(AndroidApplication)' == 'true' " />
   <Import Project="Microsoft.Android.Sdk.ILLink.targets" />
   <Import Project="Microsoft.Android.Sdk.ProjectCapabilities.targets" />
   <Import Project="Microsoft.Android.Sdk.Publish.targets" />

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.AssemblyResolution.targets

@@ -216,7 +216,17 @@ _ResolveAssemblies MSBuild target.
     </ItemGroup>
   </Target>
 
-  <Target Name="_IncludeNativeSystemLibraries">
+  <Target Name="_PrepareMonoComponentItems">
+    <ItemGroup>
+      <_MonoComponent Condition=" '$(AndroidEnableProfiler)' == 'true' " Include="diagnostics_tracing" />
+      <_MonoComponent Condition=" '$(AndroidUseInterpreter)' == 'true' " Include="hot_reload" />
+      <_MonoComponent Condition=" '$(AndroidIncludeDebugSymbols)' == 'true' " Include="debugger" />
+      <_MonoComponent Condition=" '$(_AndroidExcludeMarshalIlgenComponent)' != 'true' " Include="marshal-ilgen" />
+    </ItemGroup>
+  </Target>
+
+  <Target Name="_IncludeNativeSystemLibraries"
+          DependsOnTargets="_PrepareMonoComponentItems">
     <PropertyGroup>
       <_AndroidIncludeSystemGlobalizationNative Condition=" '$(_AndroidIncludeSystemGlobalizationNative)' == '' ">true</_AndroidIncludeSystemGlobalizationNative>
       <_AndroidEnableNativeStackTracing Condition=" '$(_AndroidEnableNativeStackTracing)' == ''">false</_AndroidEnableNativeStackTracing>
@@ -225,15 +235,12 @@ _ResolveAssemblies MSBuild target.
       <_ResolvedNativeLibraries Include="@(ResolvedFileToPublish)" Condition=" '%(ResolvedFileToPublish.Extension)' == '.so' " />
     </ItemGroup>
     <ItemGroup>
-      <_MonoComponent Condition=" '$(AndroidEnableProfiler)' == 'true' " Include="diagnostics_tracing" />
-      <_MonoComponent Condition=" '$(AndroidUseInterpreter)' == 'true' " Include="hot_reload" />
-      <_MonoComponent Condition=" '$(AndroidIncludeDebugSymbols)' == 'true' " Include="debugger" />
-      <_MonoComponent Condition=" '$(_AndroidExcludeMarshalIlgenComponent)' != 'true' " Include="marshal-ilgen" />
       <!-- Filename without extension -->
       <_ExcludedNativeLibraries Condition=" '$(_AndroidIncludeSystemGlobalizationNative)' != 'true' " Include="libSystem.Globalization.Native" />
       <_ExcludedNativeLibraries Condition=" '$(_AndroidEnableNativeStackTracing)' != 'true' " Include="libxamarin-native-tracing" />
     </ItemGroup>
     <ProcessNativeLibraries
+        NativeRuntimeLinking="$(_AndroidEnableNativeRuntimeLinking)"
         InputLibraries="@(_ResolvedNativeLibraries)"
         ExcludedLibraries="@(_ExcludedNativeLibraries)"
         Components="@(_MonoComponent->Distinct())"

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.BuildOrder.targets

@@ -75,6 +75,7 @@ properties that determine build ordering.
       _ReadAndroidManifest;
       _CompileJava;
       _CreateApplicationSharedLibraries;
+      _LinkNativeRuntime;
       _CompileDex;
       $(_AfterCompileDex);
       _CreateBaseApk;

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.NativeRuntime.targets

@@ -0,0 +1,63 @@
+<!--
+***********************************************************************************************
+Microsoft.Android.Sdk.NativeRuntime.targets
+
+Contains code to build and link the native runtime at application build time.
+
+***********************************************************************************************
+-->
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <UsingTask TaskName="Xamarin.Android.Tasks.GetNativeRuntimeComponents" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
+  <UsingTask TaskName="Xamarin.Android.Tasks.LinkNativeRuntime" AssemblyFile="$(_XamarinAndroidBuildTasksAssembly)" />
+
+  <Target Name="_PrepareUnifiedNativeRuntimeItems"
+          Condition=" '$(_AndroidEnableNativeRuntimeLinking)' == 'true' ">
+    <ItemGroup>
+      <_UnifiedNativeRuntime Include="$(_AndroidApplicationSharedLibraryPath)%(_BuildTargetAbis.Identity)\libmonodroid-unified.so">
+        <abi>%(_BuildTargetAbis.Identity)</abi>
+        <ArchiveFileName>libmonodroid.so</ArchiveFileName>
+      </_UnifiedNativeRuntime>
+    </ItemGroup>
+
+    <ItemGroup>
+      <_ResolvedNativeArchive Include="@(ResolvedFileToPublish)" Condition=" '%(ResolvedFileToPublish.Extension)' == '.a' " />
+      <_ResolvedNativeObjectFile Include="@(ResolvedFileToPublish)" Condition=" '%(ResolvedFileToPublish.Extension)' == '.o' " />
+      <_ApplicationSharedLibrary Include="@(_UnifiedNativeRuntime)" />
+    </ItemGroup>
+
+    <GetNativeRuntimeComponents
+        MonoComponents="@(_MonoComponent)"
+        ResolvedNativeObjectFiles="@(_ResolvedNativeObjectFile)"
+        ResolvedNativeArchives="@(_ResolvedNativeArchive)">
+      <Output TaskParameter="NativeArchives" ItemName="_SelectedNativeArchive" />
+      <Output TaskParameter="RequiredLibraries" ItemName="_RequiredLinkLibraries" />
+      <Output TaskParameter="LinkStartFiles" ItemName="_NativeLinkStartFiles" />
+      <Output TaskParameter="LinkEndFiles" ItemName="_NativeLinkEndFiles" />
+      <Output TaskParameter="NativeSymbolsToExport" ItemName="_NativeSymbolsToExport" />
+    </GetNativeRuntimeComponents>
+  </Target>
+
+  <Target Name="_LinkNativeRuntime"
+          DependsOnTargets="_PrepareMonoComponentItems;_CompileNativeAssemblySources;_PrepareUnifiedNativeRuntimeItems"
+          Inputs="@(_NativeAssemblyTarget);@(_SelectedNativeArchive)"
+          Outputs="@(_UnifiedNativeRuntime)"
+          Condition=" '$(_AndroidEnableNativeRuntimeLinking)' == 'true' ">
+    <LinkNativeRuntime
+        MonoComponents="@(_MonoComponent)"
+        AndroidBinUtilsDirectory="$(AndroidBinUtilsDirectory)"
+        IntermediateOutputPath="$(IntermediateOutputPath)"
+        NativeArchives="@(_SelectedNativeArchive)"
+        NativeObjectFiles="@(_NativeAssemblyTarget)"
+        NativeLinkStartFiles="@(_NativeLinkStartFiles)"
+        NativeLinkEndFiles="@(_NativeLinkEndFiles)"
+        NativeSymbolsToExport="@(_NativeSymbolsToExport)"
+        LinkLibraries="@(_RequiredLinkLibraries)"
+        OutputRuntimes="@(_UnifiedNativeRuntime)"
+        SupportedAbis="@(_BuildTargetAbis)"
+        SaveDebugSymbols="true" />
+
+    <ItemGroup>
+      <FileWrites Include="@(_UnifiedNativeRuntime)" />
+    </ItemGroup>
+  </Target>
+</Project>