Don't package empty AOT-d DSOs

Directory.Build.props

@@ -36,6 +36,7 @@
     <MonoOptionsVersion>6.12.0.148</MonoOptionsVersion>
     <SystemCollectionsImmutableVersion>1.7.1</SystemCollectionsImmutableVersion>
     <XliffTasksVersion>1.0.0-beta.20420.1</XliffTasksVersion>
+    <ELFSharpVersion>2.13.1</ELFSharpVersion>
   </PropertyGroup>
 
   <!-- Properties to help us run managed assemblies on various runtimes.

build-tools/Xamarin.Android.Tools.BootstrapTasks/Xamarin.Android.Tools.BootstrapTasks/ApkDiffCheckRegression.cs

@@ -31,7 +31,7 @@ public class ApkDiffCheckRegression : ToolTask
 		protected override string ToolName => Path.GetFileName (ApkDiffTool);
 		protected override string GenerateFullPathToTool () => ApkDiffTool;
 
-		const int ApkSizeThreshold = 50*1024;
+		const int ApkSizeThreshold = 48*1024;
 		const int AssemblySizeThreshold = 50*1024;
 
 		StringBuilder logCopy = new StringBuilder ();

build-tools/create-packs/SignList.xml

@@ -10,6 +10,7 @@
     <ThirdParty Include="INIFileParser.dll" />
     <ThirdParty Include="Irony.dll" />
     <ThirdParty Include="K4os.Compression.LZ4.dll" />
+    <ThirdParty Include="ELFSharp.dll" />
     <ThirdParty Include="protobuf-net.dll" />
     <ThirdParty Include="SgmlReaderDll.dll" />
     <ThirdParty Include="aapt2.exe" />

build-tools/installers/create-installers.targets

@@ -298,6 +298,7 @@
     <_MSBuildFiles Include="$(MSBuildSrcDir)\Xamarin.SourceWriter.pdb" />
     <_MSBuildFiles Include="$(MSBuildSrcDir)\K4os.Compression.LZ4.dll" />
     <_MSBuildFiles Include="$(MSBuildSrcDir)\K4os.Hash.xxHash.dll" />
+    <_MSBuildFiles Include="$(MSBuildSrcDir)\ELFSharp.dll" />
   </ItemGroup>
   <ItemGroup>
     <_MSBuildTargetsSrcFiles Include="$(MSBuildTargetsSrcDir)\Xamarin.Android.AvailableItems.targets" />

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

@@ -95,12 +95,11 @@ void CopyExtraBuildFiles (string destinationRoot, Context context)
 		void CopyExtraTestFiles (string destinationRoot, Context context)
 		{
 			Directory.CreateDirectory (destinationRoot);
-			var filesToCopy = new List<string> ();
 
 			var testConfigDir = Path.Combine (BuildPaths.XamarinAndroidSourceRoot, "bin", $"Test{context.Configuration}");
 			if (Directory.Exists (testConfigDir)) {
 				foreach (var fileMatch in testConfigFiles) {
-					filesToCopy.AddRange (Directory.GetFiles (testConfigDir, fileMatch));
+					Utilities.CopyFilesSimple (Directory.GetFiles (testConfigDir, fileMatch), destinationRoot, false);
 				}
 			}
 

build-tools/xaprepare/xaprepare/ThirdPartyNotices/ELFSharp.cs

@@ -0,0 +1,86 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace Xamarin.Android.Prepare
+{
+	[TPN]
+	class KonradKuczynski_ELFSharp_TPN : ThirdPartyNotice
+	{
+		static readonly Uri url = new Uri ("https://elfsharp.it/");
+
+		public override string LicenseFile => String.Empty;
+		public override string Name => "KonradKuczynski/ELFSharp";
+		public override Uri SourceUrl => url;
+		public override string LicenseText => @"
+Copyright (c) 2011 Konrad Kruczyński and other contributors
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+""Software""), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED ""AS IS"", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+This software uses ELF machine constants from the LLVM projects, whose license
+is provided below:
+
+==============================================================================
+LLVM Release License
+==============================================================================
+University of Illinois/NCSA
+Open Source License
+
+Copyright (c) 2003-2010 University of Illinois at Urbana-Champaign.
+All rights reserved.
+
+Developed by:
+
+    LLVM Team
+
+    University of Illinois at Urbana-Champaign
+
+    http://llvm.org
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the ""Software""), to deal with
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+    * Redistributions of source code must retain the above copyright notice,
+      this list of conditions and the following disclaimers.
+
+    * Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimers in the
+      documentation and/or other materials provided with the distribution.
+
+    * Neither the names of the LLVM Team, University of Illinois at
+      Urbana-Champaign, nor the names of its contributors may be used to
+      endorse or promote products derived from this Software without specific
+      prior written permission.
+
+THE SOFTWARE IS PROVIDED ""AS IS"", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+CONTRIBUTORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS WITH THE
+SOFTWARE.
+";
+		public override bool Include (bool includeExternalDeps, bool includeBuildDeps) => includeExternalDeps;
+	}
+}

src/Xamarin.Android.Build.Tasks/Tasks/BuildApk.cs

@@ -772,7 +772,12 @@ void AddNativeLibrary (ArchiveFileList files, string path, string abi, string ar
 				Log.LogCodedWarning ("XA4301", path, 0, Properties.Resources.XA4301, item.archivePath);
 				return;
 			}
-			files.Add (item);
+
+			if (!ELFHelper.IsEmptyAOTLibrary (Log, item.filePath)) {
+				files.Add (item);
+			} else {
+				Log.LogDebugMessage ($"{item.filePath} is an empty (no executable code) AOT assembly, not including it in the archive");
+			}
 		}
 
 		// This method is used only for internal warnings which will never be shown to the end user, therefore there's

src/Xamarin.Android.Build.Tasks/Utilities/ELFHelper.cs

@@ -0,0 +1,92 @@
+using System;
+using System.IO;
+
+using ELFSharp;
+using ELFSharp.ELF;
+using ELFSharp.ELF.Sections;
+using Microsoft.Android.Build.Tasks;
+using Microsoft.Build.Utilities;
+
+namespace Xamarin.Android.Tasks
+{
+	static class ELFHelper
+	{
+		public static bool IsEmptyAOTLibrary (TaskLoggingHelper log, string path)
+		{
+			if (String.IsNullOrEmpty (path) || !File.Exists (path)) {
+				return false;
+			}
+
+			try {
+				return IsEmptyAOTLibrary (log, path, ELFReader.Load (path));
+			} catch (Exception ex) {
+				log.LogWarning ($"Attempt to check whether '{path}' is a valid ELF file failed with exception, ignoring AOT check for the file.");
+				log.LogWarningFromException (ex, showStackTrace: true);
+				return false;
+			}
+
+		}
+
+		static bool IsEmptyAOTLibrary (TaskLoggingHelper log, string path, IELF elf)
+		{
+			ISymbolTable? symtab = GetSymbolTable (elf, ".dynsym");
+			if (symtab == null) {
+				// We can't be sure what the DSO is, play safe
+				return false;
+			}
+
+			bool mono_aot_file_info_found = false;
+			foreach (var entry in symtab.Entries) {
+				if (String.Compare ("mono_aot_file_info", entry.Name, StringComparison.Ordinal) == 0 && entry.Type == SymbolType.Object) {
+					mono_aot_file_info_found = true;
+					break;
+				}
+			}
+
+			if (!mono_aot_file_info_found) {
+				// Not a MonoVM AOT assembly
+				return false;
+			}
+
+			symtab = GetSymbolTable (elf, ".symtab");
+			if (symtab == null) {
+				// The DSO is stripped, we can't tell if there are any functions defined (.text will be present anyway)
+				// We perhaps **can** take a look at the .text section size, but it's not a solid check...
+				log.LogDebugMessage ($"{path} is an AOT assembly but without symbol table (stripped?). Including it in the archive.");
+				return false;
+			}
+
+			foreach (var entry in symtab.Entries) {
+				if (entry.Type == SymbolType.Function) {
+					return false;
+				}
+			}
+
+			return true;
+		}
+
+		static ISymbolTable? GetSymbolTable (IELF elf, string sectionName)
+		{
+			ISection? section = GetSection (elf, sectionName);
+			if (section == null) {
+				return null;
+			}
+
+			var symtab = section as ISymbolTable;
+			if (symtab == null) {
+				return null;
+			}
+
+			return symtab;
+		}
+
+		static ISection? GetSection (IELF elf, string sectionName)
+		{
+			if (!elf.TryGetSection (sectionName, out ISection section)) {
+				return null;
+			}
+
+			return section;
+		}
+	}
+}

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj

@@ -59,6 +59,7 @@
     <PackageReference Include="System.Runtime.InteropServices" Version="4.3.0" />
     <PackageReference Include="XliffTasks" Version="$(XliffTasksVersion)" PrivateAssets="all" />
     <PackageReference Include="K4os.Hash.xxHash" Version="1.0.6" />
+    <PackageReference Include="ELFSharp" Version="$(ELFSharpVersion)" />
   </ItemGroup>
 
   <ItemGroup>