Support DSOs embedded in the .apk (#2154)

Context: #1906

Android v6.0 (API-23) introduced a new way of dealing with the native
shared libraries shipped in the `.apk`.  Before API-23, the libraries
would be always extracted and placed in the application data
directory, thus occupying more space than necessary.  API-23 added a
new `AndroidManifest.xml` attribute,
`//application/@android:extractNativeLibs`, which if set to `false`
makes Android *not* extract the libraries to the filesystem.  API-23
added a way to instead load those libraries directly from the `.apk`.
In order to support that there are a few requirements which this
commit implements:

  * DSO (`.so`) files must be *stored uncompressed* in the `.apk`.
  * `<application android:extractNativeLibs="false"/>` must be set
  * DSOs in the `.apk` must be aligned on the memory page boundary;
    `zipalign -p` takes care of this.

This commit also implements `libmonodroid.so` suport for loading our
DSOs directly from the `.apk`.  This operation mode is enabled by the
presence of the `$__XA_DSO_IN_APK` environment variable.  This
environment variable is inserted into the application's environment
by way of placing it in the environment file (a file part of the
Xamarin.Android App project that has the `@(AndroidEnvironment)`
build action).  In this mode, the DSOs are *no longer* looked up in
the application data directory but only in the override directories
(if the APK is built in Debug configuration) and the `.apk` itself.

Currently, in order to activate the above mode, one has to perform
the following actions manually:

 1. Add the `android:extractNativeLibs="false"` attribute to the
    `<application>/` element in `Properties/AndroidManifest.xml`.

 2. Add the following property to the project file:

        <AndroidStoreUncompressedFileExtensions>.so</AndroidStoreUncompressedFileExtensions>

 3. Add an android environment file to the project with a line which says

      __XA_DSO_IN_APK=1

After that the application should work in the embedded DSO mode
without problems.

A couple of tests are provided to test building and execution of
embedded DSO application on device, as well as to validate the
built `.apk`.

TODO: fix issue #1906 by "nicely integrating" this support with the
Xamarin.Android build system so that the above manual steps are not
required.  The exact semantics still need to be determined.

Author: grendello

Xamarin.Android-Tests.sln

@@ -76,6 +76,10 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Performance-Tests", "Perfor
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "timing", "build-tools\timing\timing.csproj", "{37CAA28C-40BE-4253-BA68-CC5D7316A617}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "EmbeddedDSO", "tests\EmbeddedDSOs\EmbeddedDSO\EmbeddedDSO.csproj", "{056ED976-618F-4A3E-910E-AA25230C2296}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "EmbeddedDSO-UnitTests", "tests\EmbeddedDSOs\EmbeddedDSO-UnitTests\EmbeddedDSO-UnitTests.csproj", "{B160F0E7-799A-4EB9-92B8-D71623C7674A}"
+EndProject
 Global
 	GlobalSection(SharedMSBuildProjectFiles) = preSolution
 		tests\Xamarin.Forms-Performance-Integration\Xamarin.Forms.Performance.Integration.projitems*{195be9c2-1f91-40dc-bd6d-de860bf083fb}*SharedItemsImports = 13
@@ -194,6 +198,14 @@ Global
 		{37CAA28C-40BE-4253-BA68-CC5D7316A617}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{37CAA28C-40BE-4253-BA68-CC5D7316A617}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{37CAA28C-40BE-4253-BA68-CC5D7316A617}.Release|Any CPU.Build.0 = Release|Any CPU
+		{056ED976-618F-4A3E-910E-AA25230C2296}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{056ED976-618F-4A3E-910E-AA25230C2296}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{056ED976-618F-4A3E-910E-AA25230C2296}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{056ED976-618F-4A3E-910E-AA25230C2296}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B160F0E7-799A-4EB9-92B8-D71623C7674A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B160F0E7-799A-4EB9-92B8-D71623C7674A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B160F0E7-799A-4EB9-92B8-D71623C7674A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B160F0E7-799A-4EB9-92B8-D71623C7674A}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

build-tools/scripts/RunTests.targets

@@ -17,12 +17,14 @@
   <ItemGroup>
     <_TestAssembly Include="$(_TopDir)\bin\Test$(Configuration)\Xamarin.Android.Build.Tests.dll" />
     <_TestAssembly Include="$(_TopDir)\bin\Test$(Configuration)\CodeBehind\CodeBehindUnitTests.dll" />
+    <_TestAssembly Include="$(_TopDir)\bin\Test$(Configuration)\EmbeddedDSO\EmbeddedDSOUnitTests.dll" />
     <_ApkTestProject Include="$(_TopDir)\src\Mono.Android\Test\Mono.Android-Tests.csproj" />
     <_ApkTestProject Include="$(_TopDir)\tests\CodeGen-Binding\Xamarin.Android.JcwGen-Tests\Xamarin.Android.JcwGen-Tests.csproj" />
     <_ApkTestProject Include="$(_TopDir)\tests\CodeGen-MkBundle\Xamarin.Android.MakeBundle-Tests\Xamarin.Android.MakeBundle-Tests.csproj" />
     <_ApkTestProject Include="$(_TopDir)\tests\locales\Xamarin.Android.Locale-Tests\Xamarin.Android.Locale-Tests.csproj" />
     <_ApkTestProject Include="$(_TopDir)\tests\BCL-Tests\Xamarin.Android.Bcl-Tests\Xamarin.Android.Bcl-Tests.csproj" />
     <_ApkTestProject Include="$(_TopDir)\tests\Xamarin.Forms-Performance-Integration\Droid\Xamarin.Forms.Performance.Integration.Droid.csproj" />
+    <_ApkTestProject Include="$(_TopDir)\tests\EmbeddedDSOs\EmbeddedDSO\EmbeddedDSO.csproj" />
     <_ApkTestProjectAot Include="$(_TopDir)\src\Mono.Android\Test\Mono.Android-Tests.csproj" />
     <_ApkTestProjectBundle Include="$(_TopDir)\src\Mono.Android\Test\Mono.Android-Tests.csproj" />
   </ItemGroup>

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

@@ -36,7 +36,7 @@ protected override string GenerateCommandLineCommands ()
 			string sourceFilename = Path.GetFileNameWithoutExtension (Source.ItemSpec);
 			if (sourceFilename.EndsWith (strSignedUnaligned))
 				sourceFilename = sourceFilename.Remove (sourceFilename.Length - strSignedUnaligned.Length);
-			return string.Format ("{0} \"{1}\" \"{2}{3}{4}-Signed.apk\"",
+			return string.Format ("-p {0} \"{1}\" \"{2}{3}{4}-Signed.apk\"",
 				Alignment, Source.ItemSpec, DestinationDirectory.ItemSpec, Path.DirectorySeparatorChar, sourceFilename);
 		}
 

src/monodroid/jni/dylib-mono.c

@@ -33,25 +33,18 @@ void monodroid_dylib_mono_free (struct DylibMono *mono_imports)
 	free (mono_imports);
 }
 
-int monodroid_dylib_mono_init (struct DylibMono *mono_imports, const char *libmono_path)
+int monodroid_dylib_mono_init (struct DylibMono *mono_imports, void *libmono_handle)
 {
 	int symbols_missing = FALSE;
 
 	if (mono_imports == NULL)
 		return FALSE;
 
-	memset (mono_imports, 0, sizeof (*mono_imports));
-
-	/*
-	 * We need to use RTLD_GLOBAL so that libmono-profiler-log.so can resolve
-	 * symbols against the Mono library we're loading.
-	 */
-	mono_imports->dl_handle = dlopen (libmono_path, RTLD_LAZY | RTLD_GLOBAL);
-
-	if (!mono_imports->dl_handle) {
+	if (libmono_handle == NULL)
 		return FALSE;
-	}
 
+	memset (mono_imports, 0, sizeof (*mono_imports));
+	mono_imports->dl_handle = libmono_handle;
 	mono_imports->version   = sizeof (*mono_imports);
 
 	log_info (LOG_DEFAULT, "Loading Mono symbols...");

src/monodroid/jni/dylib-mono.h

@@ -348,6 +348,6 @@ struct DylibMono {
 
 MONO_API  struct  DylibMono*  monodroid_dylib_mono_new (const char *libmono_path);
 MONO_API  void                monodroid_dylib_mono_free (struct DylibMono *mono_imports);
-          int                 monodroid_dylib_mono_init (struct DylibMono *mono_imports, const char *libmono_path);
+          int                 monodroid_dylib_mono_init (struct DylibMono *mono_imports, void *libmono_handle);
 
 #endif /* INC_MONODROID_DYLIB_MONO_H */