[nativeaot] Next steps for the NAOT runtime

samples/NativeAOT/NativeAOT.csproj

@@ -12,4 +12,8 @@
     <!-- Only property required to opt into NativeAOT -->
     <PublishAot>true</PublishAot>
   </PropertyGroup>
-</Project>
+
+  <ItemGroup>
+    <AndroidEnvironment Include="environment.txt" />
+  </ItemGroup>
+</Project>

samples/NativeAOT/environment.txt

@@ -0,0 +1 @@
+naot.system.property=testing 1 2 3

samples/NativeAOT/run.sh

@@ -19,7 +19,7 @@ fi
 
 adb uninstall "${PACKAGE}" || true
 adb install -r -d --no-streaming --no-fastdeploy "${APK}"
-#adb shell setprop debug.mono.log default,assembly,timing=bare
+adb shell setprop debug.mono.log default,assembly,timing=bare
 adb logcat -G 128M
 adb logcat -c
 adb shell am start -S --user "0" -a "android.intent.action.MAIN" -c "android.intent.category.LAUNCHER" -n "${PACKAGE}/${ACTIVITY}" -W

src/Microsoft.Android.Runtime.NativeAOT/Android.Runtime.NativeAOT/JavaInteropRuntime.cs

@@ -17,6 +17,13 @@ static int JNI_OnLoad (IntPtr vm, IntPtr reserved)
 		try {
 			AndroidLog.Print (AndroidLogLevel.Info, "JavaInteropRuntime", "JNI_OnLoad()");
 			XA_Host_NativeAOT_JNI_OnLoad (vm, reserved);
+			// This must be called before anything else, otherwise we'll see several spurious GC invocations and log messages
+			// similar to:
+			//
+			//  09-15 14:51:01.311 11071 11071 D monodroid-gc: 1 outstanding GREFs. Performing a full GC!
+			//
+			JNIEnvInit.NativeAotInitializeMaxGrefGet ();
+
 			LogcatTextWriter.Init ();
 			return (int) JniVersion.v1_6;
 		}

src/Mono.Android/Android.Runtime/JNIEnvInit.cs

@@ -77,15 +77,20 @@ static Type TypeGetType (string typeName) =>
 			androidRuntime!.TypeManager.RegisterNativeMembers (jniType, type, methods);
 		}
 
-		// NOTE: should have different name than `Initialize` to avoid:
-		// * Assertion at /__w/1/s/src/mono/mono/metadata/icall.c:6258, condition `!only_unmanaged_callers_only' not met
-		internal static void InitializeJniRuntime (JniRuntime runtime)
+		// This must be called by NativeAOT before InitializeJniRuntime, as early as possible
+		internal static void NativeAotInitializeMaxGrefGet ()
 		{
-			androidRuntime = runtime;
 			gref_gc_threshold = RuntimeNativeMethods._monodroid_max_gref_get ();
 			if (gref_gc_threshold != int.MaxValue) {
 				gref_gc_threshold = checked((gref_gc_threshold * 9) / 10);
 			}
+		}
+
+		// NOTE: should have different name than `Initialize` to avoid:
+		// * Assertion at /__w/1/s/src/mono/mono/metadata/icall.c:6258, condition `!only_unmanaged_callers_only' not met
+		internal static void InitializeJniRuntime (JniRuntime runtime)
+		{
+			androidRuntime = runtime;
 			SetSynchronizationContext ();
 		}
 

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

@@ -28,6 +28,8 @@ protected override void Construct (LlvmIrModule module)
 		SortedDictionary<string, string>? systemProperties = null;
 		if (envBuilder.SystemProperties.Count > 0) {
 			systemProperties = new (envBuilder.SystemProperties, StringComparer.Ordinal);
+		} else {
+			systemProperties = new (StringComparer.Ordinal);
 		}
 
 		var envVarsBlob = new LlvmIrStringBlob ();
@@ -47,6 +49,25 @@ protected override void Construct (LlvmIrModule module)
 		};
 		module.Add (envVars);
 		module.AddGlobalVariable ("__naot_android_app_environment_variable_contents", envVarsBlob, LlvmIrVariableOptions.GlobalConstant);
+
+		// We reuse the same structure as for environment variables, there's no point in adding a new, identical, one
+		var sysPropsBlob = new LlvmIrStringBlob ();
+		List<StructureInstance<LlvmIrHelpers.AppEnvironmentVariable>> appSysProps = LlvmIrHelpers.MakeEnvironmentVariableList (
+			Log,
+			systemProperties,
+			sysPropsBlob,
+			appEnvironmentVariableStructureInfo
+		);
+
+		var sysPropsCount = new LlvmIrGlobalVariable ((uint)appSysProps.Count, "__naot_android_app_system_property_count");
+		module.Add (sysPropsCount);
+
+		var sysProps = new LlvmIrGlobalVariable (appSysProps, "__naot_android_app_system_properties") {
+			Comment = " System properties defined by the application",
+			Options = LlvmIrVariableOptions.GlobalConstant,
+		};
+		module.Add (sysProps);
+		module.AddGlobalVariable ("__naot_android_app_system_property_contents", sysPropsBlob, LlvmIrVariableOptions.GlobalConstant);
 	}
 
 	void MapStructures (LlvmIrModule module)

src/native/nativeaot/host/host-environment.cc

@@ -5,11 +5,6 @@
 
 using namespace xamarin::android;
 
-struct AppEnvironmentVariable {
-	uint32_t name_index;
-	uint32_t value_index;
-};
-
 extern "C" {
 	extern const uint32_t __naot_android_app_environment_variable_count;
 	extern const AppEnvironmentVariable __naot_android_app_environment_variables[];
@@ -18,16 +13,23 @@ extern "C" {
 
 void HostEnvironment::init () noexcept
 {
-	if (__naot_android_app_environment_variable_count == 0) {
-		return;
+	if (__naot_android_app_environment_variable_count > 0) {
+		log_debug (LOG_DEFAULT, "Setting environment variables ({})", __naot_android_app_environment_variable_count);
+		set_values<set_variable> (
+			__naot_android_app_environment_variable_count,
+			__naot_android_app_environment_variables,
+			__naot_android_app_environment_variable_contents
+		);
 	}
 
-	log_debug (LOG_DEFAULT, "Setting {} environment variables", __naot_android_app_environment_variable_count);
-	for (size_t i = 0; i < __naot_android_app_environment_variable_count; i++) {
-		AppEnvironmentVariable const& env_var = __naot_android_app_environment_variables[i];
-		const char *var_name = &__naot_android_app_environment_variable_contents[env_var.name_index];
-		const char *var_value = &__naot_android_app_environment_variable_contents[env_var.value_index];
-
-		set_variable (var_name, var_value);
+	if (__naot_android_app_system_property_count == 0) {
+		return;
 	}
+
+	log_debug (LOG_DEFAULT, "Setting system properties ({})", __naot_android_app_system_property_count);
+	set_values<set_system_property> (
+		__naot_android_app_system_property_count,
+		__naot_android_app_system_properties,
+		__naot_android_app_system_property_contents
+	);
 }

src/native/nativeaot/include/host/host-environment.hh

@@ -8,22 +8,55 @@
 #include <runtime-base/logger.hh>
 
 namespace xamarin::android {
+	struct AppEnvironmentVariable {
+		uint32_t name_index;
+		uint32_t value_index;
+	};
+
+	extern "C" {
+		extern const uint32_t __naot_android_app_system_property_count;
+		extern const AppEnvironmentVariable __naot_android_app_system_properties[];
+		extern const char __naot_android_app_system_property_contents[];
+	}
+
 	class HostEnvironment
 	{
 	public:
 		static void init () noexcept;
 
+		[[gnu::flatten, gnu::always_inline]]
 		static void set_variable (const char *name, const char *value) noexcept
 		{
-			log_debug (LOG_DEFAULT, " Variable {} = '{}'", name, value);
+			log_debug (LOG_DEFAULT, " Variable {} = '{}'", optional_string (name), optional_string (value));
 			if (::setenv (name, value, 1) < 0) {
 				log_warn (LOG_DEFAULT, "Failed to set environment variable '{}': {}", name, ::strerror (errno));
 			}
 		}
 
+		[[gnu::flatten, gnu::always_inline]]
 		static void set_variable (std::string_view const& name, std::string_view const& value) noexcept
 		{
 			set_variable (name.data (), value.data ());
 		}
+
+		[[gnu::flatten, gnu::always_inline]]
+		static void set_system_property (const char *name, const char *value) noexcept
+		{
+			// TODO: should we **actually** try to set the system property here? Would that even work? Needs testing
+			log_debug (LOG_DEFAULT, " System property {} = '{}'", optional_string (name), optional_string (value));
+		}
+
+	private:
+		template<void (*setter)(const char *name, const char *value) noexcept> [[gnu::flatten, gnu::always_inline]]
+		static void set_values (uint32_t const& count, AppEnvironmentVariable const (&entries)[], const char (&contents)[]) noexcept
+		{
+			for (size_t i = 0; i < count; i++) {
+				AppEnvironmentVariable const& env_var = entries[i];
+				const char *var_name = &contents[env_var.name_index];
+				const char *var_value = &contents[env_var.value_index];
+
+				setter (var_name, var_value);
+			}
+		}
 	};
 }

src/native/nativeaot/runtime-base/android-system.cc

@@ -1,11 +1,29 @@
+#include <cstring>
 #include <string_view>
 
+#include <host/host-environment.hh>
 #include <runtime-base/android-system.hh>
 
 using namespace xamarin::android;
 
 auto
-AndroidSystem::lookup_system_property ([[maybe_unused]] std::string_view const& name, [[maybe_unused]] size_t &value_len) noexcept -> const char*
+AndroidSystem::lookup_system_property (std::string_view const& name, [[maybe_unused]] size_t &value_len) noexcept -> const char*
 {
-	return nullptr; // No-op in NativeAOT
+	if (__naot_android_app_system_property_count == 0) {
+		return nullptr;
+	}
+
+	for (size_t i = 0; i < __naot_android_app_system_property_count; i++) {
+		AppEnvironmentVariable const& sys_prop = __naot_android_app_system_properties[i];
+		const char *prop_name = &__naot_android_app_system_property_contents[sys_prop.name_index];
+		if (name.compare (prop_name) != 0) {
+			continue;
+		}
+
+		const char *prop_value = &__naot_android_app_system_property_contents[sys_prop.value_index];
+		value_len = strlen (prop_value);
+		return prop_value;
+	}
+
+	return nullptr;
 }