[native] Fix JNI preload cache generation (#10547)

grendello · jonathanpeppers · commit f90e889aa8ed · 2025-10-17T12:48:00.000-05:00
Fixes: #10544 Context: 1a62af3 Context: cba39dc cba39dc introduced code to preload at startup native libraries which use JNI, to work around an issue in Android which prevents such libraries from being properly loaded at the later time of application life. Part of the workaround was support for updating handle of such a library in our shared library cache. Since every library has different entries in the cache (because we search the array using xxHash generated from various forms of the library name), after preloading it we had to update every entry in the DSO cache with the correct handle, so that the library is never loaded again. The code which generates the caches and indexes at application build time worked fine in my testing (using `dotnet build`) but it turns out that using `dotnet publish` instead breaks the code in a subtle, but nasty way. The issue is that the code which generated the index of shared libraries to preload reused an array which stored the indexes, while generating code for different RIDs. This resulted in the very first RID to process to contain valid indexes, the second one would **append** its own indexes to the preceding RID's data, the third RID would further append its own data etc. This would result in the following index code generated for the subsequend RIDs: ``` ; android-arm ; Indices into dso_cache[] of DSO libraries to preload because of JNI use @dso_jni_preloads_idx = dso_local local_unnamed_addr constant [4 x i32] [ i32 15, ; libSystem.Security.Cryptography.Native.Android.so i32 0, ; libSystem.Security.Cryptography.Native.Android i32 7, ; System.Security.Cryptography.Native.Android.so i32 8 ; System.Security.Cryptography.Native.Android ], align 4 ``` ``` ; android-arm64 ; Indices into dso_cache[] of DSO libraries to preload because of JNI use @dso_jni_preloads_idx = dso_local local_unnamed_addr constant [8 x i32] [ i32 15, ; libSystem.Security.Cryptography.Native.Android.so i32 0, ; libSystem.Security.Cryptography.Native.Android i32 7, ; System.Security.Cryptography.Native.Android.so i32 8, ; System.Security.Cryptography.Native.Android i32 10, ; Invalid index 4 i32 0, ; Invalid index 5 i32 1, ; Invalid index 6 i32 14 ; Invalid index 7 ], align 4 ``` ``` ; android-x64 ; Indices into dso_cache[] of DSO libraries to preload because of JNI use @dso_jni_preloads_idx = dso_local local_unnamed_addr constant [12 x i32] [ i32 15, ; libSystem.Security.Cryptography.Native.Android.so i32 0, ; libSystem.Security.Cryptography.Native.Android i32 7, ; System.Security.Cryptography.Native.Android.so i32 8, ; System.Security.Cryptography.Native.Android i32 10, ; Invalid index 4 i32 0, ; Invalid index 5 i32 1, ; Invalid index 6 i32 14, ; Invalid index 7 i32 10, ; Invalid index 8 i32 0, ; Invalid index 9 i32 1, ; Invalid index 10 i32 14 ; Invalid index 11 ], align 16 ``` In effect, when running on an arm64 device, we would try to load, and cache the handle, of an entirely different shared library, leading to further problems to find a requested symbol: ``` 10-17 11:25:18.062 27900 27900 F monodroid-assembly: Failed to load symbol 'AndroidCryptoNative_EcKeyCreateByKeyParameters' from shared library 'libSystem.Security.Cryptography.Native.Android' 10-17 11:25:18.110 1444 4298 I ActivityManager: Process com.companyname.test_jwt (pid 27900) has died: fg TOP 10-17 11:25:18.110 1444 1712 I libprocessgroup: Removed cgroup /sys/fs/cgroup/apps/uid_10361/pid_27900 10-17 11:25:18.111 913 913 I Zygote : Process 27900 exited cleanly (0) ``` Native code attempted to load the symbol from a library that happened to be stored at the index valid for `android-arm` but not for e.g. `android-arm64`, which was not `libSystem.Security.Cryptography.Native.Android`, leading to the above red herring error. Note: if **all** of RIDs enabled for the application are 32-bit or **all** of them are 64-bit, things would work even though the generated code would be technically incorrect. This is because all of the hashes and, thus, sort order of the `dso_cache` entries would be the same. Fix this by making sure that the index array is not shared between different RIDs when generating the DSO cache code.
diff --git a/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGenerator.cs b/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGenerator.cs
@@ -279,7 +279,7 @@ protected override void Construct (LlvmIrModule module)
 			module.AddGlobalVariable ("dso_jni_preloads_idx_stride", dsoState.NameMutationsCount);
 
 			// This variable MUST be written after `dso_cache` since it relies on sorting performed by HashAndSortDSOCache
-			var dso_jni_preloads_idx = new LlvmIrGlobalVariable (new List<uint> (), "dso_jni_preloads_idx", LlvmIrVariableOptions.GlobalConstant) {
+			var dso_jni_preloads_idx = new LlvmIrGlobalVariable (typeof(List<uint>), "dso_jni_preloads_idx", LlvmIrVariableOptions.GlobalConstant) {
 				Comment = " Indices into dso_cache[] of DSO libraries to preload because of JNI use",
 				ArrayItemCount = (uint)dsoState.JniPreloadDSOs.Count,
 				GetArrayItemCommentCallback = GetPreloadIndicesLibraryName,
@@ -369,11 +369,6 @@ void AddAssemblyStores (LlvmIrModule module)
 
 		void PopulatePreloadIndices (LlvmIrVariable variable, LlvmIrModuleTarget target, object? state)
 		{
-			var indices = variable.Value as List<uint>;
-			if (indices == null) {
-				throw new InvalidOperationException ($"Internal error: DSO preload indices list instance not present.");
-			}
-
 			var dsoState = state as DsoCacheState;
 			if (dsoState == null) {
 				throw new InvalidOperationException ($"Internal error: DSO state not present.");
@@ -382,6 +377,8 @@ void PopulatePreloadIndices (LlvmIrVariable variable, LlvmIrModuleTarget target,
 			var dsoNames = new List<string> ();
 
 			// Indices array MUST NOT be sorted, since it groups alias entries together with the main entry
+			var indices = new List<uint> ();
+			variable.Value = indices;
 			foreach (DSOCacheEntry preload in dsoState.JniPreloadDSOs) {
 				int dsoIdx = dsoState.DsoCache.FindIndex (entry => {
 					if (entry.Instance == null) {
diff --git a/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGeneratorCLR.cs b/src/Xamarin.Android.Build.Tasks/Utilities/ApplicationConfigNativeAssemblyGeneratorCLR.cs
@@ -383,7 +383,7 @@ protected override void Construct (LlvmIrModule module)
 		module.AddGlobalVariable ("dso_jni_preloads_idx_stride", dsoState.NameMutationsCount);
 
 		// This variable MUST be written after `dso_cache` since it relies on sorting performed by HashAndSortDSOCache
-		var dso_jni_preloads_idx = new LlvmIrGlobalVariable (new List<uint> (), "dso_jni_preloads_idx", LlvmIrVariableOptions.GlobalConstant) {
+		var dso_jni_preloads_idx = new LlvmIrGlobalVariable (typeof (List<uint>), "dso_jni_preloads_idx", LlvmIrVariableOptions.GlobalConstant) {
 			Comment = " Indices into dso_cache[] of DSO libraries to preload because of JNI use",
 			ArrayItemCount = (uint)dsoState.JniPreloadDSOs.Count,
 			GetArrayItemCommentCallback = GetPreloadIndicesLibraryName,
@@ -601,11 +601,6 @@ void PopulateDsoApkEntries (LlvmIrVariable variable, LlvmIrModuleTarget target,
 
 	void PopulatePreloadIndices (LlvmIrVariable variable, LlvmIrModuleTarget target, object? state)
 	{
-		var indices = variable.Value as List<uint>;
-		if (indices == null) {
-			throw new InvalidOperationException ("Internal error: DSO preload indices list instance not present.");
-		}
-
 		var dsoState = state as DsoCacheState;
 		if (dsoState == null) {
 			throw new InvalidOperationException ("Internal error: DSO state not present.");
@@ -614,6 +609,8 @@ void PopulatePreloadIndices (LlvmIrVariable variable, LlvmIrModuleTarget target,
 		var dsoNames = new List<string> ();
 
 		// Indices array MUST NOT be sorted, since it groups alias entries together with the main entry
+		var indices = new List<uint> ();
+		variable.Value = indices;
 		foreach (DSOCacheEntry preload in dsoState.JniPreloadDSOs) {
 			int dsoIdx = dsoState.DsoCache.FindIndex (entry => {
 				if (entry.Instance == null) {
diff --git a/src/native/clr/include/host/pinvoke-override-impl.hh b/src/native/clr/include/host/pinvoke-override-impl.hh
@@ -57,7 +57,7 @@ namespace xamarin::android {
 
 		void *entry_handle = MonodroidDl::monodroid_dlsym (lib_handle, symbol_name);
 		if (entry_handle == nullptr) {
-			log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", library_name, symbol_name);
+			log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", symbol_name, library_name);
 			return nullptr;
 		}
 
diff --git a/src/native/mono/pinvoke-override/pinvoke-override-api-impl.hh b/src/native/mono/pinvoke-override/pinvoke-override-api-impl.hh
@@ -37,7 +37,7 @@ namespace xamarin::android {
 
 		void *entry_handle = internal::MonodroidDl::monodroid_dlsym (lib_handle, symbol_name, nullptr, nullptr);
 		if (entry_handle == nullptr) {
-			log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", optional_string (library_name), optional_string (symbol_name));
+			log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", optional_string (symbol_name), optional_string (library_name));
 			return nullptr;
 		}
 

Original file line number	Diff line number	Diff line change
`@@ -57,7 +57,7 @@ namespace xamarin::android {`
`57`	`57`
`58`	`58`	`void *entry_handle = MonodroidDl::monodroid_dlsym (lib_handle, symbol_name);`
`59`	`59`	`if (entry_handle == nullptr) {`
`60`		`- log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", library_name, symbol_name);`
	`60`	`+ log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", symbol_name, library_name);`
`61`	`61`	`return nullptr;`
`62`	`62`	`}`
`63`	`63`
Original file line number	Diff line number	Diff line change
`@@ -37,7 +37,7 @@ namespace xamarin::android {`
`37`	`37`
`38`	`38`	`void *entry_handle = internal::MonodroidDl::monodroid_dlsym (lib_handle, symbol_name, nullptr, nullptr);`
`39`	`39`	`if (entry_handle == nullptr) {`
`40`		`- log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", optional_string (library_name), optional_string (symbol_name));`
	`40`	`+ log_warn (LOG_ASSEMBLY, "Symbol '{}' not found in shared library '{}', p/invoke may fail", optional_string (symbol_name), optional_string (library_name));`
`41`	`41`	`return nullptr;`
`42`	`42`	`}`
`43`	`43`