On Tue, 24 Oct 2023 17:01:35 GMT, Jorn Vernee <jver...@openjdk.org> wrote:
> The result of `FindClass` is a local JNI handle (in > `find_class_from_class_loader`, called from `jni_FindClass` [1]). As such, we > need to wrap the return value of `FindClass` in a global reference when > storing it inside fallbackLinker.c. > > While investigating this, I also noticed an existing bug in > `JNIHandles::handle_type`. This method is used from the implementation of > `GetObjectRefType` ([2]), and from the implementation of `-Xcheck:jni` code. > The former specifies that `JNIInvalidRefType` is a valid return value, and > the latter compares the result against `JNIInvalidRefType`. However, if the > handle is not any valid type, the implementation bottoms out in a > `ShouldNotReachHere()`, meaning `JNIHandles::handle_type` can never return > `JNIInvalidRefType`. I've fixed this by letting the enclosing if/else chain > fall through to just returning the default result, which is > `JNIInvalidRefType`. In that case, I observe the expected stack trace when > running with `-Xcheck:jni`. For example: > > > FATAL ERROR in native method: Bad global or local ref passed to JNI > at > jdk.internal.foreign.abi.fallback.LibFallback.doDowncall(java.base@22-internal/Native > Method) > at > jdk.internal.foreign.abi.fallback.LibFallback.doDowncall(java.base@22-internal/LibFallback.java:94) > at > jdk.internal.foreign.abi.fallback.FallbackLinker.doDowncall(java.base@22-internal/FallbackLinker.java:197) > at > java.lang.invoke.LambdaForm$DMH/0x000001b585008000.invokeStaticInit(java.base@22-internal/LambdaForm$DMH) > at > java.lang.invoke.LambdaForm$MH/0x000001b585029400.invoke(java.base@22-internal/LambdaForm$MH) > at > java.lang.invoke.LambdaForm$MH/0x000001b58502d000.invokeExact_MT(java.base@22-internal/LambdaForm$MH) > at TestUpcallDeopt.payload(TestUpcallDeopt.java:93) > at TestUpcallDeopt.main(TestUpcallDeopt.java:84) > at > java.lang.invoke.LambdaForm$DMH/0x000001b585006800.invokeStatic(java.base@22-internal/LambdaForm$DMH) > at > java.lang.invoke.LambdaForm$MH/0x000001b58502a800.invoke(java.base@22-internal/LambdaForm$MH) > at > java.lang.invoke.Invokers$Holder.invokeExact_MT(java.base@22-internal/Invokers$Holder) > at > jdk.internal.reflect.DirectMethodHandleAccessor.invokeImpl(java.base@22-internal/DirectMethodHandleAccessor.java:154) > at > jdk.internal.reflect.DirectMethodHandleAccessor.invoke(java.base@22-internal/DirectMethodHandleAccessor.java:103) > at > java.lang.reflect.Method.invoke(java.base@22-internal/Method.java:580... src/java.base/share/native/libfallbackLinker/fallbackLinker.c line 48: > 46: Java_jdk_internal_foreign_abi_fallback_LibFallback_init(JNIEnv* env, > jclass cls) { > 47: (*env)->GetJavaVM(env, &VM); > 48: LibFallback_class = (*env)->NewGlobalRef(env, (*env)->FindClass(env, > "jdk/internal/foreign/abi/fallback/LibFallback")); It might be better to bail if FindClass returns null as there will be pending exception. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16349#discussion_r1370739992