1.1 --- a/src/share/vm/runtime/jniHandles.hpp Thu Nov 05 11:42:42 2015 +0100
1.2 +++ b/src/share/vm/runtime/jniHandles.hpp Tue May 07 20:38:26 2019 +0000
1.3 @@ -1,5 +1,5 @@
1.4 /*
1.5 - * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
1.6 + * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved.
1.7 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.8 *
1.9 * This code is free software; you can redistribute it and/or modify it
1.10 @@ -40,7 +40,28 @@
1.11 static JNIHandleBlock* _weak_global_handles; // First weak global handle block
1.12 static oop _deleted_handle; // Sentinel marking deleted handles
1.13
1.14 + inline static bool is_jweak(jobject handle);
1.15 + inline static oop& jobject_ref(jobject handle); // NOT jweak!
1.16 + inline static oop& jweak_ref(jobject handle);
1.17 +
1.18 + template<bool external_guard> inline static oop guard_value(oop value);
1.19 + template<bool external_guard> inline static oop resolve_impl(jobject handle);
1.20 + template<bool external_guard> static oop resolve_jweak(jweak handle);
1.21 +
1.22 public:
1.23 + // Low tag bit in jobject used to distinguish a jweak. jweak is
1.24 + // type equivalent to jobject, but there are places where we need to
1.25 + // be able to distinguish jweak values from other jobjects, and
1.26 + // is_weak_global_handle is unsuitable for performance reasons. To
1.27 + // provide such a test we add weak_tag_value to the (aligned) byte
1.28 + // address designated by the jobject to produce the corresponding
1.29 + // jweak. Accessing the value of a jobject must account for it
1.30 + // being a possibly offset jweak.
1.31 + static const uintptr_t weak_tag_size = 1;
1.32 + static const uintptr_t weak_tag_alignment = (1u << weak_tag_size);
1.33 + static const uintptr_t weak_tag_mask = weak_tag_alignment - 1;
1.34 + static const int weak_tag_value = 1;
1.35 +
1.36 // Resolve handle into oop
1.37 inline static oop resolve(jobject handle);
1.38 // Resolve externally provided handle into oop with some guards
1.39 @@ -173,36 +194,85 @@
1.40 #endif
1.41 };
1.42
1.43 +inline bool JNIHandles::is_jweak(jobject handle) {
1.44 + STATIC_ASSERT(weak_tag_size == 1);
1.45 + STATIC_ASSERT(weak_tag_value == 1);
1.46 + return (reinterpret_cast<uintptr_t>(handle) & weak_tag_mask) != 0;
1.47 +}
1.48 +
1.49 +inline oop& JNIHandles::jobject_ref(jobject handle) {
1.50 + assert(!is_jweak(handle), "precondition");
1.51 + return *reinterpret_cast<oop*>(handle);
1.52 +}
1.53 +
1.54 +inline oop& JNIHandles::jweak_ref(jobject handle) {
1.55 + assert(is_jweak(handle), "precondition");
1.56 + char* ptr = reinterpret_cast<char*>(handle) - weak_tag_value;
1.57 + return *reinterpret_cast<oop*>(ptr);
1.58 +}
1.59 +
1.60 +// external_guard is true if called from resolve_external_guard.
1.61 +// Treat deleted (and possibly zapped) as NULL for external_guard,
1.62 +// else as (asserted) error.
1.63 +template<bool external_guard>
1.64 +inline oop JNIHandles::guard_value(oop value) {
1.65 + if (!external_guard) {
1.66 + assert(value != badJNIHandle, "Pointing to zapped jni handle area");
1.67 + assert(value != deleted_handle(), "Used a deleted global handle");
1.68 + } else if ((value == badJNIHandle) || (value == deleted_handle())) {
1.69 + value = NULL;
1.70 + }
1.71 + return value;
1.72 +}
1.73 +
1.74 +// external_guard is true if called from resolve_external_guard.
1.75 +template<bool external_guard>
1.76 +inline oop JNIHandles::resolve_impl(jobject handle) {
1.77 + assert(handle != NULL, "precondition");
1.78 + oop result;
1.79 + if (is_jweak(handle)) { // Unlikely
1.80 + result = resolve_jweak<external_guard>(handle);
1.81 + } else {
1.82 + result = jobject_ref(handle);
1.83 + // Construction of jobjects canonicalize a null value into a null
1.84 + // jobject, so for non-jweak the pointee should never be null.
1.85 + assert(external_guard || result != NULL,
1.86 + "Invalid value read from jni handle");
1.87 + result = guard_value<external_guard>(result);
1.88 + }
1.89 + return result;
1.90 +}
1.91
1.92 inline oop JNIHandles::resolve(jobject handle) {
1.93 - oop result = (handle == NULL ? (oop)NULL : *(oop*)handle);
1.94 - assert(result != NULL || (handle == NULL || !CheckJNICalls || is_weak_global_handle(handle)), "Invalid value read from jni handle");
1.95 - assert(result != badJNIHandle, "Pointing to zapped jni handle area");
1.96 + oop result = NULL;
1.97 + if (handle != NULL) {
1.98 + result = resolve_impl<false /* external_guard */ >(handle);
1.99 + }
1.100 return result;
1.101 -};
1.102 +}
1.103
1.104 -
1.105 +// Resolve some erroneous cases to NULL, rather than treating them as
1.106 +// possibly unchecked errors. In particular, deleted handles are
1.107 +// treated as NULL (though a deleted and later reallocated handle
1.108 +// isn't detected).
1.109 inline oop JNIHandles::resolve_external_guard(jobject handle) {
1.110 - if (handle == NULL) return NULL;
1.111 - oop result = *(oop*)handle;
1.112 - if (result == NULL || result == badJNIHandle) return NULL;
1.113 + oop result = NULL;
1.114 + if (handle != NULL) {
1.115 + result = resolve_impl<true /* external_guard */ >(handle);
1.116 + }
1.117 return result;
1.118 -};
1.119 -
1.120 +}
1.121
1.122 inline oop JNIHandles::resolve_non_null(jobject handle) {
1.123 assert(handle != NULL, "JNI handle should not be null");
1.124 - oop result = *(oop*)handle;
1.125 - assert(result != NULL, "Invalid value read from jni handle");
1.126 - assert(result != badJNIHandle, "Pointing to zapped jni handle area");
1.127 - // Don't let that private _deleted_handle object escape into the wild.
1.128 - assert(result != deleted_handle(), "Used a deleted global handle.");
1.129 + oop result = resolve_impl<false /* external_guard */ >(handle);
1.130 + assert(result != NULL, "NULL read from jni handle");
1.131 return result;
1.132 -};
1.133 +}
1.134
1.135 inline void JNIHandles::destroy_local(jobject handle) {
1.136 if (handle != NULL) {
1.137 - *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
1.138 + jobject_ref(handle) = deleted_handle();
1.139 }
1.140 }
1.141
