MemTags escaping the JVM!

Author: jdksjolen

src/hotspot/share/include/jvm.h

@@ -394,6 +394,16 @@ JNIEXPORT jobject JNICALL
 JVM_NewMultiArray(JNIEnv *env, jclass eltClass, jintArray dim);
 
 
+/*
+ * Native memory allocation via NMT.
+ */
+typedef uint16_t arena_t;
+JNIEXPORT arena_t JNICALL JVM_MakeArena(const char *name);
+JNIEXPORT void *JNICALL JVM_ArenaAlloc(size_t size, arena_t a);
+JNIEXPORT void *JNICALL JVM_ArenaRealloc(void *p, size_t size, arena_t a);
+JNIEXPORT void *JNICALL JVM_ArenaCalloc(size_t numelems, size_t elemsize, arena_t a);
+JNIEXPORT void JNICALL JVM_ArenaFree(void* ptr);
+
 /*
  * Returns the immediate caller class of the native method invoking
  * JVM_GetCallerClass.  The Method.invoke and other frames due to

src/hotspot/share/prims/jvm.cpp

@@ -3836,3 +3836,33 @@ JVM_END
 JVM_LEAF(jboolean, JVM_PrintWarningAtDynamicAgentLoad(void))
   return (EnableDynamicAgentLoading && !FLAG_IS_CMDLINE(EnableDynamicAgentLoading)) ? JNI_TRUE : JNI_FALSE;
 JVM_END
+
+JNIEXPORT arena_t JNICALL
+JVM_MakeArena(const char *name) {
+  return static_cast<arena_t>(MemTagFactory::tag(name));
+}
+
+JNIEXPORT void* JNICALL
+JVM_ArenaAlloc(size_t size, arena_t arena) {
+  return os::malloc(size, static_cast<MemTag>(arena));
+}
+
+JNIEXPORT void* JNICALL
+JVM_ArenaRealloc(void *p, size_t size, arena_t arena) {
+  return os::realloc(p, size, static_cast<MemTag>(arena));
+}
+
+JNIEXPORT void* JNICALL
+JVM_ArenaCalloc(size_t numelems, size_t elemsize, arena_t arena) {
+  // Overflow check.
+  if (std::numeric_limits<size_t>::max() / elemsize < numelems) {
+    return nullptr;
+  }
+  size_t total_size = numelems * elemsize;
+  return os::malloc(total_size, static_cast<MemTag>(arena));
+}
+
+JNIEXPORT void JNICALL
+JVM_ArenaFree(void* ptr) {
+  os::free(ptr);
+}