read bootstrap prefixes before incrementing call depth

Author: laurit

instrumentation/internal/internal-class-loader/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/internal/classloader/BootDelegationInstrumentation.java

@@ -21,6 +21,7 @@
 import io.opentelemetry.javaagent.bootstrap.CallDepth;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
+import java.util.List;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.asm.Advice.AssignReturned;
 import net.bytebuddy.description.method.MethodDescription;
@@ -69,7 +70,11 @@ public void transform(TypeTransformer transformer) {
   public static class LoadClassAdvice {
 
     @Advice.OnMethodEnter(skipOn = Advice.OnNonDefaultValue.class)
-    public static Class<?> onEnter(@Advice.Argument(0) String name) {
+    public static Class<?> onEnter(@Advice.This ClassLoader classLoader, @Advice.Argument(0) String name) {
+      // must be read before call depth is incremented as setting the call depth prevents the class
+      // loader of the instrumented class from loading BootstrapPackagePrefixesHolder itself
+      List<String> bootstrapPackagePrefixes = BootstrapPackagePrefixesHolder.getBootstrapPackagePrefixes();
+
       // need to use call depth here to prevent re-entry from call to Class.forName() below
       // because on some JVMs (e.g. IBM's, though IBM bootstrap loader is explicitly excluded above)
       // Class.forName() ends up calling loadClass() on the bootstrap loader which would then come
@@ -81,7 +86,7 @@ public static Class<?> onEnter(@Advice.Argument(0) String name) {
       }
 
       try {
-        for (String prefix : BootstrapPackagePrefixesHolder.getBoostrapPackagePrefixes()) {
+        for (String prefix : bootstrapPackagePrefixes) {
           if (name.startsWith(prefix)) {
             try {
               return Class.forName(name, false, null);

javaagent-bootstrap/src/main/java/io/opentelemetry/javaagent/bootstrap/BootstrapPackagePrefixesHolder.java

@@ -20,7 +20,7 @@ public final class BootstrapPackagePrefixesHolder {
 
   private static volatile List<String> bootstrapPackagePrefixes;
 
-  public static List<String> getBoostrapPackagePrefixes() {
+  public static List<String> getBootstrapPackagePrefixes() {
     return bootstrapPackagePrefixes;
   }
 

testing-common/integration-tests/src/test/java/instrumentation/AgentInstrumentationTest.java

@@ -39,7 +39,7 @@ class AgentInstrumentationTest {
 
   private static final ClassLoader BOOTSTRAP_CLASSLOADER = null;
   private static final List<String> BOOTSTRAP_PACKAGE_PREFIXES =
-      BootstrapPackagePrefixesHolder.getBoostrapPackagePrefixes();
+      BootstrapPackagePrefixesHolder.getBootstrapPackagePrefixes();
 
   @RegisterExtension
   static final InstrumentationExtension testing = AgentInstrumentationExtension.create();