Add command line option for dynamic agent loading

Signed-off-by: Devin Nakamura <[email protected]>
eclipse-openj9 · Jun 8, 2023 · 86e7238 · 86e7238
1 parent 26c5e55
commit 86e7238
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Showing 5 changed files with 31 additions and 3 deletions.
diff --git a/runtime/jvmti/j9jvmti.tdf b/runtime/jvmti/j9jvmti.tdf
@@ -658,3 +658,5 @@ TraceExit=Trc_JVMTI_jvmtiHookVirtualThreadUnmount_Exit Overhead=1 Level=5 Noenv
 
 TraceEntry=Trc_JVMTI_jvmtiHookVirtualThreadMount_Entry Overhead=1 Level=5 Noenv Template="HookVirtualThreadMount"
 TraceExit=Trc_JVMTI_jvmtiHookVirtualThreadMount_Exit Overhead=1 Level=5 Noenv Template="HookVirtualThreadMount"
+
+TraceEvent=Trc_JVMTI_loadAgentLibraryOnAttach_agentLoadingDisabled Overhead=1 Level=5 Noenv Template="loadAgentLibraryOnAttach: Dynamic agent loading is is disabled"
diff --git a/runtime/jvmti/jvmtiStartup.c b/runtime/jvmti/jvmtiStartup.c
@@ -575,6 +575,12 @@ loadAgentLibraryOnAttach(struct J9JavaVM * vm, const char * library, const char
 
 	Trc_JVMTI_loadAgentLibraryOnAttach_Entry(library);
 
+	if (J9_ARE_ANY_BITS_SET(vm->runtimeFlags, J9_RUNTIME_ALLOW_DYNAMIC_AGENT)){
+		Trc_JVMTI_loadAgentLibraryOnAttach_agentLoadingDisabled();
+		rc = JNI_ERR;
+		goto exit;
+	}
+
 	Assert_JVMTI_true(NULL != library); /* Library name must be non-null. */
 
 	if (NULL != options) {
@@ -701,6 +707,13 @@ loadAgentLibrary(J9JavaVM * vm, J9JVMTIAgentLibrary * agentLibrary)
 
 	Trc_JVMTI_loadAgentLibrary_Entry(agentLibrary->nativeLib.name);
 
+	/* If dynamic agent loading is disabled, the HCR/OSR flags default to off. */
+	omrthread_monitor_enter(vm->runtimeFlagsMutex);
+	if (J9_ARE_NO_BITS_SET(vm->runtimeFlags, J9_RUNTIME_ALLOW_DYNAMIC_AGENT)) {
+		vm->extendedRuntimeFlags |= (J9_EXTENDED_RUNTIME_OSR_SAFE_POINT | (UDATA)J9_EXTENDED_RUNTIME_ENABLE_HCR);
+	}
+	omrthread_monitor_exit(vm->runtimeFlagsMutex);
+
 	/* Attempt linking the agent statically, looking for Agent_OnLoad_L.
 	 * If this is not found, fall back on the regular, dynamic linking way.
 	 */

diff --git a/runtime/oti/j9consts.h b/runtime/oti/j9consts.h
@@ -286,7 +286,7 @@ extern "C" {
 #define J9_RUNTIME_ARGENCODING_UNICODE 0x2000
 #define J9_RUNTIME_ARGENCODING_LATIN 0x4000
 #define J9_RUNTIME_ARGENCODING_UTF8 0x8000
-#define J9_RUNTIME_UNUSED_0x10000 0x10000
+#define J9_RUNTIME_ALLOW_DYNAMIC_AGENT 0x10000
 #define J9_RUNTIME_UNUSED_0x20000 0x20000
 #define J9_RUNTIME_UNUSED_0x40000 0x40000
 #define J9_RUNTIME_UNUSED_0x80000 0x80000

diff --git a/runtime/oti/jvminit.h b/runtime/oti/jvminit.h
@@ -618,6 +618,9 @@ enum INIT_STAGE {
 #define VMOPT_XSYSLOG_OPT "-Xsyslog"
 #define MAPOPT_XSYSLOG_OPT_COLON "-Xsyslog:"
 
+#define VMOPT_XXENABLEDYNAMICAGENTLOADING "-XX:+EnableDynamicAgentLoading"
+#define VMOPT_XXNOENABLEDYNAMICAGENTLOADING "-XX:-EnableDynamicAgentLoading"
+
 /* Modularity command line options */
 #define VMOPT_MODULE_UPGRADE_PATH "--upgrade-module-path"
 #define VMOPT_MODULE_PATH "--module-path"

diff --git a/runtime/vm/jvminit.c b/runtime/vm/jvminit.c
@@ -3569,10 +3569,20 @@ processVMArgsFromFirstToLast(J9JavaVM * vm)
 	if (J2SE_VERSION(vm) >= J2SE_V11) {
 		vm->extendedRuntimeFlags |= (UDATA)J9_EXTENDED_RUNTIME_RESTRICT_IFA; /* Enable zAAP switching for Registered Natives and JVMTI callbacks by default in Java 9 and later. */
 	}
-	vm->extendedRuntimeFlags |= J9_EXTENDED_RUNTIME_OSR_SAFE_POINT; /* Enable OSR safe point by default */
-	vm->extendedRuntimeFlags |= (UDATA)J9_EXTENDED_RUNTIME_ENABLE_HCR; /* Enable HCR by default */
 	vm->extendedRuntimeFlags2 |= J9_EXTENDED_RUNTIME2_ENABLE_UTF_CACHE; /* Enable UTF cache by default */
 
+	{
+		IDATA noDynamicAgentLoading = FIND_AND_CONSUME_VMARG(EXACT_MATCH, VMOPT_XXNOENABLEDYNAMICAGENTLOADING, NULL);
+		IDATA dynamicAgentLoading = FIND_AND_CONSUME_VMARG(EXACT_MATCH, VMOPT_XXENABLEDYNAMICAGENTLOADING, NULL);
+		if (noDynamicAgentLoading > dynamicAgentLoading) {
+			vm->runtimeFlags &= J9_RUNTIME_ALLOW_DYNAMIC_AGENT;
+			vm->extendedRuntimeFlags &= ~(UDATA)(J9_EXTENDED_RUNTIME_OSR_SAFE_POINT | (UDATA) J9_EXTENDED_RUNTIME_ENABLE_HCR);
+		} else {
+			vm->runtimeFlags |= J9_RUNTIME_ALLOW_DYNAMIC_AGENT;
+			vm->extendedRuntimeFlags |= (J9_EXTENDED_RUNTIME_OSR_SAFE_POINT | (UDATA)J9_EXTENDED_RUNTIME_ENABLE_HCR);
+		}
+	}
+
 #if defined(J9VM_ARCH_X86) || defined(J9VM_ARCH_POWER) || defined(J9VM_ARCH_S390)
 	/* Enabled field watch by default on x86, Power, and S390 platforms */
 	vm->extendedRuntimeFlags |= J9_EXTENDED_RUNTIME_JIT_INLINE_WATCHES;
Original file line number	Diff line number	Diff line change
Expand Up		@@ -658,3 +658,5 @@ TraceExit=Trc_JVMTI_jvmtiHookVirtualThreadUnmount_Exit Overhead=1 Level=5 Noenv

		TraceEntry=Trc_JVMTI_jvmtiHookVirtualThreadMount_Entry Overhead=1 Level=5 Noenv Template="HookVirtualThreadMount"
		TraceExit=Trc_JVMTI_jvmtiHookVirtualThreadMount_Exit Overhead=1 Level=5 Noenv Template="HookVirtualThreadMount"

		TraceEvent=Trc_JVMTI_loadAgentLibraryOnAttach_agentLoadingDisabled Overhead=1 Level=5 Noenv Template="loadAgentLibraryOnAttach: Dynamic agent loading is is disabled"