minst.c

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/*
 * @(#)minst.c	1.1 06/01/28
 * 
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduce the above copyright notice, 
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may 
 * be used to endorse or promote products derived from this software without 
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL 
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, 
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY 
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, 
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */

#include "stdlib.h"

#include "minst.h"
#include "java_crw_demo.h"
	    
	   
/* ------------------------------------------------------------------- */
/* Some constant maximum sizes */

#define MAX_TOKEN_LENGTH	80
#define MAX_METHOD_NAME_LENGTH  256

/* Some constant names that tie to Java class/method names.
 *    We assume the Java class whose static methods we will be calling
 *    looks like:
 *
 * public class Minst {
 *     private static int engaged; 
 *     private static native void _method_entry(Object thr, int cnum, int mnum);
 *     public static void method_entry(int cnum, int mnum)
 *     {
 *   	   ...
 *     }
 * }
 *
 */

#define MINST_class	   Minst	    /* Name of class we are using */
#define MINST_entry        method_entry    /* Name of java entry method */
#define MINST_engaged      engaged         /* Name of java static field */

/* C macros to create strings from tokens */
#define _STRING(s) #s
#define STRING(s) _STRING(s)

/* ------------------------------------------------------------------- */

/* Global agent data structure */

typedef struct {
    /* JVMTI Environment */
    jvmtiEnv      *jvmti;
    jboolean       vm_is_dead;
    jboolean       vm_is_started;
    /* Data access Lock */
    jrawMonitorID  lock;
    /* Options */
    char           *include;
    char           *exclude;
    /* Class Count/ID */
    jint            ccount;
} GlobalAgentData;

static GlobalAgentData *gdata;

/* Enter a critical section by doing a JVMTI Raw Monitor Enter */
static void
enter_critical_section(jvmtiEnv *jvmti)
{
    jvmtiError error;
    
    error = (*jvmti)->RawMonitorEnter(jvmti, gdata->lock);
    check_jvmti_error(jvmti, error, "Cannot enter with raw monitor");
}

/* Exit a critical section by doing a JVMTI Raw Monitor Exit */
static void
exit_critical_section(jvmtiEnv *jvmti)
{
    jvmtiError error;
    
    error = (*jvmti)->RawMonitorExit(jvmti, gdata->lock);
    check_jvmti_error(jvmti, error, "Cannot exit with raw monitor");
}

/* Callback for JVMTI_EVENT_VM_START */
static void JNICALL
cbVMStart(jvmtiEnv *jvmti, JNIEnv *env)
{
    enter_critical_section(jvmti); {
        /* Indicate VM has started */
        gdata->vm_is_started = JNI_TRUE;
    } exit_critical_section(jvmti);
}

/* Callback for JVMTI_EVENT_VM_INIT */
static void JNICALL
cbVMInit(jvmtiEnv *jvmti, JNIEnv *env, jthread thread)
{
    enter_critical_section(jvmti); {
        jclass   klass;
	jfieldID field;

	/* Register Natives for class whose methods we use */
	klass = (*env)->FindClass(env, STRING(MINST_class));
	if ( klass == NULL ) {
	    fatal_error("ERROR: JNI: Cannot find %s with FindClass\n", 
			STRING(MINST_class));
	}
	
	/* Engage calls. */
	field = (*env)->GetStaticFieldID(env, klass, STRING(MINST_engaged), "I");
	if ( field == NULL ) {
	    fatal_error("ERROR: JNI: Cannot get field from %s\n", 
			STRING(MINST_class));
	}
	(*env)->SetStaticIntField(env, klass, field, 1);
    } exit_critical_section(jvmti);
}

/* Callback for JVMTI_EVENT_VM_DEATH */
static void JNICALL
cbVMDeath(jvmtiEnv *jvmti, JNIEnv *env)
{
    enter_critical_section(jvmti); {
        jclass   klass;
	jfieldID field;

	/* The VM has died. */
	stdout_message("VMDeath\n");

	/* Disengage calls in MINST_class. */
	klass = (*env)->FindClass(env, STRING(MINST_class));
	if ( klass == NULL ) {
	    fatal_error("ERROR: JNI: Cannot find %s with FindClass\n", 
			STRING(MINST_class));
	}
	field = (*env)->GetStaticFieldID(env, klass, STRING(MINST_engaged), "I");
	if ( field == NULL ) {
	    fatal_error("ERROR: JNI: Cannot get field from %s\n", 
			STRING(MINST_class));
	}
	(*env)->SetStaticIntField(env, klass, field, -1);

	/* The critical section here is important to hold back the VM death
	 *    until all other callbacks have completed.
	 */

	/* Since this critical section could be holding up other threads
	 *   in other event callbacks, we need to indicate that the VM is
	 *   dead so that the other callbacks can short circuit their work.
	 *   We don't expect any further events after VmDeath but we do need
	 *   to be careful that existing threads might be in our own agent
	 *   callback code.
	 */
	gdata->vm_is_dead = JNI_TRUE;

    } exit_critical_section(jvmti);
	
}  

/* Callback for JVMTI_EVENT_CLASS_FILE_LOAD_HOOK */
static void JNICALL
cbClassFileLoadHook(jvmtiEnv *jvmti, JNIEnv* env,
                jclass class_being_redefined, jobject loader,
                const char* name, jobject protection_domain,
                jint class_data_len, const unsigned char* class_data,
                jint* new_class_data_len, unsigned char** new_class_data)
{
    enter_critical_section(jvmti); {
	/* It's possible we get here right after VmDeath event, be careful */
	if ( !gdata->vm_is_dead ) {

	    const char *classname;

            /* Name could be NULL */
	    if ( name == NULL ) {
		classname = java_crw_demo_classname(class_data, class_data_len,
			NULL);
		if ( classname == NULL ) {
		    fatal_error("ERROR: No classname inside classfile\n");
		}
	    } else {
		classname = strdup(name);
		if ( classname == NULL ) {
		    fatal_error("ERROR: Out of malloc memory\n");
		}
	    }
	    
	    *new_class_data_len = 0;
            *new_class_data     = NULL;

            /* The tracker class itself? */
            if ( interested((char*)classname, "", gdata->include, gdata->exclude) 
		  &&  strcmp(classname, STRING(MINST_class)) != 0 ) {
                jint           cnum;
                int            system_class;
                unsigned char *new_image;
                long           new_length;

                /* Get unique number for every class file image loaded */
                cnum = gdata->ccount++;

                /* Is it a system class? If the class load is before VmStart
		 *   then we will consider it a system class that should
		 *   be treated carefully. (See java_crw_demo)
		 */
                system_class = 0;
                if ( !gdata->vm_is_started ) {
                    system_class = 1;
                }

                new_image = NULL;
                new_length = 0;