1 /*

     2  * Copyright (c) 2019 SAP SE and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 #include <stdio.h>

    25 #include <string.h>

    26 

    27 #include "jvmti.h"

    28 

    29 static jvmtiEnv *jvmti = NULL;

    30 

    31 static const char* fields[] = { "Z", "B", "C", "S", "I", "J", "F", "D" };

    32 #define NUM_FIELDS (sizeof fields / sizeof fields[0])

    33 static jfieldID fieldIDs[NUM_FIELDS];

    34 static jlong fieldAccessCount = 0;

    35 

    36 

    37 JNIEXPORT jboolean JNICALL Java_FastGetField_initFieldIDs(JNIEnv *env, jobject this, jclass c) {

    38   for (int i = 0; i < (int)NUM_FIELDS; ++i) {

    39     fieldIDs[i] = (*env)->GetFieldID(env, c, fields[i], fields[i]);

    40     if (fieldIDs[i] == NULL) {

    41       printf("field %d not found\n", i);

    42       return JNI_FALSE;

    43     }

    44   }

    45   return JNI_TRUE;

    46 }

    47 

    48 

    49 JNIEXPORT jboolean JNICALL Java_FastGetField_initWatchers(JNIEnv *env, jobject this, jclass c) {

    50   if (jvmti == NULL) {

    51     printf("jvmti is NULL\n");

    52     return JNI_FALSE;

    53   }

    54 

    55   for (int i = 0; i < (int)NUM_FIELDS; ++i) {

    56     jvmtiError err = (*jvmti)->SetFieldAccessWatch(jvmti, c, fieldIDs[i]);

    57     if (err != JVMTI_ERROR_NONE) {

    58       printf("SetFieldAccessWatch failed with error %d\n", err);

    59       return JNI_FALSE;

    60     }

    61   }

    62 

    63   return JNI_TRUE;

    64 }

    65 

    66 

    67 JNIEXPORT jlong JNICALL Java_FastGetField_accessFields(JNIEnv *env, jobject this, jobject obj) {

    68   return

    69       (*env)->GetBooleanField(env, obj, fieldIDs[0]) +

    70       (*env)->GetByteField(env, obj, fieldIDs[1]) +

    71       (*env)->GetCharField(env, obj, fieldIDs[2]) +

    72       (*env)->GetShortField(env, obj, fieldIDs[3]) +

    73       (*env)->GetIntField(env, obj, fieldIDs[4]) +

    74       (*env)->GetLongField(env, obj, fieldIDs[5]) +

    75       (jlong)((*env)->GetFloatField(env, obj, fieldIDs[6])) +

    76       (jlong)((*env)->GetDoubleField(env, obj, fieldIDs[7]));

    77 }

    78 

    79 

    80 JNIEXPORT jlong JNICALL Java_FastGetField_getFieldAccessCount(JNIEnv *env, jclass c) {

    81   return fieldAccessCount;

    82 }

    83 

    84 

    85 static void JNICALL onFieldAccess(jvmtiEnv *jvmti_env, JNIEnv* jni_env, jthread thread,

    86                                   jmethodID method, jlocation location, jclass field_klass,

    87                                   jobject object, jfieldID field) {

    88   char *fname = NULL, *mname = NULL;

    89 

    90   jvmtiError err = (*jvmti)->GetFieldName(jvmti, field_klass, field, &fname, NULL, NULL);

    91   if (err != JVMTI_ERROR_NONE) {

    92     printf("GetFieldName failed with error %d\n", err);

    93     return;

    94   }

    95 

    96   err = (*jvmti)->GetMethodName(jvmti, method, &mname, NULL, NULL);

    97   if (err != JVMTI_ERROR_NONE) {

    98     printf("GetMethodName failed with error %d\n", err);

    99     return;

   100   }

   101 

   102   printf("%s accessed field %s\n", mname, fname);

   103 

   104   err = (*jvmti)->Deallocate(jvmti, (unsigned char*)fname);

   105   if (err != JVMTI_ERROR_NONE) {

   106     printf("Deallocate failed with error %d\n", err);

   107     return;

   108   }

   109 

   110   err = (*jvmti)->Deallocate(jvmti, (unsigned char*)mname);

   111   if (err != JVMTI_ERROR_NONE) {

   112     printf("Deallocate failed with error %d\n", err);

   113     return;

   114   }

   115 

   116   fieldAccessCount++;

   117 }

   118 

   119 

   120 JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM* vm, char* options, void* reserved) {

   121   jvmtiCapabilities capa;

   122   jvmtiEventCallbacks cbs = {0};

   123 

   124   (*vm)->GetEnv(vm, (void**)&jvmti, JVMTI_VERSION_1_0);

   125 

   126   memset(&capa, 0, sizeof(capa));

   127   capa.can_generate_field_access_events = 1;

   128   (*jvmti)->AddCapabilities(jvmti, &capa);

   129 

   130   cbs.FieldAccess = &onFieldAccess;

   131   (*jvmti)->SetEventCallbacks(jvmti, &cbs, sizeof(cbs));

   132   (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, JVMTI_EVENT_FIELD_ACCESS, NULL);

   133   printf("Loaded agent\n");

   134   fflush(stdout);

   135 

   136   return 0;

   137 }