Java example source code file (agent_util.c)

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The agent_util.c Java example source code

/*
 * Copyright (c) 2004, 2011, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions 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 Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


#include <agent_util.h>

/* ------------------------------------------------------------------- */
/* Generic C utility functions */

/* Send message to stdout or whatever the data output location is */
void
stdout_message(const char * format, ...)
{
    va_list ap;

    va_start(ap, format);
    (void)vfprintf(stdout, format, ap);
    va_end(ap);
}

/* Send message to stderr or whatever the error output location is and exit  */
void
fatal_error(const char * format, ...)
{
    va_list ap;

    va_start(ap, format);
    (void)vfprintf(stderr, format, ap);
    (void)fflush(stderr);
    va_end(ap);
    exit(3);
}

/* Get a token from a string (strtok is not MT-safe)
 *    str       String to scan
 *    seps      Separation characters
 *    buf       Place to put results
 *    max       Size of buf
 *  Returns NULL if no token available or can't do the scan.
 */
char *
get_token(char *str, char *seps, char *buf, int max)
{
    int len;

    buf[0] = 0;
    if ( str==NULL || str[0]==0 ) {
        return NULL;
    }
    str += strspn(str, seps);
    if ( str[0]==0 ) {
        return NULL;
    }
    len = (int)strcspn(str, seps);
    if ( len >= max ) {
        return NULL;
    }
    (void)strncpy(buf, str, len);
    buf[len] = 0;
    return str+len;
}

/* Determines if a class/method is specified by a list item
 *   item       String that represents a pattern to match
 *                If it starts with a '*', then any class is allowed
 *                If it ends with a '*', then any method is allowed
 *   cname      Class name, e.g. "java.lang.Object"
 *   mname      Method name, e.g. "<init>"
 *  Returns 1(true) or 0(false).
 */
static int
covered_by_list_item(char *item, char *cname, char *mname)
{
    int      len;

    len = (int)strlen(item);
    if ( item[0]=='*' ) {
        if ( strncmp(mname, item+1, len-1)==0 ) {
            return 1;
        }
    } else if ( item[len-1]=='*' ) {
        if ( strncmp(cname, item, len-1)==0 ) {
            return 1;
        }
    } else {
        int cname_len;

        cname_len = (int)strlen(cname);
        if ( strncmp(cname, item, (len>cname_len?cname_len:len))==0 ) {
            if ( cname_len >= len ) {
                /* No method name supplied in item, we must have matched */
                return 1;
            } else {
                int mname_len;

                mname_len = (int)strlen(mname);
                item += cname_len+1;
                len -= cname_len+1;
                if ( strncmp(mname, item, (len>mname_len?mname_len:len))==0 ) {
                    return 1;
                }
            }
        }
    }
    return 0;
}

/* Determines if a class/method is specified by this list
 *   list       String of comma separated pattern items
 *   cname      Class name, e.g. "java.lang.Object"
 *   mname      Method name, e.g. "<init>"
 *  Returns 1(true) or 0(false).
 */
static int
covered_by_list(char *list, char *cname, char *mname)
{
    char  token[1024];
    char *next;

    if ( list[0] == 0 ) {
        return 0;
    }

    next = get_token(list, ",", token, sizeof(token));
    while ( next != NULL ) {
        if ( covered_by_list_item(token, cname, mname) ) {
            return 1;
        }
        next = get_token(next, ",", token, sizeof(token));
    }
    return 0;
}

/* Determines which class and methods we are interested in
 *   cname              Class name, e.g. "java.lang.Object"
 *   mname              Method name, e.g. "<init>"
 *   include_list       Empty or an explicit list for inclusion
 *   exclude_list       Empty or an explicit list for exclusion
 *  Returns 1(true) or 0(false).
 */
int
interested(char *cname, char *mname, char *include_list, char *exclude_list)
{
    if ( exclude_list!=NULL && exclude_list[0]!=0 &&
            covered_by_list(exclude_list, cname, mname) ) {
        return 0;
    }
    if ( include_list!=NULL && include_list[0]!=0 &&
            !covered_by_list(include_list, cname, mname) ) {
        return 0;
    }
    return 1;
}

/* ------------------------------------------------------------------- */
/* Generic JVMTI utility functions */

/* Every JVMTI interface returns an error code, which should be checked
 *   to avoid any cascading errors down the line.
 *   The interface GetErrorName() returns the actual enumeration constant
 *   name, making the error messages much easier to understand.
 */
void
check_jvmti_error(jvmtiEnv *jvmti, jvmtiError errnum, const char *str)
{
    if ( errnum != JVMTI_ERROR_NONE ) {
        char       *errnum_str;

        errnum_str = NULL;
        (void)(*jvmti)->GetErrorName(jvmti, errnum, &errnum_str);

        fatal_error("ERROR: JVMTI: %d(%s): %s\n", errnum,
                (errnum_str==NULL?"Unknown":errnum_str),
                (str==NULL?"":str));
    }
}

/* All memory allocated by JVMTI must be freed by the JVMTI Deallocate
 *   interface.
 */
void
deallocate(jvmtiEnv *jvmti, void *ptr)
{
    jvmtiError error;

    error = (*jvmti)->Deallocate(jvmti, ptr);
    check_jvmti_error(jvmti, error, "Cannot deallocate memory");
}

/* Allocation of JVMTI managed memory */
void *
allocate(jvmtiEnv *jvmti, jint len)
{
    jvmtiError error;
    void      *ptr;

    error = (*jvmti)->Allocate(jvmti, len, (unsigned char **)&ptr);
    check_jvmti_error(jvmti, error, "Cannot allocate memory");
    return ptr;
}

/* Add demo jar file to boot class path (the BCI Tracker class must be
 *     in the boot classpath)
 *
 *   WARNING: This code assumes that the jar file can be found at one of:
 *              ${JAVA_HOME}/demo/jvmti/${DEMO_NAME}/${DEMO_NAME}.jar
 *              ${JAVA_HOME}/../demo/jvmti/${DEMO_NAME}/${DEMO_NAME}.jar
 *            where JAVA_HOME may refer to the jre directory.
 *            Both these values are added to the boot classpath.
 *            These locations are only true for these demos, installed
 *            in the JDK area. Platform specific code could be used to
 *            find the location of the DLL or .so library, and construct a
 *            path name to the jar file, relative to the library location.
 */
void
add_demo_jar_to_bootclasspath(jvmtiEnv *jvmti, char *demo_name)
{
    jvmtiError error;
    char      *file_sep;
    int        max_len;
    char      *java_home;
    char       jar_path[FILENAME_MAX+1];

    java_home = NULL;
    error = (*jvmti)->GetSystemProperty(jvmti, "java.home", &java_home);
    check_jvmti_error(jvmti, error, "Cannot get java.home property value");
    if ( java_home == NULL || java_home[0] == 0 ) {
        fatal_error("ERROR: Java home not found\n");
    }

#ifdef WIN32
    file_sep = "\\";
#else
    file_sep = "/";
#endif

    max_len = (int)(strlen(java_home) + strlen(demo_name)*2 +
                         strlen(file_sep)*5 +
                         16 /* ".." "demo" "jvmti" ".jar" NULL */ );
    if ( max_len > (int)sizeof(jar_path) ) {
        fatal_error("ERROR: Path to jar file too long\n");
    }
    (void)strcpy(jar_path, java_home);
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, "demo");
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, "jvmti");
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, demo_name);
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, demo_name);
    (void)strcat(jar_path, ".jar");
    error = (*jvmti)->AddToBootstrapClassLoaderSearch(jvmti, (const char*)jar_path);
    check_jvmti_error(jvmti, error, "Cannot add to boot classpath");

    (void)strcpy(jar_path, java_home);
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, "..");
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, "demo");
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, "jvmti");
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, demo_name);
    (void)strcat(jar_path, file_sep);
    (void)strcat(jar_path, demo_name);
    (void)strcat(jar_path, ".jar");

    error = (*jvmti)->AddToBootstrapClassLoaderSearch(jvmti, (const char*)jar_path);
    check_jvmti_error(jvmti, error, "Cannot add to boot classpath");
}

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