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semeru.c
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semeru.c
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/*
* Program for loading a JVM.
* Notable environment variables: LD_LIBRARY_PATH
* Notable jvm parameters: -Djava.class.path=...
* Main method signature: public static void main(String[] args);
* Shutdown method signature: public static void shutdown();
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <pthread.h>
#include <jni.h>
#include <err.h>
#ifdef CAPS_SUPPORT
#include <pwd.h>
#include <sys/prctl.h>
#include <sys/capability.h>
static char* userName = NULL;
static char* capsText = NULL;
#endif
static pthread_mutex_t threadLock = PTHREAD_MUTEX_INITIALIZER;
static int vmArgsCount;
static char** vmArgs;
static char* className;
static int mainArgsCount;
static char** mainArgs;
static JavaVM* jvm;
static JNIEnv* mainEnv;
static jclass mainClass;
static jmethodID mainMethod;
static jmethodID shutdownMethod;
static jmethodID reloadMethod;
static volatile int lastSignal = 0;
static void syntax()
{
#ifdef CAPS_SUPPORT
printf("syntax: semeru [-u user] [-c caps] [jvm options...] <classname> [params...]\n");
#else
printf("syntax: semeru [jvm options...] <classname> [params...]\n");
#endif
exit(1);
}
static void parse_args(int argc, char *argv[])
{
int i = 1;
int vmArgsIndex;
int classNameIndex = 0;
#ifdef CAPS_SUPPORT
for (; i < argc; i++) {
if (!strcmp("-u", argv[i])) {
if (++i >= argc)
syntax();
userName = argv[i];
}
else if (!strcmp("-c", argv[i])) {
if (++i >= argc)
syntax();
capsText = argv[i];
}
else {
break;
}
}
#endif
vmArgsIndex = i;
for (; i < argc; i++) {
if (argv[i][0] != '-') {
classNameIndex = i;
break;
}
}
if (classNameIndex == 0) {
syntax();
}
vmArgsCount = classNameIndex - vmArgsIndex;
vmArgs = &argv[vmArgsIndex];
className = argv[classNameIndex];
for (i = 0; className[i] != '\0'; i++) {
if (className[i] == '.')
className[i] = '/';
}
mainArgsCount = argc - (classNameIndex + 1);
mainArgs = &argv[classNameIndex + 1];
}
#ifdef CAPS_SUPPORT
static void set_keepcaps(int enabled)
{
if ((capsText != NULL) && (prctl(PR_SET_KEEPCAPS, enabled) != 0))
err(50, "prctl(PR_SET_KEEPCAPS, %d) failed", enabled);
}
static void set_user()
{
if (userName != NULL) {
struct passwd *pwEnt = getpwnam(userName);
if (pwEnt == NULL)
errx(50, "User not found: %s", userName);
set_keepcaps(1);
if (setregid(pwEnt->pw_gid, pwEnt->pw_gid) != 0)
err(50, "Failed to change group");
if (setreuid(pwEnt->pw_uid, pwEnt->pw_uid) != 0)
err(50, "Failed to change user");
set_keepcaps(0);
}
}
static void set_caps()
{
if (capsText != NULL) {
cap_t caps = cap_from_text(capsText);
if (caps == NULL)
errx(50, "Failed to parse capabilities: %s", capsText);
if (cap_set_proc(caps) < 0)
err(50, "Failed to set capabilities");
cap_free(caps);
}
}
#endif
static void* thread_func(void* arg)
{
JNIEnv *env;
jmethodID method;
while (1) {
pthread_mutex_lock(&threadLock);
method = (lastSignal == SIGHUP) ? reloadMethod : shutdownMethod;
if ((*jvm)->AttachCurrentThreadAsDaemon(jvm, (void**)&env, NULL) != JNI_OK) {
errx(50, "AttachCurrentThreadAsDaemon() failed");
}
(*env)->CallStaticVoidMethod(env, mainClass, method);
if ((*env)->ExceptionOccurred(env) != NULL) {
(*env)->ExceptionDescribe(env);
}
(*jvm)->DetachCurrentThread(jvm);
}
return NULL;
}
static void create_thread()
{
pthread_t hthread;
pthread_mutex_lock(&threadLock);
if (pthread_create(&hthread, NULL, thread_func, jvm) != 0)
errx(50, "pthread_create() failed");
if (pthread_detach(hthread) != 0)
errx(50, "pthread_detach() failed");
}
static void create_jvm()
{
int i;
JavaVMInitArgs vm_args;
vm_args.version = JNI_VERSION_1_4;
vm_args.ignoreUnrecognized = JNI_FALSE;
vm_args.nOptions = vmArgsCount;
vm_args.options = malloc(vmArgsCount * sizeof(JavaVMOption));
for (i = 0; i < vmArgsCount; i++) {
vm_args.options[i].optionString = vmArgs[i];
vm_args.options[i].extraInfo = NULL;
}
if (JNI_CreateJavaVM(&jvm, (void**)&mainEnv, &vm_args) != 0)
errx(50, "JNI_CreateJavaVM() failed");
mainClass = (*mainEnv)->FindClass(mainEnv, className);
if (mainClass == NULL)
errx(50, "Main class not found: %s", className);
mainMethod = (*mainEnv)->GetStaticMethodID(mainEnv, mainClass, "main", "([Ljava/lang/String;)V");
if (mainMethod == NULL)
errx(50, "Main method not found in: %s", className);
shutdownMethod = (*mainEnv)->GetStaticMethodID(mainEnv, mainClass, "shutdown", "()V");
if (shutdownMethod == NULL)
errx(50, "Shutdown method not found in: %s", className);
reloadMethod = (*mainEnv)->GetStaticMethodID(mainEnv, mainClass, "reload", "()V");
(*mainEnv)->ExceptionClear(mainEnv); /* Ignore possible exception caused by missing reload() */
}
static void sighandler(int num)
{
lastSignal = num;
pthread_mutex_unlock(&threadLock);
}
static void install_sighandler()
{
struct sigaction sa;
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);
sa.sa_handler = sighandler;
if (sigaction(SIGINT, &sa, NULL) != 0)
err(50, "sigaction(SIGINT) failed");
if (sigaction(SIGTERM, &sa, NULL) != 0)
err(50, "sigaction(SIGTERM) failed");
if ((reloadMethod != NULL) && (sigaction(SIGHUP, &sa, NULL) != 0))
err(50, "sigaction(SIGHUP) failed");
}
static void run()
{
int i;
jclass stringClass;
jobjectArray args;
stringClass = (*mainEnv)->FindClass(mainEnv, "java/lang/String");
args = (*mainEnv)->NewObjectArray(mainEnv, mainArgsCount, stringClass, NULL);
for (i = 0; i < mainArgsCount; i++) {
jstring jstr = (*mainEnv)->NewStringUTF(mainEnv, mainArgs[i]);
(*mainEnv)->SetObjectArrayElement(mainEnv, args, i, jstr);
}
(*mainEnv)->CallStaticVoidMethod(mainEnv, mainClass, mainMethod, args);
/* Will never be reached if System.exit() is called */
if ((*mainEnv)->ExceptionOccurred(mainEnv)) {
(*mainEnv)->ExceptionDescribe(mainEnv);
}
(*jvm)->DestroyJavaVM(jvm);
}
int main(int argc, char *argv[])
{
parse_args(argc, argv);
#ifdef CAPS_SUPPORT
set_user();
set_caps();
#endif
create_thread();
create_jvm();
install_sighandler();
run();
return 0;
}