private void extractArguments(String[] args) {
String testArgsString = Config.getString("AutoGrader.testArgs");
if (testArgsString == null) {
testArgsString = "";
}
for (int i = 0; i < args.length; ) {
String arg = args[i++];
if (arg.length() > 0 && arg.charAt(0) == '-') {
if (arg.equals("-#")) {
Lib.assertTrue(i < args.length, "-# switch missing argument");
testArgsString = args[i++];
}
}
}
StringTokenizer st = new StringTokenizer(testArgsString, ",\n\t\f\r");
while (st.hasMoreTokens()) {
StringTokenizer pair = new StringTokenizer(st.nextToken(), "=");
Lib.assertTrue(pair.hasMoreTokens(), "test argument missing key");
String key = pair.nextToken();
Lib.assertTrue(pair.hasMoreTokens(), "test argument missing value");
String value = pair.nextToken();
testArgs.put(key, value);
}
}
/**
* Context switch between the current TCB and this TCB. This TCB will become the new current TCB.
* It is acceptable for this TCB to be the current TCB.
*/
public void contextSwitch() {
/* Probably unnecessary sanity check: we make sure that the current
* thread is bound to the current TCB. This check can only fail if
* non-Nachos threads invoke start().
*/
Lib.assertTrue(currentTCB.javaThread == Thread.currentThread());
// make sure AutoGrader.runningThread() called associateThread()
Lib.assertTrue(currentTCB.associated);
currentTCB.associated = false;
// can't switch from a TCB to itself
if (this == currentTCB) return;
/* There are some synchronization concerns here. As soon as we wake up
* the next thread, we cannot assume anything about static variables,
* or about any TCB's state. Therefore, before waking up the next
* thread, we must latch the value of currentTCB, and set its running
* flag to false (so that, in case we get interrupted before we call
* yield(), the interrupt will set the running flag and yield() won't
* block).
*/
TCB previous = currentTCB;
previous.running = false;
this.interrupt();
previous.yield();
}
private void associateThread(KThread thread) {
// make sure AutoGrader.runningThread() gets called only once per
// context switch
Lib.assertTrue(!associated);
associated = true;
Lib.assertTrue(thread != null);
if (nachosThread != null) Lib.assertTrue(thread == nachosThread);
else nachosThread = thread;
}
/**
* Destroy this TCB. This TCB must not be in use by the current thread. This TCB must also have
* been authorized to be destroyed by the autograder.
*/
public void destroy() {
// make sure the current TCB is correct
Lib.assertTrue(currentTCB != null && currentTCB.javaThread == Thread.currentThread());
// can't destroy current thread
Lib.assertTrue(this != currentTCB);
// thread must have started but not be destroyed yet
Lib.assertTrue(javaThread != null && !done);
// ensure AutoGrader.finishingCurrentThread() called authorizeDestroy()
Lib.assertTrue(nachosThread == toBeDestroyed);
toBeDestroyed = null;
this.done = true;
currentTCB.running = false;
this.interrupt();
currentTCB.waitForInterrupt();
this.javaThread = null;
}
/**
* Nachos main entry point.
*
* @param args the command line arguments.
*/
public static void main(final String[] args) {
System.out.print("nachos 5.0j initializing...");
Lib.assertTrue(Machine.args == null);
Machine.args = args;
processArgs();
Config.load(configFileName);
// get the current directory (.)
baseDirectory = new File(new File("").getAbsolutePath());
// get the nachos directory (./nachos)
nachosDirectory = new File(baseDirectory, "nachos");
String testDirectoryName = Config.getString("FileSystem.testDirectory");
// get the test directory
if (testDirectoryName != null) {
testDirectory = new File(testDirectoryName);
} else {
// use ../test
testDirectory = new File(baseDirectory.getParentFile(), "test");
}
securityManager = new NachosSecurityManager(testDirectory);
privilege = securityManager.getPrivilege();
privilege.machine = new MachinePrivilege();
TCB.givePrivilege(privilege);
privilege.stats = stats;
securityManager.enable();
createDevices();
checkUserClasses();
autoGrader = (AutoGrader) Lib.constructObject(autoGraderClassName);
new TCB()
.start(
new Runnable() {
public void run() {
autoGrader.start(privilege);
}
});
}
private void threadroot() {
// this should be running the current thread
Lib.assertTrue(javaThread == Thread.currentThread());
if (!isFirstTCB) {
/* start() is waiting for us to wake it up, signalling that it's OK
* to context switch to us. We leave the running flag false so that
* we'll still run if a context switch happens before we go to
* sleep. All we have to do is wake up the current TCB and then
* wait to get woken up by contextSwitch() or destroy().
*/
currentTCB.interrupt();
this.yield();
} else {
/* start() called us directly, so we just need to initialize
* a couple things.
*/
currentTCB = this;
running = true;
}
try {
target.run();
// no way out of here without going throw one of the catch blocks
Lib.assertNotReached();
} catch (ThreadDeath e) {
// make sure this TCB is being destroyed properly
if (!done) {
System.out.print("\nTCB terminated improperly!\n");
privilege.exit(1);
}
runningThreads.removeElement(this);
if (runningThreads.isEmpty()) privilege.exit(0);
} catch (Throwable e) {
System.out.print("\n");
e.printStackTrace();
runningThreads.removeElement(this);
if (runningThreads.isEmpty()) privilege.exit(1);
else die();
}
}
/**
* Start this autograder. Extract the <tt>-#</tt> arguments, call <tt>init()</tt>, load and
* initialize the kernel, and call <tt>run()</tt>.
*
* @param privilege encapsulates privileged access to the Nachos machine.
*/
public void start(Privilege privilege) {
Lib.assertTrue(this.privilege == null, "start() called multiple times");
this.privilege = privilege;
String[] args = Machine.getCommandLineArguments();
extractArguments(args);
System.out.print(" grader");
init();
System.out.print("\n");
kernel = (Kernel) Lib.constructObject(Config.getString("Kernel.kernel"));
kernel.initialize(args);
run();
}
private static void processArgs() {
for (int i = 0; i < args.length; ) {
String arg = args[i++];
if (arg.length() > 0 && arg.charAt(0) == '-') {
if (arg.equals("-d")) {
Lib.assertTrue(i < args.length, "switch without argument");
Lib.enableDebugFlags(args[i++]);
} else if (arg.equals("-h")) {
System.out.print(help);
System.exit(1);
} else if (arg.equals("-m")) {
Lib.assertTrue(i < args.length, "switch without argument");
try {
numPhysPages = Integer.parseInt(args[i++]);
} catch (NumberFormatException e) {
Lib.assertNotReached("bad value for -m switch");
}
} else if (arg.equals("-s")) {
Lib.assertTrue(i < args.length, "switch without argument");
try {
randomSeed = Long.parseLong(args[i++]);
} catch (NumberFormatException e) {
Lib.assertNotReached("bad value for -s switch");
}
} else if (arg.equals("-x")) {
Lib.assertTrue(i < args.length, "switch without argument");
shellProgramName = args[i++];
} else if (arg.equals("-z")) {
System.out.print(copyright);
System.exit(1);
}
// these switches are reserved for the autograder
else if (arg.equals("-[]")) {
Lib.assertTrue(i < args.length, "switch without argument");
configFileName = args[i++];
} else if (arg.equals("--")) {
Lib.assertTrue(i < args.length, "switch without argument");
autoGraderClassName = args[i++];
}
}
}
Lib.seedRandom(randomSeed);
}
/**
* Notify the autograder that a user program executed a syscall instruction.
*
* @param privilege proves the authenticity of this call.
* @return <tt>true</tt> if the kernel exception handler should be called.
*/
public boolean exceptionHandler(Privilege privilege) {
Lib.assertTrue(privilege == this.privilege, "security violation");
return true;
}
private void delay() {
long time = Machine.timer().getTime();
int amount = 1000;
ThreadedKernel.alarm.waitUntil(amount);
Lib.assertTrue(Machine.timer().getTime() >= time + amount);
}
String getStringArgument(String key) {
String value = (String) testArgs.get(key);
Lib.assertTrue(value != null, "getStringArgument(" + key + ") failed to find key");
return value;
}
/**
* Request permission to receive a packet. The autograder can use this to drop packets very
* selectively.
*
* @param privilege proves the authenticity of this call.
* @return <tt>true</tt> if the packet should be delivered to the kernel.
*/
public boolean canReceivePacket(Privilege privilege) {
Lib.assertTrue(privilege == this.privilege, "security violation");
return true;
}
private static void authorizeDestroy(KThread thread) {
// make sure AutoGrader.finishingThread() gets called only once per
// destroy
Lib.assertTrue(toBeDestroyed == null);
toBeDestroyed = thread;
}
/**
* Return the name of the shell program that a user-programming kernel must run. Make sure
* <tt>UserKernel.run()</tt> <i>always</i> uses this method to decide which program to run.
*
* @return the name of the shell program to run.
*/
public static String getShellProgramName() {
if (shellProgramName == null) shellProgramName = Config.getString("Kernel.shellProgram");
Lib.assertTrue(shellProgramName != null);
return shellProgramName;
}
/**
* Notify the autograder that a timer interrupt occurred and was handled by software if a timer
* interrupt handler was installed. Called by the hardware timer.
*
* @param privilege proves the authenticity of this call.
* @param time the actual time at which the timer interrupt was issued.
*/
public void timerInterrupt(Privilege privilege, long time) {
Lib.assertTrue(privilege == this.privilege, "security violation");
}
void level(int level) {
this.level++;
Lib.assertTrue(level == this.level, "level() advanced more than one step: test jumped ahead");
if (level == targetLevel) done();
}
/**
* Causes the thread represented by this TCB to begin execution. The specified target is run in
* the thread.
*/
public void start(Runnable target) {
/* We will not use synchronization here, because we're assuming that
* either this is the first call to start(), or we're being called in
* the context of another TCB. Since we only allow one TCB to run at a
* time, no synchronization is necessary.
*
* The only way this assumption could be broken is if one of our
* non-Nachos threads used the TCB code.
*/
/* Make sure this TCB has not already been started. If done is false,
* then destroy() has not yet set javaThread back to null, so we can
* use javaThread as a reliable indicator of whether or not start() has
* already been invoked.
*/
Lib.assertTrue(javaThread == null && !done);
/* Make sure there aren't too many running TCBs already. This
* limitation exists in an effort to prevent wild thread usage.
*/
Lib.assertTrue(runningThreads.size() < maxThreads);
isFirstTCB = (currentTCB == null);
/* Probably unnecessary sanity check: if this is not the first TCB, we
* make sure that the current thread is bound to the current TCB. This
* check can only fail if non-Nachos threads invoke start().
*/
if (!isFirstTCB) Lib.assertTrue(currentTCB.javaThread == Thread.currentThread());
/* At this point all checks are complete, so we go ahead and start the
* TCB. Whether or not this is the first TCB, it gets added to
* runningThreads, and we save the target closure.
*/
runningThreads.add(this);
this.target = target;
if (!isFirstTCB) {
/* If this is not the first TCB, we have to make a new Java thread
* to run it. Creating Java threads is a privileged operation.
*/
tcbTarget =
new Runnable() {
public void run() {
threadroot();
}
};
privilege.doPrivileged(
new Runnable() {
public void run() {
javaThread = new Thread(tcbTarget);
}
});
/* The Java thread hasn't yet started, but we need to get it
* blocking in yield(). We do this by temporarily turning off the
* current TCB, starting the new Java thread, and waiting for it
* to wake us up from threadroot(). Once the new TCB wakes us up,
* it's safe to context switch to the new TCB.
*/
currentTCB.running = false;
this.javaThread.start();
currentTCB.waitForInterrupt();
} else {
/* This is the first TCB, so we don't need to make a new Java
* thread to run it; we just steal the current Java thread.
*/
javaThread = Thread.currentThread();
/* All we have to do now is invoke threadroot() directly. */
threadroot();
}
}
public void associateThread(KThread thread) {
Lib.assertTrue(currentTCB != null);
currentTCB.associateThread(thread);
}
/**
* Return the name of the process class that the kernel should use. In the multi-programming
* project, returns <tt>nachos.userprog.UserProcess</tt>. In the VM project, returns
* <tt>nachos.vm.VMProcess</tt>. In the networking project, returns
* <tt>nachos.network.NetProcess</tt>.
*
* @return the name of the process class that the kernel should use.
* @see nachos.userprog.UserKernel#run
* @see nachos.userprog.UserProcess
* @see nachos.vm.VMProcess
* @see nachos.network.NetProcess
*/
public static String getProcessClassName() {
if (processClassName == null) processClassName = Config.getString("Kernel.processClassName");
Lib.assertTrue(processClassName != null);
return processClassName;
}
/**
* Notify the autograder that <tt>Processor.run()</tt> was invoked. This can be used to simulate
* user programs.
*
* @param privilege proves the authenticity of this call.
*/
public void runProcessor(Privilege privilege) {
Lib.assertTrue(privilege == this.privilege, "security violation");
}