/**
* Handle a syscall exception. Called by <tt>handleException()</tt>. The <i>syscall</i> argument
* identifies which syscall the user executed:
*
* <table>
* <tr><td>syscall#</td><td>syscall prototype</td></tr>
* <tr><td>0</td><td><tt>void halt();</tt></td></tr>
* <tr><td>1</td><td><tt>void exit(int status);</tt></td></tr>
* <tr><td>2</td><td><tt>int exec(char *name, int argc, char **argv);
* </tt></td></tr>
* <tr><td>3</td><td><tt>int join(int pid, int *status);</tt></td></tr>
* <tr><td>4</td><td><tt>int creat(char *name);</tt></td></tr>
* <tr><td>5</td><td><tt>int open(char *name);</tt></td></tr>
* <tr><td>6</td><td><tt>int read(int fd, char *buffer, int size);
* </tt></td></tr>
* <tr><td>7</td><td><tt>int write(int fd, char *buffer, int size);
* </tt></td></tr>
* <tr><td>8</td><td><tt>int close(int fd);</tt></td></tr>
* <tr><td>9</td><td><tt>int unlink(char *name);</tt></td></tr>
* </table>
*
* @param syscall the syscall number.
* @param a0 the first syscall argument.
* @param a1 the second syscall argument.
* @param a2 the third syscall argument.
* @param a3 the fourth syscall argument.
* @return the value to be returned to the user.
*/
public int handleSyscall(int syscall, int a0, int a1, int a2, int a3) {
switch (syscall) {
case syscallHalt:
return handleHalt();
case syscallCreate:
return handleCreate(a0);
case syscallOpen:
return handleOpen(a0);
case syscallRead:
return handleRead(a0, a1, a2);
case syscallWrite:
return handleWrite(a0, a1, a2);
case syscallClose:
return handleClose(a0);
case syscallUnlink:
return handleUnlink(a0);
case syscallExit:
handleExit(a0);
case syscallExec:
return handleExec(a0, a1, a2);
case syscallJoin:
return handleJoin(a0, a1);
default:
Lib.debug(dbgProcess, "Unknown syscall " + syscall);
Lib.assertNotReached("Unknown system call!");
}
return 0;
}
/** Handle the halt() system call. */
private int handleHalt() {
if (this.process_id != ROOT) {
return 0;
}
Machine.halt();
Lib.assertNotReached("Machine.halt() did not halt machine!");
return 0;
}
private void handleExit(int status) {
if (myChildProcess != null) {
myChildProcess.status = status;
}
// close all the opened files
for (int i = 0; i < 16; i++) {
handleClose(i);
}
// part2 implemented
this.unloadSections();
if (this.process_id == ROOT) {
Kernel.kernel.terminate();
} else {
KThread.finish();
Lib.assertNotReached();
}
}
/**
* Handle a user exception. Called by <tt>UserKernel.exceptionHandler()</tt>. The <i>cause</i>
* argument identifies which exception occurred; see the <tt>Processor.exceptionZZZ</tt>
* constants.
*
* @param cause the user exception that occurred.
*/
public void handleException(int cause) {
Processor processor = Machine.processor();
switch (cause) {
case Processor.exceptionSyscall:
int result =
handleSyscall(
processor.readRegister(Processor.regV0),
processor.readRegister(Processor.regA0),
processor.readRegister(Processor.regA1),
processor.readRegister(Processor.regA2),
processor.readRegister(Processor.regA3));
processor.writeRegister(Processor.regV0, result);
processor.advancePC();
break;
default:
Lib.debug(dbgProcess, "Unexpected exception: " + Processor.exceptionNames[cause]);
handleExit(-1);
Lib.assertNotReached("Unexpected exception");
}
}