/**
* Initialize the processor's registers in preparation for running the program loaded into this
* process. Set the PC register to point at the start function, set the stack pointer register to
* point at the top of the stack, set the A0 and A1 registers to argc and argv, respectively, and
* initialize all other registers to 0.
*/
public void initRegisters() {
Processor processor = Machine.processor();
// by default, everything's 0
for (int i = 0; i < processor.numUserRegisters; i++) processor.writeRegister(i, 0);
// initialize PC and SP according
processor.writeRegister(Processor.regPC, initialPC);
processor.writeRegister(Processor.regSP, initialSP);
// initialize the first two argument registers to argc and argv
processor.writeRegister(Processor.regA0, argc);
processor.writeRegister(Processor.regA1, argv);
}
/**
* 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");
}
}