nachos.vm
Class VMProcess

java.lang.Object
  |
  +--nachos.userprog.UserProcess
        |
        +--nachos.vm.VMProcess

Direct Known Subclasses:

NetProcess

public class VMProcess

extends UserProcess

A UserProcess that supports demand-paging.

Fields inherited from class nachos.userprog.UserProcess

coff, numPages, pageTable, stackPages

Constructor Summary

VMProcess()
Allocate a new process.

Method Summary

void	handleException(int cause) Handle a user exception.
int	handleSyscall(int syscall, int a0, int a1, int a2, int a3) Handle a syscall exception.
protected boolean	loadSections() Initializes page tables for this process so that the executable can be demand-paged.
void	restoreState() Restore the state of this process after a context switch.
void	saveState() Save the state of this process in preparation for a context switch.
protected void	unloadSections() Release any resources allocated by loadSections().

Methods inherited from class nachos.userprog.UserProcess

execute, initRegisters, newUserProcess, readVirtualMemory, readVirtualMemory, readVirtualMemoryString, writeVirtualMemory, writeVirtualMemory

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

VMProcess

public VMProcess()

Allocate a new process.

Method Detail

saveState

public void saveState()

Save the state of this process in preparation for a context switch. Called by UThread.saveState().

Overrides:

saveState in class UserProcess

restoreState

public void restoreState()

Restore the state of this process after a context switch. Called by UThread.restoreState().

Overrides:

restoreState in class UserProcess

loadSections

protected boolean loadSections()

Initializes page tables for this process so that the executable can be demand-paged.

Overrides:

loadSections in class UserProcess

Returns:

true if successful.

unloadSections

protected void unloadSections()

Release any resources allocated by loadSections().

Overrides:

unloadSections in class UserProcess

handleSyscall

public int handleSyscall(int syscall,
                         int a0,
                         int a1,
                         int a2,
                         int a3)

Handle a syscall exception. Called by handleException(). The syscall argument identifies which syscall the user executed:

syscall#	syscall prototype
10	int mmap(int fd, char *address);

Overrides:

handleSyscall in class UserProcess

Parameters:

syscall - the syscall number.

a0 - the first syscall argument.

a1 - the second syscall argument.

a2 - the third syscall argument.

a3 - the fourth syscall argument.

Returns:

the value to be returned to the user.

handleException

public void handleException(int cause)

Handle a user exception. Called by UserKernel.exceptionHandler(). The cause argument identifies which exception occurred; see the Processor.exceptionZZZ constants.

Overrides:

handleException in class UserProcess

Parameters:

cause - the user exception that occurred.