CMSC 412 Programming Assignment #1 - Checklist

This document provides a checklist of things that need to be done as part of project #1.

Creating libuser.c

Start from supplied template

Add new system calls

Add Readln

Add _Entry

Adding system calls to kernel

Create a table of functions to find function to invoke

For each system call

Add entry to handler function table

Write handler function for that system call

Copy and validate parameters as needed

Implement functionality

Write a routine to validate pointers passed into kernel space

add basePtr to any address to get kernel address of user location

Enable the supplied filesystem and disk drivers

Call Init_IDE, Init_Floppy, and Init_PFAT

- must call in that order

- put calls in main thread of your OS kernel.

Print System Call

Just call print after copying string from user space

Getkey

Call Wait_For_Key_Atomic and return value to user space

Exit System Call

Delete user context (including freeing memory)

Disable Interrupts

Call Detach_Thread

Set g_killCurrentThread and g_needReschedule to TRUE

Wait System Call

Need to use Join kernel call to wait for a process (really a kernel thread)

User Mode (this is the implementation of the system call spawn)

Load a program into memory (loadElfProgram)

Use ReadFileAndAllocate to get the file into memory

Write the function called Create_User_Process

See handout for description

Context Switch Code (at the .restore label & in RestoreThread in lowlevel.asm)

Add a call to Switch_User_Context

Write Switch_User_Context

If (returning to user mode – check rpl of state)

Load ldt of user context

Fill out

g_theTSS.esp0 = top of kernel thread’s stack

g_theTSS.ss0 = KERNEL_DS

Start the first User Mode Process

Call the routines used in spawn to load the program /a/a.exe and run it

This routine is called from the Main of your system.