/**************************************************************************************
 Copyright (c) 2002
      The UbixOS Project

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 $Id: createvirtualspace.c,v 1.1 2003/04/19 11:31:35 reddawg Exp $
**************************************************************************************/

#include <vmm/paging.h>


/************************************************************************

Function: void *createVirtualSpace(pid_t);
Description: Creates A Virtual Space For A New Task
Notes:

07/30/02 - This Is Going To Create A New VM Space However Its Going To
           Share The Same Top 1GB Space With The Kernels VM And Lower
           1MB Of VM Space With The Kernel

07/30/02 - Note This Is Going To Get The Top 1Gig And Lower 1MB Region
           From The Currently Loaded Page Directory This Is Safe Because
           All VM Spaces Will Share These Regions

07/30/02 - Note I Realized A Mistake The First Page Table Will Need To Be
           A Copy But The Page Tables For The Top 1GB Will Not Reason For
           This Is That We Just Share The First 1MB In The First Page Table
           So We Will Just Share Physical Pages.

08/02/02 - Added Passing Of pid_t pid For Better Tracking Of Who Has Which
           Set Of Pages

************************************************************************/
void *createVirtualSpace(pid_t pid) {
  void *newPageDirectoryAddress = 0x0;
  uLong *parentPageDirectory = 0x0,*newPageDirectory = 0x0;
  uLong *parentPageTable = 0x0,*newPageTable = 0x0;
  int x = 0;
  //Set Address Of Parent Page Directory
  parentPageDirectory = (uLong *)parentPageDirAddr;
  //Allocate A New Page For The New Page Directory
  newPageDirectory = (uLong *)getFreePage(pid);
  //Set newPageDirectoryAddress To The Newly Created Page Directories Page
  newPageDirectoryAddress = getPhysicalAddr((uLong)newPageDirectory);
  //First Set Up A Flushed Page Directory
  for (x=0;x<pageEntries;x++) {
    newPageDirectory[x] = (uLong)0x0;
    }
  //Map The Top 1GB Region Of The VM Space
  for (x=768;x<pageEntries;x++) {
    newPageDirectory[x] = parentPageDirectory[x];
    }
  /*
  Allocate A New Page For The The First Page Table Where We Will Map The
  Lower Region
  */
  newPageTable = (uLong *)getFreePage(pid);
  //Flush The Page From Garbage In Memory
  for (x=0;x<pageEntries;x++) {
    newPageTable[x] = (uLong)0x0;
    }
  //Map This Into The Page Directory
  newPageDirectory[0] = ((uLong)getPhysicalAddr((uLong)newPageTable) | pageDefault);
  //Set Address Of Parents Page Table
  parentPageTable = (uLong *)tablesBaseAddress;
  //Map The First 1MB Worth Of Pages
  for (x=0;x<(pageEntries/4);x++) {
    newPageTable[x] = parentPageTable[x];
    }
  //Set Virtual Mapping For Page Directory
  newPageTable[256] = ((uLong)getPhysicalAddr((uLong)newPageDirectory) | pageDefault);
  /*
  Now The Fun Stuff Build The Initial Virtual Page Space So We Don't
  Have To Worry About Mapping Them In Later How Ever I'm Concerned This
  May Become A Security Issue
  */
  //First Lets Unmap The Previously Allocated Page Table
  unmapPage((uLong)newPageTable,1);
  //Allocate A New Page Table
  newPageTable = (uLong *)getFreePage(pid);
  //First Set Our Page Directory To Contain This
  newPageDirectory[767] = (uLong)getPhysicalAddr((uLong)newPageTable) | pageDefault;
  //Now Lets Build The Page Table
  for (x=0;x<pageEntries;x++) {
    newPageTable[x] = newPageDirectory[x];
    }
  //Now We Are Done So Lets Unmap This Page
  unmapPage((uLong)newPageTable,1);
  //Now We Are Done With The Page Directory So Lets Unmap That Too
  unmapPage((uLong)newPageDirectory,1);
  //Return Physical Address Of Page Directory
  return(newPageDirectoryAddress);
  }