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

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 $Id: copyvirtualspace.c,v 1.2 2003/04/24 00:16:30 reddawg Exp $
**************************************************************************************/

#include <vmm/paging.h>
#include <vmm/memory.h>

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

Function: void *copyVirtualSpace(pid_t pid);
Description: Creates A Copy Of A Virtual Space And Set All NON Kernel
             Space To COW For A Fork This Will Also Alter The Parents
             VM Space To Make That COW As Well
Notes:

08/02/02 - Added Passing Of pid_t pid So We Can Better Keep Track Of
           Which Task Has Which Physical Pages

************************************************************************/
void *copyVirtualSpace(pid_t pid) {
  void *newPageDirectoryAddress = 0x0;
  uLong *parentPageDirectory = 0x0,*newPageDirectory = 0x0;
  uLong *parentPageTable = 0x0,*newPageTable = 0x0;
  uLong *parentStackPage = 0x0,*newStackPage = 0x0;
  int x = 0,i = 0,s = 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];
    }
  /*
  Now For The Fun Stuff For Page Tables 1-766 We Must Map These And Set
  The Permissions On Every Mapped Pages To COW This Will Conserve
  Memory Because The Two VM Spaces Will Be Sharing Some Pages
  */
  for (x=1;x<=766;x++) {
    //If Page Table Exists Map It
    if (parentPageDirectory[x] != 0) {
      //Set Parent  To Propper Page Table
      parentPageTable = (uLong *)(tablesBaseAddress + (4096 * x));
      //Allocate A New Page Table
      newPageTable = (uLong *)getFreePage(pid);
      //Set Parent And New Pages To COW
      for (i=0;i<pageEntries;i++) {
        //If Page Is Mapped
        if (parentPageTable[i] != 0x0) {
          //Check To See If Its A Stack Page
          if (((uLong)parentPageTable[i] & pageStack) == pageStack) {
            //Alloc A New Page For This Stack Page
            newStackPage = (uLong *)getFreePage(pid);
            //Set Pointer To Parents Stack Page
            parentStackPage = (uLong *) (((1024*4096)*x)+(4096*i));
            //Copy The Tack Byte For Byte (I Should Find A Faster Way)
            for (s=0;s<pageEntries;s++) {
              newStackPage[s] = parentStackPage[s];
              }
            //Insert New Stack Into Page Table
            newPageTable[i] = ((uLong)getPhysicalAddr((uLong)newStackPage) | pageDefault | pageStack);
            //Unmap From Kernel Space
            unmapPage((uLong)newStackPage,1);
            }
          else {
            //Set Page To COW In Parent And Child Space
            newPageTable[i] = (((uLong)parentPageTable[i] & 0xFFFFF000) | (pagePresent | pageCow));
           //Increment The COW Counter For This Page
            if (((uLong)parentPageTable[i] & pageCow) == pageCow) {
              adjustCowCounter(((uLong)parentPageTable[i] & 0xFFFFF000),1);
              }
            else {
              adjustCowCounter(((uLong)parentPageTable[i] & 0xFFFFF000),2);
              parentPageTable[i] = newPageTable[i];
              }
            }
          }
        else {
          newPageTable[i] = (uLong)0x0;
          }
        }
      //Put New Page Table Into New Page Directory
      newPageDirectory[x] = ((uLong)getPhysicalAddr((uLong)newPageTable) | pageDefault);
      //Unmap Page From Kernel Space But Keep It Marked As Not Avail
      unmapPage((uLong)newPageTable,1);
      }
    else {
      newPageDirectory[x] = (uLong)0x0;
      }
    }
  /*
  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];
    }
  //Map The Next 3MB Worth Of Pages But Make Them COW
  for (x=(pageEntries/4)+1;x<pageEntries;x++) {
    //If Page Is Avaiable Map It
    if (parentPageTable[x] != 0) {
      //Set Pages To COW
      newPageTable[x] = (((uLong)parentPageTable[x] & 0xFFFFF000) | (pagePresent | pageCow));
      //Increment The COW Counter For This Page
      if (((uLong)parentPageTable[x] & pageCow) == pageCow) {
        adjustCowCounter(((uLong)parentPageTable[x] & 0xFFFFF000),1);
        }
      else {
        adjustCowCounter(((uLong)parentPageTable[x] & 0xFFFFF000),2);
        parentPageTable[x] = newPageTable[x];
        }
      }
    else {
      newPageTable[x] = (uLong)0x0;
      }
    }
  //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);
  //kprintf("Test: [%i]\n",pid);
  //Return Physical Address Of Page Directory
  return(newPageDirectoryAddress);
  }
