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

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions, the following disclaimer and the list of authors.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions, the following disclaimer and the list of authors
in the documentation and/or other materials provided with the distribution. Neither the name of the UbixOS Project nor the names of its
contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 $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);
  }