/**************************************************************************************
 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.
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 $Id: getfreevirtualpage.c,v 1.3 2003/04/24 00:16:30 reddawg Exp $
**************************************************************************************/

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

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

Function: void *getFreeVirtualPage(pid_t pid,int count);
Description: Returns A Free Page Mapped To The VM Space
Notes:

08/11/02 - This Will Return Next Avilable Free Page Of Tasks VM Space

************************************************************************/
void *getFreeVirtualPage(pid_t pid,int count) {
  int x=0,y=0,c=0;
  uInt32 *pageTableSrc = 0x0;
  uInt32 *pageDir     = (uInt32 *)parentPageDirAddr;

  //Lets Search For A Free Page
  for (x=(_current->oInfo.vmStart/(1024*4096));x<1024;x++) {
    //Set Page Table Address
    if ((pageDir[x] & pagePresent) != pagePresent) {
      //If Page Table Is Non Existant Then Set It Up
      pageDir[x] = (uLong)findFreePage(_current->id) | pageDefault;
      //Also Add It To Virtual Space So We Can Make Changes Later
      pageTableSrc = (uLong *)(tablesBaseAddress + (4096 * 767));
      pageTableSrc[x] = pageDir[x];
      //Reload Page Directory
      asm(
        "movl %cr3,%eax\n"
        "movl %eax,%cr3\n"
        );
      }    
    pageTableSrc = (uInt32 *)(tablesBaseAddress + (0x1000*x));
    for (y=0;y<1024;y++) {
      //Loop Through The Page Table Find An UnAllocated Page
      if ((uInt32)pageTableSrc[y] == (uInt32)0x0) {
        if (count > 0x1) {
          for (c=0;c<count;c++) {
            if ((uInt32)pageTableSrc[y+c] != (uInt32)0x0) {
              c = -1;
              break;
              }
            }
          if (c != -1) {
            for (c=0;c<count;c++) {
              remapPage((uInt32)findFreePage(pid),((x*(1024*4096))+((y+c)*4096)));
              clearVirtualPage((uInt32)((x*(1024*4096))+((y+c)*4096)));
              }
            return((void *)((x*(1024*4096))+(y*4096)));
            }
          }
        else {
          //Map A Physical Page To The Virtual Page
          //remapPage((uInt32)findFreePage(pid),((x*(1024*4096))+(y*4096)),pid);
          remapPage((uInt32)findFreePage(pid),((x*(1024*4096))+(y*4096)));
          //Clear This Page So No Garbage Is There
          clearVirtualPage((uInt32)((x*(1024*4096))+(y*4096)));
          //Return The Address Of The Newly Allocate Page
          return((void *)((x*(1024*4096))+(y*4096)));
          }
        }
      }
    }
  //If No Free Page Was Found Return NULL
  return(0x0);
  }