getfreepage.c

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/*****************************************************************************************
 Copyright (c) 2002 The UbixOS Project
 All rights reserved.

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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
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 $Id: getfreepage_8c-source.html 88 2016-01-12 00:11:29Z reddawg $

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

#include <vmm/vmm.h>
#include <ubixos/kpanic.h>
#include <ubixos/spinlock.h>

static spinLock_t vmmGFPlock = SPIN_LOCK_INITIALIZER;

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

Function: void *vmmGetFreePage(pidType pid);

Description: Returns A Free Page Mapped To The VM Space

Notes:

07/30/02 - This Returns A Free Page In The Top 1GB For The Kernel

************************************************************************/
void           *
vmmGetFreePage(pidType pid)
{
  uInt16             x = 0x0, y = 0x0;
  uInt32         *pageTableSrc = 0x0;
  
  spinLock(&vmmGFPlock);
  
  /* Lets Search For A Free Page */
  for (x = 768; x < 1024; x++) {

    /* Set Page Table Address */
    pageTableSrc = (uInt32 *) (tablesBaseAddress + (0x1000 * x));
    for (y = 0x0; y < 1024; y++) {
      /* Loop Through The Page Table Find An UnAllocated Page */
      if ((uInt32) pageTableSrc[y] == (uInt32) 0x0) {
        /* Map A Physical Page To The Virtual Page */
        if ((vmm_remapPage(vmmFindFreePage(pid), ((x * 0x400000) + (y * 0x1000)),KERNEL_PAGE_DEFAULT)) == 0x0)
          kpanic("vmmRemapPage: vmmGetFreePage\n");
        /* Clear This Page So No Garbage Is There */
        vmmClearVirtualPage((uInt32) ((x * 0x400000) + (y * 0x1000)));
        /* Return The Address Of The Newly Allocate Page */
        spinUnlock(&vmmGFPlock);
        return ((void *)((x * 0x400000) + (y * 0x1000)));
      }
    }
  }
  /* If No Free Page Was Found Return NULL */
  spinUnlock(&vmmGFPlock);
  return (0x0);
}

/***
 END
 ***/

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