pagefault.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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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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 $Id: pagefault_8c-source.html 88 2016-01-12 00:11:29Z reddawg $

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

#include <vmm/vmm.h>
#include <ubixos/sched.h>
#include <ubixos/kpanic.h>
#include <ubixos/spinlock.h>
#include <lib/kprintf.h>

static spinLock_t pageFaultSpinLock = SPIN_LOCK_INITIALIZER;

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

 Function:    void vmm_pageFault(uInt32 memAddr,uInt32 eip,uInt32 esp);
 Description: This is the page fault handler, it will handle COW and trap all other
              exceptions and segfault the thread.

 Notes:
 
07/30/02 - Fixed COW However I Need To Think Of A Way To Impliment
           A Paging System Also Start To Add Security Levels
    
07/27/04 - Added spin locking to ensure that we are thread safe. I know that spining a 
           cpu is a waste of resources but for now it prevents errors.

*****************************************************************************************/
void vmm_pageFault(uInt32 memAddr,uInt32 eip,uInt32 esp) {
  uInt32 i = 0x0, pageTableIndex = 0x0,pageDirectoryIndex = 0x0;
  uInt32 *pageDir = 0x0,*pageTable = 0x0;
  uInt32 *src = 0x0,*dst = 0x0;

  /* Try to aquire lock otherwise spin till we do */
  spinLock(&pageFaultSpinLock);

  /* Set page dir pointer to the address of the visable page directory */
  pageDir = (uInt32 *)parentPageDirAddr;

  /* UBU - This is a temp panic for 0x0 read write later on I will handle this differently */
  if (memAddr == 0x0) {
    kprintf("Segfault At Address: [0x%X][0x%X][%i][0x%X]\n",memAddr,esp,_current->id,eip);
    kpanic("Error We Wrote To 0x0\n");
    }

  /* Calculate The Page Directory Index */
  pageDirectoryIndex = (memAddr >> 22);
  
  /* Calculate The Page Table Index     */
  pageTableIndex = ((memAddr >> 12) & 0x3FF);

  /* UBU - This is a temporary routine for handling access to a page of a non existant page table */
  if (pageDir[pageDirectoryIndex] == 0x0) {
    kprintf("Segfault At Address: [0x%X][0x%X][%i][0x%X], Not A Valid Page Table\n",memAddr,esp,_current->id,eip);
    spinUnlock(&pageFaultSpinLock);
    endTask(_current->id);
    }
  else {
    /* Set pageTable To Point To Virtual Address Of Page Table */
    pageTable = (uInt32 *)(tablesBaseAddress + (0x1000 * pageDirectoryIndex));
    
    /* Test if this is a COW on page */
    if (((uInt32)pageTable[pageTableIndex] & PAGE_COW) == PAGE_COW) {
      /* Set Src To Base Address Of Page To Copy */
      src = (uInt32 *)(memAddr & 0xFFFFF000);
      /* Allocate A Free Page For Destination */
      /* USE vmInfo */
      dst = (uInt32 *) vmmGetFreeVirtualPage(_current->id,1,0x1);
      /* Copy Memory */
      for (i=0;i<pageEntries;i++) {
        dst[i] = src[i];
        }
      /* Adjust The COW Counter For Physical Page */
      adjustCowCounter(((uInt32)pageTable[pageTableIndex] & 0xFFFFF000),-1);
      /* Remap In New Page */
      pageTable[pageTableIndex] = (uInt32)(vmm_getPhysicalAddr((uInt32)dst)|(memAddr & 0xFFF));
      /* Unlink From Memory Map Allocated Page */
      vmmUnmapPage((uInt32)dst,1);
      }
    else if (pageTable[pageTableIndex] != 0x0) {
      kprintf("Security failed pagetable not user permission\n");
      kprintf("pageTable: [0x%X:0x%X:0x%X:0x%X]\n",pageTable[pageTableIndex],pageTableIndex,pageDirectoryIndex,eip);
      kprintf("Segfault At Address: [0x%X][0x%X][%i][0x%X] Non Mapped\n",memAddr,esp,_current->id,eip);
      spinUnlock(&pageFaultSpinLock);
      endTask(_current->id);
      }
    else if (memAddr < (_current->td.vm_dsize + _current->td.vm_daddr)) {
      pageTable[pageTableIndex] = (uInt32)vmmFindFreePage(_current->id) | PAGE_DEFAULT;
      }
    else {
      spinUnlock(&pageFaultSpinLock);
      /* Need To Create A Routine For Attempting To Access Non Mapped Memory */
      kprintf("Segfault At Address: [0x%X][0x%X][%i][0x%X] Non Mapped\n",memAddr,esp,_current->id,eip);
      kprintf("Out Of Stack Space: [0x%X]\n",memAddr & 0xFF0000);
      spinUnlock(&pageFaultSpinLock);
      endTask(_current->id);
      }
    }
  asm volatile(
    "movl %cr3,%eax\n"
    "movl %eax,%cr3\n"
    );
  
  /* Release the spin lock */
  spinUnlock(&pageFaultSpinLock);
  return;
  }
  
/***
 $Log: pagefault_8c-source.html,v $
 Revision 1.7  2006/12/15 17:47:06  reddawg
 Updates

 Revision 1.6  2006/12/05 14:10:21  reddawg
 Workign Distro

 Revision 1.5  2006/12/01 05:12:35  reddawg
 We're almost there... :)

 Revision 1.4  2006/11/21 13:25:49  reddawg
 A handful of changes ;)

 Revision 1.3  2006/11/06 19:10:12  reddawg
 Lots Of Updates... Still having issues with brk();

 Revision 1.2  2006/10/31 20:44:19  reddawg
 Lots of changes

 Revision 1.1.1.1  2006/06/01 12:46:13  reddawg
 ubix2

 Revision 1.2  2005/10/12 00:13:38  reddawg
 Removed

 Revision 1.1.1.1  2005/09/26 17:24:52  reddawg
 no message

 Revision 1.14  2004/08/25 22:02:41  reddawg
 task switching - We now are using software switching to be consistant with the rest of the world because all of this open source freaks gave me a hard time about something I liked. There doesn't seem to be any gain in performance but it is working fine and flawlessly

 Revision 1.13  2004/08/24 05:24:37  reddawg
 TCA Is A BONER!!!!

 Revision 1.12  2004/08/14 11:23:03  reddawg
 Changes

 Revision 1.11  2004/07/28 15:05:43  reddawg
 Major:
   Pages now have strict security enforcement.
   Many null dereferences have been resolved.
   When apps loaded permissions set for pages rw and ro

 Revision 1.10  2004/07/28 00:22:56  reddawg
 bah

 Revision 1.9  2004/07/28 00:17:05  reddawg
 Major:
   Disconnected page 0x0 from the system... Unfortunately this broke many things
   all of which have been fixed. This was good because nothing deferences NULL
   any more.

 Things affected:
   malloc,kmalloc,getfreepage,getfreevirtualpage,pagefault,fork,exec,ld,ld.so,exec,file

 Revision 1.8  2004/07/27 07:09:38  reddawg
 Put in a test for 0x0

 Revision 1.7  2004/07/26 19:15:49  reddawg
 test code, fixes and the like

 Revision 1.6  2004/07/24 23:04:44  reddawg
 Changes... mark let me know if you fault at pid 185 when you type stress

 Revision 1.5  2004/07/24 20:00:51  reddawg
 Lots of changes to the vmm subsystem.... Page faults have been adjust to now be blocking on a per thread basis not system wide. This has resulted in no more deadlocks.. also the addition of per thread locking has removed segfaults as a result of COW in which two tasks fault the same COW page and try to modify it.

 Revision 1.4  2004/07/24 17:47:28  reddawg
 vmm_pageFault: deadlock resolved thanks to a propper solution suggested by geist

 Revision 1.3  2004/07/19 02:05:26  reddawg
 vmmPageFault: had a potential memory leak here for one page it was still using sysID on certain COW scenarios

 Revision 1.2  2004/06/10 22:23:56  reddawg
 Volatiles

 Revision 1.1.1.1  2004/04/15 12:06:52  reddawg
 UbixOS v1.0

 Revision 1.4  2004/04/13 16:36:34  reddawg
 Changed our copyright, it is all now under a BSD-Style license

 END
 ***/

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