mmulib.c

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/* MMU_UNLOCK and MMU_LOCK are used to access page table entries that are in
 * virtual memory that has been invalidated to protect it from being corrupted
 */

#define MMU_UNLOCK(wasEnabled, oldLevel) \
(((wasEnabled) = mmuEnabled) ? ((oldLevel) = intLock (), mmuOff ()) : 0)

#define MMU_LOCK(wasEnabled, oldLevel) ((wasEnabled) ? (mmuOn (), intUnlock (oldLevel)) : 0)


/******************************************************************************
*
* mmuLibInit - initialize module
*
* Build a dummy translation table that will hold the page table entries
* for the global translation table.  The mmu remains disabled upon
* completion.
*
* RETURNS: OK if no error, ERROR otherwise
*
* ERRNO: S_mmuLib_INVALID_PAGE_SIZE
*/

STATUS mmuLibInit 
    (
    int pageSize	/* system pageSize (must be 4096 for i86) */
    )
    {

    PTE *pDirectoryTable;
    int i;
    char gdtr[6];

    /* re-initialize the GDT to disable the limit-check */

    bcopy ((char *)sysGdt, (char *)pSysGdt, GDT_ENTRIES * sizeof(GDT));
    *(short *)&gdtr[0]	= GDT_ENTRIES * sizeof(GDT) - 1;
    *(int *)&gdtr[2]	= (int)pSysGdt;
    i = intLock();				/* LOCK INTERRUPTS */
    sysLoadGdt (gdtr);
    intUnlock(i);				/* UNLOCK INTERRUPTS */

    /* initialize the data objects that are shared with vmLib.c */

    mmuStateTransArray = &mmuStateTransArrayLocal [0];

    mmuStateTransArraySize =
          sizeof (mmuStateTransArrayLocal) / sizeof (STATE_TRANS_TUPLE);

    mmuLibFuncs = mmuLibFuncsLocal;

    mmuPageBlockSize = PAGE_BLOCK_SIZE;

    /* we assume a 4096 byte page size */

    if (pageSize != PAGE_SIZE)
	{
	errno = S_mmuLib_INVALID_PAGE_SIZE;
	return (ERROR);
	}

    mmuEnabled = FALSE;

    mmuPageSize = pageSize;

    /* allocate the global page block array to keep track of which parts
     * of virtual memory are handled by the global translation tables.
     * Allocate on page boundry so we can write protect it.
     */

    globalPageBlock = (BOOL *) memalign (pageSize, pageSize);
    bzero ((char *) globalPageBlock, pageSize);

    /* build a dummy translation table which will hold the pte's for
     * global memory.  All real translation tables will point to this
     * one for controling the state of the global virtual memory  
     */

    /* allocate a page to hold the directory table */

    mmuGlobalTransTbl.pDirectoryTable = pDirectoryTable = 
	(PTE *) memalign (pageSize, pageSize);

    if (pDirectoryTable == NULL)
	return (ERROR);

    /* invalidate all the directory table entries */

    for (i = 0; i < (PAGE_SIZE / sizeof(PTE)) ;i++)
	{
	pDirectoryTable[i].field.present	= 0;
	pDirectoryTable[i].field.rw		= 0;
	pDirectoryTable[i].field.us		= 0;
	pDirectoryTable[i].field.pwt		= 0;
	pDirectoryTable[i].field.pcd		= 0;
	pDirectoryTable[i].field.access	= 0;
	pDirectoryTable[i].field.dirty		= 0;
	pDirectoryTable[i].field.zero		= 0;
	pDirectoryTable[i].field.avail		= 0;
	pDirectoryTable[i].field.page		= -1;
	}

    return (OK);
    }

/******************************************************************************
*
* mmuPteGet - get the pte for a given page
*
* mmuPteGet traverses a translation table and returns the (physical) address of
* the pte for the given virtual address.
*
* RETURNS: OK or ERROR if there is no virtual space for the given address 
*
*/

LOCAL STATUS mmuPteGet 
    (
    MMU_TRANS_TBL *pTransTbl, 	/* translation table */
    void *virtAddr,		/* virtual address */ 
    PTE **result		/* result is returned here */
    )
    {

    PTE *pDte;
    PTE *pPageTable;

    pDte = &pTransTbl->pDirectoryTable [(UINT) virtAddr >> DIRECTORY_INDEX];
    pPageTable = (PTE *) (pDte->bits & PTE_TO_ADDR); 

    if ((UINT) pPageTable == 0xfffff000)
	return (ERROR);

    *result = &pPageTable[((UINT) virtAddr & TABLE_BITS) >> TABLE_INDEX];

    return (OK);
    }

/******************************************************************************
*
* mmuTransTblCreate - create a new translation table.
*
* create a i86 translation table.  Allocates space for the MMU_TRANS_TBL
* data structure and calls mmuTransTblInit on that object.  
*
* RETURNS: address of new object or NULL if allocation failed,
*          or NULL if initialization failed.
*/

LOCAL MMU_TRANS_TBL *mmuTransTblCreate 
    (
    )
    {

    MMU_TRANS_TBL *newTransTbl;

    newTransTbl = (MMU_TRANS_TBL *) malloc (sizeof (MMU_TRANS_TBL));

    if (newTransTbl == NULL)
	return (NULL);

    if (mmuTransTblInit (newTransTbl) == ERROR)
	{
	free ((char *) newTransTbl);
	return (NULL);
	}

    return (newTransTbl);
    }


/******************************************************************************
*
* mmuTransTblInit - initialize a new translation table 
*
* Initialize a new translation table.  The directory table is copyed from the
* global translation mmuGlobalTransTbl, so that we
* will share the global virtual memory with all
* other translation tables.
* 
* RETURNS: OK or ERROR if unable to allocate memory for directory table.
*/

LOCAL STATUS mmuTransTblInit 
    (
    MMU_TRANS_TBL *newTransTbl		/* translation table to be inited */
    )
    {

    FAST PTE *pDirectoryTable;

    /* allocate a page to hold the directory table */

    newTransTbl->pDirectoryTable = pDirectoryTable = 
	(PTE *) memalign (mmuPageSize, mmuPageSize);

    if (pDirectoryTable == NULL)
	return (ERROR);

    /* copy the directory table from mmuGlobalTransTbl,
     * so we get the global virtual memory 
     */

    bcopy ((char *) mmuGlobalTransTbl.pDirectoryTable, 
	   (char *) pDirectoryTable, mmuPageSize);

    /* write protect virtual memory pointing to the the directory table in 
     * the global translation table to insure that it can't be corrupted 
     */

    mmuStateSet (&mmuGlobalTransTbl, (void *) pDirectoryTable, 
		 MMU_STATE_MASK_WRITABLE, MMU_STATE_WRITABLE_NOT);

    return (OK);
    }

/******************************************************************************
*
* mmuTransTblDelete - delete a translation table.
* 
* mmuTransTblDelete deallocates all the memory used to store the translation
* table entries.  It does not deallocate physical pages mapped into the
* virtual memory space.
*
* RETURNS: OK
*
*/

LOCAL STATUS mmuTransTblDelete 
    (
    MMU_TRANS_TBL *transTbl		/* translation table to be deleted */
    )
    {
    FAST int i;
    FAST PTE *pDte = transTbl->pDirectoryTable;
    FAST PTE *pPageTable;

    /* write enable the physical page containing the directory table */

    mmuStateSet (&mmuGlobalTransTbl, transTbl->pDirectoryTable, 
		 MMU_STATE_MASK_WRITABLE, MMU_STATE_WRITABLE);

    /* deallocate only non-global page blocks */

    for (i = 0; i < (PAGE_SIZE / sizeof(PTE)); i++, pDte++)
	if ((pDte->field.present == 1) && !globalPageBlock[i]) 
	    {
	    pPageTable = (PTE *) (pDte->bits & PTE_TO_ADDR);
	    mmuStateSet (&mmuGlobalTransTbl, pPageTable,
			 MMU_STATE_MASK_WRITABLE, MMU_STATE_WRITABLE);
	    free (pPageTable);
	    }

    /* free the page holding the directory table */

    free (transTbl->pDirectoryTable);

    /* free the translation table data structure */

    free (transTbl);
    
    return (OK);
    }

/******************************************************************************
*
* mmuVirtualPageCreate - set up translation tables for a virtual page
*
* simply check if there's already a page table that has a
* pte for the given virtual page.  If there isn't, create one.
*
* RETURNS OK or ERROR if couldn't allocate space for a page table.
*/

LOCAL STATUS mmuVirtualPageCreate 
    (
    MMU_TRANS_TBL *thisTbl, 		/* translation table */
    void *virtPageAddr			/* virtual addr to create */
    )
    {
    PTE *pDte;
    FAST PTE *pPageTable;
    FAST UINT i;
    PTE *dummy;

    if (mmuPteGet (thisTbl, virtPageAddr, &dummy) == OK)
	return (OK);

    pPageTable = (PTE *) memalign (mmuPageSize, mmuPageSize);

    if (pPageTable == NULL)
	return (ERROR);

    /* invalidate every page in the new page block */

    for (i = 0; i < (PAGE_SIZE / sizeof(PTE)); i++)
	{
	pPageTable[i].field.present	= 0;
	pPageTable[i].field.rw		= 0;
	pPageTable[i].field.us		= 0;
	pPageTable[i].field.pwt		= 0;
	pPageTable[i].field.pcd		= 0;
	pPageTable[i].field.access	= 0;
	pPageTable[i].field.dirty	= 0;
	pPageTable[i].field.zero	= 0;
	pPageTable[i].field.avail	= 0;
	pPageTable[i].field.page	= -1;
	}

    /* write protect the new physical page containing the pte's
       for this new page block */

    mmuStateSet (&mmuGlobalTransTbl, pPageTable, 
   		 MMU_STATE_MASK_WRITABLE, MMU_STATE_WRITABLE_NOT); 

    /* unlock the physical page containing the directory table,
       so we can modify it */

    mmuStateSet (&mmuGlobalTransTbl, thisTbl->pDirectoryTable,