pte121.h

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

#ifndef PPC_TRIVIAL_PTE_MAPPING_H
#define PPC_TRIVIAL_PTE_MAPPING_H
/* $Id: pte121.h,v 1.1 2002/05/15 19:22:13 joel Exp $ */

/* Rudimentary page/hash table support for Powerpc
 *
 * A simple, static (i.e. no 'per-process' virtual
 * address space etc.) page table providing
 * one-to-one effective <-> virtual <-> physical
 * address mapping.
 *
 * PURPOSE:
 *    1) allow write-protection of text/read-only data areas
 *    2) provide more effective-address space in case 
 *       the BATs are not enough
 * LIMITATIONS:
 *    -  once activated, the page table cannot be changed
 *    -  no PTE replacement (makes no sense in a real-time
 *       environment, anyway) -> the page table just MUST
 *       be big enough!.
 *    -  only one page table supported.
 */

/* Author: Till Straumann <[e-mail]>, 4/2002 */

/* Abstract handle for a page table */
typedef struct Triv121PgTblRec_ *Triv121PgTbl;

/* Initialize a trivial page table
 * using 2^ldSize bytes of memory starting at
 * 'base'.
 *
 * RETURNS: a handle to the internal data structure
 *          used to manage the page table. NULL on
 *          error.
 *          
 * NOTES:   - 'base' must be aligned to the size
 *          - minimal ldSize is 16 (== 64k)
 *          - this routine maps the page table itself
 *            with read-only access. While this prevents
 *            the CPU from overwriting the page table,
 *            it can still be corrupted by PCI bus masters
 *            (like DMA engines, [VME] bridges etc.) and
 *			  even by this CPU if either the MMU is off 
 *			  or if there is a DBAT mapping granting write
 *            access...
 */
Triv121PgTbl
triv121PgTblInit(unsigned long base, unsigned ldSize);

/* get the log2 of the minimal page table size needed
 * for mapping 'size' bytes.
 *
 * EXAMPLE: create a page table which maps the entire
 *          physical memory. The page table itself shall
 *          be allocated at the top of the available
 *          memory (assuming 'memsize' is a power of two):
 *
 *	ldSize = triv121PgTblLdMinSize(memsize);
 *  memsize -= (1<<ldSize);	/ * reduce memory available to RTEMS * /
 *  pgTbl  = triv121PgTblInit(memsize,ldSize);
 * 
 */
unsigned long
triv121PgTblLdMinSize(unsigned long size);

/* Map an address range 1:1 in pgTbl with the given protection;
 *
 * RETURNS: -1 (TRIV121_MAP_SUCCESS) on success; the page index
 *          for which no PTE could be allocated, on failure.
 *
 * NOTES:   - This routine returns MINUS ONE ON SUCCESS
 *          - (parts) of a mapping which overlap with
 *            already existing PTEs are silently ignored.
 *
 *            Therefore, you can e.g. first create
 *            a couple of write protected maps and
 *            finally map the entire memory r/w. This
 *            will leave the write protected maps
 *            intact.
 */
long
triv121PgTblMap(
				Triv121PgTbl  pgTbl,			/* handle, returned by Init or Get */

				long          vsid,				/* vsid for this mapping (contains topmost 4 bits of EA);
												 *
												 * NOTE: it is allowed to pass a VSID < 0 to tell this
												 *       routine it should use a VSID corresponding to a
												 *       1:1:1  effective - virtual - physical  mapping
												 */

				unsigned long start,			/* segment offset (lowermost 28 bits of EA) of address range
												 *
												 * NOTE: if VSID < 0 (TRIV121_121_VSID), 'start' is inter-
												 *       preted as an effective address (EA), i.e. all 32
												 *       bits are used - the most significant four going into
												 *       to the VSID...
											   	 */

				unsigned long numPages,			/* number of pages to map */

				unsigned wimgAttr,				/* 'wimg' attributes
												 * (Write thru, cache Inhibit, coherent Memory,
												 *  Guarded memory)
												 */

				unsigned protection				/* 'pp' access protection: Super      User
												 *
												 *   0                      r/w       none
												 *   1                      r/w       ro   
												 *   2                      r/w       r/w
												 *   3                      ro        ro
												 */
				);

#define TRIV121_ATTR_W	8	
#define TRIV121_ATTR_I	4
#define TRIV121_ATTR_M	2
#define TRIV121_ATTR_G	1

/* for I/O pages (e.g. PCI, VME addresses) use cache inhibited
 * and guarded pages. RTM about the 'eieio' instruction!
 */
#define TRIV121_ATTR_IO_PAGE	(TRIV121_ATTR_I|TRIV121_ATTR_G)

#define TRIV121_PP_RO_PAGE		(3)  /* read-only for everyone */
#define TRIV121_PP_RW_PAGE		(2)  /* read-write for everyone */

#define TRIV121_121_VSID		(-1) /* use 1:1 effective<->virtual address mapping */

#define TRIV121_MAP_SUCCESS		(-1) /* triv121PgTblMap() returns this on SUCCESS */

/* get a handle to the one and only page table
 * (must have been initialized/allocated)
 *
 * RETURNS: NULL if the page table has not been initialized/allocated.
 */
Triv121PgTbl
triv121PgTblGet(void);

/*
 * compute the SDR1 register value for the page table
 */

unsigned long
triv121PgTblSDR1(Triv121PgTbl pgTbl);

/*
 * Activate the page table:
 *	- set up the segment registers for a 1:1 effective <-> virtual address mapping,
 *    give user and supervisor keys.
 *  - set up the SDR1 register
 *  - flush all tlbs
 *  - 'lock' pgTbl, i.e. prevent all further modifications.
 *
 * NOTE: This routine does not change any BATs. Since these
 *       have priority over the page table, the user
 *       may have to switch overlapping BATs OFF in order
 *       for the page table mappings to take effect.
 */
void
triv121PgTblActivate(Triv121PgTbl pgTbl);

#endif