source: rtems/c/src/lib/libbsp/powerpc/shared/startup/pgtbl_setup.c @ 6128a4a

/* $Id$ */

#include <rtems.h>
#include <libcpu/mmu.h>
#include <libcpu/page.h>
#include <rtems/bspIo.h>
#include <libcpu/pte121.h>


/* Default setup of the page tables. This is a weak
 * alias, so applications may easily override this
 * default setup.
 *
 * NOTE: while it is possible to change the individual
 *       mappings, the page table itself MUST be
 *       allocated at the top of the physical memory!
 *       bspstart.c RELIES on this.
 *       Also, the 'setup' routine must reduce
 *       *pmemsize by the size of the page table.
 */

/* Author: Till Straumann, <strauman@slac.stanford.edu>, 4/2002 */

Triv121PgTbl
BSP_pgtbl_setup(unsigned long) __attribute__ (( weak, alias("__BSP_default_pgtbl_setup") ));


Triv121PgTbl
__BSP_default_pgtbl_setup(unsigned int *pmemsize)
{
Triv121PgTbl    pt;
unsigned                ldPtSize,tmp;

  /* Allocate a page table large enough to map
   * the entire physical memory. We put the page
   * table at the top of the physical memory.
   */

  /* get minimal size (log base 2) of PT for
   * this board's memory
   */
  ldPtSize = triv121PgTblLdMinSize(*pmemsize);
  ldPtSize++; /* double this amount -- then why? */

  /* allocate the page table at the top of the physical
   * memory - THIS IS NOT AN OPTION - bspstart.c RELIES
   * ON THIS LAYOUT! (the size, however may be changed)
   */
  if ( (pt = triv121PgTblInit(*pmemsize - (1<<ldPtSize), ldPtSize)) ) {
        /* get those from the linker script.
         * NOTE THAT THE CORRECTNESS OF THE LINKER SCRIPT IS CRUCIAL
         */
        extern unsigned long __DATA_START__[], _etext[];

        /* map text and RO data read-only */
        tmp = triv121PgTblMap(
                                                pt,
                                                TRIV121_121_VSID,
                                                0,
                                                (PAGE_ALIGN((unsigned long)_etext) - 0) >> PG_SHIFT,
                                                0, /* WIMG */
                                                TRIV121_PP_RO_PAGE);
        if (TRIV121_MAP_SUCCESS != tmp) {
                printk("Unable to map page index %i; reverting to BAT0\n",
                                tmp);
                pt = 0;
        } else {
                /* map the rest (without the page table itself) RW */
                tmp = triv121PgTblMap(
                                                pt,
                                                TRIV121_121_VSID,
                                                (unsigned long)__DATA_START__,
                                                (*pmemsize - (1<<ldPtSize) -  (unsigned long)__DATA_START__ )>> PG_SHIFT,
                                                0, /* WIMG */
                                                TRIV121_PP_RW_PAGE);
                if (TRIV121_MAP_SUCCESS != tmp) {
                        printk("Unable to map page index %i; reverting to BAT0\n",
                                        tmp);
                        pt = 0;
                }
        }
  } else {
        printk("WARNING: unable to allocate page table, keeping DBAT0\n");
  }
  if (pt) {
#ifdef SHOW_MORE_INIT_SETTINGS
        printk("Setting up page table mappings; protecting text/read-only data from write access\n");
#endif
        /* SUCCESS; reduce available memory by size of the page table */
        *pmemsize -= (1<<ldPtSize);
  }
  return pt;
}