page_pt.c

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/*
 * Copyright (C) 2006 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <genarch/mm/page_pt.h>
#include <mm/page.h>
#include <mm/frame.h>
#include <mm/as.h>
#include <arch/mm/page.h>
#include <arch/mm/as.h>
#include <arch/types.h>
#include <typedefs.h>
#include <arch/asm.h>
#include <memstr.h>

static void pt_mapping_insert(as_t *as, __address page, __address frame, int flags);
static void pt_mapping_remove(as_t *as, __address page);
static pte_t *pt_mapping_find(as_t *as, __address page);

page_mapping_operations_t pt_mapping_operations = {
        .mapping_insert = pt_mapping_insert,
        .mapping_remove = pt_mapping_remove,
        .mapping_find = pt_mapping_find
};

void pt_mapping_insert(as_t *as, __address page, __address frame, int flags)
{
        pte_t *ptl0, *ptl1, *ptl2, *ptl3;
        __address newpt;

        ptl0 = (pte_t *) PA2KA((__address) as->page_table);

        if (GET_PTL1_FLAGS(ptl0, PTL0_INDEX(page)) & PAGE_NOT_PRESENT) {
                newpt = PA2KA(PFN2ADDR(frame_alloc(ONE_FRAME, FRAME_KA)));
                memsetb(newpt, PAGE_SIZE, 0);
                SET_PTL1_ADDRESS(ptl0, PTL0_INDEX(page), KA2PA(newpt));
                SET_PTL1_FLAGS(ptl0, PTL0_INDEX(page), PAGE_PRESENT | PAGE_USER | PAGE_EXEC | PAGE_CACHEABLE | PAGE_WRITE);
        }

        ptl1 = (pte_t *) PA2KA(GET_PTL1_ADDRESS(ptl0, PTL0_INDEX(page)));

        if (GET_PTL2_FLAGS(ptl1, PTL1_INDEX(page)) & PAGE_NOT_PRESENT) {
                newpt = PA2KA(PFN2ADDR(frame_alloc(ONE_FRAME, FRAME_KA)));
                memsetb(newpt, PAGE_SIZE, 0);
                SET_PTL2_ADDRESS(ptl1, PTL1_INDEX(page), KA2PA(newpt));
                SET_PTL2_FLAGS(ptl1, PTL1_INDEX(page), PAGE_PRESENT | PAGE_USER | PAGE_EXEC | PAGE_CACHEABLE | PAGE_WRITE);
        }

        ptl2 = (pte_t *) PA2KA(GET_PTL2_ADDRESS(ptl1, PTL1_INDEX(page)));

        if (GET_PTL3_FLAGS(ptl2, PTL2_INDEX(page)) & PAGE_NOT_PRESENT) {
                newpt = PA2KA(PFN2ADDR(frame_alloc(ONE_FRAME, FRAME_KA)));
                memsetb(newpt, PAGE_SIZE, 0);
                SET_PTL3_ADDRESS(ptl2, PTL2_INDEX(page), KA2PA(newpt));
                SET_PTL3_FLAGS(ptl2, PTL2_INDEX(page), PAGE_PRESENT | PAGE_USER | PAGE_EXEC | PAGE_CACHEABLE | PAGE_WRITE);
        }

        ptl3 = (pte_t *) PA2KA(GET_PTL3_ADDRESS(ptl2, PTL2_INDEX(page)));

        SET_FRAME_ADDRESS(ptl3, PTL3_INDEX(page), frame);
        SET_FRAME_FLAGS(ptl3, PTL3_INDEX(page), flags);
}

void pt_mapping_remove(as_t *as, __address page)
{
        pte_t *ptl0, *ptl1, *ptl2, *ptl3;
        bool empty = true;
        int i;

        /*
         * First, remove the mapping, if it exists.
         */

        ptl0 = (pte_t *) PA2KA((__address) as->page_table);

        if (GET_PTL1_FLAGS(ptl0, PTL0_INDEX(page)) & PAGE_NOT_PRESENT)
                return;

        ptl1 = (pte_t *) PA2KA(GET_PTL1_ADDRESS(ptl0, PTL0_INDEX(page)));

        if (GET_PTL2_FLAGS(ptl1, PTL1_INDEX(page)) & PAGE_NOT_PRESENT)
                return;

        ptl2 = (pte_t *) PA2KA(GET_PTL2_ADDRESS(ptl1, PTL1_INDEX(page)));

        if (GET_PTL3_FLAGS(ptl2, PTL2_INDEX(page)) & PAGE_NOT_PRESENT)
                return;

        ptl3 = (pte_t *) PA2KA(GET_PTL3_ADDRESS(ptl2, PTL2_INDEX(page)));

        /* Destroy the mapping. Setting to PAGE_NOT_PRESENT is not sufficient. */
        memsetb((__address) &ptl3[PTL3_INDEX(page)], sizeof(pte_t), 0);

        /*
         * Second, free all empty tables along the way from PTL3 down to PTL0.
         */
        
        /* check PTL3 */
        for (i = 0; i < PTL3_ENTRIES; i++) {
                if (PTE_VALID(&ptl3[i])) {
                        empty = false;
                        break;
                }
        }
        if (empty) {
                /*
                 * PTL3 is empty.
                 * Release the frame and remove PTL3 pointer from preceding table.
                 */
                frame_free(ADDR2PFN(KA2PA((__address) ptl3)));
                if (PTL2_ENTRIES)
                        memsetb((__address) &ptl2[PTL2_INDEX(page)], sizeof(pte_t), 0);
                else if (PTL1_ENTRIES)
                        memsetb((__address) &ptl1[PTL1_INDEX(page)], sizeof(pte_t), 0);
                else
                        memsetb((__address) &ptl0[PTL0_INDEX(page)], sizeof(pte_t), 0);
        } else {
                /*
                 * PTL3 is not empty.
                 * Therefore, there must be a path from PTL0 to PTL3 and
                 * thus nothing to free in higher levels.
                 */
                return;
        }
        
        /* check PTL2, empty is still true */
        if (PTL2_ENTRIES) {
                for (i = 0; i < PTL2_ENTRIES; i++) {
                        if (PTE_VALID(&ptl2[i])) {
                                empty = false;
                                break;
                        }
                }
                if (empty) {
                        /*
                         * PTL2 is empty.
                         * Release the frame and remove PTL2 pointer from preceding table.
                         */
                        frame_free(ADDR2PFN(KA2PA((__address) ptl2)));
                        if (PTL1_ENTRIES)
                                memsetb((__address) &ptl1[PTL1_INDEX(page)], sizeof(pte_t), 0);
                        else
                                memsetb((__address) &ptl0[PTL0_INDEX(page)], sizeof(pte_t), 0);
                }
                else {
                        /*
                         * PTL2 is not empty.
                         * Therefore, there must be a path from PTL0 to PTL2 and
                         * thus nothing to free in higher levels.
                         */
                        return;
                }
        }

        /* check PTL1, empty is still true */
        if (PTL1_ENTRIES) {
                for (i = 0; i < PTL1_ENTRIES; i++) {
                        if (PTE_VALID(&ptl1[i])) {
                                empty = false;
                                break;
                        }
                }
                if (empty) {
                        /*
                         * PTL1 is empty.
                         * Release the frame and remove PTL1 pointer from preceding table.
                         */
                        frame_free(ADDR2PFN(KA2PA((__address) ptl1)));
                        memsetb((__address) &ptl0[PTL0_INDEX(page)], sizeof(pte_t), 0);
                }
        }

}

pte_t *pt_mapping_find(as_t *as, __address page)
{
        pte_t *ptl0, *ptl1, *ptl2, *ptl3;

        ptl0 = (pte_t *) PA2KA((__address) as->page_table);

        if (GET_PTL1_FLAGS(ptl0, PTL0_INDEX(page)) & PAGE_NOT_PRESENT)
                return NULL;

        ptl1 = (pte_t *) PA2KA(GET_PTL1_ADDRESS(ptl0, PTL0_INDEX(page)));

        if (GET_PTL2_FLAGS(ptl1, PTL1_INDEX(page)) & PAGE_NOT_PRESENT)
                return NULL;

        ptl2 = (pte_t *) PA2KA(GET_PTL2_ADDRESS(ptl1, PTL1_INDEX(page)));

        if (GET_PTL3_FLAGS(ptl2, PTL2_INDEX(page)) & PAGE_NOT_PRESENT)
                return NULL;

        ptl3 = (pte_t *) PA2KA(GET_PTL3_ADDRESS(ptl2, PTL2_INDEX(page)));

        return &ptl3[PTL3_INDEX(page)];
}

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