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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.

 */

/** @addtogroup genericmm

 * @{

 */

/**

 * @file

 * @brief   Backend for anonymous memory address space areas.

 *

 */

#include <mm/as.h>

#include <mm/page.h>

#include <genarch/mm/page_pt.h>

#include <genarch/mm/page_ht.h>

#include <mm/frame.h>

#include <mm/slab.h>

#include <synch/mutex.h>

#include <adt/list.h>

#include <adt/btree.h>

#include <errno.h>

#include <arch/types.h>

#include <typedefs.h>

#include <align.h>

#include <arch.h>

static int anon_page_fault(as_area_t *area, __address addr, pf_access_t access);

static void anon_frame_free(as_area_t *area, __address page, __address frame);

static void anon_share(as_area_t *area);

mem_backend_t anon_backend = {

    .page_fault = anon_page_fault,

    .frame_free = anon_frame_free,

    .share = anon_share

};

/** Service a page fault in the anonymous memory address space area.

 *

 * The address space area and page tables must be already locked.

 *

 * @param area Pointer to the address space area.

 * @param addr Faulting virtual address.

 * @param access Access mode that caused the fault (i.e. read/write/exec).

 *

 * @return AS_PF_FAULT on failure (i.e. page fault) or AS_PF_OK on success (i.e. serviced).

 */

int anon_page_fault(as_area_t *area, __address addr, pf_access_t access)

{

    __address frame;

    if (!as_area_check_access(area, access))

        return AS_PF_FAULT;

    if (area->sh_info) {

        btree_node_t *leaf;

        /*

         * The area is shared, chances are that the mapping can be found

         * in the pagemap of the address space area share info structure.

         * In the case that the pagemap does not contain the respective

         * mapping, a new frame is allocated and the mapping is created.

         */

        mutex_lock(&area->sh_info->lock);

        frame = (__address) btree_search(&area->sh_info->pagemap,

            ALIGN_DOWN(addr, PAGE_SIZE) - area->base, &leaf);

        if (!frame) {

            bool allocate = true;

            int i;

            /*

             * Zero can be returned as a valid frame address.

             * Just a small workaround.

             */

            for (i = 0; i < leaf->keys; i++) {

                if (leaf->key[i] == ALIGN_DOWN(addr, PAGE_SIZE)) {

                    allocate = false;

                    break;

                }

            }

            if (allocate) {

                frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));

                memsetb(PA2KA(frame), FRAME_SIZE, 0);

                /*

                 * Insert the address of the newly allocated frame to the pagemap.

                 */

                btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base, (void *) frame, leaf);

            }

        }

        frame_reference_add(ADDR2PFN(frame));

        mutex_unlock(&area->sh_info->lock);

    } else {

        /*

         * In general, there can be several reasons that

         * can have caused this fault.

         *

         * - non-existent mapping: the area is an anonymous

         *   area (e.g. heap or stack) and so far has not been

         *   allocated a frame for the faulting page

         *

         * - non-present mapping: another possibility,

         *   currently not implemented, would be frame

         *   reuse; when this becomes a possibility,

         *   do not forget to distinguish between

         *   the different causes

         */

        frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));

        memsetb(PA2KA(frame), FRAME_SIZE, 0);

    }

    /*

     * Map 'page' to 'frame'.

     * Note that TLB shootdown is not attempted as only new information is being

     * inserted into page tables.

     */

    page_mapping_insert(AS, addr, frame, as_area_get_flags(area));

    if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))

        panic("Could not insert used space.\n");

    return AS_PF_OK;

}

/** Free a frame that is backed by the anonymous memory backend.

 *

 * The address space area and page tables must be already locked.

 *

 * @param area Ignored.

 * @param page Ignored.

 * @param frame Frame to be released.

 */

void anon_frame_free(as_area_t *area, __address page, __address frame)

{

    frame_free(ADDR2PFN(frame));

}

/** Share the anonymous address space area.

 *

 * Sharing of anonymous area is done by duplicating its entire mapping

 * to the pagemap. Page faults will primarily search for frames there.

 *

 * The address space and address space area must be already locked.

 *

 * @param area Address space area to be shared.

 */

void anon_share(as_area_t *area)

{

    link_t *cur;

    /*

     * Copy used portions of the area to sh_info's page map.

     */

    mutex_lock(&area->sh_info->lock);

    for (cur = area->used_space.leaf_head.next; cur != &area->used_space.leaf_head; cur = cur->next) {

        btree_node_t *node;

        int i;

        node = list_get_instance(cur, btree_node_t, leaf_link);

        for (i = 0; i < node->keys; i++) {

            __address base = node->key[i];

            count_t count = (count_t) node->value[i];

            int j;

            for (j = 0; j < count; j++) {

                pte_t *pte;

                page_table_lock(area->as, false);

                pte = page_mapping_find(area->as, base + j*PAGE_SIZE);

                ASSERT(pte && PTE_VALID(pte) && PTE_PRESENT(pte));

                btree_insert(&area->sh_info->pagemap, (base + j*PAGE_SIZE) - area->base,

                    (void *) PTE_GET_FRAME(pte), NULL);

                page_table_unlock(area->as, false);

                frame_reference_add(ADDR2PFN(PTE_GET_FRAME(pte)));

            }

        }

    }

    mutex_unlock(&area->sh_info->lock);

}

/** @}

 */