source: mainline/generic/src/mm/backend_anon.c@ 1ec1fd8

/*
 * 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.
 */

/**
 * @file        backend_anon.c
 * @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);
                        }
                }
                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);
                        }
                                
                }
        }
        mutex_unlock(&area->sh_info->lock);
}