source: mainline/kernel/generic/src/mm/backend_anon.c@ 692bd3f2

/*
 * 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 <mm/reserve.h>
#include <genarch/mm/page_pt.h>
#include <genarch/mm/page_ht.h>
#include <mm/frame.h>
#include <mm/slab.h>
#include <mm/km.h>
#include <synch/mutex.h>
#include <adt/list.h>
#include <adt/btree.h>
#include <errno.h>
#include <typedefs.h>
#include <align.h>
#include <memstr.h>
#include <arch.h>

static bool anon_create(as_area_t *);
static bool anon_resize(as_area_t *, size_t);
static void anon_share(as_area_t *);
static void anon_destroy(as_area_t *);

static int anon_page_fault(as_area_t *, uintptr_t, pf_access_t);
static void anon_frame_free(as_area_t *, uintptr_t, uintptr_t);

mem_backend_t anon_backend = {
        .create = anon_create,
        .resize = anon_resize,
        .share = anon_share,
        .destroy = anon_destroy,

        .page_fault = anon_page_fault,
        .frame_free = anon_frame_free,
};

bool anon_create(as_area_t *area)
{
        if (area->flags & AS_AREA_NORESERVE)
                return true;

        return reserve_try_alloc(area->pages);
}

bool anon_resize(as_area_t *area, size_t new_pages)
{
        if (area->flags & AS_AREA_NORESERVE)
                return true;

        if (new_pages > area->pages)
                return reserve_try_alloc(new_pages - area->pages);
        else if (new_pages < area->pages)
                reserve_free(area->pages - new_pages);

        return true;
}

/** 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)
{
        ASSERT(mutex_locked(&area->as->lock));
        ASSERT(mutex_locked(&area->lock));
        ASSERT(!(area->flags & AS_AREA_NORESERVE));

        /*
         * Copy used portions of the area to sh_info's page map.
         */
        mutex_lock(&area->sh_info->lock);
        list_foreach(area->used_space.leaf_list, cur) {
                btree_node_t *node;
                unsigned int i;
                
                node = list_get_instance(cur, btree_node_t, leaf_link);
                for (i = 0; i < node->keys; i++) {
                        uintptr_t base = node->key[i];
                        size_t count = (size_t) node->value[i];
                        unsigned int j;
                        
                        for (j = 0; j < count; j++) {
                                pte_t *pte;
                        
                                page_table_lock(area->as, false);
                                pte = page_mapping_find(area->as,
                                    base + P2SZ(j), false);
                                ASSERT(pte && PTE_VALID(pte) &&
                                    PTE_PRESENT(pte));
                                btree_insert(&area->sh_info->pagemap,
                                    (base + P2SZ(j)) - area->base,
                                    (void *) PTE_GET_FRAME(pte), NULL);
                                page_table_unlock(area->as, false);

                                pfn_t pfn = ADDR2PFN(PTE_GET_FRAME(pte));
                                frame_reference_add(pfn);
                        }

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

void anon_destroy(as_area_t *area)
{
        if (area->flags & AS_AREA_NORESERVE)
                return;

        reserve_free(area->pages);
}


/** 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, uintptr_t addr, pf_access_t access)
{
        uintptr_t upage = ALIGN_DOWN(addr, PAGE_SIZE);
        uintptr_t kpage;
        uintptr_t frame;

        ASSERT(page_table_locked(AS));
        ASSERT(mutex_locked(&area->lock));

        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 = (uintptr_t) btree_search(&area->sh_info->pagemap,
                    upage - area->base, &leaf);
                if (!frame) {
                        bool allocate = true;
                        unsigned 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] == upage - area->base) {
                                        allocate = false;
                                        break;
                                }
                        }
                        if (allocate) {
                                kpage = km_temporary_page_get(&frame,
                                    FRAME_NO_RESERVE);
                                memsetb((void *) kpage, PAGE_SIZE, 0);
                                km_temporary_page_put(kpage);
                                
                                /*
                                 * Insert the address of the newly allocated
                                 * frame to the pagemap.
                                 */
                                btree_insert(&area->sh_info->pagemap,
                                    upage - 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
                 */

                unsigned int flags;

                if (area->flags & AS_AREA_NORESERVE) {
                        /*
                         * This is a NORESERVE area, which means that no
                         * physical memory has been reserved beforehands.
                         * We therefore need to make an atomic and reserving
                         * allocation.
                         */
                        flags = FRAME_ATOMIC;
                } else {
                        /*
                         * The physical memory has already been reserved
                         * when this part of the area was created. Avoid
                         * double reservation by using the appropriate flag.
                         */
                        flags = FRAME_NO_RESERVE;
                }

                kpage = km_temporary_page_get(&frame, flags);
                if (!kpage)
                        return AS_PF_FAULT;
                memsetb((void *) kpage, PAGE_SIZE, 0);
                km_temporary_page_put(kpage);
        }
        
        /*
         * Map 'upage' to 'frame'.
         * Note that TLB shootdown is not attempted as only new information is
         * being inserted into page tables.
         */
        page_mapping_insert(AS, upage, frame, as_area_get_flags(area));
        if (!used_space_insert(area, upage, 1))
                panic("Cannot insert used space.");
                
        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 Virtual address of the page corresponding to the frame.
 * @param frame Frame to be released.
 */
void anon_frame_free(as_area_t *area, uintptr_t page, uintptr_t frame)
{
        ASSERT(page_table_locked(area->as));
        ASSERT(mutex_locked(&area->lock));

        if (area->flags & AS_AREA_NORESERVE) {
                /*
                 * In case of the NORESERVE areas, physical memory will not be
                 * unreserved when the area is destroyed so we need to use the
                 * normal unreserving frame_free().
                 */
                frame_free(frame);
        } else {
                /*
                 * The reserve will be given back when the area is destroyed or
                 * resized, so use the frame_free_noreserve() which does not
                 * manipulate the reserve or it would be given back twice.
                 */
                frame_free_noreserve(frame);
        }
}

/** @}
 */