Subversion Repositories HelenOS

/** Change adress area flags.

 *

 * The idea is to have the same data, but with a different access mode.

 * This is needed e.g. for writing code into memory and then executing it.

 * In order for this to work properly, this may copy the data

 * into private anonymous memory (unless it's already there).

 *

 * @param as Address space.

 * @param flags Flags of the area memory.

 * @param address Address withing the area to be changed.

 *

 * @return Zero on success or a value from @ref errno.h on failure.

 */

int as_area_change_flags(as_t *as, int flags, uintptr_t address)

{

    as_area_t *area;

    uintptr_t base;

    link_t *cur;

    ipl_t ipl;

    int page_flags;

    uintptr_t *old_frame;

    index_t frame_idx;

    count_t used_pages;

    /* Flags for the new memory mapping */

    page_flags = area_flags_to_page_flags(flags);

    ipl = interrupts_disable();

    mutex_lock(&as->lock);

    area = find_area_and_lock(as, address);

    if (!area) {

        mutex_unlock(&as->lock);

        interrupts_restore(ipl);

        return ENOENT;

    }

    if (area->sh_info || area->backend != &anon_backend) {

        /* Copying shared areas not supported yet */

        /* Copying non-anonymous memory not supported yet */

        mutex_unlock(&area->lock);

        mutex_unlock(&as->lock);

        interrupts_restore(ipl);

        return ENOTSUP;

    }

    base = area->base;

    /*

     * Compute total number of used pages in the used_space B+tree

     */

    used_pages = 0;

    for (cur = area->used_space.leaf_head.next;

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

        btree_node_t *node;

        unsigned int i;

        node = list_get_instance(cur, btree_node_t, leaf_link);

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

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

        }

    }

    /* An array for storing frame numbers */

    old_frame = malloc(used_pages * sizeof(uintptr_t), 0);

    /*

     * Start TLB shootdown sequence.

     */

    tlb_shootdown_start(TLB_INVL_PAGES, as->asid, area->base, area->pages);

    /*

     * Remove used pages from page tables and remember their frame

     * numbers.

     */

    frame_idx = 0;

    for (cur = area->used_space.leaf_head.next;

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

        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 b = node->key[i];

            count_t j;

            pte_t *pte;

            for (j = 0; j < (count_t) node->value[i]; j++) {

                page_table_lock(as, false);

                pte = page_mapping_find(as, b + j * PAGE_SIZE);

                ASSERT(pte && PTE_VALID(pte) &&

                    PTE_PRESENT(pte));

                old_frame[frame_idx++] = PTE_GET_FRAME(pte);

                /* Remove old mapping */

                page_mapping_remove(as, b + j * PAGE_SIZE);

                page_table_unlock(as, false);

            }

        }

    }

    /*

     * Finish TLB shootdown sequence.

     */

    tlb_invalidate_pages(as->asid, area->base, area->pages);

    /*

     * Invalidate potential software translation caches (e.g. TSB on

     * sparc64).

     */

    as_invalidate_translation_cache(as, area->base, area->pages);

    tlb_shootdown_finalize();

    /*

     * Map pages back in with new flags. This step is kept separate

     * so that there's no instant when the memory area could be

     * accesed with both the old and the new flags at once.

     */

    frame_idx = 0;

    for (cur = area->used_space.leaf_head.next;

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

        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 b = node->key[i];

            count_t j;

            for (j = 0; j < (count_t) node->value[i]; j++) {

                page_table_lock(as, false);

                /* Insert the new mapping */

                page_mapping_insert(as, b + j * PAGE_SIZE,

                    old_frame[frame_idx++], page_flags);

                page_table_unlock(as, false);

            }

        }

    }

    free(old_frame);

    mutex_unlock(&area->lock);

    mutex_unlock(&as->lock);

    interrupts_restore(ipl);

    return 0;

}

/** Wrapper for as_area_change_flags(). */

unative_t sys_as_area_change_flags(uintptr_t address, int flags)

{

    return (unative_t) as_area_change_flags(AS, flags, address);

}