예제 #1
0
void destroy_area(struct vm_address_space *space, struct vm_area *area)
{
    struct vm_cache *cache;
    unsigned int va;
    unsigned int ptentry;

    rwlock_lock_write(&space->mut);
    cache = area->cache;

    // Unmap all pages in this area
    for (va = area->low_address; va < area->high_address; va += PAGE_SIZE)
    {
        ptentry = query_translation_map(space->translation_map, va);
        if ((ptentry & PAGE_PRESENT) != 0)
        {
            VM_DEBUG("destroy_area: decrementing page ref for va %08x pa %08x\n",
                    va, PAGE_ALIGN(ptentry));
            dec_page_ref(pa_to_page(ptentry));
        }
    }

    destroy_vm_area(area);
    rwlock_unlock_write(&space->mut);
    if (cache)
        dec_cache_ref(cache);
}
예제 #2
0
void destroy_translation_map(struct vm_translation_map *map)
{
    int i;
    unsigned int *pgdir;
    int old_flags;

    old_flags = acquire_spinlock_int(&kernel_space_lock);
    list_remove_node(map);
    release_spinlock_int(&kernel_space_lock, old_flags);

    // Free user space page tables
    pgdir = (unsigned int*) PA_TO_VA(map->page_dir);
    for (i = 0; i < 768; i++)
    {
        if (pgdir[i] & PAGE_PRESENT)
            dec_page_ref(pa_to_page(PAGE_ALIGN(pgdir[i])));
    }

    dec_page_ref(pa_to_page(map->page_dir));
    slab_free(&translation_map_slab, map);
}
예제 #3
0
void free_page_structure(uint32_t *page_dir)
{
    uint16_t idx, i;
    uint32_t *page_table;
    for(idx = 2; idx < 1024; ++idx) { /* start from 2 to skip the kernel space */
        if(page_dir[idx] & 0x1) {
            page_table = (uint32_t *)(page_dir[idx] & 0xfffff000);
            for(i = 0; i < 1024; ++i) {
                if(page_table[i] & 0x1)
                    dec_page_ref(page_table[i] >> 12);
            }
            dec_page_ref(PT_NUM_ADDR(page_table));
        }
    }
예제 #4
0
//
// This is always called with the address space lock held, so the area is
// guaranteed not to change. Returns 1 if it sucessfully satisfied the fault, 0
// if it failed for some reason.
//
static int soft_fault(struct vm_address_space *space, const struct vm_area *area,
                      unsigned int address, int is_store)
{
    int got;
    unsigned int page_flags;
    struct vm_page *source_page;
    struct vm_page *dummy_page = 0;
    unsigned int cache_offset;
    struct vm_cache *cache;
    int old_flags;
    int is_cow_page = 0;
    int size_to_read;

    VM_DEBUG("soft fault va %08x %s\n", address, is_store ? "store" : "load");

    // XXX check area protections and fail if this shouldn't be allowed
    if (is_store && (area->flags & AREA_WRITABLE) == 0)
    {
        kprintf("store to read only area %s @%08x\n", area->name, address);
        return 0;
    }

    cache_offset = PAGE_ALIGN(address - area->low_address + area->cache_offset);
    old_flags = disable_interrupts();
    lock_vm_cache();
    assert(area->cache);

    for (cache = area->cache; cache; cache = cache->source)
    {
        VM_DEBUG("searching in cache %p\n", cache);
        source_page = lookup_cache_page(cache, cache_offset);
        if (source_page)
            break;

        if (cache->file && address - area->low_address < area->cache_length)
        {
            VM_DEBUG("reading page from file\n");

            // Read the page from this cache.
            source_page = vm_allocate_page();

            // Insert the page first so, if a collided fault occurs, it will not
            // load a different page (the vm cache lock protects the busy bit)
            source_page->busy = 1;
            insert_cache_page(cache, cache_offset, source_page);
            unlock_vm_cache();
            restore_interrupts(old_flags);

            if (area->cache_length - cache_offset < PAGE_SIZE)
                size_to_read = area->cache_length - cache_offset;
            else
                size_to_read = PAGE_SIZE;

            got = read_file(cache->file, cache_offset,
                            (void*) PA_TO_VA(page_to_pa(source_page)), size_to_read);
            if (got < 0)
            {
                kprintf("failed to read from file\n");
                dec_page_ref(source_page);
                if (dummy_page != 0)
                {
                    disable_interrupts();
                    lock_vm_cache();
                    remove_cache_page(dummy_page);
                    unlock_vm_cache();
                    restore_interrupts(old_flags);
                    dec_page_ref(dummy_page);
                }

                return 0;
            }

            // For BSS, clear out data past the end of the file
            if (size_to_read < PAGE_SIZE)
            {
                memset((char*) PA_TO_VA(page_to_pa(source_page)) + size_to_read, 0,
                       PAGE_SIZE - size_to_read);
            }

            disable_interrupts();
            lock_vm_cache();
            source_page->busy = 0;
            break;
        }

        // Otherwise scan the next cache
        is_cow_page = 1;

        if (cache == area->cache)
        {
            // Insert a dummy page in the top level cache to catch collided faults.
            dummy_page = vm_allocate_page();
            dummy_page->busy = 1;
            insert_cache_page(cache, cache_offset, dummy_page);
        }
    }

    if (source_page == 0)
    {
        assert(dummy_page != 0);

        VM_DEBUG("source page was not found, use empty page\n");

        // No page found, just use the dummy page
        dummy_page->busy = 0;
        source_page = dummy_page;
    }
    else if (is_cow_page)
    {
        // is_cow_page means source_page belongs to another cache.
        assert(dummy_page != 0);
        if (is_store)
        {
            // The dummy page have the contents of the source page copied into it,
            // and will be inserted into the top cache (it's not really a dummy page
            // any more).
            memcpy((void*) PA_TO_VA(page_to_pa(dummy_page)),
                (void*) PA_TO_VA(page_to_pa(source_page)),
                PAGE_SIZE);
            VM_DEBUG("write copy page va %08x dest pa %08x source pa %08x\n",
                address, page_to_pa(dummy_page), page_to_pa(source_page));
            source_page = dummy_page;
            dummy_page->busy = 0;
        }
        else
        {
            // We will map in the read-only page from the source cache.
            // Remove the dummy page from this cache (we do not insert
            // the page into this cache, because we don't own it page).
            remove_cache_page(dummy_page);
            dec_page_ref(dummy_page);

            VM_DEBUG("mapping read-only source page va %08x pa %08x\n", address,
                page_to_pa(source_page));
        }
    }

    assert(source_page != 0);

    // Grab a ref because we are going to map this page
    inc_page_ref(source_page);

    unlock_vm_cache();
    restore_interrupts(old_flags);

    // XXX busy wait for page to finish loading
    while (source_page->busy)
        reschedule();

    if (is_store)
        source_page->dirty = 1; // XXX Locking?

    // It's possible two threads will fault on the same VA and end up mapping
    // the page twice. This is fine, because the code above ensures it will
    // be the same page.
    page_flags = PAGE_PRESENT;

    // If the page is clean, we will mark it not writable. This will fault
    // on the next write, allowing us to update the dirty flag.
    if ((area->flags & AREA_WRITABLE) != 0 && (source_page->dirty || is_store))
        page_flags |= PAGE_WRITABLE;

    if (area->flags & AREA_EXECUTABLE)
        page_flags |= PAGE_EXECUTABLE;

    if (space == &kernel_address_space)
        page_flags |= PAGE_SUPERVISOR | PAGE_GLOBAL;

    vm_map_page(space->translation_map, address, page_to_pa(source_page)
        | page_flags);

    return 1;
}