Subversion Repositories HelenOS

/*

 * 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 address space areas backed by an ELF image.

 */

#include <lib/elf.h>

#include <debug.h>

#include <arch/types.h>

#include <mm/as.h>

#include <mm/frame.h>

#include <mm/slab.h>

#include <mm/page.h>

#include <genarch/mm/page_pt.h>

#include <genarch/mm/page_ht.h>

#include <align.h>

#include <memstr.h>

#include <macros.h>

#include <arch.h>

#include <arch/barrier.h>

#ifdef CONFIG_VIRT_IDX_DCACHE

#include <arch/mm/cache.h>

#endif

static int elf_page_fault(as_area_t *area, uintptr_t addr, pf_access_t access);

static void elf_frame_free(as_area_t *area, uintptr_t page, uintptr_t frame);

static void elf_share(as_area_t *area);

mem_backend_t elf_backend = {

    .page_fault = elf_page_fault,

    .frame_free = elf_frame_free,

    .share = elf_share

};

/** Service a page fault in the ELF backend 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 elf_page_fault(as_area_t *area, uintptr_t addr, pf_access_t access)

{

    elf_header_t *elf = area->backend_data.elf;

    elf_segment_header_t *entry = area->backend_data.segment;

    btree_node_t *leaf;

    uintptr_t base, frame, page, start_anon;

    index_t i;

    bool dirty = false;

    if (!as_area_check_access(area, access))

        return AS_PF_FAULT;

    ASSERT((addr >= ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE)) &&

        (addr < entry->p_vaddr + entry->p_memsz));

    i = (addr - ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE)) >> PAGE_WIDTH;

    base = (uintptr_t)

        (((void *) elf) + ALIGN_DOWN(entry->p_offset, PAGE_SIZE));

    /* Virtual address of faulting page*/

    page = ALIGN_DOWN(addr, PAGE_SIZE);

    /* Virtual address of the end of initialized part of segment */

    start_anon = entry->p_vaddr + entry->p_filesz;

    if (area->sh_info) {

        bool found = false;

        /*

         * The address space area is shared.

         */

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

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

            page - area->base, &leaf);

        if (!frame) {

            unsigned int i;

            /*

             * Workaround for valid NULL address.

             */

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

                if (leaf->key[i] == page) {

                    found = true;

                    break;

                }

            }

        }

        if (frame || found) {

            frame_reference_add(ADDR2PFN(frame));

            page_mapping_insert(AS, addr, frame,

                as_area_get_flags(area));

            if (!used_space_insert(area, page, 1))

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

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

            return AS_PF_OK;

        }

    }

    /*

     * The area is either not shared or the pagemap does not contain the

     * mapping.

     */

    if (page >= entry->p_vaddr && page + PAGE_SIZE <= start_anon) {

        /*

         * Initialized portion of the segment. The memory is backed

         * directly by the content of the ELF image. Pages are

         * only copied if the segment is writable so that there

         * can be more instantions of the same memory ELF image

         * used at a time. Note that this could be later done

         * as COW.

         */

        if (entry->p_flags & PF_W) {

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

            memcpy((void *) PA2KA(frame),

                (void *) (base + i * FRAME_SIZE), FRAME_SIZE);

            if (entry->p_flags & PF_X) {

                smc_coherence_block((void *) PA2KA(frame),

                    FRAME_SIZE);

            }

            dirty = true;

        } else {

            frame = KA2PA(base + i * FRAME_SIZE);

        }  

    } else if (page >= start_anon) {

        /*

         * This is the uninitialized portion of the segment.

         * It is not physically present in the ELF image.

         * To resolve the situation, a frame must be allocated

         * and cleared.

         */

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

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

        dirty = true;

    } else {

        size_t pad_lo, pad_hi;

        /*

         * The mixed case.

         *

         * The middle part is backed by the ELF image and

         * the lower and upper parts are anonymous memory.

         * (The segment can be and often is shorter than 1 page).

         */

        if (page < entry->p_vaddr)

            pad_lo = entry->p_vaddr - page;

        else

            pad_lo = 0;

        if (start_anon < page + PAGE_SIZE)

            pad_hi = page + PAGE_SIZE - start_anon;

        else

            pad_hi = 0;

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

        memcpy((void *) (PA2KA(frame) + pad_lo),

            (void *) (base + i * FRAME_SIZE + pad_lo),

            FRAME_SIZE - pad_lo - pad_hi);

        if (entry->p_flags & PF_X) {

            smc_coherence_block((void *) (PA2KA(frame) + pad_lo),

                FRAME_SIZE - pad_lo - pad_hi);

        }

        memsetb((void *) PA2KA(frame), pad_lo, 0);

        memsetb((void *) (PA2KA(frame) + FRAME_SIZE - pad_hi), pad_hi,

            0);

        dirty = true;

    }

    if (dirty && area->sh_info) {

        frame_reference_add(ADDR2PFN(frame));

        btree_insert(&area->sh_info->pagemap, page - area->base,

            (void *) frame, leaf);

    }

    if (area->sh_info)

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

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

    if (!used_space_insert(area, page, 1))

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

    return AS_PF_OK;

}

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

 *

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

 *

 * @param area      Pointer to the address space area.

 * @param page      Page that is mapped to frame. Must be aligned to

 *          PAGE_SIZE.

 * @param frame     Frame to be released.

 *

 */

void elf_frame_free(as_area_t *area, uintptr_t page, uintptr_t frame)

{

    elf_header_t *elf = area->backend_data.elf;

    elf_segment_header_t *entry = area->backend_data.segment;

    uintptr_t base, start_anon;

    index_t i;

    ASSERT((page >= ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE)) &&

        (page < entry->p_vaddr + entry->p_memsz));

    i = (page - ALIGN_DOWN(entry->p_vaddr, PAGE_SIZE)) >> PAGE_WIDTH;

    base = (uintptr_t) (((void *) elf) +

        ALIGN_DOWN(entry->p_offset, FRAME_SIZE));

    start_anon = entry->p_vaddr + entry->p_filesz;

    if (page >= entry->p_vaddr && page + PAGE_SIZE <= start_anon) {

        if (entry->p_flags & PF_W) {

            /*

             * Free the frame with the copy of writable segment

             * data.

             */

            frame_free(frame);

        }

    } else {

        /*

         * The frame is either anonymous memory or the mixed case (i.e.

         * lower part is backed by the ELF image and the upper is

         * anonymous). In any case, a frame needs to be freed.

         */

        frame_free(frame);

    }

}

/** Share ELF image backed address space area.

 *

 * If the area is writable, then all mapped pages are duplicated in the pagemap.

 * Otherwise only portions of the area that are not backed by the ELF image

 * are put into the pagemap.

 *

 * The address space and address space area must be locked prior to the call.

 *

 * @param area      Address space area.

 */

void elf_share(as_area_t *area)

{

    elf_segment_header_t *entry = area->backend_data.segment;

    link_t *cur;

    btree_node_t *leaf, *node;

    uintptr_t start_anon = entry->p_vaddr + entry->p_filesz;

    /*

     * Find the node in which to start linear search.

     */

    if (area->flags & AS_AREA_WRITE) {

        node = list_get_instance(area->used_space.leaf_head.next,

            btree_node_t, leaf_link);

    } else {

        (void) btree_search(&area->sh_info->pagemap, start_anon, &leaf);

        node = btree_leaf_node_left_neighbour(&area->sh_info->pagemap,

            leaf);

        if (!node)

            node = leaf;

    }

    /*

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

     */

    mutex_lock(&area->sh_info->lock);

    for (cur = &node->leaf_link; cur != &area->used_space.leaf_head;

        cur = cur->next) {

        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];

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

            unsigned int j;

            /*

             * Skip read-only areas of used space that are backed

             * by the ELF image.

             */

            if (!(area->flags & AS_AREA_WRITE))

                if (base >= entry->p_vaddr &&

                    base + count * PAGE_SIZE <= start_anon)

                    continue;

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

                pte_t *pte;

                /*

                 * Skip read-only pages that are backed by the

                 * ELF image.

                 */

                if (!(area->flags & AS_AREA_WRITE))

                    if (base >= entry->p_vaddr &&

                        base + (j + 1) * PAGE_SIZE <=

                        start_anon)

                        continue;

                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);

                pfn_t pfn = ADDR2PFN(PTE_GET_FRAME(pte));

                frame_reference_add(pfn);

            }

        }

    }

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

}

/** @}

 */