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/*

 * 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    page_ht.c

 * @brief   Virtual Address Translation (VAT) for global page hash table.

 */

#include <genarch/mm/page_ht.h>

#include <mm/page.h>

#include <arch/mm/page.h>

#include <mm/frame.h>

#include <mm/slab.h>

#include <mm/as.h>

#include <arch/mm/asid.h>

#include <arch/types.h>

#include <typedefs.h>

#include <arch/asm.h>

#include <synch/spinlock.h>

#include <arch.h>

#include <debug.h>

#include <memstr.h>

#include <adt/hash_table.h>

#include <align.h>

static index_t hash(__native key[]);

static bool compare(__native key[], count_t keys, link_t *item);

static void remove_callback(link_t *item);

static void ht_mapping_insert(as_t *as, __address page, __address frame, int flags);

static void ht_mapping_remove(as_t *as, __address page);

static pte_t *ht_mapping_find(as_t *as, __address page);

/**

 * This lock protects the page hash table. It must be acquired

 * after address space lock and after any address space area

 * locks.

 */

mutex_t page_ht_lock;

/**

 * Page hash table.

 * The page hash table may be accessed only when page_ht_lock is held.

 */

hash_table_t page_ht;

/** Hash table operations for page hash table. */

hash_table_operations_t ht_operations = {

    .hash = hash,

    .compare = compare,

    .remove_callback = remove_callback

};

/** Page mapping operations for page hash table architectures. */

page_mapping_operations_t ht_mapping_operations = {

    .mapping_insert = ht_mapping_insert,

    .mapping_remove = ht_mapping_remove,

    .mapping_find = ht_mapping_find

};

/** Compute page hash table index.

 *

 * @param key Array of two keys (i.e. page and address space).

 *

 * @return Index into page hash table.

 */

index_t hash(__native key[])

{

    as_t *as = (as_t *) key[KEY_AS];

    __address page = (__address) key[KEY_PAGE];

    index_t index;

    /*

     * Virtual page addresses have roughly the same probability

     * of occurring. Least significant bits of VPN compose the

     * hash index.

     */

    index = ((page >> PAGE_WIDTH) & (PAGE_HT_ENTRIES-1));

    /*

     * Address space structures are likely to be allocated from

     * similar addresses. Least significant bits compose the

     * hash index.

     */

    index |= ((__native) as) & (PAGE_HT_ENTRIES-1);

    return index;

}

/** Compare page hash table item with page and/or address space.

 *

 * @param key Array of one or two keys (i.e. page and/or address space).

 * @param keys Number of keys passed.

 * @param item Item to compare the keys with.

 *

 * @return true on match, false otherwise.

 */

bool compare(__native key[], count_t keys, link_t *item)

{

    pte_t *t;

    ASSERT(item);

    ASSERT((keys > 0) && (keys <= PAGE_HT_KEYS));

    /*

     * Convert item to PTE.

     */

    t = hash_table_get_instance(item, pte_t, link);

    if (keys == PAGE_HT_KEYS) {

        return (key[KEY_AS] == (__address) t->as) && (key[KEY_PAGE] == t->page);

    } else {

        return (key[KEY_AS] == (__address) t->as);

    }

}

/** Callback on page hash table item removal.

 *

 * @param item Page hash table item being removed.

 */

void remove_callback(link_t *item)

{

    pte_t *t;

    ASSERT(item);

    /*

     * Convert item to PTE.

     */

    t = hash_table_get_instance(item, pte_t, link);

    free(t);

}

/** Map page to frame using page hash table.

 *

 * Map virtual address page to physical address frame

 * using flags.

 *

 * The page table must be locked and interrupts must be disabled.

 *

 * @param as Address space to which page belongs.

 * @param page Virtual address of the page to be mapped.

 * @param frame Physical address of memory frame to which the mapping is done.

 * @param flags Flags to be used for mapping.

 */

void ht_mapping_insert(as_t *as, __address page, __address frame, int flags)

{

    pte_t *t;

    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };

    if (!hash_table_find(&page_ht, key)) {

        t = (pte_t *) malloc(sizeof(pte_t), FRAME_ATOMIC);

        ASSERT(t != NULL);

        t->g = (flags & PAGE_GLOBAL) != 0;

        t->x = (flags & PAGE_EXEC) != 0;

        t->w = (flags & PAGE_WRITE) != 0;

        t->k = !(flags & PAGE_USER);

        t->c = (flags & PAGE_CACHEABLE) != 0;

        t->p = !(flags & PAGE_NOT_PRESENT);

        t->as = as;

        t->page = page;

        t->frame = frame;

        hash_table_insert(&page_ht, key, &t->link);

    }

}

/** Remove mapping of page from page hash table.

 *

 * Remove any mapping of page within address space as.

 * TLB shootdown should follow in order to make effects of

 * this call visible.

 *

 * The page table must be locked and interrupts must be disabled.

 *

 * @param as Address space to wich page belongs.

 * @param page Virtual address of the page to be demapped.

 */

void ht_mapping_remove(as_t *as, __address page)

{

    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };

    /*

     * Note that removed PTE's will be freed

     * by remove_callback().

     */

    hash_table_remove(&page_ht, key, 2);

}

/** Find mapping for virtual page in page hash table.

 *

 * Find mapping for virtual page.

 *

 * The page table must be locked and interrupts must be disabled.

 *

 * @param as Address space to wich page belongs.

 * @param page Virtual page.

 *

 * @return NULL if there is no such mapping; requested mapping otherwise.

 */

pte_t *ht_mapping_find(as_t *as, __address page)

{

    link_t *hlp;

    pte_t *t = NULL;

    __native key[2] = { (__address) as, page = ALIGN_DOWN(page, PAGE_SIZE) };

    hlp = hash_table_find(&page_ht, key);

    if (hlp)

        t = hash_table_get_instance(hlp, pte_t, link);

    return t;

}