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/*

 * Copyright (C) 2005 Martin Decky

 * 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.

 */

#include <arch/mm/page.h>

#include <genarch/mm/page_pt.h>

#include <arch/mm/frame.h>

#include <arch/asm.h>

#include <mm/frame.h>

#include <mm/page.h>

#include <mm/as.h>

#include <arch.h>

#include <arch/types.h>

#include <arch/exception.h>

#include <config.h>

#include <print.h>

#include <symtab.h>

static phte_t *phte;

/** Try to find PTE for faulting address

 *

 * Try to find PTE for faulting address.

 * The AS->lock must be held on entry to this function.

 *

 * @param badvaddr Faulting virtual address.

 * @param istate   Pointer to interrupted state.

 * @param pfrc     Pointer to variable where as_page_fault() return code will be stored.

 * @return         PTE on success, NULL otherwise.

 *

 */

static pte_t *find_mapping_and_check(__address badvaddr, istate_t *istate, int *pfcr)

{

    /*

     * Check if the mapping exists in page tables.

     */

    pte_t *pte = page_mapping_find(AS, badvaddr);

    if ((pte) && (pte->p)) {

        /*

         * Mapping found in page tables.

         * Immediately succeed.

         */

        return pte;

    } else {

        int rc;

        /*

         * Mapping not found in page tables.

         * Resort to higher-level page fault handler.

         */

        page_table_unlock(AS, true);

        switch (rc = as_page_fault(badvaddr, istate)) {

            case AS_PF_OK:

                /*

                 * The higher-level page fault handler succeeded,

                 * The mapping ought to be in place.

                 */

                page_table_lock(AS, true);

                pte = page_mapping_find(AS, badvaddr);

                ASSERT((pte) && (pte->p));

                return pte;

            case AS_PF_DEFER:

                page_table_lock(AS, true);

                *pfcr = rc;

                return NULL;

            case AS_PF_FAULT:

                page_table_lock(AS, true);

                printf("Page fault.\n");

                *pfcr = rc;

                return NULL;

            default:

                panic("unexpected rc (%d)\n", rc);

        }  

    }

}

static void pht_refill_fail(__address badvaddr, istate_t *istate)

{

    char *symbol = "";

    char *sym2 = "";

    char *s = get_symtab_entry(istate->pc);

    if (s)

        symbol = s;

    s = get_symtab_entry(istate->lr);

    if (s)

        sym2 = s;

    panic("%p: PHT Refill Exception at %p (%s<-%s)\n", badvaddr, istate->pc, symbol, sym2);

}

static void pht_insert(const __address vaddr, const pfn_t pfn)

{

    __u32 page = (vaddr >> 12) & 0xffff;

    __u32 api = (vaddr >> 22) & 0x3f;

    __u32 vsid;

    asm volatile (

        "mfsrin %0, %1\n"

        : "=r" (vsid)

        : "r" (vaddr)

    );

    /* Primary hash (xor) */

    __u32 hash = ((vsid ^ page) & 0x3ff) << 3;

    __u32 i;

    bool found = false;

    /* Find unused PTE in PTEG */

    for (i = 0; i < 8; i++) {

        if (!phte[hash + i].v) {

            found = true;

            break;

        }

    }

    if (!found) {

        /* Secondary hash (not) */

        hash = ~hash;

        /* Find unused PTE in PTEG */

        for (i = 0; i < 8; i++) {

            if (!phte[hash + i].v) {

                found = true;

                break;

            }

        }

        if (!found) {

            // TODO: A/C precedence groups

            i = page % 8;

        }

    }

    phte[hash + i].v = 1;

    phte[hash + i].vsid = vsid;

    phte[hash + i].h = 0;

    phte[hash + i].api = api;

    phte[hash + i].rpn = pfn;

    phte[hash + i].r = 0;

    phte[hash + i].c = 0;

    phte[hash + i].pp = 2; // FIXME

}

/** Process Instruction/Data Storage Interrupt

 *

 * @param data   True if Data Storage Interrupt.

 * @param istate Interrupted register context.

 *

 */

void pht_refill(bool data, istate_t *istate)

{

    asid_t asid;

    __address badvaddr;

    pte_t *pte;

    int pfcr;

    if (data) {

        asm volatile (

            "mfdar %0\n"

            : "=r" (badvaddr)

        );

    } else

        badvaddr = istate->pc;

    spinlock_lock(&AS->lock);

    asid = AS->asid;

    spinlock_unlock(&AS->lock);

    page_table_lock(AS, true);

    pte = find_mapping_and_check(badvaddr, istate, &pfcr);

    if (!pte) {

        switch (pfcr) {

            case AS_PF_FAULT:

                goto fail;

                break;

            case AS_PF_DEFER:

                /*

                 * The page fault came during copy_from_uspace()

                 * or copy_to_uspace().

                 */

                page_table_unlock(AS, true);

                return;

            default:

                panic("Unexpected pfrc (%d)\n", pfcr);

        }

    }

    pte->a = 1; /* Record access to PTE */

    pht_insert(badvaddr, pte->pfn);

    page_table_unlock(AS, true);

    return;

fail:

    page_table_unlock(AS, true);

    pht_refill_fail(badvaddr, istate);

}

void pht_init(void)

{

    memsetb((__address) phte, 1 << PHT_BITS, 0);

}

void page_arch_init(void)

{

    if (config.cpu_active == 1) {

        page_mapping_operations = &pt_mapping_operations;

        /*

         * PA2KA(identity) mapping for all frames until last_frame.

         */

        __address cur;

        int flags;

        for (cur = 0; cur < last_frame; cur += FRAME_SIZE) {

            flags = PAGE_CACHEABLE;

            if ((PA2KA(cur) >= config.base) && (PA2KA(cur) < config.base + config.kernel_size))

                flags |= PAGE_GLOBAL;

            page_mapping_insert(AS_KERNEL, PA2KA(cur), cur, flags);

        }

        /* Allocate page hash table */

        phte_t *physical_phte = (phte_t *) PFN2ADDR(frame_alloc(PHT_ORDER, FRAME_KA | FRAME_PANIC));

        phte = (phte_t *) PA2KA((__address) physical_phte);

        ASSERT((__address) physical_phte % (1 << PHT_BITS) == 0);

        pht_init();

        asm volatile (

            "mtsdr1 %0\n"

            :

            : "r" ((__address) physical_phte)

        );

    }

}