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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)

		);

	}

}