/*
* 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 backend_anon.c
* @brief Backend for anonymous memory address space areas.
*
*/
#include <mm/as.h>
#include <mm/page.h>
#include <genarch/mm/page_pt.h>
#include <genarch/mm/page_ht.h>
#include <mm/frame.h>
#include <mm/slab.h>
#include <synch/mutex.h>
#include <adt/list.h>
#include <adt/btree.h>
#include <errno.h>
#include <arch/types.h>
#include <typedefs.h>
#include <align.h>
#include <arch.h>
static int anon_page_fault(as_area_t *area, __address addr, pf_access_t access);
static void anon_frame_free(as_area_t *area, __address page, __address frame);
static void anon_share(as_area_t *area);
/*
* Anonymous memory backend.
*/
mem_backend_t anon_backend = {
.page_fault = anon_page_fault,
.frame_free = anon_frame_free,
.share = anon_share
};
/** Service a page fault in the anonymous memory 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 anon_page_fault(as_area_t *area, __address addr, pf_access_t access)
{
__address frame;
if (!as_area_check_access(area, access))
return AS_PF_FAULT;
if (area->sh_info) {
btree_node_t *leaf;
/*
* The area is shared, chances are that the mapping can be found
* in the pagemap of the address space area share info structure.
* In the case that the pagemap does not contain the respective
* mapping, a new frame is allocated and the mapping is created.
*/
mutex_lock(&area->sh_info->lock);
frame = (__address) btree_search(&area->sh_info->pagemap,
ALIGN_DOWN(addr, PAGE_SIZE) - area->base, &leaf);
if (!frame) {
bool allocate = true;
int i;
/*
* Zero can be returned as a valid frame address.
* Just a small workaround.
*/
for (i = 0; i < leaf->keys; i++) {
if (leaf->key[i] == ALIGN_DOWN(addr, PAGE_SIZE)) {
allocate = false;
break;
}
}
if (allocate) {
frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
memsetb(PA2KA(frame), FRAME_SIZE, 0);
/*
* Insert the address of the newly allocated frame to the pagemap.
*/
btree_insert(&area->sh_info->pagemap, ALIGN_DOWN(addr, PAGE_SIZE) - area->base, (void *) frame, leaf);
}
}
mutex_unlock(&area->sh_info->lock);
} else {
/*
* In general, there can be several reasons that
* can have caused this fault.
*
* - non-existent mapping: the area is an anonymous
* area (e.g. heap or stack) and so far has not been
* allocated a frame for the faulting page
*
* - non-present mapping: another possibility,
* currently not implemented, would be frame
* reuse; when this becomes a possibility,
* do not forget to distinguish between
* the different causes
*/
frame = PFN2ADDR(frame_alloc(ONE_FRAME, 0));
memsetb(PA2KA(frame), FRAME_SIZE, 0);
}
/*
* Map 'page' to 'frame'.
* Note that TLB shootdown is not attempted as only new information is being
* inserted into page tables.
*/
page_mapping_insert(AS, addr, frame, as_area_get_flags(area));
if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
panic("Could not insert used space.\n");
return AS_PF_OK;
}
/** Free a frame that is backed by the anonymous memory backend.
*
* The address space area and page tables must be already locked.
*
* @param area Ignored.
* @param page Ignored.
* @param frame Frame to be released.
*/
void anon_frame_free(as_area_t *area, __address page, __address frame)
{
frame_free(ADDR2PFN(frame));
}
/** Share the anonymous address space area.
*
* Sharing of anonymous area is done by duplicating its entire mapping
* to the pagemap. Page faults will primarily search for frames there.
*
* The address space area and page tables must be already locked.
*
* @param area Address space area to be shared.
*/
void anon_share(as_area_t *area)
{
link_t *cur;
/*
* Copy used portions of the area to sh_info's page map.
*/
mutex_lock(&area->sh_info->lock);
for (cur = area->used_space.leaf_head.next; cur != &area->used_space.leaf_head; cur = cur->next) {
btree_node_t *node;
int i;
node = list_get_instance(cur, btree_node_t, leaf_link);
for (i = 0; i < node->keys; i++) {
__address base = node->key[i];
count_t count = (count_t) node->value[i];
int j;
for (j = 0; j < count; j++) {
pte_t *pte;
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);
}
}
}
mutex_unlock(&area->sh_info->lock);
}