/**
* Initializes memory mirror.
*
* Memory mirror allocates all available ram to specific range address.
* If 1GB paging is supported, 1GB paging is used, otherwise only 4KB
* paging is used, which means much more physical ram is used.
*/
void initialize_memory_mirror() {
section_info_t* head = frame_pool;
frame_pool = NULL;
bool first_set = false;
if (is_1GB_paging_supported() != 0) {
for (puint_t start=0; start < maxram; start+=1<<30) {
puint_t vaddress = start + ADDRESS_OFFSET(RESERVED_KBLOCK_RAM_MAPPINGS);
v_address_t va;
memcpy(&va, &vaddress, 8);
puint_t* pml4 = (puint_t*)ALIGN(physical_to_virtual(get_active_page()));
if (!PRESENT(pml4[va.pml])) {
pdpt_t pdpt;
memset(&pdpt, 0, sizeof(pdpt_t));
pdpt.number = get_free_frame();
pdpt.flaggable.present = 1;
pdpt.flaggable.us = 0;
pdpt.flaggable.rw = 1;
pml4[va.pml] = pdpt.number;
memset((void*)physical_to_virtual(ALIGN(pdpt.number)), 0, 0x1000);
}
puint_t* pdpt = (puint_t*)ALIGN(physical_to_virtual(pml4[va.pml]));
page_directory1GB_t dir;
memset(&dir, 0, sizeof(page_directory1GB_t));
dir.number = start;
dir.flaggable.present = 1;
dir.flaggable.ps = 1;
dir.flaggable.rw = 1;
pdpt[va.directory_ptr] = dir.number;
if (!first_set) {
first_set = true;
frame_pool = head;
}
}
} else {
for (puint_t start=0; start < maxram; start+=0x1000) {
puint_t kend = kernel_tmp_heap_start - 0xFFFFFFFF80000000 + 0x40000;
if (kend+0x4000 >= tmp_heap && !first_set) {
first_set = true;
frame_pool = head;
}
puint_t vaddress = start + ADDRESS_OFFSET(RESERVED_KBLOCK_RAM_MAPPINGS);
puint_t* paddress = get_page(vaddress, get_active_page(), true);
page_t page;
memset(&page, 0, sizeof(page_t));
page.address = start;
page.flaggable.present = 1;
page.flaggable.rw = 1;
page.flaggable.us = 0;
*paddress = page.address;
}
}
}
int arp_register()
{
uint32_t output_size = 0;
ncp_header m_ncp ;
volatile frame * my_frame = get_free_frame();
create_arp_req(my_frame);
TransmitPacket(my_frame->f_data, my_frame->f_len);
release_frame(my_frame);
return 0;
}
int client_register()
{
uint32_t output_size = 0;
ncp_header m_ncp ;
volatile frame * my_frame = get_free_frame();
ncp_register(&m_ncp,NCP_HEADER_SIZE);
my_frame->f_len = create_packiet(my_frame->f_data,ETHER_MAX_LEN,&m_ncp,NCP_HEADER_SIZE);
TransmitPacket(my_frame->f_data, my_frame->f_len);
release_frame(my_frame);
return 0;
}
/* get the output surface */
static QSVFrame *query_frame(QSVVPPContext *s, AVFilterLink *outlink)
{
AVFilterContext *ctx = outlink->src;
QSVFrame *out_frame;
int ret;
clear_unused_frames(s->out_frame_list);
out_frame = get_free_frame(&s->out_frame_list);
if (!out_frame)
return NULL;
/* For video memory, get a hw frame;
* For system memory, get a sw frame and map it into a mfx_surface. */
if (!IS_SYSTEM_MEMORY(s->out_mem_mode)) {
out_frame->frame = av_frame_alloc();
if (!out_frame->frame)
return NULL;
ret = av_hwframe_get_buffer(outlink->hw_frames_ctx, out_frame->frame, 0);
if (ret < 0) {
av_log(ctx, AV_LOG_ERROR, "Can't allocate a surface.\n");
return NULL;
}
out_frame->surface = (mfxFrameSurface1 *)out_frame->frame->data[3];
} else {
/* Get a frame with aligned dimensions.
* Libmfx need system memory being 128x64 aligned */
out_frame->frame = ff_get_video_buffer(outlink,
FFALIGN(outlink->w, 128),
FFALIGN(outlink->h, 64));
if (!out_frame->frame)
return NULL;
out_frame->frame->width = outlink->w;
out_frame->frame->height = outlink->h;
ret = map_frame_to_surface(out_frame->frame,
&out_frame->surface_internal);
if (ret < 0)
return NULL;
out_frame->surface = &out_frame->surface_internal;
}
out_frame->surface->Info = s->vpp_param.vpp.Out;
return out_frame;
}
int arp_response(frame * arp)
{
frame *output;
uint32_t output_size = 0;
frame *m_frame = get_free_frame();
create_arp_res(arp,output);
TransmitPacket(output->f_data, output->f_len);
release_frame(output);
return 0;
}
void interrupt_memory(ExceptionStackFrame *frame){
dprintf("in interrupt_memory", 0);
int f;
int i;
struct pte *page_table;
unsigned int addr = ((long)frame->addr);
int addr_page = get_page_index(addr);
page_table = pcb_current->page_table_p;
if(addr_page > pcb_current->brk_index && addr_page<pcb_current->stack_limit_index){
if(addr_page - pcb_current->brk_index <= 1){
printf("Stack overflow, address 0x%061x \n", addr);
Exit(ERROR);
}
if(pcb_current->stack_limit_index - addr_page > len_free_frames()){
printf("Not enough physical memory. address 0x%061x \n", addr);
Exit(ERROR);
}
int k = 0;
for(i = 0; i<pcb_current->stack_limit_index - addr_page; i++){
f = get_free_frame();
(page_table + pcb_current->stack_limit_index - i-1)->valid = PTE_VALID;
(page_table + pcb_current->stack_limit_index - i-1)->pfn = f;
(page_table + pcb_current->stack_limit_index - i-1)->uprot = (PROT_READ | PROT_WRITE);
(page_table + pcb_current->stack_limit_index - i-1)->kprot = (PROT_READ | PROT_WRITE);
//Not sure about the actual index
WriteRegister(REG_TLB_FLUSH, TLB_FLUSH_0);
k++;
}
pcb_current->stack_limit_index = pcb_current->stack_limit_index - k - 1;
}
else{
printf("Process %d: NOOBS ACCESSING INVALID MEMORY AT 0x%061x WITH CODE %d\n", pcb_current->pid, addr, frame->code);
Exit(ERROR);
}
}
static int submit_frame(QSVEncContext *q, const AVFrame *frame,
mfxFrameSurface1 **surface)
{
QSVFrame *qf;
int ret;
ret = get_free_frame(q, &qf);
if (ret < 0)
return ret;
if (frame->format == AV_PIX_FMT_QSV) {
ret = av_frame_ref(qf->frame, frame);
if (ret < 0)
return ret;
qf->surface = (mfxFrameSurface1*)qf->frame->data[3];
*surface = qf->surface;
return 0;
}
/* make a copy if the input is not padded as libmfx requires */
if ( frame->height & (q->height_align - 1) ||
frame->linesize[0] & (q->width_align - 1)) {
qf->frame->height = FFALIGN(frame->height, q->height_align);
qf->frame->width = FFALIGN(frame->width, q->width_align);
ret = ff_get_buffer(q->avctx, qf->frame, AV_GET_BUFFER_FLAG_REF);
if (ret < 0)
return ret;
qf->frame->height = frame->height;
qf->frame->width = frame->width;
ret = av_frame_copy(qf->frame, frame);
if (ret < 0) {
av_frame_unref(qf->frame);
return ret;
}
} else {
ret = av_frame_ref(qf->frame, frame);
if (ret < 0)
return ret;
}
qf->surface_internal.Info = q->param.mfx.FrameInfo;
qf->surface_internal.Info.PicStruct =
!frame->interlaced_frame ? MFX_PICSTRUCT_PROGRESSIVE :
frame->top_field_first ? MFX_PICSTRUCT_FIELD_TFF :
MFX_PICSTRUCT_FIELD_BFF;
if (frame->repeat_pict == 1)
qf->surface_internal.Info.PicStruct |= MFX_PICSTRUCT_FIELD_REPEATED;
else if (frame->repeat_pict == 2)
qf->surface_internal.Info.PicStruct |= MFX_PICSTRUCT_FRAME_DOUBLING;
else if (frame->repeat_pict == 4)
qf->surface_internal.Info.PicStruct |= MFX_PICSTRUCT_FRAME_TRIPLING;
qf->surface_internal.Data.PitchLow = qf->frame->linesize[0];
qf->surface_internal.Data.Y = qf->frame->data[0];
qf->surface_internal.Data.UV = qf->frame->data[1];
qf->surface_internal.Data.TimeStamp = av_rescale_q(frame->pts, q->avctx->time_base, (AVRational){1, 90000});
qf->surface = &qf->surface_internal;
*surface = qf->surface;
return 0;
}
/* get the input surface */
static QSVFrame *submit_frame(QSVVPPContext *s, AVFilterLink *inlink, AVFrame *picref)
{
QSVFrame *qsv_frame;
AVFilterContext *ctx = inlink->dst;
clear_unused_frames(s->in_frame_list);
qsv_frame = get_free_frame(&s->in_frame_list);
if (!qsv_frame)
return NULL;
/* Turn AVFrame into mfxFrameSurface1.
* For video/opaque memory mode, pix_fmt is AV_PIX_FMT_QSV, and
* mfxFrameSurface1 is stored in AVFrame->data[3];
* for system memory mode, raw video data is stored in
* AVFrame, we should map it into mfxFrameSurface1.
*/
if (!IS_SYSTEM_MEMORY(s->in_mem_mode)) {
if (picref->format != AV_PIX_FMT_QSV) {
av_log(ctx, AV_LOG_ERROR, "QSVVPP gets a wrong frame.\n");
return NULL;
}
qsv_frame->frame = av_frame_clone(picref);
qsv_frame->surface = (mfxFrameSurface1 *)qsv_frame->frame->data[3];
} else {
/* make a copy if the input is not padded as libmfx requires */
if (picref->height & 31 || picref->linesize[0] & 31) {
qsv_frame->frame = ff_get_video_buffer(inlink,
FFALIGN(inlink->w, 32),
FFALIGN(inlink->h, 32));
if (!qsv_frame->frame)
return NULL;
qsv_frame->frame->width = picref->width;
qsv_frame->frame->height = picref->height;
if (av_frame_copy(qsv_frame->frame, picref) < 0) {
av_frame_free(&qsv_frame->frame);
return NULL;
}
av_frame_copy_props(qsv_frame->frame, picref);
av_frame_free(&picref);
} else
qsv_frame->frame = av_frame_clone(picref);
if (map_frame_to_surface(qsv_frame->frame,
&qsv_frame->surface_internal) < 0) {
av_log(ctx, AV_LOG_ERROR, "Unsupported frame.\n");
return NULL;
}
qsv_frame->surface = &qsv_frame->surface_internal;
}
qsv_frame->surface->Info = s->frame_infos[FF_INLINK_IDX(inlink)];
qsv_frame->surface->Data.TimeStamp = av_rescale_q(qsv_frame->frame->pts,
inlink->time_base, default_tb);
qsv_frame->surface->Info.PicStruct =
!qsv_frame->frame->interlaced_frame ? MFX_PICSTRUCT_PROGRESSIVE :
(qsv_frame->frame->top_field_first ? MFX_PICSTRUCT_FIELD_TFF :
MFX_PICSTRUCT_FIELD_BFF);
if (qsv_frame->frame->repeat_pict == 1)
qsv_frame->surface->Info.PicStruct |= MFX_PICSTRUCT_FIELD_REPEATED;
else if (qsv_frame->frame->repeat_pict == 2)
qsv_frame->surface->Info.PicStruct |= MFX_PICSTRUCT_FRAME_DOUBLING;
else if (qsv_frame->frame->repeat_pict == 4)
qsv_frame->surface->Info.PicStruct |= MFX_PICSTRUCT_FRAME_TRIPLING;
return qsv_frame;
}
/*******************************************************************************
* Page fault handler. When the CPU encounters an invalid address mapping in a
* process' page table, it invokes the CPU via this handler. The OS then
* allocates a physical frame for the requested page (either by using a free
* frame or evicting one), changes the process' page table to reflect the
* mapping and then restarts the interrupted process.
*
* @param vpn The virtual page number requested from the current process.
* @param write If the CPU is writing to the page, this is 1. Otherwise, it's 0.
* @return The physical frame the OS has mapped to the virtual page.
*/
pfn_t pagefault_handler(vpn_t request_vpn, int write) {
pfn_t victim_pfn;
vpn_t victim_vpn;
pcb_t *victim_pcb;
/* Sanity Check */
assert(current_pagetable != NULL);
/* Find a free frame */
victim_pfn = get_free_frame();
assert(victim_pfn < CPU_NUM_FRAMES); /* make sure the victim_pfn is valid */
/* Use the reverse lookup table to find the victim. */
victim_vpn = rlt[victim_pfn].vpn;
victim_pcb = rlt[victim_pfn].pcb;
/*
* FIX ME : Problem 4
* If victim page is occupied - if it is not the pcb will be NULL:
*
* 1) If it's dirty, save it to disk with page_to_disk()
* 2) Invalidate the page's entry in the victim's page table.
* 3) Clear the victim page's TLB entry using the function tlb_clearone().
*/
pte_t *victim_entry;
if (victim_pcb != NULL) {
victim_entry = victim_pcb->pagetable + victim_vpn;
if (victim_entry->dirty == 1) {
page_to_disk(victim_pfn, victim_vpn, victim_pcb->pid);
victim_entry->dirty = 0;
}
victim_entry->valid = 0;
//victim_entry->used = 0;
tlb_clearone(victim_vpn);
}
printf("PAGE FAULT (VPN %u), evicting (PFN %u VPN %u)\n", request_vpn,
victim_pfn, victim_vpn);
/* FIX ME */
/* Update the reverse lookup table to replace the victim entry info with this
* process' info instead (pcb and vpn)
* Update the current process' page table (pfn and valid)
*/
rlt_t *rlt_entry = rlt + victim_pfn;
rlt_entry->vpn = request_vpn;
rlt_entry->pcb = current;
pte_t *current_entry = current_pagetable + request_vpn;
current_entry->valid = 1;
current_entry->pfn = victim_pfn;
/*
* Retreive the page from disk. Note that is really a lie: we save pages in
* memory (since doing file I/O for this simulation would be annoying and
* wouldn't add that much to the learning). Also, if the page technically
* does't exist yet (i.e., the page has never been accessed yet, we return a
* blank page. Real systems would check for invalid pages and possibly read
* stuff like code pages from disk. For purposes of this simulation, we won't
* worry about that. =)
*/
page_from_disk(victim_pfn, request_vpn, current->pid);
return victim_pfn;
}
/*------------------------------------------------------------------------
* sysinit -- initialize all Xinu data structeres and devices
*------------------------------------------------------------------------
*/
LOCAL
sysinit()
{
static long currsp;
int i,j, avail;
struct pentry *pptr;
struct sentry *sptr;
struct mblock *mptr;
SYSCALL pfintr();
/*********************/
set_evec(14, pfintr);
pptr = &proctab[NULLPROC]; /* initialize null process entry */
/*********************/
numproc = 0; /* initialize system variables */
nextproc = NPROC-1;
nextsem = NSEM-1;
nextqueue = NPROC; /* q[0..NPROC-1] are processes */
/* initialize free memory list */
/* PC version has to pre-allocate 640K-1024K "hole" */
if (maxaddr+1 > HOLESTART) {
memlist.mnext = mptr = (struct mblock *) roundmb(&end);
mptr->mnext = (struct mblock *)HOLEEND;
mptr->mlen = (int) truncew(((unsigned) HOLESTART -
(unsigned)&end));
mptr->mlen -= 4;
mptr = (struct mblock *) HOLEEND;
mptr->mnext = 0;
mptr->mlen = (int) truncew((unsigned)maxaddr - HOLEEND -
NULLSTK);
/*
mptr->mlen = (int) truncew((unsigned)maxaddr - (4096 - 1024 ) * 4096 - HOLEEND - NULLSTK);
*/
} else {
/* initialize free memory list */
memlist.mnext = mptr = (struct mblock *) roundmb(&end);
mptr->mnext = 0;
mptr->mlen = (int) truncew((unsigned)maxaddr - (int)&end -
NULLSTK);
}
for (i=0 ; i<NPROC ; i++) /* initialize process table */
proctab[i].pstate = PRFREE;
#ifdef MEMMARK
_mkinit(); /* initialize memory marking */
#endif
#ifdef RTCLOCK
clkinit(); /* initialize r.t.clock */
#endif
mon_init(); /* init monitor */
#ifdef NDEVS
for (i=0 ; i<NDEVS ; i++ ) {
init_dev(i);
}
#endif
pptr = &proctab[NULLPROC]; /* initialize null process entry */
pptr->pstate = PRCURR;
for (j=0; j<7; j++)
pptr->pname[j] = "prnull"[j];
pptr->plimit = (WORD)(maxaddr + 1) - NULLSTK;
pptr->pbase = (WORD) maxaddr - 3;
/*
pptr->plimit = (WORD)(maxaddr + 1) - NULLSTK - (4096 - 1024 )*4096;
pptr->pbase = (WORD) maxaddr - 3 - (4096-1024)*4096;
*/
pptr->pesp = pptr->pbase-4; /* for stkchk; rewritten before used */
*( (int *)pptr->pbase ) = MAGIC;
pptr->paddr = (WORD) nulluser;
pptr->pargs = 0;
pptr->pprio = 0;
currpid = NULLPROC;
for (i=0 ; i<NSEM ; i++) { /* initialize semaphores */
(sptr = &semaph[i])->sstate = SFREE;
sptr->sqtail = 1 + (sptr->sqhead = newqueue());
}
rdytail = 1 + (rdyhead=newqueue());/* initialize ready list */
init_bsm();
init_frm();
kprintf("initialize page tables for null process\n");
init_glb_pgs(glb_pg_tbl_frm_mapping);
// init pg dir for proc 0
frame_t *pg_dir = get_free_frame();
init_pg_dir(pg_dir, NULLPROC);
pptr->pdbr = pg_dir->frm_num;
pptr->pd = pg_dir;
return(OK);
}
/**
* Reciving singlas from ethernet controller -
* TX - transmited packet
* RX - recived packet
* LinkChange - Connected/Diconncted Ethernet Cable
*
*/
void ethernet_interrupts_simple()
{
frame *curr_frame = 0;
int filtered;
uint8_t interruption =ior(ISR); //which interruption
packet_num++;
iow(IMR, 0);
// iow(IMR, PAR_set);
// printf("ISR 0x%2X \n",interruption);
if( interruption & 0x01 ) //RX
{
iow(ISR,0x01);
curr_frame = get_free_frame();
if(curr_frame == 0)
{
return; //ERROR no more free frames
}
aaa=ReceivePacket(curr_frame->f_data,&curr_frame->f_len);
if(aaa == 0)
{
filtered = filter_packiets(curr_frame->f_data,curr_frame->f_len);
if (filtered == 0)
{
printf(" RX:UDP \n");
add_rx_frame(curr_frame);
}
else if (filtered == 10) //arp
{
printf(" RX:ARP \n");
add_rx_frame(curr_frame);
}
else
{
release_frame(curr_frame);
}
curr_frame = 0;
}
else
{
printf("%s Recived Bad Frame \n",__FUNCTION__);
release_frame(curr_frame);
curr_frame = 0;
}
/* ethernet_header *tmp = (ethernet_header *) RXT;
ether_addr adres = { 0x01, 0x60, 0x6E, 0x11, 0x01, 0x1F };
tmp->eth_src_addr = adres;
TransmitPacket(RXT,rx_len);*/
}
if(interruption & 0x02) //TX
{
iow(ISR,0x02);
tx_control = 0;
}
if(interruption & 0x20) //LinkChange
{
iow(ISR,0x20);
/* iow(0x00,0x01); // software reset
usleep(10);
enable interrupts to activate DM9000 ~on
iow(IMR, INTR_set2); IMR REG. FFH PAR=1 only, or + PTM=1& PRM=1 enable RxTx interrupts
iow(0xFF, 0x80);
enable RX (Broadcast/ ALL_MULTICAST) ~go
iow(RCR , RCR_set | RX_ENABLE | PASS_MULTICAST); RCR REG. 05 RXEN Bit [0] = 1 to enable the RX machine/ filter */
//printf(" LinkCHange \n");
if(link_control == 0)
link_control = 1;
else
link_control = 0;
}
iow(IMR, INTR_set2);
}
/**
* Returns page allocated for that virtual address.
*
* If allocate_new is specified to true, it will allocate substructures,
* if not present.Otherwise returns NULL if page structures are not present
* on the way to the virtual address. Returned pointer points to page in page
* table.
*/
static puint_t* __get_page(uintptr_t vaddress, uintptr_t cr3, bool allocate_new, bool user) {
v_address_t va;
memcpy(&va, &vaddress, 8);
puint_t* pml4 = (puint_t*)ALIGN(physical_to_virtual(cr3));
if (!PRESENT(pml4[va.pml])) {
if (!allocate_new) {
return 0;
}
pdpt_t pdpt;
memset(&pdpt, 0, sizeof(pdpt_t));
pdpt.number = get_free_frame();
if (pdpt.number == 0)
return 0;
pdpt.flaggable.present = 1;
pdpt.flaggable.us = user;
pdpt.flaggable.rw = 1;
pml4[va.pml] = pdpt.number;
memset((void*)physical_to_virtual(ALIGN(pdpt.number)), 0, 0x1000);
}
puint_t* pdpt = (puint_t*)ALIGN(physical_to_virtual(pml4[va.pml]));
if (!PRESENT(pdpt[va.directory_ptr])) {
if (!allocate_new)
return 0;
page_directory_t dir;
memset(&dir, 0, sizeof(page_directory_t));
dir.number = get_free_frame();
if (dir.number == 0) {
return 0;
}
dir.flaggable.present = 1;
dir.flaggable.us = user;
dir.flaggable.rw = 1;
pdpt[va.directory_ptr] = dir.number;
memset((void*)physical_to_virtual(ALIGN(dir.number)), 0, 0x1000);
}
puint_t* pdir = (puint_t*)ALIGN(physical_to_virtual(pdpt[va.directory_ptr]));
if (!PRESENT(pdir[va.directory])) {
if (!allocate_new)
return 0;
page_table_t pt;
memset(&pt, 0, sizeof(page_table_t));
pt.number = get_free_frame();
if (pt.number == 0) {
return 0;
}
pt.flaggable.present = 1;
pt.flaggable.us = user;
pt.flaggable.rw = 1;
pdir[va.directory] = pt.number;
memset((void*)physical_to_virtual(ALIGN(pt.number)), 0, 0x1000);
}
puint_t* pt = (puint_t*)ALIGN(physical_to_virtual(pdir[va.directory]));
return &pt[va.table];
}
/*******************************************************************************
* Page fault handler. When the CPU encounters an invalid address mapping in a
* process' page table, it invokes the CPU via this handler. The OS then
* allocates a physical frame for the requested page (either by using a free
* frame or evicting one), changes the process' page table to reflect the
* mapping and then restarts the interrupted process.
*
* @param vpn The virtual page number requested.
* @param write If the CPU is writing to the page, this is 1. Otherwise, it's 0.
* @return The physical frame the OS has mapped to the virtual page.
*/
pfn_t pagefault_handler(vpn_t request_vpn, int write) {
pfn_t victim_pfn;
vpn_t victim_vpn;
pcb_t *victim_pcb;
/* Sanity Check */
assert(current_pagetable != NULL);
/* Find a free frame */
victim_pfn = get_free_frame();
assert(victim_pfn < CPU_NUM_FRAMES); /* make sure the victim_pfn is valid */
/* Use the reverse lookup table to find the victim. */
victim_vpn = rlt[victim_pfn].vpn;
victim_pcb = rlt[victim_pfn].pcb;
/*
* FIX ME : Problem 4
* If victim page is occupied:
*
* 1) If it's dirty, save it to disk with page_to_disk()
* 2) Invalidate the page's entry in the victim's page table.
* 3) Clear the victim page's TLB entry (hint: tlb_clearone()).
*/
pte_t* victim;
pte_t current_v;
if (victim_pcb != NULL) {
victim = victim_pcb -> pagetable;
current_v = victim[victim_vpn];
if (current_v.dirty && current_v.valid) {
page_to_disk(victim_pfn, victim_vpn, victim_pcb ->pid);
}
victim[victim_vpn].valid = 0;
tlb_clearone(victim_vpn);
}
printf("****PAGE FAULT has occurred at VPN %u. Evicting (PFN %u VPN %u) as victim.\n", request_vpn,
victim_pfn, victim_vpn);
/* Update the reverse lookup table so that
it knows about the requesting process */
/* FIX ME */
rlt[victim_pfn].pcb = current;
rlt[victim_pfn].vpn = request_vpn;
/* Update the requesting process' page table */
/* FIX ME */
current_pagetable[request_vpn].pfn = victim_pfn;
current_pagetable[request_vpn].valid = 1;
current_pagetable[request_vpn].dirty = write;
current_pagetable[request_vpn].used = 1;
/*
* Retreive the page from disk. Note that is really a lie: we save pages in
* memory (since doing file I/O for this simulation would be annoying and
* wouldn't add that much to the learning). Also, if the page technically
* does't exist yet (i.e., the page has never been accessed yet, we return a
* blank page. Real systems would check for invalid pages and possibly read
* stuff like code pages from disk. For purposes of this simulation, we won't
* worry about that. =)
*/
page_from_disk(victim_pfn, request_vpn, current->pid);
return victim_pfn;
}