void os_free(uint32_t addr) {
//find the phy addres relative to the virtual address
uint32_t dir, dirFrame, pt, ptFrame, pte, pteFrame;
dir = (dccvmm_phy_read(procTable_ << 8 | currentPID_));
dirFrame = PTEFRAME(dir);
pt = dccvmm_phy_read(dirFrame << 8 | PTE1OFF(addr));
ptFrame = PTEFRAME(pt);
pte = dccvmm_phy_read(ptFrame << 8 | PTE2OFF(addr));
pteFrame = PTEFRAME(pte);
//update the page table
dccvmm_phy_write(ptFrame << 8 | PTE2OFF(addr), 0);
//update the free list:
dccvmm_phy_write(pteFrame << 8, freesStart_);
// make the freed frame the freeStart and make it point to the old freeStart
freesStart_ = pteFrame;
if (outOfMemory_)outOfMemory_ = FALSE;
int emptyFlag = TRUE;
int i = 0;
for (i = 0; i < NUMWORDS; i++) {
uint32_t pte = dccvmm_phy_read(ptFrame << 8 | i);
if ((pte & PTE_INMEM) == PTE_INMEM) {
//page Table has valid pages
emptyFlag = FALSE;
}
}
if (emptyFlag) {
ptFrame = PTEFRAME(ptFrame);
dumpPageTable(addr, dirFrame, &pt);
}
}
// responsible for the machine languare interpretation and execution
void interpreter()
{
printf("\n");
if (queueArray[currentPriority][0]->pid > 0) printf("User %d Running...\n", queueArray[currentPriority][0]->pid);
while (haltFlag == false && currentTick < TICKS_PER_USER)
{
Fetch();
Decode();
mmu(-1, -1);
Execute();
if (queueArray[currentPriority][0]->frameTick % MEMORY_LENGTH == 0)
{
queueArray[currentPriority][0]->pageTick++;
queueArray[currentPriority][0]->pCounter = userArray[queueArray[currentPriority][0]->pid].pageTable[queueArray[currentPriority][0]->pageTick] * MEMORY_LENGTH;
PC = queueArray[currentPriority][0]->pCounter;
}
}
if (haltFlag == true)
{
queueArray[currentPriority][0]->isComplete = true;
dumpPageTable();
mmu(-2, -2);
queueArray[currentPriority][0]->isRunning = false;
}
else
{
queueArray[currentPriority][0]->pCounter = PC;
queueArray[currentPriority][0]->processCC = CC;
CC = 0x0000;
int i = 0;
for (i; i < MAX_REGISTER; i++)
queueArray[currentPriority][0]->processRegisters[i] = Registers[i];
Registers[i] = 0x0000;
}
haltFlag = false; // reset halt flag for subsequent program runs
}
uint32_t getFreeFrame() {
uint32_t freeFrame;
if (outOfMemory_) {
while (TRUE) {
int count = 0;
uint32_t victimPID, dir, dirFrame, pt, ptFrame, pte, pteFrame;
victimPID = rand() % 256;
dir = dccvmm_phy_read(procTable_ << 8 | victimPID);
while (!(dir & PTE_INMEM) && count < 256) {
victimPID = (victimPID + 1) % 256;
dir = dccvmm_phy_read(procTable_ << 8 | victimPID);
count++;
}
if (count == 256)continue;
else count = 0;
dirFrame = PTEFRAME(dir);
uint32_t ptRow = rand() % 256;
pt = dccvmm_phy_read(dirFrame << 8 | ptRow);
while (!(pt & PTE_INMEM) && count < 256) {
ptRow = (ptRow + 1) % 256;
pt = dccvmm_phy_read(dirFrame << 8 | ptRow);
count++;
}
if (count == 256)continue;
else count = 0;
ptFrame = PTEFRAME(pt);
uint32_t row = rand() % 256;
pte = dccvmm_phy_read(ptFrame << 8 | row);
pteFrame = PTEFRAME(pte);
while (!(pte & PTE_INMEM) && count < 256) {
row = (row + 1) % 256;
pte = dccvmm_phy_read(ptFrame << 8 | row);
pteFrame = PTEFRAME(pte);
count++;
}
if (count == 256)continue;
else count = 0;
dumpPTE(row << 8, ptFrame);
int i = 0, empty = TRUE;
for (i = 0; i < NUMWORDS; i++) {
uint32_t entry = dccvmm_phy_read(ptFrame << 8 | i);
if ((entry & PTE_INMEM)) {
empty = FALSE;
}
}
if (empty) dumpPageTable(ptRow << 8, dirFrame, &pt);
freeFrame = pteFrame;
break;
}
} else {
freeFrame = freesStart_;
freesStart_ = dccvmm_phy_read(freeFrame << 8);
if (freesStart_ == 0) {
//this is the last free frame
//out of memory
outOfMemory_ = TRUE;
}
}
dccvmm_zero(freeFrame);
return PTEFRAME(freeFrame);
}
