/**
* Initializes page tables for this process so that the executable can be demand-paged.
*
* @return <tt>true</tt> if successful.
*/
protected boolean loadSections() {
UserKernel.memoryLock.acquire();
pageTable = new TranslationEntry[numPages];
for (int vpn = 0; vpn < numPages; vpn++) {
pageTable[vpn] = new TranslationEntry(vpn, -1, false, false, false, false);
}
UserKernel.memoryLock.release();
// load sections
for (int s = 0; s < coff.getNumSections(); s++) {
CoffSection section = coff.getSection(s);
Lib.debug(
dbgProcess,
"\tinitializing " + section.getName() + " section (" + section.getLength() + " pages)");
for (int i = 0; i < section.getLength(); i++) {
int vpn = section.getFirstVPN() + i;
pageTable[vpn].readOnly = section.isReadOnly();
// section.loadPage(i, pinVirtualPage(vpn, false));
}
}
return true;
}
/**
* Allocates memory for this process, and loads the COFF sections into memory. If this returns
* successfully, the process will definitely be run (this is the last step in process
* initialization that can fail).
*
* @return <tt>true</tt> if the sections were successfully loaded.
*/
protected boolean loadSections() {
if (numPages > Machine.processor().getNumPhysPages()) {
coff.close();
Lib.debug(dbgProcess, "\tinsufficient physical memory");
return false;
}
pageTable = new TranslationEntry[numPages];
for (int i = 0; i < numPages; i++) {
int physPage = UserKernel.allocatePage();
if (physPage < 0) {
Lib.debug(dbgProcess, "\tunable to allocate pages; tried " + numPages + ", did " + i);
for (int j = 0; j < i; j++) {
if (pageTable[j].valid) {
UserKernel.deallocatePage(pageTable[j].ppn);
pageTable[j].valid = false;
}
}
coff.close();
return false;
}
pageTable[i] = new TranslationEntry(i, physPage, true, false, false, false);
}
// load sections
for (int s = 0; s < coff.getNumSections(); s++) {
CoffSection section = coff.getSection(s);
Lib.debug(
dbgProcess,
"\tinitializing " + section.getName() + " section (" + section.getLength() + " pages)");
for (int i = 0; i < section.getLength(); i++) {
int vpn = section.getFirstVPN() + i;
// for now, just assume virtual addresses=physical addresses
int ppn = pageTable[vpn].ppn;
section.loadPage(i, ppn);
if (section.isReadOnly()) {
pageTable[vpn].readOnly = true;
}
}
}
coff.close();
return true;
}
/**
* Load the executable with the specified name into this process, and prepare to pass it the
* specified arguments. Opens the executable, reads its header information, and copies sections
* and arguments into this process's virtual memory.
*
* @param name the name of the file containing the executable.
* @param args the arguments to pass to the executable.
* @return <tt>true</tt> if the executable was successfully loaded.
*/
private boolean load(String name, String[] args) {
Lib.debug(dbgProcess, "UserProcess.load(\"" + name + "\")");
OpenFile executable = ThreadedKernel.fileSystem.open(name, false);
if (executable == null) {
Lib.debug(dbgProcess, "\topen failed");
return false;
}
try {
coff = new Coff(executable);
} catch (EOFException e) {
executable.close();
Lib.debug(dbgProcess, "\tcoff load failed");
return false;
}
// make sure the sections are contiguous and start at page 0
numPages = 0;
for (int s = 0; s < coff.getNumSections(); s++) {
CoffSection section = coff.getSection(s);
if (section.getFirstVPN() != numPages) {
coff.close();
Lib.debug(dbgProcess, "\tfragmented executable");
return false;
}
numPages += section.getLength();
}
// make sure the argv array will fit in one page
byte[][] argv = new byte[args.length][];
int argsSize = 0;
for (int i = 0; i < args.length; i++) {
argv[i] = args[i].getBytes();
// 4 bytes for argv[] pointer; then string plus one for null byte
argsSize += 4 + argv[i].length + 1;
}
if (argsSize > pageSize) {
coff.close();
Lib.debug(dbgProcess, "\targuments too long");
return false;
}
// program counter initially points at the program entry point
initialPC = coff.getEntryPoint();
// next comes the stack; stack pointer initially points to top of it
numPages += stackPages;
initialSP = numPages * pageSize;
// and finally reserve 1 page for arguments
numPages++;
if (!loadSections()) return false;
// store arguments in last page
int entryOffset = (numPages - 1) * pageSize;
int stringOffset = entryOffset + args.length * 4;
this.argc = args.length;
this.argv = entryOffset;
for (int i = 0; i < argv.length; i++) {
byte[] stringOffsetBytes = Lib.bytesFromInt(stringOffset);
Lib.assertTrue(writeVirtualMemory(entryOffset, stringOffsetBytes) == 4);
entryOffset += 4;
Lib.assertTrue(writeVirtualMemory(stringOffset, argv[i]) == argv[i].length);
stringOffset += argv[i].length;
Lib.assertTrue(writeVirtualMemory(stringOffset, new byte[] {0}) == 1);
stringOffset += 1;
}
return true;
}
private void allocatePage(int vpn) {
// System.out.println("TLBMiss: VPN:" + vpn + " of Process " + processID);
TranslationEntry t = pageTable[vpn];
if (!t.valid) {
// System.out.println("Allocating VPN: " + t.vpn);
lock.acquire();
if (UserKernel.freePages.size() > 0) {
int ppn = ((Integer) UserKernel.freePages.removeFirst()).intValue();
t.valid = true;
if (!t.dirty) {
t.ppn = ppn;
IPT[ppn] = new IPTEntry();
IPT[ppn].process = this;
IPT[ppn].tE = t;
boolean isCoffSection = false;
for (int s = 0; s < coff.getNumSections(); s++) {
if (isCoffSection) {
break;
}
CoffSection section = coff.getSection(s);
if (section.getFirstVPN() > t.vpn) {
continue;
}
for (int i = 0; i < section.getLength(); i++) {
int svpn = section.getFirstVPN() + i;
if (svpn == t.vpn) {
section.loadPage(i, pinVirtualPage(t.vpn, false));
// System.out.println("VPN \"" + t.vpn + "\" is a COFF section");
// System.out.println("COFF section loaded into VPN \"" + t.vpn + "\" PPN \"" +
// t.ppn + "\"");
isCoffSection = true;
break;
}
}
}
if (!isCoffSection) {
// System.out.println("VPN \"" + t.vpn + "\" is NOT a COFF section");
// System.out.println("PPN \"" + t.ppn + "\" Zero'd Out");
byte[] data = new byte[Processor.pageSize];
// writeVirtualMemory(t.vpn, data, 0, Processor.pageSize);
byte[] memory = Machine.processor().getMemory();
System.arraycopy(data, 0, memory, t.ppn * Processor.pageSize, Processor.pageSize);
}
} else // Dirty
{
// System.out.println("VPN \"" + t.vpn + "\" has been swapped out, swaping into
// PPN \"" + ppn + "\"");
int spn = t.ppn;
byte[] data = new byte[pageSize];
byte[] memory = Machine.processor().getMemory();
OpenFile swap = ThreadedKernel.fileSystem.open(".Nachos.swp", false);
swap.read(spn * pageSize, memory, ppn * pageSize, pageSize);
swap.close();
t.ppn = ppn;
// System.out.println(spn);
freeSwapPages.set(spn, true);
IPT[ppn] = new IPTEntry();
IPT[ppn].process = this;
IPT[ppn].tE = t;
// System.out.println("SPN \"" + spn + "\" has been swapped in.");
}
} else {
syncTLB();
// Clock Algorithm
unpinnedPageLock.acquire();
int numPinnedPages = 0;
while (IPT[victim] == null || IPT[victim].tE.used || IPT[victim].pinCount) {
if (IPT[victim] != null) {
IPT[victim].tE.used = false;
// System.out.println("PPN " + victim + " is used.");
}
if (IPT[victim].pinCount) {
numPinnedPages++;
// System.out.println("PPN " + victim + " is pinned.");
}
if (numPinnedPages == IPT.length) unpinnedPage.sleep();
// System.out.println("This Process is " + this.processID + " and the IPT's
// process is " + IPT[victim].processID);
victim = (victim + 1) % Machine.processor().getNumPhysPages();
}
// System.out.println("PPN " + victim + " will be evicted.");
unpinnedPageLock.release();
int evict = IPT[victim].tE.vpn;
VMProcess evictedOwner = IPT[victim].process;
int evictedPPN = victim;
victim = (victim + 1) % Machine.processor().getNumPhysPages();
// System.out.println("Not enough pysical memory, evicting VPN \"" + evict + "\" of process
// " + evictedOwner.processID);
// Swap Files
if (evictedOwner.isDirty(evict)) {
// System.out.println("VPN \"" + evict + "\" is dirty, swapping out.");
OpenFile swap = ThreadedKernel.fileSystem.open(".Nachos.swp", false);
int spn = 0;
for (spn = 0; spn < freeSwapPages.size(); spn++) {
if (freeSwapPages.get(spn)) {
break;
}
}
if (spn == freeSwapPages.size()) {
freeSwapPages.add(false);
} else {
freeSwapPages.set(spn, false);
}
UserKernel.freePages.add(evictedPPN);
byte[] memory = Machine.processor().getMemory();
swap.write(spn * pageSize, memory, evictedPPN * pageSize, pageSize);
swap.close();
if (evictedOwner.processID != this.processID) {
evictedOwner.evict(evict, spn);
} else {
pageTable[evict].ppn = spn;
pageTable[evict].valid = false;
}
for (int i = 0; i < Machine.processor().getTLBSize(); i++) {
TranslationEntry tE = Machine.processor().readTLBEntry(i);
if (tE.vpn == evict && tE.ppn == evictedPPN) {
// System.out.println("TLBEntry " + i + " invalid");
tE.valid = false;
Machine.processor().writeTLBEntry(i, tE);
}
}
lock.release();
// System.out.println("VPN \"" + evict + "\" of Process " + this.processID + "
// swapped out to SPN \"" + spn + "\".");
// Machine.processor().readTLBEntry(evict).valid = false;
allocatePage(vpn);
return;
} else {
if (evictedOwner.processID != this.processID) {
// System.out.println("Evicted VPN " + evict + " of Process " + this.processID);
evictedOwner.evict(evict);
} else {
pageTable[evict].valid = false;
}
UserKernel.freePages.add(evictedPPN);
for (int i = 0; i < Machine.processor().getTLBSize(); i++) {
TranslationEntry tE = Machine.processor().readTLBEntry(i);
if (tE.vpn == evict && tE.ppn == evictedPPN) {
// System.out.println("TLBEntry " + i + " invalid");
tE.valid = false;
Machine.processor().writeTLBEntry(i, tE);
}
}
lock.release();
allocatePage(vpn);
return;
}
}
lock.release();
}
for (int i = 0; i < Machine.processor().getTLBSize(); i++) {
TranslationEntry tE = Machine.processor().readTLBEntry(i);
if (!tE.valid) {
// System.out.println("Evicted TLBEntry " + i);
Machine.processor().writeTLBEntry(i, t);
// System.out.println(t.valid);
return;
}
}
syncTLB();
int evictedEntry = (int) (Math.random() * Machine.processor().getTLBSize());
TranslationEntry tE = Machine.processor().readTLBEntry(evictedEntry);
pageTable[tE.vpn] = tE;
Machine.processor().writeTLBEntry(evictedEntry, t);
// System.out.println("Evicted TLBEntry " + evictedEntry + " randomly");
// System.out.println("TE entered is VPN \"" + t.vpn + "\" PPN \"" + t.ppn + "\"");
}