/**
* 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;
}