status_t AddressSpace::HandleFault(unsigned int va, bool write, bool user)
{
va &= ~(PAGE_SIZE - 1); // Round down to a page boundry.
fAreaLock.LockRead();
int lastChangeCount = fChangeCount;
Area *area = static_cast<Area*>(fAreas.Find(va));
if (area == 0) {
fAreaLock.UnlockRead();
return E_BAD_ADDRESS;
}
PageProtection protection = area->GetProtection();
if ((user && write && !(protection & USER_WRITE))
|| (user && !write && !(protection & USER_READ))
|| (!user && write && !(protection & SYSTEM_WRITE))
|| (!user && !write && !(protection & SYSTEM_READ))) {
fAreaLock.UnlockRead();
return E_NOT_ALLOWED;
}
PageCache *cache = area->GetPageCache();
if (cache == 0) {
fAreaLock.UnlockRead();
return E_NOT_ALLOWED;
}
bool copy = cache->IsCopy();
cache->AcquireRef();
fAreaLock.UnlockRead();
off_t offset = va - area->GetBaseAddress() + area->GetCacheOffset();
Page *page = cache->GetPage(offset, write && cache->IsCopy());
cache->ReleaseRef();
if (page == 0)
return E_IO;
fAreaLock.LockRead();
if (lastChangeCount != fChangeCount) {
// Changes have occured to this address. Make sure that
// the area hasn't changed underneath the fault handler.
Area *newArea = static_cast<Area*>(fAreas.Find(va));
if (newArea != area || newArea->GetPageCache() != cache ||
newArea->GetCacheOffset() != offset)
fAreaLock.UnlockRead();
return E_BAD_ADDRESS;
}
// If this is a read from copy-on-write page, it is shared with the
// original cache. Mark it read only.
if (copy && !write)
protection &= ~(USER_WRITE | SYSTEM_WRITE);
fPhysicalMap->Map(va, page->GetPhysicalAddress(), protection);
fAreaLock.UnlockRead();
AtomicAdd(&fFaultCount, 1);
return E_NO_ERROR;
}
Area* AddressSpace::CreateArea(const char name[], unsigned int size, AreaWiring wiring,
PageProtection protection, PageCache *cache, off_t offset, unsigned int va,
int flags)
{
if (size % PAGE_SIZE != 0 || size == 0)
return 0;
if (cache != 0 && cache->Commit(offset + size) != offset + size)
return 0;
fAreaLock.LockWrite();
if (va == INVALID_PAGE)
va = FindFreeRange(size, flags);
else if (va % PAGE_SIZE != 0 || !fAreas.IsRangeFree(va, va + size - 1))
va = INVALID_PAGE;
Area *area = 0;
if (va != INVALID_PAGE) {
area = new Area(name, protection, cache, offset, wiring);
fAreas.Add(area, va, va + size - 1);
if (wiring & AREA_WIRED) {
for (unsigned int aroffs = 0; aroffs < size; aroffs += PAGE_SIZE) {
Page *page = area->GetPageCache()->GetPage(area->GetCacheOffset()
+ aroffs, false);
page->Wire();
fPhysicalMap->Map(va + aroffs, page->GetPhysicalAddress(), protection);
}
}
}
fChangeCount++;
fAreaLock.UnlockWrite();
return area;
}