gem5/src/mem/page_table.cc
Mitch Hayenga b222ba2fd3 sim: Fix two bugs relating to software caching of PageTable entries.
The existing implementation can read uninitialized data or stale information
from the cached PageTable entries.

1) Add a valid bit for the cache entries.  Simply using zero for the virtual
address to signify invalid entries is not sufficient.  Speculative, wrong-path
accesses frequently access page zero.  The current implementation would return
a uninitialized TLB entry when address zero was accessed and the PageTable
cache entry was invalid.

2) When unmapping/mapping/remaping a page, invalidate the corresponding
PageTable cache entry if one already exists.
2013-04-23 09:47:52 -04:00

237 lines
6.6 KiB
C++

/*
* Copyright (c) 2003 The Regents of The University of Michigan
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Steve Reinhardt
* Ron Dreslinski
* Ali Saidi
*/
/**
* @file
* Definitions of page table.
*/
#include <fstream>
#include <map>
#include <string>
#include "base/bitfield.hh"
#include "base/intmath.hh"
#include "base/trace.hh"
#include "config/the_isa.hh"
#include "debug/MMU.hh"
#include "mem/page_table.hh"
#include "sim/faults.hh"
#include "sim/sim_object.hh"
using namespace std;
using namespace TheISA;
PageTable::PageTable(const std::string &__name, uint64_t _pid, Addr _pageSize)
: pageSize(_pageSize), offsetMask(mask(floorLog2(_pageSize))),
pid(_pid), _name(__name)
{
assert(isPowerOf2(pageSize));
pTableCache[0].valid = false;
pTableCache[1].valid = false;
pTableCache[2].valid = false;
}
PageTable::~PageTable()
{
}
void
PageTable::map(Addr vaddr, Addr paddr, int64_t size, bool clobber)
{
// starting address must be page aligned
assert(pageOffset(vaddr) == 0);
DPRINTF(MMU, "Allocating Page: %#x-%#x\n", vaddr, vaddr+ size);
for (; size > 0; size -= pageSize, vaddr += pageSize, paddr += pageSize) {
if (!clobber && (pTable.find(vaddr) != pTable.end())) {
// already mapped
fatal("PageTable::allocate: address 0x%x already mapped", vaddr);
}
pTable[vaddr] = TheISA::TlbEntry(pid, vaddr, paddr);
eraseCacheEntry(vaddr);
updateCache(vaddr, pTable[vaddr]);
}
}
void
PageTable::remap(Addr vaddr, int64_t size, Addr new_vaddr)
{
assert(pageOffset(vaddr) == 0);
assert(pageOffset(new_vaddr) == 0);
DPRINTF(MMU, "moving pages from vaddr %08p to %08p, size = %d\n", vaddr,
new_vaddr, size);
for (; size > 0; size -= pageSize, vaddr += pageSize, new_vaddr += pageSize) {
assert(pTable.find(vaddr) != pTable.end());
pTable[new_vaddr] = pTable[vaddr];
pTable.erase(vaddr);
eraseCacheEntry(vaddr);
pTable[new_vaddr].updateVaddr(new_vaddr);
updateCache(new_vaddr, pTable[new_vaddr]);
}
}
void
PageTable::unmap(Addr vaddr, int64_t size)
{
assert(pageOffset(vaddr) == 0);
DPRINTF(MMU, "Unmapping page: %#x-%#x\n", vaddr, vaddr+ size);
for (; size > 0; size -= pageSize, vaddr += pageSize) {
assert(pTable.find(vaddr) != pTable.end());
pTable.erase(vaddr);
eraseCacheEntry(vaddr);
}
}
bool
PageTable::isUnmapped(Addr vaddr, int64_t size)
{
// starting address must be page aligned
assert(pageOffset(vaddr) == 0);
for (; size > 0; size -= pageSize, vaddr += pageSize) {
if (pTable.find(vaddr) != pTable.end()) {
return false;
}
}
return true;
}
bool
PageTable::lookup(Addr vaddr, TheISA::TlbEntry &entry)
{
Addr page_addr = pageAlign(vaddr);
if (pTableCache[0].valid && pTableCache[0].vaddr == page_addr) {
entry = pTableCache[0].entry;
return true;
}
if (pTableCache[1].valid && pTableCache[1].vaddr == page_addr) {
entry = pTableCache[1].entry;
return true;
}
if (pTableCache[2].valid && pTableCache[2].vaddr == page_addr) {
entry = pTableCache[2].entry;
return true;
}
PTableItr iter = pTable.find(page_addr);
if (iter == pTable.end()) {
return false;
}
updateCache(page_addr, iter->second);
entry = iter->second;
return true;
}
bool
PageTable::translate(Addr vaddr, Addr &paddr)
{
TheISA::TlbEntry entry;
if (!lookup(vaddr, entry)) {
DPRINTF(MMU, "Couldn't Translate: %#x\n", vaddr);
return false;
}
paddr = pageOffset(vaddr) + entry.pageStart();
DPRINTF(MMU, "Translating: %#x->%#x\n", vaddr, paddr);
return true;
}
Fault
PageTable::translate(RequestPtr req)
{
Addr paddr;
assert(pageAlign(req->getVaddr() + req->getSize() - 1)
== pageAlign(req->getVaddr()));
if (!translate(req->getVaddr(), paddr)) {
return Fault(new GenericPageTableFault(req->getVaddr()));
}
req->setPaddr(paddr);
if ((paddr & (pageSize - 1)) + req->getSize() > pageSize) {
panic("Request spans page boundaries!\n");
return NoFault;
}
return NoFault;
}
void
PageTable::serialize(std::ostream &os)
{
paramOut(os, "ptable.size", pTable.size());
PTable::size_type count = 0;
PTableItr iter = pTable.begin();
PTableItr end = pTable.end();
while (iter != end) {
os << "\n[" << csprintf("%s.Entry%d", name(), count) << "]\n";
paramOut(os, "vaddr", iter->first);
iter->second.serialize(os);
++iter;
++count;
}
assert(count == pTable.size());
}
void
PageTable::unserialize(Checkpoint *cp, const std::string &section)
{
int i = 0, count;
paramIn(cp, section, "ptable.size", count);
pTable.clear();
while (i < count) {
TheISA::TlbEntry *entry;
Addr vaddr;
paramIn(cp, csprintf("%s.Entry%d", name(), i), "vaddr", vaddr);
entry = new TheISA::TlbEntry();
entry->unserialize(cp, csprintf("%s.Entry%d", name(), i));
pTable[vaddr] = *entry;
delete entry;
++i;
}
}