src/mem/physical.cc - public/gem5 - Git at Google

 /*
  * Copyright (c) 2012, 2014, 2018 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * 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.
  */

 #include "mem/physical.hh"

 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <sys/user.h>
 #include <unistd.h>
 #include <zlib.h>

 #include <cerrno>
 #include <climits>
 #include <cstdio>
 #include <iostream>
 #include <string>

 #include "base/trace.hh"
 #include "debug/AddrRanges.hh"
 #include "debug/Checkpoint.hh"
 #include "mem/abstract_mem.hh"
 #include "sim/serialize.hh"

 /**
  * On Linux, MAP_NORESERVE allow us to simulate a very large memory
  * without committing to actually providing the swap space on the
  * host. On FreeBSD or OSX the MAP_NORESERVE flag does not exist,
  * so simply make it 0.
  */
 #if defined(__APPLE__) || defined(__FreeBSD__)
 #ifndef MAP_NORESERVE
 #define MAP_NORESERVE 0
 #endif
 #endif

 namespace gem5
 {

 PhysicalMemory::PhysicalMemory(const std::string& _name,
                                const std::vector<AbstractMemory*>& _memories,
                                bool mmap_using_noreserve,
                                const std::string& shared_backstore) :
     _name(_name), size(0), mmapUsingNoReserve(mmap_using_noreserve),
     sharedBackstore(shared_backstore)
 {
     if (mmap_using_noreserve)
         warn("Not reserving swap space. May cause SIGSEGV on actual usage\n");

     // add the memories from the system to the address map as
     // appropriate
     for (const auto& m : _memories) {
         // only add the memory if it is part of the global address map
         if (m->isInAddrMap()) {
             memories.push_back(m);

             // calculate the total size once and for all
             size += m->size();

             // add the range to our interval tree and make sure it does not
             // intersect an existing range
             fatal_if(addrMap.insert(m->getAddrRange(), m) == addrMap.end(),
                      "Memory address range for %s is overlapping\n",
                      m->name());
         } else {
             // this type of memory is used e.g. as reference memory by
             // Ruby, and they also needs a backing store, but should
             // not be part of the global address map
             DPRINTF(AddrRanges,
                     "Skipping memory %s that is not in global address map\n",
                     m->name());

             // sanity check
             fatal_if(m->getAddrRange().interleaved(),
                      "Memory %s that is not in the global address map cannot "
                      "be interleaved\n", m->name());

             // simply do it independently, also note that this kind of
             // memories are allowed to overlap in the logic address
             // map
             std::vector<AbstractMemory*> unmapped_mems{m};
             createBackingStore(m->getAddrRange(), unmapped_mems,
                                m->isConfReported(), m->isInAddrMap(),
                                m->isKvmMap());
         }
     }

     // iterate over the increasing addresses and chunks of contiguous
     // space to be mapped to backing store, create it and inform the
     // memories
     std::vector<AddrRange> intlv_ranges;
     std::vector<AbstractMemory*> curr_memories;
     for (const auto& r : addrMap) {
         // simply skip past all memories that are null and hence do
         // not need any backing store
         if (!r.second->isNull()) {
             // if the range is interleaved then save it for now
             if (r.first.interleaved()) {
                 // if we already got interleaved ranges that are not
                 // part of the same range, then first do a merge
                 // before we add the new one
                 if (!intlv_ranges.empty() &&
                     !intlv_ranges.back().mergesWith(r.first)) {
                     AddrRange merged_range(intlv_ranges);

                     AbstractMemory *f = curr_memories.front();
                     for (const auto& c : curr_memories)
                         if (f->isConfReported() != c->isConfReported() ||
                             f->isInAddrMap() != c->isInAddrMap() ||
                             f->isKvmMap() != c->isKvmMap())
                             fatal("Inconsistent flags in an interleaved "
                                   "range\n");

                     createBackingStore(merged_range, curr_memories,
                                        f->isConfReported(), f->isInAddrMap(),
                                        f->isKvmMap());

                     intlv_ranges.clear();
                     curr_memories.clear();
                 }
                 intlv_ranges.push_back(r.first);
                 curr_memories.push_back(r.second);
             } else {
                 std::vector<AbstractMemory*> single_memory{r.second};
                 createBackingStore(r.first, single_memory,
                                    r.second->isConfReported(),
                                    r.second->isInAddrMap(),
                                    r.second->isKvmMap());
             }
         }
     }

     // if there is still interleaved ranges waiting to be merged, go
     // ahead and do it
     if (!intlv_ranges.empty()) {
         AddrRange merged_range(intlv_ranges);

         AbstractMemory *f = curr_memories.front();
         for (const auto& c : curr_memories)
             if (f->isConfReported() != c->isConfReported() ||
                 f->isInAddrMap() != c->isInAddrMap() ||
                 f->isKvmMap() != c->isKvmMap())
                 fatal("Inconsistent flags in an interleaved "
                       "range\n");

         createBackingStore(merged_range, curr_memories,
                            f->isConfReported(), f->isInAddrMap(),
                            f->isKvmMap());
     }
 }

 void
 PhysicalMemory::createBackingStore(
         AddrRange range, const std::vector<AbstractMemory*>& _memories,
         bool conf_table_reported, bool in_addr_map, bool kvm_map)
 {
     panic_if(range.interleaved(),
              "Cannot create backing store for interleaved range %s\n",
               range.to_string());

     // perform the actual mmap
     DPRINTF(AddrRanges, "Creating backing store for range %s with size %d\n",
             range.to_string(), range.size());

     int shm_fd;
     int map_flags;

     if (sharedBackstore.empty()) {
         shm_fd = -1;
         map_flags =  MAP_ANON | MAP_PRIVATE;
     } else {
         DPRINTF(AddrRanges, "Sharing backing store as %s\n",
                 sharedBackstore.c_str());
         shm_fd = shm_open(sharedBackstore.c_str(), O_CREAT | O_RDWR, 0666);
         if (shm_fd == -1)
                panic("Shared memory failed");
         if (ftruncate(shm_fd, range.size()))
                panic("Setting size of shared memory failed");
         map_flags = MAP_SHARED;
     }

     // to be able to simulate very large memories, the user can opt to
     // pass noreserve to mmap
     if (mmapUsingNoReserve) {
         map_flags |= MAP_NORESERVE;
     }

     uint8_t* pmem = (uint8_t*) mmap(NULL, range.size(),
                                     PROT_READ | PROT_WRITE,
                                     map_flags, shm_fd, 0);

     if (pmem == (uint8_t*) MAP_FAILED) {
         perror("mmap");
         fatal("Could not mmap %d bytes for range %s!\n", range.size(),
               range.to_string());
     }

     // remember this backing store so we can checkpoint it and unmap
     // it appropriately
     backingStore.emplace_back(range, pmem,
                               conf_table_reported, in_addr_map, kvm_map);

     // point the memories to their backing store
     for (const auto& m : _memories) {
         DPRINTF(AddrRanges, "Mapping memory %s to backing store\n",
                 m->name());
         m->setBackingStore(pmem);
     }
 }

 PhysicalMemory::~PhysicalMemory()
 {
     // unmap the backing store
     for (auto& s : backingStore)
         munmap((char*)s.pmem, s.range.size());
 }

 bool
 PhysicalMemory::isMemAddr(Addr addr) const
 {
     return addrMap.contains(addr) != addrMap.end();
 }

 AddrRangeList
 PhysicalMemory::getConfAddrRanges() const
 {
     // this could be done once in the constructor, but since it is unlikely to
     // be called more than once the iteration should not be a problem
     AddrRangeList ranges;
     std::vector<AddrRange> intlv_ranges;
     for (const auto& r : addrMap) {
         if (r.second->isConfReported()) {
             // if the range is interleaved then save it for now
             if (r.first.interleaved()) {
                 // if we already got interleaved ranges that are not
                 // part of the same range, then first do a merge
                 // before we add the new one
                 if (!intlv_ranges.empty() &&
                     !intlv_ranges.back().mergesWith(r.first)) {
                     ranges.push_back(AddrRange(intlv_ranges));
                     intlv_ranges.clear();
                 }
                 intlv_ranges.push_back(r.first);
             } else {
                 // keep the current range
                 ranges.push_back(r.first);
             }
         }
     }

     // if there is still interleaved ranges waiting to be merged,
     // go ahead and do it
     if (!intlv_ranges.empty()) {
         ranges.push_back(AddrRange(intlv_ranges));
     }

     return ranges;
 }

 void
 PhysicalMemory::access(PacketPtr pkt)
 {
     assert(pkt->isRequest());
     const auto& m = addrMap.contains(pkt->getAddrRange());
     assert(m != addrMap.end());
     m->second->access(pkt);
 }

 void
 PhysicalMemory::functionalAccess(PacketPtr pkt)
 {
     assert(pkt->isRequest());
     const auto& m = addrMap.contains(pkt->getAddrRange());
     assert(m != addrMap.end());
     m->second->functionalAccess(pkt);
 }

 void
 PhysicalMemory::serialize(CheckpointOut &cp) const
 {
     // serialize all the locked addresses and their context ids
     std::vector<Addr> lal_addr;
     std::vector<ContextID> lal_cid;

     for (auto& m : memories) {
         const std::list<LockedAddr>& locked_addrs = m->getLockedAddrList();
         for (const auto& l : locked_addrs) {
             lal_addr.push_back(l.addr);
             lal_cid.push_back(l.contextId);
         }
     }

     SERIALIZE_CONTAINER(lal_addr);
     SERIALIZE_CONTAINER(lal_cid);

     // serialize the backing stores
     unsigned int nbr_of_stores = backingStore.size();
     SERIALIZE_SCALAR(nbr_of_stores);

     unsigned int store_id = 0;
     // store each backing store memory segment in a file
     for (auto& s : backingStore) {
         ScopedCheckpointSection sec(cp, csprintf("store%d", store_id));
         serializeStore(cp, store_id++, s.range, s.pmem);
     }
 }

 void
 PhysicalMemory::serializeStore(CheckpointOut &cp, unsigned int store_id,
                                AddrRange range, uint8_t* pmem) const
 {
     // we cannot use the address range for the name as the
     // memories that are not part of the address map can overlap
     std::string filename =
         name() + ".store" + std::to_string(store_id) + ".pmem";
     long range_size = range.size();

     DPRINTF(Checkpoint, "Serializing physical memory %s with size %d\n",
             filename, range_size);

     SERIALIZE_SCALAR(store_id);
     SERIALIZE_SCALAR(filename);
     SERIALIZE_SCALAR(range_size);

     // write memory file
     std::string filepath = CheckpointIn::dir() + "/" + filename.c_str();
     gzFile compressed_mem = gzopen(filepath.c_str(), "wb");
     if (compressed_mem == NULL)
         fatal("Can't open physical memory checkpoint file '%s'\n",
               filename);

     uint64_t pass_size = 0;

     // gzwrite fails if (int)len < 0 (gzwrite returns int)
     for (uint64_t written = 0; written < range.size();
          written += pass_size) {
         pass_size = (uint64_t)INT_MAX < (range.size() - written) ?
             (uint64_t)INT_MAX : (range.size() - written);

         if (gzwrite(compressed_mem, pmem + written,
                     (unsigned int) pass_size) != (int) pass_size) {
             fatal("Write failed on physical memory checkpoint file '%s'\n",
                   filename);
         }
     }

     // close the compressed stream and check that the exit status
     // is zero
     if (gzclose(compressed_mem))
         fatal("Close failed on physical memory checkpoint file '%s'\n",
               filename);

 }

 void
 PhysicalMemory::unserialize(CheckpointIn &cp)
 {
     // unserialize the locked addresses and map them to the
     // appropriate memory controller
     std::vector<Addr> lal_addr;
     std::vector<ContextID> lal_cid;
     UNSERIALIZE_CONTAINER(lal_addr);
     UNSERIALIZE_CONTAINER(lal_cid);
     for (size_t i = 0; i < lal_addr.size(); ++i) {
         const auto& m = addrMap.contains(lal_addr[i]);
         m->second->addLockedAddr(LockedAddr(lal_addr[i], lal_cid[i]));
     }

     // unserialize the backing stores
     unsigned int nbr_of_stores;
     UNSERIALIZE_SCALAR(nbr_of_stores);

     for (unsigned int i = 0; i < nbr_of_stores; ++i) {
         ScopedCheckpointSection sec(cp, csprintf("store%d", i));
         unserializeStore(cp);
     }

 }

 void
 PhysicalMemory::unserializeStore(CheckpointIn &cp)
 {
     const uint32_t chunk_size = 16384;

     unsigned int store_id;
     UNSERIALIZE_SCALAR(store_id);

     std::string filename;
     UNSERIALIZE_SCALAR(filename);
     std::string filepath = cp.getCptDir() + "/" + filename;

     // mmap memoryfile
     gzFile compressed_mem = gzopen(filepath.c_str(), "rb");
     if (compressed_mem == NULL)
         fatal("Can't open physical memory checkpoint file '%s'", filename);

     // we've already got the actual backing store mapped
     uint8_t* pmem = backingStore[store_id].pmem;
     AddrRange range = backingStore[store_id].range;

     long range_size;
     UNSERIALIZE_SCALAR(range_size);

     DPRINTF(Checkpoint, "Unserializing physical memory %s with size %d\n",
             filename, range_size);

     if (range_size != range.size())
         fatal("Memory range size has changed! Saw %lld, expected %lld\n",
               range_size, range.size());

     uint64_t curr_size = 0;
     long* temp_page = new long[chunk_size];
     long* pmem_current;
     uint32_t bytes_read;
     while (curr_size < range.size()) {
         bytes_read = gzread(compressed_mem, temp_page, chunk_size);
         if (bytes_read == 0)
             break;

         assert(bytes_read % sizeof(long) == 0);

         for (uint32_t x = 0; x < bytes_read / sizeof(long); x++) {
             // Only copy bytes that are non-zero, so we don't give
             // the VM system hell
             if (*(temp_page + x) != 0) {
                 pmem_current = (long*)(pmem + curr_size + x * sizeof(long));
                 *pmem_current = *(temp_page + x);
             }
         }
         curr_size += bytes_read;
     }

     delete[] temp_page;

     if (gzclose(compressed_mem))
         fatal("Close failed on physical memory checkpoint file '%s'\n",
               filename);
 }

 } // namespace gem5
	/*
	* Copyright (c) 2012, 2014, 2018 ARM Limited
	* All rights reserved
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* 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.
	*/

	#include "mem/physical.hh"

	#include <fcntl.h>
	#include <sys/mman.h>
	#include <sys/types.h>
	#include <sys/user.h>
	#include <unistd.h>
	#include <zlib.h>

	#include <cerrno>
	#include <climits>
	#include <cstdio>
	#include <iostream>
	#include <string>

	#include "base/trace.hh"
	#include "debug/AddrRanges.hh"
	#include "debug/Checkpoint.hh"
	#include "mem/abstract_mem.hh"
	#include "sim/serialize.hh"

	/**
	* On Linux, MAP_NORESERVE allow us to simulate a very large memory
	* without committing to actually providing the swap space on the
	* host. On FreeBSD or OSX the MAP_NORESERVE flag does not exist,
	* so simply make it 0.
	*/
	#if defined(__APPLE__) \|\| defined(__FreeBSD__)
	#ifndef MAP_NORESERVE
	#define MAP_NORESERVE 0
	#endif
	#endif

	namespace gem5
	{

	PhysicalMemory::PhysicalMemory(const std::string& _name,
	const std::vector<AbstractMemory*>& _memories,
	bool mmap_using_noreserve,
	const std::string& shared_backstore) :
	_name(_name), size(0), mmapUsingNoReserve(mmap_using_noreserve),
	sharedBackstore(shared_backstore)
	{
	if (mmap_using_noreserve)
	warn("Not reserving swap space. May cause SIGSEGV on actual usage\n");

	// add the memories from the system to the address map as
	// appropriate
	for (const auto& m : _memories) {
	// only add the memory if it is part of the global address map
	if (m->isInAddrMap()) {
	memories.push_back(m);

	// calculate the total size once and for all
	size += m->size();

	// add the range to our interval tree and make sure it does not
	// intersect an existing range
	fatal_if(addrMap.insert(m->getAddrRange(), m) == addrMap.end(),
	"Memory address range for %s is overlapping\n",
	m->name());
	} else {
	// this type of memory is used e.g. as reference memory by
	// Ruby, and they also needs a backing store, but should
	// not be part of the global address map
	DPRINTF(AddrRanges,
	"Skipping memory %s that is not in global address map\n",
	m->name());

	// sanity check
	fatal_if(m->getAddrRange().interleaved(),
	"Memory %s that is not in the global address map cannot "
	"be interleaved\n", m->name());

	// simply do it independently, also note that this kind of
	// memories are allowed to overlap in the logic address
	// map
	std::vector<AbstractMemory*> unmapped_mems{m};
	createBackingStore(m->getAddrRange(), unmapped_mems,
	m->isConfReported(), m->isInAddrMap(),
	m->isKvmMap());
	}
	}

	// iterate over the increasing addresses and chunks of contiguous
	// space to be mapped to backing store, create it and inform the
	// memories
	std::vector<AddrRange> intlv_ranges;
	std::vector<AbstractMemory*> curr_memories;
	for (const auto& r : addrMap) {
	// simply skip past all memories that are null and hence do
	// not need any backing store
	if (!r.second->isNull()) {
	// if the range is interleaved then save it for now
	if (r.first.interleaved()) {
	// if we already got interleaved ranges that are not
	// part of the same range, then first do a merge
	// before we add the new one
	if (!intlv_ranges.empty() &&
	!intlv_ranges.back().mergesWith(r.first)) {
	AddrRange merged_range(intlv_ranges);

	AbstractMemory *f = curr_memories.front();
	for (const auto& c : curr_memories)
	if (f->isConfReported() != c->isConfReported() \|\|
	f->isInAddrMap() != c->isInAddrMap() \|\|
	f->isKvmMap() != c->isKvmMap())
	fatal("Inconsistent flags in an interleaved "
	"range\n");

	createBackingStore(merged_range, curr_memories,
	f->isConfReported(), f->isInAddrMap(),
	f->isKvmMap());

	intlv_ranges.clear();
	curr_memories.clear();
	}
	intlv_ranges.push_back(r.first);
	curr_memories.push_back(r.second);
	} else {
	std::vector<AbstractMemory*> single_memory{r.second};
	createBackingStore(r.first, single_memory,
	r.second->isConfReported(),
	r.second->isInAddrMap(),
	r.second->isKvmMap());
	}
	}
	}

	// if there is still interleaved ranges waiting to be merged, go
	// ahead and do it
	if (!intlv_ranges.empty()) {
	AddrRange merged_range(intlv_ranges);

	AbstractMemory *f = curr_memories.front();
	for (const auto& c : curr_memories)
	if (f->isConfReported() != c->isConfReported() \|\|
	f->isInAddrMap() != c->isInAddrMap() \|\|
	f->isKvmMap() != c->isKvmMap())
	fatal("Inconsistent flags in an interleaved "
	"range\n");

	createBackingStore(merged_range, curr_memories,
	f->isConfReported(), f->isInAddrMap(),
	f->isKvmMap());
	}
	}

	void
	PhysicalMemory::createBackingStore(
	AddrRange range, const std::vector<AbstractMemory*>& _memories,
	bool conf_table_reported, bool in_addr_map, bool kvm_map)
	{
	panic_if(range.interleaved(),
	"Cannot create backing store for interleaved range %s\n",
	range.to_string());

	// perform the actual mmap
	DPRINTF(AddrRanges, "Creating backing store for range %s with size %d\n",
	range.to_string(), range.size());

	int shm_fd;
	int map_flags;

	if (sharedBackstore.empty()) {
	shm_fd = -1;
	map_flags = MAP_ANON \| MAP_PRIVATE;
	} else {
	DPRINTF(AddrRanges, "Sharing backing store as %s\n",
	sharedBackstore.c_str());
	shm_fd = shm_open(sharedBackstore.c_str(), O_CREAT \| O_RDWR, 0666);
	if (shm_fd == -1)
	panic("Shared memory failed");
	if (ftruncate(shm_fd, range.size()))
	panic("Setting size of shared memory failed");
	map_flags = MAP_SHARED;
	}

	// to be able to simulate very large memories, the user can opt to
	// pass noreserve to mmap
	if (mmapUsingNoReserve) {
	map_flags \|= MAP_NORESERVE;
	}

	uint8_t* pmem = (uint8_t*) mmap(NULL, range.size(),
	PROT_READ \| PROT_WRITE,
	map_flags, shm_fd, 0);

	if (pmem == (uint8_t*) MAP_FAILED) {
	perror("mmap");
	fatal("Could not mmap %d bytes for range %s!\n", range.size(),
	range.to_string());
	}

	// remember this backing store so we can checkpoint it and unmap
	// it appropriately
	backingStore.emplace_back(range, pmem,
	conf_table_reported, in_addr_map, kvm_map);

	// point the memories to their backing store
	for (const auto& m : _memories) {
	DPRINTF(AddrRanges, "Mapping memory %s to backing store\n",
	m->name());
	m->setBackingStore(pmem);
	}
	}

	PhysicalMemory::~PhysicalMemory()
	{
	// unmap the backing store
	for (auto& s : backingStore)
	munmap((char*)s.pmem, s.range.size());
	}

	bool
	PhysicalMemory::isMemAddr(Addr addr) const
	{
	return addrMap.contains(addr) != addrMap.end();
	}

	AddrRangeList
	PhysicalMemory::getConfAddrRanges() const
	{
	// this could be done once in the constructor, but since it is unlikely to
	// be called more than once the iteration should not be a problem
	AddrRangeList ranges;
	std::vector<AddrRange> intlv_ranges;
	for (const auto& r : addrMap) {
	if (r.second->isConfReported()) {
	// if the range is interleaved then save it for now
	if (r.first.interleaved()) {
	// if we already got interleaved ranges that are not
	// part of the same range, then first do a merge
	// before we add the new one
	if (!intlv_ranges.empty() &&
	!intlv_ranges.back().mergesWith(r.first)) {
	ranges.push_back(AddrRange(intlv_ranges));
	intlv_ranges.clear();
	}
	intlv_ranges.push_back(r.first);
	} else {
	// keep the current range
	ranges.push_back(r.first);
	}
	}
	}

	// if there is still interleaved ranges waiting to be merged,
	// go ahead and do it
	if (!intlv_ranges.empty()) {
	ranges.push_back(AddrRange(intlv_ranges));
	}

	return ranges;
	}

	void
	PhysicalMemory::access(PacketPtr pkt)
	{
	assert(pkt->isRequest());
	const auto& m = addrMap.contains(pkt->getAddrRange());
	assert(m != addrMap.end());
	m->second->access(pkt);
	}

	void
	PhysicalMemory::functionalAccess(PacketPtr pkt)
	{
	assert(pkt->isRequest());
	const auto& m = addrMap.contains(pkt->getAddrRange());
	assert(m != addrMap.end());
	m->second->functionalAccess(pkt);
	}

	void
	PhysicalMemory::serialize(CheckpointOut &cp) const
	{
	// serialize all the locked addresses and their context ids
	std::vector<Addr> lal_addr;
	std::vector<ContextID> lal_cid;

	for (auto& m : memories) {
	const std::list<LockedAddr>& locked_addrs = m->getLockedAddrList();
	for (const auto& l : locked_addrs) {
	lal_addr.push_back(l.addr);
	lal_cid.push_back(l.contextId);
	}
	}

	SERIALIZE_CONTAINER(lal_addr);
	SERIALIZE_CONTAINER(lal_cid);

	// serialize the backing stores
	unsigned int nbr_of_stores = backingStore.size();
	SERIALIZE_SCALAR(nbr_of_stores);

	unsigned int store_id = 0;
	// store each backing store memory segment in a file
	for (auto& s : backingStore) {
	ScopedCheckpointSection sec(cp, csprintf("store%d", store_id));
	serializeStore(cp, store_id++, s.range, s.pmem);
	}
	}

	void
	PhysicalMemory::serializeStore(CheckpointOut &cp, unsigned int store_id,
	AddrRange range, uint8_t* pmem) const
	{
	// we cannot use the address range for the name as the
	// memories that are not part of the address map can overlap
	std::string filename =
	name() + ".store" + std::to_string(store_id) + ".pmem";
	long range_size = range.size();

	DPRINTF(Checkpoint, "Serializing physical memory %s with size %d\n",
	filename, range_size);

	SERIALIZE_SCALAR(store_id);
	SERIALIZE_SCALAR(filename);
	SERIALIZE_SCALAR(range_size);

	// write memory file
	std::string filepath = CheckpointIn::dir() + "/" + filename.c_str();
	gzFile compressed_mem = gzopen(filepath.c_str(), "wb");
	if (compressed_mem == NULL)
	fatal("Can't open physical memory checkpoint file '%s'\n",
	filename);

	uint64_t pass_size = 0;

	// gzwrite fails if (int)len < 0 (gzwrite returns int)
	for (uint64_t written = 0; written < range.size();
	written += pass_size) {
	pass_size = (uint64_t)INT_MAX < (range.size() - written) ?
	(uint64_t)INT_MAX : (range.size() - written);

	if (gzwrite(compressed_mem, pmem + written,
	(unsigned int) pass_size) != (int) pass_size) {
	fatal("Write failed on physical memory checkpoint file '%s'\n",
	filename);
	}
	}

	// close the compressed stream and check that the exit status
	// is zero
	if (gzclose(compressed_mem))
	fatal("Close failed on physical memory checkpoint file '%s'\n",
	filename);

	}

	void
	PhysicalMemory::unserialize(CheckpointIn &cp)
	{
	// unserialize the locked addresses and map them to the
	// appropriate memory controller
	std::vector<Addr> lal_addr;
	std::vector<ContextID> lal_cid;
	UNSERIALIZE_CONTAINER(lal_addr);
	UNSERIALIZE_CONTAINER(lal_cid);
	for (size_t i = 0; i < lal_addr.size(); ++i) {
	const auto& m = addrMap.contains(lal_addr[i]);
	m->second->addLockedAddr(LockedAddr(lal_addr[i], lal_cid[i]));
	}

	// unserialize the backing stores
	unsigned int nbr_of_stores;
	UNSERIALIZE_SCALAR(nbr_of_stores);

	for (unsigned int i = 0; i < nbr_of_stores; ++i) {
	ScopedCheckpointSection sec(cp, csprintf("store%d", i));
	unserializeStore(cp);
	}

	}

	void
	PhysicalMemory::unserializeStore(CheckpointIn &cp)
	{
	const uint32_t chunk_size = 16384;

	unsigned int store_id;
	UNSERIALIZE_SCALAR(store_id);

	std::string filename;
	UNSERIALIZE_SCALAR(filename);
	std::string filepath = cp.getCptDir() + "/" + filename;

	// mmap memoryfile
	gzFile compressed_mem = gzopen(filepath.c_str(), "rb");
	if (compressed_mem == NULL)
	fatal("Can't open physical memory checkpoint file '%s'", filename);

	// we've already got the actual backing store mapped
	uint8_t* pmem = backingStore[store_id].pmem;
	AddrRange range = backingStore[store_id].range;

	long range_size;
	UNSERIALIZE_SCALAR(range_size);

	DPRINTF(Checkpoint, "Unserializing physical memory %s with size %d\n",
	filename, range_size);

	if (range_size != range.size())
	fatal("Memory range size has changed! Saw %lld, expected %lld\n",
	range_size, range.size());

	uint64_t curr_size = 0;
	long* temp_page = new long[chunk_size];
	long* pmem_current;
	uint32_t bytes_read;
	while (curr_size < range.size()) {
	bytes_read = gzread(compressed_mem, temp_page, chunk_size);
	if (bytes_read == 0)
	break;

	assert(bytes_read % sizeof(long) == 0);

	for (uint32_t x = 0; x < bytes_read / sizeof(long); x++) {
	// Only copy bytes that are non-zero, so we don't give
	// the VM system hell
	if (*(temp_page + x) != 0) {
	pmem_current = (long)(pmem + curr_size + x sizeof(long));
	pmem_current = (temp_page + x);
	}
	}
	curr_size += bytes_read;
	}

	delete[] temp_page;

	if (gzclose(compressed_mem))
	fatal("Close failed on physical memory checkpoint file '%s'\n",
	filename);
	}

	} // namespace gem5