lldb/source/Target/Memory.cpp - llvm-project - Git at Google

 //===-- Memory.cpp --------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #include "lldb/Target/Memory.h"
 #include "lldb/Target/Process.h"
 #include "lldb/Utility/DataBufferHeap.h"
 #include "lldb/Utility/LLDBLog.h"
 #include "lldb/Utility/Log.h"
 #include "lldb/Utility/RangeMap.h"
 #include "lldb/Utility/State.h"

 #include <cinttypes>
 #include <memory>

 using namespace lldb;
 using namespace lldb_private;

 // MemoryCache constructor
 MemoryCache::MemoryCache(Process &process)
     : m_mutex(), m_L1_cache(), m_L2_cache(), m_invalid_ranges(),
       m_process(process),
       m_L2_cache_line_byte_size(process.GetMemoryCacheLineSize()) {}

 // Destructor
 MemoryCache::~MemoryCache() = default;

 void MemoryCache::Clear(bool clear_invalid_ranges) {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   m_L1_cache.clear();
   m_L2_cache.clear();
   if (clear_invalid_ranges)
     m_invalid_ranges.Clear();
   m_L2_cache_line_byte_size = m_process.GetMemoryCacheLineSize();
 }

 void MemoryCache::AddL1CacheData(lldb::addr_t addr, const void *src,
                                  size_t src_len) {
   AddL1CacheData(
       addr, DataBufferSP(new DataBufferHeap(DataBufferHeap(src, src_len))));
 }

 void MemoryCache::AddL1CacheData(lldb::addr_t addr,
                                  const DataBufferSP &data_buffer_sp) {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   m_L1_cache[addr] = data_buffer_sp;
 }

 void MemoryCache::Flush(addr_t addr, size_t size) {
   if (size == 0)
     return;

   std::lock_guard<std::recursive_mutex> guard(m_mutex);

   // Erase any blocks from the L1 cache that intersect with the flush range
   if (!m_L1_cache.empty()) {
     AddrRange flush_range(addr, size);
     BlockMap::iterator pos = m_L1_cache.upper_bound(addr);
     if (pos != m_L1_cache.begin()) {
       --pos;
     }
     while (pos != m_L1_cache.end()) {
       AddrRange chunk_range(pos->first, pos->second->GetByteSize());
       if (!chunk_range.DoesIntersect(flush_range))
         break;
       pos = m_L1_cache.erase(pos);
     }
   }

   if (!m_L2_cache.empty()) {
     const uint32_t cache_line_byte_size = m_L2_cache_line_byte_size;
     const addr_t end_addr = (addr + size - 1);
     const addr_t first_cache_line_addr = addr - (addr % cache_line_byte_size);
     const addr_t last_cache_line_addr =
         end_addr - (end_addr % cache_line_byte_size);
     // Watch for overflow where size will cause us to go off the end of the
     // 64 bit address space
     uint32_t num_cache_lines;
     if (last_cache_line_addr >= first_cache_line_addr)
       num_cache_lines = ((last_cache_line_addr - first_cache_line_addr) /
                          cache_line_byte_size) +
                         1;
     else
       num_cache_lines =
           (UINT64_MAX - first_cache_line_addr + 1) / cache_line_byte_size;

     uint32_t cache_idx = 0;
     for (addr_t curr_addr = first_cache_line_addr; cache_idx < num_cache_lines;
          curr_addr += cache_line_byte_size, ++cache_idx) {
       BlockMap::iterator pos = m_L2_cache.find(curr_addr);
       if (pos != m_L2_cache.end())
         m_L2_cache.erase(pos);
     }
   }
 }

 void MemoryCache::AddInvalidRange(lldb::addr_t base_addr,
                                   lldb::addr_t byte_size) {
   if (byte_size > 0) {
     std::lock_guard<std::recursive_mutex> guard(m_mutex);
     InvalidRanges::Entry range(base_addr, byte_size);
     m_invalid_ranges.Append(range);
     m_invalid_ranges.Sort();
   }
 }

 bool MemoryCache::RemoveInvalidRange(lldb::addr_t base_addr,
                                      lldb::addr_t byte_size) {
   if (byte_size > 0) {
     std::lock_guard<std::recursive_mutex> guard(m_mutex);
     const uint32_t idx = m_invalid_ranges.FindEntryIndexThatContains(base_addr);
     if (idx != UINT32_MAX) {
       const InvalidRanges::Entry *entry = m_invalid_ranges.GetEntryAtIndex(idx);
       if (entry->GetRangeBase() == base_addr &&
           entry->GetByteSize() == byte_size)
         return m_invalid_ranges.RemoveEntryAtIndex(idx);
     }
   }
   return false;
 }

 lldb::DataBufferSP MemoryCache::GetL2CacheLine(lldb::addr_t line_base_addr,
                                                Status &error) {
   // This function assumes that the address given is aligned correctly.
   assert((line_base_addr % m_L2_cache_line_byte_size) == 0);

   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   auto pos = m_L2_cache.find(line_base_addr);
   if (pos != m_L2_cache.end())
     return pos->second;

   auto data_buffer_heap_sp =
       std::make_shared<DataBufferHeap>(m_L2_cache_line_byte_size, 0);
   size_t process_bytes_read = m_process.ReadMemoryFromInferior(
       line_base_addr, data_buffer_heap_sp->GetBytes(),
       data_buffer_heap_sp->GetByteSize(), error);

   // If we failed a read, not much we can do.
   if (process_bytes_read == 0)
     return lldb::DataBufferSP();

   // If we didn't get a complete read, we can still cache what we did get.
   if (process_bytes_read < m_L2_cache_line_byte_size)
     data_buffer_heap_sp->SetByteSize(process_bytes_read);

   m_L2_cache[line_base_addr] = data_buffer_heap_sp;
   return data_buffer_heap_sp;
 }

 size_t MemoryCache::Read(addr_t addr, void *dst, size_t dst_len,
                          Status &error) {
   if (!dst || dst_len == 0)
     return 0;

   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   // FIXME: We should do a more thorough check to make sure that we're not
   // overlapping with any invalid ranges (e.g. Read 0x100 - 0x200 but there's an
   // invalid range 0x180 - 0x280). `FindEntryThatContains` has an implementation
   // that takes a range, but it only checks to see if the argument is contained
   // by an existing invalid range. It cannot check if the argument contains
   // invalid ranges and cannot check for overlaps.
   if (m_invalid_ranges.FindEntryThatContains(addr)) {
     error = Status::FromErrorStringWithFormat(
         "memory read failed for 0x%" PRIx64, addr);
     return 0;
   }

   // Check the L1 cache for a range that contains the entire memory read.
   // L1 cache contains chunks of memory that are not required to be the size of
   // an L2 cache line. We avoid trying to do partial reads from the L1 cache to
   // simplify the implementation.
   if (!m_L1_cache.empty()) {
     AddrRange read_range(addr, dst_len);
     BlockMap::iterator pos = m_L1_cache.upper_bound(addr);
     if (pos != m_L1_cache.begin()) {
       --pos;
     }
     AddrRange chunk_range(pos->first, pos->second->GetByteSize());
     if (chunk_range.Contains(read_range)) {
       memcpy(dst, pos->second->GetBytes() + (addr - chunk_range.GetRangeBase()),
              dst_len);
       return dst_len;
     }
   }

   // If the size of the read is greater than the size of an L2 cache line, we'll
   // just read from the inferior. If that read is successful, we'll cache what
   // we read in the L1 cache for future use.
   if (dst_len > m_L2_cache_line_byte_size) {
     size_t bytes_read =
         m_process.ReadMemoryFromInferior(addr, dst, dst_len, error);
     if (bytes_read > 0)
       AddL1CacheData(addr, dst, bytes_read);
     return bytes_read;
   }

   // If the size of the read fits inside one L2 cache line, we'll try reading
   // from the L2 cache. Note that if the range of memory we're reading sits
   // between two contiguous cache lines, we'll touch two cache lines instead of
   // just one.

   // We're going to have all of our loads and reads be cache line aligned.
   addr_t cache_line_offset = addr % m_L2_cache_line_byte_size;
   addr_t cache_line_base_addr = addr - cache_line_offset;
   DataBufferSP first_cache_line = GetL2CacheLine(cache_line_base_addr, error);
   // If we get nothing, then the read to the inferior likely failed. Nothing to
   // do here.
   if (!first_cache_line)
     return 0;

   // If the cache line was not filled out completely and the offset is greater
   // than what we have available, we can't do anything further here.
   if (cache_line_offset >= first_cache_line->GetByteSize())
     return 0;

   uint8_t *dst_buf = (uint8_t *)dst;
   size_t bytes_left = dst_len;
   size_t read_size = first_cache_line->GetByteSize() - cache_line_offset;
   if (read_size > bytes_left)
     read_size = bytes_left;

   memcpy(dst_buf + dst_len - bytes_left,
          first_cache_line->GetBytes() + cache_line_offset, read_size);
   bytes_left -= read_size;

   // If the cache line was not filled out completely and we still have data to
   // read, we can't do anything further.
   if (first_cache_line->GetByteSize() < m_L2_cache_line_byte_size &&
       bytes_left > 0)
     return dst_len - bytes_left;

   // We'll hit this scenario if our read straddles two cache lines.
   if (bytes_left > 0) {
     cache_line_base_addr += m_L2_cache_line_byte_size;

     // FIXME: Until we are able to more thoroughly check for invalid ranges, we
     // will have to check the second line to see if it is in an invalid range as
     // well. See the check near the beginning of the function for more details.
     if (m_invalid_ranges.FindEntryThatContains(cache_line_base_addr)) {
       error = Status::FromErrorStringWithFormat(
           "memory read failed for 0x%" PRIx64, cache_line_base_addr);
       return dst_len - bytes_left;
     }

     DataBufferSP second_cache_line =
         GetL2CacheLine(cache_line_base_addr, error);
     if (!second_cache_line)
       return dst_len - bytes_left;

     read_size = bytes_left;
     if (read_size > second_cache_line->GetByteSize())
       read_size = second_cache_line->GetByteSize();

     memcpy(dst_buf + dst_len - bytes_left, second_cache_line->GetBytes(),
            read_size);
     bytes_left -= read_size;

     return dst_len - bytes_left;
   }

   return dst_len;
 }

 AllocatedBlock::AllocatedBlock(lldb::addr_t addr, uint32_t byte_size,
                                uint32_t permissions, uint32_t chunk_size)
     : m_range(addr, byte_size), m_permissions(permissions),
       m_chunk_size(chunk_size)
 {
   // The entire address range is free to start with.
   m_free_blocks.Append(m_range);
   assert(byte_size > chunk_size);
 }

 AllocatedBlock::~AllocatedBlock() = default;

 lldb::addr_t AllocatedBlock::ReserveBlock(uint32_t size) {
   // We must return something valid for zero bytes.
   if (size == 0)
     size = 1;
   Log *log = GetLog(LLDBLog::Process);

   const size_t free_count = m_free_blocks.GetSize();
   for (size_t i=0; i<free_count; ++i)
   {
     auto &free_block = m_free_blocks.GetEntryRef(i);
     const lldb::addr_t range_size = free_block.GetByteSize();
     if (range_size >= size)
     {
       // We found a free block that is big enough for our data. Figure out how
       // many chunks we will need and calculate the resulting block size we
       // will reserve.
       addr_t addr = free_block.GetRangeBase();
       size_t num_chunks = CalculateChunksNeededForSize(size);
       lldb::addr_t block_size = num_chunks * m_chunk_size;
       lldb::addr_t bytes_left = range_size - block_size;
       if (bytes_left == 0)
       {
         // The newly allocated block will take all of the bytes in this
         // available block, so we can just add it to the allocated ranges and
         // remove the range from the free ranges.
         m_reserved_blocks.Insert(free_block, false);
         m_free_blocks.RemoveEntryAtIndex(i);
       }
       else
       {
         // Make the new allocated range and add it to the allocated ranges.
         Range<lldb::addr_t, uint32_t> reserved_block(free_block);
         reserved_block.SetByteSize(block_size);
         // Insert the reserved range and don't combine it with other blocks in
         // the reserved blocks list.
         m_reserved_blocks.Insert(reserved_block, false);
         // Adjust the free range in place since we won't change the sorted
         // ordering of the m_free_blocks list.
         free_block.SetRangeBase(reserved_block.GetRangeEnd());
         free_block.SetByteSize(bytes_left);
       }
       LLDB_LOGV(log, "({0}) (size = {1} ({1:x})) => {2:x}", this, size, addr);
       return addr;
     }
   }

   LLDB_LOGV(log, "({0}) (size = {1} ({1:x})) => {2:x}", this, size,
             LLDB_INVALID_ADDRESS);
   return LLDB_INVALID_ADDRESS;
 }

 bool AllocatedBlock::FreeBlock(addr_t addr) {
   bool success = false;
   auto entry_idx = m_reserved_blocks.FindEntryIndexThatContains(addr);
   if (entry_idx != UINT32_MAX)
   {
     m_free_blocks.Insert(m_reserved_blocks.GetEntryRef(entry_idx), true);
     m_reserved_blocks.RemoveEntryAtIndex(entry_idx);
     success = true;
   }
   Log *log = GetLog(LLDBLog::Process);
   LLDB_LOGV(log, "({0}) (addr = {1:x}) => {2}", this, addr, success);
   return success;
 }

 AllocatedMemoryCache::AllocatedMemoryCache(Process &process)
     : m_process(process), m_mutex(), m_memory_map() {}

 AllocatedMemoryCache::~AllocatedMemoryCache() = default;

 void AllocatedMemoryCache::Clear(bool deallocate_memory) {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);
   if (m_process.IsAlive() && deallocate_memory) {
     PermissionsToBlockMap::iterator pos, end = m_memory_map.end();
     for (pos = m_memory_map.begin(); pos != end; ++pos)
       m_process.DoDeallocateMemory(pos->second->GetBaseAddress());
   }
   m_memory_map.clear();
 }

 AllocatedMemoryCache::AllocatedBlockSP
 AllocatedMemoryCache::AllocatePage(uint32_t byte_size, uint32_t permissions,
                                    uint32_t chunk_size, Status &error) {
   AllocatedBlockSP block_sp;
   const size_t page_size = 4096;
   const size_t num_pages = (byte_size + page_size - 1) / page_size;
   const size_t page_byte_size = num_pages * page_size;

   addr_t addr = m_process.DoAllocateMemory(page_byte_size, permissions, error);

   Log *log = GetLog(LLDBLog::Process);
   if (log) {
     LLDB_LOGF(log,
               "Process::DoAllocateMemory (byte_size = 0x%8.8" PRIx32
               ", permissions = %s) => 0x%16.16" PRIx64,
               (uint32_t)page_byte_size, GetPermissionsAsCString(permissions),
               (uint64_t)addr);
   }

   if (addr != LLDB_INVALID_ADDRESS) {
     block_sp = std::make_shared<AllocatedBlock>(addr, page_byte_size,
                                                 permissions, chunk_size);
     m_memory_map.insert(std::make_pair(permissions, block_sp));
   }
   return block_sp;
 }

 lldb::addr_t AllocatedMemoryCache::AllocateMemory(size_t byte_size,
                                                   uint32_t permissions,
                                                   Status &error) {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);

   addr_t addr = LLDB_INVALID_ADDRESS;
   std::pair<PermissionsToBlockMap::iterator, PermissionsToBlockMap::iterator>
       range = m_memory_map.equal_range(permissions);

   for (PermissionsToBlockMap::iterator pos = range.first; pos != range.second;
        ++pos) {
     addr = (*pos).second->ReserveBlock(byte_size);
     if (addr != LLDB_INVALID_ADDRESS)
       break;
   }

   if (addr == LLDB_INVALID_ADDRESS) {
     AllocatedBlockSP block_sp(AllocatePage(byte_size, permissions, 16, error));

     if (block_sp)
       addr = block_sp->ReserveBlock(byte_size);
   }
   Log *log = GetLog(LLDBLog::Process);
   LLDB_LOGF(log,
             "AllocatedMemoryCache::AllocateMemory (byte_size = 0x%8.8" PRIx32
             ", permissions = %s) => 0x%16.16" PRIx64,
             (uint32_t)byte_size, GetPermissionsAsCString(permissions),
             (uint64_t)addr);
   return addr;
 }

 bool AllocatedMemoryCache::DeallocateMemory(lldb::addr_t addr) {
   std::lock_guard<std::recursive_mutex> guard(m_mutex);

   PermissionsToBlockMap::iterator pos, end = m_memory_map.end();
   bool success = false;
   for (pos = m_memory_map.begin(); pos != end; ++pos) {
     if (pos->second->Contains(addr)) {
       success = pos->second->FreeBlock(addr);
       break;
     }
   }
   Log *log = GetLog(LLDBLog::Process);
   LLDB_LOGF(log,
             "AllocatedMemoryCache::DeallocateMemory (addr = 0x%16.16" PRIx64
             ") => %i",
             (uint64_t)addr, success);
   return success;
 }
	//===-- Memory.cpp --------------------------------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#include "lldb/Target/Memory.h"
	#include "lldb/Target/Process.h"
	#include "lldb/Utility/DataBufferHeap.h"
	#include "lldb/Utility/LLDBLog.h"
	#include "lldb/Utility/Log.h"
	#include "lldb/Utility/RangeMap.h"
	#include "lldb/Utility/State.h"

	#include <cinttypes>
	#include <memory>

	using namespace lldb;
	using namespace lldb_private;

	// MemoryCache constructor
	MemoryCache::MemoryCache(Process &process)
	: m_mutex(), m_L1_cache(), m_L2_cache(), m_invalid_ranges(),
	m_process(process),
	m_L2_cache_line_byte_size(process.GetMemoryCacheLineSize()) {}

	// Destructor
	MemoryCache::~MemoryCache() = default;

	void MemoryCache::Clear(bool clear_invalid_ranges) {
	std::lock_guard<std::recursive_mutex> guard(m_mutex);
	m_L1_cache.clear();
	m_L2_cache.clear();
	if (clear_invalid_ranges)
	m_invalid_ranges.Clear();
	m_L2_cache_line_byte_size = m_process.GetMemoryCacheLineSize();
	}

	void MemoryCache::AddL1CacheData(lldb::addr_t addr, const void *src,
	size_t src_len) {
	AddL1CacheData(
	addr, DataBufferSP(new DataBufferHeap(DataBufferHeap(src, src_len))));
	}

	void MemoryCache::AddL1CacheData(lldb::addr_t addr,
	const DataBufferSP &data_buffer_sp) {
	std::lock_guard<std::recursive_mutex> guard(m_mutex);
	m_L1_cache[addr] = data_buffer_sp;
	}

	void MemoryCache::Flush(addr_t addr, size_t size) {
	if (size == 0)
	return;

	std::lock_guard<std::recursive_mutex> guard(m_mutex);

	// Erase any blocks from the L1 cache that intersect with the flush range
	if (!m_L1_cache.empty()) {
	AddrRange flush_range(addr, size);
	BlockMap::iterator pos = m_L1_cache.upper_bound(addr);
	if (pos != m_L1_cache.begin()) {
	--pos;
	}
	while (pos != m_L1_cache.end()) {
	AddrRange chunk_range(pos->first, pos->second->GetByteSize());
	if (!chunk_range.DoesIntersect(flush_range))
	break;
	pos = m_L1_cache.erase(pos);
	}
	}

	if (!m_L2_cache.empty()) {
	const uint32_t cache_line_byte_size = m_L2_cache_line_byte_size;
	const addr_t end_addr = (addr + size - 1);
	const addr_t first_cache_line_addr = addr - (addr % cache_line_byte_size);
	const addr_t last_cache_line_addr =
	end_addr - (end_addr % cache_line_byte_size);
	// Watch for overflow where size will cause us to go off the end of the
	// 64 bit address space
	uint32_t num_cache_lines;
	if (last_cache_line_addr >= first_cache_line_addr)
	num_cache_lines = ((last_cache_line_addr - first_cache_line_addr) /
	cache_line_byte_size) +
	1;
	else
	num_cache_lines =
	(UINT64_MAX - first_cache_line_addr + 1) / cache_line_byte_size;

	uint32_t cache_idx = 0;
	for (addr_t curr_addr = first_cache_line_addr; cache_idx < num_cache_lines;
	curr_addr += cache_line_byte_size, ++cache_idx) {
	BlockMap::iterator pos = m_L2_cache.find(curr_addr);
	if (pos != m_L2_cache.end())
	m_L2_cache.erase(pos);
	}
	}
	}

	void MemoryCache::AddInvalidRange(lldb::addr_t base_addr,
	lldb::addr_t byte_size) {
	if (byte_size > 0) {
	std::lock_guard<std::recursive_mutex> guard(m_mutex);
	InvalidRanges::Entry range(base_addr, byte_size);
	m_invalid_ranges.Append(range);
	m_invalid_ranges.Sort();
	}
	}

	bool MemoryCache::RemoveInvalidRange(lldb::addr_t base_addr,
	lldb::addr_t byte_size) {
	if (byte_size > 0) {
	std::lock_guard<std::recursive_mutex> guard(m_mutex);
	const uint32_t idx = m_invalid_ranges.FindEntryIndexThatContains(base_addr);
	if (idx != UINT32_MAX) {
	const InvalidRanges::Entry *entry = m_invalid_ranges.GetEntryAtIndex(idx);
	if (entry->GetRangeBase() == base_addr &&
	entry->GetByteSize() == byte_size)
	return m_invalid_ranges.RemoveEntryAtIndex(idx);
	}
	}
	return false;
	}

	lldb::DataBufferSP MemoryCache::GetL2CacheLine(lldb::addr_t line_base_addr,
	Status &error) {
	// This function assumes that the address given is aligned correctly.
	assert((line_base_addr % m_L2_cache_line_byte_size) == 0);

	std::lock_guard<std::recursive_mutex> guard(m_mutex);
	auto pos = m_L2_cache.find(line_base_addr);
	if (pos != m_L2_cache.end())
	return pos->second;

	auto data_buffer_heap_sp =
	std::make_shared<DataBufferHeap>(m_L2_cache_line_byte_size, 0);
	size_t process_bytes_read = m_process.ReadMemoryFromInferior(
	line_base_addr, data_buffer_heap_sp->GetBytes(),
	data_buffer_heap_sp->GetByteSize(), error);

	// If we failed a read, not much we can do.
	if (process_bytes_read == 0)
	return lldb::DataBufferSP();

	// If we didn't get a complete read, we can still cache what we did get.
	if (process_bytes_read < m_L2_cache_line_byte_size)
	data_buffer_heap_sp->SetByteSize(process_bytes_read);

	m_L2_cache[line_base_addr] = data_buffer_heap_sp;
	return data_buffer_heap_sp;
	}

	size_t MemoryCache::Read(addr_t addr, void *dst, size_t dst_len,
	Status &error) {
	if (!dst \|\| dst_len == 0)
	return 0;

	std::lock_guard<std::recursive_mutex> guard(m_mutex);
	// FIXME: We should do a more thorough check to make sure that we're not
	// overlapping with any invalid ranges (e.g. Read 0x100 - 0x200 but there's an
	// invalid range 0x180 - 0x280). `FindEntryThatContains` has an implementation
	// that takes a range, but it only checks to see if the argument is contained
	// by an existing invalid range. It cannot check if the argument contains
	// invalid ranges and cannot check for overlaps.
	if (m_invalid_ranges.FindEntryThatContains(addr)) {
	error = Status::FromErrorStringWithFormat(
	"memory read failed for 0x%" PRIx64, addr);
	return 0;
	}

	// Check the L1 cache for a range that contains the entire memory read.
	// L1 cache contains chunks of memory that are not required to be the size of
	// an L2 cache line. We avoid trying to do partial reads from the L1 cache to
	// simplify the implementation.
	if (!m_L1_cache.empty()) {
	AddrRange read_range(addr, dst_len);
	BlockMap::iterator pos = m_L1_cache.upper_bound(addr);
	if (pos != m_L1_cache.begin()) {
	--pos;
	}
	AddrRange chunk_range(pos->first, pos->second->GetByteSize());
	if (chunk_range.Contains(read_range)) {
	memcpy(dst, pos->second->GetBytes() + (addr - chunk_range.GetRangeBase()),
	dst_len);
	return dst_len;
	}
	}

	// If the size of the read is greater than the size of an L2 cache line, we'll
	// just read from the inferior. If that read is successful, we'll cache what
	// we read in the L1 cache for future use.
	if (dst_len > m_L2_cache_line_byte_size) {
	size_t bytes_read =
	m_process.ReadMemoryFromInferior(addr, dst, dst_len, error);
	if (bytes_read > 0)
	AddL1CacheData(addr, dst, bytes_read);
	return bytes_read;
	}

	// If the size of the read fits inside one L2 cache line, we'll try reading
	// from the L2 cache. Note that if the range of memory we're reading sits
	// between two contiguous cache lines, we'll touch two cache lines instead of
	// just one.

	// We're going to have all of our loads and reads be cache line aligned.
	addr_t cache_line_offset = addr % m_L2_cache_line_byte_size;
	addr_t cache_line_base_addr = addr - cache_line_offset;
	DataBufferSP first_cache_line = GetL2CacheLine(cache_line_base_addr, error);
	// If we get nothing, then the read to the inferior likely failed. Nothing to
	// do here.
	if (!first_cache_line)
	return 0;

	// If the cache line was not filled out completely and the offset is greater
	// than what we have available, we can't do anything further here.
	if (cache_line_offset >= first_cache_line->GetByteSize())
	return 0;

	uint8_t dst_buf = (uint8_t )dst;
	size_t bytes_left = dst_len;
	size_t read_size = first_cache_line->GetByteSize() - cache_line_offset;
	if (read_size > bytes_left)
	read_size = bytes_left;

	memcpy(dst_buf + dst_len - bytes_left,
	first_cache_line->GetBytes() + cache_line_offset, read_size);
	bytes_left -= read_size;

	// If the cache line was not filled out completely and we still have data to
	// read, we can't do anything further.
	if (first_cache_line->GetByteSize() < m_L2_cache_line_byte_size &&
	bytes_left > 0)
	return dst_len - bytes_left;

	// We'll hit this scenario if our read straddles two cache lines.
	if (bytes_left > 0) {
	cache_line_base_addr += m_L2_cache_line_byte_size;

	// FIXME: Until we are able to more thoroughly check for invalid ranges, we
	// will have to check the second line to see if it is in an invalid range as
	// well. See the check near the beginning of the function for more details.
	if (m_invalid_ranges.FindEntryThatContains(cache_line_base_addr)) {
	error = Status::FromErrorStringWithFormat(
	"memory read failed for 0x%" PRIx64, cache_line_base_addr);
	return dst_len - bytes_left;
	}

	DataBufferSP second_cache_line =
	GetL2CacheLine(cache_line_base_addr, error);
	if (!second_cache_line)
	return dst_len - bytes_left;

	read_size = bytes_left;
	if (read_size > second_cache_line->GetByteSize())
	read_size = second_cache_line->GetByteSize();

	memcpy(dst_buf + dst_len - bytes_left, second_cache_line->GetBytes(),
	read_size);
	bytes_left -= read_size;

	return dst_len - bytes_left;
	}

	return dst_len;
	}

	AllocatedBlock::AllocatedBlock(lldb::addr_t addr, uint32_t byte_size,
	uint32_t permissions, uint32_t chunk_size)
	: m_range(addr, byte_size), m_permissions(permissions),
	m_chunk_size(chunk_size)
	{
	// The entire address range is free to start with.
	m_free_blocks.Append(m_range);
	assert(byte_size > chunk_size);
	}

	AllocatedBlock::~AllocatedBlock() = default;

	lldb::addr_t AllocatedBlock::ReserveBlock(uint32_t size) {
	// We must return something valid for zero bytes.
	if (size == 0)
	size = 1;
	Log *log = GetLog(LLDBLog::Process);

	const size_t free_count = m_free_blocks.GetSize();
	for (size_t i=0; i<free_count; ++i)
	{
	auto &free_block = m_free_blocks.GetEntryRef(i);
	const lldb::addr_t range_size = free_block.GetByteSize();
	if (range_size >= size)
	{
	// We found a free block that is big enough for our data. Figure out how
	// many chunks we will need and calculate the resulting block size we
	// will reserve.
	addr_t addr = free_block.GetRangeBase();
	size_t num_chunks = CalculateChunksNeededForSize(size);
	lldb::addr_t block_size = num_chunks * m_chunk_size;
	lldb::addr_t bytes_left = range_size - block_size;
	if (bytes_left == 0)
	{
	// The newly allocated block will take all of the bytes in this
	// available block, so we can just add it to the allocated ranges and
	// remove the range from the free ranges.
	m_reserved_blocks.Insert(free_block, false);
	m_free_blocks.RemoveEntryAtIndex(i);
	}
	else
	{
	// Make the new allocated range and add it to the allocated ranges.
	Range<lldb::addr_t, uint32_t> reserved_block(free_block);
	reserved_block.SetByteSize(block_size);
	// Insert the reserved range and don't combine it with other blocks in
	// the reserved blocks list.
	m_reserved_blocks.Insert(reserved_block, false);
	// Adjust the free range in place since we won't change the sorted
	// ordering of the m_free_blocks list.
	free_block.SetRangeBase(reserved_block.GetRangeEnd());
	free_block.SetByteSize(bytes_left);
	}
	LLDB_LOGV(log, "({0}) (size = {1} ({1:x})) => {2:x}", this, size, addr);
	return addr;
	}
	}

	LLDB_LOGV(log, "({0}) (size = {1} ({1:x})) => {2:x}", this, size,
	LLDB_INVALID_ADDRESS);
	return LLDB_INVALID_ADDRESS;
	}

	bool AllocatedBlock::FreeBlock(addr_t addr) {
	bool success = false;
	auto entry_idx = m_reserved_blocks.FindEntryIndexThatContains(addr);
	if (entry_idx != UINT32_MAX)
	{
	m_free_blocks.Insert(m_reserved_blocks.GetEntryRef(entry_idx), true);
	m_reserved_blocks.RemoveEntryAtIndex(entry_idx);
	success = true;
	}
	Log *log = GetLog(LLDBLog::Process);
	LLDB_LOGV(log, "({0}) (addr = {1:x}) => {2}", this, addr, success);
	return success;
	}

	AllocatedMemoryCache::AllocatedMemoryCache(Process &process)
	: m_process(process), m_mutex(), m_memory_map() {}

	AllocatedMemoryCache::~AllocatedMemoryCache() = default;

	void AllocatedMemoryCache::Clear(bool deallocate_memory) {
	std::lock_guard<std::recursive_mutex> guard(m_mutex);
	if (m_process.IsAlive() && deallocate_memory) {
	PermissionsToBlockMap::iterator pos, end = m_memory_map.end();
	for (pos = m_memory_map.begin(); pos != end; ++pos)
	m_process.DoDeallocateMemory(pos->second->GetBaseAddress());
	}
	m_memory_map.clear();
	}

	AllocatedMemoryCache::AllocatedBlockSP
	AllocatedMemoryCache::AllocatePage(uint32_t byte_size, uint32_t permissions,
	uint32_t chunk_size, Status &error) {
	AllocatedBlockSP block_sp;
	const size_t page_size = 4096;
	const size_t num_pages = (byte_size + page_size - 1) / page_size;
	const size_t page_byte_size = num_pages * page_size;

	addr_t addr = m_process.DoAllocateMemory(page_byte_size, permissions, error);

	Log *log = GetLog(LLDBLog::Process);
	if (log) {
	LLDB_LOGF(log,
	"Process::DoAllocateMemory (byte_size = 0x%8.8" PRIx32
	", permissions = %s) => 0x%16.16" PRIx64,
	(uint32_t)page_byte_size, GetPermissionsAsCString(permissions),
	(uint64_t)addr);
	}

	if (addr != LLDB_INVALID_ADDRESS) {
	block_sp = std::make_shared<AllocatedBlock>(addr, page_byte_size,
	permissions, chunk_size);
	m_memory_map.insert(std::make_pair(permissions, block_sp));
	}
	return block_sp;
	}

	lldb::addr_t AllocatedMemoryCache::AllocateMemory(size_t byte_size,
	uint32_t permissions,
	Status &error) {
	std::lock_guard<std::recursive_mutex> guard(m_mutex);

	addr_t addr = LLDB_INVALID_ADDRESS;
	std::pair<PermissionsToBlockMap::iterator, PermissionsToBlockMap::iterator>
	range = m_memory_map.equal_range(permissions);

	for (PermissionsToBlockMap::iterator pos = range.first; pos != range.second;
	++pos) {
	addr = (*pos).second->ReserveBlock(byte_size);
	if (addr != LLDB_INVALID_ADDRESS)
	break;
	}

	if (addr == LLDB_INVALID_ADDRESS) {
	AllocatedBlockSP block_sp(AllocatePage(byte_size, permissions, 16, error));

	if (block_sp)
	addr = block_sp->ReserveBlock(byte_size);
	}
	Log *log = GetLog(LLDBLog::Process);
	LLDB_LOGF(log,
	"AllocatedMemoryCache::AllocateMemory (byte_size = 0x%8.8" PRIx32
	", permissions = %s) => 0x%16.16" PRIx64,
	(uint32_t)byte_size, GetPermissionsAsCString(permissions),
	(uint64_t)addr);
	return addr;
	}

	bool AllocatedMemoryCache::DeallocateMemory(lldb::addr_t addr) {
	std::lock_guard<std::recursive_mutex> guard(m_mutex);

	PermissionsToBlockMap::iterator pos, end = m_memory_map.end();
	bool success = false;
	for (pos = m_memory_map.begin(); pos != end; ++pos) {
	if (pos->second->Contains(addr)) {
	success = pos->second->FreeBlock(addr);
	break;
	}
	}
	Log *log = GetLog(LLDBLog::Process);
	LLDB_LOGF(log,
	"AllocatedMemoryCache::DeallocateMemory (addr = 0x%16.16" PRIx64
	") => %i",
	(uint64_t)addr, success);
	return success;
	}