1 //===-- DataFileCache.cpp -------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "lldb/Core/DataFileCache.h"
10 #include "lldb/Core/Module.h"
11 #include "lldb/Core/ModuleList.h"
12 #include "lldb/Host/FileSystem.h"
13 #include "lldb/Symbol/ObjectFile.h"
14 #include "lldb/Utility/DataEncoder.h"
15 #include "lldb/Utility/LLDBLog.h"
16 #include "lldb/Utility/Log.h"
17 #include "llvm/Support/CachePruning.h"
18 
19 using namespace lldb_private;
20 
21 
22 llvm::CachePruningPolicy DataFileCache::GetLLDBIndexCachePolicy() {
23   static llvm::CachePruningPolicy policy;
24   static llvm::once_flag once_flag;
25 
26   llvm::call_once(once_flag, []() {
27     // Prune the cache based off of the LLDB settings each time we create a
28     // cache object.
29     ModuleListProperties &properties =
30         ModuleList::GetGlobalModuleListProperties();
31     // Only scan once an hour. If we have lots of debug sessions we don't want
32     // to scan this directory too often. A timestamp file is written to the
33     // directory to ensure different processes don't scan the directory too
34     // often. This setting doesn't mean that a thread will continually scan the
35     // cache directory within this process.
36     policy.Interval = std::chrono::hours(1);
37     // Get the user settings for pruning.
38     policy.MaxSizeBytes = properties.GetLLDBIndexCacheMaxByteSize();
39     policy.MaxSizePercentageOfAvailableSpace =
40         properties.GetLLDBIndexCacheMaxPercent();
41     policy.Expiration =
42         std::chrono::hours(properties.GetLLDBIndexCacheExpirationDays() * 24);
43   });
44   return policy;
45 }
46 
47 DataFileCache::DataFileCache(llvm::StringRef path, llvm::CachePruningPolicy policy) {
48   m_cache_dir.SetPath(path);
49   pruneCache(path, policy);
50 
51   // This lambda will get called when the data is gotten from the cache and
52   // also after the data was set for a given key. We only need to take
53   // ownership of the data if we are geting the data, so we use the
54   // m_take_ownership member variable to indicate if we need to take
55   // ownership.
56 
57   auto add_buffer = [this](unsigned task, const llvm::Twine &moduleName,
58                            std::unique_ptr<llvm::MemoryBuffer> m) {
59     if (m_take_ownership)
60       m_mem_buff_up = std::move(m);
61   };
62   llvm::Expected<llvm::FileCache> cache_or_err =
63       llvm::localCache("LLDBModuleCache", "lldb-module", path, add_buffer);
64   if (cache_or_err)
65     m_cache_callback = std::move(*cache_or_err);
66   else {
67     Log *log = GetLog(LLDBLog::Modules);
68     LLDB_LOG_ERROR(log, cache_or_err.takeError(),
69                    "failed to create lldb index cache directory: {0}");
70   }
71 }
72 
73 std::unique_ptr<llvm::MemoryBuffer>
74 DataFileCache::GetCachedData(llvm::StringRef key) {
75   std::lock_guard<std::mutex> guard(m_mutex);
76 
77   const unsigned task = 1;
78   m_take_ownership = true;
79   // If we call the "m_cache_callback" function and the data is cached, it will
80   // call the "add_buffer" lambda function from the constructor which will in
81   // turn take ownership of the member buffer that is passed to the callback and
82   // put it into a member variable.
83   llvm::Expected<llvm::AddStreamFn> add_stream_or_err =
84       m_cache_callback(task, key, "");
85   m_take_ownership = false;
86   // At this point we either already called the "add_buffer" lambda with
87   // the data or we haven't. We can tell if we got the cached data by checking
88   // the add_stream function pointer value below.
89   if (add_stream_or_err) {
90     llvm::AddStreamFn &add_stream = *add_stream_or_err;
91     // If the "add_stream" is nullptr, then the data was cached and we already
92     // called the "add_buffer" lambda. If it is valid, then if we were to call
93     // the add_stream function it would cause a cache file to get generated
94     // and we would be expected to fill in the data. In this function we only
95     // want to check if the data was cached, so we don't want to call
96     // "add_stream" in this function.
97     if (!add_stream)
98       return std::move(m_mem_buff_up);
99   } else {
100     Log *log = GetLog(LLDBLog::Modules);
101     LLDB_LOG_ERROR(log, add_stream_or_err.takeError(),
102                    "failed to get the cache add stream callback for key: {0}");
103   }
104   // Data was not cached.
105   return std::unique_ptr<llvm::MemoryBuffer>();
106 }
107 
108 bool DataFileCache::SetCachedData(llvm::StringRef key,
109                                   llvm::ArrayRef<uint8_t> data) {
110   std::lock_guard<std::mutex> guard(m_mutex);
111   const unsigned task = 2;
112   // If we call this function and the data is cached, it will call the
113   // add_buffer lambda function from the constructor which will ignore the
114   // data.
115   llvm::Expected<llvm::AddStreamFn> add_stream_or_err =
116       m_cache_callback(task, key, "");
117   // If we reach this code then we either already called the callback with
118   // the data or we haven't. We can tell if we had the cached data by checking
119   // the CacheAddStream function pointer value below.
120   if (add_stream_or_err) {
121     llvm::AddStreamFn &add_stream = *add_stream_or_err;
122     // If the "add_stream" is nullptr, then the data was cached. If it is
123     // valid, then if we call the add_stream function with a task it will
124     // cause the file to get generated, but we only want to check if the data
125     // is cached here, so we don't want to call it here. Note that the
126     // add_buffer will also get called in this case after the data has been
127     // provided, but we won't take ownership of the memory buffer as we just
128     // want to write the data.
129     if (add_stream) {
130       llvm::Expected<std::unique_ptr<llvm::CachedFileStream>> file_or_err =
131           add_stream(task, "");
132       if (file_or_err) {
133         llvm::CachedFileStream *cfs = file_or_err->get();
134         cfs->OS->write((const char *)data.data(), data.size());
135         return true;
136       } else {
137         Log *log = GetLog(LLDBLog::Modules);
138         LLDB_LOG_ERROR(log, file_or_err.takeError(),
139                        "failed to get the cache file stream for key: {0}");
140       }
141     }
142   } else {
143     Log *log = GetLog(LLDBLog::Modules);
144     LLDB_LOG_ERROR(log, add_stream_or_err.takeError(),
145                    "failed to get the cache add stream callback for key: {0}");
146   }
147   return false;
148 }
149 
150 FileSpec DataFileCache::GetCacheFilePath(llvm::StringRef key) {
151   FileSpec cache_file(m_cache_dir);
152   std::string filename("llvmcache-");
153   filename += key.str();
154   cache_file.AppendPathComponent(filename);
155   return cache_file;
156 }
157 
158 Status DataFileCache::RemoveCacheFile(llvm::StringRef key) {
159   FileSpec cache_file = GetCacheFilePath(key);
160   FileSystem &fs = FileSystem::Instance();
161   if (!fs.Exists(cache_file))
162     return Status();
163   return fs.RemoveFile(cache_file);
164 }
165 
166 CacheSignature::CacheSignature(lldb_private::Module *module) {
167   Clear();
168   UUID uuid = module->GetUUID();
169   if (uuid.IsValid())
170     m_uuid = uuid;
171 
172   std::time_t mod_time = 0;
173   mod_time = llvm::sys::toTimeT(module->GetModificationTime());
174   if (mod_time != 0)
175     m_mod_time = mod_time;
176 
177   mod_time = llvm::sys::toTimeT(module->GetObjectModificationTime());
178   if (mod_time != 0)
179     m_obj_mod_time = mod_time;
180 }
181 
182 CacheSignature::CacheSignature(lldb_private::ObjectFile *objfile) {
183   Clear();
184   UUID uuid = objfile->GetUUID();
185   if (uuid.IsValid())
186     m_uuid = uuid;
187 
188   std::time_t mod_time = 0;
189   // Grab the modification time of the object file's file. It isn't always the
190   // same as the module's file when you have a executable file as the main
191   // executable, and you have a object file for a symbol file.
192   FileSystem &fs = FileSystem::Instance();
193   mod_time = llvm::sys::toTimeT(fs.GetModificationTime(objfile->GetFileSpec()));
194   if (mod_time != 0)
195     m_mod_time = mod_time;
196 
197   mod_time =
198       llvm::sys::toTimeT(objfile->GetModule()->GetObjectModificationTime());
199   if (mod_time != 0)
200     m_obj_mod_time = mod_time;
201 }
202 
203 enum SignatureEncoding {
204   eSignatureUUID = 1u,
205   eSignatureModTime = 2u,
206   eSignatureObjectModTime = 3u,
207   eSignatureEnd = 255u,
208 };
209 
210 bool CacheSignature::Encode(DataEncoder &encoder) const {
211   if (!IsValid())
212     return false; // Invalid signature, return false!
213 
214   if (m_uuid) {
215     llvm::ArrayRef<uint8_t> uuid_bytes = m_uuid->GetBytes();
216     encoder.AppendU8(eSignatureUUID);
217     encoder.AppendU8(uuid_bytes.size());
218     encoder.AppendData(uuid_bytes);
219   }
220   if (m_mod_time) {
221     encoder.AppendU8(eSignatureModTime);
222     encoder.AppendU32(*m_mod_time);
223   }
224   if (m_obj_mod_time) {
225     encoder.AppendU8(eSignatureObjectModTime);
226     encoder.AppendU32(*m_obj_mod_time);
227   }
228   encoder.AppendU8(eSignatureEnd);
229   return true;
230 }
231 
232 bool CacheSignature::Decode(const lldb_private::DataExtractor &data,
233                             lldb::offset_t *offset_ptr) {
234   Clear();
235   while (uint8_t sig_encoding = data.GetU8(offset_ptr)) {
236     switch (sig_encoding) {
237     case eSignatureUUID: {
238       const uint8_t length = data.GetU8(offset_ptr);
239       const uint8_t *bytes = (const uint8_t *)data.GetData(offset_ptr, length);
240       if (bytes != nullptr && length > 0)
241         m_uuid = UUID(llvm::ArrayRef<uint8_t>(bytes, length));
242     } break;
243     case eSignatureModTime: {
244       uint32_t mod_time = data.GetU32(offset_ptr);
245       if (mod_time > 0)
246         m_mod_time = mod_time;
247     } break;
248     case eSignatureObjectModTime: {
249       uint32_t mod_time = data.GetU32(offset_ptr);
250       if (mod_time > 0)
251         m_obj_mod_time = mod_time;
252     } break;
253     case eSignatureEnd:
254       // The definition of is valid changed to only be valid if the UUID is
255       // valid so make sure that if we attempt to decode an old cache file
256       // that we will fail to decode the cache file if the signature isn't
257       // considered valid.
258       return IsValid();
259     default:
260       break;
261     }
262   }
263   return false;
264 }
265 
266 uint32_t ConstStringTable::Add(ConstString s) {
267   auto pos = m_string_to_offset.find(s);
268   if (pos != m_string_to_offset.end())
269     return pos->second;
270   const uint32_t offset = m_next_offset;
271   m_strings.push_back(s);
272   m_string_to_offset[s] = offset;
273   m_next_offset += s.GetLength() + 1;
274   return offset;
275 }
276 
277 static const llvm::StringRef kStringTableIdentifier("STAB");
278 
279 bool ConstStringTable::Encode(DataEncoder &encoder) {
280   // Write an 4 character code into the stream. This will help us when decoding
281   // to make sure we find this identifier when decoding the string table to make
282   // sure we have the rigth data. It also helps to identify the string table
283   // when dumping the hex bytes in a cache file.
284   encoder.AppendData(kStringTableIdentifier);
285   size_t length_offset = encoder.GetByteSize();
286   encoder.AppendU32(0); // Total length of all strings which will be fixed up.
287   size_t strtab_offset = encoder.GetByteSize();
288   encoder.AppendU8(0); // Start the string table with with an empty string.
289   for (auto s: m_strings) {
290     // Make sure all of the offsets match up with what we handed out!
291     assert(m_string_to_offset.find(s)->second ==
292            encoder.GetByteSize() - strtab_offset);
293     // Append the C string into the encoder
294     encoder.AppendCString(s.GetStringRef());
295   }
296   // Fixup the string table length.
297   encoder.PutU32(length_offset, encoder.GetByteSize() - strtab_offset);
298   return true;
299 }
300 
301 bool StringTableReader::Decode(const lldb_private::DataExtractor &data,
302                                lldb::offset_t *offset_ptr) {
303   llvm::StringRef identifier((const char *)data.GetData(offset_ptr, 4), 4);
304   if (identifier != kStringTableIdentifier)
305     return false;
306   const uint32_t length = data.GetU32(offset_ptr);
307   // We always have at least one byte for the empty string at offset zero.
308   if (length == 0)
309     return false;
310   const char *bytes = (const char *)data.GetData(offset_ptr, length);
311   if (bytes == nullptr)
312     return false;
313   m_data = llvm::StringRef(bytes, length);
314   return true;
315 }
316 
317 llvm::StringRef StringTableReader::Get(uint32_t offset) const {
318   if (offset >= m_data.size())
319     return llvm::StringRef();
320   return llvm::StringRef(m_data.data() + offset);
321 }
322 
323