Support empty stream, remove magic bytes

Author: Jlalond

lldb/source/Plugins/ObjectFile/Minidump/MinidumpFileBuilder.cpp

@@ -132,12 +132,7 @@ Status MinidumpFileBuilder::AddDirectory(StreamType type,
 Status MinidumpFileBuilder::AddLLDBGeneratedStream() {
   Status error;
   StreamType type = StreamType::LLDBGenerated;
-  error = AddDirectory(type, sizeof(StreamType));
-  if (error.Fail())
-    return error;
-
-  error = AddData(&type, sizeof(StreamType));
-  return error;
+  return AddDirectory(type, 0);
 }
 
 Status MinidumpFileBuilder::AddSystemInfo() {

lldb/source/Plugins/Process/minidump/MinidumpParser.cpp

@@ -49,6 +49,10 @@ llvm::ArrayRef<uint8_t> MinidumpParser::GetStream(StreamType stream_type) {
   return m_file->getRawStream(stream_type).value_or(llvm::ArrayRef<uint8_t>());
 }
 
+std::optional<llvm::ArrayRef<uint8_t>> MinidumpParser::GetRawStream(StreamType stream_type) {
+  return m_file->getRawStream(stream_type);
+}
+
 UUID MinidumpParser::GetModuleUUID(const minidump::Module *module) {
   auto cv_record =
       GetData().slice(module->CvRecord.RVA, module->CvRecord.DataSize);

lldb/source/Plugins/Process/minidump/MinidumpParser.h

@@ -59,6 +59,7 @@ class MinidumpParser {
   llvm::ArrayRef<uint8_t> GetData();
 
   llvm::ArrayRef<uint8_t> GetStream(StreamType stream_type);
+  std::optional<llvm::ArrayRef<uint8_t>> GetRawStream(StreamType stream_type);
 
   UUID GetModuleUUID(const minidump::Module *module);
 

lldb/source/Plugins/Process/minidump/ProcessMinidump.cpp

@@ -355,28 +355,12 @@ DataExtractor ProcessMinidump::GetAuxvData() {
 }
 
 bool ProcessMinidump::IsLLDBMinidump() {
-  // If we've already checked, return the cached value
-  if (m_is_lldb_generated.has_value())
-    return *m_is_lldb_generated;
-
-  // If the minidump doesn't have a LLDBGeneratedStream, it's not an LLDB
-  // We also check to see if the section was generated correctly, but not
-  // enforcing an exact size so we can change it in the future without
-  // impacting older generated Minidumps.
-  llvm::ArrayRef<uint8_t> lldbStream =
-      m_minidump_parser->GetStream(StreamType::LLDBGenerated);
-  if (lldbStream.empty() || lldbStream.size() <= sizeof(StreamType)) {
-    m_is_lldb_generated = false;
-    return false;
-  }
-
-  const uint32_t *lldbStreamType =
-      reinterpret_cast<const uint32_t *>(lldbStream.data());
-
-  m_is_lldb_generated = *lldbStreamType == (uint32_t)StreamType::LLDBGenerated;
-  return *m_is_lldb_generated;
+  std::optional<llvm::ArrayRef<uint8_t>> lldb_generated_section =
+      m_minidump_parser->GetRawStream(StreamType::LLDBGenerated);
+  return lldb_generated_section.has_value();
 }
 
+
 DynamicLoader *ProcessMinidump::GetDynamicLoader() {
   // This is a workaround for the dynamic loader not playing nice in issue
   // #119598. The specific reason we use the dynamic loader is to get the TLS

lldb/source/Plugins/Process/minidump/ProcessMinidump.h

@@ -76,8 +76,8 @@ class ProcessMinidump : public PostMortemProcess {
 
   ArchSpec GetArchitecture();
 
-  Status GetMemoryRegions(
-      lldb_private::MemoryRegionInfos &region_list) override;
+  Status
+  GetMemoryRegions(lldb_private::MemoryRegionInfos &region_list) override;
 
   bool GetProcessInfo(ProcessInstanceInfo &info) override;
 
@@ -106,7 +106,6 @@ class ProcessMinidump : public PostMortemProcess {
   JITLoaderList &GetJITLoaders() override;
 
 private:
-  std::optional<bool> m_is_lldb_generated;
   lldb::DataBufferSP m_core_data;
   llvm::ArrayRef<minidump::Thread> m_thread_list;
   std::unordered_map<uint32_t, const minidump::ExceptionStream>

llvm/include/llvm/BinaryFormat/Minidump.h

@@ -52,7 +52,6 @@ enum class StreamType : uint32_t {
 #include "llvm/BinaryFormat/MinidumpConstants.def"
   Unused = 0,
   LastReserved = 0x0000ffff,
-  LLDBGenerated = 0x4C4C4442, // ASCII for 'LLDB'
 };
 
 /// Specifies the location (and size) of various objects in the minidump file.

llvm/include/llvm/BinaryFormat/MinidumpConstants.def

@@ -85,6 +85,10 @@ HANDLE_MDMP_STREAM_TYPE(0xFACECCCC, FacebookAppStateLog)
 HANDLE_MDMP_STREAM_TYPE(0xFACEDEAD, FacebookAbortReason)
 HANDLE_MDMP_STREAM_TYPE(0xFACEE000, FacebookThreadName)
 
+// LLDB specific stream types
+// Ascii for 'LLDB'
+HANDLE_MDMP_STREAM_TYPE(0x4C4C4442, LLDBGenerated)
+
 HANDLE_MDMP_ARCH(0x0000, X86)       // PROCESSOR_ARCHITECTURE_INTEL
 HANDLE_MDMP_ARCH(0x0001, MIPS)      // PROCESSOR_ARCHITECTURE_MIPS
 HANDLE_MDMP_ARCH(0x0002, Alpha)     // PROCESSOR_ARCHITECTURE_ALPHA