Define DbiStreamBuilder::addSectionMap.

[ruiu]

Summary

This change enables LLD to construct a Section Map stream in a PDB file.
I do not understand all these fields in the Section Map yet, but it seems
like a copy of a COFF section header in another format.

With this patch, DbiStreamBuilder can emit a Section Map which
llvm-pdbdump can dump.

[zturner]

lib/DebugInfo/PDB/Raw/DbiStreamBuilder.cpp

283 ↗

(On Diff #76288)

winnt.h defines this value IMAGE_SCN_TYPE_GROUP but it is commented out and says "Reserved". I wonder if that is the same as OMFSegDescFlags::Group. You don't have to add this, just something to think about.

308–309 ↗

(On Diff #76288)

Can you use UINT16_MAX?

[ruiu]

lib/DebugInfo/PDB/Raw/DbiStreamBuilder.cpp

308–309 ↗

(On Diff #76288)

Done.

llvm/trunk/include/llvm/DebugInfo/PDB/Raw/DbiStreamBuilder.h

 #include "llvm/DebugInfo/PDB/Raw/PDBFile.h"
 #include "llvm/DebugInfo/PDB/Raw/RawConstants.h"
 #include "llvm/Support/Endian.h"
 
 namespace llvm {
 namespace msf {
 class MSFBuilder;
 }
+namespace object {
+struct coff_section;
+}
 namespace pdb {
 class DbiStream;
 struct DbiStreamHeader;
 class PDBFile;
 
 class DbiStreamBuilder {
 public:
   DbiStreamBuilder(msf::MSFBuilder &Msf);
 
   DbiStreamBuilder(const DbiStreamBuilder &) = delete;
   DbiStreamBuilder &operator=(const DbiStreamBuilder &) = delete;
 
   void setVersionHeader(PdbRaw_DbiVer V);
   void setAge(uint32_t A);
   void setBuildNumber(uint16_t B);
   void setPdbDllVersion(uint16_t V);
   void setPdbDllRbld(uint16_t R);
   void setFlags(uint16_t F);
   void setMachineType(PDB_Machine M);
+  void setSectionMap(ArrayRef<SecMapEntry> SecMap);
 
   // Add given bytes as a new stream.
   Error addDbgStream(pdb::DbgHeaderType Type, ArrayRef<uint8_t> Data);
 
   uint32_t calculateSerializedLength() const;
 
   Error addModuleInfo(StringRef ObjFile, StringRef Module);
   Error addModuleSourceFile(StringRef Module, StringRef File);
 
   Error finalizeMsfLayout();
 
   Expected<std::unique_ptr<DbiStream>> build(PDBFile &File,
                                              const msf::WritableStream &Buffer);
   Error commit(const msf::MSFLayout &Layout,
                const msf::WritableStream &Buffer);
 
+  // A helper function to create a Section Map from a COFF section header.
+  static std::vector<SecMapEntry>
+  createSectionMap(ArrayRef<llvm::object::coff_section> SecHdrs);
+
 private:
   struct DebugStream {
     ArrayRef<uint8_t> Data;
     uint16_t StreamNumber = 0;
   };
 
   Error finalize();
   uint32_t calculateModiSubstreamSize() const;
+  uint32_t calculateSectionMapStreamSize() const;
   uint32_t calculateFileInfoSubstreamSize() const;
   uint32_t calculateNamesBufferSize() const;
   uint32_t calculateDbgStreamsSize() const;
 
   Error generateModiSubstream();
   Error generateFileInfoSubstream();
 
   struct ModuleInfo {
private:
   StringMap<std::unique_ptr<ModuleInfo>> ModuleInfos;
   std::vector<ModuleInfo *> ModuleInfoList;
 
   StringMap<uint32_t> SourceFileNames;
 
   msf::WritableStreamRef NamesBuffer;
   msf::MutableByteStream ModInfoBuffer;
   msf::MutableByteStream FileInfoBuffer;
+  ArrayRef<SecMapEntry> SectionMap;
   llvm::SmallVector<DebugStream, (int)DbgHeaderType::Max> DbgStreams;
 };
 }
 }
 
 #endif

llvm/trunk/lib/DebugInfo/PDB/Raw/DbiStreamBuilder.cpp

 #include "llvm/DebugInfo/PDB/Raw/DbiStreamBuilder.h"
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/DebugInfo/MSF/MSFBuilder.h"
 #include "llvm/DebugInfo/MSF/MappedBlockStream.h"
 #include "llvm/DebugInfo/MSF/StreamWriter.h"
 #include "llvm/DebugInfo/PDB/Raw/DbiStream.h"
 #include "llvm/DebugInfo/PDB/Raw/RawError.h"
+#include "llvm/Object/COFF.h"
+#include "llvm/Support/COFF.h"
 
 using namespace llvm;
 using namespace llvm::codeview;
 using namespace llvm::msf;
 using namespace llvm::pdb;
 
 namespace {
 class ModiSubstreamBuilder {};

 void DbiStreamBuilder::setPdbDllVersion(uint16_t V) { PdbDllVersion = V; }
 
 void DbiStreamBuilder::setPdbDllRbld(uint16_t R) { PdbDllRbld = R; }
 
 void DbiStreamBuilder::setFlags(uint16_t F) { Flags = F; }
 
 void DbiStreamBuilder::setMachineType(PDB_Machine M) { MachineType = M; }
 
+void DbiStreamBuilder::setSectionMap(ArrayRef<SecMapEntry> SecMap) {
+  SectionMap = SecMap;
+}
+
 Error DbiStreamBuilder::addDbgStream(pdb::DbgHeaderType Type,
                                      ArrayRef<uint8_t> Data) {
   if (DbgStreams[(int)Type].StreamNumber)
     return make_error<RawError>(raw_error_code::duplicate_entry,
                                 "The specified stream type already exists");
   auto ExpectedIndex = Msf.addStream(Data.size());
   if (!ExpectedIndex)
     return ExpectedIndex.takeError();
   uint32_t Index = std::move(*ExpectedIndex);
   DbgStreams[(int)Type].Data = Data;
   DbgStreams[(int)Type].StreamNumber = Index;
   return Error::success();
 }
 
 uint32_t DbiStreamBuilder::calculateSerializedLength() const {
   // For now we only support serializing the header.
   return sizeof(DbiStreamHeader) + calculateFileInfoSubstreamSize() +
-         calculateModiSubstreamSize() + calculateDbgStreamsSize();
+         calculateModiSubstreamSize() + calculateSectionMapStreamSize() +
+         calculateDbgStreamsSize();
 }
 
 Error DbiStreamBuilder::addModuleInfo(StringRef ObjFile, StringRef Module) {
   auto Entry = llvm::make_unique<ModuleInfo>();
   ModuleInfo *M = Entry.get();
   Entry->Mod = Module;
   Entry->Obj = ObjFile;
   auto Result = ModuleInfos.insert(std::make_pair(Module, std::move(Entry)));
uint32_t DbiStreamBuilder::calculateModiSubstreamSize() const {
   for (const auto &M : ModuleInfoList) {
     Size += sizeof(ModuleInfoHeader);
     Size += M->Mod.size() + 1;
     Size += M->Obj.size() + 1;
   }
   return Size;
 }
 
+uint32_t DbiStreamBuilder::calculateSectionMapStreamSize() const {
+  if (SectionMap.empty())
+    return 0;
+  return sizeof(SecMapHeader) + sizeof(SecMapEntry) * SectionMap.size();
+}
+
 uint32_t DbiStreamBuilder::calculateFileInfoSubstreamSize() const {
   uint32_t Size = 0;
   Size += sizeof(ulittle16_t);                         // NumModules
   Size += sizeof(ulittle16_t);                         // NumSourceFiles
   Size += ModuleInfoList.size() * sizeof(ulittle16_t); // ModIndices
   Size += ModuleInfoList.size() * sizeof(ulittle16_t); // ModFileCounts
   uint32_t NumFileInfos = 0;
   for (const auto &M : ModuleInfoList)
Error DbiStreamBuilder::finalize() {
   H->PdbDllVersion = PdbDllVersion;
   H->MachineType = static_cast<uint16_t>(MachineType);
 
   H->ECSubstreamSize = 0;
   H->FileInfoSize = FileInfoBuffer.getLength();
   H->ModiSubstreamSize = ModInfoBuffer.getLength();
   H->OptionalDbgHdrSize = DbgStreams.size() * sizeof(uint16_t);
   H->SecContrSubstreamSize = 0;
-  H->SectionMapSize = 0;
+  H->SectionMapSize = calculateSectionMapStreamSize();
   H->TypeServerSize = 0;
   H->SymRecordStreamIndex = kInvalidStreamIndex;
   H->PublicSymbolStreamIndex = kInvalidStreamIndex;
   H->MFCTypeServerIndex = kInvalidStreamIndex;
   H->GlobalSymbolStreamIndex = kInvalidStreamIndex;
 
   Header = H;
   return Error::success();
 }
 
 Error DbiStreamBuilder::finalizeMsfLayout() {
   uint32_t Length = calculateSerializedLength();
   if (auto EC = Msf.setStreamSize(StreamDBI, Length))
     return EC;
   return Error::success();
 }
 
+static uint16_t toSecMapFlags(uint32_t Flags) {
+  uint16_t Ret = 0;
+  if (Flags & COFF::IMAGE_SCN_MEM_READ)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Read);
+  if (Flags & COFF::IMAGE_SCN_MEM_WRITE)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Write);
+  if (Flags & COFF::IMAGE_SCN_MEM_EXECUTE)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Execute);
+  if (Flags & COFF::IMAGE_SCN_MEM_EXECUTE)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Execute);
+  if (!(Flags & COFF::IMAGE_SCN_MEM_16BIT))
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::AddressIs32Bit);
+
+  // This seems always 1.
+  Ret |= static_cast<uint16_t>(OMFSegDescFlags::IsSelector);
+
+  return Ret;
+}
+
+// A utility function to create a Section Map for a given list of COFF sections.
+//
+// A Section Map seem to be a copy of a COFF section list in other format.
+// I don't know why a PDB file contains both a COFF section header and
+// a Section Map, but it seems it must be present in a PDB.
+std::vector<SecMapEntry> DbiStreamBuilder::createSectionMap(
+    ArrayRef<llvm::object::coff_section> SecHdrs) {
+  std::vector<SecMapEntry> Ret;
+  int Idx = 0;
+
+  auto Add = [&]() -> SecMapEntry & {
+    Ret.emplace_back();
+    auto &Entry = Ret.back();
+    memset(&Entry, 0, sizeof(Entry));
+
+    Entry.Frame = Idx + 1;
+
+    // We don't know the meaning of these fields yet.
+    Entry.SecName = UINT16_MAX;
+    Entry.ClassName = UINT16_MAX;
+
+    return Entry;
+  };
+
+  for (auto &Hdr : SecHdrs) {
+    auto &Entry = Add();
+    Entry.Flags = toSecMapFlags(Hdr.Characteristics);
+    Entry.SecByteLength = Hdr.VirtualSize;
+    ++Idx;
+  }
+
+  // The last entry is for absolute symbols.
+  auto &Entry = Add();
+  Entry.Flags = static_cast<uint16_t>(OMFSegDescFlags::AddressIs32Bit) |
+                static_cast<uint16_t>(OMFSegDescFlags::IsAbsoluteAddress);
+  Entry.SecByteLength = UINT32_MAX;
+
+  return Ret;
+}
+
 Expected<std::unique_ptr<DbiStream>>
 DbiStreamBuilder::build(PDBFile &File, const msf::WritableStream &Buffer) {
   if (!VerHeader.hasValue())
     return make_error<RawError>(raw_error_code::unspecified,
                                 "Missing DBI Stream Version");
   if (auto EC = finalize())
     return std::move(EC);
 
auto InfoS =
       WritableMappedBlockStream::createIndexedStream(Layout, Buffer, StreamDBI);
 
   StreamWriter Writer(*InfoS);
   if (auto EC = Writer.writeObject(*Header))
     return EC;
 
   if (auto EC = Writer.writeStreamRef(ModInfoBuffer))
     return EC;
+
+  if (!SectionMap.empty()) {
+    ulittle16_t Size = static_cast<ulittle16_t>(SectionMap.size());
+    SecMapHeader SMHeader = {Size, Size};
+    if (auto EC = Writer.writeObject(SMHeader))
+      return EC;
+    if (auto EC = Writer.writeArray(SectionMap))
+      return EC;
+  }
+
   if (auto EC = Writer.writeStreamRef(FileInfoBuffer))
     return EC;
+
   for (auto &Stream : DbgStreams)
     if (auto EC = Writer.writeInteger(Stream.StreamNumber))
       return EC;
 
   for (auto &Stream : DbgStreams) {
     if (Stream.StreamNumber == kInvalidStreamIndex)
       continue;
     auto WritableStream = WritableMappedBlockStream::createIndexedStream(