[COFF] Expose the PE debug data directory and dump it

This directory is used to find if there is a PDB associated with an
executable. I plan to use this functionality to teach llvm-symbolizer
whether it should use DIA or DWARF to symbolize a given DLL.

Reviewers: majnemer

Differential Revision: http://reviews.llvm.org/D20885

llvm-svn: 271539

llvm/lib/Object/COFFObjectFile.cpp

@@ -453,6 +453,27 @@ std::error_code COFFObjectFile::getRvaPtr(uint32_t Addr, uintptr_t &Res) const {
   return object_error::parse_failed;
 }
 
+std::error_code
+COFFObjectFile::getRvaAndSizeAsBytes(uint32_t RVA, uint32_t Size,
+                                     ArrayRef<uint8_t> &Contents) const {
+  for (const SectionRef &S : sections()) {
+    const coff_section *Section = getCOFFSection(S);
+    uint32_t SectionStart = Section->VirtualAddress;
+    // Check if this RVA is within the section bounds. Be careful about integer
+    // overflow.
+    uint32_t OffsetIntoSection = RVA - SectionStart;
+    if (SectionStart <= RVA && OffsetIntoSection < Section->VirtualSize &&
+        Size <= Section->VirtualSize - OffsetIntoSection) {
+      uintptr_t Begin =
+          uintptr_t(base()) + Section->PointerToRawData + OffsetIntoSection;
+      Contents =
+          ArrayRef<uint8_t>(reinterpret_cast<const uint8_t *>(Begin), Size);
+      return std::error_code();
+    }
+  }
+  return object_error::parse_failed;
+}
+
 // Returns hint and name fields, assuming \p Rva is pointing to a Hint/Name
 // table entry.
 std::error_code COFFObjectFile::getHintName(uint32_t Rva, uint16_t &Hint,
@@ -466,6 +487,24 @@ std::error_code COFFObjectFile::getHintName(uint32_t Rva, uint16_t &Hint,
   return std::error_code();
 }
 
+std::error_code COFFObjectFile::getDebugPDBInfo(const debug_directory *DebugDir,
+                                                const debug_pdb_info *&PDBInfo,
+                                                StringRef &PDBFileName) const {
+  ArrayRef<uint8_t> InfoBytes;
+  if (std::error_code EC = getRvaAndSizeAsBytes(
+          DebugDir->AddressOfRawData, DebugDir->SizeOfData, InfoBytes))
+    return EC;
+  if (InfoBytes.size() < sizeof(debug_pdb_info) + 1)
+    return object_error::parse_failed;
+  PDBInfo = reinterpret_cast<const debug_pdb_info *>(InfoBytes.data());
+  InfoBytes = InfoBytes.drop_front(sizeof(debug_pdb_info));
+  PDBFileName = StringRef(reinterpret_cast<const char *>(InfoBytes.data()),
+                          InfoBytes.size());
+  // Truncate the name at the first null byte. Ignore any padding.
+  PDBFileName = PDBFileName.split('\0').first;
+  return std::error_code();
+}
+
 // Find the import table.
 std::error_code COFFObjectFile::initImportTablePtr() {
   // First, we get the RVA of the import table. If the file lacks a pointer to
@@ -551,6 +590,31 @@ std::error_code COFFObjectFile::initBaseRelocPtr() {
   return std::error_code();
 }
 
+std::error_code COFFObjectFile::initDebugDirectoryPtr() {
+  // Get the RVA of the debug directory. Do nothing if it does not exist.
+  const data_directory *DataEntry;
+  if (getDataDirectory(COFF::DEBUG_DIRECTORY, DataEntry))
+    return std::error_code();
+
+  // Do nothing if the RVA is NULL.
+  if (DataEntry->RelativeVirtualAddress == 0)
+    return std::error_code();
+
+  // Check that the size is a multiple of the entry size.
+  if (DataEntry->Size % sizeof(debug_directory) != 0)
+    return object_error::parse_failed;
+
+  uintptr_t IntPtr = 0;
+  if (std::error_code EC = getRvaPtr(DataEntry->RelativeVirtualAddress, IntPtr))
+    return EC;
+  DebugDirectoryBegin = reinterpret_cast<const debug_directory *>(IntPtr);
+  if (std::error_code EC = getRvaPtr(
+          DataEntry->RelativeVirtualAddress + DataEntry->Size, IntPtr))
+    return EC;
+  DebugDirectoryEnd = reinterpret_cast<const debug_directory *>(IntPtr);
+  return std::error_code();
+}
+
 COFFObjectFile::COFFObjectFile(MemoryBufferRef Object, std::error_code &EC)
     : ObjectFile(Binary::ID_COFF, Object), COFFHeader(nullptr),
       COFFBigObjHeader(nullptr), PE32Header(nullptr), PE32PlusHeader(nullptr),
@@ -558,8 +622,8 @@ COFFObjectFile::COFFObjectFile(MemoryBufferRef Object, std::error_code &EC)
       SymbolTable32(nullptr), StringTable(nullptr), StringTableSize(0),
       ImportDirectory(nullptr), NumberOfImportDirectory(0),
       DelayImportDirectory(nullptr), NumberOfDelayImportDirectory(0),
-      ExportDirectory(nullptr), BaseRelocHeader(nullptr),
-      BaseRelocEnd(nullptr) {
+      ExportDirectory(nullptr), BaseRelocHeader(nullptr), BaseRelocEnd(nullptr),
+      DebugDirectoryBegin(nullptr), DebugDirectoryEnd(nullptr) {
   // Check that we at least have enough room for a header.
   if (!checkSize(Data, EC, sizeof(coff_file_header)))
     return;
@@ -675,6 +739,10 @@ COFFObjectFile::COFFObjectFile(MemoryBufferRef Object, std::error_code &EC)
   if ((EC = initBaseRelocPtr()))
     return;
 
+  // Initialize the pointer to the export table.
+  if ((EC = initDebugDirectoryPtr()))
+    return;
+
   EC = std::error_code();
 }