llvm-readobj: Add support for dumping the DOS header in PE files

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221333 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Object/COFF.h

@@ -36,7 +36,7 @@ typedef content_iterator<ImportedSymbolRef> imported_symbol_iterator;
 
 /// The DOS compatible header at the front of all PE/COFF executables.
 struct dos_header {
-  support::ulittle16_t Magic;
+  char                 Magic[2];
   support::ulittle16_t UsedBytesInTheLastPage;
   support::ulittle16_t FileSizeInPages;
   support::ulittle16_t NumberOfRelocationItems;
@@ -621,6 +621,11 @@ public:
       delay_import_directories() const;
   iterator_range<export_directory_iterator> export_directories() const;
 
+  const dos_header *getDOSHeader() const {
+    if (!PE32Header && !PE32PlusHeader)
+      return nullptr;
+    return reinterpret_cast<const dos_header *>(base());
+  }
   std::error_code getPE32Header(const pe32_header *&Res) const;
   std::error_code getPE32PlusHeader(const pe32plus_header *&Res) const;
   std::error_code getDataDirectory(uint32_t index,

lib/Object/COFFObjectFile.cpp

@@ -572,20 +572,20 @@ COFFObjectFile::COFFObjectFile(MemoryBufferRef Object, std::error_code &EC)
   bool HasPEHeader = false;
 
   // Check if this is a PE/COFF file.
-  if (base()[0] == 0x4d && base()[1] == 0x5a) {
+  if (checkSize(Data, EC, sizeof(dos_header) + sizeof(COFF::PEMagic))) {
     // PE/COFF, seek through MS-DOS compatibility stub and 4-byte
     // PE signature to find 'normal' COFF header.
-    if (!checkSize(Data, EC, 0x3c + 8))
-      return;
-    CurPtr = *reinterpret_cast<const ulittle16_t *>(base() + 0x3c);
-    // Check the PE magic bytes. ("PE\0\0")
-    if (std::memcmp(base() + CurPtr, COFF::PEMagic, sizeof(COFF::PEMagic)) !=
-        0) {
-      EC = object_error::parse_failed;
-      return;
+    const auto *DH = reinterpret_cast<const dos_header *>(base());
+    if (DH->Magic[0] == 'M' && DH->Magic[1] == 'Z') {
+      CurPtr = DH->AddressOfNewExeHeader;
+      // Check the PE magic bytes. ("PE\0\0")
+      if (memcmp(base() + CurPtr, COFF::PEMagic, sizeof(COFF::PEMagic)) != 0) {
+        EC = object_error::parse_failed;
+        return;
+      }
+      CurPtr += sizeof(COFF::PEMagic); // Skip the PE magic bytes.
+      HasPEHeader = true;
     }
-    CurPtr += sizeof(COFF::PEMagic); // Skip the PE magic bytes.
-    HasPEHeader = true;
   }
 
   if ((EC = getObject(COFFHeader, Data, base() + CurPtr)))
@@ -627,11 +627,11 @@ COFFObjectFile::COFFObjectFile(MemoryBufferRef Object, std::error_code &EC)
 
     const uint8_t *DataDirAddr;
     uint64_t DataDirSize;
-    if (Header->Magic == 0x10b) {
+    if (Header->Magic == COFF::PE32Header::PE32) {
       PE32Header = Header;
       DataDirAddr = base() + CurPtr + sizeof(pe32_header);
       DataDirSize = sizeof(data_directory) * PE32Header->NumberOfRvaAndSize;
-    } else if (Header->Magic == 0x20b) {
+    } else if (Header->Magic == COFF::PE32Header::PE32_PLUS) {
       PE32PlusHeader = reinterpret_cast<const pe32plus_header *>(Header);
       DataDirAddr = base() + CurPtr + sizeof(pe32plus_header);
       DataDirSize = sizeof(data_directory) * PE32PlusHeader->NumberOfRvaAndSize;

lib/Support/Path.cpp

@@ -1020,12 +1020,13 @@ file_magic identify_magic(StringRef Magic) {
         return file_magic::coff_object;
       break;
 
-    case 0x4d: // Possible MS-DOS stub on Windows PE file
-      if (Magic[1] == 0x5a) {
+    case 'M': // Possible MS-DOS stub on Windows PE file
+      if (Magic[1] == 'Z') {
         uint32_t off =
           *reinterpret_cast<const support::ulittle32_t*>(Magic.data() + 0x3c);
         // PE/COFF file, either EXE or DLL.
-        if (off < Magic.size() && memcmp(Magic.data() + off, "PE\0\0",4) == 0)
+        if (off < Magic.size() &&
+            memcmp(Magic.data()+off, COFF::PEMagic, sizeof(COFF::PEMagic)) == 0)
           return file_magic::pecoff_executable;
       }
       break;

test/tools/llvm-readobj/file-headers.test

@@ -204,6 +204,25 @@ PE32-NEXT:     ReservedRVA: 0x0
 PE32-NEXT:     ReservedSize: 0x0
 PE32-NEXT:   }
 PE32-NEXT: }
+PE32-NEXT: DOSHeader {
+PE32-NEXT:   Magic: MZ
+PE32-NEXT:   UsedBytesInTheLastPage: 144
+PE32-NEXT:   FileSizeInPages: 3
+PE32-NEXT:   NumberOfRelocationItems: 0
+PE32-NEXT:   HeaderSizeInParagraphs: 4
+PE32-NEXT:   MinimumExtraParagraphs: 0
+PE32-NEXT:   MaximumExtraParagraphs: 65535
+PE32-NEXT:   InitialRelativeSS: 0
+PE32-NEXT:   InitialSP: 184
+PE32-NEXT:   Checksum: 0
+PE32-NEXT:   InitialIP: 0
+PE32-NEXT:   InitialRelativeCS: 0
+PE32-NEXT:   AddressOfRelocationTable: 64
+PE32-NEXT:   OverlayNumber: 0
+PE32-NEXT:   OEMid: 0
+PE32-NEXT:   OEMinfo: 0
+PE32-NEXT:   AddressOfNewExeHeader: 176
+PE32-NEXT: }
 
 COFF-UNKNOWN:      Format: COFF-<unknown arch>
 COFF-UNKNOWN-NEXT: Arch: unknown

tools/llvm-readobj/COFFDumper.cpp

@@ -63,6 +63,7 @@ private:
   void printRelocation(const SectionRef &Section, const RelocationRef &Reloc);
   void printDataDirectory(uint32_t Index, const std::string &FieldName);
 
+  void printDOSHeader(const dos_header *DH);
   template <class PEHeader> void printPEHeader(const PEHeader *Hdr);
   void printBaseOfDataField(const pe32_header *Hdr);
   void printBaseOfDataField(const pe32plus_header *Hdr);
@@ -382,6 +383,30 @@ void COFFDumper::printFileHeaders() {
     return;
   if (PEPlusHeader)
     printPEHeader<pe32plus_header>(PEPlusHeader);
+
+  if (const dos_header *DH = Obj->getDOSHeader())
+    printDOSHeader(DH);
+}
+
+void COFFDumper::printDOSHeader(const dos_header *DH) {
+  DictScope D(W, "DOSHeader");
+  W.printString("Magic", StringRef(DH->Magic, sizeof(DH->Magic)));
+  W.printNumber("UsedBytesInTheLastPage", DH->UsedBytesInTheLastPage);
+  W.printNumber("FileSizeInPages", DH->FileSizeInPages);
+  W.printNumber("NumberOfRelocationItems", DH->NumberOfRelocationItems);
+  W.printNumber("HeaderSizeInParagraphs", DH->HeaderSizeInParagraphs);
+  W.printNumber("MinimumExtraParagraphs", DH->MinimumExtraParagraphs);
+  W.printNumber("MaximumExtraParagraphs", DH->MaximumExtraParagraphs);
+  W.printNumber("InitialRelativeSS", DH->InitialRelativeSS);
+  W.printNumber("InitialSP", DH->InitialSP);
+  W.printNumber("Checksum", DH->Checksum);
+  W.printNumber("InitialIP", DH->InitialIP);
+  W.printNumber("InitialRelativeCS", DH->InitialRelativeCS);
+  W.printNumber("AddressOfRelocationTable", DH->AddressOfRelocationTable);
+  W.printNumber("OverlayNumber", DH->OverlayNumber);
+  W.printNumber("OEMid", DH->OEMid);
+  W.printNumber("OEMinfo", DH->OEMinfo);
+  W.printNumber("AddressOfNewExeHeader", DH->AddressOfNewExeHeader);
 }
 
 template <class PEHeader>