[llvm-readobj][XCOFF] Add support for printing the String Table.

Summary: The patch adds the StringTable dumping to
llvm-readobj. Currently only XCOFF is supported.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D104613

Author: Esme-Yi

llvm/docs/CommandGuide/llvm-readobj.rst

@@ -123,6 +123,10 @@ file formats.
  Display the specified section(s) as a list of strings. ``section`` may be a
  section index or section name.
 
+.. option:: --string-table
+ 
+ Display contents of the string table.
+
 .. option:: --symbols, --syms, -s
 
  Display the symbol table.

llvm/include/llvm/Object/XCOFFObjectFile.h

@@ -424,6 +424,9 @@ class XCOFFObjectFile : public ObjectFile {
   // This function returns string table entry.
   Expected<StringRef> getStringTableEntry(uint32_t Offset) const;
 
+  // This function returns the string table.
+  StringRef getStringTable() const;
+
   const XCOFF::SymbolAuxType *getSymbolAuxType(uintptr_t AuxEntryAddress) const;
 
   static uintptr_t getAdvancedSymbolEntryAddress(uintptr_t CurrentAddress,

llvm/lib/Object/XCOFFObjectFile.cpp

@@ -187,6 +187,10 @@ XCOFFObjectFile::getStringTableEntry(uint32_t Offset) const {
                                         object_error::parse_failed);
 }
 
+StringRef XCOFFObjectFile::getStringTable() const {
+  return StringRef(StringTable.Data, StringTable.Size);
+}
+
 Expected<StringRef>
 XCOFFObjectFile::getCFileName(const XCOFFFileAuxEnt *CFileEntPtr) const {
   if (CFileEntPtr->NameInStrTbl.Magic != XCOFFSymbolRef::NAME_IN_STR_TBL_MAGIC)

llvm/test/tools/yaml2obj/XCOFF/long-symbol-name.yaml

@@ -1,7 +1,8 @@
 ## Test that the string table works well for long symbol names.
-## TODO: Dump the raw string table and check the contents.
 # RUN: yaml2obj %s -o %t
-# RUN: llvm-readobj --symbols %t | FileCheck %s
+# RUN: llvm-readobj --symbols --string-table %t | FileCheck %s
+
+## FIXME: The first item of StringTable should be `[     4]   .longname`.
 
 # CHECK:      AddressSize: 32bit
 # CHECK-NEXT: Symbols [
@@ -24,6 +25,9 @@
 # CHECK-NEXT:     NumberOfAuxEntries: 0
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]
+# CHECK-NEXT: StringTable {
+# CHECK-NEXT:   [     3]   ..longname
+# CHECK-NEXT: }
 
 --- !XCOFF
 FileHeader:

llvm/tools/llvm-readobj/ObjDumper.cpp

@@ -52,6 +52,25 @@ static void printAsPrintable(raw_ostream &W, const uint8_t *Start, size_t Len) {
     W << (isPrint(Start[i]) ? static_cast<char>(Start[i]) : '.');
 }
 
+void ObjDumper::printAsStringList(StringRef StringContent) {
+  const uint8_t *StrContent = StringContent.bytes_begin();
+  const uint8_t *CurrentWord = StrContent;
+  const uint8_t *StrEnd = StringContent.bytes_end();
+
+  while (CurrentWord <= StrEnd) {
+    size_t WordSize = strnlen(reinterpret_cast<const char *>(CurrentWord),
+                              StrEnd - CurrentWord);
+    if (!WordSize) {
+      CurrentWord++;
+      continue;
+    }
+    W.startLine() << format("[%6tx] ", CurrentWord - StrContent);
+    printAsPrintable(W.startLine(), CurrentWord, WordSize);
+    W.startLine() << '\n';
+    CurrentWord += WordSize + 1;
+  }
+}
+
 static std::vector<object::SectionRef>
 getSectionRefsByNameOrIndex(const object::ObjectFile &Obj,
                             ArrayRef<std::string> Sections) {
@@ -109,23 +128,7 @@ void ObjDumper::printSectionsAsString(const object::ObjectFile &Obj,
 
     StringRef SectionContent =
         unwrapOrError(Obj.getFileName(), Section.getContents());
-
-    const uint8_t *SecContent = SectionContent.bytes_begin();
-    const uint8_t *CurrentWord = SecContent;
-    const uint8_t *SecEnd = SectionContent.bytes_end();
-
-    while (CurrentWord <= SecEnd) {
-      size_t WordSize = strnlen(reinterpret_cast<const char *>(CurrentWord),
-                                SecEnd - CurrentWord);
-      if (!WordSize) {
-        CurrentWord++;
-        continue;
-      }
-      W.startLine() << format("[%6tx] ", CurrentWord - SecContent);
-      printAsPrintable(W.startLine(), CurrentWord, WordSize);
-      W.startLine() << '\n';
-      CurrentWord += WordSize + 1;
-    }
+    printAsStringList(SectionContent);
   }
 }
 

llvm/tools/llvm-readobj/ObjDumper.h

@@ -105,8 +105,13 @@ class ObjDumper {
   virtual void printMachOIndirectSymbols() { }
   virtual void printMachOLinkerOptions() { }
 
+  // Currently only implemented for XCOFF.
+  virtual void printStringTable() { }
+
   virtual void printStackMap() const = 0;
 
+  void printAsStringList(StringRef StringContent);
+
   void printSectionsAsString(const object::ObjectFile &Obj,
                              ArrayRef<std::string> Sections);
   void printSectionsAsHex(const object::ObjectFile &Obj,

llvm/tools/llvm-readobj/XCOFFDumper.cpp

@@ -34,6 +34,7 @@ class XCOFFDumper : public ObjDumper {
   void printUnwindInfo() override;
   void printStackMap() const override;
   void printNeededLibraries() override;
+  void printStringTable() override;
 
 private:
   template <typename T> void printSectionHeaders(ArrayRef<T> Sections);
@@ -456,6 +457,12 @@ void XCOFFDumper::printSymbols() {
     printSymbol(S);
 }
 
+void XCOFFDumper::printStringTable() {
+  DictScope DS(W, "StringTable");
+  StringRef StrTable = Obj.getStringTable();
+  printAsStringList(StrTable);
+}
+
 void XCOFFDumper::printDynamicSymbols() {
   llvm_unreachable("Unimplemented functionality for XCOFFDumper");
 }

llvm/tools/llvm-readobj/llvm-readobj.cpp

@@ -206,6 +206,11 @@ namespace opts {
                             cl::aliasopt(StringDump), cl::Prefix,
                             cl::NotHidden);
 
+  // --string-table
+  cl::opt<bool>
+      StringTable("string-table",
+                  cl::desc("Display the string table (only for XCOFF now)"));
+
   // --hex-dump, -x
   cl::list<std::string>
       HexDump("hex-dump", cl::value_desc("number|name"),
@@ -541,6 +546,8 @@ static void dumpObject(ObjectFile &Obj, ScopedPrinter &Writer,
     Dumper->printGnuHashTable();
   if (opts::VersionInfo)
     Dumper->printVersionInfo();
+  if (opts::StringTable)
+    Dumper->printStringTable();
   if (Obj.isELF()) {
     if (opts::DependentLibraries)
       Dumper->printDependentLibs();