[llvm-readelf]Revert --dyn-symbols behaviour to make it GNU compatible, and add new --hash-symbols switch for old behaviour

[jhenderson]

Summary

In rL287786, the behaviour of --dyn-symbols in llvm-readelf (but not llvm-readobj) was changed to print the dynamic symbols as derived from the hash table, rather than to print the dynamic symbol table contents directly. The original change was initially submitted without review, and some comments were made on the commit mailing list implying that the new behavious is GNU compatible. I argue that it is not:

• It does not include a null symbol.
• It prints the symbols based on an order derived from the hash table.
• It prints an extra column indicating which bucket it came from. This could break parsers that expect a fixed number of columns, with the first column being the symbol index.
• If the input happens to have both .hash and .gnu.hash section, it prints interpretations of them both, resulting in most symbols being printed twice.
• There is no way of just printing the raw dynamic symbol table, because --symbols also prints the static symbol table.

This patch reverts the --dyn-symbols behaviour back to its old behaviour of just printing the contents of the dynamic symbol table, similar to what is printed by --symbols. As the hashed interpretation is still desirable to validate the hash table, it puts it under a new switch "--hash-symbols". This is a no-op on all output forms except for GNU output style for ELF. If there is no hash table, it does nothing, unlike the previous behaviour which printed the raw dynamic symbol table, since the raw dynsym is available under --dyn-symbols.

The yaml input for the test is based on that in test/tools/llvm-readobj/demangle.test, but stripped down to the bare minimum to provide a valid dynamic symbol.

Note: some LLD tests needed updating. I will put up a separate review for those.

[rupprecht]

The patch description seems reasonable to me

[grimar]

Patch looks reasonable to me too.

test/tools/llvm-readobj/gnu-symbols.test

3 ↗

(On Diff #182512)

nit: seems you changed --elf-output-style to -elf-output-style. That made more lines to be shown
as changes for probably no solid reason? I would commit such changes as NFC separately if you want them.

[jhenderson]

test/tools/llvm-readobj/gnu-symbols.test

3 ↗

(On Diff #182512)

It's mostly just to make things consistent. I'll commit separately.

llvm/trunk/test/tools/llvm-readobj/gnu-hash-symbols.test

+# RUN: llvm-readelf --hash-symbols %p/Inputs/dynamic-table-exe.x86 \
+# RUN:   | FileCheck %s --check-prefix HASH
+
+# HASH:     Symbol table of .hash for image:
+# HASH-NEXT:   Num Buc:    Value  Size   Type   Bind Vis      Ndx Name
+# HASH-NEXT:     9   0: 00000000     0 FUNC    GLOBAL DEFAULT UND __gxx_personality_v0@CXXABI_1.3
+# HASH-NEXT:    13   0: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS _edata{{$}}
+# HASH-NEXT:     7   0: 00000000     0 FUNC    GLOBAL DEFAULT UND _ZNSt14basic_ifstreamIcSt11char_traitsIcEEC1EPKcSt13_Ios_Openmode@GLIBCXX_3.4
+# HASH-NEXT:     2   0: 00000000     0 NOTYPE  WEAK   DEFAULT UND _Jv_RegisterClasses{{$}}
+# HASH-NEXT:     1   0: 00000000     0 NOTYPE  WEAK   DEFAULT UND __gmon_start__{{$}}
+# HASH-NEXT:    16   1: 00000850    81 FUNC    GLOBAL DEFAULT  14 main{{$}}
+# HASH-NEXT:    10   1: 00000000     0 FUNC    GLOBAL DEFAULT UND _Unwind_Resume@GCC_3.0
+# HASH-NEXT:     8   1: 00000000     0 FUNC    GLOBAL DEFAULT UND puts@GLIBC_2.0
+# HASH-NEXT:    12   1: 00001b68     0 NOTYPE  GLOBAL DEFAULT ABS _end{{$}}
+# HASH-NEXT:     6   1: 00000000     0 FUNC    GLOBAL DEFAULT UND _ZNSt14basic_ifstreamIcSt11char_traitsIcEED1Ev@GLIBCXX_3.4
+# HASH-NEXT:     5   1: 00000000     0 NOTYPE  WEAK   DEFAULT UND _ITM_registerTMCloneTable{{$}}
+# HASH-NEXT:     4   1: 00000000     0 NOTYPE  WEAK   DEFAULT UND _ITM_deregisterTMCloneTable{{$}}
+# HASH-NEXT:     3   1: 00000000     0 FUNC    GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.0
+# HASH-NEXT:    11   2: 00000000     0 FUNC    WEAK   DEFAULT UND __cxa_finalize@GLIBC_2.1.3
+# HASH-NEXT:    15   2: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS __bss_start{{$}}
+# HASH-NEXT:    14   2: 0000093c     4 OBJECT  GLOBAL DEFAULT  16 _IO_stdin_used{{$}}
+# HASH:     Symbol table of .gnu.hash for image:
+# HASH-NEXT:   Num Buc:    Value  Size   Type   Bind Vis      Ndx Name
+# HASH-NEXT:    12   0: 00001b68     0 NOTYPE  GLOBAL DEFAULT ABS _end{{$}}
+# HASH-NEXT:    13   0: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS _edata{{$}}
+# HASH-NEXT:    14   1: 0000093c     4 OBJECT  GLOBAL DEFAULT  16 _IO_stdin_used{{$}}
+# HASH-NEXT:    15   1: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS __bss_start{{$}}
+# HASH-NEXT:    16   1: 00000850    81 FUNC    GLOBAL DEFAULT  14 main{{$}}
+
+## Show that if there are no hash sections, we do not print anything.
+# RUN: yaml2obj %s -o %t.o
+# RUN: llvm-readelf --hash-symbols %t.o \
+# RUN:   | FileCheck %s --check-prefix NO-HASH --allow-empty
+
+# NO-HASH-NOT: {{.}}
+
+## Sanity check that we can still find the dynamic symbols (i.e. the above test
+## doesn't pass due to a mistake in the dynamic section).
+# RUN: llvm-readelf --dyn-symbols %t.o | FileCheck %s --check-prefix DYNSYMS
+
+# DYNSYMS: Symbol table '.dynsym' contains 2 entries:
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_DYN
+  Machine:         EM_X86_64
+Sections:
+  ## TODO:  Replace the raw section contents with more meaningful dynamic
+  ## tags/symbols/etc, once yaml2obj supports it.
+  ## FIXME: yaml2obj does not currently allow custom addresses for .dynstr and
+  ## .dynsym if DynamicSymbols are specified.
+  ## See https://bugs.llvm.org/show_bug.cgi?id=40339
+  - Name:         .dynstr
+    Type:         SHT_STRTAB
+    Flags:        [ SHF_ALLOC ]
+    AddressAlign: 0x100
+    EntSize:      0x1
+    ## "\0_Z3fooi\0"
+    Content: "005f5a33666f6f6900"
+  - Name:         .dynsym
+    Type:         SHT_DYNSYM
+    Flags:        [ SHF_ALLOC ]
+    Link:         .dynstr
+    Info:         1
+    Address:      0x100
+    AddressAlign: 0x100
+    EntSize:      0x18
+    ## Null symbol;
+    ## st_name: 1; st_info: Global | Func; st_other: 0;
+    ##   st_shndx: .text.foo; st_value: 0x2000; st_size: 0
+    Content: "000000000000000000000000000000000000000000000000010000001200040000200000000000000000000000000000"
+  - Name:         .dynamic
+    Type:         SHT_DYNAMIC
+    Flags:        [ SHF_ALLOC ]
+    Link:         .dynstr
+    Address:      0x1000
+    AddressAlign: 0x1000
+    ## DT_STRTAB  - 0x0
+    ## DT_STRSZ   - 0x9
+    ## DT_SYMTAB  - 0x100
+    ## DT_SYMENT  - 0x18
+    ## DT_NULL    - 0x0
+    Content: "050000000000000000000000000000000a000000000000000900000000000000060000000000000000010000000000000b00000000000000180000000000000000000000000000000000000000000000"
+  - Name:  .text.foo
+    Type:  SHT_PROGBITS
+    Flags: [ SHF_ALLOC, SHF_EXECINSTR, SHF_GROUP ]
+    Size:  0x40
+    Address: 0x2000
+    AddressAlign: 0x2000
+ProgramHeaders:
+  - Type:  PT_LOAD
+    Flags: [ PF_R, PF_X ]
+    VAddr: 0x0
+    PAddr: 0x0
+    Sections:
+      - Section: .dynsym
+      - Section: .dynstr
+      - Section: .dynamic
+      - Section: .text.foo
+  - Type:  PT_DYNAMIC
+    Flags: [ PF_R ]
+    VAddr: 0x1000
+    PAddr: 0x1000
+    Sections:
+      - Section: .dynamic

llvm/trunk/test/tools/llvm-readobj/gnu-symbols.test

 RUN: llvm-readobj -symbols %p/Inputs/symbols-proc-specific.elf-hexagon \
 RUN:  --elf-output-style=GNU | FileCheck %s -check-prefix ELF32
 RUN: llvm-readobj -symbols %p/Inputs/relocs.obj.elf-x86_64 --elf-output-style=GNU \
 RUN:   | FileCheck %s -check-prefix ELF64
 RUN: llvm-readobj -symbols %p/Inputs/gnuhash.so.elf-x86_64 --elf-output-style=GNU \
-RUN:   | FileCheck %s -check-prefix DYN
-RUN: llvm-readobj -dyn-symbols %p/Inputs/dynamic-table-exe.x86 --elf-output-style=GNU \
-RUN:   | FileCheck %s -check-prefix HASH
+RUN:   | FileCheck %s -check-prefixes=SYMTAB,DYN
+RUN: llvm-readobj -dyn-symbols %p/Inputs/gnuhash.so.elf-x86_64 --elf-output-style=GNU \
+RUN:   | FileCheck %s -check-prefixes=NO-SYMTAB,DYN
 
 ELF32: Symbol table '.symtab' contains 5 entries:
 ELF32-NEXT:    Num:    Value  Size Type    Bind   Vis      Ndx Name
 ELF32-NEXT:      0: 00000000     0 NOTYPE  LOCAL  DEFAULT  UND
 ELF32-NEXT:      1: 00000000     0 FILE    LOCAL  DEFAULT  ABS a.c
 ELF32-NEXT:      2: 00000000    20 FUNC    GLOBAL DEFAULT    2 main
 ELF32-NEXT:      3: 00000004     4 OBJECT  GLOBAL DEFAULT PRC[0xff03] x
 ELF32-NEXT:      4: 00000000     4 OBJECT  GLOBAL DEFAULT    3 y
 
 ELF64: Symbol table '.symtab' contains 6 entries:
 ELF64-NEXT:   Num:    Value          Size Type    Bind   Vis      Ndx Name
 ELF64-NEXT:     0:  0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
 ELF64-NEXT:     1:  0000000000000000     0 SECTION LOCAL  DEFAULT    1
 ELF64-NEXT:     2:  0000000000000000     0 SECTION LOCAL  DEFAULT    3
 ELF64-NEXT:     3:  0000000000000000     0 SECTION LOCAL  DEFAULT    4
 ELF64-NEXT:     4:  0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND _GLOBAL_OFFSET_TABLE_
 ELF64-NEXT:     5:  0000000000000000     0 TLS     GLOBAL DEFAULT  UND sym
 
+NO-SYMTAB-NOT: Symbol table '.symtab'
+
 DYN:Symbol table '.dynsym' contains 5 entries:
 DYN-NEXT:   Num:    Value          Size Type    Bind   Vis      Ndx Name
 DYN-NEXT:     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
 DYN-NEXT:     1: 00000000000001b8     0 NOTYPE  GLOBAL DEFAULT    4 foo
 DYN-NEXT:     2: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 _edata
 DYN-NEXT:     3: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 _end
 DYN-NEXT:     4: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 __bss_start
 
-DYN: Symbol table '.symtab' contains 12 entries:
-DYN-NEXT:   Num:    Value          Size Type    Bind   Vis      Ndx Name
-DYN-NEXT:     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
-DYN-NEXT:     1: 00000000000000e8     0 SECTION LOCAL  DEFAULT    1
-DYN-NEXT:     2: 0000000000000120     0 SECTION LOCAL  DEFAULT    2
-DYN-NEXT:     3: 0000000000000198     0 SECTION LOCAL  DEFAULT    3
-DYN-NEXT:     4: 00000000000001b8     0 SECTION LOCAL  DEFAULT    4
-DYN-NEXT:     5: 00000000002001b8     0 SECTION LOCAL  DEFAULT    5
-DYN-NEXT:     6: 00000000002001b8     0 OBJECT  LOCAL  DEFAULT    5 _DYNAMIC
-DYN-NEXT:     7: 0000000000200268     0 OBJECT  LOCAL  DEFAULT    5 _GLOBAL_OFFSET_TABLE_
-DYN-NEXT:     8: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 __bss_start
-DYN-NEXT:     9: 00000000000001b8     0 NOTYPE  GLOBAL DEFAULT    4 foo
-DYN-NEXT:    10: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 _edata
-DYN-NEXT:    11: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 _end
-
-HASH:     Symbol table of .hash for image:
-HASH-NEXT:   Num Buc:    Value  Size   Type   Bind Vis      Ndx Name
-HASH-NEXT:     9   0: 00000000     0 FUNC    GLOBAL DEFAULT UND __gxx_personality_v0@CXXABI_1.3
-HASH-NEXT:    13   0: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS _edata{{$}}
-HASH-NEXT:     7   0: 00000000     0 FUNC    GLOBAL DEFAULT UND _ZNSt14basic_ifstreamIcSt11char_traitsIcEEC1EPKcSt13_Ios_Openmode@GLIBCXX_3.4
-HASH-NEXT:     2   0: 00000000     0 NOTYPE  WEAK   DEFAULT UND _Jv_RegisterClasses{{$}}
-HASH-NEXT:     1   0: 00000000     0 NOTYPE  WEAK   DEFAULT UND __gmon_start__{{$}}
-HASH-NEXT:    16   1: 00000850    81 FUNC    GLOBAL DEFAULT  14 main{{$}}
-HASH-NEXT:    10   1: 00000000     0 FUNC    GLOBAL DEFAULT UND _Unwind_Resume@GCC_3.0
-HASH-NEXT:     8   1: 00000000     0 FUNC    GLOBAL DEFAULT UND puts@GLIBC_2.0
-HASH-NEXT:    12   1: 00001b68     0 NOTYPE  GLOBAL DEFAULT ABS _end{{$}}
-HASH-NEXT:     6   1: 00000000     0 FUNC    GLOBAL DEFAULT UND _ZNSt14basic_ifstreamIcSt11char_traitsIcEED1Ev@GLIBCXX_3.4
-HASH-NEXT:     5   1: 00000000     0 NOTYPE  WEAK   DEFAULT UND _ITM_registerTMCloneTable{{$}}
-HASH-NEXT:     4   1: 00000000     0 NOTYPE  WEAK   DEFAULT UND _ITM_deregisterTMCloneTable{{$}}
-HASH-NEXT:     3   1: 00000000     0 FUNC    GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.0
-HASH-NEXT:    11   2: 00000000     0 FUNC    WEAK   DEFAULT UND __cxa_finalize@GLIBC_2.1.3
-HASH-NEXT:    15   2: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS __bss_start{{$}}
-HASH-NEXT:    14   2: 0000093c     4 OBJECT  GLOBAL DEFAULT  16 _IO_stdin_used{{$}}
-HASH:     Symbol table of .gnu.hash for image:
-HASH-NEXT:   Num Buc:    Value  Size   Type   Bind Vis      Ndx Name
-HASH-NEXT:    12   0: 00001b68     0 NOTYPE  GLOBAL DEFAULT ABS _end{{$}}
-HASH-NEXT:    13   0: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS _edata{{$}}
-HASH-NEXT:    14   1: 0000093c     4 OBJECT  GLOBAL DEFAULT  16 _IO_stdin_used{{$}}
-HASH-NEXT:    15   1: 00001b64     0 NOTYPE  GLOBAL DEFAULT ABS __bss_start{{$}}
-HASH-NEXT:    16   1: 00000850    81 FUNC    GLOBAL DEFAULT  14 main{{$}}
+NO-SYMTAB-NOT: Symbol table '.symtab'
+
+SYMTAB: Symbol table '.symtab' contains 12 entries:
+SYMTAB-NEXT:   Num:    Value          Size Type    Bind   Vis      Ndx Name
+SYMTAB-NEXT:     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
+SYMTAB-NEXT:     1: 00000000000000e8     0 SECTION LOCAL  DEFAULT    1
+SYMTAB-NEXT:     2: 0000000000000120     0 SECTION LOCAL  DEFAULT    2
+SYMTAB-NEXT:     3: 0000000000000198     0 SECTION LOCAL  DEFAULT    3
+SYMTAB-NEXT:     4: 00000000000001b8     0 SECTION LOCAL  DEFAULT    4
+SYMTAB-NEXT:     5: 00000000002001b8     0 SECTION LOCAL  DEFAULT    5
+SYMTAB-NEXT:     6: 00000000002001b8     0 OBJECT  LOCAL  DEFAULT    5 _DYNAMIC
+SYMTAB-NEXT:     7: 0000000000200268     0 OBJECT  LOCAL  DEFAULT    5 _GLOBAL_OFFSET_TABLE_
+SYMTAB-NEXT:     8: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 __bss_start
+SYMTAB-NEXT:     9: 00000000000001b8     0 NOTYPE  GLOBAL DEFAULT    4 foo
+SYMTAB-NEXT:    10: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 _edata
+SYMTAB-NEXT:    11: 0000000000200268     0 NOTYPE  GLOBAL DEFAULT    5 _end

llvm/trunk/tools/llvm-readobj/ELFDumper.cpp

public:
   ELFDumper(const object::ELFObjectFile<ELFT> *ObjF, ScopedPrinter &Writer);
 
   void printFileHeaders() override;
   void printSectionHeaders() override;
   void printRelocations() override;
   void printDynamicRelocations() override;
   void printSymbols() override;
   void printDynamicSymbols() override;
+  void printHashSymbols() override;
   void printUnwindInfo() override;
 
   void printDynamicTable() override;
   void printNeededLibraries() override;
   void printProgramHeaders() override;
   void printHashTable() override;
   void printGnuHashTable() override;
   void printLoadName() override;
public:
   virtual ~DumpStyle() = default;
 
   virtual void printFileHeaders(const ELFFile<ELFT> *Obj) = 0;
   virtual void printGroupSections(const ELFFile<ELFT> *Obj) = 0;
   virtual void printRelocations(const ELFFile<ELFT> *Obj) = 0;
   virtual void printSectionHeaders(const ELFFile<ELFT> *Obj) = 0;
   virtual void printSymbols(const ELFFile<ELFT> *Obj) = 0;
   virtual void printDynamicSymbols(const ELFFile<ELFT> *Obj) = 0;
+  virtual void printHashSymbols(const ELFFile<ELFT> *Obj) {}
   virtual void printDynamicRelocations(const ELFFile<ELFT> *Obj) = 0;
-  virtual void printSymtabMessage(const ELFFile<ELFT> *obj, StringRef Name,
+  virtual void printSymtabMessage(const ELFFile<ELFT> *Obj, StringRef Name,
                                   size_t Offset) {}
   virtual void printSymbol(const ELFFile<ELFT> *Obj, const Elf_Sym *Symbol,
                            const Elf_Sym *FirstSym, StringRef StrTable,
                            bool IsDynamic) = 0;
   virtual void printProgramHeaders(const ELFFile<ELFT> *Obj) = 0;
   virtual void printHashHistogram(const ELFFile<ELFT> *Obj) = 0;
   virtual void printCGProfile(const ELFFile<ELFT> *Obj) = 0;
   virtual void printAddrsig(const ELFFile<ELFT> *Obj) = 0;
GNUStyle(ScopedPrinter &W, ELFDumper<ELFT> *Dumper)
       : DumpStyle<ELFT>(Dumper), OS(W.getOStream()) {}
 
   void printFileHeaders(const ELFO *Obj) override;
   void printGroupSections(const ELFFile<ELFT> *Obj) override;
   void printRelocations(const ELFO *Obj) override;
   void printSectionHeaders(const ELFO *Obj) override;
   void printSymbols(const ELFO *Obj) override;
   void printDynamicSymbols(const ELFO *Obj) override;
+  void printHashSymbols(const ELFO *Obj) override;
   void printDynamicRelocations(const ELFO *Obj) override;
   void printSymtabMessage(const ELFO *Obj, StringRef Name,
                           size_t Offset) override;
   void printProgramHeaders(const ELFO *Obj) override;
   void printHashHistogram(const ELFFile<ELFT> *Obj) override;
   void printCGProfile(const ELFFile<ELFT> *Obj) override;
   void printAddrsig(const ELFFile<ELFT> *Obj) override;
   void printNotes(const ELFFile<ELFT> *Obj) override;
void ELFDumper<ELFT>::printSymbols() {
   ELFDumperStyle->printSymbols(ObjF->getELFFile());
 }
 
 template<class ELFT>
 void ELFDumper<ELFT>::printDynamicSymbols() {
   ELFDumperStyle->printDynamicSymbols(ObjF->getELFFile());
 }
 
+template<class ELFT>
+void ELFDumper<ELFT>::printHashSymbols() {
+  ELFDumperStyle->printHashSymbols(ObjF->getELFFile());
+}
+
 template <class ELFT> void ELFDumper<ELFT>::printHashHistogram() {
   ELFDumperStyle->printHashHistogram(ObjF->getELFFile());
 }
 
 template <class ELFT> void ELFDumper<ELFT>::printCGProfile() {
   ELFDumperStyle->printCGProfile(ObjF->getELFFile());
 }
 
template <class ELFT> void GNUStyle<ELFT>::printSymbols(const ELFO *Obj) {
   if (opts::DynamicSymbols)
     return;
   this->dumper()->printSymbolsHelper(true);
   this->dumper()->printSymbolsHelper(false);
 }
 
 template <class ELFT>
 void GNUStyle<ELFT>::printDynamicSymbols(const ELFO *Obj) {
+  this->dumper()->printSymbolsHelper(true);
+}
+
+template <class ELFT> void GNUStyle<ELFT>::printHashSymbols(const ELFO *Obj) {
   if (this->dumper()->getDynamicStringTable().empty())
     return;
   auto StringTable = this->dumper()->getDynamicStringTable();
   auto DynSyms = this->dumper()->dynamic_symbols();
-  auto GnuHash = this->dumper()->getGnuHashTable();
   auto SysVHash = this->dumper()->getHashTable();
 
-  // If no hash or .gnu.hash found, try using symbol table
-  if (GnuHash == nullptr && SysVHash == nullptr)
-    this->dumper()->printSymbolsHelper(true);
-
   // Try printing .hash
-  if (this->dumper()->getHashTable()) {
+  if (SysVHash) {
     OS << "\n Symbol table of .hash for image:\n";
     if (ELFT::Is64Bits)
       OS << "  Num Buc:    Value          Size   Type   Bind Vis      Ndx Name";
     else
       OS << "  Num Buc:    Value  Size   Type   Bind Vis      Ndx Name";
     OS << "\n";
 
     uint32_t NBuckets = SysVHash->nbucket;
     uint32_t NChains = SysVHash->nchain;
     auto Buckets = SysVHash->buckets();
     auto Chains = SysVHash->chains();
     for (uint32_t Buc = 0; Buc < NBuckets; Buc++) {
       if (Buckets[Buc] == ELF::STN_UNDEF)
         continue;
       for (uint32_t Ch = Buckets[Buc]; Ch < NChains; Ch = Chains[Ch]) {
         if (Ch == ELF::STN_UNDEF)
           break;
         printHashedSymbol(Obj, &DynSyms[0], Ch, StringTable, Buc);
       }
     }
   }
 
   // Try printing .gnu.hash
+  auto GnuHash = this->dumper()->getGnuHashTable();
   if (GnuHash) {
     OS << "\n Symbol table of .gnu.hash for image:\n";
     if (ELFT::Is64Bits)
       OS << "  Num Buc:    Value          Size   Type   Bind Vis      Ndx Name";
     else
       OS << "  Num Buc:    Value  Size   Type   Bind Vis      Ndx Name";
     OS << "\n";
     uint32_t NBuckets = GnuHash->nbuckets;

llvm/trunk/tools/llvm-readobj/ObjDumper.h

public:
   // Only implemented for ELF at this time.
   virtual void printDynamicRelocations() { }
   virtual void printDynamicTable() { }
   virtual void printNeededLibraries() { }
   virtual void printProgramHeaders() { }
   virtual void printSectionAsHex(StringRef SectionName) {}
   virtual void printHashTable() { }
   virtual void printGnuHashTable() { }
+  virtual void printHashSymbols() {}
   virtual void printLoadName() {}
   virtual void printVersionInfo() {}
   virtual void printGroupSections() {}
   virtual void printHashHistogram() {}
   virtual void printCGProfile() {}
   virtual void printAddrsig() {}
   virtual void printNotes() {}
   virtual void printELFLinkerOptions() {}

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

namespace opts {
 
   // -dyn-symbols, -dyn-syms
   // Also -dt in llvm-readobj mode.
   cl::opt<bool> DynamicSymbols("dyn-symbols",
     cl::desc("Display the dynamic symbol table"));
   cl::alias DynSymsGNU("dyn-syms", cl::desc("Alias for --dyn-symbols"),
                        cl::aliasopt(DynamicSymbols));
 
+  // -hash-symbols
+  cl::opt<bool> HashSymbols(
+      "hash-symbols",
+      cl::desc("Display the dynamic symbols derived from the hash section"));
+
   // -unwind, -u
   cl::opt<bool> UnwindInfo("unwind",
     cl::desc("Display unwind information"));
   cl::alias UnwindInfoShort("u",
     cl::desc("Alias for --unwind"),
     cl::aliasopt(UnwindInfo));
 
   // -dynamic-table, -dynamic, -d
static void dumpObject(const ObjectFile *Obj, ScopedPrinter &Writer) {
   if (opts::Relocations)
     Dumper->printRelocations();
   if (opts::DynRelocs)
     Dumper->printDynamicRelocations();
   if (opts::Symbols)
     Dumper->printSymbols();
   if (opts::DynamicSymbols)
     Dumper->printDynamicSymbols();
+  if (opts::HashSymbols)
+    Dumper->printHashSymbols();
   if (opts::UnwindInfo)
     Dumper->printUnwindInfo();
   if (opts::DynamicTable)
     Dumper->printDynamicTable();
   if (opts::NeededLibraries)
     Dumper->printNeededLibraries();
   if (opts::ProgramHeaders)
     Dumper->printProgramHeaders();