[lld] [ELF] Never mark the dynamic linker as DT_NEEDED

[rafaelauler]

Summary

This patch adds logic to avoid putting the dynamic linker library (ld.so) as a
DT_NEEDED entry in the dynamic table. It should only appear in PT_INTERP.

This patch fixes SPEC programs 433, 445, 450, 453, 456, 462 when running on
Ubuntu Linux x86_64 and when linking SPEC programs with LLD and glibc 2.19.

[• shankar.easwaran]

Remove it from soneeded instead.

[rafaelauler]

Makes sense, since soneeded is a stringmap. Thanks! I updated the patch.

[• shankar.easwaran]

LGTM

[rafaelauler]

Committed r218847.

lib/ReaderWriter/ELF/OutputELFWriter.h

 #include "TargetLayout.h"
 
 #include "lld/Core/Instrumentation.h"
 #include "lld/Core/Parallel.h"
 #include "lld/ReaderWriter/ELFLinkingContext.h"
 #include "lld/ReaderWriter/Writer.h"
 
 #include "llvm/ADT/StringSet.h"
+#include "llvm/Support/Path.h"
 
 namespace lld {
 namespace elf {
 using namespace llvm;
 using namespace llvm::object;
 
 template <class ELFT> class OutputELFWriter;
 template <class ELFT> class TargetLayout;
if (auto section = dyn_cast<AtomSection<ELFT>>(sec))
                                          atom->_virtualAddr, atom);
       }
   for (const auto &sla : file.sharedLibrary()) {
     if (isDynSymEntryRequired(sla))
       _dynamicSymbolTable->addSymbol(sla, ELF::SHN_UNDEF);
     if (isNeededTagRequired(sla))
       _soNeeded.insert(sla->loadName());
   }
+  // Never mark the dynamic linker as DT_NEEDED
+  _soNeeded.erase(sys::path::filename(_context.getInterpreter()));
   for (const auto &loadName : _soNeeded) {
     Elf_Dyn dyn;
     dyn.d_tag = DT_NEEDED;
     dyn.d_un.d_val = _dynamicStringTable->addString(loadName.getKey());
     _dynamicTable->addEntry(dyn);
   }
   const auto &rpathList = _context.getRpathList();
   if (!rpathList.empty()) {