[ELF] - Improve diagnostics on duplicate STT_SECTION symbol.

[grimar]

Summary

Global symbols of type STT_SECTION has section field null when reference
relocation sections, for which we do not create input sections:

• Type: STT_SECTION Section: .rela.text

In case of duplicate symbol lld crashed trying to access nullptr.

[ruiu]

This is not an obvious patch to handle corrupted input, so I'm honestly not in favor of it.

[grimar]

Rebased after latest changes, it is much simpler now.

[grimar]

In D25513#569710, @ruiu wrote:

This is not an obvious patch to handle corrupted input, so I'm honestly not in favor of it.

Latest changes in LLD allowed to simplify this. Is it ok now ?

[ruiu]

test/ELF/invalid/report-duplicates.test

4

This error message doesn't make sense.

[davide]

test/ELF/invalid/report-duplicates.test

4

ehm, a symbol with an empty name reported as duplicated to the use is not really helpful (if not misleading).

[• rafael]

How were we crashing?

The empty name I assume is orthogonal, no? Both symbols could be named foo for example.

[grimar]

Given that no well behaved producer creates a global STT_SECTION and
this was no longer crashing, abandoning it.

ELF/InputFiles.cpp

SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
   case STB_WEAK:
   case STB_GNU_UNIQUE:
     if (Sec == &InputSection<ELFT>::Discarded)
       return elf::Symtab<ELFT>::X->addUndefined(Name, Binding, Sym->st_other,
                                                 Sym->getType(),
                                                 /*CanOmitFromDynSym*/ false,
                                                 this)
           ->body();
-    return elf::Symtab<ELFT>::X->addRegular(Name, *Sym, Sec)->body();
+    return elf::Symtab<ELFT>::X->addRegular(Name, *Sym, Sec, this)->body();
   }
 }
 
 template <class ELFT> void ArchiveFile::parse() {
   File = check(Archive::create(MB), "failed to parse archive");
 
   // Read the symbol table to construct Lazy objects.
   for (const Archive::Symbol &Sym : File->symbols())

ELF/SymbolTable.h

public:
   DefinedRegular<ELFT> *addIgnored(StringRef Name,
                                    uint8_t Visibility = llvm::ELF::STV_HIDDEN);
 
   Symbol *addUndefined(StringRef Name);
   Symbol *addUndefined(StringRef Name, uint8_t Binding, uint8_t StOther,
                        uint8_t Type, bool CanOmitFromDynSym, InputFile *File);
 
   Symbol *addRegular(StringRef Name, const Elf_Sym &Sym,
-                     InputSectionBase<ELFT> *Section);
+                     InputSectionBase<ELFT> *Section, InputFile *File);
   Symbol *addRegular(StringRef Name, uint8_t Binding, uint8_t StOther);
   Symbol *addSynthetic(StringRef N, OutputSectionBase<ELFT> *Section,
                        uintX_t Value, uint8_t StOther);
   void addShared(SharedFile<ELFT> *F, StringRef Name, const Elf_Sym &Sym,
                  const typename ELFT::Verdef *Verdef);
 
   void addLazyArchive(ArchiveFile *F, const llvm::object::Archive::Symbol S);
   void addLazyObject(StringRef Name, LazyObjectFile &Obj);

ELF/SymbolTable.cpp

void SymbolTable<ELFT>::reportDuplicate(SymbolBody *Existing,
   if (Config->AllowMultipleDefinition)
     warn(Msg);
   else
     error(Msg);
 }
 
 template <typename ELFT>
 Symbol *SymbolTable<ELFT>::addRegular(StringRef Name, const Elf_Sym &Sym,
-                                      InputSectionBase<ELFT> *Section) {
+                                      InputSectionBase<ELFT> *Section,
+                                      InputFile *File) {
   Symbol *S;
   bool WasInserted;
   std::tie(S, WasInserted) = insert(Name, Sym.getType(), Sym.getVisibility(),
-                                    /*CanOmitFromDynSym*/ false,
-                                    Section ? Section->getFile() : nullptr);
+                                    /*CanOmitFromDynSym*/ false, File);
   int Cmp = compareDefinedNonCommon(S, WasInserted, Sym.getBinding());
   if (Cmp > 0)
     replaceBody<DefinedRegular<ELFT>>(S, Name, Sym, Section);
   else if (Cmp == 0)
-    reportDuplicate(S->body(), Section->getFile());
+    reportDuplicate(S->body(), File);
   return S;
 }
 
 template <typename ELFT>
 Symbol *SymbolTable<ELFT>::addRegular(StringRef Name, uint8_t Binding,
                                       uint8_t StOther) {
   Symbol *S;
   bool WasInserted;

test/ELF/invalid/report-duplicates.test

+# RUN: yaml2obj %s -o %t.o
+# RUN: not ld.lld %t.o -o %tout 2>&1 | FileCheck %s
+# CHECK: duplicate symbol: in (internal) and {{.*}}.o
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000000010
+    Content:         "00000000"
+  - Name:            .rela.text
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x0000000000000008
+    Info:            .text
+    Relocations:
+Symbols:
+  Global:
+    - Type:            STT_SECTION
+      Section:         .rela.text
+    - Type:            STT_SECTION
+      Section:         .rela.text