[llvm/Object] - Fix the error message reported for a broken SHT_SYMTAB_SHNDX section.

[grimar]

Summary

SHT_SYMTAB_SHNDX should have the same number of entries as the symbol table
associated (https://www.sco.com/developers/gabi/latest/ch4.sheader.html)

We currently can report the following message:
"SHT_SYMTAB_SHNDX section has sh_size (24) which is not equal to the number of symbols (2)"

It is just broken. This patch refines/fixes it.

[grimar]

• Removed "FIXME" fixed.

[MaskRay]

LG

[mstorsjo]

Btw, I would suggest configuring your git client to set your full name as author; right now your commits only have a user name as author, not a full name as is customary in git.

[grimar]

In D69305#1721063, @mstorsjo wrote:

Btw, I would suggest configuring your git client to set your full name as author; right now your commits only have a user name as author, not a full name as is customary in git.

I'll take a look, thanks! It also atm uses not the email I'd prefer to use..

llvm/include/llvm/Object/ELF.h

ELFFile<ELFT>::getSHNDXTable(const Elf_Shdr &Section,
   const Elf_Shdr &SymTable = **SymTableOrErr;
   if (SymTable.sh_type != ELF::SHT_SYMTAB &&
       SymTable.sh_type != ELF::SHT_DYNSYM)
     return createError("SHT_SYMTAB_SHNDX section is linked with " +
                        object::getELFSectionTypeName(getHeader()->e_machine,
                                                      SymTable.sh_type) +
                        " section (expected SHT_SYMTAB/SHT_DYNSYM)");
 
-  if (V.size() != (SymTable.sh_size / sizeof(Elf_Sym)))
-    return createError("SHT_SYMTAB_SHNDX section has sh_size (" +
-                       Twine(SymTable.sh_size) +
-                       ") which is not equal to the number of symbols (" +
-                       Twine(V.size()) + ")");
+  uint64_t Syms = SymTable.sh_size / sizeof(Elf_Sym);
+  if (V.size() != Syms)
+    return createError("SHT_SYMTAB_SHNDX has " + Twine(V.size()) +
+                       "  entries, but the symbol table associated has " +
+                       Twine(Syms));
+
   return V;
 }
 
 template <class ELFT>
 Expected<StringRef>
 ELFFile<ELFT>::getStringTableForSymtab(const Elf_Shdr &Sec) const {
   auto SectionsOrErr = sections();
   if (!SectionsOrErr)

llvm/test/Object/invalid.test

 
 ## Test that llvm-readobj reports an error if SHT_SYMTAB_SHNDX section has
 ## invalid sh_size which should be:
 ## sizeof(.symtab_shndx) = (sizeof(.symtab) / entsize(.symtab)) * entsize(.symtab_shndx)
 
 # RUN: yaml2obj %s --docnum=11 -o %t11
 # RUN: not llvm-readobj --symbols %t11 2>&1 | FileCheck --check-prefix=INVALID-XINDEX-SIZE %s
 
-# INVALID-XINDEX-SIZE: error: {{.*}}: SHT_SYMTAB_SHNDX section has sh_size (24) which is not equal to the number of symbols (2)
+# INVALID-XINDEX-SIZE: error: {{.*}}: SHT_SYMTAB_SHNDX has 2 entries, but the symbol table associated has 1
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_DYN
   Machine: EM_X86_64
 Sections:

llvm/test/tools/obj2yaml/elf-sht-symtab-shndx.yaml

 
 ## Check that yaml2obj is unable to dump an object, which has symbols with
 ## section index == SHN_XINDEX, but SHT_SYMTAB_SHNDX table contains more
 ## entries than the number of symbols in .symtab.
 
 # RUN: yaml2obj --docnum=4 %s -o %t4
 # RUN: not obj2yaml %t4 2>&1 | FileCheck %s -DFILE=%t4 --check-prefix=CASE4
 
-## FIXME: The error message below needs rewording. Size should not be equal to the number of symbols.
-## CASE4: Error reading file: [[FILE]]: SHT_SYMTAB_SHNDX section has sh_size (48) which is not equal to the number of symbols (3)
+## CASE4: Error reading file: [[FILE]]: SHT_SYMTAB_SHNDX has 3 entries, but the symbol table associated has 2
 
 --- !ELF
 FileHeader:
   Class:   ELFCLASS64
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_X86_64
 Sections: