MC, Object: Reserve a section type, SHT_LLVM_ODRTAB, for the ODR table.

This is part of the ODR checker proposal:
http://lists.llvm.org/pipermail/llvm-dev/2017-June/113820.html

Per discussion on the gnu-gabi mailing list [1] the section type range
0x6fff4c00..0x6fff4cff is reserved for LLVM.

[1] https://sourceware.org/ml/gnu-gabi/2017-q2/msg00030.html

Differential Revision: https://reviews.llvm.org/D33978

llvm-svn: 305407

llvm/include/llvm/BinaryFormat/ELF.h

@@ -683,6 +683,7 @@ enum : unsigned {
   SHT_GROUP = 17,                  // Section group.
   SHT_SYMTAB_SHNDX = 18,           // Indices for SHN_XINDEX entries.
   SHT_LOOS = 0x60000000,           // Lowest operating system-specific type.
+  SHT_LLVM_ODRTAB = 0x6fff4c00,    // LLVM ODR table.
   SHT_GNU_ATTRIBUTES = 0x6ffffff5, // Object attributes.
   SHT_GNU_HASH = 0x6ffffff6,       // GNU-style hash table.
   SHT_GNU_verdef = 0x6ffffffd,     // GNU version definitions.

llvm/lib/MC/MCParser/ELFAsmParser.cpp

@@ -603,6 +603,8 @@ EndStmt:
       Type = ELF::SHT_NOTE;
     else if (TypeName == "unwind")
       Type = ELF::SHT_X86_64_UNWIND;
+    else if (TypeName == "llvm_odrtab")
+      Type = ELF::SHT_LLVM_ODRTAB;
     else if (TypeName.getAsInteger(0, Type))
       return TokError("unknown section type");
   }

llvm/lib/MC/MCSectionELF.cpp

@@ -147,6 +147,8 @@ void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI, const Triple &T,
     // Print hex value of the flag while we do not have
     // any standard symbolic representation of the flag.
     OS << "0x7000001e";
+  else if (Type == ELF::SHT_LLVM_ODRTAB)
+    OS << "llvm_odrtab";
   else
     report_fatal_error("unsupported type 0x" + Twine::utohexstr(Type) +
                        " for section " + getSectionName());

llvm/lib/Object/ELF.cpp

@@ -192,6 +192,7 @@ StringRef llvm::object::getELFSectionTypeName(uint32_t Machine, unsigned Type) {
     STRINGIFY_ENUM_CASE(ELF, SHT_PREINIT_ARRAY);
     STRINGIFY_ENUM_CASE(ELF, SHT_GROUP);
     STRINGIFY_ENUM_CASE(ELF, SHT_SYMTAB_SHNDX);
+    STRINGIFY_ENUM_CASE(ELF, SHT_LLVM_ODRTAB);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_ATTRIBUTES);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_HASH);
     STRINGIFY_ENUM_CASE(ELF, SHT_GNU_verdef);

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -372,6 +372,7 @@ void ScalarEnumerationTraits<ELFYAML::ELF_SHT>::enumeration(
   ECase(SHT_GROUP);
   ECase(SHT_SYMTAB_SHNDX);
   ECase(SHT_LOOS);
+  ECase(SHT_LLVM_ODRTAB);
   ECase(SHT_GNU_ATTRIBUTES);
   ECase(SHT_GNU_HASH);
   ECase(SHT_GNU_verdef);

llvm/test/MC/ELF/section.s

@@ -267,3 +267,15 @@ bar:
 // CHECK-NEXT:       SHF_TLS
 // CHECK-NEXT:       SHF_WRITE
 // CHECK-NEXT:     ]
+
+// Test SHT_LLVM_ODRTAB
+
+.section .odrtab,"e",@llvm_odrtab
+// ASM: .section .odrtab,"e",@llvm_odrtab
+
+// CHECK:        Section {
+// CHECK:          Name: .odrtab
+// CHECK-NEXT:     Type: SHT_LLVM_ODRTAB
+// CHECK-NEXT:     Flags [
+// CHECK-NEXT:       SHF_EXCLUDE
+// CHECK-NEXT:     ]

llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -2629,6 +2629,8 @@ std::string getSectionTypeString(unsigned Arch, unsigned Type) {
     return "GROUP";
   case SHT_SYMTAB_SHNDX:
     return "SYMTAB SECTION INDICES";
+  case SHT_LLVM_ODRTAB:
+    return "LLVM_ODRTAB";
   // FIXME: Parse processor specific GNU attributes
   case SHT_GNU_ATTRIBUTES:
     return "ATTRIBUTES";