[PATCH] D33978: MC, Object: Reserve a section type, SHT_LLVM_ODRTAB, for the ODR table.

[Peter Collingbourne via Phabricator via llvm-commits]

pcc created this revision.
Herald added a subscriber: emaste.
Herald added a reviewer: hiraditya.

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

It appears [1] that binutils' most recent section type number
allocations in the OS-specific range have been of the form 0x6fff47XX,
where 0x47 ('G') presumably stands for GNU. So I have taken the
bold step of using 0x6fff4c00, where 0x4c ('L') stands for LLVM. If
this seems reasonable I will contact gnu-gabi to reserve the entire
0x6fff4cXX range for LLVM.

[1] https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=elfcpp/elfcpp.h;h=cce40d41dedb281c2d8f41135250c2cc39162469;hb=HEAD#l369


https://reviews.llvm.org/D33978

Files:
  llvm/include/llvm/BinaryFormat/ELF.h
  llvm/lib/MC/MCParser/ELFAsmParser.cpp
  llvm/lib/MC/MCSectionELF.cpp
  llvm/lib/Object/ELF.cpp
  llvm/lib/ObjectYAML/ELFYAML.cpp
  llvm/test/MC/ELF/section.s
  llvm/tools/llvm-readobj/ELFDumper.cpp


Index: llvm/tools/llvm-readobj/ELFDumper.cpp
===================================================================
--- llvm/tools/llvm-readobj/ELFDumper.cpp
+++ llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -2592,6 +2592,8 @@
     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";
Index: llvm/test/MC/ELF/section.s
===================================================================
--- llvm/test/MC/ELF/section.s
+++ llvm/test/MC/ELF/section.s
@@ -267,3 +267,15 @@
 // CHECK-NEXT:       SHF_TLS
 // CHECK-NEXT:       SHF_WRITE
 // CHECK-NEXT:     ]
+
+// Test SHT_LLVM_ODRTAB
+
+.section .odrtab,"e", at llvm_odrtab
+// ASM: .section .odrtab,"e", at llvm_odrtab
+
+// CHECK:        Section {
+// CHECK:          Name: .odrtab
+// CHECK-NEXT:     Type: SHT_LLVM_ODRTAB
+// CHECK-NEXT:     Flags [
+// CHECK-NEXT:       SHF_EXCLUDE
+// CHECK-NEXT:     ]
Index: llvm/lib/ObjectYAML/ELFYAML.cpp
===================================================================
--- llvm/lib/ObjectYAML/ELFYAML.cpp
+++ llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -372,6 +372,7 @@
   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);
Index: llvm/lib/Object/ELF.cpp
===================================================================
--- llvm/lib/Object/ELF.cpp
+++ llvm/lib/Object/ELF.cpp
@@ -192,6 +192,7 @@
     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);
Index: llvm/lib/MC/MCSectionELF.cpp
===================================================================
--- llvm/lib/MC/MCSectionELF.cpp
+++ llvm/lib/MC/MCSectionELF.cpp
@@ -147,6 +147,8 @@
     // 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());
Index: llvm/lib/MC/MCParser/ELFAsmParser.cpp
===================================================================
--- llvm/lib/MC/MCParser/ELFAsmParser.cpp
+++ llvm/lib/MC/MCParser/ELFAsmParser.cpp
@@ -603,6 +603,8 @@
       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");
   }
Index: llvm/include/llvm/BinaryFormat/ELF.h
===================================================================
--- llvm/include/llvm/BinaryFormat/ELF.h
+++ llvm/include/llvm/BinaryFormat/ELF.h
@@ -683,6 +683,7 @@
   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.


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