[yaml2obj][ELF] Add support for symbol indexes greater than SHN_LORESERVE

Right now Symbols must be either undefined or defined in a specific
section. Some symbols have section indexes like SHN_ABS however. This
change adds support for outputting symbols that have such section
indexes.

Patch by Jake Ehrlich

Differential Revision: https://reviews.llvm.org/D37391

llvm-svn: 312745

llvm/include/llvm/ObjectYAML/ELFYAML.h

@@ -50,6 +50,7 @@ LLVM_YAML_STRONG_TYPEDEF(uint32_t, ELF_REL)
 LLVM_YAML_STRONG_TYPEDEF(uint8_t, ELF_RSS)
 // Just use 64, since it can hold 32-bit values too.
 LLVM_YAML_STRONG_TYPEDEF(uint64_t, ELF_SHF)
+LLVM_YAML_STRONG_TYPEDEF(uint16_t, ELF_SHN)
 LLVM_YAML_STRONG_TYPEDEF(uint8_t, ELF_STT)
 LLVM_YAML_STRONG_TYPEDEF(uint8_t, ELF_STV)
 LLVM_YAML_STRONG_TYPEDEF(uint8_t, ELF_STO)
@@ -89,6 +90,7 @@ struct Symbol {
   StringRef Name;
   ELF_STT Type;
   StringRef Section;
+  Optional<ELF_SHN> Index;
   llvm::yaml::Hex64 Value;
   llvm::yaml::Hex64 Size;
   uint8_t Other;
@@ -267,6 +269,10 @@ struct ScalarBitSetTraits<ELFYAML::ELF_SHF> {
   static void bitset(IO &IO, ELFYAML::ELF_SHF &Value);
 };
 
+template <> struct ScalarEnumerationTraits<ELFYAML::ELF_SHN> {
+  static void enumeration(IO &IO, ELFYAML::ELF_SHN &Value);
+};
+
 template <>
 struct ScalarEnumerationTraits<ELFYAML::ELF_STT> {
   static void enumeration(IO &IO, ELFYAML::ELF_STT &Value);
@@ -334,6 +340,7 @@ template <> struct MappingTraits<ELFYAML::ProgramHeader> {
 template <>
 struct MappingTraits<ELFYAML::Symbol> {
   static void mapping(IO &IO, ELFYAML::Symbol &Symbol);
+  static StringRef validate(IO &IO, ELFYAML::Symbol &Symbol);
 };
 
 template <>

llvm/lib/ObjectYAML/ELFYAML.cpp

@@ -477,6 +477,28 @@ void ScalarBitSetTraits<ELFYAML::ELF_SHF>::bitset(IO &IO,
 #undef BCase
 }
 
+void ScalarEnumerationTraits<ELFYAML::ELF_SHN>::enumeration(
+    IO &IO, ELFYAML::ELF_SHN &Value) {
+#define ECase(X) IO.enumCase(Value, #X, ELF::X)
+  ECase(SHN_UNDEF);
+  ECase(SHN_LORESERVE);
+  ECase(SHN_LOPROC);
+  ECase(SHN_HIPROC);
+  ECase(SHN_LOOS);
+  ECase(SHN_HIOS);
+  ECase(SHN_ABS);
+  ECase(SHN_COMMON);
+  ECase(SHN_XINDEX);
+  ECase(SHN_HIRESERVE);
+  ECase(SHN_HEXAGON_SCOMMON);
+  ECase(SHN_HEXAGON_SCOMMON_1);
+  ECase(SHN_HEXAGON_SCOMMON_2);
+  ECase(SHN_HEXAGON_SCOMMON_4);
+  ECase(SHN_HEXAGON_SCOMMON_8);
+#undef ECase
+  IO.enumFallback<Hex32>(Value);
+}
+
 void ScalarEnumerationTraits<ELFYAML::ELF_STT>::enumeration(
     IO &IO, ELFYAML::ELF_STT &Value) {
 #define ECase(X) IO.enumCase(Value, #X, ELF::X)
@@ -701,6 +723,7 @@ void MappingTraits<ELFYAML::Symbol>::mapping(IO &IO, ELFYAML::Symbol &Symbol) {
   IO.mapOptional("Name", Symbol.Name, StringRef());
   IO.mapOptional("Type", Symbol.Type, ELFYAML::ELF_STT(0));
   IO.mapOptional("Section", Symbol.Section, StringRef());
+  IO.mapOptional("Index", Symbol.Index);
   IO.mapOptional("Value", Symbol.Value, Hex64(0));
   IO.mapOptional("Size", Symbol.Size, Hex64(0));
 
@@ -709,6 +732,20 @@ void MappingTraits<ELFYAML::Symbol>::mapping(IO &IO, ELFYAML::Symbol &Symbol) {
   IO.mapOptional("Other", Keys->Other, ELFYAML::ELF_STO(0));
 }
 
+StringRef MappingTraits<ELFYAML::Symbol>::validate(IO &IO,
+                                                   ELFYAML::Symbol &Symbol) {
+  if (Symbol.Index && Symbol.Section.data()) {
+    return "Index and Section cannot both be specified for Symbol";
+  }
+  if (Symbol.Index && *Symbol.Index == ELFYAML::ELF_SHN(ELF::SHN_XINDEX)) {
+    return "Large indexes are not supported";
+  }
+  if (Symbol.Index && *Symbol.Index < ELFYAML::ELF_SHN(ELF::SHN_LORESERVE)) {
+    return "Use a section name to define which section a symbol is defined in";
+  }
+  return StringRef();
+}
+
 void MappingTraits<ELFYAML::LocalGlobalWeakSymbols>::mapping(
     IO &IO, ELFYAML::LocalGlobalWeakSymbols &Symbols) {
   IO.mapOptional("Local", Symbols.Local);

llvm/test/tools/yaml2obj/symbol-index-invalid.yaml

@@ -0,0 +1,21 @@
+# This test insures that the user cannot have both an Index and a Section field.
+# RUN: not yaml2obj %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x0000000000000010
+    Content:         "0000000000000000"
+Symbols:
+  Global:
+    - Name:     _start
+      Section:  .text
+      Index:    SHN_ABS

llvm/test/tools/yaml2obj/symbol-index.yaml

@@ -0,0 +1,35 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-readobj -symbols %t | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+Symbols:
+  Global:
+    - Name:     test
+      Index:    SHN_ABS
+      Value:    0x1234
+
+#CHECK:     Symbols [
+#CHECK-NEXT:   Symbol {
+#CHECK-NEXT:    Name:  (0)
+#CHECK-NEXT:    Value: 0x0
+#CHECK-NEXT:    Size: 0
+#CHECK-NEXT:    Binding: Local (0x0)
+#CHECK-NEXT:    Type: None (0x0)
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: Undefined (0x0)
+#CHECK-NEXT:  }
+#CHECK-NEXT:  Symbol {
+#CHECK-NEXT:    Name: test (1)
+#CHECK-NEXT:    Value: 0x1234
+#CHECK-NEXT:    Size: 0
+#CHECK-NEXT:    Binding: Global (0x1)
+#CHECK-NEXT:    Type: None (0x0)
+#CHECK-NEXT:    Other: 0
+#CHECK-NEXT:    Section: Absolute (0xFFF1)
+#CHECK-NEXT:  }
+#CHECK-NEXT:]

llvm/tools/yaml2obj/yaml2elf.cpp

@@ -409,7 +409,10 @@ void ELFState<ELFT>::addSymbols(const std::vector<ELFYAML::Symbol> &Symbols,
         exit(1);
       }
       Symbol.st_shndx = Index;
-    } // else Symbol.st_shndex == SHN_UNDEF (== 0), since it was zero'd earlier.
+    } else if (Sym.Index) {
+      Symbol.st_shndx = *Sym.Index;
+    }
+    // else Symbol.st_shndex == SHN_UNDEF (== 0), since it was zero'd earlier.
     Symbol.st_value = Sym.Value;
     Symbol.st_other = Sym.Other;
     Symbol.st_size = Sym.Size;