[yaml2obj/obj2yaml] - Add support for the SHT_LLVM_CALL_GRAPH_PROFILE sections.

[grimar]

Summary

This is a LLVM specific section that is well described here:
https://llvm.org/docs/Extensions.html#sht-llvm-call-graph-profile-section-call-graph-profile

This patch teaches yaml2obj and obj2yaml about how to work with it.

[MaskRay]

llvm/test/tools/obj2yaml/call-graph-profile-section.yaml

7

This is verbose. Intention is to test that the section has the same representation with different EI_CLASS.

If https://reviews.llvm.org/D73821 looks good, we can add -D EI_CLASS=ELFCLASS32 and -D EI_DATA=ELFDATA2LSB to represent a similar object file.

[jhenderson]

llvm/lib/ObjectYAML/ELFEmitter.cpp

1015–1016

Nit: I think there shouldn't be a space before the "false" in these two lines.

llvm/test/tools/obj2yaml/call-graph-profile-section.yaml

111

I think this is missing a non-16 sh_entsize test case.

202–203

Why do we do this? Can't we write the invalid index as it is in the YAML below?

216–217

Again, I'm not sure about this: can't we just record the literal index value in this case, like in the YAML below?

llvm/test/tools/yaml2obj/ELF/call-graph-profile-section.yaml

22

Use a regex capture here, in case the symbol table index ever changes.

121

Delete "an"

140

Indentation of values in this YAML doesn't line up.

162–163

Isn't this test case at least partially a duplicate of the "main" test case? Could the two be combined?

llvm/tools/obj2yaml/elf2yaml.cpp

702

with use of -> by using the

Surely if the section is empty, we don't need either Content or Entries?

[grimar]

llvm/test/tools/obj2yaml/call-graph-profile-section.yaml

7

This is verbose.

Yes, that is why I placed the "TODO" comment below.

202–203

Technially it is possible, but there is a problem behind:
When we read a binary (in obj2yaml) we read the From/To fields as an integers.
If we can't map them to a symbol and want to store them as StringRef, we need to convert them
to strings and save those strings somewhere
(the case with yaml2obj is different as it has strings representation from the begining).

The solution I used for AddrsigSymbol was:

struct AddrsigSymbol {
  AddrsigSymbol(StringRef N) : Name(N), Index(None) {}
  AddrsigSymbol(llvm::yaml::Hex32 Ndx) : Name(None), Index(Ndx) {}
  AddrsigSymbol() : Name(None), Index(None) {}

  Optional<StringRef> Name;
  Optional<llvm::yaml::Hex32> Index;
};

i.e. we can convert AddrsigSymbol to SymbolOrName and reuse probably.
But I'd like to investigate another options first, perhaps it is possible to eliminate AddrsigSymbol.

Given all above I supposed that it should be done separatelly as it should
change/refactor another code and hence probably deserves a separate follow-up patch.
What do you think?

[jhenderson]

llvm/test/tools/obj2yaml/call-graph-profile-section.yaml

202–203

Given all above I supposed that it should be done separatelly as it should

change/refactor another code and hence probably deserves a separate follow-up patch.
What do you think?

That sounds fair. Thanks for the explanation!

[grimar]

• Addressed review comments.

llvm/test/tools/obj2yaml/call-graph-profile-section.yaml

111

Reasonable. Done.

llvm/test/tools/yaml2obj/ELF/call-graph-profile-section.yaml

162–163

Could the two be combined?

I would not combine them. The intention of the main test is to check we encode 32/64/LE/BE bytes correctly.
That is why I used raw data check there.

Here I check how we can use "Entires" and I use --elf-cg-profile. Using of --elf-cg-profile would be unreasonable
until we know that encode section data correctly.

Probably we can remove the "Case 2" from here as the same case was tested in the main case.
I would leave it as is though as it complements the rest of this test case which tries to test all valid cases
related to "Entries" at once.

[jhenderson]

llvm/test/tools/yaml2obj/ELF/call-graph-profile-section.yaml

162–163

I don't think there's strong reasoning for not adding an --elf-cg-profile check in addition to section data in the first test case, if you're concerned about the raw bytes matching the expected format.

That being said, testing the use of "Entries" in general terms is not needed in this case, since you are testing it in the first case. A set of tests that focuses purely on the symbol references is fine and appropriate. I think it's okay therefore to keep this set of tests here, but the headline comment really needs to emphasise that its testing that, not the "Entries" tag.

llvm/tools/obj2yaml/elf2yaml.cpp

702

Given the behaviour change "when it is empty" is no longer valid.

[grimar]

• Addressed review comments.

[jhenderson]

LGTM, with nit.

llvm/tools/obj2yaml/elf2yaml.cpp

703

neither/nor -> either/or (in this context - the "no" provides the negation, making it unnecessary here).

[grimar]

llvm/tools/obj2yaml/elf2yaml.cpp

703

Thanks!

llvm/include/llvm/ObjectYAML/ELFYAML.h

enum class ChunkKind {
     StackSizes,
     SymtabShndxSection,
     Symver,
     MipsABIFlags,
     Addrsig,
     Fill,
     LinkerOptions,
     DependentLibraries,
+    CallGraphProfile
   };
 
   ChunkKind Kind;
   StringRef Name;
 
   Chunk(ChunkKind K) : Kind(K) {}
   virtual ~Chunk();
 };
struct DependentLibrariesSection : Section {
 
   DependentLibrariesSection() : Section(ChunkKind::DependentLibraries) {}
 
   static bool classof(const Chunk *S) {
     return S->Kind == ChunkKind::DependentLibraries;
   }
 };
 
+// Represents the call graph profile section entry.
+struct CallGraphEntry {
+  // The symbol of the source of the edge.
+  StringRef From;
+  // The symbol index of the destination of the edge.
+  StringRef To;
+  // The weight of the edge.
+  uint64_t Weight;
+};
+
+struct CallGraphProfileSection : Section {
+  Optional<std::vector<CallGraphEntry>> Entries;
+  Optional<yaml::BinaryRef> Content;
+
+  CallGraphProfileSection() : Section(ChunkKind::CallGraphProfile) {}
+
+  static bool classof(const Chunk *S) {
+    return S->Kind == ChunkKind::CallGraphProfile;
+  }
+};
+
 struct SymverSection : Section {
   std::vector<uint16_t> Entries;
 
   SymverSection() : Section(ChunkKind::Symver) {}
 
   static bool classof(const Chunk *S) { return S->Kind == ChunkKind::Symver; }
 };
 

 
 } // end namespace ELFYAML
 } // end namespace llvm
 
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::AddrsigSymbol)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::StackSizeEntry)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::DynamicEntry)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::LinkerOption)
+LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::CallGraphEntry)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::NoteEntry)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::ProgramHeader)
 LLVM_YAML_IS_SEQUENCE_VECTOR(std::unique_ptr<llvm::ELFYAML::Chunk>)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::Symbol)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::VerdefEntry)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::VernauxEntry)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::VerneedEntry)
 LLVM_YAML_IS_SEQUENCE_VECTOR(llvm::ELFYAML::Relocation)

 template <> struct MappingTraits<ELFYAML::AddrsigSymbol> {
   static void mapping(IO &IO, ELFYAML::AddrsigSymbol &Sym);
 };
 
 template <> struct MappingTraits<ELFYAML::LinkerOption> {
   static void mapping(IO &IO, ELFYAML::LinkerOption &Sym);
 };
 
+template <> struct MappingTraits<ELFYAML::CallGraphEntry> {
+  static void mapping(IO &IO, ELFYAML::CallGraphEntry &E);
+};
+
 template <> struct MappingTraits<ELFYAML::Relocation> {
   static void mapping(IO &IO, ELFYAML::Relocation &Rel);
 };
 
 template <> struct MappingTraits<std::unique_ptr<ELFYAML::Chunk>> {
   static void mapping(IO &IO, std::unique_ptr<ELFYAML::Chunk> &C);
   static StringRef validate(IO &io, std::unique_ptr<ELFYAML::Chunk> &C);
 };

llvm/lib/ObjectYAML/ELFEmitter.cpp

void writeSectionContent(Elf_Shdr &SHeader,
                            const ELFYAML::GnuHashSection &Section,
                            ContiguousBlobAccumulator &CBA);
   void writeSectionContent(Elf_Shdr &SHeader,
                            const ELFYAML::LinkerOptionsSection &Section,
                            ContiguousBlobAccumulator &CBA);
   void writeSectionContent(Elf_Shdr &SHeader,
                            const ELFYAML::DependentLibrariesSection &Section,
                            ContiguousBlobAccumulator &CBA);
+  void writeSectionContent(Elf_Shdr &SHeader,
+                           const ELFYAML::CallGraphProfileSection &Section,
+                           ContiguousBlobAccumulator &CBA);
 
   void writeFill(ELFYAML::Fill &Fill, ContiguousBlobAccumulator &CBA);
 
   ELFState(ELFYAML::Object &D, yaml::ErrorHandler EH);
 
 public:
   static bool writeELF(raw_ostream &OS, ELFYAML::Object &Doc,
                        yaml::ErrorHandler EH);
for (const std::unique_ptr<ELFYAML::Chunk> &D : Doc.Chunks) {
     } else if (auto S = dyn_cast<ELFYAML::LinkerOptionsSection>(Sec)) {
       writeSectionContent(SHeader, *S, CBA);
     } else if (auto S = dyn_cast<ELFYAML::NoteSection>(Sec)) {
       writeSectionContent(SHeader, *S, CBA);
     } else if (auto S = dyn_cast<ELFYAML::GnuHashSection>(Sec)) {
       writeSectionContent(SHeader, *S, CBA);
     } else if (auto S = dyn_cast<ELFYAML::DependentLibrariesSection>(Sec)) {
       writeSectionContent(SHeader, *S, CBA);
+    } else if (auto S = dyn_cast<ELFYAML::CallGraphProfileSection>(Sec)) {
+      writeSectionContent(SHeader, *S, CBA);
     } else {
       llvm_unreachable("Unknown section type");
     }
 
     // Override section fields if requested.
     overrideFields<ELFT>(Sec, SHeader);
   }
 }
void ELFState<ELFT>::writeSectionContent(
   for (StringRef Lib : *Section.Libs) {
     OS.write(Lib.data(), Lib.size());
     OS.write('\0');
     SHeader.sh_size += Lib.size() + 1;
   }
 }
 
 template <class ELFT>
+void ELFState<ELFT>::writeSectionContent(
+    Elf_Shdr &SHeader, const ELFYAML::CallGraphProfileSection &Section,
+    ContiguousBlobAccumulator &CBA) {
+  raw_ostream &OS =
+      CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
+
+  if (Section.EntSize)
+    SHeader.sh_entsize = *Section.EntSize;
+  else
+    SHeader.sh_entsize = 16;
+
+  unsigned Link = 0;
+  if (Section.Link.empty() && SN2I.lookup(".symtab", Link))
+    SHeader.sh_link = Link;
+
+  if (Section.Content) {
+    SHeader.sh_size = writeContent(OS, Section.Content, None);
+    return;
+  }
+
+  if (!Section.Entries)
+    return;
+
+  for (const ELFYAML::CallGraphEntry &E : *Section.Entries) {
+    unsigned From = toSymbolIndex(E.From, Section.Name, /*IsDynamic=*/ false);
+    unsigned To = toSymbolIndex(E.To, Section.Name, /*IsDynamic=*/ false);
+
+    support::endian::write<uint32_t>(OS, From, ELFT::TargetEndianness);
+    support::endian::write<uint32_t>(OS, To, ELFT::TargetEndianness);
+    support::endian::write<uint64_t>(OS, E.Weight, ELFT::TargetEndianness);
+    SHeader.sh_size += 16;
+  }
+}
+
+template <class ELFT>
 void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
                                          const ELFYAML::HashSection &Section,
                                          ContiguousBlobAccumulator &CBA) {
   raw_ostream &OS =
       CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
 
   unsigned Link = 0;
   if (Section.Link.empty() && SN2I.lookup(".dynsym", Link))

llvm/lib/ObjectYAML/ELFYAML.cpp

 
 static void sectionMapping(IO &IO,
                            ELFYAML::DependentLibrariesSection &Section) {
   commonSectionMapping(IO, Section);
   IO.mapOptional("Libraries", Section.Libs);
   IO.mapOptional("Content", Section.Content);
 }
 
+static void sectionMapping(IO &IO, ELFYAML::CallGraphProfileSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Entries", Section.Entries);
+  IO.mapOptional("Content", Section.Content);
+}
+
 void MappingTraits<ELFYAML::SectionOrType>::mapping(
     IO &IO, ELFYAML::SectionOrType &sectionOrType) {
   IO.mapRequired("SectionOrType", sectionOrType.sectionNameOrType);
 }
 
 void MappingTraits<ELFYAML::SectionName>::mapping(
     IO &IO, ELFYAML::SectionName &sectionName) {
   IO.mapRequired("Section", sectionName.Section);
case ELF::SHT_LLVM_LINKER_OPTIONS:
     sectionMapping(IO, *cast<ELFYAML::LinkerOptionsSection>(Section.get()));
     break;
   case ELF::SHT_LLVM_DEPENDENT_LIBRARIES:
     if (!IO.outputting())
       Section.reset(new ELFYAML::DependentLibrariesSection());
     sectionMapping(IO,
                    *cast<ELFYAML::DependentLibrariesSection>(Section.get()));
     break;
+  case ELF::SHT_LLVM_CALL_GRAPH_PROFILE:
+    if (!IO.outputting())
+      Section.reset(new ELFYAML::CallGraphProfileSection());
+    sectionMapping(IO, *cast<ELFYAML::CallGraphProfileSection>(Section.get()));
+    break;
   default:
     if (!IO.outputting()) {
       StringRef Name;
       IO.mapOptional("Name", Name, StringRef());
       Name = ELFYAML::dropUniqueSuffix(Name);
 
       if (ELFYAML::StackSizesSection::nameMatches(Name))
         Section = std::make_unique<ELFYAML::StackSizesSection>();
StringRef MappingTraits<std::unique_ptr<ELFYAML::Chunk>>::validate(
   }
 
   if (const auto *RS = dyn_cast<ELFYAML::RelrSection>(C.get())) {
     if (RS->Entries && RS->Content)
       return "\"Entries\" and \"Content\" can't be used together";
     return {};
   }
 
+  if (const auto *CGP = dyn_cast<ELFYAML::CallGraphProfileSection>(C.get())) {
+    if (CGP->Entries && CGP->Content)
+      return "\"Entries\" and \"Content\" can't be used together";
+    return {};
+  }
+
   return {};
 }
 
 namespace {
 
 struct NormalizedMips64RelType {
   NormalizedMips64RelType(IO &)
       : Type(ELFYAML::ELF_REL(ELF::R_MIPS_NONE)),

 
 void MappingTraits<ELFYAML::LinkerOption>::mapping(IO &IO,
                                                    ELFYAML::LinkerOption &Opt) {
   assert(IO.getContext() && "The IO context is not initialized");
   IO.mapRequired("Name", Opt.Key);
   IO.mapRequired("Value", Opt.Value);
 }
 
+void MappingTraits<ELFYAML::CallGraphEntry>::mapping(
+    IO &IO, ELFYAML::CallGraphEntry &E) {
+  assert(IO.getContext() && "The IO context is not initialized");
+  IO.mapRequired("From", E.From);
+  IO.mapRequired("To", E.To);
+  IO.mapRequired("Weight", E.Weight);
+}
+
 LLVM_YAML_STRONG_TYPEDEF(uint8_t, MIPS_AFL_REG)
 LLVM_YAML_STRONG_TYPEDEF(uint8_t, MIPS_ABI_FP)
 LLVM_YAML_STRONG_TYPEDEF(uint32_t, MIPS_AFL_EXT)
 LLVM_YAML_STRONG_TYPEDEF(uint32_t, MIPS_AFL_ASE)
 LLVM_YAML_STRONG_TYPEDEF(uint32_t, MIPS_AFL_FLAGS1)
 
 } // end namespace yaml
 
 } // end namespace llvm

llvm/test/tools/obj2yaml/call-graph-profile-section.yaml

+## Test how we dump SHT_LLVM_CALL_GRAPH_PROFILE sections for 32 and 64-bit targets.
+
+## Test we use the "Entries" property when it is possible to dump values correctly.
+
+# RUN: yaml2obj --docnum=1 %s -o %t.le64
+# RUN: obj2yaml %t.le64 | FileCheck %s --check-prefix=BASIC
+# RUN: yaml2obj --docnum=2 %s -o %t.be64
+# RUN: obj2yaml %t.be64 | FileCheck %s --check-prefix=BASIC
+# RUN: yaml2obj --docnum=3 %s -o %t.le32
+# RUN: obj2yaml %t.le32 | FileCheck %s --check-prefix=BASIC
+# RUN: yaml2obj --docnum=4 %s -o %t.be32
+# RUN: obj2yaml %t.be32 | FileCheck %s --check-prefix=BASIC
+
+# BASIC:      Sections:
+# BASIC-NEXT:   - Name:    .llvm.call-graph-profile
+# BASIC-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# BASIC-NEXT:     Link:    .symtab
+# BASIC-NEXT:     EntSize: 0x0000000000000010
+# BASIC-NEXT:     Entries:
+# BASIC-NEXT:       - From:   foo
+# BASIC-NEXT:         To:     bar
+# BASIC-NEXT:         Weight: 89
+# BASIC-NEXT:       - From:   bar
+# BASIC-NEXT:         To:     foo
+# BASIC-NEXT:         Weight: 98
+# BASIC-NEXT: Symbols:
+
+## TODO: we should really improve yaml2obj somehow to be able to collapse
+##       the following four YAML descriptions into a single one.
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_386
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2MSB
+  Type:    ET_DYN
+  Machine: EM_386
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+## Check how we handle broken cases.
+
+# RUN: yaml2obj --docnum=5 %s -o %t.invalid
+# RUN: obj2yaml %t.invalid | FileCheck %s --check-prefix=INVALID
+
+# INVALID:      --- !ELF
+# INVALID-NEXT: FileHeader:
+# INVALID-NEXT:   Class:   ELFCLASS32
+# INVALID-NEXT:   Data:    ELFDATA2MSB
+# INVALID-NEXT:   Type:    ET_DYN
+# INVALID-NEXT:   Machine: EM_386
+# INVALID-NEXT: Sections:
+# INVALID-NEXT:   - Name:    .empty
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .symtab
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Content: ''
+# INVALID-NEXT:   - Name:    .multiple.16.valid
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .symtab
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Entries:
+# INVALID-NEXT:       - From:   foo
+# INVALID-NEXT:         To:     bar
+# INVALID-NEXT:         Weight: 3
+# INVALID-NEXT:   - Name:    .non.multiple.16
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .symtab
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Content: '0000000100000002000000000000000300'
+# INVALID-NEXT:   - Name:    .multiple.16.invalid
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .symtab
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Content: 00112233445566778899AABBCCDDEEFF
+# INVALID-NEXT:   - Name:    .unknown.symbol.1
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .symtab
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Content: 000000FF000000020000000000000003
+# INVALID-NEXT:   - Name:    .unknown.symbol.2
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .symtab
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Content: 00000001000000FF0000000000000003
+# INVALID-NEXT:   - Name:    .link.to.symtable
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .symtab
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Entries:
+# INVALID-NEXT:       - From:   foo
+# INVALID-NEXT:         To:     bar
+# INVALID-NEXT:         Weight: 0
+# INVALID-NEXT:   - Name:    .link.to.non.symtable.1
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Content: '00000001000000020000000000000000'
+# INVALID-NEXT:   - Name:    .link.to.non.symtable.2
+# INVALID-NEXT:     Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+# INVALID-NEXT:     Link:    .empty
+# INVALID-NEXT:     EntSize: 0x0000000000000010
+# INVALID-NEXT:     Content: '00000001000000020000000000000000'
+# INVALID-NEXT: Symbols:
+# INVALID-NEXT:   - Name: foo
+# INVALID-NEXT:   - Name: bar
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2MSB
+  Type:    ET_DYN
+  Machine: EM_386
+Sections:
+## Case 1: Content is empty.
+  - Name: .empty
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+## Case 2: Check that we use the "Entries" property to dump the data when it
+##         has a size that is a multiple of 16 and is valid (it is possible to match
+##         symbol indexes to symbols), but fallback to dumping the whole section
+##         using the "Content" property otherwise.
+## TODO: Teach yaml2obj to accept 'Size' key for SHT_LLVM_CALL_GRAPH_PROFILE
+##       sections and use Entries for cases below.
+  - Name: .multiple.16.valid
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Content: "00000001000000020000000000000003"
+  - Name: .non.multiple.16
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Content: "0000000100000002000000000000000300"
+  - Name: .multiple.16.invalid
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Content: "00112233445566778899AABBCCDDEEFF"
+## Case 3: Check we use the "Content" property when unable to match a
+##         symbol index to a symbol.
+  - Name: .unknown.symbol.1
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   0xff
+        To:     2
+        Weight: 3
+  - Name: .unknown.symbol.2
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     0xff
+        Weight: 3
+## Case 4: Check we use the "Content" property when a linked section
+##         is not a symbol table.
+  - Name: .link.to.symtable
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 0
+  - Name: .link.to.non.symtable.1
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Link: 0
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 0
+  - Name: .link.to.non.symtable.2
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Link: 1
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 0
+Symbols:
+  - Name: foo
+  - Name: bar

llvm/test/tools/yaml2obj/ELF/call-graph-profile-section.yaml

+## Test how we create SHT_LLVM_CALL_GRAPH_PROFILE sections.
+
+## Test that the content of SHT_LLVM_CALL_GRAPH_PROFILE sections
+## for 32/64-bit little/big endian targets is correct.
+# RUN: yaml2obj --docnum=1 %s -o %t.le64
+# RUN: llvm-readobj --sections --section-data %t.le64 | FileCheck %s --check-prefixes=BASIC,BASIC-LE
+# RUN: yaml2obj --docnum=2 %s -o %t.be64
+# RUN: llvm-readobj --sections --section-data %t.be64 | FileCheck %s --check-prefixes=BASIC,BASIC-BE
+# RUN: yaml2obj --docnum=3 %s -o %t.le32
+# RUN: llvm-readobj --sections --section-data %t.le32 | FileCheck %s --check-prefixes=BASIC,BASIC-LE
+# RUN: yaml2obj --docnum=4 %s -o %t.be32
+# RUN: llvm-readobj --sections --section-data %t.be32 | FileCheck %s --check-prefixes=BASIC,BASIC-BE
+
+# BASIC:        Name: .llvm.call-graph-profile
+# BASIC-NEXT:   Type: SHT_LLVM_CALL_GRAPH_PROFILE
+# BASIC-NEXT:   Flags [
+# BASIC-NEXT:   ]
+# BASIC-NEXT:   Address: 0x0
+# BASIC-NEXT:   Offset:
+# BASIC-NEXT:   Size: 32
+## Check that we link SHT_LLVM_CALL_GRAPH_PROFILE section with .symtab by default.
+# BASIC-NEXT:   Link: 2
+# BASIC-NEXT:   Info: 0
+# BASIC-NEXT:   AddressAlignment: 0
+## Check that the entry size is set to 16 by default.
+# BASIC-NEXT:   EntrySize: 16
+# BASIC-NEXT:   SectionData (
+# BASIC-LE-NEXT:  0000: 01000000 02000000 59000000 00000000
+# BASIC-LE-NEXT:  0010: 02000000 01000000 62000000 00000000
+# BASIC-BE-NEXT:  0000: 00000001 00000002 00000000 00000059
+# BASIC-BE-NEXT:  0010: 00000002 00000001 00000000 00000062
+# BASIC-NEXT:   )
+# BASIC-NEXT: }
+# BASIC-NEXT: Section {
+# BASIC-NEXT:   Index: 2
+# BASIC-NEXT:   Name: .symtab
+
+## TODO: we should really improve yaml2obj somehow to be able to collapse
+##       the following four YAML descriptions into a single one.
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2MSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_386
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2MSB
+  Type:    ET_DYN
+  Machine: EM_386
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 89
+      - From:   2
+        To:     1
+        Weight: 98
+Symbols:
+  - Name: foo
+  - Name: bar
+
+## Check we can set an arbitrary sh_link and sh_entsize values.
+## Check we can specify neither "Content" nor "Entries" tags.
+# RUN: yaml2obj --docnum=5 %s -o %t.link
+# RUN: llvm-readelf --sections %t.link | FileCheck %s --check-prefix=LINK
+
+# LINK: [Nr] Name      Type                    Address          Off    Size   ES Flg Lk
+# LINK: [ 1] .llvm.foo LLVM_CALL_GRAPH_PROFILE 0000000000000000 000040 000000 00     0
+# LINK: [ 2] .llvm.bar LLVM_CALL_GRAPH_PROFILE 0000000000000000 000040 000000 ff     255
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.foo
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Link: 0x0
+    EntSize: 0
+  - Name: .llvm.bar
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Link: 0xFF
+    EntSize: 0xFF
+
+## Check we can't specify both "Content" and "Entries" tags.
+# RUN: not yaml2obj --docnum=6 %s 2>&1 | FileCheck %s --check-prefix=BOTH
+# BOTH: error: "Entries" and "Content" can't be used together
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name:    .llvm.foo
+    Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+    Content: ""
+    Entries: []
+
+## Check we can describe SHT_LLVM_CALL_GRAPH_PROFILE sections using the "Entries" tag.
+## We can specify symbols either using names or indexes.
+# RUN: yaml2obj --docnum=7 %s -o %t.sym
+# RUN: llvm-readobj --elf-cg-profile %t.sym | FileCheck %s --check-prefix=SYMBOL-NAMES
+
+# SYMBOL-NAMES:      CGProfile [
+# SYMBOL-NAMES-NEXT:   CGProfileEntry {
+# SYMBOL-NAMES-NEXT:     From: foo (1)
+# SYMBOL-NAMES-NEXT:     To: bar (2)
+# SYMBOL-NAMES-NEXT:     Weight: 10
+# SYMBOL-NAMES-NEXT:   }
+# SYMBOL-NAMES-NEXT:   CGProfileEntry {
+# SYMBOL-NAMES-NEXT:     From: foo (1)
+# SYMBOL-NAMES-NEXT:     To: bar (2)
+# SYMBOL-NAMES-NEXT:     Weight: 20
+# SYMBOL-NAMES-NEXT:   }
+# SYMBOL-NAMES-NEXT:   CGProfileEntry {
+# SYMBOL-NAMES-NEXT:     From: foo (1)
+# SYMBOL-NAMES-NEXT:     To: foo (3)
+# SYMBOL-NAMES-NEXT:     Weight: 30
+# SYMBOL-NAMES-NEXT:   }
+# SYMBOL-NAMES-NEXT: ]
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+## Case 1: Test we can use symbol names to describe an entry.
+      - From:   foo
+        To:     bar
+        Weight: 10
+## Case 2: Test we can use symbol indexes to describe an entry.
+      - From:   1
+        To:     2
+        Weight: 20
+## Case 3: Test we can refer to symbols with suffixes.
+      - From:   foo
+        To:     'foo [1]'
+        Weight: 30
+Symbols:
+  - Name: foo
+  - Name: bar
+  - Name: 'foo [1]'
+
+## Check we can describe SHT_LLVM_CALL_GRAPH_PROFILE sections using the "Content" tag.
+# RUN: yaml2obj --docnum=8 %s -o %t.content
+# RUN: llvm-readobj --sections --section-data %t.content | FileCheck %s --check-prefix=CONTENT
+
+# CONTENT:      Name: .llvm.call-graph-profile
+# CONTENT:      SectionData (
+# CONTENT-NEXT:   0000: 11223344 |
+# CONTENT-NEXT: )
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name:    .llvm.call-graph-profile
+    Type:    SHT_LLVM_CALL_GRAPH_PROFILE
+    Content: "11223344"
+
+## Check we can't reference unknown symbols by name.
+# RUN: not yaml2obj --docnum=9 %s 2>&1 | FileCheck %s --check-prefix=UNKNOWN-NAME
+# RUN: not yaml2obj --docnum=10 %s 2>&1 | FileCheck %s --check-prefix=UNKNOWN-NAME
+# UNKNOWN-NAME: error: unknown symbol referenced: 'bar' by YAML section '.llvm.call-graph-profile'
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+## The first symbol is valid, but the second is unknown.
+    Entries:
+      - From:   foo
+        To:     bar
+        Weight: 10
+Symbols:
+  - Name: foo
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+## The first symbol is unknown, but the second is valid.
+    Entries:
+      - From:   bar
+        To:     foo
+        Weight: 10
+Symbols:
+  - Name: foo
+
+## Check we can specify arbitrary symbol indexes for an SHT_LLVM_CALL_GRAPH_PROFILE section entry.
+# RUN: yaml2obj --docnum=11 %s -o %t.unk
+# RUN: llvm-readobj --sections --section-data %t.unk | FileCheck %s --check-prefix=UNKNOWN-INDEX
+
+# UNKNOWN-INDEX:      Name: .llvm.call-graph-profile
+# UNKNOWN-INDEX:      SectionData (
+# UNKNOWN-INDEX-NEXT:   0000: 01000000 02000000 03000000 00000000 |
+# UNKNOWN-INDEX-NEXT: )
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_DYN
+  Machine: EM_X86_64
+Sections:
+  - Name: .llvm.call-graph-profile
+    Type: SHT_LLVM_CALL_GRAPH_PROFILE
+    Entries:
+      - From:   1
+        To:     2
+        Weight: 3

llvm/tools/obj2yaml/elf2yaml.cpp

class ELFDumper {
   Error dumpRelocation(const RelT *Rel, const Elf_Shdr *SymTab,
                        ELFYAML::Relocation &R);
 
   Expected<ELFYAML::AddrsigSection *> dumpAddrsigSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::LinkerOptionsSection *>
   dumpLinkerOptionsSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::DependentLibrariesSection *>
   dumpDependentLibrariesSection(const Elf_Shdr *Shdr);
+  Expected<ELFYAML::CallGraphProfileSection *>
+  dumpCallGraphProfileSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::DynamicSection *> dumpDynamicSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::RelocationSection *> dumpRelocSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::RelrSection *> dumpRelrSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::RawContentSection *>
   dumpContentSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::SymtabShndxSection *>
   dumpSymtabShndxSection(const Elf_Shdr *Shdr);
   Expected<ELFYAML::NoBitsSection *> dumpNoBitsSection(const Elf_Shdr *Shdr);
for (const Elf_Shdr &Sec : Sections) {
     case ELF::SHT_LLVM_DEPENDENT_LIBRARIES: {
       Expected<ELFYAML::DependentLibrariesSection *> SecOrErr =
           dumpDependentLibrariesSection(&Sec);
       if (!SecOrErr)
         return SecOrErr.takeError();
       Y->Chunks.emplace_back(*SecOrErr);
       break;
     }
+    case ELF::SHT_LLVM_CALL_GRAPH_PROFILE: {
+      Expected<ELFYAML::CallGraphProfileSection *> SecOrErr =
+          dumpCallGraphProfileSection(&Sec);
+      if (!SecOrErr)
+        return SecOrErr.takeError();
+      Y->Chunks.emplace_back(*SecOrErr);
+      break;
+    }
     case ELF::SHT_NULL: {
       // We only dump the SHT_NULL section at index 0 when it
       // has at least one non-null field, because yaml2obj
       // normally creates the zero section at index 0 implicitly.
       if (&Sec == &Sections[0]) {
         const uint8_t *Begin = reinterpret_cast<const uint8_t *>(&Sec);
         const uint8_t *End = Begin + sizeof(Elf_Shdr);
         if (std::find_if(Begin, End, [](uint8_t V) { return V != 0; }) == End)
for (const uint8_t *I = Content.begin(), *E = Content.end(); I < E;) {
     DL->Libs->emplace_back(Lib);
     I += Lib.size() + 1;
   }
 
   return DL.release();
 }
 
 template <class ELFT>
+Expected<ELFYAML::CallGraphProfileSection *>
+ELFDumper<ELFT>::dumpCallGraphProfileSection(const Elf_Shdr *Shdr) {
+  auto S = std::make_unique<ELFYAML::CallGraphProfileSection>();
+  if (Error E = dumpCommonSection(Shdr, *S))
+    return std::move(E);
+
+  Expected<ArrayRef<uint8_t>> ContentOrErr = Obj.getSectionContents(Shdr);
+  if (!ContentOrErr)
+    return ContentOrErr.takeError();
+  ArrayRef<uint8_t> Content = *ContentOrErr;
+
+  // Dump the section with use of Content key when it is empty or truncated.
+  if (Content.empty() || Content.size() % 16 != 0) {
+    S->Content = yaml::BinaryRef(Content);
+    return S.release();
+  }
+
+  std::vector<ELFYAML::CallGraphEntry> Entries(Content.size() / 16);
+  DataExtractor Data(Content, Obj.isLE(), /*AddressSize=*/0);
+  DataExtractor::Cursor Cur(0);
+  auto ReadEntry = [&](ELFYAML::CallGraphEntry &E) {
+    uint32_t FromSymIndex = Data.getU32(Cur);
+    uint32_t ToSymIndex = Data.getU32(Cur);
+    E.Weight = Data.getU64(Cur);
+    if (!Cur) {
+      consumeError(Cur.takeError());
+      return false;
+    }
+
+    Expected<StringRef> From = getSymbolName(Shdr->sh_link, FromSymIndex);
+    Expected<StringRef> To = getSymbolName(Shdr->sh_link, ToSymIndex);
+    if (From && To) {
+      E.From = *From;
+      E.To = *To;
+      return true;
+    }
+    consumeError(From.takeError());
+    consumeError(To.takeError());
+    return false;
+  };
+
+  for (ELFYAML::CallGraphEntry &E : Entries) {
+    if (ReadEntry(E))
+      continue;
+    S->Content = yaml::BinaryRef(Content);
+    return S.release();
+  }
+
+  S->Entries = std::move(Entries);
+  return S.release();
+}
+
+template <class ELFT>
 Expected<ELFYAML::DynamicSection *>
 ELFDumper<ELFT>::dumpDynamicSection(const Elf_Shdr *Shdr) {
   auto S = std::make_unique<ELFYAML::DynamicSection>();
   if (Error E = dumpCommonSection(Shdr, *S))
     return std::move(E);
 
   auto DynTagsOrErr = Obj.template getSectionContentsAsArray<Elf_Dyn>(Shdr);
   if (!DynTagsOrErr)