[yaml2obj, obj2yaml] - Add support for SHT_NOTE sections.

SHT_NOTE is the section that consists of
namesz, descsz, type, name + padding, desc + padding data.
This patch teaches yaml2obj, obj2yaml to dump and parse them.

This patch implements the section how it is described here:
https://docs.oracle.com/cd/E23824_01/html/819-0690/chapter6-18048.html
Which says: "For 64–bit objects and 32–bit objects, each entry is an array of 4-byte words in
the format of the target processor"

The official specification is different
http://www.sco.com/developers/gabi/latest/ch5.pheader.html#note_section
And says: "n 64-bit objects (files with e_ident[EI_CLASS] equal to ELFCLASS64), each entry is an array
of 8-byte words in the format of the target processor. In 32-bit objects (files with e_ident[EI_CLASS]
equal to ELFCLASS32), each entry is an array of 4-byte words in the format of the target processor"

Since LLVM uses the first, 32-bit way, this patch follows it.

Differential revision: https://reviews.llvm.org/D68983

2 files changed, 102 insertions, 8 deletions

diff --git a/llvm/lib/ObjectYAML/ELFEmitter.cpp b/llvm/lib/ObjectYAML/ELFEmitter.cpp
index 8ba1608254b..dae3f395993 100644
--- a/llvm/lib/ObjectYAML/ELFEmitter.cpp
+++ b/llvm/lib/ObjectYAML/ELFEmitter.cpp
@@ -36,6 +36,16 @@ class ContiguousBlobAccumulator {
   SmallVector<char, 128> Buf;
   raw_svector_ostream OS;
 
+public:
+  ContiguousBlobAccumulator(uint64_t InitialOffset_)
+      : InitialOffset(InitialOffset_), Buf(), OS(Buf) {}
+
+  template <class Integer>
+  raw_ostream &getOSAndAlignedOffset(Integer &Offset, unsigned Align) {
+    Offset = padToAlignment(Align);
+    return OS;
+  }
+
   /// \returns The new offset.
   uint64_t padToAlignment(unsigned Align) {
     if (Align == 0)
@@ -46,14 +56,6 @@ class ContiguousBlobAccumulator {
     return AlignedOffset; // == CurrentOffset;
   }
 
-public:
-  ContiguousBlobAccumulator(uint64_t InitialOffset_)
-      : InitialOffset(InitialOffset_), Buf(), OS(Buf) {}
-  template <class Integer>
-  raw_ostream &getOSAndAlignedOffset(Integer &Offset, unsigned Align) {
-    Offset = padToAlignment(Align);
-    return OS;
-  }
   void writeBlobToStream(raw_ostream &Out) { Out << OS.str(); }
 };
 
@@ -177,6 +179,9 @@ template <class ELFT> class ELFState {
   void writeSectionContent(Elf_Shdr &SHeader,
                            const ELFYAML::AddrsigSection &Section,
                            ContiguousBlobAccumulator &CBA);
+  void writeSectionContent(Elf_Shdr &SHeader,
+                           const ELFYAML::NoteSection &Section,
+                           ContiguousBlobAccumulator &CBA);
 
   ELFState(ELFYAML::Object &D, yaml::ErrorHandler EH);
 
@@ -440,6 +445,8 @@ void ELFState<ELFT>::initSectionHeaders(std::vector<Elf_Shdr> &SHeaders,
       writeSectionContent(SHeader, *S, CBA);
     } else if (auto S = dyn_cast<ELFYAML::AddrsigSection>(Sec)) {
       writeSectionContent(SHeader, *S, CBA);
+    } else if (auto S = dyn_cast<ELFYAML::NoteSection>(Sec)) {
+      writeSectionContent(SHeader, *S, CBA);
     } else {
       llvm_unreachable("Unknown section type");
     }
@@ -1035,6 +1042,55 @@ void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
   }
 }
 
+template <class ELFT>
+void ELFState<ELFT>::writeSectionContent(Elf_Shdr &SHeader,
+                                         const ELFYAML::NoteSection &Section,
+                                         ContiguousBlobAccumulator &CBA) {
+  raw_ostream &OS =
+      CBA.getOSAndAlignedOffset(SHeader.sh_offset, SHeader.sh_addralign);
+  uint64_t Offset = OS.tell();
+
+  if (Section.Content || Section.Size) {
+    SHeader.sh_size = writeContent(OS, Section.Content, Section.Size);
+    return;
+  }
+
+  for (const ELFYAML::NoteEntry &NE : *Section.Notes) {
+    // Write name size.
+    if (NE.Name.empty())
+      support::endian::write<uint32_t>(OS, 0, ELFT::TargetEndianness);
+    else
+      support::endian::write<uint32_t>(OS, NE.Name.size() + 1,
+                                       ELFT::TargetEndianness);
+
+    // Write description size.
+    if (NE.Desc.binary_size() == 0)
+      support::endian::write<uint32_t>(OS, 0, ELFT::TargetEndianness);
+    else
+      support::endian::write<uint32_t>(OS, NE.Desc.binary_size(),
+                                       ELFT::TargetEndianness);
+
+    // Write type.
+    support::endian::write<uint32_t>(OS, NE.Type, ELFT::TargetEndianness);
+
+    // Write name, null terminator and padding.
+    if (!NE.Name.empty()) {
+      support::endian::write<uint8_t>(OS, arrayRefFromStringRef(NE.Name),
+                                      ELFT::TargetEndianness);
+      support::endian::write<uint8_t>(OS, 0, ELFT::TargetEndianness);
+      CBA.padToAlignment(4);
+    }
+
+    // Write description and padding.
+    if (NE.Desc.binary_size() != 0) {
+      NE.Desc.writeAsBinary(OS);
+      CBA.padToAlignment(4);
+    }
+  }
+
+  SHeader.sh_size = OS.tell() - Offset;
+}
+
 template <class ELFT> void ELFState<ELFT>::buildSectionIndex() {
   for (unsigned I = 0, E = Doc.Sections.size(); I != E; ++I) {
     StringRef Name = Doc.Sections[I]->Name;
diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index 29585abe6e8..ad316be85e8 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -1032,6 +1032,13 @@ static void sectionMapping(IO &IO, ELFYAML::HashSection &Section) {
   IO.mapOptional("Size", Section.Size);
 }
 
+static void sectionMapping(IO &IO, ELFYAML::NoteSection &Section) {
+  commonSectionMapping(IO, Section);
+  IO.mapOptional("Content", Section.Content);
+  IO.mapOptional("Size", Section.Size);
+  IO.mapOptional("Notes", Section.Notes);
+}
+
 static void sectionMapping(IO &IO, ELFYAML::NoBitsSection &Section) {
   commonSectionMapping(IO, Section);
   IO.mapOptional("Size", Section.Size, Hex64(0));
@@ -1143,6 +1150,11 @@ void MappingTraits<std::unique_ptr<ELFYAML::Section>>::mapping(
       Section.reset(new ELFYAML::HashSection());
     sectionMapping(IO, *cast<ELFYAML::HashSection>(Section.get()));
     break;
+  case ELF::SHT_NOTE:
+    if (!IO.outputting())
+      Section.reset(new ELFYAML::NoteSection());
+    sectionMapping(IO, *cast<ELFYAML::NoteSection>(Section.get()));
+    break;
   case ELF::SHT_MIPS_ABIFLAGS:
     if (!IO.outputting())
       Section.reset(new ELFYAML::MipsABIFlags());
@@ -1270,6 +1282,24 @@ StringRef MappingTraits<std::unique_ptr<ELFYAML::Section>>::validate(
     return {};
   }
 
+  if (const auto *NS = dyn_cast<ELFYAML::NoteSection>(Section.get())) {
+    if (!NS->Content && !NS->Size && !NS->Notes)
+      return "one of \"Content\", \"Size\" or \"Notes\" must be "
+             "specified";
+
+    if (!NS->Content && !NS->Size)
+      return {};
+
+    if (NS->Size && NS->Content &&
+        (uint64_t)*NS->Size < NS->Content->binary_size())
+      return "\"Size\" must be greater than or equal to the content "
+             "size";
+
+    if (NS->Notes)
+      return "\"Notes\" cannot be used with \"Content\" or \"Size\"";
+    return {};
+  }
+
   return {};
 }
 
@@ -1313,6 +1343,14 @@ void MappingTraits<ELFYAML::DynamicEntry>::mapping(IO &IO,
   IO.mapRequired("Value", Rel.Val);
 }
 
+void MappingTraits<ELFYAML::NoteEntry>::mapping(IO &IO, ELFYAML::NoteEntry &N) {
+  assert(IO.getContext() && "The IO context is not initialized");
+
+  IO.mapOptional("Name", N.Name);
+  IO.mapOptional("Desc", N.Desc);
+  IO.mapRequired("Type", N.Type);
+}
+
 void MappingTraits<ELFYAML::VerdefEntry>::mapping(IO &IO,
                                                   ELFYAML::VerdefEntry &E) {
   assert(IO.getContext() && "The IO context is not initialized");