[yaml2obj/obj2yaml] - Add support for SHT_RELR sections.

Note: this is a reland with a trivial 2 lines fix in ELFState<ELFT>::writeSectionContent.
      It adds a check similar to ones we already have for other sections to fix the case revealed
      by bots, like http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/60744.

The encoded sequence of Elf*_Relr entries in a SHT_RELR section looks
like [ AAAAAAAA BBBBBBB1 BBBBBBB1 ... AAAAAAAA BBBBBB1 ... ]
i.e. start with an address, followed by any number of bitmaps. The address
entry encodes 1 relocation. The subsequent bitmap entries encode up to 63(31)
relocations each, at subsequent offsets following the last address entry.

More information is here:
https://github.com/llvm-mirror/llvm/blob/master/lib/Object/ELF.cpp#L272

This patch adds a support for these sections.

Differential revision: https://reviews.llvm.org/D71872

1 files changed, 33 insertions, 0 deletions

diff --git a/llvm/tools/obj2yaml/elf2yaml.cpp b/llvm/tools/obj2yaml/elf2yaml.cpp
index 75d2e427b4f..904d1ad9d0a 100644
--- a/llvm/tools/obj2yaml/elf2yaml.cpp
+++ b/llvm/tools/obj2yaml/elf2yaml.cpp
@@ -27,6 +27,7 @@ class ELFDumper {
   typedef typename ELFT::Word Elf_Word;
   typedef typename ELFT::Rel Elf_Rel;
   typedef typename ELFT::Rela Elf_Rela;
+  using Elf_Relr = typename ELFT::Relr;
   using Elf_Nhdr = typename ELFT::Nhdr;
   using Elf_Note = typename ELFT::Note;
 
@@ -66,6 +67,7 @@ class ELFDumper {
   dumpDependentLibrariesSection(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 *>
@@ -251,6 +253,13 @@ template <class ELFT> Expected<ELFYAML::Object *> ELFDumper<ELFT>::dump() {
       Y->Chunks.emplace_back(*SecOrErr);
       break;
     }
+    case ELF::SHT_RELR: {
+      Expected<ELFYAML::RelrSection *> SecOrErr = dumpRelrSection(&Sec);
+      if (!SecOrErr)
+        return SecOrErr.takeError();
+      Y->Chunks.emplace_back(*SecOrErr);
+      break;
+    }
     case ELF::SHT_GROUP: {
       Expected<ELFYAML::Group *> GroupOrErr = dumpGroup(&Sec);
       if (!GroupOrErr)
@@ -724,6 +733,30 @@ ELFDumper<ELFT>::dumpRelocSection(const Elf_Shdr *Shdr) {
 }
 
 template <class ELFT>
+Expected<ELFYAML::RelrSection *>
+ELFDumper<ELFT>::dumpRelrSection(const Elf_Shdr *Shdr) {
+  auto S = std::make_unique<ELFYAML::RelrSection>();
+  if (auto E = dumpCommonSection(Shdr, *S))
+    return std::move(E);
+
+  if (Expected<ArrayRef<Elf_Relr>> Relrs = Obj.relrs(Shdr)) {
+    S->Entries.emplace();
+    for (Elf_Relr Rel : *Relrs)
+      S->Entries->emplace_back(Rel);
+    return S.release();
+  } else {
+    // Ignore. We are going to dump the data as raw content below.
+    consumeError(Relrs.takeError());
+  }
+
+  Expected<ArrayRef<uint8_t>> ContentOrErr = Obj.getSectionContents(Shdr);
+  if (!ContentOrErr)
+    return ContentOrErr.takeError();
+  S->Content = *ContentOrErr;
+  return S.release();
+}
+
+template <class ELFT>
 Expected<ELFYAML::RawContentSection *>
 ELFDumper<ELFT>::dumpContentSection(const Elf_Shdr *Shdr) {
   auto S = std::make_unique<ELFYAML::RawContentSection>();