[llvm] [llvm-readobj] Dump callgraph section info for ELF (PR #157499)

[James Henderson via llvm-commits]

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@@ -5263,6 +5297,185 @@ template <class ELFT> void GNUELFDumper<ELFT>::printCGProfile() {
   OS << "GNUStyle::printCGProfile not implemented\n";
 }
 
+template <class ELFT>
+static std::optional<object::SectionRef>
+getCallGraphSection(const object::ELFObjectFile<ELFT> &ObjF) {
+  // Get the .llvm.callgraph section.
+  StringRef CallGraphSectionName(".llvm.callgraph");
+  for (auto Sec : ObjF.sections()) {
+    if (Expected<StringRef> NameOrErr = Sec.getName()) {
+      StringRef Name = *NameOrErr;
+      if (Name == CallGraphSectionName)
+        return Sec;
+    } else
+      consumeError(NameOrErr.takeError());
+  }
+  return std::nullopt;
+}
+
+namespace callgraph {
+LLVM_ENABLE_BITMASK_ENUMS_IN_NAMESPACE();
+enum Flags : uint8_t {
+  None = 0,
+  IsIndirectTarget = 1u << 0,
+  HasDirectCallees = 1u << 1,
+  HasIndirectCallees = 1u << 2,
+  LLVM_MARK_AS_BITMASK_ENUM(/*LargestValue*/ HasIndirectCallees)
+};
+} // namespace callgraph
+
+template <class ELFT> bool ELFDumper<ELFT>::processCallGraphSection() {
+  const Elf_Shdr *CGSection = findSectionByName(".llvm.callgraph");
+  if (!CGSection)
+    reportError(createError("No .llvm.callgraph section found."),
+                "Missing section");
+
+  Expected<ArrayRef<uint8_t>> SectionBytesOrErr =
+      Obj.getSectionContents(*CGSection);
+  if (!SectionBytesOrErr) {
+    reportError(SectionBytesOrErr.takeError(),
+                "Unable to read the .llvm.callgraph section");
+  }
+
+  auto PrintMalformedError = [&](Error &E, Twine FuncPC, StringRef Component) {
+    reportError(std::move(E),
+                Twine("While reading call graph info's [" + Component +
+                      "] for function at [0x" + FuncPC + "]")
+                    .str());
+  };
+
+  DataExtractor Data(SectionBytesOrErr.get(), Obj.isLE(),
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jh7370 wrote:

Have you looked into using the `DataExtractor::Cursor` class? I think that would simplify some of your parsing logic below.

https://github.com/llvm/llvm-project/pull/157499