[llvm-objdump] -r: support CREL

Extract the llvm-readelf decoder to `decodeCrel` (#91280) and reuse it
for llvm-objdump.

Because the section representation of LLVMObject (`SectionRef`) is
64-bit, insufficient to hold all decoder states, `section_rel_begin` is
modified to decode CREL eagerly and hold the decoded relocations inside
ELFObjectFile<ELFT>.

The test is adapted from llvm/test/tools/llvm-readobj/ELF/crel.test.

Pull Request: https://github.com/llvm/llvm-project/pull/97382

2 files changed, 15 insertions, 1 deletions

diff --git a/llvm/tools/llvm-objdump/ELFDump.cpp b/llvm/tools/llvm-objdump/ELFDump.cpp
index 8c184fc..5ac1349 100644
--- a/llvm/tools/llvm-objdump/ELFDump.cpp
+++ b/llvm/tools/llvm-objdump/ELFDump.cpp
@@ -104,7 +104,11 @@ static Error getRelocationValueString(const ELFObjectFile<ELFT> *Obj,
   // In SHT_REL case we would need to read the addend from section data.
   // GNU objdump does not do that and we just follow for simplicity atm.
   bool Undef = false;
-  if ((*SecOrErr)->sh_type == ELF::SHT_RELA) {
+  if ((*SecOrErr)->sh_type == ELF::SHT_CREL) {
+    auto ERela = Obj->getCrel(Rel);
+    Addend = ERela.r_addend;
+    Undef = ERela.getSymbol(false) == 0;
+  } else if ((*SecOrErr)->sh_type == ELF::SHT_RELA) {
     const typename ELFT::Rela *ERela = Obj->getRela(Rel);
     Addend = ERela->r_addend;
     Undef = ERela->getSymbol(false) == 0;
diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 6249be4..d124002 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -2687,6 +2687,16 @@ void Dumper::printRelocations() {
            << "VALUE\n";
 
     for (SectionRef Section : P.second) {
+      // CREL sections require decoding, each section may have its own specific
+      // decode problems.
+      if (O.isELF() && ELFSectionRef(Section).getType() == ELF::SHT_CREL) {
+        StringRef Err =
+            cast<const ELFObjectFileBase>(O).getCrelDecodeProblem(Section);
+        if (!Err.empty()) {
+          reportUniqueWarning(Err);
+          continue;
+        }
+      }
       for (const RelocationRef &Reloc : Section.relocations()) {
         uint64_t Address = Reloc.getOffset();
         SmallString<32> RelocName;