[llvm] [llvm-readobj][COFF] Implement --coff-pseudoreloc in llvm-readobj to dump runtime pseudo-relocation records (PR #151816)

[Martin Storsjö via llvm-commits]

================
@@ -2000,6 +2001,122 @@ void COFFDumper::printCOFFBaseReloc() {
   }
 }
 
+void COFFDumper::printCOFFPseudoReloc() {
+  const StringRef RelocBeginName = Obj->getArch() == Triple::x86
+                                       ? "___RUNTIME_PSEUDO_RELOC_LIST__"
+                                       : "__RUNTIME_PSEUDO_RELOC_LIST__";
+  const StringRef RelocEndName = Obj->getArch() == Triple::x86
+                                     ? "___RUNTIME_PSEUDO_RELOC_LIST_END__"
+                                     : "__RUNTIME_PSEUDO_RELOC_LIST_END__";
+
+  COFFSymbolRef RelocBegin, RelocEnd;
+  auto Count = Obj->getNumberOfSymbols();
+  if (Count == 0) {
+    W.startLine() << "The symbol table has been stripped\n";
+    return;
+  }
+  for (auto i = 0u;
+       i < Count && (!RelocBegin.getRawPtr() || !RelocEnd.getRawPtr()); ++i) {
+    auto Sym = Obj->getSymbol(i);
+    if (Sym.takeError())
+      continue;
+    auto Name = Obj->getSymbolName(*Sym);
+    if (Name.takeError())
+      continue;
+    if (*Name == RelocBeginName) {
+      if (Sym->getSectionNumber() > 0)
+        RelocBegin = *Sym;
+    } else if (*Name == RelocEndName) {
+      if (Sym->getSectionNumber() > 0)
+        RelocEnd = *Sym;
+    }
+  }
+  if (!RelocBegin.getRawPtr() || !RelocEnd.getRawPtr()) {
+    W.startLine()
+        << "The symbols for runtime pseudo-relocation are not found\n";
+    return;
+  }
+
+  ArrayRef<uint8_t> Data;
+  auto Section = Obj->getSection(RelocBegin.getSectionNumber());
+  if (auto E = Section.takeError()) {
+    reportError(std::move(E), Obj->getFileName());
+    return;
+  }
+  if (auto E = Obj->getSectionContents(*Section, Data)) {
+    reportError(std::move(E), Obj->getFileName());
+    return;
+  }
+  ArrayRef<uint8_t> RawRelocs =
+      Data.take_front(RelocEnd.getValue()).drop_front(RelocBegin.getValue());
+  struct alignas(4) PseudoRelocationHeader {
+    PseudoRelocationHeader(uint32_t Signature)
+        : Zero1(0), Zero2(0), Signature(Signature) {}
+    support::ulittle32_t Zero1;
+    support::ulittle32_t Zero2;
+    support::ulittle32_t Signature;
+  };
+  const PseudoRelocationHeader HeaderV2(1);
+  if (RawRelocs.size() < sizeof(HeaderV2) ||
+      (memcmp(RawRelocs.data(), &HeaderV2, sizeof(HeaderV2)) != 0)) {
+    reportWarning(
----------------
mstorsjo wrote:

If `RawRelocs.size() == 0`, we probably should print a different message than this? (Not sure if the linker actually ever does produce that, and what the runtime would do with it.)

https://github.com/llvm/llvm-project/pull/151816