[llvm] [Object] Parsing and dumping of SFrame FDEs (PR #149828)

[Pavel Labath via llvm-commits]

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@@ -48,7 +62,42 @@ Expected<SFrameParser<E>> SFrameParser<E>::create(ArrayRef<uint8_t> Contents) {
       getDataSliceAs<sframe::Header<E>>(Contents, 0);
   if (!Header)
     return Header.takeError();
-  return SFrameParser(Contents, *Header);
+  return SFrameParser(Contents, SectionAddress, *Header);
+}
+
+template <endianness E>
+Expected<ArrayRef<uint8_t>> SFrameParser<E>::getAuxHeader() const {
+  return getDataSlice(Data, sizeof(Header), Header.AuxHdrLen);
+}
+
+template <endianness E>
+Expected<ArrayRef<sframe::FuncDescEntry<E>>> SFrameParser<E>::fdes() const {
+  Expected<ArrayRef<uint8_t>> Slice = getDataSlice(
+      Data, getFDEBegin(), Header.NumFDEs * sizeof(sframe::FuncDescEntry<E>));
+  if (!Slice)
+    return Slice.takeError();
+  return ArrayRef(
+      reinterpret_cast<const sframe::FuncDescEntry<E> *>(Slice->data()),
+      Header.NumFDEs);
+}
+
+template <endianness E>
+uint64_t SFrameParser<E>::getAbsoluteStartAddress(
+    typename FDERange::iterator FDE) const {
+  uint64_t Result = SectionAddress + FDE->StartAddress;
+
+  if ((getPreamble().Flags.value() & sframe::Flags::FDEFuncStartPCRel) ==
+      sframe::Flags::FDEFuncStartPCRel) {
+    uintptr_t DataPtr = reinterpret_cast<uintptr_t>(Data.data());
+    uintptr_t FDEPtr = reinterpret_cast<uintptr_t>(&*FDE);
+
+    assert(DataPtr <= FDEPtr);
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labath wrote:

This doesn't check the value of the field -- only it's address. The goal is to catch the (UB) case where someone passes an FDE iterator from one object into the parser for another object. I'll add a message to the assertion to make that clearer.

https://github.com/llvm/llvm-project/pull/149828