[llvm] [llvm-objcopy][ELF] Add an option to remove notes (PR #118739)

[James Henderson via llvm-commits]

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@@ -609,6 +609,97 @@ static void addSymbol(Object &Obj, const NewSymbolInfo &SymInfo,
       Sec ? (uint16_t)SYMBOL_SIMPLE_INDEX : (uint16_t)SHN_ABS, 0);
 }
 
+namespace {
+struct RemoveNoteDetail {
+  struct DeletedRange {
+    uint64_t OldFrom;
+    uint64_t OldTo;
+    uint64_t NewPos;
+  };
+
+  template <class ELFT>
+  static std::vector<DeletedRange>
+  findNotesToRemove(ArrayRef<uint8_t> Data, size_t Align,
+                    ArrayRef<RemoveNoteInfo> NotesToRemove);
+  static std::vector<uint8_t> updateData(ArrayRef<uint8_t> OldData,
+                                         ArrayRef<DeletedRange> ToRemove);
+};
+
+} // namespace
+
+template <class ELFT>
+std::vector<RemoveNoteDetail::DeletedRange>
+RemoveNoteDetail::findNotesToRemove(ArrayRef<uint8_t> Data, size_t Align,
+                                    ArrayRef<RemoveNoteInfo> NotesToRemove) {
+  LLVM_ELF_IMPORT_TYPES_ELFT(ELFT);
+  std::vector<DeletedRange> ToRemove;
+  uint64_t CurPos = 0;
+  uint64_t NewPos = 0;
+  while (CurPos + sizeof(Elf_Nhdr) <= Data.size()) {
+    auto Nhdr = reinterpret_cast<const Elf_Nhdr *>(Data.data() + CurPos);
+    size_t FullSize = Nhdr->getSize(Align);
+    if (CurPos + FullSize > Data.size())
+      break;
+    Elf_Note Note(*Nhdr);
+    bool ShouldRemove =
+        llvm::any_of(NotesToRemove, [&Note](const RemoveNoteInfo &NoteInfo) {
+          return NoteInfo.TypeId == Note.getType() &&
+                 (NoteInfo.Name.empty() || NoteInfo.Name == Note.getName());
+        });
+    if (ShouldRemove)
+      ToRemove.push_back({CurPos, CurPos + FullSize, NewPos});
+    else
+      NewPos += FullSize;
+    CurPos += FullSize;
+  }
+  return ToRemove;
+}
+
+std::vector<uint8_t>
+RemoveNoteDetail::updateData(ArrayRef<uint8_t> OldData,
+                             ArrayRef<DeletedRange> ToRemove) {
+  std::vector<uint8_t> NewData;
+  NewData.reserve(OldData.size());
+  uint64_t CurPos = 0;
+  for (auto &RemRange : ToRemove) {
+    if (CurPos < RemRange.OldFrom) {
+      auto Slice = OldData.slice(CurPos, RemRange.OldFrom - CurPos);
+      NewData.insert(NewData.end(), Slice.begin(), Slice.end());
+    }
+    assert(RemRange.NewPos == NewData.size());
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jh7370 wrote:

This looks to be the only place `NewPos` is used and it doesn't really feel necessary to me, so I think the field can be dropped.

https://github.com/llvm/llvm-project/pull/118739