[llvm] [llvm-objcopy] Add possibility to verify .note section format (PR #90458)

[Fangrui Song via llvm-commits]

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@@ -623,6 +623,59 @@ handleUserSection(const NewSectionInfo &NewSection,
   return F(NewSection.SectionName, Data);
 }
 
+static Error verifyNoteSection(StringRef Name, endianness Endianness,
+                               ArrayRef<uint8_t> Data) {
+  // An ELF note has the following structure:
+  // Name Size: 4 bytes (integer)
+  // Desc Size: 4 bytes (integer)
+  // Type     : 4 bytes
+  // Name     : variable size, padded to a 4 byte boundary
+  // Desc     : variable size, padded to a 4 byte boundary
+
+  if (Data.empty())
+    return Error::success();
+
+  if (Data.size() < 12) {
+    std::string msg;
+    raw_string_ostream(msg)
+        << Name << " data must be either empty or at least 12 bytes long";
+    return createStringError(errc::invalid_argument, msg);
+  }
+  if (Data.size() % 4 != 0) {
+    std::string msg;
+    raw_string_ostream(msg)
+        << Name << " data size must be a  multiple of 4 bytes";
+    return createStringError(errc::invalid_argument, msg);
+  }
+  ArrayRef<uint8_t> NameSize = Data.slice(0, 4);
+  ArrayRef<uint8_t> DescSize = Data.slice(4, 4);
+
+  uint32_t NameSizeValue = *reinterpret_cast<const uint32_t *>(NameSize.data());
+  uint32_t DescSizeValue = *reinterpret_cast<const uint32_t *>(DescSize.data());
+
+  if (Endianness != endianness::native) {
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MaskRay wrote:

`endian::read32` should make byteswap unnecessary.

https://github.com/llvm/llvm-project/pull/90458