[PATCH] D30804: [llvm-readobj] Only print the real size of the note

[Petr Hosek via Phabricator via llvm-commits]

phosek created this revision.

Note payloads are padded to a multiple of 4 bytes in size, but the size of the string that should be print can be smaller e.g. the n_descsz field in gold's version note is 9, so that's the whole size of the string that should be printed. The padding is part of the format of a SHT_NOTE section or PT_NOTE segment, but it's not part of the note itself.

Printing the extra null bytes may confuse some tools, e.g. when the llvm-readobj is sent to grep, it treats the output as binary because it contains a null byte.


Repository:
  rL LLVM

https://reviews.llvm.org/D30804

Files:
  tools/llvm-readobj/ELFDumper.cpp


Index: tools/llvm-readobj/ELFDumper.cpp
===================================================================
--- tools/llvm-readobj/ELFDumper.cpp
+++ tools/llvm-readobj/ELFDumper.cpp
@@ -3367,7 +3367,8 @@
 
 template <typename ELFT>
 static void printGNUNote(raw_ostream &OS, uint32_t NoteType,
-                         ArrayRef<typename ELFFile<ELFT>::Elf_Word> Words) {
+                         ArrayRef<typename ELFFile<ELFT>::Elf_Word> Words,
+                         size_t Size) {
   switch (NoteType) {
   default:
     return;
@@ -3390,16 +3391,14 @@
   }
   case ELF::NT_GNU_BUILD_ID: {
     OS << "    Build ID: ";
-    ArrayRef<uint8_t> ID(reinterpret_cast<const uint8_t *>(Words.data()),
-                         Words.size() * 4);
+    ArrayRef<uint8_t> ID(reinterpret_cast<const uint8_t *>(Words.data()), Size);
     for (const auto &B : ID)
       OS << format_hex_no_prefix(B, 2);
     break;
   }
   case ELF::NT_GNU_GOLD_VERSION:
     OS << "    Version: "
-       << StringRef(reinterpret_cast<const char *>(Words.data()),
-                    Words.size() * 4);
+       << StringRef(reinterpret_cast<const char *>(Words.data()), Size);
     break;
   }
 
@@ -3443,7 +3442,7 @@
 
       if (Name == "GNU") {
         OS << getGNUNoteTypeName(Type) << '\n';
-        printGNUNote<ELFT>(OS, Type, Descriptor);
+        printGNUNote<ELFT>(OS, Type, Descriptor, DescriptorSize);
       } else if (Name == "FreeBSD") {
         OS << getFreeBSDNoteTypeName(Type) << '\n';
       } else {


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