[PATCH] D59018: [llvm-objdump] - Fix incorrect CompressedSection creation.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added a reviewer: jhenderson.
Herald added subscribers: jdoerfert, MaskRay, jakehehrlich, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a reviewer: alexshap.
Herald added a reviewer: rupprecht.
grimar edited the summary of this revision.

We should create `CompressedSection` only if the section has `SHF_COMPRESSED` flag
or it's name starts from '.zdebug'. Currently, we create it if data starts from `ZLIB` signature.
As a result, if you call `isa<CompressedSection>` on a section created, it would return false,
because `classof` checks the section name and not the `ZLIB` signature (what is correct):
https://github.com/llvm-mirror/llvm/blob/master/tools/llvm-objcopy/ELF/Object.h#L384

There is no test, as because of broken `isa` described such sections are handled as uncompressed:
https://github.com/llvm-mirror/llvm/blob/master/tools/llvm-objcopy/ELF/Object.cpp#L237

So patch does not change the behavior observed but allows to create the correct sections
from start.


https://reviews.llvm.org/D59018

Files:
  tools/llvm-objcopy/ELF/Object.cpp


Index: tools/llvm-objcopy/ELF/Object.cpp
===================================================================
--- tools/llvm-objcopy/ELF/Object.cpp
+++ tools/llvm-objcopy/ELF/Object.cpp
@@ -1111,7 +1111,8 @@
   default: {
     Data = unwrapOrError(ElfFile.getSectionContents(&Shdr));
 
-    if (isDataGnuCompressed(Data) || (Shdr.sh_flags & ELF::SHF_COMPRESSED)) {
+    StringRef Name = unwrapOrError(ElfFile.getSectionName(&Shdr));
+    if (Name.startswith(".zdebug") || (Shdr.sh_flags & ELF::SHF_COMPRESSED)) {
       uint64_t DecompressedSize, DecompressedAlign;
       std::tie(DecompressedSize, DecompressedAlign) =
           getDecompressedSizeAndAlignment<ELFT>(Data);


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