[PATCH] D69188: [llvm-objcopy] Preserve .ARM.attributes section when stripping files

[Tobias Hieta via Phabricator via llvm-commits]

thieta created this revision.
thieta added reviewers: rupprecht, MaskRay, grimar.
Herald added subscribers: llvm-commits, seiya, abrachet, jakehehrlich, kristof.beyls, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a reviewer: alexshap.
Herald added a reviewer: jhenderson.
Herald added a project: LLVM.

While this section is not strictly needed for modern systems there are a lot of linux-arm devices out there with older glibc and eglibc which both require that this section is part of a shared object in order to dlopen it.

Peter Smith did a similar patch against lld a couple of years ago:
https://reviews.llvm.org/D27718

There is more context and discussion on llvm-dev: http://lists.llvm.org/pipermail/llvm-dev/2019-October/135993.html

This is my first contribution to LLVM - so please let me know if I did something wrong. I am mostly unsure about how I did the test for this bug. But I was able to confirm that it fails without my patch, and passes with it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D69188

Files:
  llvm/test/tools/llvm-objcopy/ELF/strip-preserve-arm-attributes.test
  llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp


Index: llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
===================================================================
--- llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
+++ llvm/tools/llvm-objcopy/ELF/ELFObjcopy.cpp
@@ -503,6 +503,11 @@
         return false;
       if (StringRef(Sec.Name).startswith(".gnu.warning"))
         return false;
+      // While keeping this section around shouldn't be needed
+      // there are older version of glibc and eglibc that requires
+      // it around in order for dlopen to work correctly.
+      if (Sec.Type == SHT_ARM_ATTRIBUTES)
+        return false;
       if (Sec.ParentSegment != nullptr)
         return false;
       return (Sec.Flags & SHF_ALLOC) == 0;
Index: llvm/test/tools/llvm-objcopy/ELF/strip-preserve-arm-attributes.test
===================================================================
--- /dev/null
+++ llvm/test/tools/llvm-objcopy/ELF/strip-preserve-arm-attributes.test
@@ -0,0 +1,16 @@
+# RUN: yaml2obj %s > %t
+# RUN: cp %t %t3
+# RUN: llvm-objcopy --strip-all %t %t2
+# RUN: llvm-readobj --file-headers --sections %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_DYN
+  Machine:         EM_ARM
+Sections:
+  - Name:            .ARM.attributes
+    Type:            SHT_ARM_ATTRIBUTES
+
+# CHECK: Name: .ARM.attributes


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