[llvm] 2abe53a - Revert "[llvm-objcopy] Remove empty SHT_GROUP sections (#97141)"

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2024-07-08T23:47:28-07:00
New Revision: 2abe53a17f486a055a3715f19a37e3e91b4415fc

URL: https://github.com/llvm/llvm-project/commit/2abe53a17f486a055a3715f19a37e3e91b4415fc
DIFF: https://github.com/llvm/llvm-project/commit/2abe53a17f486a055a3715f19a37e3e91b4415fc.diff

LOG: Revert "[llvm-objcopy] Remove empty SHT_GROUP sections (#97141)"

This reverts commit 359c64f314ad568e78ee9a3723260286e3425c2d.

This caused heap-use-after-free. See #98106.

Added: 
    

Modified: 
    llvm/lib/ObjCopy/ELF/ELFObject.cpp
    llvm/lib/ObjCopy/ELF/ELFObject.h
    llvm/test/tools/llvm-objcopy/ELF/remove-section-in-group.test

Removed: 
    


################################################################################
diff  --git a/llvm/lib/ObjCopy/ELF/ELFObject.cpp b/llvm/lib/ObjCopy/ELF/ELFObject.cpp
index f9c5d2579be69..5e6d19b9bfa54 100644
--- a/llvm/lib/ObjCopy/ELF/ELFObject.cpp
+++ b/llvm/lib/ObjCopy/ELF/ELFObject.cpp
@@ -2239,17 +2239,8 @@ Error Object::removeSections(
   // Transfer removed sections into the Object RemovedSections container for use
   // later.
   std::move(Iter, Sections.end(), std::back_inserter(RemovedSections));
-  // Now get rid of them altogether.
+  // Now finally get rid of them all together.
   Sections.erase(Iter, std::end(Sections));
-
-  // Finally erase empty SHT_GROUP sections.
-  llvm::erase_if(Sections, [](const SecPtr &Sec) {
-    if (auto GroupSec = dyn_cast<GroupSection>(Sec.get()))
-      return GroupSec->getMembersCount() == 0;
-
-    return false;
-  });
-
   return Error::success();
 }
 

diff  --git a/llvm/lib/ObjCopy/ELF/ELFObject.h b/llvm/lib/ObjCopy/ELF/ELFObject.h
index 2a9f337c3f323..e3c0e7abda16b 100644
--- a/llvm/lib/ObjCopy/ELF/ELFObject.h
+++ b/llvm/lib/ObjCopy/ELF/ELFObject.h
@@ -964,8 +964,6 @@ class GroupSection : public SectionBase {
       const DenseMap<SectionBase *, SectionBase *> &FromTo) override;
   void onRemove() override;
 
-  size_t getMembersCount() const { return GroupMembers.size(); }
-
   static bool classof(const SectionBase *S) {
     return S->OriginalType == ELF::SHT_GROUP;
   }

diff  --git a/llvm/test/tools/llvm-objcopy/ELF/remove-section-in-group.test b/llvm/test/tools/llvm-objcopy/ELF/remove-section-in-group.test
index ccc1ede0589c1..9e683b9f68c93 100644
--- a/llvm/test/tools/llvm-objcopy/ELF/remove-section-in-group.test
+++ b/llvm/test/tools/llvm-objcopy/ELF/remove-section-in-group.test
@@ -1,6 +1,6 @@
 ## This checks that the group section is shrunk when its member is removed.
 
-# RUN: yaml2obj --docnum=1 %s -o - \
+# RUN: yaml2obj %s -o - \
 # RUN:   | llvm-objcopy -R .foo - - \
 # RUN:   | obj2yaml - \
 # RUN:   | FileCheck %s
@@ -35,51 +35,3 @@ Symbols:
   - Name:     foo_bar_grp
     Section:  .group
     Binding:  STB_GLOBAL
-
-# RUN: yaml2obj --docnum=2 %s -o %t
-# RUN: llvm-objcopy --remove-section=.debug_macro %t
-# RUN: llvm-readelf --section-groups %t | FileCheck %s --check-prefix=GROUP-REMOVED
-
---- !ELF
-FileHeader:
-  Class:      ELFCLASS64
-  Data:       ELFDATA2LSB
-  Type:       ET_REL
-  Machine:    EM_X86_64
-Sections:
-  - Name:     .group
-    Type:     SHT_GROUP
-    Info:     foo_grp
-    Members:
-      - SectionOrType:  GRP_COMDAT
-      - SectionOrType:  .debug_macro
-  - Name:     .debug_macro
-    Type:     SHT_PROGBITS
-    Flags:    [ SHF_GROUP ]
-Symbols:
-  - Name:     foo_grp
-    Section:  .group
-
-# GROUP-REMOVED: There are no section groups in this file.
-
-# RUN: yaml2obj --docnum=3 %s -o %t
-# RUN: llvm-objcopy --remove-section=.group %t
-# RUN: llvm-readelf --section-groups %t | FileCheck %s --check-prefix=EMPTY-GROUP-REMOVED
-
---- !ELF
-FileHeader:
-  Class:      ELFCLASS64
-  Data:       ELFDATA2LSB
-  Type:       ET_REL
-  Machine:    EM_X86_64
-Sections:
-  - Name:     .group
-    Type:     SHT_GROUP
-    Info:     foo_grp
-    Members:
-      - SectionOrType:  GRP_COMDAT
-Symbols:
-  - Name:     foo_grp
-    Section:  .group
-
-# EMPTY-GROUP-REMOVED: There are no section groups in this file.