[ELF] Add two new virtual functions to the `OutputELFWriter` class to control dynamic symbol table populating and DT_NEEDED tag creation

[atanasyan]

Summary

The patch adds two new virtual functions to the OutputELFWriter class to control dynamic symbol table populating and DT_NEEDED tag creation. The isDynSymEntryRequired function returns true if the specified shared library atom requires a dynamic symbol table entry. The isNeededTagRequired function returns true if we need to create DT_NEEDED tag for the shared library defined specified shared atom.

By default the both functions return true. So there is no functional changes for all targets except MIPS. Probably we need to spread the same modifications on other ELF targets but I want to implement and fully tested complete set of changes for MIPS target first.

For MIPS we create a dynamic symbol table entry for a shared library atom iif this atom is referenced by a regular defined atom. For example, if library L1 defines symbol T1, library L2 defines symbol T2 and uses symbol T1 and executable file E1 uses symbol T2 but does not use symbol T1 we create an entry in the E1 dynamic symbol table for symbol T2 and do not create an entry for T1.

The patch creates DT_NEEDED tags for shared libraries contain shared library atoms which a) referenced by regular defined atoms; b) have corresponding copy dynamic relocations (R_MIPS_COPY).

Now the patch does not take in account --as-needed / --no-as-needed command line options. So it is too restrictive and create DT_NEEDED tags for really needed shared libraries only. I plan to fix that by subsequent patches.

[ruiu]

LGTM with a nit.

lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h

70

nit: s/auto/Reference/

[atanasyan]

Thanks for review.

Closed by commit rL211674.

lib/ReaderWriter/ELF/Mips/MipsDynamicLibraryWriter.h

protected:
   void finalizeDefaultAtomValues() override;
 
   std::error_code setELFHeader() override {
     DynamicLibraryWriter<ELFT>::setELFHeader();
     _writeHelper.setELFHeader(*this->_elfHeader);
     return std::error_code();
   }
 
+  bool isDynSymEntryRequired(const SharedLibraryAtom *sla) const override {
+    return _writeHelper.isDynSymEntryRequired(sla);
+  }
+
+  bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
+    return _writeHelper.isNeededTagRequired(sla);
+  }
+
   LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
 
   LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();
 
 private:
   MipsELFWriter<ELFT> _writeHelper;
   MipsLinkingContext &_mipsContext;
   MipsTargetLayout<Mips32ElELFType> &_mipsTargetLayout;

lib/ReaderWriter/ELF/Mips/MipsELFWriters.h

if (_context.isDynamic()) {
       file->addAbsoluteAtom("_GLOBAL_OFFSET_TABLE_");
       file->addAbsoluteAtom("_gp");
       file->addAbsoluteAtom("_gp_disp");
       file->addAbsoluteAtom("__gnu_local_gp");
     }
     return file;
   }
 
+  bool isDynSymEntryRequired(const SharedLibraryAtom *sla) const {
+    return _targetLayout.isReferencedByDefinedAtom(sla);
+  }
+
+  bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
+    return _targetLayout.isReferencedByDefinedAtom(sla) ||
+           _targetLayout.isCopied(sla);
+  }
+
 private:
   MipsLinkingContext &_context;
   MipsTargetLayout<ELFT> &_targetLayout;
 
   void setAtomValue(StringRef name, uint64_t value) {
     auto atom = _targetLayout.findAbsoluteAtom(name);
     assert(atom != _targetLayout.absoluteAtoms().end());
     (*atom)->_virtualAddr = value;
   }
 };
 
 } // elf
 } // lld
 
 #endif

lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h

protected:
   void finalizeDefaultAtomValues() override;
 
   std::error_code setELFHeader() override {
     ExecutableWriter<ELFT>::setELFHeader();
     _writeHelper.setELFHeader(*this->_elfHeader);
     return std::error_code();
   }
 
+  bool isDynSymEntryRequired(const SharedLibraryAtom *sla) const override {
+    return _writeHelper.isDynSymEntryRequired(sla);
+  }
+
+  bool isNeededTagRequired(const SharedLibraryAtom *sla) const override {
+    return _writeHelper.isNeededTagRequired(sla);
+  }
+
   LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
 
   LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>) createDynamicSymbolTable();
 
 private:
   MipsELFWriter<ELFT> _writeHelper;
   MipsLinkingContext &_mipsContext;
   MipsTargetLayout<Mips32ElELFType> &_mipsTargetLayout;

lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h

 
 #include "DefaultTargetHandler.h"
 #include "MipsELFReader.h"
 #include "MipsLinkingContext.h"
 #include "MipsRelocationHandler.h"
 #include "MipsSectionChunks.h"
 #include "TargetLayout.h"
 
+#include "llvm/ADT/DenseSet.h"
+
 namespace lld {
 namespace elf {
 
 /// \brief TargetLayout for Mips
 template <class ELFType>
 class MipsTargetLayout final : public TargetLayout<ELFType> {
 public:
   MipsTargetLayout(const MipsLinkingContext &ctx)
Layout::SegmentType getSegmentType(Section<ELFType> *section) const override {
     case DefaultLayout<ELFType>::ORDER_CTORS:
     case DefaultLayout<ELFType>::ORDER_DTORS:
       return llvm::ELF::PT_LOAD;
     default:
       return TargetLayout<ELFType>::getSegmentType(section);
     }
   }
 
+  ErrorOr<const lld::AtomLayout &> addAtom(const Atom *atom) override {
+    // Maintain:
+    // 1. Set of shared library atoms referenced by regular defined atoms.
+    // 2. Set of shared library atoms have corresponding R_MIPS_COPY copies.
+    if (const auto *da = dyn_cast<DefinedAtom>(atom))
+      for (const auto *ref : *da) {
+        if (const auto *sla = dyn_cast<SharedLibraryAtom>(ref->target()))
+          _referencedDynAtoms.insert(sla);
+
+        if (ref->kindNamespace() == lld::Reference::KindNamespace::ELF) {
+          assert(ref->kindArch() == Reference::KindArch::Mips);
+          if (ref->kindValue() == llvm::ELF::R_MIPS_COPY)
+            _copiedDynSymNames.insert(atom->name());
+        }
+      }
+
+    return TargetLayout<ELFType>::addAtom(atom);
+  }
+
+  bool isReferencedByDefinedAtom(const SharedLibraryAtom *sla) const {
+    return _referencedDynAtoms.count(sla);
+  }
+
+  bool isCopied(const SharedLibraryAtom *sla) const {
+    return _copiedDynSymNames.count(sla->name());
+  }
+
   /// \brief GP offset relative to .got section.
   uint64_t getGPOffset() const { return 0x7FF0; }
 
   /// \brief Get '_gp' symbol atom layout.
   AtomLayout *getGP() {
     if (!_gpAtom.hasValue()) {
       auto atom = this->findAbsoluteAtom("_gp");
       _gpAtom = atom != this->absoluteAtoms().end() ? *atom : nullptr;
public:
   }
 
 private:
   llvm::BumpPtrAllocator _alloc;
   MipsGOTSection<ELFType> *_gotSection;
   MipsPLTSection<ELFType> *_pltSection;
   llvm::Optional<AtomLayout *> _gpAtom;
   llvm::Optional<AtomLayout *> _gpDispAtom;
+  llvm::DenseSet<const SharedLibraryAtom *> _referencedDynAtoms;
+  llvm::StringSet<> _copiedDynSymNames;
 };
 
 /// \brief Mips Runtime file.
 template <class ELFType>
 class MipsRuntimeFile final : public CRuntimeFile<ELFType> {
 public:
   MipsRuntimeFile(const MipsLinkingContext &context)
       : CRuntimeFile<ELFType>(context, "Mips runtime file") {}

lib/ReaderWriter/ELF/OutputELFWriter.h

protected:
 
   /// \brief create dynamic table.
   virtual LLD_UNIQUE_BUMP_PTR(DynamicTable<ELFT>) createDynamicTable();
 
   /// \brief create dynamic symbol table.
   virtual LLD_UNIQUE_BUMP_PTR(DynamicSymbolTable<ELFT>)
       createDynamicSymbolTable();
 
+  /// \brief Create entry in the dynamic symbols table for this atom.
+  virtual bool isDynSymEntryRequired(const SharedLibraryAtom *sla) const {
+    return true;
+  }
+
+  /// \brief Create DT_NEEDED dynamic tage for the shared library.
+  virtual bool isNeededTagRequired(const SharedLibraryAtom *sla) const {
+    return true;
+  }
+
   llvm::BumpPtrAllocator _alloc;
 
   const ELFLinkingContext &_context;
   TargetHandler<ELFT> &_targetHandler;
 
   typedef llvm::DenseMap<const Atom *, uint64_t> AtomToAddress;
   AtomToAddress _atomToAddressMap;
   TargetLayout<ELFT> &_layout;
for (auto sec : this->_layout.sections())
     if (auto section = dyn_cast<AtomSection<ELFT>>(sec))
       for (const auto &atom : section->atoms()) {
         const DefinedAtom *da = dyn_cast<const DefinedAtom>(atom->_atom);
         if (da && da->dynamicExport() == DefinedAtom::dynamicExportAlways)
           _dynamicSymbolTable->addSymbol(atom->_atom, section->ordinal(),
                                          atom->_virtualAddr, atom);
       }
   for (const auto &sla : file.sharedLibrary()) {
+    if (isDynSymEntryRequired(sla))
       _dynamicSymbolTable->addSymbol(sla, ELF::SHN_UNDEF);
+    if (isNeededTagRequired(sla))
       _soNeeded.insert(sla->loadName());
   }
   for (const auto &loadName : _soNeeded) {
     Elf_Dyn dyn;
     dyn.d_tag = DT_NEEDED;
     dyn.d_un.d_val = _dynamicStringTable->addString(loadName.getKey());
     _dynamicTable->addEntry(dyn);
   }
   const auto &rpathList = _context.getRpathList();

test/elf/Mips/dynsym-table-1.test

+# Check that LLD does not populate an executable file dynamic symbol table
+# by unnecessary symbols.
+#   1. bar.so defines T2
+#   2. foo.so defines T1 and references T2
+#   3. main.o reference T1
+#   4. a.out dynamic table should contain T1 entry only
+
+# RUN: yaml2obj -format=elf -docnum 1 %s > %t-bar.o
+# RUN: yaml2obj -format=elf -docnum 2 %s > %t-foo.o
+# RUN: yaml2obj -format=elf -docnum 3 %s > %t-main.o
+# RUN: lld -flavor gnu -target mipsel -shared -o %t-bar.so %t-bar.o
+# RUN: lld -flavor gnu -target mipsel -shared -o %t-foo.so %t-foo.o %t-bar.so
+# RUN: lld -flavor gnu -target mipsel -e T0 -o %t.exe \
+# RUN:     %t-main.o %t-foo.so %t-bar.so
+# RUN: llvm-readobj -dt -dynamic-table %t.exe | FileCheck %s
+
+# CHECK:      DynamicSymbols [
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: @ (0)
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Local (0x0)
+# CHECK-NEXT:     Type: None (0x0)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: T1@ ({{.*}})
+# CHECK-NEXT:     Value: {{.*}}
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Global (0x1)
+# CHECK-NEXT:     Type: Function (0x2)
+# CHECK-NEXT:     Other: 8
+# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+# CHECK:      0x00000003 PLTGOT 0x401000
+# CHECK-NEXT: 0x00000001 NEEDED SharedLibrary (dynsym-table-1.test.tmp-foo.so)
+# CHECK-NEXT: 0x00000000 NULL   0x0
+
+# bar.o
+---
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_MIPS
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x04
+    Size:            0x08
+Symbols:
+  Global:
+    - Name:            T2
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x08
+
+# foo.o
+---
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_MIPS
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x04
+    Size:            0x08
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Link:            .symtab
+    AddressAlign:    0x08
+    Info:            .text
+    Relocations:
+      - Offset:          0
+        Symbol:          T2
+        Type:            R_MIPS_CALL16
+Symbols:
+  Global:
+    - Name:            T1
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x08
+    - Name:            T2
+
+# main.o
+---
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_MIPS
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x04
+    Size:            0x08
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Link:            .symtab
+    AddressAlign:    0x08
+    Info:            .text
+    Relocations:
+      - Offset:          0
+        Symbol:          T1
+        Type:            R_MIPS_32
+Symbols:
+  Global:
+    - Name:            T0
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x08
+    - Name:            T1
+...

test/elf/Mips/dynsym-table-2.test

+# Check that LLD does not populate a shared library dynamic symbol table
+# by unnecessary symbols.
+#   1. bar.so defines T2 and T3
+#   2. foo.so defines T1 and references T2
+#   4. foo.so dynamic table should contain T1 and T2 entries only
+
+# RUN: yaml2obj -format=elf -docnum 1 %s > %t-bar.o
+# RUN: yaml2obj -format=elf -docnum 2 %s > %t-foo.o
+# RUN: lld -flavor gnu -target mipsel -shared -o %t-bar.so %t-bar.o
+# RUN: lld -flavor gnu -target mipsel -shared -o %t-foo.so %t-foo.o %t-bar.so
+# RUN: llvm-readobj -dt -dynamic-table %t-foo.so | FileCheck %s
+
+# CHECK:      DynamicSymbols [
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: @ (0)
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Local (0x0)
+# CHECK-NEXT:     Type: None (0x0)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: T1@ ({{.*}})
+# CHECK-NEXT:     Value: {{.*}}
+# CHECK-NEXT:     Size: 8
+# CHECK-NEXT:     Binding: Global (0x1)
+# CHECK-NEXT:     Type: Function (0x2)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: .text (0x4)
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: T2@ ({{.*}})
+# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Global (0x1)
+# CHECK-NEXT:     Type: Function (0x2)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]
+
+# CHECK:      0x00000003 PLTGOT 0x1000
+# CHECK-NEXT: 0x00000001 NEEDED SharedLibrary (dynsym-table-2.test.tmp-bar.so)
+# CHECK-NEXT: 0x00000000 NULL   0x0
+
+# bar.o
+---
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_MIPS
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x04
+    Size:            0x08
+Symbols:
+  Global:
+    - Name:            T2
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x04
+    - Name:            T3
+      Type:            STT_FUNC
+      Section:         .text
+      Value:           0x04
+      Size:            0x04
+
+# foo.o
+---
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_MIPS
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x04
+    Size:            0x08
+  - Name:            .rel.text
+    Type:            SHT_REL
+    Link:            .symtab
+    AddressAlign:    0x08
+    Info:            .text
+    Relocations:
+      - Offset:          0
+        Symbol:          T2
+        Type:            R_MIPS_CALL16
+Symbols:
+  Global:
+    - Name:            T1
+      Type:            STT_FUNC
+      Section:         .text
+      Size:            0x08
+    - Name:            T2
+...

test/elf/Mips/rel-copy.test

 # Check R_MIPS_COPY relocation emitting
 # when linking non-shared executable file.
 #
-# RUN: yaml2obj -format=elf -docnum 1 %s > %t-so.o
-# RUN: lld -flavor gnu -target mipsel -shared -o %t.so %t-so.o
-# RUN: yaml2obj -format=elf -docnum 2 %s > %t-o.o
-# RUN: lld -flavor gnu -target mipsel -e T0 -o %t.exe %t-o.o %t.so
-# RUN: llvm-readobj -dyn-symbols -relocations %t.exe | FileCheck %s
+# RUN: yaml2obj -format=elf -docnum 1 %s > %t-so1.o
+# RUN: lld -flavor gnu -target mipsel -shared -o %t1.so %t-so1.o
+# RUN: yaml2obj -format=elf -docnum 2 %s > %t-so2.o
+# RUN: lld -flavor gnu -target mipsel -shared -o %t2.so %t-so2.o
+# RUN: yaml2obj -format=elf -docnum 3 %s > %t-o.o
+# RUN: lld -flavor gnu -target mipsel -e T0 -o %t.exe %t-o.o %t1.so %t2.so
+# RUN: llvm-readobj -dt -r -dynamic-table %t.exe | FileCheck %s
 
 # CHECK:      Relocations [
 # CHECK-NEXT:   Section (5) .rel.dyn {
 # CHECK-NEXT:     0x402004 R_MIPS_REL32 D2 0x0
-# CHECK-NEXT:     0x402008 R_MIPS_COPY D1 0x0
+# CHECK-NEXT:     0x402010 R_MIPS_COPY D1 0x0
+# CHECK-NEXT:     0x402018 R_MIPS_COPY D3 0x0
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]
 
 # CHECK:      DynamicSymbols [
 # CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: @ (0)
 # CHECK-NEXT:     Value: 0x0
 # CHECK-NEXT:     Size: 0
 # CHECK-NEXT:     Binding: Local (0x0)
 # CHECK-NEXT:     Type: None (0x0)
 # CHECK-NEXT:     Other: 0
 # CHECK-NEXT:     Section: Undefined (0x0)
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
 # CHECK-NEXT:     Name: D1@ (1)
-# CHECK-NEXT:     Value: 0x402008
+# CHECK-NEXT:     Value: 0x402010
 # CHECK-NEXT:     Size: 4
 # CHECK-NEXT:     Binding: Global (0x1)
 # CHECK-NEXT:     Type: Object (0x1)
 # CHECK-NEXT:     Other: 0
 # CHECK-NEXT:     Section: .bss (0xA)
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
-# CHECK-NEXT:     Name: D1@ (1)
-# CHECK-NEXT:     Value: 0x0
+# CHECK-NEXT:     Name: D3@ (4)
+# CHECK-NEXT:     Value: 0x402018
 # CHECK-NEXT:     Size: 4
 # CHECK-NEXT:     Binding: Global (0x1)
 # CHECK-NEXT:     Type: Object (0x1)
 # CHECK-NEXT:     Other: 0
-# CHECK-NEXT:     Section: Undefined (0x0)
+# CHECK-NEXT:     Section: .bss (0xA)
 # CHECK-NEXT:   }
 # CHECK-NEXT:   Symbol {
-# CHECK-NEXT:     Name: D2@ (4)
+# CHECK-NEXT:     Name: D2@ (7)
 # CHECK-NEXT:     Value: 0x0
 # CHECK-NEXT:     Size: 4
 # CHECK-NEXT:     Binding: Global (0x1)
 # CHECK-NEXT:     Type: Object (0x1)
 # CHECK-NEXT:     Other: 0
 # CHECK-NEXT:     Section: Undefined (0x0)
 # CHECK-NEXT:   }
 # CHECK-NEXT: ]
 
-# so.o
+# CHECK:      DynamicSection [ ({{.*}} entries)
+# CHECK:        0x00000001 NEEDED  SharedLibrary (rel-copy.test.tmp1.so)
+# CHECK:        0x00000001 NEEDED  SharedLibrary (rel-copy.test.tmp2.so)
+# CHECK-NEXT:   0x00000000 NULL    0x0
+# CHECK-NEXT: ]
+
+# so1.o
 ---
 FileHeader:
   Class:   ELFCLASS32
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_MIPS
   Flags:   [EF_MIPS_PIC, EF_MIPS_CPIC]
 
- Name: D1
       Value: 0x0
       Size: 4
     - Name: D2
       Section: .data
       Type: STT_OBJECT
       Value: 0x4
       Size: 4
 
+# so2.o
+---
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_MIPS
+  Flags:   [EF_MIPS_PIC, EF_MIPS_CPIC]
+
+Sections:
+- Name:         .data
+  Type:         SHT_PROGBITS
+  Size:         0x04
+  AddressAlign: 16
+  Flags:        [SHF_WRITE, SHF_ALLOC]
+
+Symbols:
+  Global:
+    - Name: D3
+      Section: .data
+      Type: STT_OBJECT
+      Value: 0x0
+      Size: 4
+
 # o.o
 ---
 FileHeader:
   Class:   ELFCLASS32
   Data:    ELFDATA2LSB
   Type:    ET_REL
   Machine: EM_MIPS
   Flags:   [EF_MIPS_CPIC]
 
 Sections:
 - Name:         .text
   Type:         SHT_PROGBITS
   Size:         0x08
   AddressAlign: 16
   Flags:        [SHF_EXECINSTR, SHF_ALLOC]
 
 - Name:         .data
   Type:         SHT_PROGBITS
-  Size:         0x08
+  Size:         0x0C
   AddressAlign: 16
   Flags:        [SHF_WRITE, SHF_ALLOC]
 
 - Name: .rel.data
   Type: SHT_REL
   Info: .data
   AddressAlign: 4
   Relocations:
     - Offset: 0x00
       Symbol: D1
       Type: R_MIPS_HI16
     - Offset: 0x00
       Symbol: D1
       Type: R_MIPS_LO16
     - Offset: 0x04
       Symbol: D2
       Type: R_MIPS_32
+    - Offset: 0x08
+      Symbol: D3
+      Type: R_MIPS_HI16
+    - Offset: 0x08
+      Symbol: D3
+      Type: R_MIPS_LO16
 
 Symbols:
   Global:
     - Name: T0
       Section: .text
       Type: STT_FUNC
       Value: 0x0
       Size: 8
     - Name: D0
       Section: .data
       Type: STT_OBJECT
       Value: 0x0
       Size: 8
     - Name: D1
       Type: STT_OBJECT
     - Name: D2
+    - Name: D3
 ...

test/elf/Mips/rel-dynamic-01.test

 # RUN: lld -flavor gnu -target mipsel -shared -o %t.so %t-so.o
 # RUN: yaml2obj -format=elf -docnum 2 %s > %t-o.o
 # RUN: lld -flavor gnu -target mipsel -e T0 -o %t.exe %t-o.o %t.so
 # RUN: llvm-objdump -disassemble %t.exe | FileCheck -check-prefix=PLT %s
 # RUN: llvm-readobj -dt -r %t.exe | FileCheck -check-prefix=PLT-SYM %s
 
 # PLT: Disassembly of section .plt:
 # PLT-NEXT: .plt:
-# PLT-NEXT:   400210:  40 00 1c 3c  lui     $gp, 64
-# PLT-NEXT:   400214:  00 20 99 8f  lw      $25, 8192($gp)
-# PLT-NEXT:   400218:  00 20 9c 27  addiu   $gp, $gp, 8192
-# PLT-NEXT:   40021c:  23 c0 1c 03  subu    $24, $24, $gp
-# PLT-NEXT:   400220:  21 78 e0 03  move    $15, $ra
-# PLT-NEXT:   400224:  82 c0 18 00  srl     $24, $24, 2
-# PLT-NEXT:   400228:  09 f8 20 03  jalr    $25
-# PLT-NEXT:   40022c:  fe ff 18 27  addiu   $24, $24, -2
+# PLT-NEXT:   4001f0:  40 00 1c 3c  lui     $gp, 64
+# PLT-NEXT:   4001f4:  00 20 99 8f  lw      $25, 8192($gp)
+# PLT-NEXT:   4001f8:  00 20 9c 27  addiu   $gp, $gp, 8192
+# PLT-NEXT:   4001fc:  23 c0 1c 03  subu    $24, $24, $gp
+# PLT-NEXT:   400200:  21 78 e0 03  move    $15, $ra
+# PLT-NEXT:   400204:  82 c0 18 00  srl     $24, $24, 2
+# PLT-NEXT:   400208:  09 f8 20 03  jalr    $25
+# PLT-NEXT:   40020c:  fe ff 18 27  addiu   $24, $24, -2
 #
-# PLT-NEXT:   400230:  40 00 0f 3c  lui     $15, 64
-# PLT-NEXT:   400234:  08 20 f9 8d  lw      $25, 8200($15)
-# PLT-NEXT:   400238:  08 00 20 03  jr      $25
-# PLT-NEXT:   40023c:  08 20 f8 25  addiu   $24, $15, 8200
+# PLT-NEXT:   400210:  40 00 0f 3c  lui     $15, 64
+# PLT-NEXT:   400214:  08 20 f9 8d  lw      $25, 8200($15)
+# PLT-NEXT:   400218:  08 00 20 03  jr      $25
+# PLT-NEXT:   40021c:  08 20 f8 25  addiu   $24, $15, 8200
 #
-# PLT-NEXT:   400240:  40 00 0f 3c  lui     $15, 64
-# PLT-NEXT:   400244:  0c 20 f9 8d  lw      $25, 8204($15)
-# PLT-NEXT:   400248:  08 00 20 03  jr      $25
-# PLT-NEXT:   40024c:  0c 20 f8 25  addiu   $24, $15, 8204
+# PLT-NEXT:   400220:  40 00 0f 3c  lui     $15, 64
+# PLT-NEXT:   400224:  0c 20 f9 8d  lw      $25, 8204($15)
+# PLT-NEXT:   400228:  08 00 20 03  jr      $25
+# PLT-NEXT:   40022c:  0c 20 f8 25  addiu   $24, $15, 8204
 
 # PLT-SYM:      Relocations [
 # PLT-SYM-NEXT:   Section (5) .rel.dyn {
 # PLT-SYM-NEXT:     0x402014 R_MIPS_REL32 T2 0x0
 # PLT-SYM-NEXT:     0x402014 R_MIPS_REL32 D2 0x0
 # PLT-SYM-NEXT:     0x402018 R_MIPS_COPY D1 0x0
 # PLT-SYM-NEXT:   }
 # PLT-SYM-NEXT:   Section (6) .rel.plt {

 # PLT-SYM-NEXT:     Size: 0
 # PLT-SYM-NEXT:     Binding: Global (0x1)
 # PLT-SYM-NEXT:     Type: Function (0x2)
 # PLT-SYM-NEXT:     Other: 0
 # PLT-SYM-NEXT:     Section: Undefined (0x0)
 # PLT-SYM-NEXT:   }
 # PLT-SYM-NEXT:   Symbol {
 # PLT-SYM-NEXT:     Name: T1@ (7)
-# PLT-SYM-NEXT:     Value: 0x400240
+# PLT-SYM-NEXT:     Value: 0x400220
 # PLT-SYM-NEXT:     Size: 0
 # PLT-SYM-NEXT:     Binding: Global (0x1)
 # PLT-SYM-NEXT:     Type: Function (0x2)
 # PLT-SYM-NEXT:     Other: 8
 # PLT-SYM-NEXT:     Section: Undefined (0x0)
 # PLT-SYM-NEXT:   }
 # PLT-SYM-NEXT:   Symbol {
-# PLT-SYM-NEXT:     Name: D1@ (1)
-# PLT-SYM-NEXT:     Value: 0x0
-# PLT-SYM-NEXT:     Size: 4
-# PLT-SYM-NEXT:     Binding: Global (0x1)
-# PLT-SYM-NEXT:     Type: Object (0x1)
-# PLT-SYM-NEXT:     Other: 0
-# PLT-SYM-NEXT:     Section: Undefined (0x0)
-# PLT-SYM-NEXT:   }
-# PLT-SYM-NEXT:   Symbol {
 # PLT-SYM-NEXT:     Name: T2@ (10)
 # PLT-SYM-NEXT:     Value: 0x0
 # PLT-SYM-NEXT:     Size: 0
 # PLT-SYM-NEXT:     Binding: Global (0x1)
 # PLT-SYM-NEXT:     Type: Function (0x2)
 # PLT-SYM-NEXT:     Other: 0
 # PLT-SYM-NEXT:     Section: Undefined (0x0)
 # PLT-SYM-NEXT:   }