[Mips] Implement .plt and .got.plt section creation.

llvm-svn: 199516

lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.cpp

@@ -56,3 +56,16 @@ void MipsLinkingContext::addPasses(PassManager &pm) {
     pm.add(std::move(pass));
   ELFLinkingContext::addPasses(pm);
 }
+
+bool MipsLinkingContext::isPLTRelocation(const DefinedAtom &,
+                                         const Reference &r) const {
+  if (r.kindNamespace() != Reference::KindNamespace::ELF)
+    return false;
+  assert(r.kindArch() == Reference::KindArch::Mips);
+  switch (r.kindValue()) {
+  case llvm::ELF::R_MIPS_JUMP_SLOT:
+    return true;
+  default:
+    return false;
+  }
+}

lld/lib/ReaderWriter/ELF/Mips/MipsLinkingContext.h

@@ -21,7 +21,11 @@ enum {
   /// \brief The same as R_MIPS_GOT16 but for global symbols.
   LLD_R_MIPS_GLOBAL_GOT16 = 1025,
   /// \brief The same as R_MIPS_26 but for global symbols.
-  LLD_R_MIPS_GLOBAL_26 = 1026
+  LLD_R_MIPS_GLOBAL_26 = 1026,
+  /// \brief Setup hi 16 bits using the symbol this reference refers to.
+  LLD_R_MIPS_HI16 = 1027,
+  /// \brief Setup low 16 bits using the symbol this reference refers to.
+  LLD_R_MIPS_LO16 = 1028
 };
 
 typedef llvm::object::ELFType<llvm::support::little, 2, false> Mips32ElELFType;
@@ -41,6 +45,7 @@ public:
   virtual StringRef entrySymbolName() const;
   virtual StringRef getDefaultInterpreter() const;
   virtual void addPasses(PassManager &pm);
+  virtual bool isPLTRelocation(const DefinedAtom &, const Reference &r) const;
 };
 
 } // elf

lld/lib/ReaderWriter/ELF/Mips/MipsRelocationHandler.cpp

@@ -105,6 +105,18 @@ void relocCall16(uint8_t *location, uint64_t P, uint64_t S, int64_t A,
   applyReloc(location, result);
 }
 
+/// \brief LLD_R_MIPS_HI16
+void relocLldHi16(uint8_t *location, uint64_t S) {
+  int32_t result = lld::scatterBits<uint32_t>((S + 0x8000) >> 16, 0xffff);
+  applyReloc(location, result);
+}
+
+/// \brief LLD_R_MIPS_LO16
+void relocLldLo16(uint8_t *location, uint64_t S) {
+  int32_t result = lld::scatterBits<uint32_t>(S, 0xffff);
+  applyReloc(location, result);
+}
+
 } // end anon namespace
 
 MipsTargetRelocationHandler::MipsTargetRelocationHandler(
@@ -200,6 +212,9 @@ error_code MipsTargetRelocationHandler::applyRelocation(
   case R_MIPS_JALR:
     // We do not do JALR optimization now.
     break;
+  case R_MIPS_JUMP_SLOT:
+    // Ignore runtime relocations.
+    break;
   case LLD_R_MIPS_GLOBAL_GOT:
     // Do nothing.
     break;
@@ -210,6 +225,12 @@ error_code MipsTargetRelocationHandler::applyRelocation(
   case LLD_R_MIPS_GLOBAL_26:
     reloc26(location, relocVAddress, targetVAddress, false);
     break;
+  case LLD_R_MIPS_HI16:
+    relocLldHi16(location, targetVAddress);
+    break;
+  case LLD_R_MIPS_LO16:
+    relocLldLo16(location, targetVAddress);
+    break;
   default: {
     std::string str;
     llvm::raw_string_ostream s(str);

lld/lib/ReaderWriter/ELF/Mips/MipsRelocationPass.cpp

@@ -24,6 +24,26 @@ const uint8_t mipsGot0AtomContent[] = { 0x00, 0x00, 0x00, 0x00 };
 // Module pointer
 const uint8_t mipsGotModulePointerAtomContent[] = { 0x00, 0x00, 0x00, 0x80 };
 
+// PLT0 entry
+const uint8_t mipsPlt0AtomContent[] = {
+  0x00, 0x00, 0x1c, 0x3c, // lui   $28, %hi(&GOTPLT[0])
+  0x00, 0x00, 0x99, 0x8f, // lw    $25, %lo(&GOTPLT[0])($28)
+  0x00, 0x00, 0x9c, 0x27, // addiu $28, $28, %lo(&GOTPLT[0])
+  0x23, 0xc0, 0x1c, 0x03, // subu  $24, $24, $28
+  0x21, 0x78, 0xe0, 0x03, // move  $15, $31
+  0x82, 0xc0, 0x18, 0x00, // srl   $24, $24, 2
+  0x09, 0xf8, 0x20, 0x03, // jalr  $25
+  0xfe, 0xff, 0x18, 0x27  // subu  $24, $24, 2
+};
+
+// Regular PLT entry
+const uint8_t mipsPltAAtomContent[] = {
+  0x00, 0x00, 0x0f, 0x3c, // lui   $15, %hi(.got.plt entry)
+  0x00, 0x00, 0xf9, 0x8d, // l[wd] $25, %lo(.got.plt entry)($15)
+  0x08, 0x00, 0x20, 0x03, // jr    $25
+  0x00, 0x00, 0xf8, 0x25  // addiu $24, $15, %lo(.got.plt entry)
+};
+
 /// \brief Abstract base class represent MIPS GOT entries.
 class MipsGOTAtom : public GOTAtom {
 public:
@@ -52,6 +72,36 @@ public:
   }
 };
 
+class PLT0Atom : public PLTAtom {
+public:
+  PLT0Atom(const File &f) : PLTAtom(f, ".plt") {}
+
+  virtual ArrayRef<uint8_t> rawContent() const {
+    return llvm::makeArrayRef(mipsPlt0AtomContent);
+  }
+};
+
+class PLTAAtom : public PLTAtom {
+public:
+  PLTAAtom(const File &f) : PLTAtom(f, ".plt") {}
+
+  virtual ArrayRef<uint8_t> rawContent() const {
+    return llvm::makeArrayRef(mipsPltAAtomContent);
+  }
+};
+
+/// \brief MIPS GOT PLT entry
+class GOTPLTAtom : public GOTAtom {
+public:
+  GOTPLTAtom(const File &f) : GOTAtom(f, ".got.plt") {}
+
+  virtual Alignment alignment() const { return Alignment(2); }
+
+  virtual ArrayRef<uint8_t> rawContent() const {
+    return llvm::makeArrayRef(mipsGot0AtomContent);
+  }
+};
+
 class RelocationPassFile : public SimpleFile {
 public:
   RelocationPassFile(const ELFLinkingContext &ctx)
@@ -90,6 +140,20 @@ public:
       got->setOrdinal(ordinal++);
       mf->addAtom(*got);
     }
+
+    for (auto &plt : _pltVector) {
+      DEBUG_WITH_TYPE("MipsGOT", llvm::dbgs() << "[ PLT ] Adding "
+                                              << plt->name() << "\n");
+      plt->setOrdinal(ordinal++);
+      mf->addAtom(*plt);
+    }
+
+    for (auto &gotplt : _gotpltVector) {
+      DEBUG_WITH_TYPE("MipsGOT", llvm::dbgs() << "[ GOTPLT ] Adding "
+                                              << gotplt->name() << "\n");
+      gotplt->setOrdinal(ordinal++);
+      mf->addAtom(*gotplt);
+    }
   }
 
 private:
@@ -105,6 +169,15 @@ private:
   /// \brief the list of global GOT atoms.
   std::vector<GOTAtom *> _globalGotVector;
 
+  /// \brief Map Atoms to their PLT entries.
+  llvm::DenseMap<const Atom *, PLTAtom *> _pltMap;
+
+  /// \brief the list of PLT atoms.
+  std::vector<PLTAtom *> _pltVector;
+
+  /// \brief the list of GOTPLT atoms.
+  std::vector<GOTAtom *> _gotpltVector;
+
   /// \brief Handle a specific reference.
   void handleReference(const DefinedAtom &atom, const Reference &ref) {
     if (ref.kindNamespace() != lld::Reference::KindNamespace::ELF)
@@ -131,7 +204,8 @@ private:
     if (ref.kindValue() == R_MIPS_26 && !isLocal(ref.target()))
       const_cast<Reference &>(ref).setKindValue(LLD_R_MIPS_GLOBAL_26);
 
-    // FIXME (simon): Create PLT entry.
+    if (isa<SharedLibraryAtom>(ref.target()))
+      const_cast<Reference &>(ref).setTarget(getPLTEntry(ref.target()));
   }
 
   void handleGOT(const Reference &ref) {
@@ -187,6 +261,69 @@ private:
 
     return ga;
   }
+
+  void createPLTHeader() {
+    assert(_pltVector.empty() && _gotpltVector.empty());
+
+    auto pa = new (_file._alloc) PLT0Atom(_file);
+    _pltVector.push_back(pa);
+
+    auto ga0 = new (_file._alloc) GOTPLTAtom(_file);
+    _gotpltVector.push_back(ga0);
+    auto ga1 = new (_file._alloc) GOTPLTAtom(_file);
+    _gotpltVector.push_back(ga1);
+
+    // Setup reference to fixup the PLT0 entry.
+    pa->addReferenceELF_Mips(LLD_R_MIPS_HI16, 0, ga0, 0);
+    pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 4, ga0, 0);
+    pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 8, ga0, 0);
+
+    DEBUG_WITH_TYPE("MipsGOT", {
+      pa->_name = "__plt0";
+      llvm::dbgs() << "[ PLT ] Create PLT0\n";
+      ga0->_name = "__gotplt0";
+      llvm::dbgs() << "[ GOTPLT ] Create GOTPLT0\n";
+      ga1->_name = "__gotplt1";
+      llvm::dbgs() << "[ GOTPLT ] Create GOTPLT1\n";
+    });
+  }
+
+  const PLTAtom *getPLTEntry(const Atom *a) {
+    auto plt = _pltMap.find(a);
+    if (plt != _pltMap.end())
+      return plt->second;
+
+    if (_pltVector.empty())
+      createPLTHeader();
+
+    auto pa = new (_file._alloc) PLTAAtom(_file);
+    _pltMap[a] = pa;
+    _pltVector.push_back(pa);
+
+    auto ga = new (_file._alloc) GOTPLTAtom(_file);
+    _gotpltVector.push_back(ga);
+
+    // Setup reference to fixup the PLT entry.
+    pa->addReferenceELF_Mips(LLD_R_MIPS_HI16, 0, ga, 0);
+    pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 4, ga, 0);
+    pa->addReferenceELF_Mips(LLD_R_MIPS_LO16, 12, ga, 0);
+
+    // Setup reference to assign initial value to the .got.plt entry.
+    ga->addReferenceELF_Mips(R_MIPS_32, 0, _pltVector.front(), 0);
+    // Create dynamic relocation to adjust the .got.plt entry at runtime.
+    ga->addReferenceELF_Mips(R_MIPS_JUMP_SLOT, 0, a, 0);
+
+    DEBUG_WITH_TYPE("MipsGOT", {
+      pa->_name = "__plt_";
+      pa->_name += a->name();
+      llvm::dbgs() << "[ PLT ] Create " << a->name() << "\n";
+      ga->_name = "__got_plt_";
+      ga->_name += a->name();
+      llvm::dbgs() << "[ GOTPLT ] Create " << a->name() << "\n";
+    });
+
+    return pa;
+  }
 };
 
 } // end anon namespace

lld/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.cpp

@@ -201,8 +201,11 @@ const Registry::KindStrings MipsTargetHandler::kindStrings[] = {
   LLD_KIND_STRING_ENTRY(R_MIPS_GOT16),
   LLD_KIND_STRING_ENTRY(R_MIPS_CALL16),
   LLD_KIND_STRING_ENTRY(R_MIPS_JALR),
+  LLD_KIND_STRING_ENTRY(R_MIPS_JUMP_SLOT),
   LLD_KIND_STRING_ENTRY(LLD_R_MIPS_GLOBAL_GOT),
   LLD_KIND_STRING_ENTRY(LLD_R_MIPS_GLOBAL_GOT16),
   LLD_KIND_STRING_ENTRY(LLD_R_MIPS_GLOBAL_26),
+  LLD_KIND_STRING_ENTRY(LLD_R_MIPS_HI16),
+  LLD_KIND_STRING_ENTRY(LLD_R_MIPS_LO16),
   LLD_KIND_STRING_END
 };

lld/lib/ReaderWriter/ELF/Mips/MipsTargetHandler.h

@@ -35,7 +35,7 @@ public:
   createSection(StringRef name, int32_t type,
                 DefinedAtom::ContentPermissions permissions,
                 Layout::SectionOrder order) {
-    if (type == DefinedAtom::typeGOT)
+    if (type == DefinedAtom::typeGOT && name == ".got")
       return _gotSection;
     return DefaultLayout<ELFType>::createSection(name, type, permissions,
                                                  order);

lld/test/elf/Mips/plt-header.test

@@ -0,0 +1,40 @@
+# Check initialization of .plt header entries.
+
+# Build shared library
+# RUN: llvm-mc -triple=mipsel -filetype=obj -relocation-model=pic \
+# RUN:         -o=%t1 %p/Inputs/ext.s
+# RUN: lld -flavor gnu -target mipsel -shared -o %t2 %t1
+
+# Build executable
+# RUN: llvm-mc -triple=mipsel -filetype=obj -o=%t3 %s
+# RUN: lld -flavor gnu -target mipsel -e glob -o %t4 %t3 %t2
+# RUN: llvm-objdump -section-headers -disassemble %t4 | \
+# RUN:   FileCheck -check-prefix=EXE %s
+
+# EXE: Disassembly of section .plt:
+# EXE: .plt:
+# PLT0 entry. Points to the .got.plt[0]
+# EXE:   400170:  40 00 1c 3c  lui     $gp, 64
+# EXE:   400174:  00 20 99 8f  lw      $25, 8192($gp)
+# EXE:   400178:  00 20 9c 27  addiu   $gp, $gp, 8192
+# EXE:   40017c:  23 c0 1c 03  subu    $24, $24, $gp
+# EXE:   400180:  21 78 e0 03  move    $15, $ra
+# EXE:   400184:  82 c0 18 00  srl     $24, $24, 2
+# EXE:   400188:  09 f8 20 03  jalr    $25
+# EXE:   40018c:  fe ff 18 27  addiu   $24, $24, -2
+
+# EXE: Sections:
+# EXE: Idx Name          Size      Address          Type
+# EXE:   6 .plt          00000030 0000000000400170 TEXT DATA
+# EXE:  10 .got.plt      0000000c 0000000000402000 DATA
+
+    .abicalls
+    .global glob
+    .ent    glob
+glob:
+    jal     $t9
+    jal     loc
+loc:
+    jal     glob
+    jal     ext1
+    .end    glob

lld/test/elf/Mips/r26.test

@@ -7,33 +7,58 @@
 
 # Build executable
 # RUN: llvm-mc -triple=mipsel -filetype=obj -o=%t3 %s
-# RUN: llvm-objdump -r %t3 | FileCheck -check-prefix=REL %s
+# RUN: llvm-readobj -relocations %t3 | FileCheck -check-prefix=OBJ-REL %s
 # RUN: lld -flavor gnu -target mipsel -e glob -o %t4 %t3 %t2
-# RUN: llvm-objdump -disassemble %t4 | FileCheck -check-prefix=EXE %s
+# RUN: llvm-objdump -section-headers -disassemble %t4 | \
+# RUN:   FileCheck -check-prefix=EXE %s
+# RUN: llvm-readobj -relocations %t4 | FileCheck -check-prefix=EXE-REL %s
 
 # Object file has three R_MIPS_26 relocations
-# REL: RELOCATION RECORDS FOR [.rel.text]:
+# OBJ-REL: Relocations [
-# REL: 8 R_MIPS_26 Unknown
+# OBJ-REL:   Section (2) .rel.text {
-# REL: 16 R_MIPS_26 Unknown
+# OBJ-REL:      0x8 R_MIPS_26 .text 0x0
-# REL: 24 R_MIPS_26 Unknown
+# OBJ-REL:     0x10 R_MIPS_26 glob  0x0
+# OBJ-REL:     0x18 R_MIPS_26 ext1  0x0
+# OBJ-REL:   }
+# OBJ-REL: ]
+
+# Executable file has the only relocation for external symbol
+# EXE-REL: Relocations [
+# EXE-REL:   Section (5) .rela.plt {
+# EXE-REL:     0x402008 R_MIPS_JUMP_SLOT ext1 0x0
+# EXE-REL:   }
+# EXE-REL: ]
+
+# EXE: Disassembly of section .plt:
+# EXE: .plt:
+# PLTA entry. Points to the .got.plt[1]
+# EXE:   400190:  40 00 0f 3c  lui     $15, 64
+# EXE:   400194:  08 20 f9 8d  lw      $25, 8200($15)
+# EXE:   400198:  08 00 20 03  jr      $25
+# EXE:   40019c:  08 20 f8 25  addiu   $24, $15, 8200
 
 # EXE: Disassembly of section .text:
 # EXE: glob:
-# EXE:   40014c:  09 f8 20 03  jalr    $25
+# EXE:   4001a0:  09 f8 20 03  jalr    $25
-# EXE:   400150:  00 00 00 00  nop
+# EXE:   4001a4:  00 00 00 00  nop
 #
 # Jump to 'loc' label address
-# EXE:   400154:  57 00 10 0c  jal     4194652
+# EXE:   4001a8:  6c 00 10 0c  jal     4194736
-# EXE:   400158:  00 00 00 00  nop
+# EXE:   4001ac:  00 00 00 00  nop
 #
 # EXE: loc:
 # Jump to 'glob' label address
-# EXE:   40015c:  53 00 10 0c  jal     4194636
+# EXE:   4001b0:  68 00 10 0c  jal     4194720
-# EXE:   400160:  00 00 00 00  nop
+# EXE:   4001b4:  00 00 00 00  nop
 #
 # Jump to the first PLT entry (.plt + 32) for ext1 entry
-# EXE:   400164:  00 00 00 0c  jal     0
+# EXE:   4001b8:  64 00 10 0c  jal     4194704
-# EXE:   400168:  00 00 00 00  nop
+# EXE:   4001bc:  00 00 00 00  nop
+
+# EXE: Sections:
+# EXE: Idx Name          Size      Address          Type
+# EXE:   6 .plt          00000030 0000000000400170 TEXT DATA
+# EXE:  10 .got.plt      0000000c 0000000000402000 DATA
 
     .abicalls
     .global glob