[ELF2] Remove target specific code from GotPltSection.

The content of reserved entries of the .got.plt section is target specific.

In particular, on x86_64 the zero entry holds the address of the .dynamic section,
but on AArch64 the same info is stored in the zero entry of the .got section.

Differential revision: http://reviews.llvm.org/D14703

llvm-svn: 253239

3 files changed, 17 insertions, 9 deletions

diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 70d458b0..fbdbce8 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -35,17 +35,15 @@ GotPltSection<ELFT>::GotPltSection()
     : OutputSectionBase<ELFT>(".got.plt", llvm::ELF::SHT_PROGBITS,
                               llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_WRITE) {
   this->Header.sh_addralign = sizeof(uintX_t);
-  // .got.plt has 3 reserved entry
-  Entries.resize(3);
 }
 
 template <class ELFT> void GotPltSection<ELFT>::addEntry(SymbolBody *Sym) {
-  Sym->GotPltIndex = Entries.size();
+  Sym->GotPltIndex = Target->getGotPltHeaderEntriesNum() + Entries.size();
   Entries.push_back(Sym);
 }
 
 template <class ELFT> bool GotPltSection<ELFT>::empty() const {
-  return Entries.size() == 3;
+  return Entries.empty();
 }
 
 template <class ELFT>
@@ -55,15 +53,15 @@ GotPltSection<ELFT>::getEntryAddr(const SymbolBody &B) const {
 }
 
 template <class ELFT> void GotPltSection<ELFT>::finalize() {
-  this->Header.sh_size = Entries.size() * sizeof(uintX_t);
+  this->Header.sh_size =
+      (Target->getGotPltHeaderEntriesNum() + Entries.size()) * sizeof(uintX_t);
 }
 
 template <class ELFT> void GotPltSection<ELFT>::writeTo(uint8_t *Buf) {
-  write<uintX_t, ELFT::TargetEndianness, sizeof(uintX_t)>(
-      Buf, Out<ELFT>::Dynamic->getVA());
+  Target->writeGotPltHeaderEntries(Buf);
+  Buf += Target->getGotPltHeaderEntriesNum() * sizeof(uintX_t);
   for (const SymbolBody *B : Entries) {
-    if (B)
-      Target->writeGotPltEntry(Buf, Out<ELFT>::Plt->getEntryAddr(*B));
+    Target->writeGotPltEntry(Buf, Out<ELFT>::Plt->getEntryAddr(*B));
     Buf += sizeof(uintX_t);
   }
 }
diff --git a/lld/ELF/Target.cpp b/lld/ELF/Target.cpp
index d28fcfe..269a4d7 100644
--- a/lld/ELF/Target.cpp
+++ b/lld/ELF/Target.cpp
@@ -62,6 +62,7 @@ class X86_64TargetInfo final : public TargetInfo {
 public:
   X86_64TargetInfo();
   unsigned getPLTRefReloc(unsigned Type) const override;
+  void writeGotPltHeaderEntries(uint8_t *Buf) const override;
   void writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const override;
   void writePltZeroEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                          uint64_t PltEntryAddr) const override;
@@ -159,6 +160,8 @@ bool TargetInfo::isRelRelative(uint32_t Type) const { return true; }
 
 void TargetInfo::writeGotHeaderEntries(uint8_t *Buf) const {}
 
+void TargetInfo::writeGotPltHeaderEntries(uint8_t *Buf) const {}
+
 X86TargetInfo::X86TargetInfo() {
   PCRelReloc = R_386_PC32;
   GotReloc = R_386_GLOB_DAT;
@@ -226,6 +229,10 @@ X86_64TargetInfo::X86_64TargetInfo() {
   PltZeroEntrySize = 16;
 }
 
+void X86_64TargetInfo::writeGotPltHeaderEntries(uint8_t *Buf) const {
+  write64le(Buf, Out<ELF64LE>::Dynamic->getVA());
+}
+
 void X86_64TargetInfo::writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const {
   // Skip 6 bytes of "jmpq *got(%rip)"
   write32le(Buf, Plt + 6);
diff --git a/lld/ELF/Target.h b/lld/ELF/Target.h
index ae85d77..c095c67 100644
--- a/lld/ELF/Target.h
+++ b/lld/ELF/Target.h
@@ -43,8 +43,10 @@ public:
   unsigned getPltEntrySize() const { return PltEntrySize; }
   bool supportsLazyRelocations() const { return LazyRelocations; }
   unsigned getGotHeaderEntriesNum() const { return GotHeaderEntriesNum; }
+  unsigned getGotPltHeaderEntriesNum() const { return GotPltHeaderEntriesNum; }
   virtual unsigned getPLTRefReloc(unsigned Type) const;
   virtual void writeGotHeaderEntries(uint8_t *Buf) const;
+  virtual void writeGotPltHeaderEntries(uint8_t *Buf) const;
   virtual void writeGotPltEntry(uint8_t *Buf, uint64_t Plt) const = 0;
   virtual void writePltZeroEntry(uint8_t *Buf, uint64_t GotEntryAddr,
                                  uint64_t PltEntryAddr) const = 0;
@@ -86,6 +88,7 @@ protected:
   unsigned PltEntrySize = 8;
   unsigned PltZeroEntrySize = 0;
   unsigned GotHeaderEntriesNum = 0;
+  unsigned GotPltHeaderEntriesNum = 3;
   bool LazyRelocations = false;
 };