Reduce code duplication a bit

[• espindola]

Summary

The code for computing the offset of an entry in the plt is simple, but it was duplicated in quite a few places.

[ruiu]

LGTM

[• espindola]

r327536

ELF/Arch/SPARCV9.cpp

const uint8_t PltData[] = {
       0x01, 0x00, 0x00, 0x00, // nop
       0x01, 0x00, 0x00, 0x00, // nop
       0x01, 0x00, 0x00, 0x00, // nop
       0x01, 0x00, 0x00, 0x00, // nop
       0x01, 0x00, 0x00, 0x00  // nop
   };
   memcpy(Buf, PltData, sizeof(PltData));
 
-  uint64_t Off = PltHeaderSize + Index * PltEntrySize;
+  uint64_t Off = getPltEntryOffset(Index);
   relocateOne(Buf, R_SPARC_22, Off);
   relocateOne(Buf + 4, R_SPARC_WDISP19, -(Off + 4 - PltEntrySize));
 }
 
 TargetInfo *elf::getSPARCV9TargetInfo() {
   static SPARCV9 Target;
   return &Target;
 }

ELF/Arch/X86.cpp

if (Config->Pic) {
     write32le(Buf + 2, GotPltEntryAddr - Ebx);
   } else {
     // jmp *foo_in_GOT
     Buf[1] = 0x25;
     write32le(Buf + 2, GotPltEntryAddr);
   }
 
   write32le(Buf + 7, RelOff);
-  write32le(Buf + 12, -Index * PltEntrySize - PltHeaderSize - 16);
+  write32le(Buf + 12, -getPltEntryOffset(Index) - 16);
 }
 
 int64_t X86::getImplicitAddend(const uint8_t *Buf, RelType Type) const {
   switch (Type) {
   case R_386_8:
   case R_386_PC8:
     return SignExtend64<8>(*Buf);
   case R_386_16:
const uint8_t Insn[] = {
       0xe8, 0,    0, 0, 0,    // call plt+0x20
       0xe9, 0,    0, 0, 0,    // jmp plt+0x12
       0x68, 0,    0, 0, 0,    // pushl $reloc_offset
       0xe9, 0,    0, 0, 0,    // jmp plt+0
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   uint32_t Ebx = InX::Got->getVA() + InX::Got->getSize();
+  unsigned Off = getPltEntryOffset(Index);
   write32le(Buf + 3, GotPltEntryAddr - Ebx);
-  write32le(Buf + 8, -Index * PltEntrySize - PltHeaderSize - 12 + 32);
-  write32le(Buf + 13, -Index * PltEntrySize - PltHeaderSize - 17 + 18);
+  write32le(Buf + 8, -Off - 12 + 32);
+  write32le(Buf + 13, -Off - 17 + 18);
   write32le(Buf + 18, RelOff);
-  write32le(Buf + 23, -Index * PltEntrySize - PltHeaderSize - 27);
+  write32le(Buf + 23, -Off - 27);
 }
 
 RetpolineNoPic::RetpolineNoPic() {
   PltHeaderSize = 48;
   PltEntrySize = 32;
 }
 
 void RetpolineNoPic::writeGotPlt(uint8_t *Buf, const Symbol &S) const {
const uint8_t Insn[] = {
       0xa1, 0, 0, 0, 0, // 1:  mov foo_in_GOT, %eax
       0xe8, 0, 0, 0, 0, // 6:  call plt+0x20
       0xe9, 0, 0, 0, 0, // b:  jmp plt+0x11
       0x68, 0, 0, 0, 0, // 10: pushl $reloc_offset
       0xe9, 0, 0, 0, 0, // 15: jmp plt+0
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
+  unsigned Off = getPltEntryOffset(Index);
   write32le(Buf + 2, GotPltEntryAddr);
-  write32le(Buf + 7, -Index * PltEntrySize - PltHeaderSize - 11 + 32);
-  write32le(Buf + 12, -Index * PltEntrySize - PltHeaderSize - 16 + 17);
+  write32le(Buf + 7, -Off - 11 + 32);
+  write32le(Buf + 12, -Off - 16 + 17);
   write32le(Buf + 17, RelOff);
-  write32le(Buf + 22, -Index * PltEntrySize - PltHeaderSize - 26);
+  write32le(Buf + 22, -Off - 26);
 }
 
 TargetInfo *elf::getX86TargetInfo() {
   if (Config->ZRetpolineplt) {
     if (Config->Pic) {
       static RetpolinePic T;
       return &T;
     }
     static RetpolineNoPic T;
     return &T;
   }
 
   static X86 T;
   return &T;
 }

ELF/Arch/X86_64.cpp

const uint8_t Inst[] = {
       0xff, 0x25, 0, 0, 0, 0, // jmpq *got(%rip)
       0x68, 0, 0, 0, 0,       // pushq <relocation index>
       0xe9, 0, 0, 0, 0,       // jmpq plt[0]
   };
   memcpy(Buf, Inst, sizeof(Inst));
 
   write32le(Buf + 2, GotPltEntryAddr - PltEntryAddr - 6);
   write32le(Buf + 7, Index);
-  write32le(Buf + 12, -Index * PltEntrySize - PltHeaderSize - 16);
+  write32le(Buf + 12, -getPltEntryOffset(Index) - 16);
 }
 
 template <class ELFT> bool X86_64<ELFT>::isPicRel(RelType Type) const {
   return Type != R_X86_64_PC32 && Type != R_X86_64_32 &&
          Type != R_X86_64_TPOFF32;
 }
 
 template <class ELFT>
const uint8_t Insn[] = {
       0x4c, 0x8b, 0x1d, 0, 0, 0, 0, // 0:  mov foo@GOTPLT(%rip), %r11
       0xe8, 0,    0,    0, 0,       // 7:  callq plt+0x20
       0xe9, 0,    0,    0, 0,       // c:  jmp plt+0x12
       0x68, 0,    0,    0, 0,       // 11: pushq <relocation index>
       0xe9, 0,    0,    0, 0,       // 16: jmp plt+0
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
-  uint64_t Off = TargetInfo::PltHeaderSize + TargetInfo::PltEntrySize * Index;
+  uint64_t Off = TargetInfo::getPltEntryOffset(Index);
 
   write32le(Buf + 3, GotPltEntryAddr - PltEntryAddr - 7);
   write32le(Buf + 8, -Off - 12 + 32);
   write32le(Buf + 13, -Off - 17 + 18);
   write32le(Buf + 18, Index);
   write32le(Buf + 23, -Off - 27);
 }
 
void RetpolineZNow<ELFT>::writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr,
                                    unsigned RelOff) const {
   const uint8_t Insn[] = {
       0x4c, 0x8b, 0x1d, 0, 0, 0, 0, // mov foo@GOTPLT(%rip), %r11
       0xe9, 0,    0,    0, 0,       // jmp plt+0
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   write32le(Buf + 3, GotPltEntryAddr - PltEntryAddr - 7);
-  write32le(Buf + 8,
-            -Index * TargetInfo::PltEntrySize - TargetInfo::PltHeaderSize - 12);
+  write32le(Buf + 8, -TargetInfo::getPltEntryOffset(Index) - 12);
 }
 
 template <class ELFT> TargetInfo *getTargetInfo() {
   if (Config->ZRetpolineplt) {
     if (Config->ZNow) {
       static RetpolineZNow<ELFT> T;
       return &T;
     }

ELF/Symbols.cpp

 
 uint64_t Symbol::getGotPltOffset() const {
   return GotPltIndex * Target->GotPltEntrySize;
 }
 
 uint64_t Symbol::getPltVA() const {
   if (this->IsInIplt)
     return InX::Iplt->getVA() + PltIndex * Target->PltEntrySize;
-  return InX::Plt->getVA() + Target->PltHeaderSize +
-         PltIndex * Target->PltEntrySize;
+  return InX::Plt->getVA() + Target->getPltEntryOffset(PltIndex);
 }
 
 uint64_t Symbol::getSize() const {
   if (const auto *DR = dyn_cast<Defined>(this))
     return DR->Size;
   if (const auto *S = dyn_cast<SharedSymbol>(this))
     return S->Size;
   return 0;

ELF/Target.h

public:
   virtual void writePltHeader(uint8_t *Buf) const {}
 
   virtual void writePlt(uint8_t *Buf, uint64_t GotEntryAddr,
                         uint64_t PltEntryAddr, int32_t Index,
                         unsigned RelOff) const {}
   virtual void addPltHeaderSymbols(InputSection &IS) const {}
   virtual void addPltSymbols(InputSection &IS, uint64_t Off) const {}
 
+  unsigned getPltEntryOffset(unsigned Index) const {
+    return Index * PltEntrySize + PltHeaderSize;
+  }
+
   // Returns true if a relocation only uses the low bits of a value such that
   // all those bits are in in the same page. For example, if the relocation
   // only uses the low 12 bits in a system with 4k pages. If this is true, the
   // bits will always have the same value at runtime and we don't have to emit
   // a dynamic relocation.
   virtual bool usesOnlyLowPageBits(RelType Type) const;
 
   // Decide whether a Thunk is needed for the relocation from File