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//===- Thunks.cpp --------------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===---------------------------------------------------------------------===//
//
// This file contains both the Target independent and Target specific Thunk
// classes
//
// A Thunk Object represents a single Thunk that will be written to an
// InputSection when the InputSection contents are written. The InputSection
// maintains a list of Thunks that it owns.
//===---------------------------------------------------------------------===//
#include "Thunks.h"
#include "Error.h"
#include "InputFiles.h"
#include "InputSection.h"
#include "OutputSections.h"
#include "Symbols.h"
#include "Target.h"
#include "llvm/Object/ELF.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace llvm::ELF;
namespace lld {
namespace elf {
template <class ELFT> Thunk<ELFT>::~Thunk() {}
template <class ELFT>
Thunk<ELFT>::Thunk(const SymbolBody &D, const InputSection<ELFT> &O)
: Destination(D), Owner(O), Offset(O.getThunkOff() + O.getThunksSize()) {}
template <class ELFT> typename ELFT::uint Thunk<ELFT>::getVA() const {
return Owner.OutSec->getVA() + Owner.OutSecOff + Offset;
}
// ARM Target Thunks
template <class ELFT> static uint64_t getARMThunkDestVA(const SymbolBody &S) {
return S.isInPlt() ? S.getPltVA<ELFT>() : S.getVA<ELFT>();
}
// Specific ARM Thunk implementations. The naming convention is:
// Source State, TargetState, Target Requirement, ABS or PI, Range
namespace {
template <class ELFT>
class ARMToThumbV7ABSLongThunk final : public Thunk<ELFT> {
public:
uint32_t size() const override { return 12; }
void writeTo(uint8_t *Buf) const override {
const uint8_t ATData[] = {
0x00, 0xc0, 0x00, 0xe3, // movw ip,:lower16:S
0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S
0x1c, 0xff, 0x2f, 0xe1, // bx ip
};
uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
memcpy(Buf, ATData, sizeof(ATData));
Target->relocateOne(Buf, R_ARM_MOVW_ABS_NC, S);
Target->relocateOne(Buf + 4, R_ARM_MOVT_ABS, S);
}
ARMToThumbV7ABSLongThunk(const SymbolBody &Destination,
const InputSection<ELFT> &Owner)
: Thunk<ELFT>(Destination, Owner) {}
};
template <class ELFT> class ARMToThumbV7PILongThunk final : public Thunk<ELFT> {
public:
uint32_t size() const override { return 16; }
void writeTo(uint8_t *Buf) const override {
const uint8_t ATData[] = {
0xf0, 0xcf, 0x0f, 0xe3, // P: movw ip,:lower16:S - (P + (L1-P) +8)
0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S - (P + (L1-P+4) +8)
0x0f, 0xc0, 0x8c, 0xe0, // L1: add ip, ip, pc
0x1c, 0xff, 0x2f, 0xe1, // bx r12
};
uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
uint64_t P = this->getVA();
memcpy(Buf, ATData, sizeof(ATData));
Target->relocateOne(Buf, R_ARM_MOVW_PREL_NC, S - P - 16);
Target->relocateOne(Buf + 4, R_ARM_MOVT_PREL, S - P - 12);
}
ARMToThumbV7PILongThunk(const SymbolBody &Destination,
const InputSection<ELFT> &Owner)
: Thunk<ELFT>(Destination, Owner) {}
};
template <class ELFT>
class ThumbToARMV7ABSLongThunk final : public Thunk<ELFT> {
public:
uint32_t size() const override { return 10; }
void writeTo(uint8_t *Buf) const override {
const uint8_t TAData[] = {
0x40, 0xf2, 0x00, 0x0c, // movw ip, :lower16:S
0xc0, 0xf2, 0x00, 0x0c, // movt ip, :upper16:S
0x60, 0x47, // bx ip
};
uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
memcpy(Buf, TAData, sizeof(TAData));
Target->relocateOne(Buf, R_ARM_THM_MOVW_ABS_NC, S);
Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_ABS, S);
}
ThumbToARMV7ABSLongThunk(const SymbolBody &Destination,
const InputSection<ELFT> &Owner)
: Thunk<ELFT>(Destination, Owner) {}
};
template <class ELFT> class ThumbToARMV7PILongThunk final : public Thunk<ELFT> {
public:
uint32_t size() const override { return 12; }
void writeTo(uint8_t *Buf) const override {
const uint8_t TAData[] = {
0x4f, 0xf6, 0xf4, 0x7c, // P: movw ip,:lower16:S - (P + (L1-P) + 4)
0xc0, 0xf2, 0x00, 0x0c, // movt ip,:upper16:S - (P + (L1-P+4) + 4)
0xfc, 0x44, // L1: add r12, pc
0x60, 0x47, // bx r12
};
uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
uint64_t P = this->getVA();
memcpy(Buf, TAData, sizeof(TAData));
Target->relocateOne(Buf, R_ARM_THM_MOVW_PREL_NC, S - P - 12);
Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_PREL, S - P - 8);
}
ThumbToARMV7PILongThunk(const SymbolBody &Destination,
const InputSection<ELFT> &Owner)
: Thunk<ELFT>(Destination, Owner) {}
};
// Mips Thunks
// Only the MIPS LA25 Thunk is supported, the implementation is delegated
// to the MipsTargetInfo class in Target.cpp
template <class ELFT> class MipsThunk : public Thunk<ELFT> {
public:
MipsThunk(const SymbolBody &Destination, const InputSection<ELFT> &Owner);
uint32_t size() const override;
void writeTo(uint8_t *Buf) const override;
};
template <class ELFT>
MipsThunk<ELFT>::MipsThunk(const SymbolBody &Destination,
const InputSection<ELFT> &Owner)
: Thunk<ELFT>(Destination, Owner) {}
template <class ELFT> uint32_t MipsThunk<ELFT>::size() const { return 16; }
template <class ELFT> void MipsThunk<ELFT>::writeTo(uint8_t *Buf) const {
const SymbolBody &D = this->Destination;
uint64_t S = D.getVA<ELFT>();
Target->writeThunk(Buf, S);
}
}
template <class ELFT>
static void addThunkARM(uint32_t RelocType, SymbolBody &S,
InputSection<ELFT> &IS) {
if (S.hasThunk<ELFT>())
// only one Thunk supported per symbol
return;
bool NeedsPI = Config->Pic || Config->Pie || Config->Shared;
Thunk<ELFT> *thunk;
// ARM relocations need ARM to Thumb interworking Thunks, Thumb relocations
// need Thumb to ARM relocations. Use position independent Thunks if we
// require position independent code.
switch (RelocType) {
case R_ARM_PC24:
case R_ARM_PLT32:
case R_ARM_JUMP24:
if (NeedsPI)
thunk = new ARMToThumbV7PILongThunk<ELFT>(S, IS);
else
thunk = new ARMToThumbV7ABSLongThunk<ELFT>(S, IS);
break;
case R_ARM_THM_JUMP19:
case R_ARM_THM_JUMP24:
if (NeedsPI)
thunk = new ThumbToARMV7PILongThunk<ELFT>(S, IS);
else
thunk = new ThumbToARMV7ABSLongThunk<ELFT>(S, IS);
break;
default:
fatal("Unrecognised Relocation type\n");
}
// ARM Thunks are added to the same InputSection as the relocation. This
// isn't strictly necessary but it makes it more likely that a limited range
// branch can reach the Thunk, and it makes Thunks to the PLT section easier
IS.addThunk(thunk);
if (DefinedRegular<ELFT> *DR = dyn_cast<DefinedRegular<ELFT>>(&S))
DR->ThunkData.reset(thunk);
else if (SharedSymbol<ELFT> *SH = dyn_cast<SharedSymbol<ELFT>>(&S))
SH->ThunkData.reset(thunk);
else
fatal("symbol not DefinedRegular or Shared\n");
}
template <class ELFT>
static void addThunkMips(uint32_t RelocType, SymbolBody &S) {
if (S.hasThunk<ELFT>())
// only one Thunk supported per symbol
return;
// Mips Thunks are added to the InputSection defining S
auto *R = cast<DefinedRegular<ELFT>>(&S);
auto *Sec = cast<InputSection<ELFT>>(R->Section);
auto *T = new MipsThunk<ELFT>(S, *Sec);
Sec->addThunk(T);
R->ThunkData.reset(T);
}
template <class ELFT>
void addThunk(uint32_t RelocType, SymbolBody &S, InputSection<ELFT> &IS) {
if (Config->EMachine == EM_ARM)
addThunkARM<ELFT>(RelocType, S, IS);
else if (Config->EMachine == EM_MIPS)
addThunkMips<ELFT>(RelocType, S);
else
llvm_unreachable("add Thunk only supported for ARM and Mips");
}
template void addThunk<ELF32LE>(uint32_t, SymbolBody &,
InputSection<ELF32LE> &);
template void addThunk<ELF32BE>(uint32_t, SymbolBody &,
InputSection<ELF32BE> &);
template void addThunk<ELF64LE>(uint32_t, SymbolBody &,
InputSection<ELF64LE> &);
template void addThunk<ELF64BE>(uint32_t, SymbolBody &,
InputSection<ELF64BE> &);
template uint32_t Thunk<ELF32LE>::getVA() const;
template uint32_t Thunk<ELF32BE>::getVA() const;
template uint64_t Thunk<ELF64LE>::getVA() const;
template uint64_t Thunk<ELF64BE>::getVA() const;
} // namespace elf
} // namespace lld
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