270 lines
9.2 KiB
C++
270 lines
9.2 KiB
C++
//===- Thunks.cpp --------------------------------------------------------===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===---------------------------------------------------------------------===//
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//
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// This file contains Thunk subclasses.
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//
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// A thunk is a small piece of code written after an input section
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// which is used to jump between "incompatible" functions
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// such as MIPS PIC and non-PIC or ARM non-Thumb and Thumb functions.
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//
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// If a jump target is too far and its address doesn't fit to a
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// short jump instruction, we need to create a thunk too, but we
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// haven't supported it yet.
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//
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// i386 and x86-64 don't need thunks.
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//
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//===---------------------------------------------------------------------===//
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#include "Thunks.h"
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#include "Config.h"
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#include "Error.h"
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#include "InputSection.h"
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#include "Memory.h"
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#include "OutputSections.h"
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#include "Symbols.h"
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#include "SyntheticSections.h"
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#include "Target.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/ELF.h"
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#include "llvm/Support/Endian.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/MathExtras.h"
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#include <cstdint>
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#include <cstring>
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using namespace llvm;
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using namespace llvm::object;
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using namespace llvm::support::endian;
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using namespace llvm::ELF;
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namespace lld {
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namespace elf {
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namespace {
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// Specific ARM Thunk implementations. The naming convention is:
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// Source State, TargetState, Target Requirement, ABS or PI, Range
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template <class ELFT> class ARMV7ABSLongThunk final : public Thunk {
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public:
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ARMV7ABSLongThunk(const SymbolBody &Dest) : Thunk(Dest) {}
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uint32_t size() const override { return 12; }
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void writeTo(uint8_t *Buf, ThunkSection &IS) const override;
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void addSymbols(ThunkSection &IS) override;
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};
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template <class ELFT> class ARMV7PILongThunk final : public Thunk {
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public:
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ARMV7PILongThunk(const SymbolBody &Dest) : Thunk(Dest) {}
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uint32_t size() const override { return 16; }
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void writeTo(uint8_t *Buf, ThunkSection &IS) const override;
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void addSymbols(ThunkSection &IS) override;
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};
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template <class ELFT> class ThumbV7ABSLongThunk final : public Thunk {
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public:
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ThumbV7ABSLongThunk(const SymbolBody &Dest) : Thunk(Dest) {
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this->alignment = 2;
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}
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uint32_t size() const override { return 10; }
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void writeTo(uint8_t *Buf, ThunkSection &IS) const override;
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void addSymbols(ThunkSection &IS) override;
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};
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template <class ELFT> class ThumbV7PILongThunk final : public Thunk {
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public:
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ThumbV7PILongThunk(const SymbolBody &Dest) : Thunk(Dest) {
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this->alignment = 2;
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}
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uint32_t size() const override { return 12; }
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void writeTo(uint8_t *Buf, ThunkSection &IS) const override;
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void addSymbols(ThunkSection &IS) override;
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};
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// MIPS LA25 thunk
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template <class ELFT> class MipsThunk final : public Thunk {
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public:
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MipsThunk(const SymbolBody &Dest) : Thunk(Dest) {}
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uint32_t size() const override { return 16; }
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void writeTo(uint8_t *Buf, ThunkSection &IS) const override;
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void addSymbols(ThunkSection &IS) override;
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InputSection *getTargetInputSection() const override;
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};
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} // end anonymous namespace
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// ARM Target Thunks
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static uint64_t getARMThunkDestVA(const SymbolBody &S) {
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uint64_t V = S.isInPlt() ? S.getPltVA() : S.getVA();
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return SignExtend64<32>(V);
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}
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template <class ELFT>
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void ARMV7ABSLongThunk<ELFT>::writeTo(uint8_t *Buf, ThunkSection &IS) const {
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const uint8_t Data[] = {
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0x00, 0xc0, 0x00, 0xe3, // movw ip,:lower16:S
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0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S
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0x1c, 0xff, 0x2f, 0xe1, // bx ip
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};
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uint64_t S = getARMThunkDestVA(this->Destination);
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memcpy(Buf, Data, sizeof(Data));
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Target->relocateOne(Buf, R_ARM_MOVW_ABS_NC, S);
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Target->relocateOne(Buf + 4, R_ARM_MOVT_ABS, S);
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}
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template <class ELFT>
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void ARMV7ABSLongThunk<ELFT>::addSymbols(ThunkSection &IS) {
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this->ThunkSym = addSyntheticLocal<ELFT>(
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Saver.save("__ARMv7ABSLongThunk_" + this->Destination.getName()),
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STT_FUNC, this->Offset, size(), &IS);
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addSyntheticLocal<ELFT>("$a", STT_NOTYPE, this->Offset, 0, &IS);
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}
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template <class ELFT>
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void ThumbV7ABSLongThunk<ELFT>::writeTo(uint8_t *Buf, ThunkSection &IS) const {
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const uint8_t Data[] = {
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0x40, 0xf2, 0x00, 0x0c, // movw ip, :lower16:S
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0xc0, 0xf2, 0x00, 0x0c, // movt ip, :upper16:S
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0x60, 0x47, // bx ip
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};
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uint64_t S = getARMThunkDestVA(this->Destination);
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memcpy(Buf, Data, sizeof(Data));
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Target->relocateOne(Buf, R_ARM_THM_MOVW_ABS_NC, S);
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Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_ABS, S);
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}
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template <class ELFT>
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void ThumbV7ABSLongThunk<ELFT>::addSymbols(ThunkSection &IS) {
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this->ThunkSym = addSyntheticLocal<ELFT>(
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Saver.save("__Thumbv7ABSLongThunk_" + this->Destination.getName()),
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STT_FUNC, this->Offset, size(), &IS);
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addSyntheticLocal<ELFT>("$t", STT_NOTYPE, this->Offset, 0, &IS);
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}
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template <class ELFT>
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void ARMV7PILongThunk<ELFT>::writeTo(uint8_t *Buf, ThunkSection &IS) const {
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const uint8_t Data[] = {
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0xf0, 0xcf, 0x0f, 0xe3, // P: movw ip,:lower16:S - (P + (L1-P) +8)
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0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S - (P + (L1-P+4) +8)
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0x0f, 0xc0, 0x8c, 0xe0, // L1: add ip, ip, pc
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0x1c, 0xff, 0x2f, 0xe1, // bx r12
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};
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uint64_t S = getARMThunkDestVA(this->Destination);
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uint64_t P = this->ThunkSym->getVA();
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memcpy(Buf, Data, sizeof(Data));
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Target->relocateOne(Buf, R_ARM_MOVW_PREL_NC, S - P - 16);
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Target->relocateOne(Buf + 4, R_ARM_MOVT_PREL, S - P - 12);
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}
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template <class ELFT>
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void ARMV7PILongThunk<ELFT>::addSymbols(ThunkSection &IS) {
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this->ThunkSym = addSyntheticLocal<ELFT>(
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Saver.save("__ARMV7PILongThunk_" + this->Destination.getName()), STT_FUNC,
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this->Offset, size(), &IS);
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addSyntheticLocal<ELFT>("$a", STT_NOTYPE, this->Offset, 0, &IS);
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}
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template <class ELFT>
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void ThumbV7PILongThunk<ELFT>::writeTo(uint8_t *Buf, ThunkSection &IS) const {
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const uint8_t Data[] = {
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0x4f, 0xf6, 0xf4, 0x7c, // P: movw ip,:lower16:S - (P + (L1-P) + 4)
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0xc0, 0xf2, 0x00, 0x0c, // movt ip,:upper16:S - (P + (L1-P+4) + 4)
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0xfc, 0x44, // L1: add r12, pc
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0x60, 0x47, // bx r12
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};
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uint64_t S = getARMThunkDestVA(this->Destination);
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uint64_t P = this->ThunkSym->getVA();
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memcpy(Buf, Data, sizeof(Data));
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Target->relocateOne(Buf, R_ARM_THM_MOVW_PREL_NC, S - P - 12);
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Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_PREL, S - P - 8);
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}
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template <class ELFT>
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void ThumbV7PILongThunk<ELFT>::addSymbols(ThunkSection &IS) {
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this->ThunkSym = addSyntheticLocal<ELFT>(
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Saver.save("__ThumbV7PILongThunk_" + this->Destination.getName()),
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STT_FUNC, this->Offset, size(), &IS);
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addSyntheticLocal<ELFT>("$t", STT_NOTYPE, this->Offset, 0, &IS);
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}
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// Write MIPS LA25 thunk code to call PIC function from the non-PIC one.
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template <class ELFT>
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void MipsThunk<ELFT>::writeTo(uint8_t *Buf, ThunkSection &) const {
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const endianness E = ELFT::TargetEndianness;
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uint64_t S = this->Destination.getVA();
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write32<E>(Buf, 0x3c190000); // lui $25, %hi(func)
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write32<E>(Buf + 4, 0x08000000 | (S >> 2)); // j func
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write32<E>(Buf + 8, 0x27390000); // addiu $25, $25, %lo(func)
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write32<E>(Buf + 12, 0x00000000); // nop
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Target->relocateOne(Buf, R_MIPS_HI16, S);
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Target->relocateOne(Buf + 8, R_MIPS_LO16, S);
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}
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template <class ELFT> void MipsThunk<ELFT>::addSymbols(ThunkSection &IS) {
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this->ThunkSym = addSyntheticLocal<ELFT>(
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Saver.save("__LA25Thunk_" + this->Destination.getName()), STT_FUNC,
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this->Offset, size(), &IS);
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}
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template <class ELFT>
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InputSection *MipsThunk<ELFT>::getTargetInputSection() const {
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auto *DR = dyn_cast<DefinedRegular>(&this->Destination);
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return dyn_cast<InputSection>(DR->Section);
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}
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Thunk::Thunk(const SymbolBody &D) : Destination(D), Offset(0) {}
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Thunk::~Thunk() = default;
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// Creates a thunk for Thumb-ARM interworking.
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template <class ELFT> static Thunk *addThunkArm(uint32_t Reloc, SymbolBody &S) {
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// ARM relocations need ARM to Thumb interworking Thunks.
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// Thumb relocations need Thumb to ARM relocations.
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// Use position independent Thunks if we require position independent code.
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switch (Reloc) {
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case R_ARM_PC24:
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case R_ARM_PLT32:
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case R_ARM_JUMP24:
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if (Config->Pic)
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return make<ARMV7PILongThunk<ELFT>>(S);
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return make<ARMV7ABSLongThunk<ELFT>>(S);
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case R_ARM_THM_JUMP19:
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case R_ARM_THM_JUMP24:
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if (Config->Pic)
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return make<ThumbV7PILongThunk<ELFT>>(S);
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return make<ThumbV7ABSLongThunk<ELFT>>(S);
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}
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fatal("unrecognized relocation type");
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}
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template <class ELFT> static Thunk *addThunkMips(SymbolBody &S) {
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return make<MipsThunk<ELFT>>(S);
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}
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template <class ELFT> Thunk *addThunk(uint32_t RelocType, SymbolBody &S) {
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if (Config->EMachine == EM_ARM)
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return addThunkArm<ELFT>(RelocType, S);
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else if (Config->EMachine == EM_MIPS)
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return addThunkMips<ELFT>(S);
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llvm_unreachable("add Thunk only supported for ARM and Mips");
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return nullptr;
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}
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template Thunk *addThunk<ELF32LE>(uint32_t, SymbolBody &);
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template Thunk *addThunk<ELF32BE>(uint32_t, SymbolBody &);
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template Thunk *addThunk<ELF64LE>(uint32_t, SymbolBody &);
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template Thunk *addThunk<ELF64BE>(uint32_t, SymbolBody &);
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} // end namespace elf
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} // end namespace lld
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