1 //===- Thunks.cpp --------------------------------------------------------===//
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===---------------------------------------------------------------------===//
10 // This file contains Thunk subclasses.
12 // A thunk is a small piece of code written after an input section
13 // which is used to jump between "incompatible" functions
14 // such as MIPS PIC and non-PIC or ARM non-Thumb and Thumb functions.
16 // If a jump target is too far and its address doesn't fit to a
17 // short jump instruction, we need to create a thunk too, but we
18 // haven't supported it yet.
20 // i386 and x86-64 don't need thunks.
22 //===---------------------------------------------------------------------===//
26 #include "InputFiles.h"
27 #include "InputSection.h"
28 #include "OutputSections.h"
31 #include "llvm/Support/Allocator.h"
33 #include "llvm/Object/ELF.h"
34 #include "llvm/Support/ELF.h"
35 #include "llvm/Support/Endian.h"
38 using namespace llvm::object;
39 using namespace llvm::support::endian;
40 using namespace llvm::ELF;
46 // Specific ARM Thunk implementations. The naming convention is:
47 // Source State, TargetState, Target Requirement, ABS or PI, Range
49 class ARMToThumbV7ABSLongThunk final : public Thunk<ELFT> {
51 ARMToThumbV7ABSLongThunk(const SymbolBody &Dest,
52 const InputSection<ELFT> &Owner)
53 : Thunk<ELFT>(Dest, Owner) {}
55 uint32_t size() const override { return 12; }
56 void writeTo(uint8_t *Buf) const override;
59 template <class ELFT> class ARMToThumbV7PILongThunk final : public Thunk<ELFT> {
61 ARMToThumbV7PILongThunk(const SymbolBody &Dest,
62 const InputSection<ELFT> &Owner)
63 : Thunk<ELFT>(Dest, Owner) {}
65 uint32_t size() const override { return 16; }
66 void writeTo(uint8_t *Buf) const override;
70 class ThumbToARMV7ABSLongThunk final : public Thunk<ELFT> {
72 ThumbToARMV7ABSLongThunk(const SymbolBody &Dest,
73 const InputSection<ELFT> &Owner)
74 : Thunk<ELFT>(Dest, Owner) {}
76 uint32_t size() const override { return 10; }
77 void writeTo(uint8_t *Buf) const override;
80 template <class ELFT> class ThumbToARMV7PILongThunk final : public Thunk<ELFT> {
82 ThumbToARMV7PILongThunk(const SymbolBody &Dest,
83 const InputSection<ELFT> &Owner)
84 : Thunk<ELFT>(Dest, Owner) {}
86 uint32_t size() const override { return 12; }
87 void writeTo(uint8_t *Buf) const override;
91 template <class ELFT> class MipsThunk final : public Thunk<ELFT> {
93 MipsThunk(const SymbolBody &Dest, const InputSection<ELFT> &Owner)
94 : Thunk<ELFT>(Dest, Owner) {}
96 uint32_t size() const override { return 16; }
97 void writeTo(uint8_t *Buf) const override;
99 } // anonymous namespace
102 template <class ELFT> static uint64_t getARMThunkDestVA(const SymbolBody &S) {
103 return S.isInPlt() ? S.getPltVA<ELFT>() : S.getVA<ELFT>();
106 template <class ELFT>
107 void ARMToThumbV7ABSLongThunk<ELFT>::writeTo(uint8_t *Buf) const {
108 const uint8_t Data[] = {
109 0x00, 0xc0, 0x00, 0xe3, // movw ip,:lower16:S
110 0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S
111 0x1c, 0xff, 0x2f, 0xe1, // bx ip
113 uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
114 memcpy(Buf, Data, sizeof(Data));
115 Target->relocateOne(Buf, R_ARM_MOVW_ABS_NC, S);
116 Target->relocateOne(Buf + 4, R_ARM_MOVT_ABS, S);
119 template <class ELFT>
120 void ThumbToARMV7ABSLongThunk<ELFT>::writeTo(uint8_t *Buf) const {
121 const uint8_t Data[] = {
122 0x40, 0xf2, 0x00, 0x0c, // movw ip, :lower16:S
123 0xc0, 0xf2, 0x00, 0x0c, // movt ip, :upper16:S
126 uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
127 memcpy(Buf, Data, sizeof(Data));
128 Target->relocateOne(Buf, R_ARM_THM_MOVW_ABS_NC, S);
129 Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_ABS, S);
132 template <class ELFT>
133 void ARMToThumbV7PILongThunk<ELFT>::writeTo(uint8_t *Buf) const {
134 const uint8_t Data[] = {
135 0xf0, 0xcf, 0x0f, 0xe3, // P: movw ip,:lower16:S - (P + (L1-P) +8)
136 0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S - (P + (L1-P+4) +8)
137 0x0f, 0xc0, 0x8c, 0xe0, // L1: add ip, ip, pc
138 0x1c, 0xff, 0x2f, 0xe1, // bx r12
140 uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
141 uint64_t P = this->getVA();
142 memcpy(Buf, Data, sizeof(Data));
143 Target->relocateOne(Buf, R_ARM_MOVW_PREL_NC, S - P - 16);
144 Target->relocateOne(Buf + 4, R_ARM_MOVT_PREL, S - P - 12);
147 template <class ELFT>
148 void ThumbToARMV7PILongThunk<ELFT>::writeTo(uint8_t *Buf) const {
149 const uint8_t Data[] = {
150 0x4f, 0xf6, 0xf4, 0x7c, // P: movw ip,:lower16:S - (P + (L1-P) + 4)
151 0xc0, 0xf2, 0x00, 0x0c, // movt ip,:upper16:S - (P + (L1-P+4) + 4)
152 0xfc, 0x44, // L1: add r12, pc
153 0x60, 0x47, // bx r12
155 uint64_t S = getARMThunkDestVA<ELFT>(this->Destination);
156 uint64_t P = this->getVA();
157 memcpy(Buf, Data, sizeof(Data));
158 Target->relocateOne(Buf, R_ARM_THM_MOVW_PREL_NC, S - P - 12);
159 Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_PREL, S - P - 8);
162 // Write MIPS LA25 thunk code to call PIC function from the non-PIC one.
163 template <class ELFT> void MipsThunk<ELFT>::writeTo(uint8_t *Buf) const {
164 const endianness E = ELFT::TargetEndianness;
166 uint64_t S = this->Destination.template getVA<ELFT>();
167 write32<E>(Buf, 0x3c190000); // lui $25, %hi(func)
168 write32<E>(Buf + 4, 0x08000000 | (S >> 2)); // j func
169 write32<E>(Buf + 8, 0x27390000); // addiu $25, $25, %lo(func)
170 write32<E>(Buf + 12, 0x00000000); // nop
171 Target->relocateOne(Buf, R_MIPS_HI16, S);
172 Target->relocateOne(Buf + 8, R_MIPS_LO16, S);
175 template <class ELFT>
176 Thunk<ELFT>::Thunk(const SymbolBody &D, const InputSection<ELFT> &O)
177 : Destination(D), Owner(O), Offset(O.getThunkOff() + O.getThunksSize()) {}
179 template <class ELFT> typename ELFT::uint Thunk<ELFT>::getVA() const {
180 return Owner.OutSec->getVA() + Owner.OutSecOff + Offset;
183 template <class ELFT> Thunk<ELFT>::~Thunk() {}
185 // Creates a thunk for Thumb-ARM interworking.
186 template <class ELFT>
187 static Thunk<ELFT> *createThunkArm(uint32_t Reloc, SymbolBody &S,
188 InputSection<ELFT> &IS) {
189 // ARM relocations need ARM to Thumb interworking Thunks.
190 // Thumb relocations need Thumb to ARM relocations.
191 // Use position independent Thunks if we require position independent code.
192 BumpPtrAllocator &Alloc = IS.getFile()->Alloc;
198 return new (Alloc) ARMToThumbV7PILongThunk<ELFT>(S, IS);
199 return new (Alloc) ARMToThumbV7ABSLongThunk<ELFT>(S, IS);
200 case R_ARM_THM_JUMP19:
201 case R_ARM_THM_JUMP24:
203 return new (Alloc) ThumbToARMV7PILongThunk<ELFT>(S, IS);
204 return new (Alloc) ThumbToARMV7ABSLongThunk<ELFT>(S, IS);
206 fatal("unrecognized relocation type");
209 template <class ELFT>
210 static void addThunkARM(uint32_t Reloc, SymbolBody &S, InputSection<ELFT> &IS) {
211 // Only one Thunk supported per symbol.
212 if (S.hasThunk<ELFT>())
215 // ARM Thunks are added to the same InputSection as the relocation. This
216 // isn't strictly necessary but it makes it more likely that a limited range
217 // branch can reach the Thunk, and it makes Thunks to the PLT section easier
218 Thunk<ELFT> *T = createThunkArm(Reloc, S, IS);
220 if (auto *Sym = dyn_cast<DefinedRegular<ELFT>>(&S))
222 else if (auto *Sym = dyn_cast<SharedSymbol<ELFT>>(&S))
225 fatal("symbol not DefinedRegular or Shared");
228 template <class ELFT>
229 static void addThunkMips(uint32_t RelocType, SymbolBody &S,
230 InputSection<ELFT> &IS) {
231 // Only one Thunk supported per symbol.
232 if (S.hasThunk<ELFT>())
235 // Mips Thunks are added to the InputSection defining S.
236 auto *R = cast<DefinedRegular<ELFT>>(&S);
237 auto *Sec = cast<InputSection<ELFT>>(R->Section);
238 auto *T = new (IS.getFile()->Alloc) MipsThunk<ELFT>(S, *Sec);
243 template <class ELFT>
244 void addThunk(uint32_t RelocType, SymbolBody &S, InputSection<ELFT> &IS) {
245 if (Config->EMachine == EM_ARM)
246 addThunkARM<ELFT>(RelocType, S, IS);
247 else if (Config->EMachine == EM_MIPS)
248 addThunkMips<ELFT>(RelocType, S, IS);
250 llvm_unreachable("add Thunk only supported for ARM and Mips");
253 template void addThunk<ELF32LE>(uint32_t, SymbolBody &,
254 InputSection<ELF32LE> &);
255 template void addThunk<ELF32BE>(uint32_t, SymbolBody &,
256 InputSection<ELF32BE> &);
257 template void addThunk<ELF64LE>(uint32_t, SymbolBody &,
258 InputSection<ELF64LE> &);
259 template void addThunk<ELF64BE>(uint32_t, SymbolBody &,
260 InputSection<ELF64BE> &);
262 template class Thunk<ELF32LE>;
263 template class Thunk<ELF32BE>;
264 template class Thunk<ELF64LE>;
265 template class Thunk<ELF64BE>;