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 "InputSection.h"
27 #include "OutputSections.h"
29 #include "SyntheticSections.h"
31 #include "lld/Common/ErrorHandler.h"
32 #include "lld/Common/Memory.h"
33 #include "llvm/BinaryFormat/ELF.h"
34 #include "llvm/Support/Casting.h"
35 #include "llvm/Support/Endian.h"
36 #include "llvm/Support/ErrorHandling.h"
37 #include "llvm/Support/MathExtras.h"
42 using namespace llvm::object;
43 using namespace llvm::ELF;
50 // AArch64 long range Thunks
51 class AArch64ABSLongThunk final : public Thunk {
53 AArch64ABSLongThunk(Symbol &Dest) : Thunk(Dest) {}
54 uint32_t size() override { return 16; }
55 void writeTo(uint8_t *Buf) override;
56 void addSymbols(ThunkSection &IS) override;
59 class AArch64ADRPThunk final : public Thunk {
61 AArch64ADRPThunk(Symbol &Dest) : Thunk(Dest) {}
62 uint32_t size() override { return 12; }
63 void writeTo(uint8_t *Buf) override;
64 void addSymbols(ThunkSection &IS) override;
67 // Base class for ARM thunks.
69 // An ARM thunk may be either short or long. A short thunk is simply a branch
70 // (B) instruction, and it may be used to call ARM functions when the distance
71 // from the thunk to the target is less than 32MB. Long thunks can branch to any
72 // virtual address and can switch between ARM and Thumb, and they are
73 // implemented in the derived classes. This class tries to create a short thunk
74 // if the target is in range, otherwise it creates a long thunk.
75 class ARMThunk : public Thunk {
77 ARMThunk(Symbol &Dest) : Thunk(Dest) {}
79 bool mayUseShortThunk();
80 uint32_t size() override { return mayUseShortThunk() ? 4 : sizeLong(); }
81 void writeTo(uint8_t *Buf) override;
82 bool isCompatibleWith(RelType Type) const override;
84 // Returns the size of a long thunk.
85 virtual uint32_t sizeLong() = 0;
87 // Writes a long thunk to Buf.
88 virtual void writeLong(uint8_t *Buf) = 0;
91 // This field tracks whether all previously considered layouts would allow
92 // this thunk to be short. If we have ever needed a long thunk, we always
93 // create a long thunk, even if the thunk may be short given the current
94 // distance to the target. We do this because transitioning from long to short
95 // can create layout oscillations in certain corner cases which would prevent
96 // the layout from converging.
97 bool MayUseShortThunk = true;
100 // Base class for Thumb-2 thunks.
102 // This class is similar to ARMThunk, but it uses the Thumb-2 B.W instruction
103 // which has a range of 16MB.
104 class ThumbThunk : public Thunk {
106 ThumbThunk(Symbol &Dest) : Thunk(Dest) { Alignment = 2; }
108 bool mayUseShortThunk();
109 uint32_t size() override { return mayUseShortThunk() ? 4 : sizeLong(); }
110 void writeTo(uint8_t *Buf) override;
111 bool isCompatibleWith(RelType Type) const override;
113 // Returns the size of a long thunk.
114 virtual uint32_t sizeLong() = 0;
116 // Writes a long thunk to Buf.
117 virtual void writeLong(uint8_t *Buf) = 0;
120 // See comment in ARMThunk above.
121 bool MayUseShortThunk = true;
124 // Specific ARM Thunk implementations. The naming convention is:
125 // Source State, TargetState, Target Requirement, ABS or PI, Range
126 class ARMV7ABSLongThunk final : public ARMThunk {
128 ARMV7ABSLongThunk(Symbol &Dest) : ARMThunk(Dest) {}
130 uint32_t sizeLong() override { return 12; }
131 void writeLong(uint8_t *Buf) override;
132 void addSymbols(ThunkSection &IS) override;
135 class ARMV7PILongThunk final : public ARMThunk {
137 ARMV7PILongThunk(Symbol &Dest) : ARMThunk(Dest) {}
139 uint32_t sizeLong() override { return 16; }
140 void writeLong(uint8_t *Buf) override;
141 void addSymbols(ThunkSection &IS) override;
144 class ThumbV7ABSLongThunk final : public ThumbThunk {
146 ThumbV7ABSLongThunk(Symbol &Dest) : ThumbThunk(Dest) {}
148 uint32_t sizeLong() override { return 10; }
149 void writeLong(uint8_t *Buf) override;
150 void addSymbols(ThunkSection &IS) override;
153 class ThumbV7PILongThunk final : public ThumbThunk {
155 ThumbV7PILongThunk(Symbol &Dest) : ThumbThunk(Dest) {}
157 uint32_t sizeLong() override { return 12; }
158 void writeLong(uint8_t *Buf) override;
159 void addSymbols(ThunkSection &IS) override;
162 // Implementations of Thunks for older Arm architectures that do not support
163 // the movt/movw instructions. These thunks require at least Architecture v5
164 // as used on processors such as the Arm926ej-s. There are no Thumb entry
165 // points as there is no Thumb branch instruction on these architecture that
166 // can result in a thunk
167 class ARMV5ABSLongThunk final : public ARMThunk {
169 ARMV5ABSLongThunk(Symbol &Dest) : ARMThunk(Dest) {}
171 uint32_t sizeLong() override { return 8; }
172 void writeLong(uint8_t *Buf) override;
173 void addSymbols(ThunkSection &IS) override;
174 bool isCompatibleWith(uint32_t RelocType) const override;
177 class ARMV5PILongThunk final : public ARMThunk {
179 ARMV5PILongThunk(Symbol &Dest) : ARMThunk(Dest) {}
181 uint32_t sizeLong() override { return 16; }
182 void writeLong(uint8_t *Buf) override;
183 void addSymbols(ThunkSection &IS) override;
184 bool isCompatibleWith(uint32_t RelocType) const override;
187 // Implementations of Thunks for Arm v6-M. Only Thumb instructions are permitted
188 class ThumbV6MABSLongThunk final : public ThumbThunk {
190 ThumbV6MABSLongThunk(Symbol &Dest) : ThumbThunk(Dest) {}
192 uint32_t sizeLong() override { return 12; }
193 void writeLong(uint8_t *Buf) override;
194 void addSymbols(ThunkSection &IS) override;
197 class ThumbV6MPILongThunk final : public ThumbThunk {
199 ThumbV6MPILongThunk(Symbol &Dest) : ThumbThunk(Dest) {}
201 uint32_t sizeLong() override { return 16; }
202 void writeLong(uint8_t *Buf) override;
203 void addSymbols(ThunkSection &IS) override;
207 class MipsThunk final : public Thunk {
209 MipsThunk(Symbol &Dest) : Thunk(Dest) {}
211 uint32_t size() override { return 16; }
212 void writeTo(uint8_t *Buf) override;
213 void addSymbols(ThunkSection &IS) override;
214 InputSection *getTargetInputSection() const override;
217 // microMIPS R2-R5 LA25 thunk
218 class MicroMipsThunk final : public Thunk {
220 MicroMipsThunk(Symbol &Dest) : Thunk(Dest) {}
222 uint32_t size() override { return 14; }
223 void writeTo(uint8_t *Buf) override;
224 void addSymbols(ThunkSection &IS) override;
225 InputSection *getTargetInputSection() const override;
228 // microMIPS R6 LA25 thunk
229 class MicroMipsR6Thunk final : public Thunk {
231 MicroMipsR6Thunk(Symbol &Dest) : Thunk(Dest) {}
233 uint32_t size() override { return 12; }
234 void writeTo(uint8_t *Buf) override;
235 void addSymbols(ThunkSection &IS) override;
236 InputSection *getTargetInputSection() const override;
240 // PPC64 Plt call stubs.
241 // Any call site that needs to call through a plt entry needs a call stub in
242 // the .text section. The call stub is responsible for:
243 // 1) Saving the toc-pointer to the stack.
244 // 2) Loading the target functions address from the procedure linkage table into
245 // r12 for use by the target functions global entry point, and into the count
247 // 3) Transfering control to the target function through an indirect branch.
248 class PPC64PltCallStub final : public Thunk {
250 PPC64PltCallStub(Symbol &Dest) : Thunk(Dest) {}
251 uint32_t size() override { return 20; }
252 void writeTo(uint8_t *Buf) override;
253 void addSymbols(ThunkSection &IS) override;
256 // A bl instruction uses a signed 24 bit offset, with an implicit 4 byte
257 // alignment. This gives a possible 26 bits of 'reach'. If the call offset is
258 // larger then that we need to emit a long-branch thunk. The target address
259 // of the callee is stored in a table to be accessed TOC-relative. Since the
260 // call must be local (a non-local call will have a PltCallStub instead) the
261 // table stores the address of the callee's local entry point. For
262 // position-independent code a corresponding relative dynamic relocation is
264 class PPC64LongBranchThunk : public Thunk {
266 uint32_t size() override { return 16; }
267 void writeTo(uint8_t *Buf) override;
268 void addSymbols(ThunkSection &IS) override;
271 PPC64LongBranchThunk(Symbol &Dest) : Thunk(Dest) {}
274 class PPC64PILongBranchThunk final : public PPC64LongBranchThunk {
276 PPC64PILongBranchThunk(Symbol &Dest) : PPC64LongBranchThunk(Dest) {
277 assert(!Dest.IsPreemptible);
278 if (Dest.isInPPC64Branchlt())
281 In.PPC64LongBranchTarget->addEntry(Dest);
282 In.RelaDyn->addReloc({Target->RelativeRel, In.PPC64LongBranchTarget,
283 Dest.getPPC64LongBranchOffset(), true, &Dest,
284 getPPC64GlobalEntryToLocalEntryOffset(Dest.StOther)});
288 class PPC64PDLongBranchThunk final : public PPC64LongBranchThunk {
290 PPC64PDLongBranchThunk(Symbol &Dest) : PPC64LongBranchThunk(Dest) {
291 if (!Dest.isInPPC64Branchlt())
292 In.PPC64LongBranchTarget->addEntry(Dest);
296 } // end anonymous namespace
298 Defined *Thunk::addSymbol(StringRef Name, uint8_t Type, uint64_t Value,
299 InputSectionBase &Section) {
300 Defined *D = addSyntheticLocal(Name, Type, Value, /*Size=*/0, Section);
305 void Thunk::setOffset(uint64_t NewOffset) {
306 for (Defined *D : Syms)
307 D->Value = D->Value - Offset + NewOffset;
311 // AArch64 long range Thunks
313 static uint64_t getAArch64ThunkDestVA(const Symbol &S) {
314 uint64_t V = S.isInPlt() ? S.getPltVA() : S.getVA();
318 void AArch64ABSLongThunk::writeTo(uint8_t *Buf) {
319 const uint8_t Data[] = {
320 0x50, 0x00, 0x00, 0x58, // ldr x16, L0
321 0x00, 0x02, 0x1f, 0xd6, // br x16
322 0x00, 0x00, 0x00, 0x00, // L0: .xword S
323 0x00, 0x00, 0x00, 0x00,
325 uint64_t S = getAArch64ThunkDestVA(Destination);
326 memcpy(Buf, Data, sizeof(Data));
327 Target->relocateOne(Buf + 8, R_AARCH64_ABS64, S);
330 void AArch64ABSLongThunk::addSymbols(ThunkSection &IS) {
331 addSymbol(Saver.save("__AArch64AbsLongThunk_" + Destination.getName()),
333 addSymbol("$x", STT_NOTYPE, 0, IS);
334 addSymbol("$d", STT_NOTYPE, 8, IS);
337 // This Thunk has a maximum range of 4Gb, this is sufficient for all programs
338 // using the small code model, including pc-relative ones. At time of writing
339 // clang and gcc do not support the large code model for position independent
340 // code so it is safe to use this for position independent thunks without
341 // worrying about the destination being more than 4Gb away.
342 void AArch64ADRPThunk::writeTo(uint8_t *Buf) {
343 const uint8_t Data[] = {
344 0x10, 0x00, 0x00, 0x90, // adrp x16, Dest R_AARCH64_ADR_PREL_PG_HI21(Dest)
345 0x10, 0x02, 0x00, 0x91, // add x16, x16, R_AARCH64_ADD_ABS_LO12_NC(Dest)
346 0x00, 0x02, 0x1f, 0xd6, // br x16
348 uint64_t S = getAArch64ThunkDestVA(Destination);
349 uint64_t P = getThunkTargetSym()->getVA();
350 memcpy(Buf, Data, sizeof(Data));
351 Target->relocateOne(Buf, R_AARCH64_ADR_PREL_PG_HI21,
352 getAArch64Page(S) - getAArch64Page(P));
353 Target->relocateOne(Buf + 4, R_AARCH64_ADD_ABS_LO12_NC, S);
356 void AArch64ADRPThunk::addSymbols(ThunkSection &IS) {
357 addSymbol(Saver.save("__AArch64ADRPThunk_" + Destination.getName()), STT_FUNC,
359 addSymbol("$x", STT_NOTYPE, 0, IS);
363 static uint64_t getARMThunkDestVA(const Symbol &S) {
364 uint64_t V = S.isInPlt() ? S.getPltVA() : S.getVA();
365 return SignExtend64<32>(V);
368 // This function returns true if the target is not Thumb and is within 2^26, and
369 // it has not previously returned false (see comment for MayUseShortThunk).
370 bool ARMThunk::mayUseShortThunk() {
371 if (!MayUseShortThunk)
373 uint64_t S = getARMThunkDestVA(Destination);
375 MayUseShortThunk = false;
378 uint64_t P = getThunkTargetSym()->getVA();
379 int64_t Offset = S - P - 8;
380 MayUseShortThunk = llvm::isInt<26>(Offset);
381 return MayUseShortThunk;
384 void ARMThunk::writeTo(uint8_t *Buf) {
385 if (!mayUseShortThunk()) {
390 uint64_t S = getARMThunkDestVA(Destination);
391 uint64_t P = getThunkTargetSym()->getVA();
392 int64_t Offset = S - P - 8;
393 const uint8_t Data[] = {
394 0x00, 0x00, 0x00, 0xea, // b S
396 memcpy(Buf, Data, sizeof(Data));
397 Target->relocateOne(Buf, R_ARM_JUMP24, Offset);
400 bool ARMThunk::isCompatibleWith(RelType Type) const {
401 // Thumb branch relocations can't use BLX
402 return Type != R_ARM_THM_JUMP19 && Type != R_ARM_THM_JUMP24;
405 // This function returns true if the target is Thumb and is within 2^25, and
406 // it has not previously returned false (see comment for MayUseShortThunk).
407 bool ThumbThunk::mayUseShortThunk() {
408 if (!MayUseShortThunk)
410 uint64_t S = getARMThunkDestVA(Destination);
412 MayUseShortThunk = false;
415 uint64_t P = getThunkTargetSym()->getVA() & ~1;
416 int64_t Offset = S - P - 4;
417 MayUseShortThunk = llvm::isInt<25>(Offset);
418 return MayUseShortThunk;
421 void ThumbThunk::writeTo(uint8_t *Buf) {
422 if (!mayUseShortThunk()) {
427 uint64_t S = getARMThunkDestVA(Destination);
428 uint64_t P = getThunkTargetSym()->getVA();
429 int64_t Offset = S - P - 4;
430 const uint8_t Data[] = {
431 0x00, 0xf0, 0x00, 0xb0, // b.w S
433 memcpy(Buf, Data, sizeof(Data));
434 Target->relocateOne(Buf, R_ARM_THM_JUMP24, Offset);
437 bool ThumbThunk::isCompatibleWith(RelType Type) const {
438 // ARM branch relocations can't use BLX
439 return Type != R_ARM_JUMP24 && Type != R_ARM_PC24 && Type != R_ARM_PLT32;
442 void ARMV7ABSLongThunk::writeLong(uint8_t *Buf) {
443 const uint8_t Data[] = {
444 0x00, 0xc0, 0x00, 0xe3, // movw ip,:lower16:S
445 0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S
446 0x1c, 0xff, 0x2f, 0xe1, // bx ip
448 uint64_t S = getARMThunkDestVA(Destination);
449 memcpy(Buf, Data, sizeof(Data));
450 Target->relocateOne(Buf, R_ARM_MOVW_ABS_NC, S);
451 Target->relocateOne(Buf + 4, R_ARM_MOVT_ABS, S);
454 void ARMV7ABSLongThunk::addSymbols(ThunkSection &IS) {
455 addSymbol(Saver.save("__ARMv7ABSLongThunk_" + Destination.getName()),
457 addSymbol("$a", STT_NOTYPE, 0, IS);
460 void ThumbV7ABSLongThunk::writeLong(uint8_t *Buf) {
461 const uint8_t Data[] = {
462 0x40, 0xf2, 0x00, 0x0c, // movw ip, :lower16:S
463 0xc0, 0xf2, 0x00, 0x0c, // movt ip, :upper16:S
466 uint64_t S = getARMThunkDestVA(Destination);
467 memcpy(Buf, Data, sizeof(Data));
468 Target->relocateOne(Buf, R_ARM_THM_MOVW_ABS_NC, S);
469 Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_ABS, S);
472 void ThumbV7ABSLongThunk::addSymbols(ThunkSection &IS) {
473 addSymbol(Saver.save("__Thumbv7ABSLongThunk_" + Destination.getName()),
475 addSymbol("$t", STT_NOTYPE, 0, IS);
478 void ARMV7PILongThunk::writeLong(uint8_t *Buf) {
479 const uint8_t Data[] = {
480 0xf0, 0xcf, 0x0f, 0xe3, // P: movw ip,:lower16:S - (P + (L1-P) + 8)
481 0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S - (P + (L1-P) + 8)
482 0x0f, 0xc0, 0x8c, 0xe0, // L1: add ip, ip, pc
483 0x1c, 0xff, 0x2f, 0xe1, // bx ip
485 uint64_t S = getARMThunkDestVA(Destination);
486 uint64_t P = getThunkTargetSym()->getVA();
487 int64_t Offset = S - P - 16;
488 memcpy(Buf, Data, sizeof(Data));
489 Target->relocateOne(Buf, R_ARM_MOVW_PREL_NC, Offset);
490 Target->relocateOne(Buf + 4, R_ARM_MOVT_PREL, Offset);
493 void ARMV7PILongThunk::addSymbols(ThunkSection &IS) {
494 addSymbol(Saver.save("__ARMV7PILongThunk_" + Destination.getName()), STT_FUNC,
496 addSymbol("$a", STT_NOTYPE, 0, IS);
499 void ThumbV7PILongThunk::writeLong(uint8_t *Buf) {
500 const uint8_t Data[] = {
501 0x4f, 0xf6, 0xf4, 0x7c, // P: movw ip,:lower16:S - (P + (L1-P) + 4)
502 0xc0, 0xf2, 0x00, 0x0c, // movt ip,:upper16:S - (P + (L1-P) + 4)
503 0xfc, 0x44, // L1: add ip, pc
506 uint64_t S = getARMThunkDestVA(Destination);
507 uint64_t P = getThunkTargetSym()->getVA() & ~0x1;
508 int64_t Offset = S - P - 12;
509 memcpy(Buf, Data, sizeof(Data));
510 Target->relocateOne(Buf, R_ARM_THM_MOVW_PREL_NC, Offset);
511 Target->relocateOne(Buf + 4, R_ARM_THM_MOVT_PREL, Offset);
514 void ThumbV7PILongThunk::addSymbols(ThunkSection &IS) {
515 addSymbol(Saver.save("__ThumbV7PILongThunk_" + Destination.getName()),
517 addSymbol("$t", STT_NOTYPE, 0, IS);
520 void ARMV5ABSLongThunk::writeLong(uint8_t *Buf) {
521 const uint8_t Data[] = {
522 0x04, 0xf0, 0x1f, 0xe5, // ldr pc, [pc,#-4] ; L1
523 0x00, 0x00, 0x00, 0x00, // L1: .word S
525 memcpy(Buf, Data, sizeof(Data));
526 Target->relocateOne(Buf + 4, R_ARM_ABS32, getARMThunkDestVA(Destination));
529 void ARMV5ABSLongThunk::addSymbols(ThunkSection &IS) {
530 addSymbol(Saver.save("__ARMv5ABSLongThunk_" + Destination.getName()),
532 addSymbol("$a", STT_NOTYPE, 0, IS);
533 addSymbol("$d", STT_NOTYPE, 4, IS);
536 bool ARMV5ABSLongThunk::isCompatibleWith(uint32_t RelocType) const {
537 // Thumb branch relocations can't use BLX
538 return RelocType != R_ARM_THM_JUMP19 && RelocType != R_ARM_THM_JUMP24;
541 void ARMV5PILongThunk::writeLong(uint8_t *Buf) {
542 const uint8_t Data[] = {
543 0x04, 0xc0, 0x9f, 0xe5, // P: ldr ip, [pc,#4] ; L2
544 0x0c, 0xc0, 0x8f, 0xe0, // L1: add ip, pc, ip
545 0x1c, 0xff, 0x2f, 0xe1, // bx ip
546 0x00, 0x00, 0x00, 0x00, // L2: .word S - (P + (L1 - P) + 8)
548 uint64_t S = getARMThunkDestVA(Destination);
549 uint64_t P = getThunkTargetSym()->getVA() & ~0x1;
550 memcpy(Buf, Data, sizeof(Data));
551 Target->relocateOne(Buf + 12, R_ARM_REL32, S - P - 12);
554 void ARMV5PILongThunk::addSymbols(ThunkSection &IS) {
555 addSymbol(Saver.save("__ARMV5PILongThunk_" + Destination.getName()), STT_FUNC,
557 addSymbol("$a", STT_NOTYPE, 0, IS);
558 addSymbol("$d", STT_NOTYPE, 12, IS);
561 bool ARMV5PILongThunk::isCompatibleWith(uint32_t RelocType) const {
562 // Thumb branch relocations can't use BLX
563 return RelocType != R_ARM_THM_JUMP19 && RelocType != R_ARM_THM_JUMP24;
566 void ThumbV6MABSLongThunk::writeLong(uint8_t *Buf) {
567 // Most Thumb instructions cannot access the high registers r8 - r15. As the
568 // only register we can corrupt is r12 we must instead spill a low register
569 // to the stack to use as a scratch register. We push r1 even though we
570 // don't need to get some space to use for the return address.
571 const uint8_t Data[] = {
572 0x03, 0xb4, // push {r0, r1} ; Obtain scratch registers
573 0x01, 0x48, // ldr r0, [pc, #4] ; L1
574 0x01, 0x90, // str r0, [sp, #4] ; SP + 4 = S
575 0x01, 0xbd, // pop {r0, pc} ; restore r0 and branch to dest
576 0x00, 0x00, 0x00, 0x00 // L1: .word S
578 uint64_t S = getARMThunkDestVA(Destination);
579 memcpy(Buf, Data, sizeof(Data));
580 Target->relocateOne(Buf + 8, R_ARM_ABS32, S);
583 void ThumbV6MABSLongThunk::addSymbols(ThunkSection &IS) {
584 addSymbol(Saver.save("__Thumbv6MABSLongThunk_" + Destination.getName()),
586 addSymbol("$t", STT_NOTYPE, 0, IS);
587 addSymbol("$d", STT_NOTYPE, 8, IS);
590 void ThumbV6MPILongThunk::writeLong(uint8_t *Buf) {
591 // Most Thumb instructions cannot access the high registers r8 - r15. As the
592 // only register we can corrupt is ip (r12) we must instead spill a low
593 // register to the stack to use as a scratch register.
594 const uint8_t Data[] = {
595 0x01, 0xb4, // P: push {r0} ; Obtain scratch register
596 0x02, 0x48, // ldr r0, [pc, #8] ; L2
597 0x84, 0x46, // mov ip, r0 ; high to low register
598 0x01, 0xbc, // pop {r0} ; restore scratch register
599 0xe7, 0x44, // L1: add pc, ip ; transfer control
600 0xc0, 0x46, // nop ; pad to 4-byte boundary
601 0x00, 0x00, 0x00, 0x00, // L2: .word S - (P + (L1 - P) + 4)
603 uint64_t S = getARMThunkDestVA(Destination);
604 uint64_t P = getThunkTargetSym()->getVA() & ~0x1;
605 memcpy(Buf, Data, sizeof(Data));
606 Target->relocateOne(Buf + 12, R_ARM_REL32, S - P - 12);
609 void ThumbV6MPILongThunk::addSymbols(ThunkSection &IS) {
610 addSymbol(Saver.save("__Thumbv6MPILongThunk_" + Destination.getName()),
612 addSymbol("$t", STT_NOTYPE, 0, IS);
613 addSymbol("$d", STT_NOTYPE, 12, IS);
616 // Write MIPS LA25 thunk code to call PIC function from the non-PIC one.
617 void MipsThunk::writeTo(uint8_t *Buf) {
618 uint64_t S = Destination.getVA();
619 write32(Buf, 0x3c190000); // lui $25, %hi(func)
620 write32(Buf + 4, 0x08000000 | (S >> 2)); // j func
621 write32(Buf + 8, 0x27390000); // addiu $25, $25, %lo(func)
622 write32(Buf + 12, 0x00000000); // nop
623 Target->relocateOne(Buf, R_MIPS_HI16, S);
624 Target->relocateOne(Buf + 8, R_MIPS_LO16, S);
627 void MipsThunk::addSymbols(ThunkSection &IS) {
628 addSymbol(Saver.save("__LA25Thunk_" + Destination.getName()), STT_FUNC, 0,
632 InputSection *MipsThunk::getTargetInputSection() const {
633 auto &DR = cast<Defined>(Destination);
634 return dyn_cast<InputSection>(DR.Section);
637 // Write microMIPS R2-R5 LA25 thunk code
638 // to call PIC function from the non-PIC one.
639 void MicroMipsThunk::writeTo(uint8_t *Buf) {
640 uint64_t S = Destination.getVA() | 1;
641 write16(Buf, 0x41b9); // lui $25, %hi(func)
642 write16(Buf + 4, 0xd400); // j func
643 write16(Buf + 8, 0x3339); // addiu $25, $25, %lo(func)
644 write16(Buf + 12, 0x0c00); // nop
645 Target->relocateOne(Buf, R_MICROMIPS_HI16, S);
646 Target->relocateOne(Buf + 4, R_MICROMIPS_26_S1, S);
647 Target->relocateOne(Buf + 8, R_MICROMIPS_LO16, S);
650 void MicroMipsThunk::addSymbols(ThunkSection &IS) {
651 Defined *D = addSymbol(
652 Saver.save("__microLA25Thunk_" + Destination.getName()), STT_FUNC, 0, IS);
653 D->StOther |= STO_MIPS_MICROMIPS;
656 InputSection *MicroMipsThunk::getTargetInputSection() const {
657 auto &DR = cast<Defined>(Destination);
658 return dyn_cast<InputSection>(DR.Section);
661 // Write microMIPS R6 LA25 thunk code
662 // to call PIC function from the non-PIC one.
663 void MicroMipsR6Thunk::writeTo(uint8_t *Buf) {
664 uint64_t S = Destination.getVA() | 1;
665 uint64_t P = getThunkTargetSym()->getVA();
666 write16(Buf, 0x1320); // lui $25, %hi(func)
667 write16(Buf + 4, 0x3339); // addiu $25, $25, %lo(func)
668 write16(Buf + 8, 0x9400); // bc func
669 Target->relocateOne(Buf, R_MICROMIPS_HI16, S);
670 Target->relocateOne(Buf + 4, R_MICROMIPS_LO16, S);
671 Target->relocateOne(Buf + 8, R_MICROMIPS_PC26_S1, S - P - 12);
674 void MicroMipsR6Thunk::addSymbols(ThunkSection &IS) {
675 Defined *D = addSymbol(
676 Saver.save("__microLA25Thunk_" + Destination.getName()), STT_FUNC, 0, IS);
677 D->StOther |= STO_MIPS_MICROMIPS;
680 InputSection *MicroMipsR6Thunk::getTargetInputSection() const {
681 auto &DR = cast<Defined>(Destination);
682 return dyn_cast<InputSection>(DR.Section);
685 static void writePPCLoadAndBranch(uint8_t *Buf, int64_t Offset) {
686 uint16_t OffHa = (Offset + 0x8000) >> 16;
687 uint16_t OffLo = Offset & 0xffff;
689 write32(Buf + 0, 0x3d820000 | OffHa); // addis r12, r2, OffHa
690 write32(Buf + 4, 0xe98c0000 | OffLo); // ld r12, OffLo(r12)
691 write32(Buf + 8, 0x7d8903a6); // mtctr r12
692 write32(Buf + 12, 0x4e800420); // bctr
695 void PPC64PltCallStub::writeTo(uint8_t *Buf) {
696 int64_t Offset = Destination.getGotPltVA() - getPPC64TocBase();
697 // Save the TOC pointer to the save-slot reserved in the call frame.
698 write32(Buf + 0, 0xf8410018); // std r2,24(r1)
699 writePPCLoadAndBranch(Buf + 4, Offset);
702 void PPC64PltCallStub::addSymbols(ThunkSection &IS) {
703 Defined *S = addSymbol(Saver.save("__plt_" + Destination.getName()), STT_FUNC,
705 S->NeedsTocRestore = true;
708 void PPC64LongBranchThunk::writeTo(uint8_t *Buf) {
709 int64_t Offset = Destination.getPPC64LongBranchTableVA() - getPPC64TocBase();
710 writePPCLoadAndBranch(Buf, Offset);
713 void PPC64LongBranchThunk::addSymbols(ThunkSection &IS) {
714 addSymbol(Saver.save("__long_branch_" + Destination.getName()), STT_FUNC, 0,
718 Thunk::Thunk(Symbol &D) : Destination(D), Offset(0) {}
720 Thunk::~Thunk() = default;
722 static Thunk *addThunkAArch64(RelType Type, Symbol &S) {
723 if (Type != R_AARCH64_CALL26 && Type != R_AARCH64_JUMP26)
724 fatal("unrecognized relocation type");
725 if (Config->PicThunk)
726 return make<AArch64ADRPThunk>(S);
727 return make<AArch64ABSLongThunk>(S);
730 // Creates a thunk for Thumb-ARM interworking.
731 // Arm Architectures v5 and v6 do not support Thumb2 technology. This means
732 // - MOVT and MOVW instructions cannot be used
733 // - Only Thumb relocation that can generate a Thunk is a BL, this can always
734 // be transformed into a BLX
735 static Thunk *addThunkPreArmv7(RelType Reloc, Symbol &S) {
742 if (Config->PicThunk)
743 return make<ARMV5PILongThunk>(S);
744 return make<ARMV5ABSLongThunk>(S);
746 fatal("relocation " + toString(Reloc) + " to " + toString(S) +
747 " not supported for Armv5 or Armv6 targets");
750 // Create a thunk for Thumb long branch on V6-M.
751 // Arm Architecture v6-M only supports Thumb instructions. This means
752 // - MOVT and MOVW instructions cannot be used.
753 // - Only a limited number of instructions can access registers r8 and above
754 // - No interworking support is needed (all Thumb).
755 static Thunk *addThunkV6M(RelType Reloc, Symbol &S) {
757 case R_ARM_THM_JUMP19:
758 case R_ARM_THM_JUMP24:
761 return make<ThumbV6MPILongThunk>(S);
762 return make<ThumbV6MABSLongThunk>(S);
764 fatal("relocation " + toString(Reloc) + " to " + toString(S) +
765 " not supported for Armv6-M targets");
768 // Creates a thunk for Thumb-ARM interworking or branch range extension.
769 static Thunk *addThunkArm(RelType Reloc, Symbol &S) {
770 // Decide which Thunk is needed based on:
771 // Available instruction set
772 // - An Arm Thunk can only be used if Arm state is available.
773 // - A Thumb Thunk can only be used if Thumb state is available.
774 // - Can only use a Thunk if it uses instructions that the Target supports.
775 // Relocation is branch or branch and link
776 // - Branch instructions cannot change state, can only select Thunk that
777 // starts in the same state as the caller.
778 // - Branch and link relocations can change state, can select Thunks from
779 // either Arm or Thumb.
780 // Position independent Thunks if we require position independent code.
782 // Handle architectures that have restrictions on the instructions that they
783 // can use in Thunks. The flags below are set by reading the BuildAttributes
784 // of the input objects. InputFiles.cpp contains the mapping from ARM
785 // architecture to flag.
786 if (!Config->ARMHasMovtMovw) {
787 if (!Config->ARMJ1J2BranchEncoding)
788 return addThunkPreArmv7(Reloc, S);
789 return addThunkV6M(Reloc, S);
797 if (Config->PicThunk)
798 return make<ARMV7PILongThunk>(S);
799 return make<ARMV7ABSLongThunk>(S);
800 case R_ARM_THM_JUMP19:
801 case R_ARM_THM_JUMP24:
803 if (Config->PicThunk)
804 return make<ThumbV7PILongThunk>(S);
805 return make<ThumbV7ABSLongThunk>(S);
807 fatal("unrecognized relocation type");
810 static Thunk *addThunkMips(RelType Type, Symbol &S) {
811 if ((S.StOther & STO_MIPS_MICROMIPS) && isMipsR6())
812 return make<MicroMipsR6Thunk>(S);
813 if (S.StOther & STO_MIPS_MICROMIPS)
814 return make<MicroMipsThunk>(S);
815 return make<MipsThunk>(S);
818 static Thunk *addThunkPPC64(RelType Type, Symbol &S) {
819 assert(Type == R_PPC64_REL24 && "unexpected relocation type for thunk");
821 return make<PPC64PltCallStub>(S);
823 if (Config->PicThunk)
824 return make<PPC64PILongBranchThunk>(S);
826 return make<PPC64PDLongBranchThunk>(S);
829 Thunk *addThunk(RelType Type, Symbol &S) {
830 if (Config->EMachine == EM_AARCH64)
831 return addThunkAArch64(Type, S);
833 if (Config->EMachine == EM_ARM)
834 return addThunkArm(Type, S);
836 if (Config->EMachine == EM_MIPS)
837 return addThunkMips(Type, S);
839 if (Config->EMachine == EM_PPC64)
840 return addThunkPPC64(Type, S);
842 llvm_unreachable("add Thunk only supported for ARM, Mips and PowerPC");
845 } // end namespace elf
846 } // end namespace lld