1 //===- Thunks.cpp --------------------------------------------------------===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===---------------------------------------------------------------------===//
9 // This file contains Thunk subclasses.
11 // A thunk is a small piece of code written after an input section
12 // which is used to jump between "incompatible" functions
13 // such as MIPS PIC and non-PIC or ARM non-Thumb and Thumb functions.
15 // If a jump target is too far and its address doesn't fit to a
16 // short jump instruction, we need to create a thunk too, but we
17 // haven't supported it yet.
19 // i386 and x86-64 don't need thunks.
21 //===---------------------------------------------------------------------===//
25 #include "InputSection.h"
26 #include "OutputSections.h"
28 #include "SyntheticSections.h"
30 #include "lld/Common/ErrorHandler.h"
31 #include "lld/Common/Memory.h"
32 #include "llvm/BinaryFormat/ELF.h"
33 #include "llvm/Support/Casting.h"
34 #include "llvm/Support/Endian.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/MathExtras.h"
41 using namespace llvm::object;
42 using namespace llvm::ELF;
49 // AArch64 long range Thunks
50 class AArch64ABSLongThunk final : public Thunk {
52 AArch64ABSLongThunk(Symbol &dest, int64_t addend) : Thunk(dest, addend) {}
53 uint32_t size() override { return 16; }
54 void writeTo(uint8_t *buf) override;
55 void addSymbols(ThunkSection &isec) override;
58 class AArch64ADRPThunk final : public Thunk {
60 AArch64ADRPThunk(Symbol &dest, int64_t addend) : Thunk(dest, addend) {}
61 uint32_t size() override { return 12; }
62 void writeTo(uint8_t *buf) override;
63 void addSymbols(ThunkSection &isec) override;
66 // Base class for ARM thunks.
68 // An ARM thunk may be either short or long. A short thunk is simply a branch
69 // (B) instruction, and it may be used to call ARM functions when the distance
70 // from the thunk to the target is less than 32MB. Long thunks can branch to any
71 // virtual address and can switch between ARM and Thumb, and they are
72 // implemented in the derived classes. This class tries to create a short thunk
73 // if the target is in range, otherwise it creates a long thunk.
74 class ARMThunk : public Thunk {
76 ARMThunk(Symbol &dest) : Thunk(dest, 0) {}
78 bool getMayUseShortThunk();
79 uint32_t size() override { return getMayUseShortThunk() ? 4 : sizeLong(); }
80 void writeTo(uint8_t *buf) override;
81 bool isCompatibleWith(const InputSection &isec,
82 const Relocation &rel) 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, 0) { alignment = 2; }
108 bool getMayUseShortThunk();
109 uint32_t size() override { return getMayUseShortThunk() ? 4 : sizeLong(); }
110 void writeTo(uint8_t *buf) override;
111 bool isCompatibleWith(const InputSection &isec,
112 const Relocation &rel) const override;
114 // Returns the size of a long thunk.
115 virtual uint32_t sizeLong() = 0;
117 // Writes a long thunk to Buf.
118 virtual void writeLong(uint8_t *buf) = 0;
121 // See comment in ARMThunk above.
122 bool mayUseShortThunk = true;
125 // Specific ARM Thunk implementations. The naming convention is:
126 // Source State, TargetState, Target Requirement, ABS or PI, Range
127 class ARMV7ABSLongThunk final : public ARMThunk {
129 ARMV7ABSLongThunk(Symbol &dest) : ARMThunk(dest) {}
131 uint32_t sizeLong() override { return 12; }
132 void writeLong(uint8_t *buf) override;
133 void addSymbols(ThunkSection &isec) override;
136 class ARMV7PILongThunk final : public ARMThunk {
138 ARMV7PILongThunk(Symbol &dest) : ARMThunk(dest) {}
140 uint32_t sizeLong() override { return 16; }
141 void writeLong(uint8_t *buf) override;
142 void addSymbols(ThunkSection &isec) override;
145 class ThumbV7ABSLongThunk final : public ThumbThunk {
147 ThumbV7ABSLongThunk(Symbol &dest) : ThumbThunk(dest) {}
149 uint32_t sizeLong() override { return 10; }
150 void writeLong(uint8_t *buf) override;
151 void addSymbols(ThunkSection &isec) override;
154 class ThumbV7PILongThunk final : public ThumbThunk {
156 ThumbV7PILongThunk(Symbol &dest) : ThumbThunk(dest) {}
158 uint32_t sizeLong() override { return 12; }
159 void writeLong(uint8_t *buf) override;
160 void addSymbols(ThunkSection &isec) override;
163 // Implementations of Thunks for older Arm architectures that do not support
164 // the movt/movw instructions. These thunks require at least Architecture v5
165 // as used on processors such as the Arm926ej-s. There are no Thumb entry
166 // points as there is no Thumb branch instruction on these architecture that
167 // can result in a thunk
168 class ARMV5ABSLongThunk final : public ARMThunk {
170 ARMV5ABSLongThunk(Symbol &dest) : ARMThunk(dest) {}
172 uint32_t sizeLong() override { return 8; }
173 void writeLong(uint8_t *buf) override;
174 void addSymbols(ThunkSection &isec) override;
175 bool isCompatibleWith(const InputSection &isec,
176 const Relocation &rel) const override;
179 class ARMV5PILongThunk final : public ARMThunk {
181 ARMV5PILongThunk(Symbol &dest) : ARMThunk(dest) {}
183 uint32_t sizeLong() override { return 16; }
184 void writeLong(uint8_t *buf) override;
185 void addSymbols(ThunkSection &isec) override;
186 bool isCompatibleWith(const InputSection &isec,
187 const Relocation &rel) const override;
190 // Implementations of Thunks for Arm v6-M. Only Thumb instructions are permitted
191 class ThumbV6MABSLongThunk final : public ThumbThunk {
193 ThumbV6MABSLongThunk(Symbol &dest) : ThumbThunk(dest) {}
195 uint32_t sizeLong() override { return 12; }
196 void writeLong(uint8_t *buf) override;
197 void addSymbols(ThunkSection &isec) override;
200 class ThumbV6MPILongThunk final : public ThumbThunk {
202 ThumbV6MPILongThunk(Symbol &dest) : ThumbThunk(dest) {}
204 uint32_t sizeLong() override { return 16; }
205 void writeLong(uint8_t *buf) override;
206 void addSymbols(ThunkSection &isec) override;
210 class MipsThunk final : public Thunk {
212 MipsThunk(Symbol &dest) : Thunk(dest, 0) {}
214 uint32_t size() override { return 16; }
215 void writeTo(uint8_t *buf) override;
216 void addSymbols(ThunkSection &isec) override;
217 InputSection *getTargetInputSection() const override;
220 // microMIPS R2-R5 LA25 thunk
221 class MicroMipsThunk final : public Thunk {
223 MicroMipsThunk(Symbol &dest) : Thunk(dest, 0) {}
225 uint32_t size() override { return 14; }
226 void writeTo(uint8_t *buf) override;
227 void addSymbols(ThunkSection &isec) override;
228 InputSection *getTargetInputSection() const override;
231 // microMIPS R6 LA25 thunk
232 class MicroMipsR6Thunk final : public Thunk {
234 MicroMipsR6Thunk(Symbol &dest) : Thunk(dest, 0) {}
236 uint32_t size() override { return 12; }
237 void writeTo(uint8_t *buf) override;
238 void addSymbols(ThunkSection &isec) override;
239 InputSection *getTargetInputSection() const override;
242 class PPC32PltCallStub final : public Thunk {
244 // For R_PPC_PLTREL24, Thunk::addend records the addend which will be used to
245 // decide the offsets in the call stub.
246 PPC32PltCallStub(const InputSection &isec, const Relocation &rel,
248 : Thunk(dest, rel.type == R_PPC_PLTREL24 ? rel.addend : 0),
250 uint32_t size() override { return 16; }
251 void writeTo(uint8_t *buf) override;
252 void addSymbols(ThunkSection &isec) override;
253 bool isCompatibleWith(const InputSection &isec, const Relocation &rel) const override;
256 // Records the call site of the call stub.
257 const InputFile *file;
260 // PPC64 Plt call stubs.
261 // Any call site that needs to call through a plt entry needs a call stub in
262 // the .text section. The call stub is responsible for:
263 // 1) Saving the toc-pointer to the stack.
264 // 2) Loading the target functions address from the procedure linkage table into
265 // r12 for use by the target functions global entry point, and into the count
267 // 3) Transferring control to the target function through an indirect branch.
268 class PPC64PltCallStub final : public Thunk {
270 PPC64PltCallStub(Symbol &dest) : Thunk(dest, 0) {}
271 uint32_t size() override { return 20; }
272 void writeTo(uint8_t *buf) override;
273 void addSymbols(ThunkSection &isec) override;
276 // A bl instruction uses a signed 24 bit offset, with an implicit 4 byte
277 // alignment. This gives a possible 26 bits of 'reach'. If the call offset is
278 // larger then that we need to emit a long-branch thunk. The target address
279 // of the callee is stored in a table to be accessed TOC-relative. Since the
280 // call must be local (a non-local call will have a PltCallStub instead) the
281 // table stores the address of the callee's local entry point. For
282 // position-independent code a corresponding relative dynamic relocation is
284 class PPC64LongBranchThunk : public Thunk {
286 uint32_t size() override { return 16; }
287 void writeTo(uint8_t *buf) override;
288 void addSymbols(ThunkSection &isec) override;
291 PPC64LongBranchThunk(Symbol &dest, int64_t addend) : Thunk(dest, addend) {}
294 class PPC64PILongBranchThunk final : public PPC64LongBranchThunk {
296 PPC64PILongBranchThunk(Symbol &dest, int64_t addend)
297 : PPC64LongBranchThunk(dest, addend) {
298 assert(!dest.isPreemptible);
299 if (Optional<uint32_t> index =
300 in.ppc64LongBranchTarget->addEntry(&dest, addend)) {
301 mainPart->relaDyn->addReloc(
302 {target->relativeRel, in.ppc64LongBranchTarget, *index * UINT64_C(8),
304 addend + getPPC64GlobalEntryToLocalEntryOffset(dest.stOther)});
309 class PPC64PDLongBranchThunk final : public PPC64LongBranchThunk {
311 PPC64PDLongBranchThunk(Symbol &dest, int64_t addend)
312 : PPC64LongBranchThunk(dest, addend) {
313 in.ppc64LongBranchTarget->addEntry(&dest, addend);
317 } // end anonymous namespace
319 Defined *Thunk::addSymbol(StringRef name, uint8_t type, uint64_t value,
320 InputSectionBase §ion) {
321 Defined *d = addSyntheticLocal(name, type, value, /*size=*/0, section);
326 void Thunk::setOffset(uint64_t newOffset) {
327 for (Defined *d : syms)
328 d->value = d->value - offset + newOffset;
332 // AArch64 long range Thunks
334 static uint64_t getAArch64ThunkDestVA(const Symbol &s, int64_t a) {
335 uint64_t v = s.isInPlt() ? s.getPltVA() : s.getVA(a);
339 void AArch64ABSLongThunk::writeTo(uint8_t *buf) {
340 const uint8_t data[] = {
341 0x50, 0x00, 0x00, 0x58, // ldr x16, L0
342 0x00, 0x02, 0x1f, 0xd6, // br x16
343 0x00, 0x00, 0x00, 0x00, // L0: .xword S
344 0x00, 0x00, 0x00, 0x00,
346 uint64_t s = getAArch64ThunkDestVA(destination, addend);
347 memcpy(buf, data, sizeof(data));
348 target->relocateOne(buf + 8, R_AARCH64_ABS64, s);
351 void AArch64ABSLongThunk::addSymbols(ThunkSection &isec) {
352 addSymbol(saver.save("__AArch64AbsLongThunk_" + destination.getName()),
354 addSymbol("$x", STT_NOTYPE, 0, isec);
355 addSymbol("$d", STT_NOTYPE, 8, isec);
358 // This Thunk has a maximum range of 4Gb, this is sufficient for all programs
359 // using the small code model, including pc-relative ones. At time of writing
360 // clang and gcc do not support the large code model for position independent
361 // code so it is safe to use this for position independent thunks without
362 // worrying about the destination being more than 4Gb away.
363 void AArch64ADRPThunk::writeTo(uint8_t *buf) {
364 const uint8_t data[] = {
365 0x10, 0x00, 0x00, 0x90, // adrp x16, Dest R_AARCH64_ADR_PREL_PG_HI21(Dest)
366 0x10, 0x02, 0x00, 0x91, // add x16, x16, R_AARCH64_ADD_ABS_LO12_NC(Dest)
367 0x00, 0x02, 0x1f, 0xd6, // br x16
369 uint64_t s = getAArch64ThunkDestVA(destination, addend);
370 uint64_t p = getThunkTargetSym()->getVA();
371 memcpy(buf, data, sizeof(data));
372 target->relocateOne(buf, R_AARCH64_ADR_PREL_PG_HI21,
373 getAArch64Page(s) - getAArch64Page(p));
374 target->relocateOne(buf + 4, R_AARCH64_ADD_ABS_LO12_NC, s);
377 void AArch64ADRPThunk::addSymbols(ThunkSection &isec) {
378 addSymbol(saver.save("__AArch64ADRPThunk_" + destination.getName()), STT_FUNC,
380 addSymbol("$x", STT_NOTYPE, 0, isec);
384 static uint64_t getARMThunkDestVA(const Symbol &s) {
385 uint64_t v = s.isInPlt() ? s.getPltVA() : s.getVA();
386 return SignExtend64<32>(v);
389 // This function returns true if the target is not Thumb and is within 2^26, and
390 // it has not previously returned false (see comment for mayUseShortThunk).
391 bool ARMThunk::getMayUseShortThunk() {
392 if (!mayUseShortThunk)
394 uint64_t s = getARMThunkDestVA(destination);
396 mayUseShortThunk = false;
399 uint64_t p = getThunkTargetSym()->getVA();
400 int64_t offset = s - p - 8;
401 mayUseShortThunk = llvm::isInt<26>(offset);
402 return mayUseShortThunk;
405 void ARMThunk::writeTo(uint8_t *buf) {
406 if (!getMayUseShortThunk()) {
411 uint64_t s = getARMThunkDestVA(destination);
412 uint64_t p = getThunkTargetSym()->getVA();
413 int64_t offset = s - p - 8;
414 const uint8_t data[] = {
415 0x00, 0x00, 0x00, 0xea, // b S
417 memcpy(buf, data, sizeof(data));
418 target->relocateOne(buf, R_ARM_JUMP24, offset);
421 bool ARMThunk::isCompatibleWith(const InputSection &isec,
422 const Relocation &rel) const {
423 // Thumb branch relocations can't use BLX
424 return rel.type != R_ARM_THM_JUMP19 && rel.type != R_ARM_THM_JUMP24;
427 // This function returns true if the target is Thumb and is within 2^25, and
428 // it has not previously returned false (see comment for mayUseShortThunk).
429 bool ThumbThunk::getMayUseShortThunk() {
430 if (!mayUseShortThunk)
432 uint64_t s = getARMThunkDestVA(destination);
434 mayUseShortThunk = false;
437 uint64_t p = getThunkTargetSym()->getVA() & ~1;
438 int64_t offset = s - p - 4;
439 mayUseShortThunk = llvm::isInt<25>(offset);
440 return mayUseShortThunk;
443 void ThumbThunk::writeTo(uint8_t *buf) {
444 if (!getMayUseShortThunk()) {
449 uint64_t s = getARMThunkDestVA(destination);
450 uint64_t p = getThunkTargetSym()->getVA();
451 int64_t offset = s - p - 4;
452 const uint8_t data[] = {
453 0x00, 0xf0, 0x00, 0xb0, // b.w S
455 memcpy(buf, data, sizeof(data));
456 target->relocateOne(buf, R_ARM_THM_JUMP24, offset);
459 bool ThumbThunk::isCompatibleWith(const InputSection &isec,
460 const Relocation &rel) const {
461 // ARM branch relocations can't use BLX
462 return rel.type != R_ARM_JUMP24 && rel.type != R_ARM_PC24 && rel.type != R_ARM_PLT32;
465 void ARMV7ABSLongThunk::writeLong(uint8_t *buf) {
466 const uint8_t data[] = {
467 0x00, 0xc0, 0x00, 0xe3, // movw ip,:lower16:S
468 0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S
469 0x1c, 0xff, 0x2f, 0xe1, // bx ip
471 uint64_t s = getARMThunkDestVA(destination);
472 memcpy(buf, data, sizeof(data));
473 target->relocateOne(buf, R_ARM_MOVW_ABS_NC, s);
474 target->relocateOne(buf + 4, R_ARM_MOVT_ABS, s);
477 void ARMV7ABSLongThunk::addSymbols(ThunkSection &isec) {
478 addSymbol(saver.save("__ARMv7ABSLongThunk_" + destination.getName()),
480 addSymbol("$a", STT_NOTYPE, 0, isec);
483 void ThumbV7ABSLongThunk::writeLong(uint8_t *buf) {
484 const uint8_t data[] = {
485 0x40, 0xf2, 0x00, 0x0c, // movw ip, :lower16:S
486 0xc0, 0xf2, 0x00, 0x0c, // movt ip, :upper16:S
489 uint64_t s = getARMThunkDestVA(destination);
490 memcpy(buf, data, sizeof(data));
491 target->relocateOne(buf, R_ARM_THM_MOVW_ABS_NC, s);
492 target->relocateOne(buf + 4, R_ARM_THM_MOVT_ABS, s);
495 void ThumbV7ABSLongThunk::addSymbols(ThunkSection &isec) {
496 addSymbol(saver.save("__Thumbv7ABSLongThunk_" + destination.getName()),
498 addSymbol("$t", STT_NOTYPE, 0, isec);
501 void ARMV7PILongThunk::writeLong(uint8_t *buf) {
502 const uint8_t data[] = {
503 0xf0, 0xcf, 0x0f, 0xe3, // P: movw ip,:lower16:S - (P + (L1-P) + 8)
504 0x00, 0xc0, 0x40, 0xe3, // movt ip,:upper16:S - (P + (L1-P) + 8)
505 0x0f, 0xc0, 0x8c, 0xe0, // L1: add ip, ip, pc
506 0x1c, 0xff, 0x2f, 0xe1, // bx ip
508 uint64_t s = getARMThunkDestVA(destination);
509 uint64_t p = getThunkTargetSym()->getVA();
510 int64_t offset = s - p - 16;
511 memcpy(buf, data, sizeof(data));
512 target->relocateOne(buf, R_ARM_MOVW_PREL_NC, offset);
513 target->relocateOne(buf + 4, R_ARM_MOVT_PREL, offset);
516 void ARMV7PILongThunk::addSymbols(ThunkSection &isec) {
517 addSymbol(saver.save("__ARMV7PILongThunk_" + destination.getName()), STT_FUNC,
519 addSymbol("$a", STT_NOTYPE, 0, isec);
522 void ThumbV7PILongThunk::writeLong(uint8_t *buf) {
523 const uint8_t data[] = {
524 0x4f, 0xf6, 0xf4, 0x7c, // P: movw ip,:lower16:S - (P + (L1-P) + 4)
525 0xc0, 0xf2, 0x00, 0x0c, // movt ip,:upper16:S - (P + (L1-P) + 4)
526 0xfc, 0x44, // L1: add ip, pc
529 uint64_t s = getARMThunkDestVA(destination);
530 uint64_t p = getThunkTargetSym()->getVA() & ~0x1;
531 int64_t offset = s - p - 12;
532 memcpy(buf, data, sizeof(data));
533 target->relocateOne(buf, R_ARM_THM_MOVW_PREL_NC, offset);
534 target->relocateOne(buf + 4, R_ARM_THM_MOVT_PREL, offset);
537 void ThumbV7PILongThunk::addSymbols(ThunkSection &isec) {
538 addSymbol(saver.save("__ThumbV7PILongThunk_" + destination.getName()),
540 addSymbol("$t", STT_NOTYPE, 0, isec);
543 void ARMV5ABSLongThunk::writeLong(uint8_t *buf) {
544 const uint8_t data[] = {
545 0x04, 0xf0, 0x1f, 0xe5, // ldr pc, [pc,#-4] ; L1
546 0x00, 0x00, 0x00, 0x00, // L1: .word S
548 memcpy(buf, data, sizeof(data));
549 target->relocateOne(buf + 4, R_ARM_ABS32, getARMThunkDestVA(destination));
552 void ARMV5ABSLongThunk::addSymbols(ThunkSection &isec) {
553 addSymbol(saver.save("__ARMv5ABSLongThunk_" + destination.getName()),
555 addSymbol("$a", STT_NOTYPE, 0, isec);
556 addSymbol("$d", STT_NOTYPE, 4, isec);
559 bool ARMV5ABSLongThunk::isCompatibleWith(const InputSection &isec,
560 const Relocation &rel) const {
561 // Thumb branch relocations can't use BLX
562 return rel.type != R_ARM_THM_JUMP19 && rel.type != R_ARM_THM_JUMP24;
565 void ARMV5PILongThunk::writeLong(uint8_t *buf) {
566 const uint8_t data[] = {
567 0x04, 0xc0, 0x9f, 0xe5, // P: ldr ip, [pc,#4] ; L2
568 0x0c, 0xc0, 0x8f, 0xe0, // L1: add ip, pc, ip
569 0x1c, 0xff, 0x2f, 0xe1, // bx ip
570 0x00, 0x00, 0x00, 0x00, // L2: .word S - (P + (L1 - P) + 8)
572 uint64_t s = getARMThunkDestVA(destination);
573 uint64_t p = getThunkTargetSym()->getVA() & ~0x1;
574 memcpy(buf, data, sizeof(data));
575 target->relocateOne(buf + 12, R_ARM_REL32, s - p - 12);
578 void ARMV5PILongThunk::addSymbols(ThunkSection &isec) {
579 addSymbol(saver.save("__ARMV5PILongThunk_" + destination.getName()), STT_FUNC,
581 addSymbol("$a", STT_NOTYPE, 0, isec);
582 addSymbol("$d", STT_NOTYPE, 12, isec);
585 bool ARMV5PILongThunk::isCompatibleWith(const InputSection &isec,
586 const Relocation &rel) const {
587 // Thumb branch relocations can't use BLX
588 return rel.type != R_ARM_THM_JUMP19 && rel.type != R_ARM_THM_JUMP24;
591 void ThumbV6MABSLongThunk::writeLong(uint8_t *buf) {
592 // Most Thumb instructions cannot access the high registers r8 - r15. As the
593 // only register we can corrupt is r12 we must instead spill a low register
594 // to the stack to use as a scratch register. We push r1 even though we
595 // don't need to get some space to use for the return address.
596 const uint8_t data[] = {
597 0x03, 0xb4, // push {r0, r1} ; Obtain scratch registers
598 0x01, 0x48, // ldr r0, [pc, #4] ; L1
599 0x01, 0x90, // str r0, [sp, #4] ; SP + 4 = S
600 0x01, 0xbd, // pop {r0, pc} ; restore r0 and branch to dest
601 0x00, 0x00, 0x00, 0x00 // L1: .word S
603 uint64_t s = getARMThunkDestVA(destination);
604 memcpy(buf, data, sizeof(data));
605 target->relocateOne(buf + 8, R_ARM_ABS32, s);
608 void ThumbV6MABSLongThunk::addSymbols(ThunkSection &isec) {
609 addSymbol(saver.save("__Thumbv6MABSLongThunk_" + destination.getName()),
611 addSymbol("$t", STT_NOTYPE, 0, isec);
612 addSymbol("$d", STT_NOTYPE, 8, isec);
615 void ThumbV6MPILongThunk::writeLong(uint8_t *buf) {
616 // Most Thumb instructions cannot access the high registers r8 - r15. As the
617 // only register we can corrupt is ip (r12) we must instead spill a low
618 // register to the stack to use as a scratch register.
619 const uint8_t data[] = {
620 0x01, 0xb4, // P: push {r0} ; Obtain scratch register
621 0x02, 0x48, // ldr r0, [pc, #8] ; L2
622 0x84, 0x46, // mov ip, r0 ; high to low register
623 0x01, 0xbc, // pop {r0} ; restore scratch register
624 0xe7, 0x44, // L1: add pc, ip ; transfer control
625 0xc0, 0x46, // nop ; pad to 4-byte boundary
626 0x00, 0x00, 0x00, 0x00, // L2: .word S - (P + (L1 - P) + 4)
628 uint64_t s = getARMThunkDestVA(destination);
629 uint64_t p = getThunkTargetSym()->getVA() & ~0x1;
630 memcpy(buf, data, sizeof(data));
631 target->relocateOne(buf + 12, R_ARM_REL32, s - p - 12);
634 void ThumbV6MPILongThunk::addSymbols(ThunkSection &isec) {
635 addSymbol(saver.save("__Thumbv6MPILongThunk_" + destination.getName()),
637 addSymbol("$t", STT_NOTYPE, 0, isec);
638 addSymbol("$d", STT_NOTYPE, 12, isec);
641 // Write MIPS LA25 thunk code to call PIC function from the non-PIC one.
642 void MipsThunk::writeTo(uint8_t *buf) {
643 uint64_t s = destination.getVA();
644 write32(buf, 0x3c190000); // lui $25, %hi(func)
645 write32(buf + 4, 0x08000000 | (s >> 2)); // j func
646 write32(buf + 8, 0x27390000); // addiu $25, $25, %lo(func)
647 write32(buf + 12, 0x00000000); // nop
648 target->relocateOne(buf, R_MIPS_HI16, s);
649 target->relocateOne(buf + 8, R_MIPS_LO16, s);
652 void MipsThunk::addSymbols(ThunkSection &isec) {
653 addSymbol(saver.save("__LA25Thunk_" + destination.getName()), STT_FUNC, 0,
657 InputSection *MipsThunk::getTargetInputSection() const {
658 auto &dr = cast<Defined>(destination);
659 return dyn_cast<InputSection>(dr.section);
662 // Write microMIPS R2-R5 LA25 thunk code
663 // to call PIC function from the non-PIC one.
664 void MicroMipsThunk::writeTo(uint8_t *buf) {
665 uint64_t s = destination.getVA();
666 write16(buf, 0x41b9); // lui $25, %hi(func)
667 write16(buf + 4, 0xd400); // j func
668 write16(buf + 8, 0x3339); // addiu $25, $25, %lo(func)
669 write16(buf + 12, 0x0c00); // nop
670 target->relocateOne(buf, R_MICROMIPS_HI16, s);
671 target->relocateOne(buf + 4, R_MICROMIPS_26_S1, s);
672 target->relocateOne(buf + 8, R_MICROMIPS_LO16, s);
675 void MicroMipsThunk::addSymbols(ThunkSection &isec) {
676 Defined *d = addSymbol(
677 saver.save("__microLA25Thunk_" + destination.getName()), STT_FUNC, 0, isec);
678 d->stOther |= STO_MIPS_MICROMIPS;
681 InputSection *MicroMipsThunk::getTargetInputSection() const {
682 auto &dr = cast<Defined>(destination);
683 return dyn_cast<InputSection>(dr.section);
686 // Write microMIPS R6 LA25 thunk code
687 // to call PIC function from the non-PIC one.
688 void MicroMipsR6Thunk::writeTo(uint8_t *buf) {
689 uint64_t s = destination.getVA();
690 uint64_t p = getThunkTargetSym()->getVA();
691 write16(buf, 0x1320); // lui $25, %hi(func)
692 write16(buf + 4, 0x3339); // addiu $25, $25, %lo(func)
693 write16(buf + 8, 0x9400); // bc func
694 target->relocateOne(buf, R_MICROMIPS_HI16, s);
695 target->relocateOne(buf + 4, R_MICROMIPS_LO16, s);
696 target->relocateOne(buf + 8, R_MICROMIPS_PC26_S1, s - p - 12);
699 void MicroMipsR6Thunk::addSymbols(ThunkSection &isec) {
700 Defined *d = addSymbol(
701 saver.save("__microLA25Thunk_" + destination.getName()), STT_FUNC, 0, isec);
702 d->stOther |= STO_MIPS_MICROMIPS;
705 InputSection *MicroMipsR6Thunk::getTargetInputSection() const {
706 auto &dr = cast<Defined>(destination);
707 return dyn_cast<InputSection>(dr.section);
710 void writePPC32PltCallStub(uint8_t *buf, uint64_t gotPltVA,
711 const InputFile *file, int64_t addend) {
712 if (!config->isPic) {
713 write32(buf + 0, 0x3d600000 | (gotPltVA + 0x8000) >> 16); // lis r11,ha
714 write32(buf + 4, 0x816b0000 | (uint16_t)gotPltVA); // lwz r11,l(r11)
715 write32(buf + 8, 0x7d6903a6); // mtctr r11
716 write32(buf + 12, 0x4e800420); // bctr
720 if (addend >= 0x8000) {
721 // The stub loads an address relative to r30 (.got2+Addend). Addend is
722 // almost always 0x8000. The address of .got2 is different in another object
723 // file, so a stub cannot be shared.
724 offset = gotPltVA - (in.ppc32Got2->getParent()->getVA() +
725 file->ppc32Got2OutSecOff + addend);
727 // The stub loads an address relative to _GLOBAL_OFFSET_TABLE_ (which is
728 // currently the address of .got).
729 offset = gotPltVA - in.got->getVA();
731 uint16_t ha = (offset + 0x8000) >> 16, l = (uint16_t)offset;
733 write32(buf + 0, 0x817e0000 | l); // lwz r11,l(r30)
734 write32(buf + 4, 0x7d6903a6); // mtctr r11
735 write32(buf + 8, 0x4e800420); // bctr
736 write32(buf + 12, 0x60000000); // nop
738 write32(buf + 0, 0x3d7e0000 | ha); // addis r11,r30,ha
739 write32(buf + 4, 0x816b0000 | l); // lwz r11,l(r11)
740 write32(buf + 8, 0x7d6903a6); // mtctr r11
741 write32(buf + 12, 0x4e800420); // bctr
745 void PPC32PltCallStub::writeTo(uint8_t *buf) {
746 writePPC32PltCallStub(buf, destination.getGotPltVA(), file, addend);
749 void PPC32PltCallStub::addSymbols(ThunkSection &isec) {
751 raw_string_ostream os(buf);
752 os << format_hex_no_prefix(addend, 8);
754 os << ".plt_call32.";
755 else if (addend >= 0x8000)
756 os << ".got2.plt_pic32.";
759 os << destination.getName();
760 addSymbol(saver.save(os.str()), STT_FUNC, 0, isec);
763 bool PPC32PltCallStub::isCompatibleWith(const InputSection &isec,
764 const Relocation &rel) const {
765 return !config->isPic || (isec.file == file && rel.addend == addend);
768 void writePPC64LoadAndBranch(uint8_t *buf, int64_t offset) {
769 uint16_t offHa = (offset + 0x8000) >> 16;
770 uint16_t offLo = offset & 0xffff;
772 write32(buf + 0, 0x3d820000 | offHa); // addis r12, r2, OffHa
773 write32(buf + 4, 0xe98c0000 | offLo); // ld r12, OffLo(r12)
774 write32(buf + 8, 0x7d8903a6); // mtctr r12
775 write32(buf + 12, 0x4e800420); // bctr
778 void PPC64PltCallStub::writeTo(uint8_t *buf) {
779 int64_t offset = destination.getGotPltVA() - getPPC64TocBase();
780 // Save the TOC pointer to the save-slot reserved in the call frame.
781 write32(buf + 0, 0xf8410018); // std r2,24(r1)
782 writePPC64LoadAndBranch(buf + 4, offset);
785 void PPC64PltCallStub::addSymbols(ThunkSection &isec) {
786 Defined *s = addSymbol(saver.save("__plt_" + destination.getName()), STT_FUNC,
788 s->needsTocRestore = true;
789 s->file = destination.file;
792 void PPC64LongBranchThunk::writeTo(uint8_t *buf) {
793 int64_t offset = in.ppc64LongBranchTarget->getEntryVA(&destination, addend) -
795 writePPC64LoadAndBranch(buf, offset);
798 void PPC64LongBranchThunk::addSymbols(ThunkSection &isec) {
799 addSymbol(saver.save("__long_branch_" + destination.getName()), STT_FUNC, 0,
803 Thunk::Thunk(Symbol &d, int64_t a) : destination(d), addend(a), offset(0) {}
805 Thunk::~Thunk() = default;
807 static Thunk *addThunkAArch64(RelType type, Symbol &s, int64_t a) {
808 if (type != R_AARCH64_CALL26 && type != R_AARCH64_JUMP26)
809 fatal("unrecognized relocation type");
810 if (config->picThunk)
811 return make<AArch64ADRPThunk>(s, a);
812 return make<AArch64ABSLongThunk>(s, a);
815 // Creates a thunk for Thumb-ARM interworking.
816 // Arm Architectures v5 and v6 do not support Thumb2 technology. This means
817 // - MOVT and MOVW instructions cannot be used
818 // - Only Thumb relocation that can generate a Thunk is a BL, this can always
819 // be transformed into a BLX
820 static Thunk *addThunkPreArmv7(RelType reloc, Symbol &s) {
827 if (config->picThunk)
828 return make<ARMV5PILongThunk>(s);
829 return make<ARMV5ABSLongThunk>(s);
831 fatal("relocation " + toString(reloc) + " to " + toString(s) +
832 " not supported for Armv5 or Armv6 targets");
835 // Create a thunk for Thumb long branch on V6-M.
836 // Arm Architecture v6-M only supports Thumb instructions. This means
837 // - MOVT and MOVW instructions cannot be used.
838 // - Only a limited number of instructions can access registers r8 and above
839 // - No interworking support is needed (all Thumb).
840 static Thunk *addThunkV6M(RelType reloc, Symbol &s) {
842 case R_ARM_THM_JUMP19:
843 case R_ARM_THM_JUMP24:
846 return make<ThumbV6MPILongThunk>(s);
847 return make<ThumbV6MABSLongThunk>(s);
849 fatal("relocation " + toString(reloc) + " to " + toString(s) +
850 " not supported for Armv6-M targets");
853 // Creates a thunk for Thumb-ARM interworking or branch range extension.
854 static Thunk *addThunkArm(RelType reloc, Symbol &s) {
855 // Decide which Thunk is needed based on:
856 // Available instruction set
857 // - An Arm Thunk can only be used if Arm state is available.
858 // - A Thumb Thunk can only be used if Thumb state is available.
859 // - Can only use a Thunk if it uses instructions that the Target supports.
860 // Relocation is branch or branch and link
861 // - Branch instructions cannot change state, can only select Thunk that
862 // starts in the same state as the caller.
863 // - Branch and link relocations can change state, can select Thunks from
864 // either Arm or Thumb.
865 // Position independent Thunks if we require position independent code.
867 // Handle architectures that have restrictions on the instructions that they
868 // can use in Thunks. The flags below are set by reading the BuildAttributes
869 // of the input objects. InputFiles.cpp contains the mapping from ARM
870 // architecture to flag.
871 if (!config->armHasMovtMovw) {
872 if (!config->armJ1J2BranchEncoding)
873 return addThunkPreArmv7(reloc, s);
874 return addThunkV6M(reloc, s);
882 if (config->picThunk)
883 return make<ARMV7PILongThunk>(s);
884 return make<ARMV7ABSLongThunk>(s);
885 case R_ARM_THM_JUMP19:
886 case R_ARM_THM_JUMP24:
888 if (config->picThunk)
889 return make<ThumbV7PILongThunk>(s);
890 return make<ThumbV7ABSLongThunk>(s);
892 fatal("unrecognized relocation type");
895 static Thunk *addThunkMips(RelType type, Symbol &s) {
896 if ((s.stOther & STO_MIPS_MICROMIPS) && isMipsR6())
897 return make<MicroMipsR6Thunk>(s);
898 if (s.stOther & STO_MIPS_MICROMIPS)
899 return make<MicroMipsThunk>(s);
900 return make<MipsThunk>(s);
903 static Thunk *addThunkPPC32(const InputSection &isec, const Relocation &rel,
905 assert((rel.type == R_PPC_REL24 || rel.type == R_PPC_PLTREL24) &&
906 "unexpected relocation type for thunk");
907 return make<PPC32PltCallStub>(isec, rel, s);
910 static Thunk *addThunkPPC64(RelType type, Symbol &s, int64_t a) {
911 assert(type == R_PPC64_REL24 && "unexpected relocation type for thunk");
913 return make<PPC64PltCallStub>(s);
915 if (config->picThunk)
916 return make<PPC64PILongBranchThunk>(s, a);
918 return make<PPC64PDLongBranchThunk>(s, a);
921 Thunk *addThunk(const InputSection &isec, Relocation &rel) {
922 Symbol &s = *rel.sym;
923 int64_t a = rel.addend;
925 if (config->emachine == EM_AARCH64)
926 return addThunkAArch64(rel.type, s, a);
928 if (config->emachine == EM_ARM)
929 return addThunkArm(rel.type, s);
931 if (config->emachine == EM_MIPS)
932 return addThunkMips(rel.type, s);
934 if (config->emachine == EM_PPC)
935 return addThunkPPC32(isec, rel, s);
937 if (config->emachine == EM_PPC64)
938 return addThunkPPC64(rel.type, s, a);
940 llvm_unreachable("add Thunk only supported for ARM, Mips and PowerPC");
943 } // end namespace elf
944 } // end namespace lld