LLVM: lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp Source File

LLVM 22.0.0git
AArch64MachObjectWriter.cpp
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1//===-- AArch64MachObjectWriter.cpp - ARM Mach Object Writer --------------===//
2//
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
6//
7//===----------------------------------------------------------------------===//
8
9#include "MCTargetDesc/AArch64FixupKinds.h"
10#include "MCTargetDesc/AArch64MCAsmInfo.h"
11#include "MCTargetDesc/AArch64MCTargetDesc.h"
12#include "llvm/ADT/Twine.h"
13#include "llvm/BinaryFormat/MachO.h"
14#include "llvm/MC/MCAsmInfo.h"
15#include "llvm/MC/MCAsmInfoDarwin.h"
16#include "llvm/MC/MCAssembler.h"
17#include "llvm/MC/MCContext.h"
18#include "llvm/MC/MCExpr.h"
19#include "llvm/MC/MCFixup.h"
20#include "llvm/MC/MCMachObjectWriter.h"
21#include "llvm/MC/MCSection.h"
22#include "llvm/MC/MCSectionMachO.h"
23#include "llvm/MC/MCSymbol.h"
24#include "llvm/MC/MCValue.h"
25#include "llvm/Support/Casting.h"
26#include "llvm/Support/MathExtras.h"
27#include <cassert>
28#include <cstdint>
29
30using namespace llvm;
31
32namespace {
33
34class AArch64MachObjectWriter : public MCMachObjectTargetWriter {
35 bool getAArch64FixupKindMachOInfo(const MCFixup &Fixup, unsigned &RelocType,
36 AArch64::Specifier Spec, unsigned &Log2Size,
37 const MCAssembler &Asm);
38
39public:
40 AArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype, bool IsILP32)
41 : MCMachObjectTargetWriter(!IsILP32 /* is64Bit */, CPUType, CPUSubtype) {}
42
43 void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
44 const MCFragment *Fragment, const MCFixup &Fixup,
45 MCValue Target, uint64_t &FixedValue) override;
46};
47
48} // end anonymous namespace
49
50bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
51 const MCFixup &Fixup, unsigned &RelocType, AArch64::Specifier Spec,
52 unsigned &Log2Size, const MCAssembler &Asm) {
53 RelocType = unsigned(MachO::ARM64_RELOC_UNSIGNED);
54 Log2Size = ~0U;
55
56 switch (Fixup.getKind()) {
57 default:
58 return false;
59
60 case FK_Data_1:
61 Log2Size = Log2_32(1);
62 return true;
63 case FK_Data_2:
64 Log2Size = Log2_32(2);
65 return true;
66 case FK_Data_4:
67 Log2Size = Log2_32(4);
68 if (Spec == AArch64::S_MACHO_GOT)
69 RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
70 return true;
71 case FK_Data_8:
72 Log2Size = Log2_32(8);
73 if (Spec == AArch64::S_MACHO_GOT)
74 RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
75 return true;
76 case AArch64::fixup_aarch64_add_imm12:
77 case AArch64::fixup_aarch64_ldst_imm12_scale1:
78 case AArch64::fixup_aarch64_ldst_imm12_scale2:
79 case AArch64::fixup_aarch64_ldst_imm12_scale4:
80 case AArch64::fixup_aarch64_ldst_imm12_scale8:
81 case AArch64::fixup_aarch64_ldst_imm12_scale16:
82 Log2Size = Log2_32(4);
83 switch (Spec) {
84 default:
85 return false;
86 case AArch64::S_MACHO_PAGEOFF:
87 RelocType = unsigned(MachO::ARM64_RELOC_PAGEOFF12);
88 return true;
89 case AArch64::S_MACHO_GOTPAGEOFF:
90 RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12);
91 return true;
92 case AArch64::S_MACHO_TLVPPAGEOFF:
93 RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12);
94 return true;
95 }
96 case AArch64::fixup_aarch64_pcrel_adrp_imm21:
97 Log2Size = Log2_32(4);
98 // This encompasses the relocation for the whole 21-bit value.
99 switch (Spec) {
100 default:
101 reportError(Fixup.getLoc(), "ADR/ADRP relocations must be GOT relative");
102 return false;
103 case AArch64::S_MACHO_PAGE:
104 RelocType = unsigned(MachO::ARM64_RELOC_PAGE21);
105 return true;
106 case AArch64::S_MACHO_GOTPAGE:
107 RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGE21);
108 return true;
109 case AArch64::S_MACHO_TLVPPAGE:
110 RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGE21);
111 return true;
112 }
113 return true;
114 case AArch64::fixup_aarch64_pcrel_branch26:
115 case AArch64::fixup_aarch64_pcrel_call26:
116 Log2Size = Log2_32(4);
117 RelocType = unsigned(MachO::ARM64_RELOC_BRANCH26);
118 return true;
119 }
120}
121
122 static bool canUseLocalRelocation(const MCSectionMachO &Section,
123 const MCSymbol &Symbol, unsigned Log2Size) {
124 // Debug info sections can use local relocations.
125 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
126 return true;
127
128 // Otherwise, only pointer sized relocations are supported.
129 if (Log2Size != 3)
130 return false;
131
132 // But only if they don't point to a few forbidden sections.
133 if (!Symbol.isInSection())
134 return true;
135 const MCSectionMachO &RefSec =
136 static_cast<MCSectionMachO &>(Symbol.getSection());
137 if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
138 return false;
139
140 if (RefSec.getSegmentName() == "__DATA" &&
141 (RefSec.getName() == "__cfstring" ||
142 RefSec.getName() == "__objc_classrefs"))
143 return false;
144
145 return true;
146}
147
148void AArch64MachObjectWriter::recordRelocation(
149 MachObjectWriter *Writer, MCAssembler &Asm, const MCFragment *Fragment,
150 const MCFixup &Fixup, MCValue Target, uint64_t &FixedValue) {
151 unsigned IsPCRel = Fixup.isPCRel();
152
153 // See <reloc.h>.
154 uint32_t FixupOffset = Asm.getFragmentOffset(*Fragment);
155 unsigned Log2Size = 0;
156 int64_t Value = 0;
157 unsigned Index = 0;
158 unsigned Type = 0;
159 unsigned Kind = Fixup.getKind();
160 const MCSymbol *RelSymbol = nullptr;
161
162 FixupOffset += Fixup.getOffset();
163
164 // AArch64 pcrel relocation addends do not include the section offset.
165 if (IsPCRel)
166 FixedValue += FixupOffset;
167
168 // ADRP fixups use relocations for the whole symbol value and only
169 // put the addend in the instruction itself. Clear out any value the
170 // generic code figured out from the sybmol definition.
171 if (Kind == AArch64::fixup_aarch64_pcrel_adrp_imm21)
172 FixedValue = 0;
173
174 // imm19 relocations are for conditional branches, which require
175 // assembler local symbols. If we got here, that's not what we have,
176 // so complain loudly.
177 if (Kind == AArch64::fixup_aarch64_pcrel_branch19) {
178 reportError(Fixup.getLoc(), "conditional branch requires assembler-local"
179 " label. '" +
180 Target.getAddSym()->getName() +
181 "' is external.");
182 return;
183 }
184
185 // 14-bit branch relocations should only target internal labels, and so
186 // should never get here.
187 if (Kind == AArch64::fixup_aarch64_pcrel_branch14) {
188 reportError(Fixup.getLoc(), "Invalid relocation on conditional branch!");
189 return;
190 }
191
192 if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSpecifier(),
193 Log2Size, Asm)) {
194 reportError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
195 return;
196 }
197
198 Value = Target.getConstant();
199
200 if (Target.isAbsolute()) { // constant
201 // FIXME: Should this always be extern?
202 // SymbolNum of 0 indicates the absolute section.
203 Type = MachO::ARM64_RELOC_UNSIGNED;
204
205 if (IsPCRel) {
206 reportError(Fixup.getLoc(), "PC relative absolute relocation!");
207 return;
208
209 // FIXME: x86_64 sets the type to a branch reloc here. Should we do
210 // something similar?
211 }
212 } else if (auto *B = Target.getSubSym()) { // A - B + constant
213 const MCSymbol *A = Target.getAddSym();
214 const MCSymbol *A_Base = Writer->getAtom(*A);
215 const MCSymbol *B_Base = Writer->getAtom(*B);
216
217 // Check for "_foo@got - .", which comes through here as:
218 // Ltmp0:
219 // ... _foo@got - Ltmp0
220 if (Target.getSpecifier() == AArch64::S_MACHO_GOT &&
221 Asm.getSymbolOffset(*B) ==
222 Asm.getFragmentOffset(*Fragment) + Fixup.getOffset()) {
223 // SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
224 Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
225 IsPCRel = 1;
226 MachO::any_relocation_info MRE;
227 MRE.r_word0 = FixupOffset;
228 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
229 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
230 return;
231 } else if (Target.getSpecifier() != AArch64::S_None) {
232 // Otherwise, neither symbol can be modified.
233 reportError(Fixup.getLoc(), "unsupported relocation of modified symbol");
234 return;
235 }
236
237 // We don't support PCrel relocations of differences.
238 if (IsPCRel) {
239 reportError(Fixup.getLoc(), "unsupported pc-relative relocation of "
240 "difference");
241 return;
242 }
243
244 // AArch64 always uses external relocations. If there is no symbol to use as
245 // a base address (a local symbol with no preceding non-local symbol),
246 // error out.
247 //
248 // FIXME: We should probably just synthesize an external symbol and use
249 // that.
250 if (!A_Base) {
251 reportError(Fixup.getLoc(),
252 "unsupported relocation of local symbol '" + A->getName() +
253 "'. Must have non-local symbol earlier in section.");
254 return;
255 }
256 if (!B_Base) {
257 reportError(Fixup.getLoc(),
258 "unsupported relocation of local symbol '" + B->getName() +
259 "'. Must have non-local symbol earlier in section.");
260 return;
261 }
262
263 if (A_Base == B_Base && A_Base) {
264 reportError(Fixup.getLoc(), "unsupported relocation with identical base");
265 return;
266 }
267
268 Value +=
269 (!A->getFragment() ? 0 : Writer->getSymbolAddress(*A)) -
270 (!A_Base || !A_Base->getFragment() ? 0
271 : Writer->getSymbolAddress(*A_Base));
272 Value -=
273 (!B->getFragment() ? 0 : Writer->getSymbolAddress(*B)) -
274 (!B_Base || !B_Base->getFragment() ? 0
275 : Writer->getSymbolAddress(*B_Base));
276
277 Type = MachO::ARM64_RELOC_UNSIGNED;
278
279 MachO::any_relocation_info MRE;
280 MRE.r_word0 = FixupOffset;
281 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
282 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
283
284 RelSymbol = B_Base;
285 Type = MachO::ARM64_RELOC_SUBTRACTOR;
286 } else { // A + constant
287 const MCSymbol *Symbol = Target.getAddSym();
288 const MCSectionMachO &Section =
289 static_cast<const MCSectionMachO &>(*Fragment->getParent());
290
291 bool CanUseLocalRelocation =
292 canUseLocalRelocation(Section, *Symbol, Log2Size);
293 if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
294 // Make sure that the symbol is actually in a section here. If it isn't,
295 // emit an error and exit.
296 if (!Symbol->isInSection()) {
297 reportError(Fixup.getLoc(),
298 "unsupported relocation of local symbol '" +
299 Symbol->getName() +
300 "'. Must have non-local symbol earlier in section.");
301 return;
302 }
303 const MCSection &Sec = Symbol->getSection();
304 if (!MCAsmInfoDarwin::isSectionAtomizableBySymbols(Sec))
305 Symbol->setUsedInReloc();
306 }
307
308 const MCSymbol *Base = Writer->getAtom(*Symbol);
309
310 // If the symbol is a variable it can either be in a section and
311 // we have a base or it is absolute and should have been expanded.
312 assert(!Symbol->isVariable() || Base);
313
314 // Relocations inside debug sections always use local relocations when
315 // possible. This seems to be done because the debugger doesn't fully
316 // understand relocation entries and expects to find values that
317 // have already been fixed up.
318 if (Symbol->isInSection()) {
319 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
320 Base = nullptr;
321 }
322
323 // AArch64 uses external relocations as much as possible. For debug
324 // sections, and for pointer-sized relocations (.quad), we allow section
325 // relocations. It's code sections that run into trouble.
326 if (Base) {
327 RelSymbol = Base;
328
329 // Add the local offset, if needed.
330 if (Base != Symbol)
331 Value += Asm.getSymbolOffset(*Symbol) - Asm.getSymbolOffset(*Base);
332 } else if (Symbol->isInSection()) {
333 if (!CanUseLocalRelocation) {
334 reportError(Fixup.getLoc(),
335 "unsupported relocation of local symbol '" +
336 Symbol->getName() +
337 "'. Must have non-local symbol earlier in section.");
338 return;
339 }
340 // Adjust the relocation to be section-relative.
341 // The index is the section ordinal (1-based).
342 const MCSection &Sec = Symbol->getSection();
343 Index = Sec.getOrdinal() + 1;
344 Value += Writer->getSymbolAddress(*Symbol);
345
346 if (IsPCRel)
347 Value -= Writer->getFragmentAddress(Asm, Fragment) + Fixup.getOffset() +
348 (1ULL << Log2Size);
349 } else {
350 llvm_unreachable(
351 "This constant variable should have been expanded during evaluation");
352 }
353 }
354
355 // If the relocation kind is Branch26, Page21, or Pageoff12, any addend
356 // is represented via an Addend relocation, not encoded directly into
357 // the instruction.
358 if ((Type == MachO::ARM64_RELOC_BRANCH26 ||
359 Type == MachO::ARM64_RELOC_PAGE21 ||
360 Type == MachO::ARM64_RELOC_PAGEOFF12) &&
361 Value) {
362 if (!isInt<24>(Value)) {
363 reportError(Fixup.getLoc(), "addend too big for relocation");
364 return;
365 }
366
367 MachO::any_relocation_info MRE;
368 MRE.r_word0 = FixupOffset;
369 MRE.r_word1 =
370 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
371 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
372
373 // Now set up the Addend relocation.
374 Type = MachO::ARM64_RELOC_ADDEND;
375 Index = Value;
376 RelSymbol = nullptr;
377 IsPCRel = 0;
378 Log2Size = 2;
379
380 // Put zero into the instruction itself. The addend is in the relocation.
381 Value = 0;
382 }
383
384 if (Target.getSpecifier() == AArch64::S_AUTH ||
385 Target.getSpecifier() == AArch64::S_AUTHADDR) {
386 auto *Expr = cast<AArch64AuthMCExpr>(Fixup.getValue());
387
388 assert(Type == MachO::ARM64_RELOC_UNSIGNED);
389
390 if (IsPCRel) {
391 reportError(Fixup.getLoc(), "invalid PC relative auth relocation");
392 return;
393 }
394
395 if (Log2Size != 3) {
396 reportError(Fixup.getLoc(),
397 "invalid auth relocation size, must be 8 bytes");
398 return;
399 }
400
401 if (Target.getSubSym()) {
402 reportError(Fixup.getLoc(),
403 "invalid auth relocation, can't reference two symbols");
404 return;
405 }
406
407 uint16_t Discriminator = Expr->getDiscriminator();
408 AArch64PACKey::ID Key = Expr->getKey();
409
410 if (!isInt<32>(Value)) {
411 reportError(Fixup.getLoc(), "addend too big for relocation");
412 return;
413 }
414
415 Type = MachO::ARM64_RELOC_AUTHENTICATED_POINTER;
416 Value = (uint32_t(Value)) | (uint64_t(Discriminator) << 32) |
417 (uint64_t(Expr->hasAddressDiversity()) << 48) |
418 (uint64_t(Key) << 49) | (1ULL << 63);
419 }
420
421 // If there's any addend left to handle, encode it in the instruction.
422 FixedValue = Value;
423
424 // struct relocation_info (8 bytes)
425 MachO::any_relocation_info MRE;
426 MRE.r_word0 = FixupOffset;
427 MRE.r_word1 =
428 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
429 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
430}
431
432std::unique_ptr<MCObjectTargetWriter>
434 bool IsILP32) {
435 return std::make_unique<AArch64MachObjectWriter>(CPUType, CPUSubtype,
436 IsILP32);
437}
assert(UImm &&(UImm !=~static_cast< T >(0)) &&"Invalid immediate!")
static bool canUseLocalRelocation(const MCSectionMachO &Section, const MCSymbol &Symbol, unsigned Log2Size)
static Error reportError(StringRef Message)
A
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
B
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
PowerPC TLS Dynamic Call Fixup
static bool isSectionAtomizableBySymbols(const MCSection &Section)
True if the section is atomized using the symbols in it.
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition MCFixup.h:61
MCSection * getParent() const
Definition MCSection.h:165
This represents a section on a Mach-O system (used by Mac OS X).
MachO::SectionType getType() const
StringRef getSegmentName() const
unsigned getOrdinal() const
Definition MCSection.h:613
StringRef getName() const
Definition MCSection.h:590
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition MCSymbol.h:42
MCFragment * getFragment() const
Definition MCSymbol.h:346
uint64_t getFragmentAddress(const MCAssembler &Asm, const MCFragment *Fragment) const
void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, MachO::any_relocation_info &MRE)
const MCSymbol * getAtom(const MCSymbol &S) const
uint64_t getSymbolAddress(const MCSymbol &S) const
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
@ fixup_aarch64_ldst_imm12_scale4
@ fixup_aarch64_ldst_imm12_scale2
@ fixup_aarch64_ldst_imm12_scale16
@ fixup_aarch64_pcrel_adrp_imm21
@ fixup_aarch64_ldst_imm12_scale8
@ fixup_aarch64_ldst_imm12_scale1
uint16_t Specifier
@ Section
Legacy Tags.
@ S_CSTRING_LITERALS
S_CSTRING_LITERALS - Section with literal C strings.
Definition MachO.h:131
@ ARM64_RELOC_PAGEOFF12
Definition MachO.h:464
@ ARM64_RELOC_POINTER_TO_GOT
Definition MachO.h:470
@ ARM64_RELOC_AUTHENTICATED_POINTER
Definition MachO.h:478
@ ARM64_RELOC_SUBTRACTOR
Definition MachO.h:458
@ ARM64_RELOC_ADDEND
Definition MachO.h:476
@ ARM64_RELOC_UNSIGNED
Definition MachO.h:456
@ ARM64_RELOC_GOT_LOAD_PAGE21
Definition MachO.h:466
@ ARM64_RELOC_TLVP_LOAD_PAGEOFF12
Definition MachO.h:474
@ ARM64_RELOC_PAGE21
Definition MachO.h:462
@ ARM64_RELOC_GOT_LOAD_PAGEOFF12
Definition MachO.h:468
@ ARM64_RELOC_TLVP_LOAD_PAGE21
Definition MachO.h:472
@ ARM64_RELOC_BRANCH26
Definition MachO.h:460
@ S_ATTR_DEBUG
S_ATTR_DEBUG - A debug section.
Definition MachO.h:207
This is an optimization pass for GlobalISel generic memory operations.
Definition AddressRanges.h:18
FunctionAddr VTableAddr Value
Definition InstrProf.h:137
constexpr bool isInt(int64_t x)
Checks if an integer fits into the given bit width.
Definition MathExtras.h:165
unsigned Log2_32(uint32_t Value)
Return the floor log base 2 of the specified value, -1 if the value is zero.
Definition MathExtras.h:331
LLVM_ATTRIBUTE_VISIBILITY_DEFAULT AnalysisKey InnerAnalysisManagerProxy< AnalysisManagerT, IRUnitT, ExtraArgTs... >::Key
Definition PassManager.h:668
@ FK_Data_8
A eight-byte fixup.
Definition MCFixup.h:37
@ FK_Data_1
A one-byte fixup.
Definition MCFixup.h:34
@ FK_Data_4
A four-byte fixup.
Definition MCFixup.h:36
@ FK_Data_2
A two-byte fixup.
Definition MCFixup.h:35
decltype(auto) cast(const From &Val)
cast<X> - Return the argument parameter cast to the specified type.
Definition Casting.h:559
std::unique_ptr< MCObjectTargetWriter > createAArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype, bool IsILP32)
uint32_t r_word0
Definition MachO.h:998
uint32_t r_word1
Definition MachO.h:998
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