1 //===-- AArch64MachObjectWriter.cpp - ARM Mach Object Writer --------------===//
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 #include "MCTargetDesc/AArch64FixupKinds.h"
10 #include "MCTargetDesc/AArch64MCTargetDesc.h"
11 #include "llvm/ADT/Twine.h"
12 #include "llvm/BinaryFormat/MachO.h"
13 #include "llvm/MC/MCAsmInfo.h"
14 #include "llvm/MC/MCAsmLayout.h"
15 #include "llvm/MC/MCAssembler.h"
16 #include "llvm/MC/MCContext.h"
17 #include "llvm/MC/MCExpr.h"
18 #include "llvm/MC/MCFixup.h"
19 #include "llvm/MC/MCFragment.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"
34 class AArch64MachObjectWriter : public MCMachObjectTargetWriter {
35 bool getAArch64FixupKindMachOInfo(const MCFixup &Fixup, unsigned &RelocType,
36 const MCSymbolRefExpr *Sym,
37 unsigned &Log2Size, const MCAssembler &Asm);
40 AArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype, bool IsILP32)
41 : MCMachObjectTargetWriter(!IsILP32 /* is64Bit */, CPUType, CPUSubtype) {}
43 void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
44 const MCAsmLayout &Layout, const MCFragment *Fragment,
45 const MCFixup &Fixup, MCValue Target,
46 uint64_t &FixedValue) override;
49 } // end anonymous namespace
51 bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
52 const MCFixup &Fixup, unsigned &RelocType, const MCSymbolRefExpr *Sym,
53 unsigned &Log2Size, const MCAssembler &Asm) {
54 RelocType = unsigned(MachO::ARM64_RELOC_UNSIGNED);
57 switch ((unsigned)Fixup.getKind()) {
62 Log2Size = Log2_32(1);
65 Log2Size = Log2_32(2);
68 Log2Size = Log2_32(4);
69 if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
70 RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
73 Log2Size = Log2_32(8);
74 if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
75 RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
77 case AArch64::fixup_aarch64_add_imm12:
78 case AArch64::fixup_aarch64_ldst_imm12_scale1:
79 case AArch64::fixup_aarch64_ldst_imm12_scale2:
80 case AArch64::fixup_aarch64_ldst_imm12_scale4:
81 case AArch64::fixup_aarch64_ldst_imm12_scale8:
82 case AArch64::fixup_aarch64_ldst_imm12_scale16:
83 Log2Size = Log2_32(4);
84 switch (Sym->getKind()) {
87 case MCSymbolRefExpr::VK_PAGEOFF:
88 RelocType = unsigned(MachO::ARM64_RELOC_PAGEOFF12);
90 case MCSymbolRefExpr::VK_GOTPAGEOFF:
91 RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12);
93 case MCSymbolRefExpr::VK_TLVPPAGEOFF:
94 RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12);
97 case AArch64::fixup_aarch64_pcrel_adrp_imm21:
98 Log2Size = Log2_32(4);
99 // This encompasses the relocation for the whole 21-bit value.
100 switch (Sym->getKind()) {
102 Asm.getContext().reportError(Fixup.getLoc(),
103 "ADR/ADRP relocations must be GOT relative");
105 case MCSymbolRefExpr::VK_PAGE:
106 RelocType = unsigned(MachO::ARM64_RELOC_PAGE21);
108 case MCSymbolRefExpr::VK_GOTPAGE:
109 RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGE21);
111 case MCSymbolRefExpr::VK_TLVPPAGE:
112 RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGE21);
116 case AArch64::fixup_aarch64_pcrel_branch26:
117 case AArch64::fixup_aarch64_pcrel_call26:
118 Log2Size = Log2_32(4);
119 RelocType = unsigned(MachO::ARM64_RELOC_BRANCH26);
124 static bool canUseLocalRelocation(const MCSectionMachO &Section,
125 const MCSymbol &Symbol, unsigned Log2Size) {
126 // Debug info sections can use local relocations.
127 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
130 // Otherwise, only pointer sized relocations are supported.
134 // But only if they don't point to a few forbidden sections.
135 if (!Symbol.isInSection())
137 const MCSectionMachO &RefSec = cast<MCSectionMachO>(Symbol.getSection());
138 if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
141 if (RefSec.getSegmentName() == "__DATA" &&
142 RefSec.getSectionName() == "__objc_classrefs")
145 // FIXME: ld64 currently handles internal pointer-sized relocations
146 // incorrectly (applying the addend twice). We should be able to return true
147 // unconditionally by this point when that's fixed.
151 void AArch64MachObjectWriter::recordRelocation(
152 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
153 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
154 uint64_t &FixedValue) {
155 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
158 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment);
159 unsigned Log2Size = 0;
163 unsigned Kind = Fixup.getKind();
164 const MCSymbol *RelSymbol = nullptr;
166 FixupOffset += Fixup.getOffset();
168 // AArch64 pcrel relocation addends do not include the section offset.
170 FixedValue += FixupOffset;
172 // ADRP fixups use relocations for the whole symbol value and only
173 // put the addend in the instruction itself. Clear out any value the
174 // generic code figured out from the sybmol definition.
175 if (Kind == AArch64::fixup_aarch64_pcrel_adrp_imm21)
178 // imm19 relocations are for conditional branches, which require
179 // assembler local symbols. If we got here, that's not what we have,
180 // so complain loudly.
181 if (Kind == AArch64::fixup_aarch64_pcrel_branch19) {
182 Asm.getContext().reportError(Fixup.getLoc(),
183 "conditional branch requires assembler-local"
185 Target.getSymA()->getSymbol().getName() +
190 // 14-bit branch relocations should only target internal labels, and so
191 // should never get here.
192 if (Kind == AArch64::fixup_aarch64_pcrel_branch14) {
193 Asm.getContext().reportError(Fixup.getLoc(),
194 "Invalid relocation on conditional branch!");
198 if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSymA(), Log2Size,
200 Asm.getContext().reportError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
204 Value = Target.getConstant();
206 if (Target.isAbsolute()) { // constant
207 // FIXME: Should this always be extern?
208 // SymbolNum of 0 indicates the absolute section.
209 Type = MachO::ARM64_RELOC_UNSIGNED;
212 Asm.getContext().reportError(Fixup.getLoc(),
213 "PC relative absolute relocation!");
216 // FIXME: x86_64 sets the type to a branch reloc here. Should we do
217 // something similar?
219 } else if (Target.getSymB()) { // A - B + constant
220 const MCSymbol *A = &Target.getSymA()->getSymbol();
221 const MCSymbol *A_Base = Asm.getAtom(*A);
223 const MCSymbol *B = &Target.getSymB()->getSymbol();
224 const MCSymbol *B_Base = Asm.getAtom(*B);
226 // Check for "_foo@got - .", which comes through here as:
228 // ... _foo@got - Ltmp0
229 if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_GOT &&
230 Target.getSymB()->getKind() == MCSymbolRefExpr::VK_None &&
231 Layout.getSymbolOffset(*B) ==
232 Layout.getFragmentOffset(Fragment) + Fixup.getOffset()) {
233 // SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
234 Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
236 MachO::any_relocation_info MRE;
237 MRE.r_word0 = FixupOffset;
238 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
239 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
241 } else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
242 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) {
243 // Otherwise, neither symbol can be modified.
244 Asm.getContext().reportError(Fixup.getLoc(),
245 "unsupported relocation of modified symbol");
249 // We don't support PCrel relocations of differences.
251 Asm.getContext().reportError(Fixup.getLoc(),
252 "unsupported pc-relative relocation of "
257 // AArch64 always uses external relocations. If there is no symbol to use as
258 // a base address (a local symbol with no preceding non-local symbol),
261 // FIXME: We should probably just synthesize an external symbol and use
264 Asm.getContext().reportError(
266 "unsupported relocation of local symbol '" + A->getName() +
267 "'. Must have non-local symbol earlier in section.");
271 Asm.getContext().reportError(
273 "unsupported relocation of local symbol '" + B->getName() +
274 "'. Must have non-local symbol earlier in section.");
278 if (A_Base == B_Base && A_Base) {
279 Asm.getContext().reportError(
280 Fixup.getLoc(), "unsupported relocation with identical base");
284 Value += (!A->getFragment() ? 0 : Writer->getSymbolAddress(*A, Layout)) -
285 (!A_Base || !A_Base->getFragment() ? 0 : Writer->getSymbolAddress(
287 Value -= (!B->getFragment() ? 0 : Writer->getSymbolAddress(*B, Layout)) -
288 (!B_Base || !B_Base->getFragment() ? 0 : Writer->getSymbolAddress(
291 Type = MachO::ARM64_RELOC_UNSIGNED;
293 MachO::any_relocation_info MRE;
294 MRE.r_word0 = FixupOffset;
295 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
296 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
299 Type = MachO::ARM64_RELOC_SUBTRACTOR;
300 } else { // A + constant
301 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
302 const MCSectionMachO &Section =
303 static_cast<const MCSectionMachO &>(*Fragment->getParent());
305 bool CanUseLocalRelocation =
306 canUseLocalRelocation(Section, *Symbol, Log2Size);
307 if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
308 // Make sure that the symbol is actually in a section here. If it isn't,
309 // emit an error and exit.
310 if (!Symbol->isInSection()) {
311 Asm.getContext().reportError(
313 "unsupported relocation of local symbol '" + Symbol->getName() +
314 "'. Must have non-local symbol earlier in section.");
317 const MCSection &Sec = Symbol->getSection();
318 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
319 Symbol->setUsedInReloc();
322 const MCSymbol *Base = Asm.getAtom(*Symbol);
323 // If the symbol is a variable it can either be in a section and
324 // we have a base or it is absolute and should have been expanded.
325 assert(!Symbol->isVariable() || Base);
327 // Relocations inside debug sections always use local relocations when
328 // possible. This seems to be done because the debugger doesn't fully
329 // understand relocation entries and expects to find values that
330 // have already been fixed up.
331 if (Symbol->isInSection()) {
332 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
336 // AArch64 uses external relocations as much as possible. For debug
337 // sections, and for pointer-sized relocations (.quad), we allow section
338 // relocations. It's code sections that run into trouble.
342 // Add the local offset, if needed.
345 Layout.getSymbolOffset(*Symbol) - Layout.getSymbolOffset(*Base);
346 } else if (Symbol->isInSection()) {
347 if (!CanUseLocalRelocation) {
348 Asm.getContext().reportError(
350 "unsupported relocation of local symbol '" + Symbol->getName() +
351 "'. Must have non-local symbol earlier in section.");
354 // Adjust the relocation to be section-relative.
355 // The index is the section ordinal (1-based).
356 const MCSection &Sec = Symbol->getSection();
357 Index = Sec.getOrdinal() + 1;
358 Value += Writer->getSymbolAddress(*Symbol, Layout);
361 Value -= Writer->getFragmentAddress(Fragment, Layout) +
362 Fixup.getOffset() + (1ULL << Log2Size);
365 "This constant variable should have been expanded during evaluation");
369 // If the relocation kind is Branch26, Page21, or Pageoff12, any addend
370 // is represented via an Addend relocation, not encoded directly into
372 if ((Type == MachO::ARM64_RELOC_BRANCH26 ||
373 Type == MachO::ARM64_RELOC_PAGE21 ||
374 Type == MachO::ARM64_RELOC_PAGEOFF12) &&
376 assert((Value & 0xff000000) == 0 && "Added relocation out of range!");
378 MachO::any_relocation_info MRE;
379 MRE.r_word0 = FixupOffset;
381 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
382 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
384 // Now set up the Addend relocation.
385 Type = MachO::ARM64_RELOC_ADDEND;
391 // Put zero into the instruction itself. The addend is in the relocation.
395 // If there's any addend left to handle, encode it in the instruction.
398 // struct relocation_info (8 bytes)
399 MachO::any_relocation_info MRE;
400 MRE.r_word0 = FixupOffset;
402 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
403 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
406 std::unique_ptr<MCObjectTargetWriter>
407 llvm::createAArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype,
409 return llvm::make_unique<AArch64MachObjectWriter>(CPUType, CPUSubtype,