1 //===-- AArch64MachObjectWriter.cpp - ARM Mach Object Writer --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "MCTargetDesc/AArch64FixupKinds.h"
11 #include "MCTargetDesc/AArch64MCTargetDesc.h"
12 #include "llvm/ADT/Twine.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/MCMachObjectWriter.h"
20 #include "llvm/MC/MCSectionMachO.h"
21 #include "llvm/MC/MCValue.h"
22 #include "llvm/Support/ErrorHandling.h"
23 #include "llvm/Support/MachO.h"
27 class AArch64MachObjectWriter : public MCMachObjectTargetWriter {
28 bool getAArch64FixupKindMachOInfo(const MCFixup &Fixup, unsigned &RelocType,
29 const MCSymbolRefExpr *Sym,
30 unsigned &Log2Size, const MCAssembler &Asm);
33 AArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype)
34 : MCMachObjectTargetWriter(true /* is64Bit */, CPUType, CPUSubtype,
35 /*UseAggressiveSymbolFolding=*/true) {}
37 void RecordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
38 const MCAsmLayout &Layout, const MCFragment *Fragment,
39 const MCFixup &Fixup, MCValue Target,
40 uint64_t &FixedValue) override;
44 bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
45 const MCFixup &Fixup, unsigned &RelocType, const MCSymbolRefExpr *Sym,
46 unsigned &Log2Size, const MCAssembler &Asm) {
47 RelocType = unsigned(MachO::ARM64_RELOC_UNSIGNED);
50 switch ((unsigned)Fixup.getKind()) {
55 Log2Size = llvm::Log2_32(1);
58 Log2Size = llvm::Log2_32(2);
61 Log2Size = llvm::Log2_32(4);
62 if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
63 RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
66 Log2Size = llvm::Log2_32(8);
67 if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
68 RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
70 case AArch64::fixup_aarch64_add_imm12:
71 case AArch64::fixup_aarch64_ldst_imm12_scale1:
72 case AArch64::fixup_aarch64_ldst_imm12_scale2:
73 case AArch64::fixup_aarch64_ldst_imm12_scale4:
74 case AArch64::fixup_aarch64_ldst_imm12_scale8:
75 case AArch64::fixup_aarch64_ldst_imm12_scale16:
76 Log2Size = llvm::Log2_32(4);
77 switch (Sym->getKind()) {
79 llvm_unreachable("Unexpected symbol reference variant kind!");
80 case MCSymbolRefExpr::VK_PAGEOFF:
81 RelocType = unsigned(MachO::ARM64_RELOC_PAGEOFF12);
83 case MCSymbolRefExpr::VK_GOTPAGEOFF:
84 RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12);
86 case MCSymbolRefExpr::VK_TLVPPAGEOFF:
87 RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12);
90 case AArch64::fixup_aarch64_pcrel_adrp_imm21:
91 Log2Size = llvm::Log2_32(4);
92 // This encompasses the relocation for the whole 21-bit value.
93 switch (Sym->getKind()) {
95 Asm.getContext().FatalError(Fixup.getLoc(),
96 "ADR/ADRP relocations must be GOT relative");
97 case MCSymbolRefExpr::VK_PAGE:
98 RelocType = unsigned(MachO::ARM64_RELOC_PAGE21);
100 case MCSymbolRefExpr::VK_GOTPAGE:
101 RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGE21);
103 case MCSymbolRefExpr::VK_TLVPPAGE:
104 RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGE21);
108 case AArch64::fixup_aarch64_pcrel_branch26:
109 case AArch64::fixup_aarch64_pcrel_call26:
110 Log2Size = llvm::Log2_32(4);
111 RelocType = unsigned(MachO::ARM64_RELOC_BRANCH26);
116 static bool canUseLocalRelocation(const MCSectionMachO &Section,
117 const MCSymbol &Symbol, unsigned Log2Size) {
118 // Debug info sections can use local relocations.
119 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
122 // Otherwise, only pointer sized relocations are supported.
126 // But only if they don't point to a few forbidden sections.
127 if (!Symbol.isInSection())
129 const MCSectionMachO &RefSec = cast<MCSectionMachO>(Symbol.getSection());
130 if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
133 if (RefSec.getSegmentName() == "__DATA" &&
134 RefSec.getSectionName() == "__cfstring")
137 if (RefSec.getSegmentName() == "__DATA" &&
138 RefSec.getSectionName() == "__objc_classrefs")
144 void AArch64MachObjectWriter::RecordRelocation(
145 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
146 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
147 uint64_t &FixedValue) {
148 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
151 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment);
152 unsigned Log2Size = 0;
156 unsigned Kind = Fixup.getKind();
157 const MCSymbolData *RelSymbol = nullptr;
159 FixupOffset += Fixup.getOffset();
161 // AArch64 pcrel relocation addends do not include the section offset.
163 FixedValue += FixupOffset;
165 // ADRP fixups use relocations for the whole symbol value and only
166 // put the addend in the instruction itself. Clear out any value the
167 // generic code figured out from the sybmol definition.
168 if (Kind == AArch64::fixup_aarch64_pcrel_adrp_imm21)
171 // imm19 relocations are for conditional branches, which require
172 // assembler local symbols. If we got here, that's not what we have,
173 // so complain loudly.
174 if (Kind == AArch64::fixup_aarch64_pcrel_branch19) {
175 Asm.getContext().FatalError(Fixup.getLoc(),
176 "conditional branch requires assembler-local"
178 Target.getSymA()->getSymbol().getName() +
183 // 14-bit branch relocations should only target internal labels, and so
184 // should never get here.
185 if (Kind == AArch64::fixup_aarch64_pcrel_branch14) {
186 Asm.getContext().FatalError(Fixup.getLoc(),
187 "Invalid relocation on conditional branch!");
191 if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSymA(), Log2Size,
193 Asm.getContext().FatalError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
197 Value = Target.getConstant();
199 if (Target.isAbsolute()) { // constant
200 // FIXME: Should this always be extern?
201 // SymbolNum of 0 indicates the absolute section.
202 Type = MachO::ARM64_RELOC_UNSIGNED;
205 Asm.getContext().FatalError(Fixup.getLoc(),
206 "PC relative absolute relocation!");
208 // FIXME: x86_64 sets the type to a branch reloc here. Should we do
209 // something similar?
211 } else if (Target.getSymB()) { // A - B + constant
212 const MCSymbol *A = &Target.getSymA()->getSymbol();
213 const MCSymbolData &A_SD = Asm.getSymbolData(*A);
214 const MCSymbolData *A_Base = Asm.getAtom(&A_SD);
216 const MCSymbol *B = &Target.getSymB()->getSymbol();
217 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
218 const MCSymbolData *B_Base = Asm.getAtom(&B_SD);
220 // Check for "_foo@got - .", which comes through here as:
222 // ... _foo@got - Ltmp0
223 if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_GOT &&
224 Target.getSymB()->getKind() == MCSymbolRefExpr::VK_None &&
225 Layout.getSymbolOffset(&B_SD) ==
226 Layout.getFragmentOffset(Fragment) + Fixup.getOffset()) {
227 // SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
228 Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
230 MachO::any_relocation_info MRE;
231 MRE.r_word0 = FixupOffset;
232 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
233 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
235 } else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
236 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
237 // Otherwise, neither symbol can be modified.
238 Asm.getContext().FatalError(Fixup.getLoc(),
239 "unsupported relocation of modified symbol");
241 // We don't support PCrel relocations of differences.
243 Asm.getContext().FatalError(Fixup.getLoc(),
244 "unsupported pc-relative relocation of "
247 // AArch64 always uses external relocations. If there is no symbol to use as
248 // a base address (a local symbol with no preceding non-local symbol),
251 // FIXME: We should probably just synthesize an external symbol and use
254 Asm.getContext().FatalError(
256 "unsupported relocation of local symbol '" + A->getName() +
257 "'. Must have non-local symbol earlier in section.");
259 Asm.getContext().FatalError(
261 "unsupported relocation of local symbol '" + B->getName() +
262 "'. Must have non-local symbol earlier in section.");
264 if (A_Base == B_Base && A_Base)
265 Asm.getContext().FatalError(Fixup.getLoc(),
266 "unsupported relocation with identical base");
268 Value += (!A_SD.getFragment() ? 0
269 : Writer->getSymbolAddress(&A_SD, Layout)) -
270 (!A_Base || !A_Base->getFragment()
272 : Writer->getSymbolAddress(A_Base, Layout));
273 Value -= (!B_SD.getFragment() ? 0
274 : Writer->getSymbolAddress(&B_SD, Layout)) -
275 (!B_Base || !B_Base->getFragment()
277 : Writer->getSymbolAddress(B_Base, Layout));
279 Type = MachO::ARM64_RELOC_UNSIGNED;
281 MachO::any_relocation_info MRE;
282 MRE.r_word0 = FixupOffset;
283 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
284 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
287 Type = MachO::ARM64_RELOC_SUBTRACTOR;
288 } else { // A + constant
289 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
290 const MCSectionMachO &Section = static_cast<const MCSectionMachO &>(
291 Fragment->getParent()->getSection());
293 bool CanUseLocalRelocation =
294 canUseLocalRelocation(Section, *Symbol, Log2Size);
295 if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
296 const MCSection &Sec = Symbol->getSection();
297 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
298 Asm.addLocalUsedInReloc(*Symbol);
301 const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
302 const MCSymbolData *Base = Asm.getAtom(&SD);
304 // If the symbol is a variable and we weren't able to get a Base for it
305 // (i.e., it's not in the symbol table associated with a section) resolve
306 // the relocation based its expansion instead.
307 if (Symbol->isVariable() && !Base) {
308 // If the evaluation is an absolute value, just use that directly
309 // to keep things easy.
311 if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
312 Res, Layout, Writer->getSectionAddressMap())) {
317 // FIXME: Will the Target we already have ever have any data in it
318 // we need to preserve and merge with the new Target? How about
320 if (!Symbol->getVariableValue()->EvaluateAsRelocatable(Target, &Layout,
322 Asm.getContext().FatalError(Fixup.getLoc(),
323 "unable to resolve variable '" +
324 Symbol->getName() + "'");
325 return RecordRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
329 // Relocations inside debug sections always use local relocations when
330 // possible. This seems to be done because the debugger doesn't fully
331 // understand relocation entries and expects to find values that
332 // have already been fixed up.
333 if (Symbol->isInSection()) {
334 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
338 // AArch64 uses external relocations as much as possible. For debug
339 // sections, and for pointer-sized relocations (.quad), we allow section
340 // relocations. It's code sections that run into trouble.
344 // Add the local offset, if needed.
346 Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base);
347 } else if (Symbol->isInSection()) {
348 if (!CanUseLocalRelocation)
349 Asm.getContext().FatalError(
351 "unsupported relocation of local symbol '" + Symbol->getName() +
352 "'. Must have non-local symbol earlier in section.");
353 // Adjust the relocation to be section-relative.
354 // The index is the section ordinal (1-based).
355 const MCSectionData &SymSD =
356 Asm.getSectionData(SD.getSymbol().getSection());
357 Index = SymSD.getOrdinal() + 1;
358 Value += Writer->getSymbolAddress(&SD, Layout);
361 Value -= Writer->getFragmentAddress(Fragment, Layout) +
362 Fixup.getOffset() + (1ULL << Log2Size);
364 // Resolve constant variables.
365 if (SD.getSymbol().isVariable()) {
367 if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
368 Res, Layout, Writer->getSectionAddressMap())) {
373 Asm.getContext().FatalError(Fixup.getLoc(),
374 "unsupported relocation of variable '" +
375 Symbol->getName() + "'");
379 // If the relocation kind is Branch26, Page21, or Pageoff12, any addend
380 // is represented via an Addend relocation, not encoded directly into
382 if ((Type == MachO::ARM64_RELOC_BRANCH26 ||
383 Type == MachO::ARM64_RELOC_PAGE21 ||
384 Type == MachO::ARM64_RELOC_PAGEOFF12) &&
386 assert((Value & 0xff000000) == 0 && "Added relocation out of range!");
388 MachO::any_relocation_info MRE;
389 MRE.r_word0 = FixupOffset;
391 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
392 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
394 // Now set up the Addend relocation.
395 Type = MachO::ARM64_RELOC_ADDEND;
401 // Put zero into the instruction itself. The addend is in the relocation.
405 // If there's any addend left to handle, encode it in the instruction.
408 // struct relocation_info (8 bytes)
409 MachO::any_relocation_info MRE;
410 MRE.r_word0 = FixupOffset;
412 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
413 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
416 MCObjectWriter *llvm::createAArch64MachObjectWriter(raw_pwrite_stream &OS,
418 uint32_t CPUSubtype) {
419 return createMachObjectWriter(
420 new AArch64MachObjectWriter(CPUType, CPUSubtype), OS,
421 /*IsLittleEndian=*/true);