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 MCSymbol *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 MCSymbol *A_Base = Asm.getAtom(&A_SD);
216 const MCSymbol *B = &Target.getSymB()->getSymbol();
217 const MCSymbolData &B_SD = Asm.getSymbolData(*B);
218 const MCSymbol *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 ? &A_Base->getData() : nullptr,
234 Fragment->getParent(), MRE);
236 } else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
237 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
238 // Otherwise, neither symbol can be modified.
239 Asm.getContext().FatalError(Fixup.getLoc(),
240 "unsupported relocation of modified symbol");
242 // We don't support PCrel relocations of differences.
244 Asm.getContext().FatalError(Fixup.getLoc(),
245 "unsupported pc-relative relocation of "
248 // AArch64 always uses external relocations. If there is no symbol to use as
249 // a base address (a local symbol with no preceding non-local symbol),
252 // FIXME: We should probably just synthesize an external symbol and use
255 Asm.getContext().FatalError(
257 "unsupported relocation of local symbol '" + A->getName() +
258 "'. Must have non-local symbol earlier in section.");
260 Asm.getContext().FatalError(
262 "unsupported relocation of local symbol '" + B->getName() +
263 "'. Must have non-local symbol earlier in section.");
265 if (A_Base == B_Base && A_Base)
266 Asm.getContext().FatalError(Fixup.getLoc(),
267 "unsupported relocation with identical base");
270 (!A_SD.getFragment() ? 0 : Writer->getSymbolAddress(&A_SD, Layout)) -
271 (!A_Base || !A_Base->getData().getFragment()
273 : Writer->getSymbolAddress(&A_Base->getData(), Layout));
275 (!B_SD.getFragment() ? 0 : Writer->getSymbolAddress(&B_SD, Layout)) -
276 (!B_Base || !B_Base->getData().getFragment()
278 : Writer->getSymbolAddress(&B_Base->getData(), Layout));
280 Type = MachO::ARM64_RELOC_UNSIGNED;
282 MachO::any_relocation_info MRE;
283 MRE.r_word0 = FixupOffset;
284 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
285 Writer->addRelocation(A_Base ? &A_Base->getData() : nullptr,
286 Fragment->getParent(), MRE);
289 Type = MachO::ARM64_RELOC_SUBTRACTOR;
290 } else { // A + constant
291 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
292 const MCSectionMachO &Section = static_cast<const MCSectionMachO &>(
293 Fragment->getParent()->getSection());
295 bool CanUseLocalRelocation =
296 canUseLocalRelocation(Section, *Symbol, Log2Size);
297 if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
298 const MCSection &Sec = Symbol->getSection();
299 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
300 Asm.addLocalUsedInReloc(*Symbol);
303 const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
304 const MCSymbol *Base = Asm.getAtom(&SD);
306 // If the symbol is a variable and we weren't able to get a Base for it
307 // (i.e., it's not in the symbol table associated with a section) resolve
308 // the relocation based its expansion instead.
309 if (Symbol->isVariable() && !Base) {
310 // If the evaluation is an absolute value, just use that directly
311 // to keep things easy.
313 if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
314 Res, Layout, Writer->getSectionAddressMap())) {
319 // FIXME: Will the Target we already have ever have any data in it
320 // we need to preserve and merge with the new Target? How about
322 if (!Symbol->getVariableValue()->EvaluateAsRelocatable(Target, &Layout,
324 Asm.getContext().FatalError(Fixup.getLoc(),
325 "unable to resolve variable '" +
326 Symbol->getName() + "'");
327 return RecordRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
331 // Relocations inside debug sections always use local relocations when
332 // possible. This seems to be done because the debugger doesn't fully
333 // understand relocation entries and expects to find values that
334 // have already been fixed up.
335 if (Symbol->isInSection()) {
336 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
340 // AArch64 uses external relocations as much as possible. For debug
341 // sections, and for pointer-sized relocations (.quad), we allow section
342 // relocations. It's code sections that run into trouble.
346 // Add the local offset, if needed.
347 if (&Base->getData() != &SD)
348 Value += Layout.getSymbolOffset(&SD) -
349 Layout.getSymbolOffset(&Base->getData());
350 } else if (Symbol->isInSection()) {
351 if (!CanUseLocalRelocation)
352 Asm.getContext().FatalError(
354 "unsupported relocation of local symbol '" + Symbol->getName() +
355 "'. Must have non-local symbol earlier in section.");
356 // Adjust the relocation to be section-relative.
357 // The index is the section ordinal (1-based).
358 const MCSectionData &SymSD =
359 Asm.getSectionData(SD.getSymbol().getSection());
360 Index = SymSD.getOrdinal() + 1;
361 Value += Writer->getSymbolAddress(&SD, Layout);
364 Value -= Writer->getFragmentAddress(Fragment, Layout) +
365 Fixup.getOffset() + (1ULL << Log2Size);
367 // Resolve constant variables.
368 if (SD.getSymbol().isVariable()) {
370 if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
371 Res, Layout, Writer->getSectionAddressMap())) {
376 Asm.getContext().FatalError(Fixup.getLoc(),
377 "unsupported relocation of variable '" +
378 Symbol->getName() + "'");
382 // If the relocation kind is Branch26, Page21, or Pageoff12, any addend
383 // is represented via an Addend relocation, not encoded directly into
385 if ((Type == MachO::ARM64_RELOC_BRANCH26 ||
386 Type == MachO::ARM64_RELOC_PAGE21 ||
387 Type == MachO::ARM64_RELOC_PAGEOFF12) &&
389 assert((Value & 0xff000000) == 0 && "Added relocation out of range!");
391 MachO::any_relocation_info MRE;
392 MRE.r_word0 = FixupOffset;
394 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
395 Writer->addRelocation(RelSymbol ? &RelSymbol->getData() : nullptr,
396 Fragment->getParent(), MRE);
398 // Now set up the Addend relocation.
399 Type = MachO::ARM64_RELOC_ADDEND;
405 // Put zero into the instruction itself. The addend is in the relocation.
409 // If there's any addend left to handle, encode it in the instruction.
412 // struct relocation_info (8 bytes)
413 MachO::any_relocation_info MRE;
414 MRE.r_word0 = FixupOffset;
416 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
417 Writer->addRelocation(RelSymbol ? &RelSymbol->getData() : nullptr,
418 Fragment->getParent(), MRE);
421 MCObjectWriter *llvm::createAArch64MachObjectWriter(raw_pwrite_stream &OS,
423 uint32_t CPUSubtype) {
424 return createMachObjectWriter(
425 new AArch64MachObjectWriter(CPUType, CPUSubtype), OS,
426 /*IsLittleEndian=*/true);