1 //===-- ARMMachObjectWriter.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/ARMMCTargetDesc.h"
11 #include "MCTargetDesc/ARMBaseInfo.h"
12 #include "MCTargetDesc/ARMFixupKinds.h"
13 #include "llvm/ADT/Twine.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/MCFixupKindInfo.h"
20 #include "llvm/MC/MCMachOSymbolFlags.h"
21 #include "llvm/MC/MCMachObjectWriter.h"
22 #include "llvm/MC/MCValue.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/MachO.h"
28 class ARMMachObjectWriter : public MCMachObjectTargetWriter {
29 void RecordARMScatteredRelocation(MachObjectWriter *Writer,
30 const MCAssembler &Asm,
31 const MCAsmLayout &Layout,
32 const MCFragment *Fragment,
37 uint64_t &FixedValue);
38 void RecordARMScatteredHalfRelocation(MachObjectWriter *Writer,
39 const MCAssembler &Asm,
40 const MCAsmLayout &Layout,
41 const MCFragment *Fragment,
42 const MCFixup &Fixup, MCValue Target,
43 uint64_t &FixedValue);
45 bool requiresExternRelocation(MachObjectWriter *Writer,
46 const MCAssembler &Asm,
47 const MCFragment &Fragment,
48 unsigned RelocType, const MCSymbolData *SD,
52 ARMMachObjectWriter(bool Is64Bit, uint32_t CPUType,
54 : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype,
55 /*UseAggressiveSymbolFolding=*/true) {}
57 void RecordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
58 const MCAsmLayout &Layout, const MCFragment *Fragment,
59 const MCFixup &Fixup, MCValue Target,
60 uint64_t &FixedValue) override;
64 static bool getARMFixupKindMachOInfo(unsigned Kind, unsigned &RelocType,
66 RelocType = unsigned(MachO::ARM_RELOC_VANILLA);
74 Log2Size = llvm::Log2_32(1);
77 Log2Size = llvm::Log2_32(2);
80 Log2Size = llvm::Log2_32(4);
83 Log2Size = llvm::Log2_32(8);
86 // These fixups are expected to always be resolvable at assembly time and
87 // have no relocations supported.
88 case ARM::fixup_arm_ldst_pcrel_12:
89 case ARM::fixup_arm_pcrel_10:
90 case ARM::fixup_arm_adr_pcrel_12:
91 case ARM::fixup_arm_thumb_br:
94 // Handle 24-bit branch kinds.
95 case ARM::fixup_arm_condbranch:
96 case ARM::fixup_arm_uncondbranch:
97 case ARM::fixup_arm_uncondbl:
98 case ARM::fixup_arm_condbl:
99 case ARM::fixup_arm_blx:
100 RelocType = unsigned(MachO::ARM_RELOC_BR24);
101 // Report as 'long', even though that is not quite accurate.
102 Log2Size = llvm::Log2_32(4);
105 case ARM::fixup_t2_uncondbranch:
106 case ARM::fixup_arm_thumb_bl:
107 case ARM::fixup_arm_thumb_blx:
108 RelocType = unsigned(MachO::ARM_THUMB_RELOC_BR22);
109 Log2Size = llvm::Log2_32(4);
112 // For movw/movt r_type relocations they always have a pair following them and
113 // the r_length bits are used differently. The encoding of the r_length is as
115 // low bit of r_length:
116 // 0 - :lower16: for movw instructions
117 // 1 - :upper16: for movt instructions
118 // high bit of r_length:
119 // 0 - arm instructions
120 // 1 - thumb instructions
121 case ARM::fixup_arm_movt_hi16:
122 RelocType = unsigned(MachO::ARM_RELOC_HALF);
125 case ARM::fixup_t2_movt_hi16:
126 RelocType = unsigned(MachO::ARM_RELOC_HALF);
130 case ARM::fixup_arm_movw_lo16:
131 RelocType = unsigned(MachO::ARM_RELOC_HALF);
134 case ARM::fixup_t2_movw_lo16:
135 RelocType = unsigned(MachO::ARM_RELOC_HALF);
141 void ARMMachObjectWriter::
142 RecordARMScatteredHalfRelocation(MachObjectWriter *Writer,
143 const MCAssembler &Asm,
144 const MCAsmLayout &Layout,
145 const MCFragment *Fragment,
146 const MCFixup &Fixup,
148 uint64_t &FixedValue) {
149 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
150 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
151 unsigned Type = MachO::ARM_RELOC_HALF;
154 const MCSymbol *A = &Target.getSymA()->getSymbol();
155 const MCSymbolData *A_SD = &Asm.getSymbolData(*A);
157 if (!A_SD->getFragment())
158 Asm.getContext().FatalError(Fixup.getLoc(),
159 "symbol '" + A->getName() +
160 "' can not be undefined in a subtraction expression");
162 uint32_t Value = Writer->getSymbolAddress(A_SD, Layout);
165 Writer->getSectionAddress(A_SD->getFragment()->getParent());
166 FixedValue += SecAddr;
168 if (const MCSymbolRefExpr *B = Target.getSymB()) {
169 const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
171 if (!B_SD->getFragment())
172 Asm.getContext().FatalError(Fixup.getLoc(),
173 "symbol '" + B->getSymbol().getName() +
174 "' can not be undefined in a subtraction expression");
176 // Select the appropriate difference relocation type.
177 Type = MachO::ARM_RELOC_HALF_SECTDIFF;
178 Value2 = Writer->getSymbolAddress(B_SD, Layout);
179 FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent());
182 // Relocations are written out in reverse order, so the PAIR comes first.
183 // ARM_RELOC_HALF and ARM_RELOC_HALF_SECTDIFF abuse the r_length field:
185 // For these two r_type relocations they always have a pair following them and
186 // the r_length bits are used differently. The encoding of the r_length is as
188 // low bit of r_length:
189 // 0 - :lower16: for movw instructions
190 // 1 - :upper16: for movt instructions
191 // high bit of r_length:
192 // 0 - arm instructions
193 // 1 - thumb instructions
194 // the other half of the relocated expression is in the following pair
195 // relocation entry in the low 16 bits of r_address field.
196 unsigned ThumbBit = 0;
197 unsigned MovtBit = 0;
198 switch ((unsigned)Fixup.getKind()) {
200 case ARM::fixup_arm_movt_hi16:
202 // The thumb bit shouldn't be set in the 'other-half' bit of the
203 // relocation, but it will be set in FixedValue if the base symbol
204 // is a thumb function. Clear it out here.
205 if (Asm.isThumbFunc(A))
206 FixedValue &= 0xfffffffe;
208 case ARM::fixup_t2_movt_hi16:
209 if (Asm.isThumbFunc(A))
210 FixedValue &= 0xfffffffe;
213 case ARM::fixup_t2_movw_lo16:
218 if (Type == MachO::ARM_RELOC_HALF_SECTDIFF) {
219 uint32_t OtherHalf = MovtBit
220 ? (FixedValue & 0xffff) : ((FixedValue & 0xffff0000) >> 16);
222 MachO::any_relocation_info MRE;
223 MRE.r_word0 = ((OtherHalf << 0) |
224 (MachO::ARM_RELOC_PAIR << 24) |
229 MRE.r_word1 = Value2;
230 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
233 MachO::any_relocation_info MRE;
234 MRE.r_word0 = ((FixupOffset << 0) |
241 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
244 void ARMMachObjectWriter::RecordARMScatteredRelocation(MachObjectWriter *Writer,
245 const MCAssembler &Asm,
246 const MCAsmLayout &Layout,
247 const MCFragment *Fragment,
248 const MCFixup &Fixup,
252 uint64_t &FixedValue) {
253 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
254 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
257 const MCSymbol *A = &Target.getSymA()->getSymbol();
258 const MCSymbolData *A_SD = &Asm.getSymbolData(*A);
260 if (!A_SD->getFragment())
261 Asm.getContext().FatalError(Fixup.getLoc(),
262 "symbol '" + A->getName() +
263 "' can not be undefined in a subtraction expression");
265 uint32_t Value = Writer->getSymbolAddress(A_SD, Layout);
266 uint64_t SecAddr = Writer->getSectionAddress(A_SD->getFragment()->getParent());
267 FixedValue += SecAddr;
270 if (const MCSymbolRefExpr *B = Target.getSymB()) {
271 assert(Type == MachO::ARM_RELOC_VANILLA && "invalid reloc for 2 symbols");
272 const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
274 if (!B_SD->getFragment())
275 Asm.getContext().FatalError(Fixup.getLoc(),
276 "symbol '" + B->getSymbol().getName() +
277 "' can not be undefined in a subtraction expression");
279 // Select the appropriate difference relocation type.
280 Type = MachO::ARM_RELOC_SECTDIFF;
281 Value2 = Writer->getSymbolAddress(B_SD, Layout);
282 FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent());
285 // Relocations are written out in reverse order, so the PAIR comes first.
286 if (Type == MachO::ARM_RELOC_SECTDIFF ||
287 Type == MachO::ARM_RELOC_LOCAL_SECTDIFF) {
288 MachO::any_relocation_info MRE;
289 MRE.r_word0 = ((0 << 0) |
290 (MachO::ARM_RELOC_PAIR << 24) |
294 MRE.r_word1 = Value2;
295 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
298 MachO::any_relocation_info MRE;
299 MRE.r_word0 = ((FixupOffset << 0) |
305 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
308 bool ARMMachObjectWriter::requiresExternRelocation(MachObjectWriter *Writer,
309 const MCAssembler &Asm,
310 const MCFragment &Fragment,
312 const MCSymbolData *SD,
313 uint64_t FixedValue) {
314 // Most cases can be identified purely from the symbol.
315 if (Writer->doesSymbolRequireExternRelocation(SD))
317 int64_t Value = (int64_t)FixedValue; // The displacement is signed.
322 case MachO::ARM_RELOC_BR24:
323 // PC pre-adjustment of 8 for these instructions.
325 // ARM BL/BLX has a 25-bit offset.
328 case MachO::ARM_THUMB_RELOC_BR22:
329 // PC pre-adjustment of 4 for these instructions.
331 // Thumb BL/BLX has a 24-bit offset.
334 // BL/BLX also use external relocations when an internal relocation
335 // would result in the target being out of range. This gives the linker
336 // enough information to generate a branch island.
337 const MCSectionData &SymSD = Asm.getSectionData(
338 SD->getSymbol().getSection());
339 Value += Writer->getSectionAddress(&SymSD);
340 Value -= Writer->getSectionAddress(Fragment.getParent());
341 // If the resultant value would be out of range for an internal relocation,
342 // use an external instead.
343 if (Value > Range || Value < -(Range + 1))
348 void ARMMachObjectWriter::RecordRelocation(MachObjectWriter *Writer,
350 const MCAsmLayout &Layout,
351 const MCFragment *Fragment,
352 const MCFixup &Fixup, MCValue Target,
353 uint64_t &FixedValue) {
354 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
356 unsigned RelocType = MachO::ARM_RELOC_VANILLA;
357 if (!getARMFixupKindMachOInfo(Fixup.getKind(), RelocType, Log2Size))
358 // If we failed to get fixup kind info, it's because there's no legal
359 // relocation type for the fixup kind. This happens when it's a fixup that's
360 // expected to always be resolvable at assembly time and not have any
361 // relocations needed.
362 Asm.getContext().FatalError(Fixup.getLoc(),
363 "unsupported relocation on symbol");
365 // If this is a difference or a defined symbol plus an offset, then we need a
366 // scattered relocation entry. Differences always require scattered
368 if (Target.getSymB()) {
369 if (RelocType == MachO::ARM_RELOC_HALF)
370 return RecordARMScatteredHalfRelocation(Writer, Asm, Layout, Fragment,
371 Fixup, Target, FixedValue);
372 return RecordARMScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
373 Target, RelocType, Log2Size,
377 // Get the symbol data, if any.
378 const MCSymbolData *SD = nullptr;
379 if (Target.getSymA())
380 SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
382 // FIXME: For other platforms, we need to use scattered relocations for
383 // internal relocations with offsets. If this is an internal relocation with
384 // an offset, it also needs a scattered relocation entry.
386 // Is this right for ARM?
387 uint32_t Offset = Target.getConstant();
388 if (IsPCRel && RelocType == MachO::ARM_RELOC_VANILLA)
389 Offset += 1 << Log2Size;
390 if (Offset && SD && !Writer->doesSymbolRequireExternRelocation(SD))
391 return RecordARMScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
392 Target, RelocType, Log2Size,
396 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
399 const MCSymbolData *RelSymbol = nullptr;
401 if (Target.isAbsolute()) { // constant
403 report_fatal_error("FIXME: relocations to absolute targets "
404 "not yet implemented");
406 // Resolve constant variables.
407 if (SD->getSymbol().isVariable()) {
409 if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute(
410 Res, Layout, Writer->getSectionAddressMap())) {
416 // Check whether we need an external or internal relocation.
417 if (requiresExternRelocation(Writer, Asm, *Fragment, RelocType, SD,
421 // For external relocations, make sure to offset the fixup value to
422 // compensate for the addend of the symbol address, if it was
423 // undefined. This occurs with weak definitions, for example.
424 if (!SD->getSymbol().isUndefined())
425 FixedValue -= Layout.getSymbolOffset(SD);
427 // The index is the section ordinal (1-based).
428 const MCSectionData &SymSD = Asm.getSectionData(
429 SD->getSymbol().getSection());
430 Index = SymSD.getOrdinal() + 1;
431 FixedValue += Writer->getSectionAddress(&SymSD);
434 FixedValue -= Writer->getSectionAddress(Fragment->getParent());
436 // The type is determined by the fixup kind.
440 // struct relocation_info (8 bytes)
441 MachO::any_relocation_info MRE;
442 MRE.r_word0 = FixupOffset;
444 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
446 // Even when it's not a scattered relocation, movw/movt always uses
447 // a PAIR relocation.
448 if (Type == MachO::ARM_RELOC_HALF) {
449 // The other-half value only gets populated for the movt and movw
450 // relocation entries.
452 switch ((unsigned)Fixup.getKind()) {
454 case ARM::fixup_arm_movw_lo16:
455 case ARM::fixup_t2_movw_lo16:
456 Value = (FixedValue >> 16) & 0xffff;
458 case ARM::fixup_arm_movt_hi16:
459 case ARM::fixup_t2_movt_hi16:
460 Value = FixedValue & 0xffff;
463 MachO::any_relocation_info MREPair;
464 MREPair.r_word0 = Value;
465 MREPair.r_word1 = ((0xffffff << 0) |
467 (MachO::ARM_RELOC_PAIR << 28));
469 Writer->addRelocation(nullptr, Fragment->getParent(), MREPair);
472 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
475 MCObjectWriter *llvm::createARMMachObjectWriter(raw_ostream &OS, bool Is64Bit,
477 uint32_t CPUSubtype) {
478 return createMachObjectWriter(new ARMMachObjectWriter(Is64Bit,
481 OS, /*IsLittleEndian=*/true);