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/MCSection.h"
23 #include "llvm/MC/MCValue.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/MachO.h"
29 class ARMMachObjectWriter : public MCMachObjectTargetWriter {
30 void RecordARMScatteredRelocation(MachObjectWriter *Writer,
31 const MCAssembler &Asm,
32 const MCAsmLayout &Layout,
33 const MCFragment *Fragment,
38 uint64_t &FixedValue);
39 void RecordARMScatteredHalfRelocation(MachObjectWriter *Writer,
40 const MCAssembler &Asm,
41 const MCAsmLayout &Layout,
42 const MCFragment *Fragment,
43 const MCFixup &Fixup, MCValue Target,
44 uint64_t &FixedValue);
46 bool requiresExternRelocation(MachObjectWriter *Writer,
47 const MCAssembler &Asm,
48 const MCFragment &Fragment, unsigned RelocType,
49 const MCSymbol &S, uint64_t FixedValue);
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();
156 if (!A->getFragment())
157 Asm.getContext().reportFatalError(Fixup.getLoc(),
158 "symbol '" + A->getName() +
159 "' can not be undefined in a subtraction expression");
161 uint32_t Value = Writer->getSymbolAddress(*A, Layout);
163 uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent());
164 FixedValue += SecAddr;
166 if (const MCSymbolRefExpr *B = Target.getSymB()) {
167 const MCSymbol *SB = &B->getSymbol();
169 if (!SB->getFragment())
170 Asm.getContext().reportFatalError(Fixup.getLoc(),
171 "symbol '" + B->getSymbol().getName() +
172 "' can not be undefined in a subtraction expression");
174 // Select the appropriate difference relocation type.
175 Type = MachO::ARM_RELOC_HALF_SECTDIFF;
176 Value2 = Writer->getSymbolAddress(B->getSymbol(), Layout);
177 FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent());
180 // Relocations are written out in reverse order, so the PAIR comes first.
181 // ARM_RELOC_HALF and ARM_RELOC_HALF_SECTDIFF abuse the r_length field:
183 // For these two r_type relocations they always have a pair following them and
184 // the r_length bits are used differently. The encoding of the r_length is as
186 // low bit of r_length:
187 // 0 - :lower16: for movw instructions
188 // 1 - :upper16: for movt instructions
189 // high bit of r_length:
190 // 0 - arm instructions
191 // 1 - thumb instructions
192 // the other half of the relocated expression is in the following pair
193 // relocation entry in the low 16 bits of r_address field.
194 unsigned ThumbBit = 0;
195 unsigned MovtBit = 0;
196 switch ((unsigned)Fixup.getKind()) {
198 case ARM::fixup_arm_movt_hi16:
200 // The thumb bit shouldn't be set in the 'other-half' bit of the
201 // relocation, but it will be set in FixedValue if the base symbol
202 // is a thumb function. Clear it out here.
203 if (Asm.isThumbFunc(A))
204 FixedValue &= 0xfffffffe;
206 case ARM::fixup_t2_movt_hi16:
207 if (Asm.isThumbFunc(A))
208 FixedValue &= 0xfffffffe;
211 case ARM::fixup_t2_movw_lo16:
216 if (Type == MachO::ARM_RELOC_HALF_SECTDIFF) {
217 uint32_t OtherHalf = MovtBit
218 ? (FixedValue & 0xffff) : ((FixedValue & 0xffff0000) >> 16);
220 MachO::any_relocation_info MRE;
221 MRE.r_word0 = ((OtherHalf << 0) |
222 (MachO::ARM_RELOC_PAIR << 24) |
227 MRE.r_word1 = Value2;
228 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
231 MachO::any_relocation_info MRE;
232 MRE.r_word0 = ((FixupOffset << 0) |
239 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
242 void ARMMachObjectWriter::RecordARMScatteredRelocation(MachObjectWriter *Writer,
243 const MCAssembler &Asm,
244 const MCAsmLayout &Layout,
245 const MCFragment *Fragment,
246 const MCFixup &Fixup,
250 uint64_t &FixedValue) {
251 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
252 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
255 const MCSymbol *A = &Target.getSymA()->getSymbol();
257 if (!A->getFragment())
258 Asm.getContext().reportFatalError(Fixup.getLoc(),
259 "symbol '" + A->getName() +
260 "' can not be undefined in a subtraction expression");
262 uint32_t Value = Writer->getSymbolAddress(*A, Layout);
263 uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent());
264 FixedValue += SecAddr;
267 if (const MCSymbolRefExpr *B = Target.getSymB()) {
268 assert(Type == MachO::ARM_RELOC_VANILLA && "invalid reloc for 2 symbols");
269 const MCSymbol *SB = &B->getSymbol();
271 if (!SB->getFragment())
272 Asm.getContext().reportFatalError(Fixup.getLoc(),
273 "symbol '" + B->getSymbol().getName() +
274 "' can not be undefined in a subtraction expression");
276 // Select the appropriate difference relocation type.
277 Type = MachO::ARM_RELOC_SECTDIFF;
278 Value2 = Writer->getSymbolAddress(B->getSymbol(), Layout);
279 FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent());
282 // Relocations are written out in reverse order, so the PAIR comes first.
283 if (Type == MachO::ARM_RELOC_SECTDIFF ||
284 Type == MachO::ARM_RELOC_LOCAL_SECTDIFF) {
285 MachO::any_relocation_info MRE;
286 MRE.r_word0 = ((0 << 0) |
287 (MachO::ARM_RELOC_PAIR << 24) |
291 MRE.r_word1 = Value2;
292 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
295 MachO::any_relocation_info MRE;
296 MRE.r_word0 = ((FixupOffset << 0) |
302 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
305 bool ARMMachObjectWriter::requiresExternRelocation(MachObjectWriter *Writer,
306 const MCAssembler &Asm,
307 const MCFragment &Fragment,
310 uint64_t FixedValue) {
311 // Most cases can be identified purely from the symbol.
312 if (Writer->doesSymbolRequireExternRelocation(S))
314 int64_t Value = (int64_t)FixedValue; // The displacement is signed.
319 case MachO::ARM_RELOC_BR24:
320 // PC pre-adjustment of 8 for these instructions.
322 // ARM BL/BLX has a 25-bit offset.
325 case MachO::ARM_THUMB_RELOC_BR22:
326 // PC pre-adjustment of 4 for these instructions.
328 // Thumb BL/BLX has a 24-bit offset.
331 // BL/BLX also use external relocations when an internal relocation
332 // would result in the target being out of range. This gives the linker
333 // enough information to generate a branch island.
334 Value += Writer->getSectionAddress(&S.getSection());
335 Value -= Writer->getSectionAddress(Fragment.getParent());
336 // If the resultant value would be out of range for an internal relocation,
337 // use an external instead.
338 if (Value > Range || Value < -(Range + 1))
343 void ARMMachObjectWriter::RecordRelocation(MachObjectWriter *Writer,
345 const MCAsmLayout &Layout,
346 const MCFragment *Fragment,
347 const MCFixup &Fixup, MCValue Target,
348 uint64_t &FixedValue) {
349 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
351 unsigned RelocType = MachO::ARM_RELOC_VANILLA;
352 if (!getARMFixupKindMachOInfo(Fixup.getKind(), RelocType, Log2Size))
353 // If we failed to get fixup kind info, it's because there's no legal
354 // relocation type for the fixup kind. This happens when it's a fixup that's
355 // expected to always be resolvable at assembly time and not have any
356 // relocations needed.
357 Asm.getContext().reportFatalError(Fixup.getLoc(),
358 "unsupported relocation on symbol");
360 // If this is a difference or a defined symbol plus an offset, then we need a
361 // scattered relocation entry. Differences always require scattered
363 if (Target.getSymB()) {
364 if (RelocType == MachO::ARM_RELOC_HALF)
365 return RecordARMScatteredHalfRelocation(Writer, Asm, Layout, Fragment,
366 Fixup, Target, FixedValue);
367 return RecordARMScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
368 Target, RelocType, Log2Size,
372 // Get the symbol data, if any.
373 const MCSymbol *A = nullptr;
374 if (Target.getSymA())
375 A = &Target.getSymA()->getSymbol();
377 // FIXME: For other platforms, we need to use scattered relocations for
378 // internal relocations with offsets. If this is an internal relocation with
379 // an offset, it also needs a scattered relocation entry.
381 // Is this right for ARM?
382 uint32_t Offset = Target.getConstant();
383 if (IsPCRel && RelocType == MachO::ARM_RELOC_VANILLA)
384 Offset += 1 << Log2Size;
385 if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A))
386 return RecordARMScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
387 Target, RelocType, Log2Size,
391 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
394 const MCSymbol *RelSymbol = nullptr;
396 if (Target.isAbsolute()) { // constant
398 report_fatal_error("FIXME: relocations to absolute targets "
399 "not yet implemented");
401 // Resolve constant variables.
402 if (A->isVariable()) {
404 if (A->getVariableValue()->EvaluateAsAbsolute(
405 Res, Layout, Writer->getSectionAddressMap())) {
411 // Check whether we need an external or internal relocation.
412 if (requiresExternRelocation(Writer, Asm, *Fragment, RelocType, *A,
416 // For external relocations, make sure to offset the fixup value to
417 // compensate for the addend of the symbol address, if it was
418 // undefined. This occurs with weak definitions, for example.
419 if (!A->isUndefined())
420 FixedValue -= Layout.getSymbolOffset(*A);
422 // The index is the section ordinal (1-based).
423 const MCSection &Sec = A->getSection();
424 Index = Sec.getOrdinal() + 1;
425 FixedValue += Writer->getSectionAddress(&Sec);
428 FixedValue -= Writer->getSectionAddress(Fragment->getParent());
430 // The type is determined by the fixup kind.
434 // struct relocation_info (8 bytes)
435 MachO::any_relocation_info MRE;
436 MRE.r_word0 = FixupOffset;
438 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
440 // Even when it's not a scattered relocation, movw/movt always uses
441 // a PAIR relocation.
442 if (Type == MachO::ARM_RELOC_HALF) {
443 // The other-half value only gets populated for the movt and movw
444 // relocation entries.
446 switch ((unsigned)Fixup.getKind()) {
448 case ARM::fixup_arm_movw_lo16:
449 case ARM::fixup_t2_movw_lo16:
450 Value = (FixedValue >> 16) & 0xffff;
452 case ARM::fixup_arm_movt_hi16:
453 case ARM::fixup_t2_movt_hi16:
454 Value = FixedValue & 0xffff;
457 MachO::any_relocation_info MREPair;
458 MREPair.r_word0 = Value;
459 MREPair.r_word1 = ((0xffffff << 0) |
461 (MachO::ARM_RELOC_PAIR << 28));
463 Writer->addRelocation(nullptr, Fragment->getParent(), MREPair);
466 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
469 MCObjectWriter *llvm::createARMMachObjectWriter(raw_pwrite_stream &OS,
470 bool Is64Bit, uint32_t CPUType,
471 uint32_t CPUSubtype) {
472 return createMachObjectWriter(new ARMMachObjectWriter(Is64Bit,
475 OS, /*IsLittleEndian=*/true);