Bug Summary

File:lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
Location:line 561, column 9
Description:Called C++ object pointer is null

Annotated Source Code

1//===-- X86MachObjectWriter.cpp - X86 Mach-O Writer -----------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "MCTargetDesc/X86MCTargetDesc.h"
11#include "MCTargetDesc/X86FixupKinds.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/MCMachObjectWriter.h"
18#include "llvm/MC/MCSectionMachO.h"
19#include "llvm/MC/MCValue.h"
20#include "llvm/Support/ErrorHandling.h"
21#include "llvm/Support/Format.h"
22#include "llvm/Support/MachO.h"
23
24using namespace llvm;
25
26namespace {
27class X86MachObjectWriter : public MCMachObjectTargetWriter {
28 bool recordScatteredRelocation(MachObjectWriter *Writer,
29 const MCAssembler &Asm,
30 const MCAsmLayout &Layout,
31 const MCFragment *Fragment,
32 const MCFixup &Fixup,
33 MCValue Target,
34 unsigned Log2Size,
35 uint64_t &FixedValue);
36 void recordTLVPRelocation(MachObjectWriter *Writer,
37 const MCAssembler &Asm,
38 const MCAsmLayout &Layout,
39 const MCFragment *Fragment,
40 const MCFixup &Fixup,
41 MCValue Target,
42 uint64_t &FixedValue);
43
44 void RecordX86Relocation(MachObjectWriter *Writer,
45 const MCAssembler &Asm,
46 const MCAsmLayout &Layout,
47 const MCFragment *Fragment,
48 const MCFixup &Fixup,
49 MCValue Target,
50 uint64_t &FixedValue);
51 void RecordX86_64Relocation(MachObjectWriter *Writer, MCAssembler &Asm,
52 const MCAsmLayout &Layout,
53 const MCFragment *Fragment, const MCFixup &Fixup,
54 MCValue Target, uint64_t &FixedValue);
55
56public:
57 X86MachObjectWriter(bool Is64Bit, uint32_t CPUType, uint32_t CPUSubtype)
58 : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype) {}
59
60 void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
61 const MCAsmLayout &Layout, const MCFragment *Fragment,
62 const MCFixup &Fixup, MCValue Target,
63 uint64_t &FixedValue) override {
64 if (Writer->is64Bit())
65 RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
66 FixedValue);
67 else
68 RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
69 FixedValue);
70 }
71};
72}
73
74static bool isFixupKindRIPRel(unsigned Kind) {
75 return Kind == X86::reloc_riprel_4byte ||
76 Kind == X86::reloc_riprel_4byte_movq_load;
77}
78
79static unsigned getFixupKindLog2Size(unsigned Kind) {
80 switch (Kind) {
81 default:
82 llvm_unreachable("invalid fixup kind!")::llvm::llvm_unreachable_internal("invalid fixup kind!", "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn257205/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp"
, 82);
83 case FK_PCRel_1:
84 case FK_Data_1: return 0;
85 case FK_PCRel_2:
86 case FK_Data_2: return 1;
87 case FK_PCRel_4:
88 // FIXME: Remove these!!!
89 case X86::reloc_riprel_4byte:
90 case X86::reloc_riprel_4byte_movq_load:
91 case X86::reloc_signed_4byte:
92 case FK_Data_4: return 2;
93 case FK_Data_8: return 3;
94 }
95}
96
97void X86MachObjectWriter::RecordX86_64Relocation(
98 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
99 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
100 uint64_t &FixedValue) {
101 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
102 unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind());
103 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
104
105 // See <reloc.h>.
106 uint32_t FixupOffset =
107 Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
108 uint32_t FixupAddress =
109 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
110 int64_t Value = 0;
111 unsigned Index = 0;
112 unsigned IsExtern = 0;
113 unsigned Type = 0;
114 const MCSymbol *RelSymbol = nullptr;
115
116 Value = Target.getConstant();
117
118 if (IsPCRel) {
119 // Compensate for the relocation offset, Darwin x86_64 relocations only have
120 // the addend and appear to have attempted to define it to be the actual
121 // expression addend without the PCrel bias. However, instructions with data
122 // following the relocation are not accommodated for (see comment below
123 // regarding SIGNED{1,2,4}), so it isn't exactly that either.
124 Value += 1LL << Log2Size;
125 }
126
127 if (Target.isAbsolute()) { // constant
128 // SymbolNum of 0 indicates the absolute section.
129 Type = MachO::X86_64_RELOC_UNSIGNED;
130
131 // FIXME: I believe this is broken, I don't think the linker can understand
132 // it. I think it would require a local relocation, but I'm not sure if that
133 // would work either. The official way to get an absolute PCrel relocation
134 // is to use an absolute symbol (which we don't support yet).
135 if (IsPCRel) {
136 IsExtern = 1;
137 Type = MachO::X86_64_RELOC_BRANCH;
138 }
139 } else if (Target.getSymB()) { // A - B + constant
140 const MCSymbol *A = &Target.getSymA()->getSymbol();
141 if (A->isTemporary())
142 A = &Writer->findAliasedSymbol(*A);
143 const MCSymbol *A_Base = Asm.getAtom(*A);
144
145 const MCSymbol *B = &Target.getSymB()->getSymbol();
146 if (B->isTemporary())
147 B = &Writer->findAliasedSymbol(*B);
148 const MCSymbol *B_Base = Asm.getAtom(*B);
149
150 // Neither symbol can be modified.
151 if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
152 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) {
153 Asm.getContext().reportError(Fixup.getLoc(),
154 "unsupported relocation of modified symbol");
155 return;
156 }
157
158 // We don't support PCrel relocations of differences. Darwin 'as' doesn't
159 // implement most of these correctly.
160 if (IsPCRel) {
161 Asm.getContext().reportError(
162 Fixup.getLoc(), "unsupported pc-relative relocation of difference");
163 return;
164 }
165
166 // The support for the situation where one or both of the symbols would
167 // require a local relocation is handled just like if the symbols were
168 // external. This is certainly used in the case of debug sections where the
169 // section has only temporary symbols and thus the symbols don't have base
170 // symbols. This is encoded using the section ordinal and non-extern
171 // relocation entries.
172
173 // Darwin 'as' doesn't emit correct relocations for this (it ends up with a
174 // single SIGNED relocation); reject it for now. Except the case where both
175 // symbols don't have a base, equal but both NULL.
176 if (A_Base == B_Base && A_Base) {
177 Asm.getContext().reportError(
178 Fixup.getLoc(), "unsupported relocation with identical base");
179 return;
180 }
181
182 // A subtraction expression where either symbol is undefined is a
183 // non-relocatable expression.
184 if (A->isUndefined() || B->isUndefined()) {
185 StringRef Name = A->isUndefined() ? A->getName() : B->getName();
186 Asm.getContext().reportError(Fixup.getLoc(),
187 "unsupported relocation with subtraction expression, symbol '" +
188 Name + "' can not be undefined in a subtraction expression");
189 return;
190 }
191
192 Value += Writer->getSymbolAddress(*A, Layout) -
193 (!A_Base ? 0 : Writer->getSymbolAddress(*A_Base, Layout));
194 Value -= Writer->getSymbolAddress(*B, Layout) -
195 (!B_Base ? 0 : Writer->getSymbolAddress(*B_Base, Layout));
196
197 if (!A_Base)
198 Index = A->getFragment()->getParent()->getOrdinal() + 1;
199 Type = MachO::X86_64_RELOC_UNSIGNED;
200
201 MachO::any_relocation_info MRE;
202 MRE.r_word0 = FixupOffset;
203 MRE.r_word1 =
204 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
205 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
206
207 if (B_Base)
208 RelSymbol = B_Base;
209 else
210 Index = B->getFragment()->getParent()->getOrdinal() + 1;
211 Type = MachO::X86_64_RELOC_SUBTRACTOR;
212 } else {
213 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
214 if (Symbol->isTemporary() && Value) {
215 const MCSection &Sec = Symbol->getSection();
216 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
217 Symbol->setUsedInReloc();
218 }
219 RelSymbol = Asm.getAtom(*Symbol);
220
221 // Relocations inside debug sections always use local relocations when
222 // possible. This seems to be done because the debugger doesn't fully
223 // understand x86_64 relocation entries, and expects to find values that
224 // have already been fixed up.
225 if (Symbol->isInSection()) {
226 const MCSectionMachO &Section =
227 static_cast<const MCSectionMachO &>(*Fragment->getParent());
228 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
229 RelSymbol = nullptr;
230 }
231
232 // x86_64 almost always uses external relocations, except when there is no
233 // symbol to use as a base address (a local symbol with no preceding
234 // non-local symbol).
235 if (RelSymbol) {
236 // Add the local offset, if needed.
237 if (RelSymbol != Symbol)
238 Value += Layout.getSymbolOffset(*Symbol) -
239 Layout.getSymbolOffset(*RelSymbol);
240 } else if (Symbol->isInSection() && !Symbol->isVariable()) {
241 // The index is the section ordinal (1-based).
242 Index = Symbol->getFragment()->getParent()->getOrdinal() + 1;
243 Value += Writer->getSymbolAddress(*Symbol, Layout);
244
245 if (IsPCRel)
246 Value -= FixupAddress + (1 << Log2Size);
247 } else if (Symbol->isVariable()) {
248 const MCExpr *Value = Symbol->getVariableValue();
249 int64_t Res;
250 bool isAbs = Value->evaluateAsAbsolute(Res, Layout,
251 Writer->getSectionAddressMap());
252 if (isAbs) {
253 FixedValue = Res;
254 return;
255 } else {
256 Asm.getContext().reportError(Fixup.getLoc(),
257 "unsupported relocation of variable '" +
258 Symbol->getName() + "'");
259 return;
260 }
261 } else {
262 Asm.getContext().reportError(
263 Fixup.getLoc(), "unsupported relocation of undefined symbol '" +
264 Symbol->getName() + "'");
265 return;
266 }
267
268 MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
269 if (IsPCRel) {
270 if (IsRIPRel) {
271 if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
272 // x86_64 distinguishes movq foo@GOTPCREL so that the linker can
273 // rewrite the movq to an leaq at link time if the symbol ends up in
274 // the same linkage unit.
275 if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
276 Type = MachO::X86_64_RELOC_GOT_LOAD;
277 else
278 Type = MachO::X86_64_RELOC_GOT;
279 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
280 Type = MachO::X86_64_RELOC_TLV;
281 } else if (Modifier != MCSymbolRefExpr::VK_None) {
282 Asm.getContext().reportError(
283 Fixup.getLoc(), "unsupported symbol modifier in relocation");
284 return;
285 } else {
286 Type = MachO::X86_64_RELOC_SIGNED;
287
288 // The Darwin x86_64 relocation format has a problem where it cannot
289 // encode an address (L<foo> + <constant>) which is outside the atom
290 // containing L<foo>. Generally, this shouldn't occur but it does
291 // happen when we have a RIPrel instruction with data following the
292 // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
293 // adjustment Darwin x86_64 uses, the offset is still negative and the
294 // linker has no way to recognize this.
295 //
296 // To work around this, Darwin uses several special relocation types
297 // to indicate the offsets. However, the specification or
298 // implementation of these seems to also be incomplete; they should
299 // adjust the addend as well based on the actual encoded instruction
300 // (the additional bias), but instead appear to just look at the final
301 // offset.
302 switch (-(Target.getConstant() + (1LL << Log2Size))) {
303 case 1: Type = MachO::X86_64_RELOC_SIGNED_1; break;
304 case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break;
305 case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break;
306 }
307 }
308 } else {
309 if (Modifier != MCSymbolRefExpr::VK_None) {
310 Asm.getContext().reportError(
311 Fixup.getLoc(),
312 "unsupported symbol modifier in branch relocation");
313 return;
314 }
315
316 Type = MachO::X86_64_RELOC_BRANCH;
317 }
318 } else {
319 if (Modifier == MCSymbolRefExpr::VK_GOT) {
320 Type = MachO::X86_64_RELOC_GOT;
321 } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
322 // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which
323 // case all we do is set the PCrel bit in the relocation entry; this is
324 // used with exception handling, for example. The source is required to
325 // include any necessary offset directly.
326 Type = MachO::X86_64_RELOC_GOT;
327 IsPCRel = 1;
328 } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
329 Asm.getContext().reportError(
330 Fixup.getLoc(), "TLVP symbol modifier should have been rip-rel");
331 return;
332 } else if (Modifier != MCSymbolRefExpr::VK_None) {
333 Asm.getContext().reportError(
334 Fixup.getLoc(), "unsupported symbol modifier in relocation");
335 return;
336 } else {
337 Type = MachO::X86_64_RELOC_UNSIGNED;
338 unsigned Kind = Fixup.getKind();
339 if (Kind == X86::reloc_signed_4byte) {
340 Asm.getContext().reportError(
341 Fixup.getLoc(),
342 "32-bit absolute addressing is not supported in 64-bit mode");
343 return;
344 }
345 }
346 }
347 }
348
349 // x86_64 always writes custom values into the fixups.
350 FixedValue = Value;
351
352 // struct relocation_info (8 bytes)
353 MachO::any_relocation_info MRE;
354 MRE.r_word0 = FixupOffset;
355 MRE.r_word1 = (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
356 (IsExtern << 27) | (Type << 28);
357 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
358}
359
360bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer,
361 const MCAssembler &Asm,
362 const MCAsmLayout &Layout,
363 const MCFragment *Fragment,
364 const MCFixup &Fixup,
365 MCValue Target,
366 unsigned Log2Size,
367 uint64_t &FixedValue) {
368 uint64_t OriginalFixedValue = FixedValue;
369 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
370 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
371 unsigned Type = MachO::GENERIC_RELOC_VANILLA;
372
373 // See <reloc.h>.
374 const MCSymbol *A = &Target.getSymA()->getSymbol();
375
376 if (!A->getFragment()) {
377 Asm.getContext().reportError(
378 Fixup.getLoc(),
379 "symbol '" + A->getName() +
380 "' can not be undefined in a subtraction expression");
381 return false;
382 }
383
384 uint32_t Value = Writer->getSymbolAddress(*A, Layout);
385 uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent());
386 FixedValue += SecAddr;
387 uint32_t Value2 = 0;
388
389 if (const MCSymbolRefExpr *B = Target.getSymB()) {
390 const MCSymbol *SB = &B->getSymbol();
391
392 if (!SB->getFragment()) {
393 Asm.getContext().reportError(
394 Fixup.getLoc(),
395 "symbol '" + B->getSymbol().getName() +
396 "' can not be undefined in a subtraction expression");
397 return false;
398 }
399
400 // Select the appropriate difference relocation type.
401 //
402 // Note that there is no longer any semantic difference between these two
403 // relocation types from the linkers point of view, this is done solely for
404 // pedantic compatibility with 'as'.
405 Type = A->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF
406 : (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF;
407 Value2 = Writer->getSymbolAddress(B->getSymbol(), Layout);
408 FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent());
409 }
410
411 // Relocations are written out in reverse order, so the PAIR comes first.
412 if (Type == MachO::GENERIC_RELOC_SECTDIFF ||
413 Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) {
414 // If the offset is too large to fit in a scattered relocation,
415 // we're hosed. It's an unfortunate limitation of the MachO format.
416 if (FixupOffset > 0xffffff) {
417 char Buffer[32];
418 format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
419 Asm.getContext().reportError(Fixup.getLoc(),
420 Twine("Section too large, can't encode "
421 "r_address (") + Buffer +
422 ") into 24 bits of scattered "
423 "relocation entry.");
424 return false;
425 }
426
427 MachO::any_relocation_info MRE;
428 MRE.r_word0 = ((0 << 0) | // r_address
429 (MachO::GENERIC_RELOC_PAIR << 24) | // r_type
430 (Log2Size << 28) |
431 (IsPCRel << 30) |
432 MachO::R_SCATTERED);
433 MRE.r_word1 = Value2;
434 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
435 } else {
436 // If the offset is more than 24-bits, it won't fit in a scattered
437 // relocation offset field, so we fall back to using a non-scattered
438 // relocation. This is a bit risky, as if the offset reaches out of
439 // the block and the linker is doing scattered loading on this
440 // symbol, things can go badly.
441 //
442 // Required for 'as' compatibility.
443 if (FixupOffset > 0xffffff) {
444 FixedValue = OriginalFixedValue;
445 return false;
446 }
447 }
448
449 MachO::any_relocation_info MRE;
450 MRE.r_word0 = ((FixupOffset << 0) |
451 (Type << 24) |
452 (Log2Size << 28) |
453 (IsPCRel << 30) |
454 MachO::R_SCATTERED);
455 MRE.r_word1 = Value;
456 Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
457 return true;
458}
459
460void X86MachObjectWriter::recordTLVPRelocation(MachObjectWriter *Writer,
461 const MCAssembler &Asm,
462 const MCAsmLayout &Layout,
463 const MCFragment *Fragment,
464 const MCFixup &Fixup,
465 MCValue Target,
466 uint64_t &FixedValue) {
467 assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&((Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
!is64Bit() && "Should only be called with a 32-bit TLVP relocation!"
) ? static_cast<void> (0) : __assert_fail ("Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && !is64Bit() && \"Should only be called with a 32-bit TLVP relocation!\""
, "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn257205/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp"
, 469, __PRETTY_FUNCTION__))
468 !is64Bit() &&((Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
!is64Bit() && "Should only be called with a 32-bit TLVP relocation!"
) ? static_cast<void> (0) : __assert_fail ("Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && !is64Bit() && \"Should only be called with a 32-bit TLVP relocation!\""
, "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn257205/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp"
, 469, __PRETTY_FUNCTION__))
469 "Should only be called with a 32-bit TLVP relocation!")((Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
!is64Bit() && "Should only be called with a 32-bit TLVP relocation!"
) ? static_cast<void> (0) : __assert_fail ("Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && !is64Bit() && \"Should only be called with a 32-bit TLVP relocation!\""
, "/tmp/buildd/llvm-toolchain-snapshot-3.8~svn257205/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp"
, 469, __PRETTY_FUNCTION__));
470
471 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
472 uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
473 unsigned IsPCRel = 0;
474
475 // We're only going to have a second symbol in pic mode and it'll be a
476 // subtraction from the picbase. For 32-bit pic the addend is the difference
477 // between the picbase and the next address. For 32-bit static the addend is
478 // zero.
479 if (Target.getSymB()) {
480 // If this is a subtraction then we're pcrel.
481 uint32_t FixupAddress =
482 Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
483 IsPCRel = 1;
484 FixedValue =
485 FixupAddress -
486 Writer->getSymbolAddress(Target.getSymB()->getSymbol(), Layout) +
487 Target.getConstant();
488 FixedValue += 1ULL << Log2Size;
489 } else {
490 FixedValue = 0;
491 }
492
493 // struct relocation_info (8 bytes)
494 MachO::any_relocation_info MRE;
495 MRE.r_word0 = Value;
496 MRE.r_word1 =
497 (IsPCRel << 24) | (Log2Size << 25) | (MachO::GENERIC_RELOC_TLV << 28);
498 Writer->addRelocation(&Target.getSymA()->getSymbol(), Fragment->getParent(),
499 MRE);
500}
501
502void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
503 const MCAssembler &Asm,
504 const MCAsmLayout &Layout,
505 const MCFragment *Fragment,
506 const MCFixup &Fixup,
507 MCValue Target,
508 uint64_t &FixedValue) {
509 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
510 unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
511
512 // If this is a 32-bit TLVP reloc it's handled a bit differently.
513 if (Target.getSymA() &&
514 Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) {
515 recordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
516 FixedValue);
517 return;
518 }
519
520 // If this is a difference or a defined symbol plus an offset, then we need a
521 // scattered relocation entry. Differences always require scattered
522 // relocations.
523 if (Target.getSymB()) {
1
Taking false branch
→
524 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
525 Target, Log2Size, FixedValue);
526 return;
527 }
528
529 // Get the symbol data, if any.
530 const MCSymbol *A = nullptr;
2
←
'A' initialized to a null pointer value
→
531 if (Target.getSymA())
3
←
Taking false branch
→
532 A = &Target.getSymA()->getSymbol();
533
534 // If this is an internal relocation with an offset, it also needs a scattered
535 // relocation entry.
536 uint32_t Offset = Target.getConstant();
537 if (IsPCRel)
4
←
Assuming 'IsPCRel' is 0
→
5
←
Taking false branch
→
538 Offset += 1 << Log2Size;
539 // Try to record the scattered relocation if needed. Fall back to non
540 // scattered if necessary (see comments in recordScatteredRelocation()
541 // for details).
542 if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A) &&
543 recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
544 Log2Size, FixedValue))
545 return;
546
547 // See <reloc.h>.
548 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
549 unsigned Index = 0;
550 unsigned Type = 0;
551 const MCSymbol *RelSymbol = nullptr;
552
553 if (Target.isAbsolute()) { // constant
6
←
Taking false branch
→
554 // SymbolNum of 0 indicates the absolute section.
555 //
556 // FIXME: Currently, these are never generated (see code below). I cannot
557 // find a case where they are actually emitted.
558 Type = MachO::GENERIC_RELOC_VANILLA;
559 } else {
560 // Resolve constant variables.
561 if (A->isVariable()) {
7
←
Called C++ object pointer is null
562 int64_t Res;
563 if (A->getVariableValue()->evaluateAsAbsolute(
564 Res, Layout, Writer->getSectionAddressMap())) {
565 FixedValue = Res;
566 return;
567 }
568 }
569
570 // Check whether we need an external or internal relocation.
571 if (Writer->doesSymbolRequireExternRelocation(*A)) {
572 RelSymbol = A;
573 // For external relocations, make sure to offset the fixup value to
574 // compensate for the addend of the symbol address, if it was
575 // undefined. This occurs with weak definitions, for example.
576 if (!A->isUndefined())
577 FixedValue -= Layout.getSymbolOffset(*A);
578 } else {
579 // The index is the section ordinal (1-based).
580 const MCSection &Sec = A->getSection();
581 Index = Sec.getOrdinal() + 1;
582 FixedValue += Writer->getSectionAddress(&Sec);
583 }
584 if (IsPCRel)
585 FixedValue -= Writer->getSectionAddress(Fragment->getParent());
586
587 Type = MachO::GENERIC_RELOC_VANILLA;
588 }
589
590 // struct relocation_info (8 bytes)
591 MachO::any_relocation_info MRE;
592 MRE.r_word0 = FixupOffset;
593 MRE.r_word1 =
594 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
595 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
596}
597
598MCObjectWriter *llvm::createX86MachObjectWriter(raw_pwrite_stream &OS,
599 bool Is64Bit, uint32_t CPUType,
600 uint32_t CPUSubtype) {
601 return createMachObjectWriter(new X86MachObjectWriter(Is64Bit,
602 CPUType,
603 CPUSubtype),
604 OS, /*IsLittleEndian=*/true);
605}