LLVM 17.0.0git
AArch64MachObjectWriter.cpp
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1//===-- AArch64MachObjectWriter.cpp - ARM Mach Object Writer --------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
11#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/MCFragment.h"
21#include "llvm/MC/MCSection.h"
23#include "llvm/MC/MCSymbol.h"
24#include "llvm/MC/MCValue.h"
27#include <cassert>
28#include <cstdint>
29
30using namespace llvm;
31
32namespace {
33
34class AArch64MachObjectWriter : public MCMachObjectTargetWriter {
35 bool getAArch64FixupKindMachOInfo(const MCFixup &Fixup, unsigned &RelocType,
36 const MCSymbolRefExpr *Sym,
37 unsigned &Log2Size, const MCAssembler &Asm);
38
39public:
40 AArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype, bool IsILP32)
41 : MCMachObjectTargetWriter(!IsILP32 /* is64Bit */, CPUType, CPUSubtype) {}
42
44 const MCAsmLayout &Layout, const MCFragment *Fragment,
46 uint64_t &FixedValue) override;
47};
48
49} // end anonymous namespace
50
51bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
52 const MCFixup &Fixup, unsigned &RelocType, const MCSymbolRefExpr *Sym,
53 unsigned &Log2Size, const MCAssembler &Asm) {
55 Log2Size = ~0U;
56
57 switch (Fixup.getTargetKind()) {
58 default:
59 return false;
60
61 case FK_Data_1:
62 Log2Size = Log2_32(1);
63 return true;
64 case FK_Data_2:
65 Log2Size = Log2_32(2);
66 return true;
67 case FK_Data_4:
68 Log2Size = Log2_32(4);
69 if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
71 return true;
72 case FK_Data_8:
73 Log2Size = Log2_32(8);
74 if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
76 return true;
83 Log2Size = Log2_32(4);
84 switch (Sym->getKind()) {
85 default:
86 return false;
89 return true;
92 return true;
95 return true;
96 }
98 Log2Size = Log2_32(4);
99 // This encompasses the relocation for the whole 21-bit value.
100 switch (Sym->getKind()) {
101 default:
102 Asm.getContext().reportError(Fixup.getLoc(),
103 "ADR/ADRP relocations must be GOT relative");
104 return false;
107 return true;
110 return true;
113 return true;
114 }
115 return true;
118 Log2Size = Log2_32(4);
120 return true;
121 }
122}
123
124static bool canUseLocalRelocation(const MCSectionMachO &Section,
125 const MCSymbol &Symbol, unsigned Log2Size) {
126 // Debug info sections can use local relocations.
127 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
128 return true;
129
130 // Otherwise, only pointer sized relocations are supported.
131 if (Log2Size != 3)
132 return false;
133
134 // But only if they don't point to a few forbidden sections.
135 if (!Symbol.isInSection())
136 return true;
137 const MCSectionMachO &RefSec = cast<MCSectionMachO>(Symbol.getSection());
138 if (RefSec.getType() == MachO::S_CSTRING_LITERALS)
139 return false;
140
141 if (RefSec.getSegmentName() == "__DATA" &&
142 RefSec.getName() == "__objc_classrefs")
143 return false;
144
145 // FIXME: ld64 currently handles internal pointer-sized relocations
146 // incorrectly (applying the addend twice). We should be able to return true
147 // unconditionally by this point when that's fixed.
148 return false;
149}
150
151void AArch64MachObjectWriter::recordRelocation(
152 MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
153 const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
154 uint64_t &FixedValue) {
155 unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
156
157 // See <reloc.h>.
158 uint32_t FixupOffset = Layout.getFragmentOffset(Fragment);
159 unsigned Log2Size = 0;
160 int64_t Value = 0;
161 unsigned Index = 0;
162 unsigned Type = 0;
163 unsigned Kind = Fixup.getKind();
164 const MCSymbol *RelSymbol = nullptr;
165
166 FixupOffset += Fixup.getOffset();
167
168 // AArch64 pcrel relocation addends do not include the section offset.
169 if (IsPCRel)
170 FixedValue += FixupOffset;
171
172 // ADRP fixups use relocations for the whole symbol value and only
173 // put the addend in the instruction itself. Clear out any value the
174 // generic code figured out from the sybmol definition.
176 FixedValue = 0;
177
178 // imm19 relocations are for conditional branches, which require
179 // assembler local symbols. If we got here, that's not what we have,
180 // so complain loudly.
182 Asm.getContext().reportError(Fixup.getLoc(),
183 "conditional branch requires assembler-local"
184 " label. '" +
185 Target.getSymA()->getSymbol().getName() +
186 "' is external.");
187 return;
188 }
189
190 // 14-bit branch relocations should only target internal labels, and so
191 // should never get here.
193 Asm.getContext().reportError(Fixup.getLoc(),
194 "Invalid relocation on conditional branch!");
195 return;
196 }
197
198 if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSymA(), Log2Size,
199 Asm)) {
200 Asm.getContext().reportError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
201 return;
202 }
203
204 Value = Target.getConstant();
205
206 if (Target.isAbsolute()) { // constant
207 // FIXME: Should this always be extern?
208 // SymbolNum of 0 indicates the absolute section.
210
211 if (IsPCRel) {
212 Asm.getContext().reportError(Fixup.getLoc(),
213 "PC relative absolute relocation!");
214 return;
215
216 // FIXME: x86_64 sets the type to a branch reloc here. Should we do
217 // something similar?
218 }
219 } else if (Target.getSymB()) { // A - B + constant
220 const MCSymbol *A = &Target.getSymA()->getSymbol();
221 const MCSymbol *A_Base = Asm.getAtom(*A);
222
223 const MCSymbol *B = &Target.getSymB()->getSymbol();
224 const MCSymbol *B_Base = Asm.getAtom(*B);
225
226 // Check for "_foo@got - .", which comes through here as:
227 // Ltmp0:
228 // ... _foo@got - Ltmp0
229 if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_GOT &&
230 Target.getSymB()->getKind() == MCSymbolRefExpr::VK_None &&
231 Layout.getSymbolOffset(*B) ==
232 Layout.getFragmentOffset(Fragment) + Fixup.getOffset()) {
233 // SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
235 IsPCRel = 1;
237 MRE.r_word0 = FixupOffset;
238 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
239 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
240 return;
241 } else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
242 Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) {
243 // Otherwise, neither symbol can be modified.
244 Asm.getContext().reportError(Fixup.getLoc(),
245 "unsupported relocation of modified symbol");
246 return;
247 }
248
249 // We don't support PCrel relocations of differences.
250 if (IsPCRel) {
251 Asm.getContext().reportError(Fixup.getLoc(),
252 "unsupported pc-relative relocation of "
253 "difference");
254 return;
255 }
256
257 // AArch64 always uses external relocations. If there is no symbol to use as
258 // a base address (a local symbol with no preceding non-local symbol),
259 // error out.
260 //
261 // FIXME: We should probably just synthesize an external symbol and use
262 // that.
263 if (!A_Base) {
264 Asm.getContext().reportError(
265 Fixup.getLoc(),
266 "unsupported relocation of local symbol '" + A->getName() +
267 "'. Must have non-local symbol earlier in section.");
268 return;
269 }
270 if (!B_Base) {
271 Asm.getContext().reportError(
272 Fixup.getLoc(),
273 "unsupported relocation of local symbol '" + B->getName() +
274 "'. Must have non-local symbol earlier in section.");
275 return;
276 }
277
278 if (A_Base == B_Base && A_Base) {
279 Asm.getContext().reportError(
280 Fixup.getLoc(), "unsupported relocation with identical base");
281 return;
282 }
283
284 Value += (!A->getFragment() ? 0 : Writer->getSymbolAddress(*A, Layout)) -
285 (!A_Base || !A_Base->getFragment() ? 0 : Writer->getSymbolAddress(
286 *A_Base, Layout));
287 Value -= (!B->getFragment() ? 0 : Writer->getSymbolAddress(*B, Layout)) -
288 (!B_Base || !B_Base->getFragment() ? 0 : Writer->getSymbolAddress(
289 *B_Base, Layout));
290
292
294 MRE.r_word0 = FixupOffset;
295 MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
296 Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
297
298 RelSymbol = B_Base;
300 } else { // A + constant
301 const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
302 const MCSectionMachO &Section =
303 static_cast<const MCSectionMachO &>(*Fragment->getParent());
304
305 bool CanUseLocalRelocation =
306 canUseLocalRelocation(Section, *Symbol, Log2Size);
307 if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
308 // Make sure that the symbol is actually in a section here. If it isn't,
309 // emit an error and exit.
310 if (!Symbol->isInSection()) {
311 Asm.getContext().reportError(
312 Fixup.getLoc(),
313 "unsupported relocation of local symbol '" + Symbol->getName() +
314 "'. Must have non-local symbol earlier in section.");
315 return;
316 }
317 const MCSection &Sec = Symbol->getSection();
318 if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
319 Symbol->setUsedInReloc();
320 }
321
322 const MCSymbol *Base = Asm.getAtom(*Symbol);
323 // If the symbol is a variable it can either be in a section and
324 // we have a base or it is absolute and should have been expanded.
325 assert(!Symbol->isVariable() || Base);
326
327 // Relocations inside debug sections always use local relocations when
328 // possible. This seems to be done because the debugger doesn't fully
329 // understand relocation entries and expects to find values that
330 // have already been fixed up.
331 if (Symbol->isInSection()) {
332 if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
333 Base = nullptr;
334 }
335
336 // AArch64 uses external relocations as much as possible. For debug
337 // sections, and for pointer-sized relocations (.quad), we allow section
338 // relocations. It's code sections that run into trouble.
339 if (Base) {
340 RelSymbol = Base;
341
342 // Add the local offset, if needed.
343 if (Base != Symbol)
344 Value +=
345 Layout.getSymbolOffset(*Symbol) - Layout.getSymbolOffset(*Base);
346 } else if (Symbol->isInSection()) {
347 if (!CanUseLocalRelocation) {
348 Asm.getContext().reportError(
349 Fixup.getLoc(),
350 "unsupported relocation of local symbol '" + Symbol->getName() +
351 "'. Must have non-local symbol earlier in section.");
352 return;
353 }
354 // Adjust the relocation to be section-relative.
355 // The index is the section ordinal (1-based).
356 const MCSection &Sec = Symbol->getSection();
357 Index = Sec.getOrdinal() + 1;
358 Value += Writer->getSymbolAddress(*Symbol, Layout);
359
360 if (IsPCRel)
361 Value -= Writer->getFragmentAddress(Fragment, Layout) +
362 Fixup.getOffset() + (1ULL << Log2Size);
363 } else {
365 "This constant variable should have been expanded during evaluation");
366 }
367 }
368
369 // If the relocation kind is Branch26, Page21, or Pageoff12, any addend
370 // is represented via an Addend relocation, not encoded directly into
371 // the instruction.
375 Value) {
376 if (!isInt<24>(Value)) {
377 Asm.getContext().reportError(Fixup.getLoc(),
378 "addend too big for relocation");
379 return;
380 }
381
383 MRE.r_word0 = FixupOffset;
384 MRE.r_word1 =
385 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
386 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
387
388 // Now set up the Addend relocation.
390 Index = Value;
391 RelSymbol = nullptr;
392 IsPCRel = 0;
393 Log2Size = 2;
394
395 // Put zero into the instruction itself. The addend is in the relocation.
396 Value = 0;
397 }
398
399 // If there's any addend left to handle, encode it in the instruction.
400 FixedValue = Value;
401
402 // struct relocation_info (8 bytes)
404 MRE.r_word0 = FixupOffset;
405 MRE.r_word1 =
406 (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
407 Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
408}
409
410std::unique_ptr<MCObjectTargetWriter>
412 bool IsILP32) {
413 return std::make_unique<AArch64MachObjectWriter>(CPUType, CPUSubtype,
414 IsILP32);
415}
static bool canUseLocalRelocation(const MCSectionMachO &Section, const MCSymbol &Symbol, unsigned Log2Size)
static GCRegistry::Add< OcamlGC > B("ocaml", "ocaml 3.10-compatible GC")
static GCRegistry::Add< ErlangGC > A("erlang", "erlang-compatible garbage collector")
PowerPC TLS Dynamic Call Fixup
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Encapsulates the layout of an assembly file at a particular point in time.
Definition: MCAsmLayout.h:28
bool getSymbolOffset(const MCSymbol &S, uint64_t &Val) const
Get the offset of the given symbol, as computed in the current layout.
Definition: MCFragment.cpp:152
uint64_t getFragmentOffset(const MCFragment *F) const
Get the offset of the given fragment inside its containing section.
Definition: MCFragment.cpp:96
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:71
MCSection * getParent() const
Definition: MCFragment.h:95
virtual void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, uint64_t &FixedValue)=0
This represents a section on a Mach-O system (used by Mac OS X).
MachO::SectionType getType() const
StringRef getSegmentName() const
Instances of this class represent a uniqued identifier for a section in the current translation unit.
Definition: MCSection.h:39
unsigned getOrdinal() const
Definition: MCSection.h:149
StringRef getName() const
Definition: MCSection.h:124
Represent a reference to a symbol from inside an expression.
Definition: MCExpr.h:192
VariantKind getKind() const
Definition: MCExpr.h:401
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:41
MCFragment * getFragment(bool SetUsed=true) const
Definition: MCSymbol.h:395
This represents an "assembler immediate".
Definition: MCValue.h:36
uint64_t getSymbolAddress(const MCSymbol &S, const MCAsmLayout &Layout) const
void addRelocation(const MCSymbol *RelSymbol, const MCSection *Sec, MachO::any_relocation_info &MRE)
bool isFixupKindPCRel(const MCAssembler &Asm, unsigned Kind)
uint64_t getFragmentAddress(const MCFragment *Fragment, const MCAsmLayout &Layout) const
Target - Wrapper for Target specific information.
const char * getName() const
getName - Get the target name.
The instances of the Type class are immutable: once they are created, they are never changed.
Definition: Type.h:45
LLVM Value Representation.
Definition: Value.h:74
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
@ fixup_aarch64_ldst_imm12_scale16
@ S_ATTR_DEBUG
S_ATTR_DEBUG - A debug section.
Definition: MachO.h:207
@ S_CSTRING_LITERALS
S_CSTRING_LITERALS - Section with literal C strings.
Definition: MachO.h:131
@ ARM64_RELOC_PAGEOFF12
Definition: MachO.h:463
@ ARM64_RELOC_POINTER_TO_GOT
Definition: MachO.h:469
@ ARM64_RELOC_SUBTRACTOR
Definition: MachO.h:457
@ ARM64_RELOC_ADDEND
Definition: MachO.h:475
@ ARM64_RELOC_UNSIGNED
Definition: MachO.h:455
@ ARM64_RELOC_GOT_LOAD_PAGE21
Definition: MachO.h:465
@ ARM64_RELOC_TLVP_LOAD_PAGEOFF12
Definition: MachO.h:473
@ ARM64_RELOC_PAGE21
Definition: MachO.h:461
@ ARM64_RELOC_GOT_LOAD_PAGEOFF12
Definition: MachO.h:467
@ ARM64_RELOC_TLVP_LOAD_PAGE21
Definition: MachO.h:471
@ ARM64_RELOC_BRANCH26
Definition: MachO.h:459
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
unsigned Log2_32(uint32_t Value)
Return the floor log base 2 of the specified value, -1 if the value is zero.
Definition: MathExtras.h:373
@ FK_Data_8
A eight-byte fixup.
Definition: MCFixup.h:26
@ FK_Data_1
A one-byte fixup.
Definition: MCFixup.h:23
@ FK_Data_4
A four-byte fixup.
Definition: MCFixup.h:25
@ FK_Data_2
A two-byte fixup.
Definition: MCFixup.h:24
std::unique_ptr< MCObjectTargetWriter > createAArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype, bool IsILP32)