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llvm-project/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp

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//===-- AArch64MachObjectWriter.cpp - ARM Mach Object Writer --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/AArch64FixupKinds.h"
#include "MCTargetDesc/AArch64MCTargetDesc.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCMachObjectWriter.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MachO.h"
using namespace llvm;
namespace {
class AArch64MachObjectWriter : public MCMachObjectTargetWriter {
bool getAArch64FixupKindMachOInfo(const MCFixup &Fixup, unsigned &RelocType,
const MCSymbolRefExpr *Sym,
unsigned &Log2Size, const MCAssembler &Asm);
public:
AArch64MachObjectWriter(uint32_t CPUType, uint32_t CPUSubtype)
: MCMachObjectTargetWriter(true /* is64Bit */, CPUType, CPUSubtype,
/*UseAggressiveSymbolFolding=*/true) {}
void RecordRelocation(MachObjectWriter *Writer, const MCAssembler &Asm,
const MCAsmLayout &Layout, const MCFragment *Fragment,
const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) override;
};
}
bool AArch64MachObjectWriter::getAArch64FixupKindMachOInfo(
const MCFixup &Fixup, unsigned &RelocType, const MCSymbolRefExpr *Sym,
unsigned &Log2Size, const MCAssembler &Asm) {
RelocType = unsigned(MachO::ARM64_RELOC_UNSIGNED);
Log2Size = ~0U;
switch ((unsigned)Fixup.getKind()) {
default:
return false;
case FK_Data_1:
Log2Size = llvm::Log2_32(1);
return true;
case FK_Data_2:
Log2Size = llvm::Log2_32(2);
return true;
case FK_Data_4:
Log2Size = llvm::Log2_32(4);
if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
return true;
case FK_Data_8:
Log2Size = llvm::Log2_32(8);
if (Sym->getKind() == MCSymbolRefExpr::VK_GOT)
RelocType = unsigned(MachO::ARM64_RELOC_POINTER_TO_GOT);
return true;
case AArch64::fixup_aarch64_add_imm12:
case AArch64::fixup_aarch64_ldst_imm12_scale1:
case AArch64::fixup_aarch64_ldst_imm12_scale2:
case AArch64::fixup_aarch64_ldst_imm12_scale4:
case AArch64::fixup_aarch64_ldst_imm12_scale8:
case AArch64::fixup_aarch64_ldst_imm12_scale16:
Log2Size = llvm::Log2_32(4);
switch (Sym->getKind()) {
default:
llvm_unreachable("Unexpected symbol reference variant kind!");
case MCSymbolRefExpr::VK_PAGEOFF:
RelocType = unsigned(MachO::ARM64_RELOC_PAGEOFF12);
return true;
case MCSymbolRefExpr::VK_GOTPAGEOFF:
RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12);
return true;
case MCSymbolRefExpr::VK_TLVPPAGEOFF:
RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12);
return true;
}
case AArch64::fixup_aarch64_pcrel_adrp_imm21:
Log2Size = llvm::Log2_32(4);
// This encompasses the relocation for the whole 21-bit value.
switch (Sym->getKind()) {
default:
Asm.getContext().FatalError(Fixup.getLoc(),
"ADR/ADRP relocations must be GOT relative");
case MCSymbolRefExpr::VK_PAGE:
RelocType = unsigned(MachO::ARM64_RELOC_PAGE21);
return true;
case MCSymbolRefExpr::VK_GOTPAGE:
RelocType = unsigned(MachO::ARM64_RELOC_GOT_LOAD_PAGE21);
return true;
case MCSymbolRefExpr::VK_TLVPPAGE:
RelocType = unsigned(MachO::ARM64_RELOC_TLVP_LOAD_PAGE21);
return true;
}
return true;
case AArch64::fixup_aarch64_pcrel_branch26:
case AArch64::fixup_aarch64_pcrel_call26:
Log2Size = llvm::Log2_32(4);
RelocType = unsigned(MachO::ARM64_RELOC_BRANCH26);
return true;
}
}
void AArch64MachObjectWriter::RecordRelocation(
MachObjectWriter *Writer, const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) {
unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
// See <reloc.h>.
uint32_t FixupOffset = Layout.getFragmentOffset(Fragment);
unsigned Log2Size = 0;
int64_t Value = 0;
unsigned Index = 0;
unsigned IsExtern = 0;
unsigned Type = 0;
unsigned Kind = Fixup.getKind();
FixupOffset += Fixup.getOffset();
// AArch64 pcrel relocation addends do not include the section offset.
if (IsPCRel)
FixedValue += FixupOffset;
// ADRP fixups use relocations for the whole symbol value and only
// put the addend in the instruction itself. Clear out any value the
// generic code figured out from the sybmol definition.
if (Kind == AArch64::fixup_aarch64_pcrel_adrp_imm21)
FixedValue = 0;
// imm19 relocations are for conditional branches, which require
// assembler local symbols. If we got here, that's not what we have,
// so complain loudly.
if (Kind == AArch64::fixup_aarch64_pcrel_branch19) {
Asm.getContext().FatalError(Fixup.getLoc(),
"conditional branch requires assembler-local"
" label. '" +
Target.getSymA()->getSymbol().getName() +
"' is external.");
return;
}
// 14-bit branch relocations should only target internal labels, and so
// should never get here.
if (Kind == AArch64::fixup_aarch64_pcrel_branch14) {
Asm.getContext().FatalError(Fixup.getLoc(),
"Invalid relocation on conditional branch!");
return;
}
if (!getAArch64FixupKindMachOInfo(Fixup, Type, Target.getSymA(), Log2Size,
Asm)) {
Asm.getContext().FatalError(Fixup.getLoc(), "unknown AArch64 fixup kind!");
return;
}
Value = Target.getConstant();
if (Target.isAbsolute()) { // constant
// FIXME: Should this always be extern?
// SymbolNum of 0 indicates the absolute section.
Type = MachO::ARM64_RELOC_UNSIGNED;
Index = 0;
if (IsPCRel) {
IsExtern = 1;
Asm.getContext().FatalError(Fixup.getLoc(),
"PC relative absolute relocation!");
// FIXME: x86_64 sets the type to a branch reloc here. Should we do
// something similar?
}
} else if (Target.getSymB()) { // A - B + constant
const MCSymbol *A = &Target.getSymA()->getSymbol();
const MCSymbolData &A_SD = Asm.getSymbolData(*A);
const MCSymbolData *A_Base = Asm.getAtom(&A_SD);
const MCSymbol *B = &Target.getSymB()->getSymbol();
const MCSymbolData &B_SD = Asm.getSymbolData(*B);
const MCSymbolData *B_Base = Asm.getAtom(&B_SD);
// Check for "_foo@got - .", which comes through here as:
// Ltmp0:
// ... _foo@got - Ltmp0
if (Target.getSymA()->getKind() == MCSymbolRefExpr::VK_GOT &&
Target.getSymB()->getKind() == MCSymbolRefExpr::VK_None &&
Layout.getSymbolOffset(&B_SD) ==
Layout.getFragmentOffset(Fragment) + Fixup.getOffset()) {
// SymB is the PC, so use a PC-rel pointer-to-GOT relocation.
Index = A_Base->getIndex();
IsExtern = 1;
Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
IsPCRel = 1;
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
(IsExtern << 27) | (Type << 28));
Writer->addRelocation(Fragment->getParent(), MRE);
return;
} else if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
// Otherwise, neither symbol can be modified.
Asm.getContext().FatalError(Fixup.getLoc(),
"unsupported relocation of modified symbol");
// We don't support PCrel relocations of differences.
if (IsPCRel)
Asm.getContext().FatalError(Fixup.getLoc(),
"unsupported pc-relative relocation of "
"difference");
// AArch64 always uses external relocations. If there is no symbol to use as
// a base address (a local symbol with no preceding non-local symbol),
// error out.
//
// FIXME: We should probably just synthesize an external symbol and use
// that.
if (!A_Base)
Asm.getContext().FatalError(
Fixup.getLoc(),
"unsupported relocation of local symbol '" + A->getName() +
"'. Must have non-local symbol earlier in section.");
if (!B_Base)
Asm.getContext().FatalError(
Fixup.getLoc(),
"unsupported relocation of local symbol '" + B->getName() +
"'. Must have non-local symbol earlier in section.");
if (A_Base == B_Base && A_Base)
Asm.getContext().FatalError(Fixup.getLoc(),
"unsupported relocation with identical base");
Value += (!A_SD.getFragment() ? 0
: Writer->getSymbolAddress(&A_SD, Layout)) -
(!A_Base || !A_Base->getFragment()
? 0
: Writer->getSymbolAddress(A_Base, Layout));
Value -= (!B_SD.getFragment() ? 0
: Writer->getSymbolAddress(&B_SD, Layout)) -
(!B_Base || !B_Base->getFragment()
? 0
: Writer->getSymbolAddress(B_Base, Layout));
Index = A_Base->getIndex();
IsExtern = 1;
Type = MachO::ARM64_RELOC_UNSIGNED;
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
(IsExtern << 27) | (Type << 28));
Writer->addRelocation(Fragment->getParent(), MRE);
Index = B_Base->getIndex();
IsExtern = 1;
Type = MachO::ARM64_RELOC_SUBTRACTOR;
} else { // A + constant
const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
const MCSymbolData *Base = Asm.getAtom(&SD);
const MCSectionMachO &Section = static_cast<const MCSectionMachO &>(
Fragment->getParent()->getSection());
// If the symbol is a variable and we weren't able to get a Base for it
// (i.e., it's not in the symbol table associated with a section) resolve
// the relocation based its expansion instead.
if (Symbol->isVariable() && !Base) {
// If the evaluation is an absolute value, just use that directly
// to keep things easy.
int64_t Res;
if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
Res, Layout, Writer->getSectionAddressMap())) {
FixedValue = Res;
return;
}
// FIXME: Will the Target we already have ever have any data in it
// we need to preserve and merge with the new Target? How about
// the FixedValue?
if (!Symbol->getVariableValue()->EvaluateAsRelocatable(Target, &Layout))
Asm.getContext().FatalError(Fixup.getLoc(),
"unable to resolve variable '" +
Symbol->getName() + "'");
return RecordRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
FixedValue);
}
// Relocations inside debug sections always use local relocations when
// possible. This seems to be done because the debugger doesn't fully
// understand relocation entries and expects to find values that
// have already been fixed up.
if (Symbol->isInSection()) {
if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
Base = nullptr;
}
// AArch64 uses external relocations as much as possible. For debug
// sections, and for pointer-sized relocations (.quad), we allow section
// relocations. It's code sections that run into trouble.
if (Base) {
Index = Base->getIndex();
IsExtern = 1;
// Add the local offset, if needed.
if (Base != &SD)
Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base);
} else if (Symbol->isInSection()) {
// Pointer-sized relocations can use a local relocation. Otherwise,
// we have to be in a debug info section.
if (!Section.hasAttribute(MachO::S_ATTR_DEBUG) && Log2Size != 3)
Asm.getContext().FatalError(
Fixup.getLoc(),
"unsupported relocation of local symbol '" + Symbol->getName() +
"'. Must have non-local symbol earlier in section.");
// Adjust the relocation to be section-relative.
// The index is the section ordinal (1-based).
const MCSectionData &SymSD =
Asm.getSectionData(SD.getSymbol().getSection());
Index = SymSD.getOrdinal() + 1;
IsExtern = 0;
Value += Writer->getSymbolAddress(&SD, Layout);
if (IsPCRel)
Value -= Writer->getFragmentAddress(Fragment, Layout) +
Fixup.getOffset() + (1ULL << Log2Size);
} else {
// Resolve constant variables.
if (SD.getSymbol().isVariable()) {
int64_t Res;
if (SD.getSymbol().getVariableValue()->EvaluateAsAbsolute(
Res, Layout, Writer->getSectionAddressMap())) {
FixedValue = Res;
return;
}
}
Asm.getContext().FatalError(Fixup.getLoc(),
"unsupported relocation of variable '" +
Symbol->getName() + "'");
}
}
// If the relocation kind is Branch26, Page21, or Pageoff12, any addend
// is represented via an Addend relocation, not encoded directly into
// the instruction.
if ((Type == MachO::ARM64_RELOC_BRANCH26 ||
Type == MachO::ARM64_RELOC_PAGE21 ||
Type == MachO::ARM64_RELOC_PAGEOFF12) &&
Value) {
assert((Value & 0xff000000) == 0 && "Added relocation out of range!");
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
(IsExtern << 27) | (Type << 28));
Writer->addRelocation(Fragment->getParent(), MRE);
// Now set up the Addend relocation.
Type = MachO::ARM64_RELOC_ADDEND;
Index = Value;
IsPCRel = 0;
Log2Size = 2;
IsExtern = 0;
// Put zero into the instruction itself. The addend is in the relocation.
Value = 0;
}
// If there's any addend left to handle, encode it in the instruction.
FixedValue = Value;
// struct relocation_info (8 bytes)
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = ((Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
(IsExtern << 27) | (Type << 28));
Writer->addRelocation(Fragment->getParent(), MRE);
}
MCObjectWriter *llvm::createAArch64MachObjectWriter(raw_ostream &OS,
uint32_t CPUType,
uint32_t CPUSubtype) {
return createMachObjectWriter(
new AArch64MachObjectWriter(CPUType, CPUSubtype), OS,
/*IsLittleEndian=*/true);
}
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