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https://github.com/c64scene-ar/llvm-6502.git
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Apparently, the style needs to be agreed upon first. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240390 91177308-0d34-0410-b5e6-96231b3b80d8
577 lines
24 KiB
C++
577 lines
24 KiB
C++
//===-- X86MachObjectWriter.cpp - X86 Mach-O Writer -----------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "MCTargetDesc/X86MCTargetDesc.h"
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#include "MCTargetDesc/X86FixupKinds.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCAsmLayout.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCMachObjectWriter.h"
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#include "llvm/MC/MCSectionMachO.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/Format.h"
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#include "llvm/Support/MachO.h"
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using namespace llvm;
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namespace {
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class X86MachObjectWriter : public MCMachObjectTargetWriter {
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bool recordScatteredRelocation(MachObjectWriter *Writer,
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const MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment,
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const MCFixup &Fixup,
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MCValue Target,
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unsigned Log2Size,
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uint64_t &FixedValue);
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void recordTLVPRelocation(MachObjectWriter *Writer,
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const MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment,
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const MCFixup &Fixup,
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MCValue Target,
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uint64_t &FixedValue);
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void RecordX86Relocation(MachObjectWriter *Writer,
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const MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment,
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const MCFixup &Fixup,
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MCValue Target,
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uint64_t &FixedValue);
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void RecordX86_64Relocation(MachObjectWriter *Writer, MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment, const MCFixup &Fixup,
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MCValue Target, uint64_t &FixedValue);
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public:
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X86MachObjectWriter(bool Is64Bit, uint32_t CPUType, uint32_t CPUSubtype)
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: MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype) {}
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void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
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const MCAsmLayout &Layout, const MCFragment *Fragment,
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const MCFixup &Fixup, MCValue Target,
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uint64_t &FixedValue) override {
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if (Writer->is64Bit())
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RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
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FixedValue);
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else
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RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
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FixedValue);
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}
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};
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}
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static bool isFixupKindRIPRel(unsigned Kind) {
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return Kind == X86::reloc_riprel_4byte ||
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Kind == X86::reloc_riprel_4byte_movq_load;
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}
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static unsigned getFixupKindLog2Size(unsigned Kind) {
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switch (Kind) {
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default:
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llvm_unreachable("invalid fixup kind!");
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case FK_PCRel_1:
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case FK_Data_1: return 0;
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case FK_PCRel_2:
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case FK_Data_2: return 1;
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case FK_PCRel_4:
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// FIXME: Remove these!!!
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case X86::reloc_riprel_4byte:
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case X86::reloc_riprel_4byte_movq_load:
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case X86::reloc_signed_4byte:
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case FK_Data_4: return 2;
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case FK_Data_8: return 3;
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}
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}
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void X86MachObjectWriter::RecordX86_64Relocation(
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MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
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const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
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uint64_t &FixedValue) {
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unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
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unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind());
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unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
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// See <reloc.h>.
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uint32_t FixupOffset =
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Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
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uint32_t FixupAddress =
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Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
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int64_t Value = 0;
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unsigned Index = 0;
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unsigned IsExtern = 0;
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unsigned Type = 0;
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const MCSymbol *RelSymbol = nullptr;
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Value = Target.getConstant();
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if (IsPCRel) {
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// Compensate for the relocation offset, Darwin x86_64 relocations only have
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// the addend and appear to have attempted to define it to be the actual
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// expression addend without the PCrel bias. However, instructions with data
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// following the relocation are not accommodated for (see comment below
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// regarding SIGNED{1,2,4}), so it isn't exactly that either.
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Value += 1LL << Log2Size;
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}
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if (Target.isAbsolute()) { // constant
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// SymbolNum of 0 indicates the absolute section.
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Type = MachO::X86_64_RELOC_UNSIGNED;
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// FIXME: I believe this is broken, I don't think the linker can understand
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// it. I think it would require a local relocation, but I'm not sure if that
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// would work either. The official way to get an absolute PCrel relocation
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// is to use an absolute symbol (which we don't support yet).
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if (IsPCRel) {
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IsExtern = 1;
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Type = MachO::X86_64_RELOC_BRANCH;
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}
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} else if (Target.getSymB()) { // A - B + constant
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const MCSymbol *A = &Target.getSymA()->getSymbol();
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if (A->isTemporary())
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A = &Writer->findAliasedSymbol(*A);
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const MCSymbol *A_Base = Asm.getAtom(*A);
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const MCSymbol *B = &Target.getSymB()->getSymbol();
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if (B->isTemporary())
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B = &Writer->findAliasedSymbol(*B);
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const MCSymbol *B_Base = Asm.getAtom(*B);
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// Neither symbol can be modified.
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if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
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Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
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report_fatal_error("unsupported relocation of modified symbol", false);
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// We don't support PCrel relocations of differences. Darwin 'as' doesn't
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// implement most of these correctly.
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if (IsPCRel)
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report_fatal_error("unsupported pc-relative relocation of difference",
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false);
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// The support for the situation where one or both of the symbols would
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// require a local relocation is handled just like if the symbols were
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// external. This is certainly used in the case of debug sections where the
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// section has only temporary symbols and thus the symbols don't have base
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// symbols. This is encoded using the section ordinal and non-extern
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// relocation entries.
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// Darwin 'as' doesn't emit correct relocations for this (it ends up with a
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// single SIGNED relocation); reject it for now. Except the case where both
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// symbols don't have a base, equal but both NULL.
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if (A_Base == B_Base && A_Base)
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report_fatal_error("unsupported relocation with identical base", false);
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// A subtraction expression where either symbol is undefined is a
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// non-relocatable expression.
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if (A->isUndefined() || B->isUndefined()) {
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StringRef Name = A->isUndefined() ? A->getName() : B->getName();
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Asm.getContext().reportFatalError(Fixup.getLoc(),
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"unsupported relocation with subtraction expression, symbol '" +
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Name + "' can not be undefined in a subtraction expression");
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}
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Value += Writer->getSymbolAddress(*A, Layout) -
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(!A_Base ? 0 : Writer->getSymbolAddress(*A_Base, Layout));
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Value -= Writer->getSymbolAddress(*B, Layout) -
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(!B_Base ? 0 : Writer->getSymbolAddress(*B_Base, Layout));
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if (!A_Base)
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Index = A->getFragment()->getParent()->getOrdinal() + 1;
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Type = MachO::X86_64_RELOC_UNSIGNED;
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MachO::any_relocation_info MRE;
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MRE.r_word0 = FixupOffset;
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MRE.r_word1 =
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(Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
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Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
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if (B_Base)
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RelSymbol = B_Base;
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else
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Index = B->getFragment()->getParent()->getOrdinal() + 1;
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Type = MachO::X86_64_RELOC_SUBTRACTOR;
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} else {
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const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
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if (Symbol->isTemporary() && Value) {
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const MCSection &Sec = Symbol->getSection();
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if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
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Symbol->setUsedInReloc();
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}
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RelSymbol = Asm.getAtom(*Symbol);
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// Relocations inside debug sections always use local relocations when
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// possible. This seems to be done because the debugger doesn't fully
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// understand x86_64 relocation entries, and expects to find values that
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// have already been fixed up.
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if (Symbol->isInSection()) {
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const MCSectionMachO &Section =
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static_cast<const MCSectionMachO &>(*Fragment->getParent());
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if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
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RelSymbol = nullptr;
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}
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// x86_64 almost always uses external relocations, except when there is no
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// symbol to use as a base address (a local symbol with no preceding
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// non-local symbol).
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if (RelSymbol) {
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// Add the local offset, if needed.
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if (RelSymbol != Symbol)
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Value += Layout.getSymbolOffset(*Symbol) -
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Layout.getSymbolOffset(*RelSymbol);
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} else if (Symbol->isInSection() && !Symbol->isVariable()) {
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// The index is the section ordinal (1-based).
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Index = Symbol->getFragment()->getParent()->getOrdinal() + 1;
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Value += Writer->getSymbolAddress(*Symbol, Layout);
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if (IsPCRel)
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Value -= FixupAddress + (1 << Log2Size);
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} else if (Symbol->isVariable()) {
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const MCExpr *Value = Symbol->getVariableValue();
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int64_t Res;
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bool isAbs = Value->evaluateAsAbsolute(Res, Layout,
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Writer->getSectionAddressMap());
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if (isAbs) {
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FixedValue = Res;
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return;
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} else {
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report_fatal_error("unsupported relocation of variable '" +
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Symbol->getName() + "'", false);
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}
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} else {
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report_fatal_error("unsupported relocation of undefined symbol '" +
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Symbol->getName() + "'", false);
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}
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MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
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if (IsPCRel) {
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if (IsRIPRel) {
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if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
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// x86_64 distinguishes movq foo@GOTPCREL so that the linker can
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// rewrite the movq to an leaq at link time if the symbol ends up in
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// the same linkage unit.
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if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
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Type = MachO::X86_64_RELOC_GOT_LOAD;
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else
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Type = MachO::X86_64_RELOC_GOT;
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} else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
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Type = MachO::X86_64_RELOC_TLV;
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} else if (Modifier != MCSymbolRefExpr::VK_None) {
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report_fatal_error("unsupported symbol modifier in relocation",
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false);
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} else {
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Type = MachO::X86_64_RELOC_SIGNED;
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// The Darwin x86_64 relocation format has a problem where it cannot
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// encode an address (L<foo> + <constant>) which is outside the atom
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// containing L<foo>. Generally, this shouldn't occur but it does
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// happen when we have a RIPrel instruction with data following the
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// relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
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// adjustment Darwin x86_64 uses, the offset is still negative and the
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// linker has no way to recognize this.
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//
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// To work around this, Darwin uses several special relocation types
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// to indicate the offsets. However, the specification or
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// implementation of these seems to also be incomplete; they should
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// adjust the addend as well based on the actual encoded instruction
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// (the additional bias), but instead appear to just look at the final
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// offset.
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switch (-(Target.getConstant() + (1LL << Log2Size))) {
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case 1: Type = MachO::X86_64_RELOC_SIGNED_1; break;
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case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break;
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case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break;
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}
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}
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} else {
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if (Modifier != MCSymbolRefExpr::VK_None)
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report_fatal_error("unsupported symbol modifier in branch "
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"relocation", false);
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Type = MachO::X86_64_RELOC_BRANCH;
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}
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} else {
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if (Modifier == MCSymbolRefExpr::VK_GOT) {
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Type = MachO::X86_64_RELOC_GOT;
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} else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
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// GOTPCREL is allowed as a modifier on non-PCrel instructions, in which
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// case all we do is set the PCrel bit in the relocation entry; this is
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// used with exception handling, for example. The source is required to
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// include any necessary offset directly.
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Type = MachO::X86_64_RELOC_GOT;
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IsPCRel = 1;
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} else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
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report_fatal_error("TLVP symbol modifier should have been rip-rel",
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false);
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} else if (Modifier != MCSymbolRefExpr::VK_None)
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report_fatal_error("unsupported symbol modifier in relocation", false);
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else {
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Type = MachO::X86_64_RELOC_UNSIGNED;
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unsigned Kind = Fixup.getKind();
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if (Kind == X86::reloc_signed_4byte)
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report_fatal_error("32-bit absolute addressing is not supported in "
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"64-bit mode", false);
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}
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}
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}
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// x86_64 always writes custom values into the fixups.
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FixedValue = Value;
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// struct relocation_info (8 bytes)
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MachO::any_relocation_info MRE;
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MRE.r_word0 = FixupOffset;
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MRE.r_word1 = (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
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(IsExtern << 27) | (Type << 28);
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Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
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}
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bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer,
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const MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment,
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const MCFixup &Fixup,
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MCValue Target,
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unsigned Log2Size,
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uint64_t &FixedValue) {
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uint64_t OriginalFixedValue = FixedValue;
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uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
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unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
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unsigned Type = MachO::GENERIC_RELOC_VANILLA;
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// See <reloc.h>.
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const MCSymbol *A = &Target.getSymA()->getSymbol();
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if (!A->getFragment())
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report_fatal_error("symbol '" + A->getName() +
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"' can not be undefined in a subtraction expression",
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false);
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uint32_t Value = Writer->getSymbolAddress(*A, Layout);
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uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent());
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FixedValue += SecAddr;
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uint32_t Value2 = 0;
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if (const MCSymbolRefExpr *B = Target.getSymB()) {
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const MCSymbol *SB = &B->getSymbol();
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if (!SB->getFragment())
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report_fatal_error("symbol '" + B->getSymbol().getName() +
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"' can not be undefined in a subtraction expression",
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false);
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// Select the appropriate difference relocation type.
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//
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// Note that there is no longer any semantic difference between these two
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// relocation types from the linkers point of view, this is done solely for
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// pedantic compatibility with 'as'.
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Type = A->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF
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: (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF;
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Value2 = Writer->getSymbolAddress(B->getSymbol(), Layout);
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FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent());
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}
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// Relocations are written out in reverse order, so the PAIR comes first.
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if (Type == MachO::GENERIC_RELOC_SECTDIFF ||
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Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) {
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// If the offset is too large to fit in a scattered relocation,
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// we're hosed. It's an unfortunate limitation of the MachO format.
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if (FixupOffset > 0xffffff) {
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char Buffer[32];
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format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
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Asm.getContext().reportFatalError(Fixup.getLoc(),
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Twine("Section too large, can't encode "
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"r_address (") + Buffer +
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") into 24 bits of scattered "
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"relocation entry.");
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llvm_unreachable("fatal error returned?!");
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}
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MachO::any_relocation_info MRE;
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MRE.r_word0 = ((0 << 0) | // r_address
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(MachO::GENERIC_RELOC_PAIR << 24) | // r_type
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(Log2Size << 28) |
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(IsPCRel << 30) |
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MachO::R_SCATTERED);
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MRE.r_word1 = Value2;
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Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
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} else {
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// If the offset is more than 24-bits, it won't fit in a scattered
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// relocation offset field, so we fall back to using a non-scattered
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// relocation. This is a bit risky, as if the offset reaches out of
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// the block and the linker is doing scattered loading on this
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// symbol, things can go badly.
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//
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// Required for 'as' compatibility.
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if (FixupOffset > 0xffffff) {
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FixedValue = OriginalFixedValue;
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return false;
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}
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}
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MachO::any_relocation_info MRE;
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MRE.r_word0 = ((FixupOffset << 0) |
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(Type << 24) |
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(Log2Size << 28) |
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(IsPCRel << 30) |
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MachO::R_SCATTERED);
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MRE.r_word1 = Value;
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Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
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return true;
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}
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void X86MachObjectWriter::recordTLVPRelocation(MachObjectWriter *Writer,
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const MCAssembler &Asm,
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const MCAsmLayout &Layout,
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const MCFragment *Fragment,
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const MCFixup &Fixup,
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MCValue Target,
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uint64_t &FixedValue) {
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assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
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!is64Bit() &&
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"Should only be called with a 32-bit TLVP relocation!");
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unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
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uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
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unsigned IsPCRel = 0;
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// We're only going to have a second symbol in pic mode and it'll be a
|
|
// subtraction from the picbase. For 32-bit pic the addend is the difference
|
|
// between the picbase and the next address. For 32-bit static the addend is
|
|
// zero.
|
|
if (Target.getSymB()) {
|
|
// If this is a subtraction then we're pcrel.
|
|
uint32_t FixupAddress =
|
|
Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
|
|
IsPCRel = 1;
|
|
FixedValue =
|
|
FixupAddress -
|
|
Writer->getSymbolAddress(Target.getSymB()->getSymbol(), Layout) +
|
|
Target.getConstant();
|
|
FixedValue += 1ULL << Log2Size;
|
|
} else {
|
|
FixedValue = 0;
|
|
}
|
|
|
|
// struct relocation_info (8 bytes)
|
|
MachO::any_relocation_info MRE;
|
|
MRE.r_word0 = Value;
|
|
MRE.r_word1 =
|
|
(IsPCRel << 24) | (Log2Size << 25) | (MachO::GENERIC_RELOC_TLV << 28);
|
|
Writer->addRelocation(&Target.getSymA()->getSymbol(), Fragment->getParent(),
|
|
MRE);
|
|
}
|
|
|
|
void X86MachObjectWriter::RecordX86Relocation(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());
|
|
unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
|
|
|
|
// If this is a 32-bit TLVP reloc it's handled a bit differently.
|
|
if (Target.getSymA() &&
|
|
Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) {
|
|
recordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
|
|
FixedValue);
|
|
return;
|
|
}
|
|
|
|
// If this is a difference or a defined symbol plus an offset, then we need a
|
|
// scattered relocation entry. Differences always require scattered
|
|
// relocations.
|
|
if (Target.getSymB()) {
|
|
recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
|
|
Target, Log2Size, FixedValue);
|
|
return;
|
|
}
|
|
|
|
// Get the symbol data, if any.
|
|
const MCSymbol *A = nullptr;
|
|
if (Target.getSymA())
|
|
A = &Target.getSymA()->getSymbol();
|
|
|
|
// If this is an internal relocation with an offset, it also needs a scattered
|
|
// relocation entry.
|
|
uint32_t Offset = Target.getConstant();
|
|
if (IsPCRel)
|
|
Offset += 1 << Log2Size;
|
|
// Try to record the scattered relocation if needed. Fall back to non
|
|
// scattered if necessary (see comments in recordScatteredRelocation()
|
|
// for details).
|
|
if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A) &&
|
|
recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
|
|
Log2Size, FixedValue))
|
|
return;
|
|
|
|
// See <reloc.h>.
|
|
uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
|
|
unsigned Index = 0;
|
|
unsigned Type = 0;
|
|
const MCSymbol *RelSymbol = nullptr;
|
|
|
|
if (Target.isAbsolute()) { // constant
|
|
// SymbolNum of 0 indicates the absolute section.
|
|
//
|
|
// FIXME: Currently, these are never generated (see code below). I cannot
|
|
// find a case where they are actually emitted.
|
|
Type = MachO::GENERIC_RELOC_VANILLA;
|
|
} else {
|
|
// Resolve constant variables.
|
|
if (A->isVariable()) {
|
|
int64_t Res;
|
|
if (A->getVariableValue()->evaluateAsAbsolute(
|
|
Res, Layout, Writer->getSectionAddressMap())) {
|
|
FixedValue = Res;
|
|
return;
|
|
}
|
|
}
|
|
|
|
// Check whether we need an external or internal relocation.
|
|
if (Writer->doesSymbolRequireExternRelocation(*A)) {
|
|
RelSymbol = A;
|
|
// For external relocations, make sure to offset the fixup value to
|
|
// compensate for the addend of the symbol address, if it was
|
|
// undefined. This occurs with weak definitions, for example.
|
|
if (!A->isUndefined())
|
|
FixedValue -= Layout.getSymbolOffset(*A);
|
|
} else {
|
|
// The index is the section ordinal (1-based).
|
|
const MCSection &Sec = A->getSection();
|
|
Index = Sec.getOrdinal() + 1;
|
|
FixedValue += Writer->getSectionAddress(&Sec);
|
|
}
|
|
if (IsPCRel)
|
|
FixedValue -= Writer->getSectionAddress(Fragment->getParent());
|
|
|
|
Type = MachO::GENERIC_RELOC_VANILLA;
|
|
}
|
|
|
|
// struct relocation_info (8 bytes)
|
|
MachO::any_relocation_info MRE;
|
|
MRE.r_word0 = FixupOffset;
|
|
MRE.r_word1 =
|
|
(Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
|
|
Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
|
|
}
|
|
|
|
MCObjectWriter *llvm::createX86MachObjectWriter(raw_pwrite_stream &OS,
|
|
bool Is64Bit, uint32_t CPUType,
|
|
uint32_t CPUSubtype) {
|
|
return createMachObjectWriter(new X86MachObjectWriter(Is64Bit,
|
|
CPUType,
|
|
CPUSubtype),
|
|
OS, /*IsLittleEndian=*/true);
|
|
}
|