| //===-- X86MachObjectWriter.cpp - X86 Mach-O Writer -----------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "MCTargetDesc/X86FixupKinds.h" |
| #include "MCTargetDesc/X86MCTargetDesc.h" |
| #include "llvm/MC/MCAssembler.h" |
| #include "llvm/MC/MCAsmLayout.h" |
| #include "llvm/MC/MCMachObjectWriter.h" |
| #include "llvm/MC/MCSectionMachO.h" |
| #include "llvm/MC/MCValue.h" |
| #include "llvm/ADT/Twine.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Object/MachOFormat.h" |
| |
| using namespace llvm; |
| using namespace llvm::object; |
| |
| namespace { |
| class X86MachObjectWriter : public MCMachObjectTargetWriter { |
| void RecordScatteredRelocation(MachObjectWriter *Writer, |
| const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, |
| MCValue Target, |
| unsigned Log2Size, |
| uint64_t &FixedValue); |
| void RecordTLVPRelocation(MachObjectWriter *Writer, |
| const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, |
| MCValue Target, |
| uint64_t &FixedValue); |
| |
| void RecordX86Relocation(MachObjectWriter *Writer, |
| const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, |
| MCValue Target, |
| uint64_t &FixedValue); |
| void RecordX86_64Relocation(MachObjectWriter *Writer, |
| const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, |
| MCValue Target, |
| uint64_t &FixedValue); |
| public: |
| X86MachObjectWriter(bool Is64Bit, uint32_t CPUType, |
| uint32_t CPUSubtype) |
| : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype, |
| /*UseAggressiveSymbolFolding=*/Is64Bit) {} |
| |
| void RecordRelocation(MachObjectWriter *Writer, |
| const MCAssembler &Asm, const MCAsmLayout &Layout, |
| const MCFragment *Fragment, const MCFixup &Fixup, |
| MCValue Target, uint64_t &FixedValue) { |
| if (Writer->is64Bit()) |
| RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, |
| FixedValue); |
| else |
| RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target, |
| FixedValue); |
| } |
| }; |
| } |
| |
| static bool isFixupKindRIPRel(unsigned Kind) { |
| return Kind == X86::reloc_riprel_4byte || |
| Kind == X86::reloc_riprel_4byte_movq_load; |
| } |
| |
| static unsigned getFixupKindLog2Size(unsigned Kind) { |
| switch (Kind) { |
| default: |
| llvm_unreachable("invalid fixup kind!"); |
| case FK_PCRel_1: |
| case FK_Data_1: return 0; |
| case FK_PCRel_2: |
| case FK_Data_2: return 1; |
| case FK_PCRel_4: |
| // FIXME: Remove these!!! |
| case X86::reloc_riprel_4byte: |
| case X86::reloc_riprel_4byte_movq_load: |
| case X86::reloc_signed_4byte: |
| case FK_Data_4: return 2; |
| case FK_Data_8: return 3; |
| } |
| } |
| |
| void X86MachObjectWriter::RecordX86_64Relocation(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 IsRIPRel = isFixupKindRIPRel(Fixup.getKind()); |
| unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); |
| |
| // See <reloc.h>. |
| uint32_t FixupOffset = |
| Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); |
| uint32_t FixupAddress = |
| Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset(); |
| int64_t Value = 0; |
| unsigned Index = 0; |
| unsigned IsExtern = 0; |
| unsigned Type = 0; |
| |
| Value = Target.getConstant(); |
| |
| if (IsPCRel) { |
| // Compensate for the relocation offset, Darwin x86_64 relocations only have |
| // the addend and appear to have attempted to define it to be the actual |
| // expression addend without the PCrel bias. However, instructions with data |
| // following the relocation are not accommodated for (see comment below |
| // regarding SIGNED{1,2,4}), so it isn't exactly that either. |
| Value += 1LL << Log2Size; |
| } |
| |
| if (Target.isAbsolute()) { // constant |
| // SymbolNum of 0 indicates the absolute section. |
| Type = macho::RIT_X86_64_Unsigned; |
| Index = 0; |
| |
| // FIXME: I believe this is broken, I don't think the linker can understand |
| // it. I think it would require a local relocation, but I'm not sure if that |
| // would work either. The official way to get an absolute PCrel relocation |
| // is to use an absolute symbol (which we don't support yet). |
| if (IsPCRel) { |
| IsExtern = 1; |
| Type = macho::RIT_X86_64_Branch; |
| } |
| } else if (Target.getSymB()) { // A - B + constant |
| const MCSymbol *A = &Target.getSymA()->getSymbol(); |
| MCSymbolData &A_SD = Asm.getSymbolData(*A); |
| const MCSymbolData *A_Base = Asm.getAtom(&A_SD); |
| |
| const MCSymbol *B = &Target.getSymB()->getSymbol(); |
| MCSymbolData &B_SD = Asm.getSymbolData(*B); |
| const MCSymbolData *B_Base = Asm.getAtom(&B_SD); |
| |
| // Neither symbol can be modified. |
| if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None || |
| Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None) |
| report_fatal_error("unsupported relocation of modified symbol"); |
| |
| // We don't support PCrel relocations of differences. Darwin 'as' doesn't |
| // implement most of these correctly. |
| if (IsPCRel) |
| report_fatal_error("unsupported pc-relative relocation of difference"); |
| |
| // The support for the situation where one or both of the symbols would |
| // require a local relocation is handled just like if the symbols were |
| // external. This is certainly used in the case of debug sections where the |
| // section has only temporary symbols and thus the symbols don't have base |
| // symbols. This is encoded using the section ordinal and non-extern |
| // relocation entries. |
| |
| // Darwin 'as' doesn't emit correct relocations for this (it ends up with a |
| // single SIGNED relocation); reject it for now. Except the case where both |
| // symbols don't have a base, equal but both NULL. |
| if (A_Base == B_Base && A_Base) |
| report_fatal_error("unsupported relocation with identical base"); |
| |
| Value += Writer->getSymbolAddress(&A_SD, Layout) - |
| (A_Base == NULL ? 0 : Writer->getSymbolAddress(A_Base, Layout)); |
| Value -= Writer->getSymbolAddress(&B_SD, Layout) - |
| (B_Base == NULL ? 0 : Writer->getSymbolAddress(B_Base, Layout)); |
| |
| if (A_Base) { |
| Index = A_Base->getIndex(); |
| IsExtern = 1; |
| } |
| else { |
| Index = A_SD.getFragment()->getParent()->getOrdinal() + 1; |
| IsExtern = 0; |
| } |
| Type = macho::RIT_X86_64_Unsigned; |
| |
| macho::RelocationEntry MRE; |
| MRE.Word0 = FixupOffset; |
| MRE.Word1 = ((Index << 0) | |
| (IsPCRel << 24) | |
| (Log2Size << 25) | |
| (IsExtern << 27) | |
| (Type << 28)); |
| Writer->addRelocation(Fragment->getParent(), MRE); |
| |
| if (B_Base) { |
| Index = B_Base->getIndex(); |
| IsExtern = 1; |
| } |
| else { |
| Index = B_SD.getFragment()->getParent()->getOrdinal() + 1; |
| IsExtern = 0; |
| } |
| Type = macho::RIT_X86_64_Subtractor; |
| } else { |
| const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); |
| MCSymbolData &SD = Asm.getSymbolData(*Symbol); |
| const MCSymbolData *Base = Asm.getAtom(&SD); |
| |
| // Relocations inside debug sections always use local relocations when |
| // possible. This seems to be done because the debugger doesn't fully |
| // understand x86_64 relocation entries, and expects to find values that |
| // have already been fixed up. |
| if (Symbol->isInSection()) { |
| const MCSectionMachO &Section = static_cast<const MCSectionMachO&>( |
| Fragment->getParent()->getSection()); |
| if (Section.hasAttribute(MCSectionMachO::S_ATTR_DEBUG)) |
| Base = 0; |
| } |
| |
| // x86_64 almost always uses external relocations, except when there is no |
| // symbol to use as a base address (a local symbol with no preceding |
| // non-local symbol). |
| 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() && !Symbol->isVariable()) { |
| // The index is the section ordinal (1-based). |
| Index = SD.getFragment()->getParent()->getOrdinal() + 1; |
| IsExtern = 0; |
| Value += Writer->getSymbolAddress(&SD, Layout); |
| |
| if (IsPCRel) |
| Value -= FixupAddress + (1 << Log2Size); |
| } else if (Symbol->isVariable()) { |
| const MCExpr *Value = Symbol->getVariableValue(); |
| int64_t Res; |
| bool isAbs = Value->EvaluateAsAbsolute(Res, Layout, |
| Writer->getSectionAddressMap()); |
| if (isAbs) { |
| FixedValue = Res; |
| return; |
| } else { |
| report_fatal_error("unsupported relocation of variable '" + |
| Symbol->getName() + "'"); |
| } |
| } else { |
| report_fatal_error("unsupported relocation of undefined symbol '" + |
| Symbol->getName() + "'"); |
| } |
| |
| MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind(); |
| if (IsPCRel) { |
| if (IsRIPRel) { |
| if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { |
| // x86_64 distinguishes movq foo@GOTPCREL so that the linker can |
| // rewrite the movq to an leaq at link time if the symbol ends up in |
| // the same linkage unit. |
| if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load) |
| Type = macho::RIT_X86_64_GOTLoad; |
| else |
| Type = macho::RIT_X86_64_GOT; |
| } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { |
| Type = macho::RIT_X86_64_TLV; |
| } else if (Modifier != MCSymbolRefExpr::VK_None) { |
| report_fatal_error("unsupported symbol modifier in relocation"); |
| } else { |
| Type = macho::RIT_X86_64_Signed; |
| |
| // The Darwin x86_64 relocation format has a problem where it cannot |
| // encode an address (L<foo> + <constant>) which is outside the atom |
| // containing L<foo>. Generally, this shouldn't occur but it does |
| // happen when we have a RIPrel instruction with data following the |
| // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel |
| // adjustment Darwin x86_64 uses, the offset is still negative and the |
| // linker has no way to recognize this. |
| // |
| // To work around this, Darwin uses several special relocation types |
| // to indicate the offsets. However, the specification or |
| // implementation of these seems to also be incomplete; they should |
| // adjust the addend as well based on the actual encoded instruction |
| // (the additional bias), but instead appear to just look at the final |
| // offset. |
| switch (-(Target.getConstant() + (1LL << Log2Size))) { |
| case 1: Type = macho::RIT_X86_64_Signed1; break; |
| case 2: Type = macho::RIT_X86_64_Signed2; break; |
| case 4: Type = macho::RIT_X86_64_Signed4; break; |
| } |
| } |
| } else { |
| if (Modifier != MCSymbolRefExpr::VK_None) |
| report_fatal_error("unsupported symbol modifier in branch " |
| "relocation"); |
| |
| Type = macho::RIT_X86_64_Branch; |
| } |
| } else { |
| if (Modifier == MCSymbolRefExpr::VK_GOT) { |
| Type = macho::RIT_X86_64_GOT; |
| } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) { |
| // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which |
| // case all we do is set the PCrel bit in the relocation entry; this is |
| // used with exception handling, for example. The source is required to |
| // include any necessary offset directly. |
| Type = macho::RIT_X86_64_GOT; |
| IsPCRel = 1; |
| } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { |
| report_fatal_error("TLVP symbol modifier should have been rip-rel"); |
| } else if (Modifier != MCSymbolRefExpr::VK_None) |
| report_fatal_error("unsupported symbol modifier in relocation"); |
| else |
| Type = macho::RIT_X86_64_Unsigned; |
| } |
| } |
| |
| // x86_64 always writes custom values into the fixups. |
| FixedValue = Value; |
| |
| // struct relocation_info (8 bytes) |
| macho::RelocationEntry MRE; |
| MRE.Word0 = FixupOffset; |
| MRE.Word1 = ((Index << 0) | |
| (IsPCRel << 24) | |
| (Log2Size << 25) | |
| (IsExtern << 27) | |
| (Type << 28)); |
| Writer->addRelocation(Fragment->getParent(), MRE); |
| } |
| |
| void X86MachObjectWriter::RecordScatteredRelocation(MachObjectWriter *Writer, |
| const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, |
| MCValue Target, |
| unsigned Log2Size, |
| uint64_t &FixedValue) { |
| uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); |
| unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); |
| unsigned Type = macho::RIT_Vanilla; |
| |
| // See <reloc.h>. |
| const MCSymbol *A = &Target.getSymA()->getSymbol(); |
| MCSymbolData *A_SD = &Asm.getSymbolData(*A); |
| |
| if (!A_SD->getFragment()) |
| report_fatal_error("symbol '" + A->getName() + |
| "' can not be undefined in a subtraction expression"); |
| |
| uint32_t Value = Writer->getSymbolAddress(A_SD, Layout); |
| uint64_t SecAddr = Writer->getSectionAddress(A_SD->getFragment()->getParent()); |
| FixedValue += SecAddr; |
| uint32_t Value2 = 0; |
| |
| if (const MCSymbolRefExpr *B = Target.getSymB()) { |
| MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol()); |
| |
| if (!B_SD->getFragment()) |
| report_fatal_error("symbol '" + B->getSymbol().getName() + |
| "' can not be undefined in a subtraction expression"); |
| |
| // Select the appropriate difference relocation type. |
| // |
| // Note that there is no longer any semantic difference between these two |
| // relocation types from the linkers point of view, this is done solely for |
| // pedantic compatibility with 'as'. |
| Type = A_SD->isExternal() ? (unsigned)macho::RIT_Difference : |
| (unsigned)macho::RIT_Generic_LocalDifference; |
| Value2 = Writer->getSymbolAddress(B_SD, Layout); |
| FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent()); |
| } |
| |
| // Relocations are written out in reverse order, so the PAIR comes first. |
| if (Type == macho::RIT_Difference || |
| Type == macho::RIT_Generic_LocalDifference) { |
| macho::RelocationEntry MRE; |
| MRE.Word0 = ((0 << 0) | |
| (macho::RIT_Pair << 24) | |
| (Log2Size << 28) | |
| (IsPCRel << 30) | |
| macho::RF_Scattered); |
| MRE.Word1 = Value2; |
| Writer->addRelocation(Fragment->getParent(), MRE); |
| } |
| |
| macho::RelocationEntry MRE; |
| MRE.Word0 = ((FixupOffset << 0) | |
| (Type << 24) | |
| (Log2Size << 28) | |
| (IsPCRel << 30) | |
| macho::RF_Scattered); |
| MRE.Word1 = Value; |
| Writer->addRelocation(Fragment->getParent(), MRE); |
| } |
| |
| void X86MachObjectWriter::RecordTLVPRelocation(MachObjectWriter *Writer, |
| const MCAssembler &Asm, |
| const MCAsmLayout &Layout, |
| const MCFragment *Fragment, |
| const MCFixup &Fixup, |
| MCValue Target, |
| uint64_t &FixedValue) { |
| assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP && |
| !is64Bit() && |
| "Should only be called with a 32-bit TLVP relocation!"); |
| |
| unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind()); |
| uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); |
| unsigned IsPCRel = 0; |
| |
| // Get the symbol data. |
| MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol()); |
| unsigned Index = SD_A->getIndex(); |
| |
| // 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(); |
| MCSymbolData *SD_B = &Asm.getSymbolData(Target.getSymB()->getSymbol()); |
| IsPCRel = 1; |
| FixedValue = (FixupAddress - Writer->getSymbolAddress(SD_B, Layout) + |
| Target.getConstant()); |
| FixedValue += 1ULL << Log2Size; |
| } else { |
| FixedValue = 0; |
| } |
| |
| // struct relocation_info (8 bytes) |
| macho::RelocationEntry MRE; |
| MRE.Word0 = Value; |
| MRE.Word1 = ((Index << 0) | |
| (IsPCRel << 24) | |
| (Log2Size << 25) | |
| (1 << 27) | // Extern |
| (macho::RIT_Generic_TLV << 28)); // Type |
| Writer->addRelocation(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()) |
| return RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, |
| Target, Log2Size, FixedValue); |
| |
| // Get the symbol data, if any. |
| MCSymbolData *SD = 0; |
| if (Target.getSymA()) |
| SD = &Asm.getSymbolData(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; |
| if (Offset && SD && !Writer->doesSymbolRequireExternRelocation(SD)) |
| return RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, |
| Target, Log2Size, FixedValue); |
| |
| // See <reloc.h>. |
| uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); |
| unsigned Index = 0; |
| unsigned IsExtern = 0; |
| unsigned Type = 0; |
| |
| 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::RIT_Vanilla; |
| } else { |
| // Resolve constant variables. |
| if (SD->getSymbol().isVariable()) { |
| int64_t Res; |
| if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute( |
| Res, Layout, Writer->getSectionAddressMap())) { |
| FixedValue = Res; |
| return; |
| } |
| } |
| |
| // Check whether we need an external or internal relocation. |
| if (Writer->doesSymbolRequireExternRelocation(SD)) { |
| IsExtern = 1; |
| Index = SD->getIndex(); |
| // 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 (!SD->Symbol->isUndefined()) |
| FixedValue -= Layout.getSymbolOffset(SD); |
| } else { |
| // The index is the section ordinal (1-based). |
| const MCSectionData &SymSD = Asm.getSectionData( |
| SD->getSymbol().getSection()); |
| Index = SymSD.getOrdinal() + 1; |
| FixedValue += Writer->getSectionAddress(&SymSD); |
| } |
| if (IsPCRel) |
| FixedValue -= Writer->getSectionAddress(Fragment->getParent()); |
| |
| Type = macho::RIT_Vanilla; |
| } |
| |
| // struct relocation_info (8 bytes) |
| macho::RelocationEntry MRE; |
| MRE.Word0 = FixupOffset; |
| MRE.Word1 = ((Index << 0) | |
| (IsPCRel << 24) | |
| (Log2Size << 25) | |
| (IsExtern << 27) | |
| (Type << 28)); |
| Writer->addRelocation(Fragment->getParent(), MRE); |
| } |
| |
| MCObjectWriter *llvm::createX86MachObjectWriter(raw_ostream &OS, |
| bool Is64Bit, |
| uint32_t CPUType, |
| uint32_t CPUSubtype) { |
| return createMachObjectWriter(new X86MachObjectWriter(Is64Bit, |
| CPUType, |
| CPUSubtype), |
| OS, /*IsLittleEndian=*/true); |
| } |
