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Diffstat (limited to 'contrib/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp')
| -rw-r--r-- | contrib/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp | 606 |
1 files changed, 606 insertions, 0 deletions
diff --git a/contrib/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp b/contrib/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp new file mode 100644 index 000000000000..965f7de809b3 --- /dev/null +++ b/contrib/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp @@ -0,0 +1,606 @@ +//===-- 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/ADT/Twine.h" +#include "llvm/BinaryFormat/MachO.h" +#include "llvm/MC/MCAsmInfo.h" +#include "llvm/MC/MCAsmLayout.h" +#include "llvm/MC/MCAssembler.h" +#include "llvm/MC/MCContext.h" +#include "llvm/MC/MCMachObjectWriter.h" +#include "llvm/MC/MCSectionMachO.h" +#include "llvm/MC/MCValue.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/Format.h" + +using namespace llvm; + +namespace { +class X86MachObjectWriter : public MCMachObjectTargetWriter { + bool 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, 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) {} + + void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm, + const MCAsmLayout &Layout, const MCFragment *Fragment, + const MCFixup &Fixup, MCValue Target, + uint64_t &FixedValue) override { + 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 || + Kind == X86::reloc_riprel_4byte_relax || + Kind == X86::reloc_riprel_4byte_relax_rex; +} + +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_relax: + case X86::reloc_riprel_4byte_relax_rex: + case X86::reloc_riprel_4byte_movq_load: + case X86::reloc_signed_4byte: + case X86::reloc_signed_4byte_relax: + case FK_Data_4: return 2; + case FK_Data_8: return 3; + } +} + +void X86MachObjectWriter::RecordX86_64Relocation( + MachObjectWriter *Writer, 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; + const MCSymbol *RelSymbol = nullptr; + + 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::X86_64_RELOC_UNSIGNED; + + // 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::X86_64_RELOC_BRANCH; + } + } else if (Target.getSymB()) { // A - B + constant + const MCSymbol *A = &Target.getSymA()->getSymbol(); + if (A->isTemporary()) + A = &Writer->findAliasedSymbol(*A); + const MCSymbol *A_Base = Asm.getAtom(*A); + + const MCSymbol *B = &Target.getSymB()->getSymbol(); + if (B->isTemporary()) + B = &Writer->findAliasedSymbol(*B); + const MCSymbol *B_Base = Asm.getAtom(*B); + + // Neither symbol can be modified. + if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None) { + Asm.getContext().reportError(Fixup.getLoc(), + "unsupported relocation of modified symbol"); + return; + } + + // We don't support PCrel relocations of differences. Darwin 'as' doesn't + // implement most of these correctly. + if (IsPCRel) { + Asm.getContext().reportError( + Fixup.getLoc(), "unsupported pc-relative relocation of difference"); + return; + } + + // 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) { + Asm.getContext().reportError( + Fixup.getLoc(), "unsupported relocation with identical base"); + return; + } + + // A subtraction expression where either symbol is undefined is a + // non-relocatable expression. + if (A->isUndefined() || B->isUndefined()) { + StringRef Name = A->isUndefined() ? A->getName() : B->getName(); + Asm.getContext().reportError(Fixup.getLoc(), + "unsupported relocation with subtraction expression, symbol '" + + Name + "' can not be undefined in a subtraction expression"); + return; + } + + Value += Writer->getSymbolAddress(*A, Layout) - + (!A_Base ? 0 : Writer->getSymbolAddress(*A_Base, Layout)); + Value -= Writer->getSymbolAddress(*B, Layout) - + (!B_Base ? 0 : Writer->getSymbolAddress(*B_Base, Layout)); + + if (!A_Base) + Index = A->getFragment()->getParent()->getOrdinal() + 1; + Type = MachO::X86_64_RELOC_UNSIGNED; + + MachO::any_relocation_info MRE; + MRE.r_word0 = FixupOffset; + MRE.r_word1 = + (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28); + Writer->addRelocation(A_Base, Fragment->getParent(), MRE); + + if (B_Base) + RelSymbol = B_Base; + else + Index = B->getFragment()->getParent()->getOrdinal() + 1; + Type = MachO::X86_64_RELOC_SUBTRACTOR; + } else { + const MCSymbol *Symbol = &Target.getSymA()->getSymbol(); + if (Symbol->isTemporary() && Value) { + const MCSection &Sec = Symbol->getSection(); + if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec)) + Symbol->setUsedInReloc(); + } + RelSymbol = Asm.getAtom(*Symbol); + + // 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()); + if (Section.hasAttribute(MachO::S_ATTR_DEBUG)) + RelSymbol = nullptr; + } + + // 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 (RelSymbol) { + // Add the local offset, if needed. + if (RelSymbol != Symbol) + Value += Layout.getSymbolOffset(*Symbol) - + Layout.getSymbolOffset(*RelSymbol); + } else if (Symbol->isInSection() && !Symbol->isVariable()) { + // The index is the section ordinal (1-based). + Index = Symbol->getFragment()->getParent()->getOrdinal() + 1; + Value += Writer->getSymbolAddress(*Symbol, 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 { + Asm.getContext().reportError(Fixup.getLoc(), + "unsupported relocation of variable '" + + Symbol->getName() + "'"); + return; + } + } else { + Asm.getContext().reportError( + Fixup.getLoc(), "unsupported relocation of undefined symbol '" + + Symbol->getName() + "'"); + return; + } + + 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::X86_64_RELOC_GOT_LOAD; + else + Type = MachO::X86_64_RELOC_GOT; + } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { + Type = MachO::X86_64_RELOC_TLV; + } else if (Modifier != MCSymbolRefExpr::VK_None) { + Asm.getContext().reportError( + Fixup.getLoc(), "unsupported symbol modifier in relocation"); + return; + } else { + Type = MachO::X86_64_RELOC_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::X86_64_RELOC_SIGNED_1; break; + case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break; + case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break; + } + } + } else { + if (Modifier != MCSymbolRefExpr::VK_None) { + Asm.getContext().reportError( + Fixup.getLoc(), + "unsupported symbol modifier in branch relocation"); + return; + } + + Type = MachO::X86_64_RELOC_BRANCH; + } + } else { + if (Modifier == MCSymbolRefExpr::VK_GOT) { + Type = MachO::X86_64_RELOC_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::X86_64_RELOC_GOT; + IsPCRel = 1; + } else if (Modifier == MCSymbolRefExpr::VK_TLVP) { + Asm.getContext().reportError( + Fixup.getLoc(), "TLVP symbol modifier should have been rip-rel"); + return; + } else if (Modifier != MCSymbolRefExpr::VK_None) { + Asm.getContext().reportError( + Fixup.getLoc(), "unsupported symbol modifier in relocation"); + return; + } else { + Type = MachO::X86_64_RELOC_UNSIGNED; + unsigned Kind = Fixup.getKind(); + if (Kind == X86::reloc_signed_4byte) { + Asm.getContext().reportError( + Fixup.getLoc(), + "32-bit absolute addressing is not supported in 64-bit mode"); + return; + } + } + } + } + + // x86_64 always writes custom values into the fixups. + 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(RelSymbol, Fragment->getParent(), MRE); +} + +bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer, + const MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCFragment *Fragment, + const MCFixup &Fixup, + MCValue Target, + unsigned Log2Size, + uint64_t &FixedValue) { + uint64_t OriginalFixedValue = FixedValue; + uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); + unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); + unsigned Type = MachO::GENERIC_RELOC_VANILLA; + + // See <reloc.h>. + const MCSymbol *A = &Target.getSymA()->getSymbol(); + + if (!A->getFragment()) { + Asm.getContext().reportError( + Fixup.getLoc(), + "symbol '" + A->getName() + + "' can not be undefined in a subtraction expression"); + return false; + } + + uint32_t Value = Writer->getSymbolAddress(*A, Layout); + uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent()); + FixedValue += SecAddr; + uint32_t Value2 = 0; + + if (const MCSymbolRefExpr *B = Target.getSymB()) { + const MCSymbol *SB = &B->getSymbol(); + + if (!SB->getFragment()) { + Asm.getContext().reportError( + Fixup.getLoc(), + "symbol '" + SB->getName() + + "' can not be undefined in a subtraction expression"); + return false; + } + + // 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->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF + : (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF; + Value2 = Writer->getSymbolAddress(*SB, Layout); + FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent()); + } + + // Relocations are written out in reverse order, so the PAIR comes first. + if (Type == MachO::GENERIC_RELOC_SECTDIFF || + Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) { + // If the offset is too large to fit in a scattered relocation, + // we're hosed. It's an unfortunate limitation of the MachO format. + if (FixupOffset > 0xffffff) { + char Buffer[32]; + format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer)); + Asm.getContext().reportError(Fixup.getLoc(), + Twine("Section too large, can't encode " + "r_address (") + Buffer + + ") into 24 bits of scattered " + "relocation entry."); + return false; + } + + MachO::any_relocation_info MRE; + MRE.r_word0 = ((0 << 0) | // r_address + (MachO::GENERIC_RELOC_PAIR << 24) | // r_type + (Log2Size << 28) | + (IsPCRel << 30) | + MachO::R_SCATTERED); + MRE.r_word1 = Value2; + Writer->addRelocation(nullptr, Fragment->getParent(), MRE); + } else { + // If the offset is more than 24-bits, it won't fit in a scattered + // relocation offset field, so we fall back to using a non-scattered + // relocation. This is a bit risky, as if the offset reaches out of + // the block and the linker is doing scattered loading on this + // symbol, things can go badly. + // + // Required for 'as' compatibility. + if (FixupOffset > 0xffffff) { + FixedValue = OriginalFixedValue; + return false; + } + } + + MachO::any_relocation_info MRE; + MRE.r_word0 = ((FixupOffset << 0) | + (Type << 24) | + (Log2Size << 28) | + (IsPCRel << 30) | + MachO::R_SCATTERED); + MRE.r_word1 = Value; + Writer->addRelocation(nullptr, Fragment->getParent(), MRE); + return true; +} + +void X86MachObjectWriter::recordTLVPRelocation(MachObjectWriter *Writer, + const MCAssembler &Asm, + const MCAsmLayout &Layout, + const MCFragment *Fragment, + const MCFixup &Fixup, + MCValue Target, + uint64_t &FixedValue) { + const MCSymbolRefExpr *SymA = Target.getSymA(); + assert(SymA->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; + + // 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 (auto *SymB = 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(SymB->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(&SymA->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); +} + +std::unique_ptr<MCObjectWriter> +llvm::createX86MachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit, + uint32_t CPUType, uint32_t CPUSubtype) { + return createMachObjectWriter( + llvm::make_unique<X86MachObjectWriter>(Is64Bit, CPUType, CPUSubtype), OS, + /*IsLittleEndian=*/true); +} |