void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) { assert(Target.getSymA() && "Relocation must reference a symbol!"); const MCSymbol &Symbol = Target.getSymA()->getSymbol(); const MCSymbol &A = Symbol.AliasedSymbol(); if (!Asm.hasSymbolData(A)) Asm.getContext().FatalError( Fixup.getLoc(), Twine("symbol '") + A.getName() + "' can not be undefined"); MCSymbolData &A_SD = Asm.getSymbolData(A); MCSectionData const *SectionData = Fragment->getParent(); // Mark this symbol as requiring an entry in the symbol table. assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() && "Section must already have been defined in ExecutePostLayoutBinding!"); assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() && "Symbol must already have been defined in ExecutePostLayoutBinding!"); COFFSection *coff_section = SectionMap[&SectionData->getSection()]; COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()]; const MCSymbolRefExpr *SymB = Target.getSymB(); bool CrossSection = false; if (SymB) { const MCSymbol *B = &SymB->getSymbol(); MCSymbolData &B_SD = Asm.getSymbolData(*B); if (!B_SD.getFragment()) Asm.getContext().FatalError( Fixup.getLoc(), Twine("symbol '") + B->getName() + "' can not be undefined in a subtraction expression"); if (!A_SD.getFragment()) Asm.getContext().FatalError( Fixup.getLoc(), Twine("symbol '") + Symbol.getName() + "' can not be undefined in a subtraction expression"); CrossSection = &Symbol.getSection() != &B->getSection(); // Offset of the symbol in the section int64_t a = Layout.getSymbolOffset(&B_SD); // Ofeset of the relocation in the section int64_t b = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); FixedValue = b - a; // In the case where we have SymbA and SymB, we just need to store the delta // between the two symbols. Update FixedValue to account for the delta, and // skip recording the relocation. if (!CrossSection) return; } else { FixedValue = Target.getConstant(); } COFFRelocation Reloc; Reloc.Data.SymbolTableIndex = 0; Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); // Turn relocations for temporary symbols into section relocations. if (coff_symbol->MCData->getSymbol().isTemporary() || CrossSection) { Reloc.Symb = coff_symbol->Section->Symbol; FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment) + coff_symbol->MCData->getOffset(); } else Reloc.Symb = coff_symbol; ++Reloc.Symb->Relocations; Reloc.Data.VirtualAddress += Fixup.getOffset(); Reloc.Data.Type = TargetObjectWriter->getRelocType(Target, Fixup, CrossSection); // FIXME: Can anyone explain what this does other than adjust for the size // of the offset? if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 && Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) || (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 && Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32)) FixedValue += 4; coff_section->Relocations.push_back(Reloc); }
bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout, const MCFixup &Fixup, const MCFragment *DF, MCValue &Target, uint64_t &Value) const { ++stats::evaluateFixup; if (!Fixup.getValue()->EvaluateAsRelocatable(Target, Layout)) getContext().FatalError(Fixup.getLoc(), "expected relocatable expression"); bool IsPCRel = Backend.getFixupKindInfo( Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel; bool IsResolved; if (IsPCRel) { if (Target.getSymB()) { IsResolved = false; } else if (!Target.getSymA()) { IsResolved = false; } else { const MCSymbolRefExpr *A = Target.getSymA(); const MCSymbol &SA = A->getSymbol(); if (A->getKind() != MCSymbolRefExpr::VK_None || SA.AliasedSymbol().isUndefined()) { IsResolved = false; } else { const MCSymbolData &DataA = getSymbolData(SA); IsResolved = getWriter().IsSymbolRefDifferenceFullyResolvedImpl(*this, DataA, *DF, false, true); } } } else { IsResolved = Target.isAbsolute(); } Value = Target.getConstant(); if (const MCSymbolRefExpr *A = Target.getSymA()) { const MCSymbol &Sym = A->getSymbol().AliasedSymbol(); if (Sym.isDefined()) Value += Layout.getSymbolOffset(&getSymbolData(Sym)); } if (const MCSymbolRefExpr *B = Target.getSymB()) { const MCSymbol &Sym = B->getSymbol().AliasedSymbol(); if (Sym.isDefined()) Value -= Layout.getSymbolOffset(&getSymbolData(Sym)); } bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsAlignedDownTo32Bits; assert((ShouldAlignPC ? IsPCRel : true) && "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!"); if (IsPCRel) { uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset(); // A number of ARM fixups in Thumb mode require that the effective PC // address be determined as the 32-bit aligned version of the actual offset. if (ShouldAlignPC) Offset &= ~0x3; Value -= Offset; } // Let the backend adjust the fixup value if necessary, including whether // we need a relocation. Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value, IsResolved); return IsResolved; }
bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout, const MCFixup &Fixup, const MCFragment *DF, MCValue &Target, uint64_t &Value) const { ++stats::evaluateFixup; // FIXME: This code has some duplication with recordRelocation. We should // probably merge the two into a single callback that tries to evaluate a // fixup and records a relocation if one is needed. const MCExpr *Expr = Fixup.getValue(); if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) { getContext().reportError(Fixup.getLoc(), "expected relocatable expression"); // Claim to have completely evaluated the fixup, to prevent any further // processing from being done. Value = 0; return true; } bool IsPCRel = Backend.getFixupKindInfo( Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel; bool IsResolved; if (IsPCRel) { if (Target.getSymB()) { IsResolved = false; } else if (!Target.getSymA()) { IsResolved = false; } else { const MCSymbolRefExpr *A = Target.getSymA(); const MCSymbol &SA = A->getSymbol(); if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) { IsResolved = false; } else { IsResolved = getWriter().isSymbolRefDifferenceFullyResolvedImpl( *this, SA, *DF, false, true); } } } else { IsResolved = Target.isAbsolute(); } Value = Target.getConstant(); if (const MCSymbolRefExpr *A = Target.getSymA()) { const MCSymbol &Sym = A->getSymbol(); if (Sym.isDefined()) Value += Layout.getSymbolOffset(Sym); } if (const MCSymbolRefExpr *B = Target.getSymB()) { const MCSymbol &Sym = B->getSymbol(); if (Sym.isDefined()) Value -= Layout.getSymbolOffset(Sym); } bool ShouldAlignPC = Backend.getFixupKindInfo(Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsAlignedDownTo32Bits; assert((ShouldAlignPC ? IsPCRel : true) && "FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!"); if (IsPCRel) { uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset(); // A number of ARM fixups in Thumb mode require that the effective PC // address be determined as the 32-bit aligned version of the actual offset. if (ShouldAlignPC) Offset &= ~0x3; Value -= Offset; } // Let the backend adjust the fixup value if necessary, including whether // we need a relocation. Backend.processFixupValue(*this, Layout, Fixup, DF, Target, Value, IsResolved); return IsResolved; }
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::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); }
void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, uint64_t &FixedValue) { assert(Target.getSymA() != NULL && "Relocation must reference a symbol!"); const MCSymbol *A = &Target.getSymA()->getSymbol(); MCSymbolData &A_SD = Asm.getSymbolData(*A); MCSectionData const *SectionData = Fragment->getParent(); // Mark this symbol as requiring an entry in the symbol table. assert(SectionMap.find(&SectionData->getSection()) != SectionMap.end() && "Section must already have been defined in ExecutePostLayoutBinding!"); assert(SymbolMap.find(&A_SD.getSymbol()) != SymbolMap.end() && "Symbol must already have been defined in ExecutePostLayoutBinding!"); COFFSection *coff_section = SectionMap[&SectionData->getSection()]; COFFSymbol *coff_symbol = SymbolMap[&A_SD.getSymbol()]; if (Target.getSymB()) { if (&Target.getSymA()->getSymbol().getSection() != &Target.getSymB()->getSymbol().getSection()) { llvm_unreachable("Symbol relative relocations are only allowed between " "symbols in the same section"); } const MCSymbol *B = &Target.getSymB()->getSymbol(); MCSymbolData &B_SD = Asm.getSymbolData(*B); FixedValue = Layout.getSymbolOffset(&A_SD) - Layout.getSymbolOffset(&B_SD); // In the case where we have SymbA and SymB, we just need to store the delta // between the two symbols. Update FixedValue to account for the delta, and // skip recording the relocation. return; } else { FixedValue = Target.getConstant(); } COFFRelocation Reloc; Reloc.Data.SymbolTableIndex = 0; Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment); // Turn relocations for temporary symbols into section relocations. if (coff_symbol->MCData->getSymbol().isTemporary()) { Reloc.Symb = coff_symbol->Section->Symbol; FixedValue += Layout.getFragmentOffset(coff_symbol->MCData->Fragment) + coff_symbol->MCData->getOffset(); } else Reloc.Symb = coff_symbol; ++Reloc.Symb->Relocations; Reloc.Data.VirtualAddress += Fixup.getOffset(); switch ((unsigned)Fixup.getKind()) { case FK_PCRel_4: case X86::reloc_riprel_4byte: case X86::reloc_riprel_4byte_movq_load: Reloc.Data.Type = Is64Bit ? COFF::IMAGE_REL_AMD64_REL32 : COFF::IMAGE_REL_I386_REL32; // FIXME: Can anyone explain what this does other than adjust for the size // of the offset? FixedValue += 4; break; case FK_Data_4: case X86::reloc_signed_4byte: Reloc.Data.Type = Is64Bit ? COFF::IMAGE_REL_AMD64_ADDR32 : COFF::IMAGE_REL_I386_DIR32; break; case FK_Data_8: if (Is64Bit) Reloc.Data.Type = COFF::IMAGE_REL_AMD64_ADDR64; else llvm_unreachable("unsupported relocation type"); break; default: llvm_unreachable("unsupported relocation type"); } coff_section->Relocations.push_back(Reloc); }
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); }
void ELFObjectWriter::recordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, bool &IsPCRel, uint64_t &FixedValue) { const MCSectionELF &FixupSection = cast<MCSectionELF>(*Fragment->getParent()); uint64_t C = Target.getConstant(); uint64_t FixupOffset = Layout.getFragmentOffset(Fragment) + Fixup.getOffset(); MCContext &Ctx = Asm.getContext(); if (const MCSymbolRefExpr *RefB = Target.getSymB()) { assert(RefB->getKind() == MCSymbolRefExpr::VK_None && "Should not have constructed this"); // Let A, B and C being the components of Target and R be the location of // the fixup. If the fixup is not pcrel, we want to compute (A - B + C). // If it is pcrel, we want to compute (A - B + C - R). // In general, ELF has no relocations for -B. It can only represent (A + C) // or (A + C - R). If B = R + K and the relocation is not pcrel, we can // replace B to implement it: (A - R - K + C) if (IsPCRel) { Ctx.reportError( Fixup.getLoc(), "No relocation available to represent this relative expression"); return; } const auto &SymB = cast<MCSymbolELF>(RefB->getSymbol()); if (SymB.isUndefined()) { Ctx.reportError(Fixup.getLoc(), Twine("symbol '") + SymB.getName() + "' can not be undefined in a subtraction expression"); return; } assert(!SymB.isAbsolute() && "Should have been folded"); const MCSection &SecB = SymB.getSection(); if (&SecB != &FixupSection) { Ctx.reportError(Fixup.getLoc(), "Cannot represent a difference across sections"); return; } uint64_t SymBOffset = Layout.getSymbolOffset(SymB); uint64_t K = SymBOffset - FixupOffset; IsPCRel = true; C -= K; } // We either rejected the fixup or folded B into C at this point. const MCSymbolRefExpr *RefA = Target.getSymA(); const auto *SymA = RefA ? cast<MCSymbolELF>(&RefA->getSymbol()) : nullptr; bool ViaWeakRef = false; if (SymA && SymA->isVariable()) { const MCExpr *Expr = SymA->getVariableValue(); if (const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr)) { if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF) { SymA = cast<MCSymbolELF>(&Inner->getSymbol()); ViaWeakRef = true; } } } unsigned Type = getRelocType(Ctx, Target, Fixup, IsPCRel); uint64_t OriginalC = C; bool RelocateWithSymbol = shouldRelocateWithSymbol(Asm, RefA, SymA, C, Type); if (!RelocateWithSymbol && SymA && !SymA->isUndefined()) C += Layout.getSymbolOffset(*SymA); uint64_t Addend = 0; if (hasRelocationAddend()) { Addend = C; C = 0; } FixedValue = C; if (!RelocateWithSymbol) { const MCSection *SecA = (SymA && !SymA->isUndefined()) ? &SymA->getSection() : nullptr; auto *ELFSec = cast_or_null<MCSectionELF>(SecA); const auto *SectionSymbol = ELFSec ? cast<MCSymbolELF>(ELFSec->getBeginSymbol()) : nullptr; if (SectionSymbol) SectionSymbol->setUsedInReloc(); ELFRelocationEntry Rec(FixupOffset, SectionSymbol, Type, Addend, SymA, OriginalC); Relocations[&FixupSection].push_back(Rec); return; } const auto *RenamedSymA = SymA; if (SymA) { if (const MCSymbolELF *R = Renames.lookup(SymA)) RenamedSymA = R; if (ViaWeakRef) RenamedSymA->setIsWeakrefUsedInReloc(); else RenamedSymA->setUsedInReloc(); } ELFRelocationEntry Rec(FixupOffset, RenamedSymA, Type, Addend, SymA, OriginalC); Relocations[&FixupSection].push_back(Rec); }
void ARMMachObjectWriter:: RecordARMScatteredHalfRelocation(MachObjectWriter *Writer, const MCAssembler &Asm, const MCAsmLayout &Layout, const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target, uint64_t &FixedValue) { uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset(); unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind()); unsigned Type = MachO::ARM_RELOC_HALF; // See <reloc.h>. const MCSymbol *A = &Target.getSymA()->getSymbol(); const MCSymbolData *A_SD = &Asm.getSymbolData(*A); if (!A_SD->getFragment()) Asm.getContext().FatalError(Fixup.getLoc(), "symbol '" + A->getName() + "' can not be undefined in a subtraction expression"); uint32_t Value = Writer->getSymbolAddress(A_SD, Layout); uint32_t Value2 = 0; uint64_t SecAddr = Writer->getSectionAddress(A_SD->getFragment()->getParent()); FixedValue += SecAddr; if (const MCSymbolRefExpr *B = Target.getSymB()) { const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol()); if (!B_SD->getFragment()) Asm.getContext().FatalError(Fixup.getLoc(), "symbol '" + B->getSymbol().getName() + "' can not be undefined in a subtraction expression"); // Select the appropriate difference relocation type. Type = MachO::ARM_RELOC_HALF_SECTDIFF; 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. // ARM_RELOC_HALF and ARM_RELOC_HALF_SECTDIFF abuse the r_length field: // // For these two r_type relocations they always have a pair following them and // the r_length bits are used differently. The encoding of the r_length is as // follows: // low bit of r_length: // 0 - :lower16: for movw instructions // 1 - :upper16: for movt instructions // high bit of r_length: // 0 - arm instructions // 1 - thumb instructions // the other half of the relocated expression is in the following pair // relocation entry in the low 16 bits of r_address field. unsigned ThumbBit = 0; unsigned MovtBit = 0; switch ((unsigned)Fixup.getKind()) { default: break; case ARM::fixup_arm_movt_hi16: MovtBit = 1; // The thumb bit shouldn't be set in the 'other-half' bit of the // relocation, but it will be set in FixedValue if the base symbol // is a thumb function. Clear it out here. if (Asm.isThumbFunc(A)) FixedValue &= 0xfffffffe; break; case ARM::fixup_t2_movt_hi16: if (Asm.isThumbFunc(A)) FixedValue &= 0xfffffffe; MovtBit = 1; // Fallthrough case ARM::fixup_t2_movw_lo16: ThumbBit = 1; break; } if (Type == MachO::ARM_RELOC_HALF_SECTDIFF) { uint32_t OtherHalf = MovtBit ? (FixedValue & 0xffff) : ((FixedValue & 0xffff0000) >> 16); MachO::any_relocation_info MRE; MRE.r_word0 = ((OtherHalf << 0) | (MachO::ARM_RELOC_PAIR << 24) | (MovtBit << 28) | (ThumbBit << 29) | (IsPCRel << 30) | MachO::R_SCATTERED); MRE.r_word1 = Value2; Writer->addRelocation(nullptr, Fragment->getParent(), MRE); }
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); }
bool MCAssembler::EvaluateFixup(const MCAsmLayout &Layout, const MCFixup &Fixup, const MCFragment *DF, MCValue &Target, uint64_t &Value) const { ++stats::EvaluateFixup; if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout)) report_fatal_error("expected relocatable expression"); // FIXME: How do non-scattered symbols work in ELF? I presume the linker // doesn't support small relocations, but then under what criteria does the // assembler allow symbol differences? Value = Target.getConstant(); bool IsPCRel = Emitter.getFixupKindInfo( Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel; bool IsResolved = true; if (const MCSymbolRefExpr *A = Target.getSymA()) { if (A->getSymbol().isDefined()) Value += Layout.getSymbolAddress(&getSymbolData(A->getSymbol())); else IsResolved = false; } if (const MCSymbolRefExpr *B = Target.getSymB()) { if (B->getSymbol().isDefined()) Value -= Layout.getSymbolAddress(&getSymbolData(B->getSymbol())); else IsResolved = false; } // If we are using scattered symbols, determine whether this value is actually // resolved; scattering may cause atoms to move. if (IsResolved && getBackend().hasScatteredSymbols()) { if (getBackend().hasReliableSymbolDifference()) { // If this is a PCrel relocation, find the base atom (identified by its // symbol) that the fixup value is relative to. const MCSymbolData *BaseSymbol = 0; if (IsPCRel) { BaseSymbol = DF->getAtom(); if (!BaseSymbol) IsResolved = false; } if (IsResolved) IsResolved = isScatteredFixupFullyResolved(*this, Layout, Fixup, Target, BaseSymbol); } else { const MCSection *BaseSection = 0; if (IsPCRel) BaseSection = &DF->getParent()->getSection(); IsResolved = isScatteredFixupFullyResolvedSimple(*this, Fixup, Target, BaseSection); } } if (IsPCRel) Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset(); return IsResolved; }
void SVMAsmBackend::ApplyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize, uint64_t Value) const { ApplyStaticFixup(Fixup.getKind(), Data + Fixup.getOffset(), Value); }