-
- 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 += getSymbolAddress(&A_SD, Layout) -
- (A_Base == NULL ? 0 : getSymbolAddress(A_Base, Layout));
- Value -= getSymbolAddress(&B_SD, Layout) -
- (B_Base == NULL ? 0 : 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));
- Relocations[Fragment->getParent()].push_back(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 preceeding
- // 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()) {
- // The index is the section ordinal (1-based).
- Index = SD.getFragment()->getParent()->getOrdinal() + 1;
- IsExtern = 0;
- Value += 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, SectionAddress);
- 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));
- Relocations[Fragment->getParent()].push_back(MRE);