void AArch64MachObjectWriter::RecordRelocation(
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());
// See <reloc.h>.
uint32_t FixupOffset = Layout.getFragmentOffset(Fragment);
unsigned Log2Size = 0;
int64_t Value = 0;
unsigned Index = 0;
unsigned Type = 0;
unsigned Kind = Fixup.getKind();
const MCSymbolData *RelSymbol = nullptr;
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;
if (IsPCRel) {
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.
Type = MachO::ARM64_RELOC_POINTER_TO_GOT;
IsPCRel = 1;
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
Writer->addRelocation(A_Base, 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));
Type = MachO::ARM64_RELOC_UNSIGNED;
MachO::any_relocation_info MRE;
MRE.r_word0 = FixupOffset;
MRE.r_word1 = (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
Writer->addRelocation(A_Base, Fragment->getParent(), MRE);
RelSymbol = B_Base;
Type = MachO::ARM64_RELOC_SUBTRACTOR;
} else { // A + constant
const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
const MCSectionMachO &Section = static_cast<const MCSectionMachO &>(
Fragment->getParent()->getSection());
bool CanUseLocalRelocation =
canUseLocalRelocation(Section, *Symbol, Log2Size);
if (Symbol->isTemporary() && (Value || !CanUseLocalRelocation)) {
const MCSection &Sec = Symbol->getSection();
if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
Asm.addLocalUsedInReloc(*Symbol);
}
const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
const MCSymbolData *Base = Asm.getAtom(&SD);
// 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,
&Fixup))
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) {
RelSymbol = Base;
// Add the local offset, if needed.
if (Base != &SD)
Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base);
} else if (Symbol->isInSection()) {
if (!CanUseLocalRelocation)
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;
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) | (Type << 28);
Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
// Now set up the Addend relocation.
Type = MachO::ARM64_RELOC_ADDEND;
Index = Value;
RelSymbol = nullptr;
IsPCRel = 0;
Log2Size = 2;
// 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) | (Type << 28);
Writer->addRelocation(RelSymbol, 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 MCSymbolData *SD = nullptr;
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;
// Try to record the scattered relocation if needed. Fall back to non
// scattered if necessary (see comments in RecordScatteredRelocation()
// for details).
if (Offset && SD && !Writer->doesSymbolRequireExternRelocation(SD) &&
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 (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)) {
RelSymbol = &SD->getSymbol();
// 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->getSymbol().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::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);
}
SVMSymbolInfo SVMMemoryLayout::getSymbol(const MCAssembler &Asm,
const MCAsmLayout &Layout, const MCSymbol *S, bool useCodeAddresses) const
{
SVMSymbolInfo SI;
SVMDecorations Deco;
StringRef Name = Deco.Decode(S->getName());
const MCSymbol *AS = &S->AliasedSymbol();
const MCSymbolData *SD = &Asm.getSymbolData(*AS);
if (Deco.isSys) {
// Numeric syscall
if (Deco.sysNumber > 0x3FFF)
report_fatal_error("Syscall number " + Twine(Deco.sysNumber) +
" is out of range.");
SI.Kind = SVMSymbolInfo::SYS;
SI.Value = 0x80000000 | (Deco.sysNumber << 16) | Deco.isTailCall;
return SI;
}
if (!AS->isDefined())
report_fatal_error("Taking address of undefined symbol '" +
Twine(Name) + "'");
// Symbol has a value in our module. Calculate the full virtual address.
uint32_t Offset = Layout.getSymbolOffset(SD);
const MCSectionData *SecD = &Asm.getSectionData(AS->getSection());
uint32_t VA = getSectionMemAddress(SecD) + Offset + Deco.offset;
if (useCodeAddresses && AS->getSection().getKind().isText()) {
/*
* Code address:
* - Relative to segment base
* - Must be 32-bit aligned
* - Includes optional SP adjustment from FNSTACK pseudo-ops
* - Includes optional call / tail-call decoration
*/
assert(Deco.offset == 0);
uint32_t shortVA = VA & 0xfffffc;
/*
* We can reach this error if some code wasn't aligned properly,
* or if someone is calling this function with useCodeAddresses==true
* when they shouldn't be!
*/
if ((VA & 0xfffffffc) != VA)
report_fatal_error("Code symbol '" + Twine(Name) +
"' has illegal address 0x" + Twine::utohexstr(VA));
FNStackMap_t::const_iterator I = FNStackMap.find(std::make_pair(SecD, Offset));
int SPAdj = I == FNStackMap.end() ? 0 : I->second;
assert(SPAdj >= 0 && !(SPAdj & 3) && SPAdj <= (0x7F * 4));
SPAdj <<= 22;
if (Deco.isCall) {
// A Call, with SP adjustment and tail-call flag
SI.Value = shortVA | SPAdj | Deco.isTailCall;
SI.Kind = SVMSymbolInfo::CALL;
} else if (Deco.isLongBranch) {
// Encode the Long Branch addrop
SI.Value = 0xE0000000 | shortVA;
SI.Kind = SVMSymbolInfo::LB;
} else {
// Normal undecorated address. Still includes an SP adjustment
// if one is present for this symbol's address, though.
// This is important for function pointers, including the entry
// point address for main().
//
// We also set the LSB, in order to differentiate a valid function
// address from a possible NULL. We could set either of the two LSBs
// or the MSB, but this approach makes function addresses clearly
// distinct from normal VAs even with SPAdj==0.
SI.Value = shortVA | SPAdj | 1;
SI.Kind = SVMSymbolInfo::LOCAL;
}
} else {
/*
* Data address. No decoration at all.
*/
SI.Value = VA;
SI.Kind = SVMSymbolInfo::LOCAL;
}
return SI;
}
