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-rw-r--r--lib/MC/MachObjectWriter.cpp201
1 files changed, 129 insertions, 72 deletions
diff --git a/lib/MC/MachObjectWriter.cpp b/lib/MC/MachObjectWriter.cpp
index a533ccfdc642..3207e99777a4 100644
--- a/lib/MC/MachObjectWriter.cpp
+++ b/lib/MC/MachObjectWriter.cpp
@@ -16,6 +16,7 @@
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCMachOSymbolFlags.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MachO.h"
@@ -58,6 +59,20 @@ static bool isFixupKindRIPRel(unsigned Kind) {
Kind == X86::reloc_riprel_4byte_movq_load;
}
+static bool doesSymbolRequireExternRelocation(MCSymbolData *SD) {
+ // Undefined symbols are always extern.
+ if (SD->Symbol->isUndefined())
+ return true;
+
+ // References to weak definitions require external relocation entries; the
+ // definition may not always be the one in the same object file.
+ if (SD->getFlags() & SF_WeakDefinition)
+ return true;
+
+ // Otherwise, we can use an internal relocation.
+ return false;
+}
+
namespace {
class MachObjectWriterImpl {
@@ -130,7 +145,8 @@ class MachObjectWriterImpl {
RIT_Pair = 1,
RIT_Difference = 2,
RIT_PreboundLazyPointer = 3,
- RIT_LocalDifference = 4
+ RIT_LocalDifference = 4,
+ RIT_TLV = 5
};
/// X86_64 uses its own relocation types.
@@ -143,7 +159,8 @@ class MachObjectWriterImpl {
RIT_X86_64_Subtractor = 5,
RIT_X86_64_Signed1 = 6,
RIT_X86_64_Signed2 = 7,
- RIT_X86_64_Signed4 = 8
+ RIT_X86_64_Signed4 = 8,
+ RIT_X86_64_TLV = 9
};
/// MachSymbolData - Helper struct for containing some precomputed information
@@ -155,8 +172,8 @@ class MachObjectWriterImpl {
// Support lexicographic sorting.
bool operator<(const MachSymbolData &RHS) const {
- const std::string &Name = SymbolData->getSymbol().getName();
- return Name < RHS.SymbolData->getSymbol().getName();
+ return SymbolData->getSymbol().getName() <
+ RHS.SymbolData->getSymbol().getName();
}
};
@@ -170,6 +187,7 @@ class MachObjectWriterImpl {
llvm::DenseMap<const MCSectionData*,
std::vector<MachRelocationEntry> > Relocations;
+ llvm::DenseMap<const MCSectionData*, unsigned> IndirectSymBase;
/// @}
/// @name Symbol Table Data
@@ -289,9 +307,7 @@ public:
uint64_t Start = OS.tell();
(void) Start;
- // FIXME: cast<> support!
- const MCSectionMachO &Section =
- static_cast<const MCSectionMachO&>(SD.getSection());
+ const MCSectionMachO &Section = cast<MCSectionMachO>(SD.getSection());
WriteBytes(Section.getSectionName(), 16);
WriteBytes(Section.getSegmentName(), 16);
if (Is64Bit) {
@@ -312,7 +328,7 @@ public:
Write32(NumRelocations ? RelocationsStart : 0);
Write32(NumRelocations);
Write32(Flags);
- Write32(0); // reserved1
+ Write32(IndirectSymBase.lookup(&SD)); // reserved1
Write32(Section.getStubSize()); // reserved2
if (Is64Bit)
Write32(0); // reserved3
@@ -404,7 +420,7 @@ public:
// Compute the symbol address.
if (Symbol.isDefined()) {
if (Symbol.isAbsolute()) {
- llvm_unreachable("FIXME: Not yet implemented!");
+ Address = cast<MCConstantExpr>(Symbol.getVariableValue())->getValue();
} else {
Address = Layout.getSymbolAddress(&Data);
}
@@ -456,14 +472,17 @@ public:
void RecordX86_64Relocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment,
- const MCAsmFixup &Fixup, MCValue Target,
+ const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) {
- unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
- unsigned IsRIPRel = isFixupKindRIPRel(Fixup.Kind);
- unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
+ unsigned IsPCRel = isFixupKindPCRel(Fixup.getKind());
+ unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind());
+ unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
// See <reloc.h>.
- uint32_t Address = Layout.getFragmentOffset(Fragment) + Fixup.Offset;
+ uint32_t FixupOffset =
+ Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
+ uint32_t FixupAddress =
+ Layout.getFragmentAddress(Fragment) + Fixup.getOffset();
int64_t Value = 0;
unsigned Index = 0;
unsigned IsExtern = 0;
@@ -532,7 +551,7 @@ public:
Type = RIT_X86_64_Unsigned;
MachRelocationEntry MRE;
- MRE.Word0 = Address;
+ MRE.Word0 = FixupOffset;
MRE.Word1 = ((Index << 0) |
(IsPCRel << 24) |
(Log2Size << 25) |
@@ -548,6 +567,17 @@ public:
MCSymbolData &SD = Asm.getSymbolData(*Symbol);
const MCSymbolData *Base = Asm.getAtom(Layout, &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).
@@ -558,14 +588,17 @@ public:
// Add the local offset, if needed.
if (Base != &SD)
Value += Layout.getSymbolAddress(&SD) - Layout.getSymbolAddress(Base);
- } else {
+ } else if (Symbol->isInSection()) {
// The index is the section ordinal (1-based).
Index = SD.getFragment()->getParent()->getOrdinal() + 1;
IsExtern = 0;
Value += Layout.getSymbolAddress(&SD);
if (IsPCRel)
- Value -= Address + (1 << Log2Size);
+ Value -= FixupAddress + (1 << Log2Size);
+ } else {
+ report_fatal_error("unsupported relocation of undefined symbol '" +
+ Symbol->getName() + "'");
}
MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
@@ -575,14 +608,37 @@ public:
// 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.Kind) == X86::reloc_riprel_4byte_movq_load)
+ if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
Type = RIT_X86_64_GOTLoad;
else
Type = RIT_X86_64_GOT;
- } else if (Modifier != MCSymbolRefExpr::VK_None)
+ } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
+ Type = RIT_X86_64_TLV;
+ } else if (Modifier != MCSymbolRefExpr::VK_None) {
report_fatal_error("unsupported symbol modifier in relocation");
- else
+ } else {
Type = 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 = RIT_X86_64_Signed1; break;
+ case 2: Type = RIT_X86_64_Signed2; break;
+ case 4: Type = RIT_X86_64_Signed4; break;
+ }
+ }
} else {
if (Modifier != MCSymbolRefExpr::VK_None)
report_fatal_error("unsupported symbol modifier in branch "
@@ -590,27 +646,6 @@ public:
Type = RIT_X86_64_Branch;
}
-
- // 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.
- if (IsRIPRel) {
- switch (-(Target.getConstant() + (1LL << Log2Size))) {
- case 1: Type = RIT_X86_64_Signed1; break;
- case 2: Type = RIT_X86_64_Signed2; break;
- case 4: Type = RIT_X86_64_Signed4; break;
- }
- }
} else {
if (Modifier == MCSymbolRefExpr::VK_GOT) {
Type = RIT_X86_64_GOT;
@@ -621,6 +656,8 @@ public:
// required to include any necessary offset directly.
Type = 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
@@ -633,7 +670,7 @@ public:
// struct relocation_info (8 bytes)
MachRelocationEntry MRE;
- MRE.Word0 = Address;
+ MRE.Word0 = FixupOffset;
MRE.Word1 = ((Index << 0) |
(IsPCRel << 24) |
(Log2Size << 25) |
@@ -645,11 +682,11 @@ public:
void RecordScatteredRelocation(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFragment *Fragment,
- const MCAsmFixup &Fixup, MCValue Target,
+ const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) {
- uint32_t Address = Layout.getFragmentOffset(Fragment) + Fixup.Offset;
- unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
- unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
+ uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+ unsigned IsPCRel = isFixupKindPCRel(Fixup.getKind());
+ unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
unsigned Type = RIT_Vanilla;
// See <reloc.h>.
@@ -692,40 +729,49 @@ public:
}
MachRelocationEntry MRE;
- MRE.Word0 = ((Address << 0) |
- (Type << 24) |
- (Log2Size << 28) |
- (IsPCRel << 30) |
+ MRE.Word0 = ((FixupOffset << 0) |
+ (Type << 24) |
+ (Log2Size << 28) |
+ (IsPCRel << 30) |
RF_Scattered);
MRE.Word1 = Value;
Relocations[Fragment->getParent()].push_back(MRE);
}
void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
- const MCFragment *Fragment, const MCAsmFixup &Fixup,
+ const MCFragment *Fragment, const MCFixup &Fixup,
MCValue Target, uint64_t &FixedValue) {
if (Is64Bit) {
RecordX86_64Relocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
return;
}
- unsigned IsPCRel = isFixupKindPCRel(Fixup.Kind);
- unsigned Log2Size = getFixupKindLog2Size(Fixup.Kind);
+ unsigned IsPCRel = isFixupKindPCRel(Fixup.getKind());
+ unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
// 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(Asm, Layout, Fragment, Fixup,
+ Target, 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 (Target.getSymB() ||
- (Target.getSymA() && !Target.getSymA()->getSymbol().isUndefined() &&
- Offset)) {
- RecordScatteredRelocation(Asm, Layout, Fragment, Fixup,Target,FixedValue);
- return;
- }
+ if (Offset && SD && !doesSymbolRequireExternRelocation(SD))
+ return RecordScatteredRelocation(Asm, Layout, Fragment, Fixup,
+ Target, FixedValue);
// See <reloc.h>.
- uint32_t Address = Layout.getFragmentOffset(Fragment) + Fixup.Offset;
+ uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
uint32_t Value = 0;
unsigned Index = 0;
unsigned IsExtern = 0;
@@ -739,12 +785,15 @@ public:
Type = RIT_Vanilla;
Value = 0;
} else {
- const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
- MCSymbolData *SD = &Asm.getSymbolData(*Symbol);
-
- if (Symbol->isUndefined()) {
+ // Check whether we need an external or internal relocation.
+ if (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.getSymbolAddress(SD);
Value = 0;
} else {
// The index is the section ordinal (1-based).
@@ -757,7 +806,7 @@ public:
// struct relocation_info (8 bytes)
MachRelocationEntry MRE;
- MRE.Word0 = Address;
+ MRE.Word0 = FixupOffset;
MRE.Word1 = ((Index << 0) |
(IsPCRel << 24) |
(Log2Size << 25) |
@@ -775,29 +824,37 @@ public:
// FIXME: Revisit this when the dust settles.
// Bind non lazy symbol pointers first.
+ unsigned IndirectIndex = 0;
for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
- ie = Asm.indirect_symbol_end(); it != ie; ++it) {
- // FIXME: cast<> support!
+ ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
const MCSectionMachO &Section =
- static_cast<const MCSectionMachO&>(it->SectionData->getSection());
+ cast<MCSectionMachO>(it->SectionData->getSection());
if (Section.getType() != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS)
continue;
+ // Initialize the section indirect symbol base, if necessary.
+ if (!IndirectSymBase.count(it->SectionData))
+ IndirectSymBase[it->SectionData] = IndirectIndex;
+
Asm.getOrCreateSymbolData(*it->Symbol);
}
// Then lazy symbol pointers and symbol stubs.
+ IndirectIndex = 0;
for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
- ie = Asm.indirect_symbol_end(); it != ie; ++it) {
- // FIXME: cast<> support!
+ ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
const MCSectionMachO &Section =
- static_cast<const MCSectionMachO&>(it->SectionData->getSection());
+ cast<MCSectionMachO>(it->SectionData->getSection());
if (Section.getType() != MCSectionMachO::S_LAZY_SYMBOL_POINTERS &&
Section.getType() != MCSectionMachO::S_SYMBOL_STUBS)
continue;
+ // Initialize the section indirect symbol base, if necessary.
+ if (!IndirectSymBase.count(it->SectionData))
+ IndirectSymBase[it->SectionData] = IndirectIndex;
+
// Set the symbol type to undefined lazy, but only on construction.
//
// FIXME: Do not hardcode.
@@ -1111,7 +1168,7 @@ void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
void MachObjectWriter::RecordRelocation(const MCAssembler &Asm,
const MCAsmLayout &Layout,
const MCFragment *Fragment,
- const MCAsmFixup &Fixup, MCValue Target,
+ const MCFixup &Fixup, MCValue Target,
uint64_t &FixedValue) {
((MachObjectWriterImpl*) Impl)->RecordRelocation(Asm, Layout, Fragment, Fixup,
Target, FixedValue);
generated by cgit v1.2.3 (git 2.25.1) at 2025-11-04 02:58:19 +0000