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Differential D105867 Diff 359204 lld/MachO/SyntheticSections.cpp

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lld/MachO/SyntheticSections.cpp

Show First 20 Lines • Show All 276 Lines • ▼ Show 20 Linesstruct Binding {
uint64_t offset = 0; uint64_t offset = 0;
int64_t addend = 0; int64_t addend = 0;
}; };
struct BindIR { struct BindIR {
// Default value of 0xF0 is not valid opcode and should make the program // Default value of 0xF0 is not valid opcode and should make the program
// scream instead of accidentally writing "valid" values. // scream instead of accidentally writing "valid" values.
uint8_t opcode = 0xF0; uint8_t opcode = 0xF0;
uint64_t data = 0; uint64_t data = 0;
uint64_t consecutiveCount = 0;
}; };
} // namespace } // namespace
// Encode a sequence of opcodes that tell dyld to write the address of symbol + // Encode a sequence of opcodes that tell dyld to write the address of symbol +
// addend at osec->addr + outSecOff. // addend at osec->addr + outSecOff.
// //
// The bind opcode "interpreter" remembers the values of each binding field, so // The bind opcode "interpreter" remembers the values of each binding field, so
// we only need to encode the differences between bindings. Hence the use of // we only need to encode the differences between bindings. Hence the use of
// lastBinding. // lastBinding.
static void encodeBinding(const OutputSection *osec, uint64_t outSecOff, static void encodeBinding(const OutputSection *osec, uint64_t outSecOff,
int64_t addend, Binding &lastBinding, int64_t addend, Binding &lastBinding,
std::vector<BindIR> &opcodes) { std::vector<BindIR> &opcodes) {
OutputSegment *seg = osec->parent; OutputSegment *seg = osec->parent;
uint64_t offset = osec->getSegmentOffset() + outSecOff; uint64_t offset = osec->getSegmentOffset() + outSecOff;
if (lastBinding.segment != seg) { if (lastBinding.segment != seg) {
BindIR op = { opcodes.push_back(
static_cast<uint8_t>(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB | {static_cast<uint8_t>(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB |
seg->index), // opcode seg->index),
offset // data offset});
};
opcodes.push_back(op);
lastBinding.segment = seg; lastBinding.segment = seg;
lastBinding.offset = offset; lastBinding.offset = offset;
} else if (lastBinding.offset != offset) { } else if (lastBinding.offset != offset) {
BindIR op = { opcodes.push_back({BIND_OPCODE_ADD_ADDR_ULEB, offset - lastBinding.offset});
static_cast<uint8_t>(BIND_OPCODE_ADD_ADDR_ULEB), // opcode
offset - lastBinding.offset // data
};
opcodes.push_back(op);
lastBinding.offset = offset; lastBinding.offset = offset;
} }
if (lastBinding.addend != addend) { if (lastBinding.addend != addend) {
BindIR op = { opcodes.push_back(
static_cast<uint8_t>(BIND_OPCODE_SET_ADDEND_SLEB), // opcode {BIND_OPCODE_SET_ADDEND_SLEB, static_cast<uint64_t>(addend)});
static_cast<uint64_t>(addend) // data
};
opcodes.push_back(op);
lastBinding.addend = addend; lastBinding.addend = addend;
} }
BindIR op = { opcodes.push_back({BIND_OPCODE_DO_BIND, 0});
static_cast<uint8_t>(BIND_OPCODE_DO_BIND), // opcode
0 // data
};
opcodes.push_back(op);
// DO_BIND causes dyld to both perform the binding and increment the offset // DO_BIND causes dyld to both perform the binding and increment the offset
lastBinding.offset += target->wordSize; lastBinding.offset += target->wordSize;
} }
static void optimizeOpcodes(std::vector<BindIR> &opcodes) {
// Pass 1: Combine bind/add pairs
size_t i;
int pWrite = 0;
for (i = 1; i < opcodes.size(); ++i, ++pWrite) {
if ((opcodes[i].opcode == BIND_OPCODE_ADD_ADDR_ULEB) &&
(opcodes[i - 1].opcode == BIND_OPCODE_DO_BIND)) {
opcodes[pWrite].opcode = BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB;
opcodes[pWrite].data = opcodes[i].data;
++i;
} else {
opcodes[pWrite] = opcodes[i - 1];
}
}
if (i == opcodes.size())
opcodes[pWrite] = opcodes[i - 1];
opcodes.resize(pWrite + 1);
// Pass 2: Compress two or more bind_add opcodes
pWrite = 0;
for (i = 1; i < opcodes.size(); ++i, ++pWrite) {
if ((opcodes[i].opcode == BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB) &&
(opcodes[i - 1].opcode == BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB) &&
(opcodes[i].data == opcodes[i - 1].data)) {
opcodes[pWrite].opcode = BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB;
opcodes[pWrite].consecutiveCount = 2;
opcodes[pWrite].data = opcodes[i].data;
++i;
while (i < opcodes.size() &&
(opcodes[i].opcode == BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB) &&
(opcodes[i].data == opcodes[i - 1].data)) {
opcodes[pWrite].consecutiveCount++;
++i;
}
} else {
opcodes[pWrite] = opcodes[i - 1];
}
}
if (i == opcodes.size())
opcodes[pWrite] = opcodes[i - 1];
opcodes.resize(pWrite + 1);
}
int3Unsubmitted
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nit: LLVM convention is to omit braces for one-liners

int3: nit: LLVM convention is to omit braces for one-liners
static void flushOpcodes(const BindIR &op, raw_svector_ostream &os) { static void flushOpcodes(const BindIR &op, raw_svector_ostream &os) {
uint8_t opcode = op.opcode & BIND_OPCODE_MASK; uint8_t opcode = op.opcode & BIND_OPCODE_MASK;
switch (opcode) { switch (opcode) {
case BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB: case BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB:
case BIND_OPCODE_ADD_ADDR_ULEB: case BIND_OPCODE_ADD_ADDR_ULEB:
case BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB:
os << op.opcode; os << op.opcode;
encodeULEB128(op.data, os); encodeULEB128(op.data, os);
break; break;
case BIND_OPCODE_SET_ADDEND_SLEB: case BIND_OPCODE_SET_ADDEND_SLEB:
os << op.opcode; os << op.opcode;
encodeSLEB128(static_cast<int64_t>(op.data), os); encodeSLEB128(static_cast<int64_t>(op.data), os);
break; break;
case BIND_OPCODE_DO_BIND: case BIND_OPCODE_DO_BIND:
os << op.opcode; os << op.opcode;
break; break;
case BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB:
os << op.opcode;
encodeULEB128(op.consecutiveCount, os);
encodeULEB128(op.data, os);
break;
default: default:
llvm_unreachable("cannot bind to an unrecognized symbol"); llvm_unreachable("cannot bind to an unrecognized symbol");
} }
} }
// Non-weak bindings need to have their dylib ordinal encoded as well. // Non-weak bindings need to have their dylib ordinal encoded as well.
static int16_t ordinalForDylibSymbol(const DylibSymbol &dysym) { static int16_t ordinalForDylibSymbol(const DylibSymbol &dysym) {
if (config->namespaceKind == NamespaceKind::flat || dysym.isDynamicLookup()) if (config->namespaceKind == NamespaceKind::flat || dysym.isDynamicLookup())
▲ Show 20 Lines • Show All 83 Lines • ▼ Show 20 Lines if (ordinal != lastOrdinal) {
encodeDylibOrdinal(ordinal, os); encodeDylibOrdinal(ordinal, os);
lastOrdinal = ordinal; lastOrdinal = ordinal;
} }
std::vector<BindIR> opcodes; std::vector<BindIR> opcodes;
for (const BindingEntry &b : bindings) for (const BindingEntry &b : bindings)
encodeBinding(b.target.isec->parent, encodeBinding(b.target.isec->parent,
b.target.isec->getOffset(b.target.offset), b.addend, b.target.isec->getOffset(b.target.offset), b.addend,
lastBinding, opcodes); lastBinding, opcodes);
if (config->optimize > 1)
optimizeOpcodes(opcodes);
for (const auto &op : opcodes) for (const auto &op : opcodes)
flushOpcodes(op, os); flushOpcodes(op, os);
} }
if (!bindingsMap.empty()) if (!bindingsMap.empty())
os << static_cast<uint8_t>(BIND_OPCODE_DONE); os << static_cast<uint8_t>(BIND_OPCODE_DONE);
} }
void BindingSection::writeTo(uint8_t *buf) const { void BindingSection::writeTo(uint8_t *buf) const {
Show All 16 Lines for (auto &p : sortBindings(bindingsMap)) {
os << static_cast<uint8_t>(BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM) os << static_cast<uint8_t>(BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM)
<< sym->getName() << '\0' << sym->getName() << '\0'
<< static_cast<uint8_t>(BIND_OPCODE_SET_TYPE_IMM | BIND_TYPE_POINTER); << static_cast<uint8_t>(BIND_OPCODE_SET_TYPE_IMM | BIND_TYPE_POINTER);
std::vector<BindIR> opcodes; std::vector<BindIR> opcodes;
for (const BindingEntry &b : bindings) for (const BindingEntry &b : bindings)
encodeBinding(b.target.isec->parent, encodeBinding(b.target.isec->parent,
b.target.isec->getOffset(b.target.offset), b.addend, b.target.isec->getOffset(b.target.offset), b.addend,
lastBinding, opcodes); lastBinding, opcodes);
if (config->optimize > 1)
optimizeOpcodes(opcodes);
for (const auto &op : opcodes) for (const auto &op : opcodes)
flushOpcodes(op, os); flushOpcodes(op, os);
} }
if (!bindingsMap.empty() || !definitions.empty()) if (!bindingsMap.empty() || !definitions.empty())
os << static_cast<uint8_t>(BIND_OPCODE_DONE); os << static_cast<uint8_t>(BIND_OPCODE_DONE);
} }
void WeakBindingSection::writeTo(uint8_t *buf) const { void WeakBindingSection::writeTo(uint8_t *buf) const {
▲ Show 20 Lines • Show All 962 Lines • Show Last 20 Lines