diff --git a/lld/MachO/Arch/X86_64.cpp b/lld/MachO/Arch/X86_64.cpp --- a/lld/MachO/Arch/X86_64.cpp +++ b/lld/MachO/Arch/X86_64.cpp @@ -29,7 +29,7 @@ const relocation_info &) const override; void relocateOne(uint8_t *loc, const Reloc &, uint64_t val) const override; - void writeStub(uint8_t *buf, const DylibSymbol &) const override; + void writeStub(uint8_t *buf, const macho::Symbol &) const override; void writeStubHelperHeader(uint8_t *buf) const override; void writeStubHelperEntry(uint8_t *buf, const DylibSymbol &, uint64_t entryAddr) const override; @@ -182,7 +182,7 @@ 0xff, 0x25, 0, 0, 0, 0, // jmpq *__la_symbol_ptr(%rip) }; -void X86_64::writeStub(uint8_t *buf, const DylibSymbol &sym) const { +void X86_64::writeStub(uint8_t *buf, const macho::Symbol &sym) const { memcpy(buf, stub, 2); // just copy the two nonzero bytes uint64_t stubAddr = in.stubs->addr + sym.stubsIndex * sizeof(stub); writeRipRelative(buf, stubAddr, sizeof(stub), @@ -231,9 +231,23 @@ break; } case X86_64_RELOC_BRANCH: { - // TODO: weak dysyms should go into the weak binding section instead - if (auto *dysym = dyn_cast(sym)) - in.stubs->addEntry(dysym); + if (auto *dysym = dyn_cast(sym)) { + if (in.stubs->addEntry(dysym)) { + if (sym->isWeakDef()) { + in.binding->addEntry(dysym, in.lazyPointers, + sym->stubsIndex * WordSize); + in.weakBinding->addEntry(sym, in.lazyPointers, + sym->stubsIndex * WordSize); + } else { + in.lazyBinding->addEntry(dysym); + } + } + } else if (auto *defined = dyn_cast(sym)) { + if (defined->isWeakDef() && defined->isExternal()) + if (in.stubs->addEntry(sym)) + in.weakBinding->addEntry(sym, in.lazyPointers, + sym->stubsIndex * WordSize); + } break; } case X86_64_RELOC_UNSIGNED: { @@ -277,10 +291,11 @@ case X86_64_RELOC_GOT_LOAD: case X86_64_RELOC_GOT: return in.got->addr + sym.gotIndex * WordSize; - case X86_64_RELOC_BRANCH: - if (auto *dysym = dyn_cast(&sym)) - return in.stubs->addr + dysym->stubsIndex * sizeof(stub); + case X86_64_RELOC_BRANCH: { + if (sym.isInStubs()) + return in.stubs->addr + sym.stubsIndex * sizeof(stub); return sym.getVA(); + } case X86_64_RELOC_UNSIGNED: case X86_64_RELOC_SIGNED: case X86_64_RELOC_SIGNED_1: diff --git a/lld/MachO/Symbols.h b/lld/MachO/Symbols.h --- a/lld/MachO/Symbols.h +++ b/lld/MachO/Symbols.h @@ -60,11 +60,16 @@ // Whether this symbol is in the GOT or TLVPointer sections. bool isInGot() const { return gotIndex != UINT32_MAX; } + // Whether this symbol is in the StubsSection. + bool isInStubs() const { return stubsIndex != UINT32_MAX; } + // The index of this symbol in the GOT or the TLVPointer section, depending // on whether it is a thread-local. A given symbol cannot be referenced by // both these sections at once. uint32_t gotIndex = UINT32_MAX; + uint32_t stubsIndex = UINT32_MAX; + protected: Symbol(Kind k, StringRefZ name) : symbolKind(k), name(name) {} @@ -114,13 +119,13 @@ : Symbol(DylibKind, name), file(file), weakDef(isWeakDef), tlv(isTlv) {} bool isWeakDef() const override { return weakDef; } - bool isTlv() const override { return tlv; } + bool hasStubsHelper() const { return stubsHelperIndex != UINT32_MAX; } static bool classof(const Symbol *s) { return s->kind() == DylibKind; } DylibFile *file; - uint32_t stubsIndex = UINT32_MAX; + uint32_t stubsHelperIndex = UINT32_MAX; uint32_t lazyBindOffset = UINT32_MAX; private: diff --git a/lld/MachO/SyntheticSections.h b/lld/MachO/SyntheticSections.h --- a/lld/MachO/SyntheticSections.h +++ b/lld/MachO/SyntheticSections.h @@ -222,13 +222,15 @@ // The following sections implement lazy symbol binding -- very similar to the // PLT mechanism in ELF. // -// ELF's .plt section is broken up into two sections in Mach-O: StubsSection and -// StubHelperSection. Calls to functions in dylibs will end up calling into +// ELF's .plt section is broken up into two sections in Mach-O: StubsSection +// and StubHelperSection. Calls to functions in dylibs will end up calling into // StubsSection, which contains indirect jumps to addresses stored in the // LazyPointerSection (the counterpart to ELF's .plt.got). // -// Initially, the LazyPointerSection contains addresses that point into one of -// the entry points in the middle of the StubHelperSection. The code in +// We will first describe how non-weak symbols are handled. +// +// At program start, the LazyPointerSection contains addresses that point into +// one of the entry points in the middle of the StubHelperSection. The code in // StubHelperSection will push on the stack an offset into the // LazyBindingSection. The push is followed by a jump to the beginning of the // StubHelperSection (similar to PLT0), which then calls into dyld_stub_binder. @@ -236,10 +238,17 @@ // the GOT. // // The stub binder will look up the bind opcodes in the LazyBindingSection at -// the given offset. The bind opcodes will tell the binder to update the address -// in the LazyPointerSection to point to the symbol, so that subsequent calls -// don't have to redo the symbol resolution. The binder will then jump to the -// resolved symbol. +// the given offset. The bind opcodes will tell the binder to update the +// address in the LazyPointerSection to point to the symbol, so that subsequent +// calls don't have to redo the symbol resolution. The binder will then jump to +// the resolved symbol. +// +// With weak symbols, the situation is slightly different. Since there is no +// "weak lazy" lookup, function calls to weak symbols are always non-lazily +// bound. We emit both regular non-lazy bindings as well as weak bindings, in +// order that the weak bindings may overwrite the non-lazy bindings if an +// appropriate symbol is found at runtime. However, the bound addresses will +// still be written (non-lazily) into the LazyPointerSection. class StubsSection : public SyntheticSection { public: @@ -247,13 +256,13 @@ uint64_t getSize() const override; bool isNeeded() const override { return !entries.empty(); } void writeTo(uint8_t *buf) const override; - - const llvm::SetVector &getEntries() const { return entries; } - - void addEntry(DylibSymbol *sym); + const llvm::SetVector &getEntries() const { return entries; } + // Returns whether the symbol was added. Note that every stubs entry will + // have a corresponding entry in the LazyPointerSection. + bool addEntry(Symbol *); private: - llvm::SetVector entries; + llvm::SetVector entries; }; class StubHelperSection : public SyntheticSection { @@ -278,6 +287,8 @@ uint64_t getSize() const override { return WordSize; } }; +// Note that this section may also be targeted by non-lazy bindings. In +// particular, this happens when branch relocations target weak symbols. class LazyPointerSection : public SyntheticSection { public: LazyPointerSection(); @@ -291,15 +302,21 @@ LazyBindingSection(); void finalizeContents(); uint64_t getRawSize() const override { return contents.size(); } - uint32_t encode(const DylibSymbol &); // Like other sections in __LINKEDIT, the lazy binding section is special: its // offsets are recorded in the LC_DYLD_INFO_ONLY load command, instead of in // section headers. bool isHidden() const override { return true; } - bool isNeeded() const override; + bool isNeeded() const override { return !entries.empty(); } void writeTo(uint8_t *buf) const override; + // Note that every entry here will by referenced by a corresponding entry in + // the StubHelperSection. + void addEntry(DylibSymbol *dysym); + const llvm::SetVector &getEntries() const { return entries; } private: + uint32_t encode(const DylibSymbol &); + + llvm::SetVector entries; SmallVector contents; llvm::raw_svector_ostream os{contents}; }; @@ -368,6 +385,7 @@ MachHeaderSection *header = nullptr; BindingSection *binding = nullptr; WeakBindingSection *weakBinding = nullptr; + LazyBindingSection *lazyBinding = nullptr; GotSection *got = nullptr; TlvPointerSection *tlvPointers = nullptr; LazyPointerSection *lazyPointers = nullptr; diff --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp --- a/lld/MachO/SyntheticSections.cpp +++ b/lld/MachO/SyntheticSections.cpp @@ -277,15 +277,17 @@ void StubsSection::writeTo(uint8_t *buf) const { size_t off = 0; - for (const DylibSymbol *sym : in.stubs->getEntries()) { + for (const Symbol *sym : entries) { target->writeStub(buf + off, *sym); off += target->stubSize; } } -void StubsSection::addEntry(DylibSymbol *sym) { - if (entries.insert(sym)) +bool StubsSection::addEntry(Symbol *sym) { + bool inserted = entries.insert(sym); + if (inserted) sym->stubsIndex = entries.size() - 1; + return inserted; } StubHelperSection::StubHelperSection() @@ -293,17 +295,15 @@ uint64_t StubHelperSection::getSize() const { return target->stubHelperHeaderSize + - in.stubs->getEntries().size() * target->stubHelperEntrySize; + in.lazyBinding->getEntries().size() * target->stubHelperEntrySize; } -bool StubHelperSection::isNeeded() const { - return !in.stubs->getEntries().empty(); -} +bool StubHelperSection::isNeeded() const { return in.lazyBinding->isNeeded(); } void StubHelperSection::writeTo(uint8_t *buf) const { target->writeStubHelperHeader(buf); size_t off = target->stubHelperHeaderSize; - for (const DylibSymbol *sym : in.stubs->getEntries()) { + for (const DylibSymbol *sym : in.lazyBinding->getEntries()) { target->writeStubHelperEntry(buf + off, *sym, addr + off); off += target->stubHelperEntrySize; } @@ -347,10 +347,17 @@ void LazyPointerSection::writeTo(uint8_t *buf) const { size_t off = 0; - for (const DylibSymbol *sym : in.stubs->getEntries()) { - uint64_t stubHelperOffset = target->stubHelperHeaderSize + - sym->stubsIndex * target->stubHelperEntrySize; - write64le(buf + off, in.stubHelper->addr + stubHelperOffset); + for (const Symbol *sym : in.stubs->getEntries()) { + if (const auto *dysym = dyn_cast(sym)) { + if (dysym->hasStubsHelper()) { + uint64_t stubHelperOffset = + target->stubHelperHeaderSize + + dysym->stubsHelperIndex * target->stubHelperEntrySize; + write64le(buf + off, in.stubHelper->addr + stubHelperOffset); + } + } else { + write64le(buf + off, sym->getVA()); + } off += WordSize; } } @@ -358,12 +365,10 @@ LazyBindingSection::LazyBindingSection() : LinkEditSection(segment_names::linkEdit, section_names::lazyBinding) {} -bool LazyBindingSection::isNeeded() const { return in.stubs->isNeeded(); } - void LazyBindingSection::finalizeContents() { // TODO: Just precompute output size here instead of writing to a temporary // buffer - for (DylibSymbol *sym : in.stubs->getEntries()) + for (DylibSymbol *sym : entries) sym->lazyBindOffset = encode(*sym); } @@ -371,6 +376,11 @@ memcpy(buf, contents.data(), contents.size()); } +void LazyBindingSection::addEntry(DylibSymbol *dysym) { + if (entries.insert(dysym)) + dysym->stubsHelperIndex = entries.size() - 1; +} + // Unlike the non-lazy binding section, the bind opcodes in this section aren't // interpreted all at once. Rather, dyld will start interpreting opcodes at a // given offset, typically only binding a single symbol before it finds a diff --git a/lld/MachO/Target.h b/lld/MachO/Target.h --- a/lld/MachO/Target.h +++ b/lld/MachO/Target.h @@ -44,7 +44,7 @@ // Write code for lazy binding. See the comments on StubsSection for more // details. - virtual void writeStub(uint8_t *buf, const DylibSymbol &) const = 0; + virtual void writeStub(uint8_t *buf, const Symbol &) const = 0; virtual void writeStubHelperHeader(uint8_t *buf) const = 0; virtual void writeStubHelperEntry(uint8_t *buf, const DylibSymbol &, uint64_t entryAddr) const = 0; diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp --- a/lld/MachO/Writer.cpp +++ b/lld/MachO/Writer.cpp @@ -55,7 +55,6 @@ uint64_t addr = 0; uint64_t fileOff = 0; MachHeaderSection *header = nullptr; - LazyBindingSection *lazyBindingSection = nullptr; ExportSection *exportSection = nullptr; StringTableSection *stringTableSection = nullptr; SymtabSection *symtabSection = nullptr; @@ -327,8 +326,8 @@ } void Writer::createLoadCommands() { - in.header->addLoadCommand(make( - in.binding, in.weakBinding, lazyBindingSection, exportSection)); + in.header->addLoadCommand(make(in.binding, in.weakBinding, + in.lazyBinding, exportSection)); in.header->addLoadCommand(make(symtabSection, stringTableSection)); in.header->addLoadCommand(make()); for (StringRef path : config->runtimePaths) @@ -473,7 +472,6 @@ void Writer::createOutputSections() { // First, create hidden sections - lazyBindingSection = make(); stringTableSection = make(); symtabSection = make(*stringTableSection); exportSection = make(); @@ -585,7 +583,7 @@ // Fill __LINKEDIT contents. in.binding->finalizeContents(); in.weakBinding->finalizeContents(); - lazyBindingSection->finalizeContents(); + in.lazyBinding->finalizeContents(); exportSection->finalizeContents(); symtabSection->finalizeContents(); @@ -609,6 +607,7 @@ in.header = make(); in.binding = make(); in.weakBinding = make(); + in.lazyBinding = make(); in.got = make(); in.tlvPointers = make(); in.lazyPointers = make(); diff --git a/lld/test/MachO/weak-binding.s b/lld/test/MachO/weak-binding.s --- a/lld/test/MachO/weak-binding.s +++ b/lld/test/MachO/weak-binding.s @@ -4,13 +4,18 @@ # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/libfoo.s -o %t/libfoo.o # RUN: lld -flavor darwinnew -syslibroot %S/Inputs/MacOSX.sdk -dylib %t/libfoo.o -o %t/libfoo.dylib # RUN: lld -flavor darwinnew -syslibroot %S/Inputs/MacOSX.sdk %t/test.o -L%t -lfoo -o %t/test -lSystem -# RUN: llvm-objdump -d --no-show-raw-insn --bind --weak-bind --full-contents %t/test | \ +# RUN: llvm-objdump -d --no-show-raw-insn --bind --lazy-bind --weak-bind --full-contents %t/test | \ # RUN: FileCheck %s +# CHECK: Contents of section __la_symbol_ptr: +## Check that this section contains a nonzero pointer. It should point to +## _weak_external_fn, but we don't have a good way of testing the exact value as +## the bytes here are in little-endian order. +# CHECK-NEXT: {{[0-9a-f]+}} {{[0-9a-f ]*[1-9a-f]+[0-9a-f ]*}} + # CHECK: Contents of section __got: ## Check that this section contains a nonzero pointer. It should point to -## _weak_external_for_gotpcrel, but we don't have a good way of testing the exact -## value as the bytes here are in little-endian order. +## _weak_external_for_gotpcrel. # CHECK-NEXT: {{[0-9a-f]+}} {{[0-9a-f ]*[1-9a-f]+[0-9a-f ]*}} # CHECK: <_main>: @@ -19,28 +24,39 @@ # CHECK-NEXT: movq [[#]](%rip), %rax # [[#%X,WEAK_TLV_ADDR:]] # CHECK-NEXT: movq [[#]](%rip), %rax # [[#%X,WEAK_DY_TLV_ADDR:]] # CHECK-NEXT: movq [[#]](%rip), %rax # [[#%X,WEAK_INT_TLV_ADDR:]] +# CHECK-NEXT: callq 0x{{[0-9a-f]*}} +# CHECK-NEXT: callq 0x{{[0-9a-f]*}} +# CHECK-NEXT: callq 0x{{[0-9a-f]*}} # CHECK-LABEL: Bind table: -# CHECK-DAG: __DATA __data 0x[[#%x,WEAK_DY:]] pointer 0 libfoo _weak_dysym -# CHECK-DAG: __DATA __thread_vars 0x{{[0-9a-f]*}} pointer 0 libSystem __tlv_bootstrap -# CHECK-DAG: __DATA __thread_ptrs 0x[[#WEAK_DY_TLV_ADDR]] pointer 0 libfoo _weak_dysym_tlv -# CHECK-DAG: __DATA_CONST __got 0x[[#WEAK_DY_GOT_ADDR]] pointer 0 libfoo _weak_dysym_for_gotpcrel +# CHECK-DAG: __DATA __data 0x[[#%x,WEAK_DY:]] pointer 0 libfoo _weak_dysym +# CHECK-DAG: __DATA __thread_vars 0x{{[0-9a-f]*}} pointer 0 libSystem __tlv_bootstrap +# CHECK-DAG: __DATA __thread_ptrs 0x[[#WEAK_DY_TLV_ADDR]] pointer 0 libfoo _weak_dysym_tlv +# CHECK-DAG: __DATA_CONST __got 0x[[#WEAK_DY_GOT_ADDR]] pointer 0 libfoo _weak_dysym_for_gotpcrel +# CHECK-DAG: __DATA __la_symbol_ptr 0x[[#%x,WEAK_DY_FN:]] pointer 0 libfoo _weak_dysym_fn ## Check that we don't have any other bindings # CHECK-NOT: pointer +# CHECK-LABEL: Lazy bind table: +## Verify that we have no lazy bindings +# CHECK-NOT: pointer + # CHECK-LABEL: Weak bind table: -# CHECK-DAG: __DATA_CONST __got 0x[[#WEAK_DY_GOT_ADDR]] pointer 0 _weak_dysym_for_gotpcrel -# CHECK-DAG: __DATA_CONST __got 0x[[#WEAK_EXT_GOT_ADDR]] pointer 0 _weak_external_for_gotpcrel -# CHECK-DAG: __DATA __data 0x[[#WEAK_DY]] pointer 0 _weak_dysym -# CHECK-DAG: __DATA __thread_ptrs 0x[[#WEAK_TLV_ADDR]] pointer 0 _weak_tlv -# CHECK-DAG: __DATA __thread_ptrs 0x[[#WEAK_DY_TLV_ADDR]] pointer 0 _weak_dysym_tlv -# CHECK-DAG: __DATA __data 0x{{[0-9a-f]*}} pointer 2 _weak_external +# CHECK-DAG: __DATA_CONST __got 0x[[#WEAK_DY_GOT_ADDR]] pointer 0 _weak_dysym_for_gotpcrel +# CHECK-DAG: __DATA_CONST __got 0x[[#WEAK_EXT_GOT_ADDR]] pointer 0 _weak_external_for_gotpcrel +# CHECK-DAG: __DATA __data 0x[[#WEAK_DY]] pointer 0 _weak_dysym +# CHECK-DAG: __DATA __thread_ptrs 0x[[#WEAK_TLV_ADDR]] pointer 0 _weak_tlv +# CHECK-DAG: __DATA __thread_ptrs 0x[[#WEAK_DY_TLV_ADDR]] pointer 0 _weak_dysym_tlv +# CHECK-DAG: __DATA __data 0x{{[0-9a-f]*}} pointer 2 _weak_external +# CHECK-DAG: __DATA __la_symbol_ptr 0x[[#WEAK_DY_FN]] pointer 0 _weak_dysym_fn +# CHECK-DAG: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} pointer 0 _weak_external_fn ## Check that we don't have any other bindings # CHECK-NOT: pointer ## Weak internal symbols don't get bindings -# RUN: llvm-objdump --macho --bind --weak-bind %t/test | FileCheck %s --check-prefix=WEAK-INTERNAL +# RUN: llvm-objdump --macho --bind --lazy-bind --weak-bind %t/test | FileCheck %s --check-prefix=WEAK-INTERNAL # WEAK-INTERNAL-NOT: _weak_internal +# WEAK-INTERNAL-NOT: _weak_internal_fn # WEAK-INTERNAL-NOT: _weak_internal_tlv #--- libfoo.s @@ -55,6 +71,11 @@ _weak_dysym_for_gotpcrel: .quad 0x1234 +.globl _weak_dysym_fn +.weak_definition _weak_dysym_fn +_weak_dysym_fn: + ret + .section __DATA,__thread_vars,thread_local_variables .globl _weak_dysym_tlv @@ -64,8 +85,8 @@ #--- test.s -.globl _main, _weak_external, _weak_external_for_gotpcrel -.weak_definition _weak_external, _weak_external_for_gotpcrel, _weak_internal +.globl _main, _weak_external, _weak_external_for_gotpcrel, _weak_external_fn +.weak_definition _weak_external, _weak_external_for_gotpcrel, _weak_external_fn, _weak_internal, _weak_internal_fn _main: mov _weak_dysym_for_gotpcrel@GOTPCREL(%rip), %rax @@ -73,6 +94,9 @@ mov _weak_tlv@TLVP(%rip), %rax mov _weak_dysym_tlv@TLVP(%rip), %rax mov _weak_internal_tlv@TLVP(%rip), %rax + callq _weak_dysym_fn + callq _weak_external_fn + callq _weak_internal_fn mov $0, %rax ret @@ -82,9 +106,15 @@ _weak_external_for_gotpcrel: .quad 0x1234 +_weak_external_fn: + ret + _weak_internal: .quad 0x1234 +_weak_internal_fn: + ret + .data .quad _weak_dysym .quad _weak_external + 2 diff --git a/lld/test/MachO/weak-definition-order.s b/lld/test/MachO/weak-definition-order.s --- a/lld/test/MachO/weak-definition-order.s +++ b/lld/test/MachO/weak-definition-order.s @@ -23,12 +23,11 @@ # RUN: @executable_path/libweak2.dylib %t/weak2.o -o %t/libweak2.dylib # RUN: lld -flavor darwinnew -L%S/Inputs/MacOSX.sdk/usr/lib -lSystem -o %t/dylib12 -Z -L%t -lweak1 -lweak2 %t/test.o -# RUN: llvm-objdump --macho --lazy-bind %t/dylib12 | FileCheck %s --check-prefix=DYLIB1 +# RUN: llvm-objdump --macho --bind %t/dylib12 | FileCheck %s --check-prefix=DYLIB1 # RUN: lld -flavor darwinnew -L%S/Inputs/MacOSX.sdk/usr/lib -lSystem -o %t/dylib21 -Z -L%t -lweak2 -lweak1 %t/test.o -# RUN: llvm-objdump --macho --lazy-bind %t/dylib21 | FileCheck %s --check-prefix=DYLIB2 -## TODO: these should really be in the weak binding section, not the lazy binding section -# DYLIB1: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} libweak1 _foo -# DYLIB2: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} libweak2 _foo +# RUN: llvm-objdump --macho --bind %t/dylib21 | FileCheck %s --check-prefix=DYLIB2 +# DYLIB1: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} pointer 0 libweak1 _foo +# DYLIB2: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} pointer 0 libweak2 _foo .globl _main _main: