diff options
author | Jez Ng <jezng@fb.com> | 2020-09-18 08:40:46 -0700 |
---|---|---|
committer | Jez Ng <jezng@fb.com> | 2020-09-25 11:28:35 -0700 |
commit | 62a3f0c9844bb89a48173440145b26212be60f83 (patch) | |
tree | 0acbf3d9ccde7988cc417c07c3458656a4caebc7 /lld | |
parent | c7c9776f77712eb4311708d884c0c70ccaa7125b (diff) | |
download | llvm-62a3f0c9844bb89a48173440145b26212be60f83.zip llvm-62a3f0c9844bb89a48173440145b26212be60f83.tar.gz llvm-62a3f0c9844bb89a48173440145b26212be60f83.tar.bz2 |
[lld-macho] Support absolute symbols
They operate like Defined symbols but with no associated InputSection.
Note that `ld64` seems to treat the weak definition flag like a no-op for
absolute symbols, so I have replicated that behavior.
Reviewed By: #lld-macho, smeenai
Differential Revision: https://reviews.llvm.org/D87909
Diffstat (limited to 'lld')
-rw-r--r-- | lld/MachO/ExportTrie.cpp | 11 | ||||
-rw-r--r-- | lld/MachO/InputFiles.cpp | 73 | ||||
-rw-r--r-- | lld/MachO/InputFiles.h | 2 | ||||
-rw-r--r-- | lld/MachO/SymbolTable.cpp | 6 | ||||
-rw-r--r-- | lld/MachO/Symbols.cpp | 15 | ||||
-rw-r--r-- | lld/MachO/Symbols.h | 15 | ||||
-rw-r--r-- | lld/MachO/SyntheticSections.cpp | 14 | ||||
-rw-r--r-- | lld/test/MachO/abs-symbols.s | 24 | ||||
-rw-r--r-- | lld/test/MachO/invalid/abs-duplicate.s | 23 | ||||
-rw-r--r-- | lld/test/MachO/invalid/dso-handle-duplicate.s | 4 |
10 files changed, 148 insertions, 39 deletions
diff --git a/lld/MachO/ExportTrie.cpp b/lld/MachO/ExportTrie.cpp index 0093907e..bd0c000 100644 --- a/lld/MachO/ExportTrie.cpp +++ b/lld/MachO/ExportTrie.cpp @@ -62,11 +62,18 @@ struct ExportInfo { uint8_t flags = 0; ExportInfo(const Symbol &sym, uint64_t imageBase) : address(sym.getVA() - imageBase) { + // Set the symbol type. if (sym.isWeakDef()) flags |= EXPORT_SYMBOL_FLAGS_WEAK_DEFINITION; - if (sym.isTlv()) - flags |= EXPORT_SYMBOL_FLAGS_KIND_THREAD_LOCAL; // TODO: Add proper support for re-exports & stub-and-resolver flags. + + // Set the symbol kind. + if (sym.isTlv()) { + flags |= EXPORT_SYMBOL_FLAGS_KIND_THREAD_LOCAL; + } else if (auto *defined = dyn_cast<Defined>(&sym)) { + if (defined->isAbsolute()) + flags |= EXPORT_SYMBOL_FLAGS_KIND_ABSOLUTE; + } } }; diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp index ad2d6a2..35211ea 100644 --- a/lld/MachO/InputFiles.cpp +++ b/lld/MachO/InputFiles.cpp @@ -222,6 +222,50 @@ void InputFile::parseRelocations(const section_64 &sec, } } +static macho::Symbol *createDefined(const structs::nlist_64 &sym, + StringRef name, InputSection *isec, + uint32_t value) { + if (sym.n_type & N_EXT) + // Global defined symbol + return symtab->addDefined(name, isec, value, sym.n_desc & N_WEAK_DEF); + // Local defined symbol + return make<Defined>(name, isec, value, sym.n_desc & N_WEAK_DEF, + /*isExternal=*/false); +} + +// Absolute symbols are defined symbols that do not have an associated +// InputSection. They cannot be weak. +static macho::Symbol *createAbsolute(const structs::nlist_64 &sym, + StringRef name) { + if (sym.n_type & N_EXT) + return symtab->addDefined(name, nullptr, sym.n_value, /*isWeakDef=*/false); + return make<Defined>(name, nullptr, sym.n_value, /*isWeakDef=*/false, + /*isExternal=*/false); +} + +macho::Symbol *InputFile::parseNonSectionSymbol(const structs::nlist_64 &sym, + StringRef name) { + uint8_t type = sym.n_type & N_TYPE; + switch (type) { + case N_UNDF: + return sym.n_value == 0 + ? symtab->addUndefined(name) + : symtab->addCommon(name, this, sym.n_value, + 1 << GET_COMM_ALIGN(sym.n_desc)); + case N_ABS: + return createAbsolute(sym, name); + case N_PBUD: + case N_INDR: + error("TODO: support symbols of type " + std::to_string(type)); + return nullptr; + case N_SECT: + llvm_unreachable( + "N_SECT symbols should not be passed to parseNonSectionSymbol"); + default: + llvm_unreachable("invalid symbol type"); + } +} + void InputFile::parseSymbols(ArrayRef<structs::nlist_64> nList, const char *strtab, bool subsectionsViaSymbols) { // resize(), not reserve(), because we are going to create N_ALT_ENTRY symbols @@ -229,26 +273,12 @@ void InputFile::parseSymbols(ArrayRef<structs::nlist_64> nList, symbols.resize(nList.size()); std::vector<size_t> altEntrySymIdxs; - auto createDefined = [&](const structs::nlist_64 &sym, InputSection *isec, - uint32_t value) -> Symbol * { - StringRef name = strtab + sym.n_strx; - if (sym.n_type & N_EXT) - // Global defined symbol - return symtab->addDefined(name, isec, value, sym.n_desc & N_WEAK_DEF); - // Local defined symbol - return make<Defined>(name, isec, value, sym.n_desc & N_WEAK_DEF, - /*isExternal=*/false); - }; - for (size_t i = 0, n = nList.size(); i < n; ++i) { const structs::nlist_64 &sym = nList[i]; + StringRef name = strtab + sym.n_strx; - if ((sym.n_type & N_TYPE) == N_UNDF) { - StringRef name = strtab + sym.n_strx; - symbols[i] = sym.n_value == 0 - ? symtab->addUndefined(name) - : symtab->addCommon(name, this, sym.n_value, - 1 << GET_COMM_ALIGN(sym.n_desc)); + if ((sym.n_type & N_TYPE) != N_SECT) { + symbols[i] = parseNonSectionSymbol(sym, name); continue; } @@ -260,7 +290,7 @@ void InputFile::parseSymbols(ArrayRef<structs::nlist_64> nList, // use the same subsection. Otherwise, we must split the sections along // symbol boundaries. if (!subsectionsViaSymbols) { - symbols[i] = createDefined(sym, subsecMap[0], offset); + symbols[i] = createDefined(sym, name, subsecMap[0], offset); continue; } @@ -282,7 +312,7 @@ void InputFile::parseSymbols(ArrayRef<structs::nlist_64> nList, if (firstSize == 0) { // Alias of an existing symbol, or the first symbol in the section. These // are handled by reusing the existing section. - symbols[i] = createDefined(sym, firstIsec, 0); + symbols[i] = createDefined(sym, name, firstIsec, 0); continue; } @@ -298,15 +328,16 @@ void InputFile::parseSymbols(ArrayRef<structs::nlist_64> nList, subsecMap[offset] = secondIsec; // By construction, the symbol will be at offset zero in the new section. - symbols[i] = createDefined(sym, secondIsec, 0); + symbols[i] = createDefined(sym, name, secondIsec, 0); } for (size_t idx : altEntrySymIdxs) { const structs::nlist_64 &sym = nList[idx]; + StringRef name = strtab + sym.n_strx; SubsectionMap &subsecMap = subsections[sym.n_sect - 1]; uint32_t off = sym.n_value - sectionHeaders[sym.n_sect - 1].addr; InputSection *subsec = findContainingSubsection(subsecMap, &off); - symbols[idx] = createDefined(sym, subsec, off); + symbols[idx] = createDefined(sym, name, subsec, off); } } diff --git a/lld/MachO/InputFiles.h b/lld/MachO/InputFiles.h index bb83c20..59b0e41 100644 --- a/lld/MachO/InputFiles.h +++ b/lld/MachO/InputFiles.h @@ -65,6 +65,8 @@ protected: void parseSymbols(ArrayRef<lld::structs::nlist_64> nList, const char *strtab, bool subsectionsViaSymbols); + Symbol *parseNonSectionSymbol(const structs::nlist_64 &sym, StringRef name); + void parseRelocations(const llvm::MachO::section_64 &, SubsectionMap &); private: diff --git a/lld/MachO/SymbolTable.cpp b/lld/MachO/SymbolTable.cpp index 0aa8828..6a3ee92 100644 --- a/lld/MachO/SymbolTable.cpp +++ b/lld/MachO/SymbolTable.cpp @@ -131,9 +131,11 @@ Symbol *SymbolTable::addDSOHandle(const MachHeaderSection *header) { bool wasInserted; std::tie(s, wasInserted) = insert(DSOHandle::name); if (!wasInserted) { + // FIXME: Make every symbol (including absolute symbols) contain a + // reference to their originating file, then add that file name to this + // error message. if (auto *defined = dyn_cast<Defined>(s)) - error("found defined symbol from " + defined->isec->file->getName() + - " with illegal name " + DSOHandle::name); + error("found defined symbol with illegal name " + DSOHandle::name); } replaceSymbol<DSOHandle>(s, header); return s; diff --git a/lld/MachO/Symbols.cpp b/lld/MachO/Symbols.cpp index af5d9d2..75c6997 100644 --- a/lld/MachO/Symbols.cpp +++ b/lld/MachO/Symbols.cpp @@ -14,6 +14,21 @@ using namespace llvm; using namespace lld; using namespace lld::macho; +uint64_t Defined::getVA() const { + if (isAbsolute()) + return value; + return isec->getVA() + value; +} + +uint64_t Defined::getFileOffset() const { + if (isAbsolute()) { + error("absolute symbol " + toString(*this) + + " does not have a file offset"); + return 0; + } + return isec->getFileOffset() + value; +} + void LazySymbol::fetchArchiveMember() { file->fetch(sym); } // Returns a symbol for an error message. diff --git a/lld/MachO/Symbols.h b/lld/MachO/Symbols.h index 14c1ee8..f0d77d5 100644 --- a/lld/MachO/Symbols.h +++ b/lld/MachO/Symbols.h @@ -89,18 +89,17 @@ public: overridesWeakDef(false), weakDef(isWeakDef), external(isExternal) {} bool isWeakDef() const override { return weakDef; } - - bool isTlv() const override { return isThreadLocalVariables(isec->flags); } + bool isTlv() const override { + return !isAbsolute() && isThreadLocalVariables(isec->flags); + } bool isExternal() const { return external; } + bool isAbsolute() const { return isec == nullptr; } - static bool classof(const Symbol *s) { return s->kind() == DefinedKind; } - - uint64_t getVA() const override { return isec->getVA() + value; } + uint64_t getVA() const override; + uint64_t getFileOffset() const override; - uint64_t getFileOffset() const override { - return isec->getFileOffset() + value; - } + static bool classof(const Symbol *s) { return s->kind() == DefinedKind; } InputSection *isec; uint32_t value; diff --git a/lld/MachO/SyntheticSections.cpp b/lld/MachO/SyntheticSections.cpp index e40b832..5d603d6 100644 --- a/lld/MachO/SyntheticSections.cpp +++ b/lld/MachO/SyntheticSections.cpp @@ -594,11 +594,17 @@ void SymtabSection::writeTo(uint8_t *buf) const { // TODO support other symbol types // TODO populate n_desc with more flags if (auto *defined = dyn_cast<Defined>(entry.sym)) { - nList->n_type = MachO::N_EXT | MachO::N_SECT; - nList->n_sect = defined->isec->parent->index; + if (defined->isAbsolute()) { + nList->n_type = MachO::N_EXT | MachO::N_ABS; + nList->n_sect = MachO::NO_SECT; + nList->n_value = defined->value; + } else { + nList->n_type = MachO::N_EXT | MachO::N_SECT; + nList->n_sect = defined->isec->parent->index; + // For the N_SECT symbol type, n_value is the address of the symbol + nList->n_value = defined->value + defined->isec->getVA(); + } nList->n_desc |= defined->isWeakDef() ? MachO::N_WEAK_DEF : 0; - // For the N_SECT symbol type, n_value is the address of the symbol - nList->n_value = defined->value + defined->isec->getVA(); } ++nList; } diff --git a/lld/test/MachO/abs-symbols.s b/lld/test/MachO/abs-symbols.s new file mode 100644 index 0000000..25f6c87 --- /dev/null +++ b/lld/test/MachO/abs-symbols.s @@ -0,0 +1,24 @@ +# REQUIRES: x86 +# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o +# RUN: lld -flavor darwinnew -syslibroot %S/Inputs/MacOSX.sdk -lSystem %t.o -o %t +# RUN: llvm-objdump --macho --syms --exports-trie %t | FileCheck %s + +# CHECK-LABEL: SYMBOL TABLE: +# CHECK-DAG: 000000000000dead g *ABS* _foo +# CHECK-DAG: 000000000000beef g *ABS* _weakfoo + +# CHECK-LABEL: Exports trie: +# CHECK-DAG: 0x0000DEAD _foo [absolute] +# CHECK-DAG: 0x0000BEEF _weakfoo [absolute] + +.globl _foo, _weakfoo, _main +.weak_definition _weakfoo +_foo = 0xdead +_weakfoo = 0xbeef + +.text +_main: + ret + +## TODO: once we support emitting local symbols in the symtab, test local +## absolute symbols too diff --git a/lld/test/MachO/invalid/abs-duplicate.s b/lld/test/MachO/invalid/abs-duplicate.s new file mode 100644 index 0000000..e46c783 --- /dev/null +++ b/lld/test/MachO/invalid/abs-duplicate.s @@ -0,0 +1,23 @@ +# REQUIRES: x86 +# RUN: split-file %s %t +# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/test.s -o %t/test.o +# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %t/weakfoo.s -o %t/weakfoo.o +# RUN: not lld -flavor darwinnew -syslibroot %S/../Inputs/MacOSX.sdk -lSystem %t/test.o %t/weakfoo.o -o %t/test 2>&1 | FileCheck %s + +# CHECK: lld: error: duplicate symbol: _weakfoo + +#--- weakfoo.s +.globl _weakfoo +## The weak attribute is ignored for absolute symbols, so we will have a +## duplicate symbol error for _weakfoo. +.weak_definition _weakfoo +_weakfoo = 0x1234 + +#--- test.s +.globl _main, _weakfoo +.weak_definition _weakfoo +_weakfoo = 0x5678 + +.text +_main: + ret diff --git a/lld/test/MachO/invalid/dso-handle-duplicate.s b/lld/test/MachO/invalid/dso-handle-duplicate.s index 5991c6f..4390da6 100644 --- a/lld/test/MachO/invalid/dso-handle-duplicate.s +++ b/lld/test/MachO/invalid/dso-handle-duplicate.s @@ -7,8 +7,8 @@ ## far-out edge case that should be safe to ignore. # RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o -# RUN: not lld -flavor darwinnew -dylib %t.o -o %t.dylib 2>&1 | FileCheck %s -DFILE=%t.o -# CHECK: error: found defined symbol from [[FILE]] with illegal name ___dso_handle +# RUN: not lld -flavor darwinnew -dylib %t.o -o %t.dylib 2>&1 | FileCheck %s +# CHECK: error: found defined symbol with illegal name ___dso_handle .globl _main, ___dso_handle .text |