forked from OSchip/llvm-project
[lld/mac] Add support for -flat_namespace
-flat_namespace makes lld emit binaries that use name lookup that's more in line with other POSIX systems: Instead of looking up symbols as (dylib,name) pairs by dyld, they're instead looked up just by name. -flat_namespace has three effects: 1. MH_TWOLEVEL and MH_NNOUNDEFS are no longer set in the Mach-O header 2. All symbols use BIND_SPECIAL_DYLIB_FLAT_LOOKUP as ordinal 3. When a dylib is added to the link, its dependent dylibs are also added, so that lld can verify that no undefined symbols remain at the end of a link with -flat_namespace. These transitive dylibs are added for symbol resolution, but they are not emitted in LC_LOAD_COMMANDs. -undefined with -flat_namespace still isn't implemented. Before this change, it was impossible to hit that combination because -flat_namespace caused a diagnostic. Now that it no longer does, emit a dedicated temporary diagnostic when both flags are used. Differential Revision: https://reviews.llvm.org/D97641
This commit is contained in:
Nico Weber
parent
3e6b6cee00
commit
8174f33dc9
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@ -796,11 +796,6 @@ bool macho::link(ArrayRef<const char *> argsArr, bool canExitEarly,
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config->namespaceKind = arg->getOption().getID() == OPT_twolevel_namespace
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? NamespaceKind::twolevel
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: NamespaceKind::flat;
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if (config->namespaceKind == NamespaceKind::flat) {
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warn("Option '" + arg->getOption().getPrefixedName() +
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"' is not yet implemented. Stay tuned...");
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config->namespaceKind = NamespaceKind::twolevel;
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}
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}
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config->systemLibraryRoots = getSystemLibraryRoots(args);
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@ -587,15 +587,14 @@ const InterfaceFile *currentTopLevelTapi = nullptr;
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// Re-exports can either refer to on-disk files, or to documents within .tbd
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// files.
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static Optional<DylibFile *> loadReexportHelper(StringRef path,
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DylibFile *umbrella) {
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static Optional<DylibFile *> findDylib(StringRef path, DylibFile *umbrella) {
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if (path::is_absolute(path, path::Style::posix))
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for (StringRef root : config->systemLibraryRoots)
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if (Optional<std::string> dylibPath =
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resolveDylibPath((root + path).str()))
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return loadDylib(*dylibPath, umbrella);
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// TODO: Expand @loader_path, @executable_path etc
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// TODO: Expand @loader_path, @executable_path, @rpath etc, handle -dylib_path
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if (currentTopLevelTapi) {
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for (InterfaceFile &child :
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@ -609,7 +608,6 @@ static Optional<DylibFile *> loadReexportHelper(StringRef path,
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if (Optional<std::string> dylibPath = resolveDylibPath(path))
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return loadDylib(*dylibPath, umbrella);
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error("unable to locate re-export with install name " + path);
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return {};
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}
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@ -634,8 +632,10 @@ static bool isImplicitlyLinked(StringRef path) {
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}
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void loadReexport(StringRef path, DylibFile *umbrella) {
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Optional<DylibFile *> reexport = loadReexportHelper(path, umbrella);
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if (reexport && isImplicitlyLinked(path))
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Optional<DylibFile *> reexport = findDylib(path, umbrella);
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if (!reexport)
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error("unable to locate re-export with install name " + path);
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else if (isImplicitlyLinked(path))
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inputFiles.insert(*reexport);
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}
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@ -679,21 +679,33 @@ DylibFile::DylibFile(MemoryBufferRef mb, DylibFile *umbrella,
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return;
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}
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if (hdr->flags & MH_NO_REEXPORTED_DYLIBS)
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return;
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const uint8_t *p =
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reinterpret_cast<const uint8_t *>(hdr) + sizeof(mach_header_64);
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for (uint32_t i = 0, n = hdr->ncmds; i < n; ++i) {
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auto *cmd = reinterpret_cast<const load_command *>(p);
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p += cmd->cmdsize;
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if (cmd->cmd != LC_REEXPORT_DYLIB)
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continue;
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auto *c = reinterpret_cast<const dylib_command *>(cmd);
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StringRef reexportPath =
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reinterpret_cast<const char *>(c) + read32le(&c->dylib.name);
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loadReexport(reexportPath, umbrella);
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if (!(hdr->flags & MH_NO_REEXPORTED_DYLIBS) &&
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cmd->cmd == LC_REEXPORT_DYLIB) {
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const auto *c = reinterpret_cast<const dylib_command *>(cmd);
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StringRef reexportPath =
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reinterpret_cast<const char *>(c) + read32le(&c->dylib.name);
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loadReexport(reexportPath, umbrella);
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}
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// FIXME: What about LC_LOAD_UPWARD_DYLIB, LC_LAZY_LOAD_DYLIB,
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// LC_LOAD_WEAK_DYLIB, LC_REEXPORT_DYLIB (..are reexports from dylibs with
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// MH_NO_REEXPORTED_DYLIBS loaded for -flat_namespace)?
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if (config->namespaceKind == NamespaceKind::flat &&
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cmd->cmd == LC_LOAD_DYLIB) {
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const auto *c = reinterpret_cast<const dylib_command *>(cmd);
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StringRef dylibPath =
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reinterpret_cast<const char *>(c) + read32le(&c->dylib.name);
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Optional<DylibFile *> dylib = findDylib(dylibPath, umbrella);
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if (!dylib)
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error(Twine("unable to locate library '") + dylibPath +
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"' loaded from '" + toString(this) + "' for -flat_namespace");
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}
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}
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}
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@ -448,7 +448,6 @@ def alias_list : Separate<["-"], "alias_list">,
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Group<grp_resolve>;
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def flat_namespace : Flag<["-"], "flat_namespace">,
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HelpText<"Resolve symbols from all dylibs, both direct and transitive. Do not record source libraries: dyld must re-search at runtime and use the first definition found">,
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Flags<[HelpHidden]>,
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Group<grp_resolve>;
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def twolevel_namespace : Flag<["-"], "twolevel_namespace">,
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HelpText<"Make dyld look up symbols by (dylib,name) pairs (default)">,
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@ -181,12 +181,14 @@ void lld::macho::treatUndefinedSymbol(const Undefined &sym) {
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message += "\n>>> referenced by " + fileName;
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switch (config->undefinedSymbolTreatment) {
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case UndefinedSymbolTreatment::suppress:
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error("-undefined suppress unimplemented");
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break;
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case UndefinedSymbolTreatment::error:
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error(message);
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break;
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case UndefinedSymbolTreatment::warning:
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warn(message);
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error("-undefined warning unimplemented");
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break;
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case UndefinedSymbolTreatment::dynamic_lookup:
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error("dynamic_lookup unimplemented for " + message);
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@ -78,7 +78,10 @@ void MachHeaderSection::writeTo(uint8_t *buf) const {
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hdr->filetype = config->outputType;
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hdr->ncmds = loadCommands.size();
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hdr->sizeofcmds = sizeOfCmds;
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hdr->flags = MachO::MH_NOUNDEFS | MachO::MH_DYLDLINK | MachO::MH_TWOLEVEL;
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hdr->flags = MachO::MH_DYLDLINK;
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if (config->namespaceKind == NamespaceKind::twolevel)
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hdr->flags |= MachO::MH_NOUNDEFS | MachO::MH_TWOLEVEL;
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if (config->outputType == MachO::MH_DYLIB && !config->hasReexports)
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hdr->flags |= MachO::MH_NO_REEXPORTED_DYLIBS;
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@ -280,8 +283,9 @@ static void encodeBinding(const Symbol *sym, const OutputSection *osec,
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// Non-weak bindings need to have their dylib ordinal encoded as well.
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static int16_t ordinalForDylibSymbol(const DylibSymbol &dysym) {
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return dysym.isDynamicLookup() ? MachO::BIND_SPECIAL_DYLIB_FLAT_LOOKUP
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: dysym.getFile()->ordinal;
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return config->namespaceKind == NamespaceKind::flat || dysym.isDynamicLookup()
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? MachO::BIND_SPECIAL_DYLIB_FLAT_LOOKUP
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: dysym.getFile()->ordinal;
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}
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static void encodeDylibOrdinal(int16_t ordinal, raw_svector_ostream &os) {
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@ -816,13 +820,15 @@ void SymtabSection::writeTo(uint8_t *buf) const {
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nList->n_desc |= defined->isExternalWeakDef() ? MachO::N_WEAK_DEF : 0;
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} else if (auto *dysym = dyn_cast<DylibSymbol>(entry.sym)) {
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uint16_t n_desc = nList->n_desc;
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if (dysym->isDynamicLookup())
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int16_t ordinal = ordinalForDylibSymbol(*dysym);
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if (ordinal == MachO::BIND_SPECIAL_DYLIB_FLAT_LOOKUP)
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MachO::SET_LIBRARY_ORDINAL(n_desc, MachO::DYNAMIC_LOOKUP_ORDINAL);
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else if (dysym->getFile()->isBundleLoader)
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else if (ordinal == MachO::BIND_SPECIAL_DYLIB_MAIN_EXECUTABLE)
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MachO::SET_LIBRARY_ORDINAL(n_desc, MachO::EXECUTABLE_ORDINAL);
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else
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MachO::SET_LIBRARY_ORDINAL(
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n_desc, static_cast<uint8_t>(dysym->getFile()->ordinal));
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else {
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assert(ordinal > 0);
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MachO::SET_LIBRARY_ORDINAL(n_desc, static_cast<uint8_t>(ordinal));
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}
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nList->n_type = MachO::N_EXT;
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n_desc |= dysym->isWeakDef() ? MachO::N_WEAK_DEF : 0;
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@ -0,0 +1,87 @@
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# REQUIRES: x86
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# RUN: rm -rf %t
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# RUN: split-file %s %t
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/foo.o %t/foo.s
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# RUN: %lld -dylib -o %t/foo.dylib %t/foo.o
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/bar.o %t/bar.s
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# RUN: %lld -lSystem -dylib -o %t/bar.dylib %t/bar.o %t/foo.dylib
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/baz.o %t/baz.s
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# RUN: %lld -lSystem -dylib -o %t/baz.dylib %t/baz.o %t/bar.dylib
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/main.o %t/main.s
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# With flat_namespace, the linker automatically looks in foo.dylib and
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# bar.dylib too, but it doesn't add a LC_LOAD_DYLIB for it.
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# RUN: %lld -flat_namespace -lSystem %t/main.o %t/baz.dylib -o %t/out
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# RUN: llvm-objdump --macho --all-headers %t/out \
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# RUN: | FileCheck --check-prefix=HEADERBITS %s
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# RUN: llvm-objdump --macho --bind --lazy-bind --weak-bind %t/out \
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# RUN: | FileCheck --check-prefix=FLAT %s
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# RUN: llvm-nm -m %t/out | FileCheck --check-prefix=FLATSYM %s
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# RUN: llvm-readobj --syms %t/out | FileCheck --check-prefix=FLATSYM-READOBJ %s
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# HEADERBITS-NOT: NOUNDEFS
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# HEADERBITS-NOT: TWOLEVEL
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# HEADERBITS: DYLDLINK
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# HEADERBITS-NOT: foo.dylib
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# HEADERBITS-NOT: bar.dylib
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# FLAT: Bind table:
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# FLAT: __DATA_CONST __got 0x{{[0-9a-f]*}} pointer 0 flat-namespace dyld_stub_binder
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# FLAT: Lazy bind table:
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# FLAT-DAG: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} flat-namespace _bar
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# FLAT-DAG: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} flat-namespace _baz
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# FLAT-DAG: __DATA __la_symbol_ptr 0x{{[0-9a-f]*}} flat-namespace _foo
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# No "(dynamically looked up)" because llvm-nm -m doesn't print that
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# for files without MH_TWOLEVEL for some reason.
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# FLATSYM: (undefined) external _bar
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# FLATSYM: (undefined) external _baz
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# FLATSYM: (undefined) external _foo
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# ...but `llvm-readobj --syms` does, so verify we put the right thing there.
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# FLATSYM-READOBJ: Flags [ (0xFE00)
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# Undefined symbols should still cause errors by default.
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-macos \
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# RUN: -o %t/main-with-undef.o %t/main-with-undef.s
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# RUN: not %lld -flat_namespace -lSystem %t/main-with-undef.o %t/bar.dylib \
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# RUN: -o %t/out 2>&1 | FileCheck --check-prefix=UNDEF %s
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# UNDEF: error: undefined symbol: _quux
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#--- foo.s
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.globl _foo
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_foo:
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ret
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#--- bar.s
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.globl _bar
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_bar:
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callq _foo
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ret
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#--- baz.s
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.globl _baz
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_baz:
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callq _bar
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ret
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#--- main.s
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.globl _main
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_main:
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callq _foo
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callq _bar
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callq _baz
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ret
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#--- main-with-undef.s
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.globl _main
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_main:
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callq _foo
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callq _bar
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callq _baz
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callq _quux
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ret
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@ -12,8 +12,8 @@
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# RUN: llvm-objdump --macho --all-headers %t/x86-64-dylib | FileCheck %s -DCAPS=0x00
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# RUN: llvm-objdump --macho --all-headers %t/arm64-dylib | FileCheck %s -DCAPS=0x00
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# CHECK: magic cputype cpusubtype caps filetype
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# CHECK-NEXT: MH_MAGIC_64 {{.*}} ALL [[CAPS]] {{.*}}
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# CHECK: magic cputype cpusubtype caps filetype {{.*}} flags
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# CHECK-NEXT: MH_MAGIC_64 {{.*}} ALL [[CAPS]] {{.*}} NOUNDEFS {{.*}} TWOLEVEL
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.globl _main
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_main:
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