xref: /llvm-project-15.0.7/lld/MachO/Driver.cpp (revision 7a9258e9) 
1 //===- Driver.cpp ---------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "Driver.h"
10 #include "Config.h"
11 #include "InputFiles.h"
12 #include "OutputSection.h"
13 #include "OutputSegment.h"
14 #include "SymbolTable.h"
15 #include "Symbols.h"
16 #include "Target.h"
17 #include "Writer.h"
18 
19 #include "lld/Common/Args.h"
20 #include "lld/Common/Driver.h"
21 #include "lld/Common/ErrorHandler.h"
22 #include "lld/Common/LLVM.h"
23 #include "lld/Common/Memory.h"
24 #include "lld/Common/Version.h"
25 #include "llvm/ADT/DenseSet.h"
26 #include "llvm/ADT/StringExtras.h"
27 #include "llvm/ADT/StringRef.h"
28 #include "llvm/BinaryFormat/MachO.h"
29 #include "llvm/BinaryFormat/Magic.h"
30 #include "llvm/Config/config.h"
31 #include "llvm/Object/Archive.h"
32 #include "llvm/Option/ArgList.h"
33 #include "llvm/Option/Option.h"
34 #include "llvm/Support/MemoryBuffer.h"
35 #include "llvm/Support/Path.h"
36 
37 using namespace llvm;
38 using namespace llvm::MachO;
39 using namespace llvm::sys;
40 using namespace llvm::opt;
41 using namespace lld;
42 using namespace lld::macho;
43 
44 Configuration *lld::macho::config;
45 
46 // Create prefix string literals used in Options.td
47 #define PREFIX(NAME, VALUE) const char *NAME[] = VALUE;
48 #include "Options.inc"
49 #undef PREFIX
50 
51 // Create table mapping all options defined in Options.td
52 static const opt::OptTable::Info optInfo[] = {
53 #define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X7, X8, X9, X10, X11, X12)      \
54   {X1, X2, X10,         X11,         OPT_##ID, opt::Option::KIND##Class,       \
55    X9, X8, OPT_##GROUP, OPT_##ALIAS, X7,       X12},
56 #include "Options.inc"
57 #undef OPTION
58 };
59 
60 MachOOptTable::MachOOptTable() : OptTable(optInfo) {}
61 
62 opt::InputArgList MachOOptTable::parse(ArrayRef<const char *> argv) {
63   // Make InputArgList from string vectors.
64   unsigned missingIndex;
65   unsigned missingCount;
66   SmallVector<const char *, 256> vec(argv.data(), argv.data() + argv.size());
67 
68   opt::InputArgList args = ParseArgs(vec, missingIndex, missingCount);
69 
70   if (missingCount)
71     error(Twine(args.getArgString(missingIndex)) + ": missing argument");
72 
73   for (opt::Arg *arg : args.filtered(OPT_UNKNOWN))
74     error("unknown argument: " + arg->getSpelling());
75   return args;
76 }
77 
78 void MachOOptTable::printHelp(const char *argv0, bool showHidden) const {
79   PrintHelp(lld::outs(), (std::string(argv0) + " [options] file...").c_str(),
80             "LLVM Linker", showHidden);
81   lld::outs() << "\n";
82 }
83 
84 static Optional<std::string> findLibrary(StringRef name) {
85   std::string stub = (llvm::Twine("lib") + name + ".tbd").str();
86   std::string shared = (llvm::Twine("lib") + name + ".dylib").str();
87   std::string archive = (llvm::Twine("lib") + name + ".a").str();
88   llvm::SmallString<260> location;
89 
90   for (StringRef dir : config->searchPaths) {
91     for (StringRef library : {stub, shared, archive}) {
92       location = dir;
93       llvm::sys::path::append(location, library);
94       if (fs::exists(location))
95         return location.str().str();
96     }
97   }
98   return {};
99 }
100 
101 static TargetInfo *createTargetInfo(opt::InputArgList &args) {
102   StringRef arch = llvm::Triple(LLVM_DEFAULT_TARGET_TRIPLE).getArchName();
103   config->arch = llvm::MachO::getArchitectureFromName(
104       args.getLastArgValue(OPT_arch, arch));
105   switch (config->arch) {
106   case llvm::MachO::AK_x86_64:
107   case llvm::MachO::AK_x86_64h:
108     return createX86_64TargetInfo();
109   default:
110     fatal("missing or unsupported -arch " + args.getLastArgValue(OPT_arch));
111   }
112 }
113 
114 static std::vector<StringRef> getSearchPaths(opt::InputArgList &args) {
115   std::vector<StringRef> ret{args::getStrings(args, OPT_L)};
116   if (!args.hasArg(OPT_Z)) {
117     ret.push_back("/usr/lib");
118     ret.push_back("/usr/local/lib");
119   }
120   return ret;
121 }
122 
123 static void addFile(StringRef path) {
124   Optional<MemoryBufferRef> buffer = readFile(path);
125   if (!buffer)
126     return;
127   MemoryBufferRef mbref = *buffer;
128 
129   switch (identify_magic(mbref.getBuffer())) {
130   case file_magic::archive: {
131     std::unique_ptr<object::Archive> file = CHECK(
132         object::Archive::create(mbref), path + ": failed to parse archive");
133 
134     if (!file->isEmpty() && !file->hasSymbolTable())
135       error(path + ": archive has no index; run ranlib to add one");
136 
137     inputFiles.push_back(make<ArchiveFile>(std::move(file)));
138     break;
139   }
140   case file_magic::macho_object:
141     inputFiles.push_back(make<ObjFile>(mbref));
142     break;
143   case file_magic::macho_dynamically_linked_shared_lib:
144     inputFiles.push_back(make<DylibFile>(mbref));
145     break;
146   case file_magic::tapi_file: {
147     llvm::Expected<std::unique_ptr<llvm::MachO::InterfaceFile>> result =
148         TextAPIReader::get(mbref);
149     if (!result)
150       return;
151 
152     std::unique_ptr<llvm::MachO::InterfaceFile> interface{std::move(*result)};
153     inputFiles.push_back(make<DylibFile>(std::move(interface)));
154     break;
155   }
156   default:
157     error(path + ": unhandled file type");
158   }
159 }
160 
161 static std::array<StringRef, 6> archNames{"arm",    "arm64", "i386",
162                                           "x86_64", "ppc",   "ppc64"};
163 static bool isArchString(StringRef s) {
164   static DenseSet<StringRef> archNamesSet(archNames.begin(), archNames.end());
165   return archNamesSet.find(s) != archNamesSet.end();
166 }
167 
168 // An order file has one entry per line, in the following format:
169 //
170 //   <arch>:<object file>:<symbol name>
171 //
172 // <arch> and <object file> are optional. If not specified, then that entry
173 // matches any symbol of that name.
174 //
175 // If a symbol is matched by multiple entries, then it takes the lowest-ordered
176 // entry (the one nearest to the front of the list.)
177 //
178 // The file can also have line comments that start with '#'.
179 void parseOrderFile(StringRef path) {
180   Optional<MemoryBufferRef> buffer = readFile(path);
181   if (!buffer) {
182     error("Could not read order file at " + path);
183     return;
184   }
185 
186   MemoryBufferRef mbref = *buffer;
187   size_t priority = std::numeric_limits<size_t>::max();
188   for (StringRef rest : args::getLines(mbref)) {
189     StringRef arch, objectFile, symbol;
190 
191     std::array<StringRef, 3> fields;
192     uint8_t fieldCount = 0;
193     while (rest != "" && fieldCount < 3) {
194       std::pair<StringRef, StringRef> p = getToken(rest, ": \t\n\v\f\r");
195       StringRef tok = p.first;
196       rest = p.second;
197 
198       // Check if we have a comment
199       if (tok == "" || tok[0] == '#')
200         break;
201 
202       fields[fieldCount++] = tok;
203     }
204 
205     switch (fieldCount) {
206     case 3:
207       arch = fields[0];
208       objectFile = fields[1];
209       symbol = fields[2];
210       break;
211     case 2:
212       (isArchString(fields[0]) ? arch : objectFile) = fields[0];
213       symbol = fields[1];
214       break;
215     case 1:
216       symbol = fields[0];
217       break;
218     case 0:
219       break;
220     default:
221       llvm_unreachable("too many fields in order file");
222     }
223 
224     if (!arch.empty()) {
225       if (!isArchString(arch)) {
226         error("invalid arch \"" + arch + "\" in order file: expected one of " +
227               llvm::join(archNames, ", "));
228         continue;
229       }
230 
231       // TODO: Update when we extend support for other archs
232       if (arch != "x86_64")
233         continue;
234     }
235 
236     if (!objectFile.empty() && !objectFile.endswith(".o")) {
237       error("invalid object file name \"" + objectFile +
238             "\" in order file: should end with .o");
239       continue;
240     }
241 
242     if (!symbol.empty()) {
243       SymbolPriorityEntry &entry = config->priorities[symbol];
244       if (!objectFile.empty())
245         entry.objectFiles.insert(std::make_pair(objectFile, priority));
246       else
247         entry.anyObjectFile = std::max(entry.anyObjectFile, priority);
248     }
249 
250     --priority;
251   }
252 }
253 
254 // We expect sub-library names of the form "libfoo", which will match a dylib
255 // with a path of .*/libfoo.dylib.
256 static bool markSubLibrary(StringRef searchName) {
257   for (InputFile *file : inputFiles) {
258     if (auto *dylibFile = dyn_cast<DylibFile>(file)) {
259       StringRef filename = path::filename(dylibFile->getName());
260       if (filename.consume_front(searchName) && filename == ".dylib") {
261         dylibFile->reexport = true;
262         return true;
263       }
264     }
265   }
266   return false;
267 }
268 
269 static void handlePlatformVersion(const opt::Arg *arg) {
270   // TODO: implementation coming very soon ...
271 }
272 
273 static void warnIfDeprecatedOption(const opt::Option &opt) {
274   if (!opt.getGroup().isValid())
275     return;
276   if (opt.getGroup().getID() == OPT_grp_deprecated) {
277     warn("Option `" + opt.getPrefixedName() + "' is deprecated in ld64:");
278     warn(opt.getHelpText());
279   }
280 }
281 
282 static void warnIfUnimplementedOption(const opt::Option &opt) {
283   if (!opt.getGroup().isValid())
284     return;
285   switch (opt.getGroup().getID()) {
286   case OPT_grp_deprecated:
287     // warn about deprecated options elsewhere
288     break;
289   case OPT_grp_undocumented:
290     warn("Option `" + opt.getPrefixedName() +
291          "' is undocumented. Should lld implement it?");
292     break;
293   case OPT_grp_obsolete:
294     warn("Option `" + opt.getPrefixedName() +
295          "' is obsolete. Please modernize your usage.");
296     break;
297   case OPT_grp_ignored:
298     warn("Option `" + opt.getPrefixedName() + "' is ignored.");
299     break;
300   default:
301     warn("Option `" + opt.getPrefixedName() +
302          "' is not yet implemented. Stay tuned...");
303     break;
304   }
305 }
306 
307 bool macho::link(llvm::ArrayRef<const char *> argsArr, bool canExitEarly,
308                  raw_ostream &stdoutOS, raw_ostream &stderrOS) {
309   lld::stdoutOS = &stdoutOS;
310   lld::stderrOS = &stderrOS;
311 
312   stderrOS.enable_colors(stderrOS.has_colors());
313   // TODO: Set up error handler properly, e.g. the errorLimitExceededMsg
314 
315   MachOOptTable parser;
316   opt::InputArgList args = parser.parse(argsArr.slice(1));
317 
318   if (args.hasArg(OPT_help_hidden)) {
319     parser.printHelp(argsArr[0], /*showHidden=*/true);
320     return true;
321   } else if (args.hasArg(OPT_help)) {
322     parser.printHelp(argsArr[0], /*showHidden=*/false);
323     return true;
324   }
325 
326   config = make<Configuration>();
327   symtab = make<SymbolTable>();
328   target = createTargetInfo(args);
329 
330   config->entry = symtab->addUndefined(args.getLastArgValue(OPT_e, "_main"));
331   config->outputFile = args.getLastArgValue(OPT_o, "a.out");
332   config->installName =
333       args.getLastArgValue(OPT_install_name, config->outputFile);
334   config->searchPaths = getSearchPaths(args);
335   config->outputType = args.hasArg(OPT_dylib) ? MH_DYLIB : MH_EXECUTE;
336 
337   if (args.hasArg(OPT_v)) {
338     message(getLLDVersion());
339     std::vector<StringRef> &searchPaths = config->searchPaths;
340     message("Library search paths:\n" +
341             llvm::join(searchPaths.begin(), searchPaths.end(), "\n"));
342     freeArena();
343     return !errorCount();
344   }
345 
346   for (const auto &arg : args) {
347     const auto &opt = arg->getOption();
348     warnIfDeprecatedOption(opt);
349     switch (arg->getOption().getID()) {
350     case OPT_INPUT:
351       addFile(arg->getValue());
352       break;
353     case OPT_l: {
354       StringRef name = arg->getValue();
355       if (Optional<std::string> path = findLibrary(name)) {
356         addFile(*path);
357         break;
358       }
359       error("library not found for -l" + name);
360       break;
361     }
362     case OPT_platform_version:
363       handlePlatformVersion(arg);
364       break;
365     case OPT_o:
366     case OPT_dylib:
367     case OPT_e:
368     case OPT_L:
369     case OPT_Z:
370     case OPT_arch:
371       // handled elsewhere
372       break;
373     default:
374       warnIfUnimplementedOption(opt);
375       break;
376     }
377   }
378 
379   // Now that all dylibs have been loaded, search for those that should be
380   // re-exported.
381   for (opt::Arg *arg : args.filtered(OPT_sub_library)) {
382     config->hasReexports = true;
383     StringRef searchName = arg->getValue();
384     if (!markSubLibrary(searchName))
385       error("-sub_library " + searchName + " does not match a supplied dylib");
386   }
387 
388   StringRef orderFile = args.getLastArgValue(OPT_order_file);
389   if (!orderFile.empty())
390     parseOrderFile(orderFile);
391 
392   // dyld requires us to load libSystem. Since we may run tests on non-OSX
393   // systems which do not have libSystem, we mock it out here.
394   // TODO: Replace this with a stub tbd file once we have TAPI support.
395   if (StringRef(getenv("LLD_IN_TEST")) == "1" &&
396       config->outputType == MH_EXECUTE) {
397     inputFiles.push_back(DylibFile::createLibSystemMock());
398   }
399 
400   if (config->outputType == MH_EXECUTE && !isa<Defined>(config->entry)) {
401     error("undefined symbol: " + config->entry->getName());
402     return false;
403   }
404 
405   createSyntheticSections();
406 
407   // Initialize InputSections.
408   for (InputFile *file : inputFiles) {
409     for (SubsectionMap &map : file->subsections) {
410       for (auto &p : map) {
411         InputSection *isec = p.second;
412         inputSections.push_back(isec);
413       }
414     }
415   }
416 
417   // Write to an output file.
418   writeResult();
419 
420   if (canExitEarly)
421     exitLld(errorCount() ? 1 : 0);
422 
423   freeArena();
424   return !errorCount();
425 }
426