xref: /llvm-project/llvm/tools/llvm-objcopy/llvm-objcopy.cpp (revision d29bf4cb2cf77a664c0a7be35e81483c3e4a96a4) 
1 //===- llvm-objcopy.cpp ---------------------------------------------------===//
2 //
3 //                      The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "llvm-objcopy.h"
11 #include "Object.h"
12 #include "llvm/ADT/STLExtras.h"
13 #include "llvm/ADT/StringRef.h"
14 #include "llvm/ADT/Twine.h"
15 #include "llvm/BinaryFormat/ELF.h"
16 #include "llvm/Object/Binary.h"
17 #include "llvm/Object/ELFObjectFile.h"
18 #include "llvm/Object/ELFTypes.h"
19 #include "llvm/Object/Error.h"
20 #include "llvm/Option/Arg.h"
21 #include "llvm/Option/ArgList.h"
22 #include "llvm/Option/Option.h"
23 #include "llvm/Support/Casting.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/Compiler.h"
26 #include "llvm/Support/Error.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/ErrorOr.h"
29 #include "llvm/Support/FileOutputBuffer.h"
30 #include "llvm/Support/InitLLVM.h"
31 #include "llvm/Support/Path.h"
32 #include "llvm/Support/raw_ostream.h"
33 #include <algorithm>
34 #include <cassert>
35 #include <cstdlib>
36 #include <functional>
37 #include <iterator>
38 #include <memory>
39 #include <string>
40 #include <system_error>
41 #include <utility>
42 
43 using namespace llvm;
44 using namespace object;
45 using namespace ELF;
46 
47 namespace {
48 
49 enum ObjcopyID {
50   OBJCOPY_INVALID = 0, // This is not an option ID.
51 #define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM,  \
52                HELPTEXT, METAVAR, VALUES)                                      \
53   OBJCOPY_##ID,
54 #include "ObjcopyOpts.inc"
55 #undef OPTION
56 };
57 
58 #define PREFIX(NAME, VALUE) const char *const NAME[] = VALUE;
59 #include "ObjcopyOpts.inc"
60 #undef PREFIX
61 
62 static const opt::OptTable::Info ObjcopyInfoTable[] = {
63 #define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM,  \
64                HELPTEXT, METAVAR, VALUES)                                      \
65   {PREFIX,          NAME,         HELPTEXT,                                    \
66    METAVAR,         OBJCOPY_##ID, opt::Option::KIND##Class,                    \
67    PARAM,           FLAGS,        OBJCOPY_##GROUP,                             \
68    OBJCOPY_##ALIAS, ALIASARGS,    VALUES},
69 #include "ObjcopyOpts.inc"
70 #undef OPTION
71 };
72 
73 class ObjcopyOptTable : public opt::OptTable {
74 public:
75   ObjcopyOptTable() : OptTable(ObjcopyInfoTable, true) {}
76 };
77 
78 enum StripID {
79   STRIP_INVALID = 0, // This is not an option ID.
80 #define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM,  \
81                HELPTEXT, METAVAR, VALUES)                                      \
82   STRIP_##ID,
83 #include "StripOpts.inc"
84 #undef OPTION
85 };
86 
87 static const opt::OptTable::Info StripInfoTable[] = {
88 #define OPTION(PREFIX, NAME, ID, KIND, GROUP, ALIAS, ALIASARGS, FLAGS, PARAM,  \
89                HELPTEXT, METAVAR, VALUES)                                      \
90   {PREFIX,        NAME,       HELPTEXT,                                        \
91    METAVAR,       STRIP_##ID, opt::Option::KIND##Class,                        \
92    PARAM,         FLAGS,      STRIP_##GROUP,                                   \
93    STRIP_##ALIAS, ALIASARGS,  VALUES},
94 #include "StripOpts.inc"
95 #undef OPTION
96 };
97 
98 class StripOptTable : public opt::OptTable {
99 public:
100   StripOptTable() : OptTable(StripInfoTable, true) {}
101 };
102 
103 } // namespace
104 
105 // The name this program was invoked as.
106 static StringRef ToolName;
107 
108 namespace llvm {
109 
110 LLVM_ATTRIBUTE_NORETURN void error(Twine Message) {
111   errs() << ToolName << ": " << Message << ".\n";
112   errs().flush();
113   exit(1);
114 }
115 
116 LLVM_ATTRIBUTE_NORETURN void reportError(StringRef File, std::error_code EC) {
117   assert(EC);
118   errs() << ToolName << ": '" << File << "': " << EC.message() << ".\n";
119   exit(1);
120 }
121 
122 LLVM_ATTRIBUTE_NORETURN void reportError(StringRef File, Error E) {
123   assert(E);
124   std::string Buf;
125   raw_string_ostream OS(Buf);
126   logAllUnhandledErrors(std::move(E), OS, "");
127   OS.flush();
128   errs() << ToolName << ": '" << File << "': " << Buf;
129   exit(1);
130 }
131 
132 } // end namespace llvm
133 
134 struct CopyConfig {
135   StringRef OutputFilename;
136   StringRef InputFilename;
137   StringRef OutputFormat;
138   StringRef InputFormat;
139   StringRef BinaryArch;
140 
141   StringRef SplitDWO;
142   StringRef AddGnuDebugLink;
143   std::vector<StringRef> ToRemove;
144   std::vector<StringRef> Keep;
145   std::vector<StringRef> OnlyKeep;
146   std::vector<StringRef> AddSection;
147   std::vector<StringRef> SymbolsToLocalize;
148   std::vector<StringRef> SymbolsToGlobalize;
149   std::vector<StringRef> SymbolsToWeaken;
150   std::vector<StringRef> SymbolsToRemove;
151   std::vector<StringRef> SymbolsToKeep;
152   StringMap<StringRef> SymbolsToRename;
153   bool StripAll = false;
154   bool StripAllGNU = false;
155   bool StripDebug = false;
156   bool StripSections = false;
157   bool StripNonAlloc = false;
158   bool StripDWO = false;
159   bool ExtractDWO = false;
160   bool LocalizeHidden = false;
161   bool Weaken = false;
162   bool DiscardAll = false;
163   bool OnlyKeepDebug = false;
164 };
165 
166 using SectionPred = std::function<bool(const SectionBase &Sec)>;
167 
168 bool IsDWOSection(const SectionBase &Sec) { return Sec.Name.endswith(".dwo"); }
169 
170 bool OnlyKeepDWOPred(const Object &Obj, const SectionBase &Sec) {
171   // We can't remove the section header string table.
172   if (&Sec == Obj.SectionNames)
173     return false;
174   // Short of keeping the string table we want to keep everything that is a DWO
175   // section and remove everything else.
176   return !IsDWOSection(Sec);
177 }
178 
179 std::unique_ptr<Writer> CreateWriter(const CopyConfig &Config, Object &Obj,
180                                      StringRef File, ElfType OutputElfType) {
181   if (Config.OutputFormat == "binary") {
182     return llvm::make_unique<BinaryWriter>(File, Obj);
183   }
184   // Depending on the initial ELFT and OutputFormat we need a different Writer.
185   switch (OutputElfType) {
186   case ELFT_ELF32LE:
187     return llvm::make_unique<ELFWriter<ELF32LE>>(File, Obj,
188                                                  !Config.StripSections);
189   case ELFT_ELF64LE:
190     return llvm::make_unique<ELFWriter<ELF64LE>>(File, Obj,
191                                                  !Config.StripSections);
192   case ELFT_ELF32BE:
193     return llvm::make_unique<ELFWriter<ELF32BE>>(File, Obj,
194                                                  !Config.StripSections);
195   case ELFT_ELF64BE:
196     return llvm::make_unique<ELFWriter<ELF64BE>>(File, Obj,
197                                                  !Config.StripSections);
198   }
199   llvm_unreachable("Invalid output format");
200 }
201 
202 void SplitDWOToFile(const CopyConfig &Config, const Reader &Reader,
203                     StringRef File, ElfType OutputElfType) {
204   auto DWOFile = Reader.create();
205   DWOFile->removeSections(
206       [&](const SectionBase &Sec) { return OnlyKeepDWOPred(*DWOFile, Sec); });
207   auto Writer = CreateWriter(Config, *DWOFile, File, OutputElfType);
208   Writer->finalize();
209   Writer->write();
210 }
211 
212 // This function handles the high level operations of GNU objcopy including
213 // handling command line options. It's important to outline certain properties
214 // we expect to hold of the command line operations. Any operation that "keeps"
215 // should keep regardless of a remove. Additionally any removal should respect
216 // any previous removals. Lastly whether or not something is removed shouldn't
217 // depend a) on the order the options occur in or b) on some opaque priority
218 // system. The only priority is that keeps/copies overrule removes.
219 void HandleArgs(const CopyConfig &Config, Object &Obj, const Reader &Reader,
220                 ElfType OutputElfType) {
221 
222   if (!Config.SplitDWO.empty()) {
223     SplitDWOToFile(Config, Reader, Config.SplitDWO, OutputElfType);
224   }
225 
226   SectionPred RemovePred = [](const SectionBase &) { return false; };
227 
228   // Removes:
229   if (!Config.ToRemove.empty()) {
230     RemovePred = [&Config](const SectionBase &Sec) {
231       return std::find(std::begin(Config.ToRemove), std::end(Config.ToRemove),
232                        Sec.Name) != std::end(Config.ToRemove);
233     };
234   }
235 
236   if (Config.StripDWO || !Config.SplitDWO.empty())
237     RemovePred = [RemovePred](const SectionBase &Sec) {
238       return IsDWOSection(Sec) || RemovePred(Sec);
239     };
240 
241   if (Config.ExtractDWO)
242     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
243       return OnlyKeepDWOPred(Obj, Sec) || RemovePred(Sec);
244     };
245 
246   if (Config.StripAllGNU)
247     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
248       if (RemovePred(Sec))
249         return true;
250       if ((Sec.Flags & SHF_ALLOC) != 0)
251         return false;
252       if (&Sec == Obj.SectionNames)
253         return false;
254       switch (Sec.Type) {
255       case SHT_SYMTAB:
256       case SHT_REL:
257       case SHT_RELA:
258       case SHT_STRTAB:
259         return true;
260       }
261       return Sec.Name.startswith(".debug");
262     };
263 
264   if (Config.StripSections) {
265     RemovePred = [RemovePred](const SectionBase &Sec) {
266       return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0;
267     };
268   }
269 
270   if (Config.StripDebug) {
271     RemovePred = [RemovePred](const SectionBase &Sec) {
272       return RemovePred(Sec) || Sec.Name.startswith(".debug");
273     };
274   }
275 
276   if (Config.StripNonAlloc)
277     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
278       if (RemovePred(Sec))
279         return true;
280       if (&Sec == Obj.SectionNames)
281         return false;
282       return (Sec.Flags & SHF_ALLOC) == 0;
283     };
284 
285   if (Config.StripAll)
286     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
287       if (RemovePred(Sec))
288         return true;
289       if (&Sec == Obj.SectionNames)
290         return false;
291       if (Sec.Name.startswith(".gnu.warning"))
292         return false;
293       return (Sec.Flags & SHF_ALLOC) == 0;
294     };
295 
296   // Explicit copies:
297   if (!Config.OnlyKeep.empty()) {
298     RemovePred = [&Config, RemovePred, &Obj](const SectionBase &Sec) {
299       // Explicitly keep these sections regardless of previous removes.
300       if (std::find(std::begin(Config.OnlyKeep), std::end(Config.OnlyKeep),
301                     Sec.Name) != std::end(Config.OnlyKeep))
302         return false;
303 
304       // Allow all implicit removes.
305       if (RemovePred(Sec))
306         return true;
307 
308       // Keep special sections.
309       if (Obj.SectionNames == &Sec)
310         return false;
311       if (Obj.SymbolTable == &Sec || Obj.SymbolTable->getStrTab() == &Sec)
312         return false;
313 
314       // Remove everything else.
315       return true;
316     };
317   }
318 
319   if (!Config.Keep.empty()) {
320     RemovePred = [Config, RemovePred](const SectionBase &Sec) {
321       // Explicitly keep these sections regardless of previous removes.
322       if (std::find(std::begin(Config.Keep), std::end(Config.Keep), Sec.Name) !=
323           std::end(Config.Keep))
324         return false;
325       // Otherwise defer to RemovePred.
326       return RemovePred(Sec);
327     };
328   }
329 
330   Obj.removeSections(RemovePred);
331 
332   if (!Config.AddSection.empty()) {
333     for (const auto &Flag : Config.AddSection) {
334       auto SecPair = Flag.split("=");
335       auto SecName = SecPair.first;
336       auto File = SecPair.second;
337       auto BufOrErr = MemoryBuffer::getFile(File);
338       if (!BufOrErr)
339         reportError(File, BufOrErr.getError());
340       auto Buf = std::move(*BufOrErr);
341       auto BufPtr = reinterpret_cast<const uint8_t *>(Buf->getBufferStart());
342       auto BufSize = Buf->getBufferSize();
343       Obj.addSection<OwnedDataSection>(SecName,
344                                        ArrayRef<uint8_t>(BufPtr, BufSize));
345     }
346   }
347 
348   if (!Config.AddGnuDebugLink.empty())
349     Obj.addSection<GnuDebugLinkSection>(Config.AddGnuDebugLink);
350 
351   if (Obj.SymbolTable) {
352     Obj.SymbolTable->updateSymbols([&](Symbol &Sym) {
353       if ((Config.LocalizeHidden &&
354            (Sym.Visibility == STV_HIDDEN || Sym.Visibility == STV_INTERNAL)) ||
355           (!Config.SymbolsToLocalize.empty() &&
356            is_contained(Config.SymbolsToLocalize, Sym.Name)))
357         Sym.Binding = STB_LOCAL;
358 
359       if (!Config.SymbolsToGlobalize.empty() &&
360           is_contained(Config.SymbolsToGlobalize, Sym.Name))
361         Sym.Binding = STB_GLOBAL;
362 
363       if (!Config.SymbolsToWeaken.empty() &&
364           is_contained(Config.SymbolsToWeaken, Sym.Name) &&
365           Sym.Binding == STB_GLOBAL)
366         Sym.Binding = STB_WEAK;
367 
368       if (Config.Weaken && Sym.Binding == STB_GLOBAL &&
369           Sym.getShndx() != SHN_UNDEF)
370         Sym.Binding = STB_WEAK;
371 
372       const auto I = Config.SymbolsToRename.find(Sym.Name);
373       if (I != Config.SymbolsToRename.end())
374         Sym.Name = I->getValue();
375     });
376 
377     Obj.removeSymbols([&](const Symbol &Sym) {
378       if (!Config.SymbolsToKeep.empty() &&
379           is_contained(Config.SymbolsToKeep, Sym.Name))
380         return false;
381 
382       if (Config.DiscardAll && Sym.Binding == STB_LOCAL &&
383           Sym.getShndx() != SHN_UNDEF && Sym.Type != STT_FILE &&
384           Sym.Type != STT_SECTION)
385         return true;
386 
387       if (!Config.SymbolsToRemove.empty() &&
388           is_contained(Config.SymbolsToRemove, Sym.Name)) {
389         return true;
390       }
391 
392       return false;
393     });
394   }
395 }
396 
397 std::unique_ptr<Reader> CreateReader(StringRef InputFilename,
398                                      ElfType &OutputElfType) {
399   // Right now we can only read ELF files so there's only one reader;
400   auto Out = llvm::make_unique<ELFReader>(InputFilename);
401   // We need to set the default ElfType for output.
402   OutputElfType = Out->getElfType();
403   return std::move(Out);
404 }
405 
406 void ExecuteElfObjcopy(const CopyConfig &Config) {
407   ElfType OutputElfType;
408   auto Reader = CreateReader(Config.InputFilename, OutputElfType);
409   auto Obj = Reader->create();
410   auto Writer =
411       CreateWriter(Config, *Obj, Config.OutputFilename, OutputElfType);
412   HandleArgs(Config, *Obj, *Reader, OutputElfType);
413   Writer->finalize();
414   Writer->write();
415 }
416 
417 // ParseObjcopyOptions returns the config and sets the input arguments. If a
418 // help flag is set then ParseObjcopyOptions will print the help messege and
419 // exit.
420 CopyConfig ParseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
421   ObjcopyOptTable T;
422   unsigned MissingArgumentIndex, MissingArgumentCount;
423   llvm::opt::InputArgList InputArgs =
424       T.ParseArgs(ArgsArr, MissingArgumentIndex, MissingArgumentCount);
425 
426   if (InputArgs.size() == 0) {
427     T.PrintHelp(errs(), "llvm-objcopy <input> [ <output> ]", "objcopy tool");
428     exit(1);
429   }
430 
431   if (InputArgs.hasArg(OBJCOPY_help)) {
432     T.PrintHelp(outs(), "llvm-objcopy <input> [ <output> ]", "objcopy tool");
433     exit(0);
434   }
435 
436   SmallVector<const char *, 2> Positional;
437 
438   for (auto Arg : InputArgs.filtered(OBJCOPY_UNKNOWN))
439     error("unknown argument '" + Arg->getAsString(InputArgs) + "'");
440 
441   for (auto Arg : InputArgs.filtered(OBJCOPY_INPUT))
442     Positional.push_back(Arg->getValue());
443 
444   if (Positional.empty())
445     error("No input file specified");
446 
447   if (Positional.size() > 2)
448     error("Too many positional arguments");
449 
450   CopyConfig Config;
451   Config.InputFilename = Positional[0];
452   Config.OutputFilename = Positional[Positional.size() == 1 ? 0 : 1];
453   Config.InputFormat = InputArgs.getLastArgValue(OBJCOPY_input_target);
454   Config.OutputFormat = InputArgs.getLastArgValue(OBJCOPY_output_target);
455   Config.BinaryArch = InputArgs.getLastArgValue(OBJCOPY_binary_architecture);
456 
457   Config.SplitDWO = InputArgs.getLastArgValue(OBJCOPY_split_dwo);
458   Config.AddGnuDebugLink = InputArgs.getLastArgValue(OBJCOPY_add_gnu_debuglink);
459 
460   for (auto Arg : InputArgs.filtered(OBJCOPY_redefine_symbol)) {
461     if (!StringRef(Arg->getValue()).contains('='))
462       error("Bad format for --redefine-sym");
463     auto Old2New = StringRef(Arg->getValue()).split('=');
464     if (!Config.SymbolsToRename.insert(Old2New).second)
465       error("Multiple redefinition of symbol " + Old2New.first);
466   }
467 
468   for (auto Arg : InputArgs.filtered(OBJCOPY_remove_section))
469     Config.ToRemove.push_back(Arg->getValue());
470   for (auto Arg : InputArgs.filtered(OBJCOPY_keep))
471     Config.Keep.push_back(Arg->getValue());
472   for (auto Arg : InputArgs.filtered(OBJCOPY_only_keep))
473     Config.OnlyKeep.push_back(Arg->getValue());
474   for (auto Arg : InputArgs.filtered(OBJCOPY_add_section))
475     Config.AddSection.push_back(Arg->getValue());
476   Config.StripAll = InputArgs.hasArg(OBJCOPY_strip_all);
477   Config.StripAllGNU = InputArgs.hasArg(OBJCOPY_strip_all_gnu);
478   Config.StripDebug = InputArgs.hasArg(OBJCOPY_strip_debug);
479   Config.StripDWO = InputArgs.hasArg(OBJCOPY_strip_dwo);
480   Config.StripSections = InputArgs.hasArg(OBJCOPY_strip_sections);
481   Config.StripNonAlloc = InputArgs.hasArg(OBJCOPY_strip_non_alloc);
482   Config.ExtractDWO = InputArgs.hasArg(OBJCOPY_extract_dwo);
483   Config.LocalizeHidden = InputArgs.hasArg(OBJCOPY_localize_hidden);
484   Config.Weaken = InputArgs.hasArg(OBJCOPY_weaken);
485   Config.DiscardAll = InputArgs.hasArg(OBJCOPY_discard_all);
486   Config.OnlyKeepDebug = InputArgs.hasArg(OBJCOPY_only_keep_debug);
487   for (auto Arg : InputArgs.filtered(OBJCOPY_localize_symbol))
488     Config.SymbolsToLocalize.push_back(Arg->getValue());
489   for (auto Arg : InputArgs.filtered(OBJCOPY_globalize_symbol))
490     Config.SymbolsToGlobalize.push_back(Arg->getValue());
491   for (auto Arg : InputArgs.filtered(OBJCOPY_weaken_symbol))
492     Config.SymbolsToWeaken.push_back(Arg->getValue());
493   for (auto Arg : InputArgs.filtered(OBJCOPY_strip_symbol))
494     Config.SymbolsToRemove.push_back(Arg->getValue());
495   for (auto Arg : InputArgs.filtered(OBJCOPY_keep_symbol))
496     Config.SymbolsToKeep.push_back(Arg->getValue());
497 
498   return Config;
499 }
500 
501 // ParseStripOptions returns the config and sets the input arguments. If a
502 // help flag is set then ParseStripOptions will print the help messege and
503 // exit.
504 CopyConfig ParseStripOptions(ArrayRef<const char *> ArgsArr) {
505   StripOptTable T;
506   unsigned MissingArgumentIndex, MissingArgumentCount;
507   llvm::opt::InputArgList InputArgs =
508       T.ParseArgs(ArgsArr, MissingArgumentIndex, MissingArgumentCount);
509 
510   if (InputArgs.size() == 0) {
511     T.PrintHelp(errs(), "llvm-strip <input> [ <output> ]", "strip tool");
512     exit(1);
513   }
514 
515   if (InputArgs.hasArg(STRIP_help)) {
516     T.PrintHelp(outs(), "llvm-strip <input> [ <output> ]", "strip tool");
517     exit(0);
518   }
519 
520   SmallVector<const char *, 2> Positional;
521   for (auto Arg : InputArgs.filtered(STRIP_UNKNOWN))
522     error("unknown argument '" + Arg->getAsString(InputArgs) + "'");
523   for (auto Arg : InputArgs.filtered(STRIP_INPUT))
524     Positional.push_back(Arg->getValue());
525 
526   if (Positional.empty())
527     error("No input file specified");
528 
529   if (Positional.size() > 2)
530     error("Support for multiple input files is not implemented yet");
531 
532   CopyConfig Config;
533   Config.InputFilename = Positional[0];
534   Config.OutputFilename = Positional[0];
535 
536   // Strip debug info only.
537   Config.StripDebug = InputArgs.hasArg(STRIP_strip_debug);
538   if (!Config.StripDebug)
539     Config.StripAll = true;
540 
541   for (auto Arg : InputArgs.filtered(STRIP_remove_section))
542     Config.ToRemove.push_back(Arg->getValue());
543 
544   return Config;
545 }
546 
547 int main(int argc, char **argv) {
548   InitLLVM X(argc, argv);
549   ToolName = argv[0];
550   CopyConfig Config;
551   if (sys::path::stem(ToolName).endswith_lower("strip"))
552     Config = ParseStripOptions(makeArrayRef(argv + 1, argc));
553   else
554     Config = ParseObjcopyOptions(makeArrayRef(argv + 1, argc));
555   ExecuteElfObjcopy(Config);
556 }
557