xref: /llvm-project/llvm/tools/llvm-objcopy/llvm-objcopy.cpp (revision 18b5fb7b84b22e05816cec0e38241bc8f3c5c4a4) 
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   StringMap<StringRef> SymbolsToRename;
152   bool StripAll = false;
153   bool StripAllGNU = false;
154   bool StripDebug = false;
155   bool StripSections = false;
156   bool StripNonAlloc = false;
157   bool StripDWO = false;
158   bool ExtractDWO = false;
159   bool LocalizeHidden = false;
160   bool Weaken = false;
161   bool DiscardAll = false;
162 };
163 
164 using SectionPred = std::function<bool(const SectionBase &Sec)>;
165 
166 bool IsDWOSection(const SectionBase &Sec) { return Sec.Name.endswith(".dwo"); }
167 
168 bool OnlyKeepDWOPred(const Object &Obj, const SectionBase &Sec) {
169   // We can't remove the section header string table.
170   if (&Sec == Obj.SectionNames)
171     return false;
172   // Short of keeping the string table we want to keep everything that is a DWO
173   // section and remove everything else.
174   return !IsDWOSection(Sec);
175 }
176 
177 std::unique_ptr<Writer> CreateWriter(const CopyConfig &Config, Object &Obj,
178                                      StringRef File, ElfType OutputElfType) {
179   if (Config.OutputFormat == "binary") {
180     return llvm::make_unique<BinaryWriter>(File, Obj);
181   }
182   // Depending on the initial ELFT and OutputFormat we need a different Writer.
183   switch (OutputElfType) {
184   case ELFT_ELF32LE:
185     return llvm::make_unique<ELFWriter<ELF32LE>>(File, Obj,
186                                                  !Config.StripSections);
187   case ELFT_ELF64LE:
188     return llvm::make_unique<ELFWriter<ELF64LE>>(File, Obj,
189                                                  !Config.StripSections);
190   case ELFT_ELF32BE:
191     return llvm::make_unique<ELFWriter<ELF32BE>>(File, Obj,
192                                                  !Config.StripSections);
193   case ELFT_ELF64BE:
194     return llvm::make_unique<ELFWriter<ELF64BE>>(File, Obj,
195                                                  !Config.StripSections);
196   }
197   llvm_unreachable("Invalid output format");
198 }
199 
200 void SplitDWOToFile(const CopyConfig &Config, const Reader &Reader,
201                     StringRef File, ElfType OutputElfType) {
202   auto DWOFile = Reader.create();
203   DWOFile->removeSections(
204       [&](const SectionBase &Sec) { return OnlyKeepDWOPred(*DWOFile, Sec); });
205   auto Writer = CreateWriter(Config, *DWOFile, File, OutputElfType);
206   Writer->finalize();
207   Writer->write();
208 }
209 
210 // This function handles the high level operations of GNU objcopy including
211 // handling command line options. It's important to outline certain properties
212 // we expect to hold of the command line operations. Any operation that "keeps"
213 // should keep regardless of a remove. Additionally any removal should respect
214 // any previous removals. Lastly whether or not something is removed shouldn't
215 // depend a) on the order the options occur in or b) on some opaque priority
216 // system. The only priority is that keeps/copies overrule removes.
217 void HandleArgs(const CopyConfig &Config, Object &Obj, const Reader &Reader,
218                 ElfType OutputElfType) {
219 
220   if (!Config.SplitDWO.empty()) {
221     SplitDWOToFile(Config, Reader, Config.SplitDWO, OutputElfType);
222   }
223 
224   SectionPred RemovePred = [](const SectionBase &) { return false; };
225 
226   // Removes:
227   if (!Config.ToRemove.empty()) {
228     RemovePred = [&Config](const SectionBase &Sec) {
229       return std::find(std::begin(Config.ToRemove), std::end(Config.ToRemove),
230                        Sec.Name) != std::end(Config.ToRemove);
231     };
232   }
233 
234   if (Config.StripDWO || !Config.SplitDWO.empty())
235     RemovePred = [RemovePred](const SectionBase &Sec) {
236       return IsDWOSection(Sec) || RemovePred(Sec);
237     };
238 
239   if (Config.ExtractDWO)
240     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
241       return OnlyKeepDWOPred(Obj, Sec) || RemovePred(Sec);
242     };
243 
244   if (Config.StripAllGNU)
245     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
246       if (RemovePred(Sec))
247         return true;
248       if ((Sec.Flags & SHF_ALLOC) != 0)
249         return false;
250       if (&Sec == Obj.SectionNames)
251         return false;
252       switch (Sec.Type) {
253       case SHT_SYMTAB:
254       case SHT_REL:
255       case SHT_RELA:
256       case SHT_STRTAB:
257         return true;
258       }
259       return Sec.Name.startswith(".debug");
260     };
261 
262   if (Config.StripSections) {
263     RemovePred = [RemovePred](const SectionBase &Sec) {
264       return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0;
265     };
266   }
267 
268   if (Config.StripDebug) {
269     RemovePred = [RemovePred](const SectionBase &Sec) {
270       return RemovePred(Sec) || Sec.Name.startswith(".debug");
271     };
272   }
273 
274   if (Config.StripNonAlloc)
275     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
276       if (RemovePred(Sec))
277         return true;
278       if (&Sec == Obj.SectionNames)
279         return false;
280       return (Sec.Flags & SHF_ALLOC) == 0;
281     };
282 
283   if (Config.StripAll)
284     RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
285       if (RemovePred(Sec))
286         return true;
287       if (&Sec == Obj.SectionNames)
288         return false;
289       if (Sec.Name.startswith(".gnu.warning"))
290         return false;
291       return (Sec.Flags & SHF_ALLOC) == 0;
292     };
293 
294   // Explicit copies:
295   if (!Config.OnlyKeep.empty()) {
296     RemovePred = [&Config, RemovePred, &Obj](const SectionBase &Sec) {
297       // Explicitly keep these sections regardless of previous removes.
298       if (std::find(std::begin(Config.OnlyKeep), std::end(Config.OnlyKeep),
299                     Sec.Name) != std::end(Config.OnlyKeep))
300         return false;
301 
302       // Allow all implicit removes.
303       if (RemovePred(Sec))
304         return true;
305 
306       // Keep special sections.
307       if (Obj.SectionNames == &Sec)
308         return false;
309       if (Obj.SymbolTable == &Sec || Obj.SymbolTable->getStrTab() == &Sec)
310         return false;
311 
312       // Remove everything else.
313       return true;
314     };
315   }
316 
317   if (!Config.Keep.empty()) {
318     RemovePred = [Config, RemovePred](const SectionBase &Sec) {
319       // Explicitly keep these sections regardless of previous removes.
320       if (std::find(std::begin(Config.Keep), std::end(Config.Keep), Sec.Name) !=
321           std::end(Config.Keep))
322         return false;
323       // Otherwise defer to RemovePred.
324       return RemovePred(Sec);
325     };
326   }
327 
328   Obj.removeSections(RemovePred);
329 
330   if (!Config.AddSection.empty()) {
331     for (const auto &Flag : Config.AddSection) {
332       auto SecPair = Flag.split("=");
333       auto SecName = SecPair.first;
334       auto File = SecPair.second;
335       auto BufOrErr = MemoryBuffer::getFile(File);
336       if (!BufOrErr)
337         reportError(File, BufOrErr.getError());
338       auto Buf = std::move(*BufOrErr);
339       auto BufPtr = reinterpret_cast<const uint8_t *>(Buf->getBufferStart());
340       auto BufSize = Buf->getBufferSize();
341       Obj.addSection<OwnedDataSection>(SecName,
342                                        ArrayRef<uint8_t>(BufPtr, BufSize));
343     }
344   }
345 
346   if (!Config.AddGnuDebugLink.empty())
347     Obj.addSection<GnuDebugLinkSection>(Config.AddGnuDebugLink);
348 
349   if (Obj.SymbolTable) {
350     Obj.SymbolTable->updateSymbols([&](Symbol &Sym) {
351       if ((Config.LocalizeHidden &&
352            (Sym.Visibility == STV_HIDDEN || Sym.Visibility == STV_INTERNAL)) ||
353           (!Config.SymbolsToLocalize.empty() &&
354            is_contained(Config.SymbolsToLocalize, Sym.Name)))
355         Sym.Binding = STB_LOCAL;
356 
357       if (!Config.SymbolsToGlobalize.empty() &&
358           is_contained(Config.SymbolsToGlobalize, Sym.Name))
359         Sym.Binding = STB_GLOBAL;
360 
361       if (!Config.SymbolsToWeaken.empty() &&
362           is_contained(Config.SymbolsToWeaken, Sym.Name) &&
363           Sym.Binding == STB_GLOBAL)
364         Sym.Binding = STB_WEAK;
365 
366       if (Config.Weaken && Sym.Binding == STB_GLOBAL &&
367           Sym.getShndx() != SHN_UNDEF)
368         Sym.Binding = STB_WEAK;
369 
370       const auto I = Config.SymbolsToRename.find(Sym.Name);
371       if (I != Config.SymbolsToRename.end())
372         Sym.Name = I->getValue();
373     });
374 
375     Obj.removeSymbols([&](const Symbol &Sym) {
376       if (Config.DiscardAll && Sym.Binding == STB_LOCAL &&
377           Sym.getShndx() != SHN_UNDEF && Sym.Type != STT_FILE &&
378           Sym.Type != STT_SECTION)
379         return true;
380 
381       if (!Config.SymbolsToRemove.empty() &&
382           is_contained(Config.SymbolsToRemove, Sym.Name)) {
383         return true;
384       }
385 
386       return false;
387     });
388   }
389 }
390 
391 std::unique_ptr<Reader> CreateReader(StringRef InputFilename,
392                                      ElfType &OutputElfType) {
393   // Right now we can only read ELF files so there's only one reader;
394   auto Out = llvm::make_unique<ELFReader>(InputFilename);
395   // We need to set the default ElfType for output.
396   OutputElfType = Out->getElfType();
397   return std::move(Out);
398 }
399 
400 void ExecuteElfObjcopy(const CopyConfig &Config) {
401   ElfType OutputElfType;
402   auto Reader = CreateReader(Config.InputFilename, OutputElfType);
403   auto Obj = Reader->create();
404   auto Writer =
405       CreateWriter(Config, *Obj, Config.OutputFilename, OutputElfType);
406   HandleArgs(Config, *Obj, *Reader, OutputElfType);
407   Writer->finalize();
408   Writer->write();
409 }
410 
411 // ParseObjcopyOptions returns the config and sets the input arguments. If a
412 // help flag is set then ParseObjcopyOptions will print the help messege and
413 // exit.
414 CopyConfig ParseObjcopyOptions(ArrayRef<const char *> ArgsArr) {
415   ObjcopyOptTable T;
416   unsigned MissingArgumentIndex, MissingArgumentCount;
417   llvm::opt::InputArgList InputArgs =
418       T.ParseArgs(ArgsArr, MissingArgumentIndex, MissingArgumentCount);
419 
420   if (InputArgs.size() == 0) {
421     T.PrintHelp(errs(), "llvm-objcopy <input> [ <output> ]", "objcopy tool");
422     exit(1);
423   }
424 
425   if (InputArgs.hasArg(OBJCOPY_help)) {
426     T.PrintHelp(outs(), "llvm-objcopy <input> [ <output> ]", "objcopy tool");
427     exit(0);
428   }
429 
430   SmallVector<const char *, 2> Positional;
431 
432   for (auto Arg : InputArgs.filtered(OBJCOPY_UNKNOWN))
433     error("unknown argument '" + Arg->getAsString(InputArgs) + "'");
434 
435   for (auto Arg : InputArgs.filtered(OBJCOPY_INPUT))
436     Positional.push_back(Arg->getValue());
437 
438   if (Positional.empty())
439     error("No input file specified");
440 
441   if (Positional.size() > 2)
442     error("Too many positional arguments");
443 
444   CopyConfig Config;
445   Config.InputFilename = Positional[0];
446   Config.OutputFilename = Positional[Positional.size() == 1 ? 0 : 1];
447   Config.InputFormat = InputArgs.getLastArgValue(OBJCOPY_input_target);
448   Config.OutputFormat = InputArgs.getLastArgValue(OBJCOPY_output_target);
449   Config.BinaryArch = InputArgs.getLastArgValue(OBJCOPY_binary_architecture);
450 
451   Config.SplitDWO = InputArgs.getLastArgValue(OBJCOPY_split_dwo);
452   Config.AddGnuDebugLink = InputArgs.getLastArgValue(OBJCOPY_add_gnu_debuglink);
453 
454   for (auto Arg : InputArgs.filtered(OBJCOPY_redefine_symbol)) {
455     if (!StringRef(Arg->getValue()).contains('='))
456       error("Bad format for --redefine-sym");
457     auto Old2New = StringRef(Arg->getValue()).split('=');
458     if (!Config.SymbolsToRename.insert(Old2New).second)
459       error("Multiple redefinition of symbol " + Old2New.first);
460   }
461 
462   for (auto Arg : InputArgs.filtered(OBJCOPY_remove_section))
463     Config.ToRemove.push_back(Arg->getValue());
464   for (auto Arg : InputArgs.filtered(OBJCOPY_keep))
465     Config.Keep.push_back(Arg->getValue());
466   for (auto Arg : InputArgs.filtered(OBJCOPY_only_keep))
467     Config.OnlyKeep.push_back(Arg->getValue());
468   for (auto Arg : InputArgs.filtered(OBJCOPY_add_section))
469     Config.AddSection.push_back(Arg->getValue());
470   Config.StripAll = InputArgs.hasArg(OBJCOPY_strip_all);
471   Config.StripAllGNU = InputArgs.hasArg(OBJCOPY_strip_all_gnu);
472   Config.StripDebug = InputArgs.hasArg(OBJCOPY_strip_debug);
473   Config.StripDWO = InputArgs.hasArg(OBJCOPY_strip_dwo);
474   Config.StripSections = InputArgs.hasArg(OBJCOPY_strip_sections);
475   Config.StripNonAlloc = InputArgs.hasArg(OBJCOPY_strip_non_alloc);
476   Config.ExtractDWO = InputArgs.hasArg(OBJCOPY_extract_dwo);
477   Config.LocalizeHidden = InputArgs.hasArg(OBJCOPY_localize_hidden);
478   Config.Weaken = InputArgs.hasArg(OBJCOPY_weaken);
479   Config.DiscardAll = InputArgs.hasArg(OBJCOPY_discard_all);
480   for (auto Arg : InputArgs.filtered(OBJCOPY_localize_symbol))
481     Config.SymbolsToLocalize.push_back(Arg->getValue());
482   for (auto Arg : InputArgs.filtered(OBJCOPY_globalize_symbol))
483     Config.SymbolsToGlobalize.push_back(Arg->getValue());
484   for (auto Arg : InputArgs.filtered(OBJCOPY_weaken_symbol))
485     Config.SymbolsToWeaken.push_back(Arg->getValue());
486   for (auto Arg : InputArgs.filtered(OBJCOPY_strip_symbol))
487     Config.SymbolsToRemove.push_back(Arg->getValue());
488 
489   return Config;
490 }
491 
492 // ParseStripOptions returns the config and sets the input arguments. If a
493 // help flag is set then ParseStripOptions will print the help messege and
494 // exit.
495 CopyConfig ParseStripOptions(ArrayRef<const char *> ArgsArr) {
496   StripOptTable T;
497   unsigned MissingArgumentIndex, MissingArgumentCount;
498   llvm::opt::InputArgList InputArgs =
499       T.ParseArgs(ArgsArr, MissingArgumentIndex, MissingArgumentCount);
500 
501   if (InputArgs.size() == 0) {
502     T.PrintHelp(errs(), "llvm-strip <input> [ <output> ]", "strip tool");
503     exit(1);
504   }
505 
506   if (InputArgs.hasArg(STRIP_help)) {
507     T.PrintHelp(outs(), "llvm-strip <input> [ <output> ]", "strip tool");
508     exit(0);
509   }
510 
511   SmallVector<const char *, 2> Positional;
512   for (auto Arg : InputArgs.filtered(STRIP_UNKNOWN))
513     error("unknown argument '" + Arg->getAsString(InputArgs) + "'");
514   for (auto Arg : InputArgs.filtered(STRIP_INPUT))
515     Positional.push_back(Arg->getValue());
516 
517   if (Positional.empty())
518     error("No input file specified");
519 
520   if (Positional.size() > 2)
521     error("Support for multiple input files is not implemented yet");
522 
523   CopyConfig Config;
524   Config.InputFilename = Positional[0];
525   Config.OutputFilename = Positional[0];
526 
527   // Strip debug info only.
528   Config.StripDebug = InputArgs.hasArg(STRIP_strip_debug);
529   if (!Config.StripDebug)
530     Config.StripAll = true;
531 
532   for (auto Arg : InputArgs.filtered(STRIP_remove_section))
533     Config.ToRemove.push_back(Arg->getValue());
534 
535   return Config;
536 }
537 
538 int main(int argc, char **argv) {
539   InitLLVM X(argc, argv);
540   ToolName = argv[0];
541   CopyConfig Config;
542   if (sys::path::stem(ToolName).endswith_lower("strip"))
543     Config = ParseStripOptions(makeArrayRef(argv + 1, argc));
544   else
545     Config = ParseObjcopyOptions(makeArrayRef(argv + 1, argc));
546   ExecuteElfObjcopy(Config);
547 }
548