1 //===- ELFObjcopy.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 "ELFObjcopy.h"
10 #include "CommonConfig.h"
11 #include "ELFConfig.h"
12 #include "Object.h"
13 #include "llvm-objcopy.h"
14 #include "llvm/ADT/BitmaskEnum.h"
15 #include "llvm/ADT/DenseSet.h"
16 #include "llvm/ADT/Optional.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/Twine.h"
21 #include "llvm/BinaryFormat/ELF.h"
22 #include "llvm/MC/MCTargetOptions.h"
23 #include "llvm/Object/Binary.h"
24 #include "llvm/Object/ELFObjectFile.h"
25 #include "llvm/Object/ELFTypes.h"
26 #include "llvm/Object/Error.h"
27 #include "llvm/Option/Option.h"
28 #include "llvm/Support/Casting.h"
29 #include "llvm/Support/Compression.h"
30 #include "llvm/Support/Errc.h"
31 #include "llvm/Support/Error.h"
32 #include "llvm/Support/ErrorHandling.h"
33 #include "llvm/Support/ErrorOr.h"
34 #include "llvm/Support/FileSystem.h"
35 #include "llvm/Support/Memory.h"
36 #include "llvm/Support/Path.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include <algorithm>
39 #include <cassert>
40 #include <cstdlib>
41 #include <functional>
42 #include <iterator>
43 #include <memory>
44 #include <string>
45 #include <system_error>
46 #include <utility>
47
48 namespace llvm {
49 namespace objcopy {
50 namespace elf {
51
52 using namespace object;
53 using namespace ELF;
54 using SectionPred = std::function<bool(const SectionBase &Sec)>;
55
isDebugSection(const SectionBase & Sec)56 static bool isDebugSection(const SectionBase &Sec) {
57 return StringRef(Sec.Name).startswith(".debug") ||
58 StringRef(Sec.Name).startswith(".zdebug") || Sec.Name == ".gdb_index";
59 }
60
isDWOSection(const SectionBase & Sec)61 static bool isDWOSection(const SectionBase &Sec) {
62 return StringRef(Sec.Name).endswith(".dwo");
63 }
64
onlyKeepDWOPred(const Object & Obj,const SectionBase & Sec)65 static bool onlyKeepDWOPred(const Object &Obj, const SectionBase &Sec) {
66 // We can't remove the section header string table.
67 if (&Sec == Obj.SectionNames)
68 return false;
69 // Short of keeping the string table we want to keep everything that is a DWO
70 // section and remove everything else.
71 return !isDWOSection(Sec);
72 }
73
getNewShfFlags(SectionFlag AllFlags)74 uint64_t getNewShfFlags(SectionFlag AllFlags) {
75 uint64_t NewFlags = 0;
76 if (AllFlags & SectionFlag::SecAlloc)
77 NewFlags |= ELF::SHF_ALLOC;
78 if (!(AllFlags & SectionFlag::SecReadonly))
79 NewFlags |= ELF::SHF_WRITE;
80 if (AllFlags & SectionFlag::SecCode)
81 NewFlags |= ELF::SHF_EXECINSTR;
82 if (AllFlags & SectionFlag::SecMerge)
83 NewFlags |= ELF::SHF_MERGE;
84 if (AllFlags & SectionFlag::SecStrings)
85 NewFlags |= ELF::SHF_STRINGS;
86 if (AllFlags & SectionFlag::SecExclude)
87 NewFlags |= ELF::SHF_EXCLUDE;
88 return NewFlags;
89 }
90
getSectionFlagsPreserveMask(uint64_t OldFlags,uint64_t NewFlags)91 static uint64_t getSectionFlagsPreserveMask(uint64_t OldFlags,
92 uint64_t NewFlags) {
93 // Preserve some flags which should not be dropped when setting flags.
94 // Also, preserve anything OS/processor dependant.
95 const uint64_t PreserveMask =
96 (ELF::SHF_COMPRESSED | ELF::SHF_GROUP | ELF::SHF_LINK_ORDER |
97 ELF::SHF_MASKOS | ELF::SHF_MASKPROC | ELF::SHF_TLS |
98 ELF::SHF_INFO_LINK) &
99 ~ELF::SHF_EXCLUDE;
100 return (OldFlags & PreserveMask) | (NewFlags & ~PreserveMask);
101 }
102
setSectionFlagsAndType(SectionBase & Sec,SectionFlag Flags)103 static void setSectionFlagsAndType(SectionBase &Sec, SectionFlag Flags) {
104 Sec.Flags = getSectionFlagsPreserveMask(Sec.Flags, getNewShfFlags(Flags));
105
106 // In GNU objcopy, certain flags promote SHT_NOBITS to SHT_PROGBITS. This rule
107 // may promote more non-ALLOC sections than GNU objcopy, but it is fine as
108 // non-ALLOC SHT_NOBITS sections do not make much sense.
109 if (Sec.Type == SHT_NOBITS &&
110 (!(Sec.Flags & ELF::SHF_ALLOC) ||
111 Flags & (SectionFlag::SecContents | SectionFlag::SecLoad)))
112 Sec.Type = SHT_PROGBITS;
113 }
114
getOutputElfType(const Binary & Bin)115 static ElfType getOutputElfType(const Binary &Bin) {
116 // Infer output ELF type from the input ELF object
117 if (isa<ELFObjectFile<ELF32LE>>(Bin))
118 return ELFT_ELF32LE;
119 if (isa<ELFObjectFile<ELF64LE>>(Bin))
120 return ELFT_ELF64LE;
121 if (isa<ELFObjectFile<ELF32BE>>(Bin))
122 return ELFT_ELF32BE;
123 if (isa<ELFObjectFile<ELF64BE>>(Bin))
124 return ELFT_ELF64BE;
125 llvm_unreachable("Invalid ELFType");
126 }
127
getOutputElfType(const MachineInfo & MI)128 static ElfType getOutputElfType(const MachineInfo &MI) {
129 // Infer output ELF type from the binary arch specified
130 if (MI.Is64Bit)
131 return MI.IsLittleEndian ? ELFT_ELF64LE : ELFT_ELF64BE;
132 else
133 return MI.IsLittleEndian ? ELFT_ELF32LE : ELFT_ELF32BE;
134 }
135
createELFWriter(const CommonConfig & Config,Object & Obj,raw_ostream & Out,ElfType OutputElfType)136 static std::unique_ptr<Writer> createELFWriter(const CommonConfig &Config,
137 Object &Obj, raw_ostream &Out,
138 ElfType OutputElfType) {
139 // Depending on the initial ELFT and OutputFormat we need a different Writer.
140 switch (OutputElfType) {
141 case ELFT_ELF32LE:
142 return std::make_unique<ELFWriter<ELF32LE>>(Obj, Out, !Config.StripSections,
143 Config.OnlyKeepDebug);
144 case ELFT_ELF64LE:
145 return std::make_unique<ELFWriter<ELF64LE>>(Obj, Out, !Config.StripSections,
146 Config.OnlyKeepDebug);
147 case ELFT_ELF32BE:
148 return std::make_unique<ELFWriter<ELF32BE>>(Obj, Out, !Config.StripSections,
149 Config.OnlyKeepDebug);
150 case ELFT_ELF64BE:
151 return std::make_unique<ELFWriter<ELF64BE>>(Obj, Out, !Config.StripSections,
152 Config.OnlyKeepDebug);
153 }
154 llvm_unreachable("Invalid output format");
155 }
156
createWriter(const CommonConfig & Config,Object & Obj,raw_ostream & Out,ElfType OutputElfType)157 static std::unique_ptr<Writer> createWriter(const CommonConfig &Config,
158 Object &Obj, raw_ostream &Out,
159 ElfType OutputElfType) {
160 switch (Config.OutputFormat) {
161 case FileFormat::Binary:
162 return std::make_unique<BinaryWriter>(Obj, Out);
163 case FileFormat::IHex:
164 return std::make_unique<IHexWriter>(Obj, Out);
165 default:
166 return createELFWriter(Config, Obj, Out, OutputElfType);
167 }
168 }
169
170 template <class... Ts>
makeStringError(std::error_code EC,const Twine & Msg,Ts &&...Args)171 static Error makeStringError(std::error_code EC, const Twine &Msg,
172 Ts &&... Args) {
173 std::string FullMsg = (EC.message() + ": " + Msg).str();
174 return createStringError(EC, FullMsg.c_str(), std::forward<Ts>(Args)...);
175 }
176
dumpSectionToFile(StringRef SecName,StringRef Filename,Object & Obj)177 static Error dumpSectionToFile(StringRef SecName, StringRef Filename,
178 Object &Obj) {
179 for (auto &Sec : Obj.sections()) {
180 if (Sec.Name == SecName) {
181 if (Sec.Type == SHT_NOBITS)
182 return createStringError(object_error::parse_failed,
183 "cannot dump section '%s': it has no contents",
184 SecName.str().c_str());
185 Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
186 FileOutputBuffer::create(Filename, Sec.OriginalData.size());
187 if (!BufferOrErr)
188 return BufferOrErr.takeError();
189 std::unique_ptr<FileOutputBuffer> Buf = std::move(*BufferOrErr);
190 std::copy(Sec.OriginalData.begin(), Sec.OriginalData.end(),
191 Buf->getBufferStart());
192 if (Error E = Buf->commit())
193 return E;
194 return Error::success();
195 }
196 }
197 return createStringError(object_error::parse_failed, "section '%s' not found",
198 SecName.str().c_str());
199 }
200
isCompressable(const SectionBase & Sec)201 static bool isCompressable(const SectionBase &Sec) {
202 return !(Sec.Flags & ELF::SHF_COMPRESSED) &&
203 StringRef(Sec.Name).startswith(".debug");
204 }
205
replaceDebugSections(Object & Obj,SectionPred & RemovePred,function_ref<bool (const SectionBase &)> ShouldReplace,function_ref<Expected<SectionBase * > (const SectionBase *)> AddSection)206 static Error replaceDebugSections(
207 Object &Obj, SectionPred &RemovePred,
208 function_ref<bool(const SectionBase &)> ShouldReplace,
209 function_ref<Expected<SectionBase *>(const SectionBase *)> AddSection) {
210 // Build a list of the debug sections we are going to replace.
211 // We can't call `AddSection` while iterating over sections,
212 // because it would mutate the sections array.
213 SmallVector<SectionBase *, 13> ToReplace;
214 for (auto &Sec : Obj.sections())
215 if (ShouldReplace(Sec))
216 ToReplace.push_back(&Sec);
217
218 // Build a mapping from original section to a new one.
219 DenseMap<SectionBase *, SectionBase *> FromTo;
220 for (SectionBase *S : ToReplace) {
221 Expected<SectionBase *> NewSection = AddSection(S);
222 if (!NewSection)
223 return NewSection.takeError();
224
225 FromTo[S] = *NewSection;
226 }
227
228 // Now we want to update the target sections of relocation
229 // sections. Also we will update the relocations themselves
230 // to update the symbol references.
231 for (auto &Sec : Obj.sections())
232 Sec.replaceSectionReferences(FromTo);
233
234 RemovePred = [ShouldReplace, RemovePred](const SectionBase &Sec) {
235 return ShouldReplace(Sec) || RemovePred(Sec);
236 };
237
238 return Error::success();
239 }
240
isUnneededSymbol(const Symbol & Sym)241 static bool isUnneededSymbol(const Symbol &Sym) {
242 return !Sym.Referenced &&
243 (Sym.Binding == STB_LOCAL || Sym.getShndx() == SHN_UNDEF) &&
244 Sym.Type != STT_SECTION;
245 }
246
updateAndRemoveSymbols(const CommonConfig & Config,Object & Obj)247 static Error updateAndRemoveSymbols(const CommonConfig &Config, Object &Obj) {
248 // TODO: update or remove symbols only if there is an option that affects
249 // them.
250 if (!Obj.SymbolTable)
251 return Error::success();
252
253 Obj.SymbolTable->updateSymbols([&](Symbol &Sym) {
254 // Common and undefined symbols don't make sense as local symbols, and can
255 // even cause crashes if we localize those, so skip them.
256 if (!Sym.isCommon() && Sym.getShndx() != SHN_UNDEF &&
257 ((Config.LocalizeHidden &&
258 (Sym.Visibility == STV_HIDDEN || Sym.Visibility == STV_INTERNAL)) ||
259 Config.SymbolsToLocalize.matches(Sym.Name)))
260 Sym.Binding = STB_LOCAL;
261
262 // Note: these two globalize flags have very similar names but different
263 // meanings:
264 //
265 // --globalize-symbol: promote a symbol to global
266 // --keep-global-symbol: all symbols except for these should be made local
267 //
268 // If --globalize-symbol is specified for a given symbol, it will be
269 // global in the output file even if it is not included via
270 // --keep-global-symbol. Because of that, make sure to check
271 // --globalize-symbol second.
272 if (!Config.SymbolsToKeepGlobal.empty() &&
273 !Config.SymbolsToKeepGlobal.matches(Sym.Name) &&
274 Sym.getShndx() != SHN_UNDEF)
275 Sym.Binding = STB_LOCAL;
276
277 if (Config.SymbolsToGlobalize.matches(Sym.Name) &&
278 Sym.getShndx() != SHN_UNDEF)
279 Sym.Binding = STB_GLOBAL;
280
281 if (Config.SymbolsToWeaken.matches(Sym.Name) && Sym.Binding == STB_GLOBAL)
282 Sym.Binding = STB_WEAK;
283
284 if (Config.Weaken && Sym.Binding == STB_GLOBAL &&
285 Sym.getShndx() != SHN_UNDEF)
286 Sym.Binding = STB_WEAK;
287
288 const auto I = Config.SymbolsToRename.find(Sym.Name);
289 if (I != Config.SymbolsToRename.end())
290 Sym.Name = std::string(I->getValue());
291
292 if (!Config.SymbolsPrefix.empty() && Sym.Type != STT_SECTION)
293 Sym.Name = (Config.SymbolsPrefix + Sym.Name).str();
294 });
295
296 // The purpose of this loop is to mark symbols referenced by sections
297 // (like GroupSection or RelocationSection). This way, we know which
298 // symbols are still 'needed' and which are not.
299 if (Config.StripUnneeded || !Config.UnneededSymbolsToRemove.empty() ||
300 !Config.OnlySection.empty()) {
301 for (SectionBase &Sec : Obj.sections())
302 Sec.markSymbols();
303 }
304
305 auto RemoveSymbolsPred = [&](const Symbol &Sym) {
306 if (Config.SymbolsToKeep.matches(Sym.Name) ||
307 (Config.KeepFileSymbols && Sym.Type == STT_FILE))
308 return false;
309
310 if ((Config.DiscardMode == DiscardType::All ||
311 (Config.DiscardMode == DiscardType::Locals &&
312 StringRef(Sym.Name).startswith(".L"))) &&
313 Sym.Binding == STB_LOCAL && Sym.getShndx() != SHN_UNDEF &&
314 Sym.Type != STT_FILE && Sym.Type != STT_SECTION)
315 return true;
316
317 if (Config.StripAll || Config.StripAllGNU)
318 return true;
319
320 if (Config.StripDebug && Sym.Type == STT_FILE)
321 return true;
322
323 if (Config.SymbolsToRemove.matches(Sym.Name))
324 return true;
325
326 if ((Config.StripUnneeded ||
327 Config.UnneededSymbolsToRemove.matches(Sym.Name)) &&
328 (!Obj.isRelocatable() || isUnneededSymbol(Sym)))
329 return true;
330
331 // We want to remove undefined symbols if all references have been stripped.
332 if (!Config.OnlySection.empty() && !Sym.Referenced &&
333 Sym.getShndx() == SHN_UNDEF)
334 return true;
335
336 return false;
337 };
338
339 return Obj.removeSymbols(RemoveSymbolsPred);
340 }
341
replaceAndRemoveSections(const CommonConfig & Config,Object & Obj)342 static Error replaceAndRemoveSections(const CommonConfig &Config, Object &Obj) {
343 SectionPred RemovePred = [](const SectionBase &) { return false; };
344
345 // Removes:
346 if (!Config.ToRemove.empty()) {
347 RemovePred = [&Config](const SectionBase &Sec) {
348 return Config.ToRemove.matches(Sec.Name);
349 };
350 }
351
352 if (Config.StripDWO)
353 RemovePred = [RemovePred](const SectionBase &Sec) {
354 return isDWOSection(Sec) || RemovePred(Sec);
355 };
356
357 if (Config.ExtractDWO)
358 RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
359 return onlyKeepDWOPred(Obj, Sec) || RemovePred(Sec);
360 };
361
362 if (Config.StripAllGNU)
363 RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
364 if (RemovePred(Sec))
365 return true;
366 if ((Sec.Flags & SHF_ALLOC) != 0)
367 return false;
368 if (&Sec == Obj.SectionNames)
369 return false;
370 switch (Sec.Type) {
371 case SHT_SYMTAB:
372 case SHT_REL:
373 case SHT_RELA:
374 case SHT_STRTAB:
375 return true;
376 }
377 return isDebugSection(Sec);
378 };
379
380 if (Config.StripSections) {
381 RemovePred = [RemovePred](const SectionBase &Sec) {
382 return RemovePred(Sec) || Sec.ParentSegment == nullptr;
383 };
384 }
385
386 if (Config.StripDebug || Config.StripUnneeded) {
387 RemovePred = [RemovePred](const SectionBase &Sec) {
388 return RemovePred(Sec) || isDebugSection(Sec);
389 };
390 }
391
392 if (Config.StripNonAlloc)
393 RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
394 if (RemovePred(Sec))
395 return true;
396 if (&Sec == Obj.SectionNames)
397 return false;
398 return (Sec.Flags & SHF_ALLOC) == 0 && Sec.ParentSegment == nullptr;
399 };
400
401 if (Config.StripAll)
402 RemovePred = [RemovePred, &Obj](const SectionBase &Sec) {
403 if (RemovePred(Sec))
404 return true;
405 if (&Sec == Obj.SectionNames)
406 return false;
407 if (StringRef(Sec.Name).startswith(".gnu.warning"))
408 return false;
409 // We keep the .ARM.attribute section to maintain compatibility
410 // with Debian derived distributions. This is a bug in their
411 // patchset as documented here:
412 // https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=943798
413 if (Sec.Type == SHT_ARM_ATTRIBUTES)
414 return false;
415 if (Sec.ParentSegment != nullptr)
416 return false;
417 return (Sec.Flags & SHF_ALLOC) == 0;
418 };
419
420 if (Config.ExtractPartition || Config.ExtractMainPartition) {
421 RemovePred = [RemovePred](const SectionBase &Sec) {
422 if (RemovePred(Sec))
423 return true;
424 if (Sec.Type == SHT_LLVM_PART_EHDR || Sec.Type == SHT_LLVM_PART_PHDR)
425 return true;
426 return (Sec.Flags & SHF_ALLOC) != 0 && !Sec.ParentSegment;
427 };
428 }
429
430 // Explicit copies:
431 if (!Config.OnlySection.empty()) {
432 RemovePred = [&Config, RemovePred, &Obj](const SectionBase &Sec) {
433 // Explicitly keep these sections regardless of previous removes.
434 if (Config.OnlySection.matches(Sec.Name))
435 return false;
436
437 // Allow all implicit removes.
438 if (RemovePred(Sec))
439 return true;
440
441 // Keep special sections.
442 if (Obj.SectionNames == &Sec)
443 return false;
444 if (Obj.SymbolTable == &Sec ||
445 (Obj.SymbolTable && Obj.SymbolTable->getStrTab() == &Sec))
446 return false;
447
448 // Remove everything else.
449 return true;
450 };
451 }
452
453 if (!Config.KeepSection.empty()) {
454 RemovePred = [&Config, RemovePred](const SectionBase &Sec) {
455 // Explicitly keep these sections regardless of previous removes.
456 if (Config.KeepSection.matches(Sec.Name))
457 return false;
458 // Otherwise defer to RemovePred.
459 return RemovePred(Sec);
460 };
461 }
462
463 // This has to be the last predicate assignment.
464 // If the option --keep-symbol has been specified
465 // and at least one of those symbols is present
466 // (equivalently, the updated symbol table is not empty)
467 // the symbol table and the string table should not be removed.
468 if ((!Config.SymbolsToKeep.empty() || Config.KeepFileSymbols) &&
469 Obj.SymbolTable && !Obj.SymbolTable->empty()) {
470 RemovePred = [&Obj, RemovePred](const SectionBase &Sec) {
471 if (&Sec == Obj.SymbolTable || &Sec == Obj.SymbolTable->getStrTab())
472 return false;
473 return RemovePred(Sec);
474 };
475 }
476
477 if (Config.CompressionType != DebugCompressionType::None) {
478 if (Error Err = replaceDebugSections(
479 Obj, RemovePred, isCompressable,
480 [&Config, &Obj](const SectionBase *S) -> Expected<SectionBase *> {
481 Expected<CompressedSection> NewSection =
482 CompressedSection::create(*S, Config.CompressionType);
483 if (!NewSection)
484 return NewSection.takeError();
485
486 return &Obj.addSection<CompressedSection>(std::move(*NewSection));
487 }))
488 return Err;
489 } else if (Config.DecompressDebugSections) {
490 if (Error Err = replaceDebugSections(
491 Obj, RemovePred,
492 [](const SectionBase &S) { return isa<CompressedSection>(&S); },
493 [&Obj](const SectionBase *S) {
494 const CompressedSection *CS = cast<CompressedSection>(S);
495 return &Obj.addSection<DecompressedSection>(*CS);
496 }))
497 return Err;
498 }
499
500 return Obj.removeSections(Config.AllowBrokenLinks, RemovePred);
501 }
502
503 // This function handles the high level operations of GNU objcopy including
504 // handling command line options. It's important to outline certain properties
505 // we expect to hold of the command line operations. Any operation that "keeps"
506 // should keep regardless of a remove. Additionally any removal should respect
507 // any previous removals. Lastly whether or not something is removed shouldn't
508 // depend a) on the order the options occur in or b) on some opaque priority
509 // system. The only priority is that keeps/copies overrule removes.
handleArgs(const CommonConfig & Config,const ELFConfig & ELFConfig,Object & Obj)510 static Error handleArgs(const CommonConfig &Config, const ELFConfig &ELFConfig,
511 Object &Obj) {
512 if (Config.OutputArch) {
513 Obj.Machine = Config.OutputArch.getValue().EMachine;
514 Obj.OSABI = Config.OutputArch.getValue().OSABI;
515 }
516
517 if (!Config.SplitDWO.empty() && Config.ExtractDWO) {
518 return Obj.removeSections(
519 Config.AllowBrokenLinks,
520 [&Obj](const SectionBase &Sec) { return onlyKeepDWOPred(Obj, Sec); });
521 }
522
523 // Dump sections before add/remove for compatibility with GNU objcopy.
524 for (StringRef Flag : Config.DumpSection) {
525 StringRef SectionName;
526 StringRef FileName;
527 std::tie(SectionName, FileName) = Flag.split('=');
528 if (Error E = dumpSectionToFile(SectionName, FileName, Obj))
529 return E;
530 }
531
532 // It is important to remove the sections first. For example, we want to
533 // remove the relocation sections before removing the symbols. That allows
534 // us to avoid reporting the inappropriate errors about removing symbols
535 // named in relocations.
536 if (Error E = replaceAndRemoveSections(Config, Obj))
537 return E;
538
539 if (Error E = updateAndRemoveSymbols(Config, Obj))
540 return E;
541
542 if (!Config.SectionsToRename.empty()) {
543 for (SectionBase &Sec : Obj.sections()) {
544 const auto Iter = Config.SectionsToRename.find(Sec.Name);
545 if (Iter != Config.SectionsToRename.end()) {
546 const SectionRename &SR = Iter->second;
547 Sec.Name = std::string(SR.NewName);
548 if (SR.NewFlags.hasValue())
549 setSectionFlagsAndType(Sec, SR.NewFlags.getValue());
550 }
551 }
552 }
553
554 // Add a prefix to allocated sections and their relocation sections. This
555 // should be done after renaming the section by Config.SectionToRename to
556 // imitate the GNU objcopy behavior.
557 if (!Config.AllocSectionsPrefix.empty()) {
558 DenseSet<SectionBase *> PrefixedSections;
559 for (SectionBase &Sec : Obj.sections()) {
560 if (Sec.Flags & SHF_ALLOC) {
561 Sec.Name = (Config.AllocSectionsPrefix + Sec.Name).str();
562 PrefixedSections.insert(&Sec);
563 } else if (auto *RelocSec = dyn_cast<RelocationSectionBase>(&Sec)) {
564 // Rename relocation sections associated to the allocated sections.
565 // For example, if we rename .text to .prefix.text, we also rename
566 // .rel.text to .rel.prefix.text.
567 //
568 // Dynamic relocation sections (SHT_REL[A] with SHF_ALLOC) are handled
569 // above, e.g., .rela.plt is renamed to .prefix.rela.plt, not
570 // .rela.prefix.plt since GNU objcopy does so.
571 const SectionBase *TargetSec = RelocSec->getSection();
572 if (TargetSec && (TargetSec->Flags & SHF_ALLOC)) {
573 StringRef prefix;
574 switch (Sec.Type) {
575 case SHT_REL:
576 prefix = ".rel";
577 break;
578 case SHT_RELA:
579 prefix = ".rela";
580 break;
581 default:
582 llvm_unreachable("not a relocation section");
583 }
584
585 // If the relocation section comes *after* the target section, we
586 // don't add Config.AllocSectionsPrefix because we've already added
587 // the prefix to TargetSec->Name. Otherwise, if the relocation
588 // section comes *before* the target section, we add the prefix.
589 if (PrefixedSections.count(TargetSec))
590 Sec.Name = (prefix + TargetSec->Name).str();
591 else
592 Sec.Name =
593 (prefix + Config.AllocSectionsPrefix + TargetSec->Name).str();
594 }
595 }
596 }
597 }
598
599 if (!Config.SetSectionAlignment.empty()) {
600 for (SectionBase &Sec : Obj.sections()) {
601 auto I = Config.SetSectionAlignment.find(Sec.Name);
602 if (I != Config.SetSectionAlignment.end())
603 Sec.Align = I->second;
604 }
605 }
606
607 if (Config.OnlyKeepDebug)
608 for (auto &Sec : Obj.sections())
609 if (Sec.Flags & SHF_ALLOC && Sec.Type != SHT_NOTE)
610 Sec.Type = SHT_NOBITS;
611
612 for (const auto &Flag : Config.AddSection) {
613 std::pair<StringRef, StringRef> SecPair = Flag.split("=");
614 StringRef SecName = SecPair.first;
615 StringRef File = SecPair.second;
616 ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
617 MemoryBuffer::getFile(File);
618 if (!BufOrErr)
619 return createFileError(File, errorCodeToError(BufOrErr.getError()));
620 std::unique_ptr<MemoryBuffer> Buf = std::move(*BufOrErr);
621 ArrayRef<uint8_t> Data(
622 reinterpret_cast<const uint8_t *>(Buf->getBufferStart()),
623 Buf->getBufferSize());
624 OwnedDataSection &NewSection =
625 Obj.addSection<OwnedDataSection>(SecName, Data);
626 if (SecName.startswith(".note") && SecName != ".note.GNU-stack")
627 NewSection.Type = SHT_NOTE;
628 }
629
630 if (!Config.AddGnuDebugLink.empty())
631 Obj.addSection<GnuDebugLinkSection>(Config.AddGnuDebugLink,
632 Config.GnuDebugLinkCRC32);
633
634 // If the symbol table was previously removed, we need to create a new one
635 // before adding new symbols.
636 if (!Obj.SymbolTable && !ELFConfig.SymbolsToAdd.empty())
637 if (Error E = Obj.addNewSymbolTable())
638 return E;
639
640 for (const NewSymbolInfo &SI : ELFConfig.SymbolsToAdd) {
641 SectionBase *Sec = Obj.findSection(SI.SectionName);
642 uint64_t Value = Sec ? Sec->Addr + SI.Value : SI.Value;
643 Obj.SymbolTable->addSymbol(
644 SI.SymbolName, SI.Bind, SI.Type, Sec, Value, SI.Visibility,
645 Sec ? (uint16_t)SYMBOL_SIMPLE_INDEX : (uint16_t)SHN_ABS, 0);
646 }
647
648 // --set-section-flags works with sections added by --add-section.
649 if (!Config.SetSectionFlags.empty()) {
650 for (auto &Sec : Obj.sections()) {
651 const auto Iter = Config.SetSectionFlags.find(Sec.Name);
652 if (Iter != Config.SetSectionFlags.end()) {
653 const SectionFlagsUpdate &SFU = Iter->second;
654 setSectionFlagsAndType(Sec, SFU.NewFlags);
655 }
656 }
657 }
658
659 if (Config.EntryExpr)
660 Obj.Entry = Config.EntryExpr(Obj.Entry);
661 return Error::success();
662 }
663
writeOutput(const CommonConfig & Config,Object & Obj,raw_ostream & Out,ElfType OutputElfType)664 static Error writeOutput(const CommonConfig &Config, Object &Obj,
665 raw_ostream &Out, ElfType OutputElfType) {
666 std::unique_ptr<Writer> Writer =
667 createWriter(Config, Obj, Out, OutputElfType);
668 if (Error E = Writer->finalize())
669 return E;
670 return Writer->write();
671 }
672
executeObjcopyOnIHex(const CommonConfig & Config,const ELFConfig & ELFConfig,MemoryBuffer & In,raw_ostream & Out)673 Error executeObjcopyOnIHex(const CommonConfig &Config,
674 const ELFConfig &ELFConfig, MemoryBuffer &In,
675 raw_ostream &Out) {
676 IHexReader Reader(&In);
677 Expected<std::unique_ptr<Object>> Obj = Reader.create(true);
678 if (!Obj)
679 return Obj.takeError();
680
681 const ElfType OutputElfType =
682 getOutputElfType(Config.OutputArch.getValueOr(MachineInfo()));
683 if (Error E = handleArgs(Config, ELFConfig, **Obj))
684 return E;
685 return writeOutput(Config, **Obj, Out, OutputElfType);
686 }
687
executeObjcopyOnRawBinary(const CommonConfig & Config,const ELFConfig & ELFConfig,MemoryBuffer & In,raw_ostream & Out)688 Error executeObjcopyOnRawBinary(const CommonConfig &Config,
689 const ELFConfig &ELFConfig, MemoryBuffer &In,
690 raw_ostream &Out) {
691 uint8_t NewSymbolVisibility =
692 ELFConfig.NewSymbolVisibility.getValueOr((uint8_t)ELF::STV_DEFAULT);
693 BinaryReader Reader(&In, NewSymbolVisibility);
694 Expected<std::unique_ptr<Object>> Obj = Reader.create(true);
695 if (!Obj)
696 return Obj.takeError();
697
698 // Prefer OutputArch (-O<format>) if set, otherwise fallback to BinaryArch
699 // (-B<arch>).
700 const ElfType OutputElfType =
701 getOutputElfType(Config.OutputArch.getValueOr(MachineInfo()));
702 if (Error E = handleArgs(Config, ELFConfig, **Obj))
703 return E;
704 return writeOutput(Config, **Obj, Out, OutputElfType);
705 }
706
executeObjcopyOnBinary(const CommonConfig & Config,const ELFConfig & ELFConfig,object::ELFObjectFileBase & In,raw_ostream & Out)707 Error executeObjcopyOnBinary(const CommonConfig &Config,
708 const ELFConfig &ELFConfig,
709 object::ELFObjectFileBase &In, raw_ostream &Out) {
710 ELFReader Reader(&In, Config.ExtractPartition);
711 Expected<std::unique_ptr<Object>> Obj =
712 Reader.create(!ELFConfig.SymbolsToAdd.empty());
713 if (!Obj)
714 return Obj.takeError();
715 // Prefer OutputArch (-O<format>) if set, otherwise infer it from the input.
716 const ElfType OutputElfType =
717 Config.OutputArch ? getOutputElfType(Config.OutputArch.getValue())
718 : getOutputElfType(In);
719
720 if (Error E = handleArgs(Config, ELFConfig, **Obj))
721 return createFileError(Config.InputFilename, std::move(E));
722
723 if (Error E = writeOutput(Config, **Obj, Out, OutputElfType))
724 return createFileError(Config.InputFilename, std::move(E));
725
726 return Error::success();
727 }
728
729 } // end namespace elf
730 } // end namespace objcopy
731 } // end namespace llvm
732