xref: /freebsd/contrib/llvm-project/llvm/lib/Object/ELFObjectFile.cpp (revision 6132212808e8dccedc9e5d85fea4390c2f38059a) 
1 //===- ELFObjectFile.cpp - ELF object file implementation -----------------===//
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 // Part of the ELFObjectFile class implementation.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/Object/ELFObjectFile.h"
14 #include "llvm/ADT/Triple.h"
15 #include "llvm/BinaryFormat/ELF.h"
16 #include "llvm/MC/MCInstrAnalysis.h"
17 #include "llvm/MC/SubtargetFeature.h"
18 #include "llvm/Object/ELF.h"
19 #include "llvm/Object/ELFTypes.h"
20 #include "llvm/Object/Error.h"
21 #include "llvm/Support/ARMAttributeParser.h"
22 #include "llvm/Support/ARMBuildAttributes.h"
23 #include "llvm/Support/Endian.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/MathExtras.h"
26 #include "llvm/Support/RISCVAttributeParser.h"
27 #include "llvm/Support/RISCVAttributes.h"
28 #include "llvm/Support/TargetRegistry.h"
29 #include <algorithm>
30 #include <cstddef>
31 #include <cstdint>
32 #include <memory>
33 #include <string>
34 #include <system_error>
35 #include <utility>
36 
37 using namespace llvm;
38 using namespace object;
39 
40 const EnumEntry<unsigned> llvm::object::ElfSymbolTypes[NumElfSymbolTypes] = {
41     {"None", "NOTYPE", ELF::STT_NOTYPE},
42     {"Object", "OBJECT", ELF::STT_OBJECT},
43     {"Function", "FUNC", ELF::STT_FUNC},
44     {"Section", "SECTION", ELF::STT_SECTION},
45     {"File", "FILE", ELF::STT_FILE},
46     {"Common", "COMMON", ELF::STT_COMMON},
47     {"TLS", "TLS", ELF::STT_TLS},
48     {"Unknown", "<unknown>: 7", 7},
49     {"Unknown", "<unknown>: 8", 8},
50     {"Unknown", "<unknown>: 9", 9},
51     {"GNU_IFunc", "IFUNC", ELF::STT_GNU_IFUNC},
52     {"OS Specific", "<OS specific>: 11", 11},
53     {"OS Specific", "<OS specific>: 12", 12},
54     {"Proc Specific", "<processor specific>: 13", 13},
55     {"Proc Specific", "<processor specific>: 14", 14},
56     {"Proc Specific", "<processor specific>: 15", 15}
57 };
58 
59 ELFObjectFileBase::ELFObjectFileBase(unsigned int Type, MemoryBufferRef Source)
60     : ObjectFile(Type, Source) {}
61 
62 template <class ELFT>
63 static Expected<std::unique_ptr<ELFObjectFile<ELFT>>>
64 createPtr(MemoryBufferRef Object) {
65   auto Ret = ELFObjectFile<ELFT>::create(Object);
66   if (Error E = Ret.takeError())
67     return std::move(E);
68   return std::make_unique<ELFObjectFile<ELFT>>(std::move(*Ret));
69 }
70 
71 Expected<std::unique_ptr<ObjectFile>>
72 ObjectFile::createELFObjectFile(MemoryBufferRef Obj) {
73   std::pair<unsigned char, unsigned char> Ident =
74       getElfArchType(Obj.getBuffer());
75   std::size_t MaxAlignment =
76       1ULL << countTrailingZeros(uintptr_t(Obj.getBufferStart()));
77 
78   if (MaxAlignment < 2)
79     return createError("Insufficient alignment");
80 
81   if (Ident.first == ELF::ELFCLASS32) {
82     if (Ident.second == ELF::ELFDATA2LSB)
83       return createPtr<ELF32LE>(Obj);
84     else if (Ident.second == ELF::ELFDATA2MSB)
85       return createPtr<ELF32BE>(Obj);
86     else
87       return createError("Invalid ELF data");
88   } else if (Ident.first == ELF::ELFCLASS64) {
89     if (Ident.second == ELF::ELFDATA2LSB)
90       return createPtr<ELF64LE>(Obj);
91     else if (Ident.second == ELF::ELFDATA2MSB)
92       return createPtr<ELF64BE>(Obj);
93     else
94       return createError("Invalid ELF data");
95   }
96   return createError("Invalid ELF class");
97 }
98 
99 SubtargetFeatures ELFObjectFileBase::getMIPSFeatures() const {
100   SubtargetFeatures Features;
101   unsigned PlatformFlags = getPlatformFlags();
102 
103   switch (PlatformFlags & ELF::EF_MIPS_ARCH) {
104   case ELF::EF_MIPS_ARCH_1:
105     break;
106   case ELF::EF_MIPS_ARCH_2:
107     Features.AddFeature("mips2");
108     break;
109   case ELF::EF_MIPS_ARCH_3:
110     Features.AddFeature("mips3");
111     break;
112   case ELF::EF_MIPS_ARCH_4:
113     Features.AddFeature("mips4");
114     break;
115   case ELF::EF_MIPS_ARCH_5:
116     Features.AddFeature("mips5");
117     break;
118   case ELF::EF_MIPS_ARCH_32:
119     Features.AddFeature("mips32");
120     break;
121   case ELF::EF_MIPS_ARCH_64:
122     Features.AddFeature("mips64");
123     break;
124   case ELF::EF_MIPS_ARCH_32R2:
125     Features.AddFeature("mips32r2");
126     break;
127   case ELF::EF_MIPS_ARCH_64R2:
128     Features.AddFeature("mips64r2");
129     break;
130   case ELF::EF_MIPS_ARCH_32R6:
131     Features.AddFeature("mips32r6");
132     break;
133   case ELF::EF_MIPS_ARCH_64R6:
134     Features.AddFeature("mips64r6");
135     break;
136   default:
137     llvm_unreachable("Unknown EF_MIPS_ARCH value");
138   }
139 
140   switch (PlatformFlags & ELF::EF_MIPS_MACH) {
141   case ELF::EF_MIPS_MACH_NONE:
142     // No feature associated with this value.
143     break;
144   case ELF::EF_MIPS_MACH_OCTEON:
145     Features.AddFeature("cnmips");
146     break;
147   default:
148     llvm_unreachable("Unknown EF_MIPS_ARCH value");
149   }
150 
151   if (PlatformFlags & ELF::EF_MIPS_ARCH_ASE_M16)
152     Features.AddFeature("mips16");
153   if (PlatformFlags & ELF::EF_MIPS_MICROMIPS)
154     Features.AddFeature("micromips");
155 
156   return Features;
157 }
158 
159 SubtargetFeatures ELFObjectFileBase::getARMFeatures() const {
160   SubtargetFeatures Features;
161   ARMAttributeParser Attributes;
162   if (Error E = getBuildAttributes(Attributes)) {
163     consumeError(std::move(E));
164     return SubtargetFeatures();
165   }
166 
167   // both ARMv7-M and R have to support thumb hardware div
168   bool isV7 = false;
169   Optional<unsigned> Attr =
170       Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch);
171   if (Attr.hasValue())
172     isV7 = Attr.getValue() == ARMBuildAttrs::v7;
173 
174   Attr = Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch_profile);
175   if (Attr.hasValue()) {
176     switch (Attr.getValue()) {
177     case ARMBuildAttrs::ApplicationProfile:
178       Features.AddFeature("aclass");
179       break;
180     case ARMBuildAttrs::RealTimeProfile:
181       Features.AddFeature("rclass");
182       if (isV7)
183         Features.AddFeature("hwdiv");
184       break;
185     case ARMBuildAttrs::MicroControllerProfile:
186       Features.AddFeature("mclass");
187       if (isV7)
188         Features.AddFeature("hwdiv");
189       break;
190     }
191   }
192 
193   Attr = Attributes.getAttributeValue(ARMBuildAttrs::THUMB_ISA_use);
194   if (Attr.hasValue()) {
195     switch (Attr.getValue()) {
196     default:
197       break;
198     case ARMBuildAttrs::Not_Allowed:
199       Features.AddFeature("thumb", false);
200       Features.AddFeature("thumb2", false);
201       break;
202     case ARMBuildAttrs::AllowThumb32:
203       Features.AddFeature("thumb2");
204       break;
205     }
206   }
207 
208   Attr = Attributes.getAttributeValue(ARMBuildAttrs::FP_arch);
209   if (Attr.hasValue()) {
210     switch (Attr.getValue()) {
211     default:
212       break;
213     case ARMBuildAttrs::Not_Allowed:
214       Features.AddFeature("vfp2sp", false);
215       Features.AddFeature("vfp3d16sp", false);
216       Features.AddFeature("vfp4d16sp", false);
217       break;
218     case ARMBuildAttrs::AllowFPv2:
219       Features.AddFeature("vfp2");
220       break;
221     case ARMBuildAttrs::AllowFPv3A:
222     case ARMBuildAttrs::AllowFPv3B:
223       Features.AddFeature("vfp3");
224       break;
225     case ARMBuildAttrs::AllowFPv4A:
226     case ARMBuildAttrs::AllowFPv4B:
227       Features.AddFeature("vfp4");
228       break;
229     }
230   }
231 
232   Attr = Attributes.getAttributeValue(ARMBuildAttrs::Advanced_SIMD_arch);
233   if (Attr.hasValue()) {
234     switch (Attr.getValue()) {
235     default:
236       break;
237     case ARMBuildAttrs::Not_Allowed:
238       Features.AddFeature("neon", false);
239       Features.AddFeature("fp16", false);
240       break;
241     case ARMBuildAttrs::AllowNeon:
242       Features.AddFeature("neon");
243       break;
244     case ARMBuildAttrs::AllowNeon2:
245       Features.AddFeature("neon");
246       Features.AddFeature("fp16");
247       break;
248     }
249   }
250 
251   Attr = Attributes.getAttributeValue(ARMBuildAttrs::MVE_arch);
252   if (Attr.hasValue()) {
253     switch (Attr.getValue()) {
254     default:
255       break;
256     case ARMBuildAttrs::Not_Allowed:
257       Features.AddFeature("mve", false);
258       Features.AddFeature("mve.fp", false);
259       break;
260     case ARMBuildAttrs::AllowMVEInteger:
261       Features.AddFeature("mve.fp", false);
262       Features.AddFeature("mve");
263       break;
264     case ARMBuildAttrs::AllowMVEIntegerAndFloat:
265       Features.AddFeature("mve.fp");
266       break;
267     }
268   }
269 
270   Attr = Attributes.getAttributeValue(ARMBuildAttrs::DIV_use);
271   if (Attr.hasValue()) {
272     switch (Attr.getValue()) {
273     default:
274       break;
275     case ARMBuildAttrs::DisallowDIV:
276       Features.AddFeature("hwdiv", false);
277       Features.AddFeature("hwdiv-arm", false);
278       break;
279     case ARMBuildAttrs::AllowDIVExt:
280       Features.AddFeature("hwdiv");
281       Features.AddFeature("hwdiv-arm");
282       break;
283     }
284   }
285 
286   return Features;
287 }
288 
289 SubtargetFeatures ELFObjectFileBase::getRISCVFeatures() const {
290   SubtargetFeatures Features;
291   unsigned PlatformFlags = getPlatformFlags();
292 
293   if (PlatformFlags & ELF::EF_RISCV_RVC) {
294     Features.AddFeature("c");
295   }
296 
297   // Add features according to the ELF attribute section.
298   // If there are any unrecognized features, ignore them.
299   RISCVAttributeParser Attributes;
300   if (Error E = getBuildAttributes(Attributes)) {
301     // TODO Propagate Error.
302     consumeError(std::move(E));
303     return Features; // Keep "c" feature if there is one in PlatformFlags.
304   }
305 
306   Optional<StringRef> Attr = Attributes.getAttributeString(RISCVAttrs::ARCH);
307   if (Attr.hasValue()) {
308     // The Arch pattern is [rv32|rv64][i|e]version(_[m|a|f|d|c]version)*
309     // Version string pattern is (major)p(minor). Major and minor are optional.
310     // For example, a version number could be 2p0, 2, or p92.
311     StringRef Arch = Attr.getValue();
312     if (Arch.consume_front("rv32"))
313       Features.AddFeature("64bit", false);
314     else if (Arch.consume_front("rv64"))
315       Features.AddFeature("64bit");
316 
317     while (!Arch.empty()) {
318       switch (Arch[0]) {
319       default:
320         break; // Ignore unexpected features.
321       case 'i':
322         Features.AddFeature("e", false);
323         break;
324       case 'd':
325         Features.AddFeature("f"); // D-ext will imply F-ext.
326         LLVM_FALLTHROUGH;
327       case 'e':
328       case 'm':
329       case 'a':
330       case 'f':
331       case 'c':
332         Features.AddFeature(Arch.take_front());
333         break;
334       }
335 
336       // FIXME: Handle version numbers.
337       Arch = Arch.drop_until([](char c) { return c == '_' || c == '\0'; });
338       Arch = Arch.drop_while([](char c) { return c == '_'; });
339     }
340   }
341 
342   return Features;
343 }
344 
345 SubtargetFeatures ELFObjectFileBase::getFeatures() const {
346   switch (getEMachine()) {
347   case ELF::EM_MIPS:
348     return getMIPSFeatures();
349   case ELF::EM_ARM:
350     return getARMFeatures();
351   case ELF::EM_RISCV:
352     return getRISCVFeatures();
353   default:
354     return SubtargetFeatures();
355   }
356 }
357 
358 // FIXME Encode from a tablegen description or target parser.
359 void ELFObjectFileBase::setARMSubArch(Triple &TheTriple) const {
360   if (TheTriple.getSubArch() != Triple::NoSubArch)
361     return;
362 
363   ARMAttributeParser Attributes;
364   if (Error E = getBuildAttributes(Attributes)) {
365     // TODO Propagate Error.
366     consumeError(std::move(E));
367     return;
368   }
369 
370   std::string Triple;
371   // Default to ARM, but use the triple if it's been set.
372   if (TheTriple.isThumb())
373     Triple = "thumb";
374   else
375     Triple = "arm";
376 
377   Optional<unsigned> Attr =
378       Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch);
379   if (Attr.hasValue()) {
380     switch (Attr.getValue()) {
381     case ARMBuildAttrs::v4:
382       Triple += "v4";
383       break;
384     case ARMBuildAttrs::v4T:
385       Triple += "v4t";
386       break;
387     case ARMBuildAttrs::v5T:
388       Triple += "v5t";
389       break;
390     case ARMBuildAttrs::v5TE:
391       Triple += "v5te";
392       break;
393     case ARMBuildAttrs::v5TEJ:
394       Triple += "v5tej";
395       break;
396     case ARMBuildAttrs::v6:
397       Triple += "v6";
398       break;
399     case ARMBuildAttrs::v6KZ:
400       Triple += "v6kz";
401       break;
402     case ARMBuildAttrs::v6T2:
403       Triple += "v6t2";
404       break;
405     case ARMBuildAttrs::v6K:
406       Triple += "v6k";
407       break;
408     case ARMBuildAttrs::v7:
409       Triple += "v7";
410       break;
411     case ARMBuildAttrs::v6_M:
412       Triple += "v6m";
413       break;
414     case ARMBuildAttrs::v6S_M:
415       Triple += "v6sm";
416       break;
417     case ARMBuildAttrs::v7E_M:
418       Triple += "v7em";
419       break;
420     case ARMBuildAttrs::v8_A:
421       Triple += "v8a";
422       break;
423     case ARMBuildAttrs::v8_R:
424       Triple += "v8r";
425       break;
426     case ARMBuildAttrs::v8_M_Base:
427       Triple += "v8m.base";
428       break;
429     case ARMBuildAttrs::v8_M_Main:
430       Triple += "v8m.main";
431       break;
432     case ARMBuildAttrs::v8_1_M_Main:
433       Triple += "v8.1m.main";
434       break;
435     }
436   }
437   if (!isLittleEndian())
438     Triple += "eb";
439 
440   TheTriple.setArchName(Triple);
441 }
442 
443 std::vector<std::pair<DataRefImpl, uint64_t>>
444 ELFObjectFileBase::getPltAddresses() const {
445   std::string Err;
446   const auto Triple = makeTriple();
447   const auto *T = TargetRegistry::lookupTarget(Triple.str(), Err);
448   if (!T)
449     return {};
450   uint64_t JumpSlotReloc = 0;
451   switch (Triple.getArch()) {
452     case Triple::x86:
453       JumpSlotReloc = ELF::R_386_JUMP_SLOT;
454       break;
455     case Triple::x86_64:
456       JumpSlotReloc = ELF::R_X86_64_JUMP_SLOT;
457       break;
458     case Triple::aarch64:
459       JumpSlotReloc = ELF::R_AARCH64_JUMP_SLOT;
460       break;
461     default:
462       return {};
463   }
464   std::unique_ptr<const MCInstrInfo> MII(T->createMCInstrInfo());
465   std::unique_ptr<const MCInstrAnalysis> MIA(
466       T->createMCInstrAnalysis(MII.get()));
467   if (!MIA)
468     return {};
469   Optional<SectionRef> Plt = None, RelaPlt = None, GotPlt = None;
470   for (const SectionRef &Section : sections()) {
471     Expected<StringRef> NameOrErr = Section.getName();
472     if (!NameOrErr) {
473       consumeError(NameOrErr.takeError());
474       continue;
475     }
476     StringRef Name = *NameOrErr;
477 
478     if (Name == ".plt")
479       Plt = Section;
480     else if (Name == ".rela.plt" || Name == ".rel.plt")
481       RelaPlt = Section;
482     else if (Name == ".got.plt")
483       GotPlt = Section;
484   }
485   if (!Plt || !RelaPlt || !GotPlt)
486     return {};
487   Expected<StringRef> PltContents = Plt->getContents();
488   if (!PltContents) {
489     consumeError(PltContents.takeError());
490     return {};
491   }
492   auto PltEntries = MIA->findPltEntries(Plt->getAddress(),
493                                         arrayRefFromStringRef(*PltContents),
494                                         GotPlt->getAddress(), Triple);
495   // Build a map from GOT entry virtual address to PLT entry virtual address.
496   DenseMap<uint64_t, uint64_t> GotToPlt;
497   for (const auto &Entry : PltEntries)
498     GotToPlt.insert(std::make_pair(Entry.second, Entry.first));
499   // Find the relocations in the dynamic relocation table that point to
500   // locations in the GOT for which we know the corresponding PLT entry.
501   std::vector<std::pair<DataRefImpl, uint64_t>> Result;
502   for (const auto &Relocation : RelaPlt->relocations()) {
503     if (Relocation.getType() != JumpSlotReloc)
504       continue;
505     auto PltEntryIter = GotToPlt.find(Relocation.getOffset());
506     if (PltEntryIter != GotToPlt.end())
507       Result.push_back(std::make_pair(
508           Relocation.getSymbol()->getRawDataRefImpl(), PltEntryIter->second));
509   }
510   return Result;
511 }
512