xref: /freebsd/contrib/llvm-project/llvm/lib/Object/ELFObjectFile.cpp (revision cd0c3137f8a21968ce147251633b8dbdde8829e7) 
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/TargetRegistry.h"
27 #include <algorithm>
28 #include <cstddef>
29 #include <cstdint>
30 #include <memory>
31 #include <string>
32 #include <system_error>
33 #include <utility>
34 
35 using namespace llvm;
36 using namespace object;
37 
38 const EnumEntry<unsigned> llvm::object::ElfSymbolTypes[NumElfSymbolTypes] = {
39     {"None", "NOTYPE", ELF::STT_NOTYPE},
40     {"Object", "OBJECT", ELF::STT_OBJECT},
41     {"Function", "FUNC", ELF::STT_FUNC},
42     {"Section", "SECTION", ELF::STT_SECTION},
43     {"File", "FILE", ELF::STT_FILE},
44     {"Common", "COMMON", ELF::STT_COMMON},
45     {"TLS", "TLS", ELF::STT_TLS},
46     {"GNU_IFunc", "IFUNC", ELF::STT_GNU_IFUNC}};
47 
48 ELFObjectFileBase::ELFObjectFileBase(unsigned int Type, MemoryBufferRef Source)
49     : ObjectFile(Type, Source) {}
50 
51 template <class ELFT>
52 static Expected<std::unique_ptr<ELFObjectFile<ELFT>>>
53 createPtr(MemoryBufferRef Object) {
54   auto Ret = ELFObjectFile<ELFT>::create(Object);
55   if (Error E = Ret.takeError())
56     return std::move(E);
57   return make_unique<ELFObjectFile<ELFT>>(std::move(*Ret));
58 }
59 
60 Expected<std::unique_ptr<ObjectFile>>
61 ObjectFile::createELFObjectFile(MemoryBufferRef Obj) {
62   std::pair<unsigned char, unsigned char> Ident =
63       getElfArchType(Obj.getBuffer());
64   std::size_t MaxAlignment =
65       1ULL << countTrailingZeros(uintptr_t(Obj.getBufferStart()));
66 
67   if (MaxAlignment < 2)
68     return createError("Insufficient alignment");
69 
70   if (Ident.first == ELF::ELFCLASS32) {
71     if (Ident.second == ELF::ELFDATA2LSB)
72       return createPtr<ELF32LE>(Obj);
73     else if (Ident.second == ELF::ELFDATA2MSB)
74       return createPtr<ELF32BE>(Obj);
75     else
76       return createError("Invalid ELF data");
77   } else if (Ident.first == ELF::ELFCLASS64) {
78     if (Ident.second == ELF::ELFDATA2LSB)
79       return createPtr<ELF64LE>(Obj);
80     else if (Ident.second == ELF::ELFDATA2MSB)
81       return createPtr<ELF64BE>(Obj);
82     else
83       return createError("Invalid ELF data");
84   }
85   return createError("Invalid ELF class");
86 }
87 
88 SubtargetFeatures ELFObjectFileBase::getMIPSFeatures() const {
89   SubtargetFeatures Features;
90   unsigned PlatformFlags = getPlatformFlags();
91 
92   switch (PlatformFlags & ELF::EF_MIPS_ARCH) {
93   case ELF::EF_MIPS_ARCH_1:
94     break;
95   case ELF::EF_MIPS_ARCH_2:
96     Features.AddFeature("mips2");
97     break;
98   case ELF::EF_MIPS_ARCH_3:
99     Features.AddFeature("mips3");
100     break;
101   case ELF::EF_MIPS_ARCH_4:
102     Features.AddFeature("mips4");
103     break;
104   case ELF::EF_MIPS_ARCH_5:
105     Features.AddFeature("mips5");
106     break;
107   case ELF::EF_MIPS_ARCH_32:
108     Features.AddFeature("mips32");
109     break;
110   case ELF::EF_MIPS_ARCH_64:
111     Features.AddFeature("mips64");
112     break;
113   case ELF::EF_MIPS_ARCH_32R2:
114     Features.AddFeature("mips32r2");
115     break;
116   case ELF::EF_MIPS_ARCH_64R2:
117     Features.AddFeature("mips64r2");
118     break;
119   case ELF::EF_MIPS_ARCH_32R6:
120     Features.AddFeature("mips32r6");
121     break;
122   case ELF::EF_MIPS_ARCH_64R6:
123     Features.AddFeature("mips64r6");
124     break;
125   default:
126     llvm_unreachable("Unknown EF_MIPS_ARCH value");
127   }
128 
129   switch (PlatformFlags & ELF::EF_MIPS_MACH) {
130   case ELF::EF_MIPS_MACH_NONE:
131     // No feature associated with this value.
132     break;
133   case ELF::EF_MIPS_MACH_OCTEON:
134     Features.AddFeature("cnmips");
135     break;
136   default:
137     llvm_unreachable("Unknown EF_MIPS_ARCH value");
138   }
139 
140   if (PlatformFlags & ELF::EF_MIPS_ARCH_ASE_M16)
141     Features.AddFeature("mips16");
142   if (PlatformFlags & ELF::EF_MIPS_MICROMIPS)
143     Features.AddFeature("micromips");
144 
145   return Features;
146 }
147 
148 SubtargetFeatures ELFObjectFileBase::getARMFeatures() const {
149   SubtargetFeatures Features;
150   ARMAttributeParser Attributes;
151   if (Error E = getBuildAttributes(Attributes))
152     return SubtargetFeatures();
153 
154   // both ARMv7-M and R have to support thumb hardware div
155   bool isV7 = false;
156   if (Attributes.hasAttribute(ARMBuildAttrs::CPU_arch))
157     isV7 = Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch)
158       == ARMBuildAttrs::v7;
159 
160   if (Attributes.hasAttribute(ARMBuildAttrs::CPU_arch_profile)) {
161     switch(Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch_profile)) {
162     case ARMBuildAttrs::ApplicationProfile:
163       Features.AddFeature("aclass");
164       break;
165     case ARMBuildAttrs::RealTimeProfile:
166       Features.AddFeature("rclass");
167       if (isV7)
168         Features.AddFeature("hwdiv");
169       break;
170     case ARMBuildAttrs::MicroControllerProfile:
171       Features.AddFeature("mclass");
172       if (isV7)
173         Features.AddFeature("hwdiv");
174       break;
175     }
176   }
177 
178   if (Attributes.hasAttribute(ARMBuildAttrs::THUMB_ISA_use)) {
179     switch(Attributes.getAttributeValue(ARMBuildAttrs::THUMB_ISA_use)) {
180     default:
181       break;
182     case ARMBuildAttrs::Not_Allowed:
183       Features.AddFeature("thumb", false);
184       Features.AddFeature("thumb2", false);
185       break;
186     case ARMBuildAttrs::AllowThumb32:
187       Features.AddFeature("thumb2");
188       break;
189     }
190   }
191 
192   if (Attributes.hasAttribute(ARMBuildAttrs::FP_arch)) {
193     switch(Attributes.getAttributeValue(ARMBuildAttrs::FP_arch)) {
194     default:
195       break;
196     case ARMBuildAttrs::Not_Allowed:
197       Features.AddFeature("vfp2d16sp", false);
198       Features.AddFeature("vfp3d16sp", false);
199       Features.AddFeature("vfp4d16sp", false);
200       break;
201     case ARMBuildAttrs::AllowFPv2:
202       Features.AddFeature("vfp2");
203       break;
204     case ARMBuildAttrs::AllowFPv3A:
205     case ARMBuildAttrs::AllowFPv3B:
206       Features.AddFeature("vfp3");
207       break;
208     case ARMBuildAttrs::AllowFPv4A:
209     case ARMBuildAttrs::AllowFPv4B:
210       Features.AddFeature("vfp4");
211       break;
212     }
213   }
214 
215   if (Attributes.hasAttribute(ARMBuildAttrs::Advanced_SIMD_arch)) {
216     switch(Attributes.getAttributeValue(ARMBuildAttrs::Advanced_SIMD_arch)) {
217     default:
218       break;
219     case ARMBuildAttrs::Not_Allowed:
220       Features.AddFeature("neon", false);
221       Features.AddFeature("fp16", false);
222       break;
223     case ARMBuildAttrs::AllowNeon:
224       Features.AddFeature("neon");
225       break;
226     case ARMBuildAttrs::AllowNeon2:
227       Features.AddFeature("neon");
228       Features.AddFeature("fp16");
229       break;
230     }
231   }
232 
233   if (Attributes.hasAttribute(ARMBuildAttrs::MVE_arch)) {
234     switch(Attributes.getAttributeValue(ARMBuildAttrs::MVE_arch)) {
235     default:
236       break;
237     case ARMBuildAttrs::Not_Allowed:
238       Features.AddFeature("mve", false);
239       Features.AddFeature("mve.fp", false);
240       break;
241     case ARMBuildAttrs::AllowMVEInteger:
242       Features.AddFeature("mve.fp", false);
243       Features.AddFeature("mve");
244       break;
245     case ARMBuildAttrs::AllowMVEIntegerAndFloat:
246       Features.AddFeature("mve.fp");
247       break;
248     }
249   }
250 
251   if (Attributes.hasAttribute(ARMBuildAttrs::DIV_use)) {
252     switch(Attributes.getAttributeValue(ARMBuildAttrs::DIV_use)) {
253     default:
254       break;
255     case ARMBuildAttrs::DisallowDIV:
256       Features.AddFeature("hwdiv", false);
257       Features.AddFeature("hwdiv-arm", false);
258       break;
259     case ARMBuildAttrs::AllowDIVExt:
260       Features.AddFeature("hwdiv");
261       Features.AddFeature("hwdiv-arm");
262       break;
263     }
264   }
265 
266   return Features;
267 }
268 
269 SubtargetFeatures ELFObjectFileBase::getRISCVFeatures() const {
270   SubtargetFeatures Features;
271   unsigned PlatformFlags = getPlatformFlags();
272 
273   if (PlatformFlags & ELF::EF_RISCV_RVC) {
274     Features.AddFeature("c");
275   }
276 
277   return Features;
278 }
279 
280 SubtargetFeatures ELFObjectFileBase::getFeatures() const {
281   switch (getEMachine()) {
282   case ELF::EM_MIPS:
283     return getMIPSFeatures();
284   case ELF::EM_ARM:
285     return getARMFeatures();
286   case ELF::EM_RISCV:
287     return getRISCVFeatures();
288   default:
289     return SubtargetFeatures();
290   }
291 }
292 
293 // FIXME Encode from a tablegen description or target parser.
294 void ELFObjectFileBase::setARMSubArch(Triple &TheTriple) const {
295   if (TheTriple.getSubArch() != Triple::NoSubArch)
296     return;
297 
298   ARMAttributeParser Attributes;
299   if (Error E = getBuildAttributes(Attributes))
300     return;
301 
302   std::string Triple;
303   // Default to ARM, but use the triple if it's been set.
304   if (TheTriple.isThumb())
305     Triple = "thumb";
306   else
307     Triple = "arm";
308 
309   if (Attributes.hasAttribute(ARMBuildAttrs::CPU_arch)) {
310     switch(Attributes.getAttributeValue(ARMBuildAttrs::CPU_arch)) {
311     case ARMBuildAttrs::v4:
312       Triple += "v4";
313       break;
314     case ARMBuildAttrs::v4T:
315       Triple += "v4t";
316       break;
317     case ARMBuildAttrs::v5T:
318       Triple += "v5t";
319       break;
320     case ARMBuildAttrs::v5TE:
321       Triple += "v5te";
322       break;
323     case ARMBuildAttrs::v5TEJ:
324       Triple += "v5tej";
325       break;
326     case ARMBuildAttrs::v6:
327       Triple += "v6";
328       break;
329     case ARMBuildAttrs::v6KZ:
330       Triple += "v6kz";
331       break;
332     case ARMBuildAttrs::v6T2:
333       Triple += "v6t2";
334       break;
335     case ARMBuildAttrs::v6K:
336       Triple += "v6k";
337       break;
338     case ARMBuildAttrs::v7:
339       Triple += "v7";
340       break;
341     case ARMBuildAttrs::v6_M:
342       Triple += "v6m";
343       break;
344     case ARMBuildAttrs::v6S_M:
345       Triple += "v6sm";
346       break;
347     case ARMBuildAttrs::v7E_M:
348       Triple += "v7em";
349       break;
350     }
351   }
352   if (!isLittleEndian())
353     Triple += "eb";
354 
355   TheTriple.setArchName(Triple);
356 }
357 
358 std::vector<std::pair<DataRefImpl, uint64_t>>
359 ELFObjectFileBase::getPltAddresses() const {
360   std::string Err;
361   const auto Triple = makeTriple();
362   const auto *T = TargetRegistry::lookupTarget(Triple.str(), Err);
363   if (!T)
364     return {};
365   uint64_t JumpSlotReloc = 0;
366   switch (Triple.getArch()) {
367     case Triple::x86:
368       JumpSlotReloc = ELF::R_386_JUMP_SLOT;
369       break;
370     case Triple::x86_64:
371       JumpSlotReloc = ELF::R_X86_64_JUMP_SLOT;
372       break;
373     case Triple::aarch64:
374       JumpSlotReloc = ELF::R_AARCH64_JUMP_SLOT;
375       break;
376     default:
377       return {};
378   }
379   std::unique_ptr<const MCInstrInfo> MII(T->createMCInstrInfo());
380   std::unique_ptr<const MCInstrAnalysis> MIA(
381       T->createMCInstrAnalysis(MII.get()));
382   if (!MIA)
383     return {};
384   Optional<SectionRef> Plt = None, RelaPlt = None, GotPlt = None;
385   for (const SectionRef &Section : sections()) {
386     StringRef Name;
387     if (Section.getName(Name))
388       continue;
389     if (Name == ".plt")
390       Plt = Section;
391     else if (Name == ".rela.plt" || Name == ".rel.plt")
392       RelaPlt = Section;
393     else if (Name == ".got.plt")
394       GotPlt = Section;
395   }
396   if (!Plt || !RelaPlt || !GotPlt)
397     return {};
398   Expected<StringRef> PltContents = Plt->getContents();
399   if (!PltContents) {
400     consumeError(PltContents.takeError());
401     return {};
402   }
403   auto PltEntries = MIA->findPltEntries(Plt->getAddress(),
404                                         arrayRefFromStringRef(*PltContents),
405                                         GotPlt->getAddress(), Triple);
406   // Build a map from GOT entry virtual address to PLT entry virtual address.
407   DenseMap<uint64_t, uint64_t> GotToPlt;
408   for (const auto &Entry : PltEntries)
409     GotToPlt.insert(std::make_pair(Entry.second, Entry.first));
410   // Find the relocations in the dynamic relocation table that point to
411   // locations in the GOT for which we know the corresponding PLT entry.
412   std::vector<std::pair<DataRefImpl, uint64_t>> Result;
413   for (const auto &Relocation : RelaPlt->relocations()) {
414     if (Relocation.getType() != JumpSlotReloc)
415       continue;
416     auto PltEntryIter = GotToPlt.find(Relocation.getOffset());
417     if (PltEntryIter != GotToPlt.end())
418       Result.push_back(std::make_pair(
419           Relocation.getSymbol()->getRawDataRefImpl(), PltEntryIter->second));
420   }
421   return Result;
422 }
423