1 //===- WasmObjectFile.cpp - Wasm object file implementation ---------------===//
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/ADT/ArrayRef.h"
11 #include "llvm/ADT/STLExtras.h"
12 #include "llvm/ADT/StringRef.h"
13 #include "llvm/ADT/Triple.h"
14 #include "llvm/BinaryFormat/Wasm.h"
15 #include "llvm/MC/SubtargetFeature.h"
16 #include "llvm/Object/Binary.h"
17 #include "llvm/Object/Error.h"
18 #include "llvm/Object/ObjectFile.h"
19 #include "llvm/Object/SymbolicFile.h"
20 #include "llvm/Object/Wasm.h"
21 #include "llvm/Support/Endian.h"
22 #include "llvm/Support/Error.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/LEB128.h"
25 #include <algorithm>
26 #include <cassert>
27 #include <cstdint>
28 #include <cstring>
29 #include <system_error>
30 
31 #define DEBUG_TYPE "wasm-object"
32 
33 using namespace llvm;
34 using namespace object;
35 
36 Expected<std::unique_ptr<WasmObjectFile>>
37 ObjectFile::createWasmObjectFile(MemoryBufferRef Buffer) {
38   Error Err = Error::success();
39   auto ObjectFile = llvm::make_unique<WasmObjectFile>(Buffer, Err);
40   if (Err)
41     return std::move(Err);
42 
43   return std::move(ObjectFile);
44 }
45 
46 #define VARINT7_MAX ((1<<7)-1)
47 #define VARINT7_MIN (-(1<<7))
48 #define VARUINT7_MAX (1<<7)
49 #define VARUINT1_MAX (1)
50 
51 static uint8_t readUint8(const uint8_t *&Ptr) { return *Ptr++; }
52 
53 static uint32_t readUint32(const uint8_t *&Ptr) {
54   uint32_t Result = support::endian::read32le(Ptr);
55   Ptr += sizeof(Result);
56   return Result;
57 }
58 
59 static int32_t readFloat32(const uint8_t *&Ptr) {
60   int32_t Result = 0;
61   memcpy(&Result, Ptr, sizeof(Result));
62   Ptr += sizeof(Result);
63   return Result;
64 }
65 
66 static int64_t readFloat64(const uint8_t *&Ptr) {
67   int64_t Result = 0;
68   memcpy(&Result, Ptr, sizeof(Result));
69   Ptr += sizeof(Result);
70   return Result;
71 }
72 
73 static uint64_t readULEB128(const uint8_t *&Ptr) {
74   unsigned Count;
75   uint64_t Result = decodeULEB128(Ptr, &Count);
76   Ptr += Count;
77   return Result;
78 }
79 
80 static StringRef readString(const uint8_t *&Ptr) {
81   uint32_t StringLen = readULEB128(Ptr);
82   StringRef Return = StringRef(reinterpret_cast<const char *>(Ptr), StringLen);
83   Ptr += StringLen;
84   return Return;
85 }
86 
87 static int64_t readLEB128(const uint8_t *&Ptr) {
88   unsigned Count;
89   uint64_t Result = decodeSLEB128(Ptr, &Count);
90   Ptr += Count;
91   return Result;
92 }
93 
94 static uint8_t readVaruint1(const uint8_t *&Ptr) {
95   int64_t result = readLEB128(Ptr);
96   assert(result <= VARUINT1_MAX && result >= 0);
97   return result;
98 }
99 
100 static int8_t readVarint7(const uint8_t *&Ptr) {
101   int64_t result = readLEB128(Ptr);
102   assert(result <= VARINT7_MAX && result >= VARINT7_MIN);
103   return result;
104 }
105 
106 static uint8_t readVaruint7(const uint8_t *&Ptr) {
107   uint64_t result = readULEB128(Ptr);
108   assert(result <= VARUINT7_MAX);
109   return result;
110 }
111 
112 static int32_t readVarint32(const uint8_t *&Ptr) {
113   int64_t result = readLEB128(Ptr);
114   assert(result <= INT32_MAX && result >= INT32_MIN);
115   return result;
116 }
117 
118 static uint32_t readVaruint32(const uint8_t *&Ptr) {
119   uint64_t result = readULEB128(Ptr);
120   assert(result <= UINT32_MAX);
121   return result;
122 }
123 
124 static int64_t readVarint64(const uint8_t *&Ptr) {
125   return readLEB128(Ptr);
126 }
127 
128 static uint8_t readOpcode(const uint8_t *&Ptr) {
129   return readUint8(Ptr);
130 }
131 
132 static Error readInitExpr(wasm::WasmInitExpr &Expr, const uint8_t *&Ptr) {
133   Expr.Opcode = readOpcode(Ptr);
134 
135   switch (Expr.Opcode) {
136   case wasm::WASM_OPCODE_I32_CONST:
137     Expr.Value.Int32 = readVarint32(Ptr);
138     break;
139   case wasm::WASM_OPCODE_I64_CONST:
140     Expr.Value.Int64 = readVarint64(Ptr);
141     break;
142   case wasm::WASM_OPCODE_F32_CONST:
143     Expr.Value.Float32 = readFloat32(Ptr);
144     break;
145   case wasm::WASM_OPCODE_F64_CONST:
146     Expr.Value.Float64 = readFloat64(Ptr);
147     break;
148   case wasm::WASM_OPCODE_GET_GLOBAL:
149     Expr.Value.Global = readULEB128(Ptr);
150     break;
151   default:
152     return make_error<GenericBinaryError>("Invalid opcode in init_expr",
153                                           object_error::parse_failed);
154   }
155 
156   uint8_t EndOpcode = readOpcode(Ptr);
157   if (EndOpcode != wasm::WASM_OPCODE_END) {
158     return make_error<GenericBinaryError>("Invalid init_expr",
159                                           object_error::parse_failed);
160   }
161   return Error::success();
162 }
163 
164 static wasm::WasmLimits readLimits(const uint8_t *&Ptr) {
165   wasm::WasmLimits Result;
166   Result.Flags = readVaruint1(Ptr);
167   Result.Initial = readVaruint32(Ptr);
168   if (Result.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX)
169     Result.Maximum = readVaruint32(Ptr);
170   return Result;
171 }
172 
173 static wasm::WasmTable readTable(const uint8_t *&Ptr) {
174   wasm::WasmTable Table;
175   Table.ElemType = readVarint7(Ptr);
176   Table.Limits = readLimits(Ptr);
177   return Table;
178 }
179 
180 static Error readSection(WasmSection &Section, const uint8_t *&Ptr,
181                          const uint8_t *Start) {
182   // TODO(sbc): Avoid reading past EOF in the case of malformed files.
183   Section.Offset = Ptr - Start;
184   Section.Type = readVaruint7(Ptr);
185   uint32_t Size = readVaruint32(Ptr);
186   if (Size == 0)
187     return make_error<StringError>("Zero length section",
188                                    object_error::parse_failed);
189   Section.Content = ArrayRef<uint8_t>(Ptr, Size);
190   Ptr += Size;
191   return Error::success();
192 }
193 
194 WasmObjectFile::WasmObjectFile(MemoryBufferRef Buffer, Error &Err)
195     : ObjectFile(Binary::ID_Wasm, Buffer) {
196   LinkingData.DataAlignment = 0;
197   LinkingData.DataSize = 0;
198 
199   ErrorAsOutParameter ErrAsOutParam(&Err);
200   Header.Magic = getData().substr(0, 4);
201   if (Header.Magic != StringRef("\0asm", 4)) {
202     Err = make_error<StringError>("Bad magic number",
203                                   object_error::parse_failed);
204     return;
205   }
206 
207   const uint8_t *Eof = getPtr(getData().size());
208   const uint8_t *Ptr = getPtr(4);
209 
210   if (Ptr + 4 > Eof) {
211     Err = make_error<StringError>("Missing version number",
212                                   object_error::parse_failed);
213     return;
214   }
215 
216   Header.Version = readUint32(Ptr);
217   if (Header.Version != wasm::WasmVersion) {
218     Err = make_error<StringError>("Bad version number",
219                                   object_error::parse_failed);
220     return;
221   }
222 
223   WasmSection Sec;
224   while (Ptr < Eof) {
225     if ((Err = readSection(Sec, Ptr, getPtr(0))))
226       return;
227     if ((Err = parseSection(Sec)))
228       return;
229 
230     Sections.push_back(Sec);
231   }
232 }
233 
234 Error WasmObjectFile::parseSection(WasmSection &Sec) {
235   const uint8_t* Start = Sec.Content.data();
236   const uint8_t* End = Start + Sec.Content.size();
237   switch (Sec.Type) {
238   case wasm::WASM_SEC_CUSTOM:
239     return parseCustomSection(Sec, Start, End);
240   case wasm::WASM_SEC_TYPE:
241     return parseTypeSection(Start, End);
242   case wasm::WASM_SEC_IMPORT:
243     return parseImportSection(Start, End);
244   case wasm::WASM_SEC_FUNCTION:
245     return parseFunctionSection(Start, End);
246   case wasm::WASM_SEC_TABLE:
247     return parseTableSection(Start, End);
248   case wasm::WASM_SEC_MEMORY:
249     return parseMemorySection(Start, End);
250   case wasm::WASM_SEC_GLOBAL:
251     return parseGlobalSection(Start, End);
252   case wasm::WASM_SEC_EXPORT:
253     return parseExportSection(Start, End);
254   case wasm::WASM_SEC_START:
255     return parseStartSection(Start, End);
256   case wasm::WASM_SEC_ELEM:
257     return parseElemSection(Start, End);
258   case wasm::WASM_SEC_CODE:
259     return parseCodeSection(Start, End);
260   case wasm::WASM_SEC_DATA:
261     return parseDataSection(Start, End);
262   default:
263     return make_error<GenericBinaryError>("Bad section type",
264                                           object_error::parse_failed);
265   }
266 }
267 
268 Error WasmObjectFile::parseNameSection(const uint8_t *Ptr, const uint8_t *End) {
269   while (Ptr < End) {
270     uint8_t Type = readVarint7(Ptr);
271     uint32_t Size = readVaruint32(Ptr);
272     const uint8_t *SubSectionEnd = Ptr + Size;
273     switch (Type) {
274     case wasm::WASM_NAMES_FUNCTION: {
275       uint32_t Count = readVaruint32(Ptr);
276       while (Count--) {
277         uint32_t Index = readVaruint32(Ptr);
278         StringRef Name = readString(Ptr);
279         if (!Name.empty())
280           Symbols.emplace_back(Name,
281                                WasmSymbol::SymbolType::DEBUG_FUNCTION_NAME,
282                                Sections.size(), Index);
283       }
284       break;
285     }
286     // Ignore local names for now
287     case wasm::WASM_NAMES_LOCAL:
288     default:
289       Ptr += Size;
290       break;
291     }
292     if (Ptr != SubSectionEnd)
293       return make_error<GenericBinaryError>("Name sub-section ended prematurely",
294                                             object_error::parse_failed);
295   }
296 
297   if (Ptr != End)
298     return make_error<GenericBinaryError>("Name section ended prematurely",
299                                           object_error::parse_failed);
300   return Error::success();
301 }
302 
303 void WasmObjectFile::populateSymbolTable() {
304   // Add imports to symbol table
305   size_t ImportIndex = 0;
306   for (const wasm::WasmImport& Import : Imports) {
307     switch (Import.Kind) {
308     case wasm::WASM_EXTERNAL_GLOBAL:
309       assert(Import.Global.Type == wasm::WASM_TYPE_I32);
310       SymbolMap.try_emplace(Import.Field, Symbols.size());
311       Symbols.emplace_back(Import.Field, WasmSymbol::SymbolType::GLOBAL_IMPORT,
312                            ImportSection, ImportIndex);
313       DEBUG(dbgs() << "Adding import: " << Symbols.back()
314                    << " sym index:" << Symbols.size() << "\n");
315       break;
316     case wasm::WASM_EXTERNAL_FUNCTION:
317       SymbolMap.try_emplace(Import.Field, Symbols.size());
318       Symbols.emplace_back(Import.Field,
319                            WasmSymbol::SymbolType::FUNCTION_IMPORT,
320                            ImportSection, ImportIndex);
321       DEBUG(dbgs() << "Adding import: " << Symbols.back()
322                    << " sym index:" << Symbols.size() << "\n");
323       break;
324     default:
325       break;
326     }
327     ImportIndex++;
328   }
329 
330   // Add exports to symbol table
331   size_t ExportIndex = 0;
332   for (const wasm::WasmExport& Export : Exports) {
333     if (Export.Kind == wasm::WASM_EXTERNAL_FUNCTION ||
334         Export.Kind == wasm::WASM_EXTERNAL_GLOBAL) {
335       WasmSymbol::SymbolType ExportType =
336           Export.Kind == wasm::WASM_EXTERNAL_FUNCTION
337               ? WasmSymbol::SymbolType::FUNCTION_EXPORT
338               : WasmSymbol::SymbolType::GLOBAL_EXPORT;
339       auto Pair = SymbolMap.try_emplace(Export.Name, Symbols.size());
340       if (Pair.second) {
341         Symbols.emplace_back(Export.Name, ExportType,
342                              ExportSection, ExportIndex);
343         DEBUG(dbgs() << "Adding export: " << Symbols.back()
344                      << " sym index:" << Symbols.size() << "\n");
345       } else {
346         uint32_t SymIndex = Pair.first->second;
347         Symbols[SymIndex] =
348             WasmSymbol(Export.Name, ExportType, ExportSection, ExportIndex);
349         DEBUG(dbgs() << "Replacing existing symbol:  " << Symbols[SymIndex]
350                      << " sym index:" << SymIndex << "\n");
351       }
352     }
353     ExportIndex++;
354   }
355 }
356 
357 Error WasmObjectFile::parseLinkingSection(const uint8_t *Ptr,
358                                           const uint8_t *End) {
359   HasLinkingSection = true;
360 
361   // Only populate the symbol table with imports and exports if the object
362   // has a linking section (i.e. its a relocatable object file). Otherwise
363   // the global might not represent symbols at all.
364   populateSymbolTable();
365 
366   while (Ptr < End) {
367     uint8_t Type = readVarint7(Ptr);
368     uint32_t Size = readVaruint32(Ptr);
369     const uint8_t *SubSectionEnd = Ptr + Size;
370     switch (Type) {
371     case wasm::WASM_SYMBOL_INFO: {
372       uint32_t Count = readVaruint32(Ptr);
373       while (Count--) {
374         StringRef Symbol = readString(Ptr);
375         DEBUG(dbgs() << "reading syminfo: " << Symbol << "\n");
376         uint32_t Flags = readVaruint32(Ptr);
377         auto iter = SymbolMap.find(Symbol);
378         if (iter == SymbolMap.end()) {
379           return make_error<GenericBinaryError>(
380               "Invalid symbol name in linking section: " + Symbol,
381               object_error::parse_failed);
382         }
383         uint32_t SymIndex = iter->second;
384         assert(SymIndex < Symbols.size());
385         Symbols[SymIndex].Flags = Flags;
386         DEBUG(dbgs() << "Set symbol flags index:"
387                      << SymIndex << " name:"
388                      << Symbols[SymIndex].Name << " exptected:"
389                      << Symbol << " flags: " << Flags << "\n");
390       }
391       break;
392     }
393     case wasm::WASM_DATA_SIZE:
394       LinkingData.DataSize = readVaruint32(Ptr);
395       break;
396     case wasm::WASM_DATA_ALIGNMENT:
397       LinkingData.DataAlignment = readVaruint32(Ptr);
398       break;
399     case wasm::WASM_SEGMENT_NAMES: {
400       uint32_t Count = readVaruint32(Ptr);
401       if (Count > DataSegments.size())
402         return make_error<GenericBinaryError>("Too many segment names",
403                                               object_error::parse_failed);
404       for (uint32_t i = 0; i < Count; i++)
405         DataSegments[i].Data.Name = readString(Ptr);
406       break;
407     }
408     case wasm::WASM_STACK_POINTER:
409     default:
410       Ptr += Size;
411       break;
412     }
413     if (Ptr != SubSectionEnd)
414       return make_error<GenericBinaryError>(
415           "Linking sub-section ended prematurely", object_error::parse_failed);
416   }
417   if (Ptr != End)
418     return make_error<GenericBinaryError>("Linking section ended prematurely",
419                                           object_error::parse_failed);
420   return Error::success();
421 }
422 
423 WasmSection* WasmObjectFile::findCustomSectionByName(StringRef Name) {
424   for (WasmSection& Section : Sections) {
425     if (Section.Type == wasm::WASM_SEC_CUSTOM && Section.Name == Name)
426       return &Section;
427   }
428   return nullptr;
429 }
430 
431 WasmSection* WasmObjectFile::findSectionByType(uint32_t Type) {
432   assert(Type != wasm::WASM_SEC_CUSTOM);
433   for (WasmSection& Section : Sections) {
434     if (Section.Type == Type)
435       return &Section;
436   }
437   return nullptr;
438 }
439 
440 Error WasmObjectFile::parseRelocSection(StringRef Name, const uint8_t *Ptr,
441                                         const uint8_t *End) {
442   uint8_t SectionCode = readVarint7(Ptr);
443   WasmSection* Section = nullptr;
444   if (SectionCode == wasm::WASM_SEC_CUSTOM) {
445     StringRef Name = readString(Ptr);
446     Section = findCustomSectionByName(Name);
447   } else {
448     Section = findSectionByType(SectionCode);
449   }
450   if (!Section)
451     return make_error<GenericBinaryError>("Invalid section code",
452                                           object_error::parse_failed);
453   uint32_t RelocCount = readVaruint32(Ptr);
454   while (RelocCount--) {
455     wasm::WasmRelocation Reloc;
456     memset(&Reloc, 0, sizeof(Reloc));
457     Reloc.Type = readVaruint32(Ptr);
458     Reloc.Offset = readVaruint32(Ptr);
459     Reloc.Index = readVaruint32(Ptr);
460     switch (Reloc.Type) {
461     case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
462     case wasm::R_WEBASSEMBLY_TABLE_INDEX_SLEB:
463     case wasm::R_WEBASSEMBLY_TABLE_INDEX_I32:
464     case wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB:
465     case wasm::R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
466       break;
467     case wasm::R_WEBASSEMBLY_MEMORY_ADDR_LEB:
468     case wasm::R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
469     case wasm::R_WEBASSEMBLY_MEMORY_ADDR_I32:
470       Reloc.Addend = readVarint32(Ptr);
471       break;
472     default:
473       return make_error<GenericBinaryError>("Bad relocation type: " +
474                                                 Twine(Reloc.Type),
475                                             object_error::parse_failed);
476     }
477     Section->Relocations.push_back(Reloc);
478   }
479   if (Ptr != End)
480     return make_error<GenericBinaryError>("Reloc section ended prematurely",
481                                           object_error::parse_failed);
482   return Error::success();
483 }
484 
485 Error WasmObjectFile::parseCustomSection(WasmSection &Sec,
486                                          const uint8_t *Ptr, const uint8_t *End) {
487   Sec.Name = readString(Ptr);
488   if (Sec.Name == "name") {
489     if (Error Err = parseNameSection(Ptr, End))
490       return Err;
491   } else if (Sec.Name == "linking") {
492     if (Error Err = parseLinkingSection(Ptr, End))
493       return Err;
494   } else if (Sec.Name.startswith("reloc.")) {
495     if (Error Err = parseRelocSection(Sec.Name, Ptr, End))
496       return Err;
497   }
498   return Error::success();
499 }
500 
501 Error WasmObjectFile::parseTypeSection(const uint8_t *Ptr, const uint8_t *End) {
502   uint32_t Count = readVaruint32(Ptr);
503   Signatures.reserve(Count);
504   while (Count--) {
505     wasm::WasmSignature Sig;
506     Sig.ReturnType = wasm::WASM_TYPE_NORESULT;
507     int8_t Form = readVarint7(Ptr);
508     if (Form != wasm::WASM_TYPE_FUNC) {
509       return make_error<GenericBinaryError>("Invalid signature type",
510                                             object_error::parse_failed);
511     }
512     uint32_t ParamCount = readVaruint32(Ptr);
513     Sig.ParamTypes.reserve(ParamCount);
514     while (ParamCount--) {
515       uint32_t ParamType = readVarint7(Ptr);
516       Sig.ParamTypes.push_back(ParamType);
517     }
518     uint32_t ReturnCount = readVaruint32(Ptr);
519     if (ReturnCount) {
520       if (ReturnCount != 1) {
521         return make_error<GenericBinaryError>(
522             "Multiple return types not supported", object_error::parse_failed);
523       }
524       Sig.ReturnType = readVarint7(Ptr);
525     }
526     Signatures.push_back(Sig);
527   }
528   if (Ptr != End)
529     return make_error<GenericBinaryError>("Type section ended prematurely",
530                                           object_error::parse_failed);
531   return Error::success();
532 }
533 
534 Error WasmObjectFile::parseImportSection(const uint8_t *Ptr, const uint8_t *End) {
535   ImportSection = Sections.size();
536   uint32_t Count = readVaruint32(Ptr);
537   Imports.reserve(Count);
538   for (uint32_t i = 0; i < Count; i++) {
539     wasm::WasmImport Im;
540     Im.Module = readString(Ptr);
541     Im.Field = readString(Ptr);
542     Im.Kind = readUint8(Ptr);
543     switch (Im.Kind) {
544     case wasm::WASM_EXTERNAL_FUNCTION:
545       NumImportedFunctions++;
546       Im.SigIndex = readVaruint32(Ptr);
547       break;
548     case wasm::WASM_EXTERNAL_GLOBAL:
549       NumImportedGlobals++;
550       Im.Global.Type = readVarint7(Ptr);
551       Im.Global.Mutable = readVaruint1(Ptr);
552       break;
553     case wasm::WASM_EXTERNAL_MEMORY:
554       Im.Memory = readLimits(Ptr);
555       break;
556     case wasm::WASM_EXTERNAL_TABLE:
557       Im.Table = readTable(Ptr);
558       if (Im.Table.ElemType != wasm::WASM_TYPE_ANYFUNC)
559         return make_error<GenericBinaryError>("Invalid table element type",
560                                               object_error::parse_failed);
561       break;
562     default:
563       return make_error<GenericBinaryError>(
564           "Unexpected import kind", object_error::parse_failed);
565     }
566     Imports.push_back(Im);
567   }
568   if (Ptr != End)
569     return make_error<GenericBinaryError>("Import section ended prematurely",
570                                           object_error::parse_failed);
571   return Error::success();
572 }
573 
574 Error WasmObjectFile::parseFunctionSection(const uint8_t *Ptr, const uint8_t *End) {
575   uint32_t Count = readVaruint32(Ptr);
576   FunctionTypes.reserve(Count);
577   while (Count--) {
578     FunctionTypes.push_back(readVaruint32(Ptr));
579   }
580   if (Ptr != End)
581     return make_error<GenericBinaryError>("Function section ended prematurely",
582                                           object_error::parse_failed);
583   return Error::success();
584 }
585 
586 Error WasmObjectFile::parseTableSection(const uint8_t *Ptr, const uint8_t *End) {
587   uint32_t Count = readVaruint32(Ptr);
588   Tables.reserve(Count);
589   while (Count--) {
590     Tables.push_back(readTable(Ptr));
591     if (Tables.back().ElemType != wasm::WASM_TYPE_ANYFUNC) {
592       return make_error<GenericBinaryError>("Invalid table element type",
593                                             object_error::parse_failed);
594     }
595   }
596   if (Ptr != End)
597     return make_error<GenericBinaryError>("Table section ended prematurely",
598                                           object_error::parse_failed);
599   return Error::success();
600 }
601 
602 Error WasmObjectFile::parseMemorySection(const uint8_t *Ptr, const uint8_t *End) {
603   uint32_t Count = readVaruint32(Ptr);
604   Memories.reserve(Count);
605   while (Count--) {
606     Memories.push_back(readLimits(Ptr));
607   }
608   if (Ptr != End)
609     return make_error<GenericBinaryError>("Memory section ended prematurely",
610                                           object_error::parse_failed);
611   return Error::success();
612 }
613 
614 Error WasmObjectFile::parseGlobalSection(const uint8_t *Ptr, const uint8_t *End) {
615   uint32_t Count = readVaruint32(Ptr);
616   Globals.reserve(Count);
617   while (Count--) {
618     wasm::WasmGlobal Global;
619     Global.Type = readVarint7(Ptr);
620     Global.Mutable = readVaruint1(Ptr);
621     if (Error Err = readInitExpr(Global.InitExpr, Ptr))
622       return Err;
623     Globals.push_back(Global);
624   }
625   if (Ptr != End)
626     return make_error<GenericBinaryError>("Global section ended prematurely",
627                                           object_error::parse_failed);
628   return Error::success();
629 }
630 
631 Error WasmObjectFile::parseExportSection(const uint8_t *Ptr, const uint8_t *End) {
632   ExportSection = Sections.size();
633   uint32_t Count = readVaruint32(Ptr);
634   Exports.reserve(Count);
635   for (uint32_t i = 0; i < Count; i++) {
636     wasm::WasmExport Ex;
637     Ex.Name = readString(Ptr);
638     Ex.Kind = readUint8(Ptr);
639     Ex.Index = readVaruint32(Ptr);
640     switch (Ex.Kind) {
641     case wasm::WASM_EXTERNAL_FUNCTION:
642       if (Ex.Index >= FunctionTypes.size() + NumImportedFunctions)
643         return make_error<GenericBinaryError>("Invalid function export",
644                                               object_error::parse_failed);
645       break;
646     case wasm::WASM_EXTERNAL_GLOBAL: {
647       if (Ex.Index >= Globals.size() + NumImportedGlobals)
648         return make_error<GenericBinaryError>("Invalid global export",
649                                               object_error::parse_failed);
650       break;
651     }
652     case wasm::WASM_EXTERNAL_MEMORY:
653     case wasm::WASM_EXTERNAL_TABLE:
654       break;
655     default:
656       return make_error<GenericBinaryError>(
657           "Unexpected export kind", object_error::parse_failed);
658     }
659     Exports.push_back(Ex);
660   }
661   if (Ptr != End)
662     return make_error<GenericBinaryError>("Export section ended prematurely",
663                                           object_error::parse_failed);
664   return Error::success();
665 }
666 
667 Error WasmObjectFile::parseStartSection(const uint8_t *Ptr, const uint8_t *End) {
668   StartFunction = readVaruint32(Ptr);
669   if (StartFunction >= FunctionTypes.size())
670     return make_error<GenericBinaryError>("Invalid start function",
671                                           object_error::parse_failed);
672   return Error::success();
673 }
674 
675 Error WasmObjectFile::parseCodeSection(const uint8_t *Ptr, const uint8_t *End) {
676   uint32_t FunctionCount = readVaruint32(Ptr);
677   if (FunctionCount != FunctionTypes.size()) {
678     return make_error<GenericBinaryError>("Invalid function count",
679                                           object_error::parse_failed);
680   }
681 
682   CodeSection = ArrayRef<uint8_t>(Ptr, End - Ptr);
683 
684   while (FunctionCount--) {
685     wasm::WasmFunction Function;
686     uint32_t FunctionSize = readVaruint32(Ptr);
687     const uint8_t *FunctionEnd = Ptr + FunctionSize;
688 
689     uint32_t NumLocalDecls = readVaruint32(Ptr);
690     Function.Locals.reserve(NumLocalDecls);
691     while (NumLocalDecls--) {
692       wasm::WasmLocalDecl Decl;
693       Decl.Count = readVaruint32(Ptr);
694       Decl.Type = readVarint7(Ptr);
695       Function.Locals.push_back(Decl);
696     }
697 
698     uint32_t BodySize = FunctionEnd - Ptr;
699     Function.Body = ArrayRef<uint8_t>(Ptr, BodySize);
700     Ptr += BodySize;
701     assert(Ptr == FunctionEnd);
702     Functions.push_back(Function);
703   }
704   if (Ptr != End)
705     return make_error<GenericBinaryError>("Code section ended prematurely",
706                                           object_error::parse_failed);
707   return Error::success();
708 }
709 
710 Error WasmObjectFile::parseElemSection(const uint8_t *Ptr, const uint8_t *End) {
711   uint32_t Count = readVaruint32(Ptr);
712   ElemSegments.reserve(Count);
713   while (Count--) {
714     wasm::WasmElemSegment Segment;
715     Segment.TableIndex = readVaruint32(Ptr);
716     if (Segment.TableIndex != 0) {
717       return make_error<GenericBinaryError>("Invalid TableIndex",
718                                             object_error::parse_failed);
719     }
720     if (Error Err = readInitExpr(Segment.Offset, Ptr))
721       return Err;
722     uint32_t NumElems = readVaruint32(Ptr);
723     while (NumElems--) {
724       Segment.Functions.push_back(readVaruint32(Ptr));
725     }
726     ElemSegments.push_back(Segment);
727   }
728   if (Ptr != End)
729     return make_error<GenericBinaryError>("Elem section ended prematurely",
730                                           object_error::parse_failed);
731   return Error::success();
732 }
733 
734 Error WasmObjectFile::parseDataSection(const uint8_t *Ptr, const uint8_t *End) {
735   const uint8_t *Start = Ptr;
736   uint32_t Count = readVaruint32(Ptr);
737   DataSegments.reserve(Count);
738   while (Count--) {
739     WasmSegment Segment;
740     Segment.Data.MemoryIndex = readVaruint32(Ptr);
741     if (Error Err = readInitExpr(Segment.Data.Offset, Ptr))
742       return Err;
743     uint32_t Size = readVaruint32(Ptr);
744     Segment.Data.Content = ArrayRef<uint8_t>(Ptr, Size);
745     Segment.SectionOffset = Ptr - Start;
746     Ptr += Size;
747     DataSegments.push_back(Segment);
748   }
749   if (Ptr != End)
750     return make_error<GenericBinaryError>("Data section ended prematurely",
751                                           object_error::parse_failed);
752   return Error::success();
753 }
754 
755 const uint8_t *WasmObjectFile::getPtr(size_t Offset) const {
756   return reinterpret_cast<const uint8_t *>(getData().substr(Offset, 1).data());
757 }
758 
759 const wasm::WasmObjectHeader &WasmObjectFile::getHeader() const {
760   return Header;
761 }
762 
763 void WasmObjectFile::moveSymbolNext(DataRefImpl &Symb) const { Symb.d.a++; }
764 
765 uint32_t WasmObjectFile::getSymbolFlags(DataRefImpl Symb) const {
766   uint32_t Result = SymbolRef::SF_None;
767   const WasmSymbol &Sym = getWasmSymbol(Symb);
768 
769   DEBUG(dbgs() << "getSymbolFlags: ptr=" << &Sym << " " << Sym << "\n");
770   if (Sym.isWeak())
771     Result |= SymbolRef::SF_Weak;
772   if (!Sym.isLocal())
773     Result |= SymbolRef::SF_Global;
774 
775   switch (Sym.Type) {
776   case WasmSymbol::SymbolType::FUNCTION_IMPORT:
777     Result |= SymbolRef::SF_Undefined | SymbolRef::SF_Executable;
778     break;
779   case WasmSymbol::SymbolType::FUNCTION_EXPORT:
780     Result |= SymbolRef::SF_Executable;
781     break;
782   case WasmSymbol::SymbolType::DEBUG_FUNCTION_NAME:
783     Result |= SymbolRef::SF_Executable;
784     Result |= SymbolRef::SF_FormatSpecific;
785     break;
786   case WasmSymbol::SymbolType::GLOBAL_IMPORT:
787     Result |= SymbolRef::SF_Undefined;
788     break;
789   case WasmSymbol::SymbolType::GLOBAL_EXPORT:
790     break;
791   }
792 
793   return Result;
794 }
795 
796 basic_symbol_iterator WasmObjectFile::symbol_begin() const {
797   DataRefImpl Ref;
798   Ref.d.a = 0;
799   return BasicSymbolRef(Ref, this);
800 }
801 
802 basic_symbol_iterator WasmObjectFile::symbol_end() const {
803   DataRefImpl Ref;
804   Ref.d.a = Symbols.size();
805   return BasicSymbolRef(Ref, this);
806 }
807 
808 const WasmSymbol &WasmObjectFile::getWasmSymbol(const DataRefImpl &Symb) const {
809   return Symbols[Symb.d.a];
810 }
811 
812 const WasmSymbol &WasmObjectFile::getWasmSymbol(const SymbolRef &Symb) const {
813   return getWasmSymbol(Symb.getRawDataRefImpl());
814 }
815 
816 Expected<StringRef> WasmObjectFile::getSymbolName(DataRefImpl Symb) const {
817   return getWasmSymbol(Symb).Name;
818 }
819 
820 Expected<uint64_t> WasmObjectFile::getSymbolAddress(DataRefImpl Symb) const {
821   return getSymbolValue(Symb);
822 }
823 
824 uint64_t WasmObjectFile::getWasmSymbolValue(const WasmSymbol& Sym) const {
825   switch (Sym.Type) {
826   case WasmSymbol::SymbolType::FUNCTION_IMPORT:
827   case WasmSymbol::SymbolType::GLOBAL_IMPORT:
828     return 0;
829   case WasmSymbol::SymbolType::FUNCTION_EXPORT:
830     return Exports[Sym.ElementIndex].Index;
831   case WasmSymbol::SymbolType::GLOBAL_EXPORT: {
832     uint32_t GlobalIndex = Exports[Sym.ElementIndex].Index - NumImportedGlobals;
833     assert(GlobalIndex < Globals.size());
834     const wasm::WasmGlobal& Global = Globals[GlobalIndex];
835     // WasmSymbols correspond only to I32_CONST globals
836     assert(Global.InitExpr.Opcode == wasm::WASM_OPCODE_I32_CONST);
837     return Global.InitExpr.Value.Int32;
838   }
839   case WasmSymbol::SymbolType::DEBUG_FUNCTION_NAME:
840     return Sym.ElementIndex;
841   }
842   llvm_unreachable("invalid symbol type");
843 }
844 
845 uint64_t WasmObjectFile::getSymbolValueImpl(DataRefImpl Symb) const {
846   return getWasmSymbolValue(getWasmSymbol(Symb));
847 }
848 
849 uint32_t WasmObjectFile::getSymbolAlignment(DataRefImpl Symb) const {
850   llvm_unreachable("not yet implemented");
851   return 0;
852 }
853 
854 uint64_t WasmObjectFile::getCommonSymbolSizeImpl(DataRefImpl Symb) const {
855   llvm_unreachable("not yet implemented");
856   return 0;
857 }
858 
859 Expected<SymbolRef::Type>
860 WasmObjectFile::getSymbolType(DataRefImpl Symb) const {
861   const WasmSymbol &Sym = getWasmSymbol(Symb);
862 
863   switch (Sym.Type) {
864   case WasmSymbol::SymbolType::FUNCTION_IMPORT:
865   case WasmSymbol::SymbolType::FUNCTION_EXPORT:
866   case WasmSymbol::SymbolType::DEBUG_FUNCTION_NAME:
867     return SymbolRef::ST_Function;
868   case WasmSymbol::SymbolType::GLOBAL_IMPORT:
869   case WasmSymbol::SymbolType::GLOBAL_EXPORT:
870     return SymbolRef::ST_Data;
871   }
872 
873   llvm_unreachable("Unknown WasmSymbol::SymbolType");
874   return SymbolRef::ST_Other;
875 }
876 
877 Expected<section_iterator>
878 WasmObjectFile::getSymbolSection(DataRefImpl Symb) const {
879   DataRefImpl Ref;
880   Ref.d.a = getWasmSymbol(Symb).Section;
881   return section_iterator(SectionRef(Ref, this));
882 }
883 
884 void WasmObjectFile::moveSectionNext(DataRefImpl &Sec) const { Sec.d.a++; }
885 
886 std::error_code WasmObjectFile::getSectionName(DataRefImpl Sec,
887                                                StringRef &Res) const {
888   const WasmSection &S = Sections[Sec.d.a];
889 #define ECase(X)                                                               \
890   case wasm::WASM_SEC_##X:                                                     \
891     Res = #X;                                                                  \
892     break
893   switch (S.Type) {
894     ECase(TYPE);
895     ECase(IMPORT);
896     ECase(FUNCTION);
897     ECase(TABLE);
898     ECase(MEMORY);
899     ECase(GLOBAL);
900     ECase(EXPORT);
901     ECase(START);
902     ECase(ELEM);
903     ECase(CODE);
904     ECase(DATA);
905   case wasm::WASM_SEC_CUSTOM:
906     Res = S.Name;
907     break;
908   default:
909     return object_error::invalid_section_index;
910   }
911 #undef ECase
912   return std::error_code();
913 }
914 
915 uint64_t WasmObjectFile::getSectionAddress(DataRefImpl Sec) const { return 0; }
916 
917 uint64_t WasmObjectFile::getSectionIndex(DataRefImpl Sec) const {
918   return Sec.d.a;
919 }
920 
921 uint64_t WasmObjectFile::getSectionSize(DataRefImpl Sec) const {
922   const WasmSection &S = Sections[Sec.d.a];
923   return S.Content.size();
924 }
925 
926 std::error_code WasmObjectFile::getSectionContents(DataRefImpl Sec,
927                                                    StringRef &Res) const {
928   const WasmSection &S = Sections[Sec.d.a];
929   // This will never fail since wasm sections can never be empty (user-sections
930   // must have a name and non-user sections each have a defined structure).
931   Res = StringRef(reinterpret_cast<const char *>(S.Content.data()),
932                   S.Content.size());
933   return std::error_code();
934 }
935 
936 uint64_t WasmObjectFile::getSectionAlignment(DataRefImpl Sec) const {
937   return 1;
938 }
939 
940 bool WasmObjectFile::isSectionCompressed(DataRefImpl Sec) const {
941   return false;
942 }
943 
944 bool WasmObjectFile::isSectionText(DataRefImpl Sec) const {
945   return getWasmSection(Sec).Type == wasm::WASM_SEC_CODE;
946 }
947 
948 bool WasmObjectFile::isSectionData(DataRefImpl Sec) const {
949   return getWasmSection(Sec).Type == wasm::WASM_SEC_DATA;
950 }
951 
952 bool WasmObjectFile::isSectionBSS(DataRefImpl Sec) const { return false; }
953 
954 bool WasmObjectFile::isSectionVirtual(DataRefImpl Sec) const { return false; }
955 
956 bool WasmObjectFile::isSectionBitcode(DataRefImpl Sec) const { return false; }
957 
958 relocation_iterator WasmObjectFile::section_rel_begin(DataRefImpl Ref) const {
959   DataRefImpl RelocRef;
960   RelocRef.d.a = Ref.d.a;
961   RelocRef.d.b = 0;
962   return relocation_iterator(RelocationRef(RelocRef, this));
963 }
964 
965 relocation_iterator WasmObjectFile::section_rel_end(DataRefImpl Ref) const {
966   const WasmSection &Sec = getWasmSection(Ref);
967   DataRefImpl RelocRef;
968   RelocRef.d.a = Ref.d.a;
969   RelocRef.d.b = Sec.Relocations.size();
970   return relocation_iterator(RelocationRef(RelocRef, this));
971 }
972 
973 void WasmObjectFile::moveRelocationNext(DataRefImpl &Rel) const {
974   Rel.d.b++;
975 }
976 
977 uint64_t WasmObjectFile::getRelocationOffset(DataRefImpl Ref) const {
978   const wasm::WasmRelocation &Rel = getWasmRelocation(Ref);
979   return Rel.Offset;
980 }
981 
982 symbol_iterator WasmObjectFile::getRelocationSymbol(DataRefImpl Rel) const {
983   llvm_unreachable("not yet implemented");
984   SymbolRef Ref;
985   return symbol_iterator(Ref);
986 }
987 
988 uint64_t WasmObjectFile::getRelocationType(DataRefImpl Ref) const {
989   const wasm::WasmRelocation &Rel = getWasmRelocation(Ref);
990   return Rel.Type;
991 }
992 
993 void WasmObjectFile::getRelocationTypeName(
994     DataRefImpl Ref, SmallVectorImpl<char> &Result) const {
995   const wasm::WasmRelocation& Rel = getWasmRelocation(Ref);
996   StringRef Res = "Unknown";
997 
998 #define WASM_RELOC(name, value)  \
999   case wasm::name:              \
1000     Res = #name;               \
1001     break;
1002 
1003   switch (Rel.Type) {
1004 #include "llvm/BinaryFormat/WasmRelocs/WebAssembly.def"
1005   }
1006 
1007 #undef WASM_RELOC
1008 
1009   Result.append(Res.begin(), Res.end());
1010 }
1011 
1012 section_iterator WasmObjectFile::section_begin() const {
1013   DataRefImpl Ref;
1014   Ref.d.a = 0;
1015   return section_iterator(SectionRef(Ref, this));
1016 }
1017 
1018 section_iterator WasmObjectFile::section_end() const {
1019   DataRefImpl Ref;
1020   Ref.d.a = Sections.size();
1021   return section_iterator(SectionRef(Ref, this));
1022 }
1023 
1024 uint8_t WasmObjectFile::getBytesInAddress() const { return 4; }
1025 
1026 StringRef WasmObjectFile::getFileFormatName() const { return "WASM"; }
1027 
1028 unsigned WasmObjectFile::getArch() const { return Triple::wasm32; }
1029 
1030 SubtargetFeatures WasmObjectFile::getFeatures() const {
1031   return SubtargetFeatures();
1032 }
1033 
1034 bool WasmObjectFile::isRelocatableObject() const {
1035   return HasLinkingSection;
1036 }
1037 
1038 const WasmSection &WasmObjectFile::getWasmSection(DataRefImpl Ref) const {
1039   assert(Ref.d.a < Sections.size());
1040   return Sections[Ref.d.a];
1041 }
1042 
1043 const WasmSection &
1044 WasmObjectFile::getWasmSection(const SectionRef &Section) const {
1045   return getWasmSection(Section.getRawDataRefImpl());
1046 }
1047 
1048 const wasm::WasmRelocation &
1049 WasmObjectFile::getWasmRelocation(const RelocationRef &Ref) const {
1050   return getWasmRelocation(Ref.getRawDataRefImpl());
1051 }
1052 
1053 const wasm::WasmRelocation &
1054 WasmObjectFile::getWasmRelocation(DataRefImpl Ref) const {
1055   assert(Ref.d.a < Sections.size());
1056   const WasmSection& Sec = Sections[Ref.d.a];
1057   assert(Ref.d.b < Sec.Relocations.size());
1058   return Sec.Relocations[Ref.d.b];
1059 }
1060