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1 //===-- ArchiveReader.cpp - Read LLVM archive files -------------*- C++ -*-===//
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 // Builds up standard unix archive files (.a) containing LLVM bitcode.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "ArchiveInternals.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/Bitcode/ReaderWriter.h"
17 #include "llvm/Support/MemoryBuffer.h"
18 #include "llvm/Module.h"
19 #include <cstdio>
20 #include <cstdlib>
21 #include <memory>
22 using namespace llvm;
23 
24 /// Read a variable-bit-rate encoded unsigned integer
readInteger(const char * & At,const char * End)25 static inline unsigned readInteger(const char*&At, const char*End) {
26   unsigned Shift = 0;
27   unsigned Result = 0;
28 
29   do {
30     if (At == End)
31       return Result;
32     Result |= (unsigned)((*At++) & 0x7F) << Shift;
33     Shift += 7;
34   } while (At[-1] & 0x80);
35   return Result;
36 }
37 
38 // Completely parse the Archive's symbol table and populate symTab member var.
39 bool
parseSymbolTable(const void * data,unsigned size,std::string * error)40 Archive::parseSymbolTable(const void* data, unsigned size, std::string* error) {
41   const char* At = (const char*) data;
42   const char* End = At + size;
43   while (At < End) {
44     unsigned offset = readInteger(At, End);
45     if (At == End) {
46       if (error)
47         *error = "Ran out of data reading vbr_uint for symtab offset!";
48       return false;
49     }
50     unsigned length = readInteger(At, End);
51     if (At == End) {
52       if (error)
53         *error = "Ran out of data reading vbr_uint for symtab length!";
54       return false;
55     }
56     if (At + length > End) {
57       if (error)
58         *error = "Malformed symbol table: length not consistent with size";
59       return false;
60     }
61     // we don't care if it can't be inserted (duplicate entry)
62     symTab.insert(std::make_pair(std::string(At, length), offset));
63     At += length;
64   }
65   symTabSize = size;
66   return true;
67 }
68 
69 // This member parses an ArchiveMemberHeader that is presumed to be pointed to
70 // by At. The At pointer is updated to the byte just after the header, which
71 // can be variable in size.
72 ArchiveMember*
parseMemberHeader(const char * & At,const char * End,std::string * error)73 Archive::parseMemberHeader(const char*& At, const char* End, std::string* error)
74 {
75   if (At + sizeof(ArchiveMemberHeader) >= End) {
76     if (error)
77       *error = "Unexpected end of file";
78     return 0;
79   }
80 
81   // Cast archive member header
82   const ArchiveMemberHeader* Hdr = (const ArchiveMemberHeader*)At;
83   At += sizeof(ArchiveMemberHeader);
84 
85   int flags = 0;
86   int MemberSize = atoi(Hdr->size);
87   assert(MemberSize >= 0);
88 
89   // Check the size of the member for sanity
90   if (At + MemberSize > End) {
91     if (error)
92       *error = "invalid member length in archive file";
93     return 0;
94   }
95 
96   // Check the member signature
97   if (!Hdr->checkSignature()) {
98     if (error)
99       *error = "invalid file member signature";
100     return 0;
101   }
102 
103   // Convert and check the member name
104   // The empty name ( '/' and 15 blanks) is for a foreign (non-LLVM) symbol
105   // table. The special name "//" and 14 blanks is for a string table, used
106   // for long file names. This library doesn't generate either of those but
107   // it will accept them. If the name starts with #1/ and the remainder is
108   // digits, then those digits specify the length of the name that is
109   // stored immediately following the header. The special name
110   // __LLVM_SYM_TAB__ identifies the symbol table for LLVM bitcode.
111   // Anything else is a regular, short filename that is terminated with
112   // a '/' and blanks.
113 
114   std::string pathname;
115   switch (Hdr->name[0]) {
116     case '#':
117       if (Hdr->name[1] == '1' && Hdr->name[2] == '/') {
118         if (isdigit(Hdr->name[3])) {
119           unsigned len = atoi(&Hdr->name[3]);
120           const char *nulp = (const char *)memchr(At, '\0', len);
121           pathname.assign(At, nulp != 0 ? (uintptr_t)(nulp - At) : len);
122           At += len;
123           MemberSize -= len;
124           flags |= ArchiveMember::HasLongFilenameFlag;
125         } else {
126           if (error)
127             *error = "invalid long filename";
128           return 0;
129         }
130       } else if (Hdr->name[1] == '_' &&
131                  (0 == memcmp(Hdr->name, ARFILE_LLVM_SYMTAB_NAME, 16))) {
132         // The member is using a long file name (>15 chars) format.
133         // This format is standard for 4.4BSD and Mac OSX operating
134         // systems. LLVM uses it similarly. In this format, the
135         // remainder of the name field (after #1/) specifies the
136         // length of the file name which occupy the first bytes of
137         // the member's data. The pathname already has the #1/ stripped.
138         pathname.assign(ARFILE_LLVM_SYMTAB_NAME);
139         flags |= ArchiveMember::LLVMSymbolTableFlag;
140       }
141       break;
142     case '/':
143       if (Hdr->name[1]== '/') {
144         if (0 == memcmp(Hdr->name, ARFILE_STRTAB_NAME, 16)) {
145           pathname.assign(ARFILE_STRTAB_NAME);
146           flags |= ArchiveMember::StringTableFlag;
147         } else {
148           if (error)
149             *error = "invalid string table name";
150           return 0;
151         }
152       } else if (Hdr->name[1] == ' ') {
153         if (0 == memcmp(Hdr->name, ARFILE_SVR4_SYMTAB_NAME, 16)) {
154           pathname.assign(ARFILE_SVR4_SYMTAB_NAME);
155           flags |= ArchiveMember::SVR4SymbolTableFlag;
156         } else {
157           if (error)
158             *error = "invalid SVR4 symbol table name";
159           return 0;
160         }
161       } else if (isdigit(Hdr->name[1])) {
162         unsigned index = atoi(&Hdr->name[1]);
163         if (index < strtab.length()) {
164           const char* namep = strtab.c_str() + index;
165           const char* endp = strtab.c_str() + strtab.length();
166           const char* p = namep;
167           const char* last_p = p;
168           while (p < endp) {
169             if (*p == '\n' && *last_p == '/') {
170               pathname.assign(namep, last_p - namep);
171               flags |= ArchiveMember::HasLongFilenameFlag;
172               break;
173             }
174             last_p = p;
175             p++;
176           }
177           if (p >= endp) {
178             if (error)
179               *error = "missing name termiantor in string table";
180             return 0;
181           }
182         } else {
183           if (error)
184             *error = "name index beyond string table";
185           return 0;
186         }
187       }
188       break;
189     case '_':
190       if (Hdr->name[1] == '_' &&
191           (0 == memcmp(Hdr->name, ARFILE_BSD4_SYMTAB_NAME, 16))) {
192         pathname.assign(ARFILE_BSD4_SYMTAB_NAME);
193         flags |= ArchiveMember::BSD4SymbolTableFlag;
194         break;
195       }
196       /* FALL THROUGH */
197 
198     default:
199       const char* slash = (const char*) memchr(Hdr->name, '/', 16);
200       if (slash == 0)
201         slash = Hdr->name + 16;
202       pathname.assign(Hdr->name, slash - Hdr->name);
203       break;
204   }
205 
206   // Determine if this is a bitcode file
207   switch (sys::IdentifyFileType(At, 4)) {
208     case sys::Bitcode_FileType:
209       flags |= ArchiveMember::BitcodeFlag;
210       break;
211     default:
212       flags &= ~ArchiveMember::BitcodeFlag;
213       break;
214   }
215 
216   // Instantiate the ArchiveMember to be filled
217   ArchiveMember* member = new ArchiveMember(this);
218 
219   // Fill in fields of the ArchiveMember
220   member->parent = this;
221   member->path.set(pathname);
222   member->info.fileSize = MemberSize;
223   member->info.modTime.fromEpochTime(atoi(Hdr->date));
224   unsigned int mode;
225   sscanf(Hdr->mode, "%o", &mode);
226   member->info.mode = mode;
227   member->info.user = atoi(Hdr->uid);
228   member->info.group = atoi(Hdr->gid);
229   member->flags = flags;
230   member->data = At;
231 
232   return member;
233 }
234 
235 bool
checkSignature(std::string * error)236 Archive::checkSignature(std::string* error) {
237   // Check the magic string at file's header
238   if (mapfile->getBufferSize() < 8 || memcmp(base, ARFILE_MAGIC, 8)) {
239     if (error)
240       *error = "invalid signature for an archive file";
241     return false;
242   }
243   return true;
244 }
245 
246 // This function loads the entire archive and fully populates its ilist with
247 // the members of the archive file. This is typically used in preparation for
248 // editing the contents of the archive.
249 bool
loadArchive(std::string * error)250 Archive::loadArchive(std::string* error) {
251 
252   // Set up parsing
253   members.clear();
254   symTab.clear();
255   const char *At = base;
256   const char *End = mapfile->getBufferEnd();
257 
258   if (!checkSignature(error))
259     return false;
260 
261   At += 8;  // Skip the magic string.
262 
263   bool seenSymbolTable = false;
264   bool foundFirstFile = false;
265   while (At < End) {
266     // parse the member header
267     const char* Save = At;
268     ArchiveMember* mbr = parseMemberHeader(At, End, error);
269     if (!mbr)
270       return false;
271 
272     // check if this is the foreign symbol table
273     if (mbr->isSVR4SymbolTable() || mbr->isBSD4SymbolTable()) {
274       // We just save this but don't do anything special
275       // with it. It doesn't count as the "first file".
276       if (foreignST) {
277         // What? Multiple foreign symbol tables? Just chuck it
278         // and retain the last one found.
279         delete foreignST;
280       }
281       foreignST = mbr;
282       At += mbr->getSize();
283       if ((intptr_t(At) & 1) == 1)
284         At++;
285     } else if (mbr->isStringTable()) {
286       // Simply suck the entire string table into a string
287       // variable. This will be used to get the names of the
288       // members that use the "/ddd" format for their names
289       // (SVR4 style long names).
290       strtab.assign(At, mbr->getSize());
291       At += mbr->getSize();
292       if ((intptr_t(At) & 1) == 1)
293         At++;
294       delete mbr;
295     } else if (mbr->isLLVMSymbolTable()) {
296       // This is the LLVM symbol table for the archive. If we've seen it
297       // already, its an error. Otherwise, parse the symbol table and move on.
298       if (seenSymbolTable) {
299         if (error)
300           *error = "invalid archive: multiple symbol tables";
301         return false;
302       }
303       if (!parseSymbolTable(mbr->getData(), mbr->getSize(), error))
304         return false;
305       seenSymbolTable = true;
306       At += mbr->getSize();
307       if ((intptr_t(At) & 1) == 1)
308         At++;
309       delete mbr; // We don't need this member in the list of members.
310     } else {
311       // This is just a regular file. If its the first one, save its offset.
312       // Otherwise just push it on the list and move on to the next file.
313       if (!foundFirstFile) {
314         firstFileOffset = Save - base;
315         foundFirstFile = true;
316       }
317       members.push_back(mbr);
318       At += mbr->getSize();
319       if ((intptr_t(At) & 1) == 1)
320         At++;
321     }
322   }
323   return true;
324 }
325 
326 // Open and completely load the archive file.
327 Archive*
OpenAndLoad(const sys::Path & file,LLVMContext & C,std::string * ErrorMessage)328 Archive::OpenAndLoad(const sys::Path& file, LLVMContext& C,
329                      std::string* ErrorMessage) {
330   std::auto_ptr<Archive> result ( new Archive(file, C));
331   if (result->mapToMemory(ErrorMessage))
332     return 0;
333   if (!result->loadArchive(ErrorMessage))
334     return 0;
335   return result.release();
336 }
337 
338 // Get all the bitcode modules from the archive
339 bool
getAllModules(std::vector<Module * > & Modules,std::string * ErrMessage)340 Archive::getAllModules(std::vector<Module*>& Modules,
341                        std::string* ErrMessage) {
342 
343   for (iterator I=begin(), E=end(); I != E; ++I) {
344     if (I->isBitcode()) {
345       std::string FullMemberName = archPath.str() +
346         "(" + I->getPath().str() + ")";
347       MemoryBuffer *Buffer =
348         MemoryBuffer::getMemBufferCopy(StringRef(I->getData(), I->getSize()),
349                                        FullMemberName.c_str());
350 
351       Module *M = ParseBitcodeFile(Buffer, Context, ErrMessage);
352       delete Buffer;
353       if (!M)
354         return true;
355 
356       Modules.push_back(M);
357     }
358   }
359   return false;
360 }
361 
362 // Load just the symbol table from the archive file
363 bool
loadSymbolTable(std::string * ErrorMsg)364 Archive::loadSymbolTable(std::string* ErrorMsg) {
365 
366   // Set up parsing
367   members.clear();
368   symTab.clear();
369   const char *At = base;
370   const char *End = mapfile->getBufferEnd();
371 
372   // Make sure we're dealing with an archive
373   if (!checkSignature(ErrorMsg))
374     return false;
375 
376   At += 8; // Skip signature
377 
378   // Parse the first file member header
379   const char* FirstFile = At;
380   ArchiveMember* mbr = parseMemberHeader(At, End, ErrorMsg);
381   if (!mbr)
382     return false;
383 
384   if (mbr->isSVR4SymbolTable() || mbr->isBSD4SymbolTable()) {
385     // Skip the foreign symbol table, we don't do anything with it
386     At += mbr->getSize();
387     if ((intptr_t(At) & 1) == 1)
388       At++;
389     delete mbr;
390 
391     // Read the next one
392     FirstFile = At;
393     mbr = parseMemberHeader(At, End, ErrorMsg);
394     if (!mbr) {
395       delete mbr;
396       return false;
397     }
398   }
399 
400   if (mbr->isStringTable()) {
401     // Process the string table entry
402     strtab.assign((const char*)mbr->getData(), mbr->getSize());
403     At += mbr->getSize();
404     if ((intptr_t(At) & 1) == 1)
405       At++;
406     delete mbr;
407     // Get the next one
408     FirstFile = At;
409     mbr = parseMemberHeader(At, End, ErrorMsg);
410     if (!mbr) {
411       delete mbr;
412       return false;
413     }
414   }
415 
416   // See if its the symbol table
417   if (mbr->isLLVMSymbolTable()) {
418     if (!parseSymbolTable(mbr->getData(), mbr->getSize(), ErrorMsg)) {
419       delete mbr;
420       return false;
421     }
422 
423     At += mbr->getSize();
424     if ((intptr_t(At) & 1) == 1)
425       At++;
426     delete mbr;
427     // Can't be any more symtab headers so just advance
428     FirstFile = At;
429   } else {
430     // There's no symbol table in the file. We have to rebuild it from scratch
431     // because the intent of this method is to get the symbol table loaded so
432     // it can be searched efficiently.
433     // Add the member to the members list
434     members.push_back(mbr);
435   }
436 
437   firstFileOffset = FirstFile - base;
438   return true;
439 }
440 
441 // Open the archive and load just the symbol tables
OpenAndLoadSymbols(const sys::Path & file,LLVMContext & C,std::string * ErrorMessage)442 Archive* Archive::OpenAndLoadSymbols(const sys::Path& file,
443                                      LLVMContext& C,
444                                      std::string* ErrorMessage) {
445   std::auto_ptr<Archive> result ( new Archive(file, C) );
446   if (result->mapToMemory(ErrorMessage))
447     return 0;
448   if (!result->loadSymbolTable(ErrorMessage))
449     return 0;
450   return result.release();
451 }
452 
453 // Look up one symbol in the symbol table and return the module that defines
454 // that symbol.
455 Module*
findModuleDefiningSymbol(const std::string & symbol,std::string * ErrMsg)456 Archive::findModuleDefiningSymbol(const std::string& symbol,
457                                   std::string* ErrMsg) {
458   SymTabType::iterator SI = symTab.find(symbol);
459   if (SI == symTab.end())
460     return 0;
461 
462   // The symbol table was previously constructed assuming that the members were
463   // written without the symbol table header. Because VBR encoding is used, the
464   // values could not be adjusted to account for the offset of the symbol table
465   // because that could affect the size of the symbol table due to VBR encoding.
466   // We now have to account for this by adjusting the offset by the size of the
467   // symbol table and its header.
468   unsigned fileOffset =
469     SI->second +                // offset in symbol-table-less file
470     firstFileOffset;            // add offset to first "real" file in archive
471 
472   // See if the module is already loaded
473   ModuleMap::iterator MI = modules.find(fileOffset);
474   if (MI != modules.end())
475     return MI->second.first;
476 
477   // Module hasn't been loaded yet, we need to load it
478   const char* modptr = base + fileOffset;
479   ArchiveMember* mbr = parseMemberHeader(modptr, mapfile->getBufferEnd(),
480                                          ErrMsg);
481   if (!mbr)
482     return 0;
483 
484   // Now, load the bitcode module to get the Module.
485   std::string FullMemberName = archPath.str() + "(" +
486     mbr->getPath().str() + ")";
487   MemoryBuffer *Buffer =
488     MemoryBuffer::getMemBufferCopy(StringRef(mbr->getData(), mbr->getSize()),
489                                    FullMemberName.c_str());
490 
491   Module *m = getLazyBitcodeModule(Buffer, Context, ErrMsg);
492   if (!m)
493     return 0;
494 
495   modules.insert(std::make_pair(fileOffset, std::make_pair(m, mbr)));
496 
497   return m;
498 }
499 
500 // Look up multiple symbols in the symbol table and return a set of
501 // Modules that define those symbols.
502 bool
findModulesDefiningSymbols(std::set<std::string> & symbols,SmallVectorImpl<Module * > & result,std::string * error)503 Archive::findModulesDefiningSymbols(std::set<std::string>& symbols,
504                                     SmallVectorImpl<Module*>& result,
505                                     std::string* error) {
506   if (!mapfile || !base) {
507     if (error)
508       *error = "Empty archive invalid for finding modules defining symbols";
509     return false;
510   }
511 
512   if (symTab.empty()) {
513     // We don't have a symbol table, so we must build it now but lets also
514     // make sure that we populate the modules table as we do this to ensure
515     // that we don't load them twice when findModuleDefiningSymbol is called
516     // below.
517 
518     // Get a pointer to the first file
519     const char* At  = base + firstFileOffset;
520     const char* End = mapfile->getBufferEnd();
521 
522     while ( At < End) {
523       // Compute the offset to be put in the symbol table
524       unsigned offset = At - base - firstFileOffset;
525 
526       // Parse the file's header
527       ArchiveMember* mbr = parseMemberHeader(At, End, error);
528       if (!mbr)
529         return false;
530 
531       // If it contains symbols
532       if (mbr->isBitcode()) {
533         // Get the symbols
534         std::vector<std::string> symbols;
535         std::string FullMemberName = archPath.str() + "(" +
536           mbr->getPath().str() + ")";
537         Module* M =
538           GetBitcodeSymbols(At, mbr->getSize(), FullMemberName, Context,
539                             symbols, error);
540 
541         if (M) {
542           // Insert the module's symbols into the symbol table
543           for (std::vector<std::string>::iterator I = symbols.begin(),
544                E=symbols.end(); I != E; ++I ) {
545             symTab.insert(std::make_pair(*I, offset));
546           }
547           // Insert the Module and the ArchiveMember into the table of
548           // modules.
549           modules.insert(std::make_pair(offset, std::make_pair(M, mbr)));
550         } else {
551           if (error)
552             *error = "Can't parse bitcode member: " +
553               mbr->getPath().str() + ": " + *error;
554           delete mbr;
555           return false;
556         }
557       }
558 
559       // Go to the next file location
560       At += mbr->getSize();
561       if ((intptr_t(At) & 1) == 1)
562         At++;
563     }
564   }
565 
566   // At this point we have a valid symbol table (one way or another) so we
567   // just use it to quickly find the symbols requested.
568 
569   SmallPtrSet<Module*, 16> Added;
570   for (std::set<std::string>::iterator I=symbols.begin(),
571          Next = I,
572          E=symbols.end(); I != E; I = Next) {
573     // Increment Next before we invalidate it.
574     ++Next;
575 
576     // See if this symbol exists
577     Module* m = findModuleDefiningSymbol(*I,error);
578     if (!m)
579       continue;
580     bool NewMember = Added.insert(m);
581     if (!NewMember)
582       continue;
583 
584     // The symbol exists, insert the Module into our result.
585     result.push_back(m);
586 
587     // Remove the symbol now that its been resolved.
588     symbols.erase(I);
589   }
590   return true;
591 }
592 
isBitcodeArchive()593 bool Archive::isBitcodeArchive() {
594   // Make sure the symTab has been loaded. In most cases this should have been
595   // done when the archive was constructed, but still,  this is just in case.
596   if (symTab.empty())
597     if (!loadSymbolTable(0))
598       return false;
599 
600   // Now that we know it's been loaded, return true
601   // if it has a size
602   if (symTab.size()) return true;
603 
604   // We still can't be sure it isn't a bitcode archive
605   if (!loadArchive(0))
606     return false;
607 
608   std::vector<Module *> Modules;
609   std::string ErrorMessage;
610 
611   // Scan the archive, trying to load a bitcode member.  We only load one to
612   // see if this works.
613   for (iterator I = begin(), E = end(); I != E; ++I) {
614     if (!I->isBitcode())
615       continue;
616 
617     std::string FullMemberName =
618       archPath.str() + "(" + I->getPath().str() + ")";
619 
620     MemoryBuffer *Buffer =
621       MemoryBuffer::getMemBufferCopy(StringRef(I->getData(), I->getSize()),
622                                      FullMemberName.c_str());
623     Module *M = ParseBitcodeFile(Buffer, Context);
624     delete Buffer;
625     if (!M)
626       return false;  // Couldn't parse bitcode, not a bitcode archive.
627     delete M;
628     return true;
629   }
630 
631   return false;
632 }
633