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1 //===-- ArchiveWriter.cpp - Write LLVM archive files ----------------------===//
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 an LLVM archive file (.a) containing LLVM bitcode.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "ArchiveInternals.h"
15 #include "llvm/Module.h"
16 #include "llvm/ADT/OwningPtr.h"
17 #include "llvm/Bitcode/ReaderWriter.h"
18 #include "llvm/Support/FileSystem.h"
19 #include "llvm/Support/MemoryBuffer.h"
20 #include "llvm/Support/Process.h"
21 #include "llvm/Support/Signals.h"
22 #include "llvm/Support/system_error.h"
23 #include <fstream>
24 #include <ostream>
25 #include <iomanip>
26 using namespace llvm;
27 
28 // Write an integer using variable bit rate encoding. This saves a few bytes
29 // per entry in the symbol table.
writeInteger(unsigned num,std::ofstream & ARFile)30 static inline void writeInteger(unsigned num, std::ofstream& ARFile) {
31   while (1) {
32     if (num < 0x80) { // done?
33       ARFile << (unsigned char)num;
34       return;
35     }
36 
37     // Nope, we are bigger than a character, output the next 7 bits and set the
38     // high bit to say that there is more coming...
39     ARFile << (unsigned char)(0x80 | ((unsigned char)num & 0x7F));
40     num >>= 7;  // Shift out 7 bits now...
41   }
42 }
43 
44 // Compute how many bytes are taken by a given VBR encoded value. This is needed
45 // to pre-compute the size of the symbol table.
numVbrBytes(unsigned num)46 static inline unsigned numVbrBytes(unsigned num) {
47 
48   // Note that the following nested ifs are somewhat equivalent to a binary
49   // search. We split it in half by comparing against 2^14 first. This allows
50   // most reasonable values to be done in 2 comparisons instead of 1 for
51   // small ones and four for large ones. We expect this to access file offsets
52   // in the 2^10 to 2^24 range and symbol lengths in the 2^0 to 2^8 range,
53   // so this approach is reasonable.
54   if (num < 1<<14) {
55     if (num < 1<<7)
56       return 1;
57     else
58       return 2;
59   }
60   if (num < 1<<21)
61     return 3;
62 
63   if (num < 1<<28)
64     return 4;
65   return 5; // anything >= 2^28 takes 5 bytes
66 }
67 
68 // Create an empty archive.
CreateEmpty(const sys::Path & FilePath,LLVMContext & C)69 Archive* Archive::CreateEmpty(const sys::Path& FilePath, LLVMContext& C) {
70   Archive* result = new Archive(FilePath, C);
71   return result;
72 }
73 
74 // Fill the ArchiveMemberHeader with the information from a member. If
75 // TruncateNames is true, names are flattened to 15 chars or less. The sz field
76 // is provided here instead of coming from the mbr because the member might be
77 // stored compressed and the compressed size is not the ArchiveMember's size.
78 // Furthermore compressed files have negative size fields to identify them as
79 // compressed.
80 bool
fillHeader(const ArchiveMember & mbr,ArchiveMemberHeader & hdr,int sz,bool TruncateNames) const81 Archive::fillHeader(const ArchiveMember &mbr, ArchiveMemberHeader& hdr,
82                     int sz, bool TruncateNames) const {
83 
84   // Set the permissions mode, uid and gid
85   hdr.init();
86   char buffer[32];
87   sprintf(buffer, "%-8o", mbr.getMode());
88   memcpy(hdr.mode,buffer,8);
89   sprintf(buffer,  "%-6u", mbr.getUser());
90   memcpy(hdr.uid,buffer,6);
91   sprintf(buffer,  "%-6u", mbr.getGroup());
92   memcpy(hdr.gid,buffer,6);
93 
94   // Set the last modification date
95   uint64_t secondsSinceEpoch = mbr.getModTime().toEpochTime();
96   sprintf(buffer,"%-12u", unsigned(secondsSinceEpoch));
97   memcpy(hdr.date,buffer,12);
98 
99   // Get rid of trailing blanks in the name
100   std::string mbrPath = mbr.getPath().str();
101   size_t mbrLen = mbrPath.length();
102   while (mbrLen > 0 && mbrPath[mbrLen-1] == ' ') {
103     mbrPath.erase(mbrLen-1,1);
104     mbrLen--;
105   }
106 
107   // Set the name field in one of its various flavors.
108   bool writeLongName = false;
109   if (mbr.isStringTable()) {
110     memcpy(hdr.name,ARFILE_STRTAB_NAME,16);
111   } else if (mbr.isSVR4SymbolTable()) {
112     memcpy(hdr.name,ARFILE_SVR4_SYMTAB_NAME,16);
113   } else if (mbr.isBSD4SymbolTable()) {
114     memcpy(hdr.name,ARFILE_BSD4_SYMTAB_NAME,16);
115   } else if (mbr.isLLVMSymbolTable()) {
116     memcpy(hdr.name,ARFILE_LLVM_SYMTAB_NAME,16);
117   } else if (TruncateNames) {
118     const char* nm = mbrPath.c_str();
119     unsigned len = mbrPath.length();
120     size_t slashpos = mbrPath.rfind('/');
121     if (slashpos != std::string::npos) {
122       nm += slashpos + 1;
123       len -= slashpos +1;
124     }
125     if (len > 15)
126       len = 15;
127     memcpy(hdr.name,nm,len);
128     hdr.name[len] = '/';
129   } else if (mbrPath.length() < 16 && mbrPath.find('/') == std::string::npos) {
130     memcpy(hdr.name,mbrPath.c_str(),mbrPath.length());
131     hdr.name[mbrPath.length()] = '/';
132   } else {
133     std::string nm = "#1/";
134     nm += utostr(mbrPath.length());
135     memcpy(hdr.name,nm.data(),nm.length());
136     if (sz < 0)
137       sz -= mbrPath.length();
138     else
139       sz += mbrPath.length();
140     writeLongName = true;
141   }
142 
143   // Set the size field
144   if (sz < 0) {
145     buffer[0] = '-';
146     sprintf(&buffer[1],"%-9u",(unsigned)-sz);
147   } else {
148     sprintf(buffer, "%-10u", (unsigned)sz);
149   }
150   memcpy(hdr.size,buffer,10);
151 
152   return writeLongName;
153 }
154 
155 // Insert a file into the archive before some other member. This also takes care
156 // of extracting the necessary flags and information from the file.
157 bool
addFileBefore(const sys::Path & filePath,iterator where,std::string * ErrMsg)158 Archive::addFileBefore(const sys::Path& filePath, iterator where,
159                         std::string* ErrMsg) {
160   bool Exists;
161   if (sys::fs::exists(filePath.str(), Exists) || !Exists) {
162     if (ErrMsg)
163       *ErrMsg = "Can not add a non-existent file to archive";
164     return true;
165   }
166 
167   ArchiveMember* mbr = new ArchiveMember(this);
168 
169   mbr->data = 0;
170   mbr->path = filePath;
171   const sys::FileStatus *FSInfo = mbr->path.getFileStatus(false, ErrMsg);
172   if (!FSInfo) {
173     delete mbr;
174     return true;
175   }
176   mbr->info = *FSInfo;
177 
178   unsigned flags = 0;
179   bool hasSlash = filePath.str().find('/') != std::string::npos;
180   if (hasSlash)
181     flags |= ArchiveMember::HasPathFlag;
182   if (hasSlash || filePath.str().length() > 15)
183     flags |= ArchiveMember::HasLongFilenameFlag;
184 
185   sys::LLVMFileType type;
186   if (sys::fs::identify_magic(mbr->path.str(), type))
187     type = sys::Unknown_FileType;
188   switch (type) {
189     case sys::Bitcode_FileType:
190       flags |= ArchiveMember::BitcodeFlag;
191       break;
192     default:
193       break;
194   }
195   mbr->flags = flags;
196   members.insert(where,mbr);
197   return false;
198 }
199 
200 // Write one member out to the file.
201 bool
writeMember(const ArchiveMember & member,std::ofstream & ARFile,bool CreateSymbolTable,bool TruncateNames,bool ShouldCompress,std::string * ErrMsg)202 Archive::writeMember(
203   const ArchiveMember& member,
204   std::ofstream& ARFile,
205   bool CreateSymbolTable,
206   bool TruncateNames,
207   bool ShouldCompress,
208   std::string* ErrMsg
209 ) {
210 
211   unsigned filepos = ARFile.tellp();
212   filepos -= 8;
213 
214   // Get the data and its size either from the
215   // member's in-memory data or directly from the file.
216   size_t fSize = member.getSize();
217   const char *data = (const char*)member.getData();
218   MemoryBuffer *mFile = 0;
219   if (!data) {
220     OwningPtr<MemoryBuffer> File;
221     if (error_code ec = MemoryBuffer::getFile(member.getPath().c_str(), File)) {
222       if (ErrMsg)
223         *ErrMsg = ec.message();
224       return true;
225     }
226     mFile = File.take();
227     data = mFile->getBufferStart();
228     fSize = mFile->getBufferSize();
229   }
230 
231   // Now that we have the data in memory, update the
232   // symbol table if it's a bitcode file.
233   if (CreateSymbolTable && member.isBitcode()) {
234     std::vector<std::string> symbols;
235     std::string FullMemberName = archPath.str() + "(" + member.getPath().str()
236       + ")";
237     Module* M =
238       GetBitcodeSymbols(data, fSize, FullMemberName, Context, symbols, ErrMsg);
239 
240     // If the bitcode parsed successfully
241     if ( M ) {
242       for (std::vector<std::string>::iterator SI = symbols.begin(),
243            SE = symbols.end(); SI != SE; ++SI) {
244 
245         std::pair<SymTabType::iterator,bool> Res =
246           symTab.insert(std::make_pair(*SI,filepos));
247 
248         if (Res.second) {
249           symTabSize += SI->length() +
250                         numVbrBytes(SI->length()) +
251                         numVbrBytes(filepos);
252         }
253       }
254       // We don't need this module any more.
255       delete M;
256     } else {
257       delete mFile;
258       if (ErrMsg)
259         *ErrMsg = "Can't parse bitcode member: " + member.getPath().str()
260           + ": " + *ErrMsg;
261       return true;
262     }
263   }
264 
265   int hdrSize = fSize;
266 
267   // Compute the fields of the header
268   ArchiveMemberHeader Hdr;
269   bool writeLongName = fillHeader(member,Hdr,hdrSize,TruncateNames);
270 
271   // Write header to archive file
272   ARFile.write((char*)&Hdr, sizeof(Hdr));
273 
274   // Write the long filename if its long
275   if (writeLongName) {
276     ARFile.write(member.getPath().str().data(),
277                  member.getPath().str().length());
278   }
279 
280   // Write the (possibly compressed) member's content to the file.
281   ARFile.write(data,fSize);
282 
283   // Make sure the member is an even length
284   if ((ARFile.tellp() & 1) == 1)
285     ARFile << ARFILE_PAD;
286 
287   // Close the mapped file if it was opened
288   delete mFile;
289   return false;
290 }
291 
292 // Write out the LLVM symbol table as an archive member to the file.
293 void
writeSymbolTable(std::ofstream & ARFile)294 Archive::writeSymbolTable(std::ofstream& ARFile) {
295 
296   // Construct the symbol table's header
297   ArchiveMemberHeader Hdr;
298   Hdr.init();
299   memcpy(Hdr.name,ARFILE_LLVM_SYMTAB_NAME,16);
300   uint64_t secondsSinceEpoch = sys::TimeValue::now().toEpochTime();
301   char buffer[32];
302   sprintf(buffer, "%-8o", 0644);
303   memcpy(Hdr.mode,buffer,8);
304   sprintf(buffer, "%-6u", sys::Process::GetCurrentUserId());
305   memcpy(Hdr.uid,buffer,6);
306   sprintf(buffer, "%-6u", sys::Process::GetCurrentGroupId());
307   memcpy(Hdr.gid,buffer,6);
308   sprintf(buffer,"%-12u", unsigned(secondsSinceEpoch));
309   memcpy(Hdr.date,buffer,12);
310   sprintf(buffer,"%-10u",symTabSize);
311   memcpy(Hdr.size,buffer,10);
312 
313   // Write the header
314   ARFile.write((char*)&Hdr, sizeof(Hdr));
315 
316 #ifndef NDEBUG
317   // Save the starting position of the symbol tables data content.
318   unsigned startpos = ARFile.tellp();
319 #endif
320 
321   // Write out the symbols sequentially
322   for ( Archive::SymTabType::iterator I = symTab.begin(), E = symTab.end();
323         I != E; ++I)
324   {
325     // Write out the file index
326     writeInteger(I->second, ARFile);
327     // Write out the length of the symbol
328     writeInteger(I->first.length(), ARFile);
329     // Write out the symbol
330     ARFile.write(I->first.data(), I->first.length());
331   }
332 
333 #ifndef NDEBUG
334   // Now that we're done with the symbol table, get the ending file position
335   unsigned endpos = ARFile.tellp();
336 #endif
337 
338   // Make sure that the amount we wrote is what we pre-computed. This is
339   // critical for file integrity purposes.
340   assert(endpos - startpos == symTabSize && "Invalid symTabSize computation");
341 
342   // Make sure the symbol table is even sized
343   if (symTabSize % 2 != 0 )
344     ARFile << ARFILE_PAD;
345 }
346 
347 // Write the entire archive to the file specified when the archive was created.
348 // This writes to a temporary file first. Options are for creating a symbol
349 // table, flattening the file names (no directories, 15 chars max) and
350 // compressing each archive member.
351 bool
writeToDisk(bool CreateSymbolTable,bool TruncateNames,bool Compress,std::string * ErrMsg)352 Archive::writeToDisk(bool CreateSymbolTable, bool TruncateNames, bool Compress,
353                      std::string* ErrMsg)
354 {
355   // Make sure they haven't opened up the file, not loaded it,
356   // but are now trying to write it which would wipe out the file.
357   if (members.empty() && mapfile && mapfile->getBufferSize() > 8) {
358     if (ErrMsg)
359       *ErrMsg = "Can't write an archive not opened for writing";
360     return true;
361   }
362 
363   // Create a temporary file to store the archive in
364   sys::Path TmpArchive = archPath;
365   if (TmpArchive.createTemporaryFileOnDisk(ErrMsg))
366     return true;
367 
368   // Make sure the temporary gets removed if we crash
369   sys::RemoveFileOnSignal(TmpArchive);
370 
371   // Create archive file for output.
372   std::ios::openmode io_mode = std::ios::out | std::ios::trunc |
373                                std::ios::binary;
374   std::ofstream ArchiveFile(TmpArchive.c_str(), io_mode);
375 
376   // Check for errors opening or creating archive file.
377   if (!ArchiveFile.is_open() || ArchiveFile.bad()) {
378     TmpArchive.eraseFromDisk();
379     if (ErrMsg)
380       *ErrMsg = "Error opening archive file: " + archPath.str();
381     return true;
382   }
383 
384   // If we're creating a symbol table, reset it now
385   if (CreateSymbolTable) {
386     symTabSize = 0;
387     symTab.clear();
388   }
389 
390   // Write magic string to archive.
391   ArchiveFile << ARFILE_MAGIC;
392 
393   // Loop over all member files, and write them out. Note that this also
394   // builds the symbol table, symTab.
395   for (MembersList::iterator I = begin(), E = end(); I != E; ++I) {
396     if (writeMember(*I, ArchiveFile, CreateSymbolTable,
397                      TruncateNames, Compress, ErrMsg)) {
398       TmpArchive.eraseFromDisk();
399       ArchiveFile.close();
400       return true;
401     }
402   }
403 
404   // Close archive file.
405   ArchiveFile.close();
406 
407   // Write the symbol table
408   if (CreateSymbolTable) {
409     // At this point we have written a file that is a legal archive but it
410     // doesn't have a symbol table in it. To aid in faster reading and to
411     // ensure compatibility with other archivers we need to put the symbol
412     // table first in the file. Unfortunately, this means mapping the file
413     // we just wrote back in and copying it to the destination file.
414     sys::Path FinalFilePath = archPath;
415 
416     // Map in the archive we just wrote.
417     {
418     OwningPtr<MemoryBuffer> arch;
419     if (error_code ec = MemoryBuffer::getFile(TmpArchive.c_str(), arch)) {
420       if (ErrMsg)
421         *ErrMsg = ec.message();
422       return true;
423     }
424     const char* base = arch->getBufferStart();
425 
426     // Open another temporary file in order to avoid invalidating the
427     // mmapped data
428     if (FinalFilePath.createTemporaryFileOnDisk(ErrMsg))
429       return true;
430     sys::RemoveFileOnSignal(FinalFilePath);
431 
432     std::ofstream FinalFile(FinalFilePath.c_str(), io_mode);
433     if (!FinalFile.is_open() || FinalFile.bad()) {
434       TmpArchive.eraseFromDisk();
435       if (ErrMsg)
436         *ErrMsg = "Error opening archive file: " + FinalFilePath.str();
437       return true;
438     }
439 
440     // Write the file magic number
441     FinalFile << ARFILE_MAGIC;
442 
443     // If there is a foreign symbol table, put it into the file now. Most
444     // ar(1) implementations require the symbol table to be first but llvm-ar
445     // can deal with it being after a foreign symbol table. This ensures
446     // compatibility with other ar(1) implementations as well as allowing the
447     // archive to store both native .o and LLVM .bc files, both indexed.
448     if (foreignST) {
449       if (writeMember(*foreignST, FinalFile, false, false, false, ErrMsg)) {
450         FinalFile.close();
451         TmpArchive.eraseFromDisk();
452         return true;
453       }
454     }
455 
456     // Put out the LLVM symbol table now.
457     writeSymbolTable(FinalFile);
458 
459     // Copy the temporary file contents being sure to skip the file's magic
460     // number.
461     FinalFile.write(base + sizeof(ARFILE_MAGIC)-1,
462       arch->getBufferSize()-sizeof(ARFILE_MAGIC)+1);
463 
464     // Close up shop
465     FinalFile.close();
466     } // free arch.
467 
468     // Move the final file over top of TmpArchive
469     if (FinalFilePath.renamePathOnDisk(TmpArchive, ErrMsg))
470       return true;
471   }
472 
473   // Before we replace the actual archive, we need to forget all the
474   // members, since they point to data in that old archive. We need to do
475   // this because we cannot replace an open file on Windows.
476   cleanUpMemory();
477 
478   if (TmpArchive.renamePathOnDisk(archPath, ErrMsg))
479     return true;
480 
481   // Set correct read and write permissions after temporary file is moved
482   // to final destination path.
483   if (archPath.makeReadableOnDisk(ErrMsg))
484     return true;
485   if (archPath.makeWriteableOnDisk(ErrMsg))
486     return true;
487 
488   return false;
489 }
490