apt-pkg/contrib/mmap.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: mmap.cc,v 1.22 2001/05/27 05:19:30 jgg Exp $
   4 /* ######################################################################
   5
   6    MMap Class - Provides 'real' mmap or a faked mmap using read().
   7
   8    MMap cover class.
   9
  10    Some broken versions of glibc2 (libc6) have a broken definition
  11    of mmap that accepts a char * -- all other systems (and libc5) use
  12    void *. We can't safely do anything here that would be portable, so
  13    libc6 generates warnings -- which should be errors, g++ isn't properly
  14    strict.
  15
  16    ##################################################################### */
  17                                                                         /*}}}*/
  18 // Include Files                                                        /*{{{*/
  19 #define _DEFAULT_SOURCE
  20 #include <config.h>
  21
  22 #include <apt-pkg/mmap.h>
  23 #include <apt-pkg/error.h>
  24 #include <apt-pkg/fileutl.h>
  25 #include <apt-pkg/macros.h>
  26
  27 #include <string>
  28 #include <sys/mman.h>
  29 #include <unistd.h>
  30 #include <stdlib.h>
  31 #include <errno.h>
  32 #include <cstring>
  33
  34 #include <apti18n.h>
  35                                                                         /*}}}*/
  36
  37 // MMap::MMap - Constructor                                             /*{{{*/
  38 // ---------------------------------------------------------------------
  39 /* */
  40 MMap::MMap(FileFd &F,unsigned long Flags) : Flags(Flags), iSize(0),
  41                      Base(nullptr), SyncToFd(nullptr)
  42 {
  43       Map(F);
  44 }
  45                                                                         /*}}}*/
  46 // MMap::MMap - Constructor                                             /*{{{*/
  47 // ---------------------------------------------------------------------
  48 /* */
  49 MMap::MMap(unsigned long Flags) : Flags(Flags), iSize(0),
  50                      Base(nullptr), SyncToFd(nullptr)
  51 {
  52 }
  53                                                                         /*}}}*/
  54 // MMap::~MMap - Destructor                                             /*{{{*/
  55 // ---------------------------------------------------------------------
  56 /* */
  57 MMap::~MMap()
  58 {
  59    Close();
  60 }
  61                                                                         /*}}}*/
  62 // MMap::Map - Perform the mapping                                      /*{{{*/
  63 // ---------------------------------------------------------------------
  64 /* */
  65 bool MMap::Map(FileFd &Fd)
  66 {
  67    iSize = Fd.Size();
  68
  69    // Set the permissions.
  70    int Prot = PROT_READ;
  71    int Map = MAP_SHARED;
  72    if ((Flags & ReadOnly) != ReadOnly)
  73       Prot |= PROT_WRITE;
  74    if ((Flags & Public) != Public)
  75       Map = MAP_PRIVATE;
  76
  77    if (iSize == 0)
  78       return _error->Error(_("Can't mmap an empty file"));
  79
  80    // We can't mmap compressed fd's directly, so we need to read it completely
  81    if (Fd.IsCompressed() == true)
  82    {
  83       if ((Flags & ReadOnly) != ReadOnly)
  84          return _error->Error("Compressed file %s can only be mapped readonly", Fd.Name().c_str());
  85       Base = malloc(iSize);
  86       if (unlikely(Base == nullptr))
  87          return _error->Errno("MMap-compressed-malloc", _("Couldn't make mmap of %llu bytes"), iSize);
  88       SyncToFd = new FileFd();
  89       if (Fd.Seek(0L) == false || Fd.Read(Base, iSize) == false)
  90          return _error->Error("Compressed file %s can't be read into mmap", Fd.Name().c_str());
  91       return true;
  92    }
  93
  94    // Map it.
  95    Base = (Flags & Fallback) ? MAP_FAILED : mmap(0,iSize,Prot,Map,Fd.Fd(),0);
  96    if (Base == MAP_FAILED)
  97    {
  98       if (errno == ENODEV || errno == EINVAL || (Flags & Fallback))
  99       {
 100          // The filesystem doesn't support this particular kind of mmap.
 101          // So we allocate a buffer and read the whole file into it.
 102          if ((Flags & ReadOnly) == ReadOnly)
 103          {
 104             // for readonly, we don't need sync, so make it simple
 105             Base = malloc(iSize);
 106             if (unlikely(Base == nullptr))
 107                return _error->Errno("MMap-malloc", _("Couldn't make mmap of %llu bytes"), iSize);
 108             SyncToFd = new FileFd();
 109             return Fd.Read(Base, iSize);
 110          }
 111          // FIXME: Writing to compressed fd's ?
 112          int const dupped_fd = dup(Fd.Fd());
 113          if (dupped_fd == -1)
 114             return _error->Errno("mmap", _("Couldn't duplicate file descriptor %i"), Fd.Fd());
 115
 116          Base = calloc(iSize, 1);
 117          if (unlikely(Base == nullptr))
 118             return _error->Errno("MMap-calloc", _("Couldn't make mmap of %llu bytes"), iSize);
 119          SyncToFd = new FileFd (dupped_fd);
 120          if (!SyncToFd->Seek(0L) || !SyncToFd->Read(Base, iSize))
 121             return false;
 122       }
 123       else
 124          return _error->Errno("MMap-mmap", _("Couldn't make mmap of %llu bytes"), iSize);
 125      }
 126
 127    return true;
 128 }
 129                                                                         /*}}}*/
 130 // MMap::Close - Close the map                                          /*{{{*/
 131 // ---------------------------------------------------------------------
 132 /* */
 133 bool MMap::Close(bool DoSync)
 134 {
 135    if ((Flags & UnMapped) == UnMapped || validData() == false || iSize == 0)
 136       return true;
 137
 138    if (DoSync == true)
 139       Sync();
 140
 141    if (SyncToFd != NULL)
 142    {
 143       free(Base);
 144       delete SyncToFd;
 145       SyncToFd = NULL;
 146    }
 147    else
 148    {
 149       if (munmap((char *)Base, iSize) != 0)
 150          _error->WarningE("mmap", _("Unable to close mmap"));
 151    }
 152
 153    iSize = 0;
 154    Base = 0;
 155    return true;
 156 }
 157                                                                         /*}}}*/
 158 // MMap::Sync - Syncronize the map with the disk                        /*{{{*/
 159 // ---------------------------------------------------------------------
 160 /* This is done in syncronous mode - the docs indicate that this will
 161    not return till all IO is complete */
 162 bool MMap::Sync()
 163 {
 164    if ((Flags & UnMapped) == UnMapped)
 165       return true;
 166
 167    if ((Flags & ReadOnly) != ReadOnly)
 168    {
 169       if (SyncToFd != NULL)
 170       {
 171          if (!SyncToFd->Seek(0) || !SyncToFd->Write(Base, iSize))
 172             return false;
 173       }
 174       else
 175       {
 176 #ifdef _POSIX_SYNCHRONIZED_IO
 177          if (msync((char *)Base, iSize, MS_SYNC) < 0)
 178             return _error->Errno("msync", _("Unable to synchronize mmap"));
 179 #endif
 180       }
 181    }
 182    return true;
 183 }
 184                                                                         /*}}}*/
 185 // MMap::Sync - Syncronize a section of the file to disk                /*{{{*/
 186 // ---------------------------------------------------------------------
 187 /* */
 188 bool MMap::Sync(unsigned long Start,unsigned long Stop)
 189 {
 190    if ((Flags & UnMapped) == UnMapped)
 191       return true;
 192
 193    if ((Flags & ReadOnly) != ReadOnly)
 194    {
 195       if (SyncToFd != 0)
 196       {
 197          if (!SyncToFd->Seek(0) ||
 198              !SyncToFd->Write (((char *)Base)+Start, Stop-Start))
 199             return false;
 200       }
 201       else
 202       {
 203 #ifdef _POSIX_SYNCHRONIZED_IO
 204          unsigned long long const PSize = sysconf(_SC_PAGESIZE);
 205          if (msync((char *)Base+(Start/PSize)*PSize, Stop - Start, MS_SYNC) < 0)
 206             return _error->Errno("msync", _("Unable to synchronize mmap"));
 207 #endif
 208       }
 209    }
 210    return true;
 211 }
 212                                                                         /*}}}*/
 213
 214 // DynamicMMap::DynamicMMap - Constructor                               /*{{{*/
 215 // ---------------------------------------------------------------------
 216 /* */
 217 DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long const &Workspace,
 218                          unsigned long const &Grow, unsigned long const &Limit) :
 219                 MMap(Flags), Fd(&F), WorkSpace(Workspace),
 220                 GrowFactor(Grow), Limit(Limit)
 221 {
 222    // disable Moveable if we don't grow
 223    if (Grow == 0)
 224       this->Flags &= ~Moveable;
 225
 226 #ifndef __linux__
 227    // kfreebsd doesn't have mremap, so we use the fallback
 228    if ((this->Flags & Moveable) == Moveable)
 229       this->Flags |= Fallback;
 230 #endif
 231
 232    unsigned long long EndOfFile = Fd->Size();
 233    if (EndOfFile > WorkSpace)
 234       WorkSpace = EndOfFile;
 235    else if(WorkSpace > 0)
 236    {
 237       Fd->Seek(WorkSpace - 1);
 238       char C = 0;
 239       Fd->Write(&C,sizeof(C));
 240    }
 241
 242    Map(F);
 243    iSize = EndOfFile;
 244 }
 245                                                                         /*}}}*/
 246 // DynamicMMap::DynamicMMap - Constructor for a non-file backed map     /*{{{*/
 247 // ---------------------------------------------------------------------
 248 /* We try here to use mmap to reserve some space - this is much more
 249    cooler than the fallback solution to simply allocate a char array
 250    and could come in handy later than we are able to grow such an mmap */
 251 DynamicMMap::DynamicMMap(unsigned long Flags,unsigned long const &WorkSpace,
 252                          unsigned long const &Grow, unsigned long const &Limit) :
 253                 MMap(Flags | UnMapped), Fd(0), WorkSpace(WorkSpace),
 254                 GrowFactor(Grow), Limit(Limit)
 255 {
 256         // disable Moveable if we don't grow
 257         if (Grow == 0)
 258                 this->Flags &= ~Moveable;
 259
 260 #ifndef __linux__
 261         // kfreebsd doesn't have mremap, so we use the fallback
 262         if ((this->Flags & Moveable) == Moveable)
 263                 this->Flags |= Fallback;
 264 #endif
 265
 266 #ifdef _POSIX_MAPPED_FILES
 267         if ((this->Flags & Fallback) != Fallback) {
 268                 // Set the permissions.
 269                 int Prot = PROT_READ;
 270 #ifdef MAP_ANONYMOUS
 271                 int Map = MAP_PRIVATE | MAP_ANONYMOUS;
 272 #else
 273                 int Map = MAP_PRIVATE | MAP_ANON;
 274 #endif
 275                 if ((this->Flags & ReadOnly) != ReadOnly)
 276                         Prot |= PROT_WRITE;
 277                 if ((this->Flags & Public) == Public)
 278 #ifdef MAP_ANONYMOUS
 279                         Map = MAP_SHARED | MAP_ANONYMOUS;
 280 #else
 281                         Map = MAP_SHARED | MAP_ANON;
 282 #endif
 283
 284                 // use anonymous mmap() to get the memory
 285                 Base = (unsigned char*) mmap(0, WorkSpace, Prot, Map, -1, 0);
 286
 287                 if(Base == MAP_FAILED)
 288                         _error->Errno("DynamicMMap",_("Couldn't make mmap of %lu bytes"),WorkSpace);
 289
 290                 iSize = 0;
 291                 return;
 292         }
 293 #endif
 294         // fallback to a static allocated space
 295         Base = calloc(WorkSpace, 1);
 296         iSize = 0;
 297 }
 298                                                                         /*}}}*/
 299 // DynamicMMap::~DynamicMMap - Destructor                               /*{{{*/
 300 // ---------------------------------------------------------------------
 301 /* We truncate the file to the size of the memory data set */
 302 DynamicMMap::~DynamicMMap()
 303 {
 304    if (Fd == 0)
 305    {
 306       if (validData() == false)
 307          return;
 308 #ifdef _POSIX_MAPPED_FILES
 309       munmap(Base, WorkSpace);
 310 #else
 311       free(Base);
 312 #endif
 313       return;
 314    }
 315
 316    unsigned long long EndOfFile = iSize;
 317    iSize = WorkSpace;
 318    Close(false);
 319    if(ftruncate(Fd->Fd(),EndOfFile) < 0)
 320       _error->Errno("ftruncate", _("Failed to truncate file"));
 321 }
 322                                                                         /*}}}*/
 323 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 324 // ---------------------------------------------------------------------
 325 /* This allocates a block of memory aligned to the given size */
 326 unsigned long DynamicMMap::RawAllocate(unsigned long long Size,unsigned long Aln)
 327 {
 328    unsigned long long Result = iSize;
 329    if (Aln != 0)
 330       Result += Aln - (iSize%Aln);
 331
 332    iSize = Result + Size;
 333
 334    // try to grow the buffer
 335    while(Result + Size > WorkSpace)
 336    {
 337       if(!Grow())
 338       {
 339          _error->Fatal(_("Dynamic MMap ran out of room. Please increase the size "
 340                          "of APT::Cache-Start. Current value: %lu. (man 5 apt.conf)"), WorkSpace);
 341          return 0;
 342       }
 343    }
 344    return Result;
 345 }
 346                                                                         /*}}}*/
 347 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 348 // ---------------------------------------------------------------------
 349 /* This allocates an Item of size ItemSize so that it is aligned to its
 350    size in the file. */
 351 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 352 {
 353    if (unlikely(ItemSize == 0))
 354    {
 355       _error->Fatal("Can't allocate an item of size zero");
 356       return 0;
 357    }
 358
 359    // Look for a matching pool entry
 360    Pool *I;
 361    Pool *Empty = 0;
 362    for (I = Pools; I != Pools + PoolCount; ++I)
 363    {
 364       if (I->ItemSize == 0)
 365          Empty = I;
 366       if (I->ItemSize == ItemSize)
 367          break;
 368    }
 369    // No pool is allocated, use an unallocated one
 370    if (I == Pools + PoolCount)
 371    {
 372       // Woops, we ran out, the calling code should allocate more.
 373       if (Empty == 0)
 374       {
 375          _error->Error("Ran out of allocation pools");
 376          return 0;
 377       }
 378
 379       I = Empty;
 380       I->ItemSize = ItemSize;
 381       I->Count = 0;
 382    }
 383
 384    unsigned long Result = 0;
 385    // Out of space, allocate some more
 386    if (I->Count == 0)
 387    {
 388       const unsigned long size = 20*1024;
 389       I->Count = size/ItemSize;
 390       Pool* oldPools = Pools;
 391       _error->PushToStack();
 392       Result = RawAllocate(size,ItemSize);
 393       bool const newError = _error->PendingError();
 394       _error->MergeWithStack();
 395       if (Pools != oldPools)
 396          I += Pools - oldPools;
 397
 398       // Does the allocation failed ?
 399       if (Result == 0 && newError)
 400          return 0;
 401       I->Start = Result;
 402    }
 403    else
 404       Result = I->Start;
 405
 406    I->Count--;
 407    I->Start += ItemSize;
 408    return Result/ItemSize;
 409 }
 410                                                                         /*}}}*/
 411 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 412 // ---------------------------------------------------------------------
 413 /* Strings are aligned to 16 bytes */
 414 unsigned long DynamicMMap::WriteString(const char *String,
 415                                        unsigned long Len)
 416 {
 417    if (Len == (unsigned long)-1)
 418       Len = strlen(String);
 419
 420    _error->PushToStack();
 421    unsigned long Result = RawAllocate(Len+1+sizeof(uint16_t),sizeof(uint16_t));
 422    bool const newError = _error->PendingError();
 423    _error->MergeWithStack();
 424
 425    if (Base == NULL || (Result == 0 && newError))
 426       return 0;
 427
 428    if (Len >= std::numeric_limits<uint16_t>::max())
 429       abort();
 430
 431    uint16_t LenToWrite = Len;
 432    memcpy((char *)Base + Result, &LenToWrite, sizeof(LenToWrite));
 433    Result += + sizeof(LenToWrite);
 434
 435    memcpy((char *)Base + Result,String,Len);
 436    ((char *)Base)[Result + Len] = 0;
 437    return Result;
 438 }
 439                                                                         /*}}}*/
 440 // DynamicMMap::Grow - Grow the mmap                                    /*{{{*/
 441 // ---------------------------------------------------------------------
 442 /* This method is a wrapper around different methods to (try to) grow
 443    a mmap (or our char[]-fallback). Encounterable environments:
 444    1. Moveable + !Fallback + linux -> mremap with MREMAP_MAYMOVE
 445    2. Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 446    3. Moveable + Fallback -> realloc
 447    4. !Moveable + !Fallback + linux -> mremap alone - which will fail in 99,9%
 448    5. !Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 449    6. !Moveable + Fallback -> not possible
 450    [ While Moveable and Fallback stands for the equally named flags and
 451      "linux" indicates a linux kernel instead of a freebsd kernel. ]
 452    So what you can see here is, that a MMAP which want to be growable need
 453    to be moveable to have a real chance but that this method will at least try
 454    the nearly impossible 4 to grow it before it finally give up: Never say never. */
 455 bool DynamicMMap::Grow() {
 456         if (Limit != 0 && WorkSpace >= Limit)
 457                 return _error->Error(_("Unable to increase the size of the MMap as the "
 458                                        "limit of %lu bytes is already reached."), Limit);
 459         if (GrowFactor <= 0)
 460                 return _error->Error(_("Unable to increase size of the MMap as automatic growing is disabled by user."));
 461
 462         unsigned long long const newSize = WorkSpace + GrowFactor;
 463
 464         if(Fd != 0) {
 465                 Fd->Seek(newSize - 1);
 466                 char C = 0;
 467                 Fd->Write(&C,sizeof(C));
 468         }
 469
 470         unsigned long const poolOffset = Pools - ((Pool*) Base);
 471
 472         if ((Flags & Fallback) != Fallback) {
 473 #if defined(_POSIX_MAPPED_FILES) && defined(__linux__)
 474    #ifdef MREMAP_MAYMOVE
 475
 476                 if ((Flags & Moveable) == Moveable)
 477                         Base = mremap(Base, WorkSpace, newSize, MREMAP_MAYMOVE);
 478                 else
 479    #endif
 480                         Base = mremap(Base, WorkSpace, newSize, 0);
 481
 482                 if(Base == MAP_FAILED)
 483                         return false;
 484 #else
 485                 return false;
 486 #endif
 487         } else {
 488                 if ((Flags & Moveable) != Moveable)
 489                         return false;
 490
 491                 Base = realloc(Base, newSize);
 492                 if (Base == NULL)
 493                         return false;
 494                 else
 495                         /* Set new memory to 0 */
 496                         memset((char*)Base + WorkSpace, 0, newSize - WorkSpace);
 497         }
 498
 499         Pools =(Pool*) Base + poolOffset;
 500         WorkSpace = newSize;
 501         return true;
 502 }
 503                                                                         /*}}}*/