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.Seek(0L) && 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 = malloc(iSize);
 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(Start) ||
 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          Start = (Start/PSize)*PSize;
 206          if (msync((char *)Base+Start, Stop - Start, MS_SYNC) < 0)
 207             return _error->Errno("msync", _("Unable to synchronize mmap"));
 208 #endif
 209       }
 210    }
 211    return true;
 212 }
 213                                                                         /*}}}*/
 214
 215 // DynamicMMap::DynamicMMap - Constructor                               /*{{{*/
 216 // ---------------------------------------------------------------------
 217 /* */
 218 DynamicMMap::DynamicMMap(FileFd &F,unsigned long Flags,unsigned long const &Workspace,
 219                          unsigned long const &Grow, unsigned long const &Limit) :
 220                 MMap(Flags), Fd(&F), WorkSpace(Workspace),
 221                 GrowFactor(Grow), Limit(Limit)
 222 {
 223    // disable Moveable if we don't grow
 224    if (Grow == 0)
 225       this->Flags &= ~Moveable;
 226
 227 #ifndef __linux__
 228    // kfreebsd doesn't have mremap, so we use the fallback
 229    if ((this->Flags & Moveable) == Moveable)
 230       this->Flags |= Fallback;
 231 #endif
 232
 233    unsigned long long EndOfFile = Fd->Size();
 234    if (EndOfFile > WorkSpace)
 235       WorkSpace = EndOfFile;
 236    else if(WorkSpace > 0)
 237    {
 238       Fd->Seek(WorkSpace - 1);
 239       char C = 0;
 240       Fd->Write(&C,sizeof(C));
 241    }
 242
 243    Map(F);
 244    iSize = EndOfFile;
 245 }
 246                                                                         /*}}}*/
 247 // DynamicMMap::DynamicMMap - Constructor for a non-file backed map     /*{{{*/
 248 // ---------------------------------------------------------------------
 249 /* We try here to use mmap to reserve some space - this is much more
 250    cooler than the fallback solution to simply allocate a char array
 251    and could come in handy later than we are able to grow such an mmap */
 252 DynamicMMap::DynamicMMap(unsigned long Flags,unsigned long const &WorkSpace,
 253                          unsigned long const &Grow, unsigned long const &Limit) :
 254                 MMap(Flags | UnMapped), Fd(0), WorkSpace(WorkSpace),
 255                 GrowFactor(Grow), Limit(Limit)
 256 {
 257         // disable Moveable if we don't grow
 258         if (Grow == 0)
 259                 this->Flags &= ~Moveable;
 260
 261 #ifndef __linux__
 262         // kfreebsd doesn't have mremap, so we use the fallback
 263         if ((this->Flags & Moveable) == Moveable)
 264                 this->Flags |= Fallback;
 265 #endif
 266
 267 #ifdef _POSIX_MAPPED_FILES
 268         if ((this->Flags & Fallback) != Fallback) {
 269                 // Set the permissions.
 270                 int Prot = PROT_READ;
 271 #ifdef MAP_ANONYMOUS
 272                 int Map = MAP_PRIVATE | MAP_ANONYMOUS;
 273 #else
 274                 int Map = MAP_PRIVATE | MAP_ANON;
 275 #endif
 276                 if ((this->Flags & ReadOnly) != ReadOnly)
 277                         Prot |= PROT_WRITE;
 278                 if ((this->Flags & Public) == Public)
 279 #ifdef MAP_ANONYMOUS
 280                         Map = MAP_SHARED | MAP_ANONYMOUS;
 281 #else
 282                         Map = MAP_SHARED | MAP_ANON;
 283 #endif
 284
 285                 // use anonymous mmap() to get the memory
 286                 Base = (unsigned char*) mmap(0, WorkSpace, Prot, Map, -1, 0);
 287
 288                 if(Base == MAP_FAILED)
 289                         _error->Errno("DynamicMMap",_("Couldn't make mmap of %lu bytes"),WorkSpace);
 290
 291                 iSize = 0;
 292                 return;
 293         }
 294 #endif
 295         // fallback to a static allocated space
 296         Base = calloc(WorkSpace, 1);
 297         iSize = 0;
 298 }
 299                                                                         /*}}}*/
 300 // DynamicMMap::~DynamicMMap - Destructor                               /*{{{*/
 301 // ---------------------------------------------------------------------
 302 /* We truncate the file to the size of the memory data set */
 303 DynamicMMap::~DynamicMMap()
 304 {
 305    if (Fd == 0)
 306    {
 307       if (validData() == false)
 308          return;
 309 #ifdef _POSIX_MAPPED_FILES
 310       if ((Flags & Fallback) != Fallback) {
 311          munmap(Base, WorkSpace);
 312       } else
 313 #endif
 314       free(Base);
 315       return;
 316    }
 317
 318    unsigned long long EndOfFile = iSize;
 319    iSize = WorkSpace;
 320    Close(false);
 321    if(ftruncate(Fd->Fd(),EndOfFile) < 0)
 322       _error->Errno("ftruncate", _("Failed to truncate file"));
 323 }
 324                                                                         /*}}}*/
 325 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 326 // ---------------------------------------------------------------------
 327 /* This allocates a block of memory aligned to the given size */
 328 unsigned long DynamicMMap::RawAllocate(unsigned long long Size,unsigned long Aln)
 329 {
 330    unsigned long long Result = iSize;
 331    if (Aln != 0)
 332       Result += Aln - (iSize%Aln);
 333
 334    iSize = Result + Size;
 335
 336    // try to grow the buffer
 337    while(Result + Size > WorkSpace)
 338    {
 339       if(!Grow())
 340       {
 341          _error->Fatal(_("Dynamic MMap ran out of room. Please increase the size "
 342                          "of APT::Cache-Start. Current value: %lu. (man 5 apt.conf)"), WorkSpace);
 343          return 0;
 344       }
 345    }
 346    return Result;
 347 }
 348                                                                         /*}}}*/
 349 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 350 // ---------------------------------------------------------------------
 351 /* This allocates an Item of size ItemSize so that it is aligned to its
 352    size in the file. */
 353 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 354 {
 355    if (unlikely(ItemSize == 0))
 356    {
 357       _error->Fatal("Can't allocate an item of size zero");
 358       return 0;
 359    }
 360
 361    // Look for a matching pool entry
 362    Pool *I;
 363    Pool *Empty = 0;
 364    for (I = Pools; I != Pools + PoolCount; ++I)
 365    {
 366       if (I->ItemSize == 0)
 367          Empty = I;
 368       if (I->ItemSize == ItemSize)
 369          break;
 370    }
 371    // No pool is allocated, use an unallocated one
 372    if (I == Pools + PoolCount)
 373    {
 374       // Woops, we ran out, the calling code should allocate more.
 375       if (Empty == 0)
 376       {
 377          _error->Error("Ran out of allocation pools");
 378          return 0;
 379       }
 380
 381       I = Empty;
 382       I->ItemSize = ItemSize;
 383       I->Count = 0;
 384    }
 385
 386    unsigned long Result = 0;
 387    // Out of space, allocate some more
 388    if (I->Count == 0)
 389    {
 390       const unsigned long size = 20*1024;
 391       I->Count = size/ItemSize;
 392       Pool* oldPools = Pools;
 393       _error->PushToStack();
 394       Result = RawAllocate(size,ItemSize);
 395       bool const newError = _error->PendingError();
 396       _error->MergeWithStack();
 397       if (Pools != oldPools)
 398          I += Pools - oldPools;
 399
 400       // Does the allocation failed ?
 401       if (Result == 0 && newError)
 402          return 0;
 403       I->Start = Result;
 404    }
 405    else
 406       Result = I->Start;
 407
 408    I->Count--;
 409    I->Start += ItemSize;
 410    return Result/ItemSize;
 411 }
 412                                                                         /*}}}*/
 413 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 414 // ---------------------------------------------------------------------
 415 /* Strings are aligned to 16 bytes */
 416 unsigned long DynamicMMap::WriteString(const char *String,
 417                                        unsigned long Len)
 418 {
 419    if (Len == (unsigned long)-1)
 420       Len = strlen(String);
 421
 422    _error->PushToStack();
 423    unsigned long Result = RawAllocate(Len+1+sizeof(uint16_t),sizeof(uint16_t));
 424    bool const newError = _error->PendingError();
 425    _error->MergeWithStack();
 426
 427    if (Base == NULL || (Result == 0 && newError))
 428       return 0;
 429
 430    if (Len >= std::numeric_limits<uint16_t>::max())
 431       abort();
 432
 433    uint16_t LenToWrite = Len;
 434    memcpy((char *)Base + Result, &LenToWrite, sizeof(LenToWrite));
 435    Result += + sizeof(LenToWrite);
 436
 437    memcpy((char *)Base + Result,String,Len);
 438    ((char *)Base)[Result + Len] = 0;
 439    return Result;
 440 }
 441                                                                         /*}}}*/
 442 // DynamicMMap::Grow - Grow the mmap                                    /*{{{*/
 443 // ---------------------------------------------------------------------
 444 /* This method is a wrapper around different methods to (try to) grow
 445    a mmap (or our char[]-fallback). Encounterable environments:
 446    1. Moveable + !Fallback + linux -> mremap with MREMAP_MAYMOVE
 447    2. Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 448    3. Moveable + Fallback -> realloc
 449    4. !Moveable + !Fallback + linux -> mremap alone - which will fail in 99,9%
 450    5. !Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 451    6. !Moveable + Fallback -> not possible
 452    [ While Moveable and Fallback stands for the equally named flags and
 453      "linux" indicates a linux kernel instead of a freebsd kernel. ]
 454    So what you can see here is, that a MMAP which want to be growable need
 455    to be moveable to have a real chance but that this method will at least try
 456    the nearly impossible 4 to grow it before it finally give up: Never say never. */
 457 bool DynamicMMap::Grow() {
 458         if (Limit != 0 && WorkSpace >= Limit)
 459                 return _error->Error(_("Unable to increase the size of the MMap as the "
 460                                        "limit of %lu bytes is already reached."), Limit);
 461         if (GrowFactor <= 0)
 462                 return _error->Error(_("Unable to increase size of the MMap as automatic growing is disabled by user."));
 463
 464         unsigned long long const newSize = WorkSpace + GrowFactor;
 465
 466         if(Fd != 0) {
 467                 Fd->Seek(newSize - 1);
 468                 char C = 0;
 469                 Fd->Write(&C,sizeof(C));
 470         }
 471
 472         unsigned long const poolOffset = Pools - ((Pool*) Base);
 473
 474         if ((Flags & Fallback) != Fallback) {
 475 #if defined(_POSIX_MAPPED_FILES) && defined(__linux__)
 476    #ifdef MREMAP_MAYMOVE
 477
 478                 if ((Flags & Moveable) == Moveable)
 479                         Base = mremap(Base, WorkSpace, newSize, MREMAP_MAYMOVE);
 480                 else
 481    #endif
 482                         Base = mremap(Base, WorkSpace, newSize, 0);
 483
 484                 if(Base == MAP_FAILED)
 485                         return false;
 486 #else
 487                 return false;
 488 #endif
 489         } else {
 490                 if ((Flags & Moveable) != Moveable)
 491                         return false;
 492
 493                 auto Temp = realloc(Base, newSize);
 494                 if (Temp == NULL)
 495                         return false;
 496                 else {
 497                         Base = Temp;
 498                         /* Set new memory to 0 */
 499                         memset((char*)Base + WorkSpace, 0, newSize - WorkSpace);
 500                 }
 501         }
 502
 503         Pools =(Pool*) Base + poolOffset;
 504         WorkSpace = newSize;
 505         return true;
 506 }
 507                                                                         /*}}}*/