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