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