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