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    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(nullptr), SyncToFd(nullptr)
  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       if (unlikely(Base == nullptr))
  88          return _error->Errno("MMap-compressed-malloc", _("Couldn't make mmap of %llu bytes"), iSize);
  89       SyncToFd = new FileFd();
  90       if (Fd.Seek(0L) == false || Fd.Read(Base, iSize) == false)
  91          return _error->Error("Compressed file %s can't be read into mmap", Fd.Name().c_str());
  92       return true;
  93    }
  94
  95    // Map it.
  96    Base = (Flags & Fallback) ? MAP_FAILED : mmap(0,iSize,Prot,Map,Fd.Fd(),0);
  97    if (Base == MAP_FAILED)
  98    {
  99       if (errno == ENODEV || errno == EINVAL || (Flags & Fallback))
 100       {
 101          // The filesystem doesn't support this particular kind of mmap.
 102          // So we allocate a buffer and read the whole file into it.
 103          if ((Flags & ReadOnly) == ReadOnly)
 104          {
 105             // for readonly, we don't need sync, so make it simple
 106             Base = malloc(iSize);
 107             if (unlikely(Base == nullptr))
 108                return _error->Errno("MMap-malloc", _("Couldn't make mmap of %llu bytes"), iSize);
 109             SyncToFd = new FileFd();
 110             return Fd.Read(Base, iSize);
 111          }
 112          // FIXME: Writing to compressed fd's ?
 113          int const dupped_fd = dup(Fd.Fd());
 114          if (dupped_fd == -1)
 115             return _error->Errno("mmap", _("Couldn't duplicate file descriptor %i"), Fd.Fd());
 116
 117          Base = calloc(iSize, 1);
 118          if (unlikely(Base == nullptr))
 119             return _error->Errno("MMap-calloc", _("Couldn't make mmap of %llu bytes"), iSize);
 120          SyncToFd = new FileFd (dupped_fd);
 121          if (!SyncToFd->Seek(0L) || !SyncToFd->Read(Base, iSize))
 122             return false;
 123       }
 124       else
 125          return _error->Errno("MMap-mmap", _("Couldn't make mmap of %llu bytes"), iSize);
 126      }
 127
 128    return true;
 129 }
 130                                                                         /*}}}*/
 131 // MMap::Close - Close the map                                          /*{{{*/
 132 // ---------------------------------------------------------------------
 133 /* */
 134 bool MMap::Close(bool DoSync)
 135 {
 136    if ((Flags & UnMapped) == UnMapped || validData() == false || iSize == 0)
 137       return true;
 138
 139    if (DoSync == true)
 140       Sync();
 141
 142    if (SyncToFd != NULL)
 143    {
 144       free(Base);
 145       delete SyncToFd;
 146       SyncToFd = NULL;
 147    }
 148    else
 149    {
 150       if (munmap((char *)Base, iSize) != 0)
 151          _error->WarningE("mmap", _("Unable to close mmap"));
 152    }
 153
 154    iSize = 0;
 155    Base = 0;
 156    return true;
 157 }
 158                                                                         /*}}}*/
 159 // MMap::Sync - Syncronize the map with the disk                        /*{{{*/
 160 // ---------------------------------------------------------------------
 161 /* This is done in syncronous mode - the docs indicate that this will
 162    not return till all IO is complete */
 163 bool MMap::Sync()
 164 {
 165    if ((Flags & UnMapped) == UnMapped)
 166       return true;
 167
 168    if ((Flags & ReadOnly) != ReadOnly)
 169    {
 170       if (SyncToFd != NULL)
 171       {
 172          if (!SyncToFd->Seek(0) || !SyncToFd->Write(Base, iSize))
 173             return false;
 174       }
 175       else
 176       {
 177 #ifdef _POSIX_SYNCHRONIZED_IO
 178          if (msync((char *)Base, iSize, MS_SYNC) < 0)
 179             return _error->Errno("msync", _("Unable to synchronize mmap"));
 180 #endif
 181       }
 182    }
 183    return true;
 184 }
 185                                                                         /*}}}*/
 186 // MMap::Sync - Syncronize a section of the file to disk                /*{{{*/
 187 // ---------------------------------------------------------------------
 188 /* */
 189 bool MMap::Sync(unsigned long Start,unsigned long Stop)
 190 {
 191    if ((Flags & UnMapped) == UnMapped)
 192       return true;
 193
 194    if ((Flags & ReadOnly) != ReadOnly)
 195    {
 196       if (SyncToFd != 0)
 197       {
 198          if (!SyncToFd->Seek(0) ||
 199              !SyncToFd->Write (((char *)Base)+Start, Stop-Start))
 200             return false;
 201       }
 202       else
 203       {
 204 #ifdef _POSIX_SYNCHRONIZED_IO
 205          unsigned long long const PSize = sysconf(_SC_PAGESIZE);
 206          if (msync((char *)Base+(Start/PSize)*PSize, 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(F,Flags | NoImmMap), 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 | NoImmMap | 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       munmap(Base, WorkSpace);
 311 #else
 312       free(Base);
 313 #endif
 314       return;
 315    }
 316
 317    unsigned long long EndOfFile = iSize;
 318    iSize = WorkSpace;
 319    Close(false);
 320    if(ftruncate(Fd->Fd(),EndOfFile) < 0)
 321       _error->Errno("ftruncate", _("Failed to truncate file"));
 322 }
 323                                                                         /*}}}*/
 324 // DynamicMMap::RawAllocate - Allocate a raw chunk of unaligned space   /*{{{*/
 325 // ---------------------------------------------------------------------
 326 /* This allocates a block of memory aligned to the given size */
 327 unsigned long DynamicMMap::RawAllocate(unsigned long long Size,unsigned long Aln)
 328 {
 329    unsigned long long Result = iSize;
 330    if (Aln != 0)
 331       Result += Aln - (iSize%Aln);
 332
 333    iSize = Result + Size;
 334
 335    // try to grow the buffer
 336    while(Result + Size > WorkSpace)
 337    {
 338       if(!Grow())
 339       {
 340          _error->Fatal(_("Dynamic MMap ran out of room. Please increase the size "
 341                          "of APT::Cache-Start. Current value: %lu. (man 5 apt.conf)"), WorkSpace);
 342          return 0;
 343       }
 344    }
 345    return Result;
 346 }
 347                                                                         /*}}}*/
 348 // DynamicMMap::Allocate - Pooled aligned allocation                    /*{{{*/
 349 // ---------------------------------------------------------------------
 350 /* This allocates an Item of size ItemSize so that it is aligned to its
 351    size in the file. */
 352 unsigned long DynamicMMap::Allocate(unsigned long ItemSize)
 353 {
 354    if (unlikely(ItemSize == 0))
 355    {
 356       _error->Fatal("Can't allocate an item of size zero");
 357       return 0;
 358    }
 359
 360    // Look for a matching pool entry
 361    Pool *I;
 362    Pool *Empty = 0;
 363    for (I = Pools; I != Pools + PoolCount; ++I)
 364    {
 365       if (I->ItemSize == 0)
 366          Empty = I;
 367       if (I->ItemSize == ItemSize)
 368          break;
 369    }
 370    // No pool is allocated, use an unallocated one
 371    if (I == Pools + PoolCount)
 372    {
 373       // Woops, we ran out, the calling code should allocate more.
 374       if (Empty == 0)
 375       {
 376          _error->Error("Ran out of allocation pools");
 377          return 0;
 378       }
 379
 380       I = Empty;
 381       I->ItemSize = ItemSize;
 382       I->Count = 0;
 383    }
 384
 385    unsigned long Result = 0;
 386    // Out of space, allocate some more
 387    if (I->Count == 0)
 388    {
 389       const unsigned long size = 20*1024;
 390       I->Count = size/ItemSize;
 391       Pool* oldPools = Pools;
 392       _error->PushToStack();
 393       Result = RawAllocate(size,ItemSize);
 394       bool const newError = _error->PendingError();
 395       _error->MergeWithStack();
 396       if (Pools != oldPools)
 397          I += Pools - oldPools;
 398
 399       // Does the allocation failed ?
 400       if (Result == 0 && newError)
 401          return 0;
 402       I->Start = Result;
 403    }
 404    else
 405       Result = I->Start;
 406
 407    I->Count--;
 408    I->Start += ItemSize;
 409    return Result/ItemSize;
 410 }
 411                                                                         /*}}}*/
 412 // DynamicMMap::WriteString - Write a string to the file                /*{{{*/
 413 // ---------------------------------------------------------------------
 414 /* Strings are aligned to 16 bytes */
 415 unsigned long DynamicMMap::WriteString(const char *String,
 416                                        unsigned long Len)
 417 {
 418    if (Len == (unsigned long)-1)
 419       Len = strlen(String);
 420
 421    _error->PushToStack();
 422    unsigned long Result = RawAllocate(Len+1+sizeof(uint16_t),sizeof(uint16_t));
 423    bool const newError = _error->PendingError();
 424    _error->MergeWithStack();
 425
 426    if (Base == NULL || (Result == 0 && newError))
 427       return 0;
 428
 429    if (Len >= std::numeric_limits<uint16_t>::max())
 430       abort();
 431
 432    uint16_t LenToWrite = Len;
 433    memcpy((char *)Base + Result, &LenToWrite, sizeof(LenToWrite));
 434    Result += + sizeof(LenToWrite);
 435
 436    memcpy((char *)Base + Result,String,Len);
 437    ((char *)Base)[Result + Len] = 0;
 438    return Result;
 439 }
 440                                                                         /*}}}*/
 441 // DynamicMMap::Grow - Grow the mmap                                    /*{{{*/
 442 // ---------------------------------------------------------------------
 443 /* This method is a wrapper around different methods to (try to) grow
 444    a mmap (or our char[]-fallback). Encounterable environments:
 445    1. Moveable + !Fallback + linux -> mremap with MREMAP_MAYMOVE
 446    2. Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 447    3. Moveable + Fallback -> realloc
 448    4. !Moveable + !Fallback + linux -> mremap alone - which will fail in 99,9%
 449    5. !Moveable + !Fallback + !linux -> not possible (forbidden by constructor)
 450    6. !Moveable + Fallback -> not possible
 451    [ While Moveable and Fallback stands for the equally named flags and
 452      "linux" indicates a linux kernel instead of a freebsd kernel. ]
 453    So what you can see here is, that a MMAP which want to be growable need
 454    to be moveable to have a real chance but that this method will at least try
 455    the nearly impossible 4 to grow it before it finally give up: Never say never. */
 456 bool DynamicMMap::Grow() {
 457         if (Limit != 0 && WorkSpace >= Limit)
 458                 return _error->Error(_("Unable to increase the size of the MMap as the "
 459                                        "limit of %lu bytes is already reached."), Limit);
 460         if (GrowFactor <= 0)
 461                 return _error->Error(_("Unable to increase size of the MMap as automatic growing is disabled by user."));
 462
 463         unsigned long long const newSize = WorkSpace + GrowFactor;
 464
 465         if(Fd != 0) {
 466                 Fd->Seek(newSize - 1);
 467                 char C = 0;
 468                 Fd->Write(&C,sizeof(C));
 469         }
 470
 471         unsigned long const poolOffset = Pools - ((Pool*) Base);
 472
 473         if ((Flags & Fallback) != Fallback) {
 474 #if defined(_POSIX_MAPPED_FILES) && defined(__linux__)
 475    #ifdef MREMAP_MAYMOVE
 476
 477                 if ((Flags & Moveable) == Moveable)
 478                         Base = mremap(Base, WorkSpace, newSize, MREMAP_MAYMOVE);
 479                 else
 480    #endif
 481                         Base = mremap(Base, WorkSpace, newSize, 0);
 482
 483                 if(Base == MAP_FAILED)
 484                         return false;
 485 #else
 486                 return false;
 487 #endif
 488         } else {
 489                 if ((Flags & Moveable) != Moveable)
 490                         return false;
 491
 492                 Base = realloc(Base, newSize);
 493                 if (Base == NULL)
 494                         return false;
 495                 else
 496                         /* Set new memory to 0 */
 497                         memset((char*)Base + WorkSpace, 0, newSize - WorkSpace);
 498         }
 499
 500         Pools =(Pool*) Base + poolOffset;
 501         WorkSpace = newSize;
 502         return true;
 503 }
 504                                                                         /*}}}*/