src/transwalkers.cpp

   1 /*
   2  * Copyright (c) 2003-2004 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 //
  26 // transwalkers - server side transition data walking support
  27 //
  28 // These are data walker operators for securely marshaling and unmarshaling
  29 // data structures across IPC. They are also in charge of fixing byte order
  30 // inconsistencies between server and clients.
  31 //
  32 #include <transwalkers.h>
  33
  34
  35 using LowLevelMemoryUtilities::increment;
  36 using LowLevelMemoryUtilities::difference;
  37
  38
  39 bool flipClient()
  40 {
  41         return Server::process().byteFlipped();
  42 }
  43
  44
  45 //
  46 // CheckingRelocateWalkers
  47 //
  48 CheckingReconstituteWalker::CheckingReconstituteWalker(void *ptr, void *base, size_t size, bool flip)
  49         : mBase(base), mFlip(flip)
  50 {
  51         if (mFlip)
  52                 Flippers::flip(mBase);  // came in reversed; fix for base use
  53         mOffset = difference(ptr, mBase);
  54         mLimit = increment(mBase, size);
  55 }
  56
  57
  58 //
  59 // Relocation support
  60 //
  61 void relocate(Context &context, void *base, Context::Attr *attrs, uint32 attrSize)
  62 {
  63         flip(context);
  64         CheckingReconstituteWalker relocator(attrs, base, attrSize, flipClient());
  65         context.ContextAttributes = attrs;      // fix context->attr vector link
  66         for (uint32 n = 0; n < context.attributesInUse(); n++)
  67                 walk(relocator, context[n]);
  68 }
  69
  70
  71 //
  72 // Outbound flipping support
  73 //
  74 FlipWalker::~FlipWalker()
  75 {
  76         for (set<Flipper>::const_iterator it = mFlips.begin(); it != mFlips.end(); it++)
  77                 delete it->impl;
  78 }
  79
  80 void FlipWalker::doFlips(bool active)
  81 {
  82         if (active) {
  83                 secdebug("flipwalkers", "starting outbound flips");
  84                 for (set<Flipper>::const_iterator it = mFlips.begin(); it != mFlips.end(); it++)
  85                         it->impl->flip();
  86                 secdebug("flipwalkers", "outbound flips done");
  87         }
  88 }
  89
  90
  91 //
  92 // Choose a Database from a choice of two sources, giving preference
  93 // to persistent stores and to earlier sources.
  94 //
  95 Database *pickDb(Database *db1, Database *db2)
  96 {
  97         // persistent db1 always wins
  98         if (db1 && !db1->transient())
  99                 return db1;
 100
 101         // persistent db2 is next choice
 102         if (db2 && !db2->transient())
 103                 return db2;
 104
 105         // pick any existing transient database
 106         if (db1)
 107                 return db1;
 108         if (db2)
 109                 return db2;
 110
 111         // none at all. use the canonical transient store
 112         return Server::optionalDatabase(noDb);
 113 }