src/other/PruneTrie.cpp

   1 /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*-
   2  *
   3  * Copyright (c) 2008 Apple Inc. All rights reserved.
   4  *
   5  * @APPLE_LICENSE_HEADER_START@
   6  *
   7  * This file contains Original Code and/or Modifications of Original Code
   8  * as defined in and that are subject to the Apple Public Source License
   9  * Version 2.0 (the 'License'). You may not use this file except in
  10  * compliance with the License. Please obtain a copy of the License at
  11  * http://www.opensource.apple.com/apsl/ and read it before using this
  12  * file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  19  * Please see the License for the specific language governing rights and
  20  * limitations under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 #include <vector>
  25
  26 #include "MachOFileAbstraction.hpp"
  27 #include "MachOTrie.hpp"
  28 #include "prune_trie.h"
  29
  30
  31
  32
  33 /*
  34  * prune_trie() is a C vended function that is used by strip(1) to prune out
  35  * defined exported symbols from the export trie.  It is passed a pointer to
  36  * the start of bytes of the the trie and the size.  The prune() funciton
  37  * passed is called with each symbol name in the trie to determine if it is
  38  * to be pruned (retuning 1) or not (returning 0).  It writes the new trie
  39  * back into the trie buffer and returns the new size in trie_new_size.
  40  * If the pruning succeeds, NULL is returned.  If there was an error processing
  41  * the trie (e.f. it is malformed), then an error message string is returned.
  42  * The error string can be freed.
  43  */
  44 const char*
  45 prune_trie(
  46         uint8_t*        trie_start,
  47         uint32_t        trie_start_size,
  48         int                     (*prune)(const char *name),
  49         uint32_t*       trie_new_size)
  50 {
  51         // convert trie to vector of entries
  52         std::vector<mach_o::trie::Entry> originalExports;
  53         try {
  54                 parseTrie(trie_start, trie_start+trie_start_size, originalExports);
  55         }
  56         catch (const char* msg) {
  57                 return strdup(msg);
  58         }
  59         catch (...) {
  60                 return strdup("unexpected exception processing trie");
  61         }
  62
  63         // prune entries into new vector of entries
  64         std::vector<mach_o::trie::Entry> newExports;
  65         newExports.reserve(originalExports.size());
  66         for(std::vector<mach_o::trie::Entry>::iterator it = originalExports.begin(); it != originalExports.end(); ++it) {
  67                 if ( prune(it->name) == 0 )
  68                         newExports.push_back(*it);
  69         }
  70
  71         // create new export trie
  72         std::vector<uint8_t> newExportTrieBytes;
  73         newExportTrieBytes.reserve(trie_start_size);
  74         mach_o::trie::makeTrie(newExports, newExportTrieBytes);
  75         // Need to align trie to 8 or 4 bytes.  We don't know the arch, but if the incoming trie
  76         // was not 8-byte aligned, then it can't be a 64-bit arch, so use 4-byte alignement.
  77         if ( (trie_start_size % 8) != 0 ) {
  78                 // 4-byte align
  79                 while ( (newExportTrieBytes.size() % 4 ) != 0)
  80                         newExportTrieBytes.push_back(0);
  81         }
  82         else {
  83                 // 8-byte align
  84                 while ( (newExportTrieBytes.size() % 8 ) != 0)
  85                         newExportTrieBytes.push_back(0);
  86         }
  87
  88         // copy into place, zero pad
  89         *trie_new_size = newExportTrieBytes.size();
  90         if ( *trie_new_size > trie_start_size ) {
  91                 char* msg;
  92                 asprintf(&msg, "new trie is larger (%d) than original (%d)", *trie_new_size, trie_start_size);
  93                 return msg;
  94         }
  95         memcpy(trie_start, &newExportTrieBytes[0], *trie_new_size);
  96         bzero(trie_start+*trie_new_size, trie_start_size - *trie_new_size);
  97
  98         // success
  99         return NULL;
 100 }