1 /*
   2  * Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 
  27 #ifdef __APPLE__
  28 #include "decoder_machO.hpp"
  29 
  30 #include <cxxabi.h>
  31 #include <mach-o/loader.h>
  32 #include <mach-o/nlist.h>
  33 
  34 
  35 bool MachODecoder::demangle(const char* symbol, char *buf, int buflen) {
  36   int   status;
  37   char* result;
  38   size_t size = (size_t)buflen;
  39   // Don't pass buf to __cxa_demangle. In case of the 'buf' is too small,
  40   // __cxa_demangle will call system "realloc" for additional memory, which
  41   // may use different malloc/realloc mechanism that allocates 'buf'.
  42   if ((result = abi::__cxa_demangle(symbol, NULL, NULL, &status)) != NULL) {
  43     jio_snprintf(buf, buflen, "%s", result);
  44       // call c library's free
  45       ::free(result);
  46       return true;
  47   }
  48   return false;
  49 }
  50 
  51 bool MachODecoder::decode(address addr, char *buf,
  52       int buflen, int *offset, const void *mach_base) {
  53   struct symtab_command * symt = (struct symtab_command *)
  54     mach_find_command((struct mach_header_64 *)mach_base, LC_SYMTAB);
  55   if (symt == NULL) {
  56     DEBUG_ONLY(tty->print_cr("no symtab in mach file at 0x%lx", p2i(mach_base)));
  57     return false;
  58   }
  59   uint32_t off = symt->symoff;          /* symbol table offset (within this mach file) */
  60   uint32_t nsyms = symt->nsyms;         /* number of symbol table entries */
  61   uint32_t stroff = symt->stroff;       /* string table offset */
  62   uint32_t strsize = symt->strsize;     /* string table size in bytes */
  63 
  64   // iterate through symbol table trying to match our offset
  65 
  66   uint32_t addr_relative = (uintptr_t) mach_base - (uintptr_t) addr; // offset we seek in the symtab
  67   void * symtab_addr = (void*) ((uintptr_t) mach_base + off);
  68   struct nlist_64 *cur_nlist = (struct nlist_64 *) symtab_addr;
  69   struct nlist_64 *last_nlist = cur_nlist;  // no size stored in an entry, so keep previously seen nlist
  70 
  71   int32_t found_strx = 0;
  72   int32_t found_symval = 0;
  73 
  74   for (uint32_t i=0; i < nsyms; i++) {
  75     uint32_t this_value = cur_nlist->n_value;
  76 
  77     if (addr_relative == this_value) {
  78       found_strx =  cur_nlist->n_un.n_strx;
  79       found_symval = this_value;
  80       break;
  81     } else if (addr_relative > this_value) {
  82       // gone past it, use previously seen nlist:
  83       found_strx = last_nlist->n_un.n_strx;
  84       found_symval = last_nlist->n_value;
  85       break;
  86     }
  87     last_nlist = cur_nlist;
  88     cur_nlist = cur_nlist + sizeof(struct nlist_64);
  89   }
  90   if (found_strx == 0) {
  91     return false;
  92   }
  93   // write the offset:
  94   *offset = addr_relative - found_symval;
  95 
  96   // lookup found_strx in the string table
  97   char * symname = mach_find_in_stringtable((char*) ((uintptr_t)mach_base + stroff), strsize, found_strx);
  98   if (symname) {
  99       strncpy(buf, symname, buflen);
 100       return true;
 101   }
 102   DEBUG_ONLY(tty->print_cr("no string or null string found."));
 103   return false;
 104 }
 105 
 106 void* MachODecoder::mach_find_command(struct mach_header_64 * mach_base, uint32_t command_wanted) {
 107   // possibly verify it is a mach_header, use magic number.
 108   // commands begin immediately after the header.
 109   struct load_command *pos = (struct load_command *) mach_base + sizeof(struct mach_header_64);
 110   for (uint32_t i = 0; i < mach_base->ncmds; i++) {
 111     struct load_command *this_cmd = (struct load_command *) pos;
 112     if (this_cmd->cmd == command_wanted) {
 113        return pos;
 114     }
 115     int cmdsize = this_cmd->cmdsize;
 116     pos += cmdsize;
 117   }
 118   return NULL;
 119 }
 120 
 121 char* MachODecoder::mach_find_in_stringtable(char *strtab, uint32_t tablesize, int strx_wanted) {
 122 
 123   if (strx_wanted == 0) {
 124     return NULL;
 125   }
 126   char *strtab_end = strtab + tablesize;
 127 
 128   // find the first string, skip over the space char
 129   // (or the four zero bytes we see e.g. in libclient)
 130   if (*strtab == ' ') {
 131       strtab++;
 132       if (*strtab != 0) {
 133           DEBUG_ONLY(tty->print_cr("string table has leading space but no following zero."));
 134           return NULL;
 135       }
 136       strtab++;
 137   } else {
 138       if ((uint32_t) *strtab != 0) {
 139           DEBUG_ONLY(tty->print_cr("string table without leading space or leading int of zero."));
 140           return NULL;
 141       }
 142       strtab+=4;
 143   }
 144   // read the real strings starting at index 1
 145   int cur_strx = 1;
 146   while (strtab < strtab_end) {
 147     if (cur_strx == strx_wanted) {
 148         return strtab;
 149     }
 150     // find start of next string
 151     while (*strtab != 0) {
 152         strtab++;
 153     }
 154     strtab++; // skip the terminating zero
 155     cur_strx++;
 156   }
 157   DEBUG_ONLY(tty->print_cr("string number %d not found.", strx_wanted));
 158   return NULL;
 159 }
 160 
 161 
 162 #endif
 163 
 164