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 /*

  * Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 #include "precompiled.hpp"

 #ifdef __APPLE__

 #include "decoder_machO.hpp"

 #include <cxxabi.h>

 #include <mach-o/loader.h>

 #include <mach-o/nlist.h>

 bool MachODecoder::demangle(const char* symbol, char *buf, int buflen) {

   int   status;

   char* result;

   size_t size = (size_t)buflen;

   // Don't pass buf to __cxa_demangle. In case of the 'buf' is too small,

   // __cxa_demangle will call system "realloc" for additional memory, which

   // may use different malloc/realloc mechanism that allocates 'buf'.

   if ((result = abi::__cxa_demangle(symbol, NULL, NULL, &status)) != NULL) {

     jio_snprintf(buf, buflen, "%s", result);

       // call c library's free

       ::free(result);

       return true;

   }

   return false;

 }

 bool MachODecoder::decode(address addr, char *buf,

       int buflen, int *offset, const void *mach_base) {

   struct symtab_command * symt = (struct symtab_command *)

     mach_find_command((struct mach_header_64 *)mach_base, LC_SYMTAB);

   if (symt == NULL) {

     DEBUG_ONLY(tty->print_cr("no symtab in mach file at 0x%lx", mach_base));

     return false;

   }

   uint32_t off = symt->symoff;          /* symbol table offset (within this mach file) */

   uint32_t nsyms = symt->nsyms;         /* number of symbol table entries */

   uint32_t stroff = symt->stroff;       /* string table offset */

   uint32_t strsize = symt->strsize;     /* string table size in bytes */

   // iterate through symbol table trying to match our offset

   uint32_t addr_relative = (uintptr_t) mach_base - (uintptr_t) addr; // offset we seek in the symtab

   void * symtab_addr = (void*) ((uintptr_t) mach_base + off);

   struct nlist_64 *cur_nlist = (struct nlist_64 *) symtab_addr;

   struct nlist_64 *last_nlist = cur_nlist;  // no size stored in an entry, so keep previously seen nlist

   int32_t found_strx = 0;

   int32_t found_symval = 0;

   for (uint32_t i=0; i < nsyms; i++) {

     uint32_t this_value = cur_nlist->n_value;

     if (addr_relative == this_value) {

       found_strx =  cur_nlist->n_un.n_strx;

       found_symval = this_value;

       break;

     } else if (addr_relative > this_value) {

       // gone past it, use previously seen nlist:

       found_strx = last_nlist->n_un.n_strx;

       found_symval = last_nlist->n_value;

       break;

     }

     last_nlist = cur_nlist;

     cur_nlist = cur_nlist + sizeof(struct nlist_64);

   }

   if (found_strx == 0) {

     return false;

   }

   // write the offset:

   *offset = addr_relative - found_symval;

   // lookup found_strx in the string table

   char * symname = mach_find_in_stringtable((char*) ((uintptr_t)mach_base + stroff), strsize, found_strx);

   if (symname) {

       strncpy(buf, symname, buflen);

       return true;

   }

   DEBUG_ONLY(tty->print_cr("no string or null string found."));

   return false;

 }

 void* MachODecoder::mach_find_command(struct mach_header_64 * mach_base, uint32_t command_wanted) {

   // possibly verify it is a mach_header, use magic number.

   // commands begin immediately after the header.

   struct load_command *pos = (struct load_command *) mach_base + sizeof(struct mach_header_64);

   for (uint32_t i = 0; i < mach_base->ncmds; i++) {

     struct load_command *this_cmd = (struct load_command *) pos;

     if (this_cmd->cmd == command_wanted) {

        return pos;

     }

     int cmdsize = this_cmd->cmdsize;

     pos += cmdsize;

   }

   return NULL;

 }

 char* MachODecoder::mach_find_in_stringtable(char *strtab, uint32_t tablesize, int strx_wanted) {

   if (strx_wanted == 0) {

     return NULL;

   }

   char *strtab_end = strtab + tablesize;

   // find the first string, skip over the space char

   // (or the four zero bytes we see e.g. in libclient)

   if (*strtab == ' ') {

       strtab++;

       if (*strtab != 0) {

           DEBUG_ONLY(tty->print_cr("string table has leading space but no following zero."));

           return NULL;

       }

       strtab++;

   } else {

       if ((uint32_t) *strtab != 0) {

           DEBUG_ONLY(tty->print_cr("string table without leading space or leading int of zero."));

           return NULL;

       }

       strtab+=4;

   }

   // read the real strings starting at index 1

   int cur_strx = 1;

   while (strtab < strtab_end) {

     if (cur_strx == strx_wanted) {

         return strtab;

     }

     // find start of next string

     while (*strtab != 0) {

         strtab++;

     }

     strtab++; // skip the terminating zero

     cur_strx++;

   }

   DEBUG_ONLY(tty->print_cr("string number %d not found.", strx_wanted));

   return NULL;

 }

 #endif