decoder_machO.cpp revision 6412:53a41e7cbe05 
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
35bool 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
51bool 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
106void* 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
121char* 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
165