/*

 * Copyright (c) 2011, 2017, 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 "jvm.h"

#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", p2i(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);

      buf[buflen - 1] = '\0';

      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