jdk

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/*
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 * Copyright (c) 2011, 2023, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#ifdef __APPLE__
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#include "decoder_machO.hpp"
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#include "jvm.h"
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#include "memory/allocation.inline.hpp"
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#include <cxxabi.h>
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#include <mach-o/loader.h>
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#include <mach-o/nlist.h>
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bool MachODecoder::demangle(const char* symbol, char *buf, int buflen) {
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  int   status;
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  char* result;
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  size_t size = (size_t)buflen;
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  // Don't pass buf to __cxa_demangle. In case of the 'buf' is too small,
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  // __cxa_demangle will call system "realloc" for additional memory, which
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  // may use different malloc/realloc mechanism that allocates 'buf'.
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  if ((result = abi::__cxa_demangle(symbol, nullptr, nullptr, &status)) != nullptr) {
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    jio_snprintf(buf, buflen, "%s", result);
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      // call c library's free
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      ::free(result);
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      return true;
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  }
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  return false;
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}
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bool MachODecoder::decode(address addr, char *buf,
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      int buflen, int *offset, const void *mach_base) {
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  if (addr == (address)(intptr_t)-1) {
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    // dladdr() in macOS12/Monterey returns success for -1, but that addr value
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    // won't work in this function. Should have been handled by the caller.
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    ShouldNotReachHere();
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    return false;
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  }
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  struct symtab_command * symt = (struct symtab_command *)
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    mach_find_command((struct mach_header_64 *)mach_base, LC_SYMTAB);
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  if (symt == nullptr) {
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    DEBUG_ONLY(tty->print_cr("no symtab in mach file at 0x%lx", p2i(mach_base)));
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    return false;
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  }
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  uint32_t off = symt->symoff;          /* symbol table offset (within this mach file) */
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  uint32_t nsyms = symt->nsyms;         /* number of symbol table entries */
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  uint32_t stroff = symt->stroff;       /* string table offset */
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  uint32_t strsize = symt->strsize;     /* string table size in bytes */
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  // iterate through symbol table trying to match our offset
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  uint32_t addr_relative = (uintptr_t) mach_base - (uintptr_t) addr; // offset we seek in the symtab
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  void * symtab_addr = (void*) ((uintptr_t) mach_base + off);
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  struct nlist_64 *cur_nlist = (struct nlist_64 *) symtab_addr;
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  struct nlist_64 *last_nlist = cur_nlist;  // no size stored in an entry, so keep previously seen nlist
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  int32_t found_strx = 0;
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  int32_t found_symval = 0;
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  for (uint32_t i=0; i < nsyms; i++) {
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    uint32_t this_value = cur_nlist->n_value;
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    if (addr_relative == this_value) {
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      found_strx =  cur_nlist->n_un.n_strx;
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      found_symval = this_value;
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      break;
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    } else if (addr_relative > this_value) {
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      // gone past it, use previously seen nlist:
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      found_strx = last_nlist->n_un.n_strx;
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      found_symval = last_nlist->n_value;
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      break;
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    }
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    last_nlist = cur_nlist;
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    cur_nlist = cur_nlist + sizeof(struct nlist_64);
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  }
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  if (found_strx == 0) {
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    return false;
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  }
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  // write the offset:
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  *offset = addr_relative - found_symval;
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  // lookup found_strx in the string table
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  char * symname = mach_find_in_stringtable((char*) ((uintptr_t)mach_base + stroff), strsize, found_strx);
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  if (symname) {
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      strncpy(buf, symname, buflen);
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      buf[buflen - 1] = '\0';
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      return true;
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  }
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  DEBUG_ONLY(tty->print_cr("no string or null string found."));
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  return false;
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}
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void* MachODecoder::mach_find_command(struct mach_header_64 * mach_base, uint32_t command_wanted) {
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  // possibly verify it is a mach_header, use magic number.
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  // commands begin immediately after the header.
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  struct load_command *pos = (struct load_command *) mach_base + sizeof(struct mach_header_64);
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  for (uint32_t i = 0; i < mach_base->ncmds; i++) {
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    struct load_command *this_cmd = (struct load_command *) pos;
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    if (this_cmd->cmd == command_wanted) {
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       return pos;
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    }
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    int cmdsize = this_cmd->cmdsize;
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    pos += cmdsize;
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  }
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  return nullptr;
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}
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char* MachODecoder::mach_find_in_stringtable(char *strtab, uint32_t tablesize, int strx_wanted) {
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  if (strx_wanted == 0) {
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    return nullptr;
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  }
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  char *strtab_end = strtab + tablesize;
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  // find the first string, skip over the space char
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  // (or the four zero bytes we see e.g. in libclient)
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  if (*strtab == ' ') {
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      strtab++;
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      if (*strtab != 0) {
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          DEBUG_ONLY(tty->print_cr("string table has leading space but no following zero."));
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          return nullptr;
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      }
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      strtab++;
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  } else {
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      if ((uint32_t) *strtab != 0) {
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          DEBUG_ONLY(tty->print_cr("string table without leading space or leading int of zero."));
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          return nullptr;
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      }
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      strtab+=4;
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  }
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  // read the real strings starting at index 1
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  int cur_strx = 1;
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  while (strtab < strtab_end) {
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    if (cur_strx == strx_wanted) {
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        return strtab;
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    }
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    // find start of next string
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    while (*strtab != 0) {
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        strtab++;
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    }
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    strtab++; // skip the terminating zero
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    cur_strx++;
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  }
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  DEBUG_ONLY(tty->print_cr("string number %d not found.", strx_wanted));
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  return nullptr;
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}
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#endif
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