1 /*
   2  * Copyright (c) 1997, 2018, 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 "jvm.h"
  26 #include "utilities/decoder_elf.hpp"
  27 #include "utilities/elfFile.hpp"
  28 
  29 #include <cxxabi.h>
  30 
  31 bool ElfDecoder::demangle(const char* symbol, char *buf, int buflen) {
  32   int   status;
  33   char* result;
  34   size_t size = (size_t)buflen;
  35 
  36 #ifdef PPC64
  37   // On PPC64 ElfDecoder::decode() may return a dot (.) prefixed name
  38   // (see elfFuncDescTable.hpp for details)
  39   if (symbol && *symbol == '.') symbol += 1;
  40 #endif
  41 
  42   // Don't pass buf to __cxa_demangle. In case of the 'buf' is too small,
  43   // __cxa_demangle will call system "realloc" for additional memory, which
  44   // may use different malloc/realloc mechanism that allocates 'buf'.
  45   if ((result = abi::__cxa_demangle(symbol, NULL, NULL, &status)) != NULL) {
  46     jio_snprintf(buf, buflen, "%s", result);
  47       // call c library's free
  48       ::free(result);
  49       return true;
  50   }
  51   return false;
  52 }
  53 
  54 // Returns true if the elf file is marked NOT to require an executable stack,
  55 // or if the file could not be opened.
  56 // Returns false if the elf file requires an executable stack, the stack flag
  57 // is not set at all, or if the file can not be read.
  58 bool ElfFile::specifies_noexecstack(const char* filepath) {
  59   if (filepath == NULL) return true;
  60 
  61   FILE* file = fopen(filepath, "r");
  62   if (file == NULL)  return true;
  63 
  64   // AARCH64 defaults to noexecstack. All others default to execstack.
  65   bool result = AARCH64_ONLY(true) NOT_AARCH64(false);
  66 
  67   // Read file header
  68   Elf_Ehdr head;
  69   if (fread(&head, sizeof(Elf_Ehdr), 1, file) == 1 &&
  70       is_elf_file(head) &&
  71       fseek(file, head.e_phoff, SEEK_SET) == 0) {
  72 
  73     // Read program header table
  74     Elf_Phdr phdr;
  75     for (int index = 0; index < head.e_phnum; index ++) {
  76       if (fread((void*)&phdr, sizeof(Elf_Phdr), 1, file) != 1) {
  77         result = false;
  78         break;
  79       }
  80       if (phdr.p_type == PT_GNU_STACK) {
  81         result = (phdr.p_flags == (PF_R | PF_W));
  82         break;
  83       }
  84     }
  85   }
  86   fclose(file);
  87   return result;
  88 }