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 #ifndef SHARE_VM_UTILITIES_ELF_FILE_HPP
  26 #define SHARE_VM_UTILITIES_ELF_FILE_HPP
  27 
  28 #if !defined(_WINDOWS) && !defined(__APPLE__)
  29 
  30 #if defined(__OpenBSD__)
  31 #include <sys/exec_elf.h>
  32 #else
  33 #include <elf.h>
  34 #endif
  35 #include <stdio.h>
  36 
  37 #ifdef _LP64
  38 
  39 typedef Elf64_Half      Elf_Half;
  40 typedef Elf64_Word      Elf_Word;
  41 typedef Elf64_Off       Elf_Off;
  42 typedef Elf64_Addr      Elf_Addr;
  43 
  44 typedef Elf64_Ehdr      Elf_Ehdr;
  45 typedef Elf64_Shdr      Elf_Shdr;
  46 typedef Elf64_Phdr      Elf_Phdr;
  47 typedef Elf64_Sym       Elf_Sym;
  48 
  49 #if !defined(_ALLBSD_SOURCE) || defined(__APPLE__)
  50 #define ELF_ST_TYPE ELF64_ST_TYPE
  51 #endif
  52 
  53 #else
  54 
  55 typedef Elf32_Half      Elf_Half;
  56 typedef Elf32_Word      Elf_Word;
  57 typedef Elf32_Off       Elf_Off;
  58 typedef Elf32_Addr      Elf_Addr;
  59 
  60 typedef Elf32_Ehdr      Elf_Ehdr;
  61 typedef Elf32_Shdr      Elf_Shdr;
  62 typedef Elf32_Phdr      Elf_Phdr;
  63 typedef Elf32_Sym       Elf_Sym;
  64 
  65 #if !defined(_ALLBSD_SOURCE) || defined(__APPLE__)
  66 #define ELF_ST_TYPE ELF32_ST_TYPE
  67 #endif
  68 #endif
  69 
  70 #include "globalDefinitions.hpp"
  71 #include "memory/allocation.hpp"
  72 #include "utilities/decoder.hpp"
  73 
  74 class ElfStringTable;
  75 class ElfSymbolTable;
  76 class ElfFuncDescTable;
  77 
  78 // ELF section, may or may not have cached data
  79 class ElfSection VALUE_OBJ_CLASS_SPEC {
  80 private:
  81   Elf_Shdr      _section_hdr;
  82   void*         _section_data;
  83   NullDecoder::decoder_status _stat;
  84 public:
  85   ElfSection(FILE* fd, const Elf_Shdr& hdr);
  86   ~ElfSection();
  87 
  88   NullDecoder::decoder_status status() const { return _stat; }
  89 
  90   const Elf_Shdr* section_header() const { return &_section_hdr; }
  91   const void*     section_data()   const { return (const void*)_section_data; }
  92 private:
  93   // load this section.
  94   // it return no_error, when it fails to cache the section data due to lack of memory
  95   NullDecoder::decoder_status load_section(FILE* const file, const Elf_Shdr& hdr);
  96 };
  97 
  98 class FileReader : public StackObj {
  99 protected:
 100   FILE* const _fd;
 101 public:
 102   FileReader(FILE* const fd) : _fd(fd) {};
 103   bool read(void* buf, size_t size);
 104   int  read_buffer(void* buf, size_t size);
 105   bool set_position(long offset);
 106 };
 107 
 108 // Mark current position, so we can get back to it after
 109 // reads.
 110 class MarkedFileReader : public FileReader {
 111 private:
 112   long  _marked_pos;
 113 public:
 114   MarkedFileReader(FILE* const fd);
 115   ~MarkedFileReader();
 116 
 117   bool has_mark() const { return _marked_pos >= 0; }
 118 };
 119 
 120 // ElfFile is basically an elf file parser, which can lookup the symbol
 121 // that is the nearest to the given address.
 122 // Beware, this code is called from vm error reporting code, when vm is already
 123 // in "error" state, so there are scenarios, lookup will fail. We want this
 124 // part of code to be very defensive, and bait out if anything went wrong.
 125 class ElfFile: public CHeapObj<mtInternal> {
 126   friend class ElfDecoder;
 127 
 128 private:
 129   // link ElfFiles
 130   ElfFile*          _next;
 131 
 132   // Elf file
 133   char*             _filepath;
 134   FILE*             _file;
 135 
 136   // Elf header
 137   Elf_Ehdr          _elfHdr;
 138 
 139   // symbol tables
 140   ElfSymbolTable*   _symbol_tables;
 141 
 142   // regular string tables
 143   ElfStringTable*   _string_tables;
 144 
 145   // section header string table, used for finding section name
 146   ElfStringTable*   _shdr_string_table;
 147 
 148   // function descriptors table
 149   ElfFuncDescTable* _funcDesc_table;
 150 
 151   NullDecoder::decoder_status  _status;
 152 
 153 public:
 154   ElfFile(const char* filepath);
 155   ~ElfFile();
 156 
 157   bool decode(address addr, char* buf, int buflen, int* offset);
 158 
 159   const char* filepath() const {
 160     return _filepath;
 161   }
 162 
 163   bool same_elf_file(const char* filepath) const {
 164     assert(filepath != NULL, "null file path");
 165     return (_filepath != NULL && !strcmp(filepath, _filepath));
 166   }
 167 
 168   NullDecoder::decoder_status get_status() const {
 169     return _status;
 170   }
 171 
 172   // Returns true if the elf file is marked NOT to require an executable stack,
 173   // or if the file could not be opened.
 174   // Returns false if the elf file requires an executable stack, the stack flag
 175   // is not set at all, or if the file can not be read.
 176   // On systems other than linux it always returns false.
 177   static bool specifies_noexecstack(const char* filepath) NOT_LINUX({ return false; });
 178 private:
 179   // sanity check, if the file is a real elf file
 180   static bool is_elf_file(Elf_Ehdr&);
 181 
 182   // parse this elf file
 183   NullDecoder::decoder_status parse_elf(const char* filename);
 184 
 185   // load string, symbol and function descriptor tables from the elf file
 186   NullDecoder::decoder_status load_tables();
 187 
 188   ElfFile*  next() const { return _next; }
 189   void set_next(ElfFile* file) { _next = file; }
 190 
 191   // find a section by name, return section index
 192   // if there is no such section, return -1
 193   int section_by_name(const char* name, Elf_Shdr& hdr);
 194 
 195   // string tables are stored in a linked list
 196   void add_string_table(ElfStringTable* table);
 197 
 198   // symbol tables are stored in a linked list
 199   void add_symbol_table(ElfSymbolTable* table);
 200 
 201   // return a string table at specified section index
 202   ElfStringTable* get_string_table(int index);
 203 
 204 
 205   FILE* const fd() const { return _file; }
 206 
 207   // Cleanup string, symbol and function descriptor tables
 208   void cleanup_tables();
 209 
 210 public:
 211   // For whitebox test
 212   static bool _do_not_cache_elf_section;
 213 };
 214 
 215 #endif // !_WINDOWS && !__APPLE__
 216 
 217 #endif // SHARE_VM_UTILITIES_ELF_FILE_HPP