/*

 * Copyright (c) 1997, 2013, 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"

#if !defined(_WINDOWS) && !defined(__APPLE__)

#include <string.h>

#include <stdio.h>

#include <limits.h>

#include <new>

#include "memory/allocation.inline.hpp"

#include "utilities/decoder.hpp"

#include "utilities/elfFile.hpp"

#include "utilities/elfFuncDescTable.hpp"

#include "utilities/elfStringTable.hpp"

#include "utilities/elfSymbolTable.hpp"

ElfFile::ElfFile(const char* filepath) {

  assert(filepath, "null file path");

  memset(&m_elfHdr, 0, sizeof(m_elfHdr));

  m_string_tables = NULL;

  m_symbol_tables = NULL;

  m_funcDesc_table = NULL;

  m_next = NULL;

  m_status = NullDecoder::no_error;

  int len = strlen(filepath) + 1;

  m_filepath = (const char*)os::malloc(len * sizeof(char), mtInternal);

  if (m_filepath != NULL) {

    strcpy((char*)m_filepath, filepath);

    m_file = fopen(filepath, "r");

    if (m_file != NULL) {

      load_tables();

    } else {

      m_status = NullDecoder::file_not_found;

    }

  } else {

    m_status = NullDecoder::out_of_memory;

  }

}

ElfFile::~ElfFile() {

  if (m_string_tables != NULL) {

    delete m_string_tables;

  }

  if (m_symbol_tables != NULL) {

    delete m_symbol_tables;

  }

  if (m_file != NULL) {

    fclose(m_file);

  }

  if (m_filepath != NULL) {

    os::free((void*)m_filepath);

  }

  if (m_next != NULL) {

    delete m_next;

  }

};

//Check elf header to ensure the file is valid.

bool ElfFile::is_elf_file(Elf_Ehdr& hdr) {

  return (ELFMAG0 == hdr.e_ident[EI_MAG0] &&

      ELFMAG1 == hdr.e_ident[EI_MAG1] &&

      ELFMAG2 == hdr.e_ident[EI_MAG2] &&

      ELFMAG3 == hdr.e_ident[EI_MAG3] &&

      ELFCLASSNONE != hdr.e_ident[EI_CLASS] &&

      ELFDATANONE != hdr.e_ident[EI_DATA]);

}

bool ElfFile::load_tables() {

  assert(m_file, "file not open");

  assert(!NullDecoder::is_error(m_status), "already in error");

  // read elf file header

  if (fread(&m_elfHdr, sizeof(m_elfHdr), 1, m_file) != 1) {

    m_status = NullDecoder::file_invalid;

    return false;

  }

  if (!is_elf_file(m_elfHdr)) {

    m_status = NullDecoder::file_invalid;

    return false;

  }

  // walk elf file's section headers, and load string tables

  Elf_Shdr shdr;

  if (!fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {

    if (NullDecoder::is_error(m_status)) return false;

    for (int index = 0; index < m_elfHdr.e_shnum; index ++) {

      if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {

        m_status = NullDecoder::file_invalid;

        return false;

      }

      if (shdr.sh_type == SHT_STRTAB) {

        // string tables

        ElfStringTable* table = new (std::nothrow) ElfStringTable(m_file, shdr, index);

        if (table == NULL) {

          m_status = NullDecoder::out_of_memory;

          return false;

        }

        add_string_table(table);

      } else if (shdr.sh_type == SHT_SYMTAB || shdr.sh_type == SHT_DYNSYM) {

        // symbol tables

        ElfSymbolTable* table = new (std::nothrow) ElfSymbolTable(m_file, shdr);

        if (table == NULL) {

          m_status = NullDecoder::out_of_memory;

          return false;

        }

        add_symbol_table(table);

      }

    }

#if defined(PPC64) && !defined(ABI_ELFv2)

    // Now read the .opd section wich contains the PPC64 function descriptor table.

    // The .opd section is only available on PPC64 (see for example:

    // http://refspecs.linuxfoundation.org/LSB_3.1.1/LSB-Core-PPC64/LSB-Core-PPC64/specialsections.html)

    // so this code should do no harm on other platforms but because of performance reasons we only

    // execute it on PPC64 platforms.

    // Notice that we can only find the .opd section after we have successfully read in the string

    // tables in the previous loop, because we need to query the name of each section which is

    // contained in one of the string tables (i.e. the one with the index m_elfHdr.e_shstrndx).

    // Reset the file pointer

    if (fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {

      m_status = NullDecoder::file_invalid;

      return false;

    }

    for (int index = 0; index < m_elfHdr.e_shnum; index ++) {

      if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {

        m_status = NullDecoder::file_invalid;

        return false;

      }

      if (m_elfHdr.e_shstrndx != SHN_UNDEF && shdr.sh_type == SHT_PROGBITS) {

        ElfStringTable* string_table = get_string_table(m_elfHdr.e_shstrndx);

        if (string_table == NULL) {

          m_status = NullDecoder::file_invalid;

          return false;

        }

        char buf[8]; // '8' is enough because we only want to read ".opd"

        if (string_table->string_at(shdr.sh_name, buf, sizeof(buf)) && !strncmp(".opd", buf, 4)) {

          m_funcDesc_table = new (std::nothrow) ElfFuncDescTable(m_file, shdr, index);

          if (m_funcDesc_table == NULL) {

            m_status = NullDecoder::out_of_memory;

            return false;

          }

          break;

        }

      }

    }

#endif

  }

  return true;

}

bool ElfFile::decode(address addr, char* buf, int buflen, int* offset) {

  // something already went wrong, just give up

  if (NullDecoder::is_error(m_status)) {

    return false;

  }

  ElfSymbolTable* symbol_table = m_symbol_tables;

  int string_table_index;

  int pos_in_string_table;

  int off = INT_MAX;

  bool found_symbol = false;

  while (symbol_table != NULL) {

    if (symbol_table->lookup(addr, &string_table_index, &pos_in_string_table, &off, m_funcDesc_table)) {

      found_symbol = true;

      break;

    }

    symbol_table = symbol_table->m_next;

  }

  if (!found_symbol) return false;

  ElfStringTable* string_table = get_string_table(string_table_index);

  if (string_table == NULL) {

    m_status = NullDecoder::file_invalid;

    return false;

  }

  if (offset) *offset = off;

  return string_table->string_at(pos_in_string_table, buf, buflen);

}

void ElfFile::add_symbol_table(ElfSymbolTable* table) {

  if (m_symbol_tables == NULL) {

    m_symbol_tables = table;

  } else {

    table->m_next = m_symbol_tables;

    m_symbol_tables = table;

  }

}

void ElfFile::add_string_table(ElfStringTable* table) {

  if (m_string_tables == NULL) {

    m_string_tables = table;

  } else {

    table->m_next = m_string_tables;

    m_string_tables = table;

  }

}

ElfStringTable* ElfFile::get_string_table(int index) {

  ElfStringTable* p = m_string_tables;

  while (p != NULL) {

    if (p->index() == index) return p;

    p = p->m_next;

  }

  return NULL;

}

#ifdef LINUX

bool ElfFile::specifies_noexecstack() {

  Elf_Phdr phdr;

  if (!m_file)  return true;

  if (!fseek(m_file, m_elfHdr.e_phoff, SEEK_SET)) {

    for (int index = 0; index < m_elfHdr.e_phnum; index ++) {

      if (fread((void*)&phdr, sizeof(Elf_Phdr), 1, m_file) != 1) {

        m_status = NullDecoder::file_invalid;

        return false;

      }

      if (phdr.p_type == PT_GNU_STACK) {

        if (phdr.p_flags == (PF_R | PF_W))  {

          return true;

        } else {

          return false;

        }

      }

    }

  }

// AARCH64 defaults to noexecstack. All others default to execstack.

#ifdef AARCH64

  return true;

#else

  return false;

#endif

}

#endif

#endif // !_WINDOWS && !__APPLE__