osprey/libelf/lib/strptr.c

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/*
 * Copyright 2005 PathScale, Inc.  All Rights Reserved.
 */

/*
strptr.c - implementation of the elf_strptr(3) function.
Copyright (C) 1995 - 2000, 2003 Michael Riepe <michael@stud.uni-hannover.de>

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.

This library 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#include <private.h>

#ifndef lint
static const char rcsid[] = "@(#) $Id: strptr.c,v 1.1.1.1 2005/10/21 19:00:00 marcel Exp $";
#endif /* lint */

char*
elf_strptr(Elf *elf, size_t section, size_t offset) {
    Elf_Data *data;
    Elf_Scn *scn;
    size_t n;
    char *s;

    if (!elf) {
  return NULL;
    }
    elf_assert(elf->e_magic == ELF_MAGIC);
    if (!(scn = elf_getscn(elf, section))) {
  return NULL;
    }
    if (scn->s_index == SHN_UNDEF) {
  seterr(ERROR_NOSTRTAB);
  return NULL;
    }
    /*
     * checking the section header is more appropriate
     */
    if (elf->e_class == ELFCLASS32) {
  if (scn->s_shdr32.sh_type != SHT_STRTAB) {
      seterr(ERROR_NOSTRTAB);
      return NULL;
  }
    }
#if __LIBELF64
    else if (elf->e_class == ELFCLASS64) {
  if (scn->s_shdr64.sh_type != SHT_STRTAB) {
      seterr(ERROR_NOSTRTAB);
      return NULL;
  }
    }
#endif /* __LIBELF64 */
    else if (valid_class(elf->e_class)) {
  seterr(ERROR_UNIMPLEMENTED);
  return NULL;
    }
    else {
  seterr(ERROR_UNKNOWN_CLASS);
  return NULL;
    }
    /*
     * Find matching buffer
     */
    n = 0;
    data = NULL;
    if (elf->e_elf_flags & ELF_F_LAYOUT) {
  /*
   * Programmer is responsible for d_off
   * Note: buffers may be in any order!
   */
  while ((data = elf_getdata(scn, data))) {
      n = data->d_off;
      if (offset >= n && offset - n < data->d_size) {
    /*
     * Found it
     */
    break;
      }
  }
    }
    else {
  /*
   * Calculate offsets myself
   */
  while ((data = elf_getdata(scn, data))) {
      if (data->d_align > 1) {
    n += data->d_align - 1;
    n -= n % data->d_align;
      }
      if (offset < n) {
    /*
     * Invalid offset: points into a hole
     */
    seterr(ERROR_BADSTROFF);
    return NULL;
      }
      if (offset - n < data->d_size) {
    /*
     * Found it
     */
    break;
      }
      n += data->d_size;
  }
    }
    if (data == NULL) {
  /*
   * Not found
   */
  seterr(ERROR_BADSTROFF);
  return NULL;
    }
    if (data->d_buf == NULL) {
  /*
   * Buffer is NULL (usually the programmers' fault)
   */
  seterr(ERROR_NULLBUF);
  return NULL;
    }
    offset -= n;
    s = (char*)data->d_buf;
    for (n = offset; n < data->d_size; n++) {
  if (s[n] == '\0') {
      /*
       * Return properly NUL terminated string
       */
      return s + offset;
  }
    }
    /*
     * String is not NUL terminated
     * Return error to avoid SEGV in application
     */
    seterr(ERROR_UNTERM);
    return NULL;
}

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