external/bsd/elftoolchain/dist/libelf/elf_strptr.c

   1 /*      $NetBSD: elf_strptr.c,v 1.2 2014/03/09 16:58:04 christos Exp $  */
   2
   3 /*-
   4  * Copyright (c) 2006,2008 Joseph Koshy
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  */
  28
  29 #if HAVE_NBTOOL_CONFIG_H
  30 # include "nbtool_config.h"
  31 #endif
  32
  33 #include <sys/param.h>
  34
  35 #include <assert.h>
  36 #include <gelf.h>
  37
  38 #include "_libelf.h"
  39
  40 __RCSID("$NetBSD: elf_strptr.c,v 1.2 2014/03/09 16:58:04 christos Exp $");
  41 ELFTC_VCSID("Id: elf_strptr.c 2271 2011-12-03 17:06:35Z jkoshy ");
  42
  43 /*
  44  * Convert an ELF section#,offset pair to a string pointer.
  45  */
  46
  47 char *
  48 elf_strptr(Elf *e, size_t scndx, size_t offset)
  49 {
  50         Elf_Scn *s;
  51         Elf_Data *d;
  52         size_t alignment, count;
  53         GElf_Shdr shdr;
  54
  55         if (e == NULL || e->e_kind != ELF_K_ELF) {
  56                 LIBELF_SET_ERROR(ARGUMENT, 0);
  57                 return (NULL);
  58         }
  59
  60         if ((s = elf_getscn(e, scndx)) == NULL ||
  61             gelf_getshdr(s, &shdr) == NULL)
  62                 return (NULL);
  63
  64         if (shdr.sh_type != SHT_STRTAB ||
  65             offset >= shdr.sh_size) {
  66                 LIBELF_SET_ERROR(ARGUMENT, 0);
  67                 return (NULL);
  68         }
  69
  70         d = NULL;
  71         if (e->e_flags & ELF_F_LAYOUT) {
  72
  73                 /*
  74                  * The application is taking responsibility for the
  75                  * ELF object's layout, so we can directly translate
  76                  * an offset to a `char *' address using the `d_off'
  77                  * members of Elf_Data descriptors.
  78                  */
  79                 while ((d = elf_getdata(s, d)) != NULL) {
  80
  81                         if (d->d_buf == 0 || d->d_size == 0)
  82                                 continue;
  83
  84                         if (d->d_type != ELF_T_BYTE) {
  85                                 LIBELF_SET_ERROR(DATA, 0);
  86                                 return (NULL);
  87                         }
  88
  89                         if (offset >= d->d_off &&
  90                             offset < d->d_off + d->d_size)
  91                                 return ((char *) d->d_buf + offset - d->d_off);
  92                 }
  93         } else {
  94                 /*
  95                  * Otherwise, the `d_off' members are not useable and
  96                  * we need to compute offsets ourselves, taking into
  97                  * account 'holes' in coverage of the section introduced
  98                  * by alignment requirements.
  99                  */
 100                 count = (size_t) 0;     /* cumulative count of bytes seen */
 101                 while ((d = elf_getdata(s, d)) != NULL && count <= offset) {
 102
 103                         if (d->d_buf == NULL || d->d_size == 0)
 104                                 continue;
 105
 106                         if (d->d_type != ELF_T_BYTE) {
 107                                 LIBELF_SET_ERROR(DATA, 0);
 108                                 return (NULL);
 109                         }
 110
 111                         if ((alignment = d->d_align) > 1) {
 112                                 if ((alignment & (alignment - 1)) != 0) {
 113                                         LIBELF_SET_ERROR(DATA, 0);
 114                                         return (NULL);
 115                                 }
 116                                 count = roundup2(count, alignment);
 117                         }
 118
 119                         if (offset < count) {
 120                                 /* offset starts in the 'hole' */
 121                                 LIBELF_SET_ERROR(ARGUMENT, 0);
 122                                 return (NULL);
 123                         }
 124
 125                         if (offset < count + d->d_size) {
 126                                 if (d->d_buf != NULL)
 127                                         return ((char *) d->d_buf +
 128                                             offset - count);
 129                                 LIBELF_SET_ERROR(DATA, 0);
 130                                 return (NULL);
 131                         }
 132
 133                         count += d->d_size;
 134                 }
 135         }
 136
 137         LIBELF_SET_ERROR(ARGUMENT, 0);
 138         return (NULL);
 139 }