external/bsd/libelf/dist/elf_strptr.c

   1 /*      $NetBSD$        */
   2
   3 /*-
   4  * Copyright (c) 2006 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 #include <sys/cdefs.h>
  30 /* __FBSDID("$FreeBSD: src/lib/libelf/elf_strptr.c,v 1.2.2.1.2.1 2009/10/25 01:10:29 kensmith Exp $"); */
  31
  32 #include <sys/param.h>
  33
  34 #include <assert.h>
  35 #include <gelf.h>
  36
  37 #include "_libelf.h"
  38
  39 /*
  40  * Convert an ELF section#,offset pair to a string pointer.
  41  */
  42
  43 char *
  44 elf_strptr(Elf *e, size_t scndx, size_t offset)
  45 {
  46         Elf_Scn *s;
  47         Elf_Data *d;
  48         size_t alignment, count;
  49         GElf_Shdr shdr;
  50
  51         if (e == NULL || e->e_kind != ELF_K_ELF) {
  52                 LIBELF_SET_ERROR(ARGUMENT, 0);
  53                 return (NULL);
  54         }
  55
  56         if ((s = elf_getscn(e, scndx)) == NULL ||
  57             gelf_getshdr(s, &shdr) == NULL)
  58                 return (NULL);
  59
  60         if (/*shdr.sh_type != SHT_STRTAB || */
  61             offset >= shdr.sh_size) {
  62                 LIBELF_SET_ERROR(ARGUMENT, 0);
  63                 return (NULL);
  64         }
  65
  66         d = NULL;
  67         if (e->e_flags & ELF_F_LAYOUT) {
  68
  69                 /*
  70                  * The application is taking responsibility for the
  71                  * ELF object's layout, so we can directly translate
  72                  * an offset to a `char *' address using the `d_off'
  73                  * members of Elf_Data descriptors.
  74                  */
  75                 while ((d = elf_getdata(s, d)) != NULL) {
  76
  77                         if (d->d_buf == 0 || d->d_size == 0)
  78                                 continue;
  79
  80                         if (d->d_type != ELF_T_BYTE) {
  81                                 LIBELF_SET_ERROR(DATA, 0);
  82                                 return (NULL);
  83                         }
  84
  85                         if (offset >= d->d_off &&
  86                             offset < d->d_off + d->d_size)
  87                                 return ((char *) d->d_buf + offset - d->d_off);
  88                 }
  89         } else {
  90                 /*
  91                  * Otherwise, the `d_off' members are not useable and
  92                  * we need to compute offsets ourselves, taking into
  93                  * account 'holes' in coverage of the section introduced
  94                  * by alignment requirements.
  95                  */
  96                 count = (size_t) 0;     /* cumulative count of bytes seen */
  97                 while ((d = elf_getdata(s, d)) != NULL && count <= offset) {
  98
  99                         if (d->d_buf == NULL || d->d_size == 0)
 100                                 continue;
 101
 102                         if (d->d_type != ELF_T_BYTE) {
 103                                 LIBELF_SET_ERROR(DATA, 0);
 104                                 return (NULL);
 105                         }
 106
 107                         if ((alignment = d->d_align) > 1) {
 108                                 if ((alignment & (alignment - 1)) != 0) {
 109                                         LIBELF_SET_ERROR(DATA, 0);
 110                                         return (NULL);
 111                                 }
 112                                 count = roundup2(count, alignment);
 113                         }
 114
 115                         if (offset < count) {
 116                                 /* offset starts in the 'hole' */
 117                                 LIBELF_SET_ERROR(ARGUMENT, 0);
 118                                 return (NULL);
 119                         }
 120
 121                         if (offset < count + d->d_size) {
 122                                 if (d->d_buf != NULL)
 123                                         return ((char *) d->d_buf +
 124                                             offset - count);
 125                                 LIBELF_SET_ERROR(DATA, 0);
 126                                 return (NULL);
 127                         }
 128
 129                         count += d->d_size;
 130                 }
 131         }
 132
 133         LIBELF_SET_ERROR(ARGUMENT, 0);
 134         return (NULL);
 135 }