contrib/elftoolchain/libelf/elf_strptr.c

   1 /*-
   2  * Copyright (c) 2006,2008 Joseph Koshy
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  24  * SUCH DAMAGE.
  25  */
  26
  27 #include <sys/param.h>
  28
  29 #include <assert.h>
  30 #include <gelf.h>
  31
  32 #include "_libelf.h"
  33
  34 ELFTC_VCSID("$Id: elf_strptr.c 2990 2014-03-17 09:56:58Z jkoshy $");
  35
  36 /*
  37  * Convert an ELF section#,offset pair to a string pointer.
  38  */
  39
  40 char *
  41 elf_strptr(Elf *e, size_t scndx, size_t offset)
  42 {
  43         Elf_Scn *s;
  44         Elf_Data *d;
  45         GElf_Shdr shdr;
  46         uint64_t alignment, count;
  47
  48         if (e == NULL || e->e_kind != ELF_K_ELF) {
  49                 LIBELF_SET_ERROR(ARGUMENT, 0);
  50                 return (NULL);
  51         }
  52
  53         if ((s = elf_getscn(e, scndx)) == NULL ||
  54             gelf_getshdr(s, &shdr) == NULL)
  55                 return (NULL);
  56
  57         if (shdr.sh_type != SHT_STRTAB ||
  58             offset >= shdr.sh_size) {
  59                 LIBELF_SET_ERROR(ARGUMENT, 0);
  60                 return (NULL);
  61         }
  62
  63         d = NULL;
  64         if (e->e_flags & ELF_F_LAYOUT) {
  65
  66                 /*
  67                  * The application is taking responsibility for the
  68                  * ELF object's layout, so we can directly translate
  69                  * an offset to a `char *' address using the `d_off'
  70                  * members of Elf_Data descriptors.
  71                  */
  72                 while ((d = elf_getdata(s, d)) != NULL) {
  73
  74                         if (d->d_buf == 0 || d->d_size == 0)
  75                                 continue;
  76
  77                         if (d->d_type != ELF_T_BYTE) {
  78                                 LIBELF_SET_ERROR(DATA, 0);
  79                                 return (NULL);
  80                         }
  81
  82                         if (offset >= d->d_off &&
  83                             offset < d->d_off + d->d_size)
  84                                 return ((char *) d->d_buf + offset - d->d_off);
  85                 }
  86         } else {
  87                 /*
  88                  * Otherwise, the `d_off' members are not useable and
  89                  * we need to compute offsets ourselves, taking into
  90                  * account 'holes' in coverage of the section introduced
  91                  * by alignment requirements.
  92                  */
  93                 count = (uint64_t) 0;   /* cumulative count of bytes seen */
  94                 while ((d = elf_getdata(s, d)) != NULL && count <= offset) {
  95
  96                         if (d->d_buf == NULL || d->d_size == 0)
  97                                 continue;
  98
  99                         if (d->d_type != ELF_T_BYTE) {
 100                                 LIBELF_SET_ERROR(DATA, 0);
 101                                 return (NULL);
 102                         }
 103
 104                         if ((alignment = d->d_align) > 1) {
 105                                 if ((alignment & (alignment - 1)) != 0) {
 106                                         LIBELF_SET_ERROR(DATA, 0);
 107                                         return (NULL);
 108                                 }
 109                                 count = roundup2(count, alignment);
 110                         }
 111
 112                         if (offset < count) {
 113                                 /* offset starts in the 'hole' */
 114                                 LIBELF_SET_ERROR(ARGUMENT, 0);
 115                                 return (NULL);
 116                         }
 117
 118                         if (offset < count + d->d_size) {
 119                                 if (d->d_buf != NULL)
 120                                         return ((char *) d->d_buf +
 121                                             offset - count);
 122                                 LIBELF_SET_ERROR(DATA, 0);
 123                                 return (NULL);
 124                         }
 125
 126                         count += d->d_size;
 127                 }
 128         }
 129
 130         LIBELF_SET_ERROR(ARGUMENT, 0);
 131         return (NULL);
 132 }