1 | /*- |
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2 | * Copyright (c) 2006,2008 Joseph Koshy |
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3 | * All rights reserved. |
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4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions |
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7 | * are met: |
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8 | * 1. Redistributions of source code must retain the above copyright |
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9 | * notice, this list of conditions and the following disclaimer. |
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10 | * 2. Redistributions in binary form must reproduce the above copyright |
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11 | * notice, this list of conditions and the following disclaimer in the |
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12 | * documentation and/or other materials provided with the distribution. |
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13 | * |
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14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
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15 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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16 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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17 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
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18 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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19 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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20 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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21 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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22 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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23 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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24 | * SUCH DAMAGE. |
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25 | */ |
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26 | |
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27 | #include <assert.h> |
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28 | #include <gelf.h> |
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29 | |
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30 | #include "_libelf.h" |
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31 | |
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32 | LIBELF_VCSID("$Id: elf_strptr.c 189 2008-07-20 10:38:08Z jkoshy $"); |
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33 | |
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34 | /* |
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35 | * Convert an ELF section#,offset pair to a string pointer. |
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36 | */ |
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37 | |
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38 | char * |
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39 | elf_strptr(Elf *e, size_t scndx, size_t offset) |
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40 | { |
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41 | Elf_Scn *s; |
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42 | Elf_Data *d; |
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43 | size_t alignment, count; |
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44 | GElf_Shdr shdr; |
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45 | |
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46 | if (e == NULL || e->e_kind != ELF_K_ELF) { |
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47 | LIBELF_SET_ERROR(ARGUMENT, 0); |
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48 | return (NULL); |
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49 | } |
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50 | |
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51 | if ((s = elf_getscn(e, scndx)) == NULL || |
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52 | gelf_getshdr(s, &shdr) == NULL) |
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53 | return (NULL); |
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54 | |
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55 | if (shdr.sh_type != SHT_STRTAB || |
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56 | offset >= shdr.sh_size) { |
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57 | LIBELF_SET_ERROR(ARGUMENT, 0); |
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58 | return (NULL); |
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59 | } |
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60 | |
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61 | d = NULL; |
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62 | if (e->e_flags & ELF_F_LAYOUT) { |
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63 | |
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64 | /* |
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65 | * The application is taking responsibility for the |
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66 | * ELF object's layout, so we can directly translate |
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67 | * an offset to a `char *' address using the `d_off' |
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68 | * members of Elf_Data descriptors. |
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69 | */ |
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70 | while ((d = elf_getdata(s, d)) != NULL) { |
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71 | |
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72 | if (d->d_buf == 0 || d->d_size == 0) |
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73 | continue; |
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74 | |
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75 | if (d->d_type != ELF_T_BYTE) { |
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76 | LIBELF_SET_ERROR(DATA, 0); |
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77 | return (NULL); |
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78 | } |
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79 | |
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80 | if (offset >= d->d_off && |
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81 | offset < d->d_off + d->d_size) |
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82 | return ((char *) d->d_buf + offset - d->d_off); |
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83 | } |
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84 | } else { |
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85 | /* |
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86 | * Otherwise, the `d_off' members are not useable and |
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87 | * we need to compute offsets ourselves, taking into |
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88 | * account 'holes' in coverage of the section introduced |
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89 | * by alignment requirements. |
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90 | */ |
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91 | count = (size_t) 0; /* cumulative count of bytes seen */ |
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92 | while ((d = elf_getdata(s, d)) != NULL && count <= offset) { |
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93 | |
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94 | if (d->d_buf == NULL || d->d_size == 0) |
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95 | continue; |
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96 | |
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97 | if (d->d_type != ELF_T_BYTE) { |
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98 | LIBELF_SET_ERROR(DATA, 0); |
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99 | return (NULL); |
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100 | } |
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101 | |
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102 | if ((alignment = d->d_align) > 1) { |
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103 | if ((alignment & (alignment - 1)) != 0) { |
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104 | LIBELF_SET_ERROR(DATA, 0); |
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105 | return (NULL); |
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106 | } |
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107 | count = roundup2(count, alignment); |
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108 | } |
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109 | |
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110 | if (offset < count) { |
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111 | /* offset starts in the 'hole' */ |
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112 | LIBELF_SET_ERROR(ARGUMENT, 0); |
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113 | return (NULL); |
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114 | } |
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115 | |
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116 | if (offset < count + d->d_size) { |
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117 | if (d->d_buf != NULL) |
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118 | return ((char *) d->d_buf + |
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119 | offset - count); |
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120 | LIBELF_SET_ERROR(DATA, 0); |
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121 | return (NULL); |
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122 | } |
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123 | |
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124 | count += d->d_size; |
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125 | } |
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126 | } |
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127 | |
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128 | LIBELF_SET_ERROR(ARGUMENT, 0); |
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129 | return (NULL); |
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130 | } |
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