summaryrefslogtreecommitdiff
path: root/ext/libelf/elf_strptr.c
blob: 6a05fa1d43bfac407f9ad4de1ded94b5bab456c1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
/*-
 * Copyright (c) 2006 Joseph Koshy
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


#include <sys/param.h>
#ifdef __sun
#include <sys/sysmacros.h>
#endif

#include <assert.h>
#include "gelf.h"

#include "_libelf.h"

/*
 * Convert an ELF section#,offset pair to a string pointer.
 */

char *
elf_strptr(Elf *e, size_t scndx, size_t offset)
{
        Elf_Scn *s;
        Elf_Data *d;
        size_t alignment, count;
        GElf_Shdr shdr;

        if (e == NULL || e->e_kind != ELF_K_ELF) {
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);
        }

        if ((s = elf_getscn(e, scndx)) == NULL ||
            gelf_getshdr(s, &shdr) == NULL)
                return (NULL);

        if (shdr.sh_type != SHT_STRTAB ||
            offset >= shdr.sh_size) {
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);
        }

        d = NULL;
        if (e->e_flags & ELF_F_LAYOUT) {

                /*
                 * The application is taking responsibility for the
                 * ELF object's layout, so we can directly translate
                 * an offset to a `char *' address using the `d_off'
                 * members of Elf_Data descriptors.
                 */
                while ((d = elf_getdata(s, d)) != NULL) {

                        if (d->d_buf == 0 || d->d_size == 0)
                                continue;

                        if (d->d_type != ELF_T_BYTE) {
                                LIBELF_SET_ERROR(DATA, 0);
                                return (NULL);
                        }

                        if (offset >= d->d_off &&
                            offset < d->d_off + d->d_size)
                                return ((char *) d->d_buf + offset - d->d_off);
                }
        } else {
                /*
                 * Otherwise, the `d_off' members are not useable and
                 * we need to compute offsets ourselves, taking into
                 * account 'holes' in coverage of the section introduced
                 * by alignment requirements.
                 */
                count = (size_t) 0;	/* cumulative count of bytes seen */
                while ((d = elf_getdata(s, d)) != NULL && count <= offset) {

                        if (d->d_buf == NULL || d->d_size == 0)
                                continue;

                        if (d->d_type != ELF_T_BYTE) {
                                LIBELF_SET_ERROR(DATA, 0);
                                return (NULL);
                        }

                        if ((alignment = d->d_align) > 1) {
                                if ((alignment & (alignment - 1)) != 0) {
                                        LIBELF_SET_ERROR(DATA, 0);
                                        return (NULL);
                                }
                                count = roundup(count, alignment);
                        }

                        if (offset < count) {
                                /* offset starts in the 'hole' */
                                LIBELF_SET_ERROR(ARGUMENT, 0);
                                return (NULL);
                        }

                        if (offset < count + d->d_size) {
                                if (d->d_buf != NULL)
                                        return ((char *) d->d_buf +
                                            offset - count);
                                LIBELF_SET_ERROR(DATA, 0);
                                return (NULL);
                        }

                        count += d->d_size;
                }
        }

        LIBELF_SET_ERROR(ARGUMENT, 0);
        return (NULL);
}