1/*- 2 * Copyright (c) 2006 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/cdefs.h> 28__FBSDID("$FreeBSD: releng/10.2/lib/libelf/elf_strptr.c 179241 2008-05-23 07:35:36Z jb $"); 29 30#include <sys/param.h> 31 32#include <assert.h> 33#include <gelf.h> 34 35#include "_libelf.h" 36 37/* 38 * Convert an ELF section#,offset pair to a string pointer. 39 */ 40 41char * 42elf_strptr(Elf *e, size_t scndx, size_t offset) 43{ 44 Elf_Scn *s; 45 Elf_Data *d; 46 size_t alignment, count; 47 GElf_Shdr shdr; 48 49 if (e == NULL || e->e_kind != ELF_K_ELF) { 50 LIBELF_SET_ERROR(ARGUMENT, 0); 51 return (NULL); 52 } 53 54 if ((s = elf_getscn(e, scndx)) == NULL || 55 gelf_getshdr(s, &shdr) == NULL) 56 return (NULL); 57 58 if (/*shdr.sh_type != SHT_STRTAB || */ 59 offset >= shdr.sh_size) { 60 LIBELF_SET_ERROR(ARGUMENT, 0); 61 return (NULL); 62 } 63 64 d = NULL; 65 if (e->e_flags & ELF_F_LAYOUT) { 66 67 /* 68 * The application is taking responsibility for the 69 * ELF object's layout, so we can directly translate 70 * an offset to a `char *' address using the `d_off' 71 * members of Elf_Data descriptors. 72 */ 73 while ((d = elf_getdata(s, d)) != NULL) { 74 75 if (d->d_buf == 0 || d->d_size == 0) 76 continue; 77 78 if (d->d_type != ELF_T_BYTE) { 79 LIBELF_SET_ERROR(DATA, 0); 80 return (NULL); 81 } 82 83 if (offset >= d->d_off && 84 offset < d->d_off + d->d_size) 85 return ((char *) d->d_buf + offset - d->d_off); 86 } 87 } else { 88 /* 89 * Otherwise, the `d_off' members are not useable and 90 * we need to compute offsets ourselves, taking into 91 * account 'holes' in coverage of the section introduced 92 * by alignment requirements. 93 */ 94 count = (size_t) 0; /* cumulative count of bytes seen */ 95 while ((d = elf_getdata(s, d)) != NULL && count <= offset) { 96 97 if (d->d_buf == NULL || d->d_size == 0) 98 continue; 99 100 if (d->d_type != ELF_T_BYTE) { 101 LIBELF_SET_ERROR(DATA, 0); 102 return (NULL); 103 } 104 105 if ((alignment = d->d_align) > 1) { 106 if ((alignment & (alignment - 1)) != 0) { 107 LIBELF_SET_ERROR(DATA, 0); 108 return (NULL); 109 } 110 count = roundup2(count, alignment); 111 } 112 113 if (offset < count) { 114 /* offset starts in the 'hole' */ 115 LIBELF_SET_ERROR(ARGUMENT, 0); 116 return (NULL); 117 } 118 119 if (offset < count + d->d_size) { 120 if (d->d_buf != NULL) 121 return ((char *) d->d_buf + 122 offset - count); 123 LIBELF_SET_ERROR(DATA, 0); 124 return (NULL); 125 } 126 127 count += d->d_size; 128 } 129 } 130 131 LIBELF_SET_ERROR(ARGUMENT, 0); 132 return (NULL); 133} 134