1 /*- 2 * Copyright (c) 2006,2008-2010 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/queue.h> 28 29 #include <assert.h> 30 #include <errno.h> 31 #include <gelf.h> 32 #include <libelf.h> 33 #include <stddef.h> 34 #include <stdint.h> 35 #include <stdlib.h> 36 37 #include "_libelf.h" 38 39 ELFTC_VCSID("$Id: elf_scn.c 3177 2015-03-30 18:19:41Z emaste $"); 40 41 /* 42 * Load an ELF section table and create a list of Elf_Scn structures. 43 */ 44 int 45 _libelf_load_section_headers(Elf *e, void *ehdr) 46 { 47 Elf_Scn *scn; 48 uint64_t shoff; 49 Elf32_Ehdr *eh32; 50 Elf64_Ehdr *eh64; 51 int ec, swapbytes; 52 unsigned char *src; 53 size_t fsz, i, shnum; 54 int (*xlator)(unsigned char *_d, size_t _dsz, unsigned char *_s, 55 size_t _c, int _swap); 56 57 assert(e != NULL); 58 assert(ehdr != NULL); 59 assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0); 60 61 #define CHECK_EHDR(E,EH) do { \ 62 if (shoff > e->e_rawsize || \ 63 fsz != (EH)->e_shentsize || \ 64 shnum > SIZE_MAX / fsz || \ 65 fsz * shnum > e->e_rawsize - shoff) { \ 66 LIBELF_SET_ERROR(HEADER, 0); \ 67 return (0); \ 68 } \ 69 } while (0) 70 71 ec = e->e_class; 72 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 73 assert(fsz > 0); 74 75 shnum = e->e_u.e_elf.e_nscn; 76 77 if (ec == ELFCLASS32) { 78 eh32 = (Elf32_Ehdr *) ehdr; 79 shoff = (uint64_t) eh32->e_shoff; 80 CHECK_EHDR(e, eh32); 81 } else { 82 eh64 = (Elf64_Ehdr *) ehdr; 83 shoff = eh64->e_shoff; 84 CHECK_EHDR(e, eh64); 85 } 86 87 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec); 88 89 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder); 90 src = e->e_rawfile + shoff; 91 92 /* 93 * If the file is using extended numbering then section #0 94 * would have already been read in. 95 */ 96 97 i = 0; 98 if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 99 assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) == 100 STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next)); 101 102 i = 1; 103 src += fsz; 104 } 105 106 for (; i < shnum; i++, src += fsz) { 107 if ((scn = _libelf_allocate_scn(e, i)) == NULL) 108 return (0); 109 110 (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr), 111 src, (size_t) 1, swapbytes); 112 113 if (ec == ELFCLASS32) { 114 scn->s_offset = scn->s_rawoff = 115 scn->s_shdr.s_shdr32.sh_offset; 116 scn->s_size = scn->s_shdr.s_shdr32.sh_size; 117 } else { 118 scn->s_offset = scn->s_rawoff = 119 scn->s_shdr.s_shdr64.sh_offset; 120 scn->s_size = scn->s_shdr.s_shdr64.sh_size; 121 } 122 } 123 124 e->e_flags |= LIBELF_F_SHDRS_LOADED; 125 126 return (1); 127 } 128 129 130 Elf_Scn * 131 elf_getscn(Elf *e, size_t index) 132 { 133 int ec; 134 void *ehdr; 135 Elf_Scn *s; 136 137 if (e == NULL || e->e_kind != ELF_K_ELF || 138 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) { 139 LIBELF_SET_ERROR(ARGUMENT, 0); 140 return (NULL); 141 } 142 143 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 144 return (NULL); 145 146 if (e->e_cmd != ELF_C_WRITE && 147 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 148 _libelf_load_section_headers(e, ehdr) == 0) 149 return (NULL); 150 151 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) 152 if (s->s_ndx == index) 153 return (s); 154 155 LIBELF_SET_ERROR(ARGUMENT, 0); 156 return (NULL); 157 } 158 159 size_t 160 elf_ndxscn(Elf_Scn *s) 161 { 162 if (s == NULL) { 163 LIBELF_SET_ERROR(ARGUMENT, 0); 164 return (SHN_UNDEF); 165 } 166 return (s->s_ndx); 167 } 168 169 Elf_Scn * 170 elf_newscn(Elf *e) 171 { 172 int ec; 173 void *ehdr; 174 Elf_Scn *scn; 175 176 if (e == NULL || e->e_kind != ELF_K_ELF) { 177 LIBELF_SET_ERROR(ARGUMENT, 0); 178 return (NULL); 179 } 180 181 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 182 LIBELF_SET_ERROR(CLASS, 0); 183 return (NULL); 184 } 185 186 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 187 return (NULL); 188 189 /* 190 * The application may be asking for a new section descriptor 191 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We 192 * need to bring in the existing section information before 193 * appending a new one to the list. 194 * 195 * Per the ELF(3) API, an application is allowed to open a 196 * file using ELF_C_READ, mess with its internal structure and 197 * use elf_update(...,ELF_C_NULL) to compute its new layout. 198 */ 199 if (e->e_cmd != ELF_C_WRITE && 200 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 201 _libelf_load_section_headers(e, ehdr) == 0) 202 return (NULL); 203 204 if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 205 assert(e->e_u.e_elf.e_nscn == 0); 206 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) == 207 NULL) 208 return (NULL); 209 e->e_u.e_elf.e_nscn++; 210 } 211 212 assert(e->e_u.e_elf.e_nscn > 0); 213 214 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL) 215 return (NULL); 216 217 e->e_u.e_elf.e_nscn++; 218 219 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY); 220 221 return (scn); 222 } 223 224 Elf_Scn * 225 elf_nextscn(Elf *e, Elf_Scn *s) 226 { 227 if (e == NULL || (e->e_kind != ELF_K_ELF) || 228 (s && s->s_elf != e)) { 229 LIBELF_SET_ERROR(ARGUMENT, 0); 230 return (NULL); 231 } 232 233 return (s == NULL ? elf_getscn(e, (size_t) 1) : 234 STAILQ_NEXT(s, s_next)); 235 } 236