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 39ELFTC_VCSID("$Id: elf_scn.c,v 1.2 2019/03/19 02:31:35 jsg Exp $"); 40 41/* 42 * Load an ELF section table and create a list of Elf_Scn structures. 43 */ 44int 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 _libelf_translator_function *xlator; 55 56 assert(e != NULL); 57 assert(ehdr != NULL); 58 assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0); 59 60#define CHECK_EHDR(E,EH) do { \ 61 uintmax_t rawsize = (uintmax_t) e->e_rawsize; \ 62 if (shoff > (uintmax_t) e->e_rawsize || \ 63 fsz != (EH)->e_shentsize || \ 64 shnum > SIZE_MAX / fsz || \ 65 fsz * shnum > 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 _libelf_elfmachine(e)); 89 90 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder); 91 src = e->e_rawfile + shoff; 92 93 /* 94 * If the file is using extended numbering then section #0 95 * would have already been read in. 96 */ 97 98 i = 0; 99 if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 100 assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) == 101 STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next)); 102 103 i = 1; 104 src += fsz; 105 } 106 107 for (; i < shnum; i++, src += fsz) { 108 if ((scn = _libelf_allocate_scn(e, i)) == NULL) 109 return (0); 110 111 (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr), 112 src, (size_t) 1, swapbytes); 113 114 if (ec == ELFCLASS32) { 115 scn->s_offset = scn->s_rawoff = 116 scn->s_shdr.s_shdr32.sh_offset; 117 scn->s_size = scn->s_shdr.s_shdr32.sh_size; 118 } else { 119 scn->s_offset = scn->s_rawoff = 120 scn->s_shdr.s_shdr64.sh_offset; 121 scn->s_size = scn->s_shdr.s_shdr64.sh_size; 122 } 123 } 124 125 e->e_flags |= LIBELF_F_SHDRS_LOADED; 126 127 return (1); 128} 129 130 131Elf_Scn * 132elf_getscn(Elf *e, size_t index) 133{ 134 int ec; 135 void *ehdr; 136 Elf_Scn *s; 137 138 if (e == NULL || e->e_kind != ELF_K_ELF || 139 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) { 140 LIBELF_SET_ERROR(ARGUMENT, 0); 141 return (NULL); 142 } 143 144 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 145 return (NULL); 146 147 if (e->e_cmd != ELF_C_WRITE && 148 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 149 _libelf_load_section_headers(e, ehdr) == 0) 150 return (NULL); 151 152 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) 153 if (s->s_ndx == index) 154 return (s); 155 156 LIBELF_SET_ERROR(ARGUMENT, 0); 157 return (NULL); 158} 159 160size_t 161elf_ndxscn(Elf_Scn *s) 162{ 163 if (s == NULL) { 164 LIBELF_SET_ERROR(ARGUMENT, 0); 165 return (SHN_UNDEF); 166 } 167 return (s->s_ndx); 168} 169 170Elf_Scn * 171elf_newscn(Elf *e) 172{ 173 int ec; 174 void *ehdr; 175 Elf_Scn *scn; 176 177 if (e == NULL || e->e_kind != ELF_K_ELF) { 178 LIBELF_SET_ERROR(ARGUMENT, 0); 179 return (NULL); 180 } 181 182 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 183 LIBELF_SET_ERROR(CLASS, 0); 184 return (NULL); 185 } 186 187 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 188 return (NULL); 189 190 /* 191 * The application may be asking for a new section descriptor 192 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We 193 * need to bring in the existing section information before 194 * appending a new one to the list. 195 * 196 * Per the ELF(3) API, an application is allowed to open a 197 * file using ELF_C_READ, mess with its internal structure and 198 * use elf_update(...,ELF_C_NULL) to compute its new layout. 199 */ 200 if (e->e_cmd != ELF_C_WRITE && 201 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 202 _libelf_load_section_headers(e, ehdr) == 0) 203 return (NULL); 204 205 if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 206 assert(e->e_u.e_elf.e_nscn == 0); 207 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) == 208 NULL) 209 return (NULL); 210 e->e_u.e_elf.e_nscn++; 211 } 212 213 assert(e->e_u.e_elf.e_nscn > 0); 214 215 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL) 216 return (NULL); 217 218 e->e_u.e_elf.e_nscn++; 219 220 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY); 221 222 return (scn); 223} 224 225Elf_Scn * 226elf_nextscn(Elf *e, Elf_Scn *s) 227{ 228 if (e == NULL || (e->e_kind != ELF_K_ELF) || 229 (s && s->s_elf != e)) { 230 LIBELF_SET_ERROR(ARGUMENT, 0); 231 return (NULL); 232 } 233 234 return (s == NULL ? elf_getscn(e, (size_t) 1) : 235 STAILQ_NEXT(s, s_next)); 236} 237