elf_scn.c revision 277558
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: stable/10/lib/libelf/elf_scn.c 277558 2015-01-23 04:07:07Z emaste $"); 29 30#include <assert.h> 31#include <errno.h> 32#include <gelf.h> 33#include <libelf.h> 34#include <stdint.h> 35#include <stdlib.h> 36 37#include "_libelf.h" 38 39/* 40 * Load an ELF section table and create a list of Elf_Scn structures. 41 */ 42int 43_libelf_load_scn(Elf *e, void *ehdr) 44{ 45 int ec, swapbytes; 46 size_t fsz, i, shnum; 47 uint64_t shoff; 48 char *src; 49 Elf32_Ehdr *eh32; 50 Elf64_Ehdr *eh64; 51 Elf_Scn *scn; 52 int (*xlator)(char *_d, size_t _dsz, char *_s, size_t _c, int _swap); 53 54 assert(e != NULL); 55 assert(ehdr != NULL); 56 assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0); 57 58#define CHECK_EHDR(E,EH) do { \ 59 if (shoff > e->e_rawsize || \ 60 fsz != (EH)->e_shentsize || \ 61 shnum > SIZE_MAX / fsz || \ 62 fsz * shnum > e->e_rawsize - shoff) { \ 63 LIBELF_SET_ERROR(HEADER, 0); \ 64 return (0); \ 65 } \ 66 } while (0) 67 68 ec = e->e_class; 69 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 70 assert(fsz > 0); 71 72 shnum = e->e_u.e_elf.e_nscn; 73 74 if (ec == ELFCLASS32) { 75 eh32 = (Elf32_Ehdr *) ehdr; 76 shoff = (uint64_t) eh32->e_shoff; 77 CHECK_EHDR(e, eh32); 78 } else { 79 eh64 = (Elf64_Ehdr *) ehdr; 80 shoff = eh64->e_shoff; 81 CHECK_EHDR(e, eh64); 82 } 83 84 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec); 85 86 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder); 87 src = e->e_rawfile + shoff; 88 89 /* 90 * If the file is using extended numbering then section #0 91 * would have already been read in. 92 */ 93 94 i = 0; 95 if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 96 assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) == 97 STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next)); 98 99 i = 1; 100 src += fsz; 101 } 102 103 for (; i < shnum; i++, src += fsz) { 104 if ((scn = _libelf_allocate_scn(e, i)) == NULL) 105 return (0); 106 107 (*xlator)((char *) &scn->s_shdr, sizeof(scn->s_shdr), src, 108 (size_t) 1, swapbytes); 109 110 if (ec == ELFCLASS32) { 111 scn->s_offset = scn->s_rawoff = 112 scn->s_shdr.s_shdr32.sh_offset; 113 scn->s_size = scn->s_shdr.s_shdr32.sh_size; 114 } else { 115 scn->s_offset = scn->s_rawoff = 116 scn->s_shdr.s_shdr64.sh_offset; 117 scn->s_size = scn->s_shdr.s_shdr64.sh_size; 118 } 119 } 120 121 e->e_flags |= LIBELF_F_SHDRS_LOADED; 122 123 return (1); 124} 125 126 127Elf_Scn * 128elf_getscn(Elf *e, size_t index) 129{ 130 int ec; 131 void *ehdr; 132 Elf_Scn *s; 133 134 if (e == NULL || e->e_kind != ELF_K_ELF || 135 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) { 136 LIBELF_SET_ERROR(ARGUMENT, 0); 137 return (NULL); 138 } 139 140 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 141 return (NULL); 142 143 if (e->e_cmd != ELF_C_WRITE && 144 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 145 _libelf_load_scn(e, ehdr) == 0) 146 return (NULL); 147 148 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) 149 if (s->s_ndx == index) 150 return (s); 151 152 LIBELF_SET_ERROR(ARGUMENT, 0); 153 return (NULL); 154} 155 156size_t 157elf_ndxscn(Elf_Scn *s) 158{ 159 if (s == NULL) { 160 LIBELF_SET_ERROR(ARGUMENT, 0); 161 return (SHN_UNDEF); 162 } 163 return (s->s_ndx); 164} 165 166Elf_Scn * 167elf_newscn(Elf *e) 168{ 169 int ec; 170 void *ehdr; 171 Elf_Scn *scn; 172 173 if (e == NULL || e->e_kind != ELF_K_ELF) { 174 LIBELF_SET_ERROR(ARGUMENT, 0); 175 return (NULL); 176 } 177 178 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 179 LIBELF_SET_ERROR(CLASS, 0); 180 return (NULL); 181 } 182 183 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 184 return (NULL); 185 186 /* 187 * The application may be asking for a new section descriptor 188 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We 189 * need to bring in the existing section information before 190 * appending a new one to the list. 191 * 192 * Per the ELF(3) API, an application is allowed to open a 193 * file using ELF_C_READ, mess with its internal structure and 194 * use elf_update(...,ELF_C_NULL) to compute its new layout. 195 */ 196 if (e->e_cmd != ELF_C_WRITE && 197 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 198 _libelf_load_scn(e, ehdr) == 0) 199 return (NULL); 200 201 if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 202 assert(e->e_u.e_elf.e_nscn == 0); 203 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) == 204 NULL) 205 return (NULL); 206 e->e_u.e_elf.e_nscn++; 207 } 208 209 assert(e->e_u.e_elf.e_nscn > 0); 210 211 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL) 212 return (NULL); 213 214 e->e_u.e_elf.e_nscn++; 215 216 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY); 217 218 return (scn); 219} 220 221Elf_Scn * 222elf_nextscn(Elf *e, Elf_Scn *s) 223{ 224 if (e == NULL || (e->e_kind != ELF_K_ELF) || 225 (s && s->s_elf != e)) { 226 LIBELF_SET_ERROR(ARGUMENT, 0); 227 return (NULL); 228 } 229 230 return (s == NULL ? elf_getscn(e, (size_t) 1) : 231 STAILQ_NEXT(s, s_next)); 232} 233