elf_scn.c revision 210330
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: head/lib/libelf/elf_scn.c 210330 2010-07-21 09:47:14Z kaiw $"); 29 30#include <assert.h> 31#include <errno.h> 32#include <gelf.h> 33#include <libelf.h> 34#include <stdlib.h> 35 36#include "_libelf.h" 37 38/* 39 * Load an ELF section table and create a list of Elf_Scn structures. 40 */ 41int 42_libelf_load_scn(Elf *e, void *ehdr) 43{ 44 int ec, swapbytes; 45 size_t fsz, i, shnum; 46 uint64_t shoff; 47 char *src; 48 Elf32_Ehdr *eh32; 49 Elf64_Ehdr *eh64; 50 Elf_Scn *scn; 51 void (*xlator)(char *_d, char *_s, size_t _c, int _swap); 52 53 assert(e != NULL); 54 assert(ehdr != NULL); 55 assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0); 56 57#define CHECK_EHDR(E,EH) do { \ 58 if (fsz != (EH)->e_shentsize || \ 59 shoff + fsz * shnum > e->e_rawsize) { \ 60 LIBELF_SET_ERROR(HEADER, 0); \ 61 return (0); \ 62 } \ 63 } while (0) 64 65 ec = e->e_class; 66 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 67 assert(fsz > 0); 68 69 shnum = e->e_u.e_elf.e_nscn; 70 71 if (ec == ELFCLASS32) { 72 eh32 = (Elf32_Ehdr *) ehdr; 73 shoff = (uint64_t) eh32->e_shoff; 74 CHECK_EHDR(e, eh32); 75 } else { 76 eh64 = (Elf64_Ehdr *) ehdr; 77 shoff = eh64->e_shoff; 78 CHECK_EHDR(e, eh64); 79 } 80 81 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec); 82 83 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder); 84 src = e->e_rawfile + shoff; 85 86 /* 87 * If the file is using extended numbering then section #0 88 * would have already been read in. 89 */ 90 91 i = 0; 92 if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 93 assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) == 94 STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next)); 95 96 i = 1; 97 src += fsz; 98 } 99 100 for (; i < shnum; i++, src += fsz) { 101 if ((scn = _libelf_allocate_scn(e, i)) == NULL) 102 return (0); 103 104 (*xlator)((char *) &scn->s_shdr, src, (size_t) 1, swapbytes); 105 106 if (ec == ELFCLASS32) { 107 scn->s_offset = scn->s_rawoff = 108 scn->s_shdr.s_shdr32.sh_offset; 109 scn->s_size = scn->s_shdr.s_shdr32.sh_size; 110 } else { 111 scn->s_offset = scn->s_rawoff = 112 scn->s_shdr.s_shdr64.sh_offset; 113 scn->s_size = scn->s_shdr.s_shdr64.sh_size; 114 } 115 } 116 117 e->e_flags |= LIBELF_F_SHDRS_LOADED; 118 119 return (1); 120} 121 122 123Elf_Scn * 124elf_getscn(Elf *e, size_t index) 125{ 126 int ec; 127 void *ehdr; 128 Elf_Scn *s; 129 130 if (e == NULL || e->e_kind != ELF_K_ELF || 131 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) { 132 LIBELF_SET_ERROR(ARGUMENT, 0); 133 return (NULL); 134 } 135 136 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 137 return (NULL); 138 139 if (e->e_cmd != ELF_C_WRITE && 140 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 141 _libelf_load_scn(e, ehdr) == 0) 142 return (NULL); 143 144 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) 145 if (s->s_ndx == index) 146 return (s); 147 148 LIBELF_SET_ERROR(ARGUMENT, 0); 149 return (NULL); 150} 151 152size_t 153elf_ndxscn(Elf_Scn *s) 154{ 155 if (s == NULL) { 156 LIBELF_SET_ERROR(ARGUMENT, 0); 157 return (SHN_UNDEF); 158 } 159 return (s->s_ndx); 160} 161 162Elf_Scn * 163elf_newscn(Elf *e) 164{ 165 int ec; 166 void *ehdr; 167 Elf_Scn *scn; 168 169 if (e == NULL || e->e_kind != ELF_K_ELF) { 170 LIBELF_SET_ERROR(ARGUMENT, 0); 171 return (NULL); 172 } 173 174 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 175 LIBELF_SET_ERROR(CLASS, 0); 176 return (NULL); 177 } 178 179 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 180 return (NULL); 181 182 /* 183 * The application may be asking for a new section descriptor 184 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We 185 * need to bring in the existing section information before 186 * appending a new one to the list. 187 * 188 * Per the ELF(3) API, an application is allowed to open a 189 * file using ELF_C_READ, mess with its internal structure and 190 * use elf_update(...,ELF_C_NULL) to compute its new layout. 191 */ 192 if (e->e_cmd != ELF_C_WRITE && 193 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 194 _libelf_load_scn(e, ehdr) == 0) 195 return (NULL); 196 197 if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 198 assert(e->e_u.e_elf.e_nscn == 0); 199 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) == 200 NULL) 201 return (NULL); 202 e->e_u.e_elf.e_nscn++; 203 } 204 205 assert(e->e_u.e_elf.e_nscn > 0); 206 207 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL) 208 return (NULL); 209 210 e->e_u.e_elf.e_nscn++; 211 212 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY); 213 214 return (scn); 215} 216 217Elf_Scn * 218elf_nextscn(Elf *e, Elf_Scn *s) 219{ 220 if (e == NULL || (e->e_kind != ELF_K_ELF) || 221 (s && s->s_elf != e)) { 222 LIBELF_SET_ERROR(ARGUMENT, 0); 223 return (NULL); 224 } 225 226 return (s == NULL ? elf_getscn(e, (size_t) 1) : 227 STAILQ_NEXT(s, s_next)); 228} 229