elf_scn.c revision 4484:7c56a6c9c265
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 28#include <assert.h> 29#include <errno.h> 30#include <stddef.h> 31#include <stdlib.h> 32 33#include "gelf.h" 34#include "libelf.h" 35#include "_libelf.h" 36 37/* 38 * Load an ELF section table and create a list of Elf_Scn structures. 39 */ 40static int 41_libelf_load_scn(Elf *e, void *ehdr) 42{ 43 int ec, swapbytes; 44 size_t fsz, i, shnum; 45 uint64_t shoff; 46 char *src; 47 Elf32_Ehdr *eh32; 48 Elf64_Ehdr *eh64; 49 Elf_Scn *scn; 50 void (*xlator)(char *_d, char *_s, size_t _c, int _swap); 51 52 assert(e != NULL); 53 assert(ehdr != NULL); 54 assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0); 55 56#define CHECK_EHDR(E,EH) do { \ 57 if (fsz != (EH)->e_shentsize || \ 58 shoff + fsz * shnum > e->e_rawsize) { \ 59 LIBELF_SET_ERROR(HEADER, 0); \ 60 return (0); \ 61 } \ 62 } while (0) 63 64 ec = e->e_class; 65 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 66 assert(fsz > 0); 67 68 shnum = e->e_u.e_elf.e_nscn; 69 70 if (ec == ELFCLASS32) { 71 eh32 = (Elf32_Ehdr *) ehdr; 72 shoff = (uint64_t) eh32->e_shoff; 73 CHECK_EHDR(e, eh32); 74 } else { 75 eh64 = (Elf64_Ehdr *) ehdr; 76 shoff = eh64->e_shoff; 77 CHECK_EHDR(e, eh64); 78 } 79 80 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec); 81 82 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder); 83 src = e->e_rawfile + shoff; 84 85 /* 86 * If the file is using extended numbering then section #0 87 * would have already been read in. 88 */ 89 90 i = 0; 91 if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 92 assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) == 93 STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next)); 94 95 i = 1; 96 src += fsz; 97 } 98 99 for (; i < shnum; i++, src += fsz) { 100 if ((scn = _libelf_allocate_scn(e, i)) == NULL) 101 return (0); 102 103 (*xlator)((char *) &scn->s_shdr, src, (size_t) 1, swapbytes); 104 105 if (ec == ELFCLASS32) { 106 scn->s_offset = scn->s_rawoff = 107 scn->s_shdr.s_shdr32.sh_offset; 108 scn->s_size = scn->s_shdr.s_shdr32.sh_size; 109 } else { 110 scn->s_offset = scn->s_rawoff = 111 scn->s_shdr.s_shdr64.sh_offset; 112 scn->s_size = scn->s_shdr.s_shdr64.sh_size; 113 } 114 } 115 116 e->e_flags |= LIBELF_F_SHDRS_LOADED; 117 118 return (1); 119} 120 121 122Elf_Scn * 123elf_getscn(Elf *e, size_t index) 124{ 125 int ec; 126 void *ehdr; 127 Elf_Scn *s; 128 129 if (e == NULL || e->e_kind != ELF_K_ELF || 130 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) { 131 LIBELF_SET_ERROR(ARGUMENT, 0); 132 return (NULL); 133 } 134 135 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 136 return (NULL); 137 138 if (e->e_cmd != ELF_C_WRITE && 139 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 140 _libelf_load_scn(e, ehdr) == 0) 141 return (NULL); 142 143 STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next) 144 if (s->s_ndx == index) 145 return (s); 146 147 LIBELF_SET_ERROR(ARGUMENT, 0); 148 return (NULL); 149} 150 151size_t 152elf_ndxscn(Elf_Scn *s) 153{ 154 if (s == NULL) { 155 LIBELF_SET_ERROR(ARGUMENT, 0); 156 return (SHN_UNDEF); 157 } 158 return (s->s_ndx); 159} 160 161Elf_Scn * 162elf_newscn(Elf *e) 163{ 164 int ec; 165 void *ehdr; 166 Elf_Scn *scn; 167 168 if (e == NULL || e->e_kind != ELF_K_ELF) { 169 LIBELF_SET_ERROR(ARGUMENT, 0); 170 return (NULL); 171 } 172 173 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 174 LIBELF_SET_ERROR(CLASS, 0); 175 return (NULL); 176 } 177 178 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 179 return (NULL); 180 181 /* 182 * The application may be asking for a new section descriptor 183 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We 184 * need to bring in the existing section information before 185 * appending a new one to the list. 186 * 187 * Per the ELF(3) API, an application is allowed to open a 188 * file using ELF_C_READ, mess with its internal structure and 189 * use elf_update(...,ELF_C_NULL) to compute its new layout. 190 */ 191 if (e->e_cmd != ELF_C_WRITE && 192 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 193 _libelf_load_scn(e, ehdr) == 0) 194 return (NULL); 195 196 if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) { 197 assert(e->e_u.e_elf.e_nscn == 0); 198 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) == 199 NULL) 200 return (NULL); 201 e->e_u.e_elf.e_nscn++; 202 } 203 204 assert(e->e_u.e_elf.e_nscn > 0); 205 206 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL) 207 return (NULL); 208 209 e->e_u.e_elf.e_nscn++; 210 211 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY); 212 213 return (scn); 214} 215 216Elf_Scn * 217elf_nextscn(Elf *e, Elf_Scn *s) 218{ 219 if (e == NULL || (e->e_kind != ELF_K_ELF) || 220 (s && s->s_elf != e)) { 221 LIBELF_SET_ERROR(ARGUMENT, 0); 222 return (NULL); 223 } 224 225 return (s == NULL ? elf_getscn(e, (size_t) 1) : 226 STAILQ_NEXT(s, s_next)); 227} 228