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 3632 2018-10-10 21:12:43Z jkoshy $"); 40 41 static int 42 elfscn_cmp(struct _Elf_Scn *s1, struct _Elf_Scn *s2) 43 { 44 45 if (s1->s_ndx < s2->s_ndx) 46 return (-1); 47 if (s1->s_ndx > s2->s_ndx) 48 return (1); 49 return (0); 50 } 51 52 RB_GENERATE(scntree, _Elf_Scn, s_tree, elfscn_cmp); 53 54 /* 55 * Load an ELF section table and create a list of Elf_Scn structures. 56 */ 57 int 58 _libelf_load_section_headers(Elf *e, void *ehdr) 59 { 60 Elf_Scn *scn; 61 uint64_t shoff; 62 Elf32_Ehdr *eh32; 63 Elf64_Ehdr *eh64; 64 int ec, swapbytes; 65 unsigned char *src; 66 size_t fsz, i, shnum; 67 _libelf_translator_function *xlator; 68 69 assert(e != NULL); 70 assert(ehdr != NULL); 71 assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0); 72 73 #define CHECK_EHDR(E,EH) do { \ 74 if (shoff > e->e_rawsize || \ 75 fsz != (EH)->e_shentsize || \ 76 shnum > SIZE_MAX / fsz || \ 77 fsz * shnum > e->e_rawsize - shoff) { \ 78 LIBELF_SET_ERROR(HEADER, 0); \ 79 return (0); \ 80 } \ 81 } while (0) 82 83 ec = e->e_class; 84 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 85 assert(fsz > 0); 86 87 shnum = e->e_u.e_elf.e_nscn; 88 89 if (ec == ELFCLASS32) { 90 eh32 = (Elf32_Ehdr *) ehdr; 91 shoff = (uint64_t) eh32->e_shoff; 92 CHECK_EHDR(e, eh32); 93 } else { 94 eh64 = (Elf64_Ehdr *) ehdr; 95 shoff = eh64->e_shoff; 96 CHECK_EHDR(e, eh64); 97 } 98 99 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec, 100 _libelf_elfmachine(e)); 101 102 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder); 103 src = e->e_rawfile + shoff; 104 105 /* 106 * If the file is using extended numbering then section #0 107 * would have already been read in. 108 */ 109 110 i = 0; 111 if (!RB_EMPTY(&e->e_u.e_elf.e_scn)) { 112 assert(RB_MIN(scntree, &e->e_u.e_elf.e_scn) == 113 RB_MAX(scntree, &e->e_u.e_elf.e_scn)); 114 115 i = 1; 116 src += fsz; 117 } 118 119 for (; i < shnum; i++, src += fsz) { 120 if ((scn = _libelf_allocate_scn(e, i)) == NULL) 121 return (0); 122 123 (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr), 124 src, (size_t) 1, swapbytes); 125 126 if (ec == ELFCLASS32) { 127 scn->s_offset = scn->s_rawoff = 128 scn->s_shdr.s_shdr32.sh_offset; 129 scn->s_size = scn->s_shdr.s_shdr32.sh_size; 130 } else { 131 scn->s_offset = scn->s_rawoff = 132 scn->s_shdr.s_shdr64.sh_offset; 133 scn->s_size = scn->s_shdr.s_shdr64.sh_size; 134 } 135 } 136 137 e->e_flags |= LIBELF_F_SHDRS_LOADED; 138 139 return (1); 140 } 141 142 143 Elf_Scn * 144 elf_getscn(Elf *e, size_t index) 145 { 146 int ec; 147 void *ehdr; 148 Elf_Scn *s; 149 150 if (e == NULL || e->e_kind != ELF_K_ELF || 151 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) { 152 LIBELF_SET_ERROR(ARGUMENT, 0); 153 return (NULL); 154 } 155 156 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 157 return (NULL); 158 159 if (e->e_cmd != ELF_C_WRITE && 160 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 161 _libelf_load_section_headers(e, ehdr) == 0) 162 return (NULL); 163 164 for (s = RB_ROOT(&e->e_u.e_elf.e_scn); s != NULL;) { 165 if (s->s_ndx == index) 166 return (s); 167 168 if (s->s_ndx < index) 169 s = RB_RIGHT(s, s_tree); 170 else 171 s = RB_LEFT(s, s_tree); 172 } 173 174 LIBELF_SET_ERROR(ARGUMENT, 0); 175 return (NULL); 176 } 177 178 size_t 179 elf_ndxscn(Elf_Scn *s) 180 { 181 if (s == NULL) { 182 LIBELF_SET_ERROR(ARGUMENT, 0); 183 return (SHN_UNDEF); 184 } 185 return (s->s_ndx); 186 } 187 188 Elf_Scn * 189 elf_newscn(Elf *e) 190 { 191 int ec; 192 void *ehdr; 193 Elf_Scn *scn; 194 195 if (e == NULL || e->e_kind != ELF_K_ELF) { 196 LIBELF_SET_ERROR(ARGUMENT, 0); 197 return (NULL); 198 } 199 200 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 201 LIBELF_SET_ERROR(CLASS, 0); 202 return (NULL); 203 } 204 205 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 206 return (NULL); 207 208 /* 209 * The application may be asking for a new section descriptor 210 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We 211 * need to bring in the existing section information before 212 * appending a new one to the list. 213 * 214 * Per the ELF(3) API, an application is allowed to open a 215 * file using ELF_C_READ, mess with its internal structure and 216 * use elf_update(...,ELF_C_NULL) to compute its new layout. 217 */ 218 if (e->e_cmd != ELF_C_WRITE && 219 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 220 _libelf_load_section_headers(e, ehdr) == 0) 221 return (NULL); 222 223 if (RB_EMPTY(&e->e_u.e_elf.e_scn)) { 224 assert(e->e_u.e_elf.e_nscn == 0); 225 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) == 226 NULL) 227 return (NULL); 228 e->e_u.e_elf.e_nscn++; 229 } 230 231 assert(e->e_u.e_elf.e_nscn > 0); 232 233 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL) 234 return (NULL); 235 236 e->e_u.e_elf.e_nscn++; 237 238 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY); 239 240 return (scn); 241 } 242 243 Elf_Scn * 244 elf_nextscn(Elf *e, Elf_Scn *s) 245 { 246 if (e == NULL || (e->e_kind != ELF_K_ELF) || 247 (s && s->s_elf != e)) { 248 LIBELF_SET_ERROR(ARGUMENT, 0); 249 return (NULL); 250 } 251 252 return (s == NULL ? elf_getscn(e, (size_t) 1) : 253 RB_NEXT(scntree, &e->e_u.e_elf.e_scn, s)); 254 } 255