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 3712 2019-03-16 22:23:34Z 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 uintmax_t rawsize = (uintmax_t) e->e_rawsize; \ 75 if (shoff > (uintmax_t) e->e_rawsize || \ 76 fsz != (EH)->e_shentsize || \ 77 shnum > SIZE_MAX / fsz || \ 78 fsz * shnum > rawsize - shoff) { \ 79 LIBELF_SET_ERROR(HEADER, 0); \ 80 return (0); \ 81 } \ 82 } while (0) 83 84 ec = e->e_class; 85 fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1); 86 assert(fsz > 0); 87 88 shnum = e->e_u.e_elf.e_nscn; 89 90 if (ec == ELFCLASS32) { 91 eh32 = (Elf32_Ehdr *) ehdr; 92 shoff = (uint64_t) eh32->e_shoff; 93 CHECK_EHDR(e, eh32); 94 } else { 95 eh64 = (Elf64_Ehdr *) ehdr; 96 shoff = eh64->e_shoff; 97 CHECK_EHDR(e, eh64); 98 } 99 100 xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec, 101 _libelf_elfmachine(e)); 102 103 swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder); 104 src = e->e_rawfile + shoff; 105 106 /* 107 * If the file is using extended numbering then section #0 108 * would have already been read in. 109 */ 110 111 i = 0; 112 if (!RB_EMPTY(&e->e_u.e_elf.e_scn)) { 113 assert(RB_MIN(scntree, &e->e_u.e_elf.e_scn) == 114 RB_MAX(scntree, &e->e_u.e_elf.e_scn)); 115 116 i = 1; 117 src += fsz; 118 } 119 120 for (; i < shnum; i++, src += fsz) { 121 if ((scn = _libelf_allocate_scn(e, i)) == NULL) 122 return (0); 123 124 (*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr), 125 src, (size_t) 1, swapbytes); 126 127 if (ec == ELFCLASS32) { 128 scn->s_offset = scn->s_rawoff = 129 scn->s_shdr.s_shdr32.sh_offset; 130 scn->s_size = scn->s_shdr.s_shdr32.sh_size; 131 } else { 132 scn->s_offset = scn->s_rawoff = 133 scn->s_shdr.s_shdr64.sh_offset; 134 scn->s_size = scn->s_shdr.s_shdr64.sh_size; 135 } 136 } 137 138 e->e_flags |= LIBELF_F_SHDRS_LOADED; 139 140 return (1); 141 } 142 143 144 Elf_Scn * 145 elf_getscn(Elf *e, size_t index) 146 { 147 int ec; 148 void *ehdr; 149 Elf_Scn *s; 150 151 if (e == NULL || e->e_kind != ELF_K_ELF || 152 ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) { 153 LIBELF_SET_ERROR(ARGUMENT, 0); 154 return (NULL); 155 } 156 157 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 158 return (NULL); 159 160 if (e->e_cmd != ELF_C_WRITE && 161 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 162 _libelf_load_section_headers(e, ehdr) == 0) 163 return (NULL); 164 165 for (s = RB_ROOT(&e->e_u.e_elf.e_scn); s != NULL;) { 166 if (s->s_ndx == index) 167 return (s); 168 169 if (s->s_ndx < index) 170 s = RB_RIGHT(s, s_tree); 171 else 172 s = RB_LEFT(s, s_tree); 173 } 174 175 LIBELF_SET_ERROR(ARGUMENT, 0); 176 return (NULL); 177 } 178 179 size_t 180 elf_ndxscn(Elf_Scn *s) 181 { 182 if (s == NULL) { 183 LIBELF_SET_ERROR(ARGUMENT, 0); 184 return (SHN_UNDEF); 185 } 186 return (s->s_ndx); 187 } 188 189 Elf_Scn * 190 elf_newscn(Elf *e) 191 { 192 int ec; 193 void *ehdr; 194 Elf_Scn *scn; 195 196 if (e == NULL || e->e_kind != ELF_K_ELF) { 197 LIBELF_SET_ERROR(ARGUMENT, 0); 198 return (NULL); 199 } 200 201 if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) { 202 LIBELF_SET_ERROR(CLASS, 0); 203 return (NULL); 204 } 205 206 if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL) 207 return (NULL); 208 209 /* 210 * The application may be asking for a new section descriptor 211 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ. We 212 * need to bring in the existing section information before 213 * appending a new one to the list. 214 * 215 * Per the ELF(3) API, an application is allowed to open a 216 * file using ELF_C_READ, mess with its internal structure and 217 * use elf_update(...,ELF_C_NULL) to compute its new layout. 218 */ 219 if (e->e_cmd != ELF_C_WRITE && 220 (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 && 221 _libelf_load_section_headers(e, ehdr) == 0) 222 return (NULL); 223 224 if (RB_EMPTY(&e->e_u.e_elf.e_scn)) { 225 assert(e->e_u.e_elf.e_nscn == 0); 226 if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) == 227 NULL) 228 return (NULL); 229 e->e_u.e_elf.e_nscn++; 230 } 231 232 assert(e->e_u.e_elf.e_nscn > 0); 233 234 if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL) 235 return (NULL); 236 237 e->e_u.e_elf.e_nscn++; 238 239 (void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY); 240 241 return (scn); 242 } 243 244 Elf_Scn * 245 elf_nextscn(Elf *e, Elf_Scn *s) 246 { 247 if (e == NULL || (e->e_kind != ELF_K_ELF) || 248 (s && s->s_elf != e)) { 249 LIBELF_SET_ERROR(ARGUMENT, 0); 250 return (NULL); 251 } 252 253 return (s == NULL ? elf_getscn(e, (size_t) 1) : 254 RB_NEXT(scntree, &e->e_u.e_elf.e_scn, s)); 255 } 256