1 /* $OpenBSD: nlist.c,v 1.71 2019/06/28 13:32:41 deraadt Exp $ */ 2 /* 3 * Copyright (c) 1989, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 #include <sys/types.h> 32 #include <sys/mman.h> 33 #include <sys/stat.h> 34 35 #include <errno.h> 36 #include <fcntl.h> 37 #include <stdint.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 #include <unistd.h> 42 #include <a.out.h> /* pulls in nlist.h */ 43 #include <elf.h> 44 45 #define MINIMUM(a, b) (((a) < (b)) ? (a) : (b)) 46 47 int __fdnlist(int, struct nlist *); 48 PROTO_NORMAL(__fdnlist); 49 50 #define ISLAST(p) (p->n_un.n_name == 0 || p->n_un.n_name[0] == 0) 51 52 /* 53 * __elf_is_okay__ - Determine if ehdr really 54 * is ELF and valid for the target platform. 55 * 56 * WARNING: This is NOT a ELF ABI function and 57 * as such its use should be restricted. 58 */ 59 static int 60 __elf_is_okay__(Elf_Ehdr *ehdr) 61 { 62 int retval = 0; 63 /* 64 * We need to check magic, class size, endianess, 65 * and version before we look at the rest of the 66 * Elf_Ehdr structure. These few elements are 67 * represented in a machine independent fashion. 68 */ 69 if (IS_ELF(*ehdr) && 70 ehdr->e_ident[EI_CLASS] == ELF_TARG_CLASS && 71 ehdr->e_ident[EI_DATA] == ELF_TARG_DATA && 72 ehdr->e_ident[EI_VERSION] == ELF_TARG_VER) { 73 74 /* Now check the machine dependent header */ 75 if (ehdr->e_machine == ELF_TARG_MACH && 76 ehdr->e_version == ELF_TARG_VER) 77 retval = 1; 78 } 79 80 if (ehdr->e_shentsize != sizeof(Elf_Shdr)) 81 return 0; 82 83 return retval; 84 } 85 86 int 87 __fdnlist(int fd, struct nlist *list) 88 { 89 struct nlist *p; 90 caddr_t strtab; 91 Elf_Off symoff = 0, symstroff = 0; 92 Elf_Word symsize = 0, symstrsize = 0; 93 Elf_Sword nent, cc, i; 94 Elf_Sym sbuf[1024]; 95 Elf_Sym *s; 96 Elf_Ehdr ehdr; 97 Elf_Shdr *shdr = NULL; 98 Elf_Word shdr_size; 99 struct stat st; 100 int usemalloc = 0; 101 size_t left, len; 102 103 /* Make sure obj is OK */ 104 if (pread(fd, &ehdr, sizeof(Elf_Ehdr), 0) != sizeof(Elf_Ehdr) || 105 !__elf_is_okay__(&ehdr) || fstat(fd, &st) == -1) 106 return (-1); 107 108 /* calculate section header table size */ 109 shdr_size = ehdr.e_shentsize * ehdr.e_shnum; 110 111 /* Make sure it's not too big to mmap */ 112 if (SIZE_MAX - ehdr.e_shoff < shdr_size || 113 (S_ISREG(st.st_mode) && ehdr.e_shoff + shdr_size > st.st_size)) { 114 errno = EFBIG; 115 return (-1); 116 } 117 118 /* mmap section header table */ 119 shdr = mmap(NULL, shdr_size, PROT_READ, MAP_SHARED|MAP_FILE, fd, 120 ehdr.e_shoff); 121 if (shdr == MAP_FAILED) { 122 usemalloc = 1; 123 if ((shdr = malloc(shdr_size)) == NULL) 124 return (-1); 125 126 if (pread(fd, shdr, shdr_size, ehdr.e_shoff) != shdr_size) { 127 free(shdr); 128 return (-1); 129 } 130 } 131 132 /* 133 * Find the symbol table entry and its corresponding 134 * string table entry. Version 1.1 of the ABI states 135 * that there is only one symbol table but that this 136 * could change in the future. 137 */ 138 for (i = 0; i < ehdr.e_shnum; i++) { 139 if (shdr[i].sh_type == SHT_SYMTAB) { 140 if (shdr[i].sh_link >= ehdr.e_shnum) 141 continue; 142 symoff = shdr[i].sh_offset; 143 symsize = shdr[i].sh_size; 144 symstroff = shdr[shdr[i].sh_link].sh_offset; 145 symstrsize = shdr[shdr[i].sh_link].sh_size; 146 break; 147 } 148 } 149 150 /* Flush the section header table */ 151 if (usemalloc) 152 free(shdr); 153 else 154 munmap((caddr_t)shdr, shdr_size); 155 156 /* 157 * clean out any left-over information for all valid entries. 158 * Type and value defined to be 0 if not found; historical 159 * versions cleared other and desc as well. Also figure out 160 * the largest string length so don't read any more of the 161 * string table than we have to. 162 * 163 * XXX clearing anything other than n_type and n_value violates 164 * the semantics given in the man page. 165 */ 166 nent = 0; 167 for (p = list; !ISLAST(p); ++p) { 168 p->n_type = 0; 169 p->n_other = 0; 170 p->n_desc = 0; 171 p->n_value = 0; 172 ++nent; 173 } 174 175 /* Don't process any further if object is stripped. */ 176 /* ELFism - dunno if stripped by looking at header */ 177 if (symoff == 0) 178 return nent; 179 180 /* Check for files too large to mmap. */ 181 if (SIZE_MAX - symstrsize < symstroff || 182 (S_ISREG(st.st_mode) && symstrsize + symstroff > st.st_size)) { 183 errno = EFBIG; 184 return (-1); 185 } 186 187 /* 188 * Map string table into our address space. This gives us 189 * an easy way to randomly access all the strings, without 190 * making the memory allocation permanent as with malloc/free 191 * (i.e., munmap will return it to the system). 192 */ 193 if (usemalloc) { 194 if ((strtab = malloc(symstrsize)) == NULL) 195 return (-1); 196 if (pread(fd, strtab, symstrsize, symstroff) != symstrsize) { 197 free(strtab); 198 return (-1); 199 } 200 } else { 201 strtab = mmap(NULL, symstrsize, PROT_READ, MAP_SHARED|MAP_FILE, 202 fd, symstroff); 203 if (strtab == MAP_FAILED) 204 return (-1); 205 } 206 207 while (symsize >= sizeof(Elf_Sym)) { 208 cc = MINIMUM(symsize, sizeof(sbuf)); 209 if (pread(fd, sbuf, cc, symoff) != cc) 210 break; 211 symsize -= cc; 212 symoff += cc; 213 for (s = sbuf; cc > 0; ++s, cc -= sizeof(*s)) { 214 Elf_Word soff = s->st_name; 215 216 if (soff == 0 || soff >= symstrsize) 217 continue; 218 left = symstrsize - soff; 219 220 for (p = list; !ISLAST(p); p++) { 221 char *sym; 222 223 /* 224 * First we check for the symbol as it was 225 * provided by the user. If that fails 226 * and the first char is an '_', skip over 227 * the '_' and try again. 228 * XXX - What do we do when the user really 229 * wants '_foo' and there are symbols 230 * for both 'foo' and '_foo' in the 231 * table and 'foo' is first? 232 */ 233 sym = p->n_un.n_name; 234 len = strlen(sym); 235 236 if ((len >= left || 237 strcmp(&strtab[soff], sym) != 0) && 238 (sym[0] != '_' || len - 1 >= left || 239 strcmp(&strtab[soff], sym + 1) != 0)) 240 continue; 241 242 p->n_value = s->st_value; 243 244 /* XXX - type conversion */ 245 /* is pretty rude. */ 246 switch(ELF_ST_TYPE(s->st_info)) { 247 case STT_NOTYPE: 248 switch (s->st_shndx) { 249 case SHN_UNDEF: 250 p->n_type = N_UNDF; 251 break; 252 case SHN_ABS: 253 p->n_type = N_ABS; 254 break; 255 case SHN_COMMON: 256 p->n_type = N_COMM; 257 break; 258 default: 259 p->n_type = N_COMM | N_EXT; 260 break; 261 } 262 break; 263 case STT_OBJECT: 264 p->n_type = N_DATA; 265 break; 266 case STT_FUNC: 267 p->n_type = N_TEXT; 268 break; 269 case STT_FILE: 270 p->n_type = N_FN; 271 break; 272 } 273 if (ELF_ST_BIND(s->st_info) == STB_LOCAL) 274 p->n_type = N_EXT; 275 p->n_desc = 0; 276 p->n_other = 0; 277 if (--nent <= 0) 278 break; 279 } 280 } 281 } 282 if (usemalloc) 283 free(strtab); 284 else 285 munmap(strtab, symstrsize); 286 return (nent); 287 } 288 DEF_STRONG(__fdnlist); 289 290 int 291 nlist(const char *name, struct nlist *list) 292 { 293 int fd, n; 294 295 fd = open(name, O_RDONLY | O_CLOEXEC); 296 if (fd == -1) 297 return (-1); 298 n = __fdnlist(fd, list); 299 (void)close(fd); 300 return (n); 301 } 302