1 /* Extract symbol list from binary. 2 Copyright (C) 1998, 1999, 2000, 2001, 2002, 2005, 2007, 2015 Red Hat, Inc. 3 This file is part of elfutils. 4 Written by Ulrich Drepper <drepper (at) redhat.com>, 1998. 5 6 This file is free software; you can redistribute it and/or modify 7 it under the terms of either 8 9 * the GNU Lesser General Public License as published by the Free 10 Software Foundation; either version 3 of the License, or (at 11 your option) any later version 12 13 or 14 15 * the GNU General Public License as published by the Free 16 Software Foundation; either version 2 of the License, or (at 17 your option) any later version 18 19 or both in parallel, as here. 20 21 elfutils is distributed in the hope that it will be useful, but 22 WITHOUT ANY WARRANTY; without even the implied warranty of 23 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 24 General Public License for more details. 25 26 You should have received copies of the GNU General Public License and 27 the GNU Lesser General Public License along with this program. If 28 not, see <http://www.gnu.org/licenses/>. */ 29 30 #ifdef HAVE_CONFIG_H 31 # include <config.h> 32 #endif 33 34 #include <fcntl.h> 35 #include <gelf.h> 36 #include <libelf.h> 37 #include <nlist.h> 38 #include <unistd.h> 39 40 #include "libelfP.h" 41 42 43 struct hashentry 44 { 45 const char *str; 46 GElf_Sym sym; 47 }; 48 #define TYPE struct hashentry 49 /* XXX Use a better hash function some day. */ 50 #define HASHFCT(str, len) INTUSE(elf_hash) (str) 51 #define COMPARE(p1, p2) strcmp ((p1)->str, (p2)->str) 52 #define CLASS static 53 #define PREFIX nlist_ 54 #define xcalloc(n, m) calloc (n, m) 55 #define next_prime(s) __libelf_next_prime (s) 56 #include <fixedsizehash.h> 57 58 59 int 60 nlist (const char *filename, struct nlist *nl) 61 { 62 int fd; 63 Elf *elf; 64 Elf_Scn *scn = NULL; 65 Elf_Scn *symscn = NULL; 66 GElf_Shdr shdr_mem; 67 GElf_Shdr *shdr = NULL; 68 Elf_Data *data; 69 struct nlist_fshash *table; 70 size_t nsyms; 71 size_t cnt; 72 73 /* Open the file. */ 74 fd = open (filename, O_RDONLY); 75 if (fd == -1) 76 { 77 __libelf_seterrno (ELF_E_NOFILE); 78 goto fail; 79 } 80 81 /* For compatibility reasons (`nlist' existed before ELF and libelf) 82 we don't expect the caller to set the ELF version. Do this here 83 if it hasn't happened yet. */ 84 if (__libelf_version_initialized == 0) 85 INTUSE(elf_version) (EV_CURRENT); 86 87 /* Now get an ELF descriptor. */ 88 elf = INTUSE(elf_begin) (fd, ELF_C_READ_MMAP, NULL); 89 if (elf == NULL) 90 goto fail_fd; 91 92 /* Find a symbol table. We prefer the real symbol table but if it 93 does not exist use the dynamic symbol table. */ 94 while ((scn = INTUSE(elf_nextscn) (elf, scn)) != NULL) 95 { 96 shdr = INTUSE(gelf_getshdr) (scn, &shdr_mem); 97 if (shdr == NULL) 98 goto fail_close; 99 100 /* That is what we are looking for. */ 101 if (shdr->sh_type == SHT_SYMTAB) 102 { 103 symscn = scn; 104 break; 105 } 106 107 /* Better than nothing. Remember this section. */ 108 if (shdr->sh_type == SHT_DYNSYM) 109 symscn = scn; 110 } 111 112 if (symscn == NULL) 113 /* We haven't found anything. Fail. */ 114 goto fail_close; 115 116 /* Re-get the section header in case we found only the dynamic symbol 117 table. */ 118 if (scn == NULL) 119 { 120 shdr = INTUSE(gelf_getshdr) (symscn, &shdr_mem); 121 if (unlikely (shdr == NULL)) 122 goto fail_close; 123 } 124 /* SHDR->SH_LINK now contains the index of the string section. */ 125 126 /* Get the data for the symbol section. */ 127 data = INTUSE(elf_getdata) (symscn, NULL); 128 if (data == NULL) 129 goto fail_close; 130 131 /* How many symbols are there? */ 132 nsyms = (shdr->sh_size 133 / INTUSE(gelf_fsize) (elf, ELF_T_SYM, 1, EV_CURRENT)); 134 135 /* Create the hash table. */ 136 table = nlist_fshash_init (nsyms); 137 if (table == NULL) 138 { 139 __libelf_seterrno (ELF_E_NOMEM); 140 goto fail_close; 141 } 142 143 /* Iterate over all the symbols in the section. */ 144 for (cnt = 0; cnt < nsyms; ++cnt) 145 { 146 struct hashentry mem; 147 GElf_Sym *sym; 148 149 /* Get the symbol. */ 150 sym = INTUSE(gelf_getsym) (data, cnt, &mem.sym); 151 if (sym == NULL) 152 goto fail_dealloc; 153 154 /* Get the name of the symbol. */ 155 mem.str = INTUSE(elf_strptr) (elf, shdr->sh_link, sym->st_name); 156 if (mem.str == NULL) 157 goto fail_dealloc; 158 159 /* Don't allow zero-length strings. */ 160 if (mem.str[0] == '\0') 161 continue; 162 163 /* And add it to the hash table. Note that we are using the 164 overwrite version. This will ensure that 165 a) global symbols are preferred over local symbols since 166 they are all located at the end 167 b) if there are multiple local symbols with the same name 168 the last one is used. 169 */ 170 (void) nlist_fshash_overwrite (table, mem.str, 0, &mem); 171 } 172 173 /* Now it is time to look for the symbols the user asked for. 174 XXX What is a `null name/null string'? This is what the 175 standard says terminates the list. Is it a null pointer 176 or a zero-length string? We test for both... */ 177 while (nl->n_name != NULL && nl->n_name[0] != '\0') 178 { 179 struct hashentry search; 180 const struct hashentry *found; 181 182 /* Search for a matching entry in the hash table. */ 183 search.str = nl->n_name; 184 found = nlist_fshash_find (table, nl->n_name, 0, &search); 185 186 if (found != NULL) 187 { 188 /* Found it. */ 189 nl->n_value = found->sym.st_value; 190 nl->n_scnum = found->sym.st_shndx; 191 nl->n_type = GELF_ST_TYPE (found->sym.st_info); 192 /* XXX What shall we fill in the next fields? */ 193 nl->n_sclass = 0; 194 nl->n_numaux = 0; 195 } 196 else 197 { 198 /* Not there. */ 199 nl->n_value = 0; 200 nl->n_scnum = 0; 201 nl->n_type = 0; 202 nl->n_sclass = 0; 203 nl->n_numaux = 0; 204 } 205 206 /* Next search request. */ 207 ++nl; 208 } 209 210 /* Free the resources. */ 211 nlist_fshash_fini (table); 212 213 /* We do not need the ELF descriptor anymore. */ 214 (void) INTUSE(elf_end) (elf); 215 216 /* Neither the file descriptor. */ 217 (void) close (fd); 218 219 return 0; 220 221 fail_dealloc: 222 nlist_fshash_fini (table); 223 224 fail_close: 225 /* We do not need the ELF descriptor anymore. */ 226 (void) INTUSE(elf_end) (elf); 227 228 fail_fd: 229 /* Neither the file descriptor. */ 230 (void) close (fd); 231 232 fail: 233 /* We have to set all entries to zero. */ 234 while (nl->n_name != NULL && nl->n_name[0] != '\0') 235 { 236 nl->n_value = 0; 237 nl->n_scnum = 0; 238 nl->n_type = 0; 239 nl->n_sclass = 0; 240 nl->n_numaux = 0; 241 242 /* Next entry. */ 243 ++nl; 244 } 245 246 return -1; 247 } 248
