1 /* $NetBSD: symtab.c,v 1.2 2013/08/29 15:01:57 christos Exp $ */ 2 3 /*- 4 * Copyright (c) 2012 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Christos Zoulas. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 #include <sys/cdefs.h> 32 __RCSID("$NetBSD: symtab.c,v 1.2 2013/08/29 15:01:57 christos Exp $"); 33 34 #include <stdlib.h> 35 #include <stdio.h> 36 #include <string.h> 37 #include <stdint.h> 38 #include <err.h> 39 #include <dlfcn.h> 40 41 #include <libelf.h> 42 #include <gelf.h> 43 #ifndef ELF_ST_BIND 44 #define ELF_ST_BIND(x) ((x) >> 4) 45 #endif 46 #ifndef ELF_ST_TYPE 47 #define ELF_ST_TYPE(x) (((unsigned int)x) & 0xf) 48 #endif 49 50 51 #include "symtab.h" 52 53 struct symbol { 54 char *st_name; 55 uintptr_t st_value; 56 uintptr_t st_info; 57 }; 58 59 struct symtab { 60 size_t nsymbols; 61 struct symbol *symbols; 62 }; 63 64 static int 65 address_compare(const void *a, const void *b) 66 { 67 const struct symbol *sa = a; 68 const struct symbol *sb = b; 69 return (int)(intmax_t)(sa->st_value - sb->st_value); 70 } 71 72 void 73 symtab_destroy(symtab_t *s) 74 { 75 if (s == NULL) 76 return; 77 for (size_t i = 0; i < s->nsymbols; i++) 78 free(s->symbols[i].st_name); 79 free(s->symbols); 80 free(s); 81 } 82 83 symtab_t * 84 symtab_create(int fd, int bind, int type) 85 { 86 Elf *elf; 87 symtab_t *st; 88 Elf_Scn *scn = NULL; 89 90 if (elf_version(EV_CURRENT) == EV_NONE) { 91 warnx("Elf Library is out of date."); 92 return NULL; 93 } 94 95 elf = elf_begin(fd, ELF_C_READ, NULL); 96 if (elf == NULL) { 97 warnx("Error opening elf file: %s", elf_errmsg(elf_errno())); 98 return NULL; 99 } 100 st = calloc(1, sizeof(*st)); 101 if (st == NULL) { 102 warnx("Error allocating symbol table"); 103 elf_end(elf); 104 return NULL; 105 } 106 107 while ((scn = elf_nextscn(elf, scn)) != NULL) { 108 GElf_Shdr shdr; 109 Elf_Data *edata; 110 size_t ns; 111 struct symbol *s; 112 113 gelf_getshdr(scn, &shdr); 114 if(shdr.sh_type != SHT_SYMTAB) 115 continue; 116 117 edata = elf_getdata(scn, NULL); 118 ns = shdr.sh_size / shdr.sh_entsize; 119 s = calloc(ns, sizeof(*s)); 120 if (s == NULL) { 121 warn("Cannot allocate %zu symbols", ns); 122 goto out; 123 } 124 st->symbols = s; 125 126 for (size_t i = 0; i < ns; i++) { 127 GElf_Sym sym; 128 gelf_getsym(edata, (int)i, &sym); 129 130 if (bind != -1 && 131 (unsigned)bind != ELF_ST_BIND(sym.st_info)) 132 continue; 133 134 if (type != -1 && 135 (unsigned)type != ELF_ST_TYPE(sym.st_info)) 136 continue; 137 138 s->st_value = sym.st_value; 139 s->st_info = sym.st_info; 140 s->st_name = strdup( 141 elf_strptr(elf, shdr.sh_link, sym.st_name)); 142 if (s->st_name == NULL) 143 goto out; 144 s++; 145 } 146 st->nsymbols = s - st->symbols; 147 if (st->nsymbols == 0) { 148 warnx("No symbols found"); 149 goto out; 150 } 151 qsort(st->symbols, st->nsymbols, sizeof(*st->symbols), 152 address_compare); 153 elf_end(elf); 154 return st; 155 } 156 out: 157 symtab_destroy(st); 158 elf_end(elf); 159 return NULL; 160 } 161 162 163 int 164 symtab_find(const symtab_t *st, const void *p, Dl_info *dli) 165 { 166 struct symbol *s = st->symbols; 167 size_t ns = st->nsymbols; 168 size_t hi = ns; 169 size_t lo = 0; 170 size_t mid = ns / 2; 171 uintptr_t dd, sd, me = (uintptr_t)p; 172 173 for (;;) { 174 if (s[mid].st_value < me) 175 lo = mid; 176 else if (s[mid].st_value > me) 177 hi = mid; 178 else 179 break; 180 if (hi - lo == 1) { 181 mid = lo; 182 break; 183 } 184 mid = (hi + lo) / 2; 185 } 186 dd = me - (uintptr_t)dli->dli_saddr; 187 sd = me - s[mid].st_value; 188 if (dd > sd) { 189 dli->dli_saddr = (void *)s[mid].st_value; 190 dli->dli_sname = s[mid].st_name; 191 } 192 return 1; 193 } 194