1 /* $NetBSD: symtab.c,v 1.5 2016/04/20 14:00:16 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 1.5 2016/04/20 14:00:16 christos Exp $"); 33 34 #include <stdlib.h> 35 #include <stdio.h> 36 #include <string.h> 37 #include <stdint.h> 38 #include <stdbool.h> 39 #include <err.h> 40 #include <dlfcn.h> 41 42 #include <libelf.h> 43 #include <gelf.h> 44 #ifndef ELF_ST_BIND 45 #define ELF_ST_BIND(x) ((x) >> 4) 46 #endif 47 #ifndef ELF_ST_TYPE 48 #define ELF_ST_TYPE(x) (((unsigned int)x) & 0xf) 49 #endif 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 bool ispie; 63 }; 64 65 static int 66 address_compare(const void *a, const void *b) 67 { 68 const struct symbol *sa = a; 69 const struct symbol *sb = b; 70 return (int)(intmax_t)(sa->st_value - sb->st_value); 71 } 72 73 void 74 symtab_destroy(symtab_t *s) 75 { 76 if (s == NULL) 77 return; 78 for (size_t i = 0; i < s->nsymbols; i++) 79 free(s->symbols[i].st_name); 80 free(s->symbols); 81 free(s); 82 } 83 84 symtab_t * 85 symtab_create(int fd, int bind, int type) 86 { 87 Elf *elf; 88 symtab_t *st; 89 Elf_Scn *scn = NULL; 90 GElf_Ehdr ehdr; 91 92 if (elf_version(EV_CURRENT) == EV_NONE) { 93 warnx("Elf Library is out of date."); 94 return NULL; 95 } 96 97 elf = elf_begin(fd, ELF_C_READ, NULL); 98 if (elf == NULL) { 99 warnx("Error opening elf file: %s", elf_errmsg(elf_errno())); 100 return NULL; 101 } 102 st = calloc(1, sizeof(*st)); 103 if (st == NULL) { 104 warnx("Error allocating symbol table"); 105 elf_end(elf); 106 return NULL; 107 } 108 if (gelf_getehdr(elf, &ehdr) == NULL) { 109 warnx("Error getting ELF Ehdr"); 110 elf_end(elf); 111 return NULL; 112 } 113 114 st->ispie = ehdr.e_type == ET_DYN; 115 116 while ((scn = elf_nextscn(elf, scn)) != NULL) { 117 GElf_Shdr shdr; 118 Elf_Data *edata; 119 size_t ns; 120 struct symbol *s; 121 122 gelf_getshdr(scn, &shdr); 123 if(shdr.sh_type != SHT_SYMTAB) 124 continue; 125 126 edata = elf_getdata(scn, NULL); 127 ns = shdr.sh_size / shdr.sh_entsize; 128 s = calloc(ns, sizeof(*s)); 129 if (s == NULL) { 130 warn("Cannot allocate %zu symbols", ns); 131 goto out; 132 } 133 st->symbols = s; 134 135 for (size_t i = 0; i < ns; i++) { 136 GElf_Sym sym; 137 gelf_getsym(edata, (int)i, &sym); 138 139 #ifdef SYMTAB_DEBUG 140 fprintf(stderr, "%s: %s@%#jx=%d,%d\n", __func__, 141 elf_strptr(elf, shdr.sh_link, sym.st_name), 142 (uintmax_t)sym.st_value, ELF_ST_BIND(sym.st_info), 143 ELF_ST_TYPE(sym.st_info)); 144 #endif 145 146 if (bind != -1 && 147 (unsigned)bind != ELF_ST_BIND(sym.st_info)) 148 continue; 149 150 if (type != -1 && 151 (unsigned)type != ELF_ST_TYPE(sym.st_info)) 152 continue; 153 154 s->st_value = sym.st_value; 155 s->st_info = sym.st_info; 156 s->st_name = strdup( 157 elf_strptr(elf, shdr.sh_link, sym.st_name)); 158 if (s->st_name == NULL) 159 goto out; 160 s++; 161 } 162 st->nsymbols = s - st->symbols; 163 if (st->nsymbols == 0) { 164 warnx("No symbols found"); 165 goto out; 166 } 167 qsort(st->symbols, st->nsymbols, sizeof(*st->symbols), 168 address_compare); 169 elf_end(elf); 170 return st; 171 } 172 out: 173 symtab_destroy(st); 174 elf_end(elf); 175 return NULL; 176 } 177 178 179 int 180 symtab_find(const symtab_t *st, const void *p, Dl_info *dli) 181 { 182 struct symbol *s = st->symbols; 183 size_t ns = st->nsymbols; 184 size_t hi = ns; 185 size_t lo = 0; 186 size_t mid = ns / 2; 187 uintptr_t fbase = st->ispie ? (uintptr_t)dli->dli_fbase : 0; 188 uintptr_t dd, sd, me = (uintptr_t)p - fbase; 189 uintptr_t ad = (uintptr_t)dli->dli_saddr - fbase; 190 191 #ifdef SYMTAB_DEBUG 192 fprintf(stderr, "%s: [fbase=%#jx, saddr=%p, me=%#jx ad=%#jx]\n", 193 __func__, (uintmax_t)fbase, dli->dli_saddr, (uintmax_t)me, 194 (uintmax_t)ad); 195 #endif 196 for (;;) { 197 if (s[mid].st_value < me) 198 lo = mid; 199 else if (s[mid].st_value > me) 200 hi = mid; 201 else 202 break; 203 if (hi - lo == 1) { 204 mid = lo; 205 break; 206 } 207 mid = (hi + lo) / 2; 208 } 209 dd = me - ad; 210 sd = me - s[mid].st_value; 211 if (dd > sd) { 212 dli->dli_saddr = (void *)s[mid].st_value; 213 dli->dli_sname = s[mid].st_name; 214 #ifdef SYMTAB_DEBUG 215 fprintf(stderr, "%s: me=%#jx -> [%#jx, %s]\n", __func__, 216 (uintmax_t)me, (uintmax_t)sd, dli->dli_sname); 217 #endif 218 } 219 #ifdef SYMTAB_DEBUG 220 else 221 fprintf(stderr, "%s: %#jx -> [%#jx, ***]\n", __func__, 222 (uintmax_t)me, (uintmax_t)sd); 223 #endif 224 return 1; 225 } 226