1 /* $NetBSD: symtab.c,v 1.3 2013/09/03 08:44:45 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 1.3 2013/09/03 08:44:45 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
address_compare(const void * a,const void * b)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
symtab_destroy(symtab_t * s)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 *
symtab_create(int fd,int bind,int type)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 warn("Cannot allocate symbol");
144 goto out;
145 }
146 s++;
147 }
148 st->nsymbols = s - st->symbols;
149 if (st->nsymbols == 0) {
150 warnx("No symbols found");
151 goto out;
152 }
153 qsort(st->symbols, st->nsymbols, sizeof(*st->symbols),
154 address_compare);
155 elf_end(elf);
156 return st;
157 }
158 out:
159 symtab_destroy(st);
160 elf_end(elf);
161 return NULL;
162 }
163
164
165 int
symtab_find(const symtab_t * st,const void * p,Dl_info * dli)166 symtab_find(const symtab_t *st, const void *p, Dl_info *dli)
167 {
168 struct symbol *s = st->symbols;
169 size_t ns = st->nsymbols;
170 size_t hi = ns;
171 size_t lo = 0;
172 size_t mid = ns / 2;
173 uintptr_t dd, sd, me = (uintptr_t)p;
174
175 for (;;) {
176 if (s[mid].st_value < me)
177 lo = mid;
178 else if (s[mid].st_value > me)
179 hi = mid;
180 else
181 break;
182 if (hi - lo == 1) {
183 mid = lo;
184 break;
185 }
186 mid = (hi + lo) / 2;
187 }
188 dd = me - (uintptr_t)dli->dli_saddr;
189 sd = me - s[mid].st_value;
190 if (dd > sd) {
191 dli->dli_saddr = (void *)s[mid].st_value;
192 dli->dli_sname = s[mid].st_name;
193 }
194 return 1;
195 }
196