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 #include <stdlib.h>
33 #include <stdio.h>
34 #include <string.h>
35 #include <stdint.h>
36 #include <err.h>
37 #include <dlfcn.h>
38
39 #if 1
40 #include "private_libelf.h"
41 #else
42 #include <libelf.h>
43 #include <gelf.h>
44 #endif
45 #ifndef ELF_ST_BIND
46 #define ELF_ST_BIND(x) ((x) >> 4)
47 #endif
48 #ifndef ELF_ST_TYPE
49 #define ELF_ST_TYPE(x) (((unsigned int)x) & 0xf)
50 #endif
51
52
53 #include "symtab.h"
54
55 struct symbol {
56 char *st_name;
57 uintptr_t st_value;
58 uintptr_t st_info;
59 };
60
61 struct symtab {
62 size_t nsymbols;
63 struct symbol *symbols;
64 };
65
66 static int
address_compare(const void * a,const void * b)67 address_compare(const void *a, const void *b)
68 {
69 const struct symbol *sa = a;
70 const struct symbol *sb = b;
71 return (int)(intmax_t)(sa->st_value - sb->st_value);
72 }
73
74 void
symtab_destroy(symtab_t * s)75 symtab_destroy(symtab_t *s)
76 {
77 if (s == NULL)
78 return;
79 for (size_t i = 0; i < s->nsymbols; i++)
80 free(s->symbols[i].st_name);
81 free(s->symbols);
82 free(s);
83 }
84
85 symtab_t *
symtab_create(int fd,int bind,int type)86 symtab_create(int fd, int bind, int type)
87 {
88 Elf *elf;
89 symtab_t *st;
90 Elf_Scn *scn = NULL;
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
109 while ((scn = elf_nextscn(elf, scn)) != NULL) {
110 GElf_Shdr shdr;
111 Elf_Data *edata;
112 size_t ns;
113 struct symbol *s;
114
115 if (gelf_getshdr(scn, &shdr) == NULL)
116 goto out; /* XXX prevent use of uninitialized */
117 if(shdr.sh_type != SHT_SYMTAB)
118 continue;
119
120 edata = elf_getdata(scn, NULL);
121 ns = shdr.sh_size / shdr.sh_entsize;
122 s = calloc(ns, sizeof(*s));
123 if (s == NULL) {
124 warn("Cannot allocate %zu symbols", ns);
125 goto out;
126 }
127 st->symbols = s;
128
129 for (size_t i = 0; i < ns; i++) {
130 GElf_Sym sym;
131 if (gelf_getsym(edata, (int)i, &sym) == NULL)
132 goto out; /* XXX prevent uninitialized */
133
134 if (bind != -1 &&
135 (unsigned)bind != ELF_ST_BIND(sym.st_info))
136 continue;
137
138 if (type != -1 &&
139 (unsigned)type != ELF_ST_TYPE(sym.st_info))
140 continue;
141
142 s->st_value = sym.st_value;
143 s->st_info = sym.st_info;
144 s->st_name = strdup(
145 elf_strptr(elf, shdr.sh_link, sym.st_name));
146 if (s->st_name == NULL)
147 goto out;
148 s++;
149 }
150 st->nsymbols = s - st->symbols;
151 if (st->nsymbols == 0) {
152 warnx("No symbols found");
153 goto out;
154 }
155 qsort(st->symbols, st->nsymbols, sizeof(*st->symbols),
156 address_compare);
157 elf_end(elf);
158 return st;
159 }
160 out:
161 symtab_destroy(st);
162 elf_end(elf);
163 return NULL;
164 }
165
166
167 int
symtab_find(const symtab_t * st,const void * p,Dl_info * dli)168 symtab_find(const symtab_t *st, const void *p, Dl_info *dli)
169 {
170 struct symbol *s = st->symbols;
171 size_t ns = st->nsymbols;
172 size_t hi = ns;
173 size_t lo = 0;
174 size_t mid = ns / 2;
175 uintptr_t dd, sd, me = (uintptr_t)p;
176
177 for (;;) {
178 if (s[mid].st_value < me)
179 lo = mid;
180 else if (s[mid].st_value > me)
181 hi = mid;
182 else
183 break;
184 if (hi - lo == 1) {
185 mid = lo;
186 break;
187 }
188 mid = (hi + lo) / 2;
189 }
190 dd = me - (uintptr_t)dli->dli_saddr;
191 sd = me - s[mid].st_value;
192 if (dd > sd) {
193 dli->dli_saddr = (void *)s[mid].st_value;
194 dli->dli_sname = s[mid].st_name;
195 }
196 return 1;
197 }
198