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
address_compare(const void * a,const void * b)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
symtab_destroy(symtab_t * s)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 *
symtab_create(int fd,int bind,int type)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
symtab_find(const symtab_t * st,const void * p,Dl_info * dli)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