1 /* $NetBSD: symtab.c,v 1.10 2023/08/23 12:24:59 rin 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 1.10 2023/08/23 12:24:59 rin 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 "symbol.h"
52 #include "symtab.h"
53
54 #ifdef SYMTAB_DEBUG
55 #define DPRINTF(fmt, ...) fprintf(stderr, "%s: " fmt "\n", __func__, __VA_ARGS__)
56 #else
57 #define DPRINTF(fmt, ...)
58 #endif
59
60 struct symbol {
61 char *st_name;
62 uintptr_t st_value;
63 uintptr_t st_info;
64 };
65
66 struct symtab {
67 size_t nsymbols;
68 struct symbol *symbols;
69 bool ispie;
70 };
71
72 static int
address_compare(const void * a,const void * b)73 address_compare(const void *a, const void *b)
74 {
75 const struct symbol *sa = a;
76 const struct symbol *sb = b;
77 return (int)(intmax_t)(sa->st_value - sb->st_value);
78 }
79
80 void
symtab_destroy(symtab_t * s)81 symtab_destroy(symtab_t *s)
82 {
83 if (s == NULL)
84 return;
85 for (size_t i = 0; i < s->nsymbols; i++)
86 free(s->symbols[i].st_name);
87 free(s->symbols);
88 free(s);
89 }
90
91 symtab_t *
symtab_create(int fd,int bind,int type)92 symtab_create(int fd, int bind, int type)
93 {
94 Elf *elf;
95 symtab_t *st;
96 Elf_Scn *scn = NULL;
97 GElf_Ehdr ehdr;
98
99 if (elf_version(EV_CURRENT) == EV_NONE) {
100 warnx("Elf Library is out of date.");
101 return NULL;
102 }
103
104 elf = elf_begin(fd, ELF_C_READ, NULL);
105 if (elf == NULL) {
106 warnx("Error opening elf file: %s", elf_errmsg(elf_errno()));
107 return NULL;
108 }
109 st = calloc(1, sizeof(*st));
110 if (st == NULL) {
111 warnx("Error allocating symbol table");
112 elf_end(elf);
113 return NULL;
114 }
115 if (gelf_getehdr(elf, &ehdr) == NULL) {
116 warnx("Error getting ELF Ehdr");
117 elf_end(elf);
118 return NULL;
119 }
120
121 st->ispie = ehdr.e_type == ET_DYN;
122
123 while ((scn = elf_nextscn(elf, scn)) != NULL) {
124 GElf_Shdr shdr;
125 Elf_Data *edata;
126 size_t ns;
127 struct symbol *s;
128
129 gelf_getshdr(scn, &shdr);
130 if(shdr.sh_type != SHT_SYMTAB)
131 continue;
132
133 edata = elf_getdata(scn, NULL);
134 ns = shdr.sh_size / shdr.sh_entsize;
135 s = calloc(ns, sizeof(*s));
136 if (s == NULL) {
137 warn("Cannot allocate %zu symbols", ns);
138 goto out;
139 }
140 st->symbols = s;
141
142 for (size_t i = 0; i < ns; i++) {
143 GElf_Sym sym;
144 gelf_getsym(edata, (int)i, &sym);
145
146 DPRINTF("%s@%#jx=%d,%d",
147 elf_strptr(elf, shdr.sh_link, sym.st_name),
148 (uintmax_t)sym.st_value, ELF_ST_BIND(sym.st_info),
149 ELF_ST_TYPE(sym.st_info));
150
151 if (bind != -1 &&
152 (unsigned)bind != ELF_ST_BIND(sym.st_info))
153 continue;
154
155 if (type != -1 &&
156 (unsigned)type != ELF_ST_TYPE(sym.st_info))
157 continue;
158
159 s->st_value = sym.st_value;
160 s->st_info = sym.st_info;
161 s->st_name = strdup(
162 elf_strptr(elf, shdr.sh_link, sym.st_name));
163 if (s->st_name == NULL) {
164 warn("Cannot allocate symbol");
165 goto out;
166 }
167 s++;
168 }
169 st->nsymbols = s - st->symbols;
170 if (st->nsymbols == 0) {
171 warnx("No symbols found");
172 goto out;
173 }
174 qsort(st->symbols, st->nsymbols, sizeof(*st->symbols),
175 address_compare);
176 elf_end(elf);
177 return st;
178 }
179 out:
180 symtab_destroy(st);
181 elf_end(elf);
182 return NULL;
183 }
184
185
186 int
symtab_find(const symtab_t * st,const void * p,Dl_info * dli)187 symtab_find(const symtab_t *st, const void *p, Dl_info *dli)
188 {
189 struct symbol *s = st->symbols;
190 size_t ns = st->nsymbols;
191 size_t hi = ns;
192 size_t lo = 0;
193 size_t mid = ns / 2;
194 uintptr_t fbase = st->ispie ? (uintptr_t)dli->dli_fbase : 0;
195 uintptr_t dd, sd, me = (uintptr_t)p - fbase;
196 uintptr_t sa = SYMBOL_CANONICALIZE(dli->dli_saddr);
197 uintptr_t ad = sa - fbase;
198
199 DPRINTF("[fbase=%#jx, saddr=%p, sa=%#jx, me=%#jx ad=%#jx]",
200 (uintmax_t)fbase, dli->dli_saddr, (uintmax_t)sa,
201 (uintmax_t)me, (uintmax_t)ad);
202
203 for (;;) {
204 if (s[mid].st_value < me)
205 lo = mid;
206 else if (s[mid].st_value > me)
207 hi = mid;
208 else
209 break;
210 if (hi - lo == 1) {
211 mid = lo;
212 break;
213 }
214 mid = (hi + lo) / 2;
215 }
216 dd = me - ad;
217 sd = me - s[mid].st_value;
218 if (dd > sd) {
219 dli->dli_saddr = (void *)s[mid].st_value;
220 dli->dli_sname = s[mid].st_name;
221 DPRINTF("me=%#jx -> [%#jx, %s]", (uintmax_t)me, (uintmax_t)sd,
222 dli->dli_sname);
223 } else {
224 DPRINTF("%#jx -> [%#jx, ***]", (uintmax_t)me, (uintmax_t)sd);
225 }
226
227 return 1;
228 }
229