symtab.c revision 254688 
1/*	$NetBSD: symtab.c,v 1.1 2012/05/26 22:02:29 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 1.1 2012/05/26 22:02:29 christos Exp $");
33
34#include <stdlib.h>
35#include <stdio.h>
36#include <string.h>
37#include <err.h>
38#include <dlfcn.h>
39
40#include <libelf.h>
41#include <gelf.h>
42#ifndef ELF_ST_BIND
43#define ELF_ST_BIND(x)          ((x) >> 4)
44#endif
45#ifndef ELF_ST_TYPE
46#define ELF_ST_TYPE(x)          (((unsigned int)x) & 0xf)
47#endif
48
49
50#include "symtab.h"
51
52struct symbol {
53	char *st_name;
54	uintptr_t st_value;
55	uintptr_t st_info;
56};
57
58struct symtab {
59	size_t nsymbols;
60	struct symbol *symbols;
61};
62
63static int
64address_compare(const void *a, const void *b)
65{
66	const struct symbol *sa = a;
67	const struct symbol *sb = b;
68	return (int)(intmax_t)(sa->st_value - sb->st_value);
69}
70
71void
72symtab_destroy(symtab_t *s)
73{
74	if (s == NULL)
75		return;
76	for (size_t i = 0; i < s->nsymbols; i++)
77		free(s->symbols[i].st_name);
78	free(s->symbols);
79	free(s);
80}
81
82symtab_t *
83symtab_create(int fd, int bind, int type)
84{
85	Elf *elf;
86	symtab_t *st;
87	Elf_Scn *scn = NULL;
88
89	if (elf_version(EV_CURRENT) == EV_NONE) {
90		warnx("Elf Library is out of date.");
91		return NULL;
92	}
93
94	elf = elf_begin(fd, ELF_C_READ, NULL);
95	if (elf == NULL) {
96		warnx("Error opening elf file: %s", elf_errmsg(elf_errno()));
97		return NULL;
98	}
99	st = calloc(1, sizeof(*st));
100	if (st == NULL) {
101		warnx("Error allocating symbol table");
102		elf_end(elf);
103		return NULL;
104	}
105
106	while ((scn = elf_nextscn(elf, scn)) != NULL) {
107		GElf_Shdr shdr;
108		Elf_Data *edata;
109		size_t ns;
110		struct symbol *s;
111
112		gelf_getshdr(scn, &shdr);
113		if(shdr.sh_type != SHT_SYMTAB)
114			continue;
115
116		edata = elf_getdata(scn, NULL);
117		ns = shdr.sh_size / shdr.sh_entsize;
118		s = calloc(ns, sizeof(*s));
119		if (s == NULL) {
120			warn("Cannot allocate %zu symbols", ns);
121			goto out;
122		}
123		st->symbols = s;
124
125		for (size_t i = 0; i < ns; i++) {
126			GElf_Sym sym;
127                        gelf_getsym(edata, (int)i, &sym);
128
129			if (bind != -1 &&
130			    (unsigned)bind != ELF_ST_BIND(sym.st_info))
131				continue;
132
133			if (type != -1 &&
134			    (unsigned)type != ELF_ST_TYPE(sym.st_info))
135				continue;
136
137			s->st_value = sym.st_value;
138			s->st_info = sym.st_info;
139			s->st_name = strdup(
140			    elf_strptr(elf, shdr.sh_link, sym.st_name));
141			if (s->st_name == NULL)
142				goto out;
143			s++;
144                }
145		st->nsymbols = s - st->symbols;
146		if (st->nsymbols == 0) {
147			warnx("No symbols found");
148			goto out;
149		}
150		qsort(st->symbols, st->nsymbols, sizeof(*st->symbols),
151		    address_compare);
152		elf_end(elf);
153		return st;
154	}
155out:
156	symtab_destroy(st);
157	elf_end(elf);
158	return NULL;
159}
160
161
162int
163symtab_find(const symtab_t *st, const void *p, Dl_info *dli)
164{
165	struct symbol *s = st->symbols;
166	size_t ns = st->nsymbols;
167	size_t hi = ns;
168	size_t lo = 0;
169	size_t mid = ns / 2;
170	uintptr_t dd, sd, me = (uintptr_t)p;
171
172	for (;;) {
173		if (s[mid].st_value < me)
174			lo = mid;
175		else if (s[mid].st_value > me)
176			hi = mid;
177		else
178			break;
179		if (hi - lo == 1) {
180			mid = lo;
181			break;
182		}
183		mid = (hi + lo) / 2;
184	}
185	dd = me - (uintptr_t)dli->dli_saddr;
186	sd = me - s[mid].st_value;
187	if (dd > sd) {
188		dli->dli_saddr = (void *)s[mid].st_value;
189		dli->dli_sname = s[mid].st_name;
190	}
191	return 1;
192}
193