symtab.c revision 255033 
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__RCSID("$NetBSD: symtab.c,v 1.2 2013/08/29 15:01:57 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
53struct symbol {
54	char *st_name;
55	uintptr_t st_value;
56	uintptr_t st_info;
57};
58
59struct symtab {
60	size_t nsymbols;
61	struct symbol *symbols;
62};
63
64static int
65address_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
72void
73symtab_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
83symtab_t *
84symtab_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				goto out;
144			s++;
145                }
146		st->nsymbols = s - st->symbols;
147		if (st->nsymbols == 0) {
148			warnx("No symbols found");
149			goto out;
150		}
151		qsort(st->symbols, st->nsymbols, sizeof(*st->symbols),
152		    address_compare);
153		elf_end(elf);
154		return st;
155	}
156out:
157	symtab_destroy(st);
158	elf_end(elf);
159	return NULL;
160}
161
162
163int
164symtab_find(const symtab_t *st, const void *p, Dl_info *dli)
165{
166	struct symbol *s = st->symbols;
167	size_t ns = st->nsymbols;
168	size_t hi = ns;
169	size_t lo = 0;
170	size_t mid = ns / 2;
171	uintptr_t dd, sd, me = (uintptr_t)p;
172
173	for (;;) {
174		if (s[mid].st_value < me)
175			lo = mid;
176		else if (s[mid].st_value > me)
177			hi = mid;
178		else
179			break;
180		if (hi - lo == 1) {
181			mid = lo;
182			break;
183		}
184		mid = (hi + lo) / 2;
185	}
186	dd = me - (uintptr_t)dli->dli_saddr;
187	sd = me - s[mid].st_value;
188	if (dd > sd) {
189		dli->dli_saddr = (void *)s[mid].st_value;
190		dli->dli_sname = s[mid].st_name;
191	}
192	return 1;
193}
194