backtrace.c revision 254688 
1/*	$NetBSD: backtrace.c,v 1.2 2012/07/09 03:11:59 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: backtrace.c,v 1.2 2012/07/09 03:11:59 christos Exp $");
33
34#include <sys/param.h>
35#include <assert.h>
36#include <stdio.h>
37#include <string.h>
38#include <stdlib.h>
39#include <stdarg.h>
40#include <stdint.h>
41#include <stddef.h>
42#include <unistd.h>
43#include <fcntl.h>
44#include <dlfcn.h>
45#include <elf.h>
46
47#include "execinfo.h"
48#include "symtab.h"
49
50#ifdef __linux__
51#define SELF	"/proc/self/exe"
52#else
53#define SELF	"/proc/curproc/file"
54#endif
55
56static int __printflike(4, 5)
57rasprintf(char **buf, size_t *bufsiz, size_t offs, const char *fmt, ...)
58{
59	for (;;) {
60		size_t nbufsiz;
61		char *nbuf;
62
63		if (*buf && offs < *bufsiz) {
64			va_list ap;
65			int len;
66
67			va_start(ap, fmt);
68			len = vsnprintf(*buf + offs, *bufsiz - offs, fmt, ap);
69			va_end(ap);
70
71			if (len < 0 || (size_t)len < *bufsiz - offs)
72				return len;
73			nbufsiz = MAX(*bufsiz + 512, (size_t)len + 1);
74		} else
75			nbufsiz = MAX(offs, *bufsiz) + 512;
76
77		nbuf = realloc(*buf, nbufsiz);
78		if (nbuf == NULL)
79			return -1;
80		*buf = nbuf;
81		*bufsiz = nbufsiz;
82	}
83}
84
85/*
86 * format specifiers:
87 *	%a	= address
88 *	%n	= symbol_name
89 *	%d	= symbol_address - address
90 *	%D	= if symbol_address == address "" else +%d
91 *	%f	= filename
92 */
93static ssize_t
94format_string(char **buf, size_t *bufsiz, size_t offs, const char *fmt,
95    Dl_info *dli, const void *addr)
96{
97	ptrdiff_t diff = (const char *)addr - (const char *)dli->dli_saddr;
98	size_t o = offs;
99	int len;
100
101	for (; *fmt; fmt++) {
102		if (*fmt != '%')
103			goto printone;
104		switch (*++fmt) {
105		case 'a':
106			len = rasprintf(buf, bufsiz, o, "%p", addr);
107			break;
108		case 'n':
109			len = rasprintf(buf, bufsiz, o, "%s", dli->dli_sname);
110			break;
111		case 'D':
112			if (diff)
113				len = rasprintf(buf, bufsiz, o, "+0x%tx", diff);
114			else
115				len = 0;
116			break;
117		case 'd':
118			len = rasprintf(buf, bufsiz, o, "0x%tx", diff);
119			break;
120		case 'f':
121			len = rasprintf(buf, bufsiz, o, "%s", dli->dli_fname);
122			break;
123		default:
124		printone:
125			len = rasprintf(buf, bufsiz, o, "%c", *fmt);
126			break;
127		}
128		if (len == -1)
129			return -1;
130		o += len;
131	}
132	return o - offs;
133}
134
135static ssize_t
136format_address(symtab_t *st, char **buf, size_t *bufsiz, size_t offs,
137    const char *fmt, const void *addr)
138{
139	Dl_info dli;
140
141	memset(&dli, 0, sizeof(dli));
142	(void)dladdr(addr, &dli);
143	if (st)
144		symtab_find(st, addr, &dli);
145
146	if (dli.dli_sname == NULL)
147		dli.dli_sname = "???";
148	if (dli.dli_fname == NULL)
149		dli.dli_fname = "???";
150	if (dli.dli_saddr == NULL)
151		dli.dli_saddr = (void *)(intptr_t)addr;
152
153	return format_string(buf, bufsiz, offs, fmt, &dli, addr);
154}
155
156char **
157backtrace_symbols_fmt(void *const *trace, size_t len, const char *fmt)
158{
159
160	static const size_t slen = sizeof(char *) + 64;	/* estimate */
161	char *ptr;
162	symtab_t *st;
163	int fd;
164
165	if ((fd = open(SELF, O_RDONLY)) != -1)
166		st = symtab_create(fd, -1, STT_FUNC);
167	else
168		st = NULL;
169
170	if ((ptr = calloc(len, slen)) == NULL)
171		goto out;
172
173	size_t psize = len * slen;
174	size_t offs = len * sizeof(char *);
175
176	/* We store only offsets in the first pass because of realloc */
177	for (size_t i = 0; i < len; i++) {
178		ssize_t x;
179		((char **)(void *)ptr)[i] = (void *)offs;
180		x = format_address(st, &ptr, &psize, offs, fmt, trace[i]);
181		if (x == -1) {
182			free(ptr);
183			ptr = NULL;
184			goto out;
185		}
186		offs += x;
187		ptr[offs++] = '\0';
188		assert(offs < psize);
189	}
190
191	/* Change offsets to pointers */
192	for (size_t j = 0; j < len; j++)
193		((char **)(void *)ptr)[j] += (intptr_t)ptr;
194
195out:
196	symtab_destroy(st);
197	if (fd != -1)
198		(void)close(fd);
199
200	return (void *)ptr;
201}
202
203int
204backtrace_symbols_fd_fmt(void *const *trace, size_t len, int fd,
205    const char *fmt)
206{
207	char **s = backtrace_symbols_fmt(trace, len, fmt);
208	if (s == NULL)
209		return -1;
210	for (size_t i = 0; i < len; i++)
211		if (dprintf(fd, "%s\n", s[i]) < 0)
212			break;
213	free(s);
214	return 0;
215}
216
217static const char fmt[] = "%a <%n%D> at %f";
218
219char **
220backtrace_symbols(void *const *trace, size_t len)
221{
222	return backtrace_symbols_fmt(trace, len, fmt);
223}
224
225int
226backtrace_symbols_fd(void *const *trace, size_t len, int fd)
227{
228	return backtrace_symbols_fd_fmt(trace, len, fd, fmt);
229}
230