1/*	$NetBSD: backtrace.c,v 1.3 2013/08/29 14:58:56 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 1.3 2013/08/29 14:58:56 christos Exp $");
33
34#include <sys/param.h>
35#include <assert.h>
36#define _WITH_DPRINTF
37#include <stdio.h>
38#include <string.h>
39#include <stdlib.h>
40#include <stdarg.h>
41#include <stdint.h>
42#include <stddef.h>
43#include <unistd.h>
44#include <fcntl.h>
45#include <dlfcn.h>
46#include <elf.h>
47
48#include "execinfo.h"
49#include "symtab.h"
50
51#ifdef __linux__
52#define SELF	"/proc/self/exe"
53#else
54#include <sys/sysctl.h>
55#define SELF	"/proc/curproc/file"
56#endif
57
58static int
59open_self(int flags)
60{
61	const char *pathname = SELF;
62#ifdef KERN_PROC_PATHNAME
63	static const int name[] = {
64		CTL_KERN, KERN_PROC, KERN_PROC_PATHNAME, -1,
65	};
66	char path[MAXPATHLEN];
67	size_t len;
68
69	len = sizeof(path);
70	if (sysctl(name, 4, path, &len, NULL, 0) != -1)
71		pathname = path;
72#endif
73	return open(pathname, flags);
74}
75
76
77static int __printflike(4, 5)
78rasprintf(char **buf, size_t *bufsiz, size_t offs, const char *fmt, ...)
79{
80	for (;;) {
81		size_t nbufsiz;
82		char *nbuf;
83
84		if (*buf && offs < *bufsiz) {
85			va_list ap;
86			int len;
87
88			va_start(ap, fmt);
89			len = vsnprintf(*buf + offs, *bufsiz - offs, fmt, ap);
90			va_end(ap);
91
92			if (len < 0 || (size_t)len + 1 < *bufsiz - offs)
93				return len;
94			nbufsiz = MAX(*bufsiz + 512, (size_t)len + 1);
95		} else
96			nbufsiz = MAX(offs, *bufsiz) + 512;
97
98		nbuf = realloc(*buf, nbufsiz);
99		if (nbuf == NULL)
100			return -1;
101		*buf = nbuf;
102		*bufsiz = nbufsiz;
103	}
104}
105
106/*
107 * format specifiers:
108 *	%a	= address
109 *	%n	= symbol_name
110 *	%d	= symbol_address - address
111 *	%D	= if symbol_address == address "" else +%d
112 *	%f	= filename
113 */
114static ssize_t
115format_string(char **buf, size_t *bufsiz, size_t offs, const char *fmt,
116    Dl_info *dli, const void *addr)
117{
118	ptrdiff_t diff = (const char *)addr - (const char *)dli->dli_saddr;
119	size_t o = offs;
120	int len;
121
122	for (; *fmt; fmt++) {
123		if (*fmt != '%')
124			goto printone;
125		switch (*++fmt) {
126		case 'a':
127			len = rasprintf(buf, bufsiz, o, "%p", addr);
128			break;
129		case 'n':
130			len = rasprintf(buf, bufsiz, o, "%s", dli->dli_sname);
131			break;
132		case 'D':
133			if (diff)
134				len = rasprintf(buf, bufsiz, o, "+0x%tx", diff);
135			else
136				len = 0;
137			break;
138		case 'd':
139			len = rasprintf(buf, bufsiz, o, "0x%tx", diff);
140			break;
141		case 'f':
142			len = rasprintf(buf, bufsiz, o, "%s", dli->dli_fname);
143			break;
144		default:
145		printone:
146			len = rasprintf(buf, bufsiz, o, "%c", *fmt);
147			break;
148		}
149		if (len == -1)
150			return -1;
151		o += len;
152	}
153	return o - offs;
154}
155
156static ssize_t
157format_address(symtab_t *st, char **buf, size_t *bufsiz, size_t offs,
158    const char *fmt, const void *addr)
159{
160	Dl_info dli;
161
162	memset(&dli, 0, sizeof(dli));
163	(void)dladdr(addr, &dli);
164	if (st)
165		symtab_find(st, addr, &dli);
166
167	if (dli.dli_sname == NULL)
168		dli.dli_sname = "???";
169	if (dli.dli_fname == NULL)
170		dli.dli_fname = "???";
171	if (dli.dli_saddr == NULL)
172		dli.dli_saddr = (void *)(intptr_t)addr;
173
174	return format_string(buf, bufsiz, offs, fmt, &dli, addr);
175}
176
177char **
178backtrace_symbols_fmt(void *const *trace, size_t len, const char *fmt)
179{
180
181	static const size_t slen = sizeof(char *) + 64;	/* estimate */
182	char *ptr;
183	symtab_t *st;
184	int fd;
185
186	if ((fd = open_self(O_RDONLY)) != -1)
187		st = symtab_create(fd, -1, STT_FUNC);
188	else
189		st = NULL;
190
191	if ((ptr = calloc(len, slen)) == NULL)
192		goto out;
193
194	size_t psize = len * slen;
195	size_t offs = len * sizeof(char *);
196
197	/* We store only offsets in the first pass because of realloc */
198	for (size_t i = 0; i < len; i++) {
199		ssize_t x;
200		((char **)(void *)ptr)[i] = (void *)offs;
201		x = format_address(st, &ptr, &psize, offs, fmt, trace[i]);
202		if (x == -1) {
203			free(ptr);
204			ptr = NULL;
205			goto out;
206		}
207		offs += x;
208		ptr[offs++] = '\0';
209		assert(offs < psize);
210	}
211
212	/* Change offsets to pointers */
213	for (size_t j = 0; j < len; j++)
214		((char **)(void *)ptr)[j] += (intptr_t)ptr;
215
216out:
217	symtab_destroy(st);
218	if (fd != -1)
219		(void)close(fd);
220
221	return (void *)ptr;
222}
223
224int
225backtrace_symbols_fd_fmt(void *const *trace, size_t len, int fd,
226    const char *fmt)
227{
228	char **s = backtrace_symbols_fmt(trace, len, fmt);
229	if (s == NULL)
230		return -1;
231	for (size_t i = 0; i < len; i++)
232		if (dprintf(fd, "%s\n", s[i]) < 0)
233			break;
234	free(s);
235	return 0;
236}
237
238static const char fmt[] = "%a <%n%D> at %f";
239
240char **
241backtrace_symbols(void *const *trace, size_t len)
242{
243	return backtrace_symbols_fmt(trace, len, fmt);
244}
245
246int
247backtrace_symbols_fd(void *const *trace, size_t len, int fd)
248{
249	return backtrace_symbols_fd_fmt(trace, len, fd, fmt);
250}
251