1 /* $OpenBSD: backtrace.c,v 1.1 2021/06/09 19:37:43 mortimer 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
33 #include <sys/param.h>
34 #include <assert.h>
35 #include <stdio.h>
36 #include <string.h>
37 #include <stdlib.h>
38 #include <stdarg.h>
39 #include <stdint.h>
40 #include <stddef.h>
41 #include <unistd.h>
42 #include <fcntl.h>
43 #include <dlfcn.h>
44
45 #include "execinfo.h"
46
47 static int
rasprintf(char ** buf,size_t * bufsiz,size_t offs,const char * fmt,...)48 rasprintf(char **buf, size_t *bufsiz, size_t offs, const char *fmt, ...)
49 {
50 for (;;) {
51 size_t nbufsiz;
52 char *nbuf;
53
54 if (*buf && offs < *bufsiz) {
55 va_list ap;
56 int len;
57
58 va_start(ap, fmt);
59 len = vsnprintf(*buf + offs, *bufsiz - offs, fmt, ap);
60 va_end(ap);
61
62 if (len < 0 || (size_t)len + 1 < *bufsiz - offs)
63 return len;
64 nbufsiz = MAX(*bufsiz + 512, (size_t)len + 1);
65 } else
66 nbufsiz = MAX(offs, *bufsiz) + 512;
67
68 nbuf = realloc(*buf, nbufsiz);
69 if (nbuf == NULL)
70 return -1;
71 *buf = nbuf;
72 *bufsiz = nbufsiz;
73 }
74 }
75
76 /*
77 * format specifiers:
78 * %a = address
79 * %n = symbol_name
80 * %d = symbol_address - address
81 * %D = if symbol_address == address "" else +%d
82 * %f = filename
83 */
84 static ssize_t
format_string(char ** buf,size_t * bufsiz,size_t offs,const char * fmt,Dl_info * dli,const void * addr)85 format_string(char **buf, size_t *bufsiz, size_t offs, const char *fmt,
86 Dl_info *dli, const void *addr)
87 {
88 ptrdiff_t diff = (const char *)addr - (const char *)dli->dli_saddr;
89 size_t o = offs;
90 int len;
91
92 for (; *fmt; fmt++) {
93 if (*fmt != '%')
94 goto printone;
95 switch (*++fmt) {
96 case 'a':
97 len = rasprintf(buf, bufsiz, o, "%p", addr);
98 break;
99 case 'n':
100 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_sname);
101 break;
102 case 'D':
103 if (diff)
104 len = rasprintf(buf, bufsiz, o, "+0x%tx", diff);
105 else
106 len = 0;
107 break;
108 case 'd':
109 len = rasprintf(buf, bufsiz, o, "0x%tx", diff);
110 break;
111 case 'f':
112 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_fname);
113 break;
114 default:
115 printone:
116 len = rasprintf(buf, bufsiz, o, "%c", *fmt);
117 break;
118 }
119 if (len == -1)
120 return -1;
121 o += len;
122 }
123 return o - offs;
124 }
125
126 static ssize_t
format_address(char ** buf,size_t * bufsiz,size_t offs,const char * fmt,const void * addr)127 format_address(char **buf, size_t *bufsiz, size_t offs,
128 const char *fmt, const void *addr)
129 {
130 Dl_info dli;
131
132 memset(&dli, 0, sizeof(dli));
133 (void)dladdr(addr, &dli);
134
135 if (dli.dli_sname == NULL)
136 dli.dli_sname = "???";
137 if (dli.dli_fname == NULL)
138 dli.dli_fname = "???";
139 if (dli.dli_saddr == NULL)
140 dli.dli_saddr = (void *)(intptr_t)addr;
141
142 return format_string(buf, bufsiz, offs, fmt, &dli, addr);
143 }
144
145 char **
backtrace_symbols_fmt(void * const * trace,size_t len,const char * fmt)146 backtrace_symbols_fmt(void *const *trace, size_t len, const char *fmt)
147 {
148
149 static const size_t slen = sizeof(char *) + 64; /* estimate */
150 char *ptr;
151
152 if ((ptr = calloc(len, slen)) == NULL)
153 goto out;
154
155 size_t psize = len * slen;
156 size_t offs = len * sizeof(char *);
157
158 /* We store only offsets in the first pass because of realloc */
159 for (size_t i = 0; i < len; i++) {
160 ssize_t x;
161 ((char **)(void *)ptr)[i] = (void *)offs;
162 x = format_address(&ptr, &psize, offs, fmt, trace[i]);
163 if (x == -1) {
164 free(ptr);
165 ptr = NULL;
166 goto out;
167 }
168 offs += x;
169 ptr[offs++] = '\0';
170 assert(offs < psize);
171 }
172
173 /* Change offsets to pointers */
174 for (size_t j = 0; j < len; j++)
175 ((char **)(void *)ptr)[j] += (intptr_t)ptr;
176
177 out:
178 return (void *)ptr;
179 }
180
181 int
backtrace_symbols_fd_fmt(void * const * trace,size_t len,int fd,const char * fmt)182 backtrace_symbols_fd_fmt(void *const *trace, size_t len, int fd,
183 const char *fmt)
184 {
185 char **s = backtrace_symbols_fmt(trace, len, fmt);
186 if (s == NULL)
187 return -1;
188 for (size_t i = 0; i < len; i++)
189 if (dprintf(fd, "%s\n", s[i]) < 0)
190 break;
191 free(s);
192 return 0;
193 }
194
195 static const char fmt[] = "%a <%n%D> at %f";
196
197 char **
backtrace_symbols(void * const * trace,size_t len)198 backtrace_symbols(void *const *trace, size_t len)
199 {
200 return backtrace_symbols_fmt(trace, len, fmt);
201 }
202
203 int
backtrace_symbols_fd(void * const * trace,size_t len,int fd)204 backtrace_symbols_fd(void *const *trace, size_t len, int fd)
205 {
206 return backtrace_symbols_fd_fmt(trace, len, fd, fmt);
207 }
208