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
58 static int
open_self(int flags)59 open_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
77 static int __printflike(4, 5)
rasprintf(char ** buf,size_t * bufsiz,size_t offs,const char * fmt,...)78 rasprintf(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 */
114 static ssize_t
format_string(char ** buf,size_t * bufsiz,size_t offs,const char * fmt,Dl_info * dli,const void * addr)115 format_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
156 static ssize_t
format_address(symtab_t * st,char ** buf,size_t * bufsiz,size_t offs,const char * fmt,const void * addr)157 format_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
177 char **
backtrace_symbols_fmt(void * const * trace,size_t len,const char * fmt)178 backtrace_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
216 out:
217 symtab_destroy(st);
218 if (fd != -1)
219 (void)close(fd);
220
221 return (void *)ptr;
222 }
223
224 int
backtrace_symbols_fd_fmt(void * const * trace,size_t len,int fd,const char * fmt)225 backtrace_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
238 static const char fmt[] = "%a <%n%D> at %f";
239
240 char **
backtrace_symbols(void * const * trace,size_t len)241 backtrace_symbols(void *const *trace, size_t len)
242 {
243 return backtrace_symbols_fmt(trace, len, fmt);
244 }
245
246 int
backtrace_symbols_fd(void * const * trace,size_t len,int fd)247 backtrace_symbols_fd(void *const *trace, size_t len, int fd)
248 {
249 return backtrace_symbols_fd_fmt(trace, len, fd, fmt);
250 }
251