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 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) 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 < *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 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 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 ** 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 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 ** 241 backtrace_symbols(void *const *trace, size_t len) 242 { 243 return backtrace_symbols_fmt(trace, len, fmt); 244 } 245 246 int 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