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 56 static int __printflike(4, 5) 57 rasprintf(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 */ 93 static ssize_t 94 format_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 } 134 135 static ssize_t 136 format_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 } 155 156 char ** 157 backtrace_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; 194 195 out: 196 symtab_destroy(st); 197 if (fd != -1) 198 (void)close(fd); 199 200 return (void *)ptr; 201 } 202 203 int 204 backtrace_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 } 216 217 static const char fmt[] = "%a <%n%D> at %f"; 218 219 char ** 220 backtrace_symbols(void *const *trace, size_t len) 221 { 222 return backtrace_symbols_fmt(trace, len, fmt); 223 } 224 225 int 226 backtrace_symbols_fd(void *const *trace, size_t len, int fd) 227 { 228 return backtrace_symbols_fd_fmt(trace, len, fd, fmt); 229 } 230