backtrace.c revision 1.7
1 /* $NetBSD: backtrace.c,v 1.7 2022/06/23 09:48:00 skrll 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 1.7 2022/06/23 09:48:00 skrll 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 #include <sys/sysctl.h> 54 #define SELF "/proc/curproc/file" 55 #endif 56 57 static int 58 open_self(int flags) 59 { 60 const char *pathname = SELF; 61 #ifdef KERN_PROC_PATHNAME 62 static const int name[] = { 63 CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME, 64 }; 65 char path[MAXPATHLEN]; 66 size_t len; 67 68 len = sizeof(path); 69 if (sysctl(name, __arraycount(name), path, &len, NULL, 0) != -1) 70 pathname = path; 71 #endif 72 return open(pathname, flags); 73 } 74 75 76 static int __printflike(4, 5) 77 rasprintf(char **buf, size_t *bufsiz, size_t offs, const char *fmt, ...) 78 { 79 for (;;) { 80 size_t nbufsiz; 81 char *nbuf; 82 83 if (*buf && offs < *bufsiz) { 84 va_list ap; 85 int len; 86 87 va_start(ap, fmt); 88 len = vsnprintf(*buf + offs, *bufsiz - offs, fmt, ap); 89 va_end(ap); 90 91 if (len < 0 || (size_t)len + 1 < *bufsiz - offs) 92 return len; 93 nbufsiz = MAX(*bufsiz + 512, (size_t)len + 1); 94 } else 95 nbufsiz = MAX(offs, *bufsiz) + 512; 96 97 nbuf = realloc(*buf, nbufsiz); 98 if (nbuf == NULL) 99 return -1; 100 *buf = nbuf; 101 *bufsiz = nbufsiz; 102 } 103 } 104 105 /* 106 * format specifiers: 107 * %a = address 108 * %n = symbol_name 109 * %d = symbol_address - address 110 * %D = if symbol_address == address "" else +%d 111 * %f = filename 112 */ 113 static ssize_t 114 format_string(char **buf, size_t *bufsiz, size_t offs, const char *fmt, 115 Dl_info *dli, const void *addr) 116 { 117 ptrdiff_t diff = (const char *)addr - (const char *)dli->dli_saddr; 118 size_t o = offs; 119 int len; 120 121 for (; *fmt; fmt++) { 122 if (*fmt != '%') 123 goto printone; 124 switch (*++fmt) { 125 case 'a': 126 len = rasprintf(buf, bufsiz, o, "%p", addr); 127 break; 128 case 'n': 129 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_sname); 130 break; 131 case 'D': 132 if (diff) 133 len = rasprintf(buf, bufsiz, o, "+0x%tx", diff); 134 else 135 len = 0; 136 break; 137 case 'd': 138 len = rasprintf(buf, bufsiz, o, "0x%tx", diff); 139 break; 140 case 'f': 141 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_fname); 142 break; 143 default: 144 printone: 145 len = rasprintf(buf, bufsiz, o, "%c", *fmt); 146 break; 147 } 148 if (len == -1) 149 return -1; 150 o += len; 151 } 152 return o - offs; 153 } 154 155 static ssize_t 156 format_address(symtab_t *st, char **buf, size_t *bufsiz, size_t offs, 157 const char *fmt, const void *addr) 158 { 159 Dl_info dli; 160 161 memset(&dli, 0, sizeof(dli)); 162 (void)dladdr(addr, &dli); 163 if (st) 164 symtab_find(st, addr, &dli); 165 166 if (dli.dli_sname == NULL) 167 dli.dli_sname = "???"; 168 if (dli.dli_fname == NULL) 169 dli.dli_fname = "???"; 170 if (dli.dli_saddr == NULL) 171 dli.dli_saddr = (void *)(intptr_t)addr; 172 173 return format_string(buf, bufsiz, offs, fmt, &dli, addr); 174 } 175 176 char ** 177 backtrace_symbols_fmt(void *const *trace, size_t len, const char *fmt) 178 { 179 180 static const size_t slen = sizeof(char *) + 64; /* estimate */ 181 char *ptr; 182 symtab_t *st; 183 int fd; 184 185 if ((fd = open_self(O_RDONLY)) != -1) 186 st = symtab_create(fd, -1, STT_FUNC); 187 else 188 st = NULL; 189 190 if ((ptr = calloc(len, slen)) == NULL) 191 goto out; 192 193 size_t psize = len * slen; 194 size_t offs = len * sizeof(char *); 195 196 /* We store only offsets in the first pass because of realloc */ 197 for (size_t i = 0; i < len; i++) { 198 ssize_t x; 199 ((char **)(void *)ptr)[i] = (void *)offs; 200 x = format_address(st, &ptr, &psize, offs, fmt, trace[i]); 201 if (x == -1) { 202 free(ptr); 203 ptr = NULL; 204 goto out; 205 } 206 offs += x; 207 ptr[offs++] = '\0'; 208 assert(offs < psize); 209 } 210 211 /* Change offsets to pointers */ 212 for (size_t j = 0; j < len; j++) 213 ((char **)(void *)ptr)[j] += (intptr_t)ptr; 214 215 out: 216 symtab_destroy(st); 217 if (fd != -1) 218 (void)close(fd); 219 220 return (void *)ptr; 221 } 222 223 int 224 backtrace_symbols_fd_fmt(void *const *trace, size_t len, int fd, 225 const char *fmt) 226 { 227 char **s = backtrace_symbols_fmt(trace, len, fmt); 228 if (s == NULL) 229 return -1; 230 for (size_t i = 0; i < len; i++) 231 if (dprintf(fd, "%s\n", s[i]) < 0) 232 break; 233 free(s); 234 return 0; 235 } 236 237 static const char fmt[] = "%a <%n%D> at %f"; 238 239 char ** 240 backtrace_symbols(void *const *trace, size_t len) 241 { 242 return backtrace_symbols_fmt(trace, len, fmt); 243 } 244 245 int 246 backtrace_symbols_fd(void *const *trace, size_t len, int fd) 247 { 248 return backtrace_symbols_fd_fmt(trace, len, fd, fmt); 249 } 250
Indexes created Thu Sep 25 16:09:42 GMT 2025