1 /* $NetBSD: backtrace.c,v 1.8 2022/06/25 06:51:37 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 1.8 2022/06/25 06:51:37 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 "symbol.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_ARGS, -1, KERN_PROC_PATHNAME, 65 }; 66 char path[MAXPATHLEN]; 67 size_t len; 68 69 len = sizeof(path); 70 if (sysctl(name, __arraycount(name), 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 + 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 115 format_string(char **buf, size_t *bufsiz, size_t offs, const char *fmt, 116 Dl_info *dli, const void *addr) 117 { 118 const uintptr_t symaddr = SYMBOL_CANONICALIZE(dli->dli_saddr); 119 ptrdiff_t diff = (const char *)addr - (const char *)symaddr; 120 size_t o = offs; 121 int len; 122 123 for (; *fmt; fmt++) { 124 if (*fmt != '%') 125 goto printone; 126 switch (*++fmt) { 127 case 'a': 128 len = rasprintf(buf, bufsiz, o, "%p", addr); 129 break; 130 case 'n': 131 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_sname); 132 break; 133 case 'D': 134 if (diff) 135 len = rasprintf(buf, bufsiz, o, "+0x%tx", diff); 136 else 137 len = 0; 138 break; 139 case 'd': 140 len = rasprintf(buf, bufsiz, o, "0x%tx", diff); 141 break; 142 case 'f': 143 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_fname); 144 break; 145 default: 146 printone: 147 len = rasprintf(buf, bufsiz, o, "%c", *fmt); 148 break; 149 } 150 if (len == -1) 151 return -1; 152 o += len; 153 } 154 return o - offs; 155 } 156 157 static ssize_t 158 format_address(symtab_t *st, char **buf, size_t *bufsiz, size_t offs, 159 const char *fmt, const void *addr) 160 { 161 Dl_info dli; 162 163 memset(&dli, 0, sizeof(dli)); 164 (void)dladdr(addr, &dli); 165 if (st) 166 symtab_find(st, addr, &dli); 167 168 if (dli.dli_sname == NULL) 169 dli.dli_sname = "???"; 170 if (dli.dli_fname == NULL) 171 dli.dli_fname = "???"; 172 if (dli.dli_saddr == NULL) 173 dli.dli_saddr = (void *)(intptr_t)addr; 174 175 return format_string(buf, bufsiz, offs, fmt, &dli, addr); 176 } 177 178 char ** 179 backtrace_symbols_fmt(void *const *trace, size_t len, const char *fmt) 180 { 181 182 static const size_t slen = sizeof(char *) + 64; /* estimate */ 183 char *ptr; 184 symtab_t *st; 185 int fd; 186 187 if ((fd = open_self(O_RDONLY)) != -1) 188 st = symtab_create(fd, -1, STT_FUNC); 189 else 190 st = NULL; 191 192 if ((ptr = calloc(len, slen)) == NULL) 193 goto out; 194 195 size_t psize = len * slen; 196 size_t offs = len * sizeof(char *); 197 198 /* We store only offsets in the first pass because of realloc */ 199 for (size_t i = 0; i < len; i++) { 200 ssize_t x; 201 ((char **)(void *)ptr)[i] = (void *)offs; 202 x = format_address(st, &ptr, &psize, offs, fmt, trace[i]); 203 if (x == -1) { 204 free(ptr); 205 ptr = NULL; 206 goto out; 207 } 208 offs += x; 209 ptr[offs++] = '\0'; 210 assert(offs < psize); 211 } 212 213 /* Change offsets to pointers */ 214 for (size_t j = 0; j < len; j++) 215 ((char **)(void *)ptr)[j] += (intptr_t)ptr; 216 217 out: 218 symtab_destroy(st); 219 if (fd != -1) 220 (void)close(fd); 221 222 return (void *)ptr; 223 } 224 225 int 226 backtrace_symbols_fd_fmt(void *const *trace, size_t len, int fd, 227 const char *fmt) 228 { 229 char **s = backtrace_symbols_fmt(trace, len, fmt); 230 if (s == NULL) 231 return -1; 232 for (size_t i = 0; i < len; i++) 233 if (dprintf(fd, "%s\n", s[i]) < 0) 234 break; 235 free(s); 236 return 0; 237 } 238 239 static const char fmt[] = "%a <%n%D> at %f"; 240 241 char ** 242 backtrace_symbols(void *const *trace, size_t len) 243 { 244 return backtrace_symbols_fmt(trace, len, fmt); 245 } 246 247 int 248 backtrace_symbols_fd(void *const *trace, size_t len, int fd) 249 { 250 return backtrace_symbols_fd_fmt(trace, len, fd, fmt); 251 } 252