1 /* $NetBSD: backtrace.c,v 1.9 2025/01/23 12:08:12 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 1.9 2025/01/23 12:08:12 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 "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 self_fd = -1; 59 60 static int 61 open_self(int flags) 62 { 63 const char *pathname = SELF; 64 #ifdef KERN_PROC_PATHNAME 65 static const int name[] = { 66 CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME, 67 }; 68 char path[MAXPATHLEN]; 69 size_t len; 70 71 len = sizeof(path); 72 if (sysctl(name, __arraycount(name), path, &len, NULL, 0) != -1) 73 pathname = path; 74 #endif 75 return open(pathname, flags); 76 } 77 78 int 79 backtrace_sandbox_init(void) 80 { 81 82 if (self_fd == -1) 83 self_fd = open_self(O_RDONLY); 84 return self_fd >= 0 ? 0 : -1; 85 } 86 87 void 88 backtrace_sandbox_fini(void) 89 { 90 assert(self_fd >= 0); 91 92 close(self_fd); 93 self_fd = -1; 94 } 95 96 static int __printflike(4, 5) 97 rasprintf(char **buf, size_t *bufsiz, size_t offs, const char *fmt, ...) 98 { 99 for (;;) { 100 size_t nbufsiz; 101 char *nbuf; 102 103 if (*buf && offs < *bufsiz) { 104 va_list ap; 105 int len; 106 107 va_start(ap, fmt); 108 len = vsnprintf(*buf + offs, *bufsiz - offs, fmt, ap); 109 va_end(ap); 110 111 if (len < 0 || (size_t)len + 1 < *bufsiz - offs) 112 return len; 113 nbufsiz = MAX(*bufsiz + 512, (size_t)len + 1); 114 } else 115 nbufsiz = MAX(offs, *bufsiz) + 512; 116 117 nbuf = realloc(*buf, nbufsiz); 118 if (nbuf == NULL) 119 return -1; 120 *buf = nbuf; 121 *bufsiz = nbufsiz; 122 } 123 } 124 125 /* 126 * format specifiers: 127 * %a = address 128 * %n = symbol_name 129 * %d = symbol_address - address 130 * %D = if symbol_address == address "" else +%d 131 * %f = filename 132 */ 133 static ssize_t 134 format_string(char **buf, size_t *bufsiz, size_t offs, const char *fmt, 135 Dl_info *dli, const void *addr) 136 { 137 const uintptr_t symaddr = SYMBOL_CANONICALIZE(dli->dli_saddr); 138 ptrdiff_t diff = (const char *)addr - (const char *)symaddr; 139 size_t o = offs; 140 int len; 141 142 for (; *fmt; fmt++) { 143 if (*fmt != '%') 144 goto printone; 145 switch (*++fmt) { 146 case 'a': 147 len = rasprintf(buf, bufsiz, o, "%p", addr); 148 break; 149 case 'n': 150 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_sname); 151 break; 152 case 'D': 153 if (diff) 154 len = rasprintf(buf, bufsiz, o, "+0x%tx", diff); 155 else 156 len = 0; 157 break; 158 case 'd': 159 len = rasprintf(buf, bufsiz, o, "0x%tx", diff); 160 break; 161 case 'f': 162 len = rasprintf(buf, bufsiz, o, "%s", dli->dli_fname); 163 break; 164 default: 165 printone: 166 len = rasprintf(buf, bufsiz, o, "%c", *fmt); 167 break; 168 } 169 if (len == -1) 170 return -1; 171 o += len; 172 } 173 return o - offs; 174 } 175 176 static ssize_t 177 format_address(symtab_t *st, char **buf, size_t *bufsiz, size_t offs, 178 const char *fmt, const void *addr) 179 { 180 Dl_info dli; 181 182 memset(&dli, 0, sizeof(dli)); 183 (void)dladdr(addr, &dli); 184 if (st) 185 symtab_find(st, addr, &dli); 186 187 if (dli.dli_sname == NULL) 188 dli.dli_sname = "???"; 189 if (dli.dli_fname == NULL) 190 dli.dli_fname = "???"; 191 if (dli.dli_saddr == NULL) 192 dli.dli_saddr = (void *)(intptr_t)addr; 193 194 return format_string(buf, bufsiz, offs, fmt, &dli, addr); 195 } 196 197 char ** 198 backtrace_symbols_fmt(void *const *trace, size_t len, const char *fmt) 199 { 200 201 static const size_t slen = sizeof(char *) + 64; /* estimate */ 202 char *ptr; 203 symtab_t *st; 204 int fd = self_fd; 205 206 if (fd != -1 || (fd = open_self(O_RDONLY)) != -1) 207 st = symtab_create(fd, -1, STT_FUNC); 208 else 209 st = NULL; 210 211 if ((ptr = calloc(len, slen)) == NULL) 212 goto out; 213 214 size_t psize = len * slen; 215 size_t offs = len * sizeof(char *); 216 217 /* We store only offsets in the first pass because of realloc */ 218 for (size_t i = 0; i < len; i++) { 219 ssize_t x; 220 ((char **)(void *)ptr)[i] = (void *)offs; 221 x = format_address(st, &ptr, &psize, offs, fmt, trace[i]); 222 if (x == -1) { 223 free(ptr); 224 ptr = NULL; 225 goto out; 226 } 227 offs += x; 228 ptr[offs++] = '\0'; 229 assert(offs < psize); 230 } 231 232 /* Change offsets to pointers */ 233 for (size_t j = 0; j < len; j++) 234 ((char **)(void *)ptr)[j] += (intptr_t)ptr; 235 236 out: 237 symtab_destroy(st); 238 if (fd != -1 && fd != self_fd) 239 (void)close(fd); 240 241 return (void *)ptr; 242 } 243 244 int 245 backtrace_symbols_fd_fmt(void *const *trace, size_t len, int fd, 246 const char *fmt) 247 { 248 char **s = backtrace_symbols_fmt(trace, len, fmt); 249 if (s == NULL) 250 return -1; 251 for (size_t i = 0; i < len; i++) 252 if (dprintf(fd, "%s\n", s[i]) < 0) 253 break; 254 free(s); 255 return 0; 256 } 257 258 static const char fmt[] = "%a <%n%D> at %f"; 259 260 char ** 261 backtrace_symbols(void *const *trace, size_t len) 262 { 263 return backtrace_symbols_fmt(trace, len, fmt); 264 } 265 266 int 267 backtrace_symbols_fd(void *const *trace, size_t len, int fd) 268 { 269 return backtrace_symbols_fd_fmt(trace, len, fd, fmt); 270 } 271
Indexes created Sat Sep 20 22:09:52 GMT 2025