1/* Standard find_debuginfo callback for libdwfl. 2 Copyright (C) 2005-2010, 2014 Red Hat, Inc. 3 This file is part of elfutils. 4 5 This file is free software; you can redistribute it and/or modify 6 it under the terms of either 7 8 * the GNU Lesser General Public License as published by the Free 9 Software Foundation; either version 3 of the License, or (at 10 your option) any later version 11 12 or 13 14 * the GNU General Public License as published by the Free 15 Software Foundation; either version 2 of the License, or (at 16 your option) any later version 17 18 or both in parallel, as here. 19 20 elfutils is distributed in the hope that it will be useful, but 21 WITHOUT ANY WARRANTY; without even the implied warranty of 22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 23 General Public License for more details. 24 25 You should have received copies of the GNU General Public License and 26 the GNU Lesser General Public License along with this program. If 27 not, see <http://www.gnu.org/licenses/>. */ 28 29#include "libdwflP.h" 30#include <stdio.h> 31#include <fcntl.h> 32#include <unistd.h> 33#include <sys/stat.h> 34#include "system.h" 35 36 37/* Try to open64 [DIR/][SUBDIR/]DEBUGLINK, return file descriptor or -1. 38 On success, *DEBUGINFO_FILE_NAME has the malloc'd name of the open file. */ 39static int 40try_open (const struct stat64 *main_stat, 41 const char *dir, const char *subdir, const char *debuglink, 42 char **debuginfo_file_name) 43{ 44 char *fname; 45 if (dir == NULL && subdir == NULL) 46 { 47 fname = strdup (debuglink); 48 if (fname == NULL) 49 return -1; 50 } 51 else if ((subdir == NULL ? asprintf (&fname, "%s/%s", dir, debuglink) 52 : dir == NULL ? asprintf (&fname, "%s/%s", subdir, debuglink) 53 : asprintf (&fname, "%s/%s/%s", dir, subdir, debuglink)) < 0) 54 return -1; 55 56 struct stat64 st; 57 int fd = TEMP_FAILURE_RETRY (open64 (fname, O_RDONLY)); 58 if (fd < 0) 59 free (fname); 60 else if (fstat64 (fd, &st) == 0 61 && st.st_ino == main_stat->st_ino 62 && st.st_dev == main_stat->st_dev) 63 { 64 /* This is the main file by another name. Don't look at it again. */ 65 close (fd); 66 errno = ENOENT; 67 fd = -1; 68 } 69 else 70 *debuginfo_file_name = fname; 71 72 return fd; 73} 74 75/* Return true iff the FD's contents CRC matches DEBUGLINK_CRC. */ 76static inline bool 77check_crc (int fd, GElf_Word debuglink_crc) 78{ 79 uint32_t file_crc; 80 return (__libdwfl_crc32_file (fd, &file_crc) == 0 81 && file_crc == debuglink_crc); 82} 83 84static bool 85validate (Dwfl_Module *mod, int fd, bool check, GElf_Word debuglink_crc) 86{ 87 /* For alt debug files always check the build-id from the Dwarf and alt. */ 88 if (mod->dw != NULL) 89 { 90 bool valid = false; 91 const void *build_id; 92 const char *altname; 93 ssize_t build_id_len = INTUSE(dwelf_dwarf_gnu_debugaltlink) (mod->dw, 94 &altname, 95 &build_id); 96 if (build_id_len > 0) 97 { 98 /* We need to open an Elf handle on the file so we can check its 99 build ID note for validation. Backdoor the handle into the 100 module data structure since we had to open it early anyway. */ 101 Dwfl_Error error = __libdw_open_file (&fd, &mod->alt_elf, 102 false, false); 103 if (error != DWFL_E_NOERROR) 104 __libdwfl_seterrno (error); 105 else 106 { 107 const void *alt_build_id; 108 ssize_t alt_len = INTUSE(dwelf_elf_gnu_build_id) (mod->alt_elf, 109 &alt_build_id); 110 if (alt_len > 0 && alt_len == build_id_len 111 && memcmp (build_id, alt_build_id, alt_len) == 0) 112 valid = true; 113 else 114 { 115 /* A mismatch! */ 116 elf_end (mod->alt_elf); 117 mod->alt_elf = NULL; 118 close (fd); 119 fd = -1; 120 } 121 } 122 } 123 return valid; 124 } 125 126 /* If we have a build ID, check only that. */ 127 if (mod->build_id_len > 0) 128 { 129 /* We need to open an Elf handle on the file so we can check its 130 build ID note for validation. Backdoor the handle into the 131 module data structure since we had to open it early anyway. */ 132 133 mod->debug.valid = false; 134 Dwfl_Error error = __libdw_open_file (&fd, &mod->debug.elf, false, false); 135 if (error != DWFL_E_NOERROR) 136 __libdwfl_seterrno (error); 137 else if (likely (__libdwfl_find_build_id (mod, false, 138 mod->debug.elf) == 2)) 139 /* Also backdoor the gratuitous flag. */ 140 mod->debug.valid = true; 141 else 142 { 143 /* A mismatch! */ 144 elf_end (mod->debug.elf); 145 mod->debug.elf = NULL; 146 close (fd); 147 fd = -1; 148 } 149 150 return mod->debug.valid; 151 } 152 153 return !check || check_crc (fd, debuglink_crc); 154} 155 156static int 157find_debuginfo_in_path (Dwfl_Module *mod, const char *file_name, 158 const char *debuglink_file, GElf_Word debuglink_crc, 159 char **debuginfo_file_name) 160{ 161 bool cancheck = debuglink_crc != (GElf_Word) 0; 162 163 const char *file_basename = file_name == NULL ? NULL : basename (file_name); 164 if (debuglink_file == NULL) 165 { 166 /* For a alt debug multi file we need a name, for a separate debug 167 name we may be able to fall back on file_basename.debug. */ 168 if (file_basename == NULL || mod->dw != NULL) 169 { 170 errno = 0; 171 return -1; 172 } 173 174 size_t len = strlen (file_basename); 175 char *localname = alloca (len + sizeof ".debug"); 176 memcpy (localname, file_basename, len); 177 memcpy (&localname[len], ".debug", sizeof ".debug"); 178 debuglink_file = localname; 179 cancheck = false; 180 } 181 182 /* Look for a file named DEBUGLINK_FILE in the directories 183 indicated by the debug directory path setting. */ 184 185 const Dwfl_Callbacks *const cb = mod->dwfl->callbacks; 186 char *path = strdupa ((cb->debuginfo_path ? *cb->debuginfo_path : NULL) 187 ?: DEFAULT_DEBUGINFO_PATH); 188 189 /* A leading - or + in the whole path sets whether to check file CRCs. */ 190 bool defcheck = true; 191 if (path[0] == '-' || path[0] == '+') 192 { 193 defcheck = path[0] == '+'; 194 ++path; 195 } 196 197 /* XXX dev/ino should be cached in struct dwfl_file. */ 198 struct stat64 main_stat; 199 if (unlikely ((mod->main.fd != -1 ? fstat64 (mod->main.fd, &main_stat) 200 : file_name != NULL ? stat64 (file_name, &main_stat) 201 : -1) < 0)) 202 { 203 main_stat.st_dev = 0; 204 main_stat.st_ino = 0; 205 } 206 207 char *file_dirname = (file_basename == file_name ? NULL 208 : strndupa (file_name, file_basename - 1 - file_name)); 209 char *p; 210 while ((p = strsep (&path, ":")) != NULL) 211 { 212 /* A leading - or + says whether to check file CRCs for this element. */ 213 bool check = defcheck; 214 if (*p == '+' || *p == '-') 215 check = *p++ == '+'; 216 check = check && cancheck; 217 218 const char *dir, *subdir, *file; 219 switch (p[0]) 220 { 221 case '\0': 222 /* An empty entry says to try the main file's directory. */ 223 dir = file_dirname; 224 subdir = NULL; 225 file = debuglink_file; 226 break; 227 case '/': 228 /* An absolute path says to look there for a subdirectory 229 named by the main file's absolute directory. This cannot 230 be applied to a relative file name. For alt debug files 231 it means to look for the basename file in that dir or the 232 .dwz subdir (see below). */ 233 if (mod->dw == NULL 234 && (file_dirname == NULL || file_dirname[0] != '/')) 235 continue; 236 dir = p; 237 if (mod->dw == NULL) 238 { 239 subdir = file_dirname + 1; 240 file = debuglink_file; 241 } 242 else 243 { 244 subdir = NULL; 245 file = basename (debuglink_file); 246 } 247 break; 248 default: 249 /* A relative path says to try a subdirectory of that name 250 in the main file's directory. */ 251 dir = file_dirname; 252 subdir = p; 253 file = debuglink_file; 254 break; 255 } 256 257 char *fname = NULL; 258 int fd = try_open (&main_stat, dir, subdir, file, &fname); 259 if (fd < 0) 260 switch (errno) 261 { 262 case ENOENT: 263 case ENOTDIR: 264 /* If we are looking for the alt file also try the .dwz subdir. 265 But only if this is the empty or absolute path. */ 266 if (mod->dw != NULL && (p[0] == '\0' || p[0] == '/')) 267 { 268 fd = try_open (&main_stat, dir, ".dwz", 269 basename (file), &fname); 270 if (fd < 0) 271 { 272 if (errno != ENOENT && errno != ENOTDIR) 273 return -1; 274 else 275 continue; 276 } 277 break; 278 } 279 continue; 280 default: 281 return -1; 282 } 283 if (validate (mod, fd, check, debuglink_crc)) 284 { 285 *debuginfo_file_name = fname; 286 return fd; 287 } 288 free (fname); 289 close (fd); 290 } 291 292 /* No dice. */ 293 errno = 0; 294 return -1; 295} 296 297int 298dwfl_standard_find_debuginfo (Dwfl_Module *mod, 299 void **userdata __attribute__ ((unused)), 300 const char *modname __attribute__ ((unused)), 301 GElf_Addr base __attribute__ ((unused)), 302 const char *file_name, 303 const char *debuglink_file, 304 GElf_Word debuglink_crc, 305 char **debuginfo_file_name) 306{ 307 /* First try by build ID if we have one. If that succeeds or fails 308 other than just by finding nothing, that's all we do. */ 309 const unsigned char *bits; 310 GElf_Addr vaddr; 311 if (INTUSE(dwfl_module_build_id) (mod, &bits, &vaddr) > 0) 312 { 313 /* Dropping most arguments means we cannot rely on them in 314 dwfl_build_id_find_debuginfo. But leave it that way since 315 some user code out there also does this, so we'll have to 316 handle it anyway. */ 317 int fd = INTUSE(dwfl_build_id_find_debuginfo) (mod, 318 NULL, NULL, 0, 319 NULL, NULL, 0, 320 debuginfo_file_name); 321 322 /* Did the build_id callback find something or report an error? 323 Then we are done. Otherwise fallback on path based search. */ 324 if (fd >= 0 325 || (mod->dw == NULL && mod->debug.elf != NULL) 326 || (mod->dw != NULL && mod->alt_elf != NULL) 327 || errno != 0) 328 return fd; 329 } 330 331 /* Failing that, search the path by name. */ 332 int fd = find_debuginfo_in_path (mod, file_name, 333 debuglink_file, debuglink_crc, 334 debuginfo_file_name); 335 336 if (fd < 0 && errno == 0) 337 { 338 /* If FILE_NAME is a symlink, the debug file might be associated 339 with the symlink target name instead. */ 340 341 char *canon = canonicalize_file_name (file_name); 342 if (canon != NULL && strcmp (file_name, canon)) 343 fd = find_debuginfo_in_path (mod, canon, 344 debuglink_file, debuglink_crc, 345 debuginfo_file_name); 346 free (canon); 347 } 348 349 return fd; 350} 351INTDEF (dwfl_standard_find_debuginfo) 352