1 /* 2 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 3 * Licensed under the GPL 4 */ 5 6 #include <stdio.h> 7 #include <stdlib.h> 8 #include <dirent.h> 9 #include <errno.h> 10 #include <fcntl.h> 11 #include <signal.h> 12 #include <string.h> 13 #include <unistd.h> 14 #include <sys/stat.h> 15 #include <init.h> 16 #include <os.h> 17 18 #define UML_DIR "~/.uml/" 19 20 #define UMID_LEN 64 21 22 /* Changed by set_umid, which is run early in boot */ 23 static char umid[UMID_LEN] = { 0 }; 24 25 /* Changed by set_uml_dir and make_uml_dir, which are run early in boot */ 26 static char *uml_dir = UML_DIR; 27 28 static int __init make_uml_dir(void) 29 { 30 char dir[512] = { '\0' }; 31 int len, err; 32 33 if (*uml_dir == '~') { 34 char *home = getenv("HOME"); 35 36 err = -ENOENT; 37 if (home == NULL) { 38 printk(UM_KERN_ERR 39 "%s: no value in environment for $HOME\n", 40 __func__); 41 goto err; 42 } 43 strlcpy(dir, home, sizeof(dir)); 44 uml_dir++; 45 } 46 strlcat(dir, uml_dir, sizeof(dir)); 47 len = strlen(dir); 48 if (len > 0 && dir[len - 1] != '/') 49 strlcat(dir, "/", sizeof(dir)); 50 51 err = -ENOMEM; 52 uml_dir = malloc(strlen(dir) + 1); 53 if (uml_dir == NULL) { 54 printk(UM_KERN_ERR "%s : malloc failed, errno = %d\n", 55 __func__, errno); 56 goto err; 57 } 58 strcpy(uml_dir, dir); 59 60 if ((mkdir(uml_dir, 0777) < 0) && (errno != EEXIST)) { 61 printk(UM_KERN_ERR "Failed to mkdir '%s': %s\n", 62 uml_dir, strerror(errno)); 63 err = -errno; 64 goto err_free; 65 } 66 return 0; 67 68 err_free: 69 free(uml_dir); 70 err: 71 uml_dir = NULL; 72 return err; 73 } 74 75 /* 76 * Unlinks the files contained in @dir and then removes @dir. 77 * Doesn't handle directory trees, so it's not like rm -rf, but almost such. We 78 * ignore ENOENT errors for anything (they happen, strangely enough - possibly 79 * due to races between multiple dying UML threads). 80 */ 81 static int remove_files_and_dir(char *dir) 82 { 83 DIR *directory; 84 struct dirent *ent; 85 int len; 86 char file[256]; 87 int ret; 88 89 directory = opendir(dir); 90 if (directory == NULL) { 91 if (errno != ENOENT) 92 return -errno; 93 else 94 return 0; 95 } 96 97 while ((ent = readdir(directory)) != NULL) { 98 if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, "..")) 99 continue; 100 len = strlen(dir) + sizeof("/") + strlen(ent->d_name) + 1; 101 if (len > sizeof(file)) { 102 ret = -E2BIG; 103 goto out; 104 } 105 106 sprintf(file, "%s/%s", dir, ent->d_name); 107 if (unlink(file) < 0 && errno != ENOENT) { 108 ret = -errno; 109 goto out; 110 } 111 } 112 113 if (rmdir(dir) < 0 && errno != ENOENT) { 114 ret = -errno; 115 goto out; 116 } 117 118 ret = 0; 119 out: 120 closedir(directory); 121 return ret; 122 } 123 124 /* 125 * This says that there isn't already a user of the specified directory even if 126 * there are errors during the checking. This is because if these errors 127 * happen, the directory is unusable by the pre-existing UML, so we might as 128 * well take it over. This could happen either by 129 * the existing UML somehow corrupting its umid directory 130 * something other than UML sticking stuff in the directory 131 * this boot racing with a shutdown of the other UML 132 * In any of these cases, the directory isn't useful for anything else. 133 * 134 * Boolean return: 1 if in use, 0 otherwise. 135 */ 136 static inline int is_umdir_used(char *dir) 137 { 138 char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")]; 139 char pid[sizeof("nnnnn\0")], *end; 140 int dead, fd, p, n, err; 141 142 n = snprintf(file, sizeof(file), "%s/pid", dir); 143 if (n >= sizeof(file)) { 144 printk(UM_KERN_ERR "is_umdir_used - pid filename too long\n"); 145 err = -E2BIG; 146 goto out; 147 } 148 149 dead = 0; 150 fd = open(file, O_RDONLY); 151 if (fd < 0) { 152 fd = -errno; 153 if (fd != -ENOENT) { 154 printk(UM_KERN_ERR "is_umdir_used : couldn't open pid " 155 "file '%s', err = %d\n", file, -fd); 156 } 157 goto out; 158 } 159 160 err = 0; 161 n = read(fd, pid, sizeof(pid)); 162 if (n < 0) { 163 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 164 "'%s', err = %d\n", file, errno); 165 goto out_close; 166 } else if (n == 0) { 167 printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file " 168 "'%s', 0-byte read\n", file); 169 goto out_close; 170 } 171 172 p = strtoul(pid, &end, 0); 173 if (end == pid) { 174 printk(UM_KERN_ERR "is_umdir_used : couldn't parse pid file " 175 "'%s', errno = %d\n", file, errno); 176 goto out_close; 177 } 178 179 if ((kill(p, 0) == 0) || (errno != ESRCH)) { 180 printk(UM_KERN_ERR "umid \"%s\" is already in use by pid %d\n", 181 umid, p); 182 return 1; 183 } 184 185 out_close: 186 close(fd); 187 out: 188 return 0; 189 } 190 191 /* 192 * Try to remove the directory @dir unless it's in use. 193 * Precondition: @dir exists. 194 * Returns 0 for success, < 0 for failure in removal or if the directory is in 195 * use. 196 */ 197 static int umdir_take_if_dead(char *dir) 198 { 199 int ret; 200 if (is_umdir_used(dir)) 201 return -EEXIST; 202 203 ret = remove_files_and_dir(dir); 204 if (ret) { 205 printk(UM_KERN_ERR "is_umdir_used - remove_files_and_dir " 206 "failed with err = %d\n", ret); 207 } 208 return ret; 209 } 210 211 static void __init create_pid_file(void) 212 { 213 char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")]; 214 char pid[sizeof("nnnnn\0")]; 215 int fd, n; 216 217 if (umid_file_name("pid", file, sizeof(file))) 218 return; 219 220 fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644); 221 if (fd < 0) { 222 printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: " 223 "%s\n", file, strerror(errno)); 224 return; 225 } 226 227 snprintf(pid, sizeof(pid), "%d\n", getpid()); 228 n = write(fd, pid, strlen(pid)); 229 if (n != strlen(pid)) 230 printk(UM_KERN_ERR "Write of pid file failed - err = %d\n", 231 errno); 232 233 close(fd); 234 } 235 236 int __init set_umid(char *name) 237 { 238 if (strlen(name) > UMID_LEN - 1) 239 return -E2BIG; 240 241 strlcpy(umid, name, sizeof(umid)); 242 243 return 0; 244 } 245 246 /* Changed in make_umid, which is called during early boot */ 247 static int umid_setup = 0; 248 249 static int __init make_umid(void) 250 { 251 int fd, err; 252 char tmp[256]; 253 254 if (umid_setup) 255 return 0; 256 257 make_uml_dir(); 258 259 if (*umid == '\0') { 260 strlcpy(tmp, uml_dir, sizeof(tmp)); 261 strlcat(tmp, "XXXXXX", sizeof(tmp)); 262 fd = mkstemp(tmp); 263 if (fd < 0) { 264 printk(UM_KERN_ERR "make_umid - mkstemp(%s) failed: " 265 "%s\n", tmp, strerror(errno)); 266 err = -errno; 267 goto err; 268 } 269 270 close(fd); 271 272 set_umid(&tmp[strlen(uml_dir)]); 273 274 /* 275 * There's a nice tiny little race between this unlink and 276 * the mkdir below. It'd be nice if there were a mkstemp 277 * for directories. 278 */ 279 if (unlink(tmp)) { 280 err = -errno; 281 goto err; 282 } 283 } 284 285 snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid); 286 err = mkdir(tmp, 0777); 287 if (err < 0) { 288 err = -errno; 289 if (err != -EEXIST) 290 goto err; 291 292 if (umdir_take_if_dead(tmp) < 0) 293 goto err; 294 295 err = mkdir(tmp, 0777); 296 } 297 if (err) { 298 err = -errno; 299 printk(UM_KERN_ERR "Failed to create '%s' - err = %d\n", umid, 300 errno); 301 goto err; 302 } 303 304 umid_setup = 1; 305 306 create_pid_file(); 307 308 err = 0; 309 err: 310 return err; 311 } 312 313 static int __init make_umid_init(void) 314 { 315 if (!make_umid()) 316 return 0; 317 318 /* 319 * If initializing with the given umid failed, then try again with 320 * a random one. 321 */ 322 printk(UM_KERN_ERR "Failed to initialize umid \"%s\", trying with a " 323 "random umid\n", umid); 324 *umid = '\0'; 325 make_umid(); 326 327 return 0; 328 } 329 330 __initcall(make_umid_init); 331 332 int __init umid_file_name(char *name, char *buf, int len) 333 { 334 int n, err; 335 336 err = make_umid(); 337 if (err) 338 return err; 339 340 n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name); 341 if (n >= len) { 342 printk(UM_KERN_ERR "umid_file_name : buffer too short\n"); 343 return -E2BIG; 344 } 345 346 return 0; 347 } 348 349 char *get_umid(void) 350 { 351 return umid; 352 } 353 354 static int __init set_uml_dir(char *name, int *add) 355 { 356 if (*name == '\0') { 357 os_warn("uml_dir can't be an empty string\n"); 358 return 0; 359 } 360 361 if (name[strlen(name) - 1] == '/') { 362 uml_dir = name; 363 return 0; 364 } 365 366 uml_dir = malloc(strlen(name) + 2); 367 if (uml_dir == NULL) { 368 os_warn("Failed to malloc uml_dir - error = %d\n", errno); 369 370 /* 371 * Return 0 here because do_initcalls doesn't look at 372 * the return value. 373 */ 374 return 0; 375 } 376 sprintf(uml_dir, "%s/", name); 377 378 return 0; 379 } 380 381 __uml_setup("uml_dir=", set_uml_dir, 382 "uml_dir=<directory>\n" 383 " The location to place the pid and umid files.\n\n" 384 ); 385 386 static void remove_umid_dir(void) 387 { 388 char dir[strlen(uml_dir) + UMID_LEN + 1], err; 389 390 sprintf(dir, "%s%s", uml_dir, umid); 391 err = remove_files_and_dir(dir); 392 if (err) 393 os_warn("%s - remove_files_and_dir failed with err = %d\n", 394 __func__, err); 395 } 396 397 __uml_exitcall(remove_umid_dir); 398