xref: /openbmc/linux/arch/um/os-Linux/umid.c (revision 63dc02bd)
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 "make_uml_dir : no value in "
39 			       "environment for $HOME\n");
40 			goto err;
41 		}
42 		strlcpy(dir, home, sizeof(dir));
43 		uml_dir++;
44 	}
45 	strlcat(dir, uml_dir, sizeof(dir));
46 	len = strlen(dir);
47 	if (len > 0 && dir[len - 1] != '/')
48 		strlcat(dir, "/", sizeof(dir));
49 
50 	err = -ENOMEM;
51 	uml_dir = malloc(strlen(dir) + 1);
52 	if (uml_dir == NULL) {
53 		printf("make_uml_dir : malloc failed, errno = %d\n", errno);
54 		goto err;
55 	}
56 	strcpy(uml_dir, dir);
57 
58 	if ((mkdir(uml_dir, 0777) < 0) && (errno != EEXIST)) {
59 	        printf("Failed to mkdir '%s': %s\n", uml_dir, strerror(errno));
60 		err = -errno;
61 		goto err_free;
62 	}
63 	return 0;
64 
65 err_free:
66 	free(uml_dir);
67 err:
68 	uml_dir = NULL;
69 	return err;
70 }
71 
72 /*
73  * Unlinks the files contained in @dir and then removes @dir.
74  * Doesn't handle directory trees, so it's not like rm -rf, but almost such. We
75  * ignore ENOENT errors for anything (they happen, strangely enough - possibly
76  * due to races between multiple dying UML threads).
77  */
78 static int remove_files_and_dir(char *dir)
79 {
80 	DIR *directory;
81 	struct dirent *ent;
82 	int len;
83 	char file[256];
84 	int ret;
85 
86 	directory = opendir(dir);
87 	if (directory == NULL) {
88 		if (errno != ENOENT)
89 			return -errno;
90 		else
91 			return 0;
92 	}
93 
94 	while ((ent = readdir(directory)) != NULL) {
95 		if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, ".."))
96 			continue;
97 		len = strlen(dir) + sizeof("/") + strlen(ent->d_name) + 1;
98 		if (len > sizeof(file)) {
99 			ret = -E2BIG;
100 			goto out;
101 		}
102 
103 		sprintf(file, "%s/%s", dir, ent->d_name);
104 		if (unlink(file) < 0 && errno != ENOENT) {
105 			ret = -errno;
106 			goto out;
107 		}
108 	}
109 
110 	if (rmdir(dir) < 0 && errno != ENOENT) {
111 		ret = -errno;
112 		goto out;
113 	}
114 
115 	ret = 0;
116 out:
117 	closedir(directory);
118 	return ret;
119 }
120 
121 /*
122  * This says that there isn't already a user of the specified directory even if
123  * there are errors during the checking.  This is because if these errors
124  * happen, the directory is unusable by the pre-existing UML, so we might as
125  * well take it over.  This could happen either by
126  * 	the existing UML somehow corrupting its umid directory
127  * 	something other than UML sticking stuff in the directory
128  *	this boot racing with a shutdown of the other UML
129  * In any of these cases, the directory isn't useful for anything else.
130  *
131  * Boolean return: 1 if in use, 0 otherwise.
132  */
133 static inline int is_umdir_used(char *dir)
134 {
135 	char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
136 	char pid[sizeof("nnnnn\0")], *end;
137 	int dead, fd, p, n, err;
138 
139 	n = snprintf(file, sizeof(file), "%s/pid", dir);
140 	if (n >= sizeof(file)) {
141 		printk(UM_KERN_ERR "is_umdir_used - pid filename too long\n");
142 		err = -E2BIG;
143 		goto out;
144 	}
145 
146 	dead = 0;
147 	fd = open(file, O_RDONLY);
148 	if (fd < 0) {
149 		fd = -errno;
150 		if (fd != -ENOENT) {
151 			printk(UM_KERN_ERR "is_umdir_used : couldn't open pid "
152 			       "file '%s', err = %d\n", file, -fd);
153 		}
154 		goto out;
155 	}
156 
157 	err = 0;
158 	n = read(fd, pid, sizeof(pid));
159 	if (n < 0) {
160 		printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file "
161 		       "'%s', err = %d\n", file, errno);
162 		goto out_close;
163 	} else if (n == 0) {
164 		printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file "
165 		       "'%s', 0-byte read\n", file);
166 		goto out_close;
167 	}
168 
169 	p = strtoul(pid, &end, 0);
170 	if (end == pid) {
171 		printk(UM_KERN_ERR "is_umdir_used : couldn't parse pid file "
172 		       "'%s', errno = %d\n", file, errno);
173 		goto out_close;
174 	}
175 
176 	if ((kill(p, 0) == 0) || (errno != ESRCH)) {
177 		printk(UM_KERN_ERR "umid \"%s\" is already in use by pid %d\n",
178 		       umid, p);
179 		return 1;
180 	}
181 
182 out_close:
183 	close(fd);
184 out:
185 	return 0;
186 }
187 
188 /*
189  * Try to remove the directory @dir unless it's in use.
190  * Precondition: @dir exists.
191  * Returns 0 for success, < 0 for failure in removal or if the directory is in
192  * use.
193  */
194 static int umdir_take_if_dead(char *dir)
195 {
196 	int ret;
197 	if (is_umdir_used(dir))
198 		return -EEXIST;
199 
200 	ret = remove_files_and_dir(dir);
201 	if (ret) {
202 		printk(UM_KERN_ERR "is_umdir_used - remove_files_and_dir "
203 		       "failed with err = %d\n", ret);
204 	}
205 	return ret;
206 }
207 
208 static void __init create_pid_file(void)
209 {
210 	char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
211 	char pid[sizeof("nnnnn\0")];
212 	int fd, n;
213 
214 	if (umid_file_name("pid", file, sizeof(file)))
215 		return;
216 
217 	fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644);
218 	if (fd < 0) {
219 		printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: "
220 		       "%s\n", file, strerror(errno));
221 		return;
222 	}
223 
224 	snprintf(pid, sizeof(pid), "%d\n", getpid());
225 	n = write(fd, pid, strlen(pid));
226 	if (n != strlen(pid))
227 		printk(UM_KERN_ERR "Write of pid file failed - err = %d\n",
228 		       errno);
229 
230 	close(fd);
231 }
232 
233 int __init set_umid(char *name)
234 {
235 	if (strlen(name) > UMID_LEN - 1)
236 		return -E2BIG;
237 
238 	strlcpy(umid, name, sizeof(umid));
239 
240 	return 0;
241 }
242 
243 /* Changed in make_umid, which is called during early boot */
244 static int umid_setup = 0;
245 
246 static int __init make_umid(void)
247 {
248 	int fd, err;
249 	char tmp[256];
250 
251 	if (umid_setup)
252 		return 0;
253 
254 	make_uml_dir();
255 
256 	if (*umid == '\0') {
257 		strlcpy(tmp, uml_dir, sizeof(tmp));
258 		strlcat(tmp, "XXXXXX", sizeof(tmp));
259 		fd = mkstemp(tmp);
260 		if (fd < 0) {
261 			printk(UM_KERN_ERR "make_umid - mkstemp(%s) failed: "
262 			       "%s\n", tmp, strerror(errno));
263 			err = -errno;
264 			goto err;
265 		}
266 
267 		close(fd);
268 
269 		set_umid(&tmp[strlen(uml_dir)]);
270 
271 		/*
272 		 * There's a nice tiny little race between this unlink and
273 		 * the mkdir below.  It'd be nice if there were a mkstemp
274 		 * for directories.
275 		 */
276 		if (unlink(tmp)) {
277 			err = -errno;
278 			goto err;
279 		}
280 	}
281 
282 	snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid);
283 	err = mkdir(tmp, 0777);
284 	if (err < 0) {
285 		err = -errno;
286 		if (err != -EEXIST)
287 			goto err;
288 
289 		if (umdir_take_if_dead(tmp) < 0)
290 			goto err;
291 
292 		err = mkdir(tmp, 0777);
293 	}
294 	if (err) {
295 		err = -errno;
296 		printk(UM_KERN_ERR "Failed to create '%s' - err = %d\n", umid,
297 		       errno);
298 		goto err;
299 	}
300 
301 	umid_setup = 1;
302 
303 	create_pid_file();
304 
305 	err = 0;
306  err:
307 	return err;
308 }
309 
310 static int __init make_umid_init(void)
311 {
312 	if (!make_umid())
313 		return 0;
314 
315 	/*
316 	 * If initializing with the given umid failed, then try again with
317 	 * a random one.
318 	 */
319 	printk(UM_KERN_ERR "Failed to initialize umid \"%s\", trying with a "
320 	       "random umid\n", umid);
321 	*umid = '\0';
322 	make_umid();
323 
324 	return 0;
325 }
326 
327 __initcall(make_umid_init);
328 
329 int __init umid_file_name(char *name, char *buf, int len)
330 {
331 	int n, err;
332 
333 	err = make_umid();
334 	if (err)
335 		return err;
336 
337 	n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name);
338 	if (n >= len) {
339 		printk(UM_KERN_ERR "umid_file_name : buffer too short\n");
340 		return -E2BIG;
341 	}
342 
343 	return 0;
344 }
345 
346 char *get_umid(void)
347 {
348 	return umid;
349 }
350 
351 static int __init set_uml_dir(char *name, int *add)
352 {
353 	if (*name == '\0') {
354 		printf("uml_dir can't be an empty string\n");
355 		return 0;
356 	}
357 
358 	if (name[strlen(name) - 1] == '/') {
359 		uml_dir = name;
360 		return 0;
361 	}
362 
363 	uml_dir = malloc(strlen(name) + 2);
364 	if (uml_dir == NULL) {
365 		printf("Failed to malloc uml_dir - error = %d\n", errno);
366 
367 		/*
368 		 * Return 0 here because do_initcalls doesn't look at
369 		 * the return value.
370 		 */
371 		return 0;
372 	}
373 	sprintf(uml_dir, "%s/", name);
374 
375 	return 0;
376 }
377 
378 __uml_setup("uml_dir=", set_uml_dir,
379 "uml_dir=<directory>\n"
380 "    The location to place the pid and umid files.\n\n"
381 );
382 
383 static void remove_umid_dir(void)
384 {
385 	char dir[strlen(uml_dir) + UMID_LEN + 1], err;
386 
387 	sprintf(dir, "%s%s", uml_dir, umid);
388 	err = remove_files_and_dir(dir);
389 	if (err)
390 		printf("remove_umid_dir - remove_files_and_dir failed with "
391 		       "err = %d\n", err);
392 }
393 
394 __uml_exitcall(remove_umid_dir);
395