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 */
23static char umid[UMID_LEN] = { 0 };
24
25/* Changed by set_uml_dir and make_uml_dir, which are run early in boot */
26static char *uml_dir = UML_DIR;
27
28static 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
65err_free:
66	free(uml_dir);
67err:
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 */
78static 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;
116out:
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 */
133static 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
182out_close:
183	close(fd);
184out:
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 */
194static 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
208static 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
233int __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 */
244static int umid_setup = 0;
245
246static 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
310static 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
329int __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
346char *get_umid(void)
347{
348	return umid;
349}
350
351static 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
383static 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