aboutsummaryrefslogtreecommitdiff
path: root/arch/um/os-Linux/umid.c
blob: 4832eb519f8dfa9492803de9615e6d04b896faa3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
/*
 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include "init.h"
#include "os.h"

#define UML_DIR "~/.uml/"

#define UMID_LEN 64

/* Changed by set_umid, which is run early in boot */
static char umid[UMID_LEN] = { 0 };

/* Changed by set_uml_dir and make_uml_dir, which are run early in boot */
static char *uml_dir = UML_DIR;

static int __init make_uml_dir(void)
{
	char dir[512] = { '\0' };
	int len, err;

	if (*uml_dir == '~') {
		char *home = getenv("HOME");

		err = -ENOENT;
		if (home == NULL) {
			printk(UM_KERN_ERR "make_uml_dir : no value in "
			       "environment for $HOME\n");
			goto err;
		}
		strlcpy(dir, home, sizeof(dir));
		uml_dir++;
	}
	strlcat(dir, uml_dir, sizeof(dir));
	len = strlen(dir);
	if (len > 0 && dir[len - 1] != '/')
		strlcat(dir, "/", sizeof(dir));

	err = -ENOMEM;
	uml_dir = malloc(strlen(dir) + 1);
	if (uml_dir == NULL) {
		printf("make_uml_dir : malloc failed, errno = %d\n", errno);
		goto err;
	}
	strcpy(uml_dir, dir);

	if ((mkdir(uml_dir, 0777) < 0) && (errno != EEXIST)) {
	        printf("Failed to mkdir '%s': %s\n", uml_dir, strerror(errno));
		err = -errno;
		goto err_free;
	}
	return 0;

err_free:
	free(uml_dir);
err:
	uml_dir = NULL;
	return err;
}

/*
 * Unlinks the files contained in @dir and then removes @dir.
 * Doesn't handle directory trees, so it's not like rm -rf, but almost such. We
 * ignore ENOENT errors for anything (they happen, strangely enough - possibly
 * due to races between multiple dying UML threads).
 */
static int remove_files_and_dir(char *dir)
{
	DIR *directory;
	struct dirent *ent;
	int len;
	char file[256];
	int ret;

	directory = opendir(dir);
	if (directory == NULL) {
		if (errno != ENOENT)
			return -errno;
		else
			return 0;
	}

	while ((ent = readdir(directory)) != NULL) {
		if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, ".."))
			continue;
		len = strlen(dir) + sizeof("/") + strlen(ent->d_name) + 1;
		if (len > sizeof(file)) {
			ret = -E2BIG;
			goto out;
		}

		sprintf(file, "%s/%s", dir, ent->d_name);
		if (unlink(file) < 0 && errno != ENOENT) {
			ret = -errno;
			goto out;
		}
	}

	if (rmdir(dir) < 0 && errno != ENOENT) {
		ret = -errno;
		goto out;
	}

	ret = 0;
out:
	closedir(directory);
	return ret;
}

/*
 * This says that there isn't already a user of the specified directory even if
 * there are errors during the checking.  This is because if these errors
 * happen, the directory is unusable by the pre-existing UML, so we might as
 * well take it over.  This could happen either by
 * 	the existing UML somehow corrupting its umid directory
 * 	something other than UML sticking stuff in the directory
 *	this boot racing with a shutdown of the other UML
 * In any of these cases, the directory isn't useful for anything else.
 *
 * Boolean return: 1 if in use, 0 otherwise.
 */
static inline int is_umdir_used(char *dir)
{
	char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
	char pid[sizeof("nnnnn\0")], *end;
	int dead, fd, p, n, err;

	n = snprintf(file, sizeof(file), "%s/pid", dir);
	if (n >= sizeof(file)) {
		printk(UM_KERN_ERR "is_umdir_used - pid filename too long\n");
		err = -E2BIG;
		goto out;
	}

	dead = 0;
	fd = open(file, O_RDONLY);
	if (fd < 0) {
		fd = -errno;
		if (fd != -ENOENT) {
			printk(UM_KERN_ERR "is_umdir_used : couldn't open pid "
			       "file '%s', err = %d\n", file, -fd);
		}
		goto out;
	}

	err = 0;
	n = read(fd, pid, sizeof(pid));
	if (n < 0) {
		printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file "
		       "'%s', err = %d\n", file, errno);
		goto out_close;
	} else if (n == 0) {
		printk(UM_KERN_ERR "is_umdir_used : couldn't read pid file "
		       "'%s', 0-byte read\n", file);
		goto out_close;
	}

	p = strtoul(pid, &end, 0);
	if (end == pid) {
		printk(UM_KERN_ERR "is_umdir_used : couldn't parse pid file "
		       "'%s', errno = %d\n", file, errno);
		goto out_close;
	}

	if ((kill(p, 0) == 0) || (errno != ESRCH)) {
		printk(UM_KERN_ERR "umid \"%s\" is already in use by pid %d\n",
		       umid, p);
		return 1;
	}

out_close:
	close(fd);
out:
	return 0;
}

/*
 * Try to remove the directory @dir unless it's in use.
 * Precondition: @dir exists.
 * Returns 0 for success, < 0 for failure in removal or if the directory is in
 * use.
 */
static int umdir_take_if_dead(char *dir)
{
	int ret;
	if (is_umdir_used(dir))
		return -EEXIST;

	ret = remove_files_and_dir(dir);
	if (ret) {
		printk(UM_KERN_ERR "is_umdir_used - remove_files_and_dir "
		       "failed with err = %d\n", ret);
	}
	return ret;
}

static void __init create_pid_file(void)
{
	char file[strlen(uml_dir) + UMID_LEN + sizeof("/pid\0")];
	char pid[sizeof("nnnnn\0")];
	int fd, n;

	if (umid_file_name("pid", file, sizeof(file)))
		return;

	fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0644);
	if (fd < 0) {
		printk(UM_KERN_ERR "Open of machine pid file \"%s\" failed: "
		       "%s\n", file, strerror(errno));
		return;
	}

	snprintf(pid, sizeof(pid), "%d\n", getpid());
	n = write(fd, pid, strlen(pid));
	if (n != strlen(pid))
		printk(UM_KERN_ERR "Write of pid file failed - err = %d\n",
		       errno);

	close(fd);
}

int __init set_umid(char *name)
{
	if (strlen(name) > UMID_LEN - 1)
		return -E2BIG;

	strlcpy(umid, name, sizeof(umid));

	return 0;
}

/* Changed in make_umid, which is called during early boot */
static int umid_setup = 0;

static int __init make_umid(void)
{
	int fd, err;
	char tmp[256];

	if (umid_setup)
		return 0;

	make_uml_dir();

	if (*umid == '\0') {
		strlcpy(tmp, uml_dir, sizeof(tmp));
		strlcat(tmp, "XXXXXX", sizeof(tmp));
		fd = mkstemp(tmp);
		if (fd < 0) {
			printk(UM_KERN_ERR "make_umid - mkstemp(%s) failed: "
			       "%s\n", tmp, strerror(errno));
			err = -errno;
			goto err;
		}

		close(fd);

		set_umid(&tmp[strlen(uml_dir)]);

		/*
		 * There's a nice tiny little race between this unlink and
		 * the mkdir below.  It'd be nice if there were a mkstemp
		 * for directories.
		 */
		if (unlink(tmp)) {
			err = -errno;
			goto err;
		}
	}

	snprintf(tmp, sizeof(tmp), "%s%s", uml_dir, umid);
	err = mkdir(tmp, 0777);
	if (err < 0) {
		err = -errno;
		if (err != -EEXIST)
			goto err;

		if (umdir_take_if_dead(tmp) < 0)
			goto err;

		err = mkdir(tmp, 0777);
	}
	if (err) {
		err = -errno;
		printk(UM_KERN_ERR "Failed to create '%s' - err = %d\n", umid,
		       errno);
		goto err;
	}

	umid_setup = 1;

	create_pid_file();

	err = 0;
 err:
	return err;
}

static int __init make_umid_init(void)
{
	if (!make_umid())
		return 0;

	/*
	 * If initializing with the given umid failed, then try again with
	 * a random one.
	 */
	printk(UM_KERN_ERR "Failed to initialize umid \"%s\", trying with a "
	       "random umid\n", umid);
	*umid = '\0';
	make_umid();

	return 0;
}

__initcall(make_umid_init);

int __init umid_file_name(char *name, char *buf, int len)
{
	int n, err;

	err = make_umid();
	if (err)
		return err;

	n = snprintf(buf, len, "%s%s/%s", uml_dir, umid, name);
	if (n >= len) {
		printk(UM_KERN_ERR "umid_file_name : buffer too short\n");
		return -E2BIG;
	}

	return 0;
}

char *get_umid(void)
{
	return umid;
}

static int __init set_uml_dir(char *name, int *add)
{
	if (*name == '\0') {
		printf("uml_dir can't be an empty string\n");
		return 0;
	}

	if (name[strlen(name) - 1] == '/') {
		uml_dir = name;
		return 0;
	}

	uml_dir = malloc(strlen(name) + 2);
	if (uml_dir == NULL) {
		printf("Failed to malloc uml_dir - error = %d\n", errno);

		/*
		 * Return 0 here because do_initcalls doesn't look at
		 * the return value.
		 */
		return 0;
	}
	sprintf(uml_dir, "%s/", name);

	return 0;
}

__uml_setup("uml_dir=", set_uml_dir,
"uml_dir=<directory>\n"
"    The location to place the pid and umid files.\n\n"
);

static void remove_umid_dir(void)
{
	char dir[strlen(uml_dir) + UMID_LEN + 1], err;

	sprintf(dir, "%s%s", uml_dir, umid);
	err = remove_files_and_dir(dir);
	if (err)
		printf("remove_umid_dir - remove_files_and_dir failed with "
		       "err = %d\n", err);
}

__uml_exitcall(remove_umid_dir);